Gas phase glycerol dehydration over H-ZSM-5 zeolite modified by alkaline treatment with Na 2 CO 3

LAGO, C.D.; DECOLATTI, H.P.; TONUTTI, LUCAS G.; DALLA COSTA, B.O.; QUERINI, C.A.

JOURNAL OF CATALYSIS

ACADEMIC PRESS INC ELSEVIER SCIENCE

Año: 2018 vol. 366 p. 16 - 27

0021-9517

Modified H-ZSM-5 zeolite catalysts were studied for the dehydration of glycerol to acrolein in gas phase.The modifications were made by alkaline treatment using Na2CO3 solutions in different concentrations,followed by consecutive ion exchanges with NH4NO3 solution in order to recover the acidic form of thematerials. The mild conditions selected (alkali concentrations, time and temperature) allowed to preservethe crystallinity and framework characteristic in the zeolite, selectively removing silicon while maintainingpractically all the aluminum content. This process has important advantages over the alkaline treatmentwith NaOH (at an equivalent pH), such as high selectivity to remove silicon instead of aluminum,and in addition the yield of synthesized material respect to the initial mass is markedly higher (80% vs50%). This treatment with Na2CO3 solutions leads to multiple positive effects as: increments in the mesoporosityand external surface area; and changes in the nature and accessibility to the acid active sites. Thecatalytic activity and selectivity were greatly improved. Further, the deactivation by coke deposition wasattenuated.