CO在Cu/ZnO/Al_2O_3型低变催化剂上的TPD研究

本文采用程序升温脱附(TPD)法研究了CO在Cu/ZnO/Al_2O_3型低变催化剂上的脱附动力学。结果表明,在350℃以内,该催化剂对CO显示出一种能量分布的活泼部位,主要由催化剂中的Cu所提供。以T_f法结合脱附速率等温线法进行了TPD谱图的定量解析,求出了脱附动力学参数,建立了脱附速率方程。并发现Cu/ZnO/Al_2O_3型低变催化剂对CO的总有效表面虽为非均匀的,但该催化剂在350℃以内对CO显示的活泼部位所提供的有效表面却具有均匀表面的能量特征。由分析脱附级数,可推测出CO的吸附以缔合式吸附为主。     

Pt/Ba-Al-O催化剂储存NOx的性能和机理研究

采用共沉淀法制备了Pt/Ba-Al-O样品.用XRD、 NO-TPD以及NOx储存量测量等手段对样品进行了表征, 并对NOx的储存机理进行了探讨.结果表明, 样品中的主要成分是BaAl2O4, 有少量BaCO3存在.在催化剂表面的Pt有两种吸附位,吸附位1为NO提供了吸附位,对应低温区的NO脱附峰;吸附位2使NO和O2在催化剂表面反应生成硝酸盐和亚硝酸盐,对应高温区的NO脱附峰.当吸附温度为300℃、 O2的体积分数为1.3%时, NO的脱附量达到了最大值.经过还原处理样品的NO吸附能力比经过氧化预处理的样品强得多.样品储存NOx的最佳温区为300～450℃.     

NO气体在TiO2表面的吸附行为

采用TPD (Temperature Programmed Desorption)试验方法测定了NO在TiO₂表面吸附后的脱附谱, 揭示了气体脱附量的变化规律. 结果表明, NO在TiO₂表面吸附后可在两个峰值温度450和980 K脱附出N₂气体, 其活化能分别是0.48 和2.5 eV. TiO₂表面经预覆氧处理后, N₂的脱附量降低. N₂的脱附量随NO气体暴露量增加而增加, 但当气体覆盖度超过一定值后, 脱附量趋于定值. 脱附峰值温度随气体暴露量的增加而降低.     

NO气体在TiO2表面的吸附行为

采用TPD (Temperature Programmed Desorption)试验方法测定了NO在TiO₂表面吸附后的脱附谱, 揭示了气体脱附量的变化规律. 结果表明, NO在TiO₂表面吸附后可在两个峰值温度450和980 K脱附出N₂气体, 其活化能分别是0.48 和2.5 eV. TiO₂表面经预覆氧处理后, N₂的脱附量降低. N₂的脱附量随NO气体暴露量增加而增加, 但当气体覆盖度超过一定值后, 脱附量趋于定值. 脱附峰值温度随气体暴露量的增加而降低.     

不同Mn/（Mn+Ce）质量比对整体式MnOx-CeO2/WO3-ZrO2催化剂NH3-SCR性能的影响（英文）

制备了一系列不同Mn/(Mn+Ce)质量比的MnOx-CeO2/WO3-ZrO2整体式催化剂用于富氧条件下的NH3选择性催化还原NOx(NH3-SCR),并采用N2吸脱附、储氧量、X射线衍射、X光电子能谱、NH3/NO程序升温脱附以及H2程序升温还原等手段对催化剂进行表征.结果表明,当Mn/(Mn+Ce)质量比为0.5时,整体式催化剂具有较好的NH3-SCR性能,在空速10000h-1和173~355oC条件反应下,NOx转化率达90%以上.这是由于该MnOx-CeO2/WO3-ZrO2催化剂具有更高的NO氧化活性、更高的表面Ce和Mn原子浓度以及Ce3+/Ce值较低的NH3和NO脱附温度以及优异的氧化还原性能所致.     

