纤维素热解过程中活性纤维素的生成研究

热重分析发现活性纤维素的生成始于530 K左右,对应于失重图上的肩部及SDTA曲线中强烈的放热峰.在辐射加热闪速热裂解试验台上获取了一种可溶于水、高温下易分解、室温下呈固态且稳定存在的黄色中间产物.扫描电镜图片证明在热裂解初期纤维素经历了一个熔化和相互粘结的状态,产物的红外谱图证实了大量的羰基和羧基官能团的生成.高效液相色谱分析证明其主要成分是一系列聚合度不同的低聚糖,推断该低聚糖即为活性纤维素.     

紫外光谱法快速测定生物质乙醇/水水解液中糠醛和5-羟甲基糠醛含量

木质纤维类生物质水解过程中产生的可溶性木素、呋喃类化合物在紫外波长范围内均有吸收峰,且吸收峰相互叠加。研究提出了一种基于紫外光谱法快速测定生物质水解液中糠醛(F)和5-羟甲基糠醛(5-HMF)混合物(M)的方法。研究发现,M中5-HMF的含量百分率(W_(5-HMF))和最大吸收波长(λ_(max))存在良好的线性关系,R2=0.998 4。进一步研究表明M中W_(5-HMF)不变时,混合物浓度(cM)和吸光度值(A)之间也存在良好的线性关系,R2在0.998 6~1.000 0之间,且重现性均良好。因此,基于A,cM及λ_(max),W_(5-HMF)之间的良好线性关系,可以准确地检测出F和5-HMF的含量,其相对偏差、回收率及RSD分别为5.6%和3.7%,89%~96%,0.21%~0.85%。该方法简单、快捷、准确,适应于乙醇法精炼木质纤维类生物质水解液中F和5-HMF混合物的测定。     

Ni/TPC催化剂的制备、表征及在秸秆热解燃气重整中的应用

以废弃汽车外轮胎热解后的副产物轮胎热解焦（Tyre pyrolysis char,TPC）为原料,利用均匀沉淀法制备以轮胎焦为载体的负载型Ni/TPC催化剂,采用EDX、SEM、XRD、TG、BET手段对催化剂进行了表征与分析,同时使用管式炉测试了Ni/TPC催化剂在秸秆热解燃气重整中的催化性能,并考察了热解温度、保温时间、镍负载量及催化时间对秸秆热解燃气重整效果的影响。研究结果表明,TPC富含焦和金属,Ni/TPC催化剂分散均匀,热稳定性好,比表面积为62 m²/g。催化剂活性测试显示,Ni/TPC催化剂用于作物秸秆热解燃气重整具有很强的催化活性,可显著提高燃气中可燃气体含量;热解温度在750℃、保温时间10 min、30%的Ni负载量时Ni/TPC催化剂的催化效率最高,连续使用850 min后,燃气中的H₂含量仍相对提高到50%以上,长时间使用后活性结构由Ni₃ZnC_0.7转变成FeNi₃,催化活性依然较强且趋于稳定,TPC可以作为良好的新型镍基催化剂载体。     

Controlled pinewood fractionation with supercritical ethanol: A prerequisite toward pinewood conversion into chemicals and biofuels

The objective of this work was to investigate the ability of supercritical (SC) ethanol conditions to attack preferentially the lignin fraction against the carbohydrate fraction and their effects on the product distribution among gases, light products, bio-oils, and chars. In this study, the conversion of each pinewood component was determined by the analysis of solid residues to quantify cellulose, hemicellulose, lignin, and char contents. It is shown that, by tuning the temperature, hemicellulose and lignin are already transformed in subcritical ethanol conditions, lignin being more reactive than hemicellulose. In contrast, native wood cellulose is recalcitrant to liquefaction in SC ethanol near the critical point (T_c = 241 °C and P_c = 61 bar), but 20% of native wood cellulose is converted in SC ethanol at 280 °C. Besides, the severity of the conditions, in terms of temperature and treatment time, does not significantly influence the yields of gases, light products, and bio-oils but strongly enhances char formation. Interestingly, the increase in SC ethanol density does not change the conversion of biomass components but has a marked effect on bio-oil yield and prevents char formation. The optimum fractionation conditions to convert the lignin component, while keeping unattacked the cellulose fraction with a minimum formation of char, are dense SC ethanol, at 250 °C for 1 h, in batch conditions. However, although lignin is more reactive than hemicellulose under these conditions, these fractions are converted, in a parallel way, to around 50% and 60%, respectively.     

