polyko technology for the production of olefins pdf-1514859394

8/18/2019 Polyko Technology for the Production of Olefins PDF-1514859394

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TECHNOLOGY FOR THE

PRODUCTION OF OLEFINS

23.2.2010


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TECHNOLOGY FOR THE

PRODUCTION OF OLEFINS•Plastics production and consumption

•Family portrait of olefin technologies

•Feed stocks

•Crude Oil•Coal

•Natural gas

•Biomass

•Waste recycling

•CO2

•Cracking operations•Steam cracking

•Coking

•Hydrocracking

•Fluidized catalytic cracking

•Ethylene producing methods

•Propylene producing methods

•Recent technology advances


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• Metathesis

• OCT

• SHOP

• Gas to liquid (GTL)

• Syn-gas

• Fischer-Tropsch

• Methane to Olefins

• Methanol routes

• Methanol to propylene

• Oxidative coupling of Methane• Dehydrogenation

• Oxidative

• Dehydrogenation

• Catalytic Pyrolysis

• Summaries of Gas to Olefins routes

•

Biomass• Waste recycling

• CO2• Considerations” regarding technologies: green ethylene, process energy consumption, process

CO2 production.

TECHNOLOGY FOR THE

PRODUCTION OF OLEFINS


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Plastics production and

consumption [1]


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PE and PP consumption [2]


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Global polyolefin market


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Family portrait of olefin

technologies: current and future


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Abbreviations in the family portrait

of olefin technologies• BATH: Bio-acid acetone to hydrocarbons (e.g. olefins).

• CC: Catalytic Cracking or Catalytic Pyrolysis.

• DCC: Deep Catalytic Cracking, etc.

• DH: De-hydration process (e.g. methanol to olefins, methanol to propylene and ethanol dehydration).

• FM: Fermentation

• FP: Flash pyrolysis, sometimes in the presence of methane.

• FT: Fischer-Tropsch synthesis (using syngas CO and H2 mixture to synthesize methanol or other products).

• GAS: Gasification and liquefaction.

• GS: Gas stream reactor technologies, e.g. shockwave reactors.

• HG: Hydrogenation

• HP: Hydro-Pyrolysis

• HTUL: Hydro-Thermal Upgrading Liquefaction which produces naphtha from biomass feedstock.

• OC: Oxidative coupling of methane via ethane.

• OD: Oxidative Dehydrogenation of ethane.

• OM: Olefin Metathesis, e.g. ABB-Lummus Olefin Conversion Technology, IFP-CPC meta-4.

• OU: Olefins Upgrading (conversion of C4

- C10

) to light olefins, e.g. Superflex, Propylur and Olefins Cracking.

• PD: Propane dehydrogenation.

• RCY: Re-cycling pyrolysis using organic waste, such as discarded plastics, used rubber, etc.

• REC: Recovery of refinery off gases, which contains ethylene, propylene, propane, etc.

• REF: Refinery processes. Distillation of crude oil produces naphtha and heavy oil. Catalytic cracking produces off gases.Cryogenic separation and absorption produces ethane and LPG.

• SC: Steam cracking (conventional).

• SEP: Gas separation process which produces methane, ethane and propane.

• SR: Steam Reforming of natural gas to produce methanol.

• HVC: Include light olefins and non-olefin chemicals. Light olefins are ethylene, propylene, butadiene and butylene. Non-olefinchemicals are mostly aromatics (and a small amount of C5+ hydrocarbons) in the case of steam cracking routes and

mostly gasoline (and a small amount of butanes and C5+) in the case of C1 routes. Backflows from naphtha steamcracking to the refinery (8–10% yield on a mass basis) are of very low economic value and are therefore not counted as

HVCs.

• OCT: Olefins conversion technology.

• LPG: Liquefied petroleum gas.

• NAPHTHA: Liquid mixtures of hydrocarbons, i.e. a distillation product from petroleum or coal tar, a broad termencompassing any volatile, flammable liquid hydrocarbon mixture. Naphtha is used primarily as feedstock.

• FEM: Fermentation


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Feedstock’s to make olefins

• Crude oil

• Natural gas

• Coal

• BiomassOrganic waste-Recycled plastics

• CO2


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Crude oil feedstock• Composition by weight

• Hydrocarbon Average Range

• Paraffins 30% 15 to 60%

• Naphthenes 49% 30 to 60%

• Aromatics 15% 3 to 30%

• Asphaltics 6% remainder

• Crude oil is very diverse in compositiondepending on the source


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Total world oil reservesIn the last 10 years has polyolefin industry had a great

interest in improving the refinery cracking process in

order to neutralize the falling profit in producing

polyolefin’s. (OAn)

Naphthenes =

Cycloalkanes, especially if

from petroleum sources.

Paraffins =

The common name for the

alkane hydrocarbons.


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Crude oil feed stock view

[3]


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Crude oil feed stock view• DCC: Deep Catalytic Cracking, etc.

• REC: Recovery of refinery off gases, which contains

ethylene, propylene, propane, etc.• PD: Propane *dehydrogenation.

