Efficient Utilization of Nanospace of Layered Transition Metal Oxide HNbMoO₆as a Strong, Water-Tolerant Solid Acid Catalyst

Abstract

Layered HNbMoO6 was found to function as a strong solid acid catalyst, exceeding the activity of zeolites and ion-exchange resins for Friedel-Crafts alkylation. HNbMoO6 also exhibited high catalytic activity for esterification of hydrocarboxylic acid and hydration. The catalytic performance of layered HNbMoO6 is attributed to the intercalation of reactants into the interlayer and the development of strong acidity.

Brønsted Acid Generation over Alumina-Supported Niobia by Calcination at 1173 K

“…On the other hand, previous XAFS study [7] of supported niobium oxide showed that a niobic acid-like compound is stabilized on Al 2 O 3 surface at higher temperatures than 673 K at somewhat high loading of niobium oxide and predicted that highly loaded Nb 2 O 5 / Al 2 O 3 would act as a stable Brønsted acid. In the present paper, we prepared a series of Nb 2 O 5 /Al 2 O 3 with various loading of Nb 2 O 5 and examined its unique acid property using a so-called Friedel-Crafts reaction of anisole and benzyl alcohol to be promoted on Brønsted acid [8][9][10][11][12][13][14].…”

Intercalation-induced Esterification over a Layered Transition Metal Oxide

“…Recently, the present authors found that a protonated layered transition metal oxide, HNbMoO 6 , functions as an efficient solid acid catalyst for several acid-catalyzed reactions [16,17]. Among the protonated layered transition metal oxides, HNbMoO 6 is unusual in that it intercalates several substrates such as alcohol and ketone.…”

“…In this case, the layered niobium molybdate exhibited activity comparable to that of the ion-exchange resins, achieving a turnover frequency of 15.1 h -1 . The acid amount of the layered HNbMoO 6 is estimated to be 1.9 mmol g -1 on the basis of 31 P magic angle spinning (MAS) nuclear magnetic resonance (NMR) spectroscopy using trimethylphosphine oxide as a probe molecule [16]. The activity of HNbMoO 6 was also compared with H-beta zeolite and sulfated zirconia.…”

Ultrasound assisted synthesis of Cs2.5H0.5PW12O40: An efficient nano-catalyst for preparation of β-amino ketones via aza-Michael addition reactions

“…The HPAs-based catalysts, with the strong Brønsted and Lewis acid nature, have many advantages over the other catalysts [19][20][21][22]. For example, Keggin-type HPAs are wellknown [23][24][25][26][27][28] which among them Cs 2.5 H 0.5 PW 12 O 40 (CsPW) with a high specific surface acidity has been applied as an effective acid catalyst [29].…”