Papers by Keyword: Hydroxylation

Abstract: Fe-SBA-15 materials with different Fe content have been prepared using tetraethyl orthosilicate (TEOS) and iron nitrate (Fe (NO₃)_3·H₂O as precursors and Pluronic P123 as structure directing agent through evaporation-induced self-assembly (EISA) method. The materials were characterized by nitrogen sorption, powder X-ray diffraction and TEM. All the Fe-SBA-15 samples appeared ordered 2D hexagonal mesostructure. The BET surface area and pore diameter were about 500 m²/g and 4 nm respectively. In the reaction of phenol hydroxylation to dihydroxybenzenes, the Fe-SBA-15 materials showed good catalytic activity, giving 20.2% of phenol conversion, 58.2% of selectivity for o-dihydroxy benzene and 41.8% of selectivity for p-dihydroxy benzene. After five cycles, the product yield was 25.2%, while selectivities of o-dihydroxy benzene and p-dihydroxy benzene were 58.2% and 41.8%, respectively. All these findings indicated the potential of Fe-SBA-15-10 could be used as a cost-effective, environment-friendly catalyst.

Abstract: A sapphire substrate is essential for epitaxial growth of GaN, which is used for high brightness light-emitting diodes (LEDs), high-power and high-frequency devices. However, the material removal rate (MRR) of sapphire in conventional polishing is very low because of its high hardness and chemical inertness. We proposed application of plasma assisted polishing using a resin-bonded silica grinding stone for finishing of sapphire surface and investigated basic removal properties. The results of a ball-on-disc type test results showed that irradiation of water vapor containing atmospheric pressure Ar gas plasma promoted the MRR of sapphire by a factor of 7.4. Strong emission from hydroxyl radical was observed by an optical emission spectroscopy measurement of the plasma. XPS measurements revealed that the surface of both sapphire and silica were hydroxylated after the plasma irradiation. From these experimental and measurement results, we proposed the removal model in plasma assisted polishing of sapphire as follows. Firstly, irradiation of water vapor plasma hydroxylates the surfaces of sapphire and silica. Then, Al-O-Si bonding is formed by dehydration reaction between sapphire and silica surfaces. Finally, surface atom of sapphire is removed by the motion of silica abrasive. In this paper, we describe the preliminary experimental results and measurement results which support the proposed removal model in plasma assisted polishing of sapphire.

Abstract: Microbial transformation of androst-4-en-3,17-dione (AD; 1) using Colletotrichum lini AS3. 4486 resulted in the production of two metabolites 2 and 3. The structures of these compounds were elucidated by spectroscopic analysis (LC-MS, FTIR and NMR) as 15α-hydroxyandrost-4-en-3,17-dione (15α-OH-AD; 2) and 11α,15α-dihydroxyandrost-4-en-3,17-dione (11α,15α-diOH-AD; 3). AD underwent regioselective hydroxylation at 15α position, subsequently hydroxylated at 11α position and converted to compound 3. 11α,15α-diOH-AD as an important metabolic product was pharmaceutical intermediate and the yield was up to 97.58% when the concentration of substrate was 4 g L^-1.

Abstract: In this paper, hydroxylated CNTs/Fe₂O₃ precursors were prepared on the basis of Fenton reagent treatment using aqueous ammonia (NH₃H₂O), sodium carbonate (Na₂CO₃) and urea (CO(NH₂)₂) as precipitants. And then three kinds of hydroxylated CNTs/Fe₂O₃ compound particles were obtained by calcining the precursors at 523K for 2h. The change of hydroxyl group, phase structure, morphology, thermogravimetric behavior, magnetic property and electrical conductivity of the compound particles were investigated, respectively. The results show that hydroxyl groups exist on surface of CNTs, and Fe₂O₃ particles in composite particles exhibit high purity and integrated crystalline structure. For NH₃H₂O precipitant, α-Fe₂O₃ particles is produced with crystallite size of 62.5nm and no saturation magnetization (Ms). For Na₂CO₃ precipitant, γ-Fe₂O₃ is produced with crystallite size of 37.6nm and Ms of 10.5emug^-1, and the compound particles are drastically agglomerated. For CO(NH₂)₂ precipitant, γ-Fe₂O₃ is produced with crystallite size of 35.1nm and Ms is 9.7 emug^-1, and the compound particles are homogeneous with the lowest volume resistivity of 100 Ωcm.

