98-01-1

Mesoporous tantalum phosphates: Preparation, acidity and catalytic performance for xylose dehydration to produce furfural

Xing, Yanran,Yan, Bo,Yuan, Zifei,Sun, Keqiang

, p. 59081 - 59090 (2016)

Mesoporous tantalum phosphates (TaOPO4-m) with varying P/Ta molar ratios (m = 0.41-0.89) were prepared, comprehensively characterized by ICP-AES, N2 physisorption, small-angle XRD, TEM, Raman, FT-IR, NH3-TPD and IR of pyridine adsorption and employed to catalyze the dehydration of xylose to produce furfural in a biphasic batch reactor. The physicochemical properties of these TaOPO4-m samples were affected significantly by variation of m. More ordered mesopores were formed in the sample with a higher m. On the other hand, the density of acidity decreased but the ratio of Br?nsted acidity to Lewis acidity (B/L) increased with the increase in m. TaOPO4-0.84, which showed adequate mesoporosity and a high B/L ratio, was identified as the best performing catalyst among these TaOPO4-m catalysts in terms of high furfural selectivity (ca. 72 mol%). Correlating the catalyst performance with its acid property showed that the xylose consumption rate decreased with the increasing B/L ratio, while furfural selectivity showed a volcano-type dependence on the B/L ratio. Besides, the huge decrease in the furfural selectivity after poisoning the Br?nsted acid sites by adding 2,6-dimethyl pyridine revealed a kind of Br?nsted acid catalysis for selective furfural production.

Improving Biocatalytic Synthesis of Furfuryl Alcohol by Effective Conversion of D-Xylose into Furfural with Tin-Loaded Sulfonated Carbon Nanotube in Cyclopentylmethyl Ether-Water Media

Li, Qi,Hu, Yun,Tao, Yong-You,Zhang, Peng-Qi,Ma, Cui-Luan,Zhou, Yu-Jie,He, Yu-Cai

, p. 3189 - 3196 (2021)

Carbon nanotube (CNT) was utilized as as the precursor to synthesize solid acid (tin-loaded sulfonated carbon nanotube, SO42?/SnO2-CNT) for catalyzing D-xylose into furfural. Fourier transform infrared spectroscopy, Roman spectroscopy, X-ray diffraction analysis, and scanning electron microscope techniques were used for characterizing SO42?/SnO2-CNT. Different loading of D-xylose (20–100?g/L) were converted into furfural (81.6–299.1?mM) at 41.9–61.2% yield by SO42?/SnO2-CNT (3.5 wt%) within 15?min at 180 °C in cyclopentylmethyl ether-water (1:2, v:v) biphasic media. Subsequently, whole-cells of recombinant Escherichia coli CG-19 cells expressing reductase catalyzed D-xylose-derived furfural at 35 ℃ and pH 7.5. Within 3?h, the prepared D-xylose (81.6–299.1?mM) could be converted into furfuryl alcohol at 32.7–61.2% yield (based on the D-xylose loading). Sequential conversion of D-xylose with SO42?/SnO2-CNT and reductase catalysts was established for the effective production of furfuryl alcohol. Graphic Abstract: [Figure not available: see fulltext.]

Conversion of xylose, xylan and rice husk into furfural via betaine and formic acid mixture as novel homogeneous catalyst in biphasic system by microwave-assisted dehydration

Delbecq, Frederic,Wang, Yantao,Len, Christophe

, p. 520 - 525 (2016)

Dehydration of D-xylose and direct transformation of xylan into furfural were achieved by means of betaine-formic acid (HCOOH) catalytic system. All reactions were microwave-assisted and carried out in a CPME-water biphasic system. At 170?°C, in a pH range between 1.9 and 2.3, highest yields of 80% and 76% were obtained respectively for the pentose and the polysaccharide. Time dependence of the dehydration and influence of the temperature on the reaction kinetics were studied. Besides, at 190?°C, using the optimized condition of the reaction, rice husk was also employed as a source of furfural with a single stage reaction.

