With the continuous development and progress of society, the application of technology and requirements is stronger. With the continuous development of science and technology, chemical industry has become an important basic industry of national economy. For our high school students, through the process of doing problems can be preliminary understanding of chemical knowledge, for the future to lay a good foundation. Today xiaobian for you to introduce a little about the basic problems in chemical production, which is not only helpful for you to solve the problem, but also to make your thinking more rigorous.
I. determine the production process
Chemical production is based on reaction principle and laboratory research. Therefore, when determining the production process, chemical principle as a breakthrough, will be able to achieve twice the result with half the effort. Take the industrial production of sulfuric acid as an example:
1. From the composition of H2SO4 and H2SO, the raw materials should be sulfur containing substances existing in nature, such as sulfur yellow and pyrite (main component FeS2).
2. The valency of S in H2SO4 is +6. Since H2SO4 cannot be directly obtained from S or FeS2, it needs to go through an intermediate step to get SO3 first and then get H2SO4 through the reaction between SO3 and H2O.
3. S or FeS2 reacts with O2, resulting in SO2, which can be further reacted with O2 to form SO3.
Therefore, the main chemical process of producing H2SO can be divided into two stages: the formation of SO2 and the transformation of SO2 into SO3.
At present, the basic production principle of sulphuric acid in industry is as follows:
1. Preparation of SO2S(s)+O2(g)=SO2(g) from sulfur (exothermic reaction)
2. Use catalytic oxidation reaction to oxidize SO2 into SO catalyst 2SO2(g)+O2(g)2SO3(g)(exothermic reaction)
3. Sulfur trioxide is converted into sulfuric acid SO2+H2O=H2SO4
The early production took pyrite as raw material :4FeS+1O=2Fe2O+8SO2. Due to too much waste generated in the production and high treatment cost, this process is being phased out gradually. In the actual production, 98% of sulfuric acid is used instead of H2O to absorb SO2, which can avoid the formation of acid fog and improve the absorption rate.
Ii. Selection of raw materials
In chemical production, in addition to the selection of raw materials in accordance with the principle of chemical reaction, there are many factors to consider, such as site selection, raw materials, energy, etc. We still take the industrial production of sulfuric acid as an example.
1. From the aspects of capital construction investment, processing cost and environmental protection, the device for sulfuric acid production with sulfur is superior to the device for sulfuric acid production with pyrite;
2. China is short of natural sulfur resources and has complex mining conditions;
3. The reserves of pyrite in China are larger than that of natural sulfur, but there is a trend that demand exceeds supply;
4. Compared with pyrite sulfuric acid production process, sulfuric acid production from sulfur is shorter and the equipment is simpler. "three wastes" (waste gas, waste liquid and waste residue) treatment amount is small.
5. Due to the large amount of imported raw materials, the cost of sulfuric acid production from sulfur is slightly higher than that from pyrite; Large-scale equipment can reduce the cost; In fact, in the early quite a period of time, China is mainly pyrite as raw materials for sulfuric acid.
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