The reaction was carried out in a flow reactor (Ou Shisheng (Beijing) Technology Co., Ltd.). First, the flow reactor reaction tube was filled with magnets that could adsorb 100 mg of catalyst to make sure that the thickness of the catalyst on each magnet is about 1mm, and the reaction tube was maintained at a specific reaction temperature (the temperature is detected by the thermocouple in the reactor) and H2 pressure. Then, the vanillin reaction raw material with a concentration of 0.083 mol/L was passed through.