Synthesis of HZSM-5 zeolites with excellent DME aromatization properties by orthogonal test

Abstract

The synthesis conditions of HZSM-5 zeolite, including crystallization temperature, crystallization time and raw material ratio, were investigated by L₃₂ (4⁸) orthogonal test to specifically optimize its performance in dimethyl ether (DME) aromatization for the first time. Based on the total yield of aromatic products, the synthesis conditions of HZSM-5 zeolite with the best DME aromatization properties were obtained by comprehensive analysis and validation experiments. The relationship between the aromatization performance, crystalline structure, pore structure, and acidity of HZSM-5 zeolite were analyzed. The results showed that the HZSM-5 zeolite accompanied by hierarchical structure, an appropriate Brønsted and Lewis acid content and uniform crystal morphology, was successfully synthesized under optimized conditions. Over this unmodified and un-doped catalyst, the conversion of DME approached to 99.3% and the total yield of aromatics reached was 53.5%.     

高中化学科学方法教育现状调查与问题对策

20世纪70年代后,世界各国开始进行基础教育课程改革,通过加强科学教育以全面提高科学素养, 科学方法作为科学素养中的核心要素在教育中得到了空前的重视。     

玉米秆粉粒体塑性压缩成型过程的有限元分析

保护环境,节约资源是人类的共识,本以我国丰富的农作物副产物-玉米秸秆为原料,采用弹塑性增量有限元法对玉米秆粉粒体的成型过程进行了研究,有限元计算结果与实验结果比较一致,此研究为玉米秸秆等农林副产物转化为高附加值产品提供了理论依据。     

部分剪力连接钢—砼组合梁的滑移及曲率分析

对受均布荷载作用的简支部分剪力连接钢－砼组合梁的滑移应变和滑移的分布规律进行了理论分析,得出部分剪力连接钢－砼组合梁的剪力连接程度系数与滑移应变和滑移的关系。分析了考虑滑移效应的梁的曲率及其与剪力连接程度系数之间的关系。结果与结构在弹性阶段的实验相当吻合,对组合梁挠度的精确计算有指导意义。     

On Mixed Error Estimates for Elliptic Obstacle Problems

We establish in this paper sharp error estimates of residual type for finite element approximation to elliptic obstacle problems. The estimates are of mixed nature, which are neither of a pure a priori form nor of a pure a posteriori form but instead they are combined by an a priori part and an a posteriori part. The key ingredient in our derivation for the mixed error estimates is the use of a new interpolator which enables us to eliminate inactive data from the error estimators. One application of our mixed error estimates is to construct a posteriori error indicators reliable and efficient up to higher order terms, and these indicators are useful in mesh-refinements and adaptive grid generations. In particular, by approximating the a priori part with some a posteriori quantities we can successfully track the free boundary for elliptic obstacle problems.     

中国现代著名化学家成才规律浅析

我们从化学家传记、化学史著作及一些文献中,随机选取了50位中国现代著名化学家,在统计分析的基础上,努力探求其成才的一般规律。     

Dimensional reduction of a piezoelectric composite rod

In the present paper, a new generalized Timoshenko model is constructed for a composite rod with embedded or attached piezoelectric materials. This model is applicable to composite rods without prescribed electric potential along the lateral surfaces. The Variational-Asymptotic Method (VAM) is applied as a mathematical tool to carry out the dimensional reduction process. The present reduced model captured the effects of dielectric as well as the polarization of the piezoelectric material, which justifies its coupled electromechanical nature. First, the three-dimensional electromechanical enthalpy is asymptotically approximated by VAM using the slenderness of the rod as the small parameter and subsequently an equivalent one-dimensional electromechanical enthalpy is developed. Energy terms, which are asymptotically correct up to the second order are kept in the approximate enthalpy expression. For engineering applications, the approximate enthalpy is then transformed into a generalized Timoshenko model which has the traditional six mechanical degrees of freedom along with an extra one-dimensional electric degree of freedom.     

Facile Surface Superhydrophilic Modification: NVP/MBA Inverse Microemulsion Surface‐Grafting Polymerization Initiated by UV Light

Summary: Superhydrophilic modification of poly(propylene) and poly(ethylene terephthalate) films' surfaces was realized by the UV‐initiated surface photografting of a N‐vinyl pyrrolidone/N,N′‐methylenebisacrylamide inverse microemulsion. AFM characterization of the treated films' surface revealed that it was the grafted quasi‐bimodal (ca. 45 and 110 nm) particles of cross‐linked poly(N‐vinyl pyrrolidone) that led to superhydrophilicity of the surface. The grafted nanometer‐scale particles showed little influence on the transparency of the substrate's surface, but endowed long‐term stability to the superhydrophilicity.

The surface morphology of the PP film grafted with a NVP/MBA inverse microemulsion via a one‐step method. Quasi‐bimodal particles (ca. 45 nm and 110 nm) were tethered on the film's surface, and the corresponding surface water CA fell below 5°.     

Directly Fabricating Monolayer Nanoparticles on a Polymer Surface by UV‐Induced MMA/DVB Microemulsion Graft Polymerization

Summary: A sequential two‐step method was successfully used for the photografting of methyl methacrylate/1,2‐divinylbenzene (MMA/DVB) microemulsion onto the surface of a poly(propylene) (PP) film. Atomic force microscopy (AFM) images showed that nanoparticles with a cross‐section diameter of 60 nm were directly grafted onto the substrate's surface. Environment scanning electron microscope (ESEM) images proved that the particles formed just a single layer on the surface. The dormant groups on the nanoparticles' surface were a potential factor in the evolution of single layer into multilayer nanoparticles.

The surface morphology of a PP film after being grafted with a MMA/DVB microemulsion. Nanoparticles (about 60 nm in size) are clearly tethered onto the substrate's surface with just one layer.