有机酸溶木质素氢解制备单酚化合物的研究

首先利用木本类（硬木和软木）和禾本类不同生物质原料制备有机酸溶木质素，发现木本木质素的碳、氢元素含量和高位热值高于禾本木质素，软木木质素中β-O-4、β-β和β-5键含量高于硬木和禾本木质素。然后，通过不同种类木质素在乙醇/异丙醇中氢解实验发现，木本木质素氢解得到产物产率高于禾本木质素，其中杉木木质素的单酚产率最高，约为8.07%（质量分数）。此外，木本木质素解聚产生的单酚化合物以无侧链和三元碳侧链为主，而禾本木质素以二元碳侧链化合物为主。     

蒽醌-2-羧酸作为光催化剂催化解聚木质素

木质素是自然界中丰富的可再生芳香碳资源,其解聚得到的单体可以作为重要的化工原料。以蒽醌-2-羧酸作为光催化剂,在硝基苯存在和LED光源照射下,5 h内木质素模型化合物中β-O-4键有80%的转化率。对于木质素β-O-4多聚体,该体系也表现出了光催化活性,将蒽醌-2-羧酸负载在非均相载体上,在光催化降解中也可以获得77%的底物转化率。该反应涉及了木质素β-O-4中C_α—C_β键和C_β—O键的断裂,在催化剂的作用下,首先发生C_α—OH的脱氢,随后经过分子内的断键和重新成键生成苯甲醛和愈创木酚。本研究加深了对光催化木质素氧化过程中C—C键断裂过程的认识,有助于理解木质素的解聚机制。     

高温水热预处理对木质纤维素及其酶解的影响研究进展

木质素是木质纤维素的重要组成成分之一,能抑制木质纤维素的酶解,会在木质纤维素高温水热预处理过程中发生降解、重组等反应。假木质素是木质素的结构类似物,是木质纤维素在高温水热预处理过程中由碳水化合物经降解、氧化和聚合等复杂反应而形成。木质素和假木质素都能够抑制纤维素酶活性,降低木质纤维素的酶解转化率。文章综述了高温水热预处理过程中木质素的结构变化及假木质素的生成机理,探讨了降低木质素和假木质素对纤维素酶解影响以及减少假木质素生成的途径,为提高木质纤维素酶解转化率,促进工业化应用提供了参考。     

生物质高压液化

<正>生物质的高压液化与煤液化相比,生物质液化可在较温和的条件下进行。也可以把生物质的直接液化和它的水解工艺结合起来,用水解中生成的木质素残渣作液化原料。木质素的含氧量较低、能量密度较高对液化有利,已有的生物质液化研究许多是以木质素为原料的。生物质的高压液化主要有氢/供氢溶剂/催化剂路线和CO/H2O/碱金属催化剂路线。前者如德国联邦森林和林产品研     

甘油催化氢解制备丙二醇研究进展

有效利用生产生物柴油副产的甘油将有助于提高生物柴油产业的经济性。甘油催化氢解的反应机理比较复杂,由于反应条件、催化剂的不同,甘油氢解制丙二醇的机理也存在一定差异。但无论反应按哪种机理进行,都会得到1,2-丙二醇;而在碱性条件下反应时很难得到1,3-丙二醇;在同时产生1,2-丙二醇和1,3-丙二醇的情况下,很难判断哪些因素对它们的选择性具有决定性作用。典型的甘油催化氢解一般会采取液相加氢工艺,但通过增大氢油比和缩短停留时间,甘油气相加氢工艺也可以实现。此外,通过多步骤或利用超临界溶剂、保护基团等也可实现甘油氢解。甘油催化氢解采用的催化剂体系包括均相和非均相催化剂,大部分是含铜、锌等副族金属元素和第Ⅷ族金属元素如镍、钌、铂、钯和铑的催化剂。均相催化剂对1,3-丙二醇有很高的选择性,最高可以达到1,3-丙二醇/1,2-丙二醇=2;非均相催化剂对1,3-丙二醇没有选择性,主要得到1,2-丙二醇和1,3-丙二醇的混合物,且对1,2-丙二醇的选择性随催化剂种类的不同而有所差异。对甘油催化氢解制取1,2-丙二醇效果最好的是含铜的催化剂。要实现甘油催化氢解制备丙二醇的工业化生产,还需进一步探索甘油催化氢解的机理,探索助剂效应,改进催化剂体系,或者从反应工程的角度进行改进,提高催化剂的选择性,达到对1,2-丙二醇或1,3-丙二醇的高的选择性和产率。     

