Solvent feedstock effect: the insights into the deactivation mechanism of Cu/SiO2 catalysts for hydrogenation of dimethyl oxalate to ethylene glycol

Abstract

The variation of the supports on the Cu/SiO2 catalyst plays an important role in the catalytic performance for hydrogenation of dimethyl oxalate. The loss of silica in the form of tetramethoxysilane from the support under the reaction conditions is responsible for the deactivation of the Cu/SiO2 catalyst.

High-stable CuPd–Cu2O/Ti-powder catalyst for low-temperature gas-phase selective oxidation of alcohols

“…However, the benzyl alcohol conversion catalyzed by Pd/Ti-powder is just 44% ( Table 1, entries 12). Our catalyst exhibits higher activity compared with Au/Ti-powder, CuAg-4/Ti-powder, CoPd-4/Ti-powder and NiPd-4/Ti-powder catalyst ( Table 1, entries [13][14][15][16]. Compared with Au/Cu-fiber [3], the noble metal content in our catalyst is much lower ( Table 1, entry 17).…”

“…Cu-based catalyst shows high catalytic efficiency in oxidation or reduction reactions [11][12][13], but still faces some problems. For example, the loss of silica from Cu/SiO 2 catalyst in the form of TMOS leads to the decrease of copper surface area and the aggregation of copper particle, which are adverse in the hydrogenation of dimethyl oxalate [14]. Furthermore, the temperature-increase in catalyst bed is great over K-Cu-TiO 2 in gas-phase alcohol oxidation because of the strong-exothermicity of alcohol oxidation and the weak heattransfer ability of TiO 2 [15].…”

An environmentally benign and low-cost approach to synthesis of thermally stable industrial catalyst Cu/SiO2 for the hydrogenation of dimethyl oxalate to ethylene glycol

“…Although they are more thermally stable, as illustrated by the long term tests and TEM images, the detection of tetramethoxysilane (TMOS) in the product liquid phase indicates dissolution of the support, while the larger presence of Cu + in the structure as revealed by XPS/XAES seem to lead to an increase in the thermal stability of the copper structures [33]. According to Wen et al [21], this type of deactivation by the transformation of the silica support in TMOS is specific to the DMO hydrogenation systems where methanol is used as solvent for DMO, but is improbable for the systems where ethanol is used.…”

“…The sample obtained by ammonia evaporation technique using the ammonia stabilized silica sol (20Cu-AS30-AE-fresh) displays less evident peaks, signifying less crystallinity compared with the other two samples. The large peak centered near 23 • can be assigned to poorly crystalized SiO 2 structures [21,24,39]. All three samples display this peak, while the rest of the larger peaks displayed by the samples can be assigned to CuO (tenorite) [21,24,39] and some small peaks can be assigned to copper silicates [10].…”

“…This method was developed in order to generate smaller crystalline structures and a wider coverage of Cu compounds on the support, compared with incipient wetness impregnation methods [7,17], and became the common method of Cu compounds deposition on support [7,10,11,[18][19][20][21]. However, this hydrothermal method has a number of shortcomings:…”