عنوان مقاله
پدیده های وابسته به موقعیت در طول غیر فعال شدن مبدل های کاتالیزوری سه راهه در وسایل نقلیه
فهرست مطالب
چکیده
مقدمه
آزمایش ها
نتایج و بحث
نتیجه گیری
بخشی از مقاله
آزمایش ها
سه نوع از مبدل های کاتالیزوری در وسایل نقلیه در استرالیا مورد آزمون انتشار قرار گرفتند که به عنوان بخشی از یک برنامه تست شامل بیش از 4% دستگاه خودروی تصادفی انتخاب شد. مبدل چهارم به عنوان مرجع در نظر گرفته شد و بر روی وسیله ای که سفر کمتری داشته بود، نصب شد. همه چهار مبدل در بین سال های 1990 و 1992 با استفاده از آلومینا و سریا با محتوای CEO2 مشابه با درصد وزنی17 تا 20 درصد ازهمان نوع از منولیت کور دریت ساخته شده بود. اما مقادیر PGM در آن متفاوت بود.
کلمات کلیدی:
Position dependent phenomena during deactivation of three-way catalytic converters on vehicles Dennys E. Angove a,∗, Noel W. Cant b a CSIRO, Division of Energy Technology, PO Box 136, North Ryde, NSW 1670, Australia b Department of Chemistry, Macquarie University, NSW 2109, Australia Abstract Mapping procedures have been developed to characterise some of the position dependent phenomena occurring in three-way catalytic converters. The activity of small samples for the removal of CO, NO, propene and propane from a simulated mixture under slightly lean conditions was measured in a flow system and correlated with surface area. Contamination was determined by particle-induced X-ray emission (PIXE) with XRD used to follow structural changes in the washcoat. The procedures have been used to investigate a substantial set of converters which had seen extensive use on vehicles. Three of these converters, taken from vehicles which had failed a standard emission test, are discussed here. In one case, loss of surface area and CO/hydrocarbon/NO activity was greater at the front and is associated with phosphorus deposition. XRD measurements showed that operating temperatures were sufficiently high to result in the formation of cerium orthophosphate at the front and substantial growth in ceria particle size throughout which also contributed to activity loss. A second converter showed substantial loss of NO activity alone which was traced to high levels of lead, concentrated towards the front but significant throughout. A third converter of the same type had undergone a lesser loss of activity for NO removal at the front due to lead but the deterioration in CO and propene was greater towards the rear of the converter. This was associated with a loss of surface area caused by a period of overheating under net reducing conditions with XRD measurements showing the formation of cerium aluminate and a cerium barium magnesium hexaaluminate which are characteristic of such conditions. © 2000 Elsevier Science B.V. All rights reserved. Keywords: Catalytic converter; Monolith; Contamination; Cerium aluminate; Cerium barium magnesium hexaaluminate; Ceria particle size 1. Introduction Catalytic converters are central to the control of automotive emissions. The emission control system must maintain a set of conditions that ensures that the converter will function reliably over 80,000 km in Australia, and more recently, 160,000 km in US. Increased emissions can occur as a result of engine/control system component failure [1] and/or loss of catalytic ∗ Corresponding author. Tel.: +61-2-9490-8993; fax: +61-2-9490-8909. E-mail address: dennys.angove@det.csiro.au (D.E. Angove). converter performance [1–4]. In some instances component failure causes subsequent converter failure which can occur by a variety of chemical, thermal and/or mechanical processes [4]. Common causes of performance loss include contamination/poisoning [5–7], masking [6], pore-mouth plugging [8], washcoat sintering [9], platinum group metal (PGM) sintering [10,11], washcoat interactions, meltdown [4] and bypassing [4]. In some studies, thermal deactivation has been shown to be the principal cause of deactivation [12,13] while in others, contamination has been observed to play a major role [8,14]. It is difficult to determine the degree to which each 0920-5861/00/$ – see front matter © 2000 Elsevier Science B.V. All rights reserved.
