Oxychlorination of ethane

Anyway, ethane can be converted to vinyl chloride monomer by passing it over a Ziegler-Natta type catalyst at 850—900° F in the presence of chlorine and oxygen. In a single vessel, oxychlorination of ethane to vinyl chloride monomer takes place ... 

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. 

This process carries out the vapor phase oxychlorination of ethane, in the presence of oxygen or air enriched with oxygen, between 350 and 450°C, and between Oil and 10.10 Pa absolute. It employs a catalyst system based on silver doped by derivatives of manganese, cobalt or nickel, and possibly of rare earths (such as lanthanum), and which is employed in mass form or supported on a Y-type zeolite (offretite). 

In the future it might be possible to see the gas diffusion technology generating chlorine with energy consumption at 1500 kWh. The chlorine will be used in the direct chlorination of ethane to feed the vinyl chain. Side streams of HC1 will be used in oxychlorination where ethylene is available and this will use up by-product acid from isocyanates. Site integration will increase to benefit from economies of scale and optimise hydrogen chloride production. 

One of the most important challenges in the modern chemical industry is represented by the development of new processes aimed at the exploitation of alternative raw materials, in replacement of technologies that make use of building blocks derived from oil (olefins and aromatics). This has led to a scientific activity devoted to the valorization of natural gas components, through catalytic, environmentally benign processes of transformation (1). Examples include the direct exoenthalpic transformation of methane to methanol, DME or formaldehyde, the oxidation of ethane to acetic acid or its oxychlorination to vinyl chloride, the oxidation of propane to acrylic acid or its ammoxidation to acrylonitrile, the oxidation of isobutane to... 

It consists of three basic steps direct chlorination of ethylene to form 1,2-dichloro-ethane [Eq. (6.40)], cracking of 1,2-dichloroethane to vinyl chloride and HC1 [Eq. (6.41)], and oxychlorination of ethylene with HC1 [Eq. (6.42)] formed in the second step. The net reaction is the oxychlorination of ethylene to vinyl chloride [Eq. (6.43)] ... 

The technology profits from the extensive experience gained by the oxychlorination of ethylene, but is based on a completely different catalyst. The new process claims a cost reduction of about 30%, because the ethane price is about one third that of ethylene. 

A much smaller amount is produced by the thermal chlorination of ethane. This direct chlorination may be run in conjunction with another process, such as oxychlorination, which can use the byproduct HCI as feed. 

Oxychlorination of hydrocarbons refers to a chemical reaction in which oxygen and hydrogen chloride react with a hydrocarbon in the vapor phase over a supported copper chloride catalyst to produce a chlorinated hydrocarbon and water. The oxychlorination of ethylene to produce 1, 2-dichloroethane (commonly, ethylene dichloride (EDC)) is of the greatest commercial importance. EDC is the precurser for vinyl chloride monomer, which when polymerized to polyvinyl chloride (PVC), becomes one of the most conunonly used commercial plastics. The overall oxychlorination reaction of ethane is given by... 

Formation of the mixed cement-containing systems within the range of low copper concentrations with addition of alkali metal dopants as well as catalytical properties of these systems in the ethane oxidative chlorination process have been investigated. Based on the obtained data the efficient and stable copper-cement catalyst has been worked out. This catalyst will assist in the development of a new technology of the vinyl chloride production from ethane. The basic peirameters of the ethane oxychlorination process have been determined at 623-673K, time-on-stream 3-5s and reactant ratio of C2H6 HCI 02 = 1 2 1 the conversion of ethane is more than 90% and the total selectivity to ethylene and vinyl chloride is 85-90%. 

PVC), which is one of the most widely used commercial plastics. The overall oxychlorination reaction of ethane is given as follows ... 

Oxychlorination reactor feed purity can also contribute to by-product formation, although the problem usually is only with low levels of acetylene which are normally present in HCl from the EDC cracking process. Since any acetylene fed to the oxychlorination reactor will be converted to highly chlorinated C2 by-products, selective hydrogenation of this acetylene to ethylene and ethane is widely used as a preventive measure (78,98—102). 

If the production of vinyl chloride could be reduced to a single step, such as dkect chlorine substitution for hydrogen in ethylene or oxychlorination/cracking of ethylene to vinyl chloride, a major improvement over the traditional balanced process would be realized. The Hterature is filled with a variety of catalysts and processes for single-step manufacture of vinyl chloride (136—138). None has been commercialized because of the high temperatures, corrosive environments, and insufficient reaction selectivities so far encountered. Substitution of lower cost ethane or methane for ethylene in the manufacture of vinyl chloride has also been investigated. The Lummus-Transcat process (139), for instance, proposes a molten oxychlorination catalyst at 450—500°C to react ethane with chlorine to make vinyl chloride dkecfly. However, ethane conversion and selectivity to vinyl chloride are too low (30% and less than 40%, respectively) to make this process competitive. Numerous other catalysts and processes have been patented as weU, but none has been commercialized owing to problems with temperature, corrosion, and/or product selectivity (140—144). Because of the potential payback, however, this is a very active area of research. 

Commercialization of a new vinyl chloride process has been announced. Instead of the traditional three-step production (see Section 6.3.4), it is based on ethane oxy-chlorination using HC1, 02, and Cl2 carried out over a CuCl-based catalysts.285 Overchlorinated products are dehydrochlorinated and hydrogenated (together with overchlorinated alkenes) in separate reactors these product streams are then led back to the oxychlorination reactor. 

Finally, it is worthy to mention the advent of a new generation of technologies based on ethane oxychlorination, as commercialized by EVC International [10]. The process is described by the following global equation ... 

The development of this catalytic system made it necessary to investigate the formation process of mixed cement systems within the range of low copper concentrations and with addition of alkali dopants and determination of the correlation between properties of the obtained catalytical systems and their activity in the ethane oxychlorination process. 

From Ethane. Ethane is cheaper and more readily available than either ethylene or acetylene. The "Transcat" process involves cracking of a feedstock such as ethane to ethylene, which is chlorinated, oxychlorinated, and dehydrochlorinated simultaneously. Copper oxychloride acts as an oxygen carrier in this process and also functions in the recovery of HCl ... 

Oxychlorination-. In this method [147], ethylene and chlorine are reacted to form dichloro-ethane, and vinyl chloride monomer is prepared by thermal decomposition of dichloroethane in the presence of an appropriate catalyst hydrogen chloride is liberated as a by-product in this reaction. Hydrogen chloride is reacted with ethylene and oxygen to form dichloroethane. 

The production of many organic compounds requires the chlorination of feedstock chemicals (Table 3.3). This yields untreated wastewater that contains significant amounts of chlorinated methanes, ethanes, propanes, ethylenes, and propylenes. Other related processes such as chlorohydrina-tion and oxychlorination result in similar wastewater products. Furthermore, the use of vinyl chloride in the production of acrylic fibers and polyvinyl chloride resins yields chlorinated ethanes and ethylenes, whereas the production of epoxy resins results in the formation of dichloropropane and dichloropropylene through the use of epichlorohydrin (Wise and Fahrent-hold, 1981). 

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