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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-olefin

chemicals 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 steam cracking 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 term

encompassing 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 composition

depending 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. shockwave

reactors.• 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 ofCrude oil produces Naphtha and Heavy oil.

• Cryogenic separationand absorptionproduces Ethaneand LPG.

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

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

• Lignite: Brown coal, is the lowest rank of coal and used almost exclusively as fuel for electric power generation.

• Sub-bituminous coal: Properties range from those of lignite to those of bituminous coal.Used primarily as fuel for steam-electric power generation. An important source of light aromatic hydrocarbons for the chemical synthesis industry.[4]

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Coal feed stock• Bituminous coal: Dense mineral.

Primarily as fuel in steam-electric power generation, with substantial quantities also used for heat and power applications in manufacturing and to make coke.

• Anthracite: Highest rank; a harder, glossy, black coal used primarily for residential and commercial space heating.

• Graphite: Technically the highest rank, but difficult to ignite and is not so commonly used as fuel: it is mostly used in pencils and, when powdered, as a lubricant.

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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, and landfills.

• 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 regenerable

absorption 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 on the sea floor, found in vast quantities)

• are a potential future source 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• FEM: Fermentation• HG: Hydrogenation• 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.• RCY: Re-cycling pyrolysis using organic waste, such as discarded plastics, used rubber, etc.

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CO2 Feed stock view

• HG: Hydrogenation • 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 it thermally 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 and

are endothermic. • Hydrogen and methane byproducts are separated and burned in the

furnace to drive the chemistry.

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Typical flow diagram for a naphtha steam cracker

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Typical flow diagram for a naphtha 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, or sometimes 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 high pressure steam for driving compressors, etc.

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

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Typical flow diagram for a naphtha 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) are condensed and fractionated.

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

• The gaseous fraction is then passed through four or five stages of gas compression with temperatures 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 fuel oil 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 as mechanical problems. Wash oil and water are used to reduce fouling.

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Typical flow diagram for a naphtha 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 and high 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 or removed 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 required every 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 heavy feedstocks.

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 and

catalytic olefin technologies

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Simplified energy profile of conventional steam cracking and

catalytic 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 olefins

Ethylene:• 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 their respective technologies, but not to replace them.

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

• 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 process must 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 exchange of parts of two substances.

• In the reaction, AB + CD -> AC + BD

AB +          AB                    ‐>               BB              +           AA

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Metathesis mechanism models

R1

R1

R2

R2

MR1

R1

R2

R2

MR1

R1

R2

R2

M

R1

R1

R2

R2

M

R

R R R

R

R

R

RRR

M M MM M

Grubbs

Calderon

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Metathesis mechanism models

Modified mechanism by Yves Chauvin (1971)

(a)R1

R1

R1

R1

R1

R1

R1

R1 R1 R1

R1R1

+ +

(b)MM

[M]

[M]

[M]

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Catalysts development

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Catalysts development

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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 into ethene and butene, due to less propene demand at that time.

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

• for license as olefins conversion technology (OCT) for the production 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 plus recycle ethane.

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

• - WO3/SiO2 (metathesis catalyst) • - MgO (isomerization catalyst)

• The reactor is regenerated on a regular basis.

• 1-Butene in the feedstock is isomerized to 2-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 the metathesis of butene to produce 3-hexene, which is then isomerized into 1-hexene (comonomer used in the production of polyethene).

+ +

Isomerization

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The Shell Higher Olefins Process (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; so

that the Ni catalyst can be recycled repeatedly. • The C6–C18 1-alkenes are separated from the product

mixture by distillation and are used in other processes. • The remaining lighter (<C6) and heavier (>C18) alkenes

go to purification beds.

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The Shell Higher Olefins Process (SHOP)

• A large-scale industrial process incorporating olefin metathesis is the Shell higher olefins process (SHOP) for producing linear higher olefins from ethene. The process takes 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 a polar solvent (1,4-butanediol)

• Second step (olefin isomerization):– These lighter (<C6) and heavier (>C18) alkenes undergo double-

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

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The Shell Higher Olefins Process (SHOP)

• Third step (metathesis):– This mixture is passed over an alumina supported molybdate

metathesis catalyst, resulting in a statistical distribution of linear internal alkenes 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 alkenes per pass, which are subsequently separated by normal distillation.

– The isomerization and metathesis catalysts operate at 100–125 oC and 10 bar.

– The remaining lower (<C11) and higher (>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 are sold 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 gaseous

hydrocarbons into longer-chain hydrocarbons such as gasoline or diesel fuel.

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

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GTL – Gas To Liquid

Air separation

Syn gas production

Gas separation

Fischer‐Tropsch process

Natural gasAir

MethaneO2

CO          H2

Mixed Liquid  Hydrocarbons

Cracker DehydrogenationOf  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 the Fischer–Tropsch section.

• One of the biggest challenges is to optimize the energy integration between the syngas 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 with methane 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 monoxide produced.

• 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 (<2) close to the optimum needed by the Fischer–Tropsch synthesis.

• This low H2/CO ratio gas results from the very little, if any, steam that is used in the process.

CH4 + ½ O2 -> 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 to clean the gas.- Higher oxygen consumption.- Due to the absence of the water–gas shift reaction, the unconverted methane as well as the methane produced by 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 the ratio 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 of various 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 are also formed.

