Abstract
Catalytic systems based on bimetallic Pd-Au particles deposited on SiO2 were prepared by ultrasonically assisted water impregnation and used in the hydrogenation of furfural obtained by the acidic hydrolysis of waste biomass (brewery’s spent grain) in aqueous phase. Pd-Au/SiO2 catalysts containing 50 g of Pd and 2–100 g of Au per 1 kg of catalyst were characterized by high activity in the studied process and, depending on the Pd/Au ratio, selectivity to 2-methyloxolan-2-ol. The modification of 5%Pd/SiO2 by Au leads to the formation of dispersed Au-Pd solid solution phases, which was confirmed by XRD, XPS, ToF-SIMS, SEM-EDS, and H2-TPR techniques. The effect of dilution of surface palladium by gold atoms is probably crucial for modification of the reaction mechanism and formation of 2-methyloxolan-2-ol as the main product.
Highlights
Lignocellulosic biomass is a very interesting chemical raw material, which is a renewable and available source of cellulose (30–45%), hemicellulose (20–35%), and lignin (10–20%)
Only in the case of 5%Pd–1%Au/ SiO2 catalyst the crystallites of gold smaller than 10 nm, which can be active in furfural reduction, were obtained
The catalysts have been subjected to Atomic Absorption Spectrometry (AAS), x-ray diffraction (XRD), time of flight (ToF)-SIMS, scanning electron microscopy and energy-dispersive X-ray spectroscopy (SEM-EDS), and X-ray photoelectron spectroscopy (XPS) tests in order to determine their composition and metal interactions, which may affect the activity and selectivity for individual products in furfural reduction
Summary
Lignocellulosic biomass is a very interesting chemical raw material, which is a renewable and available source of cellulose (30–45%), hemicellulose (20–35%), and lignin (10–20%). Biomass is mainly used as fuel to obtain energy, especially heat, but its chemical treatment allows for the obtaining of many valuable products; e.g., furfural, levulinic acid, etc. According to the most cited mechanism, the 1,2-ethanediol is formed from pentoses and is further converted to furfural in the presence of protons derived from an acidic catalyst [3]. Nimlos et al [7] attempted to determine the energy levels of transition states for the specified mechanisms through quantum modeling. Their studies have shown that, in energy terms, intramolecular rearrangement is more beneficial than opening a sugar ring. Antal et al [9]
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