Application Progress of Rare Earth Catalytic Materials

- Nov 07, 2017 -

First, the type of rare earth catalytic material

As we all know, rare earth mine in our country mainly of light rare earth components, including lanthanum, cerium and other components account for about 60%. With China's rare earth permanent magnet materials, rare earth luminescent materials, rare earth polishing powder, rare earth in the metallurgical industry has expanded each year in the field of applications, the domestic market demand for heavy rare earth also increased rapidly. Resulting in a large backlog of high abundance of rare earths such as cerium, lanthanum and praseodymium, leading to a serious imbalance between the exploitation and application of rare earth resources in our country.

The study found that light rare earth elements due to its unique 4f electronic layer structure, making it in the chemical reaction process showed good catalytic performance and effectiveness. Therefore, the use of light rare earth as a catalytic material is a good way to comprehensive utilization of rare earth resources.

The catalyst is a kind of material that can speed up the chemical reaction and can not be consumed by itself before and after the reaction. The basic research of strengthening the rare earth catalyst not only improves the production efficiency, but also saves resources and energy, reduces the environmental pollution and meets the strategic direction of sustainable development.

So far, there are mainly three types of rare earth catalytic materials that can be applied in the industry, including molecular sieve rare earth catalytic materials, rare earth perovskite catalytic materials, and cerium zirconium solid solution catalytic materials, as shown in Table 1. Molecular sieve rare earth catalytic materials can be subdivided into mesopores, micropores, mesopores, and nano-rare earth catalytic materials and several other categories, and is currently mainly used for refining catalyst.

Due to its advantages of simple preparation, high temperature resistance and poisoning resistance, the rare earth perovskite catalytic materials are mainly used as environmental catalysts and are also widely used in the photocatalytic decomposition of water for hydrogen production and the hydrocarbon reforming reaction in the petrochemical industry aspect. At present, there are mainly perovskite type rare earth composite oxide catalysts which have been developed and applied as well as rare earth perovskite type catalysts doped with a trace amount of precious metals.

Cerium zirconium solid solution catalytic material is a kind of rare earth catalytic material that should be developed according to the demand of automobile exhaust purification market. Early use of oxygen storage performance of cerium to regulate the redox reaction in the vehicle exhaust. Later found that a single cerium oxygen storage materials, its long-lasting high temperature performance and can not meet the life expectancy of the growing automobile exhaust catalyst, and add some zirconium can significantly improve the high temperature performance of oxygen storage materials, thereby improving the catalyst durability. At present, the cerium-zirconium solid solution catalytic material is not only used for various catalytic processes in the petrochemical industry, but also widely used in automobile exhaust purification and other environmental protection fields.

Compared with the traditional noble metal catalysts, rare earth catalyst materials have strong advantages in terms of resource abundance, cost, preparation technology, and performance. Currently not only for a large number of car exhaust purification, but also extended to industrial organic waste gas, indoor air purification, catalytic combustion, and fuel cells and other fields. Since the late 1990s, the market for environmental catalysts in developed countries has been growing at a rate of 20%. Therefore, rare earth catalytic materials in the market of environmentally friendly catalyst products, especially in the purification of toxic and harmful gases, has a huge application market and development potential.


Second, car exhaust purification

In recent years, as China's automobile production and possession has been showing a rapid growth trend. Since October 2002, the average growth rate of China's automobile production has exceeded 37%. In 2002, the output was 3.25 million and in 2003 it reached more than 4.40 million. Expected 2004 vehicle production will exceed 5.1 million. Following the United States, Japan and Germany, China overtook France in 2003 and has become the fourth-largest automobile manufacturer in the world.

The heavy use of cars has caused serious air pollution in many cities in our country. Exhaust pollution control of motor vehicles, mainly rely on the installation of the catalyst containing ternary purifier. As rare earth catalytic materials can expand the operating window of the three-way catalyst to improve the purification efficiency and stability, has been widely used in vehicle exhaust purification. Globally, annual REE consumption of up to 15,000 tonnes of REO is solely for automobile exhaust gas purification.

At present, rare earths are used for purifying automobile exhaust gas and mainly used as an oxygen storage material in the active layer, replacing part of the main catalyst, and as a catalyst aid and the like. Mainly used in the dispersed layer to improve the high temperature stability of γ-Al2O3. Mainly used in carriers to improve mechanical strength and thermal stability. In addition, the oxygen sensor required for the car's electronic fuel injection system is also made of rare earth-containing ceramic material.

In addition to automobiles, our country has been the largest motorcycle manufacturer in the world since 1999, and the annual output of motorcycles has already exceeded 10 million. At present, motorcycles exported to developed countries require the installation of an exhaust gas purifier. Some domestic large and medium-sized cities have started to demand the control of the exhaust pollution of motorcycles. This is an important aspect of the application of rare earth catalytic materials.

In the exhaust gas pollution control of diesel vehicles, at present mainly relies on the installation of an oxidation purifier to oxidize and purify the soot and some gas pollutants emitted by the diesel vehicles. This is another aspect of the application of rare earth catalytic materials.

Since 2002, the output of fixed small-sized fuel-powered engines in our country has also increased rapidly. Currently mainly used for household generators, garden lawn mowers, small irrigation equipment, water power equipment, and many others. In 2003 only the small-scale export of fuel-engine reached more than 1,500 units. Some of them have requested the installation of purifiers, which in turn opens up a new field of application of rare earth catalytic materials.

From the above application field of rare earth catalytic materials, the amount of rare earth catalytic materials in China is increasing year by year. In 2003, China's domestic production of automobile exhaust gas purifier has reached more than 320 sets. Including catalysts, carriers, and oxygen sensors consumed by all types of rare earth, the total amount of rare earth reached 910 tons. It is estimated that by 2005, the market demand of China's automobile exhaust purifier will exceed 5.5 million sets, and the total rare earth consumption will reach 1560 tons.


