Pressure control is one of the core technologies for the operation of laboratory hydrogenation reactors, which needs to balance reaction requirements and safety thresholds. In hydrogenation reactions, excessive pressure may lead to seal failure, hydrogen leakage, and even explosion risks, while low pressure can reduce reaction rate and affect product yield. The commonly used pressure control methods in laboratories are mainly divided into two categories: manual control and automatic control. Manual control requires adjusting the hydrogen input rate through a pressure reducing valve, coupled with real-time monitoring by a pressure gauge, gradually adjusting the pressure according to the reaction process. It is suitable for simple reaction systems, but requires high experience from operators to avoid frequent and significant adjustments that may cause pressure fluctuations. Automatic control utilizes pressure sensors, PLC control systems, and electric regulating valves to form a closed-loop control. After setting the target pressure, the system can automatically compensate for pressure loss and suppress pressure peaks, especially suitable for high pressure and long-term reactions, which can significantly improve control accuracy and stability. Regardless of the method used, it is necessary to clarify the safe pressure range of the reaction in advance. Generally, the laboratory hydrogenation reaction pressure does not exceed 10MPa, and the kettle body needs to undergo regular pressure testing to ensure the safety of the equipment itself.

The hydrogen replacement operation is a step before starting the hydrogenation reaction, and its core purpose is to remove the air (especially oxygen) inside the reaction vessel to prevent the formation of explosive gas mixtures between hydrogen and oxygen. The standardized replacement process should follow the cyclic operation mode of "vacuum pumping hydrogen gas filling re vacuum pumping hydrogen gas filling". Firstly, close all inlet and outlet valves of the reaction kettle, turn on the vacuum pump to evacuate the kettle to -0.08MPa~-0.1MPa, maintain for 5-10 minutes, and exhaust most of the air; Then turn off the vacuum pump, slowly introduce hydrogen gas to 0.2~0.3 MPa, let it stand for 3~5 minutes, and allow the hydrogen gas to fully mix with residual air; Turn on the vacuum pump again to evacuate, repeat the above cycle 3-4 times, and ensure that the oxygen concentration in the kettle is below 1%. During the replacement process, two points should be noted: first, the rate of hydrogen gas introduction should not be too fast to avoid static electricity or sudden pressure rise inside the kettle; Secondly, after the replacement is completed, it is necessary to confirm the pressure inside the reactor again to ensure that it meets the initial reaction pressure requirements. At the same time, check the sealing of all valves to prevent leakage.

In addition, attention should be paid to detail control during the operation process. Pressure monitoring should use pressure gauges with the required accuracy and be calibrated regularly; Hydrogen replacement should be carried out in a well ventilated laboratory to avoid hydrogen accumulation; Operators need to wear protective equipment and be familiar with emergency response procedures. If there is abnormal pressure or leakage, the gas supply should be immediately stopped, ventilation equipment should be turned on, and the plan should be followed for disposal.