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

Thiswork provides an economic and environmental comparison oftwo processes (direct chlorination of methane and hydrochlorinationof 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 allof the units involved in the process. In particular, those relatedto the reactors. The optimization determines that hydrochlorinationof methanol is a more profitable process (a minimum selling priceof $1.8/kgmethyl chloride) than direct chlorination(& SIM;$5/kgmethyl chloride) since the conversionachieved in hydrochlorination is approximately 5 times greater, althoughthe desired product among all of the chloromethanes in direct chlorinationis also methyl chloride. Furthermore, direct hydrochlorination alsohas higher emissions, 16.2 kgCO2 /kgmethyl chloride vs 4.6 kgCO2 /kgmethyl chloride, for hydrochlorination of methanol. These emissions are mainly dueto the electricity required in the electrolyzer and could be reducedto -0.5 kgCO2 /kgmethyl chloride (CO2 is absorbed) if the electricity source is fullyrenewable. The renewable energy alternativesand processing routesevaluated in this work for the production of chloromethanes.

Automated summary

This study compares the economic and environmental aspects of two processes (direct chlorination and hydrochlorination of methanol) for producing chloromethanes from waste brine and CO2. The modeling of both processes using equation-based approach helps determine the optimal operating conditions, particularly related to the reactors. The optimization results show that hydrochlorination of methanol is a more profitable process (minimum selling price of $1.8/kgmethyl chloride) with approximately 5 times higher conversion compared to direct chlorination, although both processes aim to produce methyl chloride. Additionally, direct hydrochlorination has higher emissions (16.2 kgCO2/kgmethyl chloride) compared to hydrochlorination of methanol (4.6 kgCO2/kgmethyl chloride), mainly due to electricity requirements in the electrolyzer, but this can be reduced to -0.5 kgCO2/kgmethyl chloride with fully renewable electricity source. The study also evaluates renewable energy alternatives and processing routes for chloromethanes production.