As feedstock

Comparing the overall concentrations of these different carbons designated generally as structural patterns , measured before and after a process such as FCC or hydrocracking (see Chapter 10), enables the conversion to be monitored the simple knowledge of the percentage of condensed aromatic carbon of a feedstock gives an indication of its tendency to form coke. 

Table 10.7 shows the typical composition of a feedstock to an etherification unit and the average product properties obtained. 

Equations (7.40) and (7.41) suggest a second method, in addition to the copolymer composition equation, for the experimental determination of reactivity ratios. If the average sequence length can be determined for a feedstock of known composition, then rj and r2 can be evaluated. We shall return to this possibility in the next section. In anticipation of applying this idea, let us review the assumptions and limitation to which Eqs. (7.40) and (7.41) are subject ... 

The copolymer composition equation relates the r s to either the ratio [Eq. (7.15)] or the mole fraction [Eq. (7.18)] of the monomers in the feedstock and repeat units in the copolymer. To use this equation to evaluate rj and V2, the composition of a copolymer resulting from a feedstock of known composition must be measured. The composition of the feedstock itself must be known also, but we assume this poses no problems. The copolymer specimen must be obtained by proper sampling procedures, and purified of extraneous materials. Remember that monomers, initiators, and possibly solvents are involved in these reactions also, even though we have been focusing attention on the copolymer alone. The proportions of the two kinds of repeat unit in the copolymer is then determined by either chemical or physical methods. Elemental analysis has been the chemical method most widely used, although analysis for functional groups is also employed. 

The spectrum shown in Fig. 7.5 shows the appropriate portion of the spectrum for a copolymer prepared from a feedstock for which fj = 0.153 It turns out that each polyene produces a set of three bands The dyad is identified with the peaks at X = 298, 312, and 327 nm the triad, with X = 347 367, and 388 nm and the tetrad with X = 412 and 437 nm. Apparently one of the tetrad bands overlaps that of the triad and is not resolved. Likewise only one band (at 473 nm) is observed for the pentad. The identification ol these features can be confirmed with model compounds and the location and relative intensities of the peaks has been shown to be independent of copolymer composition. 

Adiponitrile is made commercially by several different processes utilizing different feedstocks. The original process, utilizing adipic acid (qv) as a feedstock, was first commercialized by DuPont in the late 1930s and was the basis for a number of adiponitrile plants. However, the adipic acid process was abandoned by DuPont in favor of two processes based on butadiene (qv). During the 1960s, Monsanto and Asahi developed routes to adiponitrile by the electrodimerization of acrylonitrile (qv). 

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. 

Approximately 50—55% of the product from a coal-tar refinery is pitch and another 30% is creosote. The remaining 15—20% is the chemical oil, about half of which is naphthalene. Creosote is used as a feedstock for production of carbon black and as a wood preservative. Because of modifications to modem coking processes, tar acids such as phenol and cresyUc acids are contained in coal tar in lower quantity than in the past. To achieve economies of scale, these tar acids are removed from cmde coal tar with a caustic wash and sent to a central processing plant where materials from a number of refiners are combined for recovery. 

The principal secondary variable that influences yields of gaseous products from petroleum feedstocks of various types is the aromatic content of the feedstock. For example, a feedstock of a given H/C (C/H) ratio that contains a large proportion of aromatic species is more likely to produce a larger proportion of Hquid products and elemental carbon than a feedstock that is predominantly paraffinic (5). 

Natural gas Hquids represent a significant source of feedstocks for the production of important chemical building blocks that form the basis for many commercial and iadustrial products. Ethyleae (qv) is produced by steam-crackiag the ethane and propane fractions obtained from natural gas, and the butane fraction can be catalyticaHy dehydrogenated to yield 1,3-butadiene, a compound used ia the preparatioa of many polymers (see Butadiene). The / -butane fractioa can also be used as a feedstock ia the manufacture of MTBE. 

