Aqueous Pretreatment Research Articles

Physiochemical Characterization of Lignocellulosic Biomass Dissolution by Flowthrough Pretreatment

Comprehensive understanding of biomass solubilization chemistry in aqueous pretreatment such as water-only and dilute acid flowthrough pretreatment is of fundamental importance to achieve the goal of valorizing biomass to fermentable sugars and lignin for biofuels production. In this study, poplar wood was flowthrough pretreated by water-only or 0.05% (w/w) sulfuric acid at different temperatures (220–270 °C), flow rate (25 mL/min), and reaction times (8–90 min), resulting in significant disruption of the lignocellulosic biomass. Ion chromatography (IC), Fourier transform infrared (FTIR) spectroscopy, X-ray diffraction (XRD) analysis, and solid state cross-polarization/magic angle spinning (CP/MAS) 13C nuclear magnetic resonance (NMR) spectroscopy were applied to characterize the pretreated biomass whole slurries in order to reveal depolymerization as well as solubilization mechanism and identify unique dissolution structural features during these pretreatments. Results showed temperature-dependent cellul...

Characterization of lignin derived from water-only and dilute acid flowthrough pretreatment of poplar wood at elevated temperatures.

BackgroundFlowthrough pretreatment of biomass is a critical step in lignin valorization via conversion of lignin derivatives to high-value products, a function vital to the economic efficiency of biorefinery plants. Comprehensive understanding of lignin behaviors and solubilization chemistry in aqueous pretreatment such as water-only and dilute acid flowthrough pretreatment is of fundamental importance to achieve the goal of providing flexible platform for lignin utilization.ResultsIn this study, the effects of flowthrough pretreatment conditions on lignin separation from poplar wood were reported as well as the characteristics of three sub-sets of lignin produced from the pretreatment, including residual lignin in pretreated solid residues (ReL), recovered insoluble lignin in pretreated liquid (RISL), and recovered soluble lignin in pretreatment liquid (RSL). Both the water-only and 0.05 % (w/w) sulfuric acid pretreatments were performed at temperatures from 160 to 270 °C on poplar wood in a flowthrough reactor system for 2–10 min. Results showed that water-only flowthrough pretreatment primarily removed syringyl (S units). Increased temperature and/or the addition of sulfuric acid enhanced the removal of guaiacyl (G units) compared to water-only pretreatments at lower temperatures, resulting in nearly complete removal of lignin from the biomass. Results also suggested that more RISL was recovered than ReL and RSL in both dilute acid and water-only flowthrough pretreatments at elevated temperatures. NMR spectra of the RISL revealed significant β-O-4 cleavage, α-β deoxygenation to form cinnamyl-like end groups, and slight β-5 repolymerization in both water-only and dilute acid flowthrough pretreatments.ConclusionsElevated temperature and/or dilute acid greatly enhanced lignin removal to almost 100 % by improving G unit removal besides S unit removal in flowthrough system. Only mild lignin structural modification was caused by flowthrough pretreatment. A lignin transformation pathway was proposed to explain the complexity of the lignin structural changes during hot water and dilute acid flowthrough pretreatment.Graphical abstractLignin transformations in water-only and dilute acid flowthrough pretreatment at elevated temperaturesElectronic supplementary materialThe online version of this article (doi:10.1186/s13068-015-0377-x) contains supplementary material, which is available to authorized users.

Side by Side Comparison of Chemical Compounds Generated by Aqueous Pretreatments of Maize Stover, Miscanthus and Sugarcane Bagasse

In order to examine the potential for coproduct generation, we have characterised chemical compounds released by a range of alkaline and acidic aqueous pretreatments as well as the effect of these pretreatments on the saccharification ability of the lignocellulosic material. Comparative experiments were performed using three biomass types chosen for their potential as second-generation biofuel feedstocks: maize stover, miscanthus and sugarcane bagasse. The release of lignin from the feedstock correlated with the residual biomass saccharification potential, which was consistently higher after alkaline pretreament for all three feedstock types. Alkaline pretreatment released more complex mixtures of pentose and hexose sugars into the pretreatment liquor than did acid pretreatment. In addition, complex mixtures of aromatic and aliphatic compounds were released into pretreatment liquors under alkaline conditions, in a temperature-dependent manner, but far less so under acidic conditions. We show that the three feedstocks characterised interact with the pretreatment conditions in a specific manner to generate different ranges of products, highlighting the need to tailor pretreatments to both the starting feedstock and desired outcomes.

