1.1 Overview of Chemical Reaction Engineering

  • Chemical engineers strive to produce chemicals on a commercial scale. These chemicals may be used directly as raw materials for the production of useful products (e.g., PVC). Some chemicals produced on a commercial scale have utility in many applications, e.g., \(\ce{H2SO4}\).

  • The job of a chemist is to formulate a synthesis route to produce a particular chemical. Chemists produce chemicals on a laboratory scale. On the other hand, chemical engineers carry out chemical reactions on a bigger scale. For example, chemists may produce chemicals of the order of gram/day, whereas chemical engineers do the same of the order of tonnes/day.

  • The vessel in which chemical reactions are carried out is called a reactor.

    • A round bottomed flask used to carry out a reaction in laboratory is a reactor.

    • A tank or a long pipe used to carry out reactions in a process industry is also a reactor.

  • Since, the volume of reaction mixture or reactants to be handled in a laboratory is small, it is very easy to perform the required unit operations. However, on an industrial scale, there will be some challenges while performing similar unit operations. For example, heating a chemical to the reaction temperature requires a Bunsen burner in a laboratory; a heat exchanger is inevitable to heat the reactant before it enters the commercial reactor.

  • In a chemical process the raw materials are subjected to several physical treatment steps before they are treated in the reactor. These steps are necessary to make the raw materials ready for the chemical transformation to be taken place in the reactor. After the raw materials spend the required amount of time in the reactor, the product mixture is subjected to further physical treatment in order to separate / purify the desired product. The typical steps involved in a chemical process are shown below:

    Step 1: Physical treatment steps (Pre-reaction).
    Step 2: Chemical treatment steps (Reaction).
    Step 3: Physical treatment steps (Post-reaction).

  • Chemical Reaction Engineering (CRE) is concerned with the chemical treatment step of a chemical process.

  • CRE provides solution to every problem that is faced by the chemical engineer in the design, operation and maintenance of a reactor.

  • CRE also gives guidelines on the optimum conditions to be maintained in order to achieve specific benefits. e.g., \(C_{R,\text{max}}\) in \(A\rightarrow R\rightarrow S\)

  • CRE utilizes inputs from a variety of areas: Thermodynamics, Chemical kinetics, Fluid mechanics, Heat transfer, Mass transfer, and Economics.

  • The chemical reactor is considered to be heart of the chemical process flow sheet, and hence careful design of reactor is essential to make the overall chemical process viable.