khan k. biodiesel kinetics & catalyst 2 (master)

7/28/2019 Khan K. Biodiesel Kinetics & Catalyst 2 (Master)

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RESEARCH INTO BIODIESEL

CATALYST SCREENING

&

DEVELOPMENT

By

Adam KHAN

A thesis submitted to theDepartment of Chemical Engineering

In partial fulfilment of the requirementsFor an Individual Inquiry Topic at


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Adam Khan Individual Inquiry B

ACKNOWLEDGEMENTS

I would like to thank my supervisor, Assoc Prof Victor Rudolph for his constant support and

much needed direction, also his perseverance with my some of my wild ideas and running

hypotheses, some of which where a little pre-emptive. From this and previous work I am

beginning to appreciate how a structured, directed and enthusiastic approach to projects such as

this has many benefits, including success. Although, in saying that there are many walls

encountered in research and without perseverance and lateral thinking some of them would never

be overcome.I would also like to thank Dr Yinghe He for his help throughout this project, although my

Chinese lessons seem to have come to an end. I would also like to thank Ms Allison Hanley for

her assistance and input on the project and the many offers of help and her laboratory skills

which saved me much needed time on several occasions.

Finally I would like to thank Fleur Khan and my daughters Whitney and Isobel for their eternal

support and understanding of my goals and aspirations. It is from them that I have drawn all of

my determination and perseverance as there have been many occasions where I have questioned

my direction and purpose. Without them I would not have been able to complete much of what Ihave done and become who I am.


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ABSTRACT

This report follows on from previous research that attempted to cover the topic of biodiesel

production with a broad stroke, highlighting some key areas of interest, of which catalyst

development is still dominate.

Catalyst development is still the Achilles heel of continuous biodiesel production. This

combined with the use of crude feedstocks is one of the most important areas of research for the

development of an economically viable and sustainable energy source. The use of crude

feedstocks achieves two objectives, firstly it utilises a waste source that would otherwise have tobe disposed of and secondly it reduces the pressure on the environment with the use of

renewable resources and lower emissions of toxic pollutants. However, crude feedstocks have

the disadvantage of having high concentrations of free fatty acids and or water which current

catalyst will not tolerate. It was found that the water and free fatty acids are major contributors to

delivering insignificant yields. Measuring these yields and the extent of reaction was resolved in

previous research.

Although gas chromatography is to date the most accurate method to assess the extent of

reaction, it is time consuming and requires extensive sample preparation. It was due to thesefactors that an alternative method was sought to grossly quantify the extent of reaction. A simple

mass balance was used to for this purpose which was conducted thorough the separation and

weighing of the individual phases. From this actual mass and a theoretical mass, the method

could be cross checked for validity.

Several heterogenous catalysts were tested and have proven to be unsuitable with the exception

of one, synthesised zirconium. This catalyst and an acidified version will undergo further testing

as at this stage they have shown promise, but have not been extensively tested. The use of

sodium hydroxide gave some interesting results including the fact that it is only marginallysoluble in the reaction mixture. This has lead to some interesting ideas including the use of

Sodium hydroxide on a support as a solid catalyst. Although it is only marginally soluble it still

seems to catalyse the reaction.

Emulsion formation proved to be a hindrance to this research and identifying the underlying

causses and preventing them would lead to more accurate results. Preliminary tests have been

conducted and some hypotheses have been established on some potential factors, but these are

not definitive.


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TABLE OF CONTENTS

1.0 INTRODUCTION........................................................................................... 6

1.1 OBJECTIVES................................................................................................... 6

1.2 IMPLIMENTATION........................................................................................ 6

2.0 LITERATURE REVIEW .............................................................................. 7

2.1 GENERAL........................................................................................................ 7

2.2 Washing ............................................................................................................ 7

2.3 WATER and FREE FATTY ACIDS................................................................ 8

2.4 HETEROGENOUS CATALYSTS .................................................................. 8

3.0 LITERATURE REVIEW CONCLUSION .................................................. 8

4.0 SCOPE ............................................................................................................. 9

4.1 PROPOSED OUTCOMES ............................................................................... 9

5.0 INTRODUCTION........................................................................................... 9

6.0 EXPERIMENTAL........................................................................................ 10

6.1 REACTION METHODOLOGY .................................................................... 10

6.1.1 Equipment............................................................................................... 10

6.1.2 Reactants ................................................................................................. 12

6.1.3 Conditions ............................................................................................... 12

6.2 ANALYSIS METHODOLOGY..................................................................... 13

6.2.1 Mass Balance Method............................................................................. 13

6.3 ANALYSIS ERROR ...................................................................................... 14

6.4 REACTIONS .................................................................................................. 14

6.4.2 High Temperature Conversion................................................................15

6.5 RESULTS ....................................................................................................... 16

6.5.1 High Temperature Conversion................................................................16

6.5.2 Traditional Catalysts ............................................................................... 17

6.5.3 Potential Heterogenous Catalyst ............................................................. 17

6.5.4 Emulsion Formation................................................................................ 17

6.5.5 Gravimetric Method................................................................................ 17

7 0 DISCUSSION 17


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7.3 Emulsion formation ........................................................................................ 19

7.4 High Temperature reactions............................................................................ 19

8.0 CONCLUSIONS ........................................................................................... 209.0 FUTURE WORK AND RESEARCH.........................................................20

10.0 REFERENCES.............................................................................................. 22

APPENDIX A................................................................................................................ 25

APPENDIX B ................................................................................................................ 28

APPENDIX C................................................................................................................ 41

TABLE OF FIGURES

Figure 6.1. Parr reactor and PID controller.................................................................. 10

Figure 6.2. Batch reactor with thermocouple and heating mantle.............................. 11

Figure 6.3 No conversion Bio0044 .................................................................................. 15

Figure 6.4 Bio0040, Bio0041 & Bio0041 with water ..................................................... 15

Figure 6.5 Formation of emulsion .................................................................................. 16

Figure 6.6 Progressive series of emulsion breaking...................................................... 16

TABLE OF TABLES

Table 6.1. List of chemicals, supplier, quantity and grade .......................................... 12

Table 6.2. List of catalysts, supplier, quantity and grade ............................................ 12

Table 6.3. Typical reaction data sheet............................................................................ 13

Table 6.4. Mass balance procedure Bio0054.................................................................. 14

Table 11.1 Mass balance Bio0046................................................................................... 25

Table 11.2 Mass balance Bio0047................................................................................... 25


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1.0 INTRODUCTION

1.1 OBJECTIVES

This project follows on from previous work into biodiesel and is directed at towards the kinetics

and catalyst development. It was found that catalyst screening trials was required to identify

suitable heterogenous candidates for the transesterification reaction. Although, a potential

catalyst was previously identified from the literature for this reaction, it was found that the

catalyst properties i.e. activity deviated substantially from the results reported in the literature,

which could not be replicated. Some potential catalysts such as titanium oxides and various

forms of zirconia have been identified for performance testing.

The use of crude feedstocks is important in the overall economics for the production of biodiesel,so catalysts will be tested with tallow and used oils. However, for simplicity and to minimise

variables, food grade oils will be used to generate kinetic data and initially determine catalyst

suitability. The development of a laboratory technique to estimate conversion will be assessed

which includes the separation of phases, a mass balance and a final washing of the ethyl esters

with reverse osmosis water.

Catalysing the reaction is by far the most crucial constraint in the development of a continuous

process for the production of biodiesel and as such the basis of this work has focused on

identifying and testing for a suitable catalyst.

1.2 IMPLIMENTATION

The development of a laboratory method for estimating conversion preceded reactions in an

attempt to decrease the turnaround time. Although, gas chromatography is currently the most

accurate method to determine product concentrations, it is also quite time consuming and

requires several hours sample preparation for each run. Including this will be an attempt to

confliction information on some problems associated with washing biodiesel.

As an additional activity the plug flow tubular reactor was assembled an pre-commissioning and

pressure testing carried out.


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2.0 LITERATURE REVIEW

2.1 GENERAL

A more comprehensive survey of the biodiesel literature is given in Appendix C. This review

focuses specifically on issues of significant practical importance poorly identified and generally

not discussed to any substantial degree in the literature.

The use of homogeneous alkali and to some extent acid catalysts, in the transesterification

reaction of animal fats and oils, is a well-established practice. Alkali catalysts are generally used

due to their relative simplicity, cost and the high levels of conversion achieved at low

temperatures. This has thus lead to extensive research being carried out on their properties,

outlining their advantages and disadvantages.The main alkali catalysts used are sodium hydroxide, sodium ethoxide (methoxide) potassium

hydroxide and potassium ethoxide (methoxide). However, it was found that sodium hydroxide is

only sparingly soluble in ethanol and was also found to promote undesirable gel and emulsion

formation during reaction (Peterson, 1995). Methanol is usually used in the production of

biodiesel as it is more cost effective, so there has been substantial research conducted on the

methanol, sodium hydroxide combination. Recognising methanol as relatively toxic, its use has

been more restricted when eventually environmental considerations are given greater weight.

