用低负载钯作催化剂的丙烯腈催化加氢反应

低负载钯(w(Pd)=0.05%)催化剂对含其它不饱和基团的双键加氢有很好的选择性和活性,应用于丙烯腈气相加氢可得到高收率的丙腈.采用积分固定床反应器,研究了丙烯腈气相加氢的最佳工艺条件∶温度140℃、n(氢气)∶n(腈)=9∶1.但催化剂失活严重,红外测试表明∶催化剂失活主要源于产物及原料在催化剂上的吸附,可通过焙烧除去吸附物,从而使活性恢复.     

Cu/ZnO催化糠醛气相加氢制2-甲基呋喃的研究

通过共沉淀法制备一系列铜锌催化剂,用于固定床上糠醛气相加氢制2-甲基呋喃的研究。采用X射线衍射仪(XRD)、N_2吸附-脱附、扫描电子显微镜(SEM)、H_2-程序升温还原(H_2-TPR)、NH_3-程序升温脱附(NH_3-TPD)表征,分析催化剂中Cu0和ZnO在催化反应中的作用。结果表明,Cu~0是糠醛加氢的活性中心,氧化锌的加入减小了催化剂晶粒粒径、增大了催化剂比表面积、利于催化剂还原和增加催化剂表面弱酸性位。当Cu/Zn物质的量比为1∶2时,Cu_1Zn_2催化剂具有适宜氧化还原活性中心及弱酸位数量,对2-甲基呋喃表现出较高的选择性。Cu_1Zn_2催化剂在常压、反应温度为200℃、氢醛物质的量比为4∶1、糠醛体积空速为0.3 h-1条件下,糠醛转化率100.0%,2-甲基呋喃选择性最高为93.6%。反应稳定运行200 h后,糠醛转化率仍为100.0%,2-甲基呋喃选择性为80.0%,糠醇选择性为11.4%。     

巴豆醛气相选择性加氢催化剂

巴豆醛是α, β-不饱和醛中最具代表性的一类有机化合物,采用气相催化巴豆醛选择加氢制备巴豆醇符合原子经济和绿色化学要求,具有重要的工业应用和学术价值。本文综述了近十年国内外巴豆醛气相选择性加氢合成巴豆醇的负载型催化剂的研究成果,评述了贵金属催化剂(铂、金、铱、银、钯)和非贵金属催化剂(钴、铜)上巴豆醛选择性加氢性能,分析了活性组分、载体、助剂以及活性组分粒径对催化剂性能的影响,探讨了巴豆醛选择性加氢的反应机理和失活机理。最后,对气相巴豆醛选择性加氢催化剂所存在的问题进行总结,并对催化剂的发展趋势作出了展望。指出了非贵金属催化剂的巴豆醛选择性加氢性能因具有价廉易得等优势,将是该领域的研究方向之一。催化剂失活是巴豆醛气相选择性加氢工业化的最大障碍,因此研究和认识反应机理,解决催化剂失活问题是重点研究方向。     

蒸氨法制备Ni/SiO_2催化剂及其在2-MF加氢制2-MTHF反应中的应用

以硝酸镍为镍源,碱性硅溶胶为硅源,采用蒸氨法制备了Ni/SiO_2催化剂。通过XRD、N_2等温吸附脱附、H_2-TPR、NH_3-TPD、XPS和TG对催化剂进行表征。采用固定床反应器,考察了催化剂焙烧温度及反应条件对催化剂应用于2-甲基呋喃(2-MF)气相加氢合成2-甲基四氢呋喃(2-MTHF)的反应性能。结果表明,蒸氨法制备的Ni/SiO_2催化剂在焙烧后均呈现层状硅酸镍结构,还原后保持了该结构,活性组分Ni晶粒尺寸较小、金属载体相互作用较强,从而具有较高的活性。催化剂的焙烧温度影响催化剂Ni晶粒尺寸及催化剂的表面酸性。在500℃焙烧条件下制备的催化剂性能最佳,优化反应条件下,2-MF转化率100%,2-MTHF选择性为93.5%,反应15 h内催化性能稳定;含碳的有机物在催化剂表面沉积是催化剂失活的主要原因。     

K-MnO/γAl2O3和Cu/SiO2催化剂应用于苯甲酸甲酯连续加氢合成无氯苯甲醇

以K-MnO/γ-Al2O3和Cu/SiO2为催化剂,利用固定床串联反应器实现了苯甲酸甲酯连续加氢合成无氯苯甲醇反应过程.K-MnO/γ-Al2O3和Cu/SiO2催化剂对于苯甲酸甲酯连续加氢合成苯甲醇具有良好的加氢活性,反应转化率可达89.2%,苯甲醇的选择性为84.1%.在苯甲酸甲酯加氢连续步骤中的氢醛比得到提高,有效地抑制了副产物甲苯的生成.XRD,SEM和TPR表征结果表明:采用吸附沉淀法制备的Cu/SiO2-C15.2催化剂,氧化铜在载体上具有良好的分散性能,并且易于还原,表现出最佳的苯甲醛加氢活性.     