多晶钯表面上CO脱附动力学的探讨

本文研究了多晶钯表面上CO脱附动力学,对各种覆盖度的脱附谱图进了划分温区的分析,对低温区首次提出恒定脱附速度的动力学解析.对于多晶钯面上CO的脱附,随脱附温度的升高,脱附反应级数减小而视活化能增加.为解释这种现象提出了活性集团假设,深入研究活性集团的动力学性能将有助于了解脱附过程的动力学特性.     

法拉第吸脱附偶联过程循环伏安行为的有限元分析

法拉第吸脱附偶联过程的电化学行为较为复杂,难以定量获得其表界面反应动力学信息. 本文通过COMSOL有限元软件对法拉第吸脱附偶联过程的循环伏安行为进行数值分析,研究了反应物或产物不同吸附条件下的循环伏安行为. 结果表明：当反应物或产物弱吸附时,可通过阴、阳极峰电流之差实现饱和吸附量的定量表征. 随着吸附平衡常数的增大,反应由弱吸附向强吸附过渡,峰电流由扩散峰与吸脱附峰相互重叠过渡到相互分离的吸脱附“前波”或“后波”特征. 该吸脱附特征峰的形状和位置与电势依赖的吸附平衡常数有关. 吸附平衡常数及其电势依赖程度越大,吸脱附峰偏离扩散峰越远,吸脱附峰越尖锐. 该模型为法拉第吸脱附偶联过程的循环伏安研究提供了一种定量研究方法,能够帮助研究者从复杂的吸脱附伏安行为中定量获得饱和吸附量和吸附平衡常数等信息,并对涉及吸脱附的电催化研究具有一定指导意义.     

半互穿海藻酸钠/聚丙烯酰胺凝胶吸附结晶紫动力学/热力学行为和吸/脱附机理

将含有大量—COO-的聚阴离子海藻酸钠(SA)引入聚丙烯酰胺(PAM)凝胶网络中,采用自由基溶液聚合法制备半互穿网络结构的SA/PAM水凝胶.采用扫描电子显微镜(SEM)、X射线光电子能谱(XPS)和傅里叶变换红外光谱(FTIR)分析了SA/PAM水凝胶吸附结晶紫(CV)前后的孔洞形态和化学组成变化,采用多种模型研究了SA/PAM水凝胶对CV分子的吸附动力学和热力学行为,并探讨了脱附效率,提出了吸脱附机理.研究结果表明,SA的引入降低了孔径尺寸,增加了孔洞数量;SA/PAM-10凝胶对CV分子吸附量最大,达到13.5838 mg/g,符合伪一级吸附动力学模型,吸附速率受膜扩散和粒子内扩散过程共同影响;等温吸附过程符合Temkin和D-R模型,属于微孔多层吸附;热力学分析结果表明,吸附过程由熵驱动引起,非化学诱导因素影响所致;采用HCl进行脱附,最大脱附率高达94.18%,加入Na OH可实现SA/PAM水凝胶的可逆吸附;较高的吸附量主要源于SA分子链上的COO-与CV分子的—C N+—存在的静电作用,低pH值时由于—COO-和—NH2质子化导致与CV分子的静电斥力增大,脱附率随之增加.     

用TG/DTG/DTA研究硅沸石与有机分子的主体/客体相互作用

用TG/DTG/DTA法研究无阳离子与Si—OH缺陷、结构完美的硅沸石上烃类、烷基醇、烷基胺的热脱附行为.有机分子从硅沸石上脱附的温度低于300℃其亲和性值A_T=T_d-T_b,式中T_d为有机分子在DTG上的失重峰温,T_b为该有机物在标准压力下的沸点.饱和烷烃的A_T值为60～90,而苯、甲苯、对二甲苯等的A_T值为6～13.电负性较强的羟基使烷基醇与硅沸石的亲和性明显下降.多羟基醇的A_T值为负值.对二甲苯、烷基醇、烷基胺在脱附时有明显吸热效应.A_T值及脱附热效应的不同是硅沸石骨架0~(2-)微孔表面与有机分子C—H基因,其它极性基因之间相互作用不同,以及受到硅沸石骨架空间限制的被吸附分子间缔合情况不同所致,反应了不同类型的主体/客体超分子相互作用.     

