Ethylene acetic acid from

Ethylene is more rapidly oxidized than propylene. Furthermore, the substituted ethylenes do not display the dependency on reactivity of allyl C—H bonds shown over bismuth molybdate (Tables XI and XII). It is clear that the C02-producing reaction is favored by unsaturation, but not by allyl hydrogens. In fact, over Pt ter<-butylethylene, without any allyl hydrogen, was oxidized about as fast as the methylethylenes. Dienes and acids were found to inhibit the oxidation of olefins over the metals. Acetone, like acetic acid from ethylene over Pd, is considered a side reaction product rather than an intermediate. The only selective oxidation observed was an oxidative dehydrogenation of cyclohexene to benzene over Pd at —20 to +30° here no CO2 was produced. 

As an alternative feedstock, chemists turned to ethylene, already available in huge quantities from the refining of natural gas and petroleum. The process of producing acetic acid from ethylene depends on the fact that in the presence of catalytic amounts of Pd + and Cu + salts, ethylene is oxidized by molecular oxygen to acetaldehyde. 

For the transfer of acetic acid from ethylene glycol to ethyl acetate the critical time observed [2] is a few second. Our theory predicts [191... 

Liquid- and vapor-phase processes have been described the latter appear to be advantageous. Supported cadmium, zinc, or mercury salts are used as catalysts. In 1963 it was estimated that 85% of U.S. vinyl acetate capacity was based on acetylene, but it has been completely replaced since about 1982 by newer technology using oxidative addition of acetic acid to ethylene (2) (see Vinyl polymers). In western Europe production of vinyl acetate from acetylene stiU remains a significant commercial route. 

Most of the vinyl acetate produced in the United States is made by the vapor-phase ethylene process. In this process, a vapor-phase mixture of ethylene, acetic acid, and oxygen is passed at elevated temperature and pressures over a fixed-bed catalyst consisting of supported palladium (85). Less than 70% oxygen, acetic acid, and ethylene conversion is realized per pass. Therefore, these components have to be recovered and returned to the reaction zone. The vinyl acetate yield using this process is typically in the 91—95% range (86). Vinyl acetate can be manufactured also from acetylene, acetaldehyde, and the hquid-phase ethylene process (see Vinyl polymers). 

A one-stage process for producing vinyl acetate directly from ethylene has also been disclosed. In this process ethylene is passed through a substantially anhydrous suspension or solution of acetic acid containing cupric chloride and copper or sodium acetate together with a palladium catalyst to yield vinyl acetate. 

The chemistry of vinyl acetate synthesis from the gas-phase oxidative coupling of acetic acid with ethylene has been shown to be facilitated by many co-catalysts. Since the inception of the ethylene-based homogeneous liquid-phase process by Moiseev et al. (1960), the active c ytic species in both the liquid and gas-phase process has always been seen to be some form of palladium acetate [Nakamura et al, 1971 Augustine and Blitz, 1993]. Many co-catalysts which help to enhance the productivity or selectivity of the catalyst have appeared in the literature over the years. The most notable promoters being gold (Au) [Sennewald et al., 1971 Bissot, 1977], cadmium acetate (Cd(OAc)j) [Hoechst, 1967], and potassium acetate (KOAc) [Sennewald et al., 1971 Bissot, 1977]. 

In homogeneous catalytic systems we witnessed a new process for the production of acetic acid from methanol and carbon monoxide using a transition metal complex, thus displacing the earlier process employing ethylene as the starting material. The use of immobilized enzymes makes possible the commercial conversion of glucose into fructose. 

Catalysts used to convert ethylene to vinyl acetate are closely related to those used to produce acetaldehyde from ethylene. Acetaldehyde was first produced industrially by the hydration of acetylene, but novel catalytic systems developed cooperatively by Farbwerke Hoechst and Wacker-Chemie have been used successfully to oxidize ethylene to acetaldehyde, and this process is now well established (7). However, since the largest use for acetaldehyde is as an intermediate in the production of acetic acid, the recent announcement of new processes for producing acetic acid from methanol and carbon monoxide leads one to speculate as to whether ethylene will continue to be the preferred raw material for acetaldehyde (and acetic acid). 

The recent dramatic increase in the price of petroleum feedstocks has made the search for high selectivities more urgent. Several new processes based on carbon monoxide sources are currently competing with older oxidation processes.103,104 The more straightforward synthesis of acetic acid from methanol carbonylation (Monsanto process) has made the Wacker process obsolete for the manufacture of acetaldehyde, which used to be one of the main acetic acid precursors. Several new methods for the synthesis of ethylene glycol have also recently emerged and will compete with the epoxidation of ethylene, which is not sufficiently selective. The direct synthesis of ethylene... 

Step 1. For this process we must be able to set the production rate of vinyl acetate while minimizing yield losses to carbon dioxide. During the lifetime of the catalyst charge, catalyst activity decreases and the control system must operate under these different conditions. To maintain safe operating conditions, the oxygen concentration in the gas loop must remain outside the explosivity region for ethylene. The azeotropic distillation column must produce an overhead product with essentially no acetic acid and a bottoms product with no vinyl acetate. The absorber must recover essentially all of the vinyl acetate, water, and acetic acid from the gas recycle loop to prevent yield losses in the CCf removal system and purge,... 

Acrylic acid is an important material for the chemical Industry, either as such or in (he form of acrylates and acrylamides. The Union Oil synthesis of acrylic acid from ethylene is performed at 140-150 C, 77 atm, C2 H4/CO 1 (Otalyst 0.1% PdOj. 0.5% CUCI2 in the presence of lithium acetate and chloride). The solvent is a mixture of acetic acid and acetic anhydride (about 20%) 24. The chemical steps of this Wacker-type catalysis are outlined ... 

This compound with potassium cyanide or concentrated acids (not acetic acid) fields ethylene. From an aqueous solution of the chloride, hydrogen sulphide precipitates all the mercury as sulphide, but from an alkaline solution potassium hydrosulphide precipitates ethanol mercuric sulphide (CHgOHCH 2Hg) gS. 

Pd (II) in acetic acid oxidizes ethylene mainly to vinyl acetate. This is the product expected from Pd( II)-hydride elimination from an oxy-palladation adduct. However, 1,1-diacetoxyethane has been reported to be a primary product under some conditions (33). Thus, as discussed above, decomposition of the adduct may not occur by simple Pd(II)-hydride elimination. 

A new CD process for the production of vinyl acetate from acetic acid, ethylene, and oxygen using a Pd-type catalyst at 338 20 K, 2-5 bar was disclosed. This illustrates the wide-ranging possibilities for the application of CD in a variety of processes for the chemical, petrochemical, and petroleum industry. The production of acetic acid from the carbonylation of dimethyl ether or methanol using RD and homogeneous catalyst was also patented. ... 

Fig. 19. The ovoall catalytic route for the synthesis for vinyl acetate formation from ethylene, acetic acid in the absence of oxygen on a model Pd(l 11) sur ce.

The vinyl acetate process shown contains seven components. The chemistry consists of two reactions, which produce vinyl acetate (C4H6O2) from ethylene, oxygen, and acetic acid (C2H4O2) and form by-products of water and carbon dioxide. 

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