Liquid phase catalytic hydrogenation of cyclopentadiene (1) to cyclopentene (2) with nickel boride and Urushibara nickel B was studied in the presence of amine under the ordinary pressure and high pressure at 0°C.
The products component of the hydrogenation under ordinary pressure was analyzed by use of vpc at appropriate time intervals. Hydrogenation of (2) to cyclopentane (3) was effectively depressed by the addition of pyridine in alcohol solution. When hydrocarbon was used as a solvent, same effect was observed by the addition of ethylamine as well as pyridine.
High pressure hydrogenation was performed at 40 kg/cm
2 without solvent. Pyridine, ethylenediamine, diethylamine, piperidine and aniline were used as additives. Pyridine and ethyenediamine were good additives to accomplish the hydrogenation of (1) to (2) selectively. For example, the product contained (1) 0%, (2) 98.8% and (3) 1.2%, using 0.2 m
l of pyridine and 0.05 g of nickel boride.
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