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CO/CO_(2)加氢制低碳醇改性费托合成催化剂研究进展

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化工进展 2024年第6期43卷 3061-3079页

作者：曾壮李柯志苑志伟杜金涛李卓师王悦中国石化催化剂有限公司工程技术研究院北京101111 天津大学化工学院教育部绿色合成与转化重点实验室天津300350

一氧化碳/二氧化碳(CO/CO_(2))加氢制低碳醇(C2+OH)是碳一化学的重要组成部分,是将煤、天然气、生物质、CO_(2)等非石油资源转化为液体燃料和高附加值化学品的重要途径。该过程具有工艺路线短、原子经济性高、操作可行性强等优点,是颇... 详细信息

一氧化碳/二氧化碳(CO/CO_(2))加氢制低碳醇(C2+OH)是碳一化学的重要组成部分,是将煤、天然气、生物质、CO_(2)等非石油资源转化为液体燃料和高附加值化学品的重要途径。该过程具有工艺路线短、原子经济性高、操作可行性强等优点,是颇具前景的合成路线。改性的费托合成催化剂是该体系最具潜力的催化剂之一,但仍存在低碳醇时空收率不理想、反应网络复杂、产物分布难以调控及稳定性差等问题,高效稳定催化剂的开发极具挑战。本文首先从热力学上分析了CO/CO_(2)加氢反应制低碳醇适宜的工艺条件;其次,对改性费托合成催化剂上CO/CO_(2)加氢制低碳醇的反应路径进行了解析,并据此提出催化剂的设计思路。随后,介绍了铁基和钴基催化剂的研究现状,详细阐述了前体结构、助剂、金属-载体相互作用等因素对催化剂性能的影响机制,重点分析了高性能催化剂的构建策略。后续可借助于先进表征技术和理论计算进一步加深对反应机理的认识,并通过催化剂结构的精细调控,获取低碳醇时空收率和催化剂稳定性的提升策略。

关键词：合成气二氧化碳低碳醇加氢催化剂

State of the art and prospects of structured sensing matrices in compressed sensing

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Frontiers of Computer Science 2015年第5期9卷 665-677页

作者： kezhi li Shuang CONG Automatic Complex Communication Networks Signal and Systems Center Royal Institute of Technology (KTH) Stockholm 10044 Sweden Department of Automation University of Science and Technology of China Hefei 230027 China

Compressed sensing （CS） enables people to acquire the compressed measurements directly and recover sparse or compressible signals faithfully even when the sampiing rate is much lower than the Nyquist rate. However, the pure random sensing matrices usually require huge memory for storage and high computational cost for signal reconstruction. Many structured sensing matrices have been proposed recently to simplify the sensing scheme and the hardware implementation in practice. Based on the restricted isometry property and coherence, couples of existing structured sensing matrices are reviewed in this paper, which have special structures, high recovery performance, and many advantages such as the simple construction, fast calculation and easy hardware implementation. The number of measurements and the universality of different structure matrices are compared.

关键词： compressed sensing structured sensing matrices RIP coherence

基于EDEM的高速穴播器排种性能仿真分析与试验

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中国农机化学报 2024年第2期45卷 48-54页

作者：卢博倪向东李克志李树峰齐庆征邵文平石河子大学机械电气工程学院新疆石河子832000

为探究穴播器转速和种子初速度对穴播器排种性能的影响,对分置式排种系统及穴播器工作原理进行阐述。利用EDEM建立棉种及穴播器的仿真模型,模拟棉种具有不同的初速度及穴播器在不同转速下排种情况,根据运动轨迹曲线、受力变化曲线、速... 详细信息