The role of xylulose as an intermediate in xylose conversion to furfural: insights via experiments and kinetic modelling

Ershova,Kanervo,Hellsten,Sixta

, p. 66727 - 66737 (2015)

An experimental work has been performed to study the relevance of xylulose as an intermediate in xylose conversion to furfural in aqueous solution. The furfural formation was investigated at the temperature range from 180 to 220 °C during non-catalyzed and acid-catalyzed conversion of xylose in a stirred microwave-assisted batch reactor. The separate experiments on xylulose and furfural conversions were carried out under similar conditions. The maximum furfural yields obtained from xylose were 48 mol% and 65 mol% for the non-catalyzed and the acid-catalyzed processes, respectively. It was shown that the furfural yield is significantly lower from xylulose than from xylose. Furthermore, the effects of initial xylose concentration and the formation of xylulose were investigated in a mechanistic modeling study. A new reaction mechanism was developed taking into account the xylulose formation from xylose. Based on the experimental results and the proposed reaction model, it was concluded that xylose isomerization to xylulose with subsequent furfural formation is not a primary reaction pathway. The obtained kinetic parameters were further used for plug flow reactor simulations to evaluate furfural yields achievable by an optimized continuous operation.

Synergy effect between solid acid catalysts and concentrated carboxylic acids solutions for efficient furfural production from xylose

Doiseau, Aude-Claire,Rataboul, Franck,Burel, Laurence,Essayem, Nadine

, p. 176 - 184 (2014)

An efficient furfural formation from xylose was demonstrated combining a concentrated aqueous solution of acetic acid and solid acid catalysts. Higher furfural yields and selectivities were obtained by comparison to the catalytic performances obtained in pure water. The evident synergy effect observed at 150 °C between the aqueous carboxylic acid solution and the solid acid catalysts is tentatively explained by the occurrence of two phenomena: 1) the contribution of Lewis acid sites which would operate in cooperation with the homogeneous weak Br?nsted acidity brought by the aqueous acetic acid solution. According to the literature, the two steps mechanism involving the xylose-xylulose isomerization over Lewis acid sites and the successive Br?nsted acid catalyzed cyclodehydration to furfural would be the prevailing reaction pathway in the heterogeneous-homogenous catalytic system at 150 °C. 2) an enhancement of the surface solid acid coverage by the carbohydrate and furfural owing to the presence of carboxylic acid in the aqueous solution as shown by comparative liquid phase adsorption experiments done in pure water and in aqueous acetic acid solutions. Among a series of solid acid catalysts, ZrW, Cs2HPW12O40, HY (Si/Al = 15), K10 and NbOH, the latter one, NbOH used non-calcinated was shown to be active, selective and stable in the aqueous acetic acid media. HY and K10 are as active and selective for furfural formation but suffer for a strong Al leaching which precludes their utilization as true solid acid catalyst in acetic acid media.

Efficient, stable, and reusable silicoaluminophosphate for the one-pot production of furfural from hemicellulose

Bhaumik, Prasenjit,Dhepe, Paresh L.

, p. 2299 - 2303 (2013)

Development of stable, reusable, and water-tolerant solid acid catalysts in the conversion of polysaccharides to give value-added chemicals is vital because catalysts are prone to undergo morphological changes during the reactions. With the anticipation that silicoaluminophosphate (SAPO) catalysts will have higher hydrothermal stability, those were synthesized, characterized, and employed in a one-pot conversion of hemicellulose. SAPO-44 catalyst at 170 C within 8 h could give 63% furfural yield with 88% mass balance and showed similar activity up to at least 8 catalytic cycles. The morphological studies revealed that SAPO catalysts having hydrophilic characteristics are stable under reaction conditions.

Supported task-specific ionic liquid catalyst for highly efficient and recyclable aerobic oxidation of benzyl alcohols

Liu, Lin,Ma, Juanjuan,Sun, Zhen,Zhang, Jianping,Huang, Jingjing,Li, Shanzhong,Tong, Zhiwei

, p. 68 - 71 (2011)

A novel catalytic system was prepared by impregnating ionic liquid immobilized 2,2,6,6-tetramethylpiperidyl-1-oxyl (TEMPO) and copper salt onto various silica supports. This catalytic system was capable of rapidly converting different benzylic and allylic alcohols into the corresponding aldehydes under O2 atmosphere with high conversion. Recycling results showed that the catalyst could be easily recovered and reused.

