Abstract
This work focuses on the hydrothermal synthesis of Na-P1 zeolite by using a kaolinite rock coming from Romana (Sassari, Italy). The kaolin is calcined at a temperature of 650 °C and then mixed with calculated quantities of NaOH. The synthesis runs are carried out at ambient pressure and at variable temperatures of 65 and 100 °C. For the first time compared to the past, the Na-P1 zeolite is synthesized without the use of additives and through a protocol that reduces both temperatures and synthesis times. The synthesis products are analysed by X-ray diffraction, high temperature X-ray diffraction, infrared spectroscopy, scanning electron microscopy and inductively coupled plasma optical emission spectrometry. The cell parameters are calculated using the Rietveld method. Density and specific surface area are also calculated. The absence of amorphous phases and impurities in synthetic powders is verified through quantitative phase analysis using the combined Rietveld and reference intensity ratio methods. The results make the experimental protocol very promising for an industrial transfer.
Highlights
This work focuses on the hydrothermal synthesis of Na-P1 zeolite by using a kaolinite rock coming from Romana (Sassari, Italy)
In this paper we present the results of a research carried out to define the most favorable conditions for the Na-P1 synthesis from metakaolin
This work describes the synthesis of zeolite Na-P1 using a kaolinitic rock
Summary
This work focuses on the hydrothermal synthesis of Na-P1 zeolite by using a kaolinite rock coming from Romana (Sassari, Italy). Zeolites are a group of tectosilicates of about 50 minerals with synthetic analogues Their structure is made of three-dimensional networks of Al/Si tetrahedra arranged to form channels containing water and exchangeable alkaline or alkaline earth cations. Three polymorphs are recognized for Na-P: the cubic phase called Na-P1, refined in I411 and with a unit cell content of N a6Al6Si10O32.12H2O; the orthorhombic one, the so-called Na-P2 with formula N a4Al4Si12O32.14H2O, crystallizing in Pnma[12]; the tetragonal one for high silica variety of Na-P (Na3.6Al3.6Si12.4O32.14H2O), refined in I41/amd[5] Another zeolite P with a strict Si/Al ratio of 1.0 is called aluminum P (MAP), whose structure was firstly refined by Albert et al.[13] in the monoclinic system, space group C2/c (Na8Al8Si8O32. Kaolinite is the most common phyllosilicate involved in successful zeolitic synthesis because of its ample/large supply and availability and the well-known reactivity of thermally treated kaolin clays (metakaolin) with alkali[3, 27,28,29,30,31]
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