Impacts of support properties on the vacuum residue slurry-phase hydrocracking performance of Mo catalysts

To deeply understand the effects of support properties on the performance of Mo-based slurry-phase hydrocracking catalysts,four Mo-based catalysts supported on amorphous silica alumina(ASA),γ-Al_(2)O_(3),ultra-stable Y(USY)zeolite and SiO_(2) were prepared by the incipient wetness impregnation method,respectively,and their catalytic performances were compared in the vacuum residue(VR)hydrocracking process.It is found that the Mo/ASA catalyst exhibits the highest VR conversion among the different catalysts,indicating that both the appropriate amount of acid sites,especially B acid sites and larger mesoporous volume of ASA can enhance the VR hydrocracking into light distillates.Furthermore,Mo catalysts supported on the different supports show quite different product distributions in VR hydrocracking.The Mo/ASA catalyst provides higher yields of naphtha and middle distillates and lower yields of gas and coke compared with other catalysts,it is attributed to the highest MoS_(2) slab dispersion,the highest sulfuration degree of Mo species,and the most Mo atoms located at the edge sites for the Mo/ASA catalyst,as observed by HRTEM and XPS analyses.These features of Mo/ASA are beneficial for the hydrogenation of intermediate products and polycyclic aromatic hydrocarbons to restrict the gas and coke formation.

Layer-structure adjustable MoS_(2) catalysts for the slurry-phase hydrogenation of polycyclic aromatic hydrocarbons

Slurry-phase hydrogenation technology is the frontier topic in the efficient conversion of heavy oils into light fractions around the world.Developing highly active dispersed MoS_(2) catalysts is the major obstacle to realize the industrial application of upgrading heavy oils.In this work,both top-down ball-milling method and bottom-up hydrothermal method were designed to synthesize MoS_(2) catalysts with controllable layer structures.The stacking layers and lateral sizes for micro-scaled MoS_(2) catalysts by ball-milling method can be reduced to their limits and stabilize at 6~8 layers and lateral size of ca.30 nm.The more flexible bottom-up hydrothermal method can construct MoS_(2) catalysts with much smaller lateral sizes and fewer stacking layers,especially,MoS_(2) catalyst fabricated with ammonium tetrathiomolybdate as Mo and S precursor possesses average stacking layers of 2 and lateral size of 5 ~ 10 nm.Polycyclic aromatic hydrocarbons anthracene,phenanthrene and naphthalene were used as model compounds of heavy oils to investigate the catalytic hydrogenation performance of designed MoS_(2) catalysts.The catalytic activities of MoS_(2) catalysts can be well correlated with their stacking layers and lateral size.The edges of top and bottom S-Mo-S atomic layers for MoS_(2) sheets,named rim sites,are positively correlated with the exposure of active sites for catalytic hydrogenation of PAHs.The highest catalytic activity of MoS_(2) catalyst results from its layer structures of 100% rim sites and the smallest lateral size of5 ~ 10 nm,which is beneficial to expose maximum active sites for catalytic hydrogenation reactions.This work can guide us to design the highly active hydrogenation catalysts,and promote the industrial application of upgrading heavy oils.

Mo supported on natural rectorite catalyst for slurry-phase hydrocracking of vacuum residue:An effect of calcination

In order to develop high-efficiency and low-cost catalyst for the slurry-phase hydrocracking of vacuum residue(VR),the catalyst supported on natural rectorite was prepared,and the effect of calcination modification of rectorite on the catalyst properties and performance was investigated.The support of rectorite and catalyst were characterized by XRD,FTIR,Py-FTIR,H_(2)-TPR and XPS to examine their structures and properties.The comparative reaction results show that VR conversions for the catalysts supported on calcined rectorite were similar with that on raw rectorite,possibly due to the VR cracking reaction controlled by the thermal cracking following free radical mechanism because of few acid sites observed on the catalysts surface.However,the yields of naphtha and middle distillates for the various catalysts were obviously different,and increased following as Rec-Mo(40.4 wt%)