Use of sustainable glucose and furfural in the synthesis of formaldehyde-free phenolic resole resins

Sustainable resol-type resins [phenol–furfural–glucose (PFuG), phenol–furfural (PFu), and phenol–glucose resins] were synthesized via alkali catalysis. The chemical structures of the PFuG resins, which had different molar ratios of glucose to furfural, were analyzed by ¹H-NMR and Fourier transform infrared spectroscopy. A possible mechanism for formation of the PFuG resin was proposed. The crosslinking curing behaviors of the PFuG resins were examined by differential scanning calorimetry analysis. The performance of the PFuG resins as wood adhesives was studied. © 2019 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2019 , 136, 47732.     

Restructuring the processes for furfural and xylose production from sugarcane bagasse in a biorefinery concept for ethanol production

This study consisted in restructuring the processes for furfural and xylose production from sugarcane bagasse in a biorefinery concept for the residues utilization on ethanol production.The dilute acid hydrolysis conditions for furfural or xylose production were firstly established on laboratory scale and then reproduced on a 10-L bench reactor fed with direct steam. The furfural production was maximum when using a 1.25% (w/w on dry fiber) H₂SO₄ solution at 175 °C during 40 min; whereas the xylose production attained the best results when using a 1% (w/v) H₂SO₄ solution in a solid/liquid ratio of 1/4 (g/mL), and the sugarcane bagasse impregnated with the acid solution during 24 h prior to the hydrolysis reaction. Enzymatic hydrolysis of the residual solid material obtained from furfural or xylose production was performed with yields of 17.4 and 9.3 g glucose/100 g initial raw material, respectively. Subsequently, ethanol was produced from the residual solid materials obtained from furfural and xylose production with yields of 87.4% and 89.3% respectively, based on the maximum theoretical value (0.51 g ethanol per g glucose in hydrolysate). Such results demonstrated the possibility of restructuring the processes for furfural or xylose production to obtain solid residues able to be used as substrate for ethanol production by fermentation.     

Dehydration of D-xylose into furfural over H-zeolites

The liquid-phase dehydration of D-xylose into furfural was carried out over various H-zeolites-H-ferrierite, H-β, H-ZSM-5, H-Y and H-mordenite-with various SiO₂/Al₂O₃ molar ratios in different solvent systems: water, dimethyl sulfoxide (DMSO) and a mixture of water and toluene (water/toluene). For comparison, γ-Al₂O₃ and silica-alumina were also examined. FT-IR spectroscopy after pyridine adsorption was conducted to probe the acidity of the H-zeolites. The D-xylose conversion and furfural yield generally decreased with increasing SiO₂/Al₂O₃ molar ratio over the H-zeolites having the same crystal structure irrespective of the kind of solvent system. This is closely related to the accessible acid sites. In a comparison study using the three different solvent systems, the D-xylose conversion and furfural selectivity generally decreased in the following order: water/toluene>DMSO>water. In water and water/toluene, H-β (25) showed the highest furfural selectivity at a similar D-xylose conversion among the tested zeolites. On the other hand, H-mordenite (20) showed the highest furfural selectivity at a similar D-xylose conversion in DMSO.     

Furfural-based phosphonic acid cation exchange resins from N-vinylcarbazole and its polymer. I

Crosslinked polymers based on the condensation of furfural with N-vinylcarbazole and poly(N-vinylcarbazole) were prepared. The effect of variation of furfural concentration on the condensation of furfural with N-vinylcarbazole and its polymer was studied. The polymers were chemically modified into phosphonic acid cation exchange resins. The effects of variation of AlCl₃, PCl₃, and furfural amounts, reaction time, and rephosphorylation on the synthesis and capacities of cation exchange resins were also studied.     

Mild autohydrolysis: an environmentally friendly technology for xylooligosaccharide production from wood

Eucalyptus globulus wood samples were subjected to hydrothermal treatments under mild operational conditions (145–190 ° C, liquor to solid ratio 6–10 g g⁻¹, reaction times up to 7.5 h). Residual xylan, xylooligosaccharides, other sugars, furfural, glucan and lignin contents were determined. Negligible effects were caused by hydrothermal treatments on both cellulose and lignin. Kinetic models were developed which describe the hydrolysis of hemicelluloses. Xylan degradation, xylooligosaccharide and xylose generation, and xylose dehydration to furfural were accurately described by models based on pseudohomogeneous, first‐order kinetics with Arrhenius‐type temperature dependence. These models are useful for a technical evaluation of this environmentally friendly technology. © 1999 Society of Chemical Industry     

Furfural production by acid hydrolysis and supercritical carbon dioxide extraction from rice husk

