When is a catalyst not just a catalyst?
According to the chemical definition, a catalyst is a substance that increases the rate of a reaction without being consumed. This definition is only true when the catalyst is still active as a catalyst. In most cases after a certain period of time or after having catalysed a limited number of reactions the catalyst decomposes and becomes inactive.
By breaking down the chemistry that allows the conversion of many different substrates, we can see the distinction between different catalytic behaviours, showing how selectivity is just as important as reactivity in engineering catalysts that can make industrial processes faster, cleaner and safer.
For heterogeneous catalysts, a solid material containing specific metals catalyses the conversion of gases into other products such as the Haber-Bosch process to produce ammonia from nitrogen and hydrogen. Homogeneous catalysts are dissolved in the reaction medium and can react very rapidly with the substrates to generate the desired conversions. Many homogeneous and heterogeneous catalysts are critical additions to processes within the chemical industry, allowing increased efficiency and facilitating the formulation of products that are more benign.
Two examples of homogenous catalysts are Catexel’s Dragon and Pegasus. Catexel developed Dragon, a manganese-based complex that works with H2O2, to increase the efficiency of oxidation and bleaching activity. Pegasus, a next generation manganese-ligand catalyst, was developed to provide greater stability in alkaline detergent solutions.
By using catalysts for improved selectivity, and not only reactivity, R&D teams can achieve the desired reaction (for example, bleaching of cotton) without the risk of undesirable side reactions, generation of unwanted impurities.
So, to go back to the initial question – ‘When is a catalyst not just a catalyst?’ – the answer is when it delivers the right level of activity in a selective way. An optimised catalyst not only accelerates the desired reaction, but also shows elevated levels of selectivity under controlled conditions. Therefore, selective catalysts can accelerate, activate and ultimately, innovate.
To find out more about how continued research in the field of bleach and oxidation catalysis is leading to new applications being developed to improve industrial processes, read Dr Ronald Hage’s latest technical paper, published in the July issue of Specialty Chemicals magazine.