Enhanced coke resistance of Ca- and Mg-incorporated Mo/V montmorillonite-supported catalysts during gas-phase glycerol conversion to allyl alcohol
The efficient production of allyl alcohol from glycerol is of great importance due to its significance as a valuable intermediate in chemical industries. While catalytic conversion of glycerol to allyl alcohol by solid acid catalysts, carbon deposition (coking) is prone to occur on the catalyst surface, leading to slow down the conversion process and fast deactivation of the catalyst. In this study, we obtained an efficient catalyst for the preparation of allyl alcohol from gas-phase glycerol by controlling the pore structure and surface acidity of the catalyst. The characterization results showed that hydrochloric acid and citric acid removed the silicon and aluminium elements from montmorillonite, and the acidity, pore volume, and surface area ratio of Na-MMT (SBET=34.5 m2 g-1, VT=0.19 cm3 g-1) of the porous montmorillonite(HA1MMT) catalyst were all improved (SBET=97.9 m2 g-1, VT=0.28 cm3 g-1); After adding MoOx and VOx, the selectivity of Mo/V-HA1MMT catalyst for allyl alcohol was improved. The XPS characterization results indicate that the synergistic effect of Mo and V can promote the transfer of electrons during the reaction process of glycerol conversion. Within 480 minutes of catalyzing glycerol dehydration reaction, Mo0.6V0.4(5)-HA1MMT was almost deactivated (Conv.= 19.5%, Sel.allyl alcohol=31.2%) due to carbon deposition. When the catalyst was doped with calcium and magnesium components, a new active phase CaMo4 was discovered on the catalyst, and the acidity of Ca0.5Mg0.5-Cat. (Cat. is Mo0.6V0.4(5)-HA1MMT) decreased to 214.0 μmol g-1. The coking resistance performance of Ca0.5Mg0.5-Cat. was improved, and after 660 minutes of reaction, the catalyst was deactivated (Conv.= 32.1%, Sel.allyl alcohol=30.1%) due to carbon deposition. During the 3rd catalyst regeneration test, Ca0.5Mg0.5-Cat. still maintained high activity (Conv.= 63.3%, Sel.allyl alcohol=35.2%, Sel.acrolein=31.2%). The results of this study indicate that suitable pore structure and acidity are crucial for designing a catalyst with coking resistance properties.
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