• SC: * Steam cracking (conventional)

• CC: * Catalytic Cracking or *Catalytic Pyrolysis.

• HP: Hydro-Pyrolysis.• GS: Gas stream reactor technologies, e.g. shockwavereactors.

• OD: * Oxidative Dehydrogenation of ethane.

• OU: Olefins Upgrading (conversion of C4- C10) to light

olefins.• OM: * Olefin Metathesis.

• LPG: Liquefied petroleum gas.


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The Oil Refinery basic process is

distillation

• Distillation of

Crude oil produces

Naphtha and Heavy oil.

• Cryogenic separation

and absorption

produces Ethaneand LPG.


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Coal feed stock• Peat: Considered to be a precursor of

coalHas industrial importance as a fuel infor example, Ireland and Finland.

• Lignite: Brown coal, is the lowest rank ofcoal and used almost exclusively as fuel

for electric power generation.• Sub-bituminous coal: Properties rangefrom those of lignite to those ofbituminous coal.Used primarily as fuel for

steam-electric power generation. Animportant source of light aromatichydrocarbons for the chemicalsynthesis industry.[4]


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Coal feed stock• Bituminous coal: Dense mineral.

Primarily as fuel in steam-electric powergeneration, with substantial quantitiesalso used for heat and powerapplications in manufacturing and tomake coke.

• Anthracite: Highest rank; a harder,

glossy, black coal used primarily forresidential and commercial spaceheating.

• Graphite: Technically the highest rank,

but difficult to ignite and is not socommonly used as fuel: it is mostly usedin pencils and, when powdered, as alubricant.


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Coal & Its uses - Coal classification


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Coal feed stock view

• GAS: Gasification and liquefaction.

• FP: Flash pyrolysis, sometimes in the presence of methane.

• FT: Fischer-Tropsch synthesis to synthesize methanol or other products.


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Natural gas• Natural gas is a gas consisting primarily of methane. It is found

associated with fossil fuels, in coal beds, as Methane Clathrates,

and is created by methanogenic organisms in marshes, bogs, andlandfills.

• The by-products of natural gas processing include ethane, propane,butanes, pentanes and higher molecular weight hydrocarbons,elemental sulfur, and sometimes helium and nitrogen.

• Acid gas = CO2 , SH2• NGL = Natural Gas Liquids

• Tail gas = CO2 + leftover S-compounds from Claus process.

• Dehydration = Remove water vapor using either the regenerableabsorption in liquid triethylene glycol (TEG), or a Pressure Swing

Adsorption (PSA) unit which is regenerable adsorption using a solidadsorbent. [5]


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Natural gas


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Natural gas feed stock view

• SEP: Gas separation process which produces methane, ethane and propane;

• SR: Steam Reforming of natural gas to produce methanol.

• OC: Oxidative coupling of methane via ethane

• OD: Oxidative Dehydrogenation of ethane


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Methane hydrates/clathrates• ice-like combinations of

methane and water onthe sea floor, found in

vast quantities)

• are a potential futuresource of methane

Methane Hydrate Phases


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Coal Bed Methane extraction


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Biomass feed stock view

• GAS: Gasification and liquefaction

• FP: Flash pyrolysis, sometimes in the presence of methane



• FT: Fischer-Tropsch synthesis to synthesize methanol or other products


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Organic waste feed stock view

• Recycling of plastic materials via retro polymerization.

• Recycling of plastic materials via flash pyrolysis.



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CO2 Feed stock view


• DH: De-hydration process (e.g. methanol to olefins, methanol to propylene and ethanol dehydration)

• OU: Olefins Upgrading (conversion of C4- C10) to light olefins, e.g. Superflex, Propylur and Olefins Cracking.


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Steam cracking• Steam cracking and its products have a

backbone status for many industrial sectors.

• The worldwide demand and production of olefins

are higher than for any other chemicals.

• In general, steam cracking plays a dominant role

in olefin production.[6]


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What is steam cracking?• Steam cracking, is a pyrolysis process

• A light hydrocarbon mixture is heated in metallic tubes inside a

furnace in the presence of steam to a temperature at which itthermally decomposes.

• For ethane the primary reaction is dehydrogenation

• C2H6 -> H2C=CH2 + H2• Other free radical reactions also occur

• - Continued dehydrogenation to form acetylene• C2H4 -> HC-CH + H2• - Association and disassociation reactions that form propylene,

butadiene, benzene, and methane.

• These reactions require a residence time of about a 0.1 to 1 s andare endothermic.

• Hydrogen and methane byproducts are separated and burned in thefurnace to drive the chemistry.


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Typical flow diagram for a naphtha

steam cracker


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steam cracker • Pyrolysis section (A):

• This is the heart of a steam cracker.

• Naphtha first enters the convection section of a pyrolysis furnace, and it is preheated to 650oC.

• Naphtha is vaporized with superheated steam and is passed into long (12–25 m), narrow (25– 125 mm) tubes,which are made of chromium nickel alloys.

• Pyrolysis takes place mainly in the radiant section of the furnace. The tubes are externally heated to 750–900oC(up to 1100oC) by fuel oil or gas fired burners.

