Degradation Of Propane Research Articles

Acid-activated α-MnO2 for photothermal co-catalytic oxidative degradation of propane: Activity and reaction mechanism

In order to further reduce the energy consumption of the conventional thermal catalytic oxidation system and improve the degradation efficiency of pollutants, photothermal synergistic catalytic oxidation (PTSCO) system was constructed in this paper with propane as simulated pollutant representing VOCs, and then the modified α-MnO2 catalysts were prepared by using the acid activation method, which were used for the catalytic oxidation of propane in PTSCO. The α-MnO2 with appropriate acid concentration possessed excellent low-temperature reducibility, abundant active oxygen species, fast oxygen migration rate and a large number of acid sites. The optimal catalyst, H0.05-MnO2, had a T90 of 204 °C in the PTSCO system, which reduced by more than 30 °C relative to the α-MnO2 (T90 of 235 °C). Moreover, H0.05-MnO2 demonstrated excellent water resistance and long-term stability (T = 45 h). It was shown that the combination of photocatalysis and thermocatalysis can improve propane degradation by examining the kinetics of propane degradation in the PTSCO system and the conformational relationship of propane degradation by catalysts. Furthermore, a multi-pathway synergistic mechanism between photocatalysis and thermocatalysis in the PTSCO system was proposed. This work provided a theoretical basis for the preparation of high-performance catalysts and the catalytic degradation of propane.

Boosted Light Alkane Deep Oxidation via Metal Bond Length Modulation-Induced C-C Bond Preferential Activation.

Light alkanes (LAs), typical VOCs existing in both stationary and mobile sources, pose significant environmental concerns. Although noble metal catalysts demonstrate strong C-H bond activation, their effectiveness in degrading LAs is hindered by inherent challenges, including poor chemical stability and water resistance. Here, from a new perspective, we propose a feasible strategy that adjusting the metal bond lengths within Pd clusters through partial substitution of smaller radius 3d transition metals (3dTMs) to prioritize the activation of low-energy C-C bonds within LAs. Benefiting from this, PdCo/CeO2 exhibits exceptional catalytic performance in propane degradation due to their high capacity for C-C cleavage stemming from the shorter Pd-Co length (2.51 Å) and lower coordination number (1.73), boosting the activation of α-H and β-H of propane simultaneously and accelerating the mobility of postactivated oxygen species to prevent Pd center deep oxidation. The presence of 3dTMs on Pd clusters improves the redox and charge transfer ability of catalysts, resulting in an amplified generation of oxygen vacancies and facilitating the adsorption and activation of reactants. Mechanistic studies and DFT calculations suggest that the substitution of 3dTMs significantly accelerate C-C bond cleavage within C3 intermediates to generate the subsequent C2 and C1 intermediates, suppressing the generation of harmful byproducts.

New insight into opposite oxidation behavior in acetone and propane catalytic oxidation over CoMn based spinel oxides

CoMn spinel (CoMn) and Zn-substituted CoMn spinel (ZnCoMn) oxides were fabricated for revealing mechanism differences in acetone and propane catalytic oxidation. The temperature-conversion profiles, intrinsic reaction rate and activation energy convinced that CoMn and ZnCoMn exhibited high catalytic performance for acetone and propane oxidation, respectively. Experimental and theoretical investigation revealed that deep oxidation determined the acetone conversion, while the degradation of propane was governed by the fracture of C-H bond and subsequently the activation of C3H7. CoMn possessed more active lattice oxygen and superior oxygen activation capacity, allowing acetone to be directly converted into carboxylates without generating aldehydes. ZnCoMn with more high valence Mn species was conductive to the C-H bond dissociation and C3H7 activation. This work revealed the mutual relations between structure–property of the spinel oxides and reactivity of the diverse VOCs, which provided new insights for the rational design of spinel oxides for catalytic oxidation of diverse VOCs.

