Chemistry! ! ! Method for producing hydrogen

I. Hydrogen production by electrolysis of water

Series electrolyzers with iron as cathode surface and nickel as anode surface are often used to electrolyze potassium hydroxide or sodium hydroxide aqueous solution. The anode produces oxygen and the cathode produces hydrogen. This method has high cost, but the product purity is high, and hydrogen with purity above 99.7% can be directly prepared. Hydrogen with this purity is commonly used in: ① reductant, shielding gas and heat treatment of permalloy used in electronics and instrumentation industries; (2) reductant used in powder metallurgy industry to manufacture tungsten, molybdenum and cemented carbide; (3) polysilicon, germanium and other semiconductor raw materials; ④ oil hydrogenation; ⑤ Cooling gas for double hydrogen-cooled generator. For example, Beijing Electron Tube Factory and Academy of Sciences Gas Factory all produce hydrogen by electrolysis with water.

Second, producing hydrogen from water gas.

Water gas (C+H2O → Co+H2 heat) is obtained by the reaction of anthracite or coke with steam at high temperature. After purification, the CO in it is converted into CO2(CO+H2O→CO2+H2) together with steam through a catalyst, so as to obtain a gas with hydrogen content above 80%, which is then pressed into water to dissolve CO2, and then the residual CO is removed from the solution containing cuprous carbamate (or cuprous acetate containing ammonia) to obtain pure hydrogen. This method has the advantages of low cost, large output and many equipment, and is often used in synthetic ammonia plants. Some factories also use carbon monoxide and H2 to synthesize methanol, and some places use gas with low purity and 80% hydrogen as artificial liquid fuel. This method is often used in Beijing Chemical Experimental Plant and small nitrogenous fertilizer plants in many places.

3. Hydrogen production from syngas and petroleum pyrolysis of natural gas

Hydrogen, a by-product of petroleum pyrolysis, has a large output and is often used in gasoline hydrogenation, petrochemical and chemical fertilizer plants. This method of hydrogen production is adopted in many countries in the world, and it is also used in petrochemical bases in China, such as Qingqing Fertilizer Plant and Bohai Oilfield.

It is also used in some places (such as Beidao, Daodao and Batan Lugo Hydrogenation Plants in the United States). ).

Four, coke oven gas freezing hydrogen production

The preliminarily purified coke oven gas is frozen and pressurized to liquefy other gases and leave hydrogen. This method is used in a few places (for example, Kemp Popper Factory in the former Soviet Union).

Verb (abbreviation for verb) Hydrogen, a by-product of electrolytic salt solution.

In chlor-alkali industry, a large amount of pure hydrogen is produced by-product, which can not only be used to synthesize hydrochloric acid, but also be purified to produce ordinary hydrogen or pure hydrogen. For example, the hydrogen used in the second chemical plant is a by-product of electrolytic brine.

Six, the by-products of the wine industry

When acetone and butanol are fermented with corn, there is more than 1/3 hydrogen in the waste gas of fermentor. After purification for many times, ordinary hydrogen (above 97%) can be produced. Using liquid nitrogen to cool general hydrogen to below-65,438+000℃ can further remove impurities (such as a small amount of N2) and produce pure hydrogen (above 99.99%), just like Beijing.

Seven, iron and steam react to produce hydrogen.

But the quality is poor, and this old method has been basically eliminated.

There are many ways. Simply put, simple substance+compound = compound+simple substance. Any simple substance can be used as long as it does not react with hydrogen. The compound only needs to contain hydrogen, such as hydrogen peroxide.

Recommendation: Hydrogen can be generated by heating potassium permanganate and manganese dioxide, and the purity of the gas obtained is higher.

In recent years, scientists all over the world have developed some new hydrogen production methods, and scientists in China have also tried some new hydrogen production methods. Now, some of these new methods are introduced as follows:

