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A stable high-temperature reaction site and the rapid and uniform heating of the feedstocks are particularly important in pyrolysis. A novel device consisting of microwave-assisted heating (MAH) coupled with atomization feeding was used for continuous pyrolysis of methyl ricinoleate (MR) using silicon carbide (SiC) as the microwave absorbent bed. The heat transfer in microwave heating and MR pyrolysis in MAH device was studied by three-dimensional simulation. The effects of number of ports and heating power in microwave heating process, flow rate, feed mode and average droplet diameter of MR in pyrolysis process were investigated. Uniform temperature distribution of SiC bed surface was obtained with different numbers of ports. Higher energy efficiency was obtained at higher microwave power, with the highest value reaching 81% at 1000 W. The maximum flow rate of MR could reach 40 mL/min at a stable high-temperature bed surface. The atomization feed mode was beneficial to the temperature uniformity of SiC bed. The heating rate of atomized MR droplets was about 50000 °C/s, significantly higher than that of dropped MR droplets. The simulated results agreed well with the experimental results. It indicated the MAH coupled with atomization feeding could provide a stable high-temperature reaction site and increase the rapid and uniform heating of the feedstocks.

Uniform temperature distribution within solid catalyst particles is important to achieving low coke formation in a high-temperature reaction. However, the issue of uneven temperature distribution exists in most fixed-bed catalytic reaction systems. Here, we developed a microwave-assisted system and used it in catalytic dehydration of glycerol for sustainable production of acrolein. A coated microwave absorbing catalyst WO3/ZrO2@SiC was prepared and employed in the catalytic reactions. The effects of reaction temperature, ZrO2/SiC ratio, and weight hourly space velocity (WHSV) on glycerol conversion and arcolein selectivity were examined. Experimental results showed that the microwave heating proved to be more effective than the conventional electric heating for glycerol dehydration to acrolein at lower temperature. The acrolein selectivity reached over 70% with complete glycerol conversion at 250 oC by microwave heating. The catalyst acidity was greatly influenced by ZrO2/SiC ratio, which in turn determined the acrolein selectivity. More importantly, much better catalyst stability was obtained in the microwave-heating process than the electric-heating process. In addition, the microwave-heating system was effective for the in-situ regeneration of deactivated catalyst.