Comparison between leached metakaolin and leached diatomaceous earth as raw materials for the synthesis of ZSM-5
Inexpensive raw materials have been used to prepare ZSM-5 zeolites with SiO2/Al2O3 molar ratios in the range 20 – 40. Kaolin or Bolivian diatomaceous earth was used as aluminosilicate raw materials and sodium hydroxide and n- butylamine were used as mineralizing agents and template. Dealumination of the raw materials by acid leaching made it possible to reach appropriate SiO2/Al2O3 ratios and to reduce the amount of iron and other impurities. After mixing the components and aging, hydrothermal treatment was carried out and the products were recovered The results clearly show for the first time that well-crystallized ZSM-5 can be directly prepared from leached metakaolin or leached diatomaceous earth using sodium hydroxide and n-butylamine as mineralizing agents and template under appropriate synthesis conditions. A longer induction time prior to crystallization was observed for reaction mixtures prepared from leached diatomaceous earth, probably due to slower digestion of the fossilized diatom skeletons as compared with that for microporous leached metakaolin. The use of leached diatomaceous earth allowed higher yield of ZSM-5 crystals within comparable synthesis times. However, low amounts of Mordenite formed, which was related to the high calcium content of diatomaceous earth. Another considerable advantage of diatomaceous earth over kaolin is that diatomaceous earth does not require heat treatment at high temperature for metakaolinization.
Influence of the reaction time on the crystal structure of Na-P1 zeolite obtained from coal fly ash microspheres
Abstract This paper presents a study of the influence of time on the mineral structure formation of GIS Na-P1 zeolite. Lightweight microspheres were used as a source of silica and aluminium. Material subjected to this study was synthesized on a quarter-technical scale using a prototype installation. Chemical, mineralogical, and textural properties of the material were determined by means of X-Ray diffraction (XRD), X-Ray fluorescence (XRF), scanning electron microscopy equipped with a system of chemical composition analysis based on energy dispersive X-ray (SEM–EDS), volumetric adsorption analyzer (ASAP 2020), Fourier transform infrared spectroscopy (FTIR) and particle size analyzer (PSA). Experimental calculations based on Miller indices show the interesting and indeed astonishing phenomenon of the lattice parameters ripening as a function of time. Both unit cell parameters (a, b, c and volume) and the amount of zeolite present increase with synthesis time. This process is clearly observed using the XRD and FTIR method. Structural, morphological and textural properties of the final product indicate that it could potentially be useful as an adsorbent for various types of environment pollution.
Thermodynamics on the Carbochlorination of Titanium-bearing Ores
The equilibrium compositions of the multi-component, multi-phase and multi-reaction system of carbochlorination of titanium-bearing ores are calculated with HSC, a computational chemistry software. The thermodynamic equilibrium calculation of the reaction system shows that a complete conversion of titanium-bearing ores is feasible at a temperature near 200oC. At temperatures ranging from 800 to 1600oC, the products of the reaction system are all in gaseous phase. Thermodynamic analysis accords with the industrial practice. The simulated results provide reasonable scientific basis for improving suitable technological conditions of the carbochlorination reduction.