Irrelevant of the actual catalyst used, all homogeneous catalysts require neutralisation at the

completion of reaction. This then raises issues of catalyst consumption and separation of the salt

produced and the product phases. It is known that the glycerol, which is produced during

reaction, tends to carry most of the catalyst with it when it is allowed to settle out (Peterson,

1995). This then limits the amount of catalyst remaining in the product phase but does not

eliminate the problem.

2.2 Washing

The purpose of washing is to purify the biodiesel by removing catalyst, residual glycerol andunreacted or partially reacted oils. Peterson found that if the reaction mixture was mixed for

around 20 minutes with pure glycerol and then 15% by weight of water was added with a further

20 minutes mixing, washing became a lot simpler and required less total washes. This method

also tended to remove all of the mono and diglycerides from the product phase. However, it

was found that vigorous stirring, before all of the contaminates had been removed with glycerol,

caused emulsions to form that where difficult to break and when any soaps where still present

the formation of gels or a high viscosity liquid was likely (Freedman, 1984). Fanguri also found

that adding water in the presence of glycerol formed and emulsion resulting in the loss in yieldof both glycerol and esters. Incomplete reactions and or reverse reactions where thought to be the

cause of formation of solids or a gel like phase, due to the emulsion formation characteristics of

mono-, di- or triglycerides (Praven, 1996).

In the transesterification reaction the forward reaction is only favoured when an excess of

alcohol is used, however it was found that ratios greater than 6:1, which is generally considered


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chloride or sulphuric acid are generally used as they are hydrophilic and considering that water is

a major problem in this reaction, this is an advantageous trait.

2.3 WATER and FREE FATTY ACIDS

One common topic that occurs throughout most literature is the affect that water and free fatty

acids (FFA) have on both esterification and transesterification reactions. The fatty acids are

problem because they form soap with the metal ion from the alkali catalysts, which hinder

separation, decrease yield and lead to emulsion formation. Water has a two fold affect it

combined with soap form the emulsions and secondly the oils can undergo hydrolysis with the

water forming fatty acids. Ma found that water was a more critical variable than was FFA, but

more importantly when both present, they acted synergistically to substantially decrease the

yield of esters (Ma, 1998). Water is detrimental to the reaction from an equilibrium standpoint as

it is a product in the reaction and will favour the reverse reaction as the concentration increases.

Refined oils are thus generally favoured due to their low concentrations of FFA and water. The

source of water is not limited to that found in the feedstock, as some water is produced with the

reaction of metal hydroxides with alcohol i.e. sodium ethoxide from sodium hydroxide and

ethanol (Schuchardt, 1997). If there is sufficient alkoxide produced then hydrolysis occurs

producing FFA and with a metal hydroxide present saponification occurs, which not only

decreases the yield of esters but also consumes catalyst possibly leading to incomplete reaction.

2.4 HETEROGENOUS CATALYSTSThe limitations of alkali and acid catalysts are well documented, however there are few reports

regarding catalysts. Catalyst development remains of primary importance in biodiesel research

and unless more tolerant catalysts can be developed, feedstock quality will remain the main

impediment. There have been brief mentions of solid catalysts throughout literature and in some

situations reasonably detailed experimentation. Calcium carbonate has been said to be a

satisfactory catalyst (Supps et al, 1996) but it is reported that alkali catalyst should be low in

carbonates, such as potassium carbonate as carbonates do not serve as satisfactory catalysts

(Peterson, 1996). Guanidines supported on an organic polymer showed some promise but havebeen found to be subject to leaching, irreversible protonation and rapid deactivation (Schuchardt,

1997). Organic tins and titanium are applied in the polymer industry for transesterification but

the combination of toxicity and separation issues make them unsuitable for biodiesel production.

3.0 LITERATURE REVIEW CONCLUSION

All of the most significant issues with biodiesel production have a common thread the inclusion

of water. Water leads to the production of FFA and the subsequent production of soap. Thus

soap increases the complexity of the separation plant very significantly, besides its obvious

detrimental effect as a by-product competing with biodiesel. Water does not need to be present in

the feed if alkali catalysts are used as it evolves with the production of alkoxides albeit in small

amounts. This does not occur with the use of acid catalysts, but the esterification of FFA

produces water which can cause the subsequent production of more FFA through hydrolysis. The

production of FFA in most industrial applications seems to be lower due to the use of refined


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4.0 SCOPE

4.1 PROPOSED OUTCOMES

Although gas chromatography was chosen to be the most suitable method of analysis for thisproject due to the complexity of the product mixture, it proved to be time consuming as it

required extensive sample preparation. In addition the lack of a dedicated facility caused

difficulties associated with access, timing and calibration. NIR was identified as being a

potentially suitable method for online qualitative analysis, but due to equipment requirements it

is not yet available. Therefore it was proposed that a suitable method of analysis be develop that

could be carried out in the laboratory that was simple, reliable and quick. It was proposed that

this method would take the form of a mass balance analysis requiring a series of separation steps.

This would represent an intermediate step between preliminary analysis and detailed analysis viagas chromatography.

This would be combined with catalyst screening with four potential catalysts being targeted.

They have been selected on the basis of their composition not necessarily their structure.

These are;

1. Rutile

2. Synthesised micro porous Zirconia

3. Synthesised micro porous Zirconia Sulphate (Super Acid)

4. Zircon Sand

There were also several runs conducted using Agro Lime (CaCO3) replicating previous trials to

try and establish why the catalytic activity reported in the literature for limes could not be

reproduced.

5.0 INTRODUCTIONThis thesis is part two of a two part project that has been designed to identify some important

aspects of biodiesel production, research and development. Part one Research into Biodiesel

Kinetics & Catalyst Development attempted to identify the kinetics of the transesterification

reaction with a suitable heterogenous catalyst, namely calcium carbonate. This part also covered

the development of a suitable analysis technique namely gas chromatography and an in depth

literature overview of biodiesel. Unfortunately the use of calcium carbonate as a

transesterification catalyst could not be confirmed, despite several attempts to exactly replicate

the reaction conditions as provided in the literature. However the analysis method which wasdeveloped based on GC proved to be effective.

Since the ultimate objective of the project is to establish a continuous process, the physical

attributes of the catalyst need to be such that it can be used within a high temperature high

pressure plug flow reactor. Therefore catalyst screening was the primary goal of this work being

targeted for suitability in the plug flow tubular reactor PFTR. The PFTR was designed and


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6.0 EXPERIMENTAL

6.1 REACTION METHODOLOGY

6.1.1 Equipment

6.1.1.1 Pressure Reactor (Batch)

The reactor was a Parr 2100 series 300ml pressure reactor. It is rated to 300bar, but is installed

with a 1981.45 psi rupture disk and for operation up to 100C without cooling and 500C with

cooling. It has a programmable PID controller that can be seen in Figure 6.1.

Figure 6.1. Parr reactor and PID controller

The procedure taken to use the reactor was as follows;

1. The initial condition of the reactor was empty and clean.

2. The reactants were weighed out in the required amounts added to

a beaker with a magnetic stirrer and mixed for several minutes.

3. The reactor was then charged with the contents of the beaker, the

manifold placed on and the bolts tightened firmly


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The second reactor that was used was a modified beaker fitted with a thermocouple, on a heating

mantle with a magnetic stirrer, as can be seen in Figure 6.2. The beaker was sealed with a rubber

stopper to minimise the loss of ethanol in the vapour phase. The reaction temperature was kept

below the boiling point of ethanol to maintain a constant pressure within the beaker. Since theinternal beaker pressure was slightly less than atmospheric, the tendency for leakage was inward.

This caused the stopper to be drawn inwards, providing an effective seal, demonstrated by a

small quantity of liquid as a bead around the outside edge.

Figure 6.2. Batch reactor with thermocouple and heating mantle.

The procedure taken to use the bench top reactor was as follows;

1. The initial condition of the reactor was empty and clean.

2. The reactants were weighed out in the required amounts and

added to the beaker with a magnetic stirrer.

3. The rubber stopper was place on the top of the beaker and

pressed down until neatly seated with the rim.

4. The thermocouple was left out until the beaker reached 65C,

then the thermo couple was inserted and the temperature was


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that the thermocouple is removed before the temperature is

decreased or the rubber stopper will be sucked into the beaker.