The aim of this research was to study the effect of furfural production from rice husk by hydrolysis accompanying supercritical CO₂ (SC-CO₂) extraction. The two-level fractional factorial design method was used to investigate the production process carried out with respect to furfural yield. The process variables are temperature range of 373–453 K, pressure 9.1–18.2 MPa, CO₂ flow rate 8.3 × 10⁻⁵–1.7 × 10⁻⁴ kg/s (5–10 g/min), sulfuric acid concentration 1 to 7 (%wt) and ratio of liquid to solid (L/S) 5 : 1 to 15 : 1 (vol/wt). The results obtained from the experimental design showed that increasing temperature, pressure, CO₂ flow rate and sulfuric acid concentration but decreasing ratio of liquid to solid would improve furfural yield. Moreover, furfural production by two-stage process (pre-hydrolysis and dehydration) can improve furfural yield further to be around 90% of theoretical maximum.     

Preliminary Studies on Furfural Production from Lignocellulosics

This study focused on the production of furfural from agricultural and industrial biomass residues by a hydrodistillation process. Corncobs, sugarcane bagasse, and eucalypt wood were treated with sulfuric, hydrochloric, and phosphoric acids as catalysts, with different acid concentrations (1.5 to 5.2 mol.L ^?1). In addition, the eucalypt liquor from the auto-hydrolysis, kraft-dissolving pulp production process was also investigated as a source of furfural, using sulfuric and hydrochloric acids as a catalyst (0.9 and 3.9 mol.L ^?1) . Furfural yields of 30.2, 25.8, and 13.9% were achieved for corncob, sugarcane bagasse, and eucalypt wood, respectively, on the basis of biomass dry weight. The efficiency of conversion from pentose to furfural using eucalypt liquor from the auto-hydrolysis kraft process was 71.5% using HCl 3.9 mol.L ^?1 . Due to the presence of a high amount of pentose, corncob produced the highest amount of furfural, followed by sugarcane bagasse and then eucalypt wood.     

Improvement of ethanol fermentation from lignocellulosic hydrolysates by the removal of inhibitors

In this study, the removal efficiency of fermentation inhibitors in a lignocellulosic hydrolysate by electrodialysis (ED) and the ethanol performance of ED-treated hydrolysate were investigated. The fermentable sugars and inhibitors concentrations in the hydrolysate differed significantly depending on the kind of biomass and acid catalysts. In the mixed hardwood, acetic acid and furfural in the hydrolysate were high as 8.41–8.57 g/L and 2.68–4.23 g/L, respectively, but 5-hydroxymethylfurfural (HMF) concentration was relatively low compared with that of mixed softwood. The ED process showed the high effectiveness for removing acetic acid and total phenolic compounds in the hydrolysate without loss of fermentable sugars. However, most of the HMF and furfural remained in the hydrolysate after ED. Ethanol fermentation was not completed in untreated and mixed hardwood ED-treated hydrolysates due to the high concentration of furfural. Meanwhile, ethanol fermentation was successfully performed in a mixed softwood ED-treated hydrolysate pretreated with dicarboxylic acid. The maximum ethanol concentration attained after fermentation with an initial fermentable sugar level of 27.78 g/L was 10.12 g/L after 48 h.     

Preparation of highly phenol substituted bio-oil–phenol–formaldehyde adhesives with enhanced bonding performance using furfural as crosslinking agent

Highly phenol substituted bio-oil–phenol–formaldehyde (BPF) adhesives were prepared via the phenolization-copolymerization method, in which furfural was used as a novel crosslinking agent to improve the bonding performance. The effects of bio-oil percentage, furfural content, curing temperature, and pressure on the performance of BPF adhesives have been studied in detail. A BPF adhesive with 75% bio-oil percentage and 15% furfural loading (named 75BPF_15) was synthesized, which was cured at 180 °C and 4 MPa. Compared to the conventional phenol–formaldehyde adhesive, the wet tensile strength of 75BPF_15 adhesive reached 2.84 MPa, which was significantly higher than the 1.54 MPa of PF. A possible mechanism of BPF adhesives crosslinked with furfural is proposed. © 2018 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2019 , 136, 46995.     

Kinetic studies of hemicellulose hydrolysis of corn stover at atmospheric pressure

The object of this work was to study the xylose production by hydrolysis of corn stover with diluted sulfuric acid at 100 °C. Several concentrations of H₂SO₄ (2%, 4% and 6% w/w) and reaction time (0–300 min) were evaluated. Kinetic parameters of mathematical models for predicting the concentrations of xylose, glucose and furfural in the hydrolysates were found. Optimal conditions for hydrolysis were 5.5% H₂SO₄ at 100 °C for 60 min; under these conditions, 86.7% of xylose yield and 2.82 g/g selectivity were attained, leading to liquors containing up to 18.73 g/l xylose, 6.64 g/l glucose and 0.63 g/l furfural. The models could be successfully used to predict the concentrations of xylose, glucose and furfural within 0–300 min under experimental acid concentrations. Furthermore, the hydrolysis process of corn stover using dilute acid could be conceived as the first stage of an integrated strategy for corn stover utilization.     

