Mesoporous Ce–Zr mixed oxides for selective oxidation of styrene in liquid phase

Abstract

This work reports the synthesis of mesoporous Ce1-x-ZrxO2-δ (x = 0.5 and 0.8) mixed oxides with distinct Ce/Zr mole ratio by inverse micelle template method and their catalytic exploration for epoxidation of styrene in isopropanol solvent using TBHP as the oxidant. Among various catalysts investigated, the Ce0.8Zr0.2O2 combination catalyst exhibited best catalytic activity with ~ 98% conversion and ~ 90% selectivity to styrene epoxide. The synthesized Ce–Zr mixed oxide catalysts were characterized by various state-of-the-art techniques. Characterization studies revealed that Ce/Zr mole ratio has an imperative influence on the physicochemical properties such as surface area, oxygen vacancy concentration, and redox nature. Interestingly, catalytic efficiency was significantly improved with the increase of Ce and decrease of Zr content in the Ce–Zr mixed oxides. Catalytic efficiency and distribution of the products for styrene oxidation under various conditions such as reaction time, solvent, temperature, and styrene to TBHP mole ratio were also evaluated. Reusability of the highly active Ce0.8Zr0.2O2 mixed oxide catalyst was also demonstrated.

Mesoporous ceria-supported vanadia catalysts for selective aerobic oxidation of ethylbenzene

“…The V 2 O 5 sample displays characteristic Raman peaks at 1000, 708, 488, 411, 290, and 151 cm À1 . 35 The contents of Ce and V elements of the synthesized catalysts were analyzed by ICP-OES analysis, as shown in Table 2. The obtained results are close to calculated metal ratio in the preparation of catalysts.…”

“…The powder was washed with absolute ethanol, centrifuged, and dried in an electrical oven overnight at 120 °C. Finally, the synthesized compound was subjected to calcination cycles at different temperatures in an air atmosphere of 150 °C for 12 h, 250 °C for 6 h, 350 °C for 4 h, 450 °C for 2 h, and 550 °C for 1 h. 35…”

“…The powder was washed with absolute ethanol, centrifuged, and dried in an electrical oven overnight at 120 1C. Finally, the synthesized compound was subjected to calcination cycles at different temperatures in an air atmosphere of 150 1C for 12 h, 250 1C for 6 h, 350 1C for 4 h, 450 1C for 2 h, and 550 1C for 1 h. 35 Catalysts with different wt% of vanadia on ceria (3, 6, and 10%) were prepared by impregnating the ceria support with ammonium metavanadate aqueous solution, which was prepared by dissolving the required quantity of the metal precursor (NH 4 VO 3 ) in aqueous solution of oxalic acid (1/2 molar ratio of NH 4 VO 3 /H 2 C 2 O 4 ). This mixture was stirred at room temperature for 6 h, dried at 120 1C with continuous stirring, and kept the sample in an oven at 120 1C for 12 h. The resultant solid compound was finely ground and calcined at 550 1C for 5 h. The prepared catalysts with different wt% of vanadia on ceria (3, 6, and 10 wt%), pristine ceria, and vanadia were denoted as CV3, CV6, CV10, CeO 2 , and V 2 O 5 , respectively.…”

Selective oxidation of styrene over nanostructured cerium–bismuth mixed oxide catalysts

“…The TPR profile of ceria shows two major peaks, the peak at lower temperatures (∼522.4 °C) is related to surface-capping oxygen reduction and the peak at higher temperatures (∼786.8 °C) is due to bulk ceria reduction. 25,27 It is observed that the TPR peaks of bismuth-doped ceria are shifted to lower temperature regions compared to those of pure CeO 2 . This observation indicates the change in the redox properties of ceria after doping with bismuth in ceria.…”

“…Previously a variety of transition metal (like Mn, Co, Fe, and Zr)-doped catalysts were developed for various oxidation reactions involving soot, 24 hydrocarbons, 25 alcohols, 26 etc. In our recent study, a mesoporous Ce-Zr mixed oxide 27 catalyst exhibited 98% conversion and 90% styrene epoxide selectivity with TBHP as the oxidant.…”