The Modification Of Supported Nickel Phosphide Catalyst And Its Hydrodesulfurization Performance Of Dibenzothiophen

The Ni₂P/Na（x）-MCM-41 and the citric acid（CA）modified supported Ni₂P/Na-MCM-41 catalysts were successfully prepared by impregnation of diammonium hydrogen phosphate（（NH4）2HPO4）and nickel nitrate solution with Na-MCM-41 support,respectively.The obtained catalysts were characterized by XRD,BET,CO uptake,TEM,Py-FT-IR,XPS,and H₂-TPR.The hydrodesulfurization（HDS）performance of catalysts were investigated on a fixed bed by using the dibenzothiophene（DBT）as model compound.The results of Ni₂P/Na（0.7）-MCM-41 over the reduction temperature of 450 oC⁶00 oC indicated that the Ni₂ P active phase was formed of all samples.However,at a reduction temperature of 500 oC the catalyst precursor can be adequately reduced to the Ni₂ P active phase,and no additional phase related to Ni and P is observed.An appropriate amount of Na is beneficial to the formation of the Ni₂ P phase and a better dispersion of Ni₂ P particles.The Na would preferentially interact with phosphate to generate the sodium phosphate and therefore could suppress the formation of stronger P-O-P bonds,which makes the phosphide catalyst be easily formed at a lower reduction temperature.The reduction temperature of Ni₂P/Na（x）-MCM-41 catalyst was 500 oC,which is decreased by about 200 oC as compared to that of the conventional phosphate（700¹000 oC）.The Ni₂P/Na（x）-MCM-41 catalyst with x = 1.0 exhibited the highest DBT HDS activity of 91.6%,which was an increase of 14.0% when compared with that found for Ni₂P/M41 without Na（80.3%）at the conditions of 340 oC,3.0 MPa,H₂/oil ratio of 600（v/v）,and a weight hourly space velocity（WHSV）of 2.0 h^-1.The CA modified supported nickel phosphide catalysts denoted as Ni₂PCA（y）/Na-M41 were successfully prepared.The results indicated that CA can enrich the pore canal of catalysts,dramatically improve the surface area.Moreover,the incorporation of CA can suppress the enrichment of phosphorus on surfaces,and promote the formation of smaller and highly dispersed Ni₂ P particles.The Ni₂PCA（y）/Na-M41 with y = 0.5 exhibited the highest dibenzothiophene hydrodesulfurization activity of 99.3%,which is an increase of 17% when compared with that found for Ni₂P/Na-M41 at the conditions of 340 oC,3.0 MPa,H₂/oil ratio of 600（v/v）,and a weight hourly space velocity（WHSV）of 2.0 h^-1.