High performance mesoporous zirconium phosphate for dehydration of xylose to furfural in aqueous-phase

Cheng, Liyuan,Guo, Xiangke,Song, Chenhai,Yu, Guiyun,Cui, Yuming,Xue, Nianhua,Peng, Luming,Guo, Xuefeng,Ding, Weiping

, p. 23228 - 23235 (2013)

The conversion of sugars to chemicals in aqueous-phase is especially important for the utilization of biomass. In current work, zirconium phosphate obtained by hydrothermal methods using organic amines as templates has been examined as a solid catalyst for the dehydration reaction of xylose to furfural in aqueous-phase. The use of dodecylamine and hexadecylamine in the synthesis process results in mesoporous zirconium phosphate with uniform pore width of ～2 nm and in morphology of nanoaggregates, which is characterized by powder X-ray diffraction, N2 isothermal sorption, NH3 temperature-programmed desorption, FT-IR, and 31P MAS NMR spectroscopy. When used as a catalyst for xylose dehydration to furfural in aqueous-phase, the mesoporous zirconium phosphate presents excellent catalytic performance with high conversions up to 96% and high furfural yields up to 52% in a short time of reaction. Moreover, the catalyst is easily regenerated by thermal treatment in air and shows quite stable activity. The open structure with numerous active sites of the Bronsted/Lewis acid sites is responsible for the high catalytic efficiency of mesoporous zirconium phosphate.

Enhanced Furfural Yields from Xylose Dehydration in the Γ-Valerolactone/Water Solvent System at Elevated Temperatures

Sener, Canan,Motagamwala, Ali Hussain,Alonso, David Martin,Dumesic, James A.

, p. 2321 - 2331 (2018)

High yields of furfural (>90 %) were achieved from xylose dehydration in a sustainable solvent system composed of γ-valerolactone (GVL), a biomass derived solvent, and water. It is identified that high reaction temperatures (e.g., 498 K) are required to achieve high furfural yield. Additionally, it is shown that the furfural yield at these temperatures is independent of the initial xylose concentration, and high furfural yield is obtained for industrially relevant xylose concentrations (10 wt %). A reaction kinetics model is developed to describe the experimental data obtained with solvent system composed of 80 wt % GVL and 20 wt % water across the range of reaction conditions studied (473–523 K, 1–10 mm acid catalyst, 66–660 mm xylose concentration). The kinetic model demonstrates that furfural loss owing to bimolecular condensation of xylose and furfural is minimized at elevated temperature, whereas carbon loss owing to xylose degradation increases with increasing temperature. Accordingly, the optimal temperature range for xylose dehydration to furfural in the GVL/H2O solvent system is identified to be from 480 to 500 K. Under these reaction conditions, furfural yield of 93 % is achieved at 97 % xylan conversion from lignocellulosic biomass (maple wood).

Reactive Extraction Enhanced by Synergic Microwave Heating: Furfural Yield Boost in Biphasic Systems

Huskens, Jurriaan,Lange, Jean-Paul,Ricciardi, Luca,Verboom, Willem

, (2020)

Reactive extraction is an emerging operation in the industry, particularly in biorefining. Here, reactive extraction was demonstrated, enhanced by microwave irradiation to selectively heat the reactive phase (for efficient reaction) without unduly heating the extractive phase (for efficient extraction). These conditions aimed at maximizing the asymmetries in dielectric constants and volumes of the reaction and extraction phases, which resulted in an asymmetric thermal response of the two phases. The efficiency improvement was demonstrated by dehydrating xylose (5 wt percent in water) to furfural with an optimal yield of approximately 80 mol percent compared with 60–65 mol percent under conventional biphasic conditions, which corresponds to approximately 50 percent reduction of byproducts.

Low-Temperature Continuous-Flow Dehydration of Xylose Over Water-Tolerant Niobia–Titania Heterogeneous Catalysts

Moreno-Marrodan, Carmen,Barbaro, Pierluigi,Caporali, Stefano,Bossola, Filippo

, p. 3649 - 3660 (2018)

