Authors:Chunyan Liu, Zhengfeng Shao, Zihui Xiao and Changhai Liang
Activated carbon supported Pt, Pd, and Pt–Pd catalysts have been successfully prepared by incipient wet impregnation with a hydrochloric solution of PdCl2 and PtCl4. Hydrodeoxygenation of benzofuran was used as a probe reaction to investigate their catalytic properties. The activated carbon supported Pt–Pd catalyst was confirmed to form Pt–Pd alloy by X-ray diffraction. All the catalysts were active in the hydrodeoxygenation of benzofuran. Pd catalyst did not only give higher hydrogenation activity, but also showed faster deoxygenation rate than the Pt catalyst. The Pt–Pd catalyst with the mole ratio of Pd/Pt = 4 showed the highest catalytic activity among all of the catalysts. 2-Ethylcyclohexanone, which was not observed over the sulfide catalysts, was detected as a new oxygen-containing intermediate in the hydrodeoxygenation of benzofuran over the activated carbon supported Pt, Pd, and Pt–Pd catalysts. A ketone/enol isomerization reaction route is proposed to happen over the activated carbon supported noble metal Pt, Pd, and Pt–Pd catalysts.
The oxidation of thioanisole to its sulfone with hydrogen peroxide (H2O2) in the presence of acetic acid and Amberlyst 15 was investigated and found to be a simple and effective method. Oxidation experiments in the absence of acetic acid or Amberlyst 15 confirmed the essentiality of these components for the complete oxidation of thioanisole to its sulfone with H2O2. In the two-step oxidation process of sulfide, in the oxidation of sulfide to sulfoxide, H2O2 plays a major role, whereas in the oxidation of sulfoxide to sulfone, peracetic acid formed with H2O2 in the presence of acetic acid and Amberlyst 15 plays a major role. Sulfone formation increased with an increase in H2O2, temperature and Amberlyst 15 and decreased with acetic acid. However, with a very low amount of acetic acid, sulfone formation decreased due to water in H2O2 and released in the reaction. Reutilization of Amberlyst 15 for six cycles resulted in a 6.8 % decrease in sulfone yield and 3.4 % decrease in oxygenation. Dialkyl, dibenzyl, diphenyl, alkylaryl, arylbenzyl, alkylbenzyl sulfides are completely oxidized with this oxidation system to their corresponding sulfones. The reactivity of sulfides is in the order dialkyl > dibenzyl > diphenyl sulfides, which is in line with their order of nucleophilicity.
Authors:Prince Osei Bonsu, Xiaomeng Lü, Jimin Xie, Deli Jiang, Min Chen and Xiaojun Wei
Brookite titania nanomaterials modified with gold nanoparticles (NPs) Au–TiO2 were prepared in this research. The photocatalytic activity of the prepared composite was assessed by the photodegradation of organic pollutants. Rhodamine blue was used as a model organic pollutant. The study determined the optimum loading ratio of Au/Ti, which will result in the best photodegradation efficiency. Also, the photocatalytic activity of gold loaded brookite titania nanomaterials was ascertained under visible light. The hydrothermal method was used to prepare brookite titania whiles, gold NPs were loaded on its surface by consecutive ion adsorption and photoreduction. The results revealed that the sample Au–TiO2 (Au/Ti = 2 % molar ratio) had the best photocatalytic degradation efficiency of 100 % after 2 h of irradiation under visible light and was also higher than commercial P25.
Authors:Mohamed Triki, Anton Dafinov, Jordi Llorca and Francisco Medina
Continuous catalytic wet air oxidation was investigated as a suitable treatment of p-hydroxybenzoic acid chosen as a phenolic compound typically found in olive mill wastewater. The reaction was conducted in a continuous reactor at 140 or 150 °C and 50 bar of air using ruthenium catalysts supported by aerogel mixed oxides (Ru/CeO2–Al2O3, Ru/CeO2–TiO2). The influence of the Ru precursor and the nature of the support were studied. The results show that supported ruthenium catalysts were active to oxidize p-hydroxybenzoic acid and that the catalytic activity is very stable.
Authors:N. Batalha, L. Pinard, S. Morisset, J. L. Lemberton, Y. Pouilloux, M. Guisnet, F. Lemos and F. R. Ribeiro
n-Hexadecane hydroisomerization at 220 °C and 30 bar was used as a model reaction for comparing the catalytic performances of a Pt/HBEA sample whose zeolite crystals were germinated on an α alumina surface with those of 1Pt/HZM-22 catalyst well-known for its high isodewaxing selectivity. Similar values of selectivity to isomers were obtained with both catalysts even at high conversions. Moreover, despite its low zeolite content (13 wt%), the Pt/HBEA Al2O3 catalyst had the important advantage to be 4.6 times more active.
