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Data sharing, applications for highlighting – Making use of catalysts to extend service life and increase production efficiency: A discussion on the use of copper alcoholate catalysts in factories. 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 methanol production without considering other aspects. To this end, this article focuses on how to make good use of catalysts, extend their service life, and increase 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 unique to China. Since the 1980s, the lifespan of methanol production catalysts has been only 2–3 months, or even less than 1 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 20+ years, the widespread use of desulfurization technologies at normal temperatures, the continuous improvement of the methanol synthesis process, the rising level of operational management, and advancements 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 4 years, with the production of methanol per cubic meter of catalyst exceeding 9,000 tons. It is hoped that manufacturers producing methanol can, by taking a series of measures, continuously develop catalysts that extend their service life and surpass the highest levels of catalyst production efficiency. Summarizing the experiences and lessons from over these 20 years, the topics addressed in this article, in the author’s view, are 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 used to enter the synthesis L section. (4) internals of the synthesis tower. (5) Control of operating temperature and space velocity. 1. The factory-quality of catalysts: Copper, zinc, and aluminum catalysts for ligand production are manufactured by over 20 catalyst factories across the country. These factories use different models and production processes, and the quality of their products varies significantly from one factory to another. At present, there are no unified product quality standards for alcohols synthesis 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 quality assessment by end-users. As a result, methanol plants in the fertilizer industry tend to choose products that are available in large quantities, have a good reputation, offer excellent technical support, and are relatively inexpensive. The quality of the catalyst at the time of leaving the factory is a prerequisite for determining its service life and the level of production efficiency. Taking our company as an example, recognizing this fact, quality management is of top-notch standard in order to ensure the survival and development of the enterprise. Each key aspect is strictly controlled to ensure the stability of product quality. In particular, extra attention is paid to the washing process; costs are incurred without hesitation to keep the sodium content in the products as low as possible. The calcination temperature is maintained at a constant level to ensure stability in the loss on ignition of the products, which is crucial for the activity of the catalysts after reduction. The technical support provided is also of top quality; our company has a highly competent team of technical specialists who are available at any time to assist customers in identifying and resolving problems. This has earned us high praise from customers, leading to an increase in sales volume, with the number of customers now exceeding 100. Our company is never satisfied with the quality of its products. Recently, we have collaborated with Xiamen University to use carbon nanotubes in catalysts, which is expected to significantly increase the surface area and lead to a new breakthrough in catalyst efficiency. 2 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 directly affects the catalyst’s activity and lifespan. Therefore, we earnestly hope that users who intend to use our company’s products will be sure to pay close attention to this aspect. Although the methods for heating and reduction are repeatedly promoted and the precautions are emphasized, as long as customers feel uneasy or have not fully understood them, technical support should be provided free of charge at their request, with on-site assistance during the heating and reduction process. The reduction of glycol using copper catalysts is discussed in detail in both our company’s product specifications and the author’s “Technical Q&A” article; however, it is briefly introduced again in this article. The newly arrived catalyst is present in the form of CuO, while 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-induced reduction, it is necessary to ensure an adequate flow rate; a space velocity of 3000–5000 h is recommended. If the reduction space velocity is too high – some companies even use values over 10,000 h – the reduction time may be reduced, but 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, undergoes a reduction reaction even at room temperature; however, the reaction rate is slow, preventing significant progress, and thus it is often overlooked. Therefore, even after the new catalyst is installed in the tower, it should be avoided to maintain pressure in an atmosphere with a certain hydrogen partial pressure (for example, with the pressure kept at 5 MPa) for long periods of time, or to use hydrogen and nitrogen for leak testing for an excessive duration; once this 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 if a small amount of unpassivated old catalyst remains 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 in this process. This period accounts for 34%–44% of the total time required for heating and reduction; the lower the space velocity, the higher this proportion becomes ； 110–140°C is the free water removal stage ； 140”–180°C is the stage for the removal of crystal water. The company has compiled the original records of temperature changes during the heating and reduction process over the years, as well as the data on water output, and created graphs showing the heating and reduction curves at different space velocities. It can be said that by following these curves when controlling the temperature using the company’s catalysts, the reduction process will proceed smoothly and safely; the catalysts will achieve their optimal activity level, thereby laying a solid foundation for enabling users to achieve the highest production rates and the longest possible service life. 3 Purification and control of the feed gas entering the synthesis section. The previous two points are prerequisites for making good use of catalysts, but operation in the future is also key. As the hydroformylation process has evolved to its current stage, the purification of feed gas has progressed from simple refining to more advanced forms of purification. However, many companies still do not even have the most basic desulfurization units that operate at room temperature; as a result, they are satisfied with using their catalysts for just over half a year. Due to the sensitivity and fragility of copper-based catalysts, they are unable to resist poisons, especially sulfur, chlorine, ammonia present in the feed gas, as well as metal carbonyl compounds and oil contaminants. It severely affects the lifespan of the catalyst. When considering the manufacturing process, it is essential to eliminate these five types of toxins completely. By achieving a level of purification that goes from 10 levels (i.e., ppm) to 10 levels (i.e., ppb), the catalyst can remain in a \"young\" state for a longer period, thereby extending its service life. Experience in practical use has shown that, in addition to removing carbonyl compounds from the feed gas by adding decarboxylating agents, care must also be taken to avoid their formation through heating and reduction, as well as during normal start-up and shutdown processes. In summary, it can be expressed as follows: \"Raise