• Naphtha is cracked into smaller molecules via a free-radical mechanism in the absence of catalysts.

• The free radicals lead to the formation of light olefins in the gaseous state.

• The hot gas mixture is subsequently quenched in the Transfer Line Exchangers (TLE) to 550–650oC, orsometimes lower to 400oC.

• TLE will then be followed by a series of heat exchangers and temperatures can drop down to 300oC.

• These heat transfer activities avoid degradation by secondary reactions and at the same time generate highpressure steam for driving compressors, etc.

• However, heat exchangers are prone to fouling and therefore need both scheduled and unscheduled shutdowns.


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steam cracker • Primary fractionation/compression (B):

• Primary fractionation applies to naphtha and gas oil feed only.

• In the primary fractionation section, gasoline and fuel oil streams (rich in aromatics) arecondensed and fractionated.

• While this liquid fraction is extracted, the gaseous fraction is desuperheated in the quench towerby a circulating oil or water stream.

• The gaseous fraction is then passed through four or five stages of gas compression withtemperatures at approximately 15–100 °C, then cooling and finally cleanup to remove acid gases,carbon dioxide and water.

• Most of the dilution steam is condensed, recovered and recycled. Products of this section are fueloil and BTX.

• BTX = benzene, toluene and xylene.

• A common problem with compression is fouling in the cracked gas compressors and after-coolers.The build-up of polymers on the rotor and other internals results in energy losses as well asmechanical problems. Wash oil and water are used to reduce fouling.


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steam cracker • Product recovery/fractionation (C):

• This is essentially a separation process through distillation, refrigeration and extraction.

• Equipment includes chilling trains and fractionation towers, which include

– refrigeration – de-methanizer Distillation at low temperatures. – de-ethanizer Distillation at low temperatures. – and others

• C2 compounds, or ethylene and ethane, separation often requires large distillation columns with 120–180 trays andhigh reflux ratios.

• Steam cracking performance has improved considerably over time. Now steam crackers typically obtain:

– ~85% ethylene selectivity – 60% ethane conversion

• Unreacted alkane is recycled after cryogenic separation, an expensive process.

• Undesired acetylene is removed through catalytic hydrogenation or extractive distillation.


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Decoking• Decoking

• Regular decoking is required in various parts of the pyrolysis section.

• Before decoking, the furnace has to be shut down.

• High pressure steam and air are fed to the furnace while it is heated up to 880–900 °C, or even up to 1100 °C.

• Coke on the inner surfaces of the wall and tubes is either burned off, washed away with high pressure water orremoved mechanically.

• Decoking process can take 20–40 h for a naphtha steam cracker.

• Depending on the feedstocks, coil configuration and severity, decoking for steam cracking furnaces is requiredevery 14–100 days on an average.

• Typically, a naphtha pyrolysis furnace is decoked every 15–40 days.

• Maximum cycle time is around 60–100 days.

• Decoking is also required for quench towers and other sections.


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Fluidized catalytic cracking (FCC)• Catalytic and other alternative olefin technologies can process conventional or heavy

feedstocks and are therefore alternatives to conventional steam cracking.{2}

• Catalytic olefin technologies basically can be divided into two categories:

i) Acidic catalytic cracking

• Is associated with zeolite catalysts, FCC-like riser/bed reactors and heavyfeedstocks.

ii) Thermal catalytic pyrolysis

• Is associated with various kinds of metal oxide catalysts and naphtha.


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Simplified energy profile of

conventional steam cracking andcatalytic olefin technologies

Si lifi d fil f


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Simplified energy profile of

conventional steam cracking andcatalytic olefin technologies

• First - lower activation energy

– Catalysts provide an alternative route to steam cracking with the use of lower activation energy for C–C bonds rupture.

– Most of the catalysts cannot withstand extremely high temperatures and pressures as in steam cracking.

– Temperatures for the catalytic naphtha cracking processes are 150–250 °C lower than those for steam crackers.

• Second - improved selectivity to desired products

– Catalysts improve selectivity to desired products, such as propylene.

– Even if the same operating conditions as those of steam cracking are applied for catalytic cracking, the total olefin yield by LG’scatalytic pyrolysis technology is still enhanced by at least 15%.{2}

– It produces more gasoline with a higher octane rating than steam cracking.

– It produces byproduct gases that are more olefinic than those produced by steam cracking.

• Third - decoking through catalyst regeneration

– Coke formed during the cracking process is constantly removed by the catalysts.

– The catalysts are decoked through exothermic catalyst regeneration with oxygen or catalyst decoking.


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FCC Schema

Adiabatic process = A process in which no heat is transferred to or from the

working fluid.

Endothermic = A process or reaction that absorbs energy in the form of heat.

Catalyst regeneration and decoking is an exothermic reaction with oxygen.


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Production of some common

olefinsEthylene:• Ethylene is the world’s largest organic chemical.• Worldwide production of approximately 100 million t/y in about 275 plants.

• Ethylene manufacture is dominated by steam cracking.• Plant size has increased two orders of magnitude from 10,000 t/y (1945) to >1 000 000 t/y (2000).

