Catalytic Oxidation Of Propylene Research Articles

Boosting catalytic oxidation of propane over CeO2-supported Co3O4 catalyst with strong interfacial interaction and electron transfer

Tuning the nanoparticle-support interaction can optimize the catalytic performance of supported metal oxide catalysts for VOCs removal. Herein, a series of Co3O4/CeO2 catalysts with different strengths of interfacial interaction and electron transfer were successfully constructed via various modified wetness impregnation procedures. With the introduction of ammonium hydroxide, citric acid or H2 pretreatment, a stronger interfacial interaction and electron transfer were achieved due to the highly Co3O4 dispersion and CeO2 surface reconstruction. The modified-synthesis Co3O4/CeO2 catalysts, particularly Co3O4/CeO2-CA (citric acid), demonstrated superior catalytic activity (T90 = 296 °C, TOF = 0.337 × 10−3 s−1) and stability for propane oxidation as compared to typical wetness impregnation Co3O4/CeO2-DI (T90 = 314 °C, TOF = 0.121 × 10−3 s−1). Through systematic characterizations and DFT calculation, the strong interfacial interaction and abundant reactive oxygen species facilitate the adsorption and activation of C3H8 and O2 on the catalyst surface, which further promote the intermediates (carbonate/carboxyl species) transformation. These findings highlight interfacial mechanism to catalytic performance optimization of supported metal oxides.

Catalytic oxidation of propane over nanorod-like TiO2 supported Ru catalysts: Structure-activity dependence and mechanistic insights

Nanorod-like titanium dioxide (TiO2-Rod) supported ruthenium catalysts with variable metal loadings (designated as x-Ru/TiO2-Rod, x = 0.1, 0.5, 1.0 and 1.5 wt.%) were prepared for the catalytic oxidation of propane. The unique nanorod-like structure and high specific surface area of TiO2-Rod support was favorable for the surface distribution of ruthenium nanoparticles, constructing highly active redox sites for propane oxidation. Light-off experimental results indicated that the x-Ru/TiO2-Rod catalysts exhibited diverse catalytic activities for propane oxidation, giving a volcanic sequence of 0.1-Ru/TiO2-Rod < 0.5-Ru/TiO2-Rod < 1.5-Ru/TiO2-Rod < 1.0-Ru/TiO2-Rod with the increasing ruthenium content. Additionally, the optimal 1.0-Ru/TiO2-Rod delivered adequate catalytic stability and CO2/water resistant ability under complex industrial conditions. Characterization results revealed that the metallic Ru0 and the surface lattice oxygen species from the Ru-TiO2 interface were demonstrated to be the catalytic active components, which played an essential role in the reaction. In situ DRIFTs analysis verified the formation of acetate, acetone and formate species as the predominant organic intermediates in propane oxidation, which may result from two plausible reaction pathways depending on the activation of terminal methyl group (–CH3) and the central methylene (CH2) group in propane molecule. This work provides fundamental guidance for the development of Ru-based catalysts and the reaction mechanism understanding for light alkanes oxidation.

Engineering Mn–O strength in manganese oxide catalyst to enhance propane catalytic oxidation

Developing highly active and thermally stable transition-metal-oxide catalysts for light alkane catalytic oxidation is of great importance but very challenging. In the work, the catalytic performance for propane deep oxidation was significantly enhanced on the Mn1NixOy solid solution catalyst by weakening the Mn–O bond strength of manganese oxide. The characterization results combined with DFT calculations demonstrated that the introduction of Ni could create additional defect sites, resulting in a significant improvement of the adsorption and the activation of both propane and oxygen molecules. The optimal Mn1Ni0.15Oy catalyst exhibits abundant oxygen vacancies with low MnO bond strength, high redox ability and oxygen mobility, which account for its superior activity. Specifically, the specific reaction rate on Mn1Ni0.15Oy is three times higher than that on pure Mn2O3. Moreover, a Mn1Ni0.15Oy/cordierite monolithic catalyst was made by wash-coating method, and exhibited remarkable catalytic performance and stability on catalytic oxidation of propane during the 45 days (1080 h) on stream, even after tens of high temperature thermal shocks (up to 650 ℃), which declared to be satisfied for practical industrial applications. This work will shed light on designing high-efficiency and long-life environmental catalyst for VOCs elimination.

