Saponite pillared

Here we report the synthesis and catalytic application of a new porous clay heterostructure material derived from synthetic saponite as the layered host. Saponite is a tetrahedrally charged smectite clay wherein the aluminum substitutes for silicon in the tetrahedral sheet of the 2 1 layer lattice structure. In alumina - pillared form saponite is an effective solid acid catalyst [8-10], but its catalytic utility is limited in part by a pore structure in the micropore domain. The PCH form of saponite should be much more accessible for large molecule catalysis. Accordingly, Friedel-Crafts alkylation of bulky 2, 4-di-tert-butylphenol (DBP) (molecular size (A) 9.5x6.1x4.4) with cinnamyl alcohol to produce 6,8-di-tert-butyl-2, 3-dihydro[4H] benzopyran (molecular size (A) 13.5x7.9x 4.9) was used as a probe reaction for SAP-PCH. This large substrate reaction also was selected in part because only mesoporous molecular sieves are known to provide the accessible acid sites for catalysis [11]. Conventional zeolites and pillared clays are poor catalysts for this reaction because the reagents cannot readily access the small micropores. 

Both natural clays and their alnminium oxide pillared analogues have also been tested for the catalytic cracking of polyethylene [49-51]. The clays investigated include mont-morillonite and saponite. They possess a layered structure which can be converted into a two-dimensional network of interconnected micropores by intercalation of molecular moieties. In the case of alnmininm pillared clays, these materials show a mild acidity... 

Comparative study of the textural properties of alumina-pillared saponites synthesised from the intercalation with various aluminium oligomers... 

A comparative study of the textural properties developed by the intercalation and pillaring of a saponite with various aluminium oligomers is reported. Three aluminium polycations, [A1 304(P2-OH)24(H20)i2] ", [Al,3(P3-OH),(p2-OH),2(teM)6(H20)6] " and... 

Although the possible catalytic applications of PILCs is the subject more extensively studied, large efforts have also been devoted to the characterisation of the microporous structure of these materials. To this end, the application of both classical and novel models based on gas adsorption has been reported in the literature. The adsorption data depend on the internal physical and chemical structure of the solid and on the nature of the adsorbate molecule. Thus, the adsorption results contain information about structural and energetic properties of the materials surface [8]. In the following, the methods considered in this work to investigate the microporous properties of several alumina-pillared saponites are briefly presented. 

The acidities of cliys and pillared clays are between those of amorphous aluminosilicates and zeolites. Pillared clays can provide large-pore two-dimensional networks. Hectorite, montmorillonite, saponite and beidellite are the clays most often used to make pillared clays. Most pillared clays coke and deactivate st. This, and low thermal and hydrothermal stabilities have so far limited catalytic applications. Al, Ti, Zr, Cr, Si, and Fe and their mixtures give more stable pillars than those tried in the past. Occelli and Robson reviewed pillrued clays [52]. 

Bergaoui, L. et al.. Porosity of synthetic saponites with variable layer charge pillared by A1j3 polycations, Langmuir, 11, 2849, 1995. 

Al-pillared clays thermally stable up to 750 C have been prepared from easily available starting materials a natural clay, namely the saponite, and a commercial aqueous solution of Chlorhydrol. 

This study deals with the pillaring of a natural clay, a saponite from Ballarat, by polyhydroxoaluminum cations provided by a commercially available solution of Chlorhydrol. Interest of these starting materials may be briefly listed. 

Table 5 gives the basal distances and the surface areas of Al-pillared saponites prepared at pH = 4.8 (process 1) and heated to SOO C at 36" /h, then to 750X at 90°/h and kept for 4 hours at this temperature. 

Fig. 4 shows the 001 line evolution of sample la with regard to the thermal treatment. Pillared clays of process 1 (Table 5) still exhibit thermal stability at 750°C. These thermal stabilities up to 750°C may be related to (i) the nature of the phyllosilicate (magnesian octahedral sheet, Si/Al substitutions) and (ii) the thermal stabilization of the intercalated saponite. 

Al-pillared saponites exhibit significant surface areas (150 - 250 m. g ) at 750°C suggesting that a good interlayer pillar repartition is reached preventing the sintering at this temperature. 

Complementary results on thermal stabilities of Al-pillared saponites are presented elsewhere (22). 

TABLE 5 Optimization of the Pillaring of a Saponite 45 Al-pillarcd saponilc characterization with regard to thermal treatment ... 

Preparation and Properties of Pillared Synthetic Boron-Containing Saponite... 

Pillaring selected synthetic clay minerals with suitable pillaring agents may lead to a breakthrough in the theory and application of pillared clays. This chapter reports on the preparation and characterization of a novel pillared synthetic heteroatom-containing clay, that is, pillared synthetic boron-containing saponite. 

Characterization of the pillared synthetic (boron-containing) saponites... 

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