Propene• Propene is obtained mainly from:

- Naphtha steam crackers (globally about 65%) as a co-product with ethene,- Fluid catalytic cracking (FCC) units at refineries as a co-product from gasoline-making.

• Relatively small amounts are produced by:- Propane dehydrogenation- Coal gasification- Fischer–Tropsch chemistry

• Strong global demand for propene, presently outpaces supply from these conventional sources.

• Propene is used for about 60% for making polypropene. The rest for producing acrylonitrile, oxoalcohol and acrylic acid.


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The Propylene Gap


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Recent technology advances –

olefin producing technology• A few engineering firms have become the repositories of process technology for petrochemical

commodities.

• Competitive forces drive these firms to continuously make incremental improvements in theirrespective technologies, but not to replace them.

• Steam cracking of hydrocarbons to produce ethylene is an example of a mature petrochemicalprocess.

• The metal upper temperature limit in the cracking furnace coils is a current limitation of the

technology that is difficult to overcome.

• The ethylene furnace has undergone modifications to improve product value, energy recovery,and capital cost but there has been no fundamental change in the way the ethylene is produced.

• Any new process must demonstrate significantly better economics than the existing process.

• Additionally, the process reliability, safety, and environmental performance of the new processmust be at least comparable to or superior to the existing process.


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The Metathesis? The substrate?

• OM: Olefin Metathesis.

• SC: Steam cracking.

• CC: Catalytic Cracking or Catalytic Pyrolysis.

• PD, DH, OD: Propane dehydrogenation, Dehydrogenation, Oxidative dehydrogenation.


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Olefin metathesis• Derived from the Greek words meta (change)

and thesis (position), metathesis is the exchangeof parts of two substances.

• In the reaction, AB + CD -> AC + BD

AB + AB ‐> BB + AA


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Metathesis mechanism models

R1

R

1

R2

R2

M

R1

R1

R2

R2

M

R1

R1

R2

R2

M

R1

R1

R2

R2

M

R

R R R

R

R

R

R

RR

M M MM M

Grubbs

Calderon


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Metathesis mechanism models

Modif ied mechanism by Yves Chauvin (1971)

(a)R1

R1

R1

R1

R1

R1

R1

R1 R1 R1

R1R1

++

(b)

M M

[M]

[M]

[M]


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Catalysts development


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Catalysts development

OCT OLEFINS CONVERSION


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OCT - OLEFINS CONVERSION

TECHNOLOGY - METATHESIS• An alternative route to propene is by applying the metathesis

reaction for the conversion of

• a mixture of ethene and 2-butene into propene.• The Phillips triolefin process, which utilizes a heterogeneous catalyst

system, was originally developed by Phillips Petroleum Co., USA,and operated from 1966 to 1972 for the conversion of propene intoethene and butene, due to less propene demand at that time.

• The Phillips process in the reverse direction, is now offered by ABBLummus Global, Houston (USA),

• for license as olefins conversion technology (OCT) for theproduction of propene.

• CH3CH2=CH2CH3 + CH2=CH2 -> 2 CH3CH2=CH2

+ +


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The OCT process• Fresh C4’s plus C4 recycle are

mixed with ethene feed plusrecycle ethane.

• The metathesis reaction takesplace in a fixed-bed reactor at >260oC and 30-35 bar over a mixture of

• - WO3/SiO2 (metathesis catalyst)

• - MgO (isomerization catalyst)

• The reactor is regenerated on aregular basis.

• 1-Butene in the feedstock is isomerized to2-butene as the original 2-butene is

consumed in the metathesis reaction.

•The conversion of butene is above 60%

per pass-•The selectivity for propene is >90%.

MgO

catalyst


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Production of 1-hexene• A semi-works unit using the OCT (olefins

conversion technology) process is used at

Sinopec’s olefin plant in Tianjin (China), for themetathesis of butene to produce 3-hexene,which is then isomerized into 1-hexene

(comonomer used in the production ofpolyethene).

+ +

Isomerization

The Shell Higher Olefins Process


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(SHOP)• SHOP gives a mixture of linear even-numbered alpha-

olefins ranging from C4 to C40.

• Product and catalyst phases are readily separated.

• The olefins formed are immiscible with the solvent; sothat the Ni catalyst can be recycled repeatedly.

• The C6 –C18 1-alkenes are separated from the productmixture by distillation and are used in other processes.

• The remaining lighter (C18) alkenesgo to purification beds.



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(SHOP)• A large-scale industrial process incorporating olefin

metathesis is the Shell higher olefins process (SHOP) for

producing linear higher olefins from ethene. The processtakes place in three stages:

• First step (oligomerization): – Ethene is oligomerized in the presence of a homogeneous

Nickel–Phosphine catalyst at 90–100 oC and 100–110 bar in apolar solvent (1,4-butanediol)

• Second step (olefin isomerization): – These lighter (C18) alkenes undergo double-

bond isomerization over a solid potassium metal catalyst to givean equilibrium mixture of internal alkenes.



