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Making Good Use of Catalysts to Extend Their Lifespan and Increase Production Efficiency – A Discussion on the Use of Copper-Alcohol Catalysts in Factories. Changshu Kaituo Catalyst Co., Ltd., Yan Tingliang. As the methanol market fluctuates, so does the market for methanol catalysts, but overall it is on an upward trend. Especially when the methanol market is booming and the profits from methanol production are high, many companies focus solely on increasing methanol output without considering other factors. Therefore, this article discusses how to make good use of catalysts, extend their lifespan, and improve the production capacity per unit volume of catalysts. Looking back at the history of China’s fertilizer industry, the co-production of methanol is an innovation of ours. In the 1980s, the lifespan of methanol production catalysts was only 2–3 months, or even less than a month; the production efficiency was such that each cubic meter of catalyst could produce only 500–800 tons of methanol, and it was not unusual for this figure to be even lower than 500 tons. Thanks to technological advancements over these past twenty-odd years, the widespread use of desulfurization technologies at normal temperatures, the continuous improvement of the hydroformylation process, the rising level of operational management, and ongoing progress in catalyst production techniques, the service life and production efficiency of catalysts have increased by 5 to 10 times; they can now be used for up to four years, with the production of methanol per cubic meter of catalyst exceeding 9,000 tons. We hope that methanol producers can, through a series of measures, continuously set new records for catalyst lifespan and achieve the highest catalyst production efficiency. Summarizing the experiences and lessons from over these twenty years, regarding the topic discussed in this article, the author believes it is inseparable from the following aspects. 1. The factory-quality of the catalyst. 2. Temperature-induced reduction of the catalyst. 3. Purification and control of the feed gas entering the synthesis section. 4. internals of the synthesis tower. 5. Control of operating temperature and space velocity. I. The quality of catalysts at the time of manufacture: Copper, zinc, and aluminum catalysts used in the production of ethanol are manufactured by more than twenty catalyst factories across the country. These factories use different models and production processes, and the quality of their products varies greatly from one factory to another. Since there are currently no unified product quality standards for aldol catalysts in our country, enterprises produce according to their own established specifications. Furthermore, since methanol producers do not have the capability to test methanol catalysts, this poses difficulties for users in conducting quality assessments. As a result, methanol production plants in the fertilizer industry tend to choose products that have a high market share, a good reputation, excellent technical support, and relatively low prices. The quality of catalysts at the time of leaving the factory is a prerequisite for determining their service life and the level of production efficiency. Taking our factory as an example, aware of this fact and in order to ensure the survival and development of the enterprise, we maintain top-notch quality control standards. Stringent control is applied at all key stages to ensure the stability of product quality; particular emphasis is placed on the washing process, and costs are incurred without hesitation to minimize the sodium content in the products ； Stabilize the calcination temperature to ensure stability in the loss on ignition of the product (which is crucial for the activity of the catalyst after reduction) ； Our technical support is also first-class; we have a highly competent team of technical support specialists who are available at any time to help users identify the causes of problems and resolve them. This has earned us high praise from our customers, leading to an increase in our sales volume, with the number of customers now exceeding 100. We are never satisfied with product quality. Recently, in collaboration with Xiamen University, we have used nanocarbon tubes in catalysts, which is expected to significantly increase the surface area and lead to a new breakthrough in catalyst activity. II. Temperature-induced reduction of the catalyst: Performing temperature-induced reduction on the catalyst for diols is the first step after it arrives at the user’s facility. The quality of this reduction process has a direct impact on the catalyst’s activity and lifespan. Therefore, we earnestly ask users who purchase our products to pay close attention to this step. Although we have repeatedly explained the methods and precautions related to temperature-induced reduction, if users still feel uncertain or have not fully understood them, we are willing to provide free technical support at their request, offering on-site assistance during the reduction process. The reduction of bifunctional alcohols using copper catalysts is discussed in detail in both our product manual and my article on \"Technical Questions and Answers,\" but it will be briefly introduced again in this article. The newly arrived catalyst exists in the form of CuO, whereas it is the metallic copper microcrystals that are active for methanol synthesis; therefore, it is necessary to ensure the proper reduction of this catalyst. Currently, in the fertilizer industry, the high-hydrogen reduction method is commonly used for the reduction of this catalyst. The gas source employed must be purified hydrogen-nitrogen gas; the catalyst is sensitive to ammonia, so fresh gas from the synthesis section is more suitable, with trace amounts of ammonia, sulfur, CO, and CO2 present. Blind flanges must be installed on the pipelines for the feed gas and alcohols to prevent gases containing CO and CO2 from leaking into the heating and reduction system. For temperature-raised reduction, it is necessary to ensure an adequate flow rate; a space velocity of 3000–5000 h-1 is recommended. If the reduction space velocity is too high – some plants even use values above 10,000 h-1 – the reduction time indeed decreases. However, at low pressures, such high gas flow rates cause excessive erosion of the catalyst, leading to its pulverization and even the transport of these particles to subsequent systems. The reduction