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Kuhnel I.,Sudan University of Science and Technology | Saake B.,Sudan University of Science and Technology | Lehnen R.,Thunen Institute of Wood Research
Industrial Crops and Products | Year: 2017

Beech wood organosolv lignin was modified with propylene carbonate (PC) in an efficient, facile and solvent-free procedure without using highly toxic and explosive propylene oxide (PO). Comparative studies of the oxyalkylation procedure were performed varying crucial reaction conditions. The results of FTIR, 1H NMR, 13C NMR and 31P NMR spectroscopic analyses revealed that the OH group activation of lignins differed significantly depending on catalyst, catalyst to lignin ratio, reaction time, temperature and PC amount. Under optimized reaction conditions using 1,8-diazabicyclo[5.4.0]undec-7-ene (DBU) as catalyst, a degree of substitution (DS) of 0.92 and chain lengths of up to 4.6 propyl units were achieved, yielding 0.3% of carbonate linkages in the grafted chain. This oxyalkylation procedure using safe and non-toxic PC represents a promising alternative to PO for the preparation of lignin polyols concerning the substitution of conventional petroleum-based polyols. © 2017 Elsevier B.V.


Elliott D.C.,Pacific Northwest National Laboratory | Oasmaa A.,VTT Technical Research Center of Finland | Meier D.,Thunen Institute of Wood Research | Preto F.,CANMET Energy | Bridgwater A.V.,Aston University
Energy and Fuels | Year: 2012

An international round robin study of the viscosity measurements and aging of fast pyrolysis bio-oil has been undertaken recently, and this work is an outgrowth from that effort. Two bio-oil samples were distributed to two laboratories for accelerated aging tests and to three laboratories of long-term aging studies. The accelerated aging test was defined as the change in viscosity of a sealed sample of bio-oil held for 24 h at 80 °C. The test was repeated 10 times over consecutive days to determine the intra-laboratory repeatability of the method. Other bio-oil samples were placed in storage at three temperatures, 21, 5, and -17 °C, for a period of up to 1 year to evaluate the change in viscosity. The variation in the results of the accelerated aging test was shown to be low within a given laboratory. The long-term aging studies showed that storage of a filtered bio-oil under refrigeration can minimize the amount of change in viscosity. The accelerated aging test gave a measure of change similar to that of 6-12 months of storage at room temperature for a filtered bio-oil. Filtration of solids was identified as a key contributor to improving the stability of the bio-oil as expressed by the viscosity based on results of the accelerated aging tests as well as long-term aging studies. Only the filtered bio-oil consistently gave useful results in the accelerated aging and long-term aging studies. The inconsistency suggests that better protocols need to be developed for sampling bio-oils. These results can be helpful in setting standards for use of bio-oil, which is just coming into the marketplace. © 2012 American Chemical Society.


Meier D.,Thunen Institute of Wood Research | Van De Beld B.,BTG | Bridgwater A.V.,Aston University | Elliott D.C.,Pacific Northwest National Laboratory | And 2 more authors.
Renewable and Sustainable Energy Reviews | Year: 2013

Fast pyrolysis of biomass is becoming increasingly important in some member countries of the International Energy Agency (IEA). Six countries have joined the IEA Task 34 of the Bioenergy Activity: Canada, Finland, Germany, Netherlands, UK, and USA. The National Task Leaders give an overview of the current activities in their countries both on research, pilot and demonstration level. © 2012 Elsevier Ltd.


Struven J.O.,Thunen Institute of Wood Research | Meier D.,Thunen Institute of Wood Research
ACS Sustainable Chemistry and Engineering | Year: 2016

Hydrothermal conversion of organosolv lignin has been conducted under a reductive hydrogen atmosphere near the critical point of water. Several Raney nickel catalysts were tested with respect to degree of liquefaction, yields of phenols, and influence on the product distribution. The application of Raney nickel catalysts is crucial for the hydrothermal liquefaction of lignin since the liquefaction rate increased approximately 2.5 times compared to hydrothermal conversion without catalysts. In addition, Raney nickel caused complete demethoxylation of guaiacyl and syringyl moieties resulting in an oil composed mainly of six highly reactive simple phenols (phenol and monoalkylated derivatives). Depending on the catalyst type, yields of these phenols were 1.3-8.0 wt % (≈2.6%-16% theoretical yield). Flash pressure release with subsequent condensation of the hot vapors proved to be a fast and easy approach to obtain a liquid fraction with a high content (25%) of phenol and para- or ortho-alkylated derivatives, which might be used in resin formulations. © 2016 American Chemical Society.


