The development history of ammonia synthesis catalysts in recent years
About 10% of the world's energy is used for ammonia synthesis production. Improvements in ammonia synthesis processes and catalysts will have a significant impact on the consumption of fossil fuels. Since the work of Haber and Mittasch, few more active catalysts have been discovered, and therefore molten iron catalysts remain the widely used catalysts in the ammonia synthesis industry. It has high intrinsic activity, that is, high activity at each active site, long service life and high density, and is cheap.
Despite the many advantages of molten iron catalysts, efforts have been made to develop new catalysts, and there is strong interest in iron-free catalysts. Since the 1970s, Japan has been actively seeking to develop ruthenium-based catalysts. Following the introduction of iron-cobalt catalysts in the ICI AMV and LCA processes, the carbon-based ruthenium catalyst used in the KAAP process has promoted the development of ammonia synthesis catalysts. Catalysts that do not contain iron or ruthenium at all, such as Cs/Co3Mo3N catalysts, have activity between molten iron and nail-based catalysts, and lower activity than ruthenium-based catalysts. Cs/Co3Mo3N catalyst, KMlR catalyst (Topsoe's molten iron catalyst) and carbon-based catalyst containing 6% barium and 6.7% ruthenium under the process conditions of hydrogen/nitrogen of 3:1 and 1:1 respectively. From the comparison, it can be seen that the kinetic characteristics of the Cs/Co3Mo3N catalyst are between those of molten iron and nail-based catalysts, but it can regenerate into oxidizing particles when burned in air at 600°C.
After the early discovery of ruthenium catalysts by Mittasch, there was no progress in the development of nail-based catalysts. Until 1970, the kinetic study of ruthenium-based catalysts using diatomaceous earth as a support for ammonia synthesis reactions was introduced to Japan. , Japanese researchers continued to study the activity of a large number of potassium-promoted metals (Co, Ni, Re, Mo, Fe, Ru, Os) on carbon supports and found that ruthenium was more active than traditional bimetallic iron catalysts. In 1972, Japan reported the first application of a nail-based ammonia synthesis catalyst using graphite as a carrier, and it was BP that actually promoted it into production after 1979. Since then, Kellogg Company accepted the catalyst technology transfer from BP Company, jointly developed and applied this catalyst in the KAAP process. In 1992, Canada's Ocelot Ammonia Production Company was the first to install a nail-type catalyst in its industrial unit. Since then, the other two plants have also been equipped with this catalyst. In 1998, two factories using the KAAP process for the first time were built and put into operation in Point Lisas and Trinidad areas, with a production capacity of 1850t/d.
After a more detailed understanding of nail-based catalysts without accelerators and with accelerators, several improved ruthenium-based catalysts have emerged, such as those developed by Ruhler et al. with higher activity and stability Based on the Ba-Ru/MgO catalyst, the Danish company Tops?e has also developed a ruthenium-containing ammonia synthesis catalyst. In these studies, nail-based catalysts supported by magnesia-aluminum spinel and high surface area graphite showed better activity. However, there are still certain problems with its stability under industrial conditions.
Recently, a nail catalyst using Ba-promoted BN (boron nitride - known as white graphite) as a carrier has been successfully developed, which has unprecedented activity and stability. BN is a very potential support material for nail-based ammonia synthesis catalysts. It has almost a similar structure to graphite (except for the slight difference in lamination on a single layer). The difference is that it performs well under all hydrogenation reactions. All are stable. At the same time, it is known for its high temperature resistance, as opposed to graphite, which is an insulating material. The developed Ba-Ru/BN catalyst contains 5.6% Ba and 6.7% Ru on a support of 81m2/g. It has been proven that its stability is very good under the conditions of 5000/h, 10MPa, 550℃ and hydrogen/nitrogen balance of 3:1.
Under specific reaction conditions (temperature, pressure, hydrogen-to-nitrogen ratio, ammonia concentration, etc.), the appropriate BN surface area, ruthenium concentration, additives and concentration, particle size and density can be selected to obtain the best Catalytic activity of Ru/BN catalyst. Moreover, a method similar to the treatment of Ba-Ru/MgO catalyst can be used to recover the useful Ba, Ru, and BN mixture in Ba-Ru/BN catalyst.
