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金属丝网蜂窝催化剂的制备及应用

2013-08-16 01:05

【中文摘要】 金属丝网蜂窝催化剂是以成型金属丝网为支撑体的新型结构化催化材料。由于其主通道壁是通透的丝网,网孔为流体径向混合提供了旁路,能明显改善流体分布、混合状况,提高传递效率。本论文以开发通用型的金属丝网蜂窝催化剂为目标,研究制备中的关键问题。在此基础上,试制了涂覆有Pd/Al2O3活性成分的金属丝网蜂窝催化剂,并以甲烷催化燃烧体系为例,与陶瓷支撑体蜂窝催化剂的反应结果进行对比验证。催化层与金属支撑体结合的牢固性是金属丝网蜂窝催化剂开发中的关键难题。本课题采用电泳沉积法在支撑体上制备铝/氧化铝复合层作为催化层与支撑体之间的过渡层。考察了乙醇、丁酮、丙酮三类悬浮液体系中各操作参数对电泳沉积结果的影响,找出了制备均匀涂层的适宜条件。即在乙醇体系中为PVP:0.2wt.%、三氯化铝:2.5mM、铝粉:1wt.%、电场强度:30V/cm、沉积时间:10min;丁酮体系中为硝化纤维:0.6wt.%、正丁胺:10vol.%、铝粉:0.2wt.%、电场强度:50V/cm、沉积时间:30min;丙酮体系中为丙酮:50mL、硝化纤维:0.1g、铝粉:1g、四甲基氢氧化铵:0.3mg、磷酸:0.25mg、电场强度:25 V/cm、沉积时间:3min。相较于乙醇、丁酮体系,丙酮悬浮液体系更加稳定,所得涂层初强度高,涂层厚度为50μm,适宜整体金属丝网的电泳沉积。将丙酮体系电泳沉积所得铝颗粒涂层进行氮气保护下的高温热处理和低浓度氨水处理得到结合牢固,比表面积大的铝/三氧化二铝载体层。金属丝网经过电泳沉积、高温热处理、化学处理和整体成型后,得到直径25 mm,高度21mm,重量10 g,几何面积37.1cm2/g的金属蜂窝丝网催化剂载体。将该载体涂覆Pb/Al2O3粉末催化剂(粉末中Pb负载量为0.33 wt.%)(催化剂中Pb负载量为0.103 wt.%),在甲烷催化燃烧反应中进行考评。该催化剂的催化活性高于陶瓷蜂窝催化剂,反应温度为600℃时,甲烷转化率比陶瓷蜂窝催化剂的高10.89%,宏观反应速率常数是后者的2.18倍

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【英文摘要】 Wire-mesh honeycomb (WMH) is a category of novel monolithic catalysts supported on structured wire-mesh substrate. As the conduct of WMH is made of mesh, whose pores provide fluids the bypass of radical mixing across the bed diameter, which effect can improve the fluid distribution and mixing state, thus raises transfer efficiency. Aimed at developing a WMH for general applications, this thesis tried to breakthrough the key difficulties in WMH preparation. For purpose of demonstration, the WMH washcoated by Pd/Al2O3 was prepared and applied in catalytic combustion of air diluted methane, with its result compared to the ceramic counterpart.The key problem in developing WHM is the fast adhesion of the active catalyst powder with the metallic mesh. To solve this problem, an aluminum/alumina coating was prepared by electrophoretic deposition (EPD) on top of wire-mesh surface. Experiments were carried out to find the optimal conditions in ethanol, butanone and acetone suspension for depositing a uniform Al particulate coating, which are concluded as below: in ethanol suspension, PVP: 0.2 wt.%, AlCl3: 2.5 mM, Al powder: 1wt.%, electric field intensity: 30 V/cm, deposition time: 10min; in butanone suspension, nitrocellulose: 0.6 wt.%, n-butylamine: 10 vol.%, Al powder: 0.2 wt.%, electrical field intensity: 50 V/cm, deposition time: 30 min, while in acetone suspension, acetone: 50 mL, nitrocellulose: 0.1 g, Al powder: 1 g, teramethyl ammonium hydroxide: 0.3 mg, phosphoric acid: 0.25 mg, electrical field intensity: 25 V/cm, deposition time: 3 min. Acetone suspension is more stable and the adherence of deposited coatings are higher than ethanol and butanone suspension, and the coating thickness is 50μm. Well adherent and porous aluminum/alumina top layers were prepared by thermal and chemical treatment of the deposited coatings in acetone suspension.After EPD, thermal & chemical treatment, and mould processing, the WMH support was prepared, which was 25 mm in diameter, 21 mm in height, 10 g in weight and 37.1 cm2/g in geometric surface area. The WMH catalyst washcoated with Pb/Al2O3 (Pb wt.% = 0.33%) was tested in catalytic combustion of air diluted methane. Compared at 600℃, CH4 conversion in WMH is 10.89% higher than the catalyst supported on ceramic substrate and the overall reaction rate constant more than doubled.

【中文关键词】 金属丝网蜂窝催化剂; 电泳沉积; 热处理; 化学处理; 甲烷催化燃烧 （科教作文网 zw.nseac.com整理）
【英文关键词】 wire-mesh honeycomb catalyst; electrophoretic deposition; thermal treatment; chemical treatment; catalytic combustion of methane
【毕业论文目录】
摘要 4-6
ABSTRACT 6-7
第一章 绪论 10-28
    1.1 研究背景 10-11
    1.2 整体式催化剂 11-17
        1.2.1 整体式催化剂组成 11-13
        1.2.2 整体式催化剂特点 13-14
        1.2.3 整体式催化剂研究与进展 14-15
        1.2.4 整体式催化剂应用前景 15-17