Substrates and products

What are a substrate and a product of a chemical reaction?

In chemistry, a substrate is a name used for substances, chemical compounds, elements or ions that undergo transformations during reactions involving chemical processes. Products are the result of these transformations. In industrial processes, most often there are several products. Apart from the main products, processes also result in so-called byproducts. These, in turn, may become substrates for other technological processes.

Substrates and products in chemical processes are very important both on laboratory and industrial scales. These processes are subject to a number of laws, rules and principles. Here are some of them:

• Chemical equilibrium

It is a dynamic state related to a reversible chemical reaction, where the rate of transformation of substrates into products is the same as in the reverse process, i.e. in the transformation of products into substrates. This is true under specific conditions including concentration, temperature and pressure. When a chemical equilibrium occurs, the concentrations of substrates and products are the same. It should be remembered, however, that this is not a permanent state. The nature of a chemical equilibrium is dynamic. Even a slight interference with the conditions of the reaction changes it.

• Le Chatelier’s principle (the Equilibrium Law)

Le Chatelier’s principle states that when a system in chemical equilibrium is subjected to a specific stimulus (e.g. a change in temperature), the conditions of the occurring reaction change in such a way as to partly counteract the applied change. Also, the concentration of substrates and products influences the chemical equilibrium. Any change in the amount of any of the constituents changes the established equilibrium. If one product is removed from the system, the system will respond in such a way that a certain amount of the substrate will react to reconstitute the removed substance. A similar situation will occur when a substrate is removed from the system. Le Chatelier’s principle enables (especially in technological processes) to control the course of a chemical process. It may be used to either increase the efficiency of an ongoing reaction or counteract unwanted reactions.

• Chemical reaction rate

The rate of a chemical reaction or process is defined as the decrease in the molar concentration of the substrates, or the increase in the molar concentration of the products, per time unit. The value of the reaction rate is determined experimentally, by measuring the changes in the concentration of the reactants over time. The rate of a chemical reaction is influenced by the concentration of the substrates. The reaction rate is directly proportional to the concentration of the reactants.

Substrates and products in chemical technology processes

It is a daunting task to translate the concept of a chemical process from the laboratory scale to the industrial scale. Among other things, it includes an adequate selection of substrates (raw materials). It should be cost-effective to obtain the substrates, compliant with environmental principles and all the required procedures for their prior processing (e.g. purification of extracted metal ores). In chemical technology, the process must also be reviewed in terms of the products to be obtained because in addition to the main product(s), often so-called byproducts are formed. It is a common solution to locate installations that produce different components close to each other. An unwanted byproduct in one process may be a key raw material in a different technology. It is also recommended that substrates which didn’t undergo the reaction are recycled in a loop. The above principles, and a number of other rules, enable to perform technological processes much more efficiently and at a lower energy expenditure.

For chemical technology processes, a material balance is developed for every installation. It indicates the amounts of materials consumed or produced, i.e. substrates and products. The material balance constitutes the basis for designing and developing an economic account for an existing or planned chemical process. It is based on the principle of mass conservation. A well-prepared material balance provides a clear overview of the amounts of substrates needed, the amounts of products obtained, and takes account of waste generation. Graphically, it may be illustrated using a Sankey chart.

The importance of substrates and products in the context of green chemistry

Petroleum is the primary raw material in chemistry today. Biomass and other substrates that can be obtained from renewable sources and therefore match the principles of green chemistry are becoming increasingly important. The trend is expected to continue in the coming years. Biomass is important not only as a raw material for energy purposes, but it can also be effectively used to obtain chemicals, such as additives for pharmaceuticals, cosmetics and food. Advancements in biomass processing technologies enable to extract high value-added materials and chemicals from it. The development of methods for obtaining substrates especially from plant parts, such as stems, leaves or roots, is equally dynamic. We are now able, for example, to synthesise silver nanoparticles using cabbage leaf extracts.

Particularly in large volume processes, an important issue is the management of by-products resulting from chemical processes. It will be beneficial to obtain materials that are easily biodegradable. Degradable polymers, for example, are gaining in importance. These are polymers that can break down in the environment much faster than conventional polymers. They can degrade when exposed to radiation, microorganisms, enzymes or certain chemicals.