Recent advances in hydrodeoxygenation of biomass-derived oxygenates over heterogeneous catalysts

Adsorption and surface reactions of acetone vapor were observed on the title oxides at room and higher temperatures (up to 400 °C), using in situ infrared spectroscopy. The results were correlated with results of infrared spectroscopy of adsorbed pyridine, to assess impacts of the surface acid−base properties. It was found that the availability of Lewis acid sites is essential for anchoring acetone molecules to the surface. Coexisting Lewis base sites catalyze condensation of the acetone molecules into mesityl oxide surface species, via formation and subsequent decomposition of enolate and diacetone alcohol species. When intimately coupled, the Lewis acid and base sites generate pair sites of particularly strong adsorption capacity toward condensation products thus formed. Consequently, surface active sites are blocked and adsorptive and catalytic interactions of acetone are largely suppressed.

Surface Reactions of Acetone on Al2O3, TiO2, ZrO2, and CeO2: IR Spectroscopic Assessment of Impacts of the Surface Acid−Base Properties

Hydrotreatment of pyrolysis bio-oil: A review

Iron complexes generated in situ catalyze homogeneously the transfer hydrogenation of aliphatic and aromatic ketones by utilizing 2-propanol as a hydrogen donor in the presence of base. The influence of different reaction parameters on the catalytic activity is investigated in detail by applying a three-component catalyst system composed of an iron salt, 2,2':6',2''-terpyridine, and PPh3. The scope and limitations of the described catalyst is shown in the reduction of 11 different ketones. In most cases, high conversion and excellent chemoselectivity are obtained. Mechanistic studies indicate a monohydride reaction pathway for the homogeneous iron catalyst.

An environmentally benign process for the hydrogenation of ketones with homogeneous iron catalysts.

The initial reaction rates on a per site basis for aqueous-phase hydrogenation (APH) of different oxygenated compounds: including acetaldehyde, propanal, acetone, xylose, furfural, and furfuryl alcohol and aqueous-phase hydrogenolysis of tetrahydrofurfuryl alcohol (THFA) and xylitol were measured over various alumina-supported monometallic catalysts (Pd, Pt, Ru, Rh, Ni, and Co) in a high-throughput reactor. These oxygenated compounds have the same functionality that is found in aqueous solutions derived from biomass including pyrolysis oils and aqueous hydrolysis solutions. The initial rate of APH of the different carbonyls groups was dependent on the functionality of the feed molecule and catalyst used. Ru was the most active metal for APH of acetaldehyde, propanal, acetone, and xylose. Pd was the most active metal for APH of furfural and furfuryl alcohol. Only Pt and Ni catalysts were able to produce 1,2-pentanediol and 1,5-pentanediol from aqueous-phase hydrogenolysis of THFA. Ru was active for conversion of THFA but only made coke. The initial activity for aqueous-phase hydrogenolysis of xylitol decreased in the order of Ru > Co > Pt > Ni ≥ Pd. The initial rates of APH of carbonyl groups (C O bond) measured in this study decreased in the order: hydrogenation of acetone > hydrogenation of acetaldehyde and propanal > hydrogenation of xylose > hydrogenation of furfural. The initial rates of aqueous-phase hydrogenolysis of THFA and xylitol were much lower than the initial rate for APH of C O and C C bonds.

High-throughput screening of monometallic catalysts for aqueous-phase hydrogenation of biomass-derived oxygenates

Co-precipitated Ni/Al2O3, Co/Al2O3 and Fe/Al2O3 catalysts containing 10–50 wt.% of metal are prepared and characterized by BET surface area, pore volume and XRD. Hydrogen chemisorption and oxygen uptake measurements are used to estimate the extent of reduction and the available surface metal sites. Acetone hydrogenation under vapour phase conditions is carried out over the catalysts in the temperature region 373–523 K. Conversion and selectivity of the catalysts are compared and are correlated with their hydrogen and oxygen uptake characteristics. Nickel catalysts are very active followed by cobalt and iron. A dual function mechanism involving both metal and acidic properties decide the selectivity of the products. The selectivity for propan-2-ol depends only on the metal availability whereas the selectivity for isobutyl methyl ketone depends on both acidic and metallic character of the catalyst. A mechanism explaining the different products formed is postulated.

Ramachandranpillai Unnikrishnan

Papers

Acetone hydrogenation over co-precipitated Ni/Al2O3, Co/Al2O3 and Fe/Al2O3 catalysts