With the rapid development of aquaculture towards scale, the healthy problems of aquatic animals caused by the abuse of antibiotics had become increasingly prominent. Therefore, the development of green and efficient alternatives to antibiotics had emerged. Plant polyphenols had become one of the excellent alternatives of antibiotics, because of their effects of promoting growth, antioxidant, antibacterial, anti-inflammatory and promoting intestinal health, as well as no side effects and drug residues. According to the results of relevant studies, plant polyphenols in appropriate dosage had a positive effect on the growth and physiological status of aquatic animals. This article summarized research advances on the effects of plant polyphenols on the growth performance, antioxidant capacity, anti-inflammatory, antibacterial and intestinal health of aquatic animals.
Solvent liquefaction was an effective process which could utilize biomass raw materials efficiently and comprehensively. Compared with water as a single solvent, the mixed solvent system could reduce the reaction temperature and pressure, improve the conversion of biomass, reduce the oxygen content in bio-oil, and increase the yield of the target product. This paper reviewed the common water mixed solvent systems in recent years, including the role of alcohol-water cosolvent, polar aprotic solvent-water system and ionic liquid-water system in the degradation process of lignocellulosic biomass, especially the application characteristics of ethanol-water cosolvent, tetrahydrofuran (THF)-water cosolvent and γ-valerolactone (GVL)-water cosolvent in biomass liquefaction. This paper also gave the shortage and suggestions of these solvents in biomass liquefaction field. Finally, based on the consideration of the economic value, recovery and safety performance of the solvent itself, it is pointed out that the development of low-cost, environment-friendly and sustainable liquefying solvents would be the key development direction in the future.
Lignin oligomers were prepared by ultrasonic-assisted depolymerization using corn cob lignin as raw material. The effects of depolymerization conditions on the yield and relative molecular mass of lignin oligomers were investigated, and the lignin oligomers were characterized by gel permeation chromatography(GPC), infrared spectroscopy(FT-IR), two-dimensional nuclear magnetic resonance spectroscopy (2D-HSQC NMR) and nuclear magnetic resonance phosphorus spectroscopy (31P NMR). The results showed that the yield of resultant lignin oligomer reached 40.2% and the number-average molecular weight ( Mn) of obtained lignin oligomer was 710 under the conditions of ultrasonic treatment (frequency 40 kHz, power 240 W) for 3 h and the solid-liquid ratio of lignin to solvent 200:1(g: L) in methanol/water (4:1, v: v) solvent system. The polydispersity index (PDI) was 1.62, which reserved the main molecular structure units of lignin, and the total hydroxyl content was 10.49 mmol/g.
Traditional polymer materials were divided into thermoplastic materials and thermoset materials. Thermoplastic materials could be processed twice but not rigid enough, and thermoset materials were rigid but difficult to recycle. The glass-like polymer material was between thermoplastic material and thermosetting material, which was a kind of material with high crosslinking density network and could be processed twice. Based on the network exchange mechanism of Vitrimer, this paper focused on the development history and research progress of bio-based glass polymers. Bio-vitrimers based on different covalent bonds were introduced in detail. Generally, the conditions of dynamic transesterification reaction were relatively mild, the reaction speed was fast, and the reaction materials were extensive, while the mechanical properties and reversibility of materials were poor. The reversibility and controllability of dynamic disulfide bond exchange were better, and the reaction was not harsh to the external acid-base environment, while the reaction substrate generally had toxic behavior and pungent odor. Dynamic imine bond exchange could make the material had good mechanical properties and durability, and good biocompatibility, while the reaction conditions and raw material selection were relatively simple. The application and advantages of bio-based Vitrimer materials were reviewed. The introduction of dynamic covalent bonds made up for the shortcomings of traditional 3D printing materials, such as insufficient rigidity and single function, enhanced the comprehensive performance of carbon fiber composites, and improved the service life and self-healing efficiency of elastomer materials. Finally, the paper gived a prospect of the future development.
Chitosan (CS) was modified by amidation with 7-hydroxycoumarin to improve its water solubility and enhance the bacteriostatic property by reducing the hydrogen bonding between chitosan molecules. 7-Hydroxycoumarin was firstly acylated by oxalyl chloride as a linker, and then coumarin was grafted onto chitosan molecules through a non-homogeneous amidation reaction to produce 7-hydroxycoumarin acylation-modified chitosan (CS-C). The coumarin-modified chitosan products were characterized by infrared spectrometry (FT-IR), X-ray diffraction (XRD) instrument, and thermal gravimetry, etc., for the solubility, antibacterial activity, crystalline, and thermal stability. The results showed that the chitosan had been amidated by coumarin, and the modified groups were mainly in the NH2 and chloride as well as ester bonds. The highest degree of substitution of NH2 was found when the mass ratio of chitosan to coumarin was 1:3, and the solubility mass fraction of the CS-C-3 prepared in this case could reach 79% in a neutral environment. Its bacteriostatic property was better than that of CS, with a minimum inhibitory concentration (MIC) of 0.5 g/L for Escherichia coli and a MIC of 1 g/L for Staphylococcus aureus. A minimum bactericidal concentration (MBC) value of 4 g/L for E. coli and a MBC value of 2 g/L for S. aureus.
