Preparation of Delaminated Clay Having a Narrow Micropore Distribution in the Presence of Hydroxyaluminum Cations and Polyvinyl Alcohol

Abstract

Abstract--The pillaring of Na-montmorillonite with cationic oligomers of hydroxyaluminum (COHA) in the presence of an aqueous solution of polyvinyl alcohol resulted in the formation of a clay having a large surface area and pore volume. The pore-size distribution determined from a N2 adsorptiorddesorption hysteresis was narrow and centered at about 25 ~. The peak width at half height in the distribution curve was < 5 /~. As a result of delamination, the layer structure of the prepared clay was found from X-ray powder diffraction measurements to be lost. Short-range ordering, however, still existed in this delaminated clay, because exchangeable cations in the montmorillonite completely exchanged with A13+, a requisite step for pillaring.The order of adding the starting materials (Na-montmorillonite, polyvinyl alcohol, and COHA) greatly affected the surface area and the pore volume of the delaminated clay. Two orders of addition (Namontmorillonite, then COHA, then polyvinyl alcohol; and COHA, then Na-montmorillonite, then polyvinyl alcohol) gave no measurable surface area and pore volume. Two other orders of addition (polyvinyl alcohol, then COHA, then Na-montmoriUonite; and polyvinyl alcohol, then Na-montmorillonite, then COHA) gave surface areas of 107 and 160 mVg and pore volumes of 0.13 and 0.29 cm3/g, respectively. The amounts of the COHA solution and polyvinyl alcohol added greatly influenced the surface area and pore volume of the delaminated clay. Both properties increased monotonically with increasing amount of added polyvinyl alcohol, and increased to a maximum and then decreased with increasing amount of added COHA solution. The maximum surface area of the prepared delaminated clay was 330 m2/g.

Preparation of Silica-Pillared Fluorohectorite by Cointercalation of Polysiloxane and Polyvinyl Alcohol

“…5, these pillared clays had BET surface areas from 160 to 270 m 2 g of which were half that of the other pillared montmorillonite. 6,11,13 This result also conformed to that of fluorine mica. 15,16 This contraction might be due to the insufficiency of the clay delamination.…”

“…12 The polysiloxane pillared clay provided micropores below 1 nm. The method that improves the pore properties can employ the cointercalation of nonionic templates, which are water-soluble polymer [13][14][15][16] or are nonionic surfactants, 9,17,18 other than the cationic surfactants. We have prepared silica-pillared clays with larger surface areas and pore volumes using polysiloxane and polyvinyl alcohol PVA 19 as with the alumina-pillared clay or zirconia-pillared clay by the PVA method.…”

“…We have prepared silica-pillared clays with larger surface areas and pore volumes using polysiloxane and polyvinyl alcohol PVA 19 as with the alumina-pillared clay or zirconia-pillared clay by the PVA method. [13][14][15][16] The presence of PVA in the interlayer space left the distance between the silicate layers expanded. PVA was incorporated into the interlayer region of expandable clays without interfering with the ion exchange process.…”

“…The 001 peaks of the pillared clay with PVA 2ಚc, 4ಚd, 6ಚ e, and 8ಚf were observed at 2uࢼ1.91cdࢼ4.62 nm, 2uࢼ1.71cdࢼ5.16 nm, 2uࢼ1.64cdࢼ5.38 nm, and 2uࢼ 1.53cdࢼ5.77 nm, respectively. We assigned the peaks of d001 of approximately 12 and 13 to the high order reflections 00l as with other pillared clays with PVA method, [13][14][15][16] although the peaks at around 3.5 nm and 5.5 nm were not distinct due to the broad pattern. The peaks at a low diffraction angle correspond to the basal spacings enlarged by the simultaneous intercalation of the polysiloxane and PVA between the clay layers.…”

Layered Zn2[Co(CN)6](CH3COO) double metal cyanide: a two-dimensional DMC phase with excellent catalytic performance

“…25,26 Additionally, their potential for modication through, for instance, exfoliation has been extensively investigated in the case of clays, layered zeolite precursors or layered double hydroxides. [27][28][29][30][31][32][33][34][35] During our investigation of Zn 3 [Co(CN) 6 ] 2 DMCs, we discovered single crystals of a phase that was not cubic, but instead, consisted of positively charged DMC layers linked by acetate anions. To the best of our knowledge, such a cationic, layered DMC structure has not yet been reported in the literature.…”