Highly active Ru/TiO2 nanostructures for total catalytic oxidation of propane.

Ruthenium is a robust catalyst for a variety of applications in environmental heterogeneous catalysis. The catalytic performance of Ru/TiO2 materials, synthesized by using the deposition precipitation with urea method, was assessed in the catalytic oxidation of C3H8, varying the ruthenium loading. The highest catalytic reactivity was obtained for a Ru loading of 2 wt. % in comparison with the 1, 1.5, 3, and 4 wt. % Ru catalysts. The physicochemical properties of the synthesized materials were investigated by XRD, N2 adsorption, TEM, FT-IR pyridine, H2-TPR, and XPS. The size of ruthenium particles was found to be greatly dependent on the pretreatment gas (air or hydrogen) and the catalytic activity was enhanced by the small-size ruthenium metal nanoparticles, leading to changes in the reduction degree of ruthenium, which also increased the Brönsted and Lewis acidity. Metal to support charge transfer enhanced the reactant adsorption sites while oxygen vacancies on the interface enabled the dissociation of O2 molecules as revealed through DFT calculations. The outstanding catalytic activity of the 2Ru/TiO2 catalysts allowed to convert C3H8 into CO2 at reaction temperatures of about 100°C. This high activity may be attributed to the metal/support interaction between Ru and TiO2, which promoted the reducibility of Ti4+/Ti3+ and Ru4+/Ru0 species, and to the fast migration of TiO2 lattice oxygen in the catalyst. Furthermore, the Ru/TiO2 catalyst exhibited high stability and reusability for 30h under reaction conditions, using a GHSV of 45,000h-1. The underlying alkane-metal interactions were explored theoretically in order to explain the C-H bond activation in propane by the catalyst.

In-situ modulation of α-MnO2 surface oxygen vacancies for photothermal catalytic oxidation of propane: Insights into activity and synergistic mechanism

Crystallographic effects in photothermal synergistic catalytic oxidation (PTSCO) system for VOCs removal are essential but still lack in-depth systematic studies. Therefore, key factors and synergistic mechanism of propane removal by MnO2 with different crystal planes in PTSCO system were investigated. The results showed that 160-M−300 with the mainly exposed (110) crystal plane displayed the optimal activity (T90 = 235℃, TOF = 4.90 × 10-7·s−1) and long-term stability (40 h) due to the abundant oxygen vacancies (OVs) controlled by the crystal planes, outstanding low temperature reduction ability and higher oxygen mobility. OVs substantially enhanced the adsorption and activation of propane and O2, and accelerated the efficient separation of photogenerated electrons and holes by capturing the electrons. Correspondingly, density functional theory (DFT) calculations confirmed that (110) crystal facet had the lowest OVs generation energy and work function, based on which, a multi-pathway enhancement mechanism of PTSCO was proposed. This study clarified the crystal-PTSCO activity dependence, provided theoretical support for the efficient and energy-saving removal of low-carbon alkanes.

Improved catalytic oxidation of propane over phosphate-modified Pd/Al2O3-TiO2 catalyst

Al-Ti oxides supported noble-metal catalysts were prepared by combining the mechanical ball-milling method and incipient wetness impregnation method, in which the Al-Ti mixed oxides were etched by various concentrations of phosphoric acid for improving the performance of propane oxidation. Phosphate-modified Pd/Al2O3-TiO2 catalyst with Al/P ratios of 3:1 showed high catalytic activity that more than 90 % C3H8 was converted completely at 380 °C and GHSV of 100000 h−1, with 5 vol% H2O and 10 vol% CO2. Characterization results revealed that the mixing of Al2O3 and TiO2 provided a high specific surface area and excellent pore structure, while the modification of phosphate supplied a stronger interaction between Pd species and supporter which is favorable to their dispersion and enhancing the catalytic stability in the tough conditions. The H2-TPR and O2-TPD results suggested that marked brilliant redox ability and abundant surface oxygen species of phosphate-modified Pd/Al2O3-TiO2 catalysts are beneficial to the activation of O2 and the increase of catalytic activity. Moreover, the XPS spectra indicated that phosphate induced some electromigration and made the content of Pd0 and Pd2+ in an appropriate ratio which enable the Pd species to display brilliant ability in supplying active oxygen species and breaking the C-H bond, which improved the C3H8 catalytic activity of noble-metal catalyst greatly.