2 Newly developed ammonia synthesis catalyst
Researchers at Halldor Topsoe Research Laboratory in Denmark have successfully developed a series of products that can replace traditional iron catalysts. The researchers found that under industrial unit operating conditions, ternary nitrides, such as Fe3Mo3N, Co3Mo3N and Ni2Mo3N, have high activity and good stability when used as ammonia synthesis catalysts. In addition, if cesium is added to the Co3Mo3N catalyst, the activity will be higher than the iron catalyst currently used. It is reported that under the same operating conditions (temperature 400°C, pressure 20MPa, hydrogen/nitrogen ratio 3:1), the activity of Co3Mo3N using cesium as a cocatalyst is twice that of traditional iron catalysts.
Ruhr University in Germany has developed an ammonia catalyst composed of metal barium, metal ruthenium and magnesium oxide. It is said to produce more ammonia and last longer than existing ammonia synthesis catalysts. According to reports, the activity of this barium-ruthenium catalyst is 2-4 times higher than that of traditional iron-based catalysts or other types of ruthenium-based catalysts. The developed barium-ruthenium catalyst can increase ammonia production compared with cerium-ruthenium catalysts. Double. Ammonia production can be further increased if the ratio of barium to ruthenium is optimized.
3 Current status of my country’s R&D and production of ammonia synthesis catalysts
China is the world’s largest ammonia-producing country. It needs about 20kt of various types of hydrogen production catalysts every year. It is estimated that the demand in 2010 will be 27kt. Currently, The device capacity is sufficient. The scale and diversity of raw materials make my country's catalyst unit consumption of 10,000 tons of ammonia higher than the foreign average. However, the use of catalysts in large ammonia plants has reached the international advanced level.
The overall level of catalyst use by my country's large-scale fertilizer companies is relatively high. The use of catalysts shows the characteristics of increasing localization rate year by year, gradual reduction in consumption, further reduction in types and total amount, and the increasing application of new catalysts. . The demand for various types of ammonia production catalysts in China in recent years is shown in Table 1.
Table 1 Demand for various types of ammonia production catalysts in recent years t/a
Catalyst 2000 200 years
Hydroconversion 130 170
Purification agent ① 4500 1800
Steam reforming ② 800 1040
Iron series high change 11200 11400
Iron molybdenum wide change 2300 2500
Copper series low variability 1200 1400
Methanation 450 500
Ammonia synthesis 5160 5360
Total 25740 24170
Note: ①Includes Zinc oxide desulfurizer, iron oxide desulfurizer, dechlorination agent, arsenic removal agent, etc.
②Includes one-stage conversion, light oil conversion, and two-stage conversion.
3.1 Organosulfur hydrogenation conversion catalysts
There are two main types of organic sulfur hydrogenation conversion catalysts: cobalt-molybdenum catalysts and iron-molybdenum catalysts. The average service life of this type of catalyst in large-scale ammonia synthesis units has exceeded 10 years, and the technology used has reached the advanced level abroad. It is the future development trend to reduce bed resistance, bulk density and operating temperature, improve activity and realize external pre-vulcanization.
The Catalyst Factory of Nanjing Chemical Industry Company actively participates in the competition in the international petrochemical market and accelerates the launch of new products. The NC9802 refinery gas hydrogenation catalyst developed by the plant in cooperation with Anqing Petrochemical and Jinling Petrochemical makes it a reality that refinery gas can replace naphtha as a raw material for hydrogen production of large fertilizers, greatly reducing the cost of hydrogen production. The appraisal believes that this technology has filled the domestic gap and is of international advanced level. The NC9802 hydrogenation catalyst has the characteristics of high space velocity, low sulfur resistance, and natural sulfurization. It is used to change the route of large-scale chemical fertilizer raw materials. It uses coking dry gas instead of naphtha to produce synthetic ammonia, which can effectively reduce production costs. Jinling Petrochemical uses it in a refinery gas unit with an annual processing capacity of 60kt. The catalyst has good activity, selectivity and stability.
3.2 Desulfurizers and other purification agents
Desulfurizers mainly include zinc oxide desulfurizers, iron-manganese desulfurizers and iron oxide desulfurizers. High-temperature composite oxide desulfurizers are the future development. trend. Other purification agents mainly include dechlorination agents, arsenic removal agents, etc.
