Traditionally, catalysts have been compared in two ways: a) through the ability to improve the selectivity and/or activity of an existing process, or b) development of a new catalyst to convert a more inexpensive feedstock into the desired product. Today, many companies are seeking to minimize the total environmental effect of their processes, which allows the use of a new tool for catalyst comparison. Life Cycle Assessment (LCA) can be used to compare the environmental impacts of different catalytic reaction processes, even when one may not yet be fully developed. In this case, the production of acrylic acid from two different feedstocks, propylene and propane, is examined. The only existing commercial process for making acrylic acid requires a two-step reaction system, first making the intermediate acrolein from propylene. Since the propylene of the current process is first produced from propane, or as a by-product of petroleum refining, and is a more expensive feedstock than propane, the desirability of a one-step reaction starting directly with propane is clear. Currently there is ongoing research to develop catalysts which will produce acrylic acid directly from propane. This presentation looks at using LCA to compare the environmental impacts of these two different processes and to determine the minimum yield from the propane reaction necessary to achieve a lower environmental impact than the existing propylene process.

SimaPro 7 was used to conduct the LCA calculations, and the Eco-Indicator 99 method is used for the impact assessment. The production of 1000kg of acrylic acid for each process was used as the basis of this analysis. For the propylene reaction, the high value of 87% yield to acrylic acid is used for the calculations. Since the propane process doesn't have existing catalysts available to efficiently produce acrylic acid, values ranging from 0% to 100% yield were used and environmental impacts are calculated for each point and compared with that of the propylene process. Also, costs of the raw materials for the two different reactions are taken into account. The analysis is independent of the as of yet unidentified catalyst for production of acrylic acid from propane.

The results show that acrylic acid could be produced more cheaply and with less impact on the environment, even at lower yields to acrylic acid than the current process using propylene, if a suitable catalyst for this reaction can be developed. At an overall yield of 63%, the propane process has an equivalent total impact to that of the propylene process at 87% yield. For a theoretical propane yield to acrylic acid of 100%, the impact will be almost 40% less than the propylene process. Although the actual catalyst for this process has not yet been identified, it has negligible effect on the LCA since most of the mass of the system is in the reactants and products. The 63% overall yield is a goal for future catalysis research in this process that needs to be reached in order to have a more sustainable process. Therefore, LCA offers an additional means for comparing the effectiveness of catalysts, and also provides a new tool to help guide future decisions in catalysis research.