Liquefaction of lignocellulosics in model solvents: Creosote oil and ethylene glycol

The UDES-S liquefaction process treats concentrated pastes (20% of initially present solids) of finely divided (d_p < 0.5 mm) lignocellulosics in organo-solvolytic media by means of thermo-mechanical action in homogenizing valves. The work described in this paper was carried out with Populus Deltoides in a process development unit capable of processing up to 4 kg of dry wood per hour. The model solvents used were creosote oil and ethylene glycol, which represent solvents that could be derived from the process or its products. Liquefaction mechanisms depend upon the solvent-substrate interaction: with creosote oil, pyrolysis mechanisms predominate and lead to integral liquefaction of the wood while with ethylene glycol only fractional liquefaction was possible, apparently as a result of a complex formation between ethylene glycol and cellulose which protects the chain polymeric from being solubilized.     

Polyurethane foams derived from liquefied mountain pine beetle‐infested barks

In this study, lodgepole pine (Pinus contorta Dougl.) bark infested by the mountain pine beetles (Dendroctonus ponderosae hopkins) was liquefied using either polyethylene glycol (PEG) or polyethylene glycol/glycerol (PEG/G) as the solvent. It was found that the addition of glycerol to PEG reduced the residue ratio during bark liquefaction. The liquefied bark fraction obtained by using PEG/G had a slightly higher hydroxyl number than that obtained by using PEG. The residue from PEG/G liquefaction contained less lignin and more cellulose than the residue from PEG liquefaction. Various polyurethane foams containing liquefied bark fractions were made, and it was found that the weight ratios of liquefied bark to pMDI used in foam formulation and bark liquefaction solvents affected the density, gel content, thermal stability, mechanical properties, and the cell structure of the resulting foams. © 2011 Wiley Periodicals, Inc. J Appl Polym Sci, 2012     

Behavior of cellulose liquefaction after pretreatment using ionic liquids with water mixtures

Ionic liquid (IL)‐water mixtures were applied in cellulose pretreatment experiment and the pretreated cellulose was used in subsequent phenol liquefaction process as a new application method. Cellulose recovery rate and the average molecular weight (M_w) of pretreated cellulose were investigated to understand the influence of these mixtures on cellulose structure. X‐ray diffraction, Fourier transform infrared, gel permeation chromatograph, and scanning electron microscope were used to clarify the changes of pretreated cellulose. The liquefied residues from untreated cellulose and pretreated cellulose were considered as significant index to determine the effect of IL‐water mixtures on cellulose. Moreover, liquefied residues were initially characterized by the variation of the average M_w. It was suggested that the lower M_w of cellulose obtained in IL‐water mixtures, and the crystalline structure was disrupted. So, some cracks were found on the cellulose surface obviously. The liquefied residues result suggested that the pretreated cellulose obtained the lower residues at the same time or the same amount of residues by using the less time. The behavior of cellulose liquefaction efficiency using IL‐water mixture pretreatment was discussed. The lower M_w of cellulose was the major factor, which accelerates the cellulose phenol liquefaction process efficiency. © 2014 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2014 , 131, 40255.     

Liquefaction characteristics of selected vitrinite- and liptinite-rich coals from British Columbia,Canada

Four coals from British Columbia, Canada are described micropetrographically, and their liquefaction potential was tested in a rocking autoclave system. Rank was determined by measuring vitrinite reflectances and was found to range from subbituminous C to high volatile A bituminous. Composition was determined by maceral analysis. All four coals were found to be extremely high in the reactive maceral groups vitrinite and liptinite (> 97%) and were thus considered to be susceptible for liquefaction.Results of the liquefaction experiments indicate that in fact all four coals were converted easily into liquid and gaseous products. Overall conversion was found to be >90% and liquid yields (THF solubles) were beyond 80%. Alginite-rich coals from southeastern British Columbia were found to produce greater amounts of gases, indicating that temperatures used in the experiments might have been excessive for liquefaction of alginite-rich coals. Higher liquid yields and less gaseous products were obtained from the vitrinite-rich coals from northeastern British Columbia, indicating that these coals might have the optimum blend of vitrinite/liptinite macerals.     