Enhanced activity of plasma catalysis for propane decomposition via metal-support interactions of Pt/CeMnyOx

The elimination of light alkanes has been the subject of extensive research. Rational tuning of the surface electronic structure of catalysts can optimize the adsorption and activation behavior of reactant molecules. Therefore, the role of metal-support interactions in plasma catalysis deserves in-depth investigation. In this study, a simple strategy was employed to synthesize Pt-based catalysts loaded on Ce-based binary oxide supports. The interactions between Pt noble metal and supports were regulated by varying the metal element type of the supports and the ratio of the support metal elements. Among them, 0.3 %Pt/CeMn0.2Ox catalyst was the most effective for the synergistic plasma degradation of propane. Various characterizations showed that the redox ability and Pt species dispersion of 0.3 %Pt/CeMn0.2Ox catalyst were significantly enhanced by strong metal-support interactions. It induced more Pt0 and Ce3+ on the surface for the activation of oxygen or water vapor to generate surface reactive oxygen species. Moreover, the plasma in turn facilitated the electron transfer of Pt/CeMn0.2Ox catalyst and enhanced the metal-support interactions. The reactive oxygen species generated by plasma participated in the oxidation of propane and the oxygen cycle of Pt/CeMn0.2Ox catalyst, thus enhancing the synergistic catalysis. The present work provides insight into the design of catalysts with high plasma catalytic synergy.

Elucidating the role of confinement and shielding effect over zeolite enveloped Ru catalysts for propane low temperature degradation.

Volatile organic compounds (VOCs) are the main precursor for ozone formation and hazardous to human health. Light alkane as one of the typical VOCs is difficult to degrade to CO2 and H2O by catalytic degradation method due to its strong C-H bond. Herein, a series of ultrafine Ru nanoclusters (<0.95nm) enveloped in silicalite-1 (S-1) zeolite catalysts were designed and prepared by a simple one-pot method and applied for catalytic degradation of propane. The results demonstrate that the enveloped Ru1@S-1 catalyst has excellent propane degradation performance. Its T95 is as low as 294°C with moisture, and the turnover frequency (TOF) value is up to 5.07 × 10-3 s-1, evidently higher than that of the comparison supported catalyst (Ru1/S-1). Importantly, Ru1@S-1 exhibits superior thermal stability, water resistance and recyclability, which should be attributed to the confinement and shielding effect of the S-1 shell. The in-situ DRIFTS result reveals that the propane degradation over Ru1@S-1 follows the Mars-van-Krevelen (MvK) mechanism, where the hydroxy from the framework of zeolite can provide the active oxygen species. Our work provides a new candidate and guideline for an efficient and stable catalyst for the low-temperature degradation of the light alkane VOCs.

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 %.

Catalytic combustion of propane over Zr-modified Co3O4 catalysts: An experimental and theoretical study

As one of the domain volatile organic compounds (VOC), short chain alkane is an obstacle for low-temperature purification. Here, cobalt-zirconium oxides catalysts in a range of Co/Zr ratios were synthesized by sol-gel method for the catalytic combustion of propane. The result indicates that the catalyst with a ratio of Co to Zr of 4 (Co4Zr1) not only exhibits the superior catalytic performance with 90% conversion at 242 °C, but also maintains high thermal stability and water resistance. The synergistic effect between Co and Zr over cobalt-zirconium oxides catalysts contributes to the high increase of catalytic activity, which are relevant to the formation of ZrO2-Co3O4 solid solution. Additionally, the introduced Zr leads to more surface Co3+ species and surface-absorbed oxygen over Co4Zr1 catalyst. Moreover, high-resolution transmission electron microscopy (HRTEM) reveals Co4Zr1 catalyst exposes abundant (220) crystal face. Density functional theory (DFT) suggests that Co3O4 (220) shows lowest adsorption energy (−0.71 eV) and the formation of oxygen defects will reduce the adsorption energy (−1.03 eV). All these results confirm that the CoxZry catalysts are promising alternative for propane degradation and provide important guiding significance for the design of catalysts and catalytic combustion kinetics.

Enhancement of propane combustion activity over CoOx catalysts by introducing C2–C5 diols

C2–C5 diols effectively promote the degradation of propane by weakening the Co–O bond strength of CoOx.

Hierarchical zeolite enveloping Pd-CeO2 nanowires: An efficient adsorption/catalysis bifunctional catalyst for low temperature propane total degradation

