Efficient Selective Oxidation Research Articles

Morphology evolution of acetic acid-modulated MIL-53(Fe) for efficient selective oxidation of H2S

MIL-53(Fe) was synthesized using a “modulator approach” that utilizes acetic acid (HAc) as an additive to control the size and morphology of the resulting crystals. We demonstrate that after activation under vaccum at 100 °C, the MIL-53(Fe) functions well for H2S selective oxidation. The introduction of acetic acid in the presence of benzene-1,4-dicarboxylic acid (H2BDC) would result in a series of MIL-53(Fe) nanocrystals (denoted as MIL-53(Fe)-xH, x stands for the volume of added HAc with morphology evoluting from irregular particles to short hexagonal columns. The vacuum treatment facilitates the removal of acetate groups, thus generating Fe3+ Lewis acid sites. Consequently, the resulted MIL-53(Fe)-xH exhibits good catalytic activity (98% H2S conversion and 92% sulfur selectivity) at moderate reaction temperatures (100–190 °C). The MIL-53(Fe)-5H is superior to the traditional iron-based catalysts, showing stable performance in a test period of 55 h.

Photoredox dual reaction for selective alcohol oxidation and hydrogen evolution over nickel surface-modified ZnIn2S4

The photocatalytic coupling reaction can be conducted in one pot to realize the simultaneous utilization of electrons and holes, thereby obtaining value-added fine chemicals and fuels. Herein, we report a binary nickel modified ZnIn2S4 (Ni:ZIS) for highly efficient photocatalytic selective oxidation of benzyl alcohol (BA) to benzaldehyde (BAD) integrated with hydrogen (H2) evolution, in which Ni can promote photogenerated charge transfer for enhancing photoactivity. Particularly, the products of converting BA to aromatic compounds over blank ZnIn2S4 (ZIS) and Ni:ZIS show a marked difference under the same reaction conditions. Hydrobenzoin (HB) is the primary product over blank ZIS. After the introduction of Ni, the formation of HB is dramatically suppressed, resulting in higher selectivity of BAD, because the introduction of Ni facilitates the α-H abstraction. In addition, an analogous phenomenon has been observed on Ni-based compounds modified ZIS, such as NixP and NiS. It is hoped that this work would provide a feasible paradigm for modifying the surface of photocatalysts to tune the selectivity of product-oriented alcohols oxidation coupled with H2 evolution in water.

Efficient selective oxidation of benzyl alcohol with oxygen in a continuous fixed bed reactor over NiGa hydrotalcite derived catalyst

A series of NiGa catalysts have been prepared by calcining Ni5Ga-LDH under different temperatures, detailedly characterized, and investigated in the aerobic oxidation of benzyl alcohol to benzaldehyde in a fixed-bed reactor. The results indicated that calcination has a key effect on the composition of the catalyst and the catalytic performance, and the NiGa hydrotalcite calcined at 250 ℃ (Ni5Ga-LDH-250) exhibited the highest activity, which probably was due to the highest amount of surface basic site and the composition of Ni species. Under the optimized conditions, an excellent 91.5 % yield of benzaldehyde could be continuously obtained. Moreover, the catalytic performance kept almost steady in 170 h, and the catalyst could be regenerated and reused with slight reduction of the catalytic performance. According to the analysis of structure-activity relationship and the results of controlled experiments, possible reaction pathways for the aerobic oxidation of benzyl alcohol over Ni5Ga-LDH-250 are proposed.

The oversolubility of methane gas in nano-confined water in nanoporous silica materials

Abstract The oversolubility of the non-polar methane (CH4) gas in nano-confined liquid in nanoporous silica materials is investigated. A series of mesoporous silica materials with different pore sizes, pore volumes, and different amounts of nano-confined water (H2O) are prepared using a pore-expanding reagent and surfactants of different chain-lengths, and the CH4 absorption by the silica nano-materials is studied at 298 K under low CH4 gas pressures. Analysis of the CH4 absorption data reveals unequivocal evidence for oversolubility of CH4 in the nano-confined H2O of all the hydrated nano-materials. The solubility enhancements are several hundred fold relative to the CH4 solubility in bulk H2O. Interestingly, the enhancements are 25–30% higher when a tricopper cluster complex capable of efficient selective CH4 oxidation under ambient conditions is immobilized into the nano-channels of the silica materials. This dramatic enhancement of the CH4 solubility is attributed to specific CH4 binding to the tricopper cluster complexes embedded within the mesopores of the nanoporous materials.

