J.-L. Berna et al.: LCI far LAS

l L. Berna, Madrid/Spain, L. Cavalli, Milano/ltaly,and C. Renta, Madrid/Spain

llntroductionThe resource requirements and environmental emissionsinvolved in the production of Linear Alkylbenzene Sulpho-nate (LAS) from petrochemical feedstocks are presented. Theraw material requirements for the production of 1000 kg ofLAS are 841 kg of crude oil, 100 kg of Sulphur (via S03) and99 kg of salt (for caustic soda). The energy is provided by162 kg of natural gas, 183 kg of crude oil and 170 kg of coal.Process energy accounts for 37 % of the total energy for LASproduction which is 60.9 GJ/lOOOkg. 74 % ofthe total energyrequired for the production of LAS is supplied by crude oil.Fuel related emissions account for 80 % of the total salidwaste which is 64.7 kg/1000 kg of LAS. Emissions from theproduction and combustion of fuels account for most of theatmospheric emissions. In contrast, processing accounts formost of the waterborne emissions.

Es werden der Energie- und Materialbedarf bei der Rohstoff-gewinnung und die Umweltemissionen bei der Herstellungvan LAS auf petrochemischer Grundlage aufgezeigt. Zur Pro-duktion van 1000 kg LAS werden an Rohstoffen 841 kgRohol, 100 kg Schwefel (beim S03-Verfahren) und 99 kg Salz(für Atznatron) benotigt. Die erforderliche Energie wirddurch 162 kg Erdgas, 183 kg Rohol und 170 kg Kohle gelie-fert. Die Prozej3energie betriigt 37 % der Gesamtenergie derLAS-Herstellung, das sind 60,9 Gl/1000 kg LAS. 74 % dergesamten für die Herstellung van LAS benotigten Energiewerden durch Rohol gedeckt. Brennstoffbezogene Emissionenmachen 80 % des gesamten testen Abfalls aus, das sind64,7 kg/1.000 kg LAS. Emissionen aus der Produktion undVerfeuerung der Treibstoffe tragen das meiste zu den Luft-emissionen bei, wiihrend der Prozej3 selber den Groj3teil derWasserverunreinigungen verursacht.

dífferent processes: the Alummium Chloricle tAl(.;13) process,

~

Fig. l. Flow diagram for the production of1000 kg of LAS in Europe (Numbers repre-sent kilograms of material alter coproductcredit has been applied. Masses may not bal-ance exacdy due to conventions and bound-ary conditions; see Janzen, Tenside 32(1995) 2, p. 110-121)

Tenside Surf. Deto 32 (1995) 2@ Carl Hanser Verlag, München122

Linear A1kylbenzene Sulphonate (LAS) is an anionic surfac-tanto Since its introduction into the market in fue early 60's,it has been the predominant surfactant in commercial deter-gent preparations, such as powders and liquids for textile,dish washing, industrial and 1 & 1 cleaners, due to its compat-ibility and synergistic interaction with other ingredients, lead-ing to enhanced performance.

The world LAS production in 1993 was nearly 2 milliontonnes and 510,000 tonnes in West Europe. LAS productionin both cases represents approximately 1/3 rd of the total sur-factant production, excluding soap.

European LAS is a mixture of different homologues (CIO-Cl3 alkyl chains) with all positional isomers with the excep-tion of 1-alkyl substituted ones. The typical homologue distri-bution is 15, 30, 30 and 25 % for CIO, Cll, Cl2 and Cl3 with anaverage alkyl chain of CII.6 and an average molecular weightof 342 as the sodium salto

2 Manufacturing process

LAS is produced by sulphonation of LAB (linear alkylben-zene) followed by neutralization of the corresponding sul-phonic acid with caustic soda. The overall flow diagram isshown in Figure 1. Three important materials, n-paraffins,benzene and LAB, are directly used in LAS production. Par-affins and benzene are described in detail in a following pub-lication [4].

