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Liquid phase hydrogenation of citral on zeolite supported monometallic (Ni,Pt) and bimetallic (ni-Sn, Pt-Sn) catalysts
In this study the liquid phase citral hydrogenation reaction over zeolite supported monometallic and bimetallic Ni and Pt catalysts was studied. The zeolite support materials were Na-Y, Na-, Na-Mordenite, MCM-41, and Clinoptilolite. The catalysts were prepared by impregnation and co-impregnation techniques. Catalytic activity and selectivity tests were performed in a semi-batch reactor at 80°C temperature, 6 bar pressure and 600 rpm stirring speed with 0.25 g catalyst. The characterization studies showed that the structures of support materials were preserved during impregnation and co-impregnation. The Ni and Pt contents of the catalysts was around 8.5 % and 5 %, respectively while the Sn content changed between 0.46 and 4.10 %. The activity of the catalysts and product distribution were affected by type of active metal and type of support. The major product over monometallic and bimetallic catalysts was citronellal. The Ni/Na-Y catalyst gave the maximum yield of desired products, unsaturated alcohols and citronellal, (93 %) and citral conversion (>99 %) among the monometallic catalysts. The most selective monometallic Pt catalyst to desired products was Pt /MCM-41 with a yield of 40 %. Addition of Sn increased the unsaturated alcohol formation and decreased the acetal formation. The activity of the Ni catalyst was generally decreased while the activity of the Pt catalyst was improved. The amount of unsaturated alcohols increased with Sn/Sn+Ni ratio for bimetallic Ni catalysts. The highest yield of desired products was obtained with Ni/Na-Y (93 %) and with Ni-Sn/MCM (80 %) among monometallic and bimetallic catalysts.