Dataset in the production of composite clay-zeolite membranes made from naturally occurring clay minerals

The data presented in this article are generated as part of the research article entitled “from a naturally occurring material (clay mineral) to the production of porous ceramic membranes” (Elgamouz and Tijani, 2018) [1]. This article describe how clays as very abundant versatile materials that have many properties not available in pure materials namely, silica, alumina and zirconia can be used for the preparation of ceramic membranes (Karaborni et al., 1996; Oun et al., 2017; Hollanders et al., 2016; de Oliveira Henriques et al., 2017) [2], [3], [4], [5]. This paper presents data obtained at different stages of the fabrication of a clay-zeolite composite ceramic membrane made from a largely available clay from the central region of Morocco (Meknes). The data include the characterization of the clay powder using XRD, FTIR, thermogravimetric (TGA and TDA) analysis of the clay powder. The data of porosity, mesoporosity, specific surface area, volumes of the pores, volumes of mesopores, diameters of the pores using mercury intrusion porosimetry and adsorption desorption of nitrogen data that was computed from BET and BJH theories of the clay supports at different firing temperatures (700, 750, 800, 850 and 900 °C). Data obtained from measurement of nitrogen permeation of support alone and that of the silicalite membranes are also represented.


a b s t r a c t
The data presented in this article are generated as part of the research article entitled "from a naturally occurring material (clay mineral) to the production of porous ceramic membranes" (Elgamouz and Tijani, 2018) [1]. This article describe how clays as very abundant versatile materials that have many properties not available in pure materials namely, silica, alumina and zirconia can be used for the preparation of ceramic membranes (Karaborni et al., 1996 [2][3][4][5]. This paper presents data obtained at different stages of the fabrication of a clay-zeolite composite ceramic membrane made from a largely available clay from the central region of Morocco (Meknes). The data include the characterization of the clay powder using XRD, FTIR, thermogravimetric (TGA and TDA) analysis of the clay powder. The data of porosity, mesoporosity, specific surface area, volumes of the pores, volumes of mesopores, diameters of the pores using mercury intrusion porosimetry and adsorption desorption of nitrogen data that was computed from BET and BJH theories of the clay supports at different firing temperatures (700, 750, 800, 850 and 900°C). Value of the data

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The data presents very useful results for the applications of clay-zeolite composite ceramic membranes in gas filtration.
This data gives a detailed and complete set of experiments on the characterization of the porosity of clay-zeolite composite membranes that could be relied on to tune the pore size of the membranes.
The data would allow other researchers to identify the key parameters that need to be controlled in the fabrication of clay-zeolite composite membranes.  [2][3][4][5]. The clay used in this study was fully characterized, data for characterization are now discussed. The chemical analysis of the natural clay was performed by X-ray fluorescence (ARL-8660 X-Ray Fluorescence Spectrometer). This analysis shows that the clay consists mainly of silica SiO 2 , calcium oxide CaO, alumina Al 2 O 3 (73%), the low presence of other alkaline and alkaline earth oxides (MgO, K 2 O Table 1).

X-ray diffraction
The analysis of the clay powder fractions revealed a strong presence of silica in the form of quartz, calcite, kaolinite and illite. Fig. 1 represents the X-ray diffraction of the clay used in this study.

Infrared spectroscopy
The FTIR analysis was carried out in the spectral range (2000-4000) cm À 1 by a Bruker Platinum ATR tensor II spectrometer with a resolution of 4 cm À 1 . Fig. 2 represents the FTIR spectrum of natural clay and different vibrations attribution of the clay are represented in Table 2.

Thermogravimetric analysis
TGA shows three weight losses during calcination.
The first starts at 23°C and ends at 89°C, corresponding to the departure of the water adsorbed by the clay.  The second starts around 400°C and ends at 557°C, due to the decomposition of kaolinite.
The third begins at 639°C and ends at 736°C, due to the decomposition of carbonates.

