Cetinyokus Kilicarslan S., DOĞAN M., DOĞU T.

JOURNAL OF THE FACULTY OF ENGINEERING AND ARCHITECTURE OF GAZI UNIVERSITY, vol.29, no.3, pp.459-467, 2014 (SCI-Expanded) identifier identifier


In this study, the effects of Ca addition to Cr-MCM-41 catalysts on chromate species distribution over the catalyst and the catalyst activity were investigated. Firstly, catalysts were synthesized by impregnation method using different calcium sources (CaCO3, CaCl2, Ca(NO3)(2)). Monochromates, were known as the most active chromate species for isobutane dehydrogenation, were determined on the synthesized catalysts using CaCO3 salt so this salt was used in the forward studies. After Ca impregnation, a slight increase was observed in the amount of mono-and dichromate located in the structure of the catalysts synthesized by hydrothermal method. It was indicated that monochromate species absent before formed after Ca addition on the catalysts synthesized with impregnation technique. It was shown that in the case of Ca/Cr ratio as 0.65 in the studies conducted at different Ca/Cr (mass/mass) ratios, the peak (380nm) showing O-Cr (VI) bond in monochromate was more intense than the other catalysts from the DR-UV-vis analyzes. As regards the catalyst surface composition was examined, the highest Cr/Si ratio was also determined in that catalyst. The catalytic test studies of the synthesized catalysts according to impregnating and hydrothermal synthesis methods at a Ca/Cr ratio of 0.65 were performed at 873K temperature and at atmospheric pressure. The catalysts become privileged position in terms of isobutene selectivity, because of the products of side reactions were not observed in these tests. Although a significant decrease was seen on the surface area of the catalyst (Cr-MCM-41-EM) synthesized by impregnation method with the addition of Ca, preservation of isobutane conversion values was explained by the active monochromate species formed in the structure.