沉淀剂对CuZnAl催化剂糠醛气相加氢制糠醇选择性的影响

采用共沉淀法制得分别以NaOH、Na_2CO_3和Na_2CO_3/NaOH为沉淀剂的CuZnAl-1、CuZnAl-2和CuZnAl-3催化剂,采用X射线衍射(XRD)、N2吸附-脱附、H_2-程序升温还原(H_2-TPR)、热重和NH_3-程序升温脱附(NH3-TPD)等方法对催化剂进行了表征,并在固定床反应器上研究了沉淀剂对CuZnAl催化剂糠醛气相加氢制糠醇选择性的影响。结果表明,糠醛加氢在三种催化剂上均有较高转化率,而CuZnAl-3催化剂对糠醇有较高选择性。沉淀剂对CuZnAl催化剂的物相结构、比表面积、酸性和氧化还原性均有较大影响。以Na_2CO_3/NaOH为沉淀剂得到的CuZnAl-3催化剂具有适宜的比表面积、CuO晶相、较弱的酸性位,且表面CuO易于还原,这些因素有利于催化反应生成糠醇。CuZnAl-3催化剂上糠醛气相加氢制糠醇优化工艺参数为:常压、反应温度180℃、氢醛物质的量比为5∶1、糠醛体积空速0.3h~(-1);糠醛转化率为99.4%,糠醇选择性为98.3%。     

Ni2 在炭包覆氧化铝表面存在状态及加氢性能

采用等体积浸渍法制备了以炭包覆氧化铝(CCA)为载体的Ni基催化剂.利用低温N2物理吸附、XRD、UV-Vis DRS、H2-TPR、H2-TPD等手段对催化剂进行表征,并考察了催化剂粗1,4-丁二醇加氢反应性能.结果表明,均匀分散在表面的炭可以有效阻止Ni2+进入氧化铝表面四面体及八面体空位,Ni2+以与载体具有中等强度相互作用的物种形式存在.随Ni含量的增加,镍物种晶粒尺寸发生明显变化,当Ni含量低于10%时,NiO以高分散状态存在于载体表面,Ni含量达到14%时催化剂中出现了NiO微晶,进一步提高Ni含量,NiO晶粒尺寸有所长大,但仍保持了较高的分散度.由于Ni的聚集程度较小,随着Ni含量增加,Ni的总活性比表面积增加,催化剂加氢活性提高,至Ni含量达17%时,催化剂表现出最佳的催化加氢活性.     

4,5—环氧—2—戊烯醛多相催化加氢

研究了多相钯和镍催化剂上4,5-环氧-2-戊烯醛的催化加氢。发现钯催化剂上加氢产物为4,5-环氧戊醛(1)和2-羟基四氢吡喃(2),而镍催化剂上加氢产物为2和1,5-戊二醇(3)。1、2和3的最高收率分别为58.8%、62.0%和84.7%。讨论了不同催化剂对加氢产物组成的影响。     

Ni/γ-Al2O3催化剂的2-MF气相加氢合成2-MTHF性能研究

2-甲基四氢呋喃(2-MTHF)是极具市场潜力的生物燃料、绿色溶剂和化学中间体.采用浸渍法制备Ni/γ-Al2O3催化剂,在固定床反应器评价其2-甲基呋喃(2-MF)气相加氢合成2-甲基四氢呋喃(2-MTHF)反应性能.通过XRD、N2等温吸附-脱附、H2-TPR、NH3-TPD、TEM、H2吸附和XPS对催化剂结构和表面性质进行表征,研究Ni负载量、焙烧温度和反应条件对催化剂性能的影响规律.结果表明:Ni/γ-Al2O3催化剂的Ni金属面积、晶粒尺寸、反应温度和压力都会影响2-MF的转化率;孔结构、酸量和反应温度是影响2-MTHF选择性的主要原因,平均孔径大、酸量大和适宜的反应温度有利于提高2-MTHF选择性. 400℃焙烧的负载量为15%的Ni/γ-Al2O3催化剂, Ni金属面积大、晶粒尺寸小、总酸量多,催化剂表面的金属活性中心与酸性中心协同作用促进了2-MF呋喃环上C=C加氢生成2-MTHF,性能较优.在2 MPa、100℃、WHSV=2.7 h-1、H2/2-MF=6.4的条件下,该催化剂上2-MF转化率为99.8%, 2-MTHF选择性为98.0%,催化剂可以稳定运行40 h.     

