Feedstock for ethylene production

As indicated in Table 4, large-scale recovery of natural gas Hquid (NGL) occurs in relatively few countries. This recovery is almost always associated with the production of ethylene (qv) by thermal cracking. Some propane also is used for cracking, but most of it is used as LPG, which usually contains butanes as well. Propane and ethane also are produced in significant amounts as by-products, along with methane, in various refinery processes, eg, catalytic cracking, cmde distillation, etc (see Petroleum). They either are burned as refinery fuel or are processed to produce LPG and/or cracking feedstock for ethylene production. 

Production of maleic anhydride by oxidation of / -butane represents one of butane s largest markets. Butane and LPG are also used as feedstocks for ethylene production by thermal cracking. A relatively new use for butane of growing importance is isomerization to isobutane, followed by dehydrogenation to isobutylene for use in MTBE synthesis. Smaller chemical uses include production of acetic acid and by-products. Methyl ethyl ketone (MEK) is the principal by-product, though small amounts of formic, propionic, and butyric acid are also produced. / -Butane is also used as a solvent in Hquid—Hquid extraction of heavy oils in a deasphalting process. 

The main gas feedstock for ethylene production is ethane. Propane and butane or their mixture, LPG, are also used, but to a lesser extent. They... 

In the past, natural gas liquids - ethane, propane and butane -were the favoured feedstock for ethylene production. Propylene was extracted from the off-gas of some of the world s largest oil refineries in the same region. In recent times, naphtha crackers and flexible fiiel crackers have been built (the favoured approach in the Far East and Europe). However, as the following Figure 1.2 illustrates, natural gas liquids (ethane, propane and butane) aeeount for the major portion of the ethylene feedstoek. 

Why are the prices of coproducts depressed where naphtha and gas oil are the primary feedstocks for ethylene production ... 

Of the more than 30 billion pounds of ethylene consumed in the United States in 1980, over IIZ was used in the production of ethylene dichloride/vinyl chloride monomer and vinyl acetate. The major feedstock for ethylene production is ethane (47%), with other major feedstocks being gas oil, naphtha, and propane. 

Almost all raw materials for Japan s chemical industries come from overseas sources. The largest among them is petrochemical feedstocks. In 1990, 97.5% of the feedstock for ethylene production was naphtha, while the remaining 2.5% was LPG. 72.5% of the naphtha was imported from overseas sources, out of which more than 70% came from the Middle East region. An extremely high naphtha ratio in the feedstock structure and its high dependence on the overseas sources constitute our concern for the future. 

An early source of glycols was from hydrogenation of sugars obtained from formaldehyde condensation (18,19). Selectivities to ethylene glycol were low with a number of other glycols and polyols produced. Biomass continues to be evaluated as a feedstock for glycol production (20). 

Coal, considered a soHd hydrocarbon with a generic formula of CHq g, was explored by numerous workers (24—31) as a feedstock for the production of acetylene. Initially, the motivation for this work was to expand the market for the use of coal in the chemical process industry, and later when it was projected that the cost of ethylene would increase appreciably if pretroleum resources were depleted or constrained. 

Since the bulk of butadiene is recovered from steam crackers, its economics is very sensitive to the selection of feedstocks, operating conditions, and demand patterns. Butadiene supply and, ultimately, its price are strongly influenced by the demand for ethylene, the primary product from steam cracking. Currently there is a worldwide surplus of butadiene. Announcements of a number of new ethylene plants will likely result in additional butadiene production, more than enough to meet worldwide demand for polymers and other chemicals. When butadiene is in excess supply, ethylene manufacturers can recycle the butadiene as a feedstock for ethylene manufacture. 

Acetaldehyde. Until the early 1970s, the maia use of iadustrial ethanol was for the production of acetaldehyde [75-07-0]. By 1977, the ethanol route to acetaldehyde had largely been phased out ia the United States as ethylene and ethane became the preferred feedstocks for acetaldehyde production (286—304). Acetaldehyde usage itself has also changed two primary derivatives of acetaldehyde, acetic acid, and butanol, are now produced from feedstocks other than acetaldehyde. Acetaldehyde is stiU produced from ethanol ia India. 

Chemicals directly based on propane are few, although as mentioned, propane and LPG are important feedstocks for the production of olefins. Chapter 6 discusses a new process recently developed for the dehydrogenation of propane to propylene for petrochemical use. Propylene has always been obtained as a coproduct with ethylene from steam cracking processes. Chapter 6 also discusses the production of aromatics from LPG through the Cyclar process. ... 

