Catalytic behaviour of gallium-containing mesoporous silicas (MCM-41) in the acetylation reaction

Bachari, K.; Guerroudj, R. M.

doi:10.1134/s0023158412030032

Cited by 2 publications

(2 citation statements)

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“…20 In addition, the decrease of intensity of XRD peaks may suggest a partial degradation of structure with increase of gallium content. 21 The main XRD peaks for crystalline gallium oxide are at 2θ = 30.5, 31.7, 35.2, 38.4 and 64.69° and for the synthesized materials the XRD bands in the range of 2θ = 10-80° do not show diffraction patterns characteristic of crystalline gallium oxide phases present in mesoporous silica. This behavior may indicate that the gallium is tetrahedrally coordinated to oxygen atoms (e.g., silicon) in the framework or is well dispersed and occupies extra framework positions which are not detected by XRD.…”

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confidence: 86%

“…28 The band at 810 cm -1 is assigned to the symmetric vibration of Si−O−Si bonds, while the signal at 460 cm -1 relates to the deformation of Si−O−Si bonds. 21 The gallium content in mesoporous silica affects the long-range ordering and structural properties of synthesized materials. Thus, to analyze the morphology and structure in greater depth, SEM and TEM analyses of the catalyst MS-Ga7% were carried out and the results are shown in Figure 5.…”

Section: Catalyst Characterizationmentioning

confidence: 99%

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Gallium-Containing Mesoporous Silica: Supported Catalysts with High Catalytic Activity for Oxidation of Benzene, Toluene ando-Xylene

Schwanke¹,

Pergher²,

Probst³

et al. 2016

Journal of the Brazilian Chemical Society

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Benzene, toluene and xylene (BTX) are a particular class of volatile organic compounds, which are highly toxic pollutants. In this study, samples of gallium-containing mesoporous silica (MS-Ga7% and MS-Ga11%) were synthesized and their catalytic activity in the oxidation of BTX was investigated. The physicochemical characterization shows that the inclusion of gallium in the mesoporous silica structure leads to an increase in the number of oxygen vacancies in the structure of the MS-Ga system, which can result in an increase in the total and surface oxygen mobility. The results show the highest conversion for benzene (65%), with > 40% for toluene and > 28% for o-xylene. The high catalytic activity observed was attributed to a combination of several factors including a higher number of active sites (gallium and gallium oxide) being exposed, with a greater mobility of the active oxygen species on the surface of the catalyst promoting the catalytic activity. Keywords: gallium, mesoporous silica, catalytic oxidation, BTX IntroductionThe emission of high levels of volatile organic compounds (VOC) to the atmosphere during various industrial and commercial processes is considered detrimental to human health and the environment. [1][2][3][4][5][6] Benzene, toluene and xylene (BTX) are volatile organic compounds used as common solvents as well as raw materials in the production of other chemicals. [7][8][9] All three substances are known to be toxic. 10,11 Several VOC removal technologies, such as flame combustion, catalytic combustion, catalytic destruction using ozone and plasma, photocatalytic decomposition, adsorption processes and biological treatment, have been developed to eliminate VOCs. 2,6,[12][13][14] Catalytic oxidation is considered to be the most effective approach, mainly due to its high efficiency in the degradation to carbon dioxide and water, even in effluents with low concentrations of VOCs, and low energy cost.3,15 However, it is extremely difficult to achieve the complete combustion of VOCs at low temperatures. Thus, it is important to develop a novel active catalyst which can promote complete oxidation at the lowest possible temperatures. Conventional catalysts are supported on inorganic materials such as alumina and other metal oxides.However, the success of the catalyst is dependent on the nature of the support used. Common catalyst supports include activated carbons, silica, alumina, polymers and zeolites. Mesoporous silicas (MSs), for instance MCM-41, have been shown to be suitable supports for catalysts. 16,17 These mesoporous materials possess some important properties for catalytic purposes, such as high specific surface area, large pore volume and highly ordered pore structures with narrow pore size distributions, which are dependent on the synthesis chemicals and conditions. 18,19 The synthesis of these materials requires a source of silica, usually commercial, a structure directing agent, a solvent, a mineralizer agent, and these materials have been extensively investigated as promising cat...

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mentioning

confidence: 86%

Section: Catalyst Characterizationmentioning

confidence: 99%