Extraction and characterization of holocellulose fibers by microwave‐assisted selective liquefaction of bamboo

Microwave‐assisted selective liquefaction was proposed and used as a novel method for the isolation of holocellulose fibers. The results showed that the bamboo lignin component and extractives were almost completely removed by using a liquefaction process at 120 °C for 9 min, and the residual lignin and extractives in the solid residue were as low as 0.65% and 0.49%, respectively. Increasing the reaction temperature or time could decrease the solid yield, but they can also enhance the removal of lignin and extractives from bamboo particles and increase the holocellulose content in the solid residue. The absorbance bands that characterized functional groups of lignin on the Fourier transform infrared spectra of the solid residue weakened or disappeared. The solid residue showed high crystallinity, indicating the removal of noncellulosic material. Small cracks were observed on the SEM images of the residue, which indicated that the fibers from liquefaction may be susceptible to chemical access or enzyme attack. © 2016 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2016 , 133, 43394.     

Rigid polyurethane foams derived from cork liquefied at atmospheric pressure

The aim of this study was to evaluate the possibility of using polyols derived from liquefied cork in the production of novel bio‐based polyurethane foams (PUFs). For that purpose, different liquefaction conditions were used at atmospheric pressure and moderate temperature where poly(ethylene glycol) and glycerol were used as solvents and sulfuric acid as catalyst. The ensuing polyols were used to produce foams which were characterized using structural, morphological, thermal and mechanical analyses to demonstrate that liquefaction conditions play a crucial role in the properties of the foams. The resulting foams exhibited the typical cellular structure of PUFs with low densities (57.4–70.7 kg m^?3) and low thermal conductivities (0.038–0.040 W m^?1 K^?1). However, the mechanical properties differed significantly depending on the liquefaction conditions. The best stress–strain results were obtained for PUFs prepared using the polyol with lowest I_OH and water content (Young's modulus of 475.0 kPa, compressive stress (σ_10%) of 34.6 kPa and toughness of 7397.1 J m^?3). This PUF was thermally stable up to 200 °C and presented a glass transition temperature of around 27 °C. The results obtained demonstrate that these polyols from liquefied cork yield PUFs that are adequate materials for insulation applications. © 2014 Society of Chemical Industry     

Effects of ion-exchanged calcium, barium and magnesium on cross-linking reactions during direct liquefaction of oxidized lignite

In this work the influences of alkaline earth metals on cross-linking reactions (CLRs) during direct liquefaction of lignite were investigated. The oxidized lignite, which has been proved to be appropriate for quantitatively examine the extent of CLR during direct liquefaction, was used as a model coal to study the effects of ion-exchanged calcium, barium and magnesium on CLR during direct liquefaction of the oxidized lignite. The amounts of tetrahydrofuran (THF) insoluble solid products after liquefaction were used to quantitatively evaluate the CLR during liquefaction of the ion-exchanged coal. The results show that the oxidized coal is appropriate to quantitatively examine the extent of CLR and the targeted ions are exchanged to the oxidized coal in the form of highly-dispersed ion. The ion-exchanged Mg^2 + suppresses the CLR during direct liquefaction of coal at both low and high temperature. However, the exchanged Ca^2 + always promotes the CLR at the selected temperatures. While the exchanged Ba^2 + promotes the CLR at low temperature, but suppresses it at high temperature.     

Lignin Structural Changes During Liquefaction in Acidified Ethylene Glycol

Abstract

Beech (Fagus Sylvatica) milled-wood lignin was used as a model substrate in a study of lignin-catalyzed liquefaction in the presence of p-toluene sulfonic acid monohydrate (PTSA) or sulphuric acid as the catalysts. The structural changes that lignin undergoes during the treatment were studied by NMR spectroscopy, FTIR, size-exclusion chromatography, and high-performance liquid chromatography. For the sulphuric acid-catalyzed liquefaction, it was shown that the greater hydronium ion concentration in the reaction mixture induced formation of more condensed structures compared to the ones obtained after PTSA-catalyzed liquefaction. In addition, lignin during the PTSA-catalyzed liquefaction suffered degradation and was functionalized by the ethylene glycol. Gradual introduction of the ethylene glycol moieties into the lignin structure formed a condensed lignin-based polymeric material with predominant aromatic hydroxyl groups. HPLC and NMR analysis of the liquefied lignin with low-molecular mass fraction confirmed the presence of lignin monomers and further conversion of initially identified products into the aliphatic, aromatic (syringyl- and guaiacyl-based) esters and acids.     

