A high propylene productivity over B2O3/SiO2@honeycomb cordierite catalyst for oxidative dehydrogenation of propane

Boron-based metal-free catalysts for oxidative dehydrogenation of propane (ODHP) have drawn great attention in both academia and industry due to their impressive activity and olefin selectivity. Herein, the SiO₂ and B₂O₃ sequentially coated honeycomb cordierite catalyst is designed by a two-step wash-coat method with different B₂O₃ loadings (0.1%–10%) and calcination temperatures (600, 700, 800 °C). SiO₂ obtained by TEOS hydrolysis acts as a media layer to bridge the cordierite substrate and boron oxide via abundant SiOH groups. The well-developed straight channels of honeycomb cordierite make it possible to carry out the reactor under high gas hourly space velocity (GHSV) and the thin wash-coated B₂O₃ layer can effectively facilitate the pore diffusion on the catalyst. The prepared B₂O₃/SiO₂@HC monolithic catalyst exhibits good catalytic performance at low boron oxide loading and achieves excellent propylene selectivity (86.0%), olefin selectivity (97.6%, propylene and ethylene) and negligible CO₂ (0.1%) at 16.9% propane conversion under high GHSV of 345,600 ml·(g B₂O₃)⁻¹·h⁻¹, leading to a high propylene space time yield of 15.7 g C₃H₆·(g B₂O₃)⁻¹·h⁻¹ by suppressing the overoxidation. The obtained results strongly indicate that the boron-based monolithic catalyst can be properly fabricated to warrant the high activity and high throughput with its high gas/surface ratio and straight channels.     

Polymer nanocomposite powders and melt spun fibers filled with silica nanoparticles

Nanocomposite powders from polypropylene filled with surface modified and unmodified fumed silica have been prepared from polymer solution to achieve improved mixing and have been forwarded to fiber melt spinning. The surface of the fumed silica was modified with dodecyl alkoxy silanes. Crystallization velocity and viscosity of the PP nanocomposites thereof were determined to ensure good melt spinning processing conditions for all composite compositions. Upon addition of untreated filler particles, a shear thinning and an increased crystallization velocity of the polymer melt was found, while only minor changes were detected in the presence of surface modified fumed silica particles. The composites and the polymer fibers made from these powder composites by melt spinning were mainly characterized by optical microscopy (OM), scanning electron microscopy (SEM), mechanical measurements, differential scanning calorimetry (DSC), and solid‐state NMR. The unmodified fumed silica was found to have a strong influence on the mechanical fiber properties, while the surface modified silica only a small one. Fibers were additionally characterized with respect to the uniformity, the PP crystallinity, moisture absorption, and the water contact angle. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 103: 218–227, 2007     

回转窑筒体激光测量系统的研制

熟料回转窑系统是冶金建材行业等部门的重要烧成设备。在窑的长期生产过程中,有时由于窑体衬砖的脱落引发"红窑"事故,窑筒体会发生永久性径向变形。变形后重新砌上的衬砖粘附性较差,容易再次脱落,     

石英砂的塑性机理研究

研究了石英砂的塑性并对其进行改善,得出石英砂颗粒大小、砖坯含水率、砖坯p H值和增塑剂含量对砖坯塑性的影响规律及机理,并且为利用石英砂而采用可塑成型去制备高性能的烧结砖探索出了合适的成型工艺条件:球磨时间24h、含水率为29%、坯料p H=9和增塑剂含量为5%。     

Speech enhancement with an adaptive Wiener filter

This paper proposes an adaptive Wiener filtering method for speech enhancement. This method depends on the adaptation of the filter transfer function from sample to sample based on the speech signal statistics; the local mean and the local variance. It is implemented in the time domain rather than in the frequency domain to accommodate for the time-varying nature of the speech signals. The proposed method is compared to the traditional frequency-domain Wiener filtering, spectral subtraction and wavelet denoising methods using different speech quality metrics. The simulation results reveal the superiority of the proposed Wiener filtering method in the case of Additive White Gaussian Noise (AWGN) as well as colored noise.     

铁铵矾为催化剂对合成乙酸仲丁酯的影响研究

以铁铵矾为催化剂,对冰乙酸与仲丁醇之间的酯化反应进行了研究,考察了催化剂用量、酸醇摩尔比、反应时间对合成乙酸仲丁酯的影响,结果表明:铁铵矾有一定催化活性。当冰乙酸物质的量为0.12mol,冰乙酸、仲丁醇及铁铵矾的摩尔比为1∶2∶0.12,催化剂质量为7.0g,反应2.5h后,收率可达75.12%,所得产品无色透明。     

厌氧型888－1石油专用胶的研究与应用

厌氧型８８８－１石油专用胶是胜利油田和烟台环宇高新技术研究所联合研制的，是我国首次试用成功的厌氧型国产石油专用胶。本文阐明了该胶的固化机理、研制过程、试验数据及油田实地使用情况。８８８－１石油专用胶经专家鉴定后，很快在胜利油田各采油厂试用成功，又在中原油田、大庆油田及中国石油天然气总公司下属很多单位推广应用，均取得了明显的经济效益，充分显示了该胶的应用前景和巨大生命力。     

丁腈胶乳的加氢反应

采用水合肼/过氧化氢氧化还原体系，以硼酸为催化剂，在常压下进行丁腈胶乳的氢化反应，研究了过氧化氢加入方式，硼酸和水合肼用量，反应温度及反应时间对丁腈胶乳加氢度的影响。结果表明，过氧化氢连续滴加再附加室温条件，氢化反应效果最好。当硼酸用量为2.64mmol，水合肼用量为95.2mmol，过氧化氮用量为79.3mmol。在60℃，6h下，丁腈胶乳的加氢度可达到90%以上。     

XML keyword search with promising result type recommendations

Keyword search enables inexperienced users to easily search XML database with no specific knowledge of complex structured query languages and XML data schemas. Existing work has addressed the problem of selecting data nodes that match keywords and connecting them in a meaningful way, e.g., SLCA and ELCA. However, it is time-consuming and unnecessary to serve all the connected subtrees to the users because in general the users are only interested in part of the relevant results. In this paper, we propose a new keyword search approach which basically utilizes the statistics of underlying XML data to decide the promising result types and then quickly retrieves the corresponding results with the help of selected promising result types. To guarantee the quality of the selected promising result types, we measure the correlations between result types and a keyword query by analyzing the distribution of relevant keywords and their structures within the XML data to be searched. In addition, relevant result types can be efficiently computed without keyword query evaluation and any schema information. To directly return top-k keyword search results that conform to the suggested promising result types, we design two new algorithms to adapt to the structural sensitivity of the keyword nodes over the keyword search results. Lastly, we implement all proposed approaches and present the relevant experimental results to show the effectiveness of our approach.     

纳米TiO2光催化降解有机物的机理及其影响因素的研究

对纳米TiO2光催化降解水中有机物的机理进行了研究，并对溴苯酚降解为目标反应，系统分析了紫外光强度、TiO2浓度、温度、溶液的pH值以及杂质等对光催化降解为溴苯酚程度的影响。优化这些因素可以提高纳米TiO2光催化降解率。