Catalytic hydrotreatment of Alcell lignin fractions using a Ru/C catalyst

We here report the catalytic hydrotreatment of three different Alcell lignin fractions using a Ru/C catalyst in a batch reactor set-up (400 °C, 4 h, 100 bar H2 intake, 5 wt% catalyst on lignin). The fractions, obtained by a solvent fractionation scheme from Alcell lignin, differ in composition and molecular weight. The resulting product oils were characterized by various techniques, such as GC-MS-FID, GC × GC-FID, GPC, and 13C-NMR, to gain insight into the relationship between the feed and product yield/composition on a molecular level. The lowest molecular weight fraction (Mw = 660 g mol-1) gave the highest product oil yield after catalytic hydrotreatment (>70 wt% on lignin fraction). The main differences in molecular composition for the product oils were observed and are related to the chemical structure of the different feed fractions and less on the molecular weight. The highest amounts of valuable alkylphenolics (8.4 wt% on intake) and aromatic compounds (4.2 wt% on intake) in the product oils were obtained with the lowest molecular weight fraction. This fraction also contained the highest amounts of aliphatic hydrocarbons after the hydrotreatment reaction (14.0 wt% on intake), which were primarily linked to the presence of extractives in the Alcell lignin feed, that accumulate in this low molecular weight fraction during solvent fractionation

Experimental and modeling studies on the Ru/C catalyzed levulinic acid hydrogenation to γ–valerolactone in packed bed microreactors

The hydrogenation of levulinic acid (LA) to γ-valerolactone (GVL) was performed in perfluoroalkoxy alkane capillary microreactors packed with a carbon-supported ruthenium (Ru/C) catalyst with an average particle diameter of 0.3 or 0.45 mm. The reaction was executed under an upstream gas-liquid slug flow with 1,4-dioxane as the solvent and H2 as the hydrogen donor in the gas phase. Operating conditions (i.e., flow rate and gas to liquid flow ratio, pressure, temperature and catalyst particle size) were varied in the microreactor to determine the influence of mass transfer and kinetic characteristics on the reaction performance. At 130 °C, 12 bar H2 and a weight hourly space velocity of the liquid feed (WHSV) of 3.0 gfeed/(gcat·h), 100% LA conversion and 84% GVL yield were obtained. Under the conditions tested (70 – 130 °C and 9 – 15 bar) the reaction rate was affected by mass transfer, given the notable effect of the mixture flow rate and catalyst particle size on the LA conversion and GVL yield at a certain WHSV. A microreactor model was developed by considering gas-liquid-solid mass transfer therein and the reaction kinetics estimated from the literature correlations and data. This model well describes the measured LA conversion for varying operating conditions, provided that the internal diffusion and kinetic rates were not considered rate limiting. Liquid-solid mass transfer of hydrogen towards the external catalyst surface was thus found dominant in most experiments. The developed model can aid in the further optimization of the Ru/C catalyzed levulinic acid hydrogenation in packed bed microreactors

Catalytic hydrotreatment of fast pyrolysis liquids in batch and continuous set-ups using a bimetallic Ni-Cu catalyst with a high metal content

In this paper, an experimental study on the hydrotreatment of fast pyrolysis liquids is reported in both batch and continuous set-ups using a novel bimetallic Ni-Cu based catalyst with high Ni loading (up to 50%) prepared by a sol-gel method. The experiments were carried out in a wide temperature range (80-410 degrees C) and at a hydrogen pressure between 100-200 bar to determine product properties and catalyst performance as a function of process conditions. To gain insight into the molecular transformations, the product oils were analysed by GC x GC, H-1-NMR and GPC and reveal that the sugar fraction is reactive in the low temperature range (300 degrees C). In addition, the organic acids are very persistent and reactivity was only observed above 350 degrees C. The results are rationalized using a reaction network involving competitive hydrogenation of reactive aldehydes and ketones of the sugar fraction of fast pyrolysis liquids and thermal polymerisation. In addition, relevant macro-properties of the product oils including flash point (30 to 80 degrees C), viscosity (0.06 to 0.93 Pa s) and TG residue

Catalytic Hydrotreatment of Alcell Lignin Using Supported Ru, Pd, and Cu Catalysts

A catalyst screening study on the catalytic hydrotreatment of Alcell lignin in a batch setup was performed using supported Ru (C, Al2O3,TiO2), Pd (C, Al2O3), and a Cu/ZrO2 catalyst with the objective to determine the best catalyst for high yields of biobased aromatics and alkylphenolics. Experiments were performed at 400 °C, 4 h reaction time and an initial hydrogen pressure of 100 bar. Best results were obtained with Ru/TiO2 and a lignin oil (78 wt % on lignin intake) with 9.1 wt % alkylphenolics, 2.5 wt % aromatics, and 3.5 wt % catechols on lignin intake were obtained. The reaction products were characterized using advanced GC×GC-FID and GC×GC-TOFMS techniques in combination with GPC, 13C NMR, and GC–MS-FID measurements. Systematic studies with the Ru/C catalysts using variable batch times (0–8 h, 400 °C, and an initial hydrogen pressure of 100 bar) gave insights in the reaction pathways occurring during the catalytic hydrotreatment and these include depolymerization, hydrogenation, hydrodeoxygenation, and dehydration reactions