Liquid feedstocks for olefin production are light naphtha, full range naphtha, reformer raffinate, atmospheric gas oil, vacuum gas oil, residues, and crude oils. The ratio of olefins produced from steam cracking of these feeds depends mainly on the feed type and, to a lesser extent, on the operation variables. For example, steam cracking light naphtha produces about twice the amount of ethylene obtained from steam cracking vacuum gas oil under nearly similar conditions. Liquid feeds are usually... 

LAB is derived exclusively from petroleum- or natural gas-based feedstocks. Thus, it is referred to as a petrochemical (or synthetic) surfactant intermediate. Feedstocks for LAB production are generally paraffins (carbon chain length in the range of C8-C14) derived from kerosene and benzene. Internal olefins derived from ethylene are sometimes used in place of paraffins. 

These processes are specifically designed for ethylene production but they also yield C4 hydrocarbons as coproducts. The amount of C4 compounds produced depends on the feedstock, the cracking method, and cracking severity. Steam cracking of naphtha provides better yields than does catalytic cracking of gas oil. With more severe steam cracking both butenes and overall C4 productions decrease, whereas the relative amount of 1,3-butadiene increases. Overall C4 yields of 4-6% may be achieved. 

Natural gas liquids represent a significant source of feedstocks for the production of important chemical building blocks that form the basis for many commercial and industrial products. Ethylene (qv) is produced by steam-cracking the ethane and propane fractions obtained from natural gas, and the butane fraction can be catalytically dehydrogenated to yield 1,3-butadiene, a compound used in the preparation of many polymers (see Butadiene). The -butane fraction can also be used as a feedstock in the manufacture of MTBE. 

Even (hough there are few direct end-uses foe ethylene, it is probably the most important petrochemical feedstock, both in terms of quantities used and economic value. Ethylene is the feedstock for ethylene oxide, ethylbenzene, ethyl chloride, elhylene dichloride, ethyl alcohol, and polyethylene, most of which, in turn, are used to produce hundreds of other end-products. Most elhylene is produced by sleam cracking of ethane or propane. 

Fuel uses are a potential application which would require substantial volumes of methanol. As mentioned earlier they are reviewed in the following chapter. A fuel related potential use of methanol is as a replacement for water used to carry coal in pipelines. Methanol is being considered for this use because it would eliminate a demand for water, which is often scarce in areas where coal is mined, and methanol could be burned as a fuel with the coal at its destination. Methanol has also been touted as a good feedstock for gases used in the direct reduction of iron ore. If this use of methanol is realized, it will not be before the mid to late 1980 s. Other potential new uses for methanol include a feedstock for ethylene and propylene production (9) and a feedstock for gasoline production (10). 

There is often no single feedstock choice, since feedstock costs frequently vary erratically over a period of several years. A general guide to the influence of feedstock on capital investment of the entire pyrolysis for ethylene production is shown in Fig. 7. Net raw material costs for an ethylene plant often account for about 50-60% of the production costs, depending on whether the feedstock is a light material such as ethane or a heavier material such as naphtha. 

In the United States, the preferred feedstocks for the production of ethylene and propylene continue to be lighter hydrocarbons such as ethane, propane, and their... 

Ethane (and also propane and butane) is used as a feedstock for the production of ethylene. For this role it competes with naphtha which has a direct relationship with oil price. 

Carbon monoxide is used in industries as a feedstock for the production of methanol, acrylates, phosgene, and ethylene. It is also used in metallurgy applications and in industrial fuels. A major source of carbon monoxide is the incomplete combustion of carbon-containing materials. 

The second group includes some of the processes used for ethylene production, particularly those using naphtha or gas oil as feedstocks, which may also produce large amounts of BTX. The conditions used (temperature, pressure, feedstock ratios, etc.) to operate these processes provide some flexibility to alter the product distribution slightly in response to the distribution of the demand. 

As in any form of mediation, the result of this frequently complex process is often a compromise. The raw material may be scarcer or dearer than is desirable or, more often, the final product has to struggle to become profitable, as was the case with Buna S. In such cases, the industrial chemist may look for a more suitable raw material, as when Reppe strove to replace fermentation-based ethanol with middle oil as the feedstock for ethylene. Alternatively, he may retain the original starting material, but search for a reaction with a higher yield (the key to Buna ), or one with a more desirable outcome, such as the Reppe process, which conserved the dearly won triple bond. The Reppe process also featured the partial replacement of an expensive feedstock, since one of the costly acetylene molecules was replaced by two cheap formaldehyde molecules. It is thus clear that Reppe s work was strongly influenced by feedstock considerations. 

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