of CuO, under a certain hydrogen partial pressure, involves a reduction reaction even at room temperature; however, the reaction rate is slow, so this phenomenon is often overlooked. Therefore, even after new catalysts are installed in the tower, it is necessary to avoid keeping the system under an atmosphere with a certain hydrogen partial pressure (for example, with a pressure maintained at 5 MPa) for extended periods, or to avoid using hydrogen and nitrogen gases for leak testing for too long. If this situation persists to a certain extent, intense reduction reactions will occur, resulting in the destruction of the catalyst. After the catalyst is installed inside the inner component, it is strictly prohibited to perform any welding or heating operations right next to the catalyst layer, as this could cause the catalyst to burn in contact with air and lead to accidents. When replacing the catalyst, the old catalyst should be completely drained. If old and new catalysts are mixed together (even in small amounts as residual unpассивated old catalyst inside the components), there is a risk of the catalyst being damaged during high-hydrogen reduction. During the reduction of bifunctional alcohol catalysts, if CO gas leaks in or mixes with the gas supply, carbonyl compounds are likely to form, which can poison the reduced catalyst and render it inactive; every effort should be made to avoid this. The process of high-hydrogen reduction is divided into three stages. The temperature range of 70–110°C corresponds to the reduction stage of CuO, and it is also the critical stage for control; this period accounts for 34–44% of the total time required for heating and reduction, with a lower space velocity resulting in a higher proportion allocated to this stage. The temperature range of 110–140°C corresponds to the stage of removing free water, while the range of 140–180°C is the stage for removing crystalline water. We have analyzed the temperature changes during the heating and reduction process over the years, as well as the original records of the water output, and created curves showing the temperature progression under different space velocities. It can be said that by following this curve when controlling the temperature using our catalyst, the reduction process will proceed smoothly and safely; the catalyst will achieve its optimal activity level, which in turn lays a solid foundation for enabling users to achieve the highest production efficiency and the longest possible service life. III. Purification and control of the feed gas entering the synthesis section. The first two points mentioned are prerequisites for making good use of catalysts, but proper operation during use is also crucial. As the hydrotreated process has evolved to its current stage, the purification of feed gas has progressed from basic refining to the more advanced level of deep purification. However, many plants still lack even the most fundamental equipment for desulfurization at normal temperatures; as a result, they are satisfied with using their catalysts for just over half a year. Due to the sensitivity of copper-based catalysts, they are unable to resist poisons, especially sulfur, chlorine, ammonia present in the feed gas, as well as carbonyl metal compounds and oil contaminants. This severely affects the lifespan of the catalyst. When considering the manufacturing process, it is essential to remove all five types of toxins mentioned above. At present, purification levels have been improved from 10-6 (i.e., ppm) to 10-9 (i.e., ppb), which enables the catalyst to remain in a ‘young’ state for a longer period and thus extends its service life. Experience in practical use has shown that, in addition to removing carbonyl compounds from the feed gas by using decarbonylizing agents, it is also necessary to pay attention to reducing the temperature during reduction processes, and to avoid situations where carbonyl compounds may form during normal startup and shutdown procedures. In summary, this can be expressed as follows: “Reduce the temperature during reduction to prevent the presence of CO-containing gases”; “Avoid keeping the furnace under pressure during shutdown”; and “Use hydrogen and nitrogen gas when raising the temperature during startup”. Extend its service life. Eliminate oil contamination in the raw material gas entering the tower. When replacing the catalyst, if oil is found on the outer surface of the internal components, it is necessary to steam-clean the heat exchanger located at the bottom of those components as well as remove any remaining oil in the cleaning devices; otherwise, the new catalyst will not last long, as the oil already attached to the vessel walls will contaminate the new catalyst and cause it to fail rapidly. As for \"sulfur,\" \"chlorine,\" and \"ammonia,\" no further discussion is needed in this article; there are many relevant articles available, and people have gained deep insights through practical experience. The control of the feed gas entering the tower mainly involves three aspects: the control of CO in the feed gas ； Control of methanol content ； And the control of CO2 content. For diol alcohol, the CO content in the fresh gas is the main means of adjusting methanol production; higher CO levels result in higher methanol production. Reasonable control of the CO content in the fresh gas is an important factor for the economic operation of hydroxymethanol production. The proportion of methanol production within the total ammonia production is adjusted based on several factors; when the CO conversion rate is high, the CO content has a direct impact on the amount of methanol produced. An excessively high alcohol-to-ammonia ratio reduces the hydrogen-to-carbon ratio in the feed gas, thereby increasing side reactions during the synthesis process ； The CO content in the gas after alcohol treatment: when the CO conversion rate and the circulation volume remain constant, any change in the CO content in the fresh gas directly affects the CO content in the gas after alcohol treatment, thereby impacting the normal operation of the ammonia synthesis purification process as well as the hydrogen-to-nitrogen ratio in ammonia production. It should be considered comprehensively based on the degree of activity; there is no need to force an increase in CO content to boost methanol production. Methanol in the gas entering the tower is introduced by the recycle gas. When the methanol content in this gas is high, it not only affects the reaction