In this paper, we summarize the recent studies on shape-selective catalysis for methylation of aromatics in our group. Shape-selective methylation of toluene with methanol was studied over modified nano-scale HZSM-5, it was found that p-xylene selectivity of 28% over nano-scale HZSM-5 is close to its equilibrium value (p-xylene 24%, m-xylene 51%, o-xylene 25%) in three xylene isomers. After modification with Si, P and Mg, the catalyst exhibits higher p-xylene selectivity (near 100%). Unluckily, the conversion of toluene decreases from 23.3% to about 15% during 50 h reaction on stream. However, the catalyst modified with Pt demonstrated distinct improvement in activity. The conversion of toluene over catalyst loaded 0.3% Pt maintains a constant value of 23% and p-xylene selectivity is a constant 98% during 500 h reaction on stream. For the shape-selective methylation of biphenyl with methanol, after hydrothermal treatment, the catalytic selectivity to 4,4′-DMBP is up to 70%, while the 4-MBP conversion is about 12%. For the shape-selective methylation of naphthalene with methanol, the comprehensive modification of NH 4 F and SrO leads to an increase in the 2, 6-DMN selectivity (2, 6-DMN to DMN), up to 64.8% when 2-MN conversion is 10%. However, for the shape selective methylation of poly-aromatics, Pt modification can not improve the stability due to the isomerization of reactants.
All Science Journal Classification (ASJC) codes
- Chemical Engineering(all)