Separation of phenols and furfural by pervaporation and reverse osmosis membranes from biomass--superheated steam pyrolysis-derived aqueous solution

The separation of valuable chemicals from raw products, where a great number of chemicals coexist, is the key technology in biomass refinery. In this study, the applicability of membrane separation of valuable chemicals from our currently developed portable superheated steam (SHS) biomass pyrolysis process was demonstrated. Phenols (phenol, p-cresol, guaiacol, methyl guaiacol, and ethyl guaiacol), furfural, and acetone were successfully separated by pervaporation using the silicone rubber membrane from model solutions and an actual SHS derived aqueous solution. The solution was also concentrated effectively by reverse osmosis separation using a polyamide membrane. When a high concentration of SHS solution was fed to the pervaporation process, a phase-separated permeate was obtained, which indicated that the reverse osmosis concentration combined with pervaporation separation is useful for the superheated steam process.     

Mild hydrogenolysis of in-situ and isolated Pinus radiata lignins

The Pd/C-catalysed hydrogenolysis of in-situ and isolated lignins from Pinus radiata wood was investigated to gain a more complete understanding of the factors affecting yield and composition of the hydrogenolysis products. Such hydrogenolysis products could potentially be refined into aromatic feedstock chemicals providing sustainable alternatives to petroleum-derived phenols. Lignins were converted into solvent-soluble oils composed of monomeric, dimeric and oligomeric products in high yields, up to 89% of the original lignin. The main monomer products were dihydroconiferyl alcohol and 4-n-propyl guaiacol. Dimeric and oligomeric compounds constituted 75% of the hydrogenolysis oils and were mainly composed of dihydroconiferyl alcohol and 4-n-propyl guaiacol units linked by β-5, 5-5, 4-O-5 and β-1 linkages. Hydrogenolysis of steam exploded wood gave lower yields of lignin hydrogenolysis products compared to unmodified wood due to fewer reactive aryl-ether linkages in the lignin.     

Novel Single-step Pretreatment of Steam Explosion and Choline Chloride to De-lignify Corn Stover for Enhancing Enzymatic Edibility

It is important to develop efficient and economically feasible pretreatment methods for lignocellulosic biomass, to increase annual biomass production. A number of pretreatment methods were introduced to promote subsequent enzymatic hydrolysis of biomass for green energy processes. Pretreatment with steam explosion removes the only xylan at high severity but increases lignin content. In this study, corn stover soaked in choline chloride solution before the steam explosion is economically feasible as it reduced cost. Enzymatic hydrolysis of de-lignified corn stover is enhanced by combinatorial pretreatments of steam explosion and choline chloride. Corn stover pretreated with choline chloride at the ratio of 1:2.2 (w/w), 1.0 MPa, 184 °C, for 15 min efficiently expelled 84.7% lignin and 78.9% xylan. The residual solid comprised of 74.59% glucan and 7.51% xylan was changed to 84.2% glucose and 78.3% xylose with enzyme stacking of 10FPU/g. This single-step pretreatment had ∼ 4.5 and 6.4 times higher glucose yield than SE-pretreated and untreated corn stover, respectively. Furthermore, SEM, XRD and FTIR indicated the porosity, crystalline changes, methoxy bond-cleavage respectively due to the lignin and hemicellulose expulsion. Thus, the released acetic acid during this process introduced this novel strategy, which significantly builds the viability of biomass in short pretreatment time.     

Routes to Potential Bioproducts from Lignocellulosic Biomass Lignin and Hemicelluloses

An essential feature of proposed fermentation-based lignocellulose to biofuel conversion processes will be the co-production of higher value chemicals from lignin and hemicellulose components. Over the years, many routes for chemical conversion of lignin and hemicelluloses have been developed by the pulp and paper industry and we propose that some of these can be applied for bioproducts manufacturing. For lignin products, thermochemical, chemical pulping, and bleaching methods for production of polymeric and monomeric chemicals are reviewed. We conclude that peroxyacid chemistry for phenol and ring-opened products looks most interesting. For hemicellulose products, preextraction of hemicelluloses from woody biomass is important and influences the mixture of solubilized material obtained. Furfural, xylitol, acetic acid, and lactic acid are possible targets for commercialization, and the latter can be further converted to acrylic acid. Pre-extraction of hemicelluloses can be integrated into most biomass-to-biofuel conversion processes.     