Abstract Volatile organic compounds (VOCs) are significant ozone (O3) and particulate matter (PM) formation precursors and are deleterious to both human health and environment. Catalytic combustion can degrade VOCs to H2O and CO2 without secondary pollution, suggesting a potential sustainable technology for air pollution control. However, the concentration of exhausted VOCs is usually too low for effective decomposition. Herein, a novel adsorption/catalysis bifunctional catalyst, hierarchical silicalite-1 (S-1) zeolite enveloping Pd-CeO2 nanowires (Pd-CeO2NW@S-1), was designed and prepared using a simple one-pot two-step method and applied for the degradation of propane. Pd-CeO2NW@S-1 exhibited superior catalytic activity (T90 decreased to 296 °C) as well as increased thermal and hydrothermal stability (no obviously decrease in activity when treated at 700 °C or reacted with water gas, respectively) compared with Pd-CeO2 nanowires supported on the outer surface of S-1 (Pd-CeO2NW/S-1) and previously reported Pd based catalysts for propane degradation. In addition, the activity over Pd-CeO2NW@S-1 after five reaction cycles just with little decrease and could be restored by a simple regeneration step and without any detection of coke. The remarkable performance over Pd-CeO2NW@S-1 was attributed to the high dispersion of Pd and Ce encapsulated in hierarchical zeolite with superior propane adsorption performance and the special confinement structure according the Mars-van-Krevelen (MvK) mechanism. This confinement adsorption/catalysis bifunctional strategy can be used to design other high-performance catalysts for degradation of VOCs.

Properties and catalytic performance for propane combustion of LaMnO3 prepared under microwave-assisted glycothermal conditions: Effect of solvent diols

A microwave-assisted glycothermal method was used to prepare LaMnO3 perovskite oxides using different diols: 1,2-ethanediol, 1,2-propanediol and 1,4-butanediol as reaction medium. The effect of diols on the physicochemical properties of obtained materials was studied. The properties of these materials were characterised by various techniques (XRD, TEM/SEM, XPS, TPR-H2, TPD-O2, TPD-O2, N2 adsorption-desorption), and their catalytic performances were evaluated for the total oxidation of lean propane, which was chosen as a model molecule of volatile organic compounds (VOCs). It was shown that well-formed perovskite structures with trigonal symmetry were obtained for all samples but traces of La2O3 phase were detected for sample prepared by using 1,2-propanediol. The effect of solvent on textural properties and morphology, the amount of desorbed oxygen species, redox properties and basicity of LaMnO3 oxides was determined. The higher capacity for surface adsorbed oxygen, the most basic nature, better low-temperature reducibility and well developed surface area and pore volume, as well as higher catalytic activity for propane degradation were found when 1,2-ethanediol was used as a solvent.

Structural and Kinetic Characteristics of 1,4-Dioxane-Degrading Bacterial Consortia Containing the Phylum TM7.

1,4-Dioxane-degrading bacterial consortia were enriched from forest soil (FS) and activated sludge (AS) using a defined medium containing 1,4-dioxane as the sole carbon source. These two enrichments cultures appeared to have inducible tetrahydrofuran/dioxane and propane degradation enzymes. According to qPCR results on the 16S rRNA and soluble di-iron monooxygenase genes, the relative abundances of 1,4-dioxane-degrading bacteria to total bacteria in FS and AS were 29.4% and 57.8%, respectively. For FS, the cell growth yields (Y), maximum specific degradation rate (Vmax), and half-saturation concentration (Km) were 0.58 mg-protein/mg-dioxane, 0.037 mg-dioxane/mg-protein∙h, and 93.9 mg/l, respectively. For AS, Y, Vmax, and Km were 0.34 mg-protein/mg-dioxane, 0.078 mg-dioxane/mg-protein∙h, and 181.3 mg/l, respectively. These kinetics data of FS and AS were similar to previously reported values. Based on bacterial community analysis on 16S rRNA gene sequences of the two enrichment cultures, the FS consortium was identified to contain 38.3% of Mycobacterium and 10.6% of Afipia, similar to previously reported literature. Meanwhile, 49.5% of the AS consortium belonged to the candidate division TM7, which has never been reported to be involved in 1,4-dioxane biodegradation. However, recent studies suggested that TM7 bacteria were associated with degradation of non-biodegradable and hazardous materials. Therefore, our results showed that previously unknown 1,4-dioxane-degrading bacteria might play an important role in enriched AS. Although the metabolic capability and ecophysiological significance of the predominant TM7 bacteria in AS enrichment culture remain unclear, our data reveal hidden characteristics of the TM7 phylum and provide a perspective for studying this previously uncultured phylotype.

