Based on the above initial catalyst screening research, we used catalyst E to further test the reaction factors such as solvent, reaction temperature, hydrogen pressure, and reaction time. The schematic diagram of the Ni@C catalyst hydrogenation of acetophenone in a flow reactor is shown in Figure . Hydrogen pressure, as a key factor that usually significantly affects the hydrogenation reaction, is evaluated in the reaction of acetophenone hydrogenation to phenethyl alcohol at a reaction temperature of 120 °C and a flow rate of 0.2 mL/min. As shown in Figure , when the pressure increases from 2 MPa to 2.5 MPa, the conversion rate and selectivity decrease to a certain extent. It is speculated that the pressure may be too high to vaporize acetophenone and float above the reaction tube, resulting in a smaller contact area with the catalyst. The catalytic activity is almost unaffected when the pressure is reduced from 2 MPa to 1 MPa, only the selectivity changes slightly. When the pressure is 2 MPa, the selectivity is up to 99.9%. When the pressure is reduced from 1 MPa to 0.5 MPa, the catalytic activity of the catalyst drops sharply. In order to maintain the comprehensive conversion rate and selectivity, while making the reaction conditions as mild as possible for better application in industrialization, the pressure of 1 MPa is selected for subsequent temperature and flow rate screening. As shown in Figure , in the temperature screening process, the catalyst reactivity is best when the temperature is 100 °C, and the selectivity is improved to a certain extent compared to 120 °C. During the temperature screening process, we found that the selectivity was the worst at the reaction temperature of 120°C, indicating that the higher reaction temperature would lead to the formation of by-products. But when the temperature decreases furtherly, the conversion rate gradually drops significantly. Flow rate is also an important factor that affects industrial applications. We screened the flow rate under the selected reaction conditions of 1 MPa and 100 °C as shown in the Figure and found that appropriately increasing the flow rate can promote the selective production of phenylethanol. This indicated that short reaction time could not only reduce the production of by-products but also shortens the reaction time of the raw material acetophenone to the product phenethyl alcohol. Therefore, when the flow rate continues to increase from 0.4 mL/min to 0.8 mL/min, the rate of decline of the conversion rate also increases. We used the optimized conditions to carry out the acetophenone hydrogenation reaction again in the batch reactor. The conversion rate after 15 h was only 15.04% relative to 99.14% in the flow reactor (Figure ), indicating that the experiments we conducted in the flow reactor were very successful. Under the optimized reaction conditions, the 48-h continuous reaction of acetophenone without interruption was carried out, and phenylethanol with high selectivity remains basically unchanged, only the conversion rate is slightly reduced but still remains above 88.44%. The proposed mechanism of Ni-based catalyzed hydrogenation of ketones are showed in Figure . The hydrogen and ketone are both adsorbed on the surface of the Ni metal catalyst. Then a molecule of H2 which binds to the Ni active surface dissociates the H-H bonds and forms Ni-H (nickel hydride bonds) coordinate complex that is now ready to react with carbon-oxygen double bond of the acetophenone. In the meantime, a hydrogen in the metal-hydrogen complex is transferred to oxygen which involves a oxygen-metal bond. In the next step, the nickel-oxygen bond is broken and the second carbon-hydrogen bond is formed. After that, the desired product is desorbed from the catalyst surface.