INCAPE   05401
INSTITUTO DE INVESTIGACIONES EN CATALISIS Y PETROQUIMICA "ING. JOSE MIGUEL PARERA"
Unidad Ejecutora - UE
artículos
Título:
Gas phase imidazole methylation on zeolites and HPA/SiO2: Study of acid site requirements and catalyst deactivation
Autor/es:
M.N. VANOY-VILLAMIL; C.R. APESTEGUÍA; C.L. PADRÓ
Revista:
MICROPOROUS AND MESOPOROUS MATERIALS
Editorial:
ELSEVIER SCIENCE BV
Referencias:
Lugar: Amsterdam; Año: 2013 vol. 181 p. 54 - 60
ISSN:
1387-1811
Resumen:
The gas-phase alkylation of imidazole with methanol was studied at 523 K on HPA/SiO2 and zeolites HMCM22, HBEA, NaY, ZnY and HY. The nature, density and strength of acid sites were determined by temperature programmed desorption of NH3 coupled with infrared spectra of adsorbed pyridine. Coke formation was studied by temperature programmed oxidation technique. On all the samples, the selectivity to N-methylimidazole was greater than 98%. Catalysts presenting essentially Lewis (NaY and ZnY) or Brønsted (HPA/SiO2) acidity did not promote efficiently the methylation of imidazole and yielded less than 20% of N-methylimidazole. In contrast, on samples containing similar concentration of Lewis and Brønsted acid sites (HY, HBEA, HMCM22) the N-methylimidazole yield was between 60 % (HMCM22) and 100% (HY). All the samples deactivated during the 6 h catalytic tests and formed significant amounts of coke, between 2.3% (NaY) and 5.5% (HMCM22). Catalytic tests performed at different contact times showed that the initial activity decay diminished with increasing imidazole conversion, suggesting that catalyst deactivation is mainly related with the presence of the reactants, methanol and/or imidazole. Additional catalytic tests using different feed compositions showed that the initial catalyst deactivation followed a linear correlation with the partial pressure of imidazole which indicated that the activity decay is essentially related with the strong adsorption of imidazole on surface acid sites.