The annual world production of acrylic acid is over 6 billion pounds. Almost 95% of it is used as an intermediate in the production of acrylic esters which are used to make polymers used in coatings, paints, adhesives, and binders. The only commercial process for making acrylic acid requires a two-step reaction system, first making the intermediate acrolein from propylene. Currently there is ongoing research to produce acrylic acid directly from propane through a selective oxidation reaction. However, at this time there are no catalysts available for this reaction to challenge the high efficiency of the propylene process. 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. This presentation looks at using Life Cycle Assessment (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 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.

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