Oxychlorination of ethylene

Oxychlorination of Ethylene. When compared with direct chlorination, the oxychlorination process is characterized by higher capital investment, higher operating costs, and slightly less pure EDC product. However, use of the oxychlorination process is dictated by the need to consume the HCl generated in EDC pyrolysis. 

In oxychlorination, ethylene reacts with dry HCl and either air or pure oxygen to produce EDC and water. Various commercial oxychlorination processes differ from one another to some extent because they were developed independentiy by several different vinyl chloride producers (78,83), but in each case the reaction is carried out in the vapor phase in either a fixed- or fluidized-bed reactor containing a modified Deacon catalyst. Unlike the Deacon process for chlorine production, oxychlorination of ethylene occurs readily at temperatures weU below those requited for HCl oxidation. 

When catalysts are used in a highly exothermic reaction, an active phase may be diluted with an inert material to help dissipate heat and moderate the reaction. This technique is practiced in the commercial oxychlorination of ethylene to dichloroethane, where an alumina-supported copper haUde catalyst is mixed with a low surface area inert diluent. 

Oxychlorination of Ethylene to Dichloroethane. Ethylene (qv) is converted to dichloroethane in very high yield in fixed-bed, multitubular reactors and fluid-bed reactors by reaction with oxygen and hydrogen chloride over potassium-promoted copper(II) chloride supported on high surface area, porous alumina (84) ... 

Oxychlorination of ethylene to dichloroethane is the first reaction performed in an integrated vinyl chloride plant. In the second stage, dichloroethane is cracked thermally over alumina to give vinyl chloride and hydrogen chloride. The hydrogen chloride produced is recycled back to the oxychlorination reactor. 

Dichloroethane, an important intermediate for vinyl chloride production, is produced by catalytic chlorination of ethylene in either vapor or Hquid phase or by oxychlorination of ethylene. Thermal dehydrochlorination of 1,2-dichloroethane produces vinyl chloride and coproduct hydrogen chloride. Hydrogen chloride is commonly recycled to an oxychlorination unit to produce 1,2-dichloroethane or is processed into sales-grade anhydrous or aqueous hydrogen chloride. 

Oxychlorination of ethylene with hydrogen chloride and oxygen at 280—370°C on a fluidi2ed CUCI2—KCl (on attapulgite) catalyst bed yields... 

Oxychlorination of Ethylene or Dichloroethane. Ethylene or dichloroethane can be chlorinated to a mixture of tetrachoroethylene and trichloroethylene in the presence of oxygen and catalysts. The reaction is carried out in a fluidized-bed reactor at 425°C and 138—207 kPa (20—30 psi). The most common catalysts ate mixtures of potassium and cupric chlorides. Conversion to chlotocatbons ranges from 85—90%, with 10—15% lost as carbon monoxide and carbon dioxide (24). Temperature control is critical. Below 425°C, tetrachloroethane becomes the dominant product, 57.3 wt % of cmde product at 330°C (30). Above 480°C, excessive burning and decomposition reactions occur. Product ratios can be controlled but less readily than in the chlorination process. Reaction vessels must be constmcted of corrosion-resistant alloys. 

The third step, the oxychlorination of ethylene, uses hy-product HCl from the previous step to produce more ethylene dichloride ... 

Telescope the Process by Combining Stages. This has been done successfully in the conversion of propylene to acrylonitrile by direct ammoxidation rather than oxidation to acrolein followed by reaction with ammonia in a separate stage, as was described in the earlier patent literature. The oxychlorination of ethylene and HC1 directly to vinyl chloride monomer is another good example of the telescoping of stages to yield an economic process. 

In contrast to this direct chlorination there is the oxychlorination of ethylene using hydrogen chloride and oxygen, the other major method now used. Since the chlorine supply is sometimes short and it is difficult to balance the caustic soda and chlorine demand (both are made by the electrolysis of brine), hydrogen chloride provides a cheap alternate source for the chlorine atom. Most of the ethylene dichloride manufactured is converted into vinyl chloride by eliminating a mole of HCl, which can then be recycled and used to make more EDC by oxychlorination. EDC and vinyl chloride plants usually are physically linked. Most plants are 50 50 direct chlorinationroxychlorination to balance the output of HCl. 

Vinyl Chloride. The present-day most important process in the industrial maufac-ture of vinyl chloride is the chlorination-oxychlorination of ethylene.188-... 

