Dilute Acid Hydrolysis of Wheat Straw Oligosaccharides

The dilute acid posthydrolysis of wheat straw hemicellulosic oligosaccharides obtained by autohydrolysis was evaluated. An empirical model was used to describe the effect of catalyst concentration (sulfuric acid, 0.1–4% w/w) and reaction time (0–60 min) based on data from a Doehlert experimental design. Catalyst concentration is the main variable influencing posthydrolysis performance, as both its linear and quadratic coefficients are statistically significant for the majority of the studied variables, namely, the ones related to sugar and byproducts production. Reaction time influences xylose and furan derivatives concentrations but not phenolics or acetic acid content. Catalyst concentration and reaction time interact synergistically, minimizing sugar recovery and promoting furan derivatives production. Based on the proposed models, it was possible to delimit an operational range that enables to obtain high monosaccharides recovery together with a slight decrease in inhibitors content as compared to the standard acid hydrolysis treatment. Furthermore, this is achieved with up to 70% less acid spending or considerable savings on reaction time.     

生物质半纤维素稀酸水解反应

半纤维素是木质纤维素类生物质中第二大组分,半纤维素的高效、低成本转化是实现木质纤维素类生物质转化工艺实用化的一个技术关键。稀酸水解技术被广泛应用于水解生物质半纤维素,其对半纤维素糖的转化率高,得到的糖可进一步发酵生产燃料乙醇等。半纤维素还可直接水解制低聚糖等功能性食品和糠醛等化工产品。本文综述了半纤维素稀酸水解反应的研究进展。介绍了半纤维素的基本结构特征,解析了稀酸催化半纤维素水解的反应机理及反应网络,评述了半纤维素水解过程中反应条件等对目标产物的影响,并总结了半纤维素稀酸水解动力学模型。在此基础上,对今后半纤维素稀酸水解反应的研究方向与水解产物的利用进行了展望。     

High Xylose Yields from Dilute Acid Pretreatment of Corn Stover Under Process-Relevant Conditions

Pretreatment experiments were carried out to demonstrate high xylose yields at high solids loadings in two different batch pretreatment reactors under process-relevant conditions. Corn stover was pretreated with dilute sulfuric acid using a 4-l Steam Digester and a 4-l stirred ZipperClave® reactor. Solids were loaded at 45% dry matter (wt/wt) after sulfuric acid catalyst impregnation using nominal particle sizes of either 6 or 18 mm. Pretreatment was carried out at temperatures between 180 and 200 °C at residence times of either 90 or 105 s. Results demonstrate an ability to achieve high xylose yields (>80%) over a range of pretreatment conditions, with performance showing little dependence on particle size or pretreatment reactor type. The high xylose yields are attributed to effective catalyst impregnation and rapid rates of heat transfer during pretreatment.     

The Optimization of Dilute Acid Hydrolysis of Cotton Stalk in Xylose Production

Cotton stalk, a lignocellulosic waste material, is composed of xylose that can be used as a raw material for production of xylitol, a high-value product. There is a growing interest in the use of lignocellulosic wastes for conversion into various chemicals because of their low cost and the fact that they are renewable and abundant. The objective of the study was to determine the effects of H₂SO₄ concentration, temperature, and reaction time on the production of sugars (xylose, glucose, and arabinose) and on the reaction by-products (furfural and acetic acid). Response surface methodology was used to optimize the hydrolysis process in order to obtain high xylose yield and selectivity. The optimum reaction temperature, reaction time, and acid concentration were 140 °C, 15 min, and 6%, respectively. Under these conditions, xylose yield and selectivity were found to be 47.88% and 2.26 g g⁻¹, respectively.     

