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Conventional fixed-bed reactors have the issue of uneven temperature distribution within the catalyst bed, which influences product selectivity and catalyst stability. Microwave irradiation can realize uniform and bulk heating due to its unique penetration capability. Here, a microwave fixed-bed reactor was developed and applied in a gas-phase glycerol dehydration reaction. Nine microwave-absorbing binary metal oxide catalysts were used to verify the versatility of microwave reactors in gas–solid reactions. Compared with an electric-heating reactor, much better catalyst stability was obtained in a microwave reactor for all of the catalysts. Moreover, no obvious change in catalyst stability was observed with increasing reactor size. Numerical simulation was adopted to explore the intensification mechanism of microwave heating. The largest temperature difference in the microwave reactor was around 10 °C, much smaller than that in the electric-heating reactor which reached 57 °C. The electric field distribution within the penetration depth of microwave irradiation was homogeneous, resulting in uniform temperature distribution in the microwave reactor and hence good catalyst stability.

Pyrolysis of methyl ricinoleate (MR) can produce undecylenic acid methyl ester and heptanal which are important chemicals. Atomization feeding favors the heat exchange in the pyrolysis process and hence increases the product yield. Herein, predictive models to characterize the atomization process were developed. The effect of spray distance on Sauter mean diameter (SMD) of atomized MR droplets was examined, with the optimal spray distance to be 40–50 mm. Temperature mainly affected the physical properties of feedstock, with smaller droplet size obtained at increasing temperature. In addition, pressure had significant influence on SMD and higher pressure resulted in smaller atomized droplets. Then, a model for SMD prediction, combining temperature, pressure, spray distance, and structural parameters of nozzle, was developed through dimensionless analysis. The results showed that SMD was a power function of Reynolds number (Re), Ohnesorge number (Oh), and the ratio of spray distance to diameter of swirl chamber in the nozzle (H/dsc), with the exponents of −1.6618, −1.3205 and 0.1038, respectively. The experimental measured SMD was in good agreement with the calculated values, with the error within ±15%. Moreover, the droplet size distribution was studied by establishing the relationship between the standard deviation of droplet size and SMD. This study could provide reference to the regulation and optimization of the atomization process in MR pyrolysis.