The Effect of Various Pretreatment Methods on Oil Palm Empty Fruit Bunch (EFB) and Kenaf Core Fibers for Sugar Production

In this study, oil palm empty fruit bunch (EFB) and kenaf core fibers were converted into sugar for bioethanol production. Results of enzymatic hydrolysis showed that the untreated EFB and kenaf core fibers were hardly to be hydrolysed, in which yielded only 2.6% and 0.4% of reducing sugar (glucose), respectively. In consideration to environmentally friendliness, simple aqueous pre-treatments were carried out prior to hydrolysis aimed to increase sugar production. Based on the results obtained, it was interesting to note that by adopting merely water, acid and alkaline pre-treatments, the total glucose yields were increased to 34.9%, 34.2% and 27.9% for EFB fiber, while 19.3%, 11.7%, and 12.6% for kenaf core fiber, respectively. The results of chemical composition analysis of pre-treated fibers indicated the increase of the sugar production was highly related to the removal of hemicellulose and/or lignin in the fibers. Between the two fibers, pre-treated EFB fiber attained the highest total glucose yield in all the pre-treatments. This revealed that EFB fiber was more viable for sugar production than kenaf core fiber.

Fabrication of cationic cellulosic nanofibrils through aqueous quaternization pretreatment and their use in colloid aggregation

The aqueous pre-treatment of cellulose with periodate and Girard’ reagent T was employed as a novel and promising method to promote nanofibrillation of wood pulp and to obtain cellulosic nanofibrils with cationic functionality (CNFC). To demonstrate the feasibility of CNFCs in particle aggregation, a kaolin clay model suspension was aggregated by the CNFCs. Direct high-pressure homogenization of cationized cellulose resulted in nanofibrils exhibiting typical widths of 10–50nm and cationic charge densities ranging from 1.10 to 2.13mequiv.g−1. The nanofibril suspensions existed in the form of highly transparent gels and possessed cellulose I crystalline structures. All of the CNFCs promoted strong aggregation of kaolin and produced voluminous kaolin-CNFC aggregates with lateral dimensions of several millimeters. Moreover, the CNFCs maintained good aggregation performance through wide pH (3–9) and temperature (25–60°C) ranges. Thus, CNFCs were shown to be highly potential candidates for replacement of present synthetic soluble flocculation and coagulation aids.

Fermentable Sugars from Palm Empty Fruit Bunch Biomass for Bioethanol Production

This study investigated the effect of a dilute acid, lime and ammonia aqueous pretreatment on the fermentable sugars conversion from empty fruit bunch (EFB) biomass. The dilute acid treatment was carried out in an autoclave, at 121oC with 4% of sulfuric acid. In the lime pretreatment, 3 wt % of calcium hydroxide was used, whereas the third method was done by soaking EFB with 28% ammonia solution. The EFB biomass was then subjected to a two-stage-acid hydrolysis process. Subsequently, the hydrolysate was fermented by using instant baker’s yeast to produce bioethanol. The highest glucose yield was 890 mg/g of biomass, obtained from the sample which underwent lime pretreatment. The highest bioethanol yield of 6.1mg/g of glucose was achieved from acid pretreatment. This showed that the acid pretreatment gave the most fermentable sugars compared to the other two pretreatments.

