Preparation Of Supported Iron Oxide, Copper Oxide Catalyst And Its Hydroxylation Performance By Chemical Vapor Deposition

Catechol (CAT), hydroquinone (HQ) and benzoquinone (BQ) are important chemical intermediates widely used in the fields of pharmaceutical, pesticide, meticulous chemicals, etc. Due to the constraints of environmental protection and cost, the traditional preparation methods of dihydroxyhenzene and benzoquinone were gradually eliminated. Phenol hydroxylation to dihydroxyhenzene and benzoquinone become popular because of the low cost and pullution, and research and development of efficient phenol hydroxylation catalysts is more and more imprtant. In this dissertation, α-Fe2O3/SiO2, monoclinic-phase CuO/SiO2 and cubic-phase CuO/γ-Al2O3 catalysts were synthesized by chemical vapor deposition, and corresponding reference catalysts were also synthesized by the traditional incipient wetness impregnation. The physicochemical properties of three series of catalysts were characterized and the catalytic activity was evaluated by the reaction of phenol hydroxylation.1. Synthesis, characterization and catalytic activity of α-Fe2O3/SiO2 catalystsDifferent loadings of α-Fe2O3/SiO2 catalysts were synthesized by Chemical Vapor Deposition (CVD) with ferrocene and fumed silica (A380) as substrate and precursor, respectively. The reference catalysts were prepared by incipient wetness impregnation with the same nominal loading as the ones synthesized by CVD. The physical and chemical properties of the catalysts were characterized by AAS, HRTEM, FT-IR, XRD, H2-TPR and low-temperature nitrogen adsorption, and catalytic performances of the synthesized samples were tested by phenol hydroxylation to dihydroxyhenzene, the optimized reaction conditions were explored. The result shows that the highly-dispersed α-Fe2O3 nano-particle catalysts are successfully supported over the surface of fumed silica with a uniform diameter of 3-5 run, and the strong interaction between the a-Fe2O3 nano-particles and the support silica was confirmed by the FT-IR analysis. It was found that the α-Fe2O3/SiO2 catalysts synthesized by CVD exhibited a higher catalytic activity in phenol hydroxylation. Under the optimized reaction condition, the conversion of phenol is 45.5%, and a total selectivity of dihydroxyhenzene is 58.9%.2. Synthesis, characterization and catalytic activity of monoclinic-phase CuO/SiO2 catalystsThe monoclinic-phase CuO/SiO2 catalysts were synthesized by CVD with cupric(II) acetylacetonate (Cu(acac)2) as precursor and silica as substrate, respectively. The reference catalysts were prepared by impregnation with the same nominal loading as the ones synthesized by CVD. The physical and chemical properties of the catalysts were characterized by AAS, XRD, TEM, H2-TPR, NH3-TPD, FT-IR, XPS and low-temperature nitrogen adsorption, and catalytic performances of the synthesized samples were tested by phenol hydroxylation to dihydroxyhenzene, the optimized reaction conditions were explored. The result shows that the highly-dispersed nano-particles CuO are successfully supported on the surface of silica, and the Cu-O-Si bond between CuO and the supported silica were confirmed by the FT-IR analysis. It was found that the monoclinic-phase CuO/SiO2 catalysts synthesized by CVD exhibited a higher catalytic activity in the reaction of phenol hydroxylation. Under the optimized reaction condition, the conversion of phenol is 42.7%, a total selectivity of dihydroxyhenzene is 58.0%, and a selectivity of benzoquinone is 10.3%.3. Synthesis, characterization and catalytic activity of cubic-phase CuO/γ-Al2O3 catalystsThe cubic-phase CuO/γ-Al2O3 catalysts were synthesized by CVD with Cu(acac)2 as precursor and silica as substrate, respectively, and the reference catalysts were also prepared by impregnation with the same nominal loading as the ones synthesized by CVD. The samples were characterized in detail by AAS, XRD, TEM, H2-TPR, XPS, FT-IR and low-temperature nitrogen adsorption, catalytic performances of the synthesized samples were tested by phenol hydroxylation, and the optimized reaction conditions were explored. The results revealed that the crystal phase of CuO deposited on Al2O3 prepared by CVD shown a cubic phase, the cubic-phase CuO particles were highly dispersed on Al2O3 with a diameter around 6 nm, the cubic-phase CuO/γ-Al2O3 catalysts prepared by CVD exhibit excellent catalytic activity in the phenol hydroxylation.The a-Fe203/Si02, monoclinic-phase CuO/SiO2 and cubic-phase CuO/γ-Al2O3 catalysts were prepared by chemical vapor deposition, the synthesized catalysts exhibited high dispersion degree of active components and thus better catalytic performances than the samples synthesized by the impregnation. Further, the resulting CuO supported on the γ-Al2O3 sunstrate present cubic phase, which is different from monoclinic phase acquired by the traditional impregnation. These probes will give some useful guidelines for the controlled synthesis of the supported transitional metal oxide catalysts.