Catalytic Oxidation of Propane and Carbon Monoxide by Pd Nanoparticles on Mn/TiO2 Catalysts

The present work shows experimental results on the catalytic oxidation of C3H8 and CO by Pd nanoparticles supported on MnOx/TiO2 synthesized by the sol–gel method. The results show a strong interaction between Pd and MnOx/TiO2; likewise, the annealing temperature of the TiO2 support modified the catalytic properties of the Pd–MnOx/TiO2 catalyst. In this line, the catalysts with 1 and 2 wt% of Pd loading supported on MnOx/TiO2 showed outstanding catalytic activity oxidizing C3H8 and CO within two temperature intervals: 200–400 °C and 25–200 °C, respectively. The Pd–MnOx/TiO2 catalyst also displayed very high stability during long-term tests and the addition of Pd nanoparticles reduced greatly the oxidation temperature of MnOx/TiO2. The outcomes revealed that the Pd–Mn interaction promoted the formation of new Pd0/Pd2+ active sites as well as the formation of oxygen vacancies and reduced Ti4+ to Ti3+ species, which led to the improvement of the Mn3+ and Mn4+ redox features, thus boosting the catalytic oxidation capacity of the Pd–MnOx/TiO2 catalyst.Graphical

Catalytic Combustion of Propane over Ce-Doped Lanthanum Borate Loaded with Various 3d Transition Metals

Ce-doped LaBO3 (Ce0.05La0.95BO3) and a corresponding incorporation with 3d transition metals (TMs) were prepared and evaluated for eliminating propane. Our results showed the catalytic activity toward propane combustion has a close relationship with the loaded TMs, which promoted oxygen vacancies density and further enhanced the reduction and acidity of this material. This eventually led to 90% propane conversion at 718 K for a Cu-loaded Ce0.05La0.95BO3 catalyst. During 10 h of catalytic propane oxidation, the propane-elimination rate was maintained very well, with no degradation of the catalyst.

Insights into Boosting SO2 Tolerance for Catalytic Oxidation of Propane over Fe2O3-Promoted Co3O4/Halloysite Catalysts

In the catalytic oxidation of volatile organic compounds, Co-based oxide catalysts show excellent potential and draw more and more attention, but SO2 poisoning in actual applications is one of the key problems to be solved. In this work, a series of treated halloysite (HLS)-supported Fe-modified Co oxide catalysts were prepared. In the catalytic oxidation of propane, the catalysts with 15 wt % Co loading amounts showed the best catalytic activity, while 2 wt % Fe modifications showed the best promotional effects. The introduction of Fe not only improved the catalyst activity but also enhanced the tolerance to SO2 poisoning. Various characterizations of physical–chemical properties, in situ diffuse reflectance infrared transform spectroscopy, and density functional theory calculation results showed that the active components of Co/HLS catalysts reacted with SO2 to form sulfate species, which could not provide sufficient catalytic activity afterward. The Fe species in Fe–Co/HLS catalysts could reduce the strong adsorption of SO2 on Co oxides and inhibit the formation of stable sulfate species, thus effectively reducing the effect of SO2 poisoning on the catalysts. Furthermore, the adsorption of reactants and the formation of intermediates proceeded on the surface of Fe–Co/HLS catalysts with a greater efficiency, and SO2 on the surface mainly existed in the form of surface-adsorbed SO2 species. Only a small proportion of SO2 could form SO3 species and sulfate species, thus achieving the purpose of protecting the active sites and maintaining the catalytic activity. The present study of halloysite-supported Fe-modified Co oxide catalysts would provide help for the development of Co oxide catalysts with excellent catalytic performance and tolerance to SO2 poisoning.

