Journal of Molecular Catalysis A-Chemical, Vol.421, 92-101, 2016
Catalytic behaviour of mesoporous metal phosphates in the gas-phase glycerol transformation
The catalytic behaviour of mesoporous simple (M = Al, Fe, Co, Mn) and binary (Al/M; M =Fe,V,Ca; molar ratio Al/Fe = 50; Al/V=2; Al/Ca= 1) metal phosphates, synthesized by an economical gelation method, in the gas-phase glycerol reaction at temperatures between 220 degrees C and 280 degrees C, has been investigated. The morphology, textural properties and the acidity by pyridine TPD, of the phosphates were also determined. The activity of the phosphates in the formation of the main reaction product (acrolein) depended not only on their acidity (mainly acid sites of weak-medium strength) but also on the redox sites and morphology exhibited. Thus, the aluminium-vanadium phosphate showed the highest value of yield to acrolein, 62% (equivalent to a productivity of 0.88 g(ACR)/g(cat.h)) at 280 degrees C, whereas the amorphous FePO4 and AlPO4 were appreciably more active than the rest of the simple phosphates, exhibiting a high crystalline character. The apparent activation energy values obtained for the acrolein formation ranged between 18 and 91 kJ/mol. Based on the identified products in this study, some possible reactions involved in the glycerol transformation have been suggested. (C) 2016 Elsevier B.V. All rights reserved.
Keywords:Glycerol transformation;Acrolein formation;Acrolein formation activation energy;Amorphous metal phosphate;Amorphous aluminium phosphate;Pyridine TPD