Gas-Phase Conversion of Glycerol to Acetol: Influence of Support Acidity on the Catalytic Stability and Copper Surface Properties on the Activity

Abstract

Mesoporous mixed copper-aluminum oxides and copper-silicon oxides were synthesized with polymeric precursors route in order to evaluate the effect of the support acidity on the catalytic stability due to the carbon deposit and the copper surface characteristics on the catalytic activity for the gas-phase conversion of glycerol to acetol. The samples were characterized by different techniques such as inductively coupled plasma (ICP), thermogravimetry and differential thermal analyses (TGA-DTA), X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), N2 adsorption/desorption isotherms, temperature-programmed reduction with H 2 (H 2 -TPR) and microcalorimetry of NH 3 adsorption. The metallic copper surface was shown by XPS, which was observed an increase with the copper loading without marked changes between Si or Al support using the same copper content. The Cu-Al catalysts present acidic properties close to that of the pure alumina support while the Cu-Si solid is not acid, as expected. Reduced catalysts were evaluated in the reaction of glycerol conversion. The catalytic results showed a clear dependence of the glycerol conversion to acetol with the Cu metal surface and the initial catalytic properties did not depend on the support acidity, since the copper is the major active site. It was observed 95% of acetol selectivity and 80% of glycerol conversion for the best catalyst. However, the support acidity influenced the catalyst stability, since Cu-Al solid deactivated continuously by contrast to Cu-Si sample, which reached stability after 2 h of reaction. The higher acidity for the Al support leads to a greater carbon deposit compared to Si support, blocking the active sites and providing a rapid catalytic deactivation.

Effect of Metals on the Hydrogenolysis of Glycerol to Higher Value Sustainable and Green Chemicals Using a Supported HSiW Catalyst

“…34,35 In glycerol hydrogenolysis, the first step involves an initial protonation of the hydroxyl group that leads to the formation of a carbocation and water. 36,37 The initial acid catalyzed dehydration is the selectivity controlling step. If the primary hydroxyl group is eliminated 1,2-PD will be obtained; if the secondary alcohol is eliminated then 1,3-PD will form.…”

Continuous catalytic process for the selective dehydration of glycerol over Cu-based mixed oxide

“…Nevertheless, copper-chromite cannot be considered as an environmentally friendly catalyst due to its toxicity and, additionally, the scale-up of a reactive distillation system is not straightforward from an industrial viewpoint. In this sense, continuous catalytic processes would be more suitable, although just a few articles can be found in the literature [23][24][25], most of them involving the use of hydrogen. In this regard, it would be very interesting to develop a continuous and sustainable process for the selective dehydration of glycerol to acetol by using an efficient heterogeneous catalyst.…”

Continuous Flow Upgrading of Selected C2–C6Platform Chemicals Derived from Biomass

“…Deactivation was related to carbonaceous deposition and blockage of the active sites of the catalyst. Acid sites promoted the formation of coke, , while basic oxide such as La 2 CuO 4 gave stable catalytic activity for prolonged time-on-stream . The best results were arguably obtained by Batiot-Dupeyrat et al over La 2 CuO 4 catalyst .…”

“…In some examples, molecular hydrogen was co-fed with glycerol. Co-feeding hydrogen promoted the dehydration reaction and inhibited the formation of coke, thus preventing catalyst deactivation. , Silver-, aluminum-, cerium-, ,− chromium-, copper-, ,,− and lanthanum- , as well as cobalt- and ruthenium-based catalysts were reported as efficient heterogeneous catalysts for the reaction. The most relevant catalysts and optimized conditions for hydroxyacetone formation are summarized in Table .…”