Catalytic properties of pillared montmorillonites

From Microporous to Mesoporous Molecular Sieve Materials and Their Use in Catalysis

“…[136][137][138][139][140] Indeed there is a strong driving force in this field to replace mineral acids such as H 2 SO 4 , H 3 PO 4, AlCl 3 , HF, etc. by solid acids.…”

“…The other field of acid-catalyzed reactions where the porosity of the PLS together with their acid properties can be of use, is in the preparation of chemicals and fine chemicals. − Indeed there is a strong driving force in this field to replace mineral acids such as H 2 SO 4 , H 3 PO 4, AlCl 3 , HF, etc. by solid acids.…”

Pillaring of a Saponite with Aluminum−Chromium Oligomers. Characterization of the Solids Obtained

“…In the case of chromium, the partial hydrolysis of Cr 3+ solutions leads to the formation of polycations containing 2, 3, 4, 5, or 6 metallic atoms. Pillaring of montmorillonite with chromium polycations has been reported by different authors. − ,,,,,,− Chromium-pillared montmorillonites are thermally much less stable than the analogous aluminum-pillared solids. The pillaring of saponite with [Al 13 O 4 (OH) 24 (H 2 O) 12 ] 7+ oligomer has been recently studied, but to our knowledge the pillaring of this clay with chromium polycations has not been reported.…”

“…Pillared clays are obtained by calcination of the intercalated compounds prepared by exchange of the interlayer cations of layered clays with bulk inorganic oligomers. These oligomers are obtained by partial hydrolysis of multivalent cations, such as Al 3+ , Cr 3+ , Ti 4+ , Zr 4+ , Ga 3+ , Si 4+ , Fe 3+ , etc. − The pillaring process improves the surface area, the porosity, and the thermal stability of the clays, giving the solids obtained important catalytic applications, especially for the cracking of heavy oil fractions. − In recent years, these solids have been tested as catalysts in “fine chemistry” and as adsorbents. − …”

Acidity of montmorillonite pillared by alumina, zirconia and chromia

“…The chemical composition and characterisation of both mononionic forms is given elsewhere [8]. The pillared forms (AI, Zr and Cr) of these montmorillonites were prepared using standard techniques described in [9][10][11].…”