Chemical equation of hydrogen industrial preparation method

Hydrogen is an important industrial gas. According to the raw materials, equipment and cost, as well as the requirements for the purity of hydrogen, the industrial production of hydrogen can adopt the following methods. ① Direct current is electrolyzed into water through platinum electrode (or other inert materials), and hydrogen can be obtained at the cathode, with the purity as high as 99.5~99.8%. When chlorine and caustic soda are produced by electrolysis with saturated brine in chlor-alkali industry, hydrogen is also obtained as a by-product. (2) Water gas is produced by passing water vapor through the hot coke layer by water-gas conversion method. Then the water gas is mixed with steam, and the CO in the water gas is converted into CO2 with ferric oxide as catalyst. Carbon dioxide dissolves in water. (3) Hydrocarbon cracking method Hydrocarbons are cracked at high temperature, and the cracked gas contains a large amount of hydrogen, and 90% of hydrogen can be obtained through a low-temperature refrigeration system. For example, methane cracking: ④ Hydrocarbon steam reforming can react with steam under the action of catalyst at high temperature to obtain mixed gas mainly composed of hydrogen and carbon monoxide. For example, pure hydrogen can be obtained by removing CO by molecular sieve adsorption or water gas shift. Hydrogen can be obtained from natural gas, oilfield gas and refinery gas (by-product gas of petroleum refinery) by hydrocarbon cracking and hydrocarbon steam reforming. The second industrial hydrogen production methods are as follows: (1) electrolytic water method. In an electrolytic cell, 25% NaOH solution is electrolyzed, and the temperature is controlled at 80~85℃, so that hydrogen precipitates on the cathode and oxygen precipitates on the anode. 4h++4e on the cathode = = 2h2 4oh-= = = 2h2o+O2+4e on the anode. Because H+ and OH- come from the ionization of H2O, the reaction of electrolyzing H2O is that this method produces less hydrogen impurities with a purity of 99.7%~99.8%. (2) In chlor-alkali industry by electrolytic salt solution method, the saturated solution of electrolytic salt is controlled at 70~80℃, and chlorine gas and sodium hydroxide can be obtained at the same time. The main reactions are as follows: on the anode, 2cl-= = = Cl2+2e, on the cathode, 2h++2e = = H2 accumulates OH- ions and Na+ ions near the cathode. (3) Water gas conversion method: firstly, water vapor is made into water gas through charred anthracite or coke; Then, the water gas is mixed with excess steam, and under the action of catalyst, carbon monoxide in the water gas is converted into carbon dioxide at 450-550℃, and the content of hydrogen in the mixed gas is increased. Finally, the mixed gas of carbon dioxide and hydrogen is pressurized (12~30 atmospheric pressure), washed with water or absorbed with ammonia water to remove carbon dioxide and separate hydrogen. (4) Hydrogen is obtained from gas fuels such as natural gas, refinery gas (by-product gas of refinery) and oilfield gas. These gases contain a lot of hydrocarbons. Under certain conditions, it can react with water vapor or oxygen to produce carbon monoxide and hydrogen. For example, natural gas (with methane content above 95%) and steam with methane as the main component can be converted into carbon monoxide and hydrogen with nickel as catalyst at 800~ 1000℃. For example, refinery gas contains 9-40% hydrogen and methane, and 9 1-60% other hydrocarbons. Under the action of catalyst, oxygen and excess refinery gas are partially oxidized at high temperature to produce carbon monoxide and hydrogen. The method of separating hydrogen from the mixed gas of carbon monoxide and hydrogen is the same as the water gas shift method. The third industrial production method of hydrogen: the industrial production of hydrogen should consider raw materials, energy, cost and equipment, and also produce hydrogen according to the purity and dosage of hydrogen required. The main methods are briefly described as follows: first, a series of electrolyzers with iron as cathode surface and nickel as anode surface 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. 2. Hydrogen production from water gas: anthracite or coke reacts with steam at high temperature to obtain water gas (C+H2O→Co+H2- heat). 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) Synthetic gas and natural gas from petroleum pyrolysis produce a large amount of hydrogen, which is often used for gasoline hydrogenation and hydrogen needed by petrochemical and fertilizer plants. Many countries in the world adopt this method of hydrogen production, and petrochemical bases in China, such as Qingqing Chemical Fertilizer Plant and Bohai Oilfield, and some places (such as Bay, way and Batan Rougo Hydrogenation Plant in the United States, etc.) all adopt this method. ) .4. Hydrogen production by freezing coke oven gas Freeze and pressurize the preliminarily purified coke oven gas 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). 5. By-product hydrogen from electrolytic brine produces a large amount of pure hydrogen in chlor-alkali industry, which can be used not only to synthesize hydrochloric acid, but also to purify and produce ordinary hydrogen or pure hydrogen.