Oxidation Of Methyl Phenyl Sulfide Research Articles

Keggin-type polyoxometalates/Amberlite nanocomposites as efficient catalysts for the aqueous oxidation of sulfides: Crucial roles of mono-iron and mono-manganese substituents

The condensation of Keggin-type polyoxometalates including H3PW12O40, H3PMo12O40, and their Mn(III) and Fe(III) derivatives with nano-structured Amberlite, nanoAmbN(Me)3Cl led to the formation of electrostatically immobilized polyoxometalates on the anion exchange polymer with a size less than ca. 70 nm. The nanocomposites were characterized by FT-IR, XRD, solid state diffuse-reflectance and solution UV–vis spectroscopy, TGA, BET and FESEM-EDX-Mapping and used for the oxidation of sulfides with periodate under aqueous and non-aqueous conditions. In spite of the small difference between the catalytic activity of H3PMo12O40 and H3PW12O40, the corresponding mono-iron and manganese substituted derivatives showed significantly different catalytic activities. Furthermore, nanoAmbN(Me)3@PW11MnO39 showed a high selectivity towards sulfone (72 %), compared to the highly chemoselective formation of sulfoxide in the presence of nanoAmbN(Me)3@PW11FeO39. NanoAmbN(Me)3@PW11FeO39 as the best catalyst of the series was recovered and reused at least six times for the oxidation of methyl phenyl sulfide. The increased catalytic activity of the iron-containing polyoxometalates than that of the corresponding manganese compounds was attributed to the Jahn-Teller distortion around the manganese(III) center.

Synthesis, Characterization, and Application of a Polyoxometalates‐Based CuII Complex for Efficient Catalytic Oxidation and Electrochemical Detection

AbstractThe development of eco‐friendly, high‐efficiency polyoxometalates (POMs) catalysts is vital for advancing catalytic oxidation and electrochemical detection in environmental protection. Herein, a POM‐based CuII‐containing complex with the molecular formula [H(4‐AP)]8[Cu2(H2O)4(P2Mo5O23)2]·8H2O (1) (4‐AP = 4‐aminopyridine) is synthesized using the hydrothermal method, and the crystal structure is determined by single X‐ray diffraction (SXRD), infrared (IR) spectroscopy, and powder X‐ray diffraction (PXRD). Structurally, complex 1 exhibits a one dimension (1D) chain arrangement, composed of CuII ions and Strandberg‐type (P2Mo5O23)6− anionic clusters. These 1D chains are further interconnected through [H(4‐AP)]+ ligands, resulting in the formation of a two dimension (2D) supramolecular network. Complex 1 serves as an outstanding heterogeneous catalyst for the oxidation of methyl phenyl sulfide (MPS), demonstrating a remarkable conversion rate of 99% for MPS and a selectivity of 98% toward methyl phenyl sulfoxide (MPSO). In addition to its catalytic capabilities, complex 1 is also employed in the electrochemical detection of FeIII and CrVI ions, with low limits of detection (LODs) at 4.92 µm for FeIII and 7.82 µM for CrVI.

A comprehensive study about functionalization and de-functionalization of MOF-808 as a defect-engineered Zr-MOFs for selective catalytic oxidation

In metal–organic frameworks (MOFs), confined space as a chemical nanoreactor is as essential as coordinatively unsaturated metal site catalysis. The properties of MOFs can be adjusted through the incorporation of functional groups and open metal sites in frameworks that can modify the catalytic performance. In this regard, a set of defect-engineered MOFs, Ex-MOF-808(NH2, NO2, H) and Mix-MOF-808(NH2, NO2, H), were synthesized by ultrasonic-assisted linker exchange approach (Ex-MOFs) and solvothermal mixing ligand method (Mix-MOFs), respectively. Further, the relationship between the preparation method, structural properties, and catalytic efficiency of the prepared materials in the selective oxidation of methyl phenyl sulfide (MPS) has been investigated. By analyzing zeta potential, it was found that in the exchange method, the amount of defect and functional groups on the surface of MOFs are more than in the mixing method, which also affects the catalytic activity. In our contribution, mix-MOF-808(NO2) carrying nitro groups at their organic linkers, which has a well-dispersion of nitro groups at the framework exhibits selective conversion of MPS to sulfone (91 %). Furthermore, the performance of stable heterogeneous catalysts was investigated for three cycles, which demonstrated their great potential for advanced catalytic oxidation.