基于组分分离的毛竹转化研究

采用水热法、离子液体-乙醇-水体系及其组合预处理方法对毛竹进行组分分离,研究不同方法对毛竹组成及酶解转化的影响,并对组合预处理提取的木质素进行缓和氢解研究。结果表明:水热法主要脱除半纤维素组分,离子液体-乙醇-水体系能脱除大量的半纤维素和木质素,经水热法、离子液体-乙醇-水体系及其组合预处理后的毛竹在酶水解120 h后,葡萄糖得率分别为42.12%、57.67%和82.87%,是未处理毛竹的1.35、1.85和2.66倍。     

秸秆发酵产氢的碱性预处理方法研究

以麦秆、稻草和滤纸为发酵底料,以厌氧活性污泥为接种物,采用不同的预处理方法去除木质素并提高纤维素的降解率,从而提高其发酵产氢能力。试验表明对于相同的底料,经过NaOH预处理和纤维素酶解后的还原糖含量、总产气量、总产氢量和氢气浓度都要高于经过氨水预处理的底料,而未经过预处理的底料发酵产氢能力最差。利用10g经过NaOH预处理的麦秆和稻草,经纤维素酶解后在发酵产氢过程中的降解率分别为23.2%和12.5%,总产氢量分别为363.3mL和254.9mL,发酵产气中氢气浓度分别为23.8%和29.1%。发酵液相中主要产物为乙醇、乙酸和丁酸。     

多种金属修饰的Ce/MCM-41催化解聚木质素的研究

采用共沉淀法和化学还原法制备一系列金属修饰的Ce/MCM-41分子筛催化剂。通过透射电镜(Transmission Electron Microscope,TEM)TEM对催化剂进行表征,并对La(Ni、Co)/Ce/MCM-41系列催化剂在二氧六环-水体系中催化解聚木质素的性能进行研究。试验结果表明:在该系列催化剂中Ni/Ce/MCM-41催化效果较好,在Ni负载量为20%、反应温度为260℃、反应时间为60 min、H2压力为2 MPa的反应条件下,解聚产物中乙醚萃取物达到46.1%。其中,主要单体产物为2-甲氧基酚、4-甲基愈创木酚、4-乙基愈创木酚、4-丙基愈创木酚。     

玉米秆超临界甲醇解聚产物分析

以甲醇为溶剂对玉米秆进行超临界解聚,采用FTIR和GC/MS分析解聚产物.结果表明,超临界甲醇解聚产物(SCMD)中成分十分复杂,GC/MS分析鉴定出103种有机化合物,其中83种为含氧有机化合物,有酯、酚、醚、醇、酮和醛等,还检测出少量正构烷烃(C15-C17和C19-C27)、烯烃、芳烃、苯硫酚和含氮有机化合物,反映了SCMD的高含氧量和低含氮硫量的特性.SCMD中31.387%的苯酚类物质和5.022%的芳烃类物质可能来源于木质素在超临界甲醇中的解聚作用,而34.629%的甲酯类化合物可能是解聚产生的脂肪酸和苯内酸等与甲醇酯化的结果.由此町以推断出甲醇在玉米秆的超临界解聚过程参与了玉米秆的解聚反应.     