Characterization of primary thermal degradation features of lignocellulosic biomass after removal of inorganic metals by diverse solvents

Poplar wood powders were treated with distilled water, tap water, HCl and HF, respectively, to remove inorganics from the biomass and to investigate effect of demineralization processes on pyrolysis behavior of the biomass. TG and DTG revealed that maximum degradation temperatures rose slightly from 362°C for control to 372°C, 366°C and 368°C after demineralization with distilled water, HCl and HF, respectively. Maximum degradation rates also increased from 0.96%/°C for control to 1.15%/°C for HF-biomass, 1.23%/°C for DI-H(2)O-biomass, and 1.55%/°C for HCl-biomass. Analytical pyrolysis-GC/MS of demineralized biomasses produced approximately 45 pyrolysis compounds. Total amount of low molecular weight compounds, such as acetic acid, acetol, and 3-hydroxypropanal, was significantly lowered in the demineralized biomasses. But levoglucosan increased 2-10-folds in the demineralized biomasses. One of the features regarding lignin derivatives was the reduction of the amount of C6-type phenols, such as phenol, guaiacol, and syringol after demineralization.     

Microbial utilization of levoglucosan in wood pyrolysate as a carbon and energy source

The Waterloo Fast Pyrolysis Process (WFPP) can produce an organic liquid high in levoglucosan (1, 6-anhydro-beta-D-glucopyranose) content from suitably pretreated lignocellulosics. A variety of fungi and yeasts were screened for their ability to utilize and ferment this organic liquid. To enhance its fermentability, the pyrolysis tar was posttreated in three different ways: (1) an aqueous extract (lignin removed); (2) activated charcoal treated (lignin and aromatics removed); and (3) acid hydrolysate (lignin and aromatics removed with the levoglucosan hydrolyzed to glucose). Four fungal strains were examined. None grew in the aqueous extract, but all grew equally well in both the activated charcoal treated and the acid hydrolysate, suggesting that the aromatic species were inhibitory to growth. Seven yeast species were examined, two of which did not grow on any of the extracts. Five of the yeast strains grew well on both the aqueous extract as well as the activated charcoal extract. The hydrolysate was optimal in terms of biomass yield and ethanol production. Ethanol yields on the hydrolysate were comparable or better than those on glucose. Ethanol was also produced in the aqueous extract and activated charcoal-treated substrate, but yields were considerably lower than on the hydrolysate or glucose. It is apparent that a wood pyrolysate maximized for levoglucosan can serve as a fermentable substrate, although postpyrolysis clean-up appears necessary. (c) 1993 John Wiley & Sons, Inc.     

Phenol and phenolics from lignocellulosic biomass by catalytic microwave pyrolysis

Catalytic microwave pyrolysis of biomass using activated carbon was investigated to determine the effects of pyrolytic conditions on the yields of phenol and phenolics. The high concentrations of phenol (38.9%) and phenolics (66.9%) were obtained at the temperature of 589 K, catalyst-to-biomass ratio of 3:1 and retention time of 8 min. The increase of phenol and its derivatives compared to pyrolysis without catalysts has a close relationship with the decomposition of lignin under the performance of activated carbon. The concentration of esters was also increased using activated carbon as a catalyst. The high content of phenols obtained in this study can be used either directly as fuel after upgrading or as feedstock of bio-based phenols for chemical industry.     

Design,Construction, and Operation of a Fast Pyrolysis Plant for Biomass

A continuous fluidized‐bed plant (PDU‐scale) for fast pyrolysis of lingnocellulosic biomass gives rise to bio‐oil yields of 65 wt.‐%. The average reactor gas residence time was 1.2 s only. The gas and charcoal yields were 15–20 wt.‐%, respectively. The bio oils were chemically characterized. The main monomeric products of the thermal degradation of carbohydrates are acetic acid, hydroxyacetaldehyde, hydroxypropanone, and levoglucosan. The process described in this paper can also be used for disposal of inorganic‐, metal‐organic‐, and chlorine‐organic contaminated waste‐wood. Inorganic compounds of wood preservatives are concentrated in the charcoal fraction and can be separated easily. Chlorine‐organic wood preservatives are mostly degraded. The process has been positively tested as a technique for disposal, recycling, and exploitation of industrial biomass waste (wood waste, grinding grit, fibre sludge, cocoa shell and modern composites like HPL). Bio oil from fast pyrolysis can be used for the production of energy and chemical feedstock. Research for these purposes is ongoing.     

