Takeshi Ohnishi

Isomerization of methyl formate to acetic acid catalysed by the Ru(II)-Sn(II) heteronuclear cluster complex [Ru(SnCl3)5(PPh3)]3−

Abstract The RuII-SnII heteronuclear cluster complex [Ru(SnCl3)5(PPh3)]3− has been found to be catalytically active for the isomerization of methyl formate to acetic acid. The initial reaction rate showed a first order dependence on the catalyst concentration, and showed a saturation curve for the reactant concentration in its high-concentration region. Extra addition of PPh3 and Cl− ion considerably retarded the reaction with almost linear relationships between the reciprocal of initial rates and the concentration of additives. A rate equation derived from these kinetic data indicates the presence of a pre-equilibrium of dual ligand dissociation from the catalyst (PPh3 from RuII and Cl− from SnII) to form the catalyst-reactant complex, where the relatively soft RuII and the hard SnII interact simultaneously with the soft CO group and hard OCH3 group of methyl formate, respectively. It is postulated that such a multi-center interaction in this cluster system facilitates the overall rearrangement of CH3 group (from O atom to C atom) to realize the isomerization of methyl formate to acetic acid without CO atmosphere or iodide promoter, but with an activation energy comparable to that for Rh or Ni catalyst which requires both of them.

Selective synthesis of 3-methoxy-1-propanol from methanol and allyl alcohol with metal oxide catalysts

Abstract The addition of methanol to allyl alcohol was investigated with metal oxides and zeolites catalysts in the liquid phase. 3-Methoxy-1-propanol was selectively formed with MgO, ZrO2 and Al2O3, while zeolites gave 2-methoxy-1-propanol. This feature suggests that the generation of a methoxide ion on basic sites is an important step. The highest yield, 23.6%, was obtained with MgO treated in a hydrogen flow.

Single-step synthesis of acetic acid (methyl acetate) from methanol alone by Ru(II)-Sn(II) hetero-bimetallic catalysts

Single-step conversion of methanol into acetic acid (methyl acetate) has been found possible by use of Ru(II)-Sn(II) hetero-bimetallic catalysts. By analyzing the homogeneous solution reactions, reaction paths are elucidated. Applications of lacunary heteropolyanions as model oxide ligands and of Y-type zeolite as a unique support for the gas-phase reaction are presented.

Methanol dehydrogenation in the liquid phase with Cu-based solid catalysts

Studies of methanol dehydrogenation in the liquid phase with Cu-based solid catalysts have shown (i) the product (methylal) is totally different from that in the gas-solid phase reaction (methyl formate) even using the same catalyst, and (ii) the differences in the calcination atmosphere of the catalyst (N2 versus dry air) have a marked effect on the product selectivity (methylal versus methyl formate). These results are in contrast to the gas-phase reaction (com-monly methyl formate). he results are discussed on the basis of surface species characterized with XPS and XRD.

MECHANISM AND SELECTIVITY CONTROL OF METHYL ACETATE AND METHYL FORMATE FORMATION FROM METHANOL ALONE WITH RU(SNCL3)5(PPH3)3- AS CATALYST

Mechanistic studies have been made of the unique one-pot conversion of methanol into acetic acid (and/or methyl acetate due to rapid esterification) with [Ru(SnCl 3 ) 5 (PPh 3 )] 3- as catalyst. Addition of Cl - ion promoted the formation of methyl formate relative to methyl acetate, but scarcely changed their total rate of formation. Further, the activation energies for their formation were virtually identical (≈76 kJ mol -1 ). No 13 C was incorporated into methyl acetate even when the reaction was performed under a 13 CO atmosphere, indicating that the conversion of methanol into methyl acetate does not involve carbonylation. The effect of the addition of Cl - ion on the reaction of formaldehyde was similar to that when using methanol as substrate, but quite different activation energies were obtained for the formation of methyl acetate (27.9 kJ mol -1 ) and methyl formate (40.6 kJ mol -1 ). The results are in accord with rate-determining dehydrogenation of methanol to formaldehyde (as a common intermediate), which is then converted competitively into acetic acid and methyl formate with different activation energies. The effect of added free Cl - ion for both substrates suggests the presence of a pre-equilibrium dissociation of Cl - from the co-ordinated SnCl 3 - , which is required for the formation of acetic acid but not for methyl formate. A possible reaction scheme is presented, in which reductive elimination of methyl formate is competitive with that of acetic acid.

Shape-selective N-alkylation of melamine using alcohol as an alkylating agent with Ru/mordenite catalyst in the liquid phase

A series of Ru/mordenite (Ru/M) catalysts have been prepared by the ionexchange of Na-mordenite with [Ru(NH3)6]3+, followed by a mild thermal treatment for various periods. XRD measurement of each catalyst ensured that a high degree of crystallinity of mordenite was maintained, and that no formation of crystalline metallic ruthenium occurred. The trend of H/Ru value determined from chemisorption of H2 suggests that the reduction-aggregation took place progressively during the calcination, where the latter process preceded the former. Actually, in EXAFS spectra, the intensity of the peak for Ru-Ru bond became gradually stronger relative to that for Ru-N bond, and SBET value was decreased in the same order. Since HR-TEM photographs gave no metal particles comparable to or larger than the diameter of a mordenite pore, the extent of aggregation is not so large, which is consistent with the lack of crystalline metallic ruthenium. By use of Ru/M catalysts, moderate shape selectivty was observed in the N-methylation of melamine with methanol (suppression of the formation of N,N′, N″-tri-methylated melamine as compared to that of N-methylated or N,N′-di-methylated melamine), which is in harmony with the sizes of relevant molecules relative to the size of a mordenite pore. As the calcination condition became severe, catalytic activity decreased steeply. This fact suggests that molecular or quite high dispersion is demanded for the catalytic site, and that grown metallic ruthenium would prevent the motion and the reaction of melamine in the pores. The reactions with diols (ethylene glycol, diethylene glycol) were slower, and were accompanied by considerable side reactions. The trend of reactivity among the three substrates implies the importance of steric factors, and appreciable formation of N,N′, N″-tri-alkylated melamine for ethylene glycol suggests that the catalytic sites on the external surface contribute more than for methanol.