Modulating the Catalytic Properties of Polyoxovanadates with Transition-Metal-Complex Units for Selective Oxidation of Sulfides.

Selective oxidation of sulfides to sulfoxides is of great significance in the synthesis of pharmaceuticals, desulfurization of fuels, and detoxification of sulfur mustard chemical warfare agents. Designing selective catalysts to achieve the efficient transformation of sulfides to sulfoxides is thus highly desired. Herein, we report three transition metal-complex-functionalized polyoxovanadates, [Zn2(BPB)2][V4O12]·0.5BPB·H2O (1), [Ni(BPB)(H2O)][V2O6]·2H2O (2), and [Co(HBPB)2][V4O12] (3) (BPB = 1,4-bis(pyrid-4-yl)benzene)), and explore their applications for selective oxidation of sulfides using H2O2 as an oxidant. All three compounds were catalytically effective for the oxidation of methyl phenyl sulfide to methyl phenyl sulfoxide, with 1 being best-performing with complete conversion and a selectivity of 96.7%. In the selective oxidation of a series of aromatic and aliphatic sulfides to corresponding sulfoxides, 1 also showed satisfactory performance; in particular, the chemical warfare agent stimulant 2-chloroethyl ethyl sulfide can be completely and selectively oxidized to the nontoxic 2-chloroethyl ethyl sulfoxide within 20 min at room temperature. Catalyst 1 can be recycled and reused at least six times with uncompromised performance. The perfect performance of 1 is attributed to the synergistic effect of coordinatively unsaturated V and Zn sites in bimetallic oxide, as revealed by comparative structural and catalytic studies.

Rheologically improved microemulsion for deactivation of simulants of blister and nerve agents

The efficiency of decontamination of blister and nerve agents was studied using the example of nucleophilic decomposition of paraoxone (O,O-diethyl-O-4-nitrophenyl phosphate) and oxidation of methylphenyl sulfide. Hydrogen peroxide solutions in an oil-in-water microemulsion containing synthetic nanoclay Laponite EP and polyvinylpyrrolidone polymer were studied as reactive decontamination systems. The base of the microemulsion consisted of an aqueous phase, a codetergent (isopropanol), oil (hexane), with a variation of detergent (cetylpyridinium chloride, sodium dodecyl sulfate, and Triton X-100). It was shown that the solubility of paraoxone and methylphenyl sulfide in the studied microemulsions increases by an average of 100 times or more compared to the solubility in water, and the substrate binding constants are 2–3 times higher than the binding constants in similar microemulsion media. It was found that the presence of nanoclay in the microemulsion provides a catalytic effect, i.e. an increase in the rate of decomposition of paraoxone and methylphenyl sulfide by at least 2 times. In addition, nanoclay thickens the microemulsion and, together with the polymer, increases the viscosity of the reaction medium. The determined kinetic parameters of decontamination and solubility of substrates allow us to conclude that the use of the investigated microemulsion system provides an acceleration of nucleophilic substitution and oxidation reactions by 150–350 times compared to the reaction rate in water.