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. 

Much more important is the hydrogenation product of butynediol, 1,4-butanediol [110-63-4]. The intermediate 2-butene-l,4-diol is also commercially available but has found few uses. 1,4-Butanediol, however, is used widely in polyurethanes and is of increasing interest for the preparation of thermoplastic polyesters, especially the terephthalate. Butanediol is also used as the starting material for a further series of chemicals including tetrahydrofuran, y-butyrolactone, 2-pyrrohdinone, A/-methylpyrrohdinone, and A/-vinylpyrrohdinone (see Acetylene-DERIVED chemicals). The 1,4-butanediol market essentially represents the only growing demand for acetylene as a feedstock. This demand is reported (34) as growing from 54,000 metric tons of acetylene in 1989 to a projected level of 88,000 metric tons in 1994. 

Ethane has been investigated as a feedstock for production of vinyl chloride, at scales up to a large pilot plant, but nearly all vinyl chloride is stiH produced from ethylene. 

Other uses include use as a reaction and extraction solvent in pharmaceutical production as an intermediate for the preparation of catalysts, antioxidants (qv), and perfumes and as a feedstock in the production of methyl isopropenyl ketone, 2,3-butanedione, and methyl ethyl ketone peroxide. Concern has also arisen at the large volume of exported MEK which has been covertly diverted and used to process cocaine in Latin American countries... 

Process Technology Evolution. Maleic anhydride was first commercially produced in the early 1930s by the vapor-phase oxidation of benzene [71-43-2]. The use of benzene as a feedstock for the production of maleic anhydride was dominant in the world market well into the 1980s. Several processes have been used for the production of maleic anhydride from benzene with the most common one from Scientific Design. Small amounts of maleic acid are produced as a by-product in production of phthaHc anhydride [85-44-9]. This can be converted to either maleic anhydride or fumaric acid. Benzene, although easily oxidized to maleic anhydride with high selectivity, is an inherently inefficient feedstock since two excess carbon atoms are present in the raw material. Various compounds have been evaluated as raw material substitutes for benzene in production of maleic anhydride. Fixed- and fluid-bed processes for production of maleic anhydride from the butenes present in mixed streams have been practiced commercially. None of these... 

MMA and MAA can be produced from ethylene [74-85-1/ as a feedstock via propanol, propionic acid, or methyl propionate as intermediates. Propanal may be prepared by hydroformylation of ethylene over cobalt or rhodium catalysts. The propanal then reacts in the Hquid phase with formaldehyde in the... 

The high cost of coal handling and preparation and treatment of effluents, compounded by continuing low prices for cmde oil and natural gas, has precluded significant exploitation of coal as a feedstock for methanol. A small amount of methanol is made from coal in South Africa for local strategic reasons. Tennessee Eastman operates a 195,000-t/yr methanol plant in Tennessee based on the Texaco coal gasification process to make the methyl acetate intermediate for acetic anhydride production (15). 

Large quantities of evaporated milk are used to manufacture ice cream, bakery products, and confectionery products (see Bakery processes and LEAVENING agents). When used for manufacturing other foods, evaporated milk is not sterilized, but placed in bulk containers, refrigerated, and used fresh. This product is caHed condensed milk. Skimmed milk may be used as a feedstock to produce evaporated skimmed milk. The moisture content of other Hquid milk products can be reduced by evaporation to produce condensed whey, condensed buttermilk, and concentrated sour milk. 

By-Products From Milk. Milk is a source for numerous by-products resulting from the separation or alteration of the components. These components may be used in other so-called nondairy manufactured foods, dietary foods, pharmaceuticals (qv), and as a feedstock for numerous industries, such as casein for glue. 