2.1 LAR production

~A}3 is produced by. c.at.a~ytic alkyla~~n o~ b,e~:?~ via two

J.-L. Berna et al.: LCI for LAS

Fig. 2. Flow diagram for the production ofLAB by the HF process

AlC13 catalyzed alkylation reaction is performed. The cata-lyst, which mar be suspended or dissolved in fue crude alkyl-ate, is then separated while fue benzene and unconvertedn-paraffins are recovered by distillation and recycled. In thelast step of the process, LAB is separated from the heavyalkylate co-product.

This process requires integration with a chlorine produc-tion unit and with another plant which uses the HCl co-pro-duct. Chlorine does not become part of LAB, but rather isrequired in the reaction to form LAB from benzene and par-affins. Chlorine input and the subsequent production of theHCl, therefore, can be ignored in the reaction for fue pur-pose of this study.

For both LAB production routes (HF and AlC13), n-paraf-fins are the starting raw material and therefore their produc-tion is an important step in the LAB process. n-Paraffins(linear paraffins) will provide the linearity to the correspond-ing alkyl chain in the final LAB [4].

2.2 Sulphonation

The sulphonation of LAB is commonly accomplished withSO3 as sulphonation agent using two different types of reac-tors, cascade and falling film. The earlier commercial pro-cesses were based on oleum sulphonation, but these arebeing replaced by SO3 gas sulphonation. In the sulphonationreaction, an SO3 (Sulphonic) group is introduced in fue 4-position ("para") of the aromatic ring of the LAB moleculegiving the corresponding sulphonic acid:

and the Hydrogen Fluoride (HF) process. In the HF process,benzene is directIy alkylated with n-olefins in the presence ofHF as a catalyst in an integrated plant in which the n-olefinsare produced by catalytic dehydrogenation of n-paraffins.Such an integrated HF based plant includes 4 main steps asrepresented in the flow diagram of Figure 2.

In the first unit the raw paraffin feedstock is hydroge-nated to remove contaminants such as sulphur and nitrogencompounds. The normal paraffins contained in the hydro-treated feed are extracted using a selective molecular sieveprocess. The appropriate n-paraffins cut is subsequentIydehydrogenated to mono-olefins using a selective catalyst.The conversion of the dehydrogenation reaction is limitedwithin a range of 10 to 20 % in arder to minimize side reac-tions which mar generate undesirable by-products. Theresulting mixture of n-paraffins and n-mono olefins are redto the alkylation section together with an excess of benzene.

The n-paraffin fraction does not react in the HF alkylationreaction and is recycled to the dehydrogenation stage afterfractionation from the reaction product mix (LAB, heavyalkylate and excess benzene).

In the AlCl3 process (Fig. 3) benzene is alkylated withchloro-paraffins and/or n- olefins via an AICl3 based catalyst.Chloro-paraffins are obtained by chlorination of n-paraffinsand n-olefins are produced by catalytic dehydrogenation ofn-paraffins foUowed by a molecular sieve extraction.

In this process, the n-paraffins are partiaUy chlorinatedwith chlorine gas in a multistage reactor. The resulting prod-uct, a mixture of n-paraffins and chloroparaffins, is red,together with an excess of benzene, into a reactor where the

Fig. 3. Flow diagram far the production ofLAB by the AICl3 process

123Tenside Surf. Det. 32 (1995) 2

J.-L. Berna et al.: LCI for LAS

Table l. Overall resaurce requirements far the praductian af 1000 kgaf LAS in Eurape

acid. Most LAS consumed worldwide is in the form of Nasalto Minor quantities of other derivatives (ammonium salt...etc.) are also used but they have not been considered inthis study.

The LAS derived from both routes (HF, AlCI3) have simi-lar physico-chemical properties and can be used interchange-ably in any cleaning or detergent formulation.