Abstract: A series of ionic liquids were used as a co-solvent in the reaction of one-pot synthesis of phenols from aromatics and hydroxylamine. Then an eco-friendly catalytic system, i.e., [HSO₃-bmi [CF₃SO₃]-H₂O-HAc media with (NH₄)₆Mo₇O₂₄·4H₂O catalyst, was designed for the reaction. The results showed that aromatics were successfully hydroxylated to give the corresponding phenols. Recycling experiments suggested that the catalytic system was stable enough to be recycled.

Abstract: Microbial hydroxylation of progesterone occurred in the biotransformation by Phomopsis sp.. The conversion products were purified by column chromatography with ether/EtOAc and characterized by spectroscopic methods including ¹HNMR, ¹³C NMR, IR, UV and MS. Those conversion products were identified as 11α-hydroxyprogesterone (2), 11α,15β-dihydroxy progesterone (3),11α-dihydroxypreg-1,4-dien-3,20-dione (4), 6β,15βdihydroxypregesterone (5) and 7β,15βdihydroxypregesterone (6).

Abstract: Although heptachlor epoxide (HE) is the major metabolite of organochlorine pesticide heptachlor in soil, there is very limited information on the biodegradation of HE by microorganisms, and no systematic study on the metabolic products and pathways for HE transformation by fungi has been conducted. In this study, the metabolism of HE was performed with Cordyceps brongniartii ATCC66779, which is capable of degrading polychlorinated dibenzo-p-dioxin. This fungus removed about 27% and 21% of HE in PDB and BSM medium, respectively, after 20 days of incubation. Three hydroxylated products including heptachlor diol, 1,2-dihydroxydihydrochlordene and trihydroxychlordene were detected as metabolites of HE using GC/MS analysis, suggesting that HE was metabolized to hydrophilic products via hydrolysis, dechlorination and hydroxylation.

Abstract: A series of nano-sized iron oxide supported on 3D wormlike hierarchical mesoporous SiO₂ catalysts were synthesized by one-step hydrothermal synthesis. The samples were characterized by XRD, N₂ sorption, FT-IR, UV–Vis, TEM and ICP-AES. The catalysts were probed for the oxidation of phenol employing hydrogen peroxide. The results indicate that the materials exhibit high surface area and 3D wormlike hierarchical pore, iron ions exist as isolated framework species when the weight percentage content of iron is below 0.24 and nano-size iron oxide is dispersed in the surface (iron content above 0.24 wt%). Catalytic performance indicates that nano-size iron oxide supported on SiO₂ is useful to enhance both the catalytic activity and the selectivity of target products compared with isolated iron species.

Abstract: The biotransformation of progesterone by Colletotrichum lini AS3. 4486 was studied. The formation of the product was monitored by HPLC. Product was purified from broth culture supernatants by silica gel column chromatography and identified as 7β,12β-dihydoxylprogesterone with MS, ¹H NMR, ¹³C NMR and NOE.

Abstract: Phthalocyanine catalysts were synthesized and supported matel phthalocyanines were found to be good catalysts for benzene hydroxylation to phenol. Matel phthalocyanines were characterized by N₂ absorption-desorption, FT-IR spectroscopy, and tranmsission electron microscopy. The experimental results suggested that the supported matel phthalocyanines were good catalysts for benzene hydoxylation reaction. Supported vanadium phthalocyanine performed the best catalytic activity, on which 11.6% of phenol yield and 100% of selectivity were obtained. And it was proved to be reusable in this reaction.