1. Hydrogen production from water with cuprous oxide as catalyst

Generally, the method of generating hydrogen by electrolyzing water is expensive. In the past, some people have studied the method of producing hydrogen from water with cuprous oxide catalyst, but in the experiment, cuprous oxide is easily reduced to metal under the action of sunlight. Japanese researchers have found that making cuprous oxide into powder can avoid this problem. Their specific method is to add 0.5g cuprous oxide powder to 200 cubic centimeters of distilled water, and then irradiate it with 460-650 nm visible light emitted by glass bulbs. Under the action of cuprous oxide catalyst, water is decomposed into hydrogen and oxygen. Japanese researchers used this technology to carry out 30 experiments and obtained different proportions of hydrogen and oxygen from decomposed water. It is found in the experiment that if the obtained oxygen pressure is increased to 500 Pascal, the decomposition process of water will slow down. The service life of cuprous oxide powder can reach 1900 hours. Tokyo institute of technology plans to further study how to improve the efficiency of hydrogen production, and at the same time develop a catalyst that can be activated under longer wavelength visible light irradiation. The institute is testing a new copper-containing iron alloy oxide.

2. Hydrogen production from water with new molybdenum compounds.

Two scientists from the University of Valencia in Spain invented a low-cost method to produce hydrogen from water. They modified the catalytic converter so that water can be decomposed at a low cost. They use a chemical product extracted from molybdenum as a catalyst instead of electricity. They say that if hydrogen is used as raw material, half a liter of water will produce enough hydrogen to drive a car 633 kilometers.

3. A method of completely decomposing water by photocatalyst reaction and ultrasonic irradiation.

In the late 1960s, two Japanese scientists discovered that titanium dioxide can decompose water by light (ultraviolet) irradiation. They originally planned to produce hydrogen by this method, but the research was interrupted because the amount of hydrogen and oxygen produced was very small and uneconomical. Recently, according to the report of the Nihon Keizai Shimbun, Professor Tian Yuan Hishi of Japan's Star University and others used photocatalyst reaction and ultrasonic irradiation to completely decompose water. This "ultrasonic photocatalytic reaction" can completely decompose water because water can be decomposed into hydrogen and hydrogen peroxide under the action of ultrasonic waves, and hydrogen peroxide can be decomposed into oxygen and hydrogen through photocatalytic reaction. Although ultrasonic irradiation and titanium dioxide photocatalyst can completely decompose water, they produce less oxygen. Manganese dioxide is added, and after ultrasonic irradiation, manganese ions decomposed by manganese dioxide can be dissolved in the solution, so that hydrogen peroxide produces a large amount of oxygen.

Fourth, ceramics react with water to produce hydrogen.

Scientists in tokyo institute of technology made ceramics react with water at 300℃ to produce hydrogen. They heated the nickel ferrite (CNF) of carbon to 300℃ in the flow of argon and nitrogen, and then injected water into CNF with an injection needle, so that the water contacted with the hot CNF to generate hydrogen. Since CNF returns to inactive state after water decomposition, ferrite can be reused. In each reaction, 2 ~ 3 cubic centimeters of hydrogen can be produced on average per gram of CNF.

Verb (abbreviation for verb) produces hydrogen from methane.

1. Professor Gan Zhixing of Kyoto University in Japan used Ni-Pt rare earth oxide porous catalyst to convert methane, carbon dioxide and water into hydrogen. The composition ratio of nickel, rare earth oxide and platinum in the catalyst is 10:65:0.5. The preparation process is as follows: firstly, nickel, rare earth oxide and other raw materials are heated and melted, then ammonia gas is introduced to melt the gel, and then drying and heat treatment are carried out. The particle size of the catalyst is 2 nm ~ 100 nm, and it has high catalytic activity. Professor Gan Zhixing put the catalyst into the reaction tower, and then added carbon dioxide, methane and water vapor. Results: At atmospheric pressure and 550℃ ~ 600℃, the products were hydrogen and carbon monoxide. When the temperature rose to 650℃, the conversion rate was 80%. When the temperature is 700℃, the conversion rate almost reaches 100%.

2. Hydrogen production from methane with C60 as catalyst

The Institute of Materials Engineering and Industrial Technology of Japan University of Technology uses C60 as a catalyst to produce hydrogen from methane.

At present, C60 can only work at high temperature, so it can't be used immediately. It must be improved and made into an energy-saving catalyst that can work at low temperature. The catalyst they developed was to mix 10% C60 into carbon powder. In a container heated to 65438 0000℃, 0.65438 0 g of catalyst was put, and 20 ml of methane was introduced at the rate of 65438 0 minutes. As a result, 90% of methane is decomposed into hydrogen and carbon. As a catalyst, C60 can clean the surface with water to remove the attached carbon residue. Theoretically it can be used semi-permanently. Because of its unique shape, the surface area of particles is 5 times to 10 times that of activated carbon, so it has a strong function when used as a catalyst.

