Catalysts For Catalytic Oxidation Research Articles

Synthetic Pt-Fe(OH) x catalysts by one-pot method for CO catalytic oxidation.

Catalytic oxidation is used to control carbon monoxide (CO) emissions from industrial exhaust. In this work, The prepared Pta-Fe(OH) x catalysts (x represents the mass fraction of Pt loading (%), a = 0.5, 1 and 2) by the one-pot reduction method exhibited excellent CO catalytic activity, with the Pt2-Fe(OH) x catalyst, 70% and ∼100% CO conversion was achieved at 30°C and 60°C, respectively. In addition, the Pt2-Fe(OH) x catalyst also showed excellent H2O resistance and hydrothermal stability in comparison to the Pt2/Fe(OH) x catalyst prepared by impregnation method. Characterization results showed that the excellent catalytic performance of the catalysts was mainly attributed to the abundant surface oxygen species and Pt0 the presence of H2O, which promoted the catalytic reaction of CO, and Density functional theory (DFT) calculation showed that this was mainly attributed to the catalytic activity of the hydroxyl (-OH) species on Pt2-Fe(OH) x surface, which could easily oxidize CO to -COOH, which could be further decomposed into CO2 and H atoms. This study provides valuable insights into the design of high-efficiency non-precious metal catalysts for CO catalytic oxidation catalysts with high efficiency.

Research progress of molecular sieve supported catalysts in catalytic oxidation of chlorine-containing volatile organic compounds

Chlorinated Volatile Organic Compounds (CVOCs) come from a wide range of sources and are common precursors of PM2.5 and ozone pollution, which pose a serious threat to the environment and have adverse effects on human health. Catalytic degradation is one of the effective methods to solve CVOCs pollution, which has the advantages of low operating temperature, less chlorine-containing by-products and high degradation efficiency. The core of this technology is to design and develop catalyst materials with excellent stability and catalytic performance. At present, molecular sieve catalysts have attracted extensive attention because of their acidity and unique pore structure. In this paper, the current research status of catalysts supported by molecular sieve, such as noble metals, transition metal oxides and perovskites, and their activity, acidity, stability and selectivity in CVOCs catalytic reactions were summarized and analyzed, and the future development direction of CVOCs molecular sieve supported catalysts was prospected.

Challenges and opportunities for zeolite-based catalysts in catalytic oxidation of volatile organic compounds

Challenges and opportunities for zeolite-based catalysts in catalytic oxidations of volatile organic compounds (VOCs), which have emerged as highly promising materials for the elimination of VOCs due to their unique features.

Sulfur resistance mechanism of PdSx catalysts in catalytic oxidation of toluene

A series of catalysts were prepared by gas-phase sulfidation. The mechanism of catalytic oxidation of VOCs is the MVK mechanism.

Effects of support for cobalt catalysts in catalytic oxidation of toluene

Effects of support for cobalt catalysts in catalytic oxidation of toluene

Insights into SnO2 Nanoparticles Supported on Fibrous Mesoporous Silica for CO Catalytic Oxidation

A large surface area dendritic mesoporous silica material (KCC-1) was successfully synthesized and used as a support to confine SnO2 nanoparticles (NPs). Owing to the large specific surface area and abundant mesoporous structure of dendritic KCC-1, the SnO2 NPs were highly dispersed, resulting in significantly improved CO catalytic oxidation activity. The obtained Snx/KCC-1 catalysts (x represents the mass fraction of SnO2 loading) exhibited excellent CO catalytic activity, with the Sn7@KCC-1 catalyst achieving 90% CO conversion at about 175 °C. The SnO2 NPs on the KCC-1 surface in a highly dispersed amorphous form, as well as the excellent interaction between SnO2 NPs and KCC-1, positively contributed to the catalytic removal process of CO on the catalyst surface. The CO catalytic removal pathway was established through a combination of in situ diffuse reflectance infrared transform spectroscopy and density-functional theory calculations, revealing the sequential steps: ① CO → CO32−ads, ② CO32−ads → CO2free+SnOx−1, ③ SnOx−1+O2 → SnOx+1. This study provides valuable insights into the design of high-efficiency non-precious metal catalysts for CO catalytic oxidation catalysts with high efficiency.

