柠檬酸预处理对nMoOx·USY加氢脱硫性能的影响

Effect of citric acid pretreatment on hydrodesulfurization performance of nMoO_(x)·USY catalyst

采用等体积浸渍法和柠檬酸络合法制备了不同用量柠檬酸预处理的nMoOx·USY催化剂,利用XRD,BET,SEM,NH3-TPD对nMoOx·USY催化剂进行了表征,以0.6%(w)的二苯并噻吩/正癸烷溶液为模型反应物评价了催化剂的加氢脱硫性能。实验结果表明,Mo物种与USY分子筛形成了nMoOx·USY单相复合体,引起USY分子筛晶胞参数减小,导致催化剂比表面积下降,总酸量增多,弱酸中心比例增多,强酸中心比例减少。用12分子柠檬酸预处理制备的nMoOx·USY催化剂在270,290,310℃反应温度下的加氢脱硫转化率达58.40%,92.47%,98.32%,联苯选择性依次减少。不同用量柠檬酸预处理制备的nMoOx·USY催化剂的二苯并噻吩脱硫反应途径以加氢脱硫反应为主。

The nMoOx·USY catalysts with different dosage of pretreatment citric acid were prepared by citric acid complexation and incipient wetness impregnation methods,and characterized by XRD,BET,SEM and NH3-TPD.The hydrodesulfulrization performance of the nMoOx·USY was evaluated with 0.6%(w)dibenzothiophene/n-decane solution as the model reactant.The results indicated that the nMoOx·USY single phase complex was prepared by using solid-state reaction of MoOx with USY,which resulted in the decrease of cell parameters of USY molecular sieve and the reduction of specific surface area of the catalyst.Besides,the total acid amount and the weak acid site both increased,while the proportion of strong acid centers decreased comparatively.The dibenzothiopene conversion of the nMoOx·USY single phase complex prepared with the citric acid of 12 molecules reached to 58.40%,92.47%,98.32%at 270,290,310℃respectively and the selectivity of biphenyl decreased successively.Furthermore,the dibenzothiopene desulfurization reaction over the nMoOx·USY prepared with different amounts of citric acid was dominated by the hydrodesulfurization reaction.