Zinc oxide desulfurizer is a fine desulfurizer with ZnO as the main component and CuO, MnO, A1203, etc. as accelerator. It has high desulfurization accuracy, easy use, stable and reliable performance, and high sulfur capacity. It occupies an important position and is widely used in ammonia synthesis, hydrogen production, methanol synthesis, coal chemical industry, petroleum refining, beverage production and other industries to remove natural gas, petroleum fractions, oil field gas, refinery gas, synthesis gas (H2+CO ), hydrogen sulfide and certain organic sulfur in raw materials such as carbon dioxide. Since the zinc oxide desulfurizer can remove sulfur in the raw gas (oil) to less than 0.5-0.1 μg/g, it ensures the downstream processes of steam reforming, low temperature change, methanation, methanol, low-pressure alcohol, oxo synthesis, etc. Catalysts containing nickel, copper, iron and precious metals are protected from sulfur poisoning.
At present, the main models of zinc oxide desulfurizers in my country include T303, T304, T302Q, T305, T306, T307, KT310, etc., but in large and medium-sized ammonia plants, hydrogen production, methanol synthesis and food In grade C02 purification and desulfurization of other organic raw materials, only 5 to 6 types are commonly used. Among them, the T305 desulfurizer adopts a special composite preparation process. While ensuring sufficient ZnO content, additives and auxiliaries are introduced to make the product have a good pore structure and maximize the utilization of the inner surface for the reaction of ZnO and H2S. The main performance indicators are higher than those of foreign products, and they have good performance in domestic industrial applications.
Our country has successively developed 3703 and 0902 zinc oxide desulfurizers since 1956. At that time, they were only used in the three-catalyst process desulfurization of oil refining and coal-to-gas small synthetic ammonia plants to protect low-variability catalysts from Due to sulfur poisoning, the desulfurization accuracy can only reach less than lμg/g. Since the 1970s, due to the introduction of large-scale chemical fertilizers, the research on zinc oxide desulfurizers in my country has entered a new stage. The properties of desulfurizers have been continuously improved, the temperature range has been continuously broadened, and the scope of use has expanded year by year. It has been used for ammonia synthesis, hydrogen production, The synthetic methanol system has been expanded to TDI projects, food-grade CO2 purification projects, polypropylene and other purification projects.
At present, the large-scale ammonia plants that have been put into production in my country are filled with 1105.4m3 of zinc oxide desulfurizer, totaling 1335.8t. The actual filling density is 1.20kg/L, which is 8% higher than foreign products, and the average life is 3.5 In 2017, the annual demand of large-scale ammonia plants was approximately 400t. A newly built Braun or ICI-AMV device is filled with 79t and 103t of desulfurizer respectively, and the demand will be approximately 800t by 2005. 21 three-catalyst process medium-sized plants require 160t of desulfurizer annually. Adding the needs of small and medium-sized methanol plants, petroleum, petrochemicals and food industries, the annual demand is about 1,500t.
As of the end of 2001, there were more than 40 hydrogen production units in my country, with a total hydrogen production capacity of about 8.2×105 m3/h. The main raw materials are light oil and a small amount of natural gas. Among them, 2×105 m3/h is made of coking dry gas and catalytic dry gas. The total loading capacity of zinc oxide is about 960t. The average life of the desulfurizer is calculated as 1.2 years, and currently 640t of zinc oxide desulfurizer is required per year. Before 2005, if the hydrogen production capacity of 4×10 m3/h using coking dry gas and catalytic dry gas as raw materials is increased, the loading capacity of zinc oxide desulfurizer will increase by approximately 800t. In addition, in recent years, the raw materials of many hydrogen production units have been changed from natural gas and light oil to coking dry gas and catalytic dry gas, which has further increased the loading capacity of zinc oxide. If half of the devices are successfully transformed, the annual demand for zinc oxide will increase by about 340t. That is to say, for hydrogen production equipment alone, the demand for zinc oxide desulfurizer will reach about 2000t before 2005.
In addition, the industrial application of DDS desulfurization technology and DDS catalyst series products successfully developed by Peking University has also made breakthrough progress. So far, more than 70 companies have applied this technology to desulfurize semi-aqueous gas and shift gas in the ammonia synthesis process, and have achieved good economic and environmental benefits.
