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Measurements of the zeta potential of solid heterogeneous supports are important for preparation of metal supported catalysts and for shaping zeolites into extrudates. In the current work, different types of heterogeneous support materials such as SiO2, Al2O3, and a range of beta zeolites of different silica- to-alumina ratio were analysed. It was observed that parameters such as temperature, pH and acidity significantly affect the zeta potential. In several instances, depending on the materials’ acidity and microstructure, maxima in zeta potential were observed. The solid materials were thoroughly characterized using XRD, SEM, EDX, TEM, nitrogen physisorption, Al-NMR and FTIR with pyridine before zeta potential measurements.

Kinetics of guaiacol hydrodeoxygenation (HDO) was studied using supported Mo x C–SBA-15 and as a comparison 5 wt% Pt/C under 30 bar hydrogen at 200 °C and 300 °C. Catalyst characterization was done by a range of physical methods including also determination of the amount of coke and the nature of adsorbed species. Pt/C gave 2-methoxycyclohexanol as the main product, whereas Mo 2 C–SBA-15 promoted direct deoxygenation exhibiting also strong adsorption of guaiacol on the catalyst surface and formation of oligomers. Thermodynamics of guaiacol HDO was elucidated and the reaction network was proposed based on which kinetic modelling was done. Graphic Abstract

Kinetics of the cross aldol condensation of valeraldehyde with cyclopentanone was investigated in a batch reactor under atmospheric pressure at 130 °C using heterogeneous metal modified oxides, such as CeO 2 –MgO, FeO–MgO, FeO–CaO as well as pristine CaO as catalysts. The catalysts were prepared either by evaporation impregnation or deposition precipitation methods and characterized by XRD, TEM, SEM, nitrogen adsorption, ammonia and CO 2 TPD. The results revealed that an optimum amount of strong basic sites gives the highest ratio between cross condensation and self-condensation products of valeraldehyde. The highest yield of the desired product 2-pentylidenecyclopentanone (66%) was obtained with FeO–MgO prepared by the deposition precipitation methods. Graphical Abstract Cross-condensation of valeraldehyde with cyclopentanone was investigated over heterogeneous Fe–CaO, CeO–MgO, FeO–CaO and CaO catalysts at 130 °C using cyclopentanone as a solvent and reactant. The highest yield of the desired product, 2-pentylidene-cyclopentanone, finding applications as fragrances, flavours and pharmaceuticals, was 66% obtained over FeO–MgO catalyst exhibiting both acid and basic sites.

Herein, it has been shown that betulin can be transformed into its biologically active oxo-derivatives (betulone, betulinic and betulonic aldehydes) by liquid-phase oxidation over supported silver catalysts under mild conditions. In order to identify the main factors determining the catalytic behavior of nanosilver catalysts in betulin oxidation, silver was deposited on various alumina supports (γ-alumina and boehmite) using deposition–precipitation with NaOH and incipient wetness impregnation methods, followed by treatment in H2 or O2. Silver catalysts and the corresponding supports were characterized by X-ray diffraction, nitrogen physisorption, inductively coupled plasma optical emission spectroscopy, photoelectron spectroscopy and transmission electron microscopy. It was found that the support nature, preparation and treatment methods predetermine not only the average Ag nanoparticles size and their distribution, but also the selectivity of betulin oxidation, and thereby, the catalytic behavior of Ag catalysts. In fact, the support nature had the most considerable effect. Betulin conversion, depending on the support, increased in the following order: Ag/boehmite < Ag/boehmite (calcined) < Ag/γ-alumina. However, in the same order, the share of side reactions catalyzed by strong Lewis acid centers of the support also increased. Poisoning of the latter by NaOH during catalysts preparation can reduce side reactions. Additionally, it was revealed that the betulin oxidation catalyzed by nanosilver catalysts is a structure-sensitive reaction.

Citronellal was converted to menthol in a one-pot approach using H-Beta zeolite-based Ni catalyst in a batch reactor at 80 °C, under 20 bar of total pressure. The effects of H-Beta acidity (H-Beta-25 with the molar ratio SiO2/Al2O3 = 25 and H-Beta-300 with SiO2/Al2O3 = 300) and Ni loading (5, 10 and 15 wt %) on the catalytic performance were investigated. Ni was impregnated on H-Beta support using the evaporation-impregnation method. The physico-chemical properties of the catalysts were characterized by XRD, SEM, TEM, ICP-OES, N2 physisorption, TPR, and pyridine adsorption–desorption FTIR techniques. Activity and selectivity of catalysts were strongly affected by the Brønsted and Lewis acid sites concentration and strength, Ni loading, its particle size and dispersion. A synergetic effect of appropriate acidity and suitable Ni loading in 15 wt.% Ni/H-Beta-25 catalyst led to the best performance giving 36% yield of menthols and 77% stereoselectivity to ( ±)-menthol isomer at 93% citronellal conversion. Moreover, the catalyst was successfully regenerated and reused giving similar activity, selectivity and stereoselectivity to the desired ( ±)-menthol isomer as the fresh one.

