分子筛催化木糖制备糠醛的研究

以5(A)分子筛为催化剂、甲苯为萃取剂、木糖为原料制备了糠醛,考察了催化剂用量、溶剂用量、反应时间及反应温度对糠醛产率的影响.确定最佳工艺参数为:5 g木糖、5(A)分子筛催化剂2.0 g、蒸馏水50 mL、甲苯100 mL、反应时间4 h、反应温度170℃,糠醛最大产率为29.2%.     

蔗渣预水解液酸催化制备糠醛及其萃取分离（急）

以蔗渣为原料,在高温低酸浓度（H2SO4添加量占蔗渣绝干质量的0.176%）条件下预水解得到富含木糖的预水解糖液,再进一步深度酸解得到糠醛,并以混合有机溶剂实现了糠醛从水相中高效萃取分离。对蔗渣预水解条件、糠醛的有机溶剂萃取条件进行了探索,并采用FT-IR、XRD、SEM、TGA对蔗渣及预水解渣的形貌和结构进行了表征,利用紫外分光光度计对预水解过程中的木糖及深度酸解过程中的糠醛进行了定量检测。结果表明,在160 °C,液固比6：1,浓硫酸/蔗渣绝干质量为0.176%条件下,预水解液中木糖浓度最高（41.72 g/L）;该预水解液直接在170 °C条件下深度酸解90 min,溶液中糠醛浓度最高可达15.91 g/L,糠醛摩尔得率最高为59.60%。以v(1,2-二氯乙烷):v(正丁醇) = 9:1的比例混合有机溶剂对水溶液中糠醛进行萃取,萃取相体积比为v(有机相):v(水相) = 2:1,糠醛的萃取率可达93.53%。     

二元溶剂体系中CrCl_3催化木糖制备糠醛的研究

对木糖在甲苯/水二元溶剂体系中直接转化制备糠醛进行研究。考察了6种氯化物CrCl3·6H2O,AlCl3·6H2O,FeCl3,CuCl2·2H2O,CoCl2·6H2O,ZnCl2的催化效果,结果表明:选用的金属氯化物均具有一定的催化效果,其中CrCl3·6H2O的催化效果明显优于其他氯化物。以CrCl3·6H2O为催化剂,系统研究反应温度、反应时间、催化剂浓度、木糖质量分数、NaCl添加量对糠醛产率的影响,反应的最佳条件为:反应温度140℃、反应时间60 min,CrCl3·6H2O浓度0.1 mol/L,木糖及NaCl的质量分数分别为4%和15%。在该条件下,糠醛产率为52.55%。     

玉米芯水解制备木糖的研究

文章对玉米芯酸性水解制备木糖的工艺条件进行了研究。以硫酸作为催化剂,考察了不同的反应温度、酸浓度、反应时间、固液物料比及浓缩次数对木糖产率的影响。得出最佳的制备木糖的工艺条件为:酸浓度为3%、反应时间3小时、物料比1∶8、沸腾浓缩3次,该条件下木糖收率可达49.74%。     

离子液体中超低浓度混合酸催化纤维素制5-羟甲基糠醛

以绿色溶剂离子液体1-甲基-3-甲基咪唑磷酸二甲基盐(1-methyl-3-methyl-imidazole dimethyl phosphate,[DMIM][DMP])作为反应介质,研究超低浓度的混合酸--马来酸与盐酸(0.1%,质量分数)催化纤维素转化制备5-HMF。微波功率720W,反应时间9min,温度240℃,酸浓度0.1%,固液比1:50(质量比)为最佳反应条件,此条件下5-羟甲基糠醛的产率最高可达29.13%,转化效率为6.48mg/min。     

Al_2(SO_4)_3催化玉米芯直接液化制备糠醛研究

以玉米芯为原料,采用Al_2(SO_4)_3催化液化选择性制备糠醛,考察反应温度、催化剂添加量及水含量对玉米芯转化及糠醛产率的影响。结果表明,Al2(SO4)3催化剂对玉米芯液化及糠醛选择性制备具有明显的促进作用。研究获得玉米芯选择性制备糠醛的最佳反应条件为:反应温度150℃、催化剂添加量0. 45 g及水含量10%。最佳反应条件下玉米芯转化率为78. 5%,糠醛产率为84. 9%。玉米芯及其液化残渣的红外及热重分析表明,玉米芯中三大组分均得到了明显降解。     

