Categories and Working Principles of Hydrogenation Reactors

In experiments, we often encounter gas purging using nitrogen or hydrogen, or hydrogenation reactions, in which we need to replace the air inside the reactor with the desired reaction gas. Generally, there are two common methods: One is to first introduce the required gas, then close the inlet valve and open the exhaust valve; the other is to evacuate the reactor to a vacuum and then introduce the gas to be reacted into the laboratory reactor for the reaction. After repeating this process three times, the gas inside the hydrogenation reactor will be completely replaced. Next, let’s take a closer look at the working principle of the hydrogenation reactor.

　　Hydrogenation is a reversible, exothermic reaction involving a decrease in the number of molecules. The temperature required for hydrogenation depends on the activity of the catalyst used: the higher the catalyst activity, the lower the temperature needed. To enhance the equilibrium conversion rate, hydrogenation reactions with small equilibrium constants at the reaction temperature must be carried out under high pressure, which also helps to accelerate the reaction rate. Using an excess of hydrogen not only speeds up the reaction and increases the conversion rate of the hydrogenated substance but also facilitates the removal of reaction heat. The excess hydrogen can be recycled for subsequent use.

　　There are two commonly used types of hydrogenation reactors: One is designed for liquid-phase hydrogenation of high-boiling-point liquids or solids (solids must first be dissolved in a solvent or melted by heating), such as the hydrogenation of heavy oil products and the hydrocracking of fats and oils. Liquid-phase hydrogenation is typically carried out under pressure; this process can be either batch or continuous. Batch hydrogenation usually employs pressurized reactors equipped with agitators or bubble-column reactors. For liquid-phase hydrogenation, trickle-bed reactors or tubular reactors—where gases, liquids, and solids flow continuously in the same direction—can also be used. The other type of hydrogenation reactor is used in continuous gas-phase hydrogenation processes, such as the high-pressure gas-phase hydrogenation of carbon monoxide to produce methanol and the atmospheric-pressure gas-phase hydrogenation of benzene to produce cyclohexane. At high temperatures and pressures, hydrogen can combine with carbon atoms in steel to form methane, causing the steel to become brittle—a phenomenon known as hydrogen embrittlement. Therefore, high-pressure hydrogenation reactors are made from alloy steels. Since hydrogen is highly flammable and explosive, safety measures must be carefully considered during the hydrogenation process.

　　The hydrogenation reactor can operate under conditions of high pressure, high temperature, high rotational speed, high vacuum, suspension, and convection, ensuring that the reaction medium remains completely sealed within the reactor under these extreme conditions, thus safely facilitating reactions involving hazardous substances such as explosives, flammables, and highly toxic materials. The hydrogenation reactor boasts advantages including high-temperature resistance, corrosion resistance, and strong production capacity, making it widely used in industries such as pharmaceuticals, beverages, chemical processing, pigments, resins, and scientific research. The reactor integrates a reaction vessel with a sophisticated control system for reaction conditions, enabling precise regulation of critical parameters during the reaction process, including temperature, pressure, agitation, and the concentrations of reactants and products.