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Nanjing Tech University develops molecular sieve membranes for natural gas decarbonization to achieve efficient separation of carbon dioxide and methane. Author/Source: Sinochem News Network. Date: May 18, 2022. Clicks: 2. The team led by Professor Gu Xuehong from the Key Laboratory of Materials Chemistry and Engineering at Nanjing Tech University has developed a high-performance molecular sieve membrane for natural gas decarbonization, enabling efficient separation of carbon dioxide and methane. This achievement was recently published in the international top journal Nature Communications. “Carbon dioxide in natural gas reduces the calorific value of the fuel and corrodes the pipelines, so carbon removal is necessary before natural gas enters the distribution network. ”Gu Xuehong explained that natural gas has a much lower carbon emission level compared to coal and oil, making it a relatively clean fossil fuel. It will play an important role in the future restructuring of the energy sector, and decarbonizing it is a key step in the production process. “Membrane separation is used for carbon removal from natural gas without the need to add third components; it can significantly reduce separation energy consumption and is environmentally friendly. ”Du Peng, a doctoral student at Nanjing Tech University, said that polymer membranes used for natural gas decarbonization have attracted significant attention from the market. However, these membranes result in high methane losses during the decarbonization process, and the materials tend to become plasticized in high carbon dioxide concentrations, which affects the efficiency of decarbonization. “Compared to polymer membranes, zeolite molecular sieve membranes effectively leverage their strengths and avoid their weaknesses. ”Professor Wang Xuerui from Nanjing Tech University explained that zeolite molecular sieve membranes are a type of inorganic membrane material characterized by uniform pore sizes, as well as high separation performance and stability. “Molecular sieve membranes have regular pore structures, acting as perfect sieves that enable easy separation. ”Gu Xuehong explained that, just as when screening beans large particles remain in the sieve while small particles fall into the container, thereby achieving separation, zeolite molecular sieve membranes also function as a special type of sieve, using the size of their pores to separate gas molecules of different sizes. The molecular sieve membrane prepared by the team has a pore size of 0.36 nanometers, which lies between the kinetic diameters of carbon dioxide and methane molecules at 0.33 nanometers and 0.38 nanometers respectively; as a result, carbon dioxide can pass through the membrane while methane cannot, thereby enabling their separation. “The highest carbon dioxide/methane separation selectivity of the hollow fiber DD3R molecular sieve membranes we prepared was 1172; that is, for every 1172 carbon dioxide molecules that pass through, only 1 methane molecule passes through the membrane layer, whereas the separation selectivity of commercial polymer membranes is generally below 50. ”Wang Xuerui explained that all-silicon DD3R molecular sieve membranes are ideal materials for natural gas decarbonization, but during the conventional calcination process to remove the template agent, the crystals expand, which leads to membrane defects and a loss of separation performance. In light of this, the research team proposed a template removal strategy: by rapidly raising the temperature and carrying out instantaneous pyrolysis to control the flexibility of the DD3R molecular sieve framework, followed by continuous calcination at a moderate temperature of 550°C to remove the template, a defect-free DD3R molecular sieve membrane was obtained, whose performance far exceeds that of existing separation membranes of similar type. Associate Professor Zhang Yuting from Nanjing Tech University explained that this method has strong versatility. In addition to DD3R molecular sieve membranes, the team also used this method to prepare high-performance SSZ-13 and MFI-type molecular sieve membranes, thereby increasing the yield of these membranes during the high-temperature template removal stage. This approach holds promise for overcoming the challenges associated with the large-scale production of high-performance molecular sieve membranes, and it can facilitate their use in areas such as natural gas decarbonization, hydrogen separation, and carbon dioxide capture.