13C-NMR analysis of phenol-urea-formaldehyde prepolymers and phenol-urea-formaldehyde-tannin adhesives

Phenol-urea-formaldehyde-tannin (PUFT) adhesives were prepared by co-polymerization of Pinus pinaster bark tannins with phenol-urea-formaldehyde (PUF) prepolymers at room temperature. A detailed analysis by ¹³C-NMR spectroscopy of the resins together with an evaluation of their properties was performed in order to find suitable preparation conditions for prepolymers prior to their co-polymerization with tannins. ¹³C-NMR spectroscopy allowed identification of the different linkages formed and quantification of the main functional groups in the PUF prepolymers, which were greatly influenced by the preparation conditions. The decrease in the free formaldehyde content in the PUFT adhesives with respect to the original prepolymers was attributed to tannin methylolation at room temperature. The fast increase in the apparent viscosity of the PUFT adhesives after the blending suggested the possibility of a co-polymerization reaction between tannins and the PUF prepolymers; however, the occurrence of this reaction could not be confirmed by ¹³C-NMR.     

载银分子筛抗菌剂的研究

探讨了真空热分解法制备载银分子筛抗菌剂过程中影响银含量的因素,并以大肠杆菌为研究对象,对载银分子筛抗菌剂的抗菌性能进行了定性和定量的检测,结果表明其对大肠杆菌具有明显的杀灭作用,且载银分子筛（银含量为2．11％）对大肠杆菌的最低抑菌浓度为50μg／mL。     

氯化钙-13X分子筛复合吸附剂的实验研究

将氯化钙填充到13X分子筛的多孔结构内钊备出了氯化钙-13X分子筛复合吸附剂,并对其吸附性能进行了实验研究。实验结果表明,复合吸附剂中氯化钙含量越高,其平衡吸附量越高,当氯化钙含量为46.2%时,其平衡吸附量最大可以达到0.557g/g,是13X分子筛的2.2倍。     

脲醛树脂胶粘剂~(13)C核磁共振分析

采用常规化学分析和13C核磁共振相结合的方法,分析研究了脲醛树脂胶粘剂性能与结构的关系。结果表明:在摩尔配比F:U=1.2:1时,粘度越高,游离尿素的含量越低,羟甲基的含量越低,游离甲醛含量降低; 树脂产品的粘度低,聚合度也低,羟甲基的含量偏高,粘接性能下降,同时游离甲醛含量上升,而适量苯酚的添加可改善树脂结构,是一种优化树脂的途径。当增大摩尔配比到F:U=1.4:1时,尿素含量下降,游离甲醛含量上升。因此,摩尔配比的选择在很大程度上影响脲醛树脂的性能。     

Comparative study of cellulose isolated by totally chlorine‐free method from wood and cereal straw

Highly purified cellulose preparations were obtained by pretreatment of dewaxed barley straw, oil palm frond fiber, poplar wood, maize stems, wheat straw, rice straw, and rye straw with 2.0% H₂O₂ at 45°C and pH 11.6 for 16 h, and sequential purification with 80% acetic acid–70% nitric acid (10/1, v/v) at 120°C for 15 min. The purified cellulose obtained was relatively free of bound hemicelluloses (2.3–3.2%) and lignin (0.4–0.6%) and had a yield of 35.5% from barley straw, 39.6% from oil palm frond fiber, 40.8% from poplar wood, 36.0% from maize stems, 34.1% from wheat straw, 23.4% from rice straw, and 35.8% from rye straw. The weight‐average molecular weights of the purified cellulose ranged from 39,030 to 48,380 g/mol. The thermal stability of the purified cellulose was higher than that of the corresponding crude cellulose. In comparison, the isolated crude and purified cellulose samples were also studied by Fourier transform IR and cross‐polarization/magic‐angle spinning ¹³C‐NMR spectroscopy. © 2005 Wiley Periodicals, Inc. J Appl Polym Sci 97: 322–335, 2005     

Implicit Bayesian Inference Using Option Prices

Abstract. A Bayesian approach to option pricing is presented in which posterior inference about the underlying returns process is conducted implicitly via observed option prices. A range of models allowing for conditional leptokurtosis, skewness and time‐varying volatility in returns are considered, with posterior parameter distributions and model probabilities backed out from the option prices. Models are ranked according to several criteria, including out‐of‐sample predictive and hedging performance. The methodology accommodates heteroscedasticity and autocorrelation in the option pricing errors, as well as regime shifts across contract groups. The method is applied to intraday option price data on the S&P500 stock index for 1995. While the results provide support for models that accommodate leptokurtosis and skewness, no one model dominates when all criteria are considered.     

通讯及打印机口阻塞病毒的分析与清除

本文分析并揭示了通讯及打印机口阻塞病毒的运行规律和发作条件,根据其特点研究了该病毒的清除方法.     

13X沸石分子筛对低浓度CO2动态吸附

目前对于吸附分离技术应用于高压、低浓度CO₂脱除的研究还较少,在进行相应吸附脱碳工艺设计时也缺少相关的参考数据。为探究13X沸石分子筛对低浓度CO₂的动态吸附性能,本文利用动态吸附实验的方法,探究不同条件下低浓度（摩尔分数3%）CO₂气体在13X分子筛上的动态吸附性能,得到不同压力、温度、气体流量、填料高度及分子筛规格（尺寸、形状）等因素影响下的13X分子筛对于CO₂气体的动态吸附规律及相应的性能指标参数。结果表明：随着吸附压力的升高,13X分子筛的CO₂吸附量增加但增量逐渐减小;降低吸附温度、减小气体流量和增加填料高度均有利于增强13X分子筛的动态CO₂吸附性能,提高吸附脱碳效果,其中温度及填料高度的变化对于CO₂吸附的影响程度最大;实验还发现小尺寸及条状13X分子筛的动态吸附脱碳性能优于其他规格,并根据其特定条件下的出口CO₂浓度为50mL/m³时的CO₂吸附量指标,给出吸附剂用量与液化天然气（LNG）脱碳工艺处理量的关系系数。     

Vapor Phase Selective Catalytic Oxidation of Cyclohexane over 13X Supported Metal Oxides in the Presence of Ozone

This article reports the application of ozone for the selective oxidation of cyclohexane over 13X molecular sieve supported various metal oxides at ambient temperatures. From the SEM, XRD and HR-TEM results, the impregnated metal oxides are highly dispersed on the support. The activity results reveal that Co/MS, Mo/MS, Cu/MS, and Ag/MS catalysts produce cyclohexanone/cyclohexanol as selective oxidation products, whereas Ce/MS, Mn/MS, and V/MS catalysts yield, predominantly, CO and CO₂. Among them, Co/MS catalyst exhibits better conversion of 12.2% with selectively of 58% to cyclohexanone/cyclohexanol, which is attributed to the simultaneous activation of ozone and cyclohexane (-C-H bond) at ambient conditions.     

混合模板法低成本合成SSZ-13分子筛的研究

以硅溶胶、硫酸铝、氢氧化钠和去离子水为原料,以N,N,N-三甲基金刚烷氢氧化铵和三乙胺为模板剂,采用传统的水热法快速合成了SSZ-13分子筛。采用X射线荧光光谱（XRF）、X射线衍射（XRD）和扫描电镜（SEM）表征产物。综合考察了碱度、水量、模板剂和晶种等因素对合成SSZ-13分子筛的影响,确定了最佳合成条件。在有晶种或无晶种条件下,通过引入辅助模板剂三乙胺,晶化2 d即可得到SSZ-13分子筛。该方法缩短了生产周期,降低了生产成本,具有广泛的工业应用前景。