DDS desulfurization technology is a wet biochemical desulfurization technology improved on the basis of the "iron-alkali solution" desulfurization method. The corresponding desulfurization liquid consists of a DDS catalyst and phenols. Substances and aqueous solutions of alkaline substances. DDS catalyst is an iron-containing complex or chelate. In order to ensure its stability and activity in alkaline solution, some fungal substances need to be added to the desulfurization liquid to ensure that the DDS catalyst and its corresponding fungi are in Optimum activity is at the heart of this technology.
The desulfurization liquid that has absorbed sulfur is oxidized and regenerated with air under the simultaneous catalysis of DDS catalyst and phenolic substances, sulfur is produced as a by-product, and the solution is recycled.
A new type of high-efficiency composite ISS desulfurizer was also successfully developed by Ningbo Far East Chemical Technology Co., Ltd. and Suzhou University and put into industrial production and application, showing good promotion prospects. Compared with traditional desulfurizers, this new desulfurizer has the characteristics of high desulfurization efficiency, fast regeneration speed, low operating costs, and non-toxic and pollution-free. It can gradually replace the original desulfurization liquid without affecting production. It is suitable for all types of wet oxidation desulfurization devices and is currently one of the more ideal wet desulfurizers. According to measurements, after the variable desulfurization device is changed from tannin desulfurization to ISS desulfurization, the desulfurization efficiency can be increased by 2.5%.
3.3 Hydrocarbon steam reforming catalyst
Hydrocarbon steam reforming catalyst is mainly used in ammonia synthesis units using natural gas or coke oven gas as raw materials.
The Z112Y low-temperature and low-water-to-carbon ratio first-stage conversion catalyst successfully developed by Sichuan Chemical Catalyst Factory and the Chengdu Institute of Organic Chemistry, Chinese Academy of Sciences solves the problem of rising resistance caused by sintering and pulverization of the catalyst under low-temperature and low-water-carbon conditions. , as well as problems such as poor low-temperature reduction performance. The technical level of this catalyst reaches the domestic leading level.
The catalyst has a macroporous structure, with pore volume greater than or equal to 0.2m1/g and pore diameter greater than or equal to 300nm accounting for more than 60% of the total pore volume of the catalyst. It has the characteristics of high conversion activity, good low-temperature reduction performance, strong coking resistance, erosion resistance, and low resistance. It is especially suitable for the first-stage reforming furnace of low-water carbon low-temperature energy-saving process. It is used in the first stage furnace of traditional synthetic ammonia plant, and the use effect is better.
The catalyst is easy to load, has good low-temperature activity, and the operating temperature can be reduced by 20 to 30°C. It has strong resistance to coking, and the resistance of the furnace tube remains basically unchanged from the initial to the end of use. It has been used in two Brown process units of Sichuan Tianhua Company and Jianfeng Chemical Plant, as well as large, medium and small synthetic ammonia plants such as Sichuan Chemical and Meifeng.
3.4 High (medium) temperature shift catalysts
The average service life of high-shift catalysts in large-scale ammonia synthesis units is 5.67 years, which has entered the international advanced level. Low-chromium and chromium-free medium-temperature shift catalysts are at the international leading level.
3.5 Wide-temperature sulfur-tolerant shift catalyst
More than 20 types of Co-Mo-K catalysts have been developed domestically for medium and small ammonia synthesis units using coal coke or heavy oil as raw materials. Has partially replaced Fe-Cr catalyst.
In terms of the types and total amount of catalysts used in large chemical fertilizer units, large chemical fertilizers using light oil, natural gas, and oil field gas as raw materials use 7 types of catalysts, while large chemical fertilizers using residual oil and asphalt as raw materials use 7 types of catalysts. There are two or three types of catalysts used in fertilizers. Due to the influence of raw material price factors, some large chemical fertilizers in my country that use light oil as raw material will adjust their raw material structure in the next few years, with the main direction being to replace oil with coal; at the same time, some manufacturers will change all or part of their hydrogen production units to supply Hydrogen device. Therefore, the variety and quantity of catalysts used will be greatly reduced, while the use of sulfur-tolerant wide temperature shift catalysts will increase. In view of this, how to improve the quality and usage technology of sulfur-tolerant wide-temperature shift catalysts is a top priority for catalyst research and production units.