Hydrodeoxygenation (HDO) of isoeugenol was carried out at 200 °C and 30 bar of H 2 in a batch reactor using a series of bifunctional catalysts consisting of platinum supported on zeolite H-Beta-25 or H-Beta-300 and Bindzil as a binder. The purpose of the matrix was to understand the effect of the binder on the reaction, emulating the components of industrial catalysts and therefore facilitating catalyst scale-up. The effect of the supports acid strength, the location of metal nanoparticles, and their proximity to acid sites was also studied. The catalysts were characterized by N 2 physisorption, inductively coupled plasma atomic emission spectrometry, Fourier transform infrared spectroscopy of adsorbed pyridine and scanning and transmission electron microscopy. It was found that platinum supported only on the zeolite was more active compared to platinum located on the binder. High levels of isoeugenol conversion (ca. 100%), propylcyclohexane yield (56%) and the liquid-phase mass balance (68%) were obtained for the catalyst consisting of Pt supported on both zeolite H-Beta-25 and Bindzil.

Ni-based bi- and trimetallic Mn, Mg and aluminum containing catalysts prepared by the solution combustion synthesis (SCS) method were tested in dry reforming of methane (DRM). As a comparison 12 wt.% Ni/α-Al 2 O 3 catalyst prepared by wet impregnation was also investigated. The catalysts were characterized by means of XRD, N 2 physisorption, H 2 -TPR, CO 2 -TPD, NH 3 -TPD, TPO, CHNS, TGA, SEM and TEM. Formation of crystalline MnAl 2 O 4 was observed at high temperatures during SCS. The average nickel particle size varied in the range of 12–36 nm. Addition of Mn promoted reduction of Ni and elevated the amount and strength of the basic sites. Graphical Abstract

Vanillin hydrodeoxygenation was investigated using Pt/C catalyst in the temperature and total pressure ranges of 80–200 °C and 20–30 bar in several solvents, such as tetrahydrofuran, 2-propanol, water and in solventless conditions using 1:1 mass ratio of vanillin to guaiacol. The results revealed that the rate increased with increasing solvent polarity as follows: tetrahydrofuran < 2-propanol < water. The main product was p -creosol with 66% selectivity at complete vanillin conversion in HDO under 30 bar total pressure at 100 °C after 4 h using water as a solvent. In a solventless experiment with 1:1 mass ratio of vanillin–guaiacol as a feedstock only vanillin was transformed to p -creosol with 91% conversion in 4 h at 200 °C under 30 bar total pressure, while guaiacol did not produce any HDO products. Both thermodynamic analysis and kinetic modelling were performed. Vanillin hydrodeoxygenation resulted in formation of p -creosol over Pt/C catalyst using an optimum vanillin initial concentration in water solution. From the industrial point of view vanillin hydrodeoxygenation proceeded rapidly giving high yields of p -creosol in solventless hydrodeoxygenation of vanillin-guaiacol mixture, while guaiacol was not deoxygenated. Graphical Abstract

The lignan oxomatairesinol was synthesized from the biomass-derived lignan hydroxymatairesinol via selective aerobic oxidation over a heterogeneous gold catalyst. The catalyst was prepared by direct ion-exchange and characterized by XRD, TEM and ICP-OES methods. The reaction was carried out at 70 °C and atmospheric pressure in a semi-batch reactor. To reveal the origin of catalyst deactivation, spent catalysts were studied by TEM, XRD, nitrogen physisorption, ICP-OES, TPO, and DSC-TGA techniques. Several regeneration procedures were applied—extraction by several solvents and calcinations in the oxidizing atmosphere. The former one was found to be the most effective way for the catalyst regeneration. Graphical Abstract

The incentives for utilizing a versatile range of renewable feedstocks in novel ways are continuously increasing. Sulfated polysaccharides from green algae, such as ulvan, are interesting due to the rare sugar constituents which can be utilized for new materials and chemicals in industry. However, before valorization fractionation needs to be performed in a controlled way. In the current work, the kinetics of the aqueous extraction of ulvan was studied in the temperature range 60–130 °C. The highest yield of 97.6 wt.% was attained after 2 h of extraction at 130 °C, and the extraction efficiency was observed to be heavily temperature dependent. Interestingly, two regimes of extraction kinetics were observed, presumably due to the different ulvan fractions contained within the cell wall of green algae. The experimental data was modeled with first-order kinetics, and an apparent activation energy of 53.8 kJ mol −1 was obtained for the process. The algal residue was processed using simultaneous saccharification and fermentation, and 0.48 g ethanol g −1 of sugars was obtained.