Investigation of liquefied wood residues based on cellulose,hemicellulose, and lignin

Chinese eucalyptus was subjected to a liquefaction process using glycerol/ethylene glycol (EG) as liquefaction solvent. The effects of various liquefaction conditions, including reaction time, liquefaction temperature, acid concentration, and liquor ratio on the chemical composition of liquefied wood residues were studied. The results showed that the whole liquefaction process took place in two stages, the liquefaction yield of wood depended on the reaction temperature, acid concentration and liquor ratio. With increased acid concentration the liquefaction yield, acid‐insoluble lignin, and hemicellulose content of the residues were increased, and the relative content of cellulose was decreased. Fourier transform infrared (FT‐IR) analyses of the residues showed that hemicellulose and lignin were almost decomposed at the initial stages of reaction. © 2011 Wiley Periodicals, Inc. J Appl Polym Sci, 2011     

Kinetic study on the liquefaction of bagasse in polyhydric alcohols based on the cell wall component of the liquefied residue

Natural lignocellulose differs from the synthetic polymer due to the mineral matter which has a great influence on its degradation. To better understand lignocelluloses liquefaction, the bagasse was liquefied in alcoholic solvent [polyethylene glycol (PEG 400)/glycerol] catalyzed by sulfuric acid at 140–180 °C under atmospheric pressure. The amount of major components (cellulose, hemicellulose, lignin and ash) in the liquefied residue was used as a measurement of the extent of liquefaction. The results showed that hemicellulose is the most reactive component to liquefaction among other major cell wall components, followed by the lignin and cellulose. The content of the ash increased slowly with the reaction time under all reaction temperatures due to the re-condensation or re-precipitation of liquefied components. Based on the experimental results, the reaction kinetics for bagasse liquefaction was modeled and the activation energies, frequency factors and reaction orders for cellulose and lignin were calculated in a conventional manner. The activation energies for the liquefaction of lignin, cellulose and bagasse were 30.51 kJ mol−1, 72.83 kJ mol−1, and 67.09 kJ mol−1, respectively. The results of the enthalpy indicated the liquefaction of biomass is a highly endothermic reaction process. A better understanding to the liquefaction kinetics of biomass could be conducted based on the cell wall component of the liquefied residue.     

Pretreatment of wood flour slurries prior to liquefaction

As part of the UDES-S solvolytic approach to wood fractionation and liquefaction, a pretreatment stage has been developed using a fed batch technique to produce high solids content slurries. By using a combination of temperature and shear stress across homogenizing valves, wood flour slurries of Populus spp having concentrations of 20-32% by weight in both paraffin oil and ethylene glycol have been produced. Optical and scanning electron microscopy have shown that the recirculation loop and homogenizing valve cause structural degradation, defibration and defibrillation of the original particles as well as partial solubilization of the wood components. The maximum wood flour concentration, attainable before plugging was observed in the small scale system used, was just below 36% by weight. High concentration slurries are a prerequisite in order to obtain realistic reactor space velocities in biomass liquefaction processes.     

Liquid discharge plasma for fast biomass liquefaction at mild conditions: The effects of homogeneous catalysts

Non-thermal plasma exhibits unique advantages in biomass conversion for the sustainable production of higher-value energy carriers. Different homogeneous catalysts are usually required for plasma-enabled biomass liquefaction to achieve time-and energy-efficient conversions. However, the effects of such catalysts on the plasma-assisted liquefaction process and of the plasma on those catalysts have not been thoroughly studied. In this study, an electrical discharge plasma is employed to promote the direct liquefaction of sawdust in a mixture of polyethylene glycol 200 and glycerol. Three commonly used chemicals, sulfuric acid, nitric acid and sodium p-toluene sulfate, were selected as catalysts. The effects of the type of catalyst and concentration on the liquefaction yield were examined; further, the roles of the catalysts in the plasma liquefaction process have been discussed. The results showed that the liquefaction yield attains a value of 90% within 5 min when 1% sulfuric acid was employed as the catalyst. Compared with the other catalysts, sulfuric acid presents the highest efficiency for the liquefaction of sawdust. It was observed that hydrogen ions from the catalyst were primarily responsible for the significant thermal effects on the liquefaction system and the generation of large quantities of active species; these effects directly contributed to a higher efficacy of the plasma-enabled liquefaction process.     

