Support structure and reduction treatment effects on CO oxidation of SiO2 nanospheres and CeO2 nanorods supported ruthenium catalysts

CeO2 nanorods supported CuOx-RuOx bimetallic catalysts for low temperature CO oxidation

Bimetallic catalysts often outperform monometallic catalysts due to changeable structural orientation, synergistic effects, and integration of two different metal or metal oxide properties. Here, a series of CeO2 nanorods (NR) supported bimetallic CuOx and RuOx catalysts (Cu: Ru ratios of 9:1, 7:3, and 5:5) were prepared using a wet impregnation method. In situ DRIFTS, H2 temperature programmed reduction (H2-TPR), CO temperature programmed desorption (CO-TPD), and other characterization techniques were used to investigate the effect of the Cu:Ru ratio on the activity of low-temperature CO oxidation. Among three catalysts, CeO2 NR supported 7 wt% Cu-3 wt% Ru catalyst after a reduction activation treatment showed the best performance with 100 % CO conversion at 166 °C and the lowest activation energy of 18.37 kJ mol-1. Raman and XPS profiles revealed that the origin of the superior performance is at least partially related to the high surface oxygen vacancy concentration and other distinct oxygen species (physi-/chemi-sorbed oxygen and bulk lattice oxygen), leading to outstanding adsorption and oxidation property of CO.

Effects of chemical etching and reduction activation of CeO2 nanorods supported ruthenium catalysts on CO oxidation

In this work, pristine and NaBH₄ etched CeO₂ nanorods supported ruthenium (Ru) catalysts were synthesized and employed to investigate the effects of chemical etching and reduction activation treatment on CO oxidation. With 1 wt% Ru loading, the CeO₂ nanorods supported catalyst samples, after 6 wt% NaBH₄ etching treatment, showed significantly promoted H₂ consumption under 100 °C and low apparent activation energy (i.e., E_a ∼ 31.2 kJ/mol) for CO oxidation. In-situ CO-DRIFTS profiles revealed that, for the reduced sample, the observed CO adsorption at ∼ 2020 cm^-1 at 40 °C may be related to a strong RuO_x-CeO₂ interaction induced by the NaBH₄ etching treatment, which was supported by the oxygen vacancy analysis results of X-ray photoelectron spectroscopy and CO-temperature programmed desorption. The enriched surface defects on CeO₂ support due to the chemical etching and reduction treatments are believed to promote the interaction between RuO_x species and CeO₂, which is responsible for the enhanced activity of CO oxidation.

The Study on the Active Site Regulated RuOx/Sn0.2Ti0.8O2 Catalysts with Different Ru Precursors for the Catalytic Oxidation of Dichloromethane

Chlorine-containing volatile organic compounds (CVOCs) present in industrial exhaust gas can cause great harm to the human body and the environment. In order to further study the catalytic oxidation of CVOCs, an active site regulated RuOx/Sn0.2Ti0.8O2 catalyst with different Ru precursors was developed. With Dichloromethane as the model molecule, the activity test results showed that the optimization of Ru precursor using Ru colloid significantly increased the activity of the catalyst (T90 was reduced by about 90 °C when the Ru loading was 1 wt%). The analysis of characterization results showed that the improvement of the catalytic performance was mainly due to the improvement of the active species dispersion (the size of Ru cluster was reduced from 3–4 nm to about 1.3 nm) and the enhancement of the interaction between the active species and the support. The utilization efficiency of the active components was improved by nearly doubling TOF value, and the overall oxidation performance of the catalyst was also enhanced. The relationship between the Ru loading and the catalytic activity of the catalyst was also studied to better determine the optimal Ru loading. It could be found that with the increase in Ru loading, the dispersibility of RuOx species on the catalyst surface gradually decreased, despite the increase in their total amount. The combined influence of these two effects led to little change in the catalytic activity of the catalyst at first, and then a significant increase. Therefore, this research is meaningful for the efficient treatment of CVOCs and further reducing the content of active components in the catalysts.