equilibrium in methanol synthesis, leading to a decrease in CO conversion rate, but it also increases side reactions, as well as causing wax formation in the system, catalyst degradation, and catalyst poisoning. The methanol concentration in the gas entering the tower is almost directly proportional to the rate of formation and the amount of dimethyl ether as a side reaction, resulting in an increase in the dimethyl ether content in the gas leaving the alcohol production process as well as in the crude alcohol; this can even lead to poisoning of the ammonia synthesis catalyst. Therefore, the lower the methanol content in the gas entering the tower, the better; the water cooling temperature should not exceed 30°C. The alcohol separation unit must ensure effective separation to prevent the recycled gas from containing alcohol. Where possible, the ratio of recycled gas to fresh gas should be reduced as much as possible, which helps to lower the methanol content in the gas entering the tower. The presence of CO2 in the gas fed into the tower reduces the intensity of the methanol synthesis reaction, but it increases H2 consumption and raises the water content in methanol. This should be determined through a comprehensive assessment of factors such as the plant’s decarburization efficiency; a CO2 concentration of 0.5–1.0% in the fresh gas can be considered appropriate. This is beneficial for reducing and mitigating fluctuations in catalyst temperature. IV. Internal components of the synthesis tower. Choosing the appropriate internal components is also crucial for protecting the catalyst and extending its service life. Since the active temperature range of current diol methanol synthesis catalysts is quite narrow, typically only 60–70°C, and the exothermic amount released during the synthesis reaction is significant, the copper microcrystals, which are the main active components in copper catalysts, tend to grow rapidly under the influence of temperature; this reduces their specific surface area and thus lowers their activity. This imposes special requirements on its internal components: the heat of reaction must be removed promptly, and maintaining a uniform temperature in the catalyst bed is key to the design of these internal components. Over the past decade or so, the use of uniform-temperature type internals has indeed made significant contributions. However, as equipment sizes increase, the gas distribution and resistance associated with these internals have become their fatal weaknesses. This requires continuous technological advancement in order to overcome these two problems and develop new types of internals that can further enhance the production efficiency of catalysts. Another area we are working on to make improvements is whether a new breakthrough can be achieved in catalysts to broaden their range of activity. V. Control of operating temperature and space velocity. Copper-based catalysts are extremely sensitive to heat. According to available data, in a reducing atmosphere, after being treated at 200°C for 6 months, the minimum grain size of pure copper microcrystals exceeds 1000 Å; if treated at 300°C for 6 months, this minimum grain size exceeds 10,000 Å. The latter increased by a factor of 10; the enlargement of the grains meant that the surface area of active copper decreased, and the catalyst’s activity is linearly related to its surface area of active copper. Analyzing the specific surface area of the deactivated catalyst from a physicochemical perspective shows that it decreased from 70 m2/g for the fresh catalyst to 20 m2/g, which also illustrates the catalyst’s sensitivity to heat. Therefore, in addition to the loss of activity caused by toxic substances that poison them, thermal aging is the fatal weakness of copper-based catalysts; as the operating temperature increases, the copper microcrystals gradually grow larger. As the specific surface area of copper decreases, its activity declines more rapidly, and the rate of aging accelerates as the temperature rises. Therefore, it is essential to pay attention to the following during operation: 1. Special care must be taken during the reduction process, especially high-hydrogen reduction; one should closely monitor the heating rate during the low-temperature reduction stage to avoid a sudden rise in temperature, which could cause the crystals to grow rapidly while still under reduction, leading to premature deterioration. In response to this, the heating and reduction curve provided by our factory takes this factor fully into account; when reduction is carried out according to this curve, the water vapor concentration in the gas generated by the effluent should be around 2 g/m3, thereby preventing \"temperature spikes\". 2. During operation, follow the predetermined parameters carefully; when starting up the system, do not keep the CO level in the feed gas too high – generally 2–3% is sufficient. Once the temperature stabilizes, increase the CO concentration gradually, by no more than 0.5% at a time, in order to reduce temperature fluctuations and prevent overheating. 3. Maintain a low operating temperature as much as possible, provided that the yield and the CO content in the alcohol-containing gas remain suitable for the operations in subsequent stages. Do not increase the operating temperature easily; each increase should be done carefully, with the increment should not be too large – 2–5°C is an appropriate range. The new catalyst should make full use of its low-temperature activity, with the longer low-temperature operation time being preferable. 4. Minimize the methanol content in the gas entering the tower. It is strictly prohibited for the gas after alcohol removal to contain any alcohol liquid. 5. Strictly control gas purification to ensure that the levels of sulfur, chlorine, ammonia, carbonyl compounds, and oil contamination in fresh gas and recycled gas are kept at their lowest possible levels. 6. Appropriately increasing the CO2 content in the gas entering the tower helps to suppress the intensity of the reaction, thereby preventing overheating to a certain extent. Improve operational skills, continuously summarize operational experience to reduce temperature fluctuations. For the control of space velocity, if a bypass line or other methods are available, temperature regulation through the circulation volume should be avoided; efforts should be made to keep the circulation volume stable, rather than forcing an increase in space velocity to boost methanol production.