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101.
The same effect of temperature on the production of CO, CO2 and H2O was found during oxidative treatment of HY zeolites either impregnated with pyrene or coked. Therefore, pyrene oxidation can be used to specify the mechanism of coke oxidation. Three types of reactions can be distinguished: (a) condensation of polyaromatic molecules, (b) oxidation of polyaromatics into aldehydes, ketones, acids and anhydrides and (c) decarbonylation or decarboxylation of oxygenated compounds, all these reactions involving protonic sites. 相似文献
102.
103.
The paper describes a new powder composition specially developed for selective laser sintering (SLS). The aim is to obtain a ferro powder that can be sintered without need for a (sacrificial) polymer binder and that results in quasi dense parts that do not need any post-processing like furnace sintering, infiltration or HIP. The powder is a mixture of different types of particles (Fe, Cu, Ni and Fe3P). The composition and mixture ratio are justified by using phase diagrams. The powder has been tested using an own developed Nd: YAG SLS machine. The influence of process parameters (laser power, scan velocity, scan spacing and scan strategy) and the microstructural characteristics have been investigated. Attention is devoted to the binding mechanism (liquid phase sintering, through melting) and to the quality of resulting parts (density, balling effect,…). 相似文献
104.
Colour extension properties of individual pigments and effects on shades of foundations in cake form
AKIRA TSUGITA TAKASHI FUKISHIMA TOHRU YONEYA YASUSH INISHIJIMA 《International journal of cosmetic science》1985,7(1):15-27
The mechanism of colour change during the pigment dispersion process and during powder application to the skin surface was studied by examining the colour extension properties of Yellow. Red , and Black iron oxides in white powder bases. A new measure for the evaluation of the degree of colour extension was devised. This measure corresponded well with human visual sensation, and was found to be useful for comparing the rates of colour extension of pigments. The rate of colour extension of pigments was found to vary in the order: Yellow acicular Red granular Red Black. This result explains colour darkening and the change towards reddish tones during the pigment dispersion process, because Yellow extends fully in the early stage of the process but Red , especially in granular form, and Black continue to extend even in the later stage. Acicular Red iron oxide is more favourably employed than the granular form to attain sufficient colour extension of foundations with lower energy expenditure, and to decrease the discrepancy between the cake colour and the colour of applied powder.
Le développement des oxydes de fer et effet sur les nuances des fonds de teint compacts 相似文献
Le développement des oxydes de fer et effet sur les nuances des fonds de teint compacts 相似文献
105.
高炉煤气干法除尘技术发展现状及宝钢应用前景 总被引:1,自引:0,他引:1
在对高炉煤气干法除尘技术应用现状进行综合分析的基础上结合宝钢实际,提出宝钢应用此技术的相关建议。 相似文献
106.
SAPO-34/SiO_2催化甲醇制烯烃 总被引:2,自引:0,他引:2
采用水热法合成了SAPO-34分子筛,并用X射线粉末衍射仪和扫描电子显微镜对SAPO-34分子筛的结构进行了表征,同时探讨了黏合剂种类、甲醇分压、催化剂粒径和硅源等对SAPO-34分子筛催化甲醇制烯烃(MTO)反应性能的影响。实验结果表明,在MTO反应中,三烯(乙烯、丙烯和丁烯)选择性在反应初期存在明显的诱导期;以S iO2为黏合剂合成的SAPO-34/S iO2催化剂不但可缩短MTO反应的诱导期,三烯选择性也较未添加黏合剂或以A l2O3为黏合剂时高1~2个百分点;且当催化剂活性明显下降时,三烯选择性下降的幅度较小。催化剂粒径、甲醇分压及硅源对催化剂的诱导期也有明显的作用。在甲醇分压低于19kPa、催化剂粒径0.25~0.38mm、S iO2为黏合剂、硅酸四乙酯为硅源时,SAPO-34/S iO2催化剂的MTO性能明显提高。 相似文献
107.
溶胶-凝胶法制备磷钨酸-硅胶催化合成苹果酯 总被引:1,自引:1,他引:0
采用溶胶-凝胶法制备了一系列磷钨酸-硅胶催化剂(PW/SG),考察了该催化剂催化乙酰乙酸乙酯与乙二醇液相缩合制备苹果酯的反应性能。实验结果表明,PW质量分数为40%时的PW/SG催化剂表现出最佳的催化活性;40%PW/SG催化剂制备苹果酯的最佳工艺条件为:n(乙酰乙酸乙酯)∶n(乙二醇)=1∶1.2,催化剂用量占反应物质量的0.36%,带水剂环己烷用量占反应物体积的30%,反应温度383K,反应时间90min;在此条件下,乙酰乙酸乙酯的转化率可达95.5%,苹果酯的选择性大于97%;催化剂稳定性实验表明,经5次重复使用,40%PW/SG催化剂的活性基本保持不变,乙酰乙酸乙酯转化率稳定在95.0%左右。 相似文献
108.
109.
110.
Investigation of the reaction mechanism of chloromethane on ZSM5 is a new topic. In this work an in situ FTIR technique was employed to study the conversion processes of chloromethane, the active sites on HZSM5, and the desorption state of surface species. The catalytic conversion of chloromethane to higher hydrocarbons was also studied. It is demonstrated that chloromethane can be reversibly adsorbed on acidic sites of HZSM5 at room temperature. At 100°C chloromethane is irreversibly and dissociatively adsorbed on the strong acidic sites of HZSM5, on which surface methoxyl is formed as proved by infrared characteristic C-H stretchings of-CH3 at 2960 and 2870 cm–1. Alkoxyls are produced and adsorbed on the catalyst surface as characterized by the infrared absorption bands of -CH2-groups at 1460 and 2930 cm–1. At 100°C the adsorbed methoxyl and alkoxyls are the main surface species, and a small amount of aromatics might exist as detected by a characteristic absorption band at 1510 cm–1. Between 100 and 200°C the adsorbed surface methoxyl and alkoxyls are converted to aromatics, and the occupied OH groups partially appear. At temperature higher than 300°C the adsorbed aromatics are thermally desorbed into the gas phase. Aromatics and alkanes are the main products in catalytic conversion. These results reveal that the formation of aromatics from methoxyl and alkoxyls is easier than the desorption of aromatics from HZSM5 catalyst. An alkoxyl mechanism is proposed for the conversion of chloromethane on HZSM5 based upon the experimental results and the three assumptions: (a) The primary C-C bond is formed from surface methoxyl groups via the methoxyl group polarization and C-H bond weakening, (b) The adsorbed alkoxyls are converted to aromatics via hydrogen transfer and bond rearrangement similar to the conventional carbenium ion mechanism for the aromatization of olefins and alkanes on HZSM5. The hydrogen atoms from the aromatization stimulate the desorption of alkoxyls to alkanes. (c) At temperature higher than 300°C surface reactions and desorption of adsorbed species take place simultaneously, determining the product distribution in the catalytic conversion. 相似文献