木质素改性热塑性酚醛树脂的研究进展

木质素是自然界重要的天然酚类化合物,在一定条件下可以部分替代苯酚参与甲醛的加成缩聚反应,但木质素极低的反应活性限制了其工业化应用。随着化石资源的日趋枯竭,木质素在酚醛树脂中的应用受到越来越多的重视。文章综述了目前木质素改性热塑性酚醛树脂的主要方式,以及木质素在酚醛模塑料中的应用情况,并对其应用前景进行了展望。     

Synergistic effect of supercritical water and nano-catalyst on lignin gasification

Understand the microscopic mechanism of supercritical water catalytic gasification is of great significance for more efficient and convenient utilization of biomass energy. In this work, Pt and Ni nano-particles (NPs) were used as catalysts to accelerate the SCWG of guaiac-based lignin dimer with γ-O-4 linkages for the first time, and the SCWG processes at different conditions were simulated by reaction molecular dynamics simulation to understand the degradation mechanism and the path of gas generation. The simulation results indicate that PtNPs and NiNPs apparently reduce the temperature at which the gasification reaction can take place and the by-products of γ-O-4 lignin by increasing the degradation rate into monomer, accelerating the aromatic ring opening, and adsorbing CO, CO₂ and CH₄. Compared with NiNPs, the synergy of PtNPs and SCWG shows more excellent properties.     

Hydrogenolysis and hydrodeoxygenation of lignin in a two-step process to produce hydrocarbons and alkylphenols

Valuable fuels and chemicals production from biomass with high yields is always a big challenge in the energy utilization field. Herein, a two-step process for the catalytic conversion of lignin was proposed to form the fuels. In the first step, the depolymerization of lignin occurred efficiently via the hydrogenolysis reaction, resulting in 19.2% aromatic monomers under the catalysis of Pd/C and CrCl₃. The catalysts exhibited a synergistic effect on the cleavage of β-O-4 bonds and the hydrogenation procedure, which prevented the condensation of intermediate products remarkably. Afterwards, the aromatic monomers were extracted out with octane solvent successfully (extraction degree 89.7%) and then used as a substrate in a second hydrodeoxygenation (HDO) step. Product mixture composed of 26.5% hydrocarbons (increased from 5.5%) and 49.7% alkylphenols (increased from 42.9%) were obtained after the HDO upgrading, which exhibited high potential to be used as fuels. This two-step approach is very promising to be a practical chemical engineering process for the fuel production from lignin.     

Reactions of lignin model compounds in ionic liquids

Lignin, a readily available form of biomass, is a potential source of renewable aromatic chemicals through catalytic conversion. Recent work has demonstrated that ionic liquids are excellent solvents for processing woody biomass and lignin. Seeking to exploit ionic liquids as media for depolymerization of lignin, we investigated reactions of lignin model compounds in these solvents. Using Brønsted acid catalysts in 1-ethyl-3-methylimidazolium triflate at moderate temperatures below 200 °C, we obtained up to 11.6% molar yield of the dealkylation product 2-methoxyphenol from the model compound 2-methoxy-4-(2-propenyl)phenol and cleaved 2-phenylethyl phenyl ether, a model for lignin ethers. Despite these successes, acid catalysis failed in dealkylation of the saturated-chain model compound 4-ethyl-2-methoxyphenol and did not produce monomeric products from organosolv lignin, demonstrating that further work is required to understand the complex chemistry of lignin depolymerization.     

Comparative study on pyrolysis and catalytic pyrolysis upgrading of biomass model compounds: Thermochemical behaviors,kinetics, and aromatic hydrocarbon formation