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 catalytic oxychlorination of ethylene with HC1 and 02 to vinyl chloride can be catalyzed in the liquid phase by a PdCl2-CuCl2 mixture, or in the vapor phase over supported palladium... 

The shift from air-based, once-through processes to oxygen-based recycle processes, and the corresponding change from reactant-lean to oxidant-lean processes. This not only considerably reduces the emissions and makes purge streams more concentrated and hence more easily combusted but also may lead to improved selectivity and productivity. Examples are the oxychlorination of ethylene to 1,2-dichloroethane and the epoxidation of ethylene. 

During oxychlorination of ethylene to 1,2-dichloroethane, excess hydrogen chloride is used to maintain the reaction mixture outside the explosive limits. 

Vinyl chloride and chloroprene (2-chlorobuta- 1,3-diene) are among the major intermediates which are produced industrially on the 100,000 tonnes/year scale by thermal chlorination or oxychlorination of ethylene or butadiene. 

In contrast to this direct chlorination there is the oxychlorination of ethylene using hydrogen chloride and oxygen (Fig. 2). 

Oxychlorination of ethylene. Knowledge of the role of copper chloride and the mechanism of oxychlorination has evolved. Current theory suggests that Cu(II) chloride chlorinates ethylene, which is chemisorbed on the catalyst. 

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. 

CuCl2 supported on silica (in presence of KC1, LaCl3 or A1C13 as cocatalysts) is also an active catalyst in oxychlorination of ethylene and other hydrocarbons104. Silica is also the support of choice for a Rh(III) complex which has been discovered to activate methane for chlorination via an electrophilic mechanism105. 

Other catalytic reactions carried out in fluidized-bed reactors are the oxidation of naphthalene to phthalic anhydride [2, 6, 80] the ammoxidation of isobutane to mcthacrylonitrilc [2] the synthesis of maleic anhydride from the naphtha cracker C4 fraction (Mitsubishi process [81, 82]) or from n-butane (ALMA process [83], [84]) the reaction of acetylene with acetic acid to vinyl acetate [2] the oxychlorination of ethylene to 1,2-di-chloroethane [2, 6, 85, 86] the chlorination of methane [2], the reaction of phenol with methanol to cresol and 2,6-xylenol [2, 87] the reaction of methanol to gasoline... 

Liquid-Phase Oxychlorination of Ethylene To Produce Vinyl Chloride... 

These studies have demonstrated that the homogeneously catalyzed oxychlorination of ethylene to 1,2-dichloroethane is feasible under relatively mild operating conditions without the need for catalyst circulation and that selectivities better than 96% can be achieved in sustained operations. A rational basis for reactor design has been devised, taking into account such factors as ethylene- and oxygen-mass transfer rates, chemical kinetics, water vapor pressure over the catalyst, selectivity relation-... 

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... 

Vinyl chloride is produced in the following industrial reactions (1) the thermal cracking of 1,2-dichlor-oethane, which is produced by the chlorination and/ or oxychlorination of ethylene and (2) the hydrochlorination of acetylene. The vast majority of vinyl chloride is used for the production of polyvinyl chloride (PVC) and the manufacture of copolymers with monomers such as vinyl acetate or vinylidene chloride. A much smaller proportion of vinyl chloride is used in the production of chlorinated solvents - primarily trichloroethanes. 

Ethylene dichloride (EDC) is used to manufacture vinyl chloride monomer (VCM), which is one of the largest commodity chemicals produced in the world. EDC may be produced by the direct chlorination of ethylene or oxychlorination of ethylene in the presence of oxygen and hydrogen chloride. Pyrolysis of EDC produces VCM and an equal amount of hydrogen chloride as a co-product. This hydrogen chloride produced in the pyrolysis reactor is utilized by the oxychlorination process as one of the reactants. Therefore, the component processes of direct chlorination, EDC pyrolysis and oxychlorination are combined to develop a balanced process for the production of VCM with no net consumption or production of hydrogen chloride ... 

Vinyl chloride monomer, the basic building block of polyvinylchloride (PVC), is commercially manufactured by dehydrochlorination of 1,2-dichloroethane. The modern process for producing 1,2-dichloroethane involves oxychlorination of ethylene in a fluidized bed catalytic reactor ... 

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