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在参考金属磨削过程动态模型以及对墙地砖磨边机磨削过程分析折基础上,建立了磨边机磨削数学动态模型。该模型反映了砖的形态等因素与磨削力的关系,并提出了改进磨边机磨削质量的途径。 相似文献
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周集义 《化学推进剂与高分子材料》1993,(2)
对粘合剂的分子结构和固体推进剂的力学以及流变性能之间的关系进行了研究.由发动机中药住的操作条件对推进剂力学性能的要求以及已有的加工技术对药浆流变性能的限制出发.反推得出固体推进剂粘合剂理想的分子结构.结构和加工要求是由三种类型的火箭发动机的应用要求决定的:航天转运、运载火箭和弹道导弹以及空对空战术导弹.考虑了可满足这些应用要求的三种一般的配方.除假想的全粘合剂推进剂外,还包括传统的复合和硝酸酯增塑的推进剂配方.对这三类中的各种配方按分子量、交联密度、溶解度参数、链的刚硬性、单体的摩擦系数、填充物的体积分数和增塑剂的体积分数确定了各种聚合物的分子特性.10个聚合物粘合剂系统的特性数据说明了它们的分子结构如何影响制得的推进剂的性能. 相似文献
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在国外学习艺术玻璃这几年,谈起彩色玻璃镶嵌,自然会联想到欧洲教堂里的彩色玻璃窗。它是中世纪教堂装饰的一种独特方法,主要盛行于罗马式、哥特式和拜占庭式建筑。前两种建筑的窗户多而大,几乎布满整个建筑立面,便于采光。 相似文献
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通过对目前物理化学教材内容和讲授模式的分析,针对在概念著述和课堂讲授中存在的误区,结合物理化学家吉布斯的启发式教学典故,本文构建一种"立足客观自然、环环相扣启发"的概念教学模式,以"焓"概念的讲授为例,化抽象为直观,收了良好的教学效果。启发式模式对当前物理化学的概念教学有重要的参考价值。 相似文献
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丁二酸酐的化学简式是C4H4O3丁二酸酐是医药、染料、涂料的主要原材料,同时还是重要的药物和化学试剂成分,另外丁二酸酐可以用于生胃酮、琥珀酸胺噻唑的生产,并且可以广泛的应用于树脂的合成和制备。目前工业上对丁二酸酐的制备主要有以下两种方法:第一种方法就是对顺丁烯二酸酐的直接催化加氢法。现在对顺丁烯二酸酐直接催化加氢的生产工艺流程研究的比较广泛,特别是对丁二酸酐生产工艺中的热力学以及探索新的催化研究体系等方面的研究更为广泛;第二种方法就是直接对丁二酸进行脱水。第二种方法的主要优点就在于它对环境污染较小且不使用苯类溶剂,所以国内外很多丁二酸酐生产厂家都普遍采用第二种方法。 相似文献
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The catalytic hydrogenation of p-nitrophenol to p-aminophenol was investigated over Ni/Al2O3 catalyst on alumina support with different particle size. It is found that support particle size has significant influences on physiochemical properties and catalytic activity of the resulting Ni/Al2O3 catalyst, but little influence on the selec-tivity. At a comparable amount of Ni loading, the catalytic activity of Ni/Al2O3 prepared with alumina support of smaller particle size is lower. The reduction behavior of the catalyst is a key factor in determining the catalytic activity of Ni/Al2O3 catalyst. The supported nickel catalyst 10.3Ni/Al2O3-3 improves the life span of the membrane by reducing fouling on the membrane surface compared to nano-sized nickel. 相似文献
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针对Pd/Al2O3催化剂载体的改性进行研究,将1 000℃焙烧后的氧化铝粉末与未焙烧的活性氧化铝粉末按不同比例混合和焙烧制备载体,采用等体积浸渍法制得负载Pd的Pd/Al2O3催化剂。采用XRD、BET、NH3-TPD和HOT对载体以及催化剂进行表征,并考察催化剂的蒽醌加氢性能。结果表明,提高载体中焙烧后氧化铝粉末的比例,导致载体中γ-Al2O3减少和δ-Al2O3增多,载体酸性降低,Pd分散度变大,从而提高了催化剂氢化效率。当焙烧后氧化铝质量分数为40%时,分散度和活性表面积达到最大,晶粒度最小,氢化效率最高,催化活性最佳。 相似文献
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以γ-Al2O3为原料制备Ni-γ-Al2O3、Zn-γ-Al2O3和Al2O3载体,并采用等容浸渍法制备了钴基费-托合成用催化剂。结果表明:高温焙烧使氧化铝晶型和孔结构发生较大变化;镍添加后在载体表面形成高分散的氧化镍物种;而锌添加后与载体发生反应生成了铝酸锌;负载型催化剂中,四氧化三钴粒径大小主要取决于载体孔结构。CoPt/γ-Al2O3、CoPt/Zn-γ-Al2O3、CoPt/Ni-γ-Al2O3具有相近的费-托合成催化性能,而CoPt/Al2O3呈现出最高的催化活性和最低的甲烷选择性。表明,钴物种粒径和载体结构是影响催化剂费-托合成催化性能的主要因素。 相似文献
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油脂加氢催化剂是以金属镍为活性组分、氧化铝为载体制备的Ni/Al2O3催化剂。在制备催化剂过程中,其合成条件直接影响着催化剂的最终活性。以工业硝酸镍、碳酸钠和自制氧化铝粉为原料,利用共沉淀的方法制备加氢催化剂,考察了反应温度、反应时间、反应液pH及反应过程中搅拌转速对催化剂活性的影响。通过实验数据汇总分析,最终确定制备Ni/Al2O3油脂加氢催化剂的最佳条件:反应温度为85 ℃、反应结束时溶液pH=8.0、反应时间为1.5 h、搅拌转速为600 r/min。在此条件下制备的Ni/Al2O3催化剂,经棕榈油加氢评价后测定的碘值最低。 相似文献
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A. Olafsen C. Daniel Y. Schuurman L.B. Rberg U. Olsbye C. Mirodatos 《Catalysis Today》2006,115(1-4):179-185