工业木质素预处理及催化转化苯酚

传统化石能源日益枯竭以及环境污染压力日益加大使得开发以生物质为代表的可替代能源迫在眉睫,木质素作为仅次于纤维素的生物质中第二大主要成分用来制备高附加值化学品是提高生物质资源利用效率的关键。本文将工业木质素进行预处理后采用双液相反应体系将工业木质素转化为苯酚等化合物,使用微波辐照代替传统的加热,考察了预处理方式、温度、时间等条件对产物收率的影响。结果表明,以1-甲基-3-乙基咪唑醋酸盐([EMIM]OAc)处理的工业木质素在微波反应器输出功率为400 W、反应温度为90℃、催化剂为1-甲基-3-胺乙基咪唑四氟硼酸盐([AEMIM]BF4)双液相反应体系中反应60 min苯酚的收率最高可达8.14%。     

Influence of lignin and its degradation products on enzymatic hydrolysis of xylan

The influence of lignin, lignin model compounds, and black liquor from the kraft pulping process on the hydrolysis of xylan by xylanase was investigated. Addition of vanillic acid, acetovanillone, and protocatechuic acid increased the rate of hydrolysis of xylan by as much as 18–50% at low concentrations, but reached maxima at about 0.05% concentration. Addition of vanillin caused a 15% improvement in xylan hydrolysis, while addition of guaiacol more than doubled the hydrolysis rate. Increasing concentrations of either lignin or black liquor also increased the hydrolysis rate of xylan. Circular dichroism spectroscopy indicated a change in the structure of xylanase in the presence of black liquor.     

芳香族化合物对斑玉蕈菌丝生物量、漆酶活性及其转录水平的影响

芳香族化合物适当时间适当浓度添加到培养基中,可提高真菌漆酶活性,有助于增强其对木质纤维素的利用效率。为了增强斑玉蕈漆酶活性,本文研究了8种芳香族化合物对其酶活的影响及其与菌丝生物量的相关性。研究发现在无诱导物条件下,斑玉蕈漆酶活性和菌丝生物量相关系数r为0.9956,说明它们呈正相关,但是整个培养过程漆酶活性相对较低;供试的芳香族化合物对漆酶活性都有不同程度的诱导作用,其中添加0.1mmol/L的愈创木酚对斑玉蕈漆酶活性诱导作用最大,达到3倍以上,同时提高了斑玉蕈菌丝生长速度和菌丝生物量;而随着添加时间的延长,部分化合物对漆酶活性和菌丝生物量都产生不同程度的抑制作用,这可能因为化合物对菌丝毒性的延长导致菌丝生长变慢或死亡;进一步研究发现,斑玉蕈3个漆酶同工酶基因lcc2、lcc3和lcc4在诱导剂愈创木酚的影响下转录水平都不同程度地上调。研究结果表明诱导漆酶活性可以提高斑玉蕈菌丝生长速度和生物量,暗示可能通过提高漆酶活性的方法,提高斑玉蕈的培养基利用效率。     

Sources of Biomass Feedstock Variability and the Potential Impact on Biofuels Production

Terrestrial lignocellulosic biomass has the potential to be a carbon neutral and domestic source of fuels and chemicals. However, the innate variability of biomass resources, such as herbaceous and woody materials, and the inconsistency within a single resource due to disparate growth and harvesting conditions, presents challenges for downstream processes which often require materials that are physically and chemically consistent. Intrinsic biomass characteristics, including moisture content, carbohydrate and ash compositions, bulk density, and particle size/shape distributions are highly variable and can impact the economics of transforming biomass into value-added products. For instance, ash content increases by an order of magnitude between woody and herbaceous feedstocks (from ～0.5 to 5 %, respectively) while lignin content drops by a factor of two (from ～30 to 15 %, respectively). This increase in ash and reduction in lignin leads to biofuel conversion consequences, such as reduced pyrolysis oil yields for herbaceous products as compared to woody material. In this review, the sources of variability for key biomass characteristics are presented for multiple types of biomass. Additionally, this review investigates the major impacts of the variability in biomass composition on four conversion processes: fermentation, hydrothermal liquefaction, pyrolysis, and direct combustion. Finally, future research processes aimed at reducing the detrimental impacts of biomass variability on conversion to fuels and chemicals are proposed.© 2015 Battelle Energy Alliance, LLC, contract manager for Idaho National Laboratory.     

A sequential method to analyze the kinetics of biomass pyrolysis

The kinetics of biomass pyrolysis was studied via a sequential method including two stages. Stage one is to analyze the kinetics of biomass pyrolysis and starts with the determination of unreacted fraction of sample at the maximum reaction rate, (1-α)(m). Stage two provides a way to simulate the reaction rate profile and to verify the appropriateness of kinetic parameters calculated in the previous stage. Filter paper, xylan, and alkali lignin were used as representatives of cellulose, hemicellulose, and lignin whose pyrolysis was analyzed with the assumption of the orders of reaction being 1, 2, and 3, respectively. For most of the biomass pyrolysis, kinetic parameters were properly determined and reaction rate profiles were adequately simulated by regarding the order of reaction as 1. This new method should be applicable to most of the biomass pyrolysis and similar reactions whose (1-α)(m) is acquirable, representative, and reliable.     