Crystal Engineering of TiO2 for Enhanced Catalytic Oxidation of 1,2-Dichloroethane on a Pt/TiO2 Catalyst.

Crystal engineering of metal oxide supports represents an emerging strategy to improve the catalytic performance of noble metal catalysts in catalytic oxidation of chlorinated volatile organic compounds (CVOCs). Herein, Pt catalysts on a TiO2 support with different crystal phases (rutile, anatase, and mixed phase (P25)) were prepared for catalytic oxidation of 1,2-dichloroethane (DCE). The Pt catalyst on P25-TiO2 (Pt/TiO2-P) showed optimal activity, selectivity, and stability, even under high-space velocity and humidity conditions. Due to the strong interaction between Pt and P25-TiO2 originating from the more lattice defects of TiO2, the Pt/TiO2-P catalyst possessed stable Pt0 and Pt2+ species during DCE oxidation and superior redox property, resulting in high activity and stability. Furthermore, the Pt/TiO2-P catalyst possessed abundant hydroxyl groups, which prompted the removal of chlorine species in the form of HCl and significantly decreased the selectivity of vinyl chloride (VC) as the main byproduct. On the other hand, the Pt/TiO2-P catalyst exhibited a different reaction path, in which the hydroxyl groups on its surface activated DCE to form VC and enolic species, besides the lattice oxygen of TiO2 for the Pt catalysts on rutile and anatase TiO2. This work provides guidance for the rational design of catalysts for CVOCs.

High catalytic performance of neodymium modified Co3O4 for toluene oxidation

Co-based catalysts are the most promising catalysts in catalytic oxidation of volatile organic compounds (VOCs). Precious metal doping is adopted to improve the catalytic activity of toluene on Co3O4 catalysts, but greatly increases its cost along with it. It is found that doping a small amount of rare earth (Ce, Pr, Sm and Nd) can dramatically promote the catalytic activity of Co3O4. Especially, the Nd-doped Co3O4 catalyst exhibits excellent catalytic activity with a toluene removal rate of 90% at 162.1 °C, which is even better than that of Pt-doped Co3O4. Compared with other rare earth metal doping, the Nd doping leads to a higher ratio of Co3+/Co2+ and has more oxygen vacancies. The in situ diffuse reflectance infrared Fourier transform spectroscopy (DRIFTS) experiments show that the lattice oxygen of Nd–Co sample can be utilized at a quite low temperature, while that of pure Co3O4 cannot engage in oxidation reaction when the temperature is below 200 °C, which visually demonstrates the main reason for the improved catalytic performance of Nd–Co catalyst.

Site-Selective Nitrogen-Doped α-MnO2 for Catalytic Oxidation of Carcinogenic HCHO in Indoor Air

Developing high-efficiency formaldehyde (HCHO) catalytic oxidation catalysts is of significance and practicability for indoor air decontamination. It is generally considered that anionic doping is a traditional strategy to regulate the reaction activity of catalyst materials. However, one of the concerns worth exploring is the recognition of doping sites and their impact on catalytic performance. Herein, nitrogen atoms are successfully introduced into the MnO2 structure by high-temperature calcination with urea as the nitrogen source for the first time. By regulating the usage of urea, nitrogen atoms are selectively and successfully doped into the interstitial sites and substitutional sites. Furthermore, the effect of nitrogen-doped MnO2 on the catalytic oxidation of HCHO is studied in detail. Results indicate that nitrogen doping can promote the formation of oxygen vacancies, strengthen the activation of adsorbed O2, and enhance the adsorption of HCHO, which is conducive to catalytic decomposition of HCHO. Importantly, nitrogen doping at various doping sites has a considerable effect on catalytic decomposition activity. Although both interstitial and substitutional nitrogen doping can boost the decomposition performance of HCHO, the interstitial sites are the most suitable doping sites in the α-MnO2 lattice. The chemical environment around the interstitial sites is favorable for the creation of oxygen vacancies, as well as the adsorption/activation of HCHO and O2. Interstitial nitrogen doping can dramatically increase the HCHO catalytic activity of α-MnO2, and the complete catalytic decomposition temperature is reduced from 130 to 90 °C at the condition of GHSV = 90 L/gcat·h. This study provides a facile and effective method for site-selective nitrogen-doping and an in-depth understanding of its effect on catalytic activity.