6. Enzymes extracted from microorganisms produce hydrogen.

1. glucose deoxyenzyme. Glucose deoxygenase was extracted from pyrogenic lactic acid bacteria in Oak Cen National Laboratory. Thermogenic lactic acid bacteria were first discovered in low-temperature dry distillation coal cinder in American mines. With the help of nicotinamide adenine dinucleotide phosphate (NADP), glucose deoxyenzyme can extract hydrogen from glucose. In the process of producing hydrogen, NADP stripped a hydrogen atom from glucose, making the remaining substances into a hydrogen atom solution.

2. Hydrogenase. This enzyme is extracted from a microorganism that was once found near the crater of the seabed. The function of hydrogenase is to combine the hydrogen atoms carried by NADP into hydrogen molecules, and NADP is reduced to its original state and reused. In addition to this enzyme found in the United States, Russian scientists also found this microorganism in lakes and swamps. They put microorganisms in special containers suitable for their survival, and then collect the hydrogen produced by microorganisms in hydrogen bottles.

Seventh, make hydrogen from bacteria.

1. Many primitive lower organisms can also release hydrogen during metabolism. For example, many bacteria can release hydrogen under certain conditions. A bacterium named Trichomonas rubra was discovered in Japan, and it is an expert in hydrogen production. In glassware, this kind of bacteria can be cultivated by using starch as raw material and adding some other nutrients to make culture solution. For every 5 mm starch nutrient solution consumed, 25 ml hydrogen can be produced.

2. The American space department will take Rhodosporium, a photosynthetic bacterium, into space and use the hydrogen released by Rhodosporium as the energy source of spacecraft.

Eight, using green algae to produce hydrogen.

Scientists have discovered a new method that allows green algae to produce hydrogen as needed. Scientists at the University of California, Berkeley, say that green algae is one of the oldest plants known to mankind, and it has evolved the ability to live in two completely different environments. When green algae live in ordinary air and sunlight, it will carry out photosynthesis like other plants. Photosynthesis uses sunlight, water and carbon dioxide to produce oxygen and chemicals that plants need to sustain life. However, when green algae lack sulfur, a key nutrient, and are placed in an anaerobic environment, green algae will return to another way of life in order to survive. In this case, the green algae will produce hydrogen. According to scientists, 1 liter of green algae culture solution can produce 3 ml of hydrogen per hour, but researchers believe that the efficiency of hydrogen production by green algae can be improved by at least 100 times.

9. Biological hydrogen production by organic wastewater fermentation

Recently, the "bio-hydrogen production technology by fermentation of organic wastewater" with anaerobic active liquid as raw material was verified by pilot study in Harbin Jianzhu University, China. Professor Li, an academician of China Academy of Engineering, introduced that this research pioneered and realized the pilot technology of long-term continuous biological hydrogen production by continuous non-immobilized strains at home and abroad, which was a major breakthrough in the field of biological hydrogen production and its achievements were in the leading position in the world. The idea of biological hydrogen production was put forward in 1966, which received unprecedented attention in the 1990s. Since 1990s, some developed countries such as Germany, Japan and the United States have set up specialized institutions and formulated development plans for bio-hydrogen production, with a view to realizing industrial production in the middle of the 20th century through basic and applied research on bio-hydrogen production technology. However, so far, the research process is not ideal, and many researches still focus on the immobilization technology of bacteria and enzymes, which is far from industrial production, and there is no pilot test result so far. The professor of Harbin Jianzhu University broke through the limitation that pure bacteria and immobilized technology must be used in biological hydrogen production technology, and created a new way of hydrogen production by non-immobilized bacteria, and realized the continuous flow long-term continuous hydrogen production in pilot scale for the first time. On this basis, they successively discovered the ethanol fermentation type with high hydrogen production capacity, invented the continuous-flow bio-hydrogen production reactor, initially established the bio-hydrogen production fermentation theory, and put forward the best engineering control countermeasures. The technology and theoretical results have been fully verified in the pilot study: the hydrogen production is several times higher than that of similar pilot studies abroad; The developed industrialized bio-hydrogen production system is stable and reliable, and the production cost is obviously lower than the widely used hydropower solution.