Macroporous Monolithic Pt/γ-Al2O3 and K–Pt/γ-Al2O3 Catalysts Used for Preferential Oxidation of CO

Recent Advances in Regulating Ceramic Monolithic Catalyst Structure for Preferential Oxidation of CO in H2

Preferential oxidation of CO (CO-PROX) has tremendous significance in purifying hydrogen for fuel cells to avoid catalyst poisoning by CO molecules. Traditional powder catalysts face numerous challenges, including high pressure drop, aggregation tendency, hotspot formation, poor mass and heat transfer efficiency, and inadequate thermal stability. Accordingly, ceramic monolithic catalysts, known as their excellent thermal stability, high surface area, and superior mass and heat transfer characteristics, are gaining increasing research attention. This review examines recent studies on ceramic monolithic catalysts in CO-PROX, placing emphasis on the regulation of active sites (e.g., precious metals like Pt and Au, and non-precious metals like CuO and CeO2), monolith structures, and coating strategies. In addition, the structure-catalytic performance relationships, as well as the potential and limitations of different ceramic monolithic catalysts in practical application, are discussed. Finally, the challenges of monolithic catalysts and future research prospects in CO-PROX reactions are highlighted.

Effect of TiO2 Calcination Pretreatment on the Performance of Pt/TiO2 Catalyst for CO Oxidation

In order to improve the CO catalytic oxidation performance of a Pt/TiO₂ catalyst, a series of Pt/TiO₂ catalysts were prepared via an impregnation method in this study, and various characterization methods were used to explore the effect of TiO₂ calcination pretreatment on the CO catalytic oxidation performance of the catalysts. The results revealed that Pt/TiO₂ (700 °C) prepared by TiO₂ after calcination pretreatment at 700 °C exhibits a superior CO oxidation activity at low temperatures. After calcination pretreatment, the catalyst exhibited a suitable specific surface area and pore structure, which is beneficial to the diffusion of reactants and reaction products. At the same time, the proportion of adsorbed oxygen on the catalyst surface was increased, which promoted the oxidation of CO. After calcination pretreatment, the adsorption capacity of the catalyst for CO and CO₂ decreased, which was beneficial for the simultaneous inhibition of the CO self-poisoning of Pt sites. In addition, the Pt species exhibited a higher degree of dispersion and a smaller particle size, thereby increasing the CO oxidation activity of the Pt/TiO₂ (700 °C) catalyst.

A comparative study of ZnAl2O4 nanoparticles synthesized from different aluminum salts for use as fluorescence materials

Three ZnAl₂O₄ samples were prepared via a modified polyacrylamide gel method using a citric acid solution with different aluminum salt starting materials, including AlCl₃∙6H₂O, Al₂(SO₄)₃∙18H₂O, and Al(NO₃)₃∙9H₂O under identical conditions. The influence of different aluminum salts on the morphologies, phase purity, and optical and fluorescence properties of the as-prepared ZnAl₂O₄ nanoparticles were studied. The experimental results demonstrate that the phase purity, particle size, morphology, and optical and fluorescence properties of ZnAl₂O₄ nanoparticles can be manipulated by the use of different aluminum salts as starting materials. The energy bandgap (Eg) values of ZnAl₂O₄ nanoparticles increase with a decrease in particle size. The fluorescence spectra show that a major blue emission band around 400 nm and two weaker side bands located at 410 and 445 nm are observed when the excitation wavelength is 325 nm. The ZnAl₂O₄ nanoparticles prepared from Al(NO₃)₃∙9H₂O exhibit the largest emission intensity among the three ZnAl₂O₄ samples, followed in turn by the ZnAl₂O₄ nanoparticles prepared from Al₂(SO₄)₃∙18H₂O and AlCl₃∙6H₂O. These differences are attributed to combinational changes in Eg and the defect types of the ZnAl₂O₄ nanoparticles.

Sol-Gel Synthesis of Non-Silica Monolithic Materials

Monolithic materials have become very popular because of various applications, especially within chromatography and catalysis. Large surface areas and multimodal porosities are great advantages for these applications. New sol-gel preparation methods utilizing phase separation or nanocasting have opened the possibility for preparing materials of other oxides than silica. In this review, we present different synthesis methods for inorganic, non-silica monolithic materials. Some examples of application of the materials are also included.