In order to realize the high-value utilization of waste lignocellulose, bamboo powder was used as raw material, and the deep eutectic solvent (DES) composed of choline chloride (ChCl)/lactic acid (LA) was used to separate the components of bamboo powder. The lignin and cellulose were reconstructed by a simple hot-pressing method to prepare lignocellulosic board. In this paper, the effects of the components of DES, the amount of ferric chloride, reaction temperature and reaction time on the separation of lignocellulosic components were investigated. The structure and properties of DES-separated lignin (DESL) and cellulose (DESC), DES/FeCl3-separated lignin (DESL-FeCl3) and cellulose (DESC-FeCl3), and lignin fiberboards were analyzed by infrared spectroscopy (FT-IR), X-ray diffractometer (XRD), scanning electron microscope (SEM), Zeta potential tester, and universal testing machine. The results showed that the optimum process conditions were choline chloride and lactic acid with a molar ratio of 1:2, FeCl3 addition amount of 2%, reaction temperature of 140 ℃, and reaction time of 6 h. The yields of lignin and cellulose under these conditions were 85.57% and 48.4%, respectively. The phenolic hydroxyl number and Zeta potential of the extracted lignin were 12.86 mmol/L and -32.26 mV, respectively, and the particle size was small. The extracted cellulose had more active sites, which were favorable for the molecular reconstruction and interfacial bonding with lignin. After five cycles of recycling, DES still had good separation performance for lignocellulose. The water stability and mechanical properties of the prepared lignocellulosic board had been improved, water contact angle reached to 58.6°, and its tensile strength increased from 8.4 MPa to 53.1 MPa, which had the potential to replace petroleum-based plastics.
将木质素磺酸钠(Lgs)引入到以海藻酸钠(SA)和丙烯酰胺(AAm)为基体的溶液中,通过自由基聚合法制备得到多孔三维的复合水凝胶(SA/AAm-Lgs),使用扫描电子显微镜(SEM)、傅里叶变换红外光谱(FT-IR)和力学性能测试仪等对其结构和性能进行分析,并将其应用于去除废水中的Fe3+.研究结果表明:实验成功制备了多孔三维网状结构的复合水凝胶SA/AAm-Lgs.当Lgs用量增加时,水凝胶的断裂伸长率和抗拉强度相应增加,溶胀性能也有一定程度提高.SA/AAm-Lgs(含Lgs 7 mg)静态吸附Fe3+的较佳工艺为:水凝胶用量0.5 g、温度25℃、Fe3+初始质量浓度2 g/L,该条件下水凝胶对Fe3+的吸附量可以达到143 mg/g,吸附性良好且具有循环使用性能.吸附动力学和吸附等温线模拟结果表明该水凝胶对Fe3+的吸附过程符合准二级动力学和Langmuir模型.此外,通过固定床工艺对Fe3+进行动态吸附实验证明了 SA/AAm-Lgs具有良好的工业价值.对固定床高度、Fe3+进水质量浓度和流速对突破曲线的影响进行探讨,结果表明:随着固定床高度的增加,突破时间延长;随着Fe3+进水质量浓度增大和流速增加,突破时间急剧缩短.BDST模型能准确预测不同流速或浓度下的突破时间,理论突破时间和实际突破时间的平均误差均小于15％.
以竹屑为原料,使用氧气-水蒸气作为混合气化剂,在固定床气化反应器中进行竹屑的氧气-水蒸气气化实验,考察了气化温度、水蒸气流量和氧气用量比对竹屑气化制备富氢燃气的影响.研究结果表明:气化温度和水蒸气流量均对竹屑燃气中氢气体积分数影响较大,氢气体积分数随着气化温度的升高呈稳步增长趋势,随水蒸气流量增加呈先增加后减少趋势,分别在气化温度900℃和水蒸气流量0.7 mL/min时达到最大值;而随着氧气用量比的增加,氢气体积分数变化不明显.竹屑氧气-水蒸气气化制备富氢燃气最佳的气化条件为气化温度900℃、水蒸气流量0.7 mL/min、氧气用量比0.30,此条件下气化制备的燃气中氢气体积分数32.04％,热值11.37 MJ/m3,产气率1.40 L/g,燃气中CH4体积分数8.82％,CO体积分数26.34％,CO2体积分数30.55％,C2Hm体积分数2.24％.