6.1.2 Reactants

6.1.2.1 Chemicals

The reactants used are listed in Table 6.1.

Table 6.1. List of chemicals, supplier, quantity and grade

Chemical Grade Source Quantity

Calcium Carbonate AR 99% Univar 500g

Potassium Hydroxide AR 85% Chem Supply Pty Ltd 500g

Sodium Hydroxide AR 85% Chem Supply Pty Ltd 500g

Anhydrous Ethanol AR 99% University Chemical Store 1.5L

Sulphuric acid AR 98.2% source unknown 500ml

Canola Oil Edible Coles Pty Ltd 4L

Beef Tallow Beef City 60kg

Prime Triglycerides 100% 30kg

Save AllFFA 44%

Triglycerides 56%

30kg

6.1.2.2 Catalysts

The catalysts used that have not been mentioned in Table 6.1 can be seen in Table 6.2.

Table 6.2. List of catalysts, supplier, quantity and grade

Catalyst Source Quantity Grade Form

TiO2 R3412A Consolidated Rutile Ltd 500g 95% TiO2 5% unknown Granular

Zircon Sand

Z3094

Consolidated Rutile Ltd 500g 60% ZrO2 ~20%ZrO

~20%Unknown

Granular

ZrO Nanomac ~5g 99.9%


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Table 6.3. Typical reaction data sheet

Date Batch # Reactor Vessel

07/08/02 Bio0048 Beaker Run

Reactants: Mass g Mol Molecular WeightCanola Oil 300.00 0.35 847.40

EtOH 97.82 2.12 46.05

KOH 3.98 0.04 98.07

Reaction Conditions:

TEMPERATURE 60C

PRESSURE 1 atm

TIME 180 min

Comments:

6:1 Mole ratio of ethanol to oil ,~3% catalyst by weight

6.2 ANALYSIS METHODOLOGY

6.2.1 Mass Balance Method

The mass balance method comprises of several stages of isolating phases, weighing and washing

the final product to eliminate any un-reacted components. The underlying assumption of the

process is that the reaction gone to completion and one hundred percent of the oil has been

converted to biodiesel. This assumption can be justified when the reaction is left for an extendedperiod of time far exceeding that required for normal reaction conditions. Typical reaction times

were 3 hours. When considering that ninety five percent of the reaction is complete in the first

30min it is reasonable to assume that the reaction has gone to completion.

6.2.1.1 Reaction Procedure

Once the reaction was complete the rubber stopper and magnetic stirrer were removed and the

reactants weighed. The beaker was then periodically weighed until the loss of mass was equal to

the approximate mass of excess ethanol that was calculated theoretically. The contents of the

beaker where then place in a separating funnel and allowed to settle overnight. The glycerol was

then separated and weighed. The remaining contents of the separating funnel were also weighed

and then returned to the funnel. Some of the later batches were added to beaker with pure

glycerol allowed to mix for 20min and then returned to the funnel where the glycerol was

removed. This procedure was only conducted on some of the later batches based on earlier

experience that there were some complications with washing. This will be discussed in detail

later. The procedure outline can be found in Table 6.4.


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Table 6.4. Mass balance procedure Bio0054Component Mass (g) Adjustment Actual Theoretical Difference

a Beaker 169.1 0

b Reactants 396.5 0

c After Rxn 566.0 c-b-a 0.4

d After Evap 523.1 d-b-a 42.4 46.05 3.62 1

e Empty Beaker 171.8 e-a 171.75 169.07 2.68 2

f Glycerol Flask 116.4

g Glycerol 146.7 g-f 30.3 32.605 -2.305 3

h Biodiesel* 319.4 319.42 316.31 3.11 4

i Biodiesel#

315.7 315.7 316.31 -0.62 5

Total Mass Lost In Overall Process 394.2 396.5 -2.3

1. Mass of Excess Ethanol Evaporated2. Mass of remaining components in empty beaker usually glycerol

3. Mass of actual glycerol compared with amount theoretically predicted

4. Mass of biodiesel before washing

5. Mass of biodiesel after washing

It was found that adding the biodiesel phase back into beaker with pure glycerol, mixing for

20min and then adding 15% by mass of water, enhanced the washing step and removed the

impurities that seemed to be responsible for the formation of an emulsion. Emulsion formation

was a major restriction in this process. They tended to be formed from reactions that werecatalysed with alkalis and formed when the mixture was washed and agitated with water. The

emulsions are hard to break once formed so it is best to limit their formation. To minimise there

formation the later batches were not washed and the mass of the catalyst taken into consideration

when weighing out the esters.

6.3 ANALYSIS ERROR

Since the gravimetric method is a novel feature of this work, was entirely developed here and

noting that it requires a number of separation steps, it is appropriate to consider the errors thatmay occur.

The main areas where error occurred were in mass losses between steps, such as glycerol

sticking to the beaker when emptied into the separation funnel. Some of these where minimised

as much as possible, but where taken into consideration when calculating the mass balance. The

actual process was found to account for 99.42% of the overall mass, this seems very acceptable.

The overall error is minimised by using the highest possible mass of reactants (obviously in their

correct molar ratios).

Overall error was relatively easy to asses, whereas the error associated to the differences basedon theoretical masses and actual masses includes additional complexities. There are two

unknowns in this process and they are the molecular mass of the oil and biodiesel, which are

required for the balances but represent assumed values. There are several ways to calculate these

values, however all of them are taken as averages and range between 847g/mol 963g/mol. Fro

simplicity one value was chosen for oil based on an assumed molecular composition and used


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method. There were some difficulties with soap and emulsion formation, with soap production

leading to emulsification.

6.4.1.1 Pressure Reactor

A table of reactions can be found in Appendix B, which outlines the reaction conditions carried

out in the pressure reactor, reactants and a one-line description on the results. A close

examination of the samples in Figure 6.3 reveals a layer of ethanol across the top of each oil

layer. These samples were taken from the pressure reactor with the Khan-Guinness method. The

amount of ethanol varies across the range of samples, which is independent of the mass of oil.

This can most readily be seen from the last samples on the far right of the diagram, in which the

volume of ethanol is approximately 50% of the total volume. The final sample the larger vial is

the residual of the reactor.

Figure 6.3 No conversion Bio0044

6.4.2 High Temperature Conversion

An anomaly found with some of the reactions carried out at high temperatures with and without

catalysts can be seen in Figure 6.4. This is unusual in that the fats (solids at room temperature)have been converted to liquids at room temperature. What is also unusual is the absence of a

glycerol phase.


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6.4.2.1 Beaker

The results for the gravimetric method can be found in Appendix A, these are Bio0046 to

Bio0053. Some of the initial gravimetric methods involved washing of the final ester phase to

remove any residual glycerol or unreacted/ partially reacted oil. What can be seen from Figure6.5 (Bio0046) is the impact of this washing with the addition of rigorous agitation. The ensuing

emulsion seemed to be unbreakable, but on the addition of table salt which is used in the soap

industry, the emulsion dissipated to some extent. What can be seen in

Figure 6.6 is the progressive addition of table salt starting from left to

right, with the left most sample having no salt. The emulsion formation

is a significant problem and will be discussed further in the results

section.

Figure 6.5 Formation of emulsion

Figure 6.6 Progressive series of emulsion breaking

6.5 RESULTS

Bio0044 represents a case where no reaction occurred. It nevertheless provides useful results in

that all the samples taken, if representative of the reaction mixture, should have the same ethanol

content. It is apparent from Figure 6.3 that this not the case, indicating that the sampling system

does not provide a correctly and consistently representative sample of the pressure reactor.

Switching the mixer off briefly while taking the sample may alleviate this problem. This process

will have to be done over a short period of time to minimise any phase separation. There may be

other options but at this stage further investigation is required.

6.5.1 High Temperature Conversion

It was initially thought that calcium carbonate was capable of catalysing the transesterification

reaction. This was based on literature reports and also some early experiments which showed

total conversion of a solid fat to a liquid The only obvious difference between these experiments


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samples, although there were some differences in the detail of the procedures followed and the

work did not extend to determining the underlying reasons for the different behaviour.

6.5.2 Traditional Catalysts

One of the beaker reactions (Bio0048) was carried out with sodium hydroxide as the catalyst.

What was interesting about this reaction was that it was still catalysed despite the fact that

sodium hydroxide was obviously only marginally soluble in the reaction mixture. This poses

several questions about how this reaction is catalysed industrially when ethanol is used as the

alcohol. It was found that potassium hydroxide was readily soluble in the ethanol oil mixture and

gave reasonable qualitative results.

