Diminishing hazardous air pollutant emissions from pyrolysis of furan no-bake binders using methanesulfonic acid as the binder catalyst

The formation of hazardous air pollutants (HAPs) in thermal decomposition of furan no-bake foundry binders was investigated using analytical pyrolysis techniques. Two furan binders cured with p-xylenesulfonic acid (conventional acid catalyst used in foundries) and methanesulfonic acid (alternative catalyst proposed for diminishing HAPs) were flash pyrolyzed in a Curie-point pyrolyzer at 920 °C and slowly pyrolyzed in a thermogravimetric analyzer from 50 to 800 °C with a heating rate of 20 °C min^?1. Similar HAPs (mainly benzene, toluene, and xylenes) were identified in the emissions of the two binders. However, the HAP yields were much higher for the binder cured with p-xylenesulfonic acid than for the binder cured with methanesulfonic acid (3.74 and 1.24 mg HAPs/g binder pyrolyzed, respectively). By analyzing the HAP formation pathways, it was concluded that for the binder cured with p-xylenesulfonic acid, the aromatic HAPs were originated mainly from the acid catalyst. In addition, some HAPs (predominantly benzene) could be formed from the recombination of furan-derived fragments (e.g., C₂–C₄ radicals generated from ring-opening of furans). The results suggest that by replacing the conventionally used catalysts (arylsulfonic acids) with methanesulfonic acid, the HAP emissions from furan no-bake molds can be decreased significantly in metal casting processes.     

Direct Ab Initio Dynamics Study on the Reaction of CH3CHF2 (HFC‐152a) with the Cl Atom

A direct ab initio dynamics method is used to investigate the hydrogen‐abstraction reaction CH₃CHF₂+Cl. One transition state is located for α‐H abstraction, and two are identified for β‐H abstraction. The potential‐energy surface (PES) is obtained at the G3(MP2)//MP2/6‐311G(d, p) level. Furthermore, the rate constants of the three channels are evaluated by using canonical variational transition‐state theory (CVT) with small‐curvature tunneling (SCT) contributions over a wide temperature range of 200–2500 K. The dynamic calculations show that the reaction proceeds mainly by α‐H abstraction over the whole temperature range. The calculated rate constants and branching ratios are both in good agreement with the available experimental values.     

旋光性聚{(+)-甲基丙烯酸-2,5-二[4′-((S)-2-甲基丁氧基)苯基]苄酯}的合成与表征

设计、合成了一个带有横挂三联苯侧基的手性乙烯基单体——(+)-甲基丙烯酸-2,5-二[4′-((S)-2-甲基丁氧基)苯基]苄酯,进行了普通自由基和原子转移自由基聚合反应.所得聚合物具有比单体低30°左右的比旋光度,且在侧基的紫外吸收处呈现明显不同于单体的Cotton效应,说明其主链可能形成了具有相反旋光方向的螺旋构象.在所研究范围内,聚合条件对聚合物的旋光度没有明显的影响.在分子量较小时,聚合物的比旋光度随着分子量的增加而降低,说明主链螺旋构象的贡献在增大,而当分子量达到一定值后,聚合物的比旋光度不再随分子量的增加而显著变化.     

Hydrogen production via autothermal reforming of ethanol over noble metal catalysts supported on oxides

Hydrogen was produced over noble metal (Ir, Ru, Rh, Pd) catalysts supported on various oxides, including γ-Al2O3, CeO2, ZrO2 and La2O3, via the autothermai reforming reaction of ethanol (ATRE) and oxidative reforming reaction of ethanol (OSRE). The conversion of ethanol and selectivites for hydrogen and byproducts such as methane, ethylene and acetaldehyde were studied. It was found that lanthana alone possessed considerable activity for the ATRE reaction, which could be used as a functional support for ATRE catalysts. It was demonstrated that Ir/La2O3 prevented the formation of methane, and Rh/La2O3 encumbered the production of ethylene and acetaldehyde. ATRE reaction was carried out over La2O3-supported catalysts (Ir/La2O3) with good stability on stream, high conversion, and excellent hydrogen selectivity approaching thermodynamic limit under autothermal condition. Typically, 3.4 H2 molecules can be extracted from a pair of ethanol and water molecules over Ir(5wt%)/La2O3. The results presented in this paper indicate that Ir/La2O3 can be used as a promising catalyst for hydrogen production via ATRE reaction from renewable ethanol.     

Quantitative determination of stilbene oligomers in Jin Que-gen collected from different regions by a HPLC method

The objectives of this research were to determine simultaneously the contents of two stilbene tetramers, carasinol B (1) and kobophenol A (2), and one stilbene trimer, (+)-alpha-viniferin (3), in Jin Que-gen in different regions. A HPLC method has been developed for efficiently quantifying the three analytes in the plant. Using this method, different samples of Jin Que-gen were evaluated. The results showed that contents of the three analytes varied significantly among different samples, and the contents of the three analytes in commercial Jin Que-gen were markedly lower than those in the plants collected directly from growing regions. And for the three analytes, the longer the cultivation time, the higher the contents.     

静磁前向体波（MSFVW）激励特性研究

本文从静磁波基本方程出发导出了MSFVW的色散特性和辐射阻抗关系式,得到MSFVW和诸因素的关系,讨论了这种波型的优点。建立了MSFVW实验装置,着重研究激励特性和结构参数的关系,实验结果和理论分析基本一致.最后还指出大功率长脉冲工作时MSFVW有不稳定和噪声增强现象。这在文献上尚未见到过同样报道。     

高强声下驻波声流特性的实验研究

利用流动显示的方法研究了高强声驻波管中的声流特付。结果指出,在高强声下(声压级大于160dB),驻波管中的声流特性与一般意义上的驻波声流特性差别很大。对该现象的认识有助于进一步了解高声强下的非线性效应。     

Experimental study on the effect of substrate slope on continuously released heptane spill fires

Journal of Thermal Analysis and Calorimetry - The slope of ground has a significant impact on the spread and burning process for spill fires on land. In this paper, a series of continuous spill...     

数学抽象度概念与抽象度分析法

§1 引言 本文将给出“数学抽象度”的一般概念并论述“抽象度分析法”的基本概要。 如所熟知,抽象是认识事物本质、掌握事物内在规律的方法。凡科学中的一切概念都是抽象过程的产物,而且都有不同程度的抽象性。数学中的许多概念的抽象性更是明显地经过一系列阶段而产生的。例如,整数、有理数、无理数、复数、函数、微分、积分、变分、泛函、范畴等这些概念的抽象性几乎是一个高于一个。这说明数学内部各个概念的抽象程度是不一样的。在本文中我们要引进抽象度概念,用以刻划一个概念的抽象性层次;