The active site of nickel phosphide catalysts for the hydrodesulfurization of 4,6-DMDBT
The active site of nickel phosphide catalysts for the hydrodesulfurization of 4,6-DMDBT
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DOI：
10.1016/j.jcat.2008.06.023
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发表时间：
2008-09-10
影响因子：
7.3
通讯作者：
Lee, Yong-Kul
中科院分区：
文献类型：
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作者：
Oyama, S. Ted;Lee, Yong-Kul
采用程序升温还原（TPR）法制备了SiO2和MCM-41负载Ni2P催化剂，研究了分散对催化剂结构和加氢处理性能的影响。样品的表面积从低(Ni2P/SiO2-L, 88 m（2) g(-1)）到高(Ni2P/SiO2-H, 240 m（2) g(-1)）到高(Ni2P/MCM-41, 487 m（2) g(-1)）不等，相应的Ni2P平均晶粒尺寸从10.1减小到6.5和3.8 nm。采用x射线衍射（XRD）和扩展x射线吸收精细结构（EXAFS）研究获得了负载NO相的结构参数。在三相固定床反应器中，以含4,6-二甲基二苯并噻吩（4,6- dmdbt）和喹啉为模型进料，在613 K和3.1 MPa条件下测定了加氢脱硫（HDS）的催化活性。在标准条件下，以500 ppm S为4,6- dmdbt， 6000 ppm S为二甲二硫（DMDS）， 500 ppm N为喹啉，根据反应器中负载的等位（230 μ mol），催化活性为Ni2P/MCM-41 > Ni2P/SiO2-H > Ni2P/SiO2-L。特别是，Ni2P/MCM-41的HDS转化率为90%，远高于Ni-Mo-S/Al2O3商用催化剂的HDS转化率68%，这是基于反应器中负载的相同数量的位点（230 μ mol）。磷化物采用CO化学吸附法，硫化物采用低温O-2化学吸附法。样品的EXAFS分析证实了两种类型的位点的存在，即四面体Ni(1)位点和方锥体Ni(2)位点，后者的数量随着反应性Ni2P/MCM-41 > Ni2P/SiO2-H > Ni2P/SiO2-L的减小而增加。从对直接脱硫（DDS）产物（二甲联苯）和加氢（HYD）产物（甲基环己基甲苯和二甲基双环己基）的选择性来看，Ni(1)位点是直接脱硫（DDS）的主要活性位点，而Ni(2)位点是直接脱硫（HYD）的高活性位点。(C) 2008爱思唯尔公司版权所有。
Ni2P catalysts supported on SiO2 and MCM-41 were prepared by temperature-programmed reduction (TPR), and the effect of the dispersion on catalyst structure and hydroprocessing performance was studied. The surface areas of the samples varied from low (Ni2P/SiO2-L, 88 m(2) g(-1)) to high (Ni2P/SiO2-H, 240 m(2) g(-1)), to very high (Ni2P/MCM-41, 487 m(2) g(-1)), with corresponding Ni2P average crystallite sizes decreasing from 10.1 to 6.5 and 3.8 nm. X-ray diffraction (XRD) and extended X-ray absorption fine structure (EXAFS) studies were used to obtain structural parameters for the supported NO phase. The catalytic activity in hydrodesulfurization (HDS) was measured at 613 K and 3.1 MPa in a three-phase fixed bed reactor using a model liquid feed containing 4,6-dimethyldibenzothiophene (4,6-DMDBT) and quinoline in a tridecane solvent. At standard conditions using 500 ppm S as 4,6-DMDBT, 6000 ppm S as dimethyldisulfide (DMDS), and 500 ppm N as quinoline, the catalytic activity followed the sequence Ni2P/MCM-41 > Ni2P/SiO2-H > Ni2P/SiO2-L, based on equal sites (230 mu mol) loaded in the reactor. In particular, Ni2P/MCM-41 gave an HDS conversion of 90%, which was much higher than that of a commercial Ni-Mo-S/Al2O3 catalyst which gave an HDS conversion of 68%, based on equal number of sites (230 mu mol) loaded in the reactor. The sites were counted by CO chemisorption for the phosphide and by low-temperature O-2 chemisorption for the sulfide. EXAFS analysis of the samples confirmed the presence of two types of sites, tetrahedral Ni(1) sites and square pyramidal Ni(2) sites, with the latter growing in number in the same order as the reactivity Ni2P/MCM-41 > Ni2P/SiO2-H > Ni2P/SiO2-L, as the crystallite size decreased. From the selectivity to the direct desulfurization (DDS) product (dimethylbiphenyl) and the hydrogenation (HYD) products (methylcyclohexyltoluenes and dimethylbicyclohexyls) it is concluded that the Ni(1) sites are responsible for DDS while the Ni(2) are highly active sites for the HYD route. (C) 2008 Elsevier Inc. All rights reserved.