典型雪茄烟叶热解/燃烧特性及动力学分析

为了解雪茄烟叶原料的热解燃烧特性及气相产物释放规律,利用热重分析仪结合傅里叶红外光谱仪(TG-FTIR)研究了在氮气和空气气氛下,雪茄烟叶的热失重过程和气态产物组成,并采用Flynn-Wall-Ozawa方法计算不同气氛下的反应活化能.结果表明:①雪茄烟叶的热解和燃烧分别表现为4个失重阶段:脱水、易挥发分和半纤维素的热...     

桉木化学机械浆碱木素热解特性初步研究

采用酸析法分离桉木碱性过氧化氢法(APMP)制浆废液中的碱木素,应用热重红外联用(TG-FTIR)分析方法对碱木素的热解特性进行初步研究,并对热解过程中挥发性产物释放规律进行追踪。热重分析(TG)结果表明,热解主要分为玻璃态转化、主要热解、残留物质缓慢分解3个阶段;傅里叶红外光谱(FTIR)分析结果表明,热解阶段可挥发性产物有H2O、CO2、CO、CH4、酚醇类化合物和醛酮类化合物,反应时间在2000 s以后的高温阶段热解产物主要为CO和CO2。其中,CH4、醛酮类化合物、酚类和醇类化合物释放主要集中在300～600℃之间,且产率均较高。     

不同部位烟叶的热失重和热裂解行为研究

利用热重红外联用技术（TG-FTIR）和热裂解气相色谱－质谱联用技术（Py-GC/MS）比较研究了清香型烟叶和浓香型烟叶上、中、下三个部位的热失重和热裂解行为,考察了空气（Air）氛围和氮气（N2）氛围对各部位烟叶热解行为的影响。结果表明,⑴清香型和浓香型烟叶的热重曲线图具有相似性,两者的差异表现在不同热解阶段失重速率和气体释放情况的不同,反应了两种烟叶化学组成的差异;不同部位烟叶的热失重行为略有差异,反映在DTG曲线和红外吸收谱图上。⑵烟叶在Air和N2氛围下表现不同的热失重行为,Air氛围下样品热解更完全,主要释放较稳定的CO2气体;N2氛围下,不同的热解阶段气体的释放情况存在明显差异,惰性环境更利于热重行为的研究。⑶通过GC-MS在线分析,对两种烟叶的热裂解产物中碱性、酸性、中性香气成分分别进行了比较,实验得出,浓香型烟叶含有较高的碱性香气成分,且两者都是中上部烟叶高于下部烟叶;挥发性酸中重要的致香物质异戊酸和苯甲酸的含量也是浓香型高于清香型;中性香气成分组成较复杂,两种烟叶各组分的含量差异比较明显,反映了两者不同的致香机理。      

制革污泥热解特性的研究——基于分布活化能模型和TG-FTIR-MS联用

制革污泥中含有大量无机物、有机物和多种重金属化合物,对这类危险废物的安全处理和资源化是制革业可持续发展的关键之一。本文利用热重分析法研究了制革污泥在不同升温速率下的热解过程,采用分布活化能模型(DAEM)探讨了其热解活化能与转化率的关系。利用热重-傅里叶变换红外光谱-质谱(TG-FTIR-MS)联用技术分析了制革污泥热解逸出气体的成分,讨论了制革污泥的热解特性。结果表明,制革污泥的热失重过程可分为三个阶段,主要失重过程发生在200～600℃。制革污泥的热解活化能呈阶段性分布,主要集中在较低活化能区域。TG-FTIR-MS分析表明,制革污泥受热过程中逸出的主要气体是CO₂、H₂O、CH₄和CO等,是蛋白类大分子和碳酸钙等无机物热解的产物。     

红外光谱和热裂解气相色谱质谱联用技术鉴别芳香族聚酯纤维

运用红外光谱和热裂解气相色谱质谱技术对芳香族聚酯纤维进行鉴别。首先使用傅里叶变换红外光谱仪测试了两种纤维的红外光谱,对它们的特征峰进行了详细的解析,然后利用热裂解气相色谱质谱仪得到了两种纤维裂解后产物的结构和分布。     

烟叶热裂解产物的分析研究

为研究烟叶热裂解行为对卷烟烟气成分的影响,采用在线热裂解-气相色谱/质谱联用技术(Py-GC/MS)分析烟叶在氦气氛围中不同温度(300℃,600℃和900℃)下的热裂解产物.将热解产物直接引入气相色谱-质谱仪,用质谱法对裂解产物进行了定性分析,并用面积归一法定量分析.结果表明:300℃,600℃和900℃下的热裂解产物中分别鉴定出45种、110种和124种裂解产物;裂解温度对烟叶产生的裂解产物种类和相对含量都有较大影响,裂解出的致香成分包括酮类、醇类、醛类、酯和内酯类、酸类和氮杂环类等,其相对含量在裂解温度为600℃时达到最大.     