MoO3/SiO2催化甘油脱水氢转移还原制备烯丙醇

采用浸渍法制备了MoO3/SiO2催化剂,采用粉末X射线衍射、扫描电子显微镜、氮气吸附-脱附、NH3程序升温脱附及吸附吡啶傅里叶变换红外光谱等手段对催化剂进行了表征,并在固定床反应器中考察了催化剂负载量、反应温度、甘油浓度、空速等条件对MoO3/SiO2催化甘油制备烯丙醇反应性能的影响.结果表明,在MoO3的负载量(质量分数)为1%,330℃、常压、40%(质量分数)甘油水溶液和空速为200 h-1的反应条件下,甘油转化率、烯丙醇选择性及时空收率分别可达92.1%,34.8%和6.0 mmol.g-1.h-1.     

卷烟化学指标的因子分析

运用因子分析法对A牌号卷烟的18个化学指标进行分析,结果表明:烟丝的总糖、还原糖、总氮、总植物碱、水分、氯离子、钾离子、葡萄糖、麦芽糖、苹果酸、异戊酸、苯甲醇、茄酮、β-大马酮14个指标,及主流烟气的水分、CO、烟碱、焦油4个指标所含的信息可由8个因子来表示。该8个因子模型解释了试验数据总方差的86.7%;烟丝的致香成分、水分、糖类物质、有机酸类物质对卷烟A的质量风格具有重要影响,特别是致香成分在进行卷烟质量表征时应该重点关注。因子分析结果为卷烟的化学表征和质量控制提供了有用的参考。     

烟草中β-胡萝卜素的热裂解产物的研究

为了研究烟草中β-胡萝卜素的高温裂解产物对卷烟抽吸品质的影响,利用热裂解气相色谱/质谱联用仪在不同裂解氛围(空气、氮气中含10%O2及N2)和不同温度(300,600和900 ℃)下对β-胡萝卜素进行裂解,裂解产物用固相微萃取装置进行吸附,然后将吸附到的裂解产物用气相色谱/质谱联用仪(GC/MS)进行分析。结果表明,β-胡萝卜素在不同裂解条件下主要的裂解产物是甲苯、对二甲苯、1,2,3,4-四氢-1,1,6-三甲基萘和2,7-二甲基萘等化合物,另外还生成异佛尔酮、β-环柠檬醛、β-紫罗兰酮、二氢猕猴桃内酯等香味化合物,这些物质随裂解温度和裂解氛围的不同其含量有所差异。     

Comparative analysis of the volatile components in cut tobacco from different locations with gas chromatography-mass spectrometry (GC-MS) and combined chemometric methods

A combined approach of subwindow factor analysis and orthogonal projection resolution was used to analyze the volatile components of cut tobacco samples from different sources. After extracted with simultaneous distillation and extraction method, the volatile components in cut tobacco from five different locations were detected by GC-MS. Then, the qualitative and quantitative analysis of the volatile components of cut tobacco from Changde area was completed with the help of subwindow factor analysis resolving two-dimensional original data into pure mass spectra and chromatograms. One hundred and two volatile components among 138 separated peaks were identified and quantified, accounting for about 88.90% of the total content. Finally, orthogonal projection method was used to extract the common peaks from different locations. Among the identified components, there were 74 components coexisting in five studied samples although the relative content of each component showed difference to some extent. The results showed a fair consistency in their GC-MS fingerprints. It was the first time to apply orthogonal projection method to compare different cut tobacco samples, and it reduced the burden of qualitative analysis as well as the subjectivity. The obtained results proved the combined approach powerful for the analysis of complex cut tobacco samples. The developed method can be used to compare the sameness and differences of cut tobacco from different sources and for quality control of cigarette production and materials.     

