STUDIES ON THE CATALYTIC CONVERSION OF CANOLA OIL TO HYDROCARBONS - INFLUENCE OF HYBRID CATALYSTS AND STEAM

The conversion of canola oil (used as a representative feed material for waste oils and fats) was studied in the presence and absence of steam using silica-alumina, HZSM-5, and 4 Hybrid catalysts. The hybrid catalysts were prepared by adding H-Y to silica-alumina in the weight ratios 1:3 and 3:1 and HZSM-5 to silica-alumina in the weight ratios 1:3 and 3:1. The conversions were performed at atmospheric pressure, a temperature range of 400-550 degrees C, and weight hourly space velocities of 1.8 and 3.6 h(-1) (WHSV) in a fixed bed reactor. The objective was to investigate the production of both liquid and gaseous hydrocarbon products from the catalytic conversion of canola oil. In addition, it was intended to study the effect of steam on the product selectivities. The conversions were high on all the catalysts and ranged between 81 and 100%. Conversion to an organic liquid product (OLP) varied significantly with temperature and space velocity. The yields were between 22-53 wt % with silica-alumina and between 23 and 63 wt % with HZSM-5 catalyst. In most cases, hydrocarbons formed the major components in the OLP. HZSM-5 provided a high selectivity for aromatic hydrocarbons than silica-alumina catalyst, while the selectivity for aliphatic hydrocarbons was higher with silica-alumina than HZSM-5 catalyst in the OLP products. The olefin/paraffin ratio in the gas products was low but it increased tremendously in the presence of steam, indicating that dehydrogenation reactions were predominant in the presence of steam. The gas yield increased with temperature and decreased with increase in WHSV. Ethylene, propylene, isobutylene, propane, and n-butane were some of the major components of the gas products. Prolonged catalyst life (decrease in coke formation) and enhanced olefin formation were the main advantages of cofeeding steam during conversion. When zeolite catalysts were added to silica-alumina catalyst, the coke formation and OLP yields decreased whereas the gas yields increased. With silica-alumina-H-Y hybrid catalysts, the aromatic content of OLP increased, resulting in an overall increase in the hydrocarbon content of the OLP. On the other hand, the aromatic hydrocarbon content increased at the expense of aliphatic hydrocarbons. With silica-alumina-HZSM-5 hybrid catalysts, the hydrocarbon content of the OLP was similar to those obtained with pure HZSM-5 catalyst; i.e., they were composed mostly of aromatic hydrocarbons and only small fractions of aliphatic hydrocarbons. In general, cracking and aromatization reactions increased significantly with addition of H-Y or HZSM-5 to silica-alumina.