Facile Synthesis of Ultra-Small Few-Layer Nanostructured MoSe2 Embedded on N,P Co-Doped Bio-Carbon for High-Performance Half/Full Sodium-Ion and Potassium-Ion Batteries

Sodium/potassium-ion batteries (SIBs/PIBs) arouse intensive interest on account of the natural abundance of sodium/potassium resources, the competitive cost and appropriate redox potential. Nevertheless, the huge challenge for SIBs/PIBs lies in the scarcity of an anode material with high capacity and stable structure, which are capable of accommodating large-size ions during cycling. Furthermore, using sustainable natural biomass to fabricate electrodes for energy storage applications is a hot topic. Herein, an ultra-small few-layer nanostructured MoSe₂ embedded on N, P co-doped bio-carbon is reported, which is synthesized by using chlorella as the adsorbent and precursor. As a consequence, the MoSe₂/NP-C-2 composite represents exceedingly impressive electrochemical performance for both sodium-ion batteries (SIBs) and potassium-ion batteries (PIBs). It displays a promising reversible capacity (523 mAh g⁻¹ at 100 mA g⁻¹ after 100 cycles) and impressive long-term cycling performance (192 mAh g⁻¹ at 5 A g⁻¹ even after 1000 cycles) in SIBs, which are some of the best properties of MoSe₂-based anode materials for SIBs to date. To further probe the great potential applications, full SIBs pairing the MoSe₂/NP-C-2 composite anode with a Na₃V₂(PO₄)₃ cathode also exhibits a satisfactory capacity of 215 mAh g⁻¹ at 500 mA g⁻¹ after 100 cycles. Moreover, it also delivers a decent reversible capacity of 131 mAh g⁻¹ at 1 A g⁻¹ even after 250 cycles for PIBs.     

A model of the chemical composition and pyrolysis kinetics of lignin

This study presents a novel approach for the chemical representation of lignin for modelling the reaction kinetics of lignin in lignocellulosic biomass. This methodology relies on the definition of dimeric pseudo-components containing phenolic functionalities, i.e., p-hydroxyphenyl, guaiacyl and syringyl groups, as measured in real biomass and native lignin through wet chemistry and spectroscopic techniques. The reactivities of the lignin pseudo-components are modelled through a series of lumped unidirectional reactions, whose product formation and reaction rate constants are optimised to replicate a comprehensive experimental dataset gathered from several works available in the literature. The new kinetic model contributes to the state-of-the-art by providing a more accurate depiction of the conversion rates, selectivity of char vs. volatiles, and aromatic composition in condensable products in line with the inherent reactivity of lignin functionalities and the empirical observations of lignin depolymerisation and thermal degradation at low (<1?K/s) and high heating rates (>50?K/s).     

Reflectance and ultraviolet spectroscopy: predicting the relative growth of Saccharomyces cerevisiae in pine biomass

Ultrasound treatment favors enzymatic attack on vegetal materials and influences biological activity. The objective of this study was to develop substrates for Saccharomyces cerevisiae based on the hydrothermal treatment and ultrasound treatment of pine needle biomass. The samples subjected to ultrasound treatment at 550?°C and 650?°C showed higher reflectance bands at around 200?nm after 80?min of ultrasound treatment and lower band gap energies associated with lower IC₃₀ values. The hydrothermal treatment with 100?min of ultrasound treatment generated more promising materials for the use of the substrates with the eukaryotic model S. cerevisiae.     

Copper-Mediated Conversion of Complex Ethers to Esters: Enabling Biopolymer Depolymerisation under Mild Conditions

Selective processing of the β-O-4 unit in lignin is essential for the efficient depolymerisation of this biopolymer and therefore its successful integration into a biorefinery set-up. An approach is described in which this unit is modified to incorporate a carboxylic ester with the goal of enabling the use of mild depolymerisation conditions. Inspired by preliminary results using a Cu/TEMPO/O₂ system, a protocol was developed that gave the desired β-O-4-containing ester in high yield using certain dimeric model compounds. The optimised reaction conditions were then applied to an oligomeric lignin model system. Extensive 2D NMR analysis demonstrated that analogous chemistry could be achieved with the oligomeric substrate. Mild depolymerisation of the ester-containing oligomer delivered the expected aryl acid monomer.     

微生物燃料电池阴极脱氮

微生物燃料电池(MFC)阴极电子受体的多样性可实现其阴极脱氮,从而将产生的电能合理利用,因此阴极脱氮成为了MFC的一个研究方向,同时也为实际废水中氮素的去除提供了新的可能。然而在反应过程中有众多因素会导致NOx-N与其他电子受体竞争阳极电子的现象,影响阴极反硝化过程对于电子的利用率,从而造成脱氮效率低等现实问题。目前已有许多研究通过优化MFC自身结构弥补产电的缺陷,及将与其他工艺系统耦合实现同步硝化反硝化等方法,取长补短以增加脱氮效率,降低对碳源的需求,以此解决微生物燃料电池阴极脱氮出现的问题。本文从MFC不同的脱氮历程、MFC工艺条件(pH、C/N、DO)、极室分隔材料等影响MFC阴极脱氮的因素及影响其阴极反硝化微生物群落构成等方面,进行了综述并预测未来研究方向。     

Synthesis of furan dimer‐based polyamides with a high melting point

Polyamide composed of furan dimer, which is prepared from biomass‐derived organic molecule 2‐furfural, is synthesized. The reaction of 2,2′‐furan dimer 5,5′‐dicarbonyl chloride with several 1,ω‐diamines was carried out with a solution or interfacial polycondensation leading to the corresponding polyamide. Measurement of the melting point was performed resulting to exhibit a higher temperature compared with the related polyamide bearing a single furan ring composed of furan‐2,5‐dicarboxylic acid (FDCA). Thermal analyses (TG–DTA) also indicated higher temperatures of decomposition than those of FDCA‐derived polyamide. © 2018 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2018 , 56, 1516–1519