循环氢中杂质含量对汽油选择性加氢脱硫的影响

通过对3家炼厂OCT-M/OCT-MD装置在循环氢中不同杂质含量工况下加氢脱硫效果的对比,考察了循环氢中不同杂质(如H2S,CO和CO2)对FCC汽油重馏分加氢脱硫率和烯烃饱和率的影响。工业研究结果表明循环氢中较高浓度的H2S,不但影响脱硫率,而且因为硫化氢易与未反应的烯烃发生重排生成大分子硫醇,从而使硫醇含量增加。因此,工业装置应该将循环氢中的H2S质量分数控制在100μg/g以下;循环氢中CO和CO2对催化剂的加氢脱硫性能和烯烃饱和性能有一定的抑制作用,当循环氢中CO2的质量分数由5 900μg/g降低到1 600μg/g时,在相同脱硫率下,反应器入口温度降低10℃。当循环氢中CO的质量分数由11 000μg/g降低到2μg/g时,加氢脱硫率由57.3%增加到93.8%,烯烃加氢饱和率由26.8%增加到37.8%。因此,为了达到较高的加氢脱硫率,循环氢中CO和CO2的质量分数应控制在5μg/g以下。

Impact of impurity content in recycle hydrogen on selective hydrodesulfurization of gasoline

Through the comparison of hydrodesulfurization performances of OCT-M/OCT-MD units in three refiners at different impurities contents, the impacts of different impurities （such as H2S, CO and CO2 ） in recycle hydrogen on the hydrodesulfurization rate and olefin saturation rate of FCC gasoline＇ s heavy fraction HCN） are studied. The commercial results show that the higher contents of H2S not only affect the hydrodesul- furization rate but also increase the contents of large-molecule mercaptans because of the reaction of H2S with un-reacted olefins. Therefore, the content of H2S should be controlled to less than 100 ppm in the commercial unit. The contents of CO and CO2 can, to some extent, inhibit hydrodesulurization and olefin saturation performance of catalyst. When the content of CO2 in recycle hydrogen is reduced from 5 900 ppm to 1 600 ppm, the inlet temperature of reactor is reduced by 10 ℃ at the same hydrodesulfurization rate. When the content of CO is lowered from 11 000 ppm to 2 ppm, hydrodesulfurization rate is increased from 57.3% to 93.8% , olefin saturation rate is elevated from 26.8% to 37.8%. Therefore, the contents of CO and CO2 should be controlled to less than 5 ppm to get a higher hydrodesulfurization rate.