6.5.3 Potential Heterogenous Catalyst

It was found that the Zirconium catalyst showed significant promise, however since only a smallamount of catalyst was available, only one trial could be conducted. An acidified version of the

Zirconium catalyst has been supplied for testing but at this stage GC analysis is not available so

it will not be tested until quantitative analysis can be done. Zirconium catalyst is to date the only

heterogenous catalyst that has showed any promise in catalysing the transesterification reaction.

6.5.4 Emulsion Formation

The formation of emulsions is a significant problem. It was found that all the reactions that were

catalysed with alkali catalysts were more likely to form an emulsion if shaken with water. Atypical example of the emulsions formed can be seen in figure 6.5. These emulsions were very

hard to break and would not settle under their own accord. It was found that the acid catalysed

reactions were not susceptible to emulsion formation although this is a preliminary finding due

to the limited number of runs being conducted with an acid catalyst. The formation of soap may

be a key factor as with acid catalysed reactions there is no soap formation.

6.5.5 Gravimetric Method

There was an interesting result with the mass balance method in that the amount of glyceroltheoretically predicted was consistently half of what was actually found. This was with the

reactions that were catalysed with an alkali catalyst. The reaction that was conducted with an

acid catalyst gave almost the amount of glycerol that was theoretically predicted. There is still an

unaccountable amount of mass missing from the ethyl esters and at this stage it is not clear if this

can be found in the glycerol phase or there is an error in the procedure. All of the values for the

mass balance method can be found in Appendix A. Pure glycerol is clear and immiscible with

ethyl esters. The glycerol that is found in the biodiesel reactions is amber in colour and not quite

as viscus as that found with pure glycerol. This will be discussed in detail in the discussion

section.

The glycerol that was found from the acid catalysed reaction was found to be a lot less viscus

than that found from the alkali reactions. The quality of this will have to be analysed

quantitatively to determine its purity.

It is fairly conclusive that CaCO3 is not a suitable catalyst for this reaction since it has shown


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7.1 Catalysts

7.1.1 Sodium hydroxide

Sodium hydroxide is relatively insoluble in ethanol, but nevertheless appears, even at very lowconcentrations, to be a strongly catalytic agent. One possibility is that the sodium hydroxide is

reacted to the ethoxide form. This rases the possibility to use sodium hydroxide as a sacrificial

solid catalyst in the continuous reactor. A simple test in which the catalyst was shaken with

ethanol showed that it remained in the solid phase. This suggests that a reactor packed with

sodium hydroxide pellets may be subject to blocking over time, as the catalyst recrystallises. One

possibility to over come this would be to impregnate an inert porous carrier with sodium

hydroxide solution, evaporate of the remaining water, and use this as the plug flow reactor

packing.

7.1.2 Zirconium

If Zirconium proves to be as active as sodium hydroxide, it would be a more suitable catalyst, as

it is not sacrificial. This would reduce the frequency of catalyst replacement and eliminate the

need for post treatment. Post treatment in the form of catalyst neutralisation is required when

alkali catalysts are used as the pH of the product is generally quite high. Currently the zirconium

is supplied as a powder which is sub micron. This in its current form could not be used in a

continuous reactor as it would induce an infinite pressure drop across the bed. A suitable support

system will be required or particle size enlargement i.e. sintering to obtain a larger particle size.The trade off with this type of practice is the loss of surface area however in its current form, the

catalyst is not suitable.

7.1.3 Zirconia Sand

As the preliminary results for the zirconium were good, it was thought finding a readily available

suitable form of zirconium, could short cut the catalyst design to implementation stage. The most

readily available form found was zirconia sand. The catalysts was tested repeatedly for activity

but proved to be inactive and thus unsuitable for this purpose. Initial speculation about the formof the zirconia being unsuitable was confirmed but it the trial highlighted the importance of

molecular structure.

7.1.4 Titanium

Titanium has previously been identified from literature as being a potential catalyst for this

reaction. However the current application in a similar reaction is in a homogenous form.

Although this is reported to have a high level of activity, it is not suitable for our application as a

homogenous catalyst. Therefore as with zirconium, a heterogenous form was sought that couldbe used in a packed bed. Rutile proved to be readily available and sufficiently large enough to be

employed in a packed bed. However, after several runs with it in the batch reactor it failed to

show any signs of activity. Catalyses is complex my nature and understanding how catalysts

work is by no means a simple task. Future work may show that the other crystal form of

titanium, anatase may be more active, however rutile has proven to be unsuitable to catalyse this

i


19/41


20/41


8.0 CONCLUSIONS

The conclusion is best summarised in point form and is as follows;

1. No effective solid catalysts have been reported in literature or patents. There is several in

development but all have failed to perform.

2. Calcium carbonate is not effective, and literature reports could not be replicated.

3. Miroporous tetragonal zirconia shows good promise as a potential catalyst.

4. The sulphated zirconia (superacid) may also be a good candidate, but as yet has been

untested.

5. Zircon sand showed no catalytic activity, as did rutile.

6. Titania based zeolite may be a promising material, and should be investigated further.

7. Alkali based catalysts e.g. supported sodium hydroxide may offer opportunity for use

with refined oils, but suffer from soap formation when any fatty acids are present.

8. The gravimetric method has several finer details to be addressed, but could be a simple

method to analysis the extent of reaction.

9. Emulsion formation presents serious practical problems of separation, but is not widelyaddressed in literature.

9.0 FUTURE WORK AND RESEARCH

Future work and research will include the systematic testing of sulphated zirconia, which will

involve the acquisition of kinetic, data if it proves to be a suitable catalyst, for application in the

continuous reactor. This will also include the development of a suitable support, as the particle

size is currently unsuitable for a packed bed. Potential candidates could include but are notexclusive to aluminium, zeolite and polymers. As with acid catalysts it is proposed that

zirconium catalysts will not induce emulsions in the product.

The emulsion formation is an interesting occurrence but should only be resolved on completion

of catalyst selection. It seems that the emulsions are strongly correlated with alkali catalysts

which are significant only if an alkali catalyst is selected for this project. However, the

gravimetric method has been severely hampered by emulsion formation as the catalysts used

were alkalis. This may explain the losses in the gravimetric method.

A short term solution to this problem may lie in the back mixing of pure glycerol to reduce theconcentration of condiments to reduce or even eliminate emulsion formation. This was solution

was briefly assessed but will require more testing over various sets of conditions to confirm its

suitability. It is thought that the main contaminate responsible for the emulsion formation is fatty

acids which leads to soap production.


21/41


current method of taking samples and has been adequate up to date, but for future samples the

method will need to be modified. This would be approached by conducting a systematic

sampling regime checking the volume of ethanol across a range of sampling sizes to determine if

the proportionality of ethanol to oil is constant. This would be conducted at temperatures just

above the boiling point of ethanol and without a catalyst to reduce the reaction rate.

Work is still required on the continuous reactor as full commissioning is not yet complete.

Preliminary commissioning has already been started with modifications being made to facilitate

temperature and pressure testing. There have been some additional modifications made for

occupational health and safety reasons which were only minor. Intal pressure and temperature

tests were found to be in line with the design specifications and operational testing with reactants

can now proceed.


22/41


10.0 REFERENCES

1. Provisional specification for biodiesel fuel (B100) blend stock for distillate fuels.2. Alcantara, R. et al. Catalytic production of biodiesel from soy-bean oil, used frying oil and

tallow. Biomass and Bioenergy 18, 515-527 (2000).

3. Ali, Y., Hanna, M. A. & Borg, J. E. Optimization of diesel, methyl tallowate and ethanol

blend for reducing emissions from diesel engine. Bioresource Technology 52, 237-243

(1995).

4. Allen, C. A. W., Watts, K. C., Ackman, R. G. & Pegg, M. J. Predicting the viscosity of

biodiesel fuels from their fatty acid ester composition. Fuel 78, 1319-1326 (1998).

5. Boocock, D. G. B., Konar, S. K., Mao, V. & Sidi, H. Fast one-phase oil-rich processes for

the preparation of vegetable oil methyl esters. Biomass and Bioenergy 11, 43-50 (1995).6. Boocock, D. G. B., Konar, S. K., Mao, V., Lee, C. & Buligan, S. Fast formation of high-

purity methyl esters from vegetable oils. Journal of American Oil Chemical Society 75

(1998).

7. Boocock, D. G. B. (2001).

8. Boocock, D. G. B., Konar, S. K., Blakansky, G. V. & Zhou, W. in 51st Canadian Chemical

Engineering Conference (2001).

9. Canakci, M. & Gerpen, V. J. Biodiesel production via acid catalysis. American Society of

Agricultural Engineers 42, 1203-1210.10. Corma, A., Miquel, S., Iborra, S. & Velty, A.

