Abstract：Pd-Pb/ZSM-12 catalysts were applied in disproportionation and transalkylation of toluene with heavy aromatics to increase xylenes product yield. The effect of loading Pd, the molar ratio of Pb to Pd and reaction conditions on catalyst performances were investigated in a continuous operation miniature fixed bed reactor. The results show that addition of Pd can improve heavy aromatics conversion, but also cause hydrogenation of aromatic ring. Addition of Pb to a low Pd content catalyst is effective to reduce aromatic ring hydrogenation and maintain high xylenes yield. Furthermore, the reaction conditions of high reaction temperature, low hydrogen pressure and hydrogen purity were favorable to reduce aromatic ring hydrogenation to obtain higher product purity. The optimized bimetallic catalyst containing 0.2% Pd metal and certain amount of Pb metal (molar ratio of Pb to Pd is 3) was used to catalyze the reaction under favorable reaction conditions of reaction temperature of 390 ℃, reaction pressure of 2.5 MPa, feed space velocity of 4.0 h-1 and hydrogen/hydrocarbon ratio of 2.0 with a feedstock containing 30% toluene and 70% heavy aromatics. The conversion of toluene and heavy aromatics was 21.7% and 36.2% respectively and the product purity of benzene reached 99.5%, which exhibits improved performance on enhancing heavy aromatic conversion and xylenes yield.
Guo Hongli,Li Jingqiu,Li Huaying et al. Disproportionation and Transalkylation of Toluene with Heavy Aromatics on Pd-Pb Bimetal Catalyst[J]. 化学反应工程与工艺, 2014, 30(2): 133-139.