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(SHOP)• Third step (metathesis):

– This mixture is passed over an alumina supported molybdatemetathesis catalyst, resulting in a statistical distribution of linear internalalkenes with both odd and even numbers of carbon atoms via cross-metathesis reactions.

– Yields about 10–15 wt.% of the desired C11 –C14 linear internal alkenesper pass, which are subsequently separated by normal distillation.

– The isomerization and metathesis catalysts operate at 100–125 oC and

10 bar. – The remaining lower (C14) alkenes are recycled.

– The product consists of >96% of linear internal C11 –C14 alkenes.

• Shell Chemicals total worldwide SHOP production capacity is

1,190,000 t of linear alpha and internal olefins per year; these aresold under the trade name Neodene®. [7]


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GAS TO LIQUIDS (GTL)• Gas to liquids is a refinery process to convert natural gas or other gaseoushydrocarbons into longer-chain hydrocarbons such as gasoline or diesel fuel.

• Methane-rich gases are converted into liquid fuels either via direct conversion or viasyngas as an intermediate, for example using the Fischer-Tropsch.[8]


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GTL – Gas To LiquidAir separation

Syn gas production

Gas separation

Fischer‐Tropsch

process

Natural gasAir

MethaneO2

CO H2

Mixed Liquid Hydrocarbons

CrackerDehydrogenation

Of Ethane,

PropaneNaphtha + Wax

Light

olefins

Ethylene

Propylene

Separation processes

(LPG)LiquidPetroleum

Gas


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Natural gas to syngas• We can choose from the following well established technologies:

• i) Steam reforming.

• ii) Partial oxidation (POX).

• iii) Autothermal reforming.

• iv) Combined or two-step reforming.

• The choice of reformer technology will have an influence:

- On the thermal efficiency of the plant as a whole.

- On the capital costs of the reformer, oxygen plant (where applicable) and theFischer–Tropsch section.

• One of the biggest challenges is to optimize the energy integration between thesyngas generation and syngas conversion sections.


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Natural gas to syngasi. Steam reforming

• An obvious advantage of steam reforming is that its does not need an oxygen plant.

• At high temperatures (700 – 1100 oC) and in the presence of a metal-based catalyst (nickel), steam reacts withmethane to yield carbon monoxide and hydrogen.

• These two reactions are reversible in nature.

• CH4 + H2O -> CO + 3 H2 H = + 206,2 kJ/mol

• Additional hydrogen can be recovered by a lower-temperature gas-shift reaction with the carbon monoxideproduced.

• CO + H2O -> CO2 + H2 H = -41,2 kJ/mol

• The hydrogen must be separated from the CO2 to be able to use it.

• This is primarily done by Pressure Swing adsorption (PSA), amine scrubbing and membrane reactors


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Natural gas to syngas• ii. Partial oxidation reforming (POX)

• The non-catalytic partial combustion of methane produces syngas with a H2/CO ratio ( CO + 2 H2 H = -35,7 KJ/MOL

• Due to the absence of catalyst, the reformer operates at an exit temperature of about 1400 °C.

• Have the following disadvantages as compared to an autothermal reformer.

- Formation of soot and much higher levels of ammonia and HCN, which necessitates the use of a scrubber toclean the gas.

- Higher oxygen consumption.

- Due to the absence of the water–gas shift reaction, the unconverted methane as well as the methane producedby the Fischer–Tropsch reaction cannot be recycled to the reformer without removing the CO from the Fischer–Tropsch tail gas.


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Natural gas to syngas• iii. Autothermal reforming• Autothermal reforming of natural gas to syngas in the presence of:

- catalyst

- steam

- oxygen

• Milder operating conditions (exit temperature of ~1000 oC).

• The syngas is soot-free and less ammonia and HCN are produced as compared to a POX.

• However, at a Steam/Carbon ratio of 1.3 the syngas will have a H2/CO ratio of about 2.5, which is higher than theratio needed by the Fischer–Tropsch section.

• iv. Combined reforming

• Steam reformer + Autothermal reformer.

- Better energy utilization than the individual parts.

• The thermal efficiency of the GTL plant can be improved by about 1–2%.

- Less expensive than steam reforming.

- More expensive than autothermal reforming.

• The choice between combined and autothermal reforming will depend on the cost of the natural gas.


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Fischer-Tropsch process• The Fischer-Tropsch process is a catalyzed chemical reaction.

• Synthesis gas (syngas = carbon monoxide and hydrogen), is converted into liquid hydrocarbons ofvarious forms.

• The most common catalysts are based on Fe and Co (Ni and Ru have also been used).

• The process involves a variety of competing chemical reactions.

• (2n+1)H2 + nCO -> CnH(2n+2) + nH2O

• Most of the alkanes produced tend to be straight-chained, although some branched alkanes arealso formed.

• In addition to alkane formation, competing reactions result in the formation of alkenes, as well asalcohols and other oxygenated hydrocarbons.

• Usually, only relatively small quantities of these non-alkane products are formed, althoughcatalysts favoring some of these products have been developed.