Efficient selective oxidation of alcohols to aldehydes catalyzed by a morpholinone nitroxide

Efficient chemoselective oxidation of primary alcohols to the corresponding aldehydes is described. The transformation is promoted by a catalytic morpholinone nitroxide radical catalyst which can be easily synthesized. A broad range of substrates including aromatic and aliphatic primary alcohols are converted with excellent yields under mild conditions. The control experiments reveal that the morpholinone nitroxide can be used as a selective oxidant for primary alcohols in the presence of secondary alcohols.

Nano-WO3 -SO3 H as a New Photocatalyst Insight Through Covalently Grafted Brønsted Acid: Highly Efficient Selective Oxidation of Benzyl Alcohols to Aldehydes.

Modification of nano-WO3 with -SO3 H groups as a covalently grafted solid acid reduced its band-gap energy from 2.8 to 2.4eV and made it an ideal nominee for photocatalytic reaction under visible light irradiation. This nano-photocatalyst has been successfully used for the selective oxidation of different benzyl alcohols to corresponding aldehydes under blue LED irradiation. The reaction became approximately two times faster with excellent yields. It has shown that the nitrobenzene as an available industrial oxidant is applicable for photocatalytic oxidation of benzyl alcohol; remarkably high yield and selectivity have been observed.

Efficient selective oxidation of alcohols to carbonyl compounds catalyzed by Ru-terpyridine complexes with molecular oxygen

The oxidation of alcohols with molecular oxygen is a promising approach to produce corresponding carbonyl compounds. In this work, efficient aerobic oxidation of alcohols to carbonyl compounds catalyzed by ruthenium-terpyridine [(tpy-PhCH3)RuCl3] with isobutyraldehyde as co-substrate was developed. Various alcohols including primary and secondary alcohols are smoothly converted to corresponding carbonyl compounds in good yield. In a 100 times large-scale oxidation of benzyl alcohol, benzaldehyde was obtained with 92% isolated yield. Moreover, a plausible mechanism involving high-valence ruthenium species was proposed based on in situ UV–vis spectroscopy.

Efficient and selective photocatalytic oxidation of cyclohexane using O2 as oxidant in VOCl2 solution and mechanism insight

The efficient selective oxidation of cyclohexane to cyclohexanone and cyclohexanol (KA-oil) under mild conditions remains one of the most challenging and interesting projects in catalytic chemistry. Here, photocatalytic oxidation of cyclohexane was carried out in acetonitrile (MeCN) solution of VOCl2 under Xe lamp irradiation and pure O2 atmosphere. The results show that VOCl2 has high photocatalytic activity in pure MeCN solution, and a cyclohexane conversion of 17.8% with ca. 99% selectivity for KA-oil can be obtained after light irradiation of 4 h. It is worth noting that the use of hydrochloric acid as an additive can effectively enhance the photo-catalytic oxidation of cyclohexane, providing a cyclohexane conversion of 23.3%, which may be due to the important role of HCl in improving the light absorption, decreasing the oxidation-reduction potential of V5+/V4+ and promoting the redox process of photocatalyst. The effects of photocatalyst concentration, hydrochloric acid addition amount, O2 pressure and reaction time on photocatalytic performance were also studied. It was found that the optimization of these reaction conditions can further improve the conversion of cyclohexane and selectivity of KA-oil. A possible reaction mechanism for the photocatalytic oxidation of cyclohexane was proposed.

Nickel-Doped Excess Oxygen Defect Titanium Dioxide for Efficient Selective Photocatalytic Oxidation of Benzyl Alcohol

In this study, a novel composite Ni-OTiO2 was prepared by doping nickel and introducing excess oxygen defects in TiO2. The as-synthesized Ni-OTiO2 particles were characterized by scanning electron ...

