催化剂孔径分布对中低煤焦油脱硫性能影响的研究

Effect of pore size distribution on performance of NiMo/Al2O3-USY catalysts for desulfurization of medium-low temperature coal tar

利用聚丙烯酰胺对Al2O3-USY复合载体进行扩孔处理,通过等体积浸渍制得NiMo/Al2O3-USY系列催化剂,在200 mL固定床上考察了催化剂孔径分布对中低煤焦油脱硫性能的影响,并结合XRD、氮气吸附、NH3-TPD和H2-TPR对催化剂理化性质进行分析。结果表明,添加聚丙烯酰胺能明显增加催化剂的平均孔径,使活性组分在载体上分布更加均匀,促进了活性组分与Al2O3的相互作用,降低催化剂的还原性能,使转化率下降。在温度为395℃、压力为8 MPa、空速为0.6 h^-1、氢油比为800的条件下评价催化剂的脱硫性能,结果发现增加催化剂的平均孔径有利于降低大分子含硫化合物的空间位阻,降低产品中柴油馏分硫的质量分数,不能明显降低汽油馏分硫的质量分数,中低温煤焦油脱硫催化剂的平均孔径应控制在5.30 nm以上。

The pores of Al2O3-USY composite support are expanded by means of polyacrylamide,and a series of NiMo/Al2O3-USY catalysts are prepared by equal volume impregnation.The effect of pore size distribution of the catalysts on their performance in desulfurization of medium-low temperature coal tar is investigated in a 200 mL fixed bed.The properties of the catalysts are characterized by XRD,NH3-TPD,H2-TPR and N2 absorption technologies.It is shown from the results that the addition of polyacrylamide can expand significantly the average pore diameter of the catalyst,make active components distribute more evenly on the support and promote the interaction between active components and Al2O3,which can reduce the reduction performance of the catalyst and lower the conversion rate.The performance of the catalysts for desulfurization of medium-low temperature coal tar is investigated under conditions of t=395℃,p=8 MPa,WHSV=0.6 h^-1 and H2/feed=800.The results verify that the increasing average pore diameter is beneficial to reducing the steric hindrance of macromolecule sulfur-containing compounds,which can decrease the sulfur content in diesel fractions but it cannot significantly reduce the sulfur content in gasoline fractions.Therefore,the average pore diameter of desulfurization catalysts for medium-low temperature coal tar shall be above 5.30 nm.