Study of the effects arising from chemical and structural manipulation strategies in heterogeneous catalysts applied to CO2 hydrogenation to methanol.

Author(s)

Marco Aurélio de Lima Silva Rossi

• Document type: Doctoral Thesis
• Press: São Carlos.
• Institution: Universidade de São Paulo (USP). Instituto de Química de São Carlos (IQSC/BT)
• Defense date: 2021-02-24

Examining board members

Elisabete Moreira Assaf; Lisiane Veiga Mattos; Celso Valentim Santilli; Martin Schmal; Maria do Carmo Rangel Santos Varela

• Advisor: Elisabete Moreira Assaf

Abstract

Nowadays, factors such as population growth, indiscriminate use of water, and contamination of its sources and reservoirs created a need for actions capable of promoting sustainable management of this resource through the conscious use, treatment, and reuse of this resource. Despite the high efficiency of modern treatment systems, some aspects can still be improved, such as the proper destination of the CO2 molecules generated in the anaerobic decomposition stage of organic contaminants, considering that this is the main greenhouse gas whose high concentrations in the atmosphere have led to the recent climate issues. Among the possibilities for this purpose, one of the most promising strategies involves the conversion of this compound into molecules of high added value, such as methanol through hydrogenation reactions through the use of heterogeneous catalysts. In this context, the present work aims to apply strategies for manipulating the chemical and structural nature of catalysts based on copper and zirconia or ceria, in an attempt to achieve considerable improvements in the catalytic performance presented by them. In the first stage, the effects of modifying these materials with indium atoms were studied. As a result, it was found that a considerable increase in methanol selectivity occurred due to indium atoms effects involving changes in the intermediate adsorption and activation energy for specific stages of hydrogenation that are, in general, very high, hindering methanol production. Also, the greater basicity of these materials due to oxygen vacancies was important. In the second stage, the effects of the catalysts encapsulation by porous silica coating were studied. It was observed that the core-shell type materials presented a performance remarkably superior to the other catalysts due to the efficiency of the silica coating in minimizing particles sintering during the heat treatment steps in the synthesis procedure and in reaction steps occurring at high temperatures. In addition to the effects arising from the indium atoms presence, the low dimensions and high homogeneity of the particles obtained enabled considerable values of basicity which have led to high selectivity values for methanol. Also, the high copper dispersion and metallic area values have led to higher CO2 conversion, which associated to the high methanol selectivity, resulted in significant molar productivity for methanol in all tested temperature ranges. (AU)

• FAPESP's process: 17/10154-6 - Study on catalysts based on metal-metal oxide nanocomposites doped and encapsulated by mesoporous coating for methanol production by CO2 hydrogenation
• Grantee: Marco Aurélio de Lima Silva Rossi
• Support Opportunities: Scholarships in Brazil - Doctorate