Since the 1980s, the sulfur-tolerant shift catalysts used in more than ten large-scale ammonia synthesis units introduced in my country have all used imported catalysts. In order to localize the sulfur-tolerant shift catalyst, Sinopec Qilu Branch Research Institute Undertaken the development task of Sinopec’s key research project “Wide Temperature Sulfur Tolerant Shift Catalyst”. The institute first developed the world-leading QCS-01 sulfur-tolerant shift catalyst, overcoming the unsolved problem at home and abroad of the lack of a suitable sulfur-tolerant shift catalyst in low-sulfur feed gas, filling the international gap and replacing international famous brands. The products are used in large 300kt/a fertilizer installations in Xinjiang, Ningxia and Dalian. Then, based on the characteristics of the sulfur-tolerant transformation process of the Lucci coal gasification unit, the world's advanced QCS-04 catalyst was developed to replace foreign famous brand products in the country's largest coal-based fertilizer plant and Asia's largest fertilizer plant. Gas plant - Harbin gasification plant application. During the same period, the unique QCS-02 catalyst developed was also used in more than 200 small fertilizer plants in China. So far, the sulfur-tolerant shift catalysts developed by the institute have all replaced imported products, accounting for 100% of the domestic large-scale fertilizer sulfur-tolerant shift devices.
From 1997 to 1999 alone, direct economic benefits of 340 million yuan were achieved.
With the launch of the national “coal-to-oil” project during the “Tenth Five-Year Plan” period, the institute developed an anti-hydration type fertilizer that has reached the international advanced level based on the characteristics of my country’s new “coal-to-oil” fertilizer process. The sulfur-tolerant shift catalyst QCS-06 passed the pilot test identification of Sinopec in December 2001.
In the face of increasingly fierce market competition, Qilu Research Institute developed a new product QCS-03 with lower cost and higher strength. It was industrially applied in Shaanxi Weihe Fertilizer Factory in 2001, showing better performance than QCS 101 has superior catalytic performance; in the same year, the high-strength, low-cost QCS-10 catalyst suitable for medium and small fertilizer plants was also successfully industrially applied in Shandong Lunan Fertilizer Plant.
After more than ten years of hard work, Qilu Research Institute has successively developed sulfur-tolerant shift catalysts QCS-01, QCS-02, QCS-03, QCS-04, QCS-06, QCS-10 and other recent catalysts. Ten series of products, catalyst technology has reached the international leading, advanced and domestic leading, advanced levels respectively; has applied for 16 Chinese patents, authorized 7; and in 7 countries including the United States, Germany, Japan, South Africa, the Czech Republic and Australia Obtained patent rights; won the second prize of the National Science and Technology Progress Award, the China Invention Patent Gold Award, the National Key New Product Award 4 times, the Sinopec and Shandong Province Science and Technology Invention and Progress Award 6 times, and was included in 26 proprietary technologies by Sinopec.
In 2002, the CO sulfur-tolerant shift catalyst with excellent performance newly developed by the Sinopec Qilu Branch Research Institute won the bid again despite two international famous brand catalysts participating in the bidding, and was used in the 300kt/ a large fertilizer plant, this marks that the performance of the QCS series CO sulfur-tolerant shift catalyst developed by the institute has become more complete and mature, and its comprehensive performance has always maintained the international leading level.
3.6 Low-temperature shift catalyst
In recent years, only a few types of low-vapor-to-gas ratio catalysts have been launched in China.
3.7 Methanation Catalyst
At present, the average service life of methanation catalysts in large-scale ammonia synthesis units is 11.7 years, and the average service life of methanation catalysts in medium-sized ammonia synthesis units is 2.5 years. Spherical or bar-shaped products have been developed domestically.
3.8 Ammonia synthesis catalyst
my country has established a ferrous-based molten iron catalyst system. There are as many as 7 models of chromium-containing catalysts in China, but they are not used for low-pressure synthesis, but to reduce operating temperatures. Molten iron catalyst has been used in some medium and small ammonia synthesis plants.
