Synthesis Of Different Crystal Structures Of Alumina And The Hydrodesulfurization Performance Of The Corresponding Catalyst

With the environment pollution becoming more and more serious,more strict gasoline standards have been made all over the world.It has gradually attracted people’s attention that microwave can promote the chemical reaction due to its unique heating method.Different materials have different dielectric properties,thus they tend to show different responds with microwaves.In this paper,the synergistic effect of microwave and alumina based catalysts has been studied.Three series of alumina with different crystal stuctures were prepared by high temperture calcination of pseudo-boehmite,boehmite and β-Al₂O₃·3H2O.There were five different crystal stuctures,including γ-Al₂O₃,η-Al₂O₃,δ-Al₂O₃,θ-Al₂O₃ and α-Al₂O₃.The typical physicochemical properties of the series alumina materials were characterized by XRD,FT-IR and BET characterization methods.The difference between crystal structures of alumina were campared.Based on this work,the dielectric properties of alumina materials and their catalysts,as well as HDS performance of catalysts on thiophene,were evaluated.Finally,a series alumina marerial with good mechanical strength and evenly active component dispersion was selected to do numerical simulation in miacrowave field and the FCC gasoline HDS reaction under micrawave.It turned out that the permittivity of aluminas with different crystal structures were not high,but their sulfided catalysts showed high values.Different catalysts with different crystal structures had different dielectric properties.In addition,the type and the dispersion of active components on the surface of supports had a certain degree of influence on dielectric properties.In the FCC gasoline HDS reaction with micrawave irradiation,the FCC gasoline hydrogenation desulfurization rate and olefin saturation rate were higher than that obtained in normal condition,at the same time the selective factor was also higher than normal conditions.The desulfurization and olefin saturation ratios rose gradually with increasing reaction temperature.On the contrary,the selective factor decreased gradually.The catalyst of CoMo/θ-Al₂O₃,which had a higher dielectric properties,performed better in the HDS reaction.At 220 ℃,the desulfurization rate on CoMo/γ-Al₂O₃ reached 75.9%,14.3% higher than conventional heating under the same conditions.The desulfurization ratio based on CoMo/θ-Al₂O₃ catalyst reached 81.7%,16.5% higher than conventional heating under the same conditions.However,When the temperature reached 260 ℃,The desulfurization ratio differences based on CoMo/γ-Al₂O₃ and CoMo/θ-Al₂O₃ catalysts between microwave and conventional heating were only 2.1% and 2.4%,respectively.It is obvious that the strengthening effect of microwave irradiation on the FCC gasoline hydrodesulfurization reaction was more obvious at the low temperature range.