| 摘要 |
PURPOSE:To retard lowering of the activity of a hydrogenation catalyst in hydrorefining of gas oil, by recycling into a predistillation tower a part of hydrorefined oil obtained by separating gas components such as hydrogen sulfide from a hydrogenation reaction mixture. CONSTITUTION:A raw material gas oil such as coke oven gas oil or thermally cracked gaoline is subjected to catalytic hydrorefining by use of Pd, Co-Mo and Co-Mo-Ni catalysts in 1st-step reactors 9, 17 and 2nd-step reactor. Thermally cracked gasoline to be fed into a predistillation tower 2 and coke oven gas oil to be fed into a predistillation tower 12 are used in the ratio of 50:50 by weight. Amount of hydrorefined gas oil recycled from a line 28 to the predistillation tower 2 by the process of this invention is varied from the amount of liquid recycled from a line 30 to the predistillation tower 2 by conventional process and relations between inlet temperature and outlet diene concentration of the 1st-step reactor 9 are measured with time. As a result, even when inlet temperature of the reactor 9 is reduced by about 9 deg.C,, the outlet diene value is improved and the effect of catalyst poison upon the catalyst is lessened to a marked extent.
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