Integrating Metal Complex Units and Redox Sites into Thorium‐Based Metal–Organic Frameworks for Selective Photocatalytic Oxidation of Sulfides

AbstractA series of high‐symmetry Th6–metal‐organic frameworks (MOFs) are constructed using various metal complex units and the thorium (Th) cluster, and then being applied as a well‐defined catalyst model in the photocatalytic oxidation of methyl phenyl sulfide reactions. The integration of Th6‐MOFs by incorporating metal complex units and redox sites (Th6 cluster and single‐metal site) can effectively modulate the conversion rate and selectivity. Among them, Ni–PBA–Th6 (PBA = 4‐pyridin‐4‐yl benzoic acid) achieves up to ≈99% conversion and ≈97% selectivity for methyl phenyl sulfone. Experiments and theoretical calculations further elucidate that Th6 cluster is the catalytic site for the oxidation of methyl phenyl sulfide to methyl phenyl sulfone, while Ni–PBA is the catalytic site for the reduction of hydrogen peroxide. This work sheds new insight into the structural design and photocatalytic application of more efficient thorium‐based MOF catalysts.

What factors determine activity of UiO-66 in H2O2-based oxidation of thioethers? The role of basic sites

Zr-based metal–organic frameworks (Zr-MOFs) have attracted significant attention as selective oxidation catalysts due to their stability in aqueous and oxidative media and high activity in H2O2 activation. Oxidation of thioethers with aqueous H2O2 over Zr-MOFs reveals extremely high selectivity toward the formation of sulfones even at low conversions. Herein, the main factors determining activity of Zr-MOF in the thioether oxidation have been investigated using zirconium terephthalate UiO-66 as a model catalyst and methyl phenyl sulfide (MPS) as a model substrate. Samples of UiO-66 differing in the particle size, number of defects, and composition have been synthesized. The particle size was evaluated based on high resolution transmission electron microscopy images. Thermogravimetric analysis (TGA), proton nuclear magnetic resonance spectroscopy (1H NMR), and inductively coupled plasma atomic emission spectroscopy (ICP-OES) were employed for quantification of defects and determination of the composition of the UiO-66 samples. The number of basic sites was determined by liquid-phase adsorption of isobutyric acid. It was demonstrated that this characteristic depends on both the number of defects and specific composition of UiO-66 and can be affected by dehydration/hydration procedures. The number of basic sites turned out close to the number of terminal Zr–OH2/OH groups in the Zr-MOF defects determined by combinations of 1H NMR/TGA and 1H NMR/ICP-OES, suggesting that the basic sites are represented by Zr-OH groups at open Zr sites. Kinetic studies implicated that catalytic activity of UiO–66 in MPS oxidation is proportional to the number of basic sites provided that the particle size of the Zr-MOF does not exceed 10–20 nm. Acid additives suppress both the thioether oxidation and H2O2 dismutation, pointing to the key role of basic Zr–OH groups in these two catalytic reactions.

Synthesis, characterization and application of a highly dispersed and reactive hypervalent iodine(V)/polyvinylpyrrolidone dendrimer nanocomposite: Hetero- vs. homo-intermolecular secondary O---I bonds

Polyvinylpyrrolidone (PVP) assisted aerobic oxidation of bulk iodosylbenzene or hydrolysis/oxidation of iodobenzene diacetate under mild conditions leading to the formation of nanostructured iodylbenzene is reported. AFM and FESEM-EDX analyses confirmed the formation of dendrimer iodylbenzene-polyvinylpyrrolidone nanocomposite (PhIO2-PVP) through the two top-down approaches. The formation of PhIO2 was confirmed by 1H NMR spectroscopy. Strong interactions between iodylbenzene molecules and the polymer through secondary intermolecular O---I bonds was evident from the large difference between the morphology of PVP (cubic) and PhIO2-PVP (dendrimer) nanoparticles. FESEM images showed a maximum width and length of 70 and 1000 nm for the dendrimers, respectively. The dual role played by PVP, i.e., facilitating the oxidation of I(III) to I(V) and stabilization the hypervalent I(V) compound was attributed to the formation of strong secondary hetero-intermolecular O---I bonds, between the polymer and iodine centre. The very fine aqueous and dichloromethane suspensions of PhIO2-PVP were indistinguishable to the naked eye. Efficient direct oxidation of cyclohexene and methylene blue with PhIO2-PVP at room temperature and a short reaction time provided evidence of significantly increased reactivity of PhIO2-PVP compared to that of the bulk oxidant. PhIO2-PVP was also used in the oxidation of methyl phenyl sulfide and styrene in water and dichloroethane, using water soluble and insoluble metalloporphyrins, respectively. The former led to the formation of the corresponding sulfoxide as the sole product in the two solvents. In addition to styrene oxide formed in both solvents, benzaldehyde was also formed with a selectivity of 24% in water. Almost complete oxidation of the organic substrates was observed in dichloroethane. The results of this study show that the nanostructured iodine(V) compound can be used as an efficient terminal oxidant in biomimetic oxidations.

