Fe³⁺‐Exchanged Titanate Nanotubes: A New Kind of Highly Active Heterogeneous Catalyst for Friedel‐Crafts Type Benzylation

Abstract

Heterogeneous catalysis for Friedel-Crafts type benzylation has received much attention in recent years due to its characteristic of environmental benefits. In this paper, titanate nanotubes (TNTs) were employed as heterogeneous catalyst support, and a new kind of Fe3+-exchanged titanate nanotubes (Fe-TNTs) catalyst with highly dispersed ferric sites was constructed by an ion exchange technique. The obtained catalyst was systematically characterized by XRD, TEM, N2adsorption, XPS, and UV-vis spectra. As expected, Fe-TNTs showed excellent catalytic activities in the benzylation of benzene and benzene derivatives. The recycling tests for Fe-TNTs were also carried out, where the reason for the gradually decreased activity was carefully investigated. Superior to some reported catalysts, the catalytic ability of used Fe-TNTs could be easily recovered by ion exchange again, indicating that Fe-TNTs herein were a highly active and durable heterogeneous catalyst for Friedel-Crafts type benzylation. These results might be helpful for the design and preparation of novel heterogeneous catalysts by combining the structural advantages of titanate nanotubes and active metal ions.

Co2+-Exchanged Titanate Nanotubes as a Novel Heterogeneous Catalyst for Peroxymonosulfate Activation and Degradation of Organic Pollutants

“…Meanwhile, hydroxyl radicals will be inevitably introduced into the catalytic system, particularly under alkaline condition, they can also contribute to the oxidation process greatly. However, the pK a of PMS, namely the second pK a of H 2 SO 5 , is about 9.4, and thus strong alkaline condition can induce PMS to deprotonate and transform into less oxidative SO 5 2-, which should be responsible for the sharp decrease in degradation efficiency [11]. The recycling tests are carried out to investigate the catalytic stability of Co-TNTs (Fig.…”

“…TNTs were synthesized by a modified hydrothermal method [11]. Briefly, 1.5 g of anatase TiO 2 powder was dispersed into 50 mL of NaOH aqueous solution (10 M) under magnetic stirring for 1 h. The suspension was transferred into a Teflon-lined autoclave, sealed and hydrothermally treated at 150 °C for 16 h. The white powder was re-dispersed into excessive 0.1 M HCl solution to neutralize the residual NaOH.…”

“…It is worth noting that the unique ion-exchange ability of TNTs opens up a simple avenue for the location of various isolated metal ions, so that the resultant products may promise highly catalytic activity in many reactions. For example, Tang et al found that the incorporation of metal ions was able to extend the light absorption of TNTs to the visible-light region, thus making TNTs exhibit the visible-light photoactivity toward selective oxidation of alcohols [10]; our group previously prepared Fe 3+ -exchanged TNTs by ion-exchange method, and the obtained Fe-TNTs showed considerable activity in Friedel-Crafts type benzylation [11]. Following this direction, we reported herein the preparation of Co 2+ -exchanged TNTs and its catalytic performance in PMS oxidation of Rhodamine B (RhB) for the first time.…”