3 Overall resource requirements and environmentalemissions

The raw matrial and energy requirements as well as theenvironmental emissions for LAS production are included inthe following sections.

3:1 Prócess description

Figure 1 shows the flow diagram for the production of1000 kg of LAS in Europe. The main steps are the following:

.Crude oil production

.Crude oil refining (distillation, desalting and hydrotreat-ing)

.Benzene production.n-Paraffin production.Sulphur production.Salt mining.Caustic soda production.LAB production.LAS production (sulphonation and neutralization)

3.2 Resource requirements

The over~l resource requirements are summarized in Table 1.The raw material requirements for LAS are also described inFigure 1.

The reaction is exothermic and it requires a careful controlof the temperature to avoid undesired side reactions. Con-version to sulphonic acid is very high with minar quantitiesof unsulphonated matter (free-oil) in the reaction producto

When using the oleum process, an important co-product isthe corresponding spent sulphuric acid whose disposalrequires clase attention. In addition, the presence of residualquantities of sulphuric acid in the sulphonic acid leads tosodium sulphate during the neutralization process. This givespoor solubility properties to the final alkylbenzene sulpho-Dates (LAS).

The processes using SO3 (gas) comprise several steps,

namely:-Sulphur treatment-Process air drying-Sulphur buming to SOz-Conversion of SOz to SO3-Sulphonation-Digestion and hydrolysis-Exhaust gas cleaningSulphonation is carried out at a molar ratio of SO3/LABslightly higher tÍlan stoichiometric to achieve full conversionofLAB (>99 %).

In the cascade process the SO3 gas is mixed with liquidLAB in several reactors in series (cascade) in arder to com-plete the reaction. The residence time (contact time) of theorganic matter is relatively high and therefore this process isnot suitable to sulphate compounds such as alcohols andalcohol ethoxylates which require shorter reaction time toavoid undesirable side reactions.

In the film reactors, the organic matter is injected into thereactor tubes using different methods although all have incornmon the formation of a very thin liquid layer inside thetubes in arder to facilitate the contact with SO3 and producean almost instantaneous reaction keeping the residence timein the reactor very short. This process is very flexible and itallows LAB sulphonation, and numerous other sulphonation/sulphation reactions to prepare other surfactants like AS,AES, AOS, MES, etc.

Finally, sodium hydroxide produced from salt (NaCI) byan electrolytic process is used to neutralize the sulphonic

Table 2. Energy summary for LAS production (in GI/IOOO kg LAS)

Values may not add to totals due to rounding.Source: Franklin Associates Ltd.

124 Tenside Surto Deto 32 (1995) 2

J.-L. Berna et al.: LCI for LAS

Tabie 3. Energy profiie for LAS production (in GJ/IOOO kg LAS)

Values may not add to totals due to rounding.SouÍ"ce: Franklin Associates, Ltd.

The most important component is the crude oil whichrepresents about 66 % of the total resources.

waste derived from the different steps involved in LAS pro-duction split between fuel and process related solid wastecThe largest amounts come from LAB (27 %), caustic soda(24 %) and LAS (20 %) production steps.3.3 Energy requirements

Table 4. Summary of atmospheric and waterbome emissionsfor LAS production (in kgilOOO kg LAS)

Processemissions

Fuel-re-lated

emissions

Totalemissions

0.181.510.991.610.037

O0.059

4.2E-O7OOO

3.2E-047.8E-05

284OOOO

3.4210.912.515.20.730.0120.016

O8.3E-Q40.012

6.2E-06O

0.00771,329

O0.12

0.00770.0077

3.6012.413.516.80.760.0120.075

4.2E-078.3E-Q40.012

6.2E-063.2E-Q40.00781.613

O0.12

0.00770.0077

Table 2 gives the energy requirements (energy surnmary) íoreach step in the production oí 1000 kg oí LAS, namely pro-cess energy, transport energy and the energy oí materialresources (EMR).