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

• Usually, only relatively small quantities of these non-alkane products are formed, although catalysts 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 of the process as implemented.

• Process conditions 150-300oC.

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

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

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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 into olefins: - 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 high yield of heavy hydrocarbons.

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

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Oxidative Coupling & 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 -> <catalyst> → 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]

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Thoughts on Oxidative coupling of 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]

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Dehydrogenation of Ethane or Propane [10]

• Require high-purity approximately 90% oxygen.

• Ethane oxidative dehydrogenation

• Results in approximately 35% potential saving (including primary energy use in oxygen 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 is 12%.

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Oxidative dehydrogenation• ODH is Exothermal.

• Dehydrogenation and Cracking are Endothermal.• Process simplicity.

• (a) The combination of exothermal alkane combustion with the endothermal dehydrogenation, at temperatures higher than 700 oC. The use of O2 enables to overcome thermodynamic limitations and to avoid catalyst regeneration.

• (b) A true ODH occurring with redox-type catalysts already at temperatures lower than 500 oC. Amongst the catalysts used, the most investigated ones are those based either on vanadium oxide or on molybdenum oxide.

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Biomass feed stock view

• GAS: Gasification and liquefaction • FP: Flash pyrolysis, sometimes in the presence of methane • FEM: Fermentation• HG: Hydrogenation • FT: Fischer-Tropsch synthesis to synthesize methanol or other products

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Biomass Gasification [11]

70

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

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Olefins from Recycling of plastic materials (“solid oil”)

• Material recycling.

• Chemical recycling, retro-synthesis to monomers.

• Chemical recycling, cracking to naphtha.

• Chemical recycling, syngas production.

• Thermal recycling/energy production

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Chemical recycling, "retro-synthesis to monomers"

• Reversal of the Ziegler - Natta polymerization is theoretically possible.

• This reaction is limited because selective transfer of the relatively high depolymerization enthalpy to 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 the same way.

• In this context Dufaud and Basset have succeeded in activating the C-C bond in PE catalytically with 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 that is actively involved in the primary reaction.

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Chemical recycling, "retro-synthesis to monomers"

Mechanism of the hydrogenolysis of polyethylene (according to Dufaud and Basset). P = polymer chain.

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Chemical recycling, cracking to naphtha

• Thermal depolymerization (TDP) is a process using hydrous pyrolysis for the reduction of complex organic materials (usually waste products of various sorts, often known as biomass and plastic) into light crude oil.

• The principal candidates for thermal depolymerisation are: -PMMA-PET-Poly-urethane-Isoprene.

• [12]

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Chemical recycling, syngas production [13]

• The plasma torch jet provides a homogeneous temperature of more than 1200°C to all fractions of the syn-gas.

• This results in a complete dissociation of all hydrocarbons, even halogenated, with no indication of recombination.

• There are no toxic nor carcinogenic organic compounds present in the produced fuel gas because no such compounds can survive at this temperature.

• This means no formation of Volatile Organic Compounds (VOCs) such as dioxins and furans as are found with other technologies.

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CO2 feed stock view

• HG: Hydrogenation • 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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CO2 recycling • 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 CO into hydrocarbons.

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CO2 - Methane• 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.

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Green methanol from CO2• Any

available energy source (alternative energies such as solar, wind, geothermal, and atomic energy) can be used for the production of needed hydrogen and chemical conversion of CO2.

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Catalytic Hydrogenative Conversion of Carbon Dioxide to

Methanol• CO2 + 3 H2 -> CH3OH + H2O 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 1920-1930s commonly 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 methanol production from CO2 and H2. Operating at a temperature around 260 °C, slightly higher than conventional methanol synthesis catalyst, the selectivity to methanol is excellent.

• The general composition of the catalysts for CO2 hydrogenation such as Cu/ZnO/Al2O3 is similar to the ones used presently for methanol production via syngas.

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The hydrogen question• 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.

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Bio vs. green• (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

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Ethanol to butanol • 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), contacttime 1.78 s.

• With maximum selectivity of 76%for Butanol.

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Conclusions• Energy use and CO2 emissions in all C1 routes are much higher than

those of steam cracking.

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

• Methane based routes lead to 60–85% more CO2 emission than the state-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 slightly higher CO2 emissions than DSM OCM I and II do.

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Conclusions• By conducting a comparative analysis of the energy use, CO2

emissions and production costs of C1 technologies and steam cracking, we found that methane-based routes use more than twice as much than process energy than state-of-the-art steam cracking routes do (the energy content of products is excluded).

• Oxidative coupling routes are currently still immature due to low ethylene 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 the prices 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 steam cracking routes do.

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Sources[1] The Compelling Facts About Plastics, An analysis of plastics production, demand and recovery, for 2005 in Europe - Published Spring 2007

[2] Galli, Journal of Polymer Science, Part A, Polymer Chemistry, 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

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

[7] Refs\Belgiorno V., De Feo G., Della Rocca C., Napoli R.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 United Kingdom) (2008) 33(5) 817-833, Steam cracking and methane to olefins, Energy use CO2 emissions and production costs

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

[11] Refs\Belgiorno V., De Feo G., Della Rocca C., Napoli R.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., Applied Thermal Engineering (2002) 22(17) 1875-1883, Thermal depolymerization of scrap polymers.pdf

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