Studying the Sorption of Carbon Dioxide by Modified Silica Gel with 2-Hydroxyethylcarbamate

Abstract

The main cause of global warming is the steady increase in greenhouse gases in the atmosphere. The largest share of greenhouse gases is carbon dioxide CO₂. Therefore, it is important to efficiently separate it in different gas systems. The article examines the sorption of carbon dioxide from polysilicic acid—silica gels modified with hydroxyethyl carbamate (HEC). It is shown that the modification is optimal in 30% HEC solutions. The fact of modification is confirmed by the presence of amino, hydroxyl, and carbonyl groups in the sorbents. Thermal stability is studied by the thermogravimetric method. Sorption at high pressures is studied by the gravimetric method and sorption at atmospheric pressure is studied by the thermogravimetric method. It is found that the presence of amino groups contributes to the sorption of carbon dioxide by silica gel more than doubling. The highest sorption rates are found to be 8.8% of the mass of the sorbent at 30°C. After five cycles of sorption/desorption processes in sorbents, the maximum sorption capacity decreased by 10%. The sorption rate increases at high pressures of up to 3 atm. Sorbents modified with a 30% HEC solution at 3 atm sorb up to 9.96 mol CO₂/g. The relatively fast growth of the sorption rate at high pressures and its relatively slow growth at low pressures prove that the process corresponds to type-2 sorption. Such sorption systems are promising for use in various technological systems containing CO₂.