Al_2(SO_4)_3催化玉米芯直接液化制备糠醛研究

以玉米芯为原料,采用Al_2(SO_4)_3催化液化选择性制备糠醛,考察反应温度、催化剂添加量及水含量对玉米芯转化及糠醛产率的影响。结果表明,Al2(SO4)3催化剂对玉米芯液化及糠醛选择性制备具有明显的促进作用。研究获得玉米芯选择性制备糠醛的最佳反应条件为:反应温度150℃、催化剂添加量0. 45 g及水含量10%。最佳反应条件下玉米芯转化率为78. 5%,糠醛产率为84. 9%。玉米芯及其液化残渣的红外及热重分析表明,玉米芯中三大组分均得到了明显降解。     

在乙酸丁酯-水双相体系中玉米芯水解制备糠醛

以玉米芯为原料、硫酸铁为催化剂、乙酸丁酯为萃取剂,在乙酸丁酯-水双相体系中水解制备糠醛。考察了反应时间、催化剂浓度(硫酸铁溶液质量分数)、反应温度以及萃取剂与溶剂体积比对糠醛产率的影响,确定最佳工艺条件为:反应时间3.0h,催化剂浓度10%,反应温度160℃,萃取剂与溶剂体积比为4,在此条件下,糠醛产率达到43.49%。     

碳基固体酸催化D-木糖选择性转化合成糠醛的研究

采用固体酸催化D-木糖脱水制备糠醛具有经济价值高、易分离和环境友好等优点;本文中,主要研究了碳基固体酸在木糖脱水中的催化性能,所用的固体酸包括木质素磺酸聚合物催化剂（LF-A, LF-B, LF-C, LF-D）和磺化碳材料FS等;其中,木质素磺酸聚合物催化剂是借助酚醛缩合过程将木质素磺酸盐和醛类反应制得;磺化碳材料则是采用水热合成法以糠醛、十二烷基苯磺酸钠为原料制备;通过对催化剂种类、反应媒介、时间、催化剂用量及反应温度等条件的详细研究,发现LF-A催化剂的效果较好,当原料D-木糖为1.0 g,反应温度为170 ºC,反应时间4 h,催化剂用量为0.08 g,溶剂为γ-丁内酯时,糠醛的收率可达72.9%;同时,对固体酸催化剂进行XRD,FT-IR,TG-DTG,SEM和TEM等表征,并找出了催化剂结构与活性之间的相互关系.     

绿色溶剂γ-戊内酯中果糖催化转化为5-羟甲基糠醛

通过生物质衍生糖的酸催化转化制备生物质基平台化合物5-羟甲基糠醛受到关注。常用又有效的溶剂包括离子液体和二甲基亚砜等,但这些溶剂黏度高,易造成空气污染。以γ-戊内酯作为溶剂,研究果糖催化转化为5-羟甲基糠醛的绿色过程,系统研究酸催化剂种类、反应温度、催化剂用量、果糖初始浓度及底物种类等对5-羟甲基糠醛产率的影响。通过反应条件的优化,以HCl溶液为催化剂,在果糖初始质量浓度2%、反应温度100℃和反应时间30 min条件下,5-羟甲基糠醛产率为93.5%。5-羟甲基糠醛产率随果糖初始添加量的增加而呈下降趋势,但果糖初始质量浓度为10%时,5-羟甲基糠醛产率仍保持约90%,表明γ-戊内酯是一种将果糖催化转化为5-羟甲基糠醛的优良绿色溶剂。     

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%。     

草酸水解甜高粱秸秆渣的Saeman动力学模型

利用草酸作为催化剂水解甜高粱秸秆渣制备木糖,测定了不同温度下的木糖收率和副产物糠醛产量;依据半纤维素水解的Saeman模型,计算得到了木聚糖水解和木糖降解的动力学数据,其活化能分别为5.89×104,1.38×104J/mol。分析结果表明:木聚糖水解反应速度快,但是生成的木糖容易发生降解;模型最优化反应条件为125℃和77min,实验得到的木糖收率为52.11%。草酸作为一种有机酸,能够用于催化半纤维素水解制备木糖,副产物糠醛的产率较低。     

