The Size Control Of The Supported Ni-Mo Bimetallic Sulfide And Its Hydrodesulfurization Performance

Hydrodesulfurization?HDS?has aroused extensive attention as an important catalytic reaction for petroleum refining industry to upgrade the quality of fuels.With the increasingly stringent regulations limiting the sulfur content to less than 10 ppm in the liquid fuels,efficiently eliminating the sulfur-containing compounds with large molecular weight for deep HDS is necessary but still challenging.It is generally believed that the active sites for HDS are on the edges of the Mo S₂ slabs and promoted by Ni or Co atoms.Therefore,low stacking numbers and small nanoflake sizes of Mo S₂ can expose more edge active sites and then improve the HDS performance.However,metal nanocatalysts with ultrasmall sizes often suffer from severe aggregation and poor thermal stability for their high surface free energy.To efficiently modulate the sizes and chemical properties of 2D TMDs,many strategies such as exfoliation,chemical vapor deposition,and chemical and electrochemical intercalation,have been developed for applications in catalysis.Finding new ways to confine the growth and inhibit the aggregation of the molybdenum-based 2D TMDs would be of great importance.In article,a facile and general strategy has been developed to modulate the nanoflake sizes of a series of 2D transition metal sulfides with different sizes of ZSM-5 supports.The experimental results show that shorter average slab length and less average stacking number of the as-synthesized Ni Mo sulfide catalyst with the nano zeolite support shows excellent HDS catalytic activity,and effectively the stability and selectivity.Furthermore,we have constructed a hollow ZSM-5 zeolite support with inner surface,and successfully loaded Ni Mo S_x on inner surface.At the same time,the hollow ZSM-5 zeolite was used as the nano reactor to achieve better HDS activity and selectivity.The main research content is as follows:?1?We have demonstrated a facile and general“surface curvature-confined synthesis”strategy to prepare a series of 2D transition metal sulfides with small slab lengths and stacking numbers by tuning the radius of surface curvature of nanosized ZSM-5 supports.The unique size-confined effect of the nanosized zeolite supports benefites from the fact that the increased tensile strain derived from small surface curvature can effectively increase the diffusion barriers,which controls the growth of metal-based catalysts.Efficient Ni Mo sulfide catalysts with shorter slab length?average 3.71 nm?and less stacking number?1-2 layers?are embedded onto the nanosized ZSM-5 zeolites with the average size of 100 nm by a facile incipient wetness impregnation method.The Ni Mo S_x/ZSM-5-100 catalyst shows enhanced k _HDS value(14.05×10^-7 mol·g^-1·s^-1),stability?over 80 h?and selective?>95%?of DBT.?2?The nano-sized ZSM-5 zeolite was etched into a hollow structure with microporous and thin wall by the method of alkali solution post-treatment.Then,the metal active phase was loaded into the hollow cavity of ZSM-5 support by wet impregnation to form a composite Nanoreactor.The Ni Mo S_x/ZSM-5-hollow catalyst shows enhanced k _HDS value(10.65×10^-7 mol·g^-1·s^-1)of DBT over the Ni Mo S_x/ZSM-5catalyst.In addition,Ni Mo S_x/ZSM-5-hollow catalyst present high selectivity for direct desulfurization?DDS?.The improved k _HDS and direct desulfurization selectivity of Ni Mo S_x/ZSM-5-hollow catalyst are mainly due to the unique structural characteristics of the hollow structure,which can be used as a nanoreactor to show great potential in the field of catalysis.