Feedstock shift

The reformate stream also contains the largest concentration of benzene found in the gasoline pool (Table 7 Keesom 1991). Since light reformate is a major source of benzene in the gasoline pool e reduction in benzene requires not only a reduction in reformer severity but also feedstock shifts and additional downstream processing. Some of these processing steps include ... 

Although the rapid cost increases and shortages of petroleum-based feedstocks forecast a decade ago have yet to materialize, shift to natural gas or coal may become necessary in the new century. Under such conditions, it is possible that acrylate manufacture via acetylene, as described above, could again become attractive. It appears that condensation of formaldehyde with acetic acid might be preferred. A coal gasification complex readily provides all of the necessary intermediates for manufacture of acrylates (92). 

If a linear mbber is used as a feedstock for the mass process (85), the mbber becomes insoluble in the mixture of monomers and SAN polymer which is formed in the reactors, and discrete mbber particles are formed. This is referred to as phase inversion since the continuous phase shifts from mbber to SAN. Grafting of some of the SAN onto the mbber particles occurs as in the emulsion process. Typically, the mass-produced mbber particles are larger (0.5 to 5 llm) than those of emulsion-based ABS (0.1 to 1 llm) and contain much larger internal occlusions of SAN polymer. The reaction recipe can include polymerization initiators, chain-transfer agents, and other additives. Diluents are sometimes used to reduce the viscosity of the monomer and polymer mixture to faciUtate processing at high conversion. The product from the reactor system is devolatilized to remove the unreacted monomers and is then pelletized. Equipment used for devolatilization includes single- and twin-screw extmders, and flash and thin film evaporators. Unreacted monomers are recovered for recycle to the reactors to improve the process yield. 

These reactions show that the synthesis gas stoichiometry is dependent on both the nature of the feedstock as well as the generation process. Reactions 4 and 5, together with the water gas shift reaction 3, serve to independently determine the equiUbrium composition of the synthesis gas. 

Synthesis gas, a mixture of CO and o known as syngas, is produced for the oxo process by partial oxidation (eq. 2) or steam reforming (eq. 3) of a carbonaceous feedstock, typically methane or naphtha. The ratio of CO to may be adjusted by cofeeding carbon dioxide (qv), CO2, as illustrated in equation 4, the water gas shift reaction. 

Synthesis gas preparation consists of three steps ( /) feedstock conversion, (2) carbon monoxide conversion, and (2) gas purification. Table 4 gives the main processes for each of the feedstocks (qv) used. In each case, except for water electrolysis, concommitant to the reactions shown, the water-gas shift reaction occurs. 

Steam-Reforming Natural Gas. Natural gas is the single most common raw material for the manufacture of ammonia. A typical flow sheet for a high capacity single-train ammonia plant is iadicated ia Figure 12. The important process steps are feedstock purification, primary and secondary reforming, shift conversion, carbon dioxide removal, synthesis gas purification, ammonia synthesis, and recovery. 

Ammonia production from natural gas includes the following processes desulfurization of the feedstock primary and secondary reforming carbon monoxide shift conversion and removal of carbon dioxide, which can be used for urea manufacture methanation and ammonia synthesis. Catalysts used in the process may include cobalt, molybdenum, nickel, iron oxide/chromium oxide, copper oxide/zinc oxide, and iron. 

Since 1942, when the first FCC unit came onstream, numerous process and mechanical changes have been introduced. These changes improved the unit s reliability, allowed it to process heavier feedstocks, to operate at higher temperatures, and to shift the conversion to more valuable products. 

Approaches to the fundamental need to shift from fossil to renewable feedstocks for chemicals production wiU range from modifications to, and developments of, traditional chemical, engineering and biotechnological methods (that maybe implemented on a relatively short timescale, say, 10-15 years) to much more radical processes (such as direct capture of solar energy, through artificial photosynthesis), requiring longer time to implement (say 15-30 years). 

Using renewable and sustainable materials instead of non-renewables. For example, shifting from hydrocarbon to carbohydrate feedstocks. 

Other companies (e.g., Hoechst) have developed a slightly different process in which the water content is low in order to save CO feedstock. In the absence of water it turned out that the catalyst precipitates. Clearly, at low water concentrations the reduction of rhodium(III) back to rhodium(I) is much slower, but the formation of the trivalent rhodium species is reduced in the first place, because the HI content decreases with the water concentration. The water content is kept low by adding part of the methanol in the form of methyl acetate. Indeed, the shift reaction is now suppressed. Stabilization of the rhodium species and lowering of the HI content can be achieved by the addition of iodide salts. High reaction rates and low catalyst usage can be achieved at low reactor water concentration by the introduction of tertiary phosphine oxide additives.8 The kinetics of the title reaction with respect to [MeOH] change if H20 is used as a solvent instead of AcOH.9 Kinetic data for the Rh-catalyzed carbonylation of methanol have been critically analyzed. The discrepancy between the reaction rate constants is due to ignoring the effect of vapor-liquid equilibrium of the iodide promoter.10... 

Gasification coupled with water-gas shift is the most widely practiced process route for biomass to hydrogen. Thermal, steam, and partial oxidation gasification technologies are under development. Feedstocks include both dedicated crops and agricultural and forest product residues of hardwood, softwood, and herbaceous species. 

Direct and indirect costs are compared public and private costs are estimated at 3.5-4 times those for EPA in 1981. Among the former is loss of innovation. While several studies of this factor have been made for the industry, their reliability is questioned, due in part to lack of sound data prior to 1976. No mention was made of economic trends affecting corporate expenditures for research and development, or of trends in the maturation of industrial chemistry itself. Other indirect costs, such as concentration of manufacture within the industry, may result from costs of compliance, especially for smaller manufacturers. These factors were not compared with extrinsic factors, such as shifts in feedstock supply and commodity manufacture from the United States to other countries. 

Fischer-Tropsch synthesis requires a stochiometric H2 CO ratio of 2.1 1. If coal or biomass are used as feedstock, the raw syngas contains much less hydrogen than needed. Hence, CO is reacted with water to form C02 and hydrogen in the shift reactor. As the C02 cannot be used in the Fischer-Tropsch synthesis, part of the carbon for fuel production is lost in this process. If external hydrogen is added to increase the H2 CO ratio, the carbon of the coal or biomass is more effectively used and the hydrocarbon product yield is improved. 

In hydrogen fuel supply schemes using coal as feedstock, the same gasification processes as for the production of CTL fuels are applied. The synthesis gas from the gasifier is then converted to hydrogen by CO shift and pressure-swing adsorption (see Table 7.20). 

The formation of prepolymer can also be achieved by transesterification of dimethyl terephthalate (DMT) with EG, releasing the by-product methanol. High-purity DMT is easily obtained by distillation and in the early years of PET production, all processes were based on this feedstock. During the late 1960s, highly purified TPA was produced for the first time on an industrial scale by re-crystallization. Since then, more and more processes have shifted to TPA as the feedstock and today more than 70 % of global PET production is based on TPA. The TPA-based PET production saves approximately 8 % of total capital investment and 15% of feedstock cost (Figure 2.1). 

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