Brischke C.,Leibniz University of Hanover | Melcher E.,Thunen Institute of Wood Research
Wood Science and Technology | Year: 2015

While, for instance, oils and waxes were found to be promising for protecting wood under laboratory test conditions, long-term outdoor experience with these materials is limited. This study aimed at investigating the performance of wax-treated wood exposed aboveground in double-layer and lap-joint configurations. Wetting resistance, susceptibility to checking and durability were investigated over several years. All wax-treated wood performed better in the lap-joint exposure than in double layer, which was characterized by severe moisture trapping. However, durability and moisture performance were considerably better compared to untreated controls, but diminished with increasing exposure time. Already after 1 year of exposure, the number of cracks on lap-joint specimens was nearly identic between treated and untreated samples. Due to the wax migration observed during exposure, the formation of checks, accumulation of water in treated samples and partial infection, it can be concluded that the chosen synthetic wax types are not recommendable for practical applications. On the other hand, the principle of wood protection through moisture protection became evident in the aboveground field tests: As long as moisture exclusion was assured, the development of decay was inhibited. © 2014, Springer-Verlag Berlin Heidelberg.


Janzon R.,Sudan University of Science and Technology | Schutt F.,Thunen Institute of Wood Research | Oldenburg S.,Economy Energy | Fischer E.,DBFZ German Biomass Research Center | And 2 more authors.
Carbohydrate Polymers | Year: 2014

Steam refining of non-debarked spruce forest residues was investigated as pretreatment for enzymatic hydrolysis as well as for biogas production. Pretreatment conditions were varied in the range of 190-220 C, 5-10 min and 0-3.7% SO2 according to a statistical design. For both applications highest product yields were predicted at 220 C and 2.4% SO2, whereas the reaction time had only a minor influence. The conformity of the model results allows the conclusion that enzymatic hydrolysis is a suitable test method to evaluate the degradability of lignocellulosic biomass in the biogas process. In control experiments under optimal conditions the results of the model were verified. The yield of total monomeric carbohydrates after enzymatic hydrolysis was equivalent to 55% of all theoretically available polysaccharides. The corresponding biogas yield from the pretreated wood amounted to 304 mL/gODM. Furthermore, furans produced under optimal process conditions showed no inhibitory effect on biogas production. It can be concluded that steam refining opens the structure of wood, thus improving the enzymatic hydrolysis of the polysaccharides to fermentable monomeric sugars and subsequently enabling a higher and faster production of biogas. Anaerobic fermentation of pretreated wood is a serious alternative to alcoholic fermentation especially when low quality wood grades and residues are used. Anaerobic digestion should be further investigated in order to diversify the biorefinery options for lignocellulosic materials. © 2013 Elsevier Ltd. All rights reserved.


The study deals with younger glacial history (<5500 BP) of some remote high valleys in the Inner Himalaya. Field survey, geomorphological mapping, photo comparisons, equilibrium line altitude (ELA) lowerings, lichen findings as well as one radiocarbon date provide insights in the former behaviour of 25 subcontinental glaciers. Each glacier forefield is bordered by great lateral moraines, propably indicating the historical maximum glaciation (stage 1, <1700 yr. BP). Outside the forefield deposits occur moraine walls that were deposited during the neoglacial period (5500-2000 yr. BP). The last build up of the stage 1-moraines most likely took place during the Little IceAge (LIA)maximum(AD1600-1800). Between the stage 1-moraines and the present glacier snouts, threemore glacier stages (2, 3 and 4) were mapped. Stages 2 and 3 could be correlated to cold and humid phases in the first half of the 19th century and in the beginning of the 20th century. Photographic material documents that the stage 4-moraines were deposited from ca. AD 1974 to 1980. The very similar moraine sequences in each glacier forefield, as well as the consistently documented glacier stage 4 around 1974 to 1980, support the hypothesis that the snouts of the comparably small (due to their low avalanche nourishment) and debris poor glaciers in the Inner Himalaya, respond relatively directly to climate signals. © 2014 by the Wadia Institute of Himalayan Geology, Dehradun 248001, India.


