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ACS sustainable chemistry & engineering 9(18), 6235-6249 (2021). doi:10.1021/acssuschemeng.0c08760, Published by ACS Publ., Washington, DC

International journal of chemical kinetics (2020). doi:10.1002/kin.21453, Published by Wiley, New York, NY

A series of monometallic and bimetallic metal catalysts (Pd, Cu, Fe, PdCu, PdFe) supported on ZrO2 (6-8 nm) were synthesized and tested for the hydrogenation of bio-oil model compounds (furfural, vanillin, glucose) under 50 bar H2 at 100 °C. The catalysts were fully characterized and their properties related to their catalytic activity. The bimetallic PdFe and PdCu displayed enhanced catalytic performance compared to the monometallic catalysts for aldehyde hydrogenation (furfural, vanillin, glucose). For the best catalyst, 98% vanillin alcohol (VA) and 65.5% furfuryl alcohol (FA) conversion was obtained for 80 min batch-time. PdFe showed high selectivity toward sorbitol (74%) from glucose, though at low conversion (20%). Overall, we have demonstrated that bimetallic Fe- A nd Cu-based catalysts promoted by Pd show significantly better performance for the partial hydrogenation of bio-oil model compounds than the corresponding monometallic ones. The better performance of the Pd-doped Fe/Cu catalysts is linked to the presence of smaller and better dispersed Pd nanoparticles (STEM) and their lower acidity (∼90 μmol/g cat) than corresponding monometallic ones (∼167 μmol/g cat).

Global warming due to the accumulation of atmospheric CO2 has received great attention in recent years. Hence, it is urgent to reduce CO2 emissions into the atmosphere and develop sustainable technologies for a circular carbon economy. In this regard, CO2 capture coupled with the conversion into chemicals and fuels provides a promising solution to reduce CO2 emissions as well as to store and utilize renewable energy. Among the many possible CO2 conversion pathways, CO2 hydrogenation to higher alcohols is considered an important strategy for the synthesis of carbon-based fuels and feedstock and holds great promise for the chemical industry. Thus, this review provides an overview of advances in CO2 hydrogenation to higher alcohols that have been achieved recently in terms of catalyst design, catalytic performance, and insight into the reaction mechanism under different experimental conditions. First, the limitations provided by reaction thermodynamics and the indispensability of catalysts for CO2 hydrogenation to higher alcohols are discussed. Then, four main categories of catalysts will be introduced and discussed (i.e. Rh-, Cu-, Mo-, and Co-based catalysts). Moreover, important factors significantly influencing the efficiency of the catalytic transformation such as alkali/alkaline earth metal promoters, transition metal promoters, catalyst supports, catalyst precursors, and reaction conditions, as well as the reaction mechanism are explained. Finally, the review discusses emerging methodologies yet to be explored and future directions to achieve a high efficiency for the hydrogenation of CO2 to higher alcohols.

The pyrolytic sugar fraction, obtained by an aqueous extraction of pyrolysis oil, is an attractive source for sugar-derived platform chemicals. However, solids (humin) formation occurs to a significant extent during hydrolysis and subsequent acid-catalyzed conversion processes. In this study, we report investigations on possible conversion routes (pyrolysis, liquefaction) of such humin byproducts to biobased chemicals. Experiments were carried out with a model humin made from a representative technical pyrolytic sugar and the product was characterized by elemental analysis, GPC, TGA, HPLC, GC-MS, FT-IR and NMR. The obtained humin sample is soluble in organic solvents (dimethyl sulfoxide (DMSO), tetrahydrofuran (THF), and isopropanol (IPA)), in contrast to typical more condensed humins from glucose and fructose, allowing characterization using NMR and GPC. All analyses reveal that the humins are oligomeric in nature (M-w of about 900 g/mol) and consist of sugar and furanic fragments linked with among others (substituted) aliphatic, ester units and, in addition, phenolic fragments with methoxy groups. The humins were used as a feed for catalytic pyrolysis and catalytic liquefaction experiments. Catalytic pyrolysis experiments (mg scale, programmable temperature vaporizer (PTV)-GC-MS, 550 degrees C) with HZSM-5 50 as the catalyst gave benzene-toluene-xylene-naphthalene-ethylbenzene mixtures (BTXNE) in 5.1 wt% yield based on humin intake. Liquefaction experiments (batch reactor, 350 degrees C, 4 h, isopropanol as both the solvent and hydrogen donor and Pt/CeO2 (4.43 wt% Pt) catalyst) resulted in 80 wt% conversion of the humin feed to a product oil with considerable amounts of phenolics and aromatics (ca. 24.7 % based on GC detectables in the humin oil). These findings imply that the techno-economic viability of pyrolysis oil biorefineries can be improved by converting humin type byproducts to high value, low molecular weight biobased chemicals.

Applied catalysis / B 272, 118950 (2020). doi:10.1016/j.apcatb.2020.118950, Published by Elsevier, Amsterdam

Higher alcohols have attracted considerable interest owing to their broad range of applications. They are used as a fuel (additive) in combustion engines, are in demand in the chemical industry, and are also precursors for olefins and the preparation of plasticizers and detergents. Nowadays, higher alcohols are mainly manufactured through either fermentation technology with high energy demand, or the hydration of alkenes with very low single-pass conversion and high dependence on unsustainable petroleum oil. Therefore, new catalytic technology with sustainability advantages like the use of renewable feeds (e.g. syngas from biomass, CO2 from the atmosphere and bioethanol) needs to be developed in order to meet the increasing demand for higher alcohols.This PhD thesis presents improved catalytic systems for higher alcohol synthesis from renewable feeds with remarkable performance in terms of activity, selectivity and stability in comparison with the state-of-the-art reported in the literature. Moreover, relations between catalyst structure and performance have been established based on detailed catalyst characterization studies and in depth analyses of products.

Alcohol mixtures with high C3+ alcohols content can enhance the performance of alcohol mixtures as a blend component in gasoline. Sulfur-resistant potassium promoted molybdenum sulfide (K-MoS2) catalysts enabled synthesizing mixed alcohols through CO hydrogenation. However, the liquid oxygenate selectivity and yield of K-MoS2 catalysts are usually low, and the alcohols follow the Anderson-Schulz-Flory (ASF) distribution, which means methanol and ethanol present the main liquid oxygenates. To achieve high liquid oxygenate selectivity and yield enhancing C3+ alcohol production, we designed multilayer K-MoS2 catalysts possessing a well-contacted MoS2 and KMoS2 phase, respectively. The reduced rim site exposure and the well-contacted MoS2-KMoS2 dual site induced by the multilayer structure enhance the chain growth through CHx β-addition and CO insertion. Accordingly, the observed higher alcohol formation deviates from the ASF distribution. By tailoring the K/Mo ratio, catalysts with varying composition of MoS2 and KMoS2 phases were obtained for suppressing the formation of hydrocarbons and CO2 effectively. An optimized production of liquid oxygenates with enhanced C3+ alcohol production under appropriate reaction temperature became possible. The optimized catalysts have liquid oxygenate selectivity and yield of 29.1–32.7% and 7.9–10.6%, respectively, yet with good stability. C3+ alcohols take up more than 46% (carbon atom fraction) in the liquid oxygenate. The C3+ alcohol yield reaches 3.6–5.1%.