Vapour phase oxidation of tetralin over Cr and Fe substituted MCM-41 molecular sieves

Abstract Vapour phase oxidation of tetralin to 1-tetralone using molecular oxygen is reported for the first time on Cr and Fe substituted MCM-41 molecular sieves. Mesoporous monometallic Cr-MCM-41(Si/Cr 25, 50, 75 and 100), Fe-MCM-41(Si/Fe = 25) and bimetallic Cr-Fe-MCM-41(Si/(Cr + Fe) = 100) molecular sieves were synthesized by direct hydrothermal (DHT) process and characterized by XRD, ICP-AES, DR-UV–vis spectroscopy, EPR spectroscopy and SEM techniques. The conversion of tetralin and the selectivity for 1-tetralone were studied in the temperature range of 473–623 K. The efficiency of all the catalysts was evaluated and compared for the oxidation reaction under atmospheric pressure. Among various catalysts under study, Cr-MCM-41catalyst with Si/Cr = 25 exhibited maximum efficiency. The correlation between 1-tetralone selectivity and the catalysts physico-chemical characteristics is made. A reaction scheme is proposed for the oxidation of tetralin to 1-tetralone. The reaction is considered to occur in two steps: oxidation of tetralin to tetralol and oxidation of the latter to 1-tetralone, with the former process occurring over Cr 3+ and the latter over Cr 6+ .