The EMR contributes 61 % oí the total energy require-ments, íollowed by process energy (37 %) and transportenergy (2 %). The highest process energy requirement is íorLAB production (8.75 GJ), íollowed by benzene production(3.6 GJ) and caustic soda production (2.7 GJ). Crude oil con-tributes 38.8 GJ oí which the energy oí material resource is asignificant component (36.9 GJ).

Table 3 presents the sources oí energy (energy profile)associated with each step in the production oí LAS. As pre-viously indicated, crude oil is the largest source with 74 % oíenergy involved, íollowed by natural gas with 14 %. Theenergy oí material resource associated with crude oil produc-tion (36.9 GJ; Table 2) accounts íor 82 % oí total energy pro-viged by crude oil (45 GJ; Table 3).

3.4 Environmental emissions

Atmospheric and waterborne emissions

Table 4 lists atmospheric and waterborne emissions for LASproduction and shows that most of the atmospheric emis-sions are fuel-related. Fuel-related emissions account for95 % of the particulates, 88 % of the nitrogen oxides, 93 %of the hydrocarbons, 90 % of the sulphur oxides, 96 % of thecarbon monoxide and 82 % of the carbondioxide. Thiols andmercury are released during the production of caustic soda.

Most of the waterborne emissions originate from processoperations except for a few categories. Process related emis-sions account for 93 % of the dissolved solids, 80 % of thesuspended solids, 98 % of the BOD, 99 % of the COD andnearly all of the metals, sulphates and choride. Fuel-relatedemissions account for 91 % of the phenols and 72 % of thehydrocarbon emissions.

9.3E-04o

0.00822.930.280.471.32

6.3E-040.110.036

O .00440.00260.00110.00223.0E-051.3E-050.00168.1E-040.0170.0640.0025

1.271.32

0.00920.0082

0.00770.22

0.0620.0087

0.011

0.0079

2.1E-Q4

0.0027OOOOOOOOOO

0.011OO

0.0100.00820.0163.150.350.481.33

0.00860.110.039

0.00440.00260.00110.0022

3.0E-051.3E-050.0016

8.1E-040.0170.0640.0141.271.32

Solid waste

Atmospheric EmissionsParticulatesNitrogen OxidesHydrocarbonsSulphur OxidesCarbon MonoxideAIdehydesOther organicsOdours SulphurfIbiolsAmmoniaHydrogen FluorideLeadMercuryChlorineCarbon Dioxide (fossil)Carb. Diox. (non-fossil)HClMetalsFluorine

Waterborne emissionsAcidMetal ionFluoridesDissolved solidsSuspended solidsBODCODPhenolSulphidesOilChromiumIronaluminiumNickelMercuryLeadPhosphatesZincAmmoniaOtherchemicalsHydrocarbonsSulphatesChlorideTable 5 shows the salid waste involved in LAS production.

About 80 % of the salid waste generated for LAS is fuelrelated. Table 5 also shows the contribution to the salid Source: Franklin Associates Ltd.

126 Tenside Surf. Det. 32 (1995) 2

J.-L. Berna et al.: LCI for LAS

Table 5. Total solid waste for LAS production (in kgilOOO kg LAS)

Process-related

salid waste

Fuel-relatedsalid waste

Total solidwaste

(kg)

o3.43

0.015

0.24

2.80

0.26

3.58

O

0.91

1.94

13.2

(%)

o

5.30

0.023

0.37

4.33

0.40

5.53

O

1.41

3.00

20.4

(kg)

0.053

1.31

5.63

2.04

14.6

0.47

1.55

O

14.7

11.2

51.5

(%)

0.082

2.02

8.70

3.16

22.6

0.73

2.40

O

22.7

17.3

79.6

(kg)

0.053

4.74

5.64

2.28

17.4

0.73

5.13

O

15.6

13.1

64.7

(%)

0.082

7.32

8.72

3.53

26.9

1.13

7.93

O

24.1

20..3

100

Crude oil production

Refinery productsBenzene

n-Paraffins

LAB production

Sulfur production

Salt production

Caustic soda

Production

LAS production

LAS total

Values mar not add to totals due to rounding.SoUTce: Franklin Associates, Ltd.