Pyridinic-nitrogen-dominated nitrogen-doped graphene stabilized Cu for efficient selective oxidation of 5-hydroxymethfurfural

In this work, pyridinic-nitrogen-dominated nitrogen doped graphene with Cu incorporation (Cu/NG) are prepared via a facile and effective process. In prepared nitrogen doped graphene (NG), high nitrogen content up to 13.5 wt% was achieved and pyridinic-nitrogen dopant enriched to 11.9 at.%. Cu nanoparticles can be highly stabilized by NG materials and the stabilized Cu loading is linearly correlated with the pyridinic nitrogen content in NG. With Cu/NG as the catalyst and 2,2,6,6-tetramethyl-piperidin-1-oxyl (TEMPO) as co-catalyst, 5-hydroxymethylfurfural (HMF) was oxidized to 2,5-diformylfuran (DFF) in the new developed catalytic system under relative mild conditions (70 °C, 8 h) with high HMF conversion (99.8%) and DFF yield (99.2%). By various characterization and experimental data, Cu-N-C nano-centers were speculated to be the actives sites in catalytic oxidation of HMF. Comparison of high-resolution XPS spectra of N 1s between NG and Cu/NG material indicates the existence of strong interaction between Cu nanoparticles and pyridinic N. The developed catalytic system showed high efficiency in HMF oxidation and Cu/NG can be recycled for eight times without any obvious Cu leaching and catalytic activity loss.

Zeolite-encapsulated Co(II), Mn(II), Cu(II) and Cr(III) salen complexes as catalysts for efficient selective oxidation of benzyl alcohol

Co(II), Mn(II), Cu(II) and Cr(III) salen type complexes were synthesized in situ in Y zeolite by the reaction of ion-exchanged metal ions with the flexible ligand molecules that had diffused into the cavities. Data of characterization indicates the formation of metal salen complexes in the pores without affecting the zeolite framework structure, the absence of any extraneous species and the geometry of encapsulated complexes. The catalytic activity results show that Cosalcyen Y exhibited higher catalytic activity in the water phase selective oxidation of benzyl alcohol, which could be attributed to their geometry and the steric environment of the metal actives sites.

Aluminum(III) Chloride Promoted Oxygen Transfer: Selective Oxidation of Sulfides to Sulfoxides

An efficient selective oxidation of sulfides to sulfoxides has been developed by means of AlCl3-promoted oxygen transfer from phenyliodine diacetate [PhI(OAc)2]. AlCl3 proved to be the optimal ­Lewis acid for the activation of PhI(OAc)2. Various substituted sulfides were selectively transformed into the corresponding sulfoxides in good to excellent yields (≤99%). The high efficiency, excellent functional-group compatibility, broad substrate scope, and mild conditions render the current transformation useful for the synthesis of sulfoxides.

Efficient selective catalytic oxidation of benzylic C[sbnd]H bonds by ZIF-67 under eco-friendly conditions

We report here an efficient, mild and green protocol for the chemoselective oxidization of benzylic CH bonds. The reactions were carried out with ZIF-67 as heterogeneous catalyst and tert-butyl hydroperoxide as an oxidant. The desired ketones were achieved in moderate to excellent yields at room temperature under solvent-free and open-flask conditions. Notably, the presented method avoids the use of complex catalyst, toxic organic solvent, additives and high temperature. At the same time, the heterogeneous catalyst could be conveniently reused at least six cycles without significantly decreasing yield of desired product. The gram-scale experiments were achieved with excellent yields and provided a modest and effective method for scale up applications.

Visible-Light-Induced Efficient Selective Oxidation of Nonactivated Alcohols over {001}-Faceted TiO2 with Molecular Oxygen.

In the presence of molecular oxygen, a {001}-faceted nanocrystalline anatase TiO2 catalyst enabled the selective oxidation of nonactivated aliphatic alcohols to the corresponding aldehydes or ketones under visible light. The reaction shows excellent conversion and selectivity towards the formation of the carbonyl products without over-oxidation to the corresponding carboxylic acids. The exceptional reactivity of the catalyst is possibly due to the absorption of visible light originating from a stronger interaction of alcohol with the {001} facet, which facilitates the modification of the band structure of TiO2 , thus facilitating the photogenerated hole transfer and subsequent oxidation processes. The experimental results have also been corroborated by first-principles quantum chemical DFT calculations.