贵金属催化剂上两步法选择性降解有机溶剂型木质素

使用担载型贵金属催化剂和磷酸在不同温度下通过两步法加氢降解二氧六环木质素. 第一步反应使用Rh/C和浓度为1% (w)的磷酸为催化剂, 在270 ℃和4 MPa氢气气氛下反应后通过气相色谱(GC)和气相色谱-质谱(GC-MS)分析木质素单体和二聚体, 总收率最高可达16.9%. 通过傅里叶变换红外(FTIR)光谱、X射线光电子能谱(XPS)、元素分析(EA)和凝胶渗透色谱(GPC)等方法研究第一步反应产物的变化. 结果发现, 二氧六环木质素中的C－O－C键被打断, 木质素分子量降低, 部分羰基和羧基被脱除. 随着反应温度的上升, 产物的含氧量不断下降, 在270 ℃反应10 h 后氧含量从35% (w)降低至21% (w). 结合不同的表征方法, 提出二氧六环木质素的第一步反应路径. 第二步反应中使用Pd/C和磷酸为催化剂在250 ℃可以将木质素单体、二聚体高选择性地加氢脱氧转化为对应的烃类产物.     

Impact of alkali treatment on physico-chemical,thermal, structural and tensile properties of Carica papaya bark fibers

This study aims to examine the effect of sodium hydroxide (NaOH) treatment on the physico-chemical properties, structure, thermal, tensile and surface topography of Carica papaya fibers (CPFs). The surface of raw CPFs was modified by soaking with 5% NaOH solution for 15, 30, 45, 60, 75 and 90?min. The results of thermo-gravimetric analysis revealed that the optimum treatment time for alkali treatment was 60?min. It was found that the alkali treatment improved the properties of the CPFs. The results of TGA, FT-IR, XRD and AFM suggest that the treated CPF is a suitable alternative as reinforcement in polymer composites.     

Chemometric and trend analysis of water quality of the South Chennai lakes: an integrated environmental study

In order to bring out the nature of the factors influencing lake water composition, multivariate statistical analysis and trend analysis were performed based on the hydrochemical data of the study area, namely, South Chennai. Change in land use pattern and settlements along the banks of the lakes alters the quality and quantity of the surface water. In the present study, the R‐mode factor analysis and cluster analysis were applied to the geochemical parameters of the water to identify the factors affecting the chemical composition of the lake water. Dendograms of both the seasons give three major clusters, reflecting the groups of unpolluted to moderately polluted, polluted, and heavily polluted stations. The movement of stations from one cluster to another clearly brings out the seasonal variation in the chemical composition of the lake water. The complex hydrochemical data of the surface water were interpreted by condensing them into three major factors. Factor score analysis was used successfully to delineate the stations under study and the role of the contributing factors, and the nature of factors responsible for the variation in chemical composition of the water has been clearly brought out. Results of trend analysis using ArcGIS clearly indicate that the trend in water quality is deteriorating at a faster rate in the eastern part of the study area. It is understood that although natural shifts probably can account for some of the variation, it is most likely that human activities play a major role in affecting the water quality on a regional scale. Copyright © 2014 John Wiley & Sons, Ltd.     

On-line fermentation gas analysis: Error analysis and application of mass spectrometry

On-line fermentation gas analysis is of general interest because it permits the determination of metabolic rates in almost any biological process using living organisms. The consumption and production of gases (O₂, CO₂, CH₄, etc.) and volatile compounds may be determined without causing any risk of infection. Elemental balancing permits the determination of other metabolic rates if the stoichiometry is known. This was studied with the production of poly-β-hydroxybutyrate (PHB) by Alcaligenes latus. Estimations were based on the measurement of gas partial pressure and flow-rates, pH and alkali consumption rate. Experiments with a small quadrupole mass spectrometer showed unacceptable error propagation. Therefore, dynamic error propagation for all rates was studied using simulation. It was found that, for example, a 1% relative offset-calibration error for oxygen can result in an error in PHB estimation of > 50%. It is suggested that this culture is used in combination with elemental balancing for thorough tests of the accuracy of on-line gas analysis equipment. An on-line process gas analyser based on a quadrupole mass spectrometer (Balzers PGM 407) gave the following precision values (abs. vol.?%) during cultivation of Bacillus subtilis: nitrogen (m/z 14), 0.024; oxygen (m/z 32), 0.020; argon (m/z 40), 0.0011; and carbon dioxide (m/z 44), 0.0034. These values, combined with automatic recalibration, would be sufficient for reasonable estimation of PHB, biomass and substrates.     

