With the rapid economic development, rising oil prices and serious environmental pollution have become increasingly prominent. How to increase energy efficiency and reduce environmental pollution has become an important issue in the world. In particular, with the popularization of automobiles, the air pollution in cities has become increasingly serious. Although domestic and foreign companies have done a lot of work in reducing vehicle exhaust pollution, such as eliminating leaded gasoline, reducing the sulfur content of gasoline and diesel, reducing the content of diesel aromatics, and installing automotive exhaust gas. Purifiers, but it is difficult to fundamentally solve the problem. Efficient, clean, low-noise fuel cells and fuel cell vehicles as a new way of energy use are increasingly attracting attention. The development of fuel cells and fuel cell vehicles must first address the issue of fuel sources for fuel cells. At present, domestic and international research on fuel cell fuel for vehicles is mainly focused on hydrogen, natural gas, methanol, and light oil. This paper analyzes the advantages and disadvantages of these four fuels as raw materials for fuel cells, summarizes the research status of hydrogen conversion from natural gas, methanol, and light oil at home and abroad, and analyzes the large-scale application of fuel cells and fuel cell vehicles. Impact on the structure of refinery and natural gas chemical industry products. Hydrogen fuel cells and fuel cell vehicle prototypes currently developed are mostly based on pure hydrogen. The reason for this is that they can be fed directly, no fuel conversion hydrogen production system is needed, the battery structure is simple, and the startup is rapid; furthermore, hydrogen-based fuel cells are used. When only a small amount of clean water is discharged during operation, zero pollution can be truly achieved.
However, with the acceleration of commercialization and commercialization of fuel cell vehicles, the issue of hydrogen as fuel for fuel cell vehicles will become increasingly apparent. First, it is necessary to solve the problem of cheap and stable sources of hydrogen; second, it requires expensive infrastructure to invest in hydrogen sales and supply systems; and when hydrogen fuel cells are used in automobiles or other portable power sources, safe and reliable hydrogen storage facilities are also needed. . At present, high-pressure hydrogen storage bottles or hydrogen storage materials are generally used to carry hydrogen. The fuel cell vehicle operation project initiated by SAIC and U.S. General Motors in the first quarter of 2005 is to store hydrogen gas under high pressure with super In the hydrogen storage tank with insulation function, the FCX type fuel cell car developed by Japan's Honda Company also uses a high-pressure hydrogen tank with a filling pressure of up to 35 MPa. However, the use of such high pressure hydrogen storage bottles has safety problems, and the use of hydrogen storage materials is limited by its low hydrogen storage capacity. In order to solve the problem of cheap hydrogen sources and onboard vehicles, research institutes at home and abroad have done a lot of research work in electrolysis of water for hydrogen production, biohydrogen production, and the development of metal hydrogen storage materials, but it is still difficult to achieve industrialization.
Due to the above problems in the use of pure hydrogen as a raw material for methanol, a method of using a liquid fuel to produce hydrogen by vehicles has also been proposed. These liquid fuels include methanol, gasoline, diesel, etc., and catalytically converted to generate hydrogen-enriched hydrogen. 59 Phase 2 Wang Xianti et al.: Progress in the fuel selection of fuel cells for automobiles and hydrogen conversion from fuel conversion as fuel cell feeds. The advantages of liquid fuel hydrogen generation with the vehicle are: on the one hand, it is possible to reduce the trouble of carrying hydrogen onboard the vehicle, and on the other hand, it can use the existing fuel supply system. Methanol has a simple structure, low impurity content (especially low sulfur content), no refining, mild hydrogen production conditions (reaction temperature methanol steam reforming hydrogenation methanol steam reforming hydrogen production was first developed for industrial hydrogen production, The oldest hydrogen production method for methanol is mainly used in the industry for fine chemical plants and pharmaceutical factories that use a small amount of hydrogen and have a high requirement for hydrogen purity. The advantages are simple process flow, mild reaction conditions, and typical examples. The reaction conditions of hydrogen production equipment for hydrogen steam reforming of methanol and the composition of hydrogen-rich gas.With the proposal of hydrogen source in fuel cells, many research institutes have begun to develop small-scale methanol steam reforming hydrogen production devices that can provide hydrogen for fuel cells. The Tokyo Automobile Company of Japan successfully developed a methanol steam reforming hydrogen-proton exchange membrane fuel cell device for a fuel cell vehicle in a laboratory in 1997.
