Zr‐TUD‐1: A Lewis Acidic, Three‐Dimensional, Mesoporous, Zirconium‐Containing Catalyst

Abstract

A three-dimensional, mesoporous, silicate containing zirconium, Zr-TUD-1, was synthesized by a direct hydrothermal treatment method with triethanolamine as a complexing and templating reagent to ensure that zirconium was incorporated as isolated atoms. The mesoporosity of Zr-TUD-1 was confirmed by X-ray diffraction (XRD), N(2) sorption and high-resolution transmission electron micrograph (HR-TEM) studies. The nature and strength of the Lewis acid sites present in Zr-TUD-1 were evaluated by FTIR studies of pyridine adsorption and temperature-programmed desorption of ammonia. FTIR, X-ray photoelectron spectroscopic (XPS) and UV/Vis spectroscopic studies showed that, at Si/Zr ratios of 25 and higher, all the zirconium was tetrahedrally incorporated into the mesoporous framework, while at low Si/Zr ratios, a small part of the zirconium was present as ZrO(2) nanoparticles. Zr-TUD-1 is a Lewis acidic, stable and recyclable catalyst for the Meerwein-Ponndorf-Verley (MPV) reaction and for the Prins reaction.

Potential applications of Zr-KIT-5: Hantzsch reaction, Meerwein–Ponndorf–Verley (MPV) reduction of 4-tert-butylcyclohexanone, and Prins reaction of citronellal

“…2), increasing with the amount of incorporated Zr. These results were obtained with industrial grade citronellal containing around 5 % isopulegol which is known to inhibit the reaction, thus higher activities can be expected starting from optically pure citronellal [2]. These results are quite similar to those reported with Zr-TUD-1 catalysts [2] and far higher than those reported with other zeolite catalysts [20].…”

“…For the Prins cyclisation of citronellal, the following general protocol was applied (method reported earlier [2,17]). In a Schlenk flask of 50 mL (placed in an oven at 70°C overnight), 50 mg of catalyst (activated in an oven overnight at 100°C) were introduced.…”

“…For the Meerwein-Ponndorf-Verley reduction of 4-tert-butylcyclohexanone, the following general protocol was applied (method reported earlier [2,17]). In a Schlenk flask of 50 mL (placed in an oven at 70°C overnight), 50 mg of catalyst (freshly calcined) was introduced followed by 2 mmol of 4-tert-butylcyclohexanone (308.5 mg).…”

“…Zirconium-containing mesoporous silica composites have been investigated as solid acid catalysts based on the presence of Lewis acid sites created by Zr 4? incorporation in the framework and the large surface area, pore volume, and uniform pore size distribution [1][2][3][4]. Since the discovery of mesoporous silicates such as MCM-41 and SBA-15, two-and three-dimensional mesostructured silica materials containing Zr have been synthesized including Zr-MCM-41 [5,6], Zr-MCM-48 [7,8], Zr-SBA-15 [1,3,9], and Zr-SBA-16 [10].…”

Zr-SBA-15 Lewis Acid Catalyst: Activity in Meerwein Ponndorf Verley Reduction

“…Within this context, the incorporation of zirconium species onto mesoporous supports, most of them silicas, has revealed to be an excellent alternative to both hydrous zirconia and zirconium-functionalized zeolites. Thus, zirconium species have been incorporated onto the surface of several mesoporous silicas like MCM-41 [20,21], SBA 15 [22] and TUD-1 [23,24]. These materials display an open porous structure with pore sizes in the range of mesopores, which facilitates the diffusion of bulk molecules inside the material, minimizing mass transfer hindrances.…”