Production of Furfural from Lignocellulosic Biomass Using Beta Zeolite and Biomass-Derived Solvent

The production of furfural from the C₅ monosaccharides xylose, arabinose and ribose, as well as from real biomass (corn fiber), was studied using H-Beta zeolite as catalyst in a monophasic system with the biomass-derived solvent, gamma-valerolactone. Due to the combination of Brønsted and Lewis acid sites on this catalyst (Brønsted:Lewis ratio = 1.66), H-Beta acts as a bifunctional catalyst, being able to isomerize (Lewis acid) and dehydrate (Brønsted acid) monosaccharides. The combination of Lewis and Brønsted acid functionality of H-Beta was shown to be effective for the isomerization of xylose and arabinose, followed by dehydration. While no advantages were found in the conversion of xylose, higher furfural yields were achieved from arabinose, using H-Beta, 73 %, compared to sulfuric acid (44 %) and Mordenite (49 %). The furfural yields from corn fiber for H-Beta, H-Mordenite and sulfuric acid were 62, 44, and 55 %, respectively, showing that H-Beta is particularly effective for conversion of this biomass feedstock composed of 45 wt% hemicellulose, of which 66 % is xylose and 33 % arabinose.     

Dehydration of xylose into furfural over micro-mesoporous sulfonic acid catalysts

Surfactant-templated micro-mesoporous silicas possessing sulfonic acid groups (SAGs) have been prepared, characterized, and tested as catalysts in the dehydration of d-xylose to furfural. All of the materials possessed catalytic activity. In general, selectivity to furfural was lower for a poorly ordered microporous hybrid material, prepared via the co-condensation of (3-mercaptopropyl)trimethoxysilane with bis(trimethoxysilylethyl)benzene, than for mesoporous MCM-41 silica anchored with SAGs via postsynthesis modification. The MCM-41 material with the highest loading of SAGs (0.7 meq g⁻¹) displayed fairly high selectivity for furfural (ca. 82% in DMSO or water/toluene mixture) at high xylose conversion (>90% within 24 h, at 140 °C). Xylose conversion increased significantly with reaction temperature. At 170 °C, more than 85% conversion was achieved within 4 h with any of the sulfonic acid-functionalized catalysts. Furfural yield tended to increase with temperature. Xylose conversion increased with increasing amount of catalyst, and for a xylose/MCM-41-SO₃H ratio of 0.5, 76% conversion was achieved within 4 h, at 140 °C. Catalyst deactivation was observed after long residence times, possibly because of the interaction of reaction products with the acid sites, leading to surface loading.     

负载型Keggin杂多酸催化糠醛液相氧化制备顺酐

用不同比例的四水合钼酸铵、偏钒酸铵、钨酸、草酸和磷酸等合成了4种Keggin杂多酸,并以SiO_2为载体,采用浸渍法制备了负载型的Keggin杂多酸催化剂。采用红外光谱(FT-IR)、X射线衍射(XRD)、扫描电镜(SEM)和程序升温脱附(NH_3-TPD)等手段对催化剂进行表征。以合成的负载型杂多酸为催化剂,H_2O_2为氧化剂,二氯乙烷为溶剂,研究了催化剂催化糠醛液相氧化制备顺酐的性能,考察了催化剂种类和用量,溶剂、氧化剂用量,反应温度和反应时间对糠醛转化率和顺酐收率的影响。结果表明,以MoWP/SiO_2为催化剂,催化反应性能较好,较佳的工艺条件为反应温度60℃,反应时间3 h,催化剂与糠醛的质量比为0.09,二氯乙烷和糠醛物质的量之比为3,H_2O_2和糠醛物质的量之比为2.5,在此条件下糠醛的转化率为82.33%,顺酐的收率和选择性分别可达78.51%和95.36%。催化剂在使用5次后,顺酐的收率为64.18%,重复使用性能较好。     

A kinetic study of xylose recovery from a hemicellulose-rich biomass for xylitol fermentative production

