Novel energy efficient process for acetic acid production by methanol carbonylation

Acetic acid is an essential chemical product. The need for 'green' acetic acid has spurred new research in developing more sustainable processes. This paper presents an original conceptual design of a low-energy and low-emissions sustainable process for acetic acid manufacturing by methanol carbonylation. The emphasis is set on energy efficiency, as the exothermic reaction releases a large amount of energy that may be more effectively used. Two processes are investigated by rigorous simulation, based on homo- and heterogeneous catalysis. The latter reveals as innovative feature the full valorization of the energy released in the reaction section, along with reducing the separation sequence to only two distillation columns. The first dewatering column is driven by low-pressure steam generated by the reactor cooling. The second purification column uses heat pumping, in which the energy rejected in condenser is upgraded for reboiler heating by vapor compression (VC), using water as working fluid. The electricity for the vapor compression is ensured by applying an Organic Rankine Cycle (ORC) for waste heat recovery by the reactor cooling. In this way, the new green process needs very little energy (below 1 MJ/kg product). This eco-efficient process shows also superior sustainability metrics (e.g. low emissions of 40 gCO2e/kg) as compared to the homogeneous catalyst process.