the temperature for reduction to eliminate gases containing CO,\" \"Avoid leaving the furnace idle when it is shut down,\" and \"Use hydrogen and nitrogen gas to raise the temperature during operation\" in order to extend its service life. Eliminate oil contamination in the raw material gas entering the tower; when replacing the catalyst, if oil is found inside or outside the equipment, it is necessary to steam-clean the heat exchanger located at the bottom of this internal component and remove any remaining oil from the cleaner. Otherwise, even after installing a new catalyst, it will not last long, as the oil already attached to the walls of the equipment will be transferred to the new catalyst, causing it to fail quickly. As for “sulfur,” “chlorine,” and “ammonia,” they will not be repeated in this article; there are many relevant articles available, and people have gained deep insights from practical experience. The control of the feed gas entering the tower mainly involves three aspects: the control of CO in the feed gas, the control of methanol content, and the control of CO2 content. For diol alcohol, the CO content in the feed 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. Based on the following factors: the proportion of methanol production in the total ammonia production – when the CO conversion rate is high, the level of CO directly affects the amount of methanol produced. An excessive alcohol-to-ammonia ratio reduces methanol production. The x-catalyst and methanol production technologies also influence 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 production is affected by changes in the CO conversion rate and the circulation volume; when these remain constant, changes in the CO content in the fresh gas directly affect the CO content in the gas after alcohol production, impacting the normal operation of the ammonia purification process as well as the hydrogen-to-nitrogen ratio required for ammonia production. It should be considered comprehensively in terms of activity; the CO content should not be forced to be increased in order to boost methanol production and cause clogging. Methanol in the gas entering the tower is brought in 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, causes 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 dimethyl ether formation as a side reaction, resulting in an increase in the dimethyl ether content in the gas exiting the reaction process as well as in the crude methanol; this can even lead to catalyst poisoning in the ammonia synthesis process. 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, it is advisable to reduce the ratio of recycled gas to fresh gas, as this helps to lower the methanol content in the gas entering the tower. The presence of CO2 in the gas entering the tower reduces the intensity of the methanol synthesis reaction, but it increases H2 consumption and raises the methanol content. This decision should be made based on a comprehensive assessment of factors such as the plant’s decarburization efficiency; a CO2 content of 0.5%–1.0% in the fresh gas can be considered appropriate. This is beneficial for reducing and mitigating fluctuations in catalyst temperature. 4. internals of the synthesis tower: Choosing the appropriate internals is also extremely important for protecting the catalyst and extending its service life. Since the activity temperature range of methanol synthesis catalysts using current diol compounds is quite narrow, typically only 60–70°C, and the heat release during the synthesis reaction is significant, the copper microcrystals, which are the main active components in copper catalysts, are affected by temperature. It grows rapidly, reducing the specific surface area and thus decreasing its activity. This imposes special requirements on its internal components: the heat of reaction must be able to be removed in a timely manner, and maintaining a uniform temperature across the catalyst bed is key to the design of these internal components. Over the past decade or so, the use of uniform-temperature internal components has indeed made significant contributions. However, with the development of more advanced equipment designs, the gas distribution and resistance associated with these uniform-temperature internal components have become their fatal weaknesses. This necessitates continuous technological improvements to overcome these issues and to develop new types of internal components that can further enhance the production efficiency of catalysts. A new breakthrough in catalysts to broaden their activity range is also a direction for future improvements. 5 Control of operating temperature and space velocity: Copper-based catalysts are extremely sensitive to heat. According to available data, for pure copper microcrystals treated in a reducing atmosphere at 200°C for 6 months, the minimum grain size will exceed 1000 Å; if treated at 300°C for 6 months, the minimum grain size will exceed 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 directly proportional to its surface area of active copper. Physicochemical analysis of the specific surface area of the deactivated catalyst shows that it decreased from 70 m² to 20 m² in the fresh catalyst, which also illustrates the sensitivity of the catalyst to heat. Furthermore, in copper-based catalysts, apart from the loss of activity caused by the toxicity of harmful substances, thermal aging is their fatal weakness. As the operating temperature increases, the size of copper particles gradually increases, the specific surface area of copper decreases, and thus the activity declines more rapidly; the rate of aging accelerates as the temperature rises. Therefore, it is essential to pay attention to the following during the operation: (1) During the reduction process, especially high-hydrogen reduction, one must be extremely careful. Close attention should be paid to the low-temperature reduction stage, and the heating rate should be reduced to avoid a sudden rise in temperature, which could cause rapid grain growth while reduction is taking place. Our company’s provided heating and reduction curve takes these factors into full consideration; by following this curve, the water vapor concentration in the gases generated will remain around 2 g/m³, thus preventing a sudden rise in temperature. (2) During operation, follow the predetermined parameters carefully; when starting up the plant, the CO content in the feed gas should not be too high, generally between 2% and 3%. After the temperature stabilizes, gradually increase the inlet CO level, by no more than 0.5% at a time, in order to reduce temperature fluctuations and avoid overheating. (3) On the premise that the yield and the CO content in the alcohol-containing gas can meet the requirements of the subsequent processing stages. Maintain a low operating temperature as much as possible. The operating temperature should not be increased lightly; each increase must be done carefully, with the increase amount not being 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 contaminants in fresh gas and recycled gas are kept at their lowest levels. (6) Appropriately increasing the CO2 content in the gas entering the tower can suppress the intensity of the reaction, thereby preventing overheating to a certain extent. (7) Improve operational skills, continuously summarize operational experience, and reduce temperature fluctuations. For the control of air velocity, if it can be adjusted through the Okawa bypass or other methods, then there is no need for circulation-based temperature regulation; efforts should be made to maintain stability in the circulation process, and it is not advisable to force an increase in air velocity in order to boost methanol production. This post was last edited by hwqckr on 2009-2-16 11:29.]