Development of 'Lignin-First' Approaches for the Valorization of Lignocellulosic Biomass.

Currently, valorization of lignocellulosic biomass almost exclusively focuses on the production of pulp, paper, and bioethanol from its holocellulose constituent, while the remaining lignin part that comprises the highest carbon content, is burned and treated as waste. Lignin has a complex structure built up from propylphenolic subunits; therefore, its valorization to value-added products (aromatics, phenolics, biogasoline, etc.) is highly desirable.

Catalytic Depolymerization of Lignin and Woody Biomass in Supercritical Ethanol: Influence of Reaction Temperature and Feedstock.

The one-step ethanolysis approach to upgrade lignin to monomeric aromatics using a CuMgAl mixed oxide catalyst is studied in detail. The influence of reaction temperature (200-420 °C) on the product distribution is investigated. At low temperature (200-250 °C), recondensation is dominant, while char-forming reactions become significant at high reaction temperature (>380 °C).

Selective production of mono-aromatics from lignocellulose over Pd/C catalyst: the influence of acid co-catalysts.

The 'lignin-first' approach has recently gained attention as an alternative whole biomass pretreatment technology with improved yield and selectivity of aromatics compared with traditional upgrading processes using technical lignins. Metal triflates are effective co-catalysts that considerably speed up the removal of lignin fragments from the whole biomass. As their cost is too high in a scaled-up process, we explored here the use of HCl, HSO, HPO and CHCOOH as alternative acid co-catalysts for the tandem reductive fractionation process.

Synergy in Lignin Upgrading by a Combination of Cu-Based Mixed Oxide and Ni-Phosphide Catalysts in Supercritical Ethanol.

The depolymerization of lignin to bioaromatics usually requires a hydrodeoxygenation (HDO) step to lower the oxygen content. A mixed Cu-Mg-Al oxide (CuMgAlO ) is an effective catalyst for the depolymerization of lignin in supercritical ethanol. We explored the use of Ni-based cocatalysts, i.

Effective Release of Lignin Fragments from Lignocellulose by Lewis Acid Metal Triflates in the Lignin-First Approach.

Adding value to lignin, the most complex and recalcitrant fraction in lignocellulosic biomass, is highly relevant to costefficient operation of biorefineries. We report the use of homogeneous metal triflates to rapidly release lignin from biomass. Combined with metal-catalyzed hydrogenolysis, the process separates woody biomass into few lignin-derived alkylmethoxyphenols and cellulose under mild conditions.

Transition metal (Ti, Mo, Nb, W) nitride catalysts for lignin depolymerisation.

Metal nitrides are promising catalysts for depolymerisation of lignin in supercritical ethanol; cheap and abundant titanium nitride affords an aromatic monomer yield of 19 wt% from soda lignin. The reaction mechanism is discussed on the basis of the products and a guaiacol model compound study.

Catalytic depolymerization of lignin in supercritical ethanol.

One-step valorization of soda lignin in supercritical ethanol using a CuMgAlOx catalyst results in high monomer yield (23 wt%) without char formation. Aromatics are the main products. The catalyst combines excellent deoxygenation with low ring-hydrogenation activity.

Infrared spectroscopic investigation of CO adsorption on SBA-15- and KIT-6-supported nickel phosphide hydrotreating catalysts.

The infrared (IR) spectra of CO adsorbed on 10, 20, and 30 wt % nickel phosphide-containing reduced SBA-15 and KIT-6 mesoporous silica-supported catalysts have been studied at 300-473 K. On the catalysts containing a stoichiometric amount of phosphorus with 20 wt % loading, the most intense IR absorption band was observed at 2097-2099 cm(-1), which was assigned to CO terminally bonded to coordinatively unsaturated Ni(delta+) (0 < delta < 1) sites. The frequency of this band was 15 cm(-1), higher than that in the spectrum of a reduced Ni2P/SiO2 catalyst, indicating a modified Ni-P charge distribution.

Distribution of aluminum and boron in the periodical building units of boron-containing Beta zeolites.

Various boron only ([B]-BEA) as well as aluminum- and boron-containing beta zeolites ([Al,B]-BEA) have been prepared and modified by ion exchange of ammonium, sodium, and nickel ions. The zeolite samples have been characterized by 11B, 27Al, and 29Si MAS as well as three of them by 11B and 27Al 3Q-MAS NMR spectroscopy. The quantitative contributions of defect-free Si(nX) (n = 2, 1, 0; X = Al, B) and Si(OH)x (x = 2, 1) sites to the NMR signal intensities were calculated from the various Si/(Al + B) ratios and relative 11B, 27Al, and 29Si NMR signal intensities using the special distribution of aluminum and boron in different periodical building units of the zeolite framework.

Distribution of aluminum in different periodical building units of MOR and BEA zeolites.

Various commercial, homemade, and dealuminated mordenites (MOR) and beta (BEA) zeolites as well as cobalt modified BEAs have been characterized by 29Si- and 27Al solid-state magic angle spinning nuclear magnetic resonance (MAS-NMR) spectroscopy. The quantitative contributions of Si(nAl) and Si(OH)x sites to the NMR signal intensities were calculated from the various Si/Al ratios and relative 29Si and 27Al NMR signal intensities assuming a special distribution of aluminum in different periodical building units of the zeolite framework. A different dealumination and silanol formation mechanism for MOR and BEA was suggested.

Infrared emission and theoretical study of carbon monoxide adsorbed on alumina-supported Rh, Ir, and Pt catalysts.

The infrared emission spectra of CO adsorbed on alumina-supported 1, 3, and 5 wt % Rh, Ir, and Pt metal-containing catalysts were studied at 423 and 473 K. While CO is adsorbed in dicarbonyl (dimer), linearly (on-top) bonded and bridged carbonyl forms on rhodium and platinum, the dimer form is dominant on iridium. The relative intensity of Rh-CO and Ir-CO linear bands decrease with increasing temperature compared to the intensity of the dicarbonyl bands; the corresponding bands on Pt behave the opposite way.