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Fischer-Tropsch process• Another important reaction is the water gas shift reaction:

H2O + CO -> H2 + CO2

• It should be noted that, according to published data on the current commercial implementations of• the coal-based Fischer-Tropsch process, these plants can produce as much as 7 tons of CO2 per tons of liquid

hydrocarbon products (excluding the reaction water product).

• This is due in part to the high energy demands required by the gasification process, and in part by the design ofthe process as implemented.

• Process conditions 150-300oC.

• Higher temperatures lead to faster reactions and higher conversion rates, but also tend to favor methaneproduction.

• Increasing the pressure leads to higher conversion rates and also favors formation of long-chained alkanes both ofwhich are desirable.

• Typical pressures are in the range of one to several tens of atmospheres.

• Chemically, even higher pressures would be favorable, but the benefits may not justify the additional costs of high-pressure equipment.

Methane to Olefins vs. Gas to


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Methane to Olefins vs. Gas to

Liquid


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Methane To Olefins (MTO)• Olefins (e.g., ethylene and propylene) can also be produced from natural gas (i.e.,methane) via: - Methanol

- Oxidative coupling routes

• Methane-based routes use more than twice as much process energy than state-of-the-art steam cracking routes do (the energy content of products is excluded).

• There are two types of C1 routes through which natural gas can be converted intoolefins: - Indirect routes (via syngas or ethane)

- Direct routes (directly from methane to light olefins).

• The direct route from methane to olefins is a modified Fischer–Tropsch reaction.

• This route is technically difficult because of low selectivity to light olefins and highyield of heavy hydrocarbons.

• Today, the chemistry of the direct route remains one of the world’s major scientificchallenges while there are very few publications currently available on the topic.

Oxidative Coupling &


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p g

Dehydrogenation

• OC: Oxidative Coupling

• DH: Dehydrogenation

• PD: Propane Dehydrogenation

• OD: Oxidative Dehydrogenation


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Oxidative coupling of methane• i) Production of methane and oxygen.

- Methane is separated from natural gas and is purified.

- Oxygen is separated from air cryogenically.

• ii) Oxidative coupling (petrochemicals production).

4 CH4 + O2 -> → 4 •CH3 + 2 H2O

• This reaction is called partial oxidation of methane.

2 •CH3 -> H3C-CH3 -> H2C=CH2 + H2

H3C-CH3 -> H2C=CH2 + H2 (several other processes possible)

• The catalysts used are mostly oxides of alkali, alkaline earth and other rare earth metals.

• Hydrogen and steam are sometimes added to reduce coking on catalysts.

• After one pass, roughly 80% of the total oxygen feed by mass is consumed.

• The per-pass ethylene yield on a mass basis of methane is about 30%. [9]

Thoughts on Oxidative coupling of


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g p g

methane (OCM)• The current performance of OCM routes in terms of energy use is poorer than that of state-of-the-

art steam cracking primarily due to the following problems:

• i) Low yields.

• There is a trade-off between methane conversion and selectivity to ethylene.• Under 600 oC, the rate of reaction is slow, but above 600 oC undesired oxidations dominate the

reactions.

• ii) Separation.

• Relatively high energy use in separation and recycling.

• iii) Catalysts.

• Additional oxygen and hydrogen are required for reducing coking on catalysts.

• High temperatures at 750–1000 oC require catalysts with high thermal stability.

• iv) Other issues,

- Possible explosion due to the mixture of oxygen and hydrocarbons.

- CO and CO2 emissions, aromatic hydrocarbons, acid gas and organic acid.- Operability. [9]

Dehydrogenation of Ethane or


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y g

Propane [10]• Require high-purity approximately 90% oxygen.

• Ethane oxidative dehydrogenation

• Results in approximately 35% potential saving (including primary energy use inoxygen production) on the SEC of state-of-the-art ethane cracking.

• If the CO2 emissions from oxygen usage are included, the total CO2 emissions is 15%higher than that for ethane cracking.

H3C-C3H + ½ O2 -> H2C=C2H + H2O

• Propane oxidative dehydrogenation.

H3C-CH2C3H + ½ O2 -> H3C-CH2=C2H + H2O

• * This process produces little ethylene.

• * Ethylene yield from steam cracking of propane is up to 45% and propylene yield is12%.


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Oxidative dehydrogenation• ODH is Exothermal.

• Dehydrogenation and Cracking are Endothermal.• Process simplicity.

• (a) The combination of exothermal alkane combustion with theendothermal dehydrogenation, at temperatures higher than 700 oC.

The use of O2 enables to overcome thermodynamic limitations andto avoid catalyst regeneration.

• (b) A true ODH occurring with redox-type catalysts already attemperatures lower than 500 oC. Amongst the catalysts used, the

most investigated ones are those based either on vanadium oxide oron molybdenum oxide.


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Biomass feed stock view

• GAS: Gasification and liquefaction

• FP: Flash pyrolysis, sometimes in the presence of methane



• FT: Fischer-Tropsch synthesis to synthesize methanol or other products


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Biomass Gasification [11]


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Biomass Gasification


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Biomass Gasification [11]

Char: is the solid material that remains after light gases (e.g. coal gas) and tar (e.g. coal tar)

have been driven-out or released from a carbonaceous material, during the initial stage of

combustion, which is known as carbonization, charring, devolatilization or pyrolysis.


