Transformation mechanism

Reading this book on the synthesis of ammonia using this method should help clarify things

① CO(g)-----CO(s) ② H2O(g)---H2O(s) ③ H2O(s)---OH(s)+H(s) ④ OH(s)----H(s)+O(s) ⑤ 2H(s)----H2(s) ⑥ CO(s)+O(s)---CO2(s) ⑦ H2(s)----H2(g) ⑧ CO2(s)---CO2(g) The above are the redox mechanisms. ① CO(g)-----CO(s) ② H2O(g)---H2O(s) ③ H2O(s)---OH(s)+H(s) ④ CO(s)+OH(s)----COOH(s) ⑤ COOH(s)----CO2(s)+H(s) ⑥ H(s)+H(s)---H2(s) ⑦ H2(s)----H2(g) ⑧ CO2(s)---CO2(g) The above are the principles related to hydroxyl groups.

1. Basic principles of the carbon monoxide conversion reaction: The conversion reaction between carbon monoxide and water vapor can be expressed by the following equation: CO + H2O ⇌ CO2 + H2 + Q. This conversion reaction is exothermic and reversible; the volume of the gases remains unchanged before and after the reaction. Moreover, its reaction rate is relatively slow, and only in the presence of a catalyst does it proceed at a faster rate. 2. Reaction mechanism: a. The reaction between carbon monoxide and water vapor, if it takes place solely in the gas phase, remains very slow even at a temperature of 1000°C, despite the high amount of water vapor used. This is because, during the transformation reaction, the hydrogen-oxygen bonds in the steam molecules must first be broken; then the oxygen atoms reorganize themselves within the carbon monoxide molecules to form carbon dioxide, while the two hydrogen atoms combine with each other to form hydrogen molecules. The bond energy of the hydrogen-oxygen bond in water molecules is very high; considerable energy is required to break the H-O-H bonds. As a result, the reaction proceeds very slowly. And in the presence of a catalyst, the reaction proceeds as follows: +H2O(g)→O+H2; O+CO→+CO2. Here, --- represents the catalyst ； O—— represents an intermediate compound, where O—— denotes adsorbed oxygen; that is, the vapor molecules are first adsorbed by the active surface of the catalyst and decomposed into H2 and adsorbed oxygen atoms. The hydrogen enters the gas phase, while the adsorbed oxygen forms an adsorption layer on the catalyst surface. When carbon monoxide hits the oxygen atom adsorption layer, it is oxidized to carbon dioxide and then leaves the catalyst surface to enter the gas phase. Then the catalyst adsorbs water molecules again, and the reaction continues. In this way, less energy is required, and the speed **increases**. b. Influence of the diffusion process: Generally, for transformation reactions, the influence of internal diffusion cannot be ignored. The internal surface utilization rate is related not only to the size, structure, and reactivity of the catalyst, but also to factors such as operating temperature and pressure. For catalysts of different sizes, the utilization rate of the catalyst’s internal surface was calculated comprehensively based on the effective diffusion coefficient of CO under operating temperature and pressure, as well as the calculated reaction rate. As can be seen from Figure 3, for catalysts of the same size, an increase in temperature at constant pressure leads to an increased diffusion rate of CO; however, the rate constant for reactions on the catalyst’s internal surface increases even more rapidly, resulting in a decrease in the utilization rate of the internal surface. At the same temperature and pressure, catalysts with smaller particles have a higher internal surface utilization rate; this is because the smaller the size of the catalyst, the shorter the length of its capillary pores, which reduces internal diffusion resistance and thus increases the internal surface utilization rate. For catalysts of the same size, at the same temperature, the higher the pressure, the greater the reaction rate; the effective diffusion coefficient of CO decreases significantly, as a result of which the utilization rate of the internal surface drops rapidly with increasing pressure.

Its reaction equation is: CO + H2O = H2 + CO2. The number 2 is the subscript in the lower right corner; it indicates that carbon monoxide and water vapor react under certain temperature, pressure, and catalyst conditions to produce hydrogen and carbon dioxide. This is mainly done to adjust the concentration of carbon monoxide, while pressure has no significant effect on it; temperature, however, does have an impact. Water molecules break down into two hydrogen atoms, which then combine to form hydrogen gas; meanwhile, the free oxygen atoms combine with carbon monoxide to form carbon dioxide. The mechanism is simple, but the process control conditions are complex. Experience can be gained through practice.