Methyl ether, vapor-phase catalysts

Vapor-Phase Carbonylation of Dimethyl Ether and Methyl Acetate with Supported Transition Metal Catalysts... 

It was found that a nickel-activated carbon catalyst was effective for vapor phase carbonylation of dimethyl ether and methyl acetate under pressurized conditions in the presence of an iodide promoter. Methyl acetate was formed from dimethyl ether with a yield of 34% and a selectivity of 80% at 250 C and 40 atm, while acetic anhydride was synthesized from methyl acetate with a yield of 12% and a selectivity of 64% at 250 C and 51 atm. In both reactions, high pressure and high CO partial pressure favored the formation of the desired product. In spite of the reaction occurring under water-free conditions, a fairly large amount of acetic acid was formed in the carbonylation of methyl acetate. The route of acetic acid formation is discussed. A molybdenum-activated carbon catalyst was found to catalyze the carbonylation of dimethyl ether and methyl acetate. 

There has been an enormous technological interest in tertfa/j-butanol (tBA) dehydration during the past thirty years, first as a primary route to methyl te/f-butyl ether (MTBE) (1) and more recently for the production of isooctane and polyisobutylene (2). A number of commercializable processes have been developed for isobutylene manufacture (eq 1) in both the USA and Japan (3,4). These processes typically involve either vapor-phase tBA dehydration over a silica-alumina catalyst at 260-370°C, or liquid-phase processing utilizing either homogenous (sulfonic acid), or solid acid catalysis (e.g. acidic cationic resins). More recently, tBA dehydration has been examined using silica-supported heteropoly acids (5), montmorillonite clays (6), titanosilicates (7), as well as the use of compressed liquid water (8). 

Chemical properties of glycols. They are similar to those of aliphatic alcohols and the glycols may be oxidized (in the vapor phase and in the presence of catalysts) to the corresponding acids. They are easily estertfied by inorganic and organic acids to form, esters. Ethers (such as methyl, ethyl etc) may be prepd by treating... 

The methyl ether of 2,3-propanediol can be oxidized to methoxyacetone in the vapor or liquid phase using a suitable catalyst or oxidant, respectively. To achieve production of high purity metolachlor, which is a liquid (mp. 62.1 °), it is necessary to control the quality of all input materials, monitor reaction progress, terminate each reaction step effectively, and... 

These isomerizations, rearrangements, and cleavages are best explained by a carbonium-ion mechanism. Vapor-phase dehydration of alcohols over aluminum oxide greatly reduces the tendency for isomerization and rearrangement. The alcohol vapors are passed over the catalyst at 300-420°. In this manner, pure 1-butene is prepared from re-butyl alcohol and t-butylethylene is obtained from methyl-/-butylcatbinol (54%). The relative rates of dehydration of the simpler alcohols over alumina have been studied. The main side reaction is dehydration to ethers (method 118). 

It was well known from the literature that aniUnes can be mono- or di-alkylated with alcohols in presence of acidic catalysts. However, preliminary experiments on several solid acidic catalysts in the vapor-phase gave complex mixtures of the desired product (NAA), as well as N-methyl-, N-dimethyl-, N-propyl- and N-isopropyl-M L4 as by-products. These can be explained by cleavage of the ether group of MOIP followed by reaction of the fragments with MEA. All atten Jts to improve the selectivity of this acid catalyzed alkylation Med. Therefore, the reductive alkylation route was chosen for further investigations. 

Copper-containing mordenite catalysts have also been reported to be active for carbonylation of vapor-phase methanol [170]. Initially, the predominant reaction products were hydrocarbons resulting from methanol-to-gasoline chemistry, but after about 6 h on stream at 350 °C the selectivity of the catalyst changed to give acetic acid as the main product. A recent investigation was carried out with in situ IR and solid-state NMR spectroscopies to probe the mechanism by detecting surface-bound species. The rate of carbonylation was found to be enhanced by the presence of copper sites (compared to the metal-free system), and formation of methyl acetate was favored by preferential adsorption of CO and dimethyl ether on copper sites [171],... 

---