Carbocatalytic dehydration of xylose to furfural in water

Graphene, graphene oxide, sulfonated graphene, and sulfonated graphene oxide (SGO) have been prepared, characterized and tested for the dehydration of xylose to furfural in water. In particular, SGO was proven to be a rapid and water-tolerant solid acid catalyst even at very low catalyst loadings down to 0.5 wt.% vs xylose, maintaining its initial activity after 12 tested repetitions at 200 °C, with an average yield of 61% in comparison to 44% for the uncatalyzed system. Raman spectroscopy, energy dispersive X-ray spectroscopy, thermogravimetric analysis, X-ray photoelectron spectroscopy, ¹³C solid state nuclear magnetic resonance spectroscopy, Fourier transform infrared spectroscopy and surface area analysis suggested that the aryl sulfonic acid groups were the key active sites for high temperature production of furfural in water. They were more thermally stable under the reaction conditions and acidic than other functional groups attached to the graphene surface.     

Production of furfural and cellulose from barley straw using acidified zinc chloride

An effective fractionation process was sought to produce furfural and cellulose-rich solid from barley straw. Acidified zinc chloride (ZnCl₂) was used as a catalyst in order to achieve hemicellulose recovery in the form of liquid hydrolysate. This fractionation process recovered 55.6% of XM (xylan and mannan) in the untreated barley straw under best reaction conditions (10% acidified ZnCl₂, 150 °C, 30 min, and 1/15 of S/L ratio). Hemicellulose hydrolysate was converted into furfural using hydrothermal reaction without additional catalyst. The furfural conversion yield at various reaction temperatures (150, 180, and 210 °C) was in the range of 59.9–64.5%. The two parameters that affected performance in fractionation processing were reaction temperature and time. Reaction severity (Log R0) was used to evaluate the effects of two processing parameters on hemicellulose recovery. In the ZnCl₂ treatment, the data indicated that the proper range of severity was 2.95–3.07 because the XM recovery yield decreased as the reaction condition became more severe beyond that point.     

Recovery of Furfural from Aqueous Solution by Ionic Liquid Based Liquid–Liquid Extraction

Abstract

Liquid–liquid extraction with imidazolium based ionic liquids ([C₄mim][PF₆], [C₆mim][PF₆], and [C₈mim][PF₆]) is proposed for the separation of furfural or 5-methylfurfural from aqueous solution. Factors affecting the extraction of furfural or 5-methylfurfural have been studied. It was shown that the extraction equilibria can be achieved within 30 min and the process was less affected by the factors such as volume ratio and feed concentration. The partition coefficients of furfural and 5-methylfurfural decreased with increasing temperature. [C₆mim][PF₆] was found to have the best extraction ability among the three ionic liquids studied. Presence of small amount of NaCl or Na₂SO₄ in the aqueous phase results in the considerable increase in the partition coefficients of furfural because of the competitive hydration of the salts with furfural. A thermodynamic study revealed that the extraction process was driven mainly by hydrophobic interactions. Further experimental results indicated that furfural can be separated selectively from aqueous furfural/acetic acid mixtures.     

柠檬酸改性糠醛渣的制备

研究了柠檬酸改性糠醛渣的制备过程和条件。首先对糠醛渣进行预处理,然后分别用20%的异丙醇和20%的氢氧化钠溶液处理,最后用柠檬酸对其进行改性,得到柠檬酸改性糠醛渣。讨论了反应时间,反应温度,柠檬酸溶液浓度,固液比等因素对改性的影响。结果表明:当反应时间60 min,反应温度80℃,柠檬酸质量浓度100 g/L,固液比1︰3时获得的改性糠醛渣吸附亚甲基蓝效果最好,去除率可达到98.2%。     

Biotransamination of Furan-Based Aldehydes with Isopropylamine: Enzyme Screening and pH Influence

Furan-based amines are highly valuable compounds which can be directly obtained via reductive amination from easily accessible furfural, 5-(hydroxymethyl)furfural (HMF) and 2,5-diformylfuran (DFF). Herein the biocatalytic amination of these carbonyl derivatives is disclosed using amine transaminases (ATAs) and isopropylamine (IPA) as amine donors. Among the different biocatalysts tested, the ones from Chromobacterium violaceum (Cv-TA), Arthrobacter citreus (ArS-TA), and variants from Arthrobacter sp. (ArRmut11-TA) and Vibrio fluvialis (Vf-mut-TA), afforded high levels of product formation (>80 %) at 100–200 mM aldehyde concentration. The transformations were studied in terms of enzyme and IPA loading. The pH influence was found as a key factor and attributed to the imine/aldehyde equilibrium that can arise from the high reactivity of the carbonyl substrates with a nucleophilic amine such as IPA.     