Acid-catalyzed conversion of xylose, xylan and straw into furfural by microwave-assisted reaction

Furfural is a biomass derived-chemical that can be used to replace petrochemicals. In this study, the acid-catalyzed conversion of xylose and xylan to furfural by microwave-assisted reaction was investigated at selected ranges of temperature (140-190 °C), time (1-30 min), substrate concentration (1:5-1:200 solid:liquid ratio), and pH (2-0.13). We found that a temperature of 180 °C, a solid:liquid ratio of 1:200, a residence time of 20 min, and a pH of 1.12 gave the best furfural yields. The effect of different Brønsted acids on the conversion efficiency of xylose and xylan was also evaluated, with hydrochloric acid being found to be the most effective catalyst. The microwave-assisted process provides highly efficient conversion: furfural yields obtained from wheat straw, triticale straw, and flax shives were 48.4%, 45.7%, and 72.1%, respectively.     

Lignin depolymerization/repolymerization and its critical role for delignification of aspen wood by steam explosion

Steam explosion is an important process for the fractionation of biomass components. In order to understand the behaviour of lignin under the conditions encountered in the steam explosion process, as well as in other types of steam treatment, aspen wood and isolated lignin from aspen were subjected to steam treatment under various conditions. The lignin portion was analyzed using NMR and size exclusion chromatography as major analytical techniques. Thereby, the competition between lignin depolymerization and repolymerization was revealed and the conditions required for these two types of reaction identified. Addition of a reactive phenol, 2-naphthol, was shown to inhibit the repolymerization reaction strongly, resulting in a highly improved delignification by subsequent solvent extraction and an extracted lignin of uniform structure.     

Lignin Pyrolysis Components and Upgrading—Technology Review

Biomass pyrolysis oil has been reported as a potential renewable biofuel precursor. Although several review articles focusing on lignocellulose pyrolysis can be found, the one that particularly focus on lignin pyrolysis is still not available in literature. Lignin is the second most abundant biomass component and the primary renewable aromatic resource in nature. The pyrolysis chemistry and mechanism of lignin are significantly different from pyrolysis of cellulose or entire biomass. Therefore, different from other review articles in the field, this review particularly focuses on the recent developments in lignin pyrolysis chemistry, mechanism, catalysts, and the upgrading of the bio-oil from lignin pyrolysis. Although bio-oil production from pyrolysis of biomass has been proven on commercial scale and is a very promising option for production of renewable chemicals and fuels, there are still several drawbacks that have not been solved. The components of biomass pyrolysis oils are very complicated and related to the properties of bio-oil. In this review article, the details about pyrolysis oil components particularly those from lignin pyrolysis processes will be discussed first. Due to the poor physical and chemical property, the lignin pyrolysis oil has to be upgraded before usage. The most common method of upgrading bio-oil is hydrotreating. Catalysts have been widely used in petroleum industry for pyrolysis bio-oil upgrading. In this review paper, the mechanism of the hydrodeoxygenation reaction between the model compounds and catalysts will be discussed and the effects of the reaction condition will be summarized.     

Fractionation of wheat straw by atmospheric acetic acid process

Fractionation of wheat straw was investigated using an atmospheric acetic acid process. Under the typical conditions of 90% (v/v) aqueous AcOH, 4% H(2)SO(4) (w/w, on straw), ratio of liquor to straw (L/S) 10 (v/w), pulping temperature 105 degrees C, and pulping time 3h, wheat straw was fractionated to pulp (cellulose), lignin and monosaccharides mainly from hemicellulose with yields of approximately 50%, 15% and 35%, respectively. Acetic acid pulp from the straw had an acceptable strength for paper and could be bleached to a high brightness over 85% with a short bleaching sequence. Acetic acid pulp was also a potential feedstock for fuels and chemicals. The acetic acid process separated pentose and hexose in wheat straw to a large extent. Most of the pentose (xylan) was dissolved, whereas the hexose (glucan) remained in the pulp. Approximately 30% of carbohydrates in wheat straw were hydrolyzed to monosaccharides during acetic acid pulping, of which xylose accounted for 70% and glucose for 12%. The acetic acid lignin from wheat straw showed relatively lower molecular weight and fusibility, which made the lignin a promising raw material for many products, such as adhesive and molded products.     

