The vanadium oxide/reduced graphene oxide (VOx/RGO) composites have been prepared by a simple solvothermal method with the assistance of cationic surfactant cetyltrimethylammonium bromide (CTAB). The microstructure and morphology of the resultant VOx/RGO composites have been well characterized. The VOxnanoparticles are highly dispersed on the RGO sheets with a particle size of about 25 nm. When used as hydroxylation catalysts, the VOx/RGO composites are more efficient than individual RGO and vanadium oxide catalysts. The enhanced catalytic performance may be related to not only the well dispersed VOxactive species, but also the hydrophobic surface and huge π-electron system of RGO for the adsorption and activation of benzene. In addition, the effects of calcination conditions on the microstructure and catalytic properties of VOx/RGO composites have also been investigated. The uniform VOxnanoparticles on the separated RGO sheets show highly efficient catalytic performance, while the formation of aggregated HxV2O5and bulk V2O5species along with the destruction of RGO sheets are poor for the hydroxylation of benzene. Up to 17.4% yield of phenol is achieved under the optimized catalytic reaction conditions.Keywords:vanadium oxide;reduced graphene oxide;benzene;hydroxylation;phenol
Catalytic upgrading lignin-derived bio-oil with high oxygen content to directly usable transport fuel through hydrotreatment is highly desirable, but still remains a challenge. In this work, a series of Co-based catalysts were synthetized using metal–organic frameworks (MOFs) as a structure-directing agent and lignin as a renewable carbon precursor via a simple hydrothermal method. Among these catalysts, Co/C-EL-0.5–500 showed the best catalytic hydrotreatment activity, affording 100% guaiacol conversion with 90% cyclohexanol yield under the conditions of 240 °C, 0 MPa N 2 and 4 h. According to the characterization results of XRD, SEM, TEM, BET, ICP, NH3-TPD and XPS, the excellent performance of Co/C-EL-0.5–500 was attributed to large specific surface area, small Co particle size, and optimal acidity. The possible reaction pathway was proposed based on the product distribution. In addition, isopropanol was used as H-donor instead of extra hydrogen, and we hope that it could provide a novel strategy for bio-oil upgrading.
( R )-2-(4-hydroxyphenoxy)propionic acid (( R )-HPOPA) is an important intermediate for the synthesis of optically pure aryloxyphenoxypropionic acid herbicides. Regioselective hydroxylation of ( R )-2-phenoxypropionic acid (( R )-POPA) by microbes is one of the most useful methods for the industrial production of ( R )-HPOPA. In this study, we designed and optimized a rapid throughput assay for screening ( R )-HPOPA producing bacterial/fungal strains which can regioselectively hydroxylate ( R )-POPA. ( R )-HPOPA could react with 4-aminoantipyrine (4-AAP) in the presence of potassium hexacyanoferrate (K 3 [Fe(CN) 6 ]) to form indoxyl antipyrine, an orange-red chromophore, that can easily spectrophotometrically be determined at 550 nm. During the verification of the assay we observed an average recovery rate of between 97.3% and 104.5%. Apart from the rapid throughput, no obvious differences in detection ( R )-HPOPA in the culture broth samples were found between our rapid throughput multiplate assay and a high-performance liquid chromatography method. Our optimized assay method is simple, rapid and accurate with high repeatability. It has the potential for high throughput screening (about 3000–5000 samples/day) of the ( R )-HPOPA producing strains.
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