生物质气化具有高效率、低成本和燃料资源广等优点,其自身含有的碱金属及碱土金属(AAEMs)对气化反应的促进作用机制备受关注.本文针对不同气化剂作用下AAEMs的迁移转化以及催化作用机理进行综述.首先分析了生物质在CO2、H2O及多种混合气氛下AAEMs的迁移转化机制,归纳整理了温度、气氛、无机矿物质等对AAEMs释放的影响,并对钾、钠、钙等元素的迁移转化规律进行总结;其次根据化学反应所涉及的相态总结了催化活性位点、氧转移和生物质焦油3种非均相催化机理;并分析了气态AAEMs对水气变换反应和烃重整反应的均相催化机理;最后对生物质气化中AAEMs的研究方向进行了展望.
生物质被认为是世界上最丰富的可再生资源,对其进行高值化利用有助于绿色能源发展.生物质可高效转化为生物质基平台化合物——乙酰丙酸酯,并进一步制备高附加值化学品.本文详细介绍了传统的乙酰丙酸酯化法及生物质直接催化醇解法、糠醇醇解法制备乙酰丙酸酯的最新研究进展,指出催化剂的性能、反应原料、反应物物质的量比、反应时间和温度等都是影响反应的重要参数.详细综述了液体酸催化剂、固体酸催化剂、混酸催化剂及金属盐催化剂等不同体系催化制备乙酰丙酸酯的最新研究进展.总结比较了3种制备方法的优势和不足,并根据现有转化方法中仍存在着的原料的选择和预处理、反应过程复杂且副产物难控制以及催化剂成本较高、催化效率低、腐蚀设备、难回收等问题,对未来研究方向提出展望.
天然靛蓝来源于可再生含靛植物资源,具有杀菌消炎、清热解毒等药理作用,为探究不同提取工艺得到的靛蓝提取物的化学组成的差异,本研究以马蓝鲜叶自然发酵和生石灰打靛产生的靛蓝膏(粗靛)为原料,通过预处理去杂、盐酸酸化、葡萄糖还原和乙酸乙酯溶剂萃取等工艺,制备靛蓝粗提物(ICE)、酸化-靛蓝提取物(AIE)、葡萄糖还原-靛蓝提取物(GRIE)及乙酸乙酯萃取-靛蓝提取物(EAEI),并采用高效液相色谱(HPLC)、热裂解-气相色谱/质谱联用(Py-GC-MS)和超高效液相色谱-四级杆飞行时间串联质谱(UHPLC-TOF-MS)对提取物进行分析.研究结果表明:相比于靛蓝膏,4种提取工艺制备的靛蓝提取物中靛蓝质量分数均显著提高,灰分含量均大幅减少.其中,还原-靛蓝提取物中靛蓝质量分数由靛蓝膏的2.09％提高到85％.4种靛蓝提取物的裂解产物组分中含12～20个碳的大分子化合物较多,相应的GC含量分别是7.91％、57.09％、54.4％和62.7％.4种提取工艺中,盐酸酸化和乙酸乙酯溶剂萃取提取的靛蓝提取物的裂解产物组分数量远高于预处理去杂和葡萄糖还原工艺.AIE和EAEI分别鉴定出61和184种化合物,主要包括酸类、多糖类、黄酮类、生物碱类、苷类、多酚类、醛类、蛋白类、酯类9类物质,且EAEI中酸类、多酚类和黄酮类的相对峰面积分别是48.72％、4.56％和1.71％,均较AIE的有大幅度提高即乙酸乙酯萃取工艺实现了对靛蓝提取物中酸类、多酚类、黄酮类等有效富集.
