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Catalysis by silica overlayers
348 caprolactam). Previous work indicated that solid acid catalysts are useful for this reaction. The Amoco group now reports that a crystalline borosilicate catalyst supported on gamma alumina gives 100% conversion and 82% selectivity. This catalyst is reported to demonstrate enhanced catalyst life over a period of 225 h on-stream.
sodium-free silica carrier supporting molybdenum trioxide for the production of formaldehyde from methane. Several new methods for preparing zeolites for hydrocarbon conversion have been claimed. For example, Imperial Chemical Industries Plc have claimed (British patent 2 192 626) an improved procedure for producing EU-4 zeolite from a reaction mixture containing a source of silica, optionally a source of alumina, a source of a group IA metal oxide and a propane-l ,3_bis(trimethyl ammonium) compound. A second patent to Imperial Chemical Industries (British patent 2 193 202) claims a method for the production of a zeolite sigma-l. Shell International Research Mij BV claims (European patent 253 449) a method for preparing the zeolite ZSM-5. Mobil Oil Corporation has claimed (U.S. patent 4 709 1 14) a zeolite ZSM-58 for the conversion of methanol to hydrocarbons while National Distillers and Chemical Corporation have claimed (U.S. patent 4 707 500) a crystalline ferroborosillicate containing plantinum or palladium for the production of lower hydrocarbons from synthesis gas or methanol.
Catalysis
In a recent article in the international edition of Angew. Chemie (26 (1987) 1 182), J.M. Cogen, K. Ezaz-Nikpay, R.H. Fleming, S.M. Baumann and W.F. Maier describe the heterogeneous dehydrogenation of cyclohexene to benzene over a catalyst comprised of a platinum film supported on silicon wafers. The platinum film is covered completely with a layer of silica, forcing the dihydrogen to diffuse through the overlayer in order to become activated. The authors used a number of techniques (AES, RBS and SIMS) to verify that no platinum was on the surface of the silicon substrate; nor was there any evidence for breaks in the surface of the silica film. They suggest that dissociated hydrogen, and not exposed metal, represents the active site for the catalytic reaction. Thus they conclude that inert silica films become catalytically active in the presence of a platinum underlayer.
Other new Patents A recent Russian patent, S.U. patent 940 487-A, describes novel catalysts for the production of acrylate polymers which are based on a family of cobalt dioximes. The authors claim that better quality and less coloured polymers are made by using cobalt oximes as catalysts to control the molecular weight. These catalysts are reported to be superior to cobalt porphyrins since they adsorb less visible light than the prophyrin cobalt complexes. In a recent patent by P.E. McMahon of Amoco Corporation (U.S. patent 4 697 OlO), a process is described for the catalytic conversion of oximes (such as cyclohexanone oximes) to amides (such as
applied
catalysis
-Volume
39 NO. l-2
by Silica Overlayers
Methanol
to Gasoline
A series of three articles has appeared in ChemTech (January 1988) which demethanol-to-gasoline scribe Mobil’s technology. Articles by S.L. Meisel (p. 32). C.J. Maiden (p. 38), and J.Z. Bern (p. 42) describe the Mobil methanol-togasoline project from its inception to the construction and commissioning of the plant.
-May
1988
sodium-free silica carrier supporting molybdenum trioxide for the production of formaldehyde from methane. Several new methods for preparing zeolites for hydrocarbon conversion have been claimed. For example, Imperial Chemical Industries Plc have claimed (British patent 2 192 626) an improved procedure for producing EU-4 zeolite from a reaction mixture containing a source of silica, optionally a source of alumina, a source of a group IA metal oxide and a propane-l ,3_bis(trimethyl ammonium) compound. A second patent to Imperial Chemical Industries (British patent 2 193 202) claims a method for the production of a zeolite sigma-l. Shell International Research Mij BV claims (European patent 253 449) a method for preparing the zeolite ZSM-5. Mobil Oil Corporation has claimed (U.S. patent 4 709 1 14) a zeolite ZSM-58 for the conversion of methanol to hydrocarbons while National Distillers and Chemical Corporation have claimed (U.S. patent 4 707 500) a crystalline ferroborosillicate containing plantinum or palladium for the production of lower hydrocarbons from synthesis gas or methanol.
Catalysis
In a recent article in the international edition of Angew. Chemie (26 (1987) 1 182), J.M. Cogen, K. Ezaz-Nikpay, R.H. Fleming, S.M. Baumann and W.F. Maier describe the heterogeneous dehydrogenation of cyclohexene to benzene over a catalyst comprised of a platinum film supported on silicon wafers. The platinum film is covered completely with a layer of silica, forcing the dihydrogen to diffuse through the overlayer in order to become activated. The authors used a number of techniques (AES, RBS and SIMS) to verify that no platinum was on the surface of the silicon substrate; nor was there any evidence for breaks in the surface of the silica film. They suggest that dissociated hydrogen, and not exposed metal, represents the active site for the catalytic reaction. Thus they conclude that inert silica films become catalytically active in the presence of a platinum underlayer.
Other new Patents A recent Russian patent, S.U. patent 940 487-A, describes novel catalysts for the production of acrylate polymers which are based on a family of cobalt dioximes. The authors claim that better quality and less coloured polymers are made by using cobalt oximes as catalysts to control the molecular weight. These catalysts are reported to be superior to cobalt porphyrins since they adsorb less visible light than the prophyrin cobalt complexes. In a recent patent by P.E. McMahon of Amoco Corporation (U.S. patent 4 697 OlO), a process is described for the catalytic conversion of oximes (such as cyclohexanone oximes) to amides (such as
applied
catalysis
-Volume
39 NO. l-2
by Silica Overlayers
Methanol
to Gasoline
A series of three articles has appeared in ChemTech (January 1988) which demethanol-to-gasoline scribe Mobil’s technology. Articles by S.L. Meisel (p. 32). C.J. Maiden (p. 38), and J.Z. Bern (p. 42) describe the Mobil methanol-togasoline project from its inception to the construction and commissioning of the plant.
-May
1988