有机酸对卷烟感官风格和品质的影响研究

测定了25种成品卷烟的15种有机酸含量,采用逐步回归分析法建立了卷烟感官风格品质与有机酸之间的关系模型。根据逐步回归模型选择的变量,评价影响卷烟香韵表现与感官品质的关键有机酸成分。将回归模型成功地应用于试制卷烟香韵表现和感官品质得分预测,证明了模型的有效性及有机酸对卷烟香韵表现和感官品质的解释能力。研究结果表明,异戊酸、丙二酸、苯乙酸和柠檬酸等有机酸对卷烟香韵表现或感官品质存在正面或负面的不同影响。     

六种添加剂对烟丝挥发性与半挥发性成分含量的影响

分别配制1%(质量分数,下同)的柠檬酸、苹果酸、乳酸水溶液以及5%的(NH4)2HPO4、K2CO3、柠檬酸钾水溶液.分别取100.0g烟丝,均匀喷洒10.0mL上述水溶液,经平衡、实验室模拟烘丝、萃取后,进行气相色谱-质谱测定,分析烟丝中挥发性和半挥发性香味成分含量的变化.结果表明,喷洒柠檬酸和K2CO3水溶液可显著改变烟丝的化学成分含量.烟丝经K2CO3水溶液喷洒后,游离态的尼古丁含量大幅增加,醇类组分、巨豆三烯酮含量有所升高,酸类组分和酯类组分含量略有降低;而经柠檬酸水溶液喷洒后的烟丝的酸类、醇类和酯类组分含量升高,尼古丁含量下降.     

The important role of quinic acid in the formation of phenolic compounds from pyrolysis of chlorogenic acid

Chlorogenic acid and its two structural components, quinic acid and caffeic acid, were pyrolyzed under reaction conditions simulating the typical pyrolysis conditions inside a burning cigarette. Major phenolic products from pyrolysis of the three acids were quantified and compared to evaluate the respective contribution of the quinic and caffeic acid moieties to the overall phenolic yield in chlorogenic acid pyrolysis. The results show that the most prominent phenolic product of chlorogenic acid is catechol, followed in order by phenol, hydroquinone, and alkylcatechols. Among these phenolics, catechol and alkylcatechols are formed mainly from the caffeic acid moiety of chlorogenic acid, while phenol and hydroquinone are produced predominantly from the quinic acid moiety. The quinic acid moiety can thus contribute more than 40 % of the overall phenolic yields in chlorogenic acid pyrolysis (0.54 mol mol^?1 chlorogenic acid pyrolyzed at 600 °C). Because considerable amounts of free quinic acid and its derivatives exist in tobacco, the results of this study indicate that quinic acid can be an important source of phenolic compounds, especially hydroquinone and phenol, in tobacco smoke.     

Puff-by-puff resolved characterisation of cigarette mainstream smoke by single photon ionisation (SPI)-time-of-flight mass spectrometry (TOFMS): comparison of the 2R4F research cigarette and pure Burley, Virginia, Oriental and Maryland tobacco cigarettes

Soft single photon ionisation (SPI)-time-of-flight mass spectrometry (TOFMS) is applied for the characterisation and comparison of puff-by-puff resolved and total yields of cigarette mainstream smoke from single tobacco type cigarettes (Virginia, Oriental, Burley, and Maryland) and the 2R4F University of Kentucky research cigarette. Puff-by-puff characteristics of various smoke components within one cigarette type as well as between different cigarette types can differ tremendously. This is demonstrated by means of a few selected compounds. Puff yields vary between 15 and 106 μm for acetaldehyde, 6 and 57 μm for NO, and between 1 and 8 μm for butadiene. Thereby, cigarettes containing 100% Oriental and Burley tobacco exhibit a very unique behaviour for the first and last puff. Different cultivation and processing methods as well as burning characteristics are most likely responsible for this. Since the 2R4F cigarette contains all four tobacco types it combines features of all of them. However, for some smoke constituents, smoking of the 2R4F reference cigarette results in exceptionally high yields which might not be attributable to the four pure tobacco types, but to other factors. In addition, comparison of the different cigarettes was also carried out by normalising the yields to puff resolved particulate matter. This procedure minimises effects caused by unequal smoke formation and represents another approach in evaluating the data.     

