Liquefaction Of Lignocellulosic Biomass Research Articles

Liquefaction of Lignocellulose in Light Cycle Oil: A Process Concept Study

Lignocellulosic biocrude can be produced by direct liquefaction of lignocellulosic biomass, which can be further upgraded into biofuels in an oil refinery. Refinery streams, namely vacuum gas oil (VGO) and light cycle oil (LCO), were found suitable liquefaction solvents in our previous study. This paper reports a process concept based on the liquefaction of wood in LCO followed by recovery and recycling of the LCO. The LCO is recovered from the reactor effluent by spontaneous liquid–liquid phase split upon cooling. The feasibility of this process concept was demonstrated experimentally by conducting a series of refill experiments with LCO recovery and recycling. This series shows a steady-state liquefaction of pine wood with constant product yields (liquid yield ∼ 57 C%) and constant oil qualities over eight recycles. Most of the ash present in the wood was concentrated in the char. A techno-economic assessment estimated that the biocrude could be produced at 13.9 $/GJ, which corresponds to an energy-equi...

Directional liquefaction coupling fractionation of lignocellulosic biomass for platform chemicals

Conventional thermochemical liquefaction of lignocellulosic biomass produces an unpredictable complex mixture of oxygenated products, which creates techno-economic barriers during subsequent upgrading processes.

The effects of water tolerant Lewis acids on the hydrothermal liquefaction of lignocellulosic biomass

The objective of this study was to investigate the effects of water tolerant Lewis acids (i.e., In(OTf)3, Yb(OTf)3 and InCl3) on bio-oil and solid residue yields. For this purpose, poplar wood was liquefied at 300 °C with a residence time of 10 min without and with water tolerant Lewis acids in various concentrations from 0.5 to 10 wt% under hydrothermal conditions. The use of water tolerant Lewis acids had negative effects on bio-oil yields. The bio-oil from the run without a catalyst had a value of 17.50 wt% at 300 °C, 10 min. The highest bio-oil yields under identical conditions were the following: 14.27 wt%, 13.37 wt% and 12.42 wt% for Yb(OTf)3 (with a concentration of 0.5 wt% of the raw material), In(OTf)3 and InCl3 (with concentrations of 1 wt% of the raw material). The concentrations of catalysts used in the experiments had significant effects on both bio-oil and solid residue yields. An increase of catalyst concentrations resulted in a decrease in bio-oil yields. The catalysts changed neither the molecular nor the elemental compositions of bio-oils and solid residues significantly. The prominent compounds in bio-oils from all runs including the run without a catalyst were phenol, 2,6-dimethoxyphenol, and 2-methoxyphenol.

Polyols and polyurethane foams from base-catalyzed liquefaction of lignocellulosic biomass by crude glycerol: Effects of crude glycerol impurities

This study investigated the effects of organic impurities in crude glycerol, including free fatty acids (FFAs), methyl esters of fatty acids (FAMEs), and glycerides, on the properties of polyols and PU foams derived from crude glycerol-based liquefaction of lignocellulosic biomass catalyzed by a base. Organic impurities, particularly FFAs and FAMEs, exhibited positive influences on the properties of liquefaction-derived polyols and PU foams. Crude glycerol containing 45–70% of organic impurities was optimal for the production of polyols and PU foams. At optimal impurity levels, the polyols produced showed hydroxyl numbers and molecular weights (Mw) ranging from 405 to 794mgKOH/g and from 400 to 1000g/mol, respectively; the PU foams produced showed densities and compressive strength ranging from 0.037 to 0.048g/cm3 and from 140 to 188kPa, respectively. These properties are comparable to those of the polyols and PU foams derived from petrochemical solvent-based biomass liquefaction processes.

Effect of heating rate on biomass liquefaction: Differences between subcritical water and supercritical ethanol

This study investigates the influence of heating and cooling rate on liquefaction of lignocellulosic biomass in subH2O (subcritical water) or in scEtOH (supercritical ethanol), in dependency of final reaction temperatures (250–350 °C) and residence times (1–40 min). The heating rate has been identified as a crucial parameter in the subH2O-based liquefaction, whereas it has marginal influence in the scEtOH-based liquefaction. Detailed characterization of gas, liquid and solid products enables to identify the individual reaction steps, which results in a new insight into the reaction mechanisms, depending on the liquefaction solvents and conditions. Similar to fast pyrolysis, hydrothermal liquefaction consists of beneficial primary reactions (pyrolytic & hydrolytic degradation) and non-beneficial secondary reactions i.e. recombination and secondary cracking. In scEtOH, biomass was decomposed by pyrolysis and alcoholysis at relatively high reaction temperatures while the recombination of reaction intermediates are retarded by the unique reactions of scEtOH such as hydrogen donation and hydroxylalkylation.