Differential thermal analysis
DTA shows the presence of 5 endothermic peaks and an exothermic peak around 922°C. TGA and DTA curves are given in Fig. 3. Fig. 4. Nitrogen sorption of membrane supports made from clay only for samples sintered at 700, 750, 800 and 950°C respectively. The isotherms were shifted vertically by 40, 60, and 70 cm 3 STP g À 1 .

Clay supports fabrication
Homogeneous powder consisting of granulated natural clay (size between 250 and 315 mm) and well-determined percentages of organic additives undergoes a uni-axial pressure of up to 8 t. Pellets (flat supports) were obtained, these were maintained under a heat program to a final sintering temperature of 950°C and a final sintering time of 3 h. Three substrates were prepared, respectively made from clay only, mixture of clay and 5% of activated carbon and mixture of 20% starch. Fig. 5. Nitrogen sorption of membrane supports made from clay and 5% activated carbon for samples sintered at 700, 750, 800 and 950°C respectively. The isotherms were shifted vertically by 40, 60, and 70 cm 3 STP g À 1 .

Silicalite membranes synthesis
A precursor gel of silicalite was prepared by mixing TEOS as silica source, tetra-npropylammonium bromide (TPAOBr) as template and KOH as base in addition to de-ionized water. The molar composition was: 1000. H 2 O: 4.5 SiO 2 : 1.0 KOH: 1.0 TPABr. The support flat disc was introduced vertically, then the gel was poured into the Teflon lined tube and autoclave represented in Fig. 7. The autoclave was kept in an oven at 175°C for 24 h.

Permeation tests
A specific unit was designed and it is represented in Fig. 8 for nitrogen permeations (single gas permeation) while for the selectivity test of silicalite membranes towards N 2 , SF 6 and propane another unit was used it is represented in Fig. 9. respectively. The isotherms were shifted vertically by 40, 60, and 70 cm 3 STP g À 1 .

Permeability of pure gases
Permeability is a very important feature that helps in deciding about the quality of a membrane. Measurement of permeability of N 2 , SF 6 , propane helps assuming the Knudsen and laminar contribution of a membrane.
The difference between the pores of the MFI membrane (0.55 nm) and the kinetic diameters of the N 2 (0.364 nm), SF 6 (0.55 nm) and propane (0.42 nm) [10] gases can cause selectivity. Selectivity is defined as the ratio of nitrogen permeability and the permeability of other gases the permeability formula given in Eq. (1).  The average pressure (P av ) which represent the pressure across the membrane is equal to P av ¼ (2*P at þ ΔP)/2 (bar), where ΔP is the pressure drop of the gas across the membrane and P at is the atmospheric pressure, that was found to be equal to 1.013 bar at experiment's time. Permeation in  mol/Pa s m 2 , is defined in Eq. (1).
F: Gas volumetric flow rate that is passing through the filtration area in mL/min, measured in the experiment conditions. T work and P work are working temperature and pressure respectively. A regular non-absorbable gas Permeation flux F was found to be proportional to the average pressure of the experiment and follows expression defined in Eq. (2).
r: d/2 radius of the porous medium. ε: medium porosity (dimensionless). ι: tortuosity (dimensionless). M: molecular weight of gas (kg/mol). T: temperature (K). μ: gas viscosity (Pas). R: gas constant (R ¼ 8.314 J/mol K). Substituting each parameter by its value and holding constant values, Eq. (2) becomes, where α and β are Knudsen laminar and viscous coefficient respectively. Knudsen percentage contribution is defined as the ratio of the coefficient α and the total permeation flux at a pressure of 1.0 bar.
Eq. (4) is of great practical use; it is used to describe the transport in the gas phase of a nonabsorbable gas across a porous medium. If permeation flux defined in Eq. (3) is plotted against the  average pressure a linear graph is obtained and it is illustrated in Fig. 10, where the intercept corresponds to the Knudsen viscous contribution (α) and the slope to the laminar Knudsen coefficient (β). These parameters were determined for clay supports as well as clay-zeolite composite membranes and they are represented in Figs. 11-13.