Catalytic hydrotreatment of pyrolytic lignins to give alkylphenolics and aromatics using a supported Ru catalyst

The catalytic hydrotreatment of two pyrolytic lignins (pine and forestry residue), obtained from the corresponding fast pyrolysis oils, and organosolv Alcell lignin as a benchmark was explored in a batch set-up using Ru/C as the catalyst (400 degrees C, 4 h, 100 bar initial H-2 pressure). The highest lignin oil yield was obtained for forest residue pyrolytic lignin (> 75 wt% on intake). Advanced GCxGC techniques in combination with GPC and C-13-NMR measurements indicate that the lignin oils contain high amounts of interesting monomeric chemicals like alkylphenolics (up to 20.5 wt% on lignin feed intake) and aromatics (up to 14.1 wt% on lignin feed intake). These values are considerably higher than for Alcell lignin (6.6 wt% alkylphenolics and 9.7 wt% aromatics) and clearly indicate that pyrolytic lignins have potential to be used as feeds for the production of biobased phenolics and aromatics

Catalytic Hydrotreatment of Alcell Lignin Using Supported Ru, Pd, and Cu Catalysts

A catalyst screening study on the catalytic hydrotreatment of Alcell lignin in a batch setup was performed using supported Ru (C, Al₂O₃,TiO₂), Pd (C, Al₂O₃), and a Cu/ZrO₂ catalyst with the objective to determine the best catalyst for high yields of biobased aromatics and alkylphenolics. Experiments were performed at 400 °C, 4 h reaction time and an initial hydrogen pressure of 100 bar. Best results were obtained with Ru/TiO₂ and a lignin oil (78 wt % on lignin intake) with 9.1 wt % alkylphenolics, 2.5 wt % aromatics, and 3.5 wt % catechols on lignin intake were obtained. The reaction products were characterized using advanced GC×GC-FID and GC×GC-TOFMS techniques in combination with GPC, ¹³C NMR, and GC–MS-FID measurements. Systematic studies with the Ru/C catalysts using variable batch times (0–8 h, 400 °C, and an initial hydrogen pressure of 100 bar) gave insights in the reaction pathways occurring during the catalytic hydrotreatment and these include depolymerization, hydrogenation, hydrodeoxygenation, and dehydration reactions

Catalytic Hydrotreatment of Humins in Mixtures of Formic Acid/2-Propanol with Supported Ruthenium Catalysts

The catalytic hydrotreatment of humins, which are the solid byproducts from the conversion of C6 sugars (glucose, fructose) into 5-hydroxymethylfurfural (HMF) and levulinic acid (LA), by using supported ruthenium catalysts has been investigated. Reactions were carried out in a batch setup at elevated temperatures (400 °C) by using a hydrogen donor (formic acid (FA) in isopropanol (IPA) or hydrogen gas), with humins obtained from d-glucose. Humin conversions of up to 69 % were achieved with Ru/C and FA, whereas the performance for Ru on alumina was slightly poorer (59 % humin conversion). Humin oils were characterized by using a range of analytical techniques (GC, GC-MS, GCxGC, gel permeation chromatography) and were shown to consist of monomers, mainly alkyl phenolics (>45 % based on compounds detectable by GC) and higher oligomers. A reaction network for the reaction is proposed based on structural proposals for humins and the main reaction products

Catalytic hydrodeoxygenation and hydrocracking of Alcell (R) lignin in alcohol/formic acid mixtures using a Ru/C catalyst

The catalytic conversion of Alcell (R) lignin in iso-propanol/formic acid mixtures (1: 1 mass ratio) was explored in a batch set-up using Ru/C as the catalyst (673 K, 4 h, 28% mass lignin intake on solvent). Lignin oils were obtained in good yields (71% mass yields on lignin input) and shown to consist of a mixture of mainly aromatics (10.5% mass yields on lignin input), alkylphenolics (6% mass yields on lignin input), catechols (8.7% mass yields on lignin input), guaiacols (1.3% mass yields on lignin input), and alkanes (5.2% mass yields on lignin input), the remainder being soluble higher molecular weight compounds (GCxGC-FID and GPC). The results for the catalytic experiments using formic acid were compared with those of a non-catalysed experiment and a catalytic hydrotreatment with molecular hydrogen and Ru/C in the absence of a solvent. Distinct differences in product yields and compositions were observed, and highest lignin oil yields were obtained by catalytic solvolysis (71% mass yields on lignin input) versus 18% mass yields on lignin input for noncatalytic solvolysis and 63% mass yields on lignin input for catalytic hydrotreatment. The effect of reaction time on oil yields and product composition was established and a reaction network involving depolymerisation, and hydro(-deoxy)genation pathways is proposed to explain the product yields and composition. Besides iso-isopropanol, the use of ethanol and methanol in combination with formic acid was also explored for catalytic solvolysis. Best results were obtained in methanol (4 h, 673 K) leading to a lignin oil (68% mass yields on lignin input) containing 11% mass yields on lignin input of alkylphenolics and 19% mass yields on lignin input of aromatics. (C) 2015 Elsevier Ltd. All rights reserved