21916

21916

بررسي سنتز و رفتار پوشش دهي آلوميناهاي انتقالي به كار رفته به عنوان پوشش مياني پايه كاتاليست كوردريتي

كارشناسي ارشد

سراميك

1398/12/20

دكتر رحيم نقي زاده - دكتر علي بيت اللهي

دكتر فرهاد گلستاني فرد

مواد و متالورژي

پوشش مياني با فراهم ساختن سطح ويژه باال، نقش مهمي در ايجاد مكانهاي مناسب جهت انجتام فعّاليتت كاتاليستي ايجاد ميكند. فازهاي انتقالي آلومينا )به خصوق گاما و اتا( چنين ويژگي دارند اما چالش جتدي در ايجاد پايداري حرارتي اين فازها است تا در درماي باال با تبديل به فاز آلفتا ستطح ويتژه ختود را كتاهش ندهند. براي اين منظور در پژوهش حاضر اثر پيش مادههاي هيدروكسيدي و نيتراتي به همتراه دو افزودنتي بررسي شده است. نتايج نشان ميدهد سطح ويتژه نمونتههتاي هيدروكستيدي بتا افزودنتيهتاي H3BO3 و /g) ترتيب به Sr(NO3)2 m2 /g) و 69 ( m2 ) 71 و سطح ويژه نمونههاي نيتراتي با همتين افزودنتيهتا بته /g) ترتيب m2 /g) و 89 ( m2 ) 161 به دست آمدند. در آناليز فتازي نمونته آلومينيتوم نيتترات بتا افزودنتي H3BO3 فازهاي اتا و كاپا آلومينا به همراه فاز Al18B4O33 ، و با افزودني 2)NO3(Sr فازهاي اتا، كاپتا، گامتا- آلومينا و SrAl12O19 شناسايي شد. در نمونه آلومينيوم نيترات با افزودني H3BO3 فازهاي اتا، كاپا-آلومينتا و B2O3 ،و با افزودني 2)NO3(Sr فازهاي گاما، كاپا و اتا-آلومينا به همراه فاز SrO شناسايي گرديتد. در نهايتت دوغابي از نمونه آلومينيوم نيترات حاوي 6 درصد وزني SrO با تركيتب 40 درصتد وزنتي پتودر در pHهتاي اسيدي رفتاري تيكسوتروپ )برش رواني( دارند.

1399/02/23

Investigation of the synthesis and covering behaviuor of transitional alumina for use as washcoat of cordiret honycomb

3/10/2021 12:00:00 AM

One of the most important sources of pollution in cities is the exhaust gas pollution of cars. The three main exhaust pollutants of cars are hydrocarbons, nitrogen oxides and carbon monoxide. The main solution to convert exhaust-emitting gases is to use catalytic converters, which are placed in the exhaust and outlet of the car to convert these gases into less polluting gases from its harmful effects. Shall be reduced. These converters come from a cordierite substrate, which is a nesting process by extrusion process. An active alumina-based casing is coated with a submerged substrate in a slurry containing alumina, with The combination of precious metals performs catalytic activity. The main feature of the middle layer is the high level that increases the active sites for gas conversion and reduces the need for precious metals. The gamma-alumina phase, which has the highest specific surface area between the alumina phases, transforms into an alpha phase at high temperatures, which has a very low specific surface. A serious challenge is to create the thermal stability of the active aluminous phase with a high level, which is carried out with the help of additives that are mainly from the earth metals group. In this study, the effect of 6% SrO and 4% B2O3 on the formation and thermal stability of active alumina have been investigated using two precursors of aluminum hydroxide and aluminum nitrate. First, each of these two additives was dissolved in water and added to the suspensions and dissolved in water. After drying at 110 ° C for 24 hours and calcination at 850 ° C, a powder was prepared for analysis. . The results show that the aluminum nitrate precursor containing additive SrO with a specific surface area (m2 / g) of 161 has the highest specific area, and the slurry is mixed with 40% w / w of the powder in the acidic behavioral pH of the tisotrop.