脱墨污泥热分解特性及其热解动力学浅析

利用热重分析法和实验室自行设计的静态热解炉对脱墨污泥的热解行为及热裂解特性进行了研究,探讨了不同升温速率对脱墨污泥热解反应特性的影响,并根据微分热重曲线建立了动力学模型,计算热解反应的动力学参数.结果表明,脱墨污泥的热失重过程可分为水分析出、挥发物质析出、固定碳燃尽和碳酸钙热分解4个阶段,其热解反应动力学为3个三级反应.从利用电子探针显微技术、气相色谱和傅里叶红外分析方法对热裂解产物进行表征的结果来看,造纸脱墨污泥具有很好的资源化综合利用前景.     

板栗热解产物的制备及在电子烟中的应用

为制备具有特征风格的电子烟烟液,采用热重分析研究了板栗的热解行为,并用管式热解炉对板栗样品进行了热解反应;采用GC/MS法分析了不同热解条件下的热解产物,以热解产物总量与氧杂环类化合物总量为目标,优化了热解条件,并将热解产物进行了电子烟加香效果评价。结果表明:(1)板栗的热失重区间可分为3个阶段,其中第Ⅱ个热失重阶段(约130℃~380℃)质量损失达64.69%。(2)从板栗的热解产物中共鉴定出33种化合物,其中包括糠醛、糠醇、5-羟甲基糠醛等12种氧杂环类化合物。(3)确定的热解条件为热解温度240℃、热解时间10 min,样品含水率10.30%;在此条件下热解产物中氧杂环类化合物的产率最高。(4)热解产物应用于电子烟烟液可赋予气溶胶焦甜香、烘烤香特征。     

柠檬酸的热解特性

使用热失重/傅里叶变换红外联用( TG-FTIR)技术研究了柠檬酸的热裂解特性,测定并比较了不同氧气浓度下柠檬酸的热重(TG)和微商热重(DTG)曲线,以及柠檬酸热解气相产物相对含量和生成规律,探讨了柠檬酸可能的热解机制.结果表明:①柠檬酸的热解气相产物主要有CO2,CO,H2O,酸酐和酮类物质.CO2是气相产物中相对含量最高的物质,CO最低;水最早出现在气相产物中,酸酐是最后存在于气相产物中的物质;②柠檬酸可能有2种主要热解途径:先脱水后脱CO2的酸酐生成模式和主要脱CO2的酮生成模式.在热解初期,2种模式同时发生,氧气浓度的增加有利于酮的生成.在较高温度下,主要以酸酐生成模式为主.     

FTIR法建立葡萄籽油的红外光谱特征

采用傅里叶红外光谱法对葡萄籽油的红外光谱特性进行了研究.建立了傅里叶红外光谱仪分析葡萄籽油红外光谱的标准方法.通过分析葡萄籽油的红外光谱特征,结果表明葡萄籽油与其他品种植物油具有基本相同的红外光谱,但是葡萄籽油、橄榄油和杏仁油在1120cm-1波数附近的吸收峰相对强弱存在明显差异,此处的校正峰面积可以作为判别葡萄籽油、橄榄油和杏仁油的指标.     

一测多评法测定蜂胶类保健食品中咖啡酸等4种成分的含量

目的:建立以蜂胶为单一原料的保健食品中咖啡酸、阿魏酸、异阿魏酸及咖啡酸苯乙酯的"一测多评"含量测定方法。方法:采用高效液相色谱法,以甲醇-0.1%磷酸水溶液为流动相,梯度洗脱,以异阿魏酸为参照物,建立其与咖啡酸、阿魏酸,咖啡酸苯乙酯的相对校正因子,利用相对校正因子计算4种成分的含量,实现一测多评;并对多批样品同时采用一测多评法和标准曲线法测定,将结果进行比较,验证方法的可行性。结果:4种成分在相应的线性范围内线性关系良好,相关系数r>0.9999,平均加标回收率在99.85%~101.69%,RSD在1.7%~2.3%,咖啡酸、阿魏酸、咖啡酸苯乙酯的相对校正因子分别为0.9503、0.9276、1.3902,且在不同实验条件下重现性良好,一测多评法计算值与标准曲线法实测值相对平均偏差在0.1%~1.7%之间,测定结果基本一致。结论:本文建立的一测多评方法操作简便,重复性好,可为以蜂胶为单一原料的保健食品的质量评价提供参考。     

Demethylation of Ferulic Acid and Feruloyl-arabinoxylan by Microbial Cell Extracts