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Organic waste feed stock view

• Recycling of plastic materials via retro polymerization.

• Recycling of plastic materials via flash pyrolysis.


Olefins from Recycling of plastic


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materials (“solid oil”)• Material recycling.

• Chemical recycling, retro-synthesis tomonomers.

• Chemical recycling, cracking to naphtha.

• Chemical recycling, syngas production.

• Thermal recycling/energy production

Chemical recycling, "retro-


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synthesis to monomers"• Reversal of the Ziegler - Natta polymerization is theoretically possible.

• This reaction is limited because selective transfer of the relatively high depolymerization enthalpyto the reactants is difficult.

• After 15 h the polymer was completely degraded to ethane and methane.

• Not only polymer generated in situ, but also normal commercial polyethylene was degraded in thesame way.

• In this context Dufaud and Basset have succeeded in activating the C-C bond in PE catalyticallywith a strongly

• Electrophilic Ziegler - Natta catalyst and cleaving it by the action of hydrogen at 150 oC.

• Initially oligomers were formed which were then further cleaved to lower alkanes.

• Formally regarded this is a statistical chain cleavage which, because of the involvement of

hydrogen, may even be considered to be a retro-polycondensation.

• Never the less, this discovery is remarkable since for the first time a catalyst has been found thatis actively involved in the primary reaction.

Chemical recycling, "retro-


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synthesis to monomers"

Mechanism of the hydrogenolysis of polyethylene (according to Dufaud

and Basset). P = polymer chain.

Chemical recycling, cracking to


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naphtha

• Thermal depolymerization(TDP) is a process using

hydrous pyrolysis for thereduction of complex organicmaterials (usually wasteproducts of various sorts, oftenknown as biomass and plastic)into light crude oil.

• The principal candidates forthermal depolymerisation are:

-PMMA

-PET

-Poly-urethane

-Isoprene.

• [12]

Chemical recycling, syngas


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production [13]• The plasma torch jet provides a

homogeneous temperature ofmore than 1200°C to all fractionsof the syn-gas.

• This results in a completedissociation of allhydrocarbons, evenhalogenated, with no indicationof recombination.

• There are no toxic norcarcinogenic organiccompounds present in theproduced fuel gas because nosuch compounds can survive atthis temperature.

• This means no formation ofVolatile Organic Compounds(VOCs) such as dioxins andfurans as are found with othertechnologies.


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CO2 feed stock view


• DH: De-hydration process (e.g. methanol to olefins, methanol to propylene and ethanoldehydration)

• OU: Olefins Upgrading (conversion of C4- C10) to light olefins, e.g. Superflex, Propylur andOlefins Cracking.

CO2 recycling


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CO ecyc g

• How to collect the CO2?

• Carbon dioxide scrubbing based on potassium carbonate exists.

- Single Step methods: CO2 + H2 Methanol, “green methanol”

- Single Step methods: CO2 Hydrocarbons

- 2 Step methods: CO2 , CO Hydrocarbons

• If CO2 is heated to 2400oC, it splits into carbon monoxide and

oxygen.

• The Fischer-Tropsch process can then be used to convert the COinto hydrocarbons.

CO2 - Methane


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• The Sabatier process

• As originally reported by Sabatier in 1902, it is well known that CO2 can be

reduced by H2 over a catalyst as:

CO2 + 4 H2 -> CH4 + 2 H2O

• The global Sabatier reaction, which is reversible and exothermic H = -167

kJ/mol, proceeds catalytically at relatively low temperatures on a catalyst.

• At elevated temperatures and pressures in the presence of a nickel catalyst.

• Optionally ruthenium on alumina (aluminum oxide) makes a more efficient

catalyst.

Green methanol from CO2


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• Anyavailableenergysource

(alternativeenergiessuch assolar, wind,geothermal,and atomicenergy) can

be used fortheproductionof neededhydrogenandchemical

conversionof CO2.

Catalytic Hydrogenative


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Conversion of Carbon Dioxide toMethanol

• CO2

+ 3 H2

-> CH3OH + H

2O H298K = - 11.9 kcal/mol

• This reaction has been known to chemists for more than 80 years. In fact,some of the earliest methanol plants operating in the U.S. in the 1920-1930scommonly used carbon dioxide for methanol production.

• Lurgi AG, a leader in the methanol synthesis process, for example,developed and thoroughly tested a high activity catalyst for methanolproduction from CO2 and H2. Operating at a temperature around 260 °C,slightly higher than conventional methanol synthesis catalyst, the selectivityto methanol is excellent.

• The general composition of the catalysts for CO2 hydrogenation such asCu/ZnO/Al2O3 is similar to the ones used presently for methanol productionvia syngas.

The hydrogen question


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y g q

• A) By using still-existing significant sources of fossil fuels (mainly natural gas).