Third, industrial organic waste gas treatment

The current air pollutants are mainly from tailpipe emissions from motor vehicles and from organic waste gases emitted from industrial processes. How to address the characteristics of these types of contaminated gases, the study of effective catalytic material is the crux of the current pollution control. At the same time, with the improvement of living standard, indoor air pollution has also become the key to urban residents. Therefore, the catalytic treatment of industrial organic waste gas, as well as indoor air purification is one of the most active areas of rare earth catalyst research in recent years. Currently, the use of rare earth catalytic technology to control industrial organic waste gas mainly concentrated in the volatile organic waste gas treatment, flue gas desulfurization, nitrogen removal during combustion, nano-TiO2 photocatalytic rare earth modification, and coking wastewater catalytic purification.

At present, industrial organic waste gas pollution is very serious in the industries of organic coatings, industrial solvents, adhesives, garments, footwear, and many organic solvents. Practice at home and abroad proved that the treatment of industrial waste gas and indoor air purification, catalytic oxidation technology is the most effective technical measures. Since 1997, sales of catalysts for the purification of industrial organic waste in the United States have been growing at an average annual rate of 20% to 25%. China is a big country for chemical production, of which 95% or more of the exhaust gas has not yet been treated. Due to its good catalytic performance, unique low temperature activity and superior resistance to poisoning, rare earth catalytic materials have shown more and more superior development and application prospects in organic waste gas treatment. Among them, the rare earth composite mesoporous catalytic material has the characteristics of large surface area, suitable pore size distribution and stable structure, and has become one of the most promising catalytic materials for purifying industrial organic waste gas. In addition, nano-level design to develop advanced rare earth catalytic materials, can reduce the 90% of the amount of precious metals can still guarantee the catalytic purification efficiency doubled.

Rare earths have complex energy level structure and spectral characteristics. Doped doping modification of nano-TiO2 can effectively improve the photocatalytic efficiency and is one of the most promising technologies to solve the problem of visible light utilization. The results show that photocatalysis using nano-TiO2 under visible light and catalytic oxidation of rare-earth catalytic materials are considered as the most promising method and can be applied to the purification of living environment on a large scale.


Fourth, catalytic combustion

Within 20 years, coal and oil will still dominate China's energy structure. The traditional way of combustion combustion temperature is high, more than 1500 ℃, at this temperature combustion is easy to produce nitrogen oxides, increase global warming. In addition, the combustion efficiency is low, the noise is high, and some inexpensive fuels can not be widely used.

 The use of catalytic combustion technology can change the combustion mode, improve the combustion efficiency, reduce the combustion temperature and reduce the formation of NOx, and the combustion process low noise, low-cost fuel can also be a large number of applications, with high efficiency and energy saving, environmentally friendly, etc., is the future of combustion technology Direction of development. According to relevant information, the use of catalytic combustion technology can increase the thermal efficiency of 64%, combustion efficiency up to 99.5%, energy-saving effect of more than 15%.

 There are nearly 40 sets of oil refining installations in our country, with an annual processing capacity of more than 200 million tons of crude oil. In addition, coal-fired power plants, industrial boilers, and civil heating, the annual energy consumption of more than 1.4 billion tons of standard coal. The use of catalytic combustion technology, its energy-saving effect will be considerable. In addition, in 2002 China's gas-fired water heater production reached 76 million units, the use of catalytic combustion technology, but also can improve the combustion efficiency of civilian fuel. Therefore, catalytic combustion technology has great potential in natural gas power generation, industrial heat source and civil use.

At present, the main catalytic combustion for rare earth catalytic materials, with cheap, raw materials readily available, high temperature performance and other advantages. In particular, the use of molecular assembly technology for the preparation of rare earth catalytic materials, the rare earth and its active components at high temperatures with good stability, is to promote catalytic combustion direction. Among them, rare earth-based perovskite, hexaaluminate and other rare earth composite oxides have a good prospect in the application of high-temperature catalytic combustion of natural gas.

Fifth, fuel cells

 Fuel cell energy conversion efficiency, low or zero emission of pollutants, is the 21st century efficient, low-pollution green energy. It is estimated that by 2010, fuel cell technology can form a huge market of more than 300 billion U.S. dollars in large power plants and new distributed power plants.

Rare earth oxides have good ionic and electronic conductivity, which plays an irreplaceable role in improving the performance of solid oxide fuel cells. By choosing a suitable oxide composition, the ionic conductivity of the electrode material can be increased, reducing the activation energy of oxygen reduction. By studying the composition, the relationship between structure and conductivity, and the morphology of doped ions, we designed and synthesized a new type of composite rare earth oxides with high electrocatalytic activity and high electrical conductivity. These materials are currently used in solid oxide fuel cells Research hot spots.

Sixth, the outlook

 1. According to the characteristics of energy and environmental protection, the development of high-performance rare earth catalytic materials with independent intellectual property rights, and promote the efficient use of rare earth resources, is the key to solve the balanced use of rare earth resources.

2. China is in a period of great development of automobile industry. Using rare earth catalytic materials for automobile exhaust gas purification not only protects the environment, but also expands the application of rare earths. It is an important way to turn rare earth resources into economic advantages.

3. The rare earth catalytic materials used for industrial organic waste gas pollution control and living environment purification is one of the driving forces to promote the catalytic application of rare earth.

 4. Rare earth catalytic combustion not only improve combustion efficiency, save energy, reduce nitrogen oxide emissions, protect the environment, will become an emerging field of rare earth catalyst.

5. Rare Earth Catalytic Materials for Solid Oxide Fuel cells are an important application of rare earths in the energy field.

Article from NdFeB Industry Network

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