The O -demethylation of ferulic acid and feruloyl-arabinoxylan by the anaerobic bacteriaClostridium methoxybenzovorans (strain SR3) and the facultative aerobic bacteria Enterobacter cloacae (strain DG6) was investigated in order to produce caffeic acid and caffeoyl-arabinoxylan. As both strains produced endocellular enzymes, disrupted cell extracts from these two bacteria were prepared and tested. The SR3-disrupted cell extract was able to produce caffeic acid from free ferulic acid with 84% yield. The use of cysteine as reducing agent in the reaction medium stabilised the highly reactive caffeic acid produced. The DG6-disrupted cell extract used ferulic acid but no caffeic acid was detected, suggesting that it was only an intermediary product of the reaction. None of the two disrupted cell extracts were able to O-demethylate feruloyl-arabinoxylans.     

5种氨基酸热失重行为及其热解生成氢氰酸的研究

采用改造后的商品化热重分析仪,对不同升温速率和裂解气氛下甘氨酸(Gly)、丙氨酸(Ala)、亮氨酸(Leu)、异亮氨酸(Ile)、脯氨酸(Pro)等5种氨基酸热解特性及生成氢氰酸(HCN)的行为进行了研究。结果表明:①除Gly外,其他4种氨基酸生成HCN的产率随着升温速率的提高而增加;②当有O2存在时,HCN的产率较N2裂解气氛下有明显降低,当O2含量达到20%时,5种氨基酸生成HCN的产率均低于0.25%;③在不同的升温速率和裂解气氛下,Gly生成HCN的产率均高于其他4种氨基酸;在10%O2+90%N2气氛和40℃/min的升温速率下,5种氨基酸生成HCN产率顺序:Gly>Leu>Ile>Pro>Ala。     

几种脂肪酸甲酯的热解特性及动力学研究

采用热重分析法研究了硬脂酸甲酯、油酸甲酯和亚油酸甲酯在氮气气氛中的热分解特性,并采用Coats-Redfern积分法对硬脂酸甲酯、油酸甲酯和亚油酸甲酯的热分解过程进行动力学分析,建立热分解模型。结果表明:硬脂酸甲酯和油酸甲酯的热分解过程表现为简单的一步分解,而亚油酸甲酯则呈现出较复杂的两步分解过程;随着升温速率提高,热分解区间向高温区移动,热分解活化能和指前因子呈现出较好的动力学补偿效应,且在不同升温速率下具有不同的热分解反应机理函数;模拟计算的热分解率与实验数据误差基本在10%左右。动力学模型能够很好地预测各脂肪酸甲酯热分解过程,为进一步扩大试验和生物柴油应用中的高温热分解衰变模型提供理论依据。     

NOx and N2O precursors from biomass pyrolysis: nitrogen transformation from amino acid

Large quantities of NO(x) and N(2)O emissions can be produced from biomass burning. Understanding nitrogen behavior during biomass pyrolysis is crucial. Nitrogen in biomass is mainly in forms of proteins (amino acids). Phenylalanine, aspartic acid, and glutamic acid were used as the model compounds for the nitrogen in biomass. Release behavior tests of nitrogen species from the three amino acids during pyrolysis in argon and gasification with O(2) and CO(2) were performed using a thermogravimetric analyzer (TGA) coupled with a Fourier transform infrared (FTIR) spectrometer. The results indicate that although the influence of oxygen and CO(2) in the atmosphere on nitrogen behavior is different for the amino acids, it is interesting to find some phenomenon in common. The presence of oxygen promotes NO and HNCO formation for all the three amino acids; HCN and HNCO formation are suppressed by introduced CO(2) for all the three amino acids. This can reveal the N-conversion mechanism from biomass in depth under the same conditions.     

超声局部效应对咖啡酸稳定性及抗氧化性的影响

将超声区域定位划分成高低两个超声辐射面和5 个不同超声位置（P1、P2、P3、P4、P5）,对比研究低超声辐射面与高超声辐射面、超声位置、提取溶剂对咖啡酸稳定性及其抗氧化性的影响。结果表明,低超声辐射面能造成咖啡酸显著降解（P＜0.05）;高超声辐射面、超声能量对咖啡酸稳定性的影响不显著。溶剂类型是影响咖啡酸稳定性的主要因素之一,其中体积分数80%乙醇是咖啡酸理想的提取溶剂。超声槽不同位置上,超声能量的分布是不均一和动态变化的,咖啡酸在P4或P5位置时降解较为显著（P＜0.05）。此外,超声处理同样能显著影响咖啡酸的抗氧化性,1,1-二苯基-2-三硝基苯肼（1,1-diphenyl-2-picrylhydrazyl,DPPH）法、铁离子还原力（ferricreducing antioxidant potential assay,FRAP）法及2,2’-联氮-二（3-乙基-苯并噻唑-6-磺酸）二铵盐（2,2’-amino-di)3-ethyl-benzothiazoline 6-sulphonic acid) ammonium salt,ABTS）法3 种方法测定的咖啡酸抗氧化性的变化规律存在一定差异性。DPPH法与FRAP法同时得到P5位置是影响咖啡酸抗氧化性最显著的位置,该位置咖啡酸降解产物的抗氧化性高于咖啡酸自身的。不同超声辐射面上,ABTS法测定咖啡酸的抗氧化性与其含量成正相关,而DPPH自由基清除能力与其含量成负相关。以上表明低超声辐射面,有效的超声能量能显著影响咖啡酸的稳定性和增加其抗氧化性。     

