Estudo da desativação de zeólitas em sistemas de secagem de gás natural

• Autor(a) principal: Nascimento, Beatriz Oliveira
• Data de Publicação: 2021
• Tipo de documento: Dissertação
• Idioma: por
• Título da fonte: Repositório Institucional da Universidade Federal do Ceará (UFC)
• Texto Completo: http://www.repositorio.ufc.br/handle/riufc/59809
• topic: Zeólita; Desativação; Secagem; Gás natural

Natural gas is an important energy source with low polluting potential when compared to other fossil fuels. However, it contains contaminants in its composition such as carbon dioxide, water, sulfur compounds, among others, which must be removed to meet natural gas specifications for transport and use. Among these contaminants, water might cause undesirable effect, e.g., gas transport difficulties and equipment corrosion. The adsorption of water on molecular sieves in TSA (Temperature Swing Adsorption) processes is a commonly employed technique for natural gas dehydration. The main aim of this work is to evaluate the changes in properties of four adsorbents used in TSA process. In an accelerated aging protocol, samples underwent a humidification step for 24 h at 30°C. Then, samples were pressurized at 30 bar with a mixture of CO2 and methane (1:4) for 1 h at 30°C, followed by cycles alternating heating at 250 or 300°C and cooling down to 30°C. Solid samples were removed after 14, 24 and 35 cycles. Two sample series were generated: those aged in presences of n-heptane and those without n-heptane (blank experiments). The nature of zeolite aging was investigated by Fourier-Transform Infrared Spectroscopy (FTIR). In all samples aged with n-heptane, bands referring to the aromatic compound were found. The CO2 isotherms at 0°C indicated that micropore volume was reduced in the case of aging in presence of n-heptane, which might suggest pore blocking by coke accumulation. Blank experiments showed no significant reduction in the CO2 adsorption capacity at 0°C which indicates that the disruption of crystal structure was not the main deactivation mechanism. The aging temperature was relevant for the crystalline sample, which has a decrease in the CO2 adsorption capacity (at 25°C) with the increase of the aging temperature. However, the pelletized samples (with binder) were not significantly altered, which suggested the binder provided thermal resistance. The water vapor isotherms showed the aging process has an impact on both the adsorption capacity and intraparticle mass transport resistance.