Petroleum Pyrolysis

The BP process [7] is based on a sand fluidized-bed pyrolysis reactor. The cracking temperature is kept at 400-600°C. Low-molecular hydrocarbons can be obtained. The process mainly involves converting waste plastics into normal linear hydrocarbons, the average molecular weight of which is 300-500. Most plastics can be treated by this process. Polyolefins are decomposed into small molecules with the same linear structure. PS is converted into styrene monomers and PET into mixture of hydrocarbons, carbon monoxide and carbon dioxide. A maximum of 2% PVC is allowed in this process, and the content of chlorine in the products is lower than 5 ppm. The distribution of alkene products in this process is like that in petroleum pyrolysis. The BP process was industrialized in 1997. 

It s easy to say that the key to commercial implementation of biomass pyrolysis for tar production will be the identification of economically competitive technology for the production of higher-valued products. As the primary virtues of pyrolysis oils are those attributable to petroleum (liquid fuels and, under some pyrolytic conditionsi also olefins), it can be assumed that pyrolysis can become an avenue to petroleum-type products from renewable biomass. Is biomass pyrolysis, coupled with oil upgrading, the renewable route to petroleum Pyrolysis, after all, allows for the production of biomass-derived fuels in efficient-to-use petroleum forms. 

Petroleum. Thermal cracking (pyrolysis) of petroleum or fractions thereof was an important method for producing gas in the years following its use for increasing the heat content of water gas. Many water gas sets operations were converted into oil-gasification units (55). Some of these have been used for base-load city gas supply, but most find use for peak-load situations in the winter. 

Occidental Petroleum Coal Conversion Process. Garrett R D Co. (now the Occidental Research Co.) developed the Oxy Coal Conversion process based on mathematical simulation for heating coal particles in the pyrolysis unit. It was estimated that coal particles of 100-mm diameter could be heated throughout their volumes to decomposition temperature (450—540°C) within 0.1 s. A large pilot faciUty was constmcted at LaVeme, California, in 1971. This unit was reported to operate successfully at feed rates up to 136 kg/h (3.2 t/d). 

The petroleum generation process can be dupHcated by laboratory pyrolysis. Higher temperatures are needed to produce these reactions in a few hours or days rather than the millions of years in nature (16,17). Both dry pyrolysis and hydrous pyrolysis have been used. 

Propjiene [115-07-17, CH2CH=CH2, is perhaps the oldest petrochemical feedstock and is one of the principal light olefins (1) (see Feedstocks). It is used widely as an alkylation (qv) or polymer—ga soline feedstock for octane improvement (see Gasoline and other motor fuels). In addition, large quantities of propylene are used ia plastics as polypropylene, and ia chemicals, eg, acrylonitrile (qv), propylene oxide (qv), 2-propanol, and cumene (qv) (see Olefin POLYMERS,polypropylene Propyl ALCOHOLS). Propylene is produced primarily as a by-product of petroleum (qv) refining and of ethylene (qv) production by steam pyrolysis. 

Many other recovery alternatives have been proposed that iaclude ion exchange (qv), pyrolysis, and wet combustion. However, these have not gained general acceptance. A limited number of calcium-based mills are able to utilize their spent pulpiag liquors to produce by-products such as lignosulfates for oil-weU drilling muds, vanillin, yeast, and ethyl alcohol (see PETROLEUM Vanillin). 

Petroleum-derived benzene is commercially produced by reforming and separation, thermal or catalytic dealkylation of toluene, and disproportionation. Benzene is also obtained from pyrolysis gasoline formed ia the steam cracking of olefins (35). 

Until 1960, coal was the source material for almost all benzene produced in Europe. Petroleum benzene was first produced in Europe by the United Kingdom in 1952, by Erance in 1958, by the Eederal Republic of Germany in 1961, and by Italy in 1962. Coal has continued to decline as a benzene source in Europe, and this is evident with the closure of coke ovens in Germany (73). Most of the benzene produced in Europe is now derived from petroleum or pyrolysis gasoline. In Europe, pyrolysis gasoline is a popular source of benzene because European steam crackers mn on heavier feedstocks than those in the United States (73). 

Because of the importance of the petroleum-based processes discussed previously, only about 1% of the U.S. supply of BTX currentiy comes from coal pyrolysis (21). 

Outside the United States, coal pyrolysis is more important as a source of BTX. The proportions are about 70 20 10, but can vary greatiy depending on the coal and on the pyrolysis process used. Product quaUty is not as good as petroleum-derived BTX. This source could become more important again if petroleum costs escalate. Much higher yields of BTX from coal can be obtained by first hydrogenating the coal (22). 