Synthesis of chitosan-caffeic acid derivatives and evaluation of their antioxidant activities

In this study, the antioxidant activities of different molecular weights (M_w) and grafting ratios of chitosan–caffeic acid derivatives were investigated. The grafting process was achieved using 1-ethyl-3-(3-dimethylaminopropyl) carbodiimide hydrochloride (EDAC) as covalent connector under different conditions such as molecular-weight of chitosan, molar ratio of chitosan and caffeic acid, reaction temperature, pH, and reaction time. The half-inhibition concentrations (IC₅₀) of products were calculated by reduction of the 1,1-diphenyl picryl hydrazyl in the radical-scavenging assay and reduction of the Fe³⁺/ferricyanide complex to the ferrous form in reducing power assay. The EDAC showed maximum activity at 3-h, pH 5.0 and room temperature conditions, except high-molecular-weight chitosan in pH 2.0. The products were water-soluble in all pH and showed lower viscosity than native chitosan. The highest grafting ratio of caffeic acid was observed at 15% in low-molecular-weight chitosan. After 5% grafting of caffeic acid into chitosan, the grafting efficiency was increased by decreasing molecular-weight of chitosan at the same conditions. Caffeic acid has main role in the antioxidant activity of products. The maximum IC₅₀ of radical-scavenging activity (0.064 mg/ml) was observed at the highest caffeic acid containing derivative. Water-soluble chitosan and caffeic acid derivatives were obtained by this study without activity loss.     

Effect of pH on the antimicrobial activity and oxidative stability of oil-in-water emulsions containing caffeic acid

ABSTRACT:  Antioxidant properties in food are dependent on various parameters. These include the pH value and interactions with food components, including proteins or metal ions. Food components affect antioxidant stability and also influence the properties of microorganisms and their viability. This paper describes an investigation of the effect of pH on the antioxidant and antibacterial properties of caffeic acid in different media. The pH values studied, using an oil-in-water emulsion as model system, were 3, 5 (with and without phosphate buffer), and 9. Effects of mixtures of caffeic acid, bovine serum albumin (BSA), and Fe (III) on oxidative deterioration in the emulsion samples were studied. The results show that the antioxidant activity of caffeic acid was increased by the presence of BSA. This effect was pH dependent and was affected by the presence of iron ions. Antibacterial properties were also pH dependent. The minimum concentration of caffeic acid required to inhibit some microorganisms in the pH range of 5 to 7 was determined. A concentration of 0.4% (w/w) caffeic acid was enough to inhibit the growth of some of the studied microorganisms in the pH range of 5 to 7. However, near-neutral pH concentrations higher than 0.4% were needed to inhibit some microorganisms, including Listeria monocytogenes , E. coli, and Staphylococcus aureus , in the medium.     

咖啡酸维生素C酯的合成、抑菌活性和抗氧化性研究

研究了以3,4-二羟基苯甲醛、丙二酸和维生素C为原料,经过Knoevenagel缩合和直接酯化一锅法合成咖啡酸维生素C酯的方法,并考察了咖啡酸维生素C酯的抑菌活性和抗氧化性。在催化剂SO42-/ZrO2的作用下,3,4-二羟基苯甲醛与丙二酸首先发生Knoevenagel缩合生成咖啡酸,产物不需要分离,加入维生素C继续进行酯化反应,以85.1%的产率得到了咖啡酸维生素C酯,产物结构用1HNMR和IR进行确证。抑菌活性实验表明,咖啡酸维生素C酯对金黄色葡萄球菌、大肠杆菌、枯草杆菌、酿酒酵母、青霉、黄曲霉和黑曲霉均有较强的抑制作用,对细菌和酵母的抑制作用高于霉菌。抗氧化性实验表明,咖啡酸维生素C酯可以有效清除DPPH自由基和羟基自由基,清除效果明显好于维生素C。