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Dimethyl carbonate (DMC) was synthesized from methanol and ethylene carbonate (EC) in a reactive distillation column by transesterification using different composite oxide catalysts. The catalysts were characterized by XRD, N2 adsorption‐ desorption, CO2‐TPD, and NH3‐TPD. The results show that the Zr−Al catalyst has the most strong base sites and weak acid sites compared with other catalysts. The synergistic effect of acid‐base sites makes it show excellent catalytic performance for DMC synthesis. The operation parameters including reflux ratio, feed molar ratio, liquid hourly space velocity (LHSV) and catalyst dosage were optimized by factorial design based on response surface methodology (RSM). The best optimization conditions was: reflux ratio=5.23 : 1, feed molar ratio=6.05 : 1, LHSV=0.48 h−1, catalyst dosage=119.04 ml, the relative error between measured value and predicted value is small, which indicated that the reliability of the optimized process is high.

The hydrodemethylation reaction of 3,4-xylenol on micro/mesoporous catalysts with active component TiO 2 was studied. TiO 2 /YM-m and TiO 2 /YM-c micro/mesoporous materials were, respectively, derived by loading TiO 2 with the composition and mechanical mixing of Al-MCM-41 and HY zeolite. The effect of the bifunctional catalysts on the catalytic performance of hydroxymethylation of xylenol before and after the introduction of Al-MCM-41 into HY was investigated in this study. Compared with TiO 2 /Y catalyst, TiO 2 / MCM-41, TiO 2 /YM-m, and TiO 2 /YM-c have higher selective dealkylation products, especially the selectivity of cresol. This is attributed to the addition of Al-MCM-41 mesoporous molecular sieve to eliminate diffusion limitation. Compared with TiO 2 /YM-m catalyst, the TiO 2 /YM-c composite with Al-MCM-41 coated structure grown on the surface of HY crystals has better catalytic conversion activity and ability to inhibit secondary reactions. This is because of the existence of the special "coating" of HY zeolite, which eliminates the diffusion limitation and prevents the product and the reaction intermediate from entering the micropores for multiple reactions, thereby reducing the occurrence of side reactions. Meanwhile, TiO 2 /YM-c catalyst has the best demethylation performance under the optimal reaction conditions, the conversion of 3,4-xylenol, the selectivity to phenol, and m-cresol were 52.15%, 62.17%, and 36.32%, respectively. And the TiO 2 /YM-c catalyst has good stability within 80 h of reaction.

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