An Energy Efficient Sonochemical Selective Oxidation of Benzyl Alcohols to Benzaldehydes by Using Bio-TSIL Choline Peroxydisulfate

The present work deals with effective combination of ultrasonication (US) and biodegradable oxidizing task specific ionic liquid (bio-TSIL) choline peroxydisulfate monohydrate (ChPS·H2O) for the selective oxidation of alcohols to aldehydes/ketones. The reactions were also conducted by using a thermal heating method (TH), and the comparative studies are provided to understand the effectiveness of the ultrasound process; it was observed that the use of ultrasound significantly reduces the reaction time from 30 to 5 min. Also, a substantial energy saving (>86%) was observed when the US method (0.125 kJ/g) was compared with the TH method (0.958 kJ/g). Bio-TSIL ChPS in water as an oxidant is found to be advantageous, as it is synthesized from biodegradable and nontoxic raw materials. Incorporation of an ultrasonic energy source along with the use of biodegradable raw materials for bio-TSIL makes the process not only green but also energy efficient.

An efficient and convenient method for the preparation of disulfides from thiols using oxygen as oxidant catalyzed by tert -butyl nitrite

An efficient and convenient tert-butyl nitrite-catalyzed selective aerobic oxidation of thiols has been developed. Under the optimal reaction conditions, a number of thiol derivatives including aromatic thiols, heteroaromatic thiols and aliphatic thiols can be converted into their corresponding disulfides in good to excellent yields.

An Efficient Selective Oxidation of Alcohols with Zinc Zirconium Phosphate under Solvent‐free Conditions

AbstractZinc zirconium phosphate (ZPZn) nanoparticles have been used as an efficient catalyst for the selective oxidation of a wide range of alcohols to their corresponding ketones or aldehydes using H2O2 as an oxidizing agent without any organic solvent, phase transfer catalyst, or additive. The steric factors associated with the substrates had a significant influence on the reaction conditions. The results showed that this method can be applied for chemoselective oxidation of benzyl alcohols in the presence of aliphatic alcohols. The catalyst used in the current study was characterized by ICP‐OES, XRD, N2 adsorption‐desorption, NH3‐TPD, Py‐FTIR, SEM, and TEM. These analyses revealed that the interlayer distance in the catalyst increased from 7.5 to 8.7 Å when Zn2+ was intercalated between the layers, whereas the crystallinity of the material was reduced. This nanocatalyst could also be recovered and reused at least seven times without any discernible decrease in its catalytic activity. This new method for the oxidation of alcohols has several key advantages, including mild and environmentally friendly reaction conditions, excellent yields and a facile work‐up.

An efficient selective oxidation of alcohols with iron zirconium phosphate under solvent-free conditions

Iron zirconium phosphate nanoparticles have been used as an efficient catalyst for the selective oxidation of a wide range of alcohols to their corresponding ketones or aldehydes using H2O2 as an oxidizing agent without any organic solvent or additive. The steric factors associated with the substrates had a significant influence on the reaction conditions. The results showed that this method can be applied for chemoselective oxidation of benzyl alcohols in the presence of aliphatic alcohols. The catalyst used in the current study was characterized by ICP-OES, XRD, N2 adsorption–desorption, NH3-TPD, Py-FTIR, SEM, and TEM.

Chloroacetate-promoted selective oxidation of heterobenzylic methylenes under copper catalysis.

The efficient selective oxidation and functionalization of C-H bonds with molecular oxygen and a copper catalyst to prepare the corresponding ketones was achieved with ethyl chloroacetate as a promoter. In this transformation, various substituted N-heterocyclic compounds were well tolerated. Preliminary mechanistic investigations indicated that organic radical species were involved in the overall process. The N-heterocyclic compounds and ethyl chloroacetate work synergistically to activate C-H bonds in the methylene group, which results in the easy generation of free radical intermediates, thus leading to the corresponding ketones in good yields.

Chloroacetate‐Promoted Selective Oxidation of Heterobenzylic Methylenes under Copper Catalysis

AbstractThe efficient selective oxidation and functionalization of CH bonds with molecular oxygen and a copper catalyst to prepare the corresponding ketones was achieved with ethyl chloroacetate as a promoter. In this transformation, various substituted N‐heterocyclic compounds were well tolerated. Preliminary mechanistic investigations indicated that organic radical species were involved in the overall process. The N‐heterocyclic compounds and ethyl chloroacetate work synergistically to activate CH bonds in the methylene group, which results in the easy generation of free radical intermediates, thus leading to the corresponding ketones in good yields.