Synthesis Of A Beta-based Micro/mesoporous Composite Material And Its Application In The Hydrodealkylation Of C₁₀⁺ Heavy Aromatics

Benzene,toluene and xylene are important chemical raw materials such as synthetic fiber,synthetic plasticizer and synthetic resin.However,the composition of heavy aromatics raw materials is very complicated and the separation is very difficult.The overall utilization value is not high.The use of hydrodealkylation technology to convert heavy aromatics to benzene,toluene,xylene and other basic petrochemical products,is an important approach to improve the utilization of heavy aromatics.Therefore,the development of highly efficient hydrodealkylation?HDA?catalysts is the most efficient and economical way to achieve mass production of BTX.To improve the dispersion of active components,and to modulate the micro structure of active phased particles and to choose the appropriate support are the key to impel the activity of HDA catalyst.In this thesis,C₁₀ heavy aromatics hydrodealkylate to produce BTX over Beta-based micro/mesoporous composite material-supported metal oxide and Pt catalysts was studied.The catalysts were charactered by means of N₂ adsorption and desorption,NH₃-TPD,H₂-TPR,UV-Vis,XRD,FT-IR,SEM and TEM.Based on the preferred support type,the effect of Beta-based micro/mesoporous composite material,Ni/Beta-SBA-16,Mo/Beta-SBA-16,Pt/Beta-SBA-16 hydrodealkylation catalysts were investigated.And the MoO₃/Beta-SBA-16 catalyst was found has greatest catalytic performance.Firstly,a composite material Beta-SBA-16 was synthesized by enwrapping nano-sized Beta zeolite crystals with mesoporous SBA-16 silica.The catalytic performance of Beta-based micro/mesoporous composite material-supported molybdenum oxide showed that the Beta-SBA-16 micro/mesoporous composite material was a greatest support.For MoO₃/Beta-SBA-16,the suitable MoO₃ loading is 15wt%²0wt%,and the 20wt%MoO₃/Beta-SBA-16 catalys shows the best catalytic performance,C₁₀ aromatics conversion is 35.7%,C₉^-selectivity is 89.24%and the selectivity of BTX is 41.0%.For NiO/Beta-SBA-16,the suitable NiO loading is 1wt%³wt%;Among the Pt/Beta-SBA-16 noble metal catalysts,0.8%Pt/Beta-SBA-16 showed the best catalytic performance,but too high of noble metal loading will caused the remarkable reduction of selectivity of BTX and selectivity of C₉^-.With the increase of noble metal loading,the liquid product yield was remarkably reduced.