The sustainable conversion of vegetable biomass-derived feeds to useful chemicals requires innovative routes meeting environmental and economical criteria. The approach herein pursued is the synthesis of water-tolerant, unconventional solid acid monolithic catalysts based on a mixed niobia–titania skeleton building up a hierarchical open-cell network of meso- and macropores, and tailored for use under continuous-flow conditions. The materials were characterized by spectroscopic, microscopy, and diffraction techniques, showing a reproducible isotropic structure and an increasing Lewis/Br?nsted acid sites ratio with increasing Nb content. The catalytic dehydration reaction of xylose to furfural was investigated as a representative application. The efficiency of the catalyst was found to be dramatically affected by the niobia content in the titania lattice. The presence of as low as 2 wt % niobium resulted in the highest furfural yield at 140 °C under continuous-flow conditions, by using H2O/γ-valerolactone as a safe monophasic solvent system. The interception of a transient 2,5-anhydroxylose species suggested the dehydration process occurs via a cyclic intermediates mechanism. The catalytic activity and the formation of the anhydro intermediate were related to the Lewis acid sites (LAS)/Br?nsted acid sites (BAS) ratio and indicated a significant contribution of xylose–xylulose isomerization. No significant catalyst deactivation was observed over 4 days usage.

Catalytic dehydration of xylose to furfural: Vanadyl pyrophosphate as source of active soluble species

Sádaba, Irantzu,Lima, Sérgio,Valente, Anabela A.,López Granados, Manuel

, p. 2785 - 2791 (2011)

The acid-catalysed, aqueous phase dehydration of xylose (a monosaccharide obtainable from hemicelluloses, e.g., xylan) to furfural was investigated using vanadium phosphates (VPO) as catalysts: the precursors, VOPO4· 2H2O, VOHPO4·0.5H2O and VO(H 2PO4)2, and the materials prepared by calcination of these precursors, that is, γ-VOPO4, (VO) 2P2O7 and VO(PO3)2, respectively. The VPO precursors were completely soluble in the reaction medium. In contrast, the orthorhombic vanadyl pyrophosphate (VO)2P 2O7, prepared by calcination of VOHPO4· 0.5H2O at 550 °C/2 h, could be recycled by simply separating the solid acid from the reaction mixture by centrifugation, and no drop in catalytic activity and furfural yields was observed in consecutive 4 h-batch runs (ca. 53% furfural yield, at 170 °C). However, detailed catalytic/characterisation studies revealed that the vanadyl pyrophosphate acts as a source of active water-soluble species in this reaction. For a concentration of (VO) 2P2O7 as low as 5 mM, the catalytic reaction of xylose (ca. 0.67 M xylose in water, and toluene as solvent for the in situ extraction of furfural) gave ca. 56% furfural yield, at 170 °C/6 h reaction.

Production of furfural from xylose at atmospheric pressure by dilute sulfuric acid and inorganic salts

Rong, Chunguang,Ding, Xuefeng,Zhu, Yanchao,Li, Ying,Wang, Lili,Qu, Yuning,Ma, Xiaoyu,Wang, Zichen

, p. 77 - 80 (2012)

In this paper, the dehydration of xylose to furfural was carried out under atmospheric pressure and at the boiling temperature of a biphasic mixture of toluene and an aqueous solution of xylose, with sulfuric acid as catalyst plus an inorganic salt (NaCl or FeCl3) as promoter. The best yield of furfural was 83% under the following conditions: 150 mL of toluene and 10 mL of aqueous solution of 10% xylose (w/w), 10% H2SO4 (w/w), 2.4 g NaCl, and heating for 5 h. FeCl3 as promoter was found to be more efficient than NaCl. The addition of DMSO to the aqueous phase in the absence of an inorganic salt was shown to improve the yield of furfural.

Catalytic conversion of xylose to furfural by p-toluenesulfonic acid (Ptsa) and chlorides: Process optimization and kinetic modeling

Sajid, Muhammad,Rizwan Dilshad, Muhammad,Saif Ur Rehman, Muhammad,Liu, Dehua,Zhao, Xuebing

, (2021)

Furfural is one of the most promising precursor chemicals with an extended range of downstream derivatives. In this work, conversion of xylose to produce furfural was performed by employing p-toluenesulfonic acid (pTSA) as a catalyst in DMSO medium at moderate temperature and atmospheric pressure. The production process was optimized based on kinetic modeling of xylose conversion to furfural alongwith simultaneous formation of humin from xylose and furfural. The synergetic effects of organic acids and Lewis acids were investigated. Results showed that the catalyst pTSA-CrCl3·6H2 O was a promising combined catalyst due to the high furfural yield (53.10%) at a moderate temperature of 120? C. Observed kinetic modeling illustrated that the condensation of furfural in the DMSO solvent medium actually could be neglected. The established model was found to be satisfactory and could be well applied for process simulation and optimization with adequate accuracy. The estimated values of activation energies for xylose dehydration, condensation of xylose, and furfural to humin were 81.80, 66.50, and 93.02 kJ/mol, respectively.