Bifunctional Pd/Al-SBA-15 catalyzed one-step hydrogenation–esterification of furfural and acetic acid: A model reaction for catalytic upgrading of bio-oil

Al-SBA-15 supported palladium bifunctional catalysts were evaluated for one-step hydrogenation–esterification (OHE) of furfural and acetic acid as a model reaction for bio-oil upgrading. Experimental results show that it is viable to convert these unstable constituents of bio-oil to esters and alcohols through this simple and effective OHE reaction. The results of NH₃–TPD and catalytic performances show that Al-SBA-15 with medium ratio of Si/Al favors the OHE reaction between furfural and acetic acid. It is noteworthy that there is a synergistic effect between the metal sites and the acid sites over composite bifunctional catalyst of 5%Pd/Al-SBA-15 for the OHE reaction.     

Phthalic anhydride production from hemicellulose solutions: Technoeconomic analysis and life cycle assessment

The process synthesis, technoeconomic analysis, and life cycle assessment (LCA) of a novel route for phthalic anhydride (PAN) production from hemicellulose solutions are presented. The production contains six steps including dehydration of xylose to furfural, reductive decarbonylation of furfural to furan, oxidation of furfural to maleic anhydride (MA), Diels‐Alder cycloaddition of furan, and MA to exo?4,10‐dioxa‐tricyclo[5.2.1.0]dec‐8‐ene‐3,5‐dione followed by dehydration to PAN in the presence of mixture of methanesulfonic acid and acetic anhydride (AAN) which is converted to acetyl methanesulfonate and acetic acid (AAD), and dehydration of AAD to AAN. The minimum selling price of PAN is determined to be $810/metric ton about half of oil‐based PAN. The coproduction of high‐value products is essential to improve the economics. Biomass feedstock contributes to the majority of cost. LCA results shows that biomass‐based PAN has advantages over oil‐based PAN to reduce climate change and fossil depletion however requires more water usage. © 2015 American Institute of Chemical Engineers AIChE J, 61: 3708–3718, 2015     

Optimization of Sugarcane Bagasse Hydrolysis by Microwave‐Assisted Pretreatment for Bioethanol Production

Sugarcane bagasse hydrolysis was optimized by dilute‐acid pretreatment and subsequent enzymatic treatment. The studied parameters were microwave heating temperature, residence time, and enzyme dosage as the main factors in a central composite design. The amount of released total reducing sugars, glucose, pentose, phenolic compounds, and furfural were measured after each stage. The optimum conditions with suitable concentrations of inhibitors and reducing sugars were applied for bioethanol production. As an example, ethanol was obtained from reducing sugars by Pichia stipitis without detoxification.     

介孔分子筛MCM-41—SO3H 催化木糖脱水制备糠醛的研究

采用在MCM-41分子筛上先嫁接—SH,再经氧化和酸化的方法制备了介孔分子筛固体酸催化剂MCM-41—SO3H,对催化剂进行了表征,并对其用于木糖脱水环化生成糠醛的反应进行了研究。当木糖与催化剂的质量比为0.8、反应温度为170 ℃、反应时间为4 h时,木糖的转化率为83.4%,生成糠醛的选择性为76.7%,糠醛收率为64.0%。该催化剂的优点是糠醛收率高于硫酸作催化剂时的收率;不产生酸性废水;催化剂经再生处理后能重复使用,但糠醛收率降为39.7%。     

Extraction of Furfural with Carbon Dioxide

Abstract

A new approach to separate furfural from aqueous waste has been investigated. Recovery of furfural and acetic acid from aqueous effluents of a paper mill has successfully been applied on an industrial scale since 1981.

The process is based on the extraction of furfural and acetic acid by the solvent trooctylphosphineoxide (TOPO). Common extraction of both substances may cause the formation of resin residues. Improvement was expected by selective extraction of furfural with chlorinated hydrocarbons, but ecological reasons stopped further development of this project.

The current investigation is centered in the evaluation of extraction of furfural by supercritical carbon dioxide. The influence of temperature and pressure on the extraction properties has been worked out. The investigation has considered the multi-component system furfural-acetic acid-water-carbon dioxide. Solubility of furfural in liquid and supercritical carbon dioxide has been measured, and equilibrium data for the ternary system furfural-water-CO₂ as well as for the quaternary system furfuralacetic acid-water-CO₂ have been determined. A high-pressure extraction column has been used for evaluation of mass transfer rates.