Biological upgrading of pyrolysis-derived wastewater: Engineering Pseudomonas putida for alkylphenol,furfural, and acetone catabolism and (methyl)muconic acid production

While biomass-derived carbohydrates have been predominant substrates for biological production of renewable fuels, chemicals, and materials, organic waste streams are growing in prominence as potential alternative feedstocks to improve the sustainability of manufacturing processes. Catalytic fast pyrolysis (CFP) is a promising approach to generate biofuels from lignocellulosic biomass, but it generates a complex, carbon-rich, and toxic wastewater stream that is challenging to process catalytically but could be biologically upgraded to valuable co-products. In this work, we implemented modular, heterologous catabolic pathways in the Pseudomonas putida KT2440-derived EM42 strain along with the overexpression of native toxicity tolerance machinery to enable utilization of 89% (w/w) of carbon in CFP wastewater. The dmp monooxygenase and meta-cleavage pathway from Pseudomonas putida CF600 were constitutively expressed to enable utilization of phenol, cresols, 2- and 3-ethyl phenol, and methyl catechols, and the native chaperones clpB, groES, and groEL were overexpressed to improve toxicity tolerance to diverse aromatic substrates. Next, heterologous furfural and acetone utilization pathways were incorporated, and a native alcohol dehydrogenase was overexpressed to improve methanol utilization, generating reducing equivalents. All pathways (encoded by genes totaling ~30 kilobases of DNA) were combined into a single strain that can catabolize a mock CFP wastewater stream as a sole carbon source. Further engineering enabled conversion of all aromatic compounds in the mock wastewater stream to (methyl)muconates with a ~90% (mol/mol) yield. Biological upgrading of CFP wastewater as outlined in this work provides a roadmap for future applications in valorizing other heterogeneous waste streams.     

Dynamic consolidated bioprocessing for direct production of xylonate and shikimate from xylan by Escherichia coli

Numerous value-added chemicals can be produced using xylan as a feedstock. However, the product yields are limited by low xylan utilization efficiency, as well as by carbon flux competition between biomass production and biosynthesis. Herein, a dynamic consolidated bioprocessing strategy was developed, which coupled xylan utilization and yield optimization modules. Specifically, we achieved the efficient conversion of xylan to valuable chemicals in a fully consolidated manner by optimizing the expression level of xylanases and xylose transporter in the xylan utilization module. Moreover, a cell density-dependent, and Cre-triggered dynamic system that enabled the dynamic decoupling of biosynthesis and biomass production was constructed in the yield optimization module. The final shake flask-scale titers of xylonate, produced through an exogenous pathway, and shikimate, produced through an endogenous pathway, reached 16.85 and 3.2 g L⁻¹, respectively. This study not only provides an efficient microbial platform for the utilization of xylan, but also opens up the possibility for the large-scale production of high value-added chemicals from renewable feedstocks.     

A process for purifying xylosugars of pre-hydrolysis liquor from kraft-based dissolving pulp production process

Background

In the kraft-based dissolving pulp production process, pre-hydrolysis liquor (PHL) is produced, which contains hemicelluloses, lignin, furfural and acetic acid. PHL is currently burned in the recovery boiler of the kraft pulping process, but it can be utilized for the generation of high-valued products, such as xylitol and xylanase, via fermentation processes. However, some PHL constituents, e.g., furfural and lignin, are contaminants for fermentation processes and they must be eliminated for production of value-added products.

Results

In this work, a process is introduced for removing contaminants of PHL. Ca(OH)₂ treatment is the first step of this process, which removed 41.2% of lignin and negligible amount of sugars. In this step, a notable increase in the concentration of acetic acid was achieved (ranging from 6.2 to 11.7 g/L). In the second step, the implementation of adsorption using activated carbon (AC) at 1 wt% dosage led to additional 32% lignin and 5.9% xylosugar removals. In addition, laccase assisted activated carbon treatment led to further removal of lignin via accelerating lignin polymerization and adsorption on AC (i.e., removal from PHL). Overall, 90.7% of lignin, 100% of furfural, 5.7% of xylose, and 12% of xylan were removed from PHL, while the concentration of acetic acid became twofolds in the PHL.

Conclusions

This study reports an attractive process for purifying sugars and acetic acid of PHL. This process may be implemented for producing sugar-based value-added products from PHL. It also discusses the mechanism of Ca(OH)₂ treatment, AC adsorption and laccase assisted activated carbon treatment for lignin removal.