Hydroxymethylation of xylenol over micro/mesoporous TiO₂‐containing bifunctional catalyst: Effect of the Y zeolite incorporation with MCM‐41

Abstract

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.

Effect of seed on synthesis of binder‐free mordenite for dimethyl ether carbonylation

“…32,33 In the preparation stage, the mesoporous MOR or nano MOR were synthesized to shorten the diffusion path and overcome the diffusion resistance. 34,35 By employing the seed technique and an organosilane surfactant to generate the mesopores in the MOR, Kim et al 36 prepared MOR that resembled nanorods. It is reported that hexadecyltrimethylammonium bromide (CTAB) can regulate the morphology of molecular sieve.…”

“…Post‐treatments include methods such as selective dealumination, 25–27 metal modification, 28–31 and pyridine adsorption 32,33 . In the preparation stage, the mesoporous MOR or nano MOR were synthesized to shorten the diffusion path and overcome the diffusion resistance 34,35 . By employing the seed technique and an organosilane surfactant to generate the mesopores in the MOR, Kim et al 36 prepared MOR that resembled nanorods.…”