Hemicellulose in the complex structure of lignocellulosic substances is mainly composed of xylan which is a polymer based on monosaccharide xylose. Using acidic or enzymatic hydrolysis, hemicellulose can be depolymerized into its constituent monomer. The kinetics of hemicellulose depolymerization and decomposition in oat hull was investigated under moderate pressures with catalyst (H₂SO₄) concentration up to 0.55?N and temperatures of up to 130?°C for a total residence time of 150?min. Different trends of recovery or generation and kinetic mechanisms obtained for the components in the hydrolysate which could be described by different kinetic models, that is, a single-phase kinetic mechanism with product decomposition (two-step sequential reaction) could describe xylose generation. However, generation of arabinose, furfural, and acetic acid followed a single-phase mechanism with no decomposition (one-step reaction). Generation of glucose in the hydrolysate followed a biphasic mechanism due to the fast- and slow-releasing fractions into the liquid phase which was apparently with no decomposition. A pentose recovery of almost 80% was achieved under optimal conditions. Parameters of xylitol bioproduction indicated that a xylitol/xylose conversion yield of 0.80?g/g is achievable from the concentrated hydrolysate with no complementary treatment proving its low toxicity compared to other hemicellulose resources.     

氯化铁催化木糖降解制备糠醛反应动力学

研究了温度在443.15～483.15K时0.1mol/L氯化铁催化木糖降解生成糠醛的反应动力学过程。首先建立并验证了反应的动力学模型,根据模型得到了木糖降解、糠醛降解和缩合反应的速率常数。由阿伦尼乌斯方程拟合得到其表观活化能分别为107.94kJ/mol、65.86 kJ/mol和26.36kJ/mol。结果表明,高温和较短反应时间有利于糠醛收率的提高,在反应温度483.15K、60min条件下,最大糠醛收率可达78%。     

糠醛气相加氢制2-甲基呋喃新型配合物催化剂研究

制备了一种新型、无毒Cu-Zn-Ca/γ- Al₂O₃配合物催化剂。采用固定床反应器,进行糠醛常压气相催化加氢反应,考察反应温度、催化剂组成、空速和氢醛比等因素的影响。结果表明,在508 K、空速0.32 h^-1、还原温度保持（493～513） K、活化6 h和氢醛物质的量比为10∶1条件下,糠醛转化率达到98.90%,2-甲基呋喃选择性达92.30%,2-甲基呋喃收率达91.28%。作为一种新型的无Cr催化剂,无毒,无污染,可代替Cu-Cr催化剂用于糠醛加氢过程,高活性和高选择性地制取2-甲基呋喃。     

High selective production of tetrahydrofurfuryl alcohol: Catalytic hydrogenation of furfural and furfuryl alcohol

Tetrahydrofurfuryl alcohol could be obtained by catalytic hydrogenation of either furfural or furfuryl alcohol using Pd-, Ru-, Rh- and Ni-supported catalysts as well as their mixtures with a Cu-supported catalyst. In the case of furfural hydrogenation, the best results (97 % yield, 100 % conversion, 98 % selectivity) were obtained in the presence of Ni and Cu. However, this catalytic mixture could not be recycled. In the case of furfuryl alcohol hydrogenation, Ni-supported catalysts were the most active. Nickel-onsilica-alumina catalyst containing 59 % of metal lead to the best results (98–99 % yield, selectivity and conversion >99 %). Moreover, it could be recycled. Hydrogenation of furfuryl alcohol in the presence of this catalyst was the best procedure for the production of tetrahydrofurfuryl alcohol.     

Efficient synthesis of furfural from xylose over HCl catalyst in slug flow microreactors promoted by NaCl addition

Efficient synthesis of furfural from xylose over the HCl catalyst in a water-methyl isobutyl ketone biphasic system was achieved in slug flow microreactors, using NaCl as a promotor which facilitates xylose dehydration and suppresses xylose condensation. An optimized furfural yield of 93% was obtained from 1 M xylose over 0.2 M HCl with 10 wt% NaCl at 180°C within 4 min. A comprehensive kinetic model was developed from monophasic experiments in water in microreactors, by incorporating the acidity in water and kinetic constants as a function of the chloride ion concentration. The coupling of kinetic model with furfural extraction, with consideration of phase volume change as a function of temperature and partial phase miscibility, enables to predict the results of biphasic experiments in microreactors where mass-transfer limitation was eliminated. The aqueous phase containing HCl and NaCl could be readily recycled and reused multiple times without noticeable performance loss.