Pyrolysis and combustion of tobacco in a cigarette smoking simulator under air and nitrogen atmosphere

A coupling between a cigarette smoking simulator and a time-of-flight mass spectrometer was constructed to allow investigation of tobacco smoke formation under simulated burning conditions. The cigarette smoking simulator is designed to burn a sample in close approximation to the conditions experienced by a lit cigarette. The apparatus also permits conditions outside those of normal cigarette burning to be investigated for mechanistic understanding purposes. It allows control of parameters such as smouldering and puff temperatures, as well as combustion rate and puffing volume. In this study, the system enabled examination of the effects of “smoking” a cigarette under a nitrogen atmosphere. Time-of-flight mass spectrometry combined with a soft ionisation technique is expedient to analyse complex mixtures such as tobacco smoke with a high time resolution. The objective of the study was to separate pyrolysis from combustion processes to reveal the formation mechanism of several selected toxicants. A purposely designed adapter, with no measurable dead volume or memory effects, enables the analysis of pyrolysis and combustion gases from tobacco and tobacco products (e.g. 3R4F reference cigarette) with minimum aging. The combined system demonstrates clear distinctions between smoke composition found under air and nitrogen smoking atmospheres based on the corresponding mass spectra and visualisations using principal component analysis.     

Py-GC/MS分析烟用添加剂黄芩浸膏的热裂解产物

采用在线热裂解气相色谱-质谱法(Py-GC/MS)法研究了黄芩浸膏热裂解行为。在氦气氛围中,将黄芩浸膏分别在300、450、600、750和900℃下进行热裂解,并以GC/MS对其裂解产物进行定性和半定量分析,并用黄芩浸膏进行了卷烟加香试验。结果表明:①黄芩浸膏在这一系列裂解温度下检测到的挥发性热裂解产物分别为12种、19种、40种、55种和46种;②黄芩浸膏低温区(300℃～450℃)裂解后产生大量醛类、酮类、酯类和呋喃类物质,这些物质是构成卷烟香味的重要物质,能改善卷烟吸味、减轻刺激性;③在高温区(750℃～900℃)产生大量的芳香族化合物,如苯、甲苯、乙苯、萘等。该研究为香味物质在卷烟燃烧过程中的挥发性物质提供了例证。     

Microprobe sampling—Photo ionization-time-of-flight mass spectrometry for in situ chemical analysis of pyrolysis and combustion gases: Examination of the thermo-chemical processes within a burning cigarette

A microprobe sampling device (μ-probe) has been developed for in situ on-line photo ionization mass spectrometric analysis of volatile chemical species formed within objects consisting of organic matter during thermal processing. With this approach the chemical signature occurring during heating, pyrolysis, combustion, roasting and charring of organic material within burning objects such as burning fuel particles (e.g., biomass or coal pieces), lit cigarettes or thermally processed food products (e.g., roasting of coffee beans) can be investigated. Due to its dynamic changes between combustion and pyrolysis phases the cigarette smoking process is particularly interesting and has been chosen as first application. For this investigation the tip of the μ-probe is inserted directly into the tobacco rod and volatile organic compounds from inside the burning cigarette are extracted and real-time analyzed as the glowing front (or coal) approaches and passes the μ-probe sampling position. The combination of micro-sampling with photo ionization time-of-flight mass spectrometry (PI-TOFMS) allows on-line intrapuff-resolved analysis of species formation inside a burning cigarette. Monitoring volatile smoke compounds during cigarette puffing and smoldering cycles in this way provides unparalleled insights into formation mechanisms and their time-dependent change. Using this technique the changes from pyrolysis conditions to combustion conditions inside the coal of a cigarette could be observed directly. A comparative analysis of species formation within a burning Kentucky 2R4F reference cigarette with μ-probe analysis reveals different patterns and behaviors for nicotine, and a range of semi-volatile aromatic and aliphatic species.