Preparation And Application Of Efficient Metal-based Hydrotreating Catalysts

Hydrotreating of oil is conducive to the improvement of fuel quality and the reduction of harmful substances.It is of great significance to develop efficient hydrogenation catalysts.Platinum and nickel had good catalytic performance of hydrogenation,but they are easy to be poisoned by sulfur and nitrogen containing compounds.Carbon modification is an effective mean to promote the performance of the active component dispersion and the introduction of carbon species can also give the catalyst corresponding carbon characteristics.In this paper,supported metal catalysts were prepared with carbon-modified montmorillonite(MMT-C)as carrier,Pt and Ni as different active components,and then investigated their hydrorefining performance under different conditions.Combined with H₂-TPD,H₂-TPR,TEM and XRD methods,the influence of carbon modification and acid treatment to hydrotreating performance of catalysts was discussed.The results showed that:(1)Carbon modification could significantly promote the hydrotreating performance of Pt/MMT catalysts.This was due to the fact that carbon modification promoted the dispersion of Pt on the surface of the supporter,the dispersity was 4.3 times promoted.In addition,through the H₂-TPD characterization of MMT-C,it was found that MMT-C had a large amount of hydrogen adsorption and high adsorption strength,indicating that MMT-C has a high ability to dissociate and activate hydrogen.The carbon modification improved the ability of the catalyst to dissociate and activate hydrogen.A large amount of activated hydrogen was coated on the surface of the catalyst,so that Pt metal was not poisoned by harmful substances such as S,N,thereby promoted the hydrotreating performance of the catalyst.(2)Pt(acac)₂instead of H₂Pt Cl₆as a platinum source could eliminate the bad effects of chlorine on the catalyst,reduce the sintering of active metals,increase the dispersion of Pt components,the Pt paticle size was diminished from 3.67nm to 1.59nm,and the hydrotreating performance of Pt/MMT-C catalysts was significantly increased.Under the same conditions,not only the hydrogenation activity of the catalyst was improved,but also the catalyst achieved a stable naphthalene hydrogenation performance of n-dodecane as a solvent at 200°C.The outstanding hydrogenation performance of Pt/MMT-C prepared by Pt(acac)₂as a platinum precursor is more pronounced under mild conditions.(3)Acid modification greatly promoted the hydrotreating performance of the Pt/MMT-C catalyst with the TOF was promoted by 1.3 times.One of the main causes of the promotion was that acid modification greatly enhanced the ability of MMT-C to activate hydrogen and provide more active hydrogen during the reaction.Moreover,acid modification changed the structure of montmorillonite,the newly formed pore structure provided more diffusion paths for reactants and products,improved the diffusion efficiency and provided more active sites for the catalyst.(4)Ni/MMT-C is a high performance hydrotreating catalyst.Carbon modification can significantly improve the hydrogenation and HDS performance of Ni/MMT catalysts.And more,the catalysts still have stable HDS activity when the reaction temperature is as low as 100°C.The main role of carbon modification is to increase the dispersity of the metal and the ability of the catalyst to activate hydrogen,so that during the reaction process,the activated hydrogen continuously dissociated from the surface of the catalyst hinders the contact between the H₂S molecule and the metal nickel,thereby exhibiting relatively stable hydrotreating performance.