Monday, April 30, 2007

Transesterification of crude soybean oil with methanol in continuous reactors

Deog-Keun Kim, Jin-Suk Lee, Soon-Chul Park, Ji-Yeon Park, and Joon-Pyo Lee. Bioenergy Center, KIER, 71-2, Jang-dong, Yuseong-gu, Daejeon, 305-343, South Korea

Free fatty acids contained in crude soybean oil (CSBO) may deactivate the alkaline catalyst which is widely used for biodiesel production. To tans-esterify CSBO efficiently, the free fatty acids should be esterified by a solid acid catalyst before transesterification to get higher yield and to reduce subsequent process loads. To get high biodiesel productivity, continuous production process is adopted in most commercial plants. Tubular reactor [i.e., plug flow reactor (PFR)] is preferred to continuous stirred tank reactor (CSTR) because PFR is relatively easy to maintain, and it produces the highest conversion per volume of any of the flow reactors. The feed oil and methanol are immiscible with each other. Intense agitation is required initially to start transesterification reaction. In case of PFR, it is necessary to use pre-mixer because there is no mixing means. We have installed three in-line (static) mixers at the entrance point and every 10 M locations of totally 30 M length of PFR. The CSBO was pre-esterified successfully in a reactor packed with Amberlyst 15, which was used as a solid acid catalyst, from initial acid value of 1.6 to final acid value of 0.5-0.6. The performance data of the PFR will be presented under various operating conditions such as temperature, reaction time (total flow rate), number of static mixer, reactants flow direction (gravity vs. anti-gravity), etc. The performance of the PFR with different molar ratio of CSBO/methanol and catalyst concentrations will also be compared with those of batch and CSTR reactor.