- The Carnol process:

- Methane thermal decomposition CH4 -> C + 2 H2 H298K = 17.9 kcal/mol

(Kværner-process)- Methanol synthesis CO2 + 3 H2 -> CH3OH + H2O

- Overall Carnol process 3 CH4 + CO2 -> CH3OH + 2 H2O + 3 C

- Bireforming

- Steam reforming 2 CH4 + 2 H2O -> 2 CO + 6 H2

- Dry reforming 2 CH4 + CO2 -> 2 CO + 2 H2

- Bireforming 3 CH4 + 2 H2O + CO2 -> 4 CO + 8 H2 -> 4 CH3OH

• B) From splitting of water. H2O + e- -> H2 + ½ O2 H298K = 68.3 kcal/mol

• C) Photohydrogen- Biological hydrogen production from Algae and Bacteria.- Photoelectrochemical cell.

Bio vs. green


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g

• (Bio) H3C-CH2-OH + (Green) H2C =CH2 -> (Green) Polyethylene

• (Bio/Green) H3C-CH2CH2CH2OH -> (Green) H3C-CH2-CH=CH2

Bacteria (Clostridium acetobutylicum)

Process chemistry

1) Hydrolytic conversion.

2) Decarboxylation.

3) Reforming long‐chain alkanes.

Bio-mass

Bio‐Ethanol

Bio‐oils

Bio‐Butanol

Green Butanol

Green Butanol

Ethanol to butanol


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• 2 H3C-CH2-OH ->{HAP}-> H3C-CH2-CH2-CH2-OH + H2O

• Nonstoichiometric Hydroxyapatite HAP is represented by the formula Ca10-z(HPO4)z(PO4)6-z(OH)2-z - nH2O;

• 0 < z - 1, n = 0-2.5• Effect of reaction temperature on yields of various alcohols from ethanol on

HAP (Ca/P ratio ) 1.64), contact

time 1.78 s.

• With maximum selectivity of 76%

for Butanol.

Conclusions


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• Energy use and CO2 emissions in all C1 routes are much higher thanthose of steam cracking.

• Methane-based routes use more than twice as much processenergy than state-of-the-art steam cracking routes do.

• Methane based routes lead to 60–85% more CO2 emission than thestate-of-the-art ethane cracking.

• Among the methanol-related routes, UOP MTO is the most efficient,but its energy use is still about 150% higher compared to state-of-the-art naphtha-based steam cracking.

• Methanol-related routes have similar energy use, but cause slightlyhigher CO2 emissions than DSM OCM I and II do.

Conclusions


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• By conducting a comparative analysis of the energy use, CO2emissions and production costs of C1 technologies and steamcracking, we found that methane-based routes use more than twice

as much than process energy than state-of-the-art steam crackingroutes do (the energy content of products is excluded).

• Oxidative coupling routes are currently still immature due to lowethylene yields and other problems.

• The methane-based routes can be economically attractive in

remote, gas-rich regions where natural gas is available at low prices.• The development of liquefied natural gas (or LNG) may increase theprices of natural gas in those locations.

• While several possibilities for energy efficiency improvement doexist, none of these natural gas-based routes is likely to become

more energy efficient or lead to less CO2 emissions than steamcracking routes do.

Sources


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[1] The Compelling Facts About Plastics, An analysis ofplastics production, demand and recovery, for 2005 inEurope - Published Spring 2007

[2] Galli, Journal of Polymer Science, Part A, PolymerChemistry, 42 (2004), 396-415

[3] en.wikipedia.org/wiki/Crude_oil

[4] http://en.wikipedia.org/wiki/Coal

[5] http://en.wikipedia.org/wiki/Natural_gas

Sources


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[6] Ren T., Patel M., Blok K., Energy (AmsterdamNetherlands) (2005) Volume Date 2006 31(4) 425-451,Olefins from conventional and heavy feedstocks, Energyuse in steam cracking and alternative processes.

[7] Refs\Belgiorno V., De Feo G., Della Rocca C., NapoliR.M.A., Waste Management (Amsterdam Netherlands)(2003) 23(1) 1-15, Energy from gasification of solid

wastes.pdf

[8] en.wikipedia.org/wiki/Gas_to_liquids

[9] Ren T., Patel M.K., Blok K., Energy (Oxford UnitedKingdom) (2008) 33(5) 817-833, Steam cracking andmethane to olefins, Energy use CO2 emissions andproduction costs

Sources[10] Ren T Patel M Blok K Energ (Amsterdam


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[10] Ren T., Patel M., Blok K., Energy (AmsterdamNetherlands) (2005) Volume Date 2006 31(4) 425-451,Olefins from conventional and heavy feedstocks, Energyuse in steam cracking and alternative processes.

[11] Refs\Belgiorno V., De Feo G., Della Rocca C., NapoliR.M.A., Waste Management (Amsterdam Netherlands)(2003) 23(1) 1-15, Energy from gasification of solid

wastes.pdf

[12] Newborough M., Highgate D., Vaughan P., AppliedThermal Engineering (2002) 22(17) 1875-1883, Thermal

depolymerization of scrap polymers.pdf

[13] www.sunbayenergy.com/faq_plasma.html

polyko technology for the production of olefins pdf-1514859394

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