Petrochemicals from ethylene

This process thus enables gasoline production to be increased if the propylene can not be used for petrochemical manufacture. It recovers ethylene economically from fuel-gas. 

Absorption Process for Recovering Ethylene Hydrogen from Refinery and Petrochemical Plant Off-Gases, U.S. Patent 5,546.764. August 20, 1996. 

Ethylene is sometimes known as the king of petrochemicals hecause more commercial chemicals are produced from ethylene than from any other intermediate. This unique position of ethylene among other hydrocarbon intermediates is due to some favorable properties inherent in the ethylene molecule as well as to technical and economical factors. These could be summarized in the following ... 

Only a few of the major developments can be traced here, yet these should give a fair idea of the magnitude and importance of the aliphatic petrochemical growth. It is well to remember that some of the chemistry involved in this industry is old. Four Dutch chemists, otherwise unrecalled today, prepared ethylene dichloride by addition of chlorine to ethylene in 1795, and the synthesis of ethyl alcohol from ethylene via sulfuric acid absorption was studied by Berthelot in 1855 (8). Of course, this was coal-gas ethylene, and the commercial application of this synthesis did not occur until 75 years later, in 1929, when ethylene produced from natural gas was first converted into ethyl alcohol on a practical scale (84). 

T thylene chemistry encompasses such a broad scope that this discussion must be limited to new developments which have industrial or commercial significance. Therefore, only recent developments related to the production of heavy organic chemicals (petrochemicals) from ethylene are considered. 

The Wacker process, the oxidation of ethylene to acetaldehyde, lost its original importance over the past 30 years. While at the beginning more than 40 factories with a total capacity of more than 2 million tons of acetaldehyde per year were installed, acetaldehyde as an industrial intermediate was replaced successively by other processes. For example, compounds such as butyraldehyde/butanol are produced by the oxo process from propylene, and acetic acid by the Monsanto process from methanol and CO or by direct oxidation of ethane. The way via acetaldehyde to these products is dependent on the price of ethylene. Petrochemical ethylene from cracking processes became considerably more expensive during these years. Thus, only few factories would be necessary to meet the demand for other derivatives of acetaldehyde such as alkyl amines, pyridines, glyoxal, and pentaerythritol. 

Almost three thousand organic chemical products are currently derived from petrochemical sources. The commercial syntheses for all these products, however, can be traced back to one of six logical starting points. Consequently, this chapter has been subdivided according to the six major raw material sources chemicals derived from methane, those from ethylene, those from propylene, those from C s , those from higher aliphatics, and those from the aromatics. 

Fig. 22.12. Production of ethylene glycols from ethylene oxide. (1) Feed tank containing ethylene oxide and water (2) hydration reaction (3, 4, 5) multiple stage evaporator (6) light ends column (7, 8) vacuum distillation towers. (Hydrocarbon Processing, Petrochemicals Handbook, A/ov. 7939. p. 702. Copyright Guif Pub fishing Company and reproduced by perrriissior of the copyright owner.)...

It is also one of China s largest PVC producers. The company has annual capacities of 120 000 tonnes of LLDPE, 140 tonnes LDPE, 140 000 tonnes of HDPE, 70 000 tonnes of PP, 36 000 tonnes of PS and PVC recently expanded to 600 000 tonnes. Qilu has also expanded its annual ethylene capacity from 450 000 tonnes to 600 000 tonnes. Major products include ethylene, propylene, HDPE, LDPE, LLDPE, PVC, PP, hydrochloric acid, caustic soda, sulphur, commercial liquefied chlorine, ammonia, commercial liquid ammonia, urea, butadiene, pure benzene, toluene, p-xylene, styrene, refined methanol, butanol, octanol, maleic anhydride, phthalic anhydride, catalysts for petrochemical products, catalysts for natural gas one-stage reforming, other catalysts, dibutyl phthalate and dioctyl phthalate. 

