Characterization of AlMCM-41 synthesized with rice husk silica and utilization as supports for platinumiron catalysts (original) (raw)
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Platinum carbonyl derived catalysts on inorganic and organic supports: a comparative study
Journal of Organometallic Chemistry, 2004
Fumed silica, silica gel, silica-alumina and cross-linked (5.5%) polystyrene have been functionalized with quaternary ammonium groups and the Chini cluster [Pt 12 (CO) 24 ] 2À has been anchored onto these functionalized materials by ion pairing. A catalyst has also been prepared by the adsorption of Na 2 [Pt 12 (CO) 24 ] on unfunctionalized fumed silica. The catalytic activities of the resultant materials, and that of commercially purchased 5% platinum on alumina have been studied for the hydrogenation of a variety of unsaturated compounds. The substrates studied are: a-acetamidocinnamic acid, cyclohexanone, acetophenone, methyl pyruvate, ethyl acetoacetate, nitrobenzene and benzonitrile. Compared to the polystyrene supported catalyst, the inorganic oxide supported catalysts have higher surface areas and for most of the substrates have notably higher activities. The functionalized fumed silicabased catalyst gives higher conversions than functionalized silica gel and silica-alumina-based catalysts. In the hydrogenation of acetophenone and ethyl acetoacetate, the functionalized fumed silica-based catalyst show superior activity compared to the commercial platinum catalyst, and the catalyst made by conventional adsorption method. In benzonitrile hydrogenation with all the cluster-derived catalysts a hydrazine derivative is selectively formed, but when the commercial platinum catalyst is used benzyl amine is the main product.
Characterization of acidic and basic properties of heterogeneous catalysts by test reactions
2005
4.3 Hydrotalcite derived from mixed Mg-Al oxides………………………………………...61 4.3.1 Acid-base properties of the hydrotalcite derived from mixed magnesium aluminium oxides…………………………………………………………………………………63 4.3.2 X-ray diffraction (XRD)……………………………………………………………..64 4.3.3 Infrared spectroscopy (FTIR)………………………………………………………..66 4.3.4 Structural and chemical composition of the mixed magnesium aluminium oxides…68 4.3.5 BET measurements…………………………………………………………………..69 4.4. Methyl butynol conversion……………………………………………………………...73 4.4.1 Catalytic activity of methyl butynol over different silica alumina with different ratios at different reaction temperatures 120 °C, 180 °C……………………………73 4.4.2 Influence of reaction temperature and treatment preparations of the sample reaction behavior……………………………………………………………..77 4.4.3 Influence of the deactivation process on the methyl butynol catalytic activity ……..83 4.4.4 The dependency of the selectivity of 3-methyl-3-buten-1-yne as a function of the conversion depending on the silica content over different l ratios…………………...86 4.4.5 The formation of 3-methyl-3-butyn-2-one as a function of the conversion depending on the silica content over different silica alumina ratios……………………………..87 4.4.6 Correlations and formation of 3-methyl-3-butyn-2-one as primary product over silica alumina solids………………………………………………………………….89 4.5 Effect of water on the conversion of methyl butynol……………………………………93 4.6 Determination of activation energy in the methyl butynol conversion………………….96 4.7 Basicity of hydrotalcite derived from mixed magnisium oxides studied by methyl butynol test reaction……………………………………………………………104 4.8 Conversion of isopropanol……………………………………………………………...108 4.9 Knoevennagel condensation…………………………………………………………….112 5. Conclusions………………………………………………………………..118 6. References…………………………………………………………………122 7. Appendix…………………………………………………………………..128
Topic Catalysis, 2001
In order to obtain highly dispersed heteropolyacid (HPA) species, H 3 PW 12 O 40 was supported on various supports exhibiting different porosities and surface chemical properties. Amorphous and monoclinic amphoteric zirconias, activated montmorillonite (AC) and hexagonal silica (HMS) were chosen as supports. It was observed that the zirconia support partly decomposed HPA at low coverage, giving the lacunary anion PW 11 O 7− 39 , due to the reaction with basic hydroxyl groups, whereas montmorillonite and HMS did not. Catalytic properties for n-butane to isobutane isomerisation at 473 K and propan-2-ol decomposition at 353 K were compared for all samples as a function of HPA loadings and compared to data already published on bulk H 3 PW 12 O 40 and Cs 1.9 H 1.1 PW 12 O 40 samples. It was found for HPA/AC samples that, although their activity for propan-2-ol decomposition varied linearly with HPA loading, their activity for n-butane isomerisation was very weak, which indicates a weaker acid strength by supporting the HPA. This is probably due to the exchange of protons from the HPA by the exchangeable cations of the montmorillonite, the new protons associated with the clay being much less acidic. It also appeared, when comparing with catalytic data already published on for HPA/HMS, that HMS was the best support for HPA without modifying appreciably its catalytic and thus their acid properties, the HPA being certainly bonded to the HMS walls by hydrogen bonding. Assuming a diameter of 1.2 nm for each Keggin anion, the turnover frequency (TOF) values for n-butane isomerisation at 473 K were calculated per surface Keggin species for HPA/HMS, bulk H 3 PW 12 O 40 and Cs 1.9 H 1.1 PW 12 O 40 , and were found to be equal to 155, 113 and 100 × 10 −5 s −1 , respectively, and thus to be very close, showing that the acid strength of the three samples was comparable. It was found to equal only 3.4 × 10 −5 s −1 for the HPA/AC sample, in agreement with a weaker acid strength. At last, mesoporosity of the support was found to favour n-butane isomerisation reaction.
