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991.
992.
提升管三相流化床内的气液传质系数 总被引:3,自引:0,他引:3
采用溶氧电极法测定了以牛顿和非牛顿流体为液相的提升管三相流化床的气液传质系数(kla)。证明其值受床层流动特性的影响显著,那些能提供高气含率和增大液体循环速率的操作条件也有助于kla的提高。通过引入广义雷诺数得出了计算牛顿和非牛顿流体内kla的关联式 相似文献
993.
994.
研究了反应时间、液固比和反应气氛对水解木质素超临界降解液化的影响。通过分析产物的分布、碳氢含量和碳基的转化率及收率,表明在超临界乙醇溶液中,水解木质素在10min内就能被降解液化,反应时间的延长会导致缩合反应的加剧;液固比以10:1为宜,液固比的降低容易导致水解木质素降解不完全,而更高的液固比虽可使油分的总收率略微提高,但是溶剂用量增加,同时结果表明这是由于溶剂与木质素降解产物的反应所致。无论是在惰性气氛还是在氢气气氛下,在超临界乙醇溶剂中催化液化的结果基本一致,氢气气氛的存在无助于木质素的降解,只在一定程度上由于氢气的解理而使缩合反应有所减少。 相似文献
995.
996.
Feng Ren Shingo Ishida Nobuyuki Takeuchi 《Journal of the American Ceramic Society》1993,76(7):1825-1831
The distribution and chemical states of vanadium in V-doped ZrO2 were studied to clarify the origin of the color of vanadium-zirconium yellow pigment in comparison with vanadium-tin yellow pigment. ESCA data and measurements of lattice constants of V-doped ZrO2 revealed that vanadium was dissolved mainly as V4+ substituting for Zr in ZrO2 lattice, and its solubility limit was 0.5 wt% as V2 O5 . It was found that the yellow color of vanadium-zirconium yellow was produced predominantly by the dissolved vanadium and that the contribution of vanadium oxide on ZrO2 grains to the yellow color was about 1/30 of that of the dissolved vanadium when compared on the basis of equimolar quantity of vanadium. Most of the undissolved vanadium oxide was in an amorphous or a poorly crystallized state. 相似文献
997.
Jiangang Jia Tieming Guo Shufang Ren Jinjun Lu Qin Ma 《International Journal of Applied Ceramic Technology》2013,10(6):900-907
Phase evolution and morphology of Fe3O4‐Si‐Al powder mixtures during ball milling from 30 min to 20 h were investigated. A 3‐h critical milling was necessary for the occurrence of mechanically activated combustion reaction. The reaction results in the formation of Fe (Si), Fe3Si, and α‐Al2O3. During ball milling from 3 to 20 h, Fe (Si) and Fe3Si were combined into disordered Fe3Si intermetallic and Fe3Si‐Al2O3 composite powder was formed. The presence of in situ formed alumina leads to a decrease in crystallite and particle sizes. The Fe3Si‐Al2O3 particles after milling for 20 h had a crystalline size of 10~12 nm. 相似文献
998.
Nanocomposites of chitosan and nanoclays (MMT‐Na+ and Cloisite 30B) were prepared by solvent casting. The structural properties, thermal behaviors, and mechanical properties were characterized using X‐ray diffraction (XRD), transmission electron microscopy (TEM), atomic force microscopy, differential scanning calorimetry, thermogravimetry analyses, and an Instron universal testing machine. XRD and TEM results indicated that an exfoliated structure was formed with addition of small amounts of MMT‐Na+ to the chitosan matrix. Intercalation along with some exfoliation occurred with up to 5 wt % MMT‐Na+. Micro‐scale composite (tactoids) formed when Cloisite 30B was added to the chitosan matrix. Surface roughness increased with addition of a small amount of clay. Tensile strength of a chitosan film was enhanced and elongation‐at‐break decreased with addition of clay into the chitosan matrix. Melt behavior and thermal stability did not change significantly with addition of clays. © 2005 Wiley Periodicals, Inc. J Appl Polym Sci 99: 1684–1691, 2006 相似文献
999.
己二酸是合成尼龙-66和尼龙-46纤维的重要原料,并进一步用于生产许多重要的化工产品。工业上的己二酸多采用以硝酸为氧化剂的两步法合成,该工艺不仅工艺复杂,而且对设备有腐蚀作用,还会释放大量的温室气体N_2O。本文以负载型Pt/SiO_2、Fe/SiO_2和Pt-Fe/SiO_2为催化剂,采用过氧化氢和氧气为氧源,研究了环己烷一步氧化制己二酸的绿色合成路线。对催化剂进行ICP、BET比表面积、XRD、TEM等表征,结果表明,Pt-Fe/SiO_2催化剂中不存在与Pt或Fe对应的衍射峰。在最佳反应条件下,用高压釜进行了催化剂性能评价,结果表明,Pt-Fe/SiO_2催化活性略优于Pt/SiO_2和Fe/SiO_2。在环己烷转化率为28%的情况下,己二酸选择性达到33%。 相似文献
1000.
Ploy(vinylidene fluoride)–polytetrafluoroethylene nanofibrous membrane fabrication and direct contact membrane distillation (DCMD) process were simulated and optimized by response surface methodology (RSM). Analysis of variance was applied to develop and verify the models that predict the objectives. The three-dimensional response surfaces of different objectives were obtained. Results showed that the membrane with thickness of 70.7 μm, contact angle of 146.2°, and liquid entry pressure of 53.5 kPa was obtained within investigated experimental range under the optimum electrospinning conditions. Rejection rate of 99.99% and the permeate flux of 67.5 kg m−2 h−1 were gained under the optimum membrane distillation (MD) process parameters. The actual and predicted values show good consistency verifying the accuracy of the models. In addition, an overall investigation of the influence of heat-press temperature on the morphological and mechanical properties of electrospun membrane was carried out. Results indicated that electrospinning process and MD performance can be enhanced after the corresponding variables were optimized by RSM. This study provides a scientific way to optimize the electrospinning and DCMD parameters. © 2018 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2019 , 136, 47125. 相似文献