P -Hydroxybenzenesulfonic acid-formaldehyde solid acid resin for the conversion of fructose and glucose to 5-hydroxymethylfurfural

Li, Wenzhi,Zhang, Tingwei,Xin, Haosheng,Su, Mingxue,Ma, Longlong,Jameel, Hason,Chang, Hou-Min,Pei, Gang

, p. 27682 - 27688 (2017)

A novel solid p-hydroxybenzenesulfonic acid-formaldehyde resin (SPFR) was prepared via a straightforward hydrothermal method. The catalytic properties of SPFR solid acids were evaluated in the dehydration reaction of fructose and glucose to 5-hydroxymethylfurfural (HMF). SEM, TEM, N2 adsorption-desorption, elemental analysis (EA), thermogravimetric analysis (TGA), and FT-IR were used to explore the effects of catalyst structure and composition on the HMF preparation from fructose. The effects of reaction time and temperature on the dehydration of fructose and glucose were also investigated. An HMF yield as high as 82.6% was achieved from fructose at 140 °C after 30 min, and 33.0% was achieved from glucose at 190 °C in 30 min. Furthermore, the recyclability of SPFR for the HMF production from fructose in 5 cycles was good.

Mesoporous Nb2O5 as solid acid catalyst for dehydration of d-xylose into furfural

García-Sancho,Rubio-Caballero,Mérida-Robles,Moreno-Tost,Santamaría-González,Maireles-Torres

, p. 119 - 124 (2014)

The acid-catalyzed dehydration of d-xylose to furfural has been investigated in a biphasic water-toluene system, using a mesoporous Nb 2O5 catalyst prepared by a neutral templating route. The catalytic behavior was compared with a commercial Nb2O5. Materials were characterized by XRD, XPS, TEM, NH3-TPD, Raman spectroscopy and N2 sorption. The d-xylose conversion and furfural yield over the mesoporous niobia were found to increase with reaction temperature and time, in such a way that at 170 °C and 90 min, a d-xylose conversion and a furfural yield were higher than 90% and 50%, respectively. However, the commercial crystalline niobia displayed a low activity. The stability of the mesoporous catalyst has been demonstrated by XRD and N 2 sorption, and corroborated by the absence of significant niobium leaching in solution.

Dehydration of biomass to furfural catalyzed by reusable polymer bound sulfonic acid (PEG-OSO3H) in ionic liquid

Zhang, Zhang,Du, Bin,Quan, Zheng-Jun,Da, Yu-Xia,Wang, Xi-Cun

, p. 633 - 638 (2014)

Polymer bound sulfonic acid (PEG-OSO3H) is active for the dehydration of biomass to furfural. The furfural yield is improved when MnCl2 is added to the reaction mixture. The catalyst was mild, non-volatile, and non-corrosive and can be recycled multiple times (>10) without an intermediate regeneration step and no significant leaching of -OSO3H groups is observed.

Highly efficient and selective CO2-adjunctive dehydration of xylose to furfural in aqueous media with THF

Morais, Ana Rita C.,Bogel-Lukasik, Rafal

, p. 2331 - 2334 (2016)

The selective dehydration of xylose into furfural using high-pressure CO2 as an effective and more sustainable catalyst in an H2O/THF system is reported for the first time. The conversion of d-xylose into furfural above 83 mol% with a furfural yield of 70 mol% and a selectivity of 84% was achieved with only 50 bar of CO2 pressure within 1 hour at 180 °C.

A modified biphasic system for the dehydration of d-xylose into furfural using SO42-/TiO2-ZrO2/La 3+ as a solid catalyst

Li, Huiling,Deng, Aojie,Ren, Junli,Liu, Changyu,Wang, Wenju,Peng, Feng,Sun, Runcang

, p. 251 - 256 (2014)

One of the most promising strategies for furfural production is to extract continually the target product from the aqueous solution utilizing organic solvents. With the aim to develop an ecologically viable catalytic pathway for furfural production without the addition of mineral acids, we presented a modified biphasic system using a solid acid (SO42-/ TiO2-ZrO2/La3+) as catalyst for producing furfural from xylose. Different kinds of aprotic organic solvents (DMSO, DMF and DMI) in water phase and 2-butanol in organic phase (MIBK) were investigated as reaction media. Furfural yield and xylose conversion efficiency were dependent on the amounts of aprotic organic solvents and 2-butanol, the solid/liquid ratio, and the volume ratio of the organic phase and the aqueous phase as well as the reaction temperature and time. As a result, DMI showed the best performance on improving furfural yield during the furfural production. 3563.3 μmol of furfural/g of xylose with 97.9% xylose conversion efficiency was obtained after 12 h at 180 °C when the volume ratios of water to DMI and MIBK to 2-butanol were 8:2 and 7:3, respectively.