11. Cvengrosova, Z., Cvengros, J. & Hronec, M. Rapeseed oil ethyl esters as alternative fuels

and their quality control. Petroleum and coal 39, 36-40 (1997).

12. Foglia, T. A., Jones, K. C., Haas, M. J. & Scott, K. M. Technologies supporting the adoption

of biodiesel as an alternative fuel. The cotton gin and oil mill press (2000).

13. Freedman, B., Pryde, E. H. & Mounts, T. L. Variables affecting the yields of fatty esters

from transesterified vegetable oils. Journal of american Oil Chemical Society (1984).

14. Freedman, B., Kwolek, W. F. & Pryde, E. H. Quantitation in the analysis of transesterifiedsoybean oil by capillary gas chromatography. Journal of American Oil Chemical Society 63

(1986).

15. Graboski, M. S. & McCormick, R. L. Combustion of fat and vegetable oil derived fuels in

diesel engines. Prog. Energy Combustion Sci. 24, 125-164 (1998).

16. Holcapek, M., Jandera, P., Fischer, J. & Prokes, B. Analytical monitoring of the production

of biodiesel by high performance liquid chromatography with various detection methods.

Journal of chromatography A, 858, 13-31 (1999).

17. Knothe, G. Rapid monitoring of transesterification and assessing biodiesel fuel quality by

near-infrared spectroscopy using a fiber-optic probe. Journal of American Oil Chemical

Society 76, 795-800 (1999).

18. Knothe. Monitoring a progressing transesterification reaction by fiber-optic color near

infrared spectorscopy with correlation to 1h nuclear magnetic resonance spectroscopy.

Journal of american Oil Chemical Society 77 (2000).

19 Korbitz W in World fuel ethanol congress (Beijing China 2001)


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23. Ma, F., Clements, L. D. & Hanna, M. A. The effect of mixing on transesterification of beef

tallow. Bioresource Technology 69, 289-293 (1999).

24. Mittelbach, M. Diesel fuel derived from vegetable oils, V[1]: gas chromatographic

determination of free glycerol in transesterified vegetable oils. Chromatographia 37 (1993).

25. Mittelbach, M. Diesel fuel derived from vegetable oils, VI: specifications and quality control

of biodiesel. Bioresource Technology 56, 7-11 (1996).

26. Mittelbach, M., Roth, G. & Bergmann, A. Simultaneous gas chromatographic determination

of methanol and free glycerol in biodiesel. Chromatographia 42 (1996).

27. Muniyappa, P. R., Brammer, S. C. & Noureddini, H. Improved conversion of plant oils and

animal fats into biodiesel and co-product. Bioresource Technology 56, 19-24 (1996).

28. Peterson, C. L., Reece, D. L., Thompson, J. C., Beck, S. M. & Chase, C. Ethyl ester of

rapeseed used as a biodiesel fuel - a case study. Biomass and Bioenergy 10, 331-336 (1995).

29. Peterson, C. L. et al. 1-8 (University of Idaho, College of Agriculture, Idaho, 1996).30. Plank, C. & Lorbeer, E. Simultaneous determination of glycerol, and mono-, di- and

triglycerides in vegetable oil methyl esters by capillary gas chromatography. Journal of

chromatography A, 697, 461-468 (1995).

31. Resources, D. E. (2001).

32. Shimada, Y., Watanabe, Y., Sugihara, A. & Tominaga, Y.

33. Sonntag, N. O. V. Oleochemicals as renewable molecules; Prospects for the 21st century.

Journal of american Oil Chemical Society 59, 795A (1982).

34. Suppes, G. J. et al. Calcium carbonate catalyzed alcoholysis of fats and oils., (2001).35. Trathnigg, B. & Mittelbach, M. Analysis of triglyceride methanolysis mixtures using

isocratic hplc with density detection. Journal of liquid chromatography 13, 95-105 (1990).

36. Van Gerpen, J. H. et al. 1-28 (Iowa State University, Iowa, 1996).

37. Ali, Y. & Hanna, M. A. (1994a). Physical properties of tallow ester and diesel fuel blends.

Bioresourses Technology, 47, 131-4

38. Bondioli P, Gasparoli A, Lanzani A, Fedeli E, Veronese S, Sala M. Storagability of

biodiesel. Journal of American Chemicals Society 1995: 72:699-702.

39. Freedman B, Pryde EH, Mounts TL. Variables affecting the yields of fatty esters from

transesterified vegetable oils. Journal of American Oil Chemicals Society. 1984; 61:;1638-

43.

40. Kemp W. In: Practical organic chemistry. London: McGraw-Hill, 1967. p 99.

41. Allen CAW, Watts KC. A batch type transesterification unit for biodiesel fuels, Technical

paper 96-404, Canadian society of Agricultural Engineers, 1996.

42. Allen CAW, Watts KC, ACKMAN rg. Properties of methyl esters of interesterified

triacylglycerols Proceeding of the Third Liquid Fuel Conference. Liquid fuels and industrial

products from renewqable resources. St. Joseph, MI: ASAE, 1996 pp. 73-82.

43. Boocock DGB, Konar SK, Mao V, Lee C, Buligan S. JAOCS 1998;75:1167.44. Deslandes N, Bellenger V, Jaffiol F, Verdu J. Applied Polymer Science 1998; 69:2663

45. Freedman, B., Butterfield, R.O., Pryde, E.H., 1986. Transesterification kinetics of soybean

oil. JAOCS 63, 1375-1380.

46. Freedman, B., Pryde, E.H., Mounts, T.L., 1984. Variables affecting the yields of fatty esters

from transesterified vegetable oils JAOCS 61 1638 1643


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51. X. Zhang, C. L. Peterson, D. Reece, G. Moller and R. Haws, Biodegradability of biodiesel in

the aquatic environment. ASAE Paper No. 956742. ASAE, St. Joseph, MI 49085-9659

(1995).

52. Reference: list from Biodiesel production: a review. Fangrui Ma, Milford A. Hanna.

53. Smelser, N.J. (1987). Fats and Fatty Oils. In Ullmanns Encyclopaedia of Industrial

Chemistry. Fifth ed: Weinhein. Vol. A10, pp. 173-243.


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APPENDIX A

Table 11.1 Mass balance Bio0046Component Mass (g) Actual Theoretical Difference

a Beaker + Stirrer 176.75 0

b Total 578.73 0

c After Evap 282.35 0.4

Loss of product due to emulsion formation

Table 11.2 Mass balance Bio0047Component Mass (g) Actual Theoretical Difference

a Beaker 169.1 0

b Reactants 398.61 0

c After Rxn 561.96 -5.75

d After Evap 509 58.71 46.05 -12.66 1

e Empty Beaker 2

f Glycerol Flask

g Glycerol 3

h Biodiesel* 4

i Biodiesel#

306.07 306.07 316.31 -10.24 5

Total Mass Lost In Overall Process

1. Mass of Excess Ethanol Evaporated

2. Mass of remaining components in empty beaker usually glycerol




Table 11.3 Mass balance Bio0048

Component Mass (g) Actual Theoretical Difference

a Beaker 169.1 0


c After Rxn 377.34 0.4

d After Evap 1e Empty Beaker 2

f Glycerol Flask

g Glycerol 53.15 53.15 32.605 20.545 3

h Biodiesel* 4

i Biodiesel#

280.23 280.23 316.31 -36.08 5

Ad Kh I di id l I i B


26/41




a Beaker 185.23 0

b Reactants 396.04 0c After Rxn 390.65 390.65 396.04 -5.39

d After Evap 1

e Empty Beaker 186.97 186.97 185.23 1.74 2

f Glycerol Flask

g Glycerol 64.77 64.77 32.605 32.165 3

h Biodiesel* 266.75 266.75 316.31 -49.56 4

i Biodiesel#

5









a Beaker 169.16 0


c After Rxn 560.08 560.08 396.08 -5.16

d After Evap 517.56 47.68 46.05 -1.63 1

e Empty Beaker 2


g Glycerol 68.4 68.4 32.605 35.795 3

h Biodiesel* 258.06 258.06 316.31 -58.25 4

i Biodiesel#

5









27/41




a Beaker 169.06

b Reactants 396.08c After Rxn 562.99 393.93 396.08 -2.15

d After Evap 521.82 -41.17 46.05 -4.88 1

e Empty Beaker 173.54 173.54 169.06 4.48 2


g Glycerol 84.64 84.64 32.605 52.035 3

h Biodiesel* 319.4 260.92 316.31 -55.39 4

i Biodiesel#

315.7 5

Total Mass Lost In Overall Process1. Mass of Excess Ethanol Evaporated







28/41


APPENDIX B

LITERATURE REVIEWSCOPE

This literature survey discusses the benefits of using biodiesel as a suitable diesel substitute,

whilst briefly touching on the history behind alternative compression engine fuels. It discusses

some of the more current manufacturing techniques for the production of biodiesel as well as

some new technology that is being researched. This is primarily focusing on developments in

catalyst application, problems associated with different catalysts and the benefits of various

catalyst systems.The area of downstream processing is briefly discussed, however separation is outside the focus

of this work. Some critical analysis is discussed on the pros and cons of different systems and

details of the analysis methods available and why and why not they are implemented in this

work. Finally there is a discussion section and recommendation for further research section that

highlights the areas in this research that are in need of further development.

