Oil and water: A new energy-efficient and atom-economical catalytic route for the production of alkanes and methanol by upgrading the phenolic fraction of bio-oil has been developed. The one-pot aqueous-phase hydrodeoxygenation process is based on two catalysts facilitating consecutive hydrogenation, hydrolysis, and dehydration reactions.

A novel Ni/SiO(2)-catalyzed route for selective cleavage of ether bonds of (lignin-derived) aromatic ethers and hydrogenation of the oxygen-containing intermediates at 120 °C in presence of 6 bar H(2) in the aqueous phase is reported. The C-O bonds of α-O-4 and β-O-4 linkages are cleaved by hydrogenolysis on Ni, while the C-O bond of the 4-O-5 linkage is cleaved via parallel hydrogenolysis and hydrolysis. The difference is attributed to the fact that the C(aliphatic)-OH fragments generated from hydrolysis of α-O-4 and β-O-4 linkages can undergo further hydrogenolysis, while phenol (produced by hydrolysis of the 4-O-5 linkage) is hydrogenated to produce cyclohexanol under conditions investigated. The apparent activation energies, E(a)(α-O-4) < E(a)(β-O-4) < E(a)(4-O-5), vary proportionally with the bond dissociation energies. In the conversion of β-O-4 and 4-O-5 ether bonds, C-O bond cleavage is the rate-determining step, with the reactants competing with hydrogen for active sites, leading to a maximum reaction rate as a function of the H(2) pressure. For the very fast C-O bond cleavage of the α-O-4 linkage, increasing the H(2) pressure increases the rate-determining product desorption under the conditions tested.

Breaking down is usually hard to do…︁ The direct conversion of lignin into alkanes and methanol was carried out in a two‐step process (hydogenolysis and hydrogenation) involving initial treatment of white birch wood sawdust with H2 in dioxane/water/phosphoric acid using Rh/C as the catalyst. The resulting monomers and dimers obtained by selective CO hydrogenolysis were then hydrogenated in near‐critical water employing Pd/C as the catalyst.

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A new route to convert crude microalgae oils using ZrO(2)-promoted Ni catalysts into diesel-range alkanes in a cascade reaction is presented. Ni nanoparticles catalyze the selective cleavage of the C-O of fatty acid esters, leading to the hydrogenolysis of triglycerides. Hydrogenation of the resulting fatty acids to aldehydes (rate-determining step) is uniquely catalyzed via two parallel pathways, one via aldehyde formation on metallic Ni and the second via a synergistic action by Ni and ZrO(2) through adsorbing the carboxylic groups at the oxygen vacancies of ZrO(2) to form carboxylates and subsequently abstracting the α-hydrogen atom to produce ketene, which is in turn hydrogenated to aldehydes and decarbonylated on Ni nanoparticles.

The mechanism of the catalytic reduction of palmitic acid to n-pentadecane at 260 °C in the presence of hydrogen over catalysts combining multiple functions has been explored. The reaction involves rate-determining reduction of the carboxylic group of palmitic acid to give hexadecanal, which is catalyzed either solely by Ni or synergistically by Ni and the ZrO2 support. The latter route involves adsorption of the carboxylic acid group at an oxygen vacancy of ZrO2 and abstraction of the α-H with elimination of O to produce the ketene, which is in turn hydrogenated to the aldehyde over Ni sites. The aldehyde is subsequently decarbonylated to n-pentadecane on Ni. The rate of deoxygenation of palmitic acid is higher on Ni/ZrO2 than that on Ni/SiO2 or Ni/Al2O3, but is slower than that on H-zeolite-supported Ni. As the partial pressure of H2 is decreased, the overall deoxygenation rate decreases. In the absence of H2, ketonization catalyzed by ZrO2 is the dominant reaction. Pd/C favors direct decarboxylation (-CO2), while Pt/C and Raney Ni catalyze the direct decarbonylation pathway (-CO). The rate of deoxygenation of palmitic acid (in units of mmol moltotal metal(-1) h(-1)) decreases in the sequence r(Pt black) ≈r(Pd black) >r(Raney Ni) in the absence of H2 . In situ IR spectroscopy unequivocally shows the presence of adsorbed ketene (C=C=O) on the surface of ZrO2 during the reaction with palmitic acid at 260 °C in the presence or absence of H2.

