Preparation And Modification Of Inorganic Porous Materials For Efficient Carbon Dioxide Capture

The development of human society has significantly increased the emission of carbon dioxide（CO₂）.As of 2022,China’s CO₂emissions reached over 10 billion tons,making up nearly 30%of the world’s emissions.Greenhouse gases,such as excessive CO₂discharge,cause global warming,rising sea levels,and extreme weather conditions.Therefore,Carbon Capture,Utilization,and Storage（CCUS）technology is crucial in reducing emissions.Developing high-performance CO₂capture materials is the core of CCUS technology.This paper aims to design and produce high-performance CO₂capture materials by investigating the porous structures,elemental composition,stability,CO₂selective adsorption,and regeneration capabilities of two types of materials:carbon materials and molecular sieves.Moreover,studying the mechanisms of adsorption and desorption within the pores are essential for producing highly selective and efficient CO₂capture materials.The focus of this study is on developing high-performing CO₂capture materials to decrease CO₂emissions.Specific research contents include:1.High-capacity microporous carbon materials for CO₂adsorption were produced from peach pits,a type of biomass waste,using a two-step carbonization process.The resulting microporous carbon material displayed an outstanding proportion of micropores at 97.65%.Additionally,it exhibited outstanding CO₂adsorption capabilities,with adsorption capacities of 4.92mmol/g at 25°C and 1 bar,in addition to excellent CO₂/N₂selectivity（IAST=45）.Moreover,we further verified the separation properties of the microporous carbon materials towards CO₂and N₂mixed gas through penetration experiments.The research illustrates that pore structure and pore ratio determine the low-pressure CO₂adsorption capacity of this microporous carbon material（<1 bar）and that there is no direct correlation between the BET surface area and the low-pressure CO₂adsorption capacity（<1 bar）.Hence,we conclude that peach pits,as an abundant and easily available biomass waste material,may potentially provide an alternative option to produce micro-microporous carbon materials used for the efficient capture of CO₂.2.In this study,a method of vacuum-assisted alkaline treatment modification of molecular sieves is proposed to improve their CO₂adsorption capacity,which is currently insufficient.This method is universal for silicoaluminophosphate molecular sieves.For H-SSZ-13,T and 4A molecular sieves,their CO₂adsorption performance was improved by 7.67%to 16.99%at 25 ^oC and 1 bar after modification using this method.Vacuum-assisted treatment can remove gas inside the molecular sieve pores,resulting in more thorough processing.ICP testing revealed that the modified samples had a2.04%increase in Na⁺content.The Na⁺cation entering the molecular sieve structure increases the CO₂adsorption site/strength.Additionally,alkaline treatment can optimize the pore structure by removing silicon from the pores,increasing the micropore volume by 0.01 cm³/g and thus enhancing the CO₂capture performance.3.Silica-aluminate molecular sieves are strongly hydrophilic,and in a humid environment,the adsorption of CO₂molecules competes with water molecules for adsorption,leading to a decrease in CO₂adsorption capacity.Therefore,the hydrophobicity of the molecular sieve was enhanced by surface modification by coating a carbon film with hydrophobicity on the surface of the silica-aluminate molecular sieve.Starting from H-SSZ-13molecular sieve,a layer of polydopamine was coated on the surface of molecular sieve by using the polymerization reaction of dopamine hydrochloride under alkaline conditions,after which the carbon-coated molecular sieve was obtained by high-temperature carbonization.In the contact angle test,the carbon-coated H-SSZ-13 molecular sieve exhibited hydrophobic properties,and the measured contact angle was 134.2°,which reached the standard of superhydrophobicity.Through the Breakthrough test,the CO₂breakthrough time was compared between wet and dry environments.The results showed that the CO₂breakthrough time of the carbon coated H-SSZ-13 improved from 47.50 min/g to 106.65 min/g under dry conditions compared to the initial H-SSZ-13.In the humid environment,the CO₂breakthrough time of the carbon coated H-SSZ-13 decreased by 11.68%,while the breakthrough time of the initial H-SSZ-13 decreased by 14.9%.Although the decrease in the breakthrough time of carbon coated H-SSZ-13in the humid environment was less than that of the initial H-SSZ-13,the improvement was not significant.Although the carbon-coated molecular sieve can enhance hydrophobicity,gaseous water molecules can still enter the molecular sieve through the pore channels of the carbon-coated layer,which leads to a decrease in the CO₂adsorption performance of the carbon-coated molecular sieve in a humid environment.