The Influence of Alkali and Alkaline Earth Metals and the Role of Acid Pretreatments in Production of Sugars from Switchgrass Based on Solvent Liquefaction

This study investigated the influence of alkali and alkaline earth metals (AAEM) and the role of acid pretreatments in the production of sugars during solvent liquefaction of lignocellulosic biomass using 1,4-dioxane and water as solvents. The present study found that removal of AAEM by acid washing/water rinsing did not enhance sugar production during solvent liquefaction of pretreated switchgrass nearly to the extent observed for fast pyrolysis nor did it inhibit lignin decomposition, suggesting that AAEM play less of a role in determining product yields in solvent liquefaction. On the other hand, acid infusion greatly enhanced the yields of sugars during solvent liquefaction, presumably because the strong acid catalytically promoted both the depolymerization and the dehydration of polysaccharides. The main monomeric sugars formed were levoglucosan, glucose, and xylose. Levoglucosan was the predominant sugar when 1,4-dioxane was the solvent, whereas glucose was the major sugar when water was the solvent...

Hydrothermal liquefaction of wheat straw in hot compressed water and subcritical water–alcohol mixtures

Hydrothermal liquefaction of lignocellulosic biomass (wheat straw) into bio-oil has been investigated under subcritical conditions (temperature up to 350°C, pressure up to 200bar) in water and water–alcohol mixtures using ethanol and isopropanol in a continuously operated tubular reactor. The effect of different reaction parameters such as temperature, pressure and water–alcohol ratio on the biomass conversion, cracking products yield and the higher heating value (HHV) of the received bio-oil was studied. The water–ethanol mixture was found to be a very reactive medium showing a complete biomass conversion and >30wt% yield of high caloric oil (HCO). A maximum HHV of 28MJ/kg for HCO was achieved. In addition, Ru (5wt%) on H-Beta support was used as catalyst in a run with hydrogen in the feed showing deeper deoxygenation of reaction intermediates and highest HHV of the product oil (30MJ/kg). This work demonstrated the usability of water–ethanol mixtures for an effective depolymerization of lignocellulosic biomass to bio-oils under subcritical reaction conditions with more than doubled HHV compared to the feedstock, in particular using a catalyst and the presence of hydrogen for further deoxygenation.

Liquefaction of Lignocellulosic Biomass: Solvent, Process Parameter, and Recycle Oil Screening

The liquefaction of lignocellulosic biomass is studied for the production of liquid (transportation) fuels. The process concept uses a product recycle as a liquefaction medium and produces a bio-oil that can be co-processed in a conventional oil refinery. This all is done at medium temperature (≈ 300 °C) and pressure (≈ 60 bar). Solvent-screening experiments showed that oxygenated solvents are preferred as they allow high oil (up to 93% on carbon basis) and low solid yields (≈ 1-2% on carbon basis) and thereby outperform the liquefaction of biomass in compressed water and biomass pyrolysis. The following solvent ranking was obtained: guaiacol>hexanoic acid ≫ n-undecane. The use of wet biomass results in higher oil yields than dry biomass. However, it also results in a higher operating pressure, which would make the process more expensive. Refill experiments were also performed to evaluate the possibility to recycle the oil as the liquefaction medium. The recycled oil appeared to be very effective to liquefy the biomass and even surpassed the start-up solvent guaiacol, but became increasingly heavy and more viscous after each refill and eventually showed a molecular weight distribution that resembles that of refinery vacuum residue.

Kinetic study on the liquefaction of wood and its three cell wall component in polyhydric alcohols

To better understand liquefaction of lignocellulosic biomass, wood and its three cell wall components (lignin, hemicellulose and cellulose) were subjected to a liquefaction process using polyethylene glycol (PEG 400)/glycerol as liquefaction solvent. On the basis of the experimental results obtained at different temperatures (140, 160, and 180°C), a kinetics of liquefaction of wood and its major cell wall components was presented, and the kinetic parameters were estimated. The values of total activation energy obtained in the liquefaction were about 44.31kJmol−1 of lignin, 40.49kJmol−1 of hemicellulose, 73.25kJmol−1 of cellulose and 63.93kJmol−1 of wood. Hemicellulose was the most susceptible component to liquefaction among the three cell wall components, followed by the lignin and cellulose.

Supercritical ethanol as an enhanced medium for lignocellulosic biomass liquefaction: Influence of physical process parameters

In this study, the influence of various physical process parameters on the liquefaction of lignocellulosic biomass (pine wood) in supercritical ethanol was investigated. The parameters include reaction temperature (280–400 °C), initial nitrogen pressure (0.4–7.5 MPa), reaction time (0–240 min), and biomass-to-solvent ratio (0.06–0.25 g/g). The reaction temperature and residence time were found to have a more significant effect on biomass conversion and product yield than pressure and biomass-to-solvent ratio had; conversion in the range 34.0–98.1% and biocrude yield in the range 15.8–59.9 wt% were observed depending on the process parameters. Despite the absence of catalysts and external hydrogen source, solid biomass to liquid and gaseous products conversion of 98.1%, and a high biocrude yield of approximately 65.8 wt% were achieved at 400 °C, 120 min, and a biomass-to-solvent ratio of 0.06 g/g. Moreover, the biocrude contained considerably lower amounts of oxygen and higher amounts of carbon and hydrogen, resulting in a substantially higher heating value (>30 MJ/kg) as compared to raw feedstock (20.4 MJ/kg). A comparison with sub- or supercritical water-based liquefaction revealed that supercritical ethanol produced biocrude with a lower molecular weight and much better yield. Finally, a new biomass liquefaction reaction mechanism associated with supercritical ethanol is proposed.