The CO2 reforming of methane and propane has been compared over two different Ni catalysts: one reference Ni/SiO2 system and a Ni/Mg(Al)O hydrotalcite-derived catalyst, shown previously to display high catalytic stability for long term reforming. By combining the Tapered Element Oscillating Microbalance (TEOM), Temperature Programmed Hydrogenation (TPH), Transmission Electron Microscopy (TEM) and magnetic measurements, the formation of coke and its role on the catalyst activity has been investigated and compared for both hydrocarbons. It was found that Ni/SiO2 and Ni/Mg(Al)O are both more active for methane reforming than for propane reforming. Coke formation is much more pronounced for propane than for methane over both catalysts. However, for both hydrocarbons a much faster carbon formation is observed over the Ni/SiO2 catalyst than over the Ni/Mg(Al)O catalyst. The difference in the rates of coke formation for methane and propane is ascribed in the case of propane to partially dehydrogenated C3 adspecies, which are good coke precursors. The superior stability of the hydrotalcite-derived catalyst is due to the strong interaction of the nickel phase with the support and the capacity of the support to activate CO2 and channel oxygen to the nickel phase. 相似文献
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Chang-Jun Liu Xin-Bin Fei He Kai-Lu Yu Shen Han Qing Xia G. P. Vissokov 《Chemical Engineering Communications》2003,190(10):1371-1378
A direct preparation of Al 2 O 3 from aluminum and oxygen under plasma jet conditions has been performed in this work. The XRD characterization of such plasma-prepared alumina shows that a production of δ-Al 2 O 3 has been achieved. The size of the alumina particles ranged from several tens to 200 nm, based on SEM analysis. The effectiveness of plasma-prepared alumina as a catalyst support has been demonstrated by the catalytic synthesis of dimethyl carbonate over Pd/Al 2 O 3 . 相似文献
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This paper investigated the influences of surface properties of carbon support and nickel precursors (nickel nitrate,nickel chloride and nickel acetate) on Ni nanoparticle sizes and catalytic performances for steam reforming of toluene.Treatment with nitric acid helped to increase the amount of functional groups on the surface and hydrophilic nature of carbon support,leading to a homogeneous distribution of Ni nanoparticles.The thermal decomposition products of nickel precursor also played an important role,Ni nanoparticles supported on carbon treated with acid using nickel nitrate as the precursor exhibited the smallest mean diameter of 4.5 nm.With the loading amount increased from 6 wt% to 18 wt%,the mean particle size of Ni nanoparticles varied from 4.5 nm to 9.1 nm.The as-prepared catalyst showed a high catalytic activity and a good stability for toluene steam reforming:98.1% conversion of toluene was obtained with the Ni content of 12 wt% and the S/C ratio of 3,and the conversion only decreased to 92.0% after 700 min.Because of the high activity,good stability,and low cost,the as-prepared catalyst opens up new opportunities for tar removing. 相似文献