Construction of framework confined ordered mesoporous Pt/TixAlOy catalysts and applied for the catalytic oxidation of propane

The framework confined Pt/TixAlOy catalysts were prepared by a one-step evaporation-induced self-assembly (EISA) technique, and their activities for the catalytic oxidation of propane were investigated. The Pt/TixAlOy catalysts exhibited high specific surface area due to the ordered mesoporous structure. With the increase of TiO2 contents, the specific surface area and acidic sites of Pt/TixAlOy catalysts increased. The specific surface area and acidic sites could improve the exposure of the active sites and electron transfer of Pt and TiO2, which was beneficial to catalytic oxidation of propane. However, too high acidic sites of catalysts could lead to coke deposition and clogging of the pores, and the addition of TiO2 had the optimal value. The Pt/Ti0.1AlOy catalyst exhibited superior catalytic activity, which could be attributed to the higher specific surface area, higher the percentage of Pt2+ and lattice oxygen, abundant acid sites, and higher redox properties. In addition, the Pt/Ti0.1AlOy catalyst also exhibited superior sulfur resistance due to the multiple acidic sites of catalysts.

Multi-defects engineering of NiCo2O4 for catalytic propane oxidation

High-performance non-noble metal catalyst development is always the pursuit for the VOCs oxidation. Herein, a multi-defective spinel catalyst was intelligently built with a mechano-chemical strategy by Na assisted milling of NiCo2O4, wherein, the incorporation of Ni into the spinel oxide could introduce cationic defects, the etching by Na brought anionic defects, while the milling process fractured the bulk and facilitated the exposure of surface defects. Thereout, the obtained D-NiCo2O4 was endowed with a significantly elevated oxygen vacancies, raised active oxygen species, enhanced oxygen mobility and an increased specific surface area. The beneficial features promise D-NiCo2O4 a superb activity for propane catalytic oxidation, exhibiting a T50 (temperature at 50% propane conversion) of 187 °C and T90 (temperature at 90% propane conversion) of 194 °C at propane space velocity of 60,000 mL·g−1·h−1, which outperformed that of pristine NiCo2O4 and Co3O4 catalyst, making itself one of the most outstanding non-noble metal catalysts for propane oxidation. This work set the paradigm to enhance the VOCs oxidation performance of metal oxide catalyst by multi-defects engineering.

Direct Catalytic Oxidation of Propane: Effects of Inhibitors

Direct Catalytic Oxidation of Propane: Effects of Inhibitors

Construction of Hollow Cobalt Tetroxide Nanocages through the Metal Salt Bifunctional Etching Strategy for Catalytic Oxidation of Propane at Ultrahigh Space Velocity

Construction of Hollow Cobalt Tetroxide Nanocages through the Metal Salt Bifunctional Etching Strategy for Catalytic Oxidation of Propane at Ultrahigh Space Velocity

3D hierarchically structured Ce1-xGdxO2-x/2 mixed oxide particles: the role of microstructure, porosity and multi-level architecture stability in soot and propane oxidation.

In this paper, synoptic description of the hierarchical architecture of mixed ceria particles and its function in catalytic propane and soot oxidation has been presented. The influence of temperature and dopant concentration on the micro- to macroscale structure of the star-shaped particles has been thoroughly investigated by various physicochemical techniques. Two temperature-dependent growth modes of ceria nanoparticles has been observed and their dopant-dependent influence on mesocrystal architecture have been described. It appeared that presence of dopant changes the pattern of nanoparticles intergrowth which ultimately introduces additional porosity into 3D hierarchically structured material (rav =19 nm). Furthermore, emergent phenomenon in catalytic propane oxidation was observed. The substantial increase of propane conversion via low-temperature surface oxidation mechanism was ascribed to nanocrystallites mesoscale organization forming porous hierarchical material. No such conversion was present for a comparative sample of non-organized ceria nanoparticles. Also, increased stability of such architecture was demonstrated in soot combustion tests.

Ultra-active Ru supported on CeO2 nanosheets for catalytic combustion of Propane: Experimental insights into interfacial active sites

Catalytic oxidation of propane as a representative molecule of light hydrocarbons (LHs) is of special interest for energy utilization and pollution abatement but is challengeable due to its stable C–H bonds. Here, Ru supported on porous and defect-rich CeO2 nanosheets catalysts were prepared and investigated for catalytic oxidation of propane, and the Ru/CeO2 catalyst using chlorine-free Ru precursor (RuN/CeNS) presented an ultra-high activity with complete conversion at 150 °C. A series of well-designed experiments and characterizations illustrated that the high-density and uniform Ru-O-Ce interfaces were determinant for propane oxidation due to the possible asymmetric bridged adsorption and activation. The presence of chlorine species suppressed the dispersion of RuOx species and the formation of Ru-O-Ce interfaces, which also accelerated the sintering of CeO2 and Ru-O-Ce interfaces at high temperatures. This work highlighted the experimental insights into the active interfacial sites of ultra-active Ru/CeO2 for propane oxidation. It contributed to an in-depth understanding of the activation of C–H bonds in LHs and the preparation of supported noble metal catalysts.