Characterization of the components of urban particulate matter mediating impairment of nitric oxide-dependent relaxation in intrapulmonary arteries

We have previously shown that exposure to urban particulate matter (UPM) impairs endothelial nitric oxide (NO) bioactivity in intrapulmonary arteries. As UPM is composed of heterogeneous constituents, the aim of this study was to clarify the class of pollutants responsible for such effect. Extracts (aqueous, acidic or organic) were prepared from SRM1648, an UPM sample collected in St. Louis (MO, USA). The metal composition of extracts as well as endotoxin content was determined. The effects of each extract, metal mixture and endotoxin were evaluated on endothelium-dependent relaxation to acetylcholine (reflecting endothelial NO production) in rat isolated intrapulmonary arteries. Aqueous or organic SRM1648 pretreatment altered acetylcholine-induced relaxation, similar to that induced by native SRM1648. Organic extract induced similar attenuation of acetylcholine relaxation than organic-treated SRM1648, whereas aqueous extract had no effect. Acidic pretreatment, which impoverished metal and endotoxin content of SRM1648, prevented the impairment of acetylcholine-induced relaxation. However, neither the acidic extract enriched in metals, nor a metal mixture representative of SRM1648 content, modified acetylcholine relaxation, while endotoxin impaired it. Polymyxin B, which chelates endotoxin, prevented SRM1648-induced decrease in relaxation to acetylcholine. It is concluded that SRM1648-induced impairment of endothelial NO-dependent relaxation in intrapulmonary arteries unlikely involved a soluble factor released by vascular cells during UPM exposure, but rather an organic extractible and acidic-sensitive constituents of UPM. Endotoxin, but not metals, may be responsible for UPM-induced impairment of endothelial NO-dependent relaxation.

Aqueous pretreatment for reactive ball milling of cellulose

Aqueous swelling pretreatment of cellulose was found highly effective for reactive ball milling to prepare surface-esterified cellulose nanofibers. Compared with starting from dry cellulose, water- or 2 % NaOH-pre-swollen materials were esterified and dispersed in significantly shorter milling time. Especially commercial kraft pulp was difficult to disperse even with water pretreatment, but 2 % NaOH treatment gave full surface esterification with a bulk degree of substitution of 0.69 by 12-h ball milling, presumably because of removal of non-cellulosic components.

Effect of salt addition on hydrothermal carbonization of lignocellulosic biomass

As a renewable non-food resource, lignocellulosic biomass has great potential as an energy source. When pretreated by hydrothermal carbonization, the resulting biochar (or hydrochar) is hydrophobic and of higher energy density. Addition of ionic salts to this high pressure aqueous pretreatment reduces reaction pressure. Ca propionate, Ca acetate, Mg acetate, Ca lactate, Li chloride, Ca chloride, and Ca formate were tested in hydrothermal carbonizations at 260°C for 5min. Ca chloride and Ca lactate were found to be Ca salts whose addition increases HHV and which decrease the pretreatment pressure. Biomass pretreated with chemical addition of selected salts may have desirable properties when co-fired in existing coal boilers.

Fractionation of wheat straw by prehydrolysis, organosolv delignification and enzymatic hydrolysis for production of sugars and lignin

Wheat straw was fractionated using a three-step biorefining approach: (1) aqueous pretreatment for hemicellulose prehydrolysis into sugars, (2) organosolv delignification, and (3) enzymatic cellulose hydrolysis into glucose. Prehydrolysis was applied to avoid degradation of hemicellulose sugars during organosolv delignification. Maximum xylose yield obtained was 67% or 0.17kg/kg straw (prehydrolysis: 175°C, 30min, 20mM H2SO4) compared to 4% in case of organosolv without prehydrolysis (organosolv: 200°C, 60min, 60% w/w aqueous ethanol). Prehydrolysis was found to reduce the lignin yield by organosolv delignification due to the formation of ‘pseudo-lignin’ and lignin recondensation during prehydrolysis. This reduction could partly be compensated by increasing the temperature of the organosolv delignification step. Prehydrolysis substantially improved the enzymatic cellulose digestibility from 49% after organosolv without prehydrolysis to 80% (20FPU/g substrate). Increasing the organosolv delignification temperature to 220°C resulted in a maximum enzymatic glucose yield of 93% or 0.36kg/kg straw.