Catalytic dehydration of D-xylose to furfural over a tantalum-based catalyst in batch and continuous process

Li, Xing-Long,Pan, Tao,Deng, Jin,Fu, Yao,Xu, Hua-Jian

, p. 70139 - 70146 (2015)

Furfural is a biomass-based bulk chemical and its derivatives have potential applications as renewable fuels and chemicals. A water-tolerant and stable solid acid catalyst modified hydrated tantalum oxide (TA-p) was developed for catalytic conversion of D-xylose to furfural in water-organic solvent biphasic system. This process was performed both in a batch reactor and a continuous fixed-bed reactor. In the batch process, D-xylose conversion and furfural yield were significantly affected by the organic solvent, reaction temperature and reaction time. 1-Butanol, which could be obtained through the fermentation of biomass-based carbohydrates, was selected as organic phase and the highest furfural yield of 59% was achieved with D-xylose conversion of 96% at 180 °C in the continuous process. Moreover, the long-time stability test for 80 h under the optimal conditions showed the excellent stability of TA-p catalyst.

Conversion of C5 carbohydrates into furfural catalyzed by a Lewis acidic ionic liquid in renewable γ-valerolactone

Wang, Shurong,Zhao, Yuan,Lin, Haizhou,Chen, Jingping,Zhu, Lingjun,Luo, Zhongyang

, p. 3869 - 3879 (2017)

For the purpose of building a green reaction system to produce furfural (FF), the conversion of two important pentoses from hemicellulose, namely xylose and arabinose, was investigated in an aqueous reaction system including a Lewis acidic ionic liquid as a catalyst and renewable γ-valerolactone (GVL) as a co-solvent. The results showed that the introduction of GVL greatly improved the reactivity of pentose and inhibited the secondary decomposition reaction of FF compared to a pure-water reaction system. NMR analysis suggested that the composition of pentose conformers was greatly altered towards a reactive distribution. The highest FF yields were 79.76% (from xylose) and 58.70% (from arabinose), which were obtained at 140 °C. The influence of reaction parameters on pentose conversion was also studied. A comparison between different reaction conditions suggested that arabinose had less reactivity than xylose, leading to its lower conversion rate and FF yield. Furthermore, xylan and real biomass materials were tested in the proposed reaction system, and decent FF yields of up to 69.66% (from xylan) and 47.96% (from corn stalk) were obtained.

Furfural synthesis from D-xylose in the presence of sodium chloride: Microwave versus conventional heating

Xiouras, Christos,Radacsi, Norbert,Sturm, Guido,Stefanidis, Georgios D.

, p. 2159 - 2166 (2016)

We investigate the existence of specific/nonthermal microwave effects for the dehydration reaction of xylose to furfural in the presence of NaCl. Such effects are reported for sugars dehydration reactions in several literature reports. To this end, we adopted three approaches that compare microwave-assisted experiments with a) conventional heating experiments from the literature; b) simulated conventional heating experiments using microwave-irradiated silicon carbide (SiC) vials; and at c) different power levels but the same temperature by using forced cooling. No significant differences in the reaction kinetics are observed using any of these methods. However, microwave heating still proves advantageous as it requires 30% less forward power compared to conventional heating (SiC vial) to achieve the same furfural yield at a laboratory scale.

Dunlop

, p. 204,206 (1948)

The role of metal halides in enhancing the dehydration of xylose to furfural

Enslow, Kristopher R.,Bell, Alexis T.

