Economic and Environmental Comparison of Integrated Processes to Produce Chloromethanes from Brine Waste and CO₂

Abstract

This work provides an economic and environmental comparison of two processes (direct chlorination of methane and hydrochlorination of methanol) to produce chloromethanes from waste brine and CO2. Both processes are modeled using an equation-based approach. This allows for determining the optimal operating conditions of all of the units involved in the process. In particular, those related to the reactors. The optimization determines that hydrochlorination of methanol is a more profitable process (a minimum selling price of $1.8/kgmethyl chloride) than direct chlorination (∼$5/kgmethyl chloride) since the conversion achieved in hydrochlorination is approximately 5 times greater, although the desired product among all of the chloromethanes in direct chlorination is also methyl chloride. Furthermore, direct hydrochlorination also has higher emissions, 16.2 kgCO2 /kgmethyl chloride vs 4.6 kgCO2 /kgmethyl chloride, for hydrochlorination of methanol. These emissions are mainly due to the electricity required in the electrolyzer and could be reduced to −0.5 kgCO2 /kgmethyl chloride (CO2 is absorbed) if the electricity source is fully renewable.