Dual-tuning SiO2 nanosphere size and hydrothermal reaction temperature toward urchin-like copper phyllosilicate hollow nanospheres catalyst in dimethyl oxalate hydrogenation

Abstract

In this work, the relationship between the size of SiO₂ nanospheres (SNS) and their surface hydroxyl concentration was investigated. Three types of SNS with diameters of 510  nm, 170  nm, and 100  nm were used as supports to synthesize a series of Cu/SNS-140 catalysts via a hydrothermal method at 140 °C. The influence of SNS size on the structure and relative amount of copper phyllosilicate was explored, identifying ∼ 170  nm as the optimal SNS size for forming urchin-like copper phyllosilicate hollow nanospheres. Subsequently, the effect of hydrothermal reaction temperature on the formation of these structures was studied. The results showed that both suitable SNS size and hydrothermal reaction temperature (140 °C) are critical for achieving the ideal morphology. Among the prepared catalysts, Cu/SNS-M−140 exhibited the best performance in the hydrogenation of dimethyl oxalate (DMO), achieving a DMO conversion of 99.9 % and ethylene glycol selectivity of 96.3 % at 190 °C, with a TOF of 27.9  h⁻¹. The superior activity is attributed to its unique hollow structure, which enhances hydrogen enrichment and spatial restriction effects. This work offers valuable guidance for the rational design of copper phyllosilicate-based hollow nanostructured catalysts.