5-氯甲基糠醛(CMF)是近年来受到广泛关注的生物质基平台化合物.传统CMF制备在浓盐酸体系中进行,浓盐酸的高腐蚀性对其放大生产带来了挑战.为解决此问题,构建了一种基于酸性CaCl2溶液的反应系统,研究了反应条件、物料浓度等参数对竹浆在该体系中制备CMF的影响,研究结果表明:水相中饱和或者近饱和的氯离子可有效抑制CMF水解为HMF从而提高体系中CMF的稳定性,减少了酸性条件下不稳定中间产物HMF向腐殖质的转化;CaCl2在体系中具有极佳的催化性能,取得了最高59.2％的CMF产率,1,1,2-三氯乙烷、1,3-二氯丙烷、1,2,3-三氯丙烷等较高沸点溶剂均具有取代萃取剂1,2-二氯乙烷(DCE)的潜力.实验进一步研究了竹浆原料的不同预处理条件对其制备的CMF产率的影响,结果表明:水解氯代反应较优工艺即竹浆初始质量浓度16 g/mL,8 g H2O,1.33 mol/L HCl,5.33～6.66 mol/L CaCl2,25 mL DCE,反应温度130℃,反应时间1 h,此条件下CMF得率为59.2％.NaHSO3或固体碱活性氧蒸者(CAOSA)处理所得竹浆更适于制备CMF.稀酸氯盐水相循环性能的实验结果表明:通过补充一定量的盐酸可使本体系具有循环使用能力.对竹浆制备CMF的反应进行15倍放大实验,取得了51.8％的CMF产率,CMF粗产品在DCE溶液中具有良好的稳定性,经过4～12 d存放没有明显变质.
分子印迹技术因具有特异识别性、高预选性和高稳定性等优点,在天然产物化学领域受到广泛关注,尤其是天然活性物质分离方面.本文对分子印迹技术的基本原理、结合方式、常用原料和聚合方法进行介绍,重点分析了分子印迹聚合物制备方法中的共价作用、非共价作用和金属配位作用等结合方式的区别与联系,同时讨论了 2017～2022年分子印迹技术在分离黄酮类、多酚类、生物碱类、有机酸类、甾体类及其他天然活性成分的应用研究进展,并提出了 目前分子印迹技术存在的问题和未来研究方向.
以羟基酪醇(HT)为原料,氢化卵磷脂和胆固醇为乳化剂,采用薄膜分散法制备HT柔性纳米脂质体并研究其贮藏稳定性.以包封率为响应值,通过单因素、Plackett-Burman和Box-Behnken响应面试验得到制备的最优工艺,同时利用红外光谱、热重、差示扫描量热、透射电镜对产物进行结构表征,并考察该HT的贮藏稳定性.研究结果表明:较佳制备工艺条件为HT 1.5 mg、氢化卵磷脂与胆固醇质量比3.3∶1、叶酸-聚醚(FA-F127)用量1 mg、胆酸钠用量20.6 mg、超声波功率10％(总功率为650 W)、超声波作用时间11 min,在此条件下制备的HT柔性纳米脂质体包封率、粒径、多分散系数(PDI)、Zeta电位分别为46.78％、104.7 nm、0.231、-42.5 mV.结构表征结果表明:HT柔性纳米脂质体是一种有前途的、更高效、更安全的递送系统.贮藏稳定性研究结果显示:HT纳米脂质体分别在4、25、60℃下贮藏28 d,4 ℃下的包封率为37.56％,粒径为152.7 nm,PDI和Zeta电位变化不大,而25和60℃下的HT纳米脂质体的上述指标变化较大,因此,4℃更利于其稳定贮藏.
以茶多酚为配体,采用共沉淀法制备了催化剂茶多酚-铪,对催化剂结构进行表征,并将此催化剂用于乙酰丙酸乙酯(EL)转移加氢制备γ-戊内酯(GVL)的反应.对催化剂的制备条件如HfCl4与茶多酚物质的量比、三乙胺用量、老化温度等进行考察,探讨了不同反应条件对催化剂茶多酚-铪催化EL反应的活性影响以及催化剂的循环稳定性.结果表明:茶多酚1 mmol,n(HfCl4)∶n(茶多酚)=4∶1,三乙胺用量50 mmol,无老化处理,此条件下制备的催化剂茶多酚-铪催化活性较好.在反应温度160℃、反应时间3 h条件下,100 mg该催化剂可催化1 mmol EL制备GVL,使EL转化率达到93.5％,GVL产率达到83.7％,GVL选择性为89.5％.催化剂茶多酚-铪具有良好的循环稳定性,经过5次使用后,还能使GVL产率和EL转化率基本保持不变.
为了探寻农林废弃物高值化利用方式,以常见的玉米秸秆、稻草秸秆、大豆秸秆、松树枝条、青竹枝条和沼渣6种农林废弃物为原料,采用真空管式炉限氧控温炭化法制备生物炭.利用比表面积测定仪、扫描电镜和红外光谱等分析生物炭的理化性质及结构特点,并探究生物炭对养殖废水氨氮和总磷的吸附效果.研究结果表明:6种生物炭均呈碱性,沼渣炭碱性强于植物源生物炭;6种生物炭其产率大小排列顺序:沼渣炭(64.84％)＞大豆秸秆炭(57.22％)＞水稻秸秆炭(48.80％)＞玉米秸秆炭(46.87％)＞青竹炭(41.42％)＞松树枝炭(40.01％),其中,大豆秸秆炭比表面积(5.84 m2/g)较大,孔隙发达;6种生物炭表面均含有丰富的含氧官能团,化学稳定性较强的C-H和芳环,均具有较强的稳定性;6种生物炭对养殖废水中氨氮和总磷均有一定的吸附作用,其相应吸附容量分别为20.00～31.00和4.00～6.69 mg/g;大豆秸秆炭对氨氮、总磷的吸附效果最好,饱和吸附量分别为31.00和6.69 mg/g.
