Pillaring of bentonite clay with Al and Co

• Mixed Al/Co pillared clays were synthesized with 10% and 25% of Co.
• The sample containing 25% Co obtained basal spacing of 18.1 Å.
• The BET surface area of the sample containing 25% Co was 334 m2/g.
• The 27Al NMR results confirmed the formation of mixed Al/Co pillars.

This work describes the synthesis and characterization of mixed Al/Co pillared clays. The materials were prepared using different Co concentrations: 10%, 25%, 50%, 75% and 100%. The samples were analyzed by XRD, N2 physisorption, chemical analysis (AA), 27Al NMR, FTIR and EPMA. The use of small amounts of Co (10% and 25%) resulted in the formation of pillared clays, and the material containing 25% cobalt exhibited superior characteristics compared to an Al pillared clay (basal spacing of 18 Å and BET surface area higher than 300 m2/g). The 27Al NMR results confirmed the formation of mixed Al/Co pillars; the ratio of the AlVI/AlIV signal intensities decreased, indicating that the AlVI content decreased while the Co content increased. Thus, the Co ions isomorphically substituted for Al in the Keggin ion structure (pillaring agent). When the Co content was 50%, 75% and 100%, pillared clays did not form. Therefore, it is possible to obtain clays with mixed Al/Co pillars for Co contents of up to 25%.

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