Modification of Beta Zeolites and Their Application in Catalytic Oxidation of Propane

AbstractIn this manuscript, Beta zeolites are modified by liquid phase ion exchange method and high temperature roasting method to achieve the effect of catalytic degradation of propane. After modification by hydrochloric acid, nickel nitrate and zinc nitrate, the specific surface area, pore size and pore volume of Ni−Zn−H‐Beta zeolites catalyst increased, which greatly improved the catalytic degradation effect of propane. By high temperature roasting, the effect of conventional calcined catalyst is better than that of microwave calcined catalyst. When the gas composition is air and 1 % propane, the gas flow is 100 ml/min, the reaction temperature is 300 °C, the optimum preparation conditions of the catalyst are Ni: Zn=2 : 1, HCl pickling temperature is 70 °C, conventional roasting temperature is 500 °C, and the holding time is 60 min, the catalytic activity of Ni−Zn−H‐Beta zeolites is the best, and the degradation rate of propane is 79.6 %.

Effects of the Reaction Parameters and Light Hydrothermal Aging for Catalytic Combustion of Propane over Co-Mn-Ce Catalyst

A composite oxides’ Co-Mn-Ce catalyst was synthesized by a coprecipitation method, and the experiment was carried out to study the effects of reaction parameters and light hydrothermal aging on propane combustion over the Co-Mn-Ce catalyst. The influence of reaction temperature, propane concentration, oxygen concentration, water vapor, and hydrothermal aging was studied during the catalytic combustion of propane. The propane conversion significantly decreased by 10% when the propane concentration increased at 300°C and then further decreased from 80% to 40% as water vapor concentration increased from 0 to 10 vol.%. In addition, water vapor also prolonged the time required to reach equilibrium. After hydrothermal treatment, the catalyst obtained the lowest oxidation capacity of propane. Furthermore, the results of in situ DRIFTs and O2 temperature programmed desorption (O2-TPD) demonstrated that there were fewer oxygen species after hydrothermal aging, and carbonates were the main intermediates formed during the catalytic oxidation of propane.

Learning Design Rules for Selective Oxidation Catalysts from High-Throughput Experimentation and Artificial Intelligence.

The design of heterogeneous catalysts is challenged by the complexity of materials and processes that govern reactivity and by the fact that the number of good catalysts is very small in comparison to the number of possible materials. Here, we show how the subgroup-discovery (SGD) artificial-intelligence approach can be applied to an experimental plus theoretical data set to identify constraints on key physicochemical parameters, the so-called SG rules, which exclusively describe materials and reaction conditions with outstanding catalytic performance. By using high-throughput experimentation, 120 SiO2-supported catalysts containing ruthenium, tungsten, and phosphorus were synthesized and tested in the catalytic oxidation of propylene. As candidate descriptive parameters, the temperature and 10 parameters related to the composition and chemical nature of the catalyst materials, derived from calculated free-atom properties, were offered. The temperature, the phosphorus content, and the composition-weighted electronegativity are identified as key parameters describing high yields toward the value-added oxygenate products acrolein and acrylic acid. The SG rules not only reflect the underlying processes particularly associated with high performance but also guide the design of more complex catalysts containing up to five elements in their composition.

Reaction kinetics and mechanism of the catalytic oxidation of propane over Co–ZSM-5 zeolites

Reaction kinetics and mechanism of the catalytic oxidation of propane over Co–ZSM-5 zeolites

A theoretical study on the mechanism of conversion of C3H8 and CO2 to C3H6 and HCOOH by M4–B24N28 catalysis

In this work, we explored the reaction mechanism of metallic copper-doped modified aperiodic (BN)28 nanocages for the catalytic oxidation of propane with carbon dioxide. The DFT calculation is performed on all possible paths during the reaction process.