When used in fuel cell vehicles, it is necessary to add burners to heat, making the system bulky and slow to start. This is a fatal drawback for automotive power supplies. Therefore, in order to solve the above problems, hydrogen partial oxidation of methanol has been developed. technology. Partial Oxidation of Methanol to Hydrogenation Partial Oxidation of Methanol The principle of hydrogen production technology is that the partial oxidation of methanol to an exothermic reaction provides both the heat required to maintain the reaction temperature and the generation of hydrogen due to different oxygen to alcohol ratios (ie, air/ The reaction temperature is controlled by controlling the ratio of oxygen to alcohol. The CO in the reformed gas is converted to CO2 by a steam shift reaction. U.S. Patent No. 5,942,346 proposes a methanol partial oxidation reforming hydrogen production reactor: methanol is fed through a liquid pump into a nozzle at the top of the reactor, and the methanol is sprayed Sprayed into the reactor, air enters from the top of the other inlet of the reactor. Air and methanol are mixed and passed down the ignition coil. The heat provided by the ignition coil tube partially vaporizes the methanol and reaches the reaction temperature. Part of the vaporized methanol continues to flow. Passing through the catalyst bed, the catalyst consists of a ceramic honeycomb carrier impregnated with CuO and ZnO. The honeycomb carrier not only provides a uniform fluid distribution but also ensures a low pressure drop in the reactor; in addition, the reaction temperature is controlled by adjusting the air feed rate. And reform hydrogen gas purity. The hydrogen partial oxidation of methanol catalyst research is also relatively active, the United States Argonne National Laboratory carried out research on different metal / carrier system, of which the Cu / ZnO catalyst activity is the best; Spain's Petrochemical Catalysis Institute in the Cu / ZnO catalyst Adding Al2O3 to prepare Cu40Zn55Al5 catalyst, its activity is slightly lower than that of Cu/ZnO, but the stability and selectivity are greatly improved. The partial oxidation of methanol solves the problem of the need for heat exchangers or burners for hydrogen production from steam reforming. The reformer is simple in structure, compact and lightweight, and easy to carry. However, it also has another shortcoming: Hydrogen production from steam reforming is lower in purity than the hydrogen-rich gas produced.
Methanol Oxidation Reforming Hydrogenation Methanol Oxidation Reforming is a combination of steam reforming of methanol and partial oxidation reforming. The endothermic heat of the methanol steam reforming reaction is complementary to that of the partial oxidation reaction, and the reformer is insulated. The operation is simple in structure and easy to operate, and at the same time, it makes up for the defect of low hydrogen purity in partial oxidation reforming hydrogen production technology. AISINSEIKI company developed a set of proton exchange membrane fuel cell (PEMFC) electric vehicle methanol oxidation reforming hydrogen production system, including methanol vaporization unit, methanol reforming unit and CO removal unit in three parts, its composition as shown. The vaporization unit includes a methanol vaporizer and a super heater, and a methanol catalytic combustion chamber provides heat for the vaporizer and heater to ensure rapid start of the PEMFC system. The vaporized raw material is heated to over 200 by the heater to ensure Solidification does not occur, and then enters the reforming unit; the reforming unit combines the advantages of partial oxidation reforming and steam reforming to convert methanol, water, and air into hydrogen-rich reformed gas; the CO removal unit uses air to select the CO Oxidation can reduce CO content in reformed gas from 10% to 10g% g-1. The volume of AISINSEIKI hydrogen production unit for methanol reforming is 30L, working pressure is 015025MPa, reforming efficiency is 78%, reforming gas hydrogen content 57%, CO content is less than 10g% g-1.
In addition, the self-starting and self-heating of the methanol catalytic oxidation reformer was achieved using a catalyst and a Hotspot reactor. Dalian Institute of Chemical Physics, Dalian, also carried out a certain research on the oxidation of methanol by oxidative reforming of methanol. A methanol hydrogen reactor with a capacity of 5 kg methanol/h and a complete set of equipment have been developed. The molar ratio, molar ratio and reaction temperature of O2/CH3OH have been optimized. With various parameters, the thermal efficiency of the entire hydrogen production system can be achieved. Methanol direct feed Methanol direct feed fuel cell (abbreviated as DMFC) is a new type of battery developed in recent years. It does not require a fuel converter and a CO removal device. The fuel reforming catalyst integrates with the battery anode, which not only reduces the overall battery Cost, but also reduced battery size and weight. According to different methanol feed phases, DMFC is further divided into liquid methanol fuel cells and gaseous methanol fuel cells. Compared with liquid methanol PEMFCs, gaseous methanol PEMFCs have enhanced material transfer and improved battery performance, which is a schematic diagram of a gaseous methanol PEMFC system. Methanol and water are pumped into the vaporization chamber. The vaporization chamber is composed of dual vaporizers to ensure complete vaporization of the fuel. The gas temperature at the outlet of the vaporization chamber is controlled at 200. Unreacted materials discharged from the anode of the cell are collected by the water condenser and flow back to the fuel tank. recycle. The methanol direct feed fuel cell has a compact structure, a lighter weight, and is easy to carry. The main problem is how to improve the catalytic performance of the anode catalyst and the ability to resist impurities and corrosion. Natural gas resources are abundant, impurities are low, and metal impurities and aromatic hydrocarbons are not included. Therefore, the study of natural gas as a fuel cell fuel is also very active. 61 Phase 2 Wang Xianti et al.: Fuel selection for fuel cells for vehicles and hydrogen conversion from fuel conversion Diagram of gaseous methanol PEMFC system Fig3. Hydrogen production from natural gas has three technical routes for fuel cell feedstocks: steam reforming, partial oxidation reforming and catalytic oxidation reforming. The main reaction of natural gas steam reforming to produce hydrogen from natural gas steam reforming is: Endothermic reaction Because this reaction is an endothermic reaction, and the reaction temperature is high (about 800), it needs a lot of heat, and it needs to add a lot of water Steam, resulting in too high a thermal energy consumption of the process, is not suitable for fuel cell vehicles and will not be described in detail here.