In order to understand the pyrolysis mechanism, reaction kinetic and product properties of biomass and select suitable agricultural and forestry residues for the generation desired products, the pyrolysis and catalytic pyrolysis characteristics of three main components (hemicellulose, cellulose, and lignin) of biomass were investigated using a thermogravimetric analyzer (TGA) with a fixed-bed reactor. Fourier transform infrared spectroscopy (FTIR) and elemental analysis were used for further characterization. The results showed that: the thermal stability of hemicellulose was the worst, while that of cellulose was higher with a narrow range of pyrolysis temperatures. Lignin decomposed over a wider range of temperatures and generated a higher char yield. After catalytic pyrolysis over HZSM-5 catalyst, the conversion ratio increased. The ratio for the three components was in the following order: lignincellulose < biomass < xylan. The Starink method was introduced to analyze the thermal reaction kinetics, activation energy (Ea), and the pre-exponential factor (A). The addition of HZSM-5 improved the reactivity and decreased the activation energy in the following order: xylan (30.54%) > biomass(15.41%) > lignin (14.75%) > cellulose (6.73%). The pyrolysis of cellulose gave the highest yield of bio-oil rich in levoglucosan and other anhydrosugars with minimal coke formation. Xylan gave a high gas yield and moderate yield of bio-oil rich in furfural, while lignin gave the highest solid residue and produced the lowest yield of bio-oil that was rich in phenolic compounds. After catalytic pyrolysis, xylan gave the highest yield of monocyclic aromatic hydrocarbons, 76.40%, and showed selectivity for benzene and toluene. Cellulose showed higher selectivity for xylene and naphthalene; however, lignin showed enhanced for selectivity of C10 + polycyclic aromatic hydrocarbons. Thus, catalytic pyrolysis method can effectively improve the properties of bio-oil and bio-char.     

Enhanced hydrogenolysis of enzymatic hydrolysis lignin over in situ prepared RuNi bimetallic catalyst

Enzymatic hydrolysis lignin is a kind of byproduct from the biorefinery process, and hydrogenolysis is a promising approach to valorize the lignin waste. This work proposed an efficient hydrogenolysis of enzymatic hydrolysis lignin over in situ prepared RuNi/C bimetallic catalyst. RuNi/C catalyst exhibited a much higher catalytic activity than Ru/C catalyst with the addition of Ni species. A series of characterizations were carried out to reveal the synergistic effect of the bimetallic catalyst. The results indicated that the interaction between Ru and Ni formed an electron transfer from Ru to Ni and resulted in intensified hydrogen adsorption, which was the crucial factor for the enhanced hydrogenolysis performance. The reaction condition of lignin hydrogenolysis was optimized, and 20.4 wt% monomer product yield was achieved at the temperature of 280 °C. This catalytic system is easy to realize and promising to be employed in the field of lignin utilization.     

Catalytic hydrodeoxygenation and hydrocracking of Alcell® lignin in alcohol/formic acid mixtures using a Ru/C catalyst

The catalytic conversion of Alcell^® lignin in iso-propanol/formic acid mixtures (1:1 mass ratio) was explored in a batch set-up using Ru/C as the catalyst (673 K, 4 h, 28% mass lignin intake on solvent). Lignin oils were obtained in good yields (71% mass yields on lignin input) and shown to consist of a mixture of mainly aromatics (10.5% mass yields on lignin input), alkylphenolics (6% mass yields on lignin input), catechols (8.7% mass yields on lignin input), guaiacols (1.3% mass yields on lignin input), and alkanes (5.2% mass yields on lignin input), the remainder being soluble higher molecular weight compounds (GCxGC-FID and GPC). The results for the catalytic experiments using formic acid were compared with those of a non-catalysed experiment and a catalytic hydrotreatment with molecular hydrogen and Ru/C in the absence of a solvent. Distinct differences in product yields and compositions were observed, and highest lignin oil yields were obtained by catalytic solvolysis (71% mass yields on lignin input) versus 18% mass yields on lignin input for non-catalytic solvolysis and 63% mass yields on lignin input for catalytic hydrotreatment. The effect of reaction time on oil yields and product composition was established and a reaction network involving depolymerisation, and hydro(-deoxy)genation pathways is proposed to explain the product yields and composition. Besides iso-isopropanol, the use of ethanol and methanol in combination with formic acid was also explored for catalytic solvolysis. Best results were obtained in methanol (4 h, 673 K) leading to a lignin oil (68% mass yields on lignin input) containing 11% mass yields on lignin input of alkylphenolics and 19% mass yields on lignin input of aromatics.     

