Deacon catalyst

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. 

In the 1930s, the Raschig Co. in Germany developed a different chlorobenzene-phenol process in which steam with a calcium phosphate catalyst was used to hydrolyze chlorobenzene to produce phenol (qv) and HCl (6). The recovered HCl reacts with air and benzene over a copper catalyst (Deacon Catalyst) to produce chlorobenzene and water (7,8). In the United States, a similar process was developed by the BakeHte Division of Union Carbide Corp., which operated for many years. The Durez Co. Hcensed the Raschig process and built a plant in the United States which was later taken over by the Hooker Chemical Corp. who made significant process improvements. 

Copper chloride is universally applied as catalyst. - Known as the modified Deacon catalyst, CuCl2 is supported on alumina and contains KC1. Under operating conditions a CUCI2-CU2CI2-KCI ternary mixture, possibly in the molten state, is... 

The active phase of the Deacon catalyst is usually assumed to be a complex melt of copper or chromium and alkaline metal chlorides under reaction conditions, which is distributed within the pore network of an inert carrier [42]. Such supported liquid-phase catalysts (SLPC) are eminently suitable for adsorbing large amounts of the reacting components as sorption takes place in a bulk phase and is not restricted to only a limited number of suitable surface sites. The periodic expansion and contraction of the melt as a result of (de) sorption imposes considerable strains on the carrier structure hence, special mechanically robust support materials are needed to withstand such strains and prevent the catalyst crumbling away and disintegrating after a few cycles. In addition, even when it is immobilized on the carrier, the melt is extremely aggressive and resistant materials must be used for reactor construction. 

Of more interest mechanistically though is the liquid nature of the molten phase present in the interstices of the inert porous support. It is now recognized that, deliberately or accidentally, a number of heterogeneously catalysed processes involve a supported liquid phase (SLP) rather than a solid catalyst. SLP catalysts are reviewed by Villadsen and Livbjerg. These include the vanadium-based sulphuric acid catalysts and, of comparable antiquity, the Deacon catalysts for oxidizing hydrogen chloride, where mixtures of copper and potassium chlorides can form melts in the catalyst support under reaction conditions. Thus in addition to diflfusional restrictions arising from pellet pore structure any... 

Deacon catalyst was prepared by impregnating a suitable porous and heat-resistant solid—firebrick and pumice could be used—with an aqueous solution of copper chloride. The final catalyst contained about 10 wt% of copper chloride. 

Although the Deacon process was only used for about 40 years, it is still of interest for two reasons as an example of a catalyst selected by logical rather than empirical procedures and as an illustration of the need to remove poisons from process gases. Derivatives of the Deacon catalyst are still used in the production of ethylene dichloride, by the oxychlorination of ethylene. 

The cupric chloride catalyst was promoted with potassinm chloride and supported on activated alumina. It was related to the Deacon catalyst, which was developed for chlorine production in 1887. 

It was found, however, that the Deacon catalysts could chlorinate ethylene with a mixture of hydrogen chloride and air. The Deacon reaction did not produce molecular chlorine but chlorinated ethylene directly as chlorine species formed on the catalyst smface. Low equihbrium conversion to chlorine and its slow removal from the catalyst surface were no longer limitations and complete chlorination of the ethylene was achieved at temperatures in the range 210 -240 C. Free chlorine was never found even with low ethylene concentrations. 

Suitable catalysts are similar to the original Deacon catalyst. The copper chloride is supported on medium-smface-area alumina with pore sizes in the range 80-600 A. While copper chloride is more active than other metals it is also... 

The rate of this reaction is significantly enhanced over catalysts such as copper chloride which is the basis for the Deacon process for producing CI2 from HCl. The relationship between the equilibrium constant and the temperature in Kelvin for the reaction is expressed by equation 19. 

The next step of the UOP method of CCR regeneration is oxidation and chlorination. In this step, the catalyst is oxidized in air at about 510°C. A sufficient amount of chloride is usually added as an organic chloride, such as trichloroethane, to restore the chloride content and acid function of the catalyst to that of the fresh catalyst. If the platinum crystaUites ate smaller than about 10 nm, sufficient chlorine is present in the gas to completely tedispetse agglomerated platinum on the catalyst, as a result of the Deacon equUibtium ... 

Cataljdic reactions performed in fluid beds are not too numerous. Among these are the oxidation of o-xylene to phthalic anhydride, the Deacon process for oxidizing HCl to CI2, producing acrylonitrile from propylene and ammonia in an oxidation, and the ethylene dichloride process. In the petroleum industry, cataljdic cracking and catalyst regeneration is done in fluid beds as well as some hydroforming reactions. 

Airco A modification of the Deacon process for oxidizing hydrogen chloride to chlorine. The copper catalyst is modified with lanthanides and used in a reversing flow reactor without the need for external heat. Developed by the Air Reduction Company from the late 1930s. U.S. Patents 2,204,172 2,312,952 2,271,056 2,447,834. 

Deacon Also called Deacon-Hurter. A process for oxidizing hydrogen chloride to chlorine, using atmospheric oxygen and a heterogeneous catalyst ... 

MT-chlor [Mitsui Toatsu Chlorine] A process for recovering chlorine from hydrogen chloride. The hydrogen chloride is mixed with oxygen and passed through a fluidized bed of chromia/silica catalyst. Developed by Mitsui Toatsu and first operated in Japan in 1988. See also Deacon, Kel-Chlor. 

The process was complicated by the formation of calcium manganite, CaMn206, known as Weldon mud. Invented by W. Weldon in 1866 and developed at St. Helens from 1868 to 1870. Operated in competition with the Deacon process until both were overtaken by the electrolytic process for making chlorine from brine. Weldon mud has been used as a catalyst for oxidizing the hydrogen sulfide in coal gas to elemental sulfur. 

In SL-PC, a catalyst is supported on a solid matrix in the form of the film of a nonvolatile liquid phase adsorbed on the solid. The catalytic film can be, for example, a molten salt or a molten oxide (e.g., Deacon s catalyst (CUCI2/KCI) used to oxidize HCl with oxygen for the chlorination of ethylene in the synthesis of vinyl chloride. Figure 6.1 V2O5 for the oxidation of sulphurous to sulphuric anhydride). Alternately, it can be a liquid phase (e.g., ethylene glycol, PPh3, butyl benzyl phthalate, etc.) that contains a soluble catalytic species such as a metal complex. 

Figure 6.1 SL-PC for the synthesis of vinyl chloride with Deacon s catalyst.

The reaction is exothermic (see Exercise 12.1), but, since it is very slow, a catalyst is necessary. Nitric oxide, once again, can serve as an oxygen carrier, as in the lead chamber process (Section 10.2) and in reaction 10.8, where (CH3)2S generated in the kraft process is converted to DMSO. Even so, at the elevated temperatures required, reaction 12.1 needs to be forced to completion by absorption of the steam in concentrated sulfuric acid or some other desiccant. In variants of the Deacon process, copper chloride acts as the catalyst or as an intermediate for chlorine regeneration. 

Due to the volatility of some of the chlorides present the temperature must be maintained below 400 °C, which limits the scope for accelerating the rate-limiting oxidative regeneration step by increasing the temperature [19], For the unsteady-state adsorptive Deacon process the catalyst composition had to be modified to reduce volatility and enhance the oxidative of the reaction phase. 

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