Efficient conversion of biomass such as polysaccharides, [1] lignin, [2] and triglycerides [3] to biofuels has attracted considerable attention. Microalgae are being considered in that context as a promising renewable energy resource, having high triglyceride contents (up to 60 wt %) [4] and rapid growth rates that are 10-200 times faster than terrestrial oil crops such as soybean and rapeseed without directly competing with edible food/oil production. [5] Currently, three approaches are used for microalgae oil refining. The first technique involves transesterification of triglycerides and alcohol into fatty acid alkyl esters (FAAEs) and glycerol, which is applied in the first-generation biodiesel production. Such esters, however, have a relatively high oxygen content and poor flow property at low temperatures, limiting their application as high-grade fuels.[6] The second technique employs the conventional hydrotreating catalysts, for example, sulfided NiMo and CoMo, for upgrading. [7] However, these sulfide catalysts contaminate products through sulfur leaching, and deactivate because of its removal from the surface by a reverse Mars-van Krevelen mechanism.[8] The third technique relies on supported noble and base metal catalysts for decarboxylation and decarbonylation of carboxylic acids to alkanes at 300-330 8C, [9] but these catalysts showed low activities and selectivities for C 15 -C 18 alkanes when triglycerides were converted, and the performance was only somewhat improved by a Pt-Re/ZSM-5 catalyst.[10] Contributions addressing microalgae oil upgrading using sulfur-free catalysts have not been reported. Herein, we report for the first time a novel and scalable catalyst, that is, Ni supported on and in zeolite HBeta, to quantitatively convert crude microalgae oil under mild conditions (260 8C, 40 bar H 2 ) to diesel-range alkanes as high-grade secondgeneration transportation biofuels.Microalgae oil mainly consists of neutral lipids such as mono-, di-, and triglyceride. The microalgae oil (provided by Verfahrenstechnik Schwedt GmbH) used for this work consists of unsaturated C 18 fatty acids (88.4 wt %), saturated C 18 fatty acids (4.4 wt %), as well as some other C 14 , C 16 , C 20 , C 22 , and C 24 fatty acids (7.1 wt % in total; see Table S1 in the Supporting Information).Without any purification, the crude microalgae oil was directly hydrotreated in batch mode with 10 wt % Ni/HBeta (Si/Al = 180) at 260 8C and 40 bar H 2 (see Figure 1). After 8 h reaction time, we obtained 78 wt % yield of liquid alkanes (containing 60 wt % yield of C 18 octadecane), which was very close to the theoretical maximum liquid hydrocarbon yield of 84 wt %. Propane (3.6 wt %) and methane (0.6 wt %) were the main products in the vapor phase. The metal leaching after reaction was detected below the atomic absorption spectroscopy (AAS) detection limit (1 ppm). Figure 1 shows that saturated fatty acids were the primary products for microalgae oil conversion, that is, the yield of stearic acid exceeded 70 wt % within 1 h. Then, the...

Lignin is an abundant renewable resource with a high energy density, but it is considered to be difficult to process because of the high reactivity of its building blocks, that is, the substituted phenol units, which tend to react even at small concentrations and reaction temperatures.[1] It has been shown recently that this reactivity can be overcome by combining metallic (Pd) and acidic functions (H 3 PO 4 , CH 3 COOH, ÀSO 3 H, and ÀOH) in the appropriate concentrations in an aqueous phase or ionic liquids. [2] This has led to the successful hydrodeoxygenation of phenol derivatives and the synthesis of a pure cycloalkane product. Because of the different polarity of the substituted phenols and the alkanes, a second hydrocarbon phase is formed during the process, which can be easily separated. Noble and base metals have been found to be active for hydrogenation in the aqueous phase. Replacing liquid mineral acids by a solid acid (Nafion/SiO 2 ) allowed for an increase in efficiency. [3] In addition to the hydrodeoxygenation of phenolic monomers, the selective cleavage of the aromatic carbon-oxygen (CÀO) bonds in aryl ethers is also challenging because of the strength and stability of these linkages.[4] This cleavage is very important for facilitating the depolymerization of oxygenrich lignin by breaking down the CÀOÀC linkages, and for the hydrodeoxygenation of lignin-derived phenolic dimer fragments to the deoxygenated biofuels. Here, we report on the use of a weaker solid acid, that is, a zeolite (HZSM-5), as a selective catalyst component for the quantitative hydrodeoxygenation of diversely substituted lignin-derived mono-and binuclear phenols to cycloalkanes in combination with a noble metal (Pd) in aqueous solutions at a mild temperature (473 K).We have shown previously that phenol is converted to cyclohexane in water through the sequential hydrogenation of phenol to cyclohexanone and cyclohexanol on metal sites (Pd or Ni), dehydration of cyclohexanol on acid sites (H 3 PO 4 , CH 3 COOH, or Nafion/SiO 2 ), and finally the hydrogenation of cyclohexene to cyclohexane on metal sites. [1][2][3] To maximize the hydrodeoxygenation rate and selectivity under milder conditions (low reaction temperatures and pressures) in addition to the catalyst stability, various solid acids (acid-site densities and specific surface areas are listed in Table S1 in the Supporting Information) are explored in the presence of palladium Pd/C as hydrogenation catalyst. The characterization of the catalyst was achieved by determining the Brunauer-Emmett-Teller (BET) surface area and by using XRD, SEM, and TEM and is compiled in the Supporting Information. As a suitable solid acid should have a high acid-site density in combination with a sufficient stability in an aqueous phase above 473 K, the results (see Table S3 in the Supporting Information) for the conversion of 4-n-propylphenol show that solid Lewis acids, such as alumina, silica, and amorphous silica alumina, are not effective for oxygen removal (through dehydration of cycloalc...