Characterization and Catalytic Activities of Faujasites Synthesized by Using Coal Fly Ash.

Abstract

Coal combustion by-product fly ash was converted selectively into faujasite (Y type) zeolite and was used as a catalytic material. The conversion process tried to alleviate the disposal problem of large amounts of fly ash, and turned fly ash into useful materials. Fused fly ash powder and supernatant were used in the synthe sis of Y type zeolite. The prepared Na-Y zeolites were characterized and ion-exchanged followed by calcina tions to obtain H-Y. The catalytic properties of the solid obtained were evaluated using cumene cracking and compared with those of commercially available (standard) zeolites. It was found that most of the Si and Al components in the fly ash could be effectively transformed into Y type zeolite in the presence of seeds but not the mineral phase, such as mullite. Moreover, the supernatant of the fused powder solution can produce purer faujasites and the sediment can be reused to generate solution for the further preparation of zeolites. Investigation by NMR demonstrated that fusion plays an important role in enhancing the hydrothermal con ditions for zeolite synthesis. The H-Y zeolite derived from the supernatant of fly ash solution shows excel lent cracking activity compared to that of standard.

Synthesis of zeolites Na-A and Na-X from tablet compressed and calcinated coal fly ash

“…We then characterized the chemical composition of synthesized Na-A and Na-X samples with XRF. 48 and is typical for commercial Na-A, while that for the Na-X sample is 5.12 [30,61,62]. The high Si/Al molar ratio of Na-X is due to the introduction of silica sol to get phase-pure Na-X [60].…”

“…Zeolites are conventionally synthesized with sodium silicate and aluminate through hydrothermal crystallization. CFA is mainly composed of particles of SiO 2 and Al 2 O 3 at micrometre dimension with a weight percentage up to 85 [8,43,44] and can principally be used as the precursor of Si and Al for zeolite synthesis [45][46][47][48][49][50][51][52][53][54][55][56]. However, SiO 2 and Al 2 O 3 are in the form of their most stable minerals in CFA, such as mullite and quartz.…”

Synthesis of a Single-Phase Na-A Zeolite from Coal Fly Ash by Dialysis

“…Therefore, the recycling of Fa is necessary at present. It has been established that Fa is mainly composed of amorphous material with some crystals such as α-quartz (SiO 2 ), mullite (2SiO 2 ·3Al 2 O 3 ), hematite (α-Fe 2 O 3 ), and magnetite (Fe 3 O 4 ) and can be converted to zeolites in alkali solutions by hydrothermal treatment. − There are many reports for synthesis of zeolite from Fa, for example, faujasite, − Na-A zeolite, ,, phillipsite, and hydroxysodalite . Since Na-A zeolite possesses unique structural properties, this material is extensively used in adsorption and ion-exchange processes such as drying gases and liquids, washing builder, and separation of normal from branched paraffins.…”

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“…16 We have also studied the synthesis of a variety of zeolites using the fusion approach and, under controlled synthesis conditions, we were successful in preparing pure zeolites. 17 The use of coal fly ash as a silica and aluminium source for the preparation of mesoporous materials is very rare in the literature 18 and has not been explored in detail. Here, we report the direct synthesis of Al-MCM-41 showing increased stability and a periodic pore structure by appropriate pH adjustment using coal fly ash as the source of silica and aluminium.…”