Biofuel synthesis in a capillary fluidized bed

•Hydrotalcite, MgO, CaO and zeolite catalysts transesterify canola oil in the gas phase.•Tests were made in a 7 mm ID capillary fluidized bed into which the cold liquid feed was atomized through a sparger.•Catalyst deactivated due to coke after 2 min with FCC and 20 min for the hydrotalcite.•Carbon loading on the hydrotalcite reached 5 wt% of the total carbon fed.

Hydrotalcite, MgO, CaO and zeolites transesterify canola oil in the gas phase at temperatures above 300 °C and atmospheric pressure. Syringe pumps metered oil and alcohol through a 1/8″ tube to the bottom of a 7 mm “capillary”-fluidized bed. Argon gas entered the annular region of the bed through a sintered glass frit as supplemental fluidizing gas. Oil conversion was complete with excess methanol in the feed. Contact times were less than 0.3 s and the weight-hourly space velocity was on the order of 15 h−1 (0.15 ml min−1 oil feed rate with 0.5 g of catalyst). As the catalyst deactivates, the oil condenses and the fluidized bed collapses. The zeolite deactivated within 2 min; the hydrotalcite could operate for several minutes; the CaO and MgO operated without interruption for well over 20 min. Periodic oxidation of the catalyst maintained catalyst activity.

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