Aqueous Processing of Cellulosic Biomass for Biological Production of Sustainable Transportation Fuels

Cellulosic biomass including agricultural and forestry residues, substantial fractions of municipal solid waste, and grasses and woody plants grown for energy provide the only low cost and abundant resource that could be used for sustainable production of liquid transportation fuels on a large scale. The challenge is to develop low cost processing technologies to convert this inexpensive resource into viable transportation fuels. Biological conversion systems can apply the power of modern biotechnology to dramatically reduce the costs of converting cellulosic biomass to fuels, and ethanol represents a particularly desirable product in the near term because of its excellent fuel properties, widespread use, and compatibility with biological conversion systems. Ethanol use can also build from commercial experience gained with ethanol made from starch crops in the United States and cane sugar in Brazil. The most expensive steps in biological processing are associated with breaking down the cellulose and hemicellulose fractions of biomass to release sugars, with pretreatment particularly critical to achieving low costs and high yields Our research focuses on improving the understanding of aqueous pretreatment and its interactions with enzymatic hydrolysis with the goal of reducing costs. This presentation will summarize comparative data on pretreatment technologies, developing and applying a high throughput miniaturized approach to pretreatment and hydrolysis, and continuous fermentations to reduce enzyme use. Once successfully introduced into the marketplace, fuels from cellulosic biomass can have powerful and unique strategic, environmental, and economic benefits.

Comparisons of SPORL and dilute acid pretreatments for sugar and ethanol productions from aspen

This study reports comparative evaluations of sugar and ethanol production from a native aspen (Populus tremuloides) between sulfite pretreatment to overcome recalcitrance of lignocellulose (SPORL) and dilute acid (DA) pretreatments. All aqueous pretreatments were carried out in a laboratory wood pulping digester using wood chips at 170°C with a liquid to oven dry (od) wood ratio (L/W) of 3:1 at two levels of acid charge on wood of 0.56 and 1.11%. Sodium bisulfite charge on od wood was 0 for DA and 1.5 or 3.0% for SPORL. All substrates produced by both pretreatments (except DA with pretreatment duration of 0) had good enzymatic digestibility of over 80%. However, SPORL produced higher enzymatic digestibility than its corresponding DA pretreatment for all the experiments conducted. As a result, SPORL produced higher ethanol yield from simultaneous saccharification and fermentation of cellulosic substrate than its corresponding DA pretreatment. SPORL was more effective than its corresponding DA pretreatment in reducing energy consumption for postpretreatment wood chip size-reduction. SPORL, with lower energy input and higher sugar and ethanol yield, produced higher sugar and ethanol production energy efficiencies than the corresponding DA pretreatment.

An Experimental Study on the Effect of Aqueous Hypophosphite Pre-Treatment Used on an Aluminium Alloy Substrate before Electroless Nickel Plating

A new surface pre-treatment procedure has been developed in one of our laboratories [1] for electroless nickel (EN) plating, which appears to be an effective and environmentally benign treatment for the following deposition of a sound and high quality surface nickel coating with good adhesion. For that purpose, the aluminium substrate was immersed in a mildly acidic solution (lactic acid) of sodium hypophosphite in order to modify the passive surface and make it suitable for the reductive chemical precipitation of the nickel-phosphorus nuclei from the electroless nickel plating bath. During this novel pre-treatment technique, the surface adsorption of the hypophosphite anions play an important role therefore several advanced surface testing and analytical techniques (Scanning Electron Microscopy-SEM, Transmission Electron Microscopy-TEM, Energy Dispersive X-ray Spectrometry-EDX, X-ray Photoelectron Spectroscopy-XPS were applied in order to monitor and characterize the surface reactions and adsorption phenomena taking place during the pre-treatment. The Al excited XPS (studying P 2p, O 1s, C 1s, Al 2p, Ni 2p photoelectron lines) proved to be one of the most powerful technique in the identification of the chemical species formed and present on the surfaces examined in this study.

