Formic Acid Dehydration Using Mechanochemically Prepared TiO2‐Graphite Composites

• Published in: ChemCatChem 2024-11, Vol.16 (21), p.n/a
• Main Authors: Yruela‐Garrido, Marta, Martín‐Rodríguez, Nuria, Castillejos, Eva, Campos‐Castellanos, Eduardo, Conesa, José María, Rodríguez‐Ramos, Inmaculada, Guerrero‐Ruiz, Antonio
• Format: Article
• Language: English
• Subjects: Acids; Ammonia; Carbon dioxide; Carbon dioxide TPD; Catalysts; Catalytic activity; Composite materials; Dehydration; Formic acid; Gas flow; Graphite; Graphite support; Surface properties; TiO2 catalysts; Titanium dioxide
• ISSN: 1867-3880; 1867-3899
• DOI: 10.1002/cctc.202400897

Commercial high surface area graphite (HSAG300) and commercial TiO2 were used to produce composite materials through a simple mechanochemical method involving milling and ultrasonic treatments. The acid and basic sites exposed on the surfaces of these materials were characterized by temperature‐programmed desorption (TPD) of ammonia and carbon dioxide. The catalytic materials were tested in the dehydration reaction of formic acid to produce hydrogen‐free CO. While HSAG300 is practically inactive under reaction conditions (continuous gas flow at temperatures in the range of 100–250 °C), all samples containing TiO2 are active, exhibiting high selectivity to CO without significant deactivation at moderate reaction temperatures. It is demonstrated that the presence of graphite in the catalysts enhances the specific catalytic activity of TiO2. Assuming that the dehydration reaction is catalyzed by acid sites on the TiO2 surfaces, a comparative evaluation of the surface sites reveals that the graphite‐TiO2 interactions not only change the density of surface sites but also modify the strength of the acid centers of TiO2. In summary, the interaction of HSAG300 with TiO2 modulates the surface properties of the prepared composite catalysts, decreasing the total number of basic surface sites and increasing the strength of acidic sites compared to bare TiO2. Improving the acidic properties of TiO2 by its incorporation in graphite composites, which are prepared by mechanochemical methods. Evidence of electron transfer among the TiO2 and the graphite crystallites. Impact of the modified surface properties in the catalytic dehydration of formic acid yielding catalytic materials with increased specific activities at moderate reaction temperatures.