植物单宁在自然界中的储量非常丰富,其分子结构中含有的大量酚羟基易于化学修饰;同时,单宁具有较强的抗氧化、抗病毒和抗肿瘤等生物活性,对细菌和酶具有显著的抑制作用.为研究植物单宁在生物医药材料领域的利用范围,本文综述了单宁基水凝胶的研究进展及其在组织工程、药物输送和伤口敷料领域的潜在应用,并对材料的工业化制备方法进行了总结与概括.首先详细介绍了不同类型单宁基水凝胶的设计策略和形成机理,特别对单宁的分子结构、生化特性在水凝胶构筑过程中所起的作用进行了深入分析;然后对水凝胶的具体应用以及最新的研究热点进行了阐述;最后探讨了这类材料目前的局限性并对未来规模化的工业生产前景进行了展望.
目前使用的3个中国肉桂油标准,既不能将新法、老法肉桂油进行有效区分,又导致大多数新法肉桂油为不合格品,对行业发展没有起到标准该有的引领作用.为了使3个中国肉桂油标准在实践运用中更具有指导性,建议在标准中进一步明确"反式肉桂醛、香豆素、乙酸肉桂酯、反式邻甲氧基肉桂醛"4个特征组分的含量范围.基于对800批次肉桂油(新法肉桂油350批次,老法肉桂油450批次)中这4个特征组分的检测数据分析、统计的结果,建议将其含量范围确定如下:新法肉桂油中反式肉桂醛、香豆素、乙酸肉桂酯、反式邻甲氧基肉桂醛这4个特征组分依次为＞80.0％～88.0％、0％～1.5％、0％～1.0％、4.0％～8.5％,后三者之和为6.0％～12.0％;老法肉桂油中这4个特征组分依次为72.0％～80.0％、＞1.5％～3.0％、＞1.0％～5.0％、＞8.5％～13.0％,后三者之和为＞12.0％～18.0％.同时,将肉桂油中"相对密度"理化指标进行修改,新法为1.040～1.052,老法为＞1.052～1.070.
生物质能是一种理想的清洁能源,具有可再生、多样性并能够实现二氧化碳零排放的优点.生物质催化重整制氢是生物质热化学转换利用的一种高效、环保、经济的方式.本文从生物质催化重整过程中的关键反应参数:反应温度、水碳比、反应空速和催化剂等方面综述了生物质催化重整制氢相关研究进展,总结了反应参数、催化剂的选择和应用对热解产物的影响,梳理了天然矿石催化剂、碱金属催化剂、过渡金属催化剂和尖晶石催化剂在生物质水蒸气转化特性的影响机制,总结了通过定向调控开发稳定的高活性催化剂以提高重整反应的效率和稳定性的有效利用途径.指出了明晰催化机理还需从生物质与催化剂的交互作用机制和热解气化反应机理的角度进一步探究.
利用顶空固相微萃取技术(SPME)结合气相色谱-质谱联用(GC-MS),对自然晾干,冷冻干燥,40、60和80 ℃烘干5种不同干燥处理的迷迭香叶与新鲜迷迭香叶进行挥发性成分分析鉴定.研究结果表明:5种方式干燥后迷迭香叶的主要挥发性成分有4,6,6-三甲基-双环[3.1.1]庚-3-烯-2-酮、桉树醇、樟脑、芳樟醇、α-蒎烯、α-松油醇、乙酸龙脑酯、松香芹酮、莰烯和石竹烯等,其中,4,6,6-三甲基-双环[3.1.1]庚-3-烯-2-酮和桉树醇这两者GC含量达54.94％～60.09％.干燥后迷迭香叶的主要挥发性成分种类为烯萜类、醇类、醛酮类、烷烃类、苯类和酯类.冷冻干燥处理的迷迭香叶中挥发性成分最多,鉴定出44种挥发性物质,占总挥发性物质成分的99.61％.通过对5种不同干燥处理方式的迷迭香叶中挥发性物质的成分和含量差异进行分析,发现冷冻干燥能最大限度地保留挥发性成分.