4 Improvement opportunities direction have occurred during the course of fue present LCIstudy. Thus, in the case of the LAB production step, today'sfuel related SOx emissions (1994) have been considerablyreduced in re~pect to those occurring in 1991.

References

1. Linear AIkylbenzene (LAB) from linear olefins with AIO3 cata-Iyst. L. Cavalli, C. Divo, G. Giuffrida, 7: Pellizon, P. Radici, L.Valotorta and A. Zaffa, 3rd Cesio Intemational Surfactant Congress-London, 1992. Speciality Chemicals, Vol. 13 (4) pago 228. (1993).

2. Growth and Developments in linear alkylbenzene technologies.1: L. Berna et al. 3rd World Conference on Detergents -Montreux(Switzerland 1993).

3. UOP-CEPSA Detal LAB Process advances. A. Banerji et al. SolidAcid 1993. Houston TX (USA).

4. M. Franke, 1: L. Berna, L. CavaUi, C. Renta, H. Thomas, A Life-Cycle Inventory for the Production of Petrochemicallntermediatesin Europe : Olefins, Paraffins, Benzene, Ethylene and EthyleneOxide. To be submitted for publication in Tenside SufactantsDetergents.

The authors of this paper

Petrochemically derived surfactants are generally producedin well developed -technological processes and therefore theraw material conversion to the final product is in most casesmaximized. Some important improvements have materia-lized during the last few years, including an improved versionof the AlCl3 process [1] in which the paraffin chlorinationstep has been eliminated. Pure olefins obtained by molecularsieve extraction from dehydrogenated paraffins are now usedas raw material for the alkylation process. This change hasimproved the environmental profile of the process in termsof the energy and emissions, as well as the quality of thefinal producto It is also worth mentioning that this processimprovement may be readily applied to conventional AICl3processes, branched alkylbenzene included, with minorinvestments and small modifications.

The desirability of avoiding the use of potentially hazard-ous chemicals like HF has motivated the development byone of the leading European LAR manufacturers of a newtechnology (De tal) for LAB production [2,3], based on afixed bed alkylation process. In this technology, the aIkyl-ation step has been considerably simplified. HF is no longerused anyrnore and the energy requirement and the overallemissions have been reduced.

Moreover, recent trends in co-generation projects in largepetrochemical complexes, are providing substantial energyand emissions optimizations, in addition to the globalimprovements strategies in this field. '

In general, improvements may be obtained by improvingthe quality of fuel combusted for energy production, forexample by an increased use of oils, gas with a reduced S-contento This may not always be easy due to constraints inavailability, cost logistics, technology ...etc. Such improve-ments are continuously being made and developments in this

Mr José Luis Berna graduated in Chemistry at the University of Zar-agoza (Spain) in 1967 and in Petroleum Technology at Madrid Uni-versity in 1969. In 1971, he joined Petresa as a Research Chemist andhe is at present Research and Development Director of this com-pany.

Dr Luciano Cavalli studied Chemistry at Torino University. Hejoined first Montedison (Bollate Research Center), then SIR and in1982 Enichem Augusta, where he has been responsible for theResearch Center (Paderno Dugnano) and now the ReguIatory andEnvironmental Affairs Department in Milano.

Mr Carlos Renta graduated in Chemical Engineering in 1970 andobtained bis Doctor's degree in 1976 at fue University of Madrid(Spain) being professor for the last toUr years. Since 1976, he hasbeen working for Cepsa in R&D, process, project and managingactivities and he is at present active in the R&D afea in Petresa, asubsidiary company of the Cepsa Group. (11550)

Tenside Surt. Det. 32 (1995) 2 127