, p. 479 - 489 (2015)

The dehydration of xylose yields furfural, a product of considerable value as both a commodity chemical and a platform for producing a variety of fuels. When xylose is dehydrated in aqueous solution in the presence of a Bronsted acid catalyst, humins are formed via complex side processes that ultimately result in a loss in the yield of furfural. Such degradative processes can be minimized via the insitu extraction of furfural into an organic solvent. The partitioning of furfural from water into a given extracting solvent can be enhanced by the addition of salt to the aqueous phase, a process that increases the thermodynamic activity of furfural in water. Although the thermodynamics of using salts to improve liquid-liquid extraction are well studied, their impact on the kinetics of xylose dehydration catalyzed by a Bronsted acid are not. The aim of the present study was to understand how metal halide salts affect the mechanism and kinetics of xylose dehydration in aqueous solution. We found that the rate of xylose consumption is affected by both the nature of the salt cation and anion, increasing in the order no salt+++ and no salt---. Furfural selectivity increases similarly with respect to metal cations, but in the order no salt--- for halide anions. Multinuclear NMR was used to identify the interactions of cations and anions with xylose and to develop a model for explaining xylose-metal halide and water-metal halide interactions. The results of these experiments coupled with 18O-labeling experiments indicate that xylose dehydration is initiated by protonation at the C1OH and C2OH sites, with halide anions acting to stabilize critical intermediates. The means by which metal halides affect the formation of humins was also investigated, and the role of cations and anions in affecting the selectivity to humins is discussed. Get your kicks from kinetics: The effect of metal halides on the mechanism and kinetics of xylose dehydration in aqueous solution have been investigated. We found that both the rate of xylose consumption and furfural selectivity are affected by the nature of the salt cation and anion pairing.

Furfural from corn stover hemicelluloses. A mineral acid-free approach

Gomez Bernal, Hilda,Bernazzani, Luca,Raspolli Galletti, Anna Maria

, p. 3734 - 3740 (2014)

Furfural was obtained from corn stover hemicelluloses by a microwave-assisted, green and heterogeneously catalyzed two-step cascade process as follows: first step, hydrothermal fractionation of corn stover hemicelluloses, and second step, hydrolysis/dehydration of soluble hemicellulosic sugars over niobium phosphate to yield furfural at moderate temperatures (200 °C), with both steps being performed in water. Furfural yields of up to 23 mol% with respect to the starting raw biomass were reached. This journal is the Partner Organisations 2014.

One-pot sustainable synthesis of valuable nitrogen compounds from biomass resources

Carreira, M. Carolina A.,Fernandes, Ana C.,Oliveira, M. Concei??o

, (2022/01/11)

In this work we report a new one-pot process for the sustainable synthesis of 2-furanylquinazolines and 2-furfurylidene derivatives from carbohydrates, including xylose, fructose and xylan, with moderate overall yields, catalyzed by perrhenic acid.

Ethanolysis of selected catalysis by functionalized acidic ionic liquids: An unexpected effect of ILs structural functionalization on selectivity phenomena

Nowakowska-Bogdan, Ewa,Nowicki, Janusz

, p. 1857 - 1866 (2022/02/05)

A series of functionalized hydrogen sulfate imidazolium ILs were synthesized and applied as catalysts in the reaction of glucose, xylose and fructose with ethanol. In this research, an unexpected selectivity phenomenon was observed. It showed that in this reaction functionalized ILs should be considered as a special type of catalyst. Functionalization of alkyl imidazolium ILs, especially the addition of electronegative OH groups, causes a clear and unexpected effect manifested via visible changes in the selectivity of the reaction studied. In the case of fructose, an increase in the number of OH groups affects an increase in the selectivity towards ethyl levulinate from 14.2% for [bmim]HSO4 to 20.1% for [glymim]HSO4 with an additional increase in selectivity to 5-hydroxymethyfurfural. In turn, for xylose, the introduction of OH groups to the alkyl chain was manifested by a decrease in selectivity to furfural as its ethyl acetal and an increase in selectivity to ethylxylosides. This journal is

PhIO-Mediated oxidative dethioacetalization/dethioketalization under water-free conditions

Du, Yunfei,Ouyang, Yaxin,Wang, Xi,Wang, Xiaofan,Yu, Zhenyang,Zhao, Bingyue,Zhao, Kang

, p. 48 - 65 (2021/06/16)

Treatment of thioacetals and thioketals with iodosobenzene in anhydrous DCM conveniently afforded the corresponding carbonyl compounds in high yields under water-free conditions. The mechanistic studies indicate that this dethioacetalization/dethioketalization process does not need water and the oxygen of the carbonyl products comes from the hypervalent iodine reagent.