Oxidation Processes for Wastewater Treatment

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Publications

Platinum catalysts supported on MWNT for liquid phase degradative oxidation of nitrogen containing compounds

Publication . García, Juan; Gomes, Helder; Serp, Philippe; Kalck, Philippe; Figueiredo, José; Faria, Joaquim

Since their discovery [1], carbon nanotubes (CNT) have attracted great interest from both a fundamental and an applied point of view, due to their high mechanical strength and unique electrical and thermal properties [2]. These characteristics are also interesting in the context of using CNT as a support for heterogeneous catalysts in liquid-phase reactions. Some examples of this type of application using multiwalled carbon nanotubes (MWNT) have been reviewed recently [3]. Our experience with carbon supported noble metal catalysts applied to catalytic wet air oxidation (CWAO) of liquid effluents [4] prompted us to prepare platinum catalysts supported on surface oxidized MWNT, to be used in the liquid phase degradative oxidation of nitrogen containing compounds, such as aniline and azo dyes. The catalysts Pt1, Pt2 and Pt3 were prepared by excess solution impregnation, using different metallic precursors dissolved in various solvents, respectively [PtI2(CO)2] in toluene, H2PtCl6 in water and [Pt(CH3)2(C8H12)] in hexane. The metal dispersion (DM) was determined by H2 pulse chemisorption (Table 1). The prepared catalysts were then tested in the CWAO of aniline. The aniline conversion (XAniline), TOC abatement (XTOC) and selectivity towards CO2 formation (SCO2) obtained after 2 h of reaction at 200ºC and 6.9 bar of oxygen partial pressure are resumed on Table 1.

2004Conference object

Open access

Nanotubos de carbono como suportes para catalisadores de platina

Publication . García, Juan; Gomes, Helder; Serp, Philippe; Kalck, Philippe; Figueiredo, José; Faria, Joaquim

Desde a sua descoberta em 19911, que os nanotubos de carbono tem sido amplamente estudados, devido à sua elevada resistência mecânica, excelentes propriedades eléctricas e térmicas e adequação como suporte de catalisadores heterogéneos para reacções em fase líquida2. Neste trabalho pretendeu-se estudar a utilização de nanotubos de carbono de parede múltipla oxidados com HNO3 como suporte na preparação de catalisadores de platina para reacções de degradação oxidativa de compostos orgânicos azotados. Os catalisadores Pt1, Pt2 e Pt3 foram preparados por impregnação em excesso de solução, usando diferentes precursores metálicos, [PtI2(CO)2], H2PtCl6 e [Pt(CH3)2(C8H12)], respectivamente, tendo-se escolhido a reacção de oxidação da anilina como modelo para avaliar a sua eficiência. Na Tabela 1 são apresentados os valores da conversão de anilina (Xanilina), da redução do carbono orgânico total (XTOC) e da selectividade de mineralização total (S), obtidos após 2 h de reacção a 200ºC e 6.9 bar de pressão parcial de oxigénio.

2004Conference object

Open access

Ruthenium catalysts supported on multi walled carbon nanotubes for the catalytic wet air oxidation of aniline

Publication . García, Juan; Gomes, Helder; Serp, Philippe; Kalck, Philippe; Figueiredo, José; Faria, Joaquim

Oxidation of carbon multi-walled nanotubes (MWNTs) by nitric acid leads to the introduction of carboxylic groups that can be used to anchor a Ru metallic phase. Ruthenocene [Ru(C5H5)2], Ruthenium (1,5-cyclooctadiene, 1,3,5-cyclooctatriene) [Ru(COD)(COT)], and Ruthenium trichloride RuCl3.xH2O were used as precursors in the incipient-wetness (IW) and excess (EI) impregnation methods. The catalytic activity of the prepared materials in the wet air oxidation of aniline in aqueous solution, was found to depend on the type of Ru precursor in the following order: [Ru(COD)(COT)] > RuCl3.xH2O > [Ru(C5H5)2]. The high aniline conversions observed (complete conversion in the case of the most active catalyst) are attributed to the high external surface area of the MWNTs (SBET = 175 m2/g), which is compatible with end-closed nanotubes (zero micropore volume). This type of structure provides an efficient surface contact between the reactants (aniline) and the active sites, especially in the liquid phase where mass transfer limitations are very significant.

2004Conference object

Open access