AC3B Technology for Direct Liquefaction of Lignocellulosic Biomass: New Concepts of Coupling and Decoupling of Catalytic/Chemical Reactions for Obtaining a Very High Overall Performance

The acid-catalyzed conversion of lignocellulosic biomass (AC3B) process has been developed for the direct liquefaction of lignocellulosic biomass. In the original version, the main products, ethyl esters, are produced in acidic medium containing ethanol, using a one-pot conversion system. Our research strategy for obtaining a high overall performance is based on two general concepts: (a) coupling of catalytic/chemical reactions that lead to desired products and (b) decoupling of reactions that produce unwanted products, by decreasing the effectiveness of these reactions. Concept (a) is realized by using oxidizers (hydrogen peroxide and Fenton’s reagent) that promote a higher production of carboxylic acids as main intermediates, while concept (b) contributes to a significant decrease of undesired formation of polymeric products. As result of these reaction coupling and decoupling, the overall yield of liquid products has been multiplied by a factor of 2.5 (from 27 to over 70 wt%). Not only the yields of products from cellulose and hemicellulose components experience considerable increases, but also the lignin component starts undergoing a noticeable conversion. Essentially, the AC3B process, in the most recent version, consumes ethanol that is partly used to produce liquid fuels and chemicals from lignocellulosic biomass. The other amount of feed ethanol is converted—via diethyl ether and over ZSM-5-based catalysts—into aromatics-rich gasoline and liquefied petroleum gas—grade hydrocarbons. Sequence of actions that have significantly improved the total product yield (RP): AC = acidic medium, HP = addition of hydrogen peroxide, DL-st = use of a delignification step, FR = use of a Fenton-type reagent, PIn = use of a polymerization inhibitor

Liquefaction of cellulose in the presence of phenol using p-toluene sulfonic acid as a catalyst

The kinetics of p-toluene sulfonic acid (PTSA)-catalyzed cellulose liquefaction in the presence of phenol were investigated at 130, 140 and 150 °C. The resulting liquefied products were also analyzed to evaluate the effectiveness of PTSA as a catalyst during the phenol liquefaction. The liquefaction rate of PTSA was slightly lower than that of sulfuric acid (SA), which was used as a reference catalyst, at each liquefaction temperature. The activation energies of the PTSA and SA catalysts during the phenol liquefaction of cellulose calculated using the Arrhenius equation were 34.5 and 35.5 kcal/mol, respectively. The chemical compositions of the ether extracts in the liquefied products were very similar to both catalysts. Methylene bisphenol and its isomers, which were the primary components in the ether extracts, comprise approximately 30% of the ether extract. The GPC curves of the 80% dioxane-soluble part of the liquefied product indicated that it consists of a remarkable amount of phenol-based trimers to hexomers. The average molecular weight and the polydispersity of the liquefied products were very similar after liquefaction using both catalysts; therefore, differences in the products produced using both catalysts used were not recognized. However the level of combined phenol in the liquefied product produced using the PTSA catalyst was approximately 50% lower than that of the SA catalyst. Although it is believed that this difference may cause retardation of the rate of liquefaction, further experiments are necessary to explain differences in the effectiveness of organic sulfonic acid catalysts during the phenol liquefaction of lignocellulosic biomass.

The IBUS Process – Lignocellulosic Bioethanol Close to a Commercial Reality

AbstractIntegrated Biomass Utilization System (IBUS) is a new process for converting lignocellulosic waste biomass to bioethanol. Inbicon A/S has developed the IBUS process in a large‐scale process development unit. This plant features new continuous and energy‐efficient technology developed for pretreatment and liquefaction of lignocellulosic biomass and has now been operated and optimized for four years with promising results. In the IBUS process, biomass is converted using steam and enzymes only. The process is energy efficient due to very high dry matter content in all process steps and by integration with a power plant. Cellulose is converted to bioethanol and lignin to a high‐quality solid biofuel which supply the process energy as well as a surplus of heat and power. Hemicellulose is used as feed molasses but in the future it could also be used for additional ethanol production or other valuable products. Feasibility studies of the IBUS process show that the production price for lignocellulosic bioethanol is close to the world market price for fuel ethanol. There is still room for optimization – and lignocellulosic bioethanol is most likely a commercial alternative to fossil transport fuels before 2012.

Liquefaction of lignocellulosic biomass and its potential applications

Liquefaction of lignocellulosic biomass and its potential applications