The All0-1 and AllO-1-H ammonia synthesis catalysts produced by Sinopec Group Nanhua Catalyst Plant have been running well since they were put into use in the Lutianhua fertilizer plant in 1998, creating remarkable achievements. Economic benefits, it has become the longest-used fertilizer catalyst product in China. According to data from the National Large and Medium-sized Fertilizer Catalyst Usage Technology Liaison Station, 26 of the 29 large fertilizer units across the country use the plant's ammonia synthesis catalyst, and the service life of the catalysts in many of these units exceeds 10 years. After testing the catalyst products of the plant, Casale and Topsoe concluded: "It is one of the best catalysts in the world."
4 Evaluation of my country's Fertilizer Catalysts
Some large domestic fertilizer plants are partially transforming their original equipment to increase output and reduce consumption. New types of fertilizer catalysts that are suitable for this purpose The use of catalysts is also increasing. For example, the market share of Fe-Cr-Cu series energy-saving high-shift catalysts suitable for low steam-gas ratio is increasing year by year; QCS-01 and QCS-04 wide-temperature sulfur-tolerant shift catalysts are gradually or completely replacing BASF's K8- Type 11 products; B204-1, CB-5, and B205-1 low-temperature shift catalysts have further reduced physical water content compared with previous products, allowing the manufacturer to save startup costs; B206-1, NB207 low-temperature shift catalysts Shift catalysts also have good applications in energy-saving processes. At the same time, the appearance size of some high-low variable catalysts has been improved, from large particles to small particles, to adapt to the needs of changing the reactor from axial to axial and radial.
Currently, there are 29 imported large-scale ammonia units (annual output of 300kt of synthetic ammonia and 520kt of urea) operating across the country. Surveys show that in 2001, the localization rate of my country's large-scale fertilizer catalysts reached 93.97% , domestic catalysts can meet the requirements of ammonia production units in different processes, both in terms of variety and quality.
my country has a complete range of fertilizer catalysts, which can be applied to various large-scale ammonia production units with different process conditions. A considerable number of products have been evaluated by well-known foreign engineering companies, such as the Swiss Casali Company entrusted the German BASF Company, the Danish Topsoe Company, the Italian TECNIMONT Company entrusted the Franica Company, etc., for A110-1, A110-1-H ammonia synthesis catalyst, B206 low-temperature shift catalyst, J105 methanation catalyst, Z111, Z204, Z205 gaseous hydrocarbon conversion catalyst, T201 organic sulfur conversion catalyst, T305 zinc oxide desulfurizer, etc. were evaluated. It is believed that the quality is comparable to that of similar foreign products. In particular, the ammonia synthesis catalyst and methanation catalyst are highly evaluated. They are considered to be "one of the best varieties of similar products in the world at present" and "the best in terms of quality and service life." A completely reliable product." Recently, Casali Company was entrusted by the Yuntianhua transformation project to evaluate the B206-1 low-temperature shift catalyst from the Catalyst Plant of Nanhua Company and believed that its main quality level is comparable to the outstanding similar products in the world. It can be seen that a considerable number of major fertilizer catalysts in my country have reached a certain technical level.
my country's fertilizer catalysts still have the following four problems: ① The production scale is small and scattered, with an average scale of 1,200t/a, and there are only 3 large factories with a scale of 10,000t/a; ②Manufacturers lack technology development capabilities ;③The bulk density of some catalyst products is relatively high. The bulk density of the four catalysts for hydroconversion, methanation, high temperature shift and low temperature shift is 18% to 34% higher than that of imported catalysts, resulting in a waste of resources and energy in the production of catalysts and ammonia production. The catalyst unit consumption during ammonia production is relatively high; ④ Since the composition and process of ammonia production raw materials are different from those in foreign countries, the catalyst unit consumption during ammonia production is also high.
After entering the 21st century, the efforts of my country's ammonia production catalyst industry are: ① Reorganization and mergers of production capabilities; ② Further improve product quality, enhance testing methods, and actively participate in international market competition; ③ Cooperation between factories and schools to Accelerate the development and industrialization process of new products; ④ move from imitation to innovation; ⑤ product development and reaction engineering are closely integrated; ⑥ learn from the experience of catalysts in the oil refining and petrochemical industries to speed up product development and create conditions for improving the overall level of the synthetic ammonia industry.