Synthesis and characterization of Cr-pillared clays: modelling using factorial design methodology

Abstract

Cr-pillared interlayered clays (Cr-PILCs) have been prepared from natural calcium bentonite originating from a Romanian deposit and the effect of some parameters on the chemical and textural properties have been investigated. The crude bentonite and the derived materials were characterized by nitrogen adsorption-desorption technique, X-ray diffraction, scanning electron microscopy coupled with energy-dispersive X-ray spectroscopy and transmission electron microscopy. The specific surface area values, the pore size distribution, morphological characteristics and the basal spacing of the Cr-PILCs are strongly affected by the process parameters. The influence of three relevant factors (metal/clay ratio, calcination temperature and calcination duration) on the specific surface areas of the Romanian Cr-PILCs was investigated using a 3 3 factorial design methodology. The optimum conditions to obtain CrPILCs with a specific surface area of 183 m 2 /g (more than four times higher than the raw material) were as follows: metal/clay ratio of 10 mmols/g, calcination temperature 300°C and calcination duration 60 min. The model developed in this paper predicts very well the experimental results. Due to the high porosity and adsorption properties, the prepared Cr-PILCs have great potential in remediation of industrial liquid effluents.

Influence of Purification Process on the Characteristics of Romanian Calcium Bentonite

“…The shape of nitrogen adsorption-desorption isotherm obtained for the purified calcium bentonite is of type IV [6] (Figure 3), being similar with the raw material one, which was presented in a previous paper [7]. This isotherm is specific to mesoporous adsorbents.…”

Modeling and Optimization of Pillaring Process Using Experimental Design Procedure

“…The aim of bentonite purification is the obtaining of well defined granulometric fractions, with particles < 2 µm. This procedure was detailed in a previous paper [5]. The purified bentonite was copperexchanged, by using the experimental protocol described in a previous work [10].…”

“…In Table 3 are presented the coefficients values of polynomial mathematical model, which were calculated according to the literature specifications [5]. According to the polynomial coefficients, the mathematical model which describes the response function of the optimizing criterion is:…”

“…Montmorillonite belongs to smectite clay mineral group, with a double-layered structure (2:1), it being the most used clay in pillaring process. The synthesis of different metal oxide PILCs led to the obtaining of microporous materials with special properties, the most used metal oxides as pillars being Al, Fe, Cr, Ni, Zr, Mg, Bi, Ti, Cu, Ga, Mo [1][2][3][4][5].…”

Propane-Propylene Oligomerization Over Modified Pillared Clay Catalysts

“…Therefore, our present study was aimed to investigating catalytic properties of ruthenium and nickel supported pillared clay catalysts for propane-propylene oligomerization. [15,16]. Prior to pillaring process, the clay was saturate with sodium ISSN 2224-5286…”