Structure, Characterization and Application of Ni Hydrotalcite as Solid Base Catalysts for Organic Transformations

Abstract

Ni hydrotalcites with different kinds of metals, ions exhibit considerable activity for organic transformations. Various ratios of Ni-Al hydrotalcites are prepared by using different compositions are characterized by XRD, IR and TPR analysis. Carbonate in the brucite sheets is active for selective oxidation reactions. Upon calcination the dehydroxylation of the hydrotalcite and concurrent decomposition of the carbonate ions produce mixed oxides which exhibits activity for variety of organic transformations.

Layered Double Hydroxide Catalysts Preparation, Characterization and Applications for Process Development: An Environmentally Green Approach

“…In detail, these materials, once heated at elevated temperatures of about 650 °C in inert conditions, results in the formation of mixture of metal oxides that are easy to regenerate the hydroxide layers when exposed to water. These are highly applicable in base catalysed reactions such as Aldol, Michael, and Wittig reactions [78]. The prepared LDH-CO3 are thermally decomposed to a mixture of oxides which is easily dispersed in the desired anion solution under inert conditions in deionised water in order to avoid the CO3 2− contamination.…”

“…This is the common method used when larger anions have to be intercalated in LDHs. Hence, this method is the choice of method for intercalation, with different anions, such as Cl − or NO3 − [78]. The incorporation of competing anions is also restricted, depending on parameters such as pH value which increases leading to favour the OH − formation.…”

“…Rahman et al [106] reported for the first time reported a shortest route for molecular oxygen activation by Ni-Al hydrotalcite for selective oxidation of various substituted α-ketols, benzylic and allylic alcohols to carbonyl compounds. They studied the comparison of Cat A, Cat B and Cat C with Ni-Al ratios of 2:1, 2.5:1 and 3:1 and found that the best results with Ni-Al 2:1 ratio.…”

“…This is ascribed due to the formation of more Ni ions during the preparation of catalysts. One of the notable achievements of this methodology was Cinnamyl alcohol was oxidized to Cinnamaldehyde without disturbing the double bond [106].…”

“…Rahman et al [106] reported the reductive amination of benzaldehyde with ratios of 2:1, 2.5 and 3:1 Ni-hydrotalcite catalysts which exhibited good catalytic activity for synthesis of amines. Ni-hydrotalcite catalysts for reductive amination of benzaldehyde with NaBH4, acts as reducing agent to form in situ-Ni-boride which is generated swiftly in the formation of desired product at room temperature.…”