2-苯基环己硫醇在γ-Al_(2)O_(3)和SiO_(2)负载的MoS_(2)催化剂上的脱硫反应

Desulfurization of 2-Phenylcyclohexanethiol Over γ-Al_(2)O_(3) and SiO_(2) Supported MoS_(2) Catalysts

合成了2-苯基环己硫醇(2-PCHT),在临氢和非临氢条件下研究了其在γ-Al_(2)O_(3)和SiO_(2)担载的MoS_(2)催化剂上的脱硫反应。采用X射线衍射(XRD)、H2程序升温还原(H2-TPR)、N2吸附-脱附等温曲线和透射电镜(TEM)等手段对所制备的样品进行分析表征。结果表明:MoO3高度分散于载体γ-Al_(2)O_(3)和SiO_(2)中;在240℃和5.0 MPa H2条件下,2-PCHT在MoS_(2)上主要通过β消除、氢解和脱氢3条路径脱硫,其中β消除和氢解并重,氢解快于β消除;非临氢条件下,主要通过β消除、C-S键均裂(或氢解)以及脱氢3条平行路径脱硫,并以β消除为主,临氢和非临氢条件下,2-PCHT在MoS_(2)催化剂上β消除路径不同。临氢条件下,MoS_(2)/Al_(2)O_(3)的氢解活性高于MoS_(2)/SiO_(2);非临氢条件下,MoS_(2)/Al_(2)O_(3)的β消除活性高于MoS_(2)/SiO_(2)。含氮化合物哌啶对β消除路径和脱氢路径有较强的抑制作用,但对氢解和C-S键均裂路径几乎没有影响。MoS_(2)的加氢活性以及对2-PCHT的脱硫活性均高于WS2。

2-Phenylcyclohexanethiol(2-PCHT)was synthesized and the desulfurization of 2-PCHT overγ-Al_(2)O_(3) and SiO_(2) supported MoS_(2) catalysts both in the presence and absence of H2was investigated.X-ray diffraction(XRD),H2 temperature-programmed reduction(H2-TPR),N2 adsorption-desorption isotherm and transmission electron microscopy(TEM)were used to characterize these samples.Results indicate that MoO3 is highly dispersed in Al_(2)O_(3) and SiO_(2).At 240℃and under 5.0 MPa H2,2-PCHT undergoes desulfurization over the supported MoS_(2) catalysts by three parallel pathways:β-elimination,hydrogenolysis and dehydrogenation.β-Elimination and hydrogenolysis are the two major pathways,and the hydrogenolysis pathway is faster than theβ-elimination pathway.Under Ar atomsphere,the parallel pathways includeβ-elimination,homolytic C-S cleavage(or hydrogenolysis),and dehydrogenation,withβ-elimination as the dominate pathway.Theβ-elimination reaction under H2 differs from those under Ar in the desulfurization of 2-PCHT over MoS_(2).The hydrogenolysis activity of MoS_(2)/Al_(2)O_(3) is higher than that of MoS_(2)/SiO_(2) under H2.Under Ar,MoS_(2)/Al_(2)O_(3) is more reactive than MoS_(2)/SiO_(2) mainly due to its higherβ-elimination activity.Piperidine strongly inhibits theβ-elimination pathway and the dehydrogenation pathway,but of no impact on the hydrogenolysis and homolytic C-S cleavage pathway.The hydrogenation activity and the desulfurization activity of MoS_(2) are superior to those of WS_(2).