Ru-containing magnetic yolk-shell structured nanocomposite: a powerful, recoverable and highly durable nanocatalyst

A novel method was used to prepare a magnetic phenylene-based periodic mesoporous organosilica nanocomposite with yolk-shell structure (Fe3O4@YSPMO). The Fe3O4@YSPMO nanomaterial was prepared by using easily accessible pluronic-P123 and cetyltrimethylammonium bromide (CTAB) surfactants under basic conditions. This material was employed for effective immobilization of potassium perruthenate to prepare an Fe3O4@YSPMO@Ru nanocatalyst for the aerobic oxidation of alcohols. The physiochemical properties of the designed Fe3O4@YSPMO@Ru nanocomposite were studied using PXRD, FT-IR, TGA, SEM, TEM, ICP, VSM and XPS analyses. Fe3O4@YSPMO@Ru was effectively employed as a highly recoverable nanocatalyst in the selective aerobic oxidation of alcohols.

Photocatalysis for Organic Wastewater Treatment: From the Basis to Current Challenges for Society

Organic pollutants such as dyes, antibiotics, analgesics, herbicides, pesticides, and stimulants become major sources of water pollution. Several treatments such as absorptions, coagulation, filtration, and oxidations were introduced and experimentally carried out to overcome these problems. Nowadays, an advanced technique by photocatalytic degradation attracts the attention of most researchers due to its interesting and promising mechanism that allows spontaneous and non-spontaneous reactions as they utilized light energy to initiate the reaction. However, only a few numbers of photocatalysts reported were able to completely degrade organic pollutants. In the past decade, the number of preparation techniques of photocatalyst such as doping, morphology manipulation, metal loading, and coupling heterojunction were studied and tested. Thus, in this paper, we reviewed details on the fundamentals, common photocatalyst preparation for coupling heterojunction, morphological effect, and photocatalyst’s characterization techniques. The important variables such as catalyst dosage, pH, and initial concentration of sample pollution, irradiation time by light, temperature system, durability, and stability of the catalyst that potentially affect the efficiency of the process were also discussed. Overall, this paper offers an in-depth perspective of photocatalytic degradation of sample pollutions and its future direction.

CeO2 immobilized on magnetic core-shell microparticles for one-pot synthesis of imines from benzyl alcohols and anilines: Support effects for activity and stability

Four types of core-shell materials with magnetic Fe₃O₄ microparticles as the core were prepared through different approaches using dopamine, glucose, tetrabutyl orthotitanate (TBOT), and tetraethyl orthosilicate (TEOS) as the shell precursor, respectively. CeO₂ nanoparticles (NPs) was successfully immobilized onto these supports to fabricate efficient catalysts for the tandem catalytic synthesis of imines from benzyl alcohols and anilines at low temperature under air atmosphere. The as-prepared catalysts were detailedly characterized by TEM, EDX, XRD, FT-IR, XPS VSM, ICP, and CO₂-TPD. Interestingly, these prepared catalysts showed higher catalytic activity than reported CeO₂ catalysts. Most attractively, the catalyst with a shell ofnitrogen-doped-carbon derived from dopamine exhibited the best catalytic property, and outstanding stability and recyclability in the cycle experiment. According to the XPS and CO₂-TPD characterization, the enhanced performance of Fe₃O₄@CN@CeO₂ composites can be attributed to two reasons as follows: (1) the immobilization of CeO₂ improved its alkalinity at low reaction temperature, and alkalinity is beneficial to promote the oxidation of alcohols to benzaldehyde, which is the rate-determining step for this tandem reaction; (2) the doped nitrogen generated Lewis basic site could satisfactorily stabilize Ce³⁺/Ce⁴⁺ pair of CeO₂, which determined the catalytic activity and stability of CeO₂ based catalysts for this tandem reaction. Moreover, the prepared catalysts could be facilely recovered from the reaction mixture with an external magnet. This work may provide a useful strategy for constructing CeO₂ based catalysts for green and sustainable catalysis.