CHEMICAL REACTION ENGINEERING 

When a chemical reaction occurs, it doesn't announce at each stage about its progress or the mechanism through which it is moving ahead: well, I am kickstarting with a slow rate, reactant concentration is going down, half-life attained, the catalyst has crossed the activation energy barrier, I would now be throwing out some heat, the entropy is increasing and so on. Also at the mechanism level- I just deprotonated, hydride shifted to my carbon neighbor or the ring's a little too strained, I'd now expand to a six-membered one.

All the processes occur in tandem in a chemical reaction, very much in a flow. These are so interlinked that its kind of hard to segregate between them and know which one's actually going on. It's only possible if something goes wrong at a particular stage or if we try to freeze the discrete steps to understand what's going on. But this is still at the laboratory level. When these reactions are carried out in the industries, they are at a much larger scale and occur in chemical reactors. 

Chemical reactors act as hosts for carrying out these reactions. Designing and construction of a chemical reactor is one of the key aspects of chemical reaction engineering. All the reaction parameters come into the picture- kinetics, mechanism, flow dynamics, process control and so on. Chemists and engineers work together in this. While the chemists identify the parameters and reaction mechanism,  the engineers take part in the kinetics, working, and parameters' optimization. A chemical reaction is almost like a living entity. It hydrates, condenses, reacts, heats up and converts. The erection of a reactor takes all these aspects into the picture. It is a very intricate process with a detailed calculation of the specifications involved. There are different kinds of reactors that host chemical reactions on a daily basis in an industry. Also, scale-up of a chemical reaction is another aspect that engineers look into. For synthesizing reactions at large scales in an industry, expansion of the laboratory level reaction needs to be carried out. These need to be checked for reproducibility and feasibility at such a large scale. Sometimes, the mechanism that worked in a lab, might not work in an industry- you might not get the desired reaction intermediate that is supposed to take the reaction forward. In such cases, the mechanism and the reactor engineering might have to be modified. That's where the chemistry logic as well as creativity are applied.

Finally, the reaction end products are what we are concerned about. The starting material- reactants turning into the final outcome-products, that's the main aim. Once the reaction is completed, the products undergo several steps of fine-tuning- isolation from the reactor, purification, and testing. These end products obtained at industries are products of our daily use- medicines, food ingredients, dyes and paints that bring color to our life, pesticides and fertilizers, tyres, fibers, glues, digital displays, and whatnot. The list is endless, and so are our needs. Although there are now sustainable and green approaches to carrying out these reactions, still there's just so much that can be done, given the ever-increasing demand. Its probably high time to reduce the needs. Chemical industries employ large number of people at all levels- scientists, engineers, managers, workers, and many more. As of 2023, the Indian chemical sector hosts 11,000+ chemical companies and employees about 2 million people.

The models of these chemical reactors have evolved over time. They have turned into more efficient designs with minimum losses. The video below shows a  few models of chemical reactors featured at the ChemTech World and ChemExpo 2024. 

©Neha Kanase