Production of Xylose from Meranti Wood Sawdust by Dilute Acid Hydrolysis

Xylitol production by bioconversion of xylose can be economically interesting if the raw material can be recovered from a cheap lignocellulosic biomass (LCB). Meranti wood sawdust (MWS) is a renewable and low-cost LCB that can be used as a promising and economic source of xylose, a starting raw material for the manufacture of several specialty chemicals, especially xylitol. This study aimed to optimize the hydrolysis process of MWS and to determine the influence of temperature, H₂SO₄ concentration, and residence time on xylose release and on by-product formation (glucose, arabinose, acetic acid, furfural, hydroxymethylfurfural (HMF), and lignin degradation products (LDPs)). Batch hydrolysis was conducted under various operating conditions, and response surface methodology was adopted to achieve the highest xylose yield. Xylose production was highly affected by temperature, acid concentration, and residence time. The optimum temperature, acid concentration, and time were determined to be 124 °C, 3.26 %, and 80 min, respectively. Under these optimum conditions, xylose yield and selectivity were attained at 90.6 % and 4.05 g/g, respectively.     

Impact of Pretreatment with Dilute Sulfuric Acid Under Moderate Temperature on Hydrolysis of Corn Stover with Two Enzyme Systems

Pretreatment of corn stover with dilute sulfuric acid at moderate temperature was investigated, and glucan digestibility by Cellic CTec2 and Celluclast on the pretreated biomass was compared. Pretreatments were carried out from 60 to 180 min at the temperature from 105 to 135 °C, with acid concentrations ranging from 0.5 to 2 % (w/v). Significant portion of xylan was removed during pretreatment, and the glucan digestibility by CTec2 was significantly better than that by Celluclast in all cases. Analysis showed that glucan digestibility by both two enzymes correlated directly with the extent of xylan removal in pretreatment. Confidence interval was built to give a more precise range of glucan conversion and to test the significant difference among pretreatment conditions. Response surface model was built to obtain the optimal pretreatment condition to achieve high glucan conversion after enzymatic hydrolysis. Considering the cost and energy savings, the optimal pretreatment condition of 1.75 % acid for 160 min at 135 °C was determined, and glucan conversion can achieve the range from 72.86 to 76.69 % at 95 % confidence level after enzymatic hydrolysis, making total glucan recovery up to the range from 89.42 to 93.25 %.     

超(近)临界条件下醋酸甲酯水解过程研究

超(近)临界水作为优良的有机反应溶剂适合于针对酸碱催化类型有机反应绿色工艺的开发.本课题以具备工业生产背景的醋酸甲酯水解作为研究体系,在一管式反应器中,将原料(5%质量分数)置于体系的超(近)临界条件下(523～673K,23～32MPa)进行反应操作.实验结果表明,在无外加酸性催化剂情况下,水解反应以接近1的选择性,在150～300s内达到热力学平衡限制,同时在系统临界点附近,溶剂化作用对反应动力学影响显著.根据SN2反应机理对反应动力学方程进行了回归.     

Amino Acid Functionalization of {Ni6PW9}-Based Clusters Under Hydrothermal Conditions

Two novel hexa-nickel(II)-substituted Keggin-type {Ni₆PW₉}-based tungstophosphates [Ni₆(μ ₃-Tris)(en)₃(Pr)(damp)(H₂O)₂(B-α-PW₉O₃₄)]·10H₂O (1) and [Ni₆(μ ₃-Tris)(en)₃(damp)₂(H₂O)₂(B-α-PW₉O₃₄)]·7H₂O (2) (en = ethylenediamine, Pr = CH₃CH₂COO^?, damp = 2-aminoisobutyrate, Tris = pentaerythritol) were hydrothermally synthesized and characterized by IR spectra, elemental analyses, powder X-ray diffraction, thermogravimetric analyses, and single-crystal X-ray diffraction. Crystal data for 1: orthorhombic, Pca2₁, a = 21.6962(7) Å, b = 20.6398(5) Å, c = 14.7825(4) Å, β = 90º, V = 6619.7(3) Å³, Z = 4; for 2: orthorhombic, Pca2₁, a = 21.6978(9) Å, b = 20.6658(7) Å, c = 14.7767(4) Å, β = 90º, V = 6625.9(4) Å³, Z = 4. 1 consists of a {Ni₆(μ ₃-Tris)(en)₃(Pr)(damp)(H₂O)₂}⁹⁺ core and a [B-α-PW₉O₃₄]^9? (PW₉) unit and is covalently functionalized by one Pr and one damp, as well as en and Tris ligands. The structure of 2 is the same to 1 except that the Pr anion in 1 is substituted by the other damp ligand. Most interestingly, 1 contains four kinds of organic ligands, while 2 includes three kinds of organic ligands, which are first observed in polyoxometalate chemistry.     