INTRODUCTION

With the exception of hydroelectricity and nuclear energy, the majority of the worlds energyneeds are supplied through petrochemical sources, coal and natural gas. All of these sources are

finite and at current usage rates will be consumed by the end of the next century (Aksoy, 1990).

The depletion of world petroleum reserves and increased environmental concerns has stimulated

recent interest in alternative sources for petroleum-based fuels. Biodiesel has arisen as a potential

candidate for a diesel substitute due to the similarities it has with petroleum-based diesel.

BACKGROUND

Fats and OilsThe use of vegetable oils as alternative fuels has been around since 1900 when the inventor of

the diesel engine Rudolph Diesel first tested them, in his compression engine (Foglia, Jones,

Haas, & Scott, 2000). To date there have been many problems found with using vegetable oils

directly in diesel engines (especially in direct injection engines). These include (Ma, 1999):

1. Coking and trumpet formation on the injectors to such an extent that fuel

atomisation does not occur properly or is even prevented as a result of pluggedorifices,

2. Carbon deposits,

3. Oil ring sticking,

4. Thickening and gelling of the lubricating oil as a result of contamination by

vegetable oils, and



29/41


denotes a carbon length of 18 with on double bond. At high temperatures there can be some

problems with polymerisation of unsaturated fatty acids, this is where cross linking starts to

occur between other molecules, causing very large agglomerations to be formed and

consequently guming occurs (Pryde, 1983). This problem does not occur with fats as they have a

very low concentration of unsaturated fatty acids as can be seen in table 2.

Ethanol can be used as an additive to improve these properties, but pure vegetable oils are rarely

used for a straight diesel fuel substitute. Ethanol as an additive or a reactant is often preferred in

place of other simple alcohols, such as methanol because it is less toxic and because it is easily

produced from renewable sources such as biomass or grains (Foglia et al., 2000). Fats, due to

their high melting point and viscosity, can not be used directly in diesel engines or mixed with

diesel fuels. The degree of saturation of the fatty acids attached to the glycerol backbone

determines the boiling point of the triglyceride.

As such, compared with oils, little research has been done on their potential as diesel fuel. Some

typical composition of fats and oils can be found in tables 1& 2 (Ma, 1999). Fats and oils are

primarily composed of triglycerides, esters of glycerol (mono- & diglycerides) and fatty acids

(carboxylic acids). The term monoglyceride or diglyceride refers to the number of fatty acids

that are attached to the glycerol backbone i.e. a diglyceride would have one hydroxyl group and

two fatty acid groups attached to the glycerol backbone as in figure 1.

CH2

CH2

CH

Diglyceride

COO R

COO R

C OH

O

Fig. 1. Diglyceride with two fatty acid groups

Table 1. Typical chemical properties of vegetable oil (Groering et al., 1982*)

Fatty acid composition, % by weight

Palmitic Stearic Oleic Linoleic Linolenic arachidicVegetable oil

16:00 18:00 18:01 18:02 18:03 20:00 Acid*Value

Corn 11.67 1.85 25.16 60.6 0.48 0.24 0.11Cottonseed 28.33 0.89 13.27 57.51 0 0 0.07

Crambe 2.07 0.7 18.86 9 6.85 2.09 0.36

Peanut 11.38 2.39 48.28 31.95 0.93 1.32 0.2

Rapeseed 3.49 0.85 64.4 22.3 8.23 0 1.14

Soybean 11.75 3.15 23.26 55.53 6.31 0 0.2

S fl 6 08 3 26 16 93 73 73 0 0 0 15



30/41


Table 2. Typical fatty acid composition - of common oil source (Kincs, 1985)Fatty acid composition, % by weight

Lauric Myristic Palmitic Stearic Oleic Linoleic LinolenicLipid

12:00 14:00 16:00 18:00 18:01 18:02 18:03

Soybean 0.1 0.1 10.2 3.7 22.8 53.7 8.6

Cottonseed 0.1 0.7 20.1 2.6 19.2 55.2 0.6

Palm 0.1 1 42.8 4.5 40.5 10.1 0.2

Lard 0.1 1.4 23.6 14.2 44.2 10.7 0.4

Tallow 0.1 2.8 23.3 19.4 42.4 2.9 0.9

Coconut 46.5 19.2 9.8 3 6.9 2.2 0

Biodiesel

Subsequent research found that triglycerides could be converted into simple alkyl fatty acidesters (Biodiesel) which has similar properties to diesel see table 3 & 4. The first documented

commercial production of rapeseed oil methyl esters is reported to be in 1988 (Korbitz 2001). To

date biodiesel production can be found in over 28 countries of which Germany and France are

the worlds largest [Kusdiana, 2002].

Table 3. Comparison of typical properties of diesel, canola oil and

biodiesel

Diesel Canola Biodiesel

Density (kg/L) 0.835 0.922 0.88Gross calorific value (MJ/L) 38.3 36.9 33.3

Viscosity ( @ 37.8C) 3.86 37 4.7

C:H:O ( ratio ) 3.59 3.26 2.38

Sulphur (%) 0.15 0.0012


31/41

q y

of the US biodiesel industry can use any fat or oil feedstock, the remainder is limited to refined

vegetable oils, the least expensive of which is soy bean oil.

Although the production of biodiesel is now conducted on a large scale, there are still many

problems with using crude feed stock (Ma, 1999). Until these problems are resolved withmeasures such as a continuous process and the use of crude oils waste fats, such as used cooking

oils and abattoir fats, the cost of production will remain relatively high. The recovery of high

quality glycerol, a by-product which is required for many other processes, would also contribute

to substantially reducing production costs.

The European Union has set an objective to secure for motor biofuels a market share of 5% of

total motor fuel consumption by 2005 (a significant amount of this will be biodiesel). The US

Department of Energy estimates that up to 50% of the total diesel fuel consumption could be

replaced with biodiesel. US production of biodiesel, from both fats and oils is currentlyapproximately 7.12 billion litres ( Alcantara 2000).

PROCESS OVERVIEW

There are several generally accepted ways to make biodiesel some more common than others,

e.g. blending and transesterification, and several others that are more recent developments .e.g.

reaction with supercritical methanol. An overview of these processes is as follows;

1. Direct use and Blending, which is the use of pure vegetable oils or the blending with dieselfuel in various ratios,

2. Microemulsionswith simple alcohols,

3. Thermal Cracking(pyrolysis) to alkanes, alkenes, alkadienes etc

4. Transesterification(alcoholysis) which consists of several sub categories;i. esterification ,

ii. saponification,iii. hydrolysis (reaction with water) and

iv. aminolysis (reaction with amines)

5. Other forms of catalysisi. biocatalysts

ii. reaction with supercritical methanoliii. catalyst free

Direct use and blending

The direct use of vegetable oils in diesel engines is problematic and has many inherent failings.

It has only been researched extensively for the past couple of decades, but has been

experimented with for almost a hundred years. Although some diesel engines can run purevegetable oils engines, turbocharged direct injection engines such as trucks are prone to many

problems (BTCE, 1994). Energy consumption, with the use of pure vegetable oils, was found to

be similar to that of diesel fuel (Hemmerlein et al. 1991). For short term use ratios of 1:10 to

2:10 oil to diesel have been found to be successful (Ma, 1999). The difficulties may be grouped

into three key areas:



32/41

Further, engines can suffer coking and gumming which leads to sticking of piston rings due to

multi-bonded compounds undergoing pyrolyses. Polyunsaturated fatty acids also undergo

oxidation in storage causing gum formation and at high temperatures where complex oxidative

and thermal polymerisation can occur ( Ma 1999).

Microemulsions

Microemulsions are defined as a colloidal equilibrium dispersions of optically isotropic fluid

microstructures, with dimensions generally in the 1-150 nm range. These are formed

spontaneously from two normally immiscible liquids and one or more ionic or non-ionic

amphophiles (Schwab et al., 1987). A microemulsion is designed to tackle the problem of the

high viscosity of pure vegetable oils by reducing the viscosity of oils with solvents such as

simple alcohols.