Photoelectrochemical oxidation of methyl phenyl sulfide with oxygen atom transfer way on Mo-BiVO4 photoanode

Photoelectrochemical oxidation of methyl phenyl sulfide with water as the only oxygen source on Mo-BiVO 4 photoanode. Mo-BiVO 4 photoelectrode performs oxygen transfer reaction in PEC oxidation of MPS. • Mo-BiVO 4 photoelectrode was applied to oxidation of methyl phenyl sulfide. • PEC oxygen atom transfer (OAT) reaction was achieved on Mo-BiVO 4 photoelectrode. • Isotopic labelling experiment with H 2 18 O revealed oxygen atoms in MPSO were mainly from water. Photoelectrochemical (PEC) selective oxidation is an environment-friendly strategy to obtain value-added chemicals. Herein, we report the PEC oxidation of methyl phenyl sulfide (MPS) into methyl phenyl sulfoxide (MPSO) with 85.7% selectivity and 36.2% conversion on molybdenum doped bismuth vanadate (Mo-BiVO 4 ) photoelectrode under simulated sunlight illumination (AM 1.5 G, 100 mW cm -2 ). Isotopic labelling experiment with H 2 18 O was conducted to clearly reveal that the oxygen atoms in the MPSO were mainly from water. Based on these results, the application of Mo-BiVO 4 has been extended to PEC selective oxidation.

Acid-induced improvement of photosensitizing efficiency of porphyrins under heterogeneous aqueous conditions: High photosensitizing activity, dissociative stability and photooxidative durability

Meso-tetrakis(N-methylpyridinium-3-yl)porphyrin (H2TMPyP), electrostatically supported on the sodium salt of amberlyst 15 nanoparticles (nanoAmbSO3Na) was protonated with very weak (CH3COOH), weak (CH2ClCOOH, CHCl2COOH) and strong (CF3COOH) carboxylic acids and H2SO4 to prepare a series of new photosensitizers. NanoAmbSO3@H2TMPyP(HA)2 compounds were quite stable after separation from the aqueous solution and drying, even in the case of nanoAmbSO3@H2TMPyP(CH3COOH)2. The diacids were characterized by DR-UV–vis, AFM, TGA and DLS and used as photosensitizers in aerobic photooxidation of 1,5-dihydroxynaphthalene (DHN) and methyl phenyl sulfide. Almost no catalyst degradation was observed for the diacids in the oxidation of DHN after five successive runs. Also, the catalyst degradation was in the range of 0–68% in the oxidation of methyl phenyl sulfide at the end of the 5th run. The catalyst stability decreased as nanoAmbSO3@H2TMPyP(CF3COOH)2 >> nanoAmbSO3@H2TMPyP(CHCl2COOH)2 > nanoAmbSO3@H2TMPyP(H2SO4)2 > nanoAmbSO3@H2TMPyP(CH3COOH)2 > nanoAmbSO3@H2TMPyP(CH2ClCOOH)2. It is noteworthy that under the same conditions, ca. 50% of the non-protonated porphyrin, nanoAmbSO3@H2TMPyP, was degraded after 2 h, at the end of the first run. In other words, the formation of nanoAmbSO3@H2TMPyP(HA)2 species was associated with a significant increase in both the photocatalytic activity and oxidative stability of nanoAmbSO3@H2TMPyP, regardless of the type and strength of the acid used for diprotonation of the porphyrin. In the oxidation of methyl phenyl sulfide, nanoAmbSO3@H2TMPyP(CF3COOH)2 and nanoAmbSO3@H2TMPyP(CH2ClCOOH)2 were the most efficient catalysts of the series. The singlet oxygen quantum yields (ϕΔ), determined chemically by using 1,3-diphenylisobenzofuran as a specific quencher of singlet oxygen showed ϕΔ in the range of 0.51–0.98 for nanoAmbSO3@H2TMPyP(HA)2 and 0.66 for nanoAmbSO3@H2TMPyP.