There are little or no olefins in crude oil or straight run (direct from crude distillation) products but they are found in refining products, particularly in the fractions coming from conversion of heavy fractions whether or not these processes are thermal or catalytic. The first few compounds of this family are very important raw materials for the petrochemical Industry e.g., ethylene, propylene, and butenes. 

Properly speaking, steam cracking is not a refining process. A key petrochemical process, it has the purpose of producing ethylene, propylene, butadiene, butenes and aromatics (BTX) mainly from light fractions of crude oil (LPG, naphthas), but also from heavy fractions hydrotreated or not (paraffinic vacuum distillates, residue from hydrocracking HOC). 

Ethylene is the cornerstone of the world s mam moth petrochemical industry and is produced in vast quantities In a typical year the amount of ethylene produced in the United States (5 x 10 ° lb) exceeds the combined weight of all of its people In one process ethane from natural gas is heated to bring about its dissociation into ethylene and hydrogen... 

It is convenient to divide the petrochemical industry into two general sectors (/) olefins and (2) aromatics and their respective derivatives. Olefins ate straight- or branched-chain unsaturated hydrocarbons, the most important being ethylene (qv), [74-85-1] propjiene (qv) [115-07-17, and butadiene (qv) [106-99-0J. Aromatics are cycHc unsaturated hydrocarbons, the most important being benzene (qv) [71-43-2] toluene (qv) [108-88-3] p- s.y en.e [106-42-3] and (9-xylene [95-47-5] (see Xylenes and ethylbenzene) There are two other large-volume petrochemicals that do not fall easily into either of these two categories ammonia (qv) [7664-41-7] and methanol (qv) [67-56-1]. These two products ate derived primarily from methane [74-82-8] (natural gas) (see Hydrocarbons, c -c ). 

Because oil and gas ate not renewable resources, at some point in time alternative feedstocks will become attractive however, this point appears to be fat in the future. Of the alternatives, only biomass is a renewable resource (see Fuels frombiomass). The only chemical produced from biomass in commercial quantities at the present time is ethanol by fermentation. The cost of ethanol from biomass is not yet competitive with synthetically produced ethanol from ethylene. Ethanol (qv) can be converted into a number of petrochemical derivatives and could become a significant source. 

World Petrochemicals Program, Ethylene and Derivatives 1992, Vol. 5, private report from SRI International, Menlo Park, Calif., Jan. 1992, pp. UNlT-15 to UNIT-20. 

In general, when the product is a fraction from cmde oil that includes a large number of individual hydrocarbons, the fraction is classified as a refined product. Examples of refined products are gasoline, diesel fuel, heating oils, lubricants, waxes, asphalt, and coke. In contrast, when the product is limited to, perhaps, one or two specific hydrocarbons of high purity, the fraction is classified as a petrochemical product. Examples of petrochemicals are ethylene (qv), propylene (qv), benzene (qv), toluene, and xylene (see Btx processing). 

Aliphatics. Methane, obtained from cmde oil or natural gas, or as a product from various conversion (cracking) processes, is an important source of raw materials for aliphatic petrochemicals (Fig. 10) (see Hydrocarbons). Ethane, also available from natural gas and cracking processes, is an important source of ethylene, which, in turn, provides more valuable routes to petrochemical products (Fig. 11). 

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. 

Most refinery/petrochemical processes produce ethylene that contains trace amounts of acetylene, which is difficult to remove even with cryogenic distillation. Frequently it is necessary to lower the acetylene concentration from several hundreds ppm to < 10 ppm in order to avoid poisoning catalysts used in subsequent ethylene consuming processes, such as polymeri2ation to polyethylene. This can be accompHshed with catalytic hydrogenation according to the equation. 

Ethanol has been used in the United States to a considerable extent as an antifreeze but it has largely been replaced for such use by ethylene glycol. The use of fermentation alcohol in automotive fuel has been discussed above. Several tropical countries consider ethanol, produced from regenerable resources, an attractive petrochemical feedstock. 

O. Winter, "Ethylene from Ethanol," paper presented at First Brafilian Petrochemical Congress, Rio de Janeiro, Nov. 7—12,1976. 

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