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Recently, the project \"Research and Scale-up Tests on Hydrogenation Catalysts for Pre-hydrogenation of Ethylene Cracking By-products\", carried out by the Petrochemical Research Institute, successfully passed the project evaluation organized by China National Petroleum Corporation’s Science and Technology Management Department. This marks the beginning of large-scale industrial application of such catalysts, representing a new breakthrough by China National Petroleum Corporation in improving the overall efficiency of ethylene production facilities. It also enables the company to overcome the technical restrictions imposed by Europe and the United States and achieve self-sufficiency in catalyst imports. Ethylene in the carbon dioxide fraction is an important industrial product, mainly used to produce downstream products such as polyethylene. In addition to a large amount of ethylene, the cracked C2 fraction also contains small amounts of acetylene (0.5–2.0 v%) as impurities, which severely affects the subsequent polymerization process of ethylene. Therefore, the carbon dioxide fraction must be hydrogenated to remove acetylene before it can be used in the production of downstream products such as polyethylene. Depending on the separation process, C2 hydrogenation is divided into two processes: pre-hydrogenation and post-hydrogenation. Due to the characteristics of the carbonyl precursor hydrogenation process and the composition of the raw materials, this process involves high risks during startup and requires high performance from catalysts; as a result, it is difficult to develop catalysts for this purpose, and domestic plants have long relied on imports. With the advancement of domestic ethylene technology, the independent development of pre-hydrogenation catalysts has become urgent. Since 2007, with the support of the Petroleum Science and Technology Management Department of China National Petroleum Corporation, the Petrochemical Research Institute has completed the pilot-scale, pilot plant-scale development, and industrial production of the C2 pre-hydrogenation catalyst PEC-21. During the research and development process, the dispersion properties and transfer efficiency of the carriers were improved through the development of new multi-component composite oxide carriers; furthermore, the catalyst formulations were fine-tuned to create customized catalysts suitable for various carbon dioxide hydrogenation conditions and feedstock characteristics ； Through the synergistic control of catalyst deactivation parameters (temperature, time, oxygen content, and space velocity), the Pd2+:Pd0 ratio on the catalyst surface can be precisely controlled, enabling the controlled deactivation of the active centers in catalysts with low palladium contents. This improves the catalyst’s operational stability as well as its ability to function over extended periods of time, thus creating proprietary technology for the stable operation of carbon dioxide pre-hydrogenation units over long durations. In 2017, the PEC-21 catalyst underwent its first industrial application test in the 270,000-ton/year ethylene C2 hydrogenation first-stage reactor at Daqing Petrochemical. All indicators met the performance levels of the previously used imported catalysts, indicating that it is suitable for conducting series tests in domestic ethylene plants. In 2018, with the support of the Petroleum Technology Management Department of China, the project \"Research on Hydrogenation Catalysts for Pre-Carbon Dioxide Stage in Ethylene Cracking and Scale-Up Tests\" was launched, to carry out series application tests of the PEC-21 catalyst in the first and second reactors. The project resulted in the production of a total of 15.2 tons of catalyst, which was successfully applied in the acetylene hydrogenation reactors in the first and second stages of the 270,000 tons/year ethylene plant. So far, the device has been operating stably. The calibration results show that the reactor inlet temperature at one point was 69.2°C, with an acetylene load of 66.9% ； The inlet temperature of the two-stage reactor is 75.7°C, with an acetylene load of 31.9% ； The inlet temperature of the three-stage reactor is 77.7°C, with an acetylene load of 1.2% ； The overall MAPD conversion rate was 52.7%, the overall ethylene selectivity was 78.7%, and the overall propylene selectivity was 98.1%. The various properties of the catalyst meet the requirements for the stable operation of industrial plants, reaching the level of the imported catalysts originally used in such plants. It features high startup efficiency, good operational stability, excellent stability over long periods of operation, and a long service life. With the support of the Petroleum Technology Management Department of China, the PEC-21 catalyst, developed over a period of more than 10 years, represents another domestically developed brand of technology in the field of hydrogenation catalysts for ethylene cracking products. The main technical and economic indicators of the PEC-21 catalyst are at the international advanced level. This project passed the acceptance inspection organized by China National Petroleum Corporation, creating the conditions for the widespread use of this catalyst in large ethylene production facilities across the country. Its adoption will further enhance China National Petroleum Corporation’s competitiveness in the ethylene technology market.