Performance and poisoning analysis of organic sulfur resistance of Pd-Ce catalyst in catalytic oxidation of VOCs

In this paper, the effect of organic sulfur on the catalytic oxidation of toluene was explored. It was found that the low concentration of organic sulfur could cause rapid deactivation of the catalyst, and the activity of the catalyst could be restored to 100% after stopping the application of sulfur. The sulfation modification could significantly improve the organic sulfur resistance of the catalyst by changing the support and the sulfation modification of the support. There was a large amount of carbon deposition and a small amount of S-containing substances on the catalyst surface after the introduction of organic sulfur through the methods of TG, BET, FTIR, SEM (Mapping) and XPS. Then, through in-situ DRIFT and CH3SH-TPD, it was found that sulfation modification could inhibit the adsorption of organic sulfur on the catalyst surface and reduce the competitive adsorption. The decrease of catalyst efficiency due to the presence of organic sulfur in the reaction gas during VOCs catalytic oxidation is mainly due to the competitive adsorption of organic sulfur and VOCs molecules, and the temperature of VOCs catalytic oxidation of organic sulfur. Some polyhydrocarbons, ethyl sulfide, dimethyl sulfoxide and other substances were produced by incomplete oxidation, which covered the surface of the catalyst due to adsorption or deposition, resulting in catalyst poisoning.

Cobalt-doped alumina catalysts in catalytic oxidation of tartrazine induced by Oxone®

Porous cobalt-doped alumina catalysts were synthetized using the sol-gel method. The synthesized materials were calcined at 500 °C, 1000 °C and 1100 °C and denoted as CoA-500, CoA-1000 and CoA-1100, respectively. Catalysts were characterized using XRPD, H2-TPR and low temperature N2 physisorption techniques. Applied techniques showed that the annealing temperature affects the structural and textural properties of the catalysts. The synthesized catalysts were investigated in the degradation of tartrazine in the presence of Oxone®. The influence of the mass of catalyst, reaction time, reaction temperature and initial pH were investigated. The temperature increase was beneficial for the dye degradation rate. CoA-500 was proved to be the most efficient among the investigated catalysts. The reaction followed the pseudo-first order kinetics for all investigated temperatures for all three catalysts. All cobalt-doped alumina catalysts were found to be efficient in the Oxone® induced catalytic degradation of tartrazine with CoA-500 showing the best performance.

Co(II) impregnated Al(III)-pillared montmorillonite–Synthesis, characterization and catalytic properties in Oxone® activation for dye degradation

Aluminum pillared clay was synthesized and impregnated with Co2+ (CoAP), using incipient wetness impregnation method. The obtained CoAP was characterized by chemical analysis, XRPD, SEM with EDS, XPS and low temperature N2 physisorption. By these methods the incorporation of Co2+ was confirmed in both micro and mesoporous region. The synthesized material was investigated as a catalyst in catalytic oxidation of organic water pollutants – dyes – in the presence of Oxone® (peroxymonosulfate). Oxone® is a precursor of sulfate radicals. Tartrazine was chosen as a model dye pollutant. The influence of the mass of the catalyst, temperature and initial pH was investigated. Temperature increase was beneficial for dye degradation rate. The reaction rate was the highest for initial pH values around those corresponding to neutral conditions, somewhat slower for pH < 4 values, while for pH > 10 decolorization was significantly less expressed. Along with decolorization of tartrazine solution the formation and degradation of tartrazine catalytic oxidation products were monitored using UV–Vis spectroscopy. CoAP was found to be efficient catalyst in Oxone® induced catalytic degradation of both tartrazine and detected products of its degradation.