Pyrolysis Gas Chromatography Mass Spectrometry Studies to Evaluate High-Temperature Aqueous Pretreatment as a Way to Modify the Composition of Bio-Oil from Fast Pyrolysis of Wheat Straw

Hot water pretreatment was systematically studied to determine whether reaction selectivity of cellulose toward the production of anhydrosugars and furanics could be improved. Samples of wheat straw and α-cellulose were treated using hot compressed water at temperatures ranging between 150 and 260 °C. The effect of hot water pretreatment on pyrolysis selectivity was measured using pyrolysis gas chromatography mass spectrometry (Py-GC/MS). Various representative peak area ratios were compared and used as an index of pyrolysis selectivity. The chemical and Py-GC/MS analysis of solid residues resulting from hot water pretreatment suggest that, as the temperature increased, the hemicelluloses and amorphous cellulose were solubilized. The relative areas of the Py-GC/MS results associated with levoglucosan increased for both straw and α-cellulose with increasing treatment temperature. The results show that the selectivity of thermochemical reactions toward the production of sugars and furanics can be enhanced if the material is treated in hot water at temperatures between 220 and 260 °C, and the amount of acetic acid is reduced substantially. Thus, hot water pretreatment may be a viable method to modify the chemical composition of bio-oils produced via fast pyrolysis.

Legionnaires’ disease cluster linked to a metal product aqueous pre-treatment process, Staffordshire, England, May 2008

In May 2008, a report of two workers from the same construction equipment manufacturing plant who were admitted to hospital with Legionnaires disease confirmed by urine antigen prompted an outbreak investigation. Both cases were middle aged men, smokers, and with no travel, leisure or other common community exposure to Legionella sources. There were no wet cooling towers at the plant or in the surrounding area. No increase in respiratory disease or worker absenteeism occurred at the plant during the preceding month. Wider case ascertainment including alerts to hospitals and medical practitioners yielded no further cases. The environmental investigation (and sampling of water systems for Legionella) identified a Legionella pneumophila serogroup1 (Mab 2b) count of >3.0x10(4)cfu/l in water samples from an aqueous metal pre-treatment tunnel, which generates profuse water aerosol. Drainage, cleaning and biocide treatment using thiazalone eliminated Legionella from the system.

Aqueous pretreatment of agricultural wastes: Characterization of soluble reaction products

This work provides an assessment on the hydrothermal processing (or autohydrolysis treatments) of two lignocellulosic wastes: mixed herbs (denoted MH, mainly belonging to the Lolium species), and sunflower seed shells (denoted SS). Compositional data were obtained for both raw materials (which contained cellulose, heteroxylan and Klason lignin as major components). In autohydrolysis experiments, the raw materials presented a “susceptible fraction” which was solubilized according to a first-order kinetics. Hemicellulose degradation was followed by determination of xylooligomers, xylose and xylan substituents (arabinosyl, uronic acid and acetyl substituents). Kinetic modelling of hemicellulose degradation was carried out considering four consecutive, first-order, pseudohomogeneous reactions. The molecular weight distribution of polymeric and oligomeric fractions derived from xylan was assessed from High Performance Size Exclusion Chromatography data.

Influence of Silanisation Parameters With γ-Methacryloxypropyltrimethoxysilane on Durability of Aluminium/Acrylic Adhesive Joints

Silane coupling agents have extensively been used as adhesion promoters in the GRP (Glass Reinforced Plastic) composites. In recent years, the application of silanes in aluminium bonding process has been extensively investigated. Silane surface treatment is a more environment-friendly alternative than other treatments, which use toxic chemicals (hexavalent chromium compounds, strong acids, etc.), such as FPL (Forest Products Laboratory) etch, CAA (chromic acid anodisation) or PAA (phosphoric acid anodisation). The aim of this work was to optimize the γ-methacryloxypropyltrimethoxysilane application process to obtain the best durability in toughened acrylic bonded aluminium joints. Variables such as pH, concentration of silane in aqueous solution, drying temperature and pretreatment prior to silanisation have been investigated. The durability was tested using single-lap shear specimens and wedge tests. Specimens were exposed to 95% RH at 50°C, for 90 days. Silanisation parameters such as solution concentration and drying temperature showed a great influence on the durability; however pH had only a little influence. Adherend surface preparation prior to silanisation was found to be a significant factor. The best bond durability performance was provided by the P2 etch and grit blasting, which performed better than the other pretreatments studied.