In addition to these principal commercial uses of molybdenum catalysts, there is great research interest in molybdenum oxides, often supported on siHca, ie, MoO —Si02, as partial oxidation catalysts for such processes as methane-to-methanol or methane-to-formaldehyde (80). Both O2 and N2O have been used as oxidants, and photochemical activation of the MoO catalyst has been reported (81). The research is driven by the increased use of natural gas as a feedstock for Hquid fuels and chemicals (82). Various heteropolymolybdates (83), MoO.-containing ultrastable Y-zeoHtes (84), and certain mixed metal molybdates, eg, MnMoO Ee2(MoO)2, photoactivated CuMoO, and ZnMoO, have also been studied as partial oxidation catalysts for methane conversion to methanol or formaldehyde (80) and for the oxidation of C-4-hydrocarbons to maleic anhydride (85). Heteropolymolybdates have also been shown to effect ethylene (qv) conversion to acetaldehyde (qv) in a possible replacement for the Wacker process. 

A circulating fluidized-bed boiler, using raw shale oil as a feedstock, is being used to supply process heat for the phosphate operations and to operate a 100-MW power plant. Scale-up in the 1990s should increase the electric power generation to 1000 MW (71). 

Fig. 2. LP Oxo gas recycle flow scheme A, feedstock pretreatment B, reactor C, catalyst preparation and treatment systems D, condenser E, separator F,...

Chemical Processing. The use of oxygen in large-volume chemical and petrochemical manufacture is weU-estabHshed as a result of advantages 3) and 4). Most oxidation reactions are catalytic many begin with a feedstock initially made catalyticaHy from methane or natural gas. 

U.S. capacity is 455 x 10 t among five producers, as shown in Table 9 (33). All U.S. producers use o-xylene as a feedstock, although Koppers can switch to coal-tar naphthalene. Europe has 20 producers operating 25 plants, 18 of which use o-xylene. Demand growth in North America has averaged less than 3% annually since 1981. Prices in 1992 were 0.77—0.95/kg for molten, and 0.82—1.01/kg for flake (33). 

When natural gas is used as a feedstock to produce thermal blacks, the reaction is endothermic. In order to maintain the reaction, the reactor has to be kept at about 1300°C. When acetylene is used as the feedstock to produce acetylene blacks, the reaction is exothermic, and the reaction can be mn at a temperature between 800 and 1000°C. 

The first commercial PPS process by Phillips synthesized a low molecular weight linear PPS that had modest mechanical properties. It was usehil in coatings and as a feedstock for a variety of cured injection-molding resins. The Phillips process for preparing low molecular weight linear PPS consists of a series of nucleophilic displacement reactions that have differing reactivities (26). 

Feed Ga.s Purifica.tion. Because nickel-based reforming catalysts are quite sensitive to sulfur, halogen, and heavy metal poisons which may be found ia natural gas, a feedstock purification system is normally required. Sulfur compounds, ia both organic and inorganic forms, are the most common... 

Chemical. The use of isopropyl alcohol as a feedstock for the production of acetone is expected to remain stable, as the dominant process for acetone is cumene oxidation. Isopropyl alcohol is also consumed in the production of other chemicals such as methyl isobutyl ketone, methyl isobutyl carbinol [108-11-2] isopropjlamine, and isopropyl acetate. The use of diisopropyl ether as a fuel ether may become a significant oudet for isopropyl alcohol. 

The more modem processes adopted in the United Kingdom and some European plants (20) are also based on crystallization of the primary naphthalene oil, which is diluted with lower crystallizing material to give a feedstock crystallizing point at 55°C. This material is cooled in closed, stirred... 

Timber-preservation creosotes are mainly blends of wash oil, strained anthracene oil, and heavy oil having minor amounts of oils boiling in the 200—250°C range. Coal-tar creosote is also a feedstock for carbon black manufacture (see Carbon, carbon black). Almost any blend of tar oils is suitable for this purpose, but the heavier oils are preferred. Other smaller markets for creosote were for fluxing coal tar, pitch, and bitumen in the manufacture of road binders and for the production of horticultural winter wash oils and disinfectant emulsions. 

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