The performances of ionic and non-ionic microemulsions where found to be similar to diesel

fuel, over short term testing. They also achieved good spray characteristics, with explosive

vaporisation which improved the combustion characteristics (Ma, 1999). In longer term testing

no significant deterioration in performance was observed, however significant injector needle

sticking, carbon deposits, incomplete combustion and increasing viscosity of lubricating oils

where reported ( Ma, 1999).

Thermal Cracking

Pyrolysis is the conversion of one substance into another by means of applying heat i.e. heatingin the absence of air or oxygen with temperatures ranging from 450C 850C (Sonntag,

1979b). In some situations this is with the aid of a catalyst leading to the cleavage of chemical

bonds to yield smaller molecules (Weisz et al., 1979). Unlike direct blending, fats can be

pyrolyised successfully to produce many smaller chain compounds. The pyrolysis of fats has

been investigated for over a hundred years, especially in countries where there is a shortage of

petroleum deposits. Typical catalyst that can be employed in pyrolysis are 2SiO and 32OAl . The

ratios of light to heavy compounds are temperature and time dependent. Typical breakdown of

compounds found from pyrolyisis of safflower and soybean oil, are listed in table 5.

Table 5. Compositional data of pyrolysis of oils ( Ma 1999)Percent by weight

*HO Safflower Soybean

Alkanes 40.9 29.9

Alkenes 22 24.9

Alkadienes 13 10.9

Aromatics 2.2 1.9

Unresolved unsaturates 10.1 5.1Carboxylic acids 16.1 9.6

Unidentified 12.7 12.6

*HO High Oleic Safflower oil

The equipment for pyrolysis or thermal cracking is expensive for modest throughputs. Although,

th d t h i ll i il t h i ll b d di l l f th



33/41

alcoholysis (cleavage by an alcohol).The reaction, as shown in figure 2 is reversible and thus an

excess of alcohol is usually used to force the equilibrium to the product side. The stoichiometry

for the reaction is 3:1 alcohol to lipids; however in practice this is usually increased to 6:1 to

increase product yield. A catalyst is usually used to speed up the reaction and may be basic, acid

or enzymatic in nature (Ma, 1999). The alkalis that are generally used include NaOH, KOH,carbonates and corresponding sodium and potassium alkoxides such as sodium methoxide,

ethoxide, propoxide and butoxide. Sodium hydroxide is the most common alkali catalyst that is

used, due to economical reasons and availability. Alkali-catalysed reactions are used more often

commercially than acid catalysts, as the reactions are faster.

Only simple alcohols can be used in transesterification such as, methanol, ethanol, propanol,

butanol and amyl alcohol. Methanol is most often used for commercial and process reasonsrelated to its physical and chemical nature (shortest chain alcohol and is polar). However

ethanol is becoming more popular as it is a renewable resource and does not raise the same

toxicity concerns as methanol (Ma, 1999). The type of catalyst, the reaction conditions and the

concentration of impurities in a transesterification reaction determine the path that the reaction

follows.

For alkali catalysed transesterification, water and FFA are not favourable to the reaction, so

anhydrous triglycerides and alcohol are necessary to minimise the production of soap. Soap

production decreases the amount of esters and renders the separation of glycerol and estersdifficult. In current commercial processes using crude feed stock, excess alkali is added to

remove all the FFAs.

OHCH2

OHCH2

OHCH

COOR1 R'

COOR2 R'

COOR3 R'

CH2

CH2

CH

COO R1

COO R2

COO R3

GlycerolEstersTriglyceride

++ 3R'OH

Catalyst

Simple Alcohol

Fig. 2. Transesterification of triglycerides with alcohol

Saponification

The production of soap sometimes called alkaline hydrolysis, converts triacylglycerols to

glycerol and a mixture of salts of long-chain carboxylic acids. As can be seen from figures 3 &

4, the reaction can be carried out with an ester (i.e. triglycerides) or with carboxylic acids (i.e.free fatty acids). However, the production of fatty acids is an intermediate step when

triglycerides are directly used for saponification. The commercial production of soap is usually

conducted in two phases. The first phase is the conversion of lipids into FFAs by boiling with

aqueous sodium hydroxide until hydrolysis is complete and then adding sodium chloride to

precipitate the soap (Solomon, 1996)



34/41

or

R C OR'

O

+ NaOH R C O-Na

+

O

R'OH

Simple AlcoholSaltEster Metalic alkoxide

Water

+

Fig. 4. Saponification from ester

Esterification

The formation of esters occurs through a condensation reaction known as esterification. Thisrequires two reactants, carboxylic acids (fatty acids) and alcohols. (Solomon, 1996).

Esterification reactions are acid catalysed and proceed slowly in the absence of strong acids such

as sulphuric acid, phosphoric acid, organic sulfonic acids and hydrochloric acid. The equation

for and esterification reaction can be seen in figure 5.

R C OH

O

R'OH+

H+

R C OR'

O

+ H2O

WaterEstersFree Fatty Acid Simple Alcohol

Fig. 5. Esterification

Hydrolysis

The hydrolysis of lipids forms a heterogenous reaction system made up of two liquid phases. The

disperse aqueous phase consists of water and glycerol; the homogenous lipid phase consists of

fatty acids and glycerides. The hydrolysis of glycerides takes place in the lipid phase in severalstages via partial glycerides (diglycerides and monoglycerides) (Ullmanns, 1987). Acid

catalysts are very effective at accelerating the hydrolysis reaction. However, at high temperatures

substantial material corrosion occurs. Diabasic metal oxides have a higher activity than more

strongly alkaline monobasic metal oxides. Zinc oxide in its soap form has been suggested to be

the most active catalyst for hydrolysis reactions (Ullmanns, 1987). Reaction without a catalyst

is not economical below 210C, thus requiring the implication of high temperature, pressure

techniques. Modern continuous plants operate at pressures between 0.6-1.2 MPa at 210-260C

without a catalyst. This increased pressure allows the mutual solubility of the two phases toincreases to a point where the formation of continuous phase occurs.

OHCH2

OHCH

COOR1 H

COOR H

CH2

CH

COO R1

COO R H



35/41

Aminolysis

Esters undergo nucleophilic substitution at their acyl carbon atoms when they are treated with

primary or secondary amines. These reactions are slow but are synthetically useful (Solomon,

1996).

H N R5

R4

Amine

OHCH2

OHCH2

OHCH

CH2

CH2

CH

COO R1

COO R2

COO R3

GlycerolTriglyceride

+Heat

+

N R5

R4

R1

C

O

N R5

R4

R3

C

ON R

5

R4

R2 C

O

Amides

3

Fig.7. Aminolysis of triglycerides

Biocatalysts

Biocatalysts are usually lipases; however conditions need to be well controlled to maintain the

activity of the catalyst. Hydrolytic enzymes are generally used as biocatalysts as they are ready

available and are easily handled. They are stable, do not require co-enzymes and will often

tolerate organic solvents. Their potential for regioselective and especially for enantioseletivesynthesis makes them valuable tools [Schuchardt, 1998]. Recent patents and articles have

shown that reaction yields and times are still unfavourable compared to base-catalysed

transesterification for commercial application.

Catalyst Free

Transesterification will occur without the aid of a catalyst, however at temperatures below 300C

the rate is very low. It has been said that there are, from a broad perspective, two methods to

producing biodiesel and that is with and without a catalyst.

Supercritical Methanol

The study of the transesterification of rapeseed oil with supercritical methanol was found to be

very effect and gave a conversion of >95% within 4min. A reaction temperature of 350C,

pressure of 30MPa and a ratio of 42:1 of methanol to rapeseed oil for 240s were found to be the

best reaction conditions. The rate was substantially high from 300 to 500C but at temperatures

above 400C it was found that thermal degradation takes place. Supercritical treatment of lipids

with a suitable solvent such as methanol relies on the relationship between temperature, pressureand the thermophysical properties such as dielectric constant, viscosity, specific weight and

polarity (Kusdiana, 2000). A comparison of supercritical methanol production and alcoholysis

can be seen in table 6.

COMPARATIVE ANALYSIS OF PROCESSES



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In the base-catalysed transesterification method use of crude lipids that contain large quantities

of FFA leads to catalyst destruction. It is suggested that the concentration of FFA be as low as

possible, not exceeding 0.5%.

