Effect of the type of siliceous template and carbon precursor on physicochemical and catalytic properties of mesoporous nanostructured carbon-palladium systems

Abstract

Two series of nanostructured carbon replicas were synthesized through a hard-templating method using ordered SBA-15 or disordered mesoporous spherical silica gel as the templates and furfuryl alcohol or sucrose as the carbon source. They were explored to synthesize the Pd catalysts (ca. 1.5 wt% Pd loading) by the colloid-based microemulsion procedure which allowed preparing the catalysts of monodispersed Pd particles of similar size (4-5 nm). The palladium phase in the catalysts (e.g. the Pd particles distribution and extent of agglomeration) varied depending on the textural and surface characteristics of the carbon replicas. In the furfural hydrogenation studied as a probe reaction (2-propanol, 35 °C, 6 bar H 2), furfuryl alcohol and tetrahydrofurfuryl alcohol were the major products formed. The catalytic reactivity has been related to the properties of the Pd phase including the surface Pd concentration and the extent of the Pd particles aggregation accompanied by the nearest palladium environment expressed by the surface O/Pd atomic ratio. At high O/Pd ratio the reaction slowed down because of a facilitated furfuryl alcohol adsorption resulting most probably in a blockage of the active sites. The SiO 2 sucrose system provided the catalyst which was characterized by relatively low O/Pd ratio with well-dispersed Pd particles and the highest and stable activity for the furfural hydrogenation. The SBA-series catalysts, with lower O/Pd and more aggregated Pd particles, exhibited lower activity but somewhat higher tendency to the tetrahydrofurfuryl alcohol formation.

Microporous and Mesoporous Activated Carbons from Tea Stalk and Tea Stalk Pulps: Effect of Lignin Removal by One-Step and Two-Step Organosolv Treatment

“…After carbonization and activation, a broad hump (indicating the amorphous graphitic carbon) between 17° and 35° was observed in the x-ray diffraction pattern of ATP, ATS and AHTP (73). A weaker and broader hump at 41-47° was also observable in all patterns, which is also a characteristic diffraction of amorphous graphite structure (74). Unlike ATP and ATS, AHTP shows sharp diffraction peaks of graphitic carbon at 2=20°, 26°, 36°, 41°, 44°, 47.5°, 52°, 53.5°, 55.5°, 63°(55, 75).…”

Porous Silica Support for Immobilizing Chiral Metal Catalyst: Unravelling the Activity of Catalyst on Asymmetric Organic Transformations

“…synthesized mesoporous carbons using SBA‐15 and mesoporous silica gel as templates for loading of Pd catalysts. SBA‐15 templated carbons exhibited better entrapment of Pd than the disordered mesoporous silica gel, thus affecting the catalytic efficiency of the system [43] …”

“…synthesized mesoporous carbons using SBA‐15 and mesoporous silica gel as templates for loading of Pd catalysts. SBA‐15 templated carbons exhibited better entrapment of Pd than the disordered mesoporous silica gel, thus affecting the catalytic efficiency of the system [43] Nature of the attachment of the catalyst to the support material : The mode of attachment of metal catalyst to the support enhances the shelf life of the catalyst.…”

“…SBA-15 templated carbons exhibited better entrapment of Pd than the disordered mesoporous silica gel, thus affecting the catalytic efficiency of the system. [43] b) Nature of the attachment of the catalyst to the support material: The mode of attachment of metal catalyst to the support enhances the shelf life of the catalyst. The finetuning of the catalyst-support interface facilitates prolonged attachment, thereby preventing the leaching of the catalyst.…”