Tokuo Matsuzaki

Dimethyl carbonate synthesis and other oxidative reactions using alkyl nitrites

The oxidative reactions using the alkyl nitrites (RONO) as an oxidant have been developed by Ube Industries, Ltd. In the alkyl nitrite reactions, substrates such as CO andyor unsaturated- andyor carbonyl-compounds are oxidized over the palladium catalysts in no direct contact with molecular oxygen. The dimethyl carbonate (DMC), dialkyl oxalates and other useful chemicals are synthesized efficiently under moderate conditions by the alkyl nitrite reactions.

Catalysis and characterization of Pd/NaY for dimethyl carbonate synthesis from methyl nitrite and CO

A vapor phase synthesis of dimethyl carbonate (DMC) from carbon monoxide and methyl nitrite (MN) has been carried out over Pd/NaY catalysts at 383 K, DMC was produced in a good yield. The selectivity to DMC was >85% on the basis of consumed CO or MN. The by-products were dimethyl oxalate, CO2, N2O, methyl formate and dimethoxymethane. The catalytic properties of Pd/NaY were investigated as a function of Pd content and calcination temperature. It was found that 1 wt.% Pd/NaY calcined at 473 K in air was the optimum catalyst for the present DMC synthesis. The oxidation state and dispersion of Pd in the Pd/NaY catalysts were characterized by EXAFS and XPS. It was revealed that Pd(NH3)42+ in 1 wt.% Pd/NaY changed into Pd metal clusters during the catalytic reaction. Pd metal clusters/NaY showed a stable activity for the DMC synthesis even after 700 h. These results suggest that the cage structure of NaY and anchoring effects of protons suppress Pd metal sintering and stabilize very small Pd metal clusters (Pd13) in the zeolite cages during the reaction.

The Nature of Active Oxygen in Selective Oxidation Reactions

Temperature programmed reoxidation (TPROX) of prereduced bismuth molybdate catalysts yield profiles which can be related to various changes which occur in the catalyst during the reoxidation. The TPROX profile for γ-Bi 2 Mo0 6 of a large, low-temperature peak and a small, high-temperature peak. Using 18 0 in conjunction with TPROX, Raman and XPS investigations indicate that during low-temperature reoxidation oxygen incorporation is accompanied by reoxidation of Bi 0 to Bi 3+ and that during high-temperature reoxidation oxygen incorporation is accompanied by reoxidation of Mo 4+ to Mo 6+ . The hightemperature reoxidation process is related to the rate-limiting step for propylene oxidation to acrolein at temperatures below 400°C and is identified as the reoxidation of reduced Mo centers by lattice oxygen diffusion. The oxygen inlet site is reduced Bi. The oxygen outlet site is associated with Mo. The type of oxygen which is incorporated into acrolein from γ-Bi 2 Mo0 6 is the bridge-bonded oxygen which exists in the γ-Bi 2 Mo0 6 structure.