Modern chemical industrial processes cannot be produced and used without catalysts. According to statistics, more than 90% of the chemical industry requires the use of catalysts, otherwise it will not be able to proceed efficiently. A catalyst is a chemical that accelerates the rate of a reaction without any change in its own structural composition. However, this is only a superficial and superficial understanding. In order to understand the reaction mechanism and working of catalysts, it is necessary to have a deep knowledge of the electronic structure regulation, phase regulation, and synergy of different components interaction.
Today, we will open a special section to explain how industrial catalysts are developed. Today brings the first part of the topic, starting with the specific requirements for the use of catalysts in industry.
Requirements for the use of industrial catalysts
The first indicator is activity, which is also the most important indicator of a catalyst. It reflects the ability of an industrial catalyst to facilitate the conversion of a feedstock under simulated laboratory conditions. It is usually measured using moles per gram per hour, i.e., the amount of reactants converted per unit mass of catalyst per unit time. However, the metric may change slightly in specific applications, e.g., in the case of catalytic reforming catalyst activity, the metric is expressed in terms of the aromatic yield obtained after catalytic reforming of straight-run naphtha.
The second metric is selectivity, which evaluates how much of the feedstock can be converted to the target product by the catalyst during the promoted reaction. For example, in a light or heavy oil cracking process, there may be a variety of products such as gasoline, dry gas, coke, etc. Gasoline being the main product, the more it is produced, the better. The proportion of gasoline to the total product is the selectivity of the gasoline product.
Lifetime or stability. It should be noted that in industrial production, the products are often prepared without any downtime 24 hours a day, for example, in traditional energy coal processing plants, workers usually work in two or three shifts, the power loss caused by downtime and the interruption loss of the production line is huge. In the catalytic process, the stability of the catalyst becomes particularly important. The general industrial catalyst stability is often over thousands of hours. The lifetime is generally expressed in hours. Some links also use the amount of catalyst consumed to process a quality product to express it.
Shape and size. Depending on the reactor in the catalytic process, catalysts vary in shape and size, and also differences in shape can bring about dramatic changes in performance. As it may have an effect on the diffusion of reactants or products, which in turn affects their yield or selectivity. Depending on the conditions of use, catalysts can be made into different shapes for different applications. For example, catalysts used in moving bed catalytic cracking units are generally small balls, which facilitate the movement of the catalyst in the reactor and facilitate the transport of the catalyst, reducing its loss due to wear and tear.
Mechanical strength. In addition to the above requirements, the mechanical strength of the catalyst is also an important indicator. Since chemical reactions are often carried out at high temperatures and pressures, the catalyst is naturally required to withstand sufficient self-weight and external pressure. It also has to withstand the wear and tear that may be caused by collisions between different catalysts, i.e. the wear strength has to be high.
Chemical composition. The chemical composition is the structural information of the catalyst. It is the basis for the above reaction properties. The ratio between the different components and the structure directly affects the efficiency of the reaction.
Specific surface area and pore volume. The larger the specific surface area and the larger the pore volume, the more contact the reactants will have with the catalyst, which will undoubtedly lead to better performance.
Conclusion
In summary, a good industrial catalyst needs to have good activity, selectivity and lifetime as well as shape, particle size and distribution, mechanical strength, and certain chemical composition and pore structure requirements. Therefore, catalyst design is critical and extremely complex, as well as an extremely high value added process.
