Polyurethanes
Polyurethanes Climate-friendly polyols and polyurethanes from CO 2 and clean By: hydrogen Introduction Miia Nevander, Janne Kärki, Juha Lehtonen, VTT Technical Research Centre of Finland Espoo, Finland VTT Technical Research Centre of Finland, together with several Finnish companies and organizations are developing a proof-of-concept for a new value chain from carbon dioxide emissions and clean hydrogen to sustainable chemicals and materials. The work is carried out in an ongoing Business Finland cooperative project called BECCU. The partners involved include Valmet, Kiilto, CarbonReUse Finland, Helen, Neste, Mirka, Metener, Pirkanmaan Jätehuolto, Top Analytica, Finnfoam, Kemianteollisuus, Kleener Power Solutions, and Brightplus. CO 2 -based polycarbonate – and polyether polyols as well as polyurethanes have been chosen as the main target products of the project for their great market potential. Prior interest is towards polycarbonate polyols, which are specialty chemicals that can be used as coatings, adhesives, or building blocks for polyurethanes. So far, the industrial production of polyols has relied on the use of fossil raw materials, whereas the BECCU concept presents a sustainable route based entirely on carbon originating from CO 2 . A novel process route to fully CO 2 -based specialty chemicals VTT studies a process where up to 100 % of carbon in polyol is originating from carbon dioxide, when it has been at most 50 % in other proposed polyol production concepts based on CO 2 utilization. The studied concept applies CO 2 captured from biomass utilization, such as biomass combustion or biogas production. Hydrogen can originate from water electrolysis or from industrial side-streams. First, reverse water-gas shift (rWGS) and Fischer-Tropsch (FT) reaction steps produce olefins from CO 2 and H 2 . The formed light C2-C4 olefins are oxidized with peroxides to epoxides, which are then co-polymerized to polycarbonate polyols using CO 2 . The process is illustrated in Figure 1. Promising profitability indicated by technoeconomic assessment (TEA) The Polycarbonate polyol production process was simulated with the Aspen Plus software tool. The process was sized based on a 100-megawatt alkaline electrolyser producing 16 kilotonnes of hydrogen per year. Corresponding annual carbon dioxide demand is 100,000 tonnes, and annual production of polycarbonate polyols is 38 kt. The price for electricity and other key parameters were estimated for the year 2030. Key assumptions used in calculations are listed in Table 1. Techno-economic assessment of the process and sensitivity analyses were carried out to evaluate the economic performance and profitability of the concept. The main results can be seen in Figure 2. The calculated production cost of polycarbonate polyols was 2,180 EUR/tonne. If all byproducts of the process, excess oxygen and heat produced by the electrolyser and cyclic carbonates, were assumed to be valorised, the production cost decreased to 1,980 EUR/tonne. Most of the production cost originated from the electricity needed for electrolysis. According to market information, the price of polycarbonate polyols could be over 4,500 EUR/tonne. Some estimates Figure 2. Results of techno-economic assessment and sensitivity analysis. 42 bioplastics MAGAZINE [04/21] Vol. 16
Figure 1. Process route from captured carbon dioxide and green hydrogen to polycarbonate polyols. Polyurethanes predict a product price as high as 6,000 EUR/tonne. As the production costs identified in the techno-economic assessment are low compared to the expected selling price, the production appears very attractive. The BECCU production route presents a promising option to turn carbon dioxide emissions into specialty chemicals profitably. However, the market size of polycarbonate polyols is quite limited which was identified as a challenge for the commercialization of the process. On the other hand, polycarbonate polyols may have significant growth potential as a green polyol source, e.g., for polyurethane applications. Polyol applications: polyurethanes Polyurethanes are an important application of polyols. They are typically used as adhesives, coatings, or elastomers. Polycarbonate polyols are suitable as building blocks for high -performance applications of polyurethanes, especially when high thermal, hydrolytic, and UV stability are required. So far, polycarbonate polyols from C3 and C4 epoxides with different molecular weights have been synthesized. The next steps will be to produce larger quantities of polyols with appropriate molecular weight for the targeted polyurethane applications and to optimize the product yields. The application tests of the polyols will be performed together with the industrial project partners. Next steps The BECCU project continues until the end of 2021. The BECCU concept and the techno-economic assessment will be updated based on the additional findings from the ongoing experiments. The recognized improvements will be carried out together with a heat integration for the process. The assessment will be complemented by analysing different CO 2 capture options and electrolyser comparisons. Based on the techno-economic feasibility and life cycle assessments (LCA) of the value chain, business opportunities, future demonstrations, and impact of policy framework will be evaluated together with the project partners from the industry. https://www.beccu.fi/ Inputs Price Outputs Price Electricity (total) Hydrogen peroxide CO 2 supply 45 EUR/ MWh 550 EUR/ tonne 50 EUR/ tonne Cyclic 900 EUR/ carbonates tonne (by-product) By-product heat By-product oxygen 20 EUR/ MWh 40 EUR/ tonne Other parameters Electrolyser electricity input 100 MWe Annual plant 8,000 operation hours time Total investment cost estimate (20 years and 8 % WACC for annuity) 124 MEUR Table 1. Main assumptions used in techno-economic calculations. Figure 2. Results of technoeconomic assessment and sensitivity analysis. bioplastics MAGAZINE [04/21] Vol. 16 43