Enhanced CH4 and CO Oxidation over Ce1- xFe xO2-δ Hybrid Catalysts by Tuning the Lattice Distortion and the State of Surface Iron Species.

CeO2-Fe2O3 mixed oxides are very attractive as catalysts for catalytic oxidation. Herein, we report the structural dependence of the Ce1- xFe xO2-δ catalysts for CH4 combustion and CO oxidation via changing lattice distortion degrees, surface Fe2O3 states, and oxygen vacancy concentrations. The lattice distortion degree and oxygen vacancy concentration of Ce-Fe-O solid solution can be tuned by changing the contents of Fe and the precipitation temperatures in the preparation process. The precipitation at relatively high temperature (70 °C) promotes the lattice distortion, whereas a lower temperature (0 °C) helps the formation of surface oxygen vacancies. The in situ diffuse reflectance infrared/Raman experiments and the physicochemical characterization suggest that both the CO and CH4 oxidations mainly follow a Mars-van Krevelen mechanism. Both the lattice distortion and the surface iron species play a crucial role in determining the catalytic activity by affecting the redox property of the catalysts. The surface iron species, combined with the oxygen vacancies, improve the catalytic performance by enhancing the adsorption capacity of reactants and reducibility of catalysts. The lattice distortion of CeO2 contributes to the catalytic activity by tuning the oxygen mobility in the bulk, which promotes the re-oxidation rate of catalysts.

Adsorption characteristics of Co-anchored different graphene substrates toward O2 and NO molecules

The adsorption characteristics of O2 and NO on Co-anchored different graphene-based substrates (single vacancy, double vacancy and N atoms doped) have been investigated using density functional theory. The geometric stability of the single atom catalysts, adsorption configurations of gas molecules, adsorption energies, electronic structure and thermodynamic analysis have been performed. Co/vacancy-graphene shows high thermodynamic stability through calculating and comparing the binding energy of Co-anchored single atom catalysts and the cohesive energy of Co bulk. For O2 adsorption, it prefers to form two chemical bonds with the Co atom, and electron transfer dominates the formation of the strong chemical ionic bonds. While on Co single and double vacancy graphene substrates, N atom in NO invariably bonds to the Co atom, with electron transfer and orbital hybridization dominating the process of bonding formation respectively, afterwards ionic and covalent bonds formed between gas molecule and the metal atom. Additionally, electro-negativity and partial d-band centre are good descriptors of adsorption energies and can well reveal the relationship of adsorption energy with adsorption activity and the electronic structure. Co/single vacancy-graphene substrate with three pyridine nitrogen atoms (Co/SV-N123) is a promising catalyst in catalytic oxidation of NO. The results can provide reference for the further study of the NO oxidation mechanism on the Co/GN surface as well as the new non-noble-metal catalysts design.

Synthesis of nanoV 3.6 Mo 2.4 O 16 and their catalytic activity in the selective oxidation of toluene

Molybdenum vanadate is a novel vanadate. It is a functional material with good magnetic, electrical and catalytic properties. However, it is rarely used in the selective catalytic oxidation field, while the transition metal molybdenum and vanadium are usually used as a catalytic oxidation catalyst, the complex oxide and salt are naturally concerned. The structure of high-quality single crystalline Molybdenum vanadate (V3 .6Mo2.4O16) nanorods was synthesised by sol–gel method and high-temperature solid-state reaction. The effects of vanadium and molybdenum molar ratio and calcination temperature on the preparation of V3.6Mo2.4O16 were studied. The structure of the catalyst was characterised by X-ray diffraction, thermogravimetry, X-ray photoelectron spectroscopy, scanning electron microscope and transmission electron microscope. The experimental results show that the molar ratio of vanadium–molybdenum is 10:7 when the precursor calcination temperature is 540°C, the single crystalline V3.6Mo2.4O16 nanorods with regular shape has been obtained, the diameter of about 200 nm and the length up to tens of micrometres and the surface is smooth. Catalytic oxidation of toluene to benzaldehyde is used as a probe reaction for nanoV3.6Mo2.4O16. The catalytic activity of the catalyst is good, the conversion of toluene is 39.8% and the selectivity of benzaldehyde is 70.1%.