Determination of rank by augmentation (DRAUG)

Determining the rank of a chemical matrix is the first step in many multivariate, chemometric studies. Rank is defined as the minimum number of linearly independent factors after deletion of factors that contribute to random, nonlinear, uncorrelated errors. Adding a matrix of rank 1 to a data matrix not only increases the rank by one unit but also perturbs the primary factor axes, having little effect on the secondary axes associated with the random errors in the measurements. The primary rank of a data matrix can be determined by comparing the residual variances obtained from principal component analysis (PCA) of the original data matrix to those obtained from an augmented matrix. The ratio of the residual variances between adjacent factor levels represents a Fisher ratio that can be used to distinguish the primary factors (chemical as well as instrumental factors) from the secondary factors (experimental errors). The results gleaned from model studies as well as those from experimental studies are used to illustrate the efficacy of the proposed methodology. The method is independent of the nature of the error distribution. Limitations and precautions are discussed. An algorithm, written in MATLAB format, is included. Copyright © 2011 John Wiley & Sons, Ltd.     

新材料的发展与分析化学

文章介绍了新材料的重要性及发展方向,分析化学在新材料研制中起着耳目的作用,另一方面新材料也为分析化学的进展提供了课题与条件。微量分析、微区分析、表面分析是此领域中的重点。在未来的发展中,分析化学在材料的发展中的地位不会改变,并期待着分析灵敏度与空间分辩率的进一步提高。     

用局部拟合主成分回归计算光度分析法测定黄连生物碱

针对具有样本数据非无匀分布和非线性特点的光度分析问题，提聘种局部拟合 主成分回归法，用于中药多组分计算测定。该方法根据待测样本与各已知样本光度 分析数据的欧式距离确定相应的权值，将部分权值较大的样本组成校正集，并用分 段线性拟合算法建立待测样本的校正预测模型，将其用于分析黄连的药根碱、巴巴 亭和小檗碱等三种生物碱，所得预测均方根误差分别为0.023,0.0400和0.052，优 于主成分回归法、偏最小二乘法以及人工神经元网络法所得结果。这表明，本方法 用于中药光度分析能获得较为准确的计算分析结果。     

高效液相色谱荧光检测法测定福建乌龙茶中痕量硒

本文研究了2,3-二氨基萘(DAN)与Se(Ⅳ)反应,生成4.5-苯并苤硒脑(NSD),利用环已烷萃取反应生成的络合物。将有机相注射入填充有μ一Bondapak C_(18)固定相的色谱柱,以环已烷-四氢呋喃(90:10)为流动相,流速为1.0 mL/min,进行HPLC一荧光检测。测定了福建乌龙茶中的微量硒。方法的精密度和回收度均好。检测限达0.12 ng。     

双嘧达莫的荧光光谱分析法

以荧光光谱法研究了双嘧达莫在溴化十六烷基三甲基铵(CTMAB)、β_环糊精 (β_CD)、十二烷基硫酸钠 (SDS)等介质体系中的荧光性质 ,发现CTMAB、SDS和 β_CD对双嘧达莫均有不同程度的荧光增敏作用 ,提出了在CTMAB、SDS和 β_CD水溶液中测定双嘧达莫的荧光光谱分析法 ;该法灵敏度高 ,检出限低(3.20×10 -9mol/L) ,在6.40×10 -8～3.20×10 -6mol/L范围内荧光强度与双嘧达莫的浓度呈良好线性关系     

铁与氯气反应的产物分析

应用高温传感器测定了铁在氯气中燃烧时的温度;基于实际反应温度、压强与物质状态,对铁与氯气的相关反应进行了热力学分析,发现FeCl₃(Fe₂Cl₆)是铁与氯气反应过程中绝大多数情况下的热力学稳定产物,而铁与氯气反应生成FeCl₂的条件则较为苛刻;反应的动力学分析,FeCl₂和FeCl₃的结构分析,也表明铁与氯气反应生成FeCl₃更加有利。