Life Cycle Assessment comparison of two ways for acrylonitrile production: the SOHIO process and an alternative route using propane

Abstract

The aim of this study is to apply the LCA methodology to the industrial chemical sector, in order to compare the traditional process for acrylonitrile production from propylene with alternative routes starting from propane, while assessing which one is the cleaner production in terms of sustainability, from a life cycle perspective. The model created refers to the production of 1 kg of acrylonitrile. System boundaries of each scenario include all mass flows into and out of the reactor, all mass and energy flows into and out of the heat exchanger of the fluid bed, the amount of raw material for the production of each catalyst, the avoided impacts resulting from energy and mass recovery, and all transportations. Also, average infrastructure processes that refer to land use, building, and disposal of the chemical plant were not included. The life cycle evaluation was performed using the ReCiPe 2008 method v1.07, showing results in terms of midpoint categories such as Climate Change, Fossil Fuel Depletion, and Metal Depletion. The results from the inventory show that alternative synthetic routes starting from propane have higher impacts than the traditional processes in terms of fossil fuel depletion and climate change categories due to higher consumption of reactants, caused by the lower efficiency of catalytic systems. Conversely, impacts associated with the metal depletion category have an irregular trend, due mainly to the extraction of different percentages of resources for the catalyst production. The results were validated by a sensitivity analysis using the Monte Carlo method. This study suggests that the LCA methodology may be used as a scientific approach to identify the environmental issues associated with the chemical production of a product. In particular, it is useful in comparing alternative ways of synthesis and evaluating which process is more sustainable, and which production stage should be improved in order to ensure greater environmental sustainability.