A silica-supported Pd nanoparticle catalyst was prepared by refluxing a Pd(II) precursor in alkaline 2-propanol; it consisted of metallic Pd nanoparticles (ca. 2–8 nm) dispersed in the silica-gel pores. This catalyst exhibited much more efficient dechlorination of p-chloroanisole and 1,1-bis(4-chlorophenyl)-2,2-dichloroethylene (DDE) in an alkaline 2-propanol/methanol (99:1 v/v) solution than a conventional Pd/C catalyst.
Authors:Bing Xue, Kai Jia, Jie Xu, Na Liu, Ping Liu, Chongfu Xu and Yongxin Li
An efficient and novel method to prepare KNO3/NaY solid base catalysts was developed. High selectivity for phenetole along with high conversion of phenol was obtained in the vapor phase O-alkylation of phenol with diethyl carbonate over KNO3 modified NaY zeolite. Experimental results showed that a large number of basic sites on KNO3/NaY were generated mainly during catalytic evaluation, which was responsible for the outstanding catalytic performance. Furthermore, the excess KNO3 loadings might lead to the blockage of the pores in the NaY zeolite and decrease the catalytic activity.
Authors:Andrés Pena, Santiago Veiga, Mariángeles Sapelli, Natalia Martínez, Victoria Márquez, Eduardo Dellacassa and Juan Bussi
Liquid-phase oxidation of limonene was performed with molecular oxygen as the sole oxidizing agent under non-solvent conditions. The oxidation took place under atmospheric pressure and temperatures between 70 and 90 °C in the presence of three different nickel–aluminium hydrotalcites. The final limonene conversion at 80 °C and 6 h of reaction time was comprised between 40 and 50 %. Several oxygenated limonene derivatives such as endo- and exo-epoxides, carveol and carvone represent 45–60 % of the whole amount of products. In the absence of a catalyst, a higher initial content of peroxides in limonene lead to a higher reaction rate with no significant changes in product selectivities. Thermal decomposition of limonene peroxides took place as the initiation path of an autooxidation mechanism leading to the different products. The catalyst played an important role in the initial paths involving activation of both reactants as well as in the decomposition of limonene peroxide to form radicals.
The effects of Ru precursor, Ru loading and calcination conditions on the properties and catalytic activities of ruthenium catalysts supported on activated carbon (Ru/AC) to remove bromate ion in water were investigated. A series of Ru/AC catalysts were prepared by the impregnation method and were characterized. From the examination of X-ray photoelectron spectra, RuO2 was deemed as the major active component on the Ru/AC catalysts to reduce bromate ion. The Ru precursors have significant effect on the activities of Ru/AC catalysts, due mainly to that (NH4)2RuCl6 was prone to generate metallic Ru, while RuCl3·3H2O could form RuO2. It was also found that calcination of Ru/AC in pure nitrogen gas favored the RuO2 formation compared with those calcined in vacuum and 1.5 vol.% H2/N2. The maximum bromate reduction efficiency around 95 % can be successfully achieved by Ru/AC prepared when the Ru loading, calcination temperature and time were 0.1 wt.%, 900 °C, and 3 h, in order, in a pure N2 atmosphere. From the characterization of catalysts, it was found that the excellent performance of Ru/AC would benefit from two aspects: one is that the structure and texture of the support carbon was strengthened during the calcination process, and the other is that an even distribution of RuO2 particles was obtained.
Carbothermally reduced and nitrided Ta2O5 powder at varying temperature (680–760 °C) in flowing NH3 facilitated both nitrogen doping and the formation of the traces of TaON and Ta3N5 to a greater degree than the simply NH3-heat-treated Ta2O5. It demonstrated an enhanced visible-light absorption, an enhanced surface adsorption of rhodamine B molecules in the dark, and subsequently an improved visible-light photocatalytic activity to decompose rhodamine B in aqueous solution (via mainly surface photosensitization), as compared to the simply nitrided counterpart in NH3 atmosphere. The carbothermal reduction followed by the NH3-treatment (nitridation) is proven to be an efficient way to improve the degree of nitridation at a given temperature. The product of such process can be an efficient visible light photocatalyst.