Alkene Epoxidation and Thioether Oxidation with Hydrogen Peroxide Catalyzed by Mesoporous Zirconium-Silicates

Mesoporous zirconium-silicates have been prepared using two different methodologies, evaporation-induced self-assembly and solventless organometallic precursor dry impregnation of commercial SiO2. The samples were characterized by elemental analysis, XRD, N2 adsorption, TEM, DRS UV–vis and Raman spectroscopic techniques. The catalytic performance of the Zr-Si catalysts was assessed in the epoxidation of three representative alkenes, cyclohexene, cyclooctene and caryophyllene, as well as in the oxidation of methyl phenyl sulfide using aqueous hydrogen peroxide as a green oxidant, with special attention drawn to the structure/activity relationship and catalyst stability issues. The key factors which affect substrate conversion and epoxide selectivity have been defined. The catalysts with larger contents of oligomeric ZrO2 species revealed higher activity. The nature of alkene and, in particular, its molecular hindrance is crucial, since the adsorption of the epoxide product is the main factor leading to fast catalyst deactivation. In fact, bulky epoxides do not show this effect. After optimization, the oxidation of caryophyllene gave endocyclic monoepoxide with 77% selectivity at 87% alkene conversion. Methyl phenyl sulfoxide afforded 37% of sulfoxide and 63% of sulfone at 57% sulfide conversion. The nature of catalysis was truly heterogeneous and no Zr leaching was observed.

Immobilization of polyoxometalates via in-situ protonation and self-gelation of PEG-b-PDMAEMA-b-PTEPM triblock copolymer and its application in selective oxidation

To enrich the building block and function as well as the preparation methodology of metallopolymer system, functioned inorganic polyoxometalate clusters were introduced by using their intrinsic acidity induced multiple interactions with triblock copolymers. In the designed triblock copolymer PEG-b-PDMAEMA-b-PTEPM, the POMs clusters can be immobilized through in-situ protonation of the PDMAEMA block induced electrostatic interaction and the self-gelation of the PTEPM block, while the PEG block can improve the water solubility and dispersion of the final polyoxometalate-based hybrid catalyst (PHC). The selective oxidation activity of PHC is comparable with the homogeneous POMs catalyst as demonstrated by the model reaction of the selective oxidation of methyl phenyl sulfide (MPS) to methyl phenyl sulfoxide (MPSO). By optimizing the ratio between PHC and oxidant H2O2, the selectivity for MPSO can achieve as high as 99% with conversion above 95%. Furthermore, the multiple interactions between POMs and the polymer substrate also enhance the stability of PHC and enable the recycling of PHC. Therefore, the methodology of in-situ protonation and self-gelation by the acidity of POMs provides a facile and general strategy to prepare robust POMs-based metallopolymers, paving a new avenue towards cluster-based materials and devices.

A hypervalent iodine secondary oxidant synthesized by photosensitized singlet oxygen: Synthesis, characterization and oxidative reactivity