The pattern of commercial production of 1,3-butadiene parallels the overall development of the petrochemical industry. Since its discovery via pyrolysis of various organic materials, butadiene has been manufactured from acetylene as weU as ethanol, both via butanediols (1,3- and 1,4-) as intermediates (see Acetylene-DERIVED chemicals). On a global basis, the importance of these processes has decreased substantially because of the increasing production of butadiene from petroleum sources. China and India stiU convert ethanol to butadiene using the two-step process while Poland and the former USSR use a one-step process (229,230). In the past butadiene also was produced by the dehydrogenation of / -butane and oxydehydrogenation of / -butenes. However, butadiene is now primarily produced as a by-product in the steam cracking of hydrocarbon streams to produce ethylene. Except under market dislocation situations, butadiene is almost exclusively manufactured by this process in the United States, Western Europe, and Japan. 

Processes for hydrogen gasification, hydrogen pyrolysis, or coking of coal usually produce Hquid co-products. The Hygas process produces about 6% Hquids as benzene, toluene, and xylene. Substitution of petroleum residuum for the coal-derived process oil has been used in studies of coal Hquefaction and offers promise as a lower cost technology (104). 

Ethyleneamines are used in certain petroleum refining operations as well. Eor example, an EDA solution of sodium 2-aminoethoxide is used to extract thiols from straight-mn petroleum distillates (314) a combination of substituted phenol and AEP are used as an antioxidant to control fouling during processing of a hydrocarbon (315) AEP is used to separate alkenes from thermally cracked petroleum products (316) and TEPA is used to separate carbon disulfide from a pyrolysis fraction from ethylene production (317). EDA and DETA are used in the preparation and reprocessing of certain... 

Ethylene. Where ethylene is ia short supply and fermentation ethanol is made economically feasible, such as ia India and Bra2il, ethylene is manufactured by the vapor-phase dehydration of ethanol. The production of ethylene [74-85-1] from ethanol usiag naturally renewable resources is an active and useful alternative to the pyrolysis process based on nonrenewable petroleum. This route may make ethanol a significant raw material source for produciag other chemicals. 

Catalytic Pyrolysis. This should not be confused with fluid catalytic cracking, which is used in petroleum refining (see Catalysts, regeneration). Catalytic pyrolysis is aimed at producing primarily ethylene. There are many patents and research articles covering the last 20 years (84—89). Catalytic research until 1988 has been summarized (86). Almost all catalysts produce higher amounts of CO and CO2 than normally obtained with conventional pyrolysis. This indicates that the water gas reaction is also very active with these catalysts, and usually this leads to some deterioration of the olefin yield. Significant amounts of coke have been found in these catalysts, and thus there is a further reduction in olefin yield with on-stream time. Most of these catalysts are based on low surface area alumina catalysts (86). A notable exception is the catalyst developed in the former USSR (89). This catalyst primarily contains vanadium as the active material on pumice (89), and is claimed to produce low levels of carbon oxides. 

Dente and Ranzi (in Albright et al., eds.. Pyrolysis Theory and Industrial Practice, Academic Press, 1983, pp. 133-175) Mathematical modehng of hydrocarbon pyrolysis reactions Shah and Sharma (in Carberry and Varma, eds.. Chemical Reaction and Reaction Engineering Handbook, Dekker, 1987, pp. 713-721) Hydroxylamine phosphate manufacture in a slurry reactor Some aspects of a kinetic model of methanol synthesis are described in the first example, which is followed by a second example that describes coping with the multiphcity of reactants and reactions of some petroleum conversion processes. Then two somewhat simph-fied industrial examples are worked out in detail mild thermal cracking and production of styrene. Even these calculations are impractical without a computer. The basic data and mathematics and some of the results are presented. 

Separation of raw feedstock. The pyrolysis of petroleum feedstream is carried out at 650-900°C at normal pressure in the presence of steam. The so-called steam-cracking process involves carbon-carbon splitting of saturated, unsaturated and aromatic molecules. The following steam-cracker fractions are used as raw materials to produce hydrocarbon resins. 

The subjeet of fluidization and researeh and development in this field, probably reaehed its peak in the early 1980 s with extensive work being applied by the petroleum industry in synthetie fuels development sueh as shale oil, eoal gasifieation, pyrolysis applications. Prior to this, significant development work was done in the petroleum industry for flexieraeking and flexieoking operations. Fluidization still remains an area of aetive researeh and industry development, and the teehnology is well established in a variety of industry seetors. 

Another emerging area m biofuels is pyrolysis, which is the decomposition of biomass into other more usable fuels using a high-temperature anaerobic process. Pyrolysis converts biomass into charcoal and a liquid called biocrude. This liquid has a high energy density and is cheaper to transport and store than the unconverted biomass. Biocrude can be burned in boilers or used in a gas turbine. Biocrude also can be chemical by altered into other fuels or chemicals. Use of pyrolysis may make bioenergy more feasible in regions not near biomass sources. Biocrude is about two to four times more expensive than petroleum crude. 

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