At the same time, a higher H2 concentration is obtained. The research on hydrogen production from natural gas reforming is relatively active. However, there are no reports on the formation of hydrogen source prototypes for fuel cells. Since natural gas is gaseous at normal temperature and atmospheric pressure and is difficult to store and carry when used in automobiles or portable power sources, it is not suitable for direct use as fuel cell raw materials for vehicles. However, in regions where natural gas is abundant, hydrogen is produced from natural gas. It may be a feasible route to purify the fuel cell vehicle or to synthesize methanol and methanol to synthesize methanol and methanol as raw materials for automotive fuel cells. Light oil Because fuel gas can be conveniently provided at gas stations all over the world, the fuel cell for vehicles using gasoline and diesel fuel is attractive. On the one hand, the existing fuel supply network can be used to save huge investment in infrastructure construction; safety is also guaranteed. Domestic and foreign research institutes have developed a variety of catalytic hydrogen production technologies for gasoline and diesel fuel cells used in automotive solid oxide fuel cells. This solution solves the problem of carrying hydrogen storage tanks for diesel desulfurization. The process is as follows: Sulfur-containing diesel oil is pumped to a normal-pressure mixer at a low pressure and mixed with hydrogen. The mixture is sent to the hydrodesulfurization reactor for desulfurization after high-pressure pumping to the vaporizer section for gasification. The upper part of the desulfurization reactor is equipped with a CoMo catalyst for the hydrodesulfurization of diesel oil, and the lower part is filled with ZnO to consume the H2S generated by the reaction. The ZnO is periodically replaced. The desulfurized diesel reacts with the water generated by the fuel cell into the high pressure reforming reactor to obtain a hydrogen-rich reformed gas. The reformed gas is separated into hydrogen-rich gas and water by condensation, and the water is recycled. The hydrogen-rich gas enters a hydrogen separator and is subjected to membrane separation in a hydrogen separator to obtain hydrogen gas having a hydrogen purity of 98%. A portion of the hydrogen obtained is passed to the hydrodesulfurization reactor or storage tank, and a portion of the desorber is depressurized and sent to the anode of the fuel cell for power generation. A similar set of diesel hydrogen-solid oxide fuel cell solutions has also been proposed and will not be described in detail here.
The commercialization of these two options is not likely. Gasoline Oxidation Reforming Hydrogen Gasoline Oxidation Reforming Hydrogen production is a technology that combines the steam reforming of gasoline with partial oxidation reforming. The principle is the same as that of methanol oxidation reforming hydrogen production, through the control of gasoline/oxygen, gasoline/water The ratio achieves adiabatic operation. Due to the relatively complex composition of gasoline, it is difficult to control the air/gas molar ratio and H2O/gasoline molar ratio to achieve the self-heating operation. In addition, the reaction conditions are harsh (reaction temperature > 500), and a desulfurization system is required to remove the raw oil. Sulfur that is toxic to hydrogen production catalysts. However, the gasoline oxidation reforming should be a relatively promising route. The key to the technology lies in the development of a highly active, long-lived catalyst for catalytic hydrogen conversion to hydrogen production and a simple and practical hydrogen production system that satisfies the need to provide hydrogen for fuel cell vehicles. The car starts quickly and the power is adjustable.
At present, the technology is still in an experimental stage, and there is no commercial report. Daimlers-Chrysler has announced a petrol-powered PEMFC electric vehicle program, including gasoline hydrogen production equipment and PEMFC system, but hydrogen production from gasoline reforming The specific technical route has not been reported. The Dalian Institute of Chemical Physics of the Chinese Academy of Sciences also conducted a study on the hydrogen production from gasoline oxidation reforming. At the 13th World Hydrogen Conference held in 2000, the Institute introduced its experimental results using a model compound nC8H18 in a microretrochromatographic device. .
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