Preparation Of Highly Dispersed NiW Hydrogenation Catalyst Based On LDHs

Sulfide compounds in diesel were burned into sulfur oxides,which will release into the atmosphere,cause great pollution to the environment and a threat to human health.Hydrotreating is the most effective method for removing sulfides in diesel.Owing to the limitation of the surface area and pore structure,the limited load of the active component on the supporter,traditional supported hydrotreating catalysts are difficult to achieve high dispersion under high loading amount.As everyone knows,hydrotalcites or layered double hydroxides(LDHs)are characterized by easily exchangeable layer cations and interlayer anions.Therefore,the active metal Ni was introduced into the layers,W was introduced between the layers,which would be beneficial to hydrodesulfurization(HDS),obtained an unsupported catalyst with high active metal content and a high dispersion by calcination processing,to improve the HDS performance of the catalyst.The results were listed in the following.Firstly,the NiAl-WO4-LDHs hydrotreating catalyst were prepared by co-precipitation and ion exchange respectively.The NiAl-WO4-LDHs prepared by ion exchange had the higher wolfram dispersion after calcination processing.The WO3 could still maintain a high dispersion when the content of WO3 was 50.55 wt%,the content of NiO was 39.87 wt%.When the catalyst had the same metal content,the HDS conversion rate to DBT of the catalysts prepared by ion exchange was 12.9%higher than the catalysts prepared by coprecipitation,the HDS conversion rate to DBT of the catalysts prepared by ion exchange was 33.5%higher than the catalysts prepared by impregnation of NiW/Al2O3.When the catalysts prepared by the same method,NiAl-WO4-LDO for the HDS activity of DBT increasing with the layer ratio of Ni to Al improving,when the ratio of Ni to Al was 3,the catalysts for the HDS conversion rate of DBT were up to 70.8%.Secondly,the synthesis process of NiAlZr-WO4-LDHs was as follow:first,the Zr was introduced into LDHs laminate,which could be unfolded by swelling action of glycol.Then WO4 was exchanged to interlayer through ion exchange method.The HDS conversion rate of DBT rose gradually with the increasing of Zr content.The conversion rate was 78.53%when the molar ratio of Ni:Al:Zr was 3:0.4:0.6 with the optimum reaction activity.Compared to the catalyst with the equal content synthesized by impregnation method,the conversion rate of DBT was increased by 26.58%.