Study on peptizability of boehmite and its application for the peparation of -al2o3 in spherical shape

Journal of Chemistry, Vol. 45 (Special issue), P. 158 - 161, 2007<br /> <br /> <br /> STUDY ON PEPTIZABILITY OF BOEHMITE AND ITS APPLICATION<br /> FOR THE PEPARATION OF -Al2O3 IN SPHERICAL SHAPE<br /> Received 15 October 2007<br /> Nguyen Han Long, Tran Vinh Hoang, Pham Thanh Huyen<br /> Faculty of Chemical Technology, Hanoi University of Technology<br /> <br /> <br /> summary<br /> This paper presents the results of the peptizability of boehmite and its application for the<br /> preparation of -Al2O3 in spherical shape. The obtained -Al2O3 in spherical shape has high<br /> mechanical resistance and high surface area. The water vapor adsorption ability of sphere of -<br /> Al2O3 has also been determined. -Al2O3 in spherical shape can adsorb moisture up to 65% of<br /> their weight.<br /> <br /> I - INTRODUCTION II - EXPERIMENTAL<br /> <br /> -Al2O3 is a mesoporous material which has -Al2O3 has been synthesized from available<br /> high acidity, activity, good mechanical and domestic raw materials such as waste<br /> thermal resistance. So -Al2O3 is widely used as aluminum, Tan Binh aluminum hydroxide and<br /> the adsorbent and catalyst in the refinery and industrial aluminous material.<br /> petrochemical technology in particular, and in Other chemicals include: NaOH, H2SO4,<br /> the chemical industry in general [1, 2]. H2O2, organic additives and peptization reagent.<br /> However, in order to use it in chemical These chemicals are firstly used in pure form<br /> processes, beside the study to increase its and then in industrial form to determine the<br /> surface area [3], the formation of -Al2O3 in reiteration and prepare to manufacture in the<br /> spherical shape is very important. large scale.<br /> One of the most important properties of The procedure to synthesize -Al2O3 and to<br /> boehmite is its peptizability to be the binder for form the finished product is shown in Fig. 1.<br /> other materials that do not have this ability. So<br /> the application of boehmite as the binder has The procedure to form the sphere of -Al2O3<br /> greatly increased the value and the application is as follow: first, the viscosity of peptization<br /> solution is adjusted to a suitable value by adding<br /> range of -Al2O3 and other materials.<br /> distilled water, and then it is forced through<br /> The refinery and petrochemical industry is holes with different sizes to form spheres with<br /> being built in Vietnam. Each year, a large different diameters. These drops fall slowly<br /> amount of -Al2O3 in spherical shape is through a column containing different layers of<br /> imported to be used as the adsorbent in the oil and ammonia. At the bottom, the spheres are<br /> drying of natural gas. So finding a procedure to separated, dried and calcined.<br /> synthesize -Al2O3 in spherical shape from The obtained boehmite and -Al2O3 are<br /> cheap and available domestic raw material is characterized by X-ray diffraction (XRD) on a<br /> very necessary.<br /> 158<br />  D8 Advance (Bruker) at Petrochemical and III - RESULTS AND DISCUSSION<br /> Catalysts Material Laboratory, Hanoi University<br /> of Technology (PCM-HUT). Analysis regime is: 1. Characterization of obtained boehmite and<br /> Cu K radiation ( = 1,5406 Å), voltage of 40 -Al2O3 by XRD<br /> kV, electric current of 40 mA, temperature of XRD patterns of boehmite and -Al2O3 are<br /> 25oC, 2 = 10 - 70o, step 0,1o etc... shown in Fig. 2.<br /> <br /> <br /> <br /> <br /> Figure 1: Procedure of the synthesis and spheroidization of - Al2O3<br /> <br /> 140<br /> PCM - Bruker D8 Advance - Boehmite 60<br /> PCM - Bruker D8 Advance - gama Al2O3<br /> 130<br /> 120<br /> 110 50<br /> <br /> 100 a b<br /> Lin (Cps)<br /> <br /> <br /> <br /> <br /> 90 40<br /> Lin (Cps)<br /> <br /> <br /> <br /> <br /> 80<br /> 70 30<br /> 60<br /> 50<br /> 20<br /> 40<br /> 30<br /> 10<br /> 20<br /> 10<br /> 0 0<br /> 10 20 30 40 50 60 70 10 20 30 40 50 60 70<br /> 2-Theta - Scale 2-Theta - Scale<br /> 88-2110 (C) - Boehmite, syn - AlO(O(H.33D.67)) - Y: 50.00 % - d x by: 1. - WL: 1.5406 - Orthorhombic - a 2 29-1486 (D) - Aluminum Oxide - gamma-Al2O3 - Y: 83.33 % - d x by: 1. - WL: 1.5406<br /> <br /> <br /> Figure 2: XRD patterns of boehmite (a) and -Al2O3 (b)<br /> <br /> Fig. 2 shows that obtained boehmite and - 2. Influence of technological parameters on<br /> Al2O3 contain only single phase characterized the spheroidization of -Al2O3<br /> for boehmite and -Al2O3. It has confirmed that Through preliminary studies, it is found out<br /> the obtained products are very pure. XRD that when the content of peptization reagent was<br /> pattern of peptization boehmite gel after drying greater than 10%, the obtained gel after<br /> at 120oC is exactly the same as that of boehmite. calcination was very hard and brittle and the<br /> It means that peptized reagent has completely adsorption ability of the product was very low,<br /> been decomposed at 120oC. so it is not suitable to be used as a binder.