Liquefaction of Red Pine Wood,Pinus densiflora,Biomass Using Peg-400-Blended Crude Glycerol for Biopolyol and Biopolyurethane Production

Red pine wood, Pinus densiflora, biomass was liquefied through liquefaction using a solvent mixture of crude glycerol and PEG-400 with a sulfuric acid catalyst. The liquefaction process parameters of crude glycerol/PEG-400 blending ratio, biomass loading, acid loading, reaction temperature, and reaction time were optimized. Biopolyol with 61.9% biomass conversion was produced at 170°C within 1 h using a co-solvent of crude glycerol and PEG-400 (5/5, w/w), 15% biomass loading, and 3% sulfuric acid loading. The biopolyol possessed a 4.2 mg KOH/g acid number and 892.4 mg KOH/g hydroxyl number. Polyurethane foam was successfully synthesized from the liquefied red pine wood biomass with toluene diisocyanate. The synthesis of biopolyurethane derived from red pine wood biopolyol was confirmed with FT-IR.     

Microwave‐assisted hydrothermal liquefaction of lignin for the preparation of phenolic formaldehyde adhesive

This study aimed to produce phenolic formaldehyde (PF) adhesives using the liquefaction product of bagasse lignin (LPBL) as a partial substitute for petroleum‐based phenol. Lignin was extracted from bagasse using 93% acetic acid solution and was rapidly degraded in hot‐compressed water by microwave heating using oxalic acid as catalyst. The liquefaction yield reached 78.69% under the optimal reaction condition. Gas chromatography–mass spectrometry (GC/MS) analysis showed that the main chemical compounds of the liquefaction product included mono‐substituted and bis‐substituted phenols, such as 2,6‐dimethoxyphenol, 4‐hydroxybenzaldehyde, and so on. The LPBL was employed to replace a portion of phenol at varying ratios from 0 to 20 wt % in the preparation of PF adhesives. The molecular weight, viscosity, and adhesive strength of LPBL‐PF adhesives were found to be lower than those of pure PF adhesives. With the phenol replaced by LPBL up to 20%, the viscosity and adhesive strength of the resin were 4.046 Pa s and 1.017 MPa, respectively. © 2016 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2017 , 134, 44510.     

Hydroliquefaction of subbituminous coal Effectiveness of pretreatment by organic reduction with Na or k

Hydroliquefaction of subbituminous Taiheiyo coal, without any pretreatment and after organic reduction, was carried out in the presence of tetralin using fine iron powder as catalyst. Two pretreatment procedures were used (A) reduction of coal with Na in liquid ammonia solution and (B) treatment with K in refluxing THF. Samples of treated coal with well-dispersed iron powder were prepared by co-reduction of coal coated with FeBr₂ using both procedures. Non-catalytic liquefaction of coal treated by A showed double the yield of hexane-solubles compared with that from liquefaction of the original coal while non-catalytic liquefaction of the coal treated by B roughly tripled the hexane-solubles yield and consumed the same amount of hydrogen. The presence of iron powder increased hexane-solubles by 5 wt% while increasing benzene-solubles by 13 wt% compared with non-catalytic liquefaction of treated coal by procedure B. The coals prepared by co-reduction (A and B) showed highest conversion (73 and 77%) along with highest yield of HS (38 and 43%). This significant effect on hydroliquefaction could be correlated with a slight increase of hydrogen atoms added to coal organic materials and the loosening of clusters of aromatic sheets.     