Chemical scavenging of singlet oxygen by iodobenzene in the presence of (triethyleneglycol)monomethyl ether led to the formation of almost spherical nano-structured iodosylbenzene in water, water/acetonitrile and acetonitrile. To our knowledge, it is the first report on the direct aerobic photooxidative synthesis of iodosylbenzene. A polymer supported cationic porphyrin, nanoAmbSO3@H2TMPyP, was used as the photosensitizer. The nanoparticles, were characterized by various spectrophotometric and microscopic methods. The reactivity of the secondary oxidant for the oxidation of organic substrates was studied in the oxidation of methyl phenyl sulfide catalyzed by manganese meso-tetrakis(2-methylphenyl)porphyrin.The synthesis of the reactive secondary oxidant, PhIO, is suggested as anapplicablestrategy to overcome the problem of very short lifetime of singlet oxygen in organic solvents and water, which decreases the efficiency of singlet oxygen due to the involvement of the oxidant in unwanted physicalandchemicalquenchingpathways.It is noteworthy that due to very short lifetime of singlet oxygen, most of the singlet oxygen produced in the presence of different photosensitizers is deactivated by other species to return to its triplet ground state by physical or non-productive chemical quenching.

Photostable Ag(I)-Based Metal-Organic Framework: Synthesis, Structure, and Photocatalytic Selective Oxidation Properties.

For Ag(I)-based photocatalysts, the photoreduction of Ag+ to metallic Ag is an unignorable issue, which is the major reason for their instability. If electrically neutral excitons rather than electrons were produced over Ag(I)-based photocatalysts, the photoreduction of Ag+ is expected to be greatly suppressed. To check this assumption, a Ag-based metal-organic framework containing pyrene, which is in favor of exciton production, is synthesized (denoted as Ag-PTS-BPY) and the structure is solved via single-crystal X-ray diffraction. Ag-PTS-BPY is applied in the photocatalytic selective oxidation of methyl phenyl sulfide, which displays high conversion and selectivity. As expected, no metallic Ag is formed after five cycles of reaction according to the results of X-ray diffraction, Fourier transform infrared, and X-ray photoelectron spectroscopy, and the high conversion is also maintained. The participation of excitons suppresses the involvement of electrons, which are believed to be the reason for the high stability of Ag-PTS-BPY.

Efficient singlet oxygen generation by excitonic energy transfer on ultrathin g-C3N4 for selective photocatalytic oxidation of methyl-phenyl-sulfide with O2

Efficient generation of singlet oxygen (1O2) by an excitonic energy transfer process is highly desired on a semiconductor photocatalyst for selective oxidation of methyl phenyl sulfide (MPS). Herein, it is demonstrated that a large amount of 1O2 is produced on pristine graphitic carbon nitride (CN) nanosheet compared with bismuth oxybromide (BiOBr) and commercial P25 titanium dioxide (TiO2). This leads to a certain photoactivity of CN for MPS oxidation. The observed ∼77% selectivity for CN depends on the competitive results of excitonic energy transfer for 1O2 formation and charge carrier separation for superoxide radical (O2−) production, which are based on the phosphorescence spectra and electron paramagnetic resonance signals, respectively. Moreover, ultrathin CN nanosheets are synthesized by thermal treatment with the cyanuric acid-melamine hydrogen bonded aggregates as precursors. It is confirmed that the amount of produced 1O2 could be increased by decreasing the thickness of resultant CN nanosheets. The optimized ultrathin CN nanosheet (∼4 nm) exhibits excellent photoactivity with high selectivity (∼99%). It is suggested that the excitonic energy transfer for 1O2 formation is close related to the intrinsic exciton binding energy and the two-dimensional quantum confinement effect. This work establishes a basic mechanistic understanding on the excitonic processes in CN, and develops a feasible route to design CN-based photocatalysts for efficient 1O2 generation.

Entrapment vs. immobilization of polyoxometalates into silica and titania aerogels: Application in heterogeneous oxidation catalysis

Silica and titania aerogels were successfully used as immobilization and entrapment media for phosphomolybdic and phosphotungstic acids. The hybrid materials were investigated in the heterogeneous oxidation catalysis of phenyl methyl sulfide. The characterization of the hybrid catalysts confirmed the immobilization and entrapment of the polyoxometalates (POM) and their dispersion onto the surface of the solid support. The entrapment of these clusters was found to affect less the surface properties of the inorganic network compared to the immobilization process, thus allowing smoother access to the active sites of the polyoxometalate molecules. The catalytic activity of the POM clusters was widely maintained after immobilization and incorporation, where the chemical nature of the surface functional groups was found to affect the behavior of the catalyst. The fastest oxidation of methyl phenyl sulfide was observed for the reactions catalyzed by POM-incorporated silica aerogels, coupled with a high selectivity towards the methyl phenyl sulfoxide.

