Process modelling and techno-economic evaluation of production of CO2-based polycarbonate polyols

The search for new ways to utilize carbon dioxide (CO2) is ever accelerating due to climate change. Carbon capture utilization (CCU) is seen as a potential solution, since CO2 is a renewable yet abundant resource. The demand for carbon neutrality includes the production of different chemicals too, such as polycarbonate polyols. Historically, their production has been based on fossil materials, and even the products from the latest technologies utilizing CO2 consist of only up to 50% of CO2. Market demand and selling price of polycarbonate polyols are expected to remain high or even increase in the future. Opportunity for commercial production from carbon dioxide and clean hydrogen makes polycarbonate polyols an interesting and attractive topic to investigate.

This Master’s Thesis studies the production of carbon dioxide based polycarbonate polyols, as well as its feasibility and profitability. The focus is on presented BECCU process route, which includes reversed water gas shift, Fischer-Tropsch, epoxidation and polymerization reactions. Current options to utilize CO2 were investigated and their markets were analyzed by a literature review. The existing production routes, applications and market situation of polycarbonate polyols are presented. The production route investigated was simulated with Aspen Plus. The simulation was able to obtain an annual production of 33 211 t/a of polycarbonate polyols, which corresponds to 33% ratio of the mass of the product to the mass of used CO2. Levelized cost of polycarbonate polyol was estimated to be 2 235 €/t(product), which is less than the assumed market price of 2 500-3 000 €/t. 85% of the costs comes from operating costs, and 52% of them are due to the electricity needed in electrolysis. Other major cost factors identified were hydrogen peroxide and the total capital investment. The process was found most sensitive to the cost of electricity, but also quite sensitive to the selectivity of polycarbonate polyols and the annual operational hours. A comparison of different options to produce light olefins from carbon dioxide also suggested that BECCU route seems profitable and competitive. The investment costs appeared to be similar compared to methanol and methanol-to-olefins process route. Olefins produced through BECCU route had an estimated levelized cost of olefins of 2 428 €/t(product). The greatest cost savings for BECCU route to olefins or polycarbonate polyols can be obtained by finding an inexpensive, sustainable source of electricity.