Process assessment of renewable-based acrylic acid production from glycerol valorisation

The continuous growth of biodiesel production via transesterification is leading to an increase in the generation and availability of the by-product glycerol. In this study, a glycerol-based process for the production of acrylic acid has been designed and simulated. The valorisation of glycerol route includes a two-step conversion process where glycerol is first dehydrated to acrolein and acrolein is selectively oxidised to acrylic acid. This renewable-based process is then compared in terms of heat integration and techno-economic performance to the traditional petrochemical route from propylene from a techno-economic and environmental point of view. The study includes the detailed design of the separation train in which azeotropic distillation is also assessed along with the sensitivity analysis of the most relevant variables of the process. Using a production basis of approximately 10,250 kg h−1 of acrylic acid (purity>99.5 wt%), results show that the glycerol route generates 37.3% less CO2 emissions than the propylene-based. From the heat integration analysis, slightly lower heating (96.6%) but higher cooling (32.4%) energy savings can be attained in the glycerol route as opposed to heating (100%) and cooling (21.6%) energy savings available in the propylene-based route. In terms of economics, the glycerol-based route has a lower capital expenditure (£74.0 million) and operating expenditure (£171.4 million yr−1) compared to the propylene route (£91.3 million and £180.2 million yr−1, respectively). Nevertheless, considering the use of raw material and its cost, the glycerol route is more demanding (1.96 kg h−1 of pure glycerol per kg h−1 of acrylic acid amounting to £138.6 million yr−1) than the propylene route (0.92 kg h−1 of propylene per kg h−1 of acrylic acid at £117.2 million yr−1).