Mitsubishi Chemical hydrogenation step

Mitsubishi Chemical s 1,4-butanediol production process is composed of three main steps, namely, diacetoxylation, hydrogenation, and hydrolysis. These steps are discussed in the following sections [17,18]. 

Mitsubishi Gas Chemical Co. in Japan produces pyromellitic dianhydtide in the same unit used for trimellitic anhydtide production (105). This process starts with pseudocumene, which is first carbonylated with carbon monoxide in the presence of boron trifluotide and hydrogen fluotide to form 2,4,5-trimethylbenzaldehyde. The Hquid-phase oxidation of the trimethylbenzaldehyde to pyromellitic acid and subsequent processing steps ate much the same as described for the Mitsubishi Gas Chemical process in the trimellitic acid section. The production of pyromellitic anhydtide is in conjunction with a joint venture agreement with Du Pont. 

We noted previously that aldehydes such as benzaldehyde can be prepared by direct oxidation of the side chain in the reactant. It is also possible to go from the opposite direction and reduce a carboxylic acid to the corresponding aldehyde. In both cases, side-chain halogenation using hazardous chemicals is avoided. A one-step direct hydrogenation process has been developed by Mitsubishi using a Cr modified zirconia catalyst (Yokoyama et al., 1992), which is reported to give aldehyde selectivities of 80-97% in the hydrogenation of benzoic acid, o-methylbenzoic acid, w-phenoxybenzoic acid, dimethyl terephthalate, etc. 

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