Characterization of liquefied wood residues from different liquefaction conditions

The amount of wood residue is used as a measurement of the extent of wood liquefaction. Characterization of the residue from wood liquefaction provides a new approach to understand some fundamental aspects of the liquefaction reaction. Residues were characterized by wet chemical analyses, Fourier transform infrared (FTIR) spectroscopy, X‐ray diffraction (XRD), and scanning electron microscopy (SEM). The Klason lignin content of the residues decreased, while the holocellulose and α‐cellulose contents increased as the phenol to wood ratio (P/W) increased. A peak at 1735 cm^?1, which was attributed to the ester carbonyl group in xylan, disappeared in the FTIR spectra of the residues from liquefied wood under a sealed reaction system, indicating significantly different effects of atmospheric versus sealed liquefaction. The crystallinity index of the residues was higher than that of the untreated wood particles and slightly increased with an increase in the P/W ratio. The SEM images of the residues showed that the fiber bundles were reduced to small‐sized bundles or even single fibers as the P/W ratio increased from 1/1 to 3/1, which indicated that the lignin in the middle lamella had been dissolved prior to the cellulose during liquefaction. © 2007 Wiley Periodicals, Inc. J Appl Polym Sci, 2007     

Liquefaction behaviors of bamboo residues in a glycerol‐based solvent using microwave energy

Liquefaction of bamboo was performed in glycerol–methanol as co‐solvent using microwave energy and was evaluated by characterizing the liquefied residues. High efficiency conversion of bamboo was achieved under mild reaction conditions. Liquefaction temperature and time interacted to affect the liquefaction reaction. Fourier transform infrared analyzes of the residues indicated that hemicellulose and lignin could easily undergo recondensation. Thermogravimetric analysis results showed that residues obtained at higher temperature/longer reaction time displayed a superior thermal stability as compared to those obtained from mild conditions. Moreover, significant differences were observed in the morphology and structures of residues from different liquefaction conditions according to scanning electron microscopy images. © 2013 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2014 , 131, 40207.     

Preparation and application of phosphorous‐containing bio‐polyols in polyurethane foams

A bio‐polyol phosphonate acting as the polyol component in the preparation of polyurethane foam was synthesized from the liquefaction product of bagasse by the halogenation of the liquefaction product followed by the Michaelis–Arbuzov rearrangement. The FT‐IR spectra showed that phosphorus‐containing groups were introduced into the polyol chain. The data of the viscosity and the hydroxyl number suggested that the bio‐polyol phosphonate would be a good polyol component in the preparation of polyurethane foam. The limiting oxygen index of polyurethane foam containing bio‐polyol phosphonate varied in the range of 24–28, while that of polyurethane foam without bio‐polyol phosphonate was 23, demonstrating that the introduction of the phosphorus‐containing group into the polymer helped to improve the flame retardancy. © 2014 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2014 , 131, 40422.     

氢含量对含氢甲烷氮膨胀液化流程的影响

在以焦炉煤气或者煤制甲烷等含氢甲烷为原料生产液化天然气时,氢气含量会对液化流程产生较大影响。以氮气膨胀液化流程为考察对象,模拟了各种含氢量的含氢甲烷的液化流程。以单位功耗为第一优化目标优化流程,发现在回收率一定时,单位功耗随着含氢量的增加而增加;当含氢量一定时,随着回收率的提升,单位功耗显著增加。研究结果表明,仅采用液化而不采用精馏分离,可以从含氢天然气生产出高质量的LNG产品,流程的单位能耗和产品纯度均在可接受的范围。     

不同介质条件下竹材的液化反应动力学

采用非等温差热分析(DTA)技术,分析了竹材在苯酚和酚油介质条件下液化反应动力学的影响。运用Kissinger方程在不同的升温速率下进行动力学研究,并由动态DTA曲线求出固化反应动力学参数,进而建立体系的液化反应动力学模型。实验结果表明,苯酚竹材液化体系(PLB)和酚油竹材液化体系(POLB)反应级数分别为0.905 9和0.950 5,平均活化能分别为68.95 kJ/mol和105.43 kJ/mol,指前因子分别为4.08×104s-1和8.91×104s-1;两者的反应级数较为接近,说明PLB和POLB的液化反应模式基本相同;与POLB相比,PLB液化体系液化能耗和液化温度相对较低。由外推法得出竹材液化反应最佳工艺为:液化介质为苯酚,初始液化温度为70.4℃,液化峰高温为110.5℃,液化峰终温为126.8℃。