Influence of support and supported phases on catalytic functionalities of hydrotreating catalysts
Fuel, 2014
were prepared. The HDS activity in DBT conversion was in the order: NiMo P NiW > CoMo on alumina. Al 2 O 3 -zeolite support was the most active in HDS of DBT. The most active catalyst in HDS of DBT was NiMo supported on Al 2 O 3 -zeolite. a b s t r a c t Different mixed-oxide supports were synthesized using homogeneous co-precipitation methods. Alumina-silica, alumina-titania, and alumina-zeolite supports were prepared and then impregnated with Mo (or W) and Co (or Ni) in order to evaluate their behavior in the dibenzothiophene hydrodesulfurization. Supports and supported catalysts were characterized by atomic absorption and textural properties. The conversion of model compounds (tetralin, 1-methylnaphthalene, and decalin) was investigated with the aim of understanding ring opening reaction over the support in presence of hydrogen. The model test reactions for support as well supported sulfide catalysts were carried out in a batch reactor at 4 MPa and 340°C. Conversion of cyclo-compounds showed that decalin had the highest conversion followed by 1-methylnaphthalene and tetralin when using a silica-alumina supported catalyst. The hydrodesulfurization results as a function of support variation indicated that high acidity of support has positive effect on the hydrogenolysis of CAS bond breaking. Thus, it is inferred that a balance between metal sites of hydrogenation and cracking of the support is critical in order to synthesize a bifunctional catalyst for deep hydrodesulfurization where sulfur removal as well as cetane improvement are mandatory.
Catalysis Letters, 2000
The reactivity of different organic compounds (naphthalene, alkylnaphthalenes, decalins, tetralin and their mixtures) and the roles of the support acidity and of the noble metals were studied in Pd/Pt on MCM-41 (with different Si/Al ratios) catalysts. The catalytic tests showed that the hydrogenolysis/ring-opening reactions mainly occurred on saturated compounds, while cracking took places mainly on unsaturated compounds. The presence of alkyl side chains on the polyaromatic ring inhibited the hydrodearomatization activity, proportionally to their length and number. Mixtures of naphthalene and methylnaphthalenes gave rise to a competition between the substrates, with a decrease in both hydrogenation and hydrogenolysis/ring-opening activities. Increasing support acidity favoured hydrogenolysis/ring-opening and cracking reactions, smoothing the hydrogenation activity. Noble metals are shown to be necessary not only in hydrogenation, but also in hydrogenolysis/ring-opening reactions.
Applied Catalysis B: Environmental, 2010
The potential of mesoporous silica-alumina (MSA) modified by acid leaching as alternative support for Pt catalysts was studied in hydrodesulfurization (HDS) of thiophene and benzothiophene. The supports were characterized by N 2 adsorption, XRD, 27 AL MAS NMR, electron microscopy (SEM, HRTEM) and by activities in cyclohexene isomerization and cumene cracking. The composition of the catalysts and Pt dispersion were determined by ICP and H 2 or CO sorption, respectively. Progressive leaching of the parent MSA from 50% Al 2 O 3 to 11% Al 2 O 3 content led to increase of the BET surface area and exposition of strong acidity. This positively affected the activities of the reduced Pt catalysts in thiophene HDS. Deposition of 1.5 wt.% Pt on MSA (11% Al 2 O 3) by using Pt(NH 3) 4 (OH) 2 as precursor gave the best catalyst, several times more active in thiophene HDS than the weight equivalents of sulfided CoMo/Al 2 O 3 or reduced Pt/HY zeolite. In benzothiophene reaction, its activity was slightly above that of CoMo/Al 2 O 3 and about twofold compared to Pt/HY.
(R:Ph,H) catalyst, microstructural study
2016
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Supported Metal Catalysts: Preparation, Characterization, and Function
Journal of Catalysis, 1993
... All rights reserved. Permissions & Reprints. Regular Article. Supported Metal Catalysts: Preparation, Characterization, and Function : II. ... On the Pt/alumina, adsorption of submonolayer quantities of carbon monoxide results in a modification of the binding energy of surface ...