Synthesis and characterization of NA-JBW zeolite structure from metakaolin

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Synthesis and characterization of NA-JBW zeolite structure from metakaolin

Annotation

The JBW zeolite was prepared from hydrogels under hydrothermal conditions by alkaline reaction, using NaOH as activating agent Using the Autologous reactor (under 15 bar pressure). The synthetic zeotype was studied by analytical techniques such as X-ray powder diffraction, Fourier transformed infrared spectroscopy. Crystallographic data revealed that the JBW structure can be described by the orthorhombic space group Pmc21, with unit cell parameters a=7.506 A, b=8.229 A and c=5.2195A.

Key words : JBW structure, orthorhombic, space group, unit cell.

Аннотация

zeolite hydrogel synthetic

Цеолит JBW был получен из гидрогелей в гидротермальных условиях путём щелочной реакции использованием NaOH в качестве активирующего агента. Использование реактора Alotoglaf (под давлением 15бар). Синтетический зеотип был изучен такими аналитическими методами, как рентгеновская порошковая дифракция, Фурье - преобразованная инфракрасная спектроскопия. Кристаллогр и афические данные показали, что структура JBW может быть описана орторомбической пространственной группой Pmc21 с параметрами элементарной ячейки a = 7,506 A, b = 8,229 A, c =5,219 A.

Ключевые слова: структура JBW, ромбической, космическая группа, ячейка.

Introduction

Kaolin is considered to be a very cheap and economical raw material for the synthesis of many types of zeolites because it contains an appropriate ratio of both SiO2 and Al2O3. Zeolites are considered to be an important family of three dimensional alumino silicates. There are many types of zeolite differing in Si/Al ratio and also in the three dimensional cages type. Low silica zeolites such as zeolite A(or LTA which abbreviated to Linde type A) are the most common product prepared from kaolin or meta-kaolin without any additional silica source [1, c. 23/2, c. 150]. Healey et al. [3,c.153] synthesised pure aluminosilicate JBW[(Na3H2O)(Si3Al3O12)] abbreviated to J Barrer and White (name of scientests who discover) from the reactant with meta-kaolin in a solution of NaOH and KOH at 498K. The zeolite with a JBW structure is one of the lesser-studied zeolites. It was first reported by Barrer and White in 1952 [4, c. 1561]. Subsequent work referred it inappropriately as `nepheline hydrate'; the crystal structure was solved (with the exception of a full description of the water molecules) in 1982 by Hansen and Falth [5, c. 162]. The structure was found to be orthorhombic with cell parameters a=7.503° A, b = 8.233°A and c =5.230°A crystallising in the Pmc21 space group. The crystals studied were grown hydrothermally at 200°C from a sodium aluminosilicate glass in sodium hydroxide solution [5, c. 162].

Experimental

Apparatus and chemicals:

As initial materials for zeolite Na - J obtaining were used: kaolin from `Kaolin' Company (Bulgaria) and NaOH was obtained from `Merck' Company with 99.9% analytical grade. Kaolin has the following chemical has the following chemical composition, according producer (Table 1).

The samples were characterized by X-ray diffraction (XRD) using CuKa radiation nickel filter (1=1.54060 °A) at 40kV and 30mA from the Japanese company Ultima-Rigaka.

Optical absorption spectrum infrared device model FT-IR-4100 from the Japanese company Jasco. reactor Autoclave from the company AmAr EQuipments PVT. LTD.

Table 1. Chemical analysis of kaolinite mineral

Experimental Procedure:

Synthesis of the zeolite (Na-JBW ) in two main stages:

Thermal activation of kaolin to obtain metakaolin.

Hydrothermal treatment of metakaolin in different alkali media.

The metakaolinisation of the initial material was carried out (after drying at 110°C for 1 h) at 700 °C in a muffle oven with isothermal period of 2 h.

The hydrothermal alkali treatment of 5.55 g metakaolin and (25 ml) alkali solution of NaOH (2M) are intensely homogenised at 60DC for 30 min. The homogenised past-like mixture is the placed in an autoclave reactor and treated at 180DC and 15 bar pressure for 3 h. The product obtained is washed several times with water (pH 7-8) and then dried at 110 C for 1 h. The products synthesised were analysed by XRD, FTIR techniques.

Results and Discussion:

Metakaolinisation process. Metakaolinisation of kaolin has been described in many publications but it is important since it refers to certain type of kaolin mined in Bulgaria and synthesis of zeolite from it.

The calcinations of the initial material was carried out with isothermal periods. At 7000C. Figure1 and 2 shows the IR spectra of the initial kaolin and the calcinated at 7000C.

Figure 1. IR spectra of original kaolinite

Figure 2. IR spectra at 700oC calcined kaolinite

Figure 1 show the characteristic bands of kaolinite [6, c. 223/7, c. 8080]. OH- at 3700, 3650, 3620 cm-1, Al-OH at 913 cm-1, Si-O at 1032, 1008, 469 cm-1 and Si-O-AlVI at 538 cm-1. Absence of the detectable Al-O-H bands at 913 cm-1, and the doublet at 3700 and 3620 cm-1, is evident from Figure 2. Absence of the band at 539 and 913 cm-1 and the appearance of a new band at 800 cm-1 can be related to the change from octahedral coordination of Al3+ in kaolinite to tetrahedral coordination in metakaolinite.

The bands at 1100 and 1200 cm-1 are assigned to amorphous SiO2.

XRD patterns of (JBW) zeolite is shown in Figure 3.

Figure 3. XRD pattern of prepared Na- JBW Zeolite

Table 2 shows a comparison of lattice spacing and angle, between prepared Na-JBW zeolite and standard.

Table 2. Comparison of lattice spacing and angle, between prepared Na-JBW catalyst and standard

XRD result is shown high purity and a good crystallinity of zeolite. These results are in good agreement with those reported in JCPDS [8]. After indexation of XRD patterns of prepared zeolites, all diffraction planes (hkl) correspond to JBW phases. That is, JBW has a structure Orthorhombic. As shown in the spectrum XRD of peaks with small intensities(14, 24.4, 27.74 20) returning to the form of Cancrinite which is in agreement with Lin et al. [9,c.63]. Figure 4 shows the FT-IR spectra of Na- JBW Zeolite.

44JЬLI ПЬЩЩ 2ЬЬЩ liЬЬЬ 4ЬЬ

vVsvBiunbs-r [cm-lj

Figure 4. IR spectra of Na- JBW zeolite

The vibration bands in the region between 500 and 420 cm-1 were assigned to internal tetrahedron vibrations of Si-O and Al-O in the as-synthetized zeotypes. The range of 800-400 cm-1, which has been considered as the `fingerprint' region for and CAN in previous studies [10, c.3093/11,c. 287], also reveals the presence of the JBW zeolite.

Conclusion:

The possibility to prepare synthetic zeolite Na-JBWfrom natural kaolin using the method of hydrothermal synthesis (at 1800C, pressure 15 bar, 3 h in an autoclave reactor). The structure of the zeolite obtained was studied by IR spectroscopy and XRD.

List of references

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