TiO&amp;lt;sub&amp;gt;2&amp;lt;/sub&amp;gt; Films Synthesis over Polypropylene by Sol-Gel Assisted with Hydrothermal Treatment for the Photocatalytic Propane Degradation

The present investigation shows experimental results obtained with TiO2 thin films synthesized by the sol-gel method assisted with hydrothermal treatment over polypropylene, using the dip coating technique. Obtained coatings were characterized through SEM, XRD, UV-Vis and the photo- catalytic activity was monitored by GC. According to results, the hydrothermal treatment facilitates the crystallization of the TiO2 anatase phase, which is present in all synthesized films. Crystal size formed from precursor solutions (estimated by the Scherrer’s equation) depends on the time and temperature of the hydrothermal treatment, wherein solution exposed to a higher temperature treatment of 150。C for 1.5 h (H150/1.5) exhibited a larger crystal size compared to those synthesized at 80。C for 1.5 h and 3 h (H80/1.5 and H80/3). Sample H150/1.5 over polypropylene resulted in a uniform and crack free coating. This behavior was attributed to the precursor solution being denser than those synthesized at 80。C. Additionally, the photocatalytic activity of the coatings was evaluated through the degradation of propane. Coating H150/1.5 reached 100% conversion after 3 h of UV light irradiation.

Carbon and hydrogen stable isotope fractionation associated with the anaerobic degradation of propane and butane by marine sulfate‐reducing bacteria

The anaerobic degradation of propane and butane is typically initiated by activation via addition to fumarate. Here we investigated the mechanism of activation under sulfate-reducing conditions by one pure culture (strain BuS5) and three enrichment cultures employing stable isotope analysis. Stable isotope fractionation was compared for cultures incubated with or without substrate diffusion limitation. Bulk enrichment factors were significantly higher in mixed vs. static incubations. Two dimensional factors, given by the correlation of stable isotope fractionation of both carbon and hydrogen at their reactive positions (Lambda reactive position, Λrp), were compared to analyse the activation mechanisms. A characteristic reactive position isotope fractionation pattern was observed, distinct from aerobic degradation. Λrp values ranged from 10.5 to 11.8 for propane and from 7.8 to 9.4 for butane. Incubations of strain BuS5 with deuterium-labelled n-alkanes indicated that butane was activated solely at the subterminal C atom. In contrast, propane was activated mainly at the subterminal C atom but also significantly at the terminal C atoms. A conservative estimate suggests that about 70% of the propane activation events occurred at the subterminal C atom and about 30% at the terminal C atoms.

Anaerobic degradation of propane and butane by sulfate-reducing bacteria enriched from marine hydrocarbon cold seeps.

The short-chain, non-methane hydrocarbons propane and butane can contribute significantly to the carbon and sulfur cycles in marine environments affected by oil or natural gas seepage. In the present study, we enriched and identified novel propane and butane-degrading sulfate reducers from marine oil and gas cold seeps in the Gulf of Mexico and Hydrate Ridge. The enrichment cultures obtained were able to degrade simultaneously propane and butane, but not other gaseous alkanes. They were cold-adapted, showing highest sulfate-reduction rates between 16 and 20 °C. Analysis of 16S rRNA gene libraries, followed by whole-cell hybridizations with sequence-specific oligonucleotide probes showed that each enrichment culture was dominated by a unique phylotype affiliated with the Desulfosarcina-Desulfococcus cluster within the Deltaproteobacteria. These phylotypes formed a distinct phylogenetic cluster of propane and butane degraders, including sequences from environments associated with hydrocarbon seeps. Incubations with (13)C-labeled substrates, hybridizations with sequence-specific probes and nanoSIMS analyses showed that cells of the dominant phylotypes were the first to become enriched in (13)C, demonstrating that they were directly involved in hydrocarbon degradation. Furthermore, using the nanoSIMS data, carbon assimilation rates were calculated for the dominant cells in each enrichment culture.

Transformations in gas mixtures based on butane under irradiation in the circulation mode

Radiolysis of gaseous mixtures based on n-butane was studied in the circulation mode of irradiation, and the component composition of liquid products was measured. The apparent yield of n-butane decomposition is 13.7 molecules/100 eV. Radiolysis is accompanied by a monotonous decrease in the molecular mass of the irradiated mixture. It was shown that the liquid product contains alkanes from C5H12 to C12H26 with the prevalence of C6H14 and C8H18 isomers. The main products are 2-methylbutane, 3-methylpentane, 3,4-dimethylhexane, and 3-methylheptane. A low yield of heptane isomers (∼5%) is due to a small rate of degradation of propane and a low yield of propyl radicals as a result of propane formation mainly via the ionic mechanism.