Hydrolysis of Titanium(IV) Sulfate Solutions under Hydrothermal Conditions

The structure and the phase, granulometric, and chemical composition of hydrated titanium dioxide obtained by hydrolysis of oxotitanium(IV) sulfate and ammonium titanium(IV) oxysulfate solutions under hydrothermal conditions (130-170°C) were studied by X-ray and chemical analyses, electron microscopy, and thermogravimetry. The effect of hydrolysis conditions on the formation of samples with globular shape of particles was studied.     

气敏材料Cd2V2O7的制备和性能

用水热氧化法制备出γＭｎ２Ｏ３粉末,并在不同温度下进行烧结．采用ＸＲＤ,ＴＥＭ,ＸＰＳ,ＩＲ及紫外分光光度法等表征产物．结果表明,未烧结产物即为单相纳米晶,大部分近似球形,有轻微团聚．产物于空气中１００～５５０℃范围内烧结时热稳定性好．随烧结温度的升高粉末的平均粒子尺寸增大,产物中锰以Ｍｎ（Ⅲ）状态存在．     

Synthesis of Coordination Polymers Using Different Maleic Acid Ligands under Hydrothermal Conditions

A novel coordination polymer, [Ni(mal)(1,10′-phen)(H2O)]n(1)(mal=malate, 1,10′-phen=1,10-phenanthroline) was synthesized using malic acid which was generated from maleic acid via hydrothermal reaction. Complex 1, which displays a two-dimensional supramolecular network, was formed by the addition reaction of Ni and maleic acid with water molecules. To our knowledge, several coordination polymers have been directly synthesized from malic acid, but these types of complexes have seldom been synthesized from maleic acid via hydrothermal reactions. When Ni(Ⅱ) ion was changed to Zn(Ⅱ) ion under the same condition, two-dimensional covalent complex 2[Zn2(fma)2(1,10′-phen)2]n(fma=fumatic acid) was formed. Furthermore, complex 2 exhibits intense photoluminescent property at room temperature.     

果糖一步水热合成碳微球固体酸催化纤维素水解

纤维素水解是生物质资源转化利用中最关键的一步. 通过硫酸浸渍活性炭方法制备的磺酸基功能化活性炭是目前纤维素水解反应中应用最为广泛的固体酸之一,但这种方法存在严重的环境污染问题. 我们利用果糖的水热碳化,在150 ℃的温和条件下合成了一种新型的富含羧基和羟基的碳微球固体酸,在离子液体1-丁基-3-甲基咪唑氯盐[BMIM][Cl]溶剂体系中,该碳微球可以有效地将纤维素水解（130 ℃,反应3 h,还原糖产率45.6%）. 为了进一步提高碳微球固体酸的活性,以磺基水杨酸为共聚物,利用果糖的水热碳化反应,通过一步水热法合成了含有磺酸基的碳微球固体酸催化剂. 系统研究了该催化剂作用下反应温度、反应时间、催化剂使用量、水的添加量以及纤维素起始浓度等因素对纤维素催化水解的影响. 在[BMIM][Cl]溶剂中,纤维素水解的还原糖产率提高到了60.7% （130 ℃,反应90 min）,且催化剂循环5次后仍能保持良好催化活性. 本工作利用果糖一步水热法制备碳微球固体酸,并将其应用于纤维素的高效水解,为生物质资源的高值化提供了一条新路径.     