为探究穴播器转速和种子初速度对穴播器排种性能的影响,对分置式排种系统及穴播器工作原理进行阐述。利用EDEM建立棉种及穴播器的仿真模型,模拟棉种具有不同的初速度及穴播器在不同转速下排种情况,根据运动轨迹曲线、受力变化曲线、速度变化曲线综合分析产生漏播、重播现象的原因。使用Design-Expert进行两因素五水平二次旋转正交组合试验设计,建立评价指标的回归方程,并通过响应曲面分析排种性能。合格率随穴播器转速的增大而先增加后降低,随种子初速度的增大而降低。优化后的仿真参数组合为穴播器转速39 r/min和种子初速度2.4 m/s,最佳优化结果为漏播率3.2%,合格率95.1%,重播率1.7%。台架验证性试验结果表明仿真试验可信,穴播器排种性能满足高速精量播种要求,为新疆地区棉花机械化高速精量穴播技术及发展提供参考。

关键词：棉种排种性能穴播器精量播种离散元法

Multi-physical field coupling simulation of TCVI process for preparing carbon/carbon composites

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Science China(Technological Sciences) 2009年第11期52卷 3173-3179页

作者： JIAO YanQiong li HeJun li kezhi Research Center of Carbon/Carbon Composites Laboratory of Thermostructure Composite MaterialsNorthwestern Polytechnical UniversityXi’an 710072China

To prepare Carbon/Carbon (C/C) composites with advanced performance, the thermal gradient chemical vapor infiltration (TCVI) process has been optimized by simulation. A 2D axisymmetric unstable model was built, which included convection, conduction, diffusion, densification reactions in the pores and the evolution of the porous medium. The multi-physical field coupling model was solved by finite element method (FEM) and iterative calculation. The time evolution of the fluid, temperature and preform density field were obtained by the calculation. It is indicated that convection strongly affects the temperature field. For the preform of carbon/carbon composites infiltrated for 100 h by TCVI, the radial average densities from simulation agrees well with those from experiment. The model is validated to be reliable and the simulation has capability of forecasting the process.

关键词： C/C composites TCVI multi-physical field coupling simulation

Increasing the Tensile Property of Unidirectional Carbon/Carbon Composites by Grafting Carbon Nanotubes onto Carbon Fibers by Electrophoretic Deposition

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Journal of Materials Science & Technology 2013年第8期29卷 711-714页

作者： Qiang Song kezhi li Hejun li Qiangang Fu State Key Laboratory of Solidification Processing Northwestern Polytechnical University

Although in-situ growing carbon nanotubes （CNTs） on carbon fibers could greatly increase the matrix-dominated mechanical properties of carbon/carbon composites （C/Cs）, it always decreased the tensile strength of carbon fibers. In this work, CNTs were introduced into unidirectional carbon fiber （CF） preforms by electrophoretic deposition （EPD） and they were used to reinforce C/Cs. Effects of the content of CNTs introduced by EPD on tensile property of unidirectional C/Cs were investigated. Results demonstrated that EPD could be used as a simple and efficient method to fabricate carbon nanotube reinforced C/Cs （CNT-C/Cs） with excellent tensile strength, which pays a meaningful way to maximize the global performance of CNT-C/Cs.

关键词： Carbon nanotube Electrophoretic deposition Carbon fiber Carbon composite

Ablative and Mechanical Properties of C/C—ZrC Composites Prepared by Precursor Infiltration and Pyrolysis Process

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Journal of Materials Science & Technology 2015年第1期31卷 77-82页

作者： kezhi li Jing Xie Hejun li Qiangang Fu State Key Laboratory of Solidification Processing Carbon/Carbon Composites Research CenterNorthwestern Polytechnical University

C/C-ZrC composites with continuous ZrC matrix were prepared by precursor infiltration and pyrolysis process using zirconium-containing *** properties of the composites were investigated by oxyacetylene flame with heat flux of 2380 and 4180 kW/m2,*** results showed that C/C-ZrC composites exhibited excellent ablation resistance under the heat flux of 2380 kW/m2for 120 s and a tree-coral-like ZrO2protective layer formed after ***,when the heat flux increased to 4180 kW/m2,the maximum temperature of ablated surface reached 2500 ℃ and a strong degradation of ablation resistance was observed due to the weak bonding between the formed ZrO2layer and the *** flexural strength of C/C-ZrC composites was 110.7 ± 7.5 *** were a large number of carbon fiber bundles pull-out,and the composites exhibited a pseudo-plastic fracture behavior.