Atmospheric oxidation pathways of propane and its by‐products: Acetone, acetaldehyde, and propionaldehyde

Propane (C3H8) is one of the most abundant nonmethane hydrocarbons in the atmosphere. It is a fuel widely used, derived from petroleum products during oil and natural gas processing. It can be oxidized in the atmosphere via its reactions with hydroxyl (OH) radicals and chlorine (Cl) atoms and serves as an indicator for the presence of such oxidants. During the atmospheric degradation of propane, various carbonyl compounds are formed, with acetone, acetaldehyde, and propionaldehyde among the most prominent. Carbonyl compounds are relevant because of their toxicity and ability to produce free radicals by photolysis that give rise to stable products, thus providing valuable information about atmospheric oxidation processes. The exact mechanisms of the oxidation pathways of propane have not been properly characterized, although several speculations have been made that determine the oxidation products. The present study investigates the oxidation mechanism of propane, acetone, acetaldehyde, and propionaldehyde by ab inito molecular orbital methods. Detailed pathways leading to experimentally observed products are presented. Equilibrium geometries and energetics, as well as vibrational frequencies of species, transition states, and prereactive complexes are determined at the QCISD(T)/6‐311G(2df,2p)//MP2(full)/6‐31G(d).

Propane‐Induced biodegradation of vapor phase trichoroethylene

Microbial degradation of trichloroethylene (TCE) has been demonstrated under aerobic conditions with propane. The primary objective of this research was to evaluate the feasibility of introducing a vapor phase form of TCE in the presence of propane to batch bioreactors containing a liquid phase suspension of Mycobacterium vaccae JOB5 to accomplish degradation. The reactor system consisted of three phases: a vapor phase introducing air, propane, and TCE; a liquid phase of the microbial suspension; and a solid phase in the form of the microorganisms. Long-term and initial rate experiments were conducted on three culture sets to evaluate microbial response. In two long-term test fed propane and approximately 0.1 mg/L and 1 mg/L of TCE, respectively, propane utilization was more efficient at the high TCE concentration (600 mmol propane/mmol TCE versus 11,900 mmol propane/mmol TCE), because the propane degradation rate was approximately the same for both tests (6.73 mg/L . h and 7.85 mg/L . h for the high and low tests). In addition, TCE utilization decreased after complete propane consumption. Initial rate tests on culture sets fed propane only revealed that cells with a history of exposure to a high concentration of TCE had the highest specific growth rate, but the lowest half-saturation constant (7.60e(-3) h(-1) and 0.10 mg/L, respectively). Tests fed variable TCE concentrations (0.031 to 5.378 mg/L in the liquid phase) with no propane showed TCE depletion but no biomass growth. The tests revealed that the TCE removal increased as the TCE concentration increased, indicating a greater removal efficiency at the higher concentrations. Tests with a constant initial propane concentration and variable liquid phase TCE concentration revealed that specific propane utilization was essentially the same. (c) 1995 John Wiley & Sons, Inc.

Nitrogen limitation and nitrogen fixation during alkane biodegradation in a sandy soil

We investigated nutrient limitations during hydrocarbon degradation in a sandy soil and found that fixed nitrogen was initially a limiting nutrient but that N limitation could sometimes be overcome by N2 fixation. Hydrocarbon biodegradation was examined in an unsaturated sandy soil incubated aerobically at 20 degrees C with propane or butane and various added nutrients. Propane and butane degradation proceeded similarly during the first 3 months of incubation. That is, bacteria in soil amended with N oxidized these hydrocarbons more rapidly than in controls without nutrient additions or in soil with added phosphate or trace minerals. Both propane- and butane-amended soil apparently became N limited after the initial available inorganic N was utilized, as indicated by a decrease in the rates of hydrocarbon degradation. After 3 months, propane and butane degradation proceeded differently. Bacteria in propane-degrading soil apparently remained N limited because propane degradation rates stayed low unless more N was added. In contrast, bacteria in butane-degrading soil appeared to overcome their N limitation because butane degradation rates later increased regardless of whether more N was added. Analyses of total N and acetylene reduction assays supported this apparent surplus of N in butane-amended soil. Total N was significantly (P < 0.01) higher in soil incubated with butane and no N amendments than in soil incubated with propane, even when the latter was amended with N. Acetylene reduction occurred only in butane-amended soil. These results indicate that N2 fixation occurred in butane-amended soil but not in propane-amended soil.