Dehydrogenation of Ethylbenzene over Spinel Oxides

Abstract

NiCr2O4, ZnCr2O4, CuCr2O4, CuAl2O4, and CuFe2O4 were prepared and characterized by XRD, DRS, and IR and by measurements of surface area, acidity, and electrical conductivity. XRD analysis indicates, that chromites, aluminate, and ferrite have normal, partially inversed, and inversed spinel structure, respectively. Electrical conductivity measurements show the existence of pair localized ions which are positive in chromites and negative both in aluminate and ferrite. The catalytic activity of chromites and aluminate are comparable and higher than that of ferrite in the conversion of ethylbenzene under all experimental conditions. However selectivity to styrene formation follows in the following order: ferrite > chromites > aluminate. The ratio of B/T (benzene/toluene) is more than unity over aluminate and less than unity over chromites and ferrite. Evolution of CO2 remains constant while that of C2H4 increased with increase in temperature keeping its formation always higher over aluminate. Measurements of acidity and basicity by TGA show the presence of basic sites on chromites, acidic sites on aluminate, and both sites on ferrite which influence the conversion of ethylbenzene to various products. The XRD pattern of spent catalysts indicate the appearance of metallic copper phase over CuCr2O4, CuFe2O4, and CuAl2O4. In the case of NiCr2O4 and ZnCr2O4 no significant difference is observed.

Desidrogenação do etilbenzeno sobre compostos de ferro e alumínio

“…Uma outra amostra, à base de ferrita de alumínio, foi preparada usando o método proposto por Jebarathinan e colaboradores 28 (Amostra FA2). Uma solução contendo nitrato de ferro e de alumínio (Fe/ Al (molar)=1), foi aquecida a 60 ºC e, a esta, foi adicionada (ainda quente) uma solução de hidróxido de amônio 5%, gota a gota, sob agitação constante, mantendo-se o pH em 6,2.…”

Simple morphology-controlled fabrication of nickel chromite nanostructures via a novel route

“…One of these nanomaterials is nickel chromite (NiCr 2 O 4 ). It was found that nickel chromite with spinel structure is an important transitionmetal oxide owing to its specific electrical, magnetic, and catalytic properties [6] as well as potential applications, including catalytic materials, electronic apparatus, gas sensors, chemical industrial fields, and pigments [7][8][9][10]. NiCr 2 O 4 has a spinel-like structure [11].…”

Optimization of catalytic, surface and magnetic properties of nanocrystalline manganese ferrite

“…Nanosized ferrites with uniform particle size and narrow size distribution are one of the most important ceramic materials widely used as targeted drug delivery, ferrofluids, medical imaging and other biomedical applications, magnetic data storage as well as giving an excellent performance as catalyst or catalytic support for many chemical reactions [1][2][3][4][5][6][7][8][9][10][11][12][13]. Recent interest in the study of several spinel-type ferrites is in terms of the synthesis of their nanoparticles at low temperatures by different techniques, in view of the potential applications of these nanosized magnetic materials in different technological areas, as well as to study the intriguing magnetic properties of the nano-ferrite materials [14][15][16][17][18][19].…”