关键词： C/C composites Ceramic-matrix composites Ablation

Study on the Electromagnetic Interference of CFRC Composites by Reflectivity

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Journal of Materials Science & Technology 2008年第2期24卷 265-271页

作者： kezhi li Chuang WANG Hejun li Gengsheng JIAO Jian WEI School of Materials Science and Engineering Northwestern Polytechnical University Xi＇an 710072 China

The influence of dispersion of carbon fibers in carbon-fiber-reinforced cement-based composites （CFRC） on the mechanical properties of the composites was discussed. The microstructure of the fracture surface of the CFRC samples was observed with a scanning electron microscope （SEM）. The electromagnetic interference （EMI） was evaluated indirectly by reflectivity in the Naval Research Laboratory （NRL） testing system. The reflectivity of the electromagnetic radiation by the composites was measured in the frequency range of 8.0- 18.2 GHz for different carbon fiber contents of 0.2%, 0.4%, 0.6%, 0.8%, and 1.0% （in wt pct）, respectively. The results showed that the reflectivity decreased with the growing fiber content till the percentage of 0.6%. The minimum reflectivity was -23 dB, far less than -10 dB, and the composites were strong wave absorbers. After this percentage, the curve increased abruptly as the fiber content proceeded. The electromagnetic waves were gradually reflected. When the fiber content reached 1.0% finally, the maximum reflectivity -7.5 dB appeared and there was stronger reflection. The shielding mechanism includes mainly reflection, absorption, and multiple reflections.

关键词： Carbon fibers Cement-based Electromagnetic interference Reflectivity

Effect of Monolithic LaB_6 on the Ablation Resistance of ZrC/SiC Coating Prepared by Supersonic Plasma Spraying for C/C Composites

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Journal of Materials Science & Technology 2016年第10期32卷 996-1002页

作者： Yujun Jia Hejun li Lu li Qiangang Fu kezhi li State Key Laboratory of Solidification Processing Northwestern Polytechnical University

Ablation resistance of monolithic LaB-doped ZrC coating for SiC-coated carbon/carbon composites by supersonic atmospheric plasma spray was investigated under an oxyacetylene torch with a heat flux of 4.18 MW/m~2. Result shows that ZrC coating with 10 vol.% LaBhas a good ablation resistance compared with pure ZrC, ZrC with 20 vol.% LaBand SiC-doped ZrC coating. After ablation for 15 s, the weight is increased by 1.12 mg/s. The good ablation resistance is ascribed to the formation of a stabilized scale which consists of protective LaZrO-containing molten phase and ZrOparticles keeping the integrity of the coating.

关键词： Ceramic coating C/C composites Ablation performance

Ablation Mechanism of HfC-HfO2Protective Coating for SiC-Coated C/C Composites in an Oxyacetylene Torch Environment

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Journal of Materials Science & Technology 2017年第10期33卷 1195-1202页

作者： Yang Yang kezhi li Guanxi liu Zhigang Zhao State Key Laboratory of Solidification Processing Carbon/Carbon Composites Research Center Northwestern Polytechnical University Xi'an 710072 China

To prevent the C/C composites from ablation, HfC-HfO2 protective coating was prepared by supersonic atmospheric plasma spraying. The morphology and microstructure of HfC-HfO2 coating were characterized by X-ray diffraction and scanning electron microscopy. The ablation resistance test was carried out by an oxyacetylene torch. The results show that the as-prepared coating is dense with little pinholes and crack free. The elements Hf, C and O were uniformly distributed in the cross-section. After ablation for different time, the mass ablation rate fluctuated along with the change of ablation time. The ablation process of the surface coating could be divided into rapid oxidation and solid state sintering stages. During ablation, an Hf CxOy-HfO2 transitional layer was generated in the coating, which resulted from the active oxidation of Hf C. After cooling, some microcracks were observed on the surface of coating, and the structure of cross-section was broken, which were due to the phase transition of HfO2.

关键词： Carbon/carbon composites Supersonic atmospheric plasma spraying Protective coating Ablation property