A Brief Discussion on the Operational Experience of Hydrogenation Reactors

Hydrogenation reactors are generally used for hydrogenolysis reduction. Under conditions of high pressure and in the presence of flammable, self-igniting substances and oxygen, safety incidents can easily occur, leaving operators with lifelong regrets. Therefore, the following notes on precautions and operating procedures for using hydrogenation reactors are provided.

　　I. Precautions: 1. For those performing autoclave operations for the first time, at least one operator who is already familiar with the autoclave operation must be present. 2. Operators on site must wear cotton gloves and non-metallic shoes. 3. Do not bring mobile phones, lighters, MP3 players, or other items that could easily cause explosions or spontaneous combustion into the hydrogenation work area. 4. When handling tools and parts near the hydrogenation equipment, operators should handle them gently and avoid any rigid impacts that might generate sparks. 5. During pressure relief, exhaust gases from high-pressure reactions must be routed via a rubber hose to the outdoors or into a fume hood.

　　II. Operating Procedure: A complete hydrogenation reactor operation procedure consists of five steps: installation, hydrogenation, sampling, hydrogen venting, and material discharge.

　　(1) Check whether there are any flammable or explosive substances inside and outside the kettle, and whether there are any objects obstructing air circulation. Also, verify that the valves and the kettle itself are clean; if they’re not clean, they need to be washed. Close all valves except the vent valve, then begin adding the material. Once loading is complete, put on the kettle lid. When tightening the nuts, make sure to apply even pressure to ensure that after tightening, there’s no air leakage around the two diagonal screws. Finally, close the vent valve.

　　(2) Check the airtightness of the hydrogenation reactor. Close all valves, put on the lid, and when tightening the nuts, make sure to apply even force. Ensure that the two diagonal screws are tightened against each other to prevent any gas leakage after tightening. Open the inlet valve and introduce nitrogen gas until the pressure reaches 1 MPa; then close the inlet valve and observe any changes in pressure to confirm whether the system is leaking.

　　(3) Check whether the valves on the hydrogenation reactor are securely locked, and direct the vent hose toward an open, well-ventilated area. Open the reactor’s inlet gas valve and the nitrogen pressure-reducing valve, then introduce nitrogen gas until the internal reactor pressure reaches P = 0.2 MPa. Next, close the nitrogen pressure-reducing valve and maintain this pressure for about 2 minutes, observing whether the pressure gauge reading drops. Additionally, bend down and listen carefully to check for any leaks around the valves and the kettle lid. If no leaks are detected, slowly open the vent valve; once the internal pressure has dropped to 0.01 MPa, close the vent valve. Then, open the reactor’s inlet gas valve and the hydrogen pressure-reducing valve, and introduce hydrogen gas until the desired pressure is reached. Finally, close the inlet gas valve and the hydrogen pressure-reducing valve, and proceed to adjust other parameters to the required settings to initiate the reaction.

　　(4) Observe the hydrogenation reactor data every half hour to ensure that it is operating normally. If the pressure drops, replenish with hydrogen gas. When the hydrogen in the cylinder can no longer be discharged, maintain a certain level of pressure. When the pressure reaches 0.01 MPa, the cylinder should be scrapped and replaced. Slowly open the vent valve; when the pressure inside the hydrogenation reactor drops to 0.2 MPa, close the vent valve. Then, slowly open the sampling valve until liquid from the reaction mixture starts to flow out. Close the sampling valve immediately after obtaining the sample, and subsequently clean the sampling port thoroughly to prevent any flammable substances from remaining there.

　　(5) Hydrogen gas release. After confirming the reaction, slowly vent the hydrogen gas until the process is complete. Note that the pressure inside is extremely low; close the vent valve to prevent oxygen from entering, then open the inlet valve and flush nitrogen gas into the system until the pressure reaches 0.2 MPa. Next, close the inlet valve, gradually open the vent valve, and carefully release the mixed gas inside. At the end of the process, re-introduce nitrogen gas. After repeating this ventilation procedure three times, use a vacuum pump to extract the gas above the liquid surface. Then, open both the vent valve and the sampling valve, and begin draining from the bottom valve.