Cu-H-MCM-41, H-MCM-41 and Na-MCM-41 mesoporous molecular sieve catalysts for isomerization of 1-butene to isobutene

Cu-H-MCM-41, H-MCM-41 and Na-MCM-41 mesoporous molecular sieve catalysts were synthesized, characterized and investigated in the isomerization of 1-butene to isobutene. Introduction of copper in MCM-41 was found to play a positive role in enhancing the conversion of 1-butene and yield of isobutene and Cu-H-MCM-41 exhibited higher conversion of 1-butene and yield to isobutene than H-MCM-41 and Na-MCM-41 catalysts. The pretreatments of Cu-H-MCM-41 catalyst with synthetic air or hydrogen were observed to influence the 1-butene conversion, yield of isobutene and selectivity to isobutene. Pre-treated with the synthetic air the Cu-H-MCM-41-Ox catalyst exhibited higher conversion of 1-butene, yield of isobutene and selectivity to isobutene than hydrogen pre-treated Cu-H-MCM-41-Red. The reason for such a behavior of Cu-H-MCM-41-Red is the reduction of copper species to metallic form. The X-ray powder diffraction pattern of Cu-H-MCM-41-Red exhibited a peak attributed to the reduction of Cu²⁺ to Cu⁰. FTIR spectra of adsorbed pyridine showed the presence of Brønsted and Lewis acid sites in the H-MCM-41, Na-MCM-41 and Cu-H-MCM-41 catalysts.