<br /> <br /> 159<br /> Moreover, according to references [1, 4], the When the drops of peptized boehmite falls<br /> greater the peptization content, the lower the through oil column, under the surface tension<br /> surface area of -Al2O3. With the data obtained force, these drops tend to form the spherical<br /> in the studies of the influence of peptization shape. When they fall through the ammonia<br /> regent content on the mechanical resistance and column with the height greater than 100 mm,<br /> adsorption ability of spheres of -Al2O3, it has the outside layer will be neutralized, hardened.<br /> been realized that the content of peptization These harden drops fall to the bottom of the<br /> reagent is optimal between 6 - 7%. column and are neither distorted nor stuck<br /> together [5]. If the height of the ammonia<br /> The results obtained in the spheroidization<br /> column is less than 100 mm, the peptized<br /> of -Al2O3 with different oil, different height of boehmite drops can not be neutralized<br /> oil and ammonia column is presented in table 1. completely, so they are stuck together.<br /> Table 1: Influence of some technological So, by using the kerosene column with the<br /> parameters on the spheroidization of -Al2O3 height of 30 ÷ 40 mm and the ammonia column<br /> greater than 100 mm, we can obtain -Al2O3 in<br /> Height, spherical shape with various diameters.<br /> Column Result<br /> mm With the peptized boehmite gel, extrudates<br /> Peanut - can also be form by extrudation. The obtained<br /> oil No spheres formed extrudates are then dried and calcined to get the<br /> Bean oil - finished products.<br /> 10 flattish shape The photo of spheres and extrudates of -<br /> 20 flattish shape Al2O3 with diameter of 3mm is shown in Fig. 3.<br /> Kerosene 30 spherical shape From the above results, this procedure can<br /> 40 spherical shape be applied to form the spheres and extrudates of<br /> other materials such as zeolites to be used as<br /> 50 flattish shape<br /> catalysts or adsorbents...to increase the value<br /> 50 spheres are stuck and the application range of these materials.<br /> together<br /> 70 spheres are stuck 3. Study the adsorption ability of product<br /> Ammoni<br /> a 10% together The results that present the relationship<br /> 100 spheres are separated between adsorbed moisture content/ -Al2O3<br /> 150 spheres are separated weight (A%) and time on stream are shown in<br /> Fig. 4.<br /> <br /> <br /> <br /> <br /> Figure 3: Photo of spheres and extrudates of -Al2O3<br /> 160<br />  70<br /> <br /> <br /> 60<br /> <br /> <br /> 50<br /> Moisture Adsorption, A%<br /> <br /> 40<br /> <br /> <br /> 30<br /> <br /> <br /> 20<br /> <br /> <br /> 10<br /> <br /> <br /> 0<br /> 0 5 10 15 20 25 30<br /> T im e (d ays )<br /> <br /> Figure 4: Moisture adsorption ability of -Al2O3 in spherical shape<br /> <br /> Fig. 4 shows that spheres of -Al2O3 adsorb ability, so they can be used in the drying of<br /> moisture quickly at the beginning (< 3 days), natural gas.<br /> then the adsorption will slow down and reach<br /> the saturated level after 30 days with the REFERENCES<br /> adsorbed moisture content up to 65% of the -<br /> Al2O3 weight. 1. Bruce E. Leach. Applied industrial catalysis,<br /> These initial results prove that spheres of - Vol. 3, Academic Press (1984).<br /> Al2O3 meet the necessary requirements to be 2. R. J. Farrauto and C.H. Bartholomew,<br /> applied as the adsorbent in the drying of natural Fundamentals of Industrial Catalytic<br /> gas. Processes, Blackie Academic &<br /> Professional (1999).<br /> CONCLUSIONS 3. Pham Thanh Huyen, Nguyen Han Long,<br /> Tran Vinh Hoang. Proceedings of the 4th<br /> - -Al2O3 has been synthesized from cheap Asia-Pacific Chemical Reaction<br /> and available domestic raw materials. Engineering Symposium, Gyeongju, Korea,<br /> - The optimal technological parameters for 12-15 June 2005.<br /> the spheroidization of -Al2O3 have been found. 4. Tran Cong Khanh. Experiments of organic<br /> The obtained spheres of -Al2O3 have various synthesis. Hanoi University of Technology,<br /> desired diameters, high mechanical strength and (1976).<br /> high surface area. 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