The catalyst evaluation device is the core equipment for studying catalytic reaction kinetics, screening and optimizing catalyst formulations, and its operational standardization directly determines the credibility and repeatability of experimental data. The following provides a detailed explanation from three aspects: device characteristics, operating procedures, and key control points.
1、 System composition and functional matching
A typical evaluation device consists of a feeding unit, a reactor module, a product collection system, and online monitoring instruments. The quality flowmeter needs to be regularly calibrated to ensure the accuracy of gas/liquid flow rate, and the high-pressure reactor should be equipped with multiple insulation screens to maintain a radial temperature difference of<2 ℃. For strongly exothermic reactions, it is recommended to use a reactor with a spiral coil jacket to achieve precise temperature control through the circulation of thermal oil. For the testing of powdered catalysts, the micro fixed bed reactor needs to be equipped with a quartz wool support layer to prevent particle loss.
2、 Standardized operating procedures
Special attention should be paid to the uniformity of catalyst loading during the preprocessing stage, and vibration compaction method should be used to eliminate the difference in porosity. The activation program should strictly follow the heating rate curve, such as the step heating of metal oxide catalysts to the target temperature in a reducing atmosphere. During the reaction phase, the focus is on monitoring changes in bed pressure drop. When Δ P exceeds the initial value by 30%, it indicates the risk of coking. The sampling operation should be carried out after the system is stable. For gas-phase products, it is recommended to use a six way valve switch to achieve continuous sampling, while for liquid-phase products, the condensation temperature should be controlled to avoid component loss.
3、 Key parameter control strategy
In terms of temperature control, thermocouples should be placed in the middle of the catalyst bed and cross validated with infrared thermometers. The response speed of pressure regulating valves should match the reaction kinetics characteristics, and electric regulating valves should be selected for fast reaction systems. It is recommended to use a dual channel mass flowmeter for raw material ratio control to ensure that the H ₂/HC ratio error is less than ± 1%. To obtain intrinsic activity data, it is necessary to determine the conversion rate contact time correlation curve by changing the airspeed to eliminate the interference of mass transfer resistance.
4、 Response plan for abnormal working conditions
In the event of a sudden power outage, the backup power supply should be immediately activated to maintain inert gas purging and prevent carbon buildup from blocking the pipeline. When the phenomenon of overheating is detected, the emergency cooling system should inject the cooling medium into the reactor jacket within 30 seconds. If a significant increase in by-products is detected, the reactant concentration can be diluted by adjusting the carrier gas flow rate, and if necessary, switch to bypass circulation mode to protect the catalyst.
5、 Data processing and calibration
When calculating the conversion frequency TOF value, the background conversion rate of the blank experiment needs to be deducted. For multiphase reaction systems, internal and external diffusion criteria should be established, and when the Western number is greater than 10, it can be considered as eliminating the influence of external diffusion. It is recommended to collect full spectrum analysis every 24 hours for long-term stability testing, with a focus on the loss rate of active components and the attenuation law of specific surface area.
The effective use of this device relies on a profound understanding of fluid mechanics and principles of heat and mass transfer. Operators need to establish a standard operating procedure (SOP) that covers the entire process of quality control from catalyst preparation to data collection. By regularly calibrating instruments and optimizing reaction conditions, catalytic performance parameters with industrial guidance value can be obtained.