Perez-Cantu L.,TU Hamburg - Harburg | Schreiber A.,Sudan University of Science and Technology | Schutt F.,Thunen Institute of Wood Research | Saake B.,Sudan University of Science and Technology | And 2 more authors.
Bioresource Technology | Year: 2013

The increasing interest in lignocellulose-based biorefineries boosts the further development of the needed pretreatment methods for preprocessing biomass. There are a large number of different processes that are being investigated; however research is made mostly based on different types of biomass with the same pretreatment or several modifications of the same process for a given type of biomass. In this work a comparison of promising chemical pretreatments using the same biomass was performed. Organosolv (OS), Steam (SE) and Liquid-Hot-Water (LHW) processes were used for the pretreatment of rye straw and the treated solids further enzymatically hydrolyzed. Best results for carbohydrate and lignin yield were found for the OS pretreatment followed close by the LHW and SE with similar results. All of the processes showed satisfactory performance for the pretreatment of lignocellulosic biomass for application in the second generation biorefinery. © 2013 Elsevier Ltd.


Feng Y.,University of Hamburg | Meier D.,Thunen Institute of Wood Research
Biomass and Bioenergy | Year: 2016

Innovative extraction methods with supercritical CO2 and liquid CO2 have been employed to obtain value-added chemicals from a slow pyrolysis liquid. Sequential solvent extraction with hexane and acetone was carried out for comparison. Pyrolysis liquid was first adsorbed on silica (SiO2) with weight ratios SiO2:oil of 100:40 and 100:80. Pyrolysis liquid and extracts were mainly characterized by GC-MS/FID, elemental analysis, and water content. Results show that scCO2 extraction is mainly controlled by dissolution at the first 3 h during a 6-h extraction period and by combination of dissolution and diffusion at later extraction periods. Around 60-65% of the CO2 and hexane extracts could be identified by GC compared to 49% of the starting pyrolysis liquid. GC data confirmed that, CO2 extraction effectively enriched both non-aromatics and aromatic compounds. Hexane extracts contained lower contents of organic acids. Hexane enabled a complete extraction of aromatics. Chemical composition of extracts from scCO2 and liquid CO2 are very similar. Extraction with scCO2 and liquid CO2 proves to be an effective and innovative pre-treatment process for the production of chemicals from pyrolysis liquid. © 2016 Elsevier Ltd.


Choi H.S.,Yonsei University | Meier D.,Thunen Institute of Wood Research
Journal of Analytical and Applied Pyrolysis | Year: 2013

Screening of pyrolysis reactions has been carried out with Kraft lignin and various catalysts applying the TI-mini fast pyrolyzer. Zeolite HZSM-5, FCC and Olivine in a small fixed bed were used as catalyst to investigate their influences on the pyrolysis reaction. The characteristics of catalytic pyrolysis reactions and final products were studied by varying reaction temperature and catalyst type. The TI-mini fast pyrolyzer is especially suitable to obtain quick mass balances of main products such as char, non-condensable gases and biocrude-oil. Their yields were evaluated and the collected biocrude-oil was further analyzed using GC-MS/FID. Depending on the various catalysts as well as different pyrolysis temperatures, the overall distribution of the three main product categories and the portions of certain chemical compounds were increased or decreased. To scrutinize the catalytic effect and to highlight the severity of lignin degradation, size exclusion chromatography (SEC) was performed from extracts of the solid residue. © 2013 Elsevier B.V.

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