Table 6.Comparison between production of biodiesel

Common Method *SC MeOH method

Reaction Time 1-6h 0.067h

Reaction Condition 0.1MPa, 30-65C 35MPa, 350C

Catalyst acid or alkali none

Free Fatty Acids Saponified products methyl esters

Yield 97% (normal) 98.50%

Removal for

Purification

methanol, catalyst and saponified

products

methanol

Process Detailed Simple

*SC MeOH method - Supercritical Methanol

PROCESS OVERVIEW OF SEPARATION

Although not within the scope of this report, separation is an integral part of the production of

biodiesel and therefore some basic concepts will here within be covered. The refining of the

products from the production of biodiesel can be technically difficult and can substantiallyincrease the cost of production. The purity of biodiesel must be high and generally conform to

international standards such as the European Union (EU) standards for alternative fuels. Under

the EU standards for alternative diesel fuels free fatty acids, alcohol, free and bound glycerin and

water content must be kept to a minimum and the fuel must be at least greater than 96.5% pure

(Karaosmanoglu, 1996).

The typical product mixture of a transesterification reaction contains fatty acid esters (biodiesel),

monoglycerides, diglycerides, glycerol, alcohol and catalyst, in varying concentrations. The

primary goal is the removal of the esters from the mixture, maintaining low costs and ensuring a

high purity product. Glycerol in its pure form is seen to be a secondary product of the reaction as

it can be sold to various industries. To keep the cost of production competitive, the removal and

resale of glycerol is essential. The remaining mixture contains by-products and alcohol that

should have minimal contaminants if the conversion is high, except for the alcohol which would

be distilled off.

Alcohol

Lipids

Alcohol

Recovery

Reactor Settler Washing Purification Evaporation

Biodiesel

Gl l

~

~

~

~



37/41

If the reaction has reached a high level of conversion the product mixture will form two liquid

phases, with a solid phase if a solid catalyst has been used. The bottom phase of the mixture

would consist of glycerol and the top phase alcohol and esters. In a reaction that did not reach

full conversion the unreacted lipids and bound glycerol would solidify in the bottom layer, as can

be seen in figure 12.

For molar ratios greater than 5.67 of MeOH it was reported that there are some difficulties in

separating glycerin from methanol (Kusdiana, 2000).

Critical Analysis of the Literature

There where only two papers found that made mention of heterogenous catalysts. Of these there

were 3 potential catalysts of which only one showed any promise. There is a distinct lack of

information or research conducted on heterogenous catalysts. There are several references to

co-solvents, however none make mention of biodiesel itself. The references to THF reported thatit was suitable as a co solvent claiming it to be a low toxic compound, when the MSDS from

Chemwatch showed it to have a high level of toxicity. There was little mention of the thermal

degradation of products such as glycerol and triglycerides, particularly as glycerol degrades to a

highly toxic compound, acrolein. Generally analysis techniques focused on glycerol and

unconverted triglycerides, there was no mention of any residual components such as alcohol.

This seems to be due to the currently accepted practice of extensily washing the product before

analysis. Testing and quality control seems to focus on downstream fuel that is ready for retail

sales, not necessarily testing for optimisation purposes. There is conflicting information on theimpact of contaminants such as FFA and water. Some papers have said that water has a negative

effect on the reaction and others have implied that acid catalysed reactions are not effected.

Heterogeneously Catalysed Process

The use of hydrogenized guanidines on organic polymers as a catalyst for the transesterification

of vegetable oils has been tested by Schuchard et al (1997). Principle tests conducted in a

continuous reactor were promising and resulted in a patent (P93246, 1984). However there still

appear to be some problems with this technique. For example, catalyst activity seems todeteriorate after an hour of operation (Schuchardt, 1998). This resulted in incomplete reaction

and subsequent difficulties in phase separation. Irreversible protonation of the catalyst or

catalyst leaching are a possible cause, however no definite test to confirm this had been

conducted (Schuchardt, 1998).

Experiments conducted by Suppes et al (2000) indicate that CaCO3 may be suitable for use as a

heterogeneous alcoholysis catalyst. Preliminary batch experiments used beef tallow or soybean

oil as the triglyceride source and diethylene glycol (DEG) as the alcohol. Subsequent attempts to

verify these results where conducted using a similar batch apparatus but as yet have failed toreplicate those results obtained by Suppes et al. There is only one difference in the experimental

procedure used to replicate Suppess work which was the source of the 3CaCO , which was not

sourced from Lancaster (Windham, NH).

Trials conducted using CaO and 2)(OHCa as the catalyst also appear to have failed to achieve



38/41

and the effect of high concentrations of free fatty acids. Certain carbonate systems are also

known to promote glycerolisis however the overall effect this would have under these reaction

conditions is not yet known. Glycerolisis is the reaction of glycerol with triglycerides to form

monoglycerides.

Lancaster (Windham, NH)Iowa Limestone Co. (Des Moines, IA)

The calcium carbonate catalyst could function as a simple Bronsted base catalyst. The doublebond migration, observed in the Na2CO3 and K2CO3 catalysed reactions, indicated that at these

reaction temperatures the carbonate anion is an extremely strong base, however this has not been

proven.

PRODUCT ANALYSIS

Biodiesel can be significantly contaminated with both free and bound glycerol, triglycerides and

alcohol due to incomplete transesterification and or insufficient purification. As noted in

literature, the presence of these minor contaminates can be detrimental to both engines and theenvironment through pollution. There are currently limits on the levels of these compounds in

biodiesel that are set out in guidelines such as American Society for Testing and Materials

(ASTM) which can be found in table 8.

Over the past ten years there have been various investigations into methods to investigate the

analysis of biodiesel, its impurities and by-products. The list includes Gas Chromatography (GC)

distillation, solid phase separation, thin film liquid chromatography (TLC), High Precision

Liquid Chromatography (HPLC), Refractometry, Near Infrared Spectroscopy with a Fibre-Optic

probe (NIR) and Thin layer chromatography/flame-ionisation detection (TLC/FID) with anIactroscan instrument [Plank, 1995, Freedman et al 1984]. The analysis technique needs to be

accurate, reliable, reproducible, relatively quick and simple, and require equipment that is readily

available. Formally HPLC, but more commonly now GC analysis is by far the most accepted

methods for the analysis of biodiesel fuels (Knothe, 1998). The reasons behind this are

i li it ( th t h b t ) d th hi h l l f ith hi h th

Table 7. List of potential catalysts

4)(ORTi - Titanium IV alkoxides

OSnHC 22712 )( - bis(tri-n-butyltin)oxide - Organometallic tin complexes

32CONa - (Solubility of some of these?)

32COK

3ZnCO

3MgCO

3CaCO

ZnO - supported on alumina

COOCaCH3 - acetates of calcium and barium

COOBaCH3 (Salts or esters of ethanoic acid)



39/41

Table 8. Detailed requirements for biodiesel fuel*

Property Test Method Limits Units

Flash Point (closed cup) D93 100 min C

Water sediment D2709 0.05 max %Vol

Kinematic Viscosity D445 1.9-1.6 smm /2 Sulphated ash D874 0.02 max % mass

Sulphur D2622 0.05 max % mass

Copper strip corrosion D130 No. 3 max

Cetane number D613 40 min

Cloud Point D2500 RTC C

Carbon residue D4530 0.05 max % mass

Acid number D664 0.8 max mg KOH/g

Free glycerol F 0.02 % mass

Total glycerine F 0.24 % mass

*As out lined in ASTM PS-121 99

High Precision Liquid Chromatography

Mittelbach & Trathnigg detailed a method that is similar to GC in that the samples require

derivatisation. This was using HPLC coupled with isocratic separation, such as differential

refractometry or density detection. There where some problems associated with separation

according to molecular mass and hydroxyl content, but where over come by using a combination

of a GPC-column set and a polar column in series [Trathnigg, 1990]. Free fatty acids and

glycerol where separated from the mixture before the analysis was carried out and it was said

that the analysis time was approximately 20 minutes.

Gas Chromatography

The method proposed by Plank and Lorbeer using capillary gas chromatography, can provide

qualitative and quantitative information about the concentrations of contaminants in biodiesel.

The method is appropriate for measuring minor and major components in a sample, gives a high

reliability of results, has simple instrumentation, requires a small amount of sample preparationand has a short analysis time (Plank, 1995).

Near Infrared Spectroscopy

Near Infrared Spectroscopy (NIR) is becoming a preferred method for quality control of

biodiesel fuel. Due to its operational ease, rapidity of measurement and non-destructiveness it

can be implemented as an online assessment of conversion in the transesterification reaction. The

NIR method is less sensitive than GC for quantifying minor components, but can be used in

combination with GC analysis for a higher level of analysis. However, that being said it isaccurate to the point that it can be used in qualifying online conversion rates and major

component concentrations. Standards testing for biodiesel is time consuming and costly, but can

be superseded by NIR which would significantly reduce both the cost and the time of testing

(Knothe, 1998).

Th d i i f l l f i d ib d b B di li l (Pl k

Adam Khan Individual I

khan k. biodiesel kinetics & catalyst 2 (master)

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