Promoting Effect of Mo on Alcohol Formation in Hydroformylation of Propylene and Ethylene on Mo-Rh/SiO 2
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Catalysis Letters Vol. 103, Nos. 1–2, September 2005 ( 2005) DOI: 10.1007/s10562-005-6497-3
Promoting effect of Mo on alcohol formation in hydroformylation of propylene and ethylene on Mo-Rh/SiO2 Keiichi Tomishige, Ippei Furikado, Takashi Yamagishi, Shin-ichi Ito, and Kimio Kunimori Institute of Materials Science, University of Tsukuba, 1-1-1 Tennodai, Tsukuba, Ibaraki, 305-8573 Japan
Received 4 April 2005; accepted 17 May 2005
It is found that the addition of Mo to Rh/SiO2 (Mo-Rh/SiO2) promoted alcohol formation in hydroformylation of propylene and ethylene, at the same time it drastically enhanced the activity of hydroformylation and hydrogenation. It is suggested that H2 adsorption sites, which are not inhibited by CO adsorption, are present on Mo-Rh/SiO2. The sites can cause high H2 activation, and it can be related to the additive effect of Mo in hydroformylation reactions. KEY WORDS: hydroformylation; propylene; ethylene; alcohol; molybdenum; rhodium.
1. Introduction Hydroformylation is an important industrial process for producing oxygen containing compounds, especially aldehydes, from olefins. It has been known that rhodium is the most active catalyst for hydroformylation. Although the catalyst development for the gas-phase [1,2] and liquid-phase [3–6] hydroformylation has been performed, the additive effect of various components on heterogeneous Rh catalysts has been investigated [7–15]. It has been reported that the additives such as Fe, Zn promote the formation of alcohols in ethylene hydroformylation [1,8]. It has also been reported that Mo is an effective additive for alcohol formation in hydroformylation, and cluster-derived [11] and ZrO2-supported catalysts [16] have been investigated. In this letter, it is reported that Mo-promoted Rh/ SiO2 (Mo-Rh/SiO2), which was prepared by the conventional impregnation method, exhibited higher activity in hydroformylation of ethylene and propylene in terms of alcohol formation than previous reports. In addition, the promoting effect of Mo on hydrogen activation under the presence of CO is discussed on the basis of the characterization results by means of FTIR, TPD, and H2–D2 exchange rate measurements.
2. Experimental 2.1. Catalyst preparation All catalysts were prepared by impregnating an aqueous solution of metal salts on SiO2 support (Q-100 or G-6; Fuji Silysia Chemical Ltd.). Before the impregnation, SiO2 was calcined in air at 1173 K for 1 h to * To whom correspondence should be addressed. E-mail: [email protected]
avoid the structural change during the catalyst preparation (BET surface area: Q-100: 38 m2/g, G-6: 535 m2/ g). Rh/SiO2 (Q-100 and G-6) catalysts were prepared by the incipient wetness method using RhCl3 Æ 3H2O (N.E. Chemcat Corporation >98%). Unless otherwise stated, the SiO2 (Q-100) support was used. The preparation of Mo-added Rh catalysts (Mo-Rh/SiO2) was as follows: after the impregnation with a RhCl3 Æ 3H2O aqueous solution and drying at 383 K for 12 h, the modification with additive component was carried out by subsequent impregna
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