Carbonic acid enhancement of hydrolysis in aqueous pretreatment of corn stover

Carbonic acid and liquid hot water pretreatments were applied to corn stover. Temperatures ranged from 180 to 220 °C; reaction times varied between 2 and 32 min and prereaction carbon dioxide pressure was either 0 or 800 psig. Over the range of reaction conditions tested, it was found that the presence of carbonic acid had an effect of increasing the concentrations of xylose and furan compounds in the hydrolysate that was significant at above the 99% confidence level. Thus there appears to be an increase in the severity of the pretreatment conditions with the presence of carbonic acid. These results are contrary to previously reported results on aspen wood, where the presence of carbonic acid was not found to have an effect on either the xylose or furan concentrations. Although pretreatment conditions were more severe with the addition of carbonic acid, the presence of carbonic acid resulted in a hydrolysate with a higher final pH. Thus it appears that the higher severity conditions reduce the accumulation of organic acids in the hydrolysate. This result was consistent with previously reported work on carbonic acid pretreatment of aspen wood.

Effects of various additives on the performance of bis-GMA/barium glass powder composites

The effects of various additives on the performance of 2,2′-bis[4-(methacryloxy-2-hydroxy-propoxy)-phenyl]-propane (Bis-GMA)/barium glass powder (Ba) composites were examined. Bis-GMA/Ba composites were manufactured by curing with visible light to measure various mechanical properties. The diametral tensile strengths (DTS) of Bis-GMA/Ba composites were the primary focus of this investigation. The main additives used were trimethylolpropyltrimethacrylate (TMPT), 1,4-bis-(tri-methoxysilylethyl) benzene (BTB), and cationic styryl silane. These additives were applied as both integral blends and aqueous pretreatments. Besides the DTS, Vickers hardness of cured matrix resins and the viscosity of composite pastes were measured to study the properties of the matrix resins and the processibility of the composites, respectively. Integral blends showed similar processibility to aqueous pretreatments. The addition of TMPT to the matrix resins increased Vickers hardness of integral blend systems as a result of its trimethacrylate functional group. BTB was useful in increasing the wet DTS of Bis-GMA/silane–treated Ba composites. STS was effective in improving the performance of Bis-GMA/Ba composites in the cases of both the integral blends and aqueous pretreatments. © 2000 John Wiley & Sons, Inc. J Appl Polym Sci 76: 1085–1092, 2000

Use of polytetrafluoroethylene slurry for silica matrix removal in ETAAS direct determination of trace cobalt and nickel in silicon dioxide powder

A novel method for the direct determination of trace Co and Ni in SiO 2 powder by slurry sampling ETAAS was developed. At high temperature of the graphite furnace, a PTFE slurry in HNO 3 was used as a fluorinating reagent to convert the silica matrix into high-volatility fluoride, which was subsequently evaporated by selective vaporization prior to the atomization of analytes. In this case, the severe interference of the matrix on the vaporization and atomization of analytes was reduced significantly, and chemical attack of the excess of silica matrix on the graphite tube was also minimized. The proposed method was successfully applied to the determination of trace Co and Ni in SiO 2 powder with aqueous calibration and minimum chemical pre-treatment. For the direct analysis of high purity SiO 2 powder, the detect limits of Co and Ni were 18.8 and 35.0 ng g –1 , respectively. The analysis of NIES CRM2 Pond Sediment confirmed the reliability of the approach.