Selective oxidation of organosulfurs with a sandwich-type polyoxometalate/hydrogen peroxide system

A dimeric tungstophosphate, Na14[Co4(PW9O35)2].28H2O (1), was synthesized via a simple one-pot method and characterized by single-crystal X-ray crystallography. Nanocluster 1 was exhibited to be able to selective oxidation of aliphatic and aromatic sulfides to sulfoxides in the presence of hydrogen peroxide at room temperature with high performance. Further investigations showed that this catalyst could reuse four times without a significant reduction in its activity for the oxidation of methyl phenyl sulfide.

A fluorescent turn-on probe for detection of hypochlorus acid and its bioimaging in living cells

Hypochlorous acid has played several functions in the biological system. However, excess HOCl can cause damage to biomolecules and result in some diseases. Accordingly, a new fluorescent probe, BSP, has been developed for fast recognition of HOCl through the HOCl-induced oxidation of methyl phenyl sulfide to sulfoxide. The reaction of BSP with HOCl caused a 22-fold fluorescence enhancement (quantum yield increase from 0.006 to 0.133). The detection limit of HOCl is found to be 30nM (S/N=3). The fluorescence enhancement is due to the suppression of the photo-induced electron transfer from the methyl phenyl sulfide moiety to BODIPY. Eventually, the cellular fluorescence imaging experiment showed that BSP could be effectively used for monitoring HOCl in living cells.

Titanium substituted potassium tantalates (KTaxTi1-xO3 x= 1.0, 0.8, 0.6, 0.5): Catalysts for the methyl phenyl sulfide oxidation

B-cation titanium substituted potassium tantalates KTaxTi1-xO3 (x = 1.0; 0.8; 0.6; 0.5) materials were synthesized, characterized by XRD, N2 adsorption–desorption isotherms, FTIR, DRS-UV–vis, TGA, H2-TPR and XPS to be used as catalysts for the selective oxidation of methyl phenyl sulfide. The non-substituted KTaO3 catalyst displays a total methyl phenyl sulfide conversion greater than 87% that increases with Ti substitution. The increases in the amount of titanium substituted decrease the crystallinity and the perovskite structure is not obtained, resulting in an amorphous material. The improvement in the conversion and selectivity towards the sulfone, is attributed to the slight loss of crystallinity that allows greater mobility of the lattice oxygen, essential in oxidation reactions and to the presence of TiO2 as segregated phases. These results obtained indicate that the substitution of B-cation generates physicochemical changes in the perovskite structure which enhances the oxidation properties of the catalysts.

KNbO3 soportado en zeolita BETA: evaluación del método de incorporación

Los óxidos mixtos presentan propiedades catalíticas, sin embargo, exhiben baja área superficial, lo que limita su uso como catalizadores. Con el fin de aumentar su superficie específica, se prepararon materiales a partir de la incorporación del óxido mixto sobre materiales de elevada área superficial evaluando dos métodos de incorporación. La actividad catalítica de los materiales se evaluó en la oxidación de Metil Fenil Sulfuro.
 Los materiales resultantes se caracterizaron mediante técnicas fisicoquímicas. El área superficial disminuyó respecto la matriz sin modificar como resultado de bloqueo de los poros y/o la ubicación de las partículas dentro de los poros de las zeolitas. Mediante difracción de rayos X se determinó que la muestra obtenida por mezcla mecánica presentó las señales de la zeolita pero con una disminución de la intensidad; la muestra “in-situ” no presentó estructura zeolítica ni cristalinidad. Los resultados de evaluación catalítica demostraron la importancia de la estructura y cristalinidad.