Hydrocarbons acrylonitrile production

These processes use expensive C2 hydrocarbons as feedstocks and thus have higher overall acrylonitrile production costs compared to the propylene-based process technology. The last commercial plants using these process technologies were shut down by 1970. 

Although industrial interest in the synthesis of acetonitrile directly from C2 hydrocarbons is currently limited, with acetonitrile being mainly produced as a byproduct in acrylonitrile production, there are a number of indications regarding the future need of direct production of acetonitrile by C2 hydrocarbon (ethane, in particular) ammoxidation. In fact, acetonitrile is used as a solvent and also as an intermediate in the production of many chemicals, ranging from pesticides to perfumes. Production trends for acetonitrile generally follow those of acrylonitrile, but the growth rate for acetonitrile use is higher than that of acrylonitrile. The four... 

A second commercial route to acrylonitrile used by DuPont, American Cyanamid, and Monsanto was the catalytic addition of HCN to acetylene (46). The reaction occurs by passing HCN and a 10 1 excess of acetylene into dilute HCl at 80° C in the presence of cuprous chloride as the catalyst. These processes use expensive C2 hydrocarbons as feedstocks and thus have higher overall acrylonitrile production costs compared to the propylene-based process technology. The last commercial plants using these process technologies were shutdown by 1970. 

Amm oxida tion, a vapor-phase reaction of hydrocarbon with ammonia and oxygen (air) (eq. 2), can be used to produce hydrogen cyanide (HCN), acrylonitrile, acetonitrile (as a by-product of acrylonitrile manufacture), methacrylonitrile, hen onitrile, and toluinitnles from methane, propylene, butylene, toluene, and xylenes, respectively (4). 

This combination of monomers is unique in that the two are very different chemically, and in thek character in a polymer. Polybutadiene homopolymer has a low glass-transition temperature, remaining mbbery as low as —85° C, and is a very nonpolar substance with Htde resistance to hydrocarbon fluids such as oil or gasoline. Polyacrylonitrile, on the other hand, has a glass temperature of about 110°C, and is very polar and resistant to hydrocarbon fluids (see Acrylonitrile polymers). As a result, copolymerization of the two monomers at different ratios provides a wide choice of combinations of properties. In addition to providing the mbbery nature to the copolymer, butadiene also provides residual unsaturation, both in the main chain in the case of 1,4, or in a side chain in the case of 1,2 polymerization. This residual unsaturation is useful as a cure site for vulcanization by sulfur or by peroxides, but is also a weak point for chemical attack, such as oxidation, especially at elevated temperatures. As a result, all commercial NBR products contain small amounts ( 0.5-2.5%) of antioxidant to protect the polymer during its manufacture, storage, and use. 

Uses Production of isooctane, butyl rubber, polyisobutene resins, high octane aviation fuels, tert-butyl chloride, ferf-butyl methacrylates copolymer resins with acrylonitrile, butadiene, and other unsaturated hydrocarbons organic synthesis. 

The worldwide demand for propylene is expected to increase, primarily driven by the market demand for products made from polypropylene, acrylonitrile, and phenolic resins. Today about 70% of the global propylene is produced by steam cracking using light hydrocarbons as feedstock, and the rest is mostly recovered from the FCC process. 

Propylene is a colorless, flammable gas that follows ethylene as the second simplest alkene hydrocarbon. It has an odor similar to garlic and has wide use in the chemical industry as an intermediate in the synthesis of other derivatives such as polypropylene, propylene oxide, isopropyl alcohol, acetone, and acrylonitrile. The production of propylene is similar to ethylene and is obtained through steam cracking of hydrocarbon feedstocks. Steam cracking is a process used to break molecules into smaller molecules by injecting the catalysts with steam. 

In view of the many studies that have been made to develop practical methods of producing acetylene from natural gas hydrocarbons, it is significant that several concerns are reported 17) to have plans actively under way or under study for initiating the large scale commercial production of acetylene from petroleum feed stocks, some of which is to be used directly for the production of acrylonitrile. 

Acrylonitrile is obtained from propylene and ammonia. 1,3-Butadiene is a petroleum hydrocarbon obtained from the C4 fraction of steam cracking. An overview on the issues of the production of butadiene is given in the literature (5). Styrene monomer is made by the dehydrogenation of ethylbenzene, which is obtained by the Friedel-Crafts reaction of ethylene and benzene. 

Catalytic oxidation is the most important technology for the conversion of hydrocarbon feedstocks (olefins, aromatics and alkanes) to a variety of bulk industrial chemicals.1 In general, two types of processes are used heterogeneous, gas phase oxidation and homogeneous liquid phase oxidation. The former tend to involve supported metal or metal oxide catalysts e.g. in tne manufacture of ethylene oxide, acrylonitrile and maleic anhydride whilst the latter generally employ dissolved metal salts, e.g. in the production of terephthalic acid, benzoic acid, acetic acid, phenol and propylene oxide. 

Sugino 448 obtained the crossed coupling product 147 in 70% yield and current efficiency on coelectrolysis of acrylonitrile and acetone in aqueous sulfuric acid at a mercury cathode. At lead and cadmium mixed couplingwas suppressed and hydrocarbon formation increased. With methyl ethyl ketone and diethyl ketone crossed coupling was achieved in 60% and 30% yield, respectively. With acetone and maleic acid 10% terebic acid (148) was obtained. Tomilov 449- coupled acetone and acrylic acid in 95% yield (70% current efficiency) to... 

Further evidence for the hypothesis was found in the patent describing the isoprene—acrylonitrile—zinc chloride system (23). On adding a four-fold excess of isoprene to an equimolar mixture of acrylonitrile and zinc chloride, in the absence of a free radical catalyst, an exothermic reaction occurs after approximately 30 minutes. The recovered polymer is insoluble in hydrocarbons, chloroform, and acetone. This eliminates polyisoprene and the alternating copolymer. The yield of product is 12%, calculated a polyacrylonitrile, compared with the 16.8% yield of copolymer obtained when excess acrylonitrile and a free radical catalyst are used. 

Thus, in ammonia synthesis, mixed oxide base catalysts allowed new progress towards operating conditions (lower pressure) approaching optimal thermodynamic conditions. Catalytic systems of the same type, with high weight productivity, achieved a decrease of up to 35 per cent in the size of the reactor for the synthesis of acrylonitrile by ammoxidation. Also worth mentioning is the vast development enjoyed as catalysis by artificial zeolites (molecular sieves). Their use as a precious metal support, or as a substitute for conventional silico-aluminaies. led to catalytic systems with much higher activity and selectivity in aromatic hydrocarbon conversion processes (xylene isomerization, toluene dismutation), in benzene alkylation, and even in the oxychlorination of ethane to vinyl chloride. 

The activation of light saturated hydrocarbons becomes increasingly more difficult as the molecules become smaller, with methane reactions being the most difficult to control. On the other hand, the occurrence of non-catalysed gas phase oxidation makes selectivity control very complicted. This is a problem common to almost all oxidations, unless one of the products is extremely stable examples are unsaturated nitriles (e.g. acrylonitrile in the ammoxidation of propane) or maleic anhydride (in the oxidation of butane). There is a parallel trend in the changes of reactivity with molecular weight in catalytic and non catalytic (gas phase) oxidation. The challenge to catalysis to achieve selective reactions at lower temperature is thus equally important for all light hydrocarbons. 

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