Agnieszka M. Ruppert

Ru catalysts for levulinic acid hydrogenation with formic acid as a hydrogen source

The catalytic hydrogenation of levulinic acid (LA) with formic acid (FA) as a hydrogen source into γ-valerolactone (GVL) is considered as one of the crucial sustainable processes in todays biorefinery schemes. In the current work, we investigated the modification of Ru/C as efficient catalysts for both formic acid decomposition and levulinic acid hydrogenation in comparison with Pd and Pt catalysts. In order to better understand what features are responsible for high catalytic performance, we combined experimental tests, DFT calculations together with extensive material characterization. In LA hydrogenation with FA as a hydrogen source, the intermediate surface formate inhibits at least partially the LA hydrogenation. In addition, the FA decomposition is highly sensitive to the kind of the preparation method of the Ru/C catalyst: (i) the process looks structure sensitive favored on larger particles and (ii) residual chlorine decreases significantly the FA decomposition rate.

Activity of Ni catalysts for hydrogen production via biomass pyrolysis

Ni catalysts were tested in the catalytic pyrolysis of biomass. The influence of Ni loading and various catalytic supports (ZrO2, Al2O3, ZrO2 + Al2O3, CeO2, SiO2) was studied. Although the gas phase was the main object of this study, solid and liquid residues were tested as well (mainly by TOC and GC-MS methods). Activity tests were performed in a batch reactor with mechanical stirring, equipped with on-line GC. Reaction was conducted at 700°C, with α-cellulose as a biomass model and with waste paper as an example of raw lignocellulosic material. Reactions in the presence of a catalyst gave a higher hydrogen yield. The most promising results were obtained with Ni/ZrO2.

Application of 1H and 27Al magic angle spinning solid state NMR at 60 kHz for studies of Au and Au-Ni catalysts supported on boehmite/alumina☆

In this work for the first time we show the power of solid state NMR spectroscopy in structural analysis of alumina and catalysts supported on the alumina surface employing very fast (60kHz) magic angle spinning (MAS) technique. In the methodological part we demonstrate that under such MAS condition, cross-polarization (CP) from proton to aluminum is an efficient process when a very weak 27Al RF field is applied. The mechanism of CP transfer and the Hartmann-Hahn (H-H) matching conditions were tested for 27Al RF fields equal to 3.3 and 8.3kHz. It has been found that double quantum (DQ) CP/MAS is the best choice for H-H set with RF =3.3kHz. It has been also proved that the quality of 1H-27Al CP/MAS spectra strongly depends on 27Al carrier offset. Applied to γ-alumina, this method revealed that 1H-27Al CP/MAS at 60kHz is extremely useful for mapping the distribution of hydroxyl groups on the surface. Indeed, the AlV sites, which are not easily detected with Single Pulse Experiment (SPE), are clearly seen when 1H-27Al CP/MAS is applied. Utilizing 2D 1H-27Al CP/MAS HETCOR experiment it was possible to assign the proton positions and to correlate them with aluminum centers. Studies of mono- (Au) and bi- (Au-Ni) metallic catalysts supported on boehmite/alumina carrier employing 1D and 2D HETCOR experiments clearly show that distributions of hydroxyl groups for both systems are dramatically different.

Hydrogen production from biomass woodchips using Ni/CaO–ZrO2 catalysts

This work aimed at the determination of the influence of various types of lignocellulosic biomass on the performance of Ni/ZrO2 catalyst modified by CaO in the production of hydrogen rich gas from lignocellulosic feedstock. The catalysts were prepared by co-impregnation and sequential impregnation methods. The catalytic activity of the synthesized materials was examined in the high temperature conversion of cellulose (model compound) and real biomass samples—woodchips from pine, beech, birch and poplar. The surface properties of Ni/CaO–ZrO2 catalysts were characterized by X-ray diffraction (XRD), time-of-flight secondary ion mass spectrometry (ToF–SIMS), thermogravimetric analysis (TG–DTA–MS) and BET methods. The obtained results revealed that an incorporation of calcium into the structure of the catalyst led to a decrease in the coke formation rate on its surface. Moreover, the influence of the preparation method on the material composition and related properties was demonstrated.

Supported gold–nickel nano-alloy as a highly efficient catalyst in levulinic acid hydrogenation with formic acid as an internal hydrogen source

Gamma-valerolactone (GVL) is one of the key products of future biorefineries. We show here for the first time the superior activity of Ni-based, Au doped catalysts in levulinic acid hydrogenation towards GVL using formic acid as a hydrogen source. Their performances are strongly influenced by the preparation method, and the highest GVL yield is achieved for bimetallic Au–Ni catalysts prepared via co-impregnation of both metallic salts with a reductive thermal treatment under hydrogen. The very high catalytic activity is explained by the use of DFT calculations and the extensive characterization of the catalyst surface and bulk properties. We highlight the pivotal role played by the incorporated isolated metallic Ni atoms within Au nanoparticles. The nano-alloy composition is determined. It allows establishment of a surface model of such an alloy, thanks to which the high activity can be explained by the presence of an optimum energetic span of FA adsorption. The existence of strong interaction between Au and Ni in a surface alloy, Au–Ni, favors selective and fast decomposition of formic acid into hydrogen that consequently facilitates strongly the combined hydrogenation process.