Dft Study on the Co Catalytic Oxidation Reaction on Ptcu-Embedded Graphene

PtCu-embedded graphene (PtCu/graphene) is one of the high-efficiency catalysts in catalytic oxidation of CO. In this paper, CO catalytic oxidation on PtCu/graphene is studied by density functional theory. According to the calculation, the coadsorption configuration is more stable than the configuration of O2 or CO adsorption on PtCu/graphene. Thus, the reaction mechanism of catalytic CO oxidation is the LH mechanism, which proceeds via two steps with barrier energies of 0.21 eV and 0.52 eV, respectively. Compared with pure Pt/graphene and Cu/graphene, Pt mixed in Cu can lower the barrier energy, improving the catalytic activity. Therefore, the research of PtCu/graphene can provide a certain reference value and guidance for the study of another similar catalytic CO oxidation.

Novel cobalt nitride-induced oxygen activation on Pt-based catalyst for catalytic oxidation

Cobalt nitride as a new type of O2 activator was used to modify Pt-based catalyst for catalytic oxidation. The nitrided Co/Pt/γ-Al2O3 catalyst system was highly efficient for preferential CO oxidation in excess H2 at low temperatures, which was attributed to a noncompetitive dual-site reaction pathway.

Properties of Pd, Pt and Ru-Based Catalysts in Catalytic Oxidation of Methanol.

Catalytic oxidation of methanol was investigated using Pd, Pt and Ru-based catalysts. Experiment was conducted at reaction temperature of 100-220 degrees C with methanol concentration of 3000 ppm and gas hourly space velocity (GHSV) of 16,000 hr(-1). Catalysts were characterized by using Brunauer-Emmett-Teller (BET) method, X-ray diffraction (XRD), field transmission electron microscopy (FE-TEM) and temperature programmed reduction (TPR). Based on complete oxidation temperature of methanol, the activity order was: 0.16 wt% Pd /0.16 wt% Pt/0.16 wt% Ru/gamma-Al2O3 > 0.5 wt% Pt/gamma-Al2O3 > 0.5 wt% Ru/gamma-AlO3 > 0.5 wt% Pd/gamma-Al2O3. Therefore, the activity of ternary metal-based catalyst was superior to single metal-based catalyst.

ChemInform Abstract: Supported Catalysts Based on Layered Double Hydroxides for Catalytic Oxidation and Hydrogenation: General Functionality and Promising Application Prospects

AbstractReview: 220 refs.

Roles of Acid Sites on Pt/H-ZSM5 Catalyst in Catalytic Oxidation of Diesel soot

Pt/H-ZSM5 and Pt/Al2O3 with similar surface Pt particle sizes and chemical states were prepared by incipient wetness impregnation as catalysts for soot oxidation. Pt/H-ZSM5 exhibits obviously higher activities in both O2 and NO + O2 than Pt/Al2O3. On the basis of the results obtained with in situ DRIFT and other structural and surface property characterizations, the high catalytic activity of Pt/H-ZSM5 is currently attributed to two main factors. First, the acidic H-ZSM5 support inhibits NO2 adsorption on the catalyst, leading to a preferential adsorption of NO2 on the surface of soot and providing more chances for NO2–soot reactions. Second, the strong acid sites on the surface of Pt/H-ZSM5 can participate in the catalytic formation and decomposition of surface oxygenated complexes. Consequently, a high catalytic efficiency for soot oxidation is achieved on the Pt/H-ZSM5 catalyst.