生物质三组分的催化气化特性研究

以生物质三组分(纤维素、半纤维素和木质素)作为实验原料,采用常用的白云石作为催化剂,在小型气流床气化炉上进行气化催化实验。重点研究了白云石对生物质三组分的催化气化特性以及焦油析出特性的差异。结果表明:白云石对纤维素、半纤维素、木质素均起到正向催化作用,提高了三者的碳转化率、气化效率以及气体热值;同时,白云石对三组分的催化作用存在明显差异,其中,对半纤维素的促进催化作用最为显著,木质素次之,对纤维素的促进作用不明显。因此,针对不同组分含量和特性的生物质选择适当的催化剂是必要的。     

纤维素催化热解定向调控制取不含氧烃类液体燃料

为了将生物质能高效转化为高品位不含氧的液体燃料,以纤维素为例,研究了以催化热解方式将热解产物转化为芳香烃类液体燃料的过程.实验发现,纤维素热解产生的含氧有机小分子,可以通过催化热解的形式高效转化为不含氧的芳香烃类液体.催化剂采用HZSM-5(23)、催化剂原料质量比例为5∶1、热解温度为650℃、升温速率为10000 K/s的工况为纤维素催化热解的最佳工况,单环芳烃、多环芳烃产率分别为9.90%和12.91%,总芳香烃类产率为22.81%.热解温度提升至650℃前,更高的热解温度能获得更高的芳香烃产率.继续提高热解温度,单环芳烃、多环芳烃分子间还可能进一步发生聚合反应,最终产生积碳.同时本文也提出了一种可行的纤维素催化热解中的反应途径,与本文实验结果较为匹配.     

Thermal characterization of softwood lignin modification by termite Coptotermes formosanus (Shiraki)

Wood-feeding termites (WFT) pretreat wood cell walls to achieve efficient cellulose utilization by modifying the protecting lignin polymers. An analytical protocol consisting of three-stage-pyrolysis-gas chromatography/mass spectrometry (Py-GC/MS) and thermogravimetry (TG/DTG) was employed along with attenuated total reflectance fourier transform infrared (ATR-FTIR) spectroscopy to investigate softwood degradation by the lower termite Coptotermes formosanus. The results revealed that softwood-lignin moieties were altered during termite digestion. This was characterized by preferential ring demethoxylation, dehydroxylation, and methylation, side chain carboxylation and oxidation, methylation, and oxidation on the ring hydroxyl group, as well as depolymerization and ring destruction. The TG/DTG data demonstrated remarkable changes in the thermal behavior of the processed softwood and also in termite feces, showing decreased activation energy and pre-exponential factor at the second stage (330-400 °C) of lignin pyrolysis. Meanwhile, ATR-FTIR analysis suggested aromatic ring destruction, methoxyl and hydroxyl group modification, C-H deformations in -CH₃ and -CH₂ groups, splitting/modification of aliphatic side chains in lignin, and conformation changes of lignin. Such modifications induced changes in pyrolysis products and bond energies in lignin, and provided information on softwood digestion by termite.     

氧化生物质制备甲酸过程中木质素结构变化的表征

表征生物质酸性氧化制备甲酸过程中木质素结构变化是木质素高值化利用的关键之一。以O₂为氧化剂,对松木粉在NaVO₃-DMSO-H₂SO₄体系中氧化生成甲酸进行研究,考察反应时间、催化剂和固液比对木质素结构变化的影响。采用高效液相色谱（HPLC）、傅里叶变换红外光谱（FT-IR）、凝胶渗透色谱（GPC）、气相色谱（GC）和二维异核单量子相干核磁光谱（2D-HSQC）对固体残渣和已溶解的木质素碎片进行分析。结果显示,在H₂SO₄浓度为0.7wt.%的NaVO₃-DMSO-H₂SO₄体系中,当固液比为1∶50时,甲酸的碳摩尔收率为75.1%。在氧化解聚过程中,木质素通过断裂C—O键被降解形成125 ~ 900 g/mol之间的碎片,而且木质素碎片中的芳环结构被氧化成醌类结构。