Catalytic Synthesis of 3-Alkoxyacrylic Acid Esters Under Neat Conditions

Triethylamine or Ph₃P (0.05 eq.) was found to catalyze the addition of alcohols to alkyl propiolates. The reaction occurred much more rapidly without solvent than in solvent. The E/Z ratio was relative to the reaction temperature. Water was found to inhibit the reaction.     

苯甲酸稀溶液的萃取特性

磷酸三丁酯;正辛醇;苯甲酸稀溶液的萃取特性     

Optimization of High Solids Dilute Acid Hydrolysis of Spent Coffee Ground at Mild Temperature for Enzymatic Saccharification and Microbial Oil Fermentation

Soluble coffee, being one of the world’s most popular consuming drinks, produces a considerable amount of spent coffee ground (SCG) along with its production. The SCG could function as a potential lignocellulosic feedstock for production of bioproducts. The objective of this study is to investigate the possible optimal condition of dilute acid hydrolysis (DAH) at high solids and mild temperature condition to release the reducing sugars from SCG. The optimal condition was found to be 5.3 % (w/w) sulfuric acid concentration and 118 min reaction time. Under the optimal condition, the mean yield of reducing sugars from enzymatic saccharification of defatted SCG acid hydrolysate was 563 mg/g. The SCG hydrolysate was then successfully applied to culture Lipomyces starkeyi for microbial oil fermentation without showing any inhibition. The results suggested that dilute acid hydrolysis followed by enzymatic saccharification has the great potential to convert SCG carbohydrates to reducing sugars. This study is useful for the further developing of biorefinery using SCG as feedstock at a large scale.     

Raman Spectroscopy of Aqueous ZnSO4 Solutions under Hydrothermal Conditions: Solubility, Hydrolysis, and Sulfate Ion Pairing

Raman spectra have been measured for aqueous ZnSO₄ solutions under hydrothermal conditions at steam saturation to 244°C; solubility has been recorded as a function of temperature from 25 to 256°C. The high-temperature Raman spectra contained two polarized bands, which suggest that a second sulfato complex, possibly bidentate, is formed in solution, in addition to the 1:1 zinc(II) sulfato complex, which is the only ion pair identified at lower temperatures. Under hydrothermal conditions, it was possible to observe the hydrolysis of the zinc(II) aquo ion by measuring the relative intensity of bands due to SO ₄ ^2– and HSO ₄ ^– according to the equilibrium reaction Zn(OH₂)₆]²⁺ + SO ₄ ^2– [Zn(OH₂)₅OH]⁺ + HSO ₄ ^– The precipitate in equilibrium with the solution at 210°C could be characterized as ZnSO₄ · H₂O (gunningite) by x-ray diffraction (XRD) and Raman and infrared spectroscopy. At 244°C the equilibrium precipitate could be identified as ZnSO₄ (zincosite).     

Hydrolysis of Nitrosylsulfuric Acid

The statics and kinetics of hydrolysis of nitrosylsulfuric acid were studied at the initial sulfuric acid concentrations in the range 60-76 wt % and temperatures in the range 20-100°C or 30-130°C. The results were compared with the published data.     

Unusual Reaction of Sodium 1,6-Dioxo-2,4-alkadiene-3,4-diolates under Acid Hydrolysis Conditions

The reaction of sodium 1,6-dioxo-2,4-alkadiene-3,4-diolates with HCl solution afforded unexpected hydrolysis products, namely (2Z)-2-hydroxy-4-oxobut-2-enoic (2,4-dioxobutanoic) acid esters. The structural features of the synthesized compounds were discussed on the basis of IR, ¹H NMR spectroscopy, mass spectrometry and X-ray diffraction analysis data.