Silica supported Ni catalyst

An apparent particle size effect for the hydrodechlorination of 2-chlorophenol and 2,4-dichlorophenol was observed by Keane et al. [147], Investigating silica supported Ni catalysts (derived from either nickel nitrate or nickel ethane-diamine) with particles in the size range between 1.4 and 16.8 nm, enhanced rates for both reactions were observed with increased size over the full range (Figure 13). As electronic factors can be ruled out in this dimension, the observed behavior is traced back to some sort of ensemble effect, known from CFC transformations over Pd/Al203... 

The authors showed that the Grabke-type kinetic model can explain the results at a low carbon activity for Ni-Cu catalysts, but that at higher carbon activities, the rates for the Ni0 9Cu0 j catalysts are higher than the model-predicted rates. Low-temperature decomposition of methane over the silica-supported Ni catalyst has been reported by Kuijpers et al. [101]. It was demonstrated that at temperatures as low as 175°C, methane adsorbed on the Ni catalysts dissociates completely into adsorbed carbon atoms and hydrogen. 

The formation of filamentous carbon deposits on transition metal catalysts (Fe, Co, Ni) and their alloys have been investigated in some detail over the past two decades.21,38-40 Among them, nickel is the most promising candidate since it forms carbon deposits at temperatures as low as 723-823 K using CH4, C2H6 or CO + H2 feeds. Carbon fibres are usually produced during these reactions. Typical forms of the carbon produced from CH4 decomposition on silica-supported Ni catalysts are shown in Fig. 7.1. The pyrolysis of methane at temperatures somewhat lower than 873 K produces fish-bone type nanofibres.41 The Ni metal particles are present at the tip of each carbon fibre, and catalyse methane decomposition as well as growth... 

Identification of supported phases produced in the preparation of silica-supported Ni catalysts by competitive cationic exchange... 

In the present work, some promising results obtained with this kind of asymmetric heterogeneous catalyst, based on silica-supported Ni, Rh and Pt, chemically modified with chiral organotin compounds, are presented. The systems were tested in the enantioselective hydrogenation of ethyl pymvate, acetophenone and 3,4-dimethoxyacetophenone. The stabiUty of these catalysts was also studied to check if they could be reused. 

Sachtler s group (73) and Yasumori (64) studied the IR spectra of silica-supported Ni modified with amino acid and 2-hydroxy acid and the XPS of TA-MRNi. Both authors deduced almost the same model as proposed by Suetaka. Recently Sachtler s group proposed other models as shown in Fig. 22 from results obtained in enantio-differentiating hydrogenations of MAA with nickel catalysts modified with nickel and copper tartrates (74). The nickel tartrate adsorbs at the vacant coordination site of nickel in this model. 

These were prepared by tethering Rh and Pt complexes to silica-supported metal catalysts (metal = Pd, Ni, Ru, Au). The catalysts are very active in the hydrogenation of benzene derivatives to the corresponding substituted cyclohexanes under mild conditions. The activities are higher than those of the separate homogeneous complexes, complexes just tethered to silica, or the silica-supported heterogeneous catalysts. When the sol-gel-entrapped [Rh2Co2(CO)12] complex was heat-treated at 100°C, immobilized metallic nanoparticles were formed.425 The catalyst thus prepared efficiently catalyzed substituted benzene derivatives. 

A few reports on the hydrogenation of polystyrenes with heteroatom-containing substituents have been made. The hydrogenation of poly(styrene-co-methyl acrylate) was performed using a silica/alumina-supported Ni catalyst... 

Coulier, L., V. H. J. de Beer, J. A. R. van Veen, and J W. Niemantsverdriet, Correlation between Hydrodesulfurization Activity and Order of Ni and Mo Sulfidation in Planar Silica-Supported NiMo Catalysts the Influence of Chelating Agents , J. Catal 197, Issue 1,1 January 2001, pp 26-33. 

We investigated two methods of preparation observing that the wet impregnation produces a more stable catalyst with an increased dispersion of the metal due to the Ni(OH)2 precursor. About the support, La203 used as pure support or as a promoter on Si02 puts in evidence the support effect as it modifies the conversions and the carbon deposition. Indeed investigating more deeply about the differences of CO2 reactivity between silica and lanthana supported Ni catalysts, particularly from the tests on reduced and unreduced catalyst, it appears that the oxidation degree of the catalytic surface plays a relevant role on the reactivity. 

Remarkable hydrodechlorination activity has been reported over silica supported Ni-Au catalysts [588]. In gas-phase catalytic 2,4-dichlorophenol hydrodechlorination, a co-impregnated, thermally treated Au-Ni/SiOg catalyst was significantly more active than the equivalent Ni catalyst. 

The supported Ni catalysts (Ni content in % w/w) were prepared by the precipitation technique (7). The supports (United Catalysis India Ltd., India) were calcined at 773 K for 4 h prior to use. Ammonium carbonate (Loba Chemie, India) was used for precipitating Ni from Ni(N03)2.6H20 (S.D. Fine, India). The catalysts were calcined in a static air furnace at 773 K for 10 h and reduced in an activation furnace using silica-quartz tube at 773 K in H2 flow of 50 cm /min for 10 h. The reduced catalysts were passivated under N2 flow of 30 cmVmin for 2 h. 

A commercial silica-supported nickel catalyst (Hoechst RCH 53/35, 69 wt.% Ni, 13 wt.% Cr, specific surface area 100 m /g) was used in experiments performed with butyr- and propionaldehyde in aqueous as well as methanolic solvent. The catalyst particles were cylindrical with a height of 5 mm and diameter of 6 mm. The particles were crashed and sieved to a fraction of45-150 pm in order to avoid diflfusional resistances inside the catalyst particles. 

Because the hydrogenation of the nitrile group takes place on the Pt sites, the rate enhancement observed upon addition of tin can only be explained by the cooperation of Pt and tin sites on the surface of alloy-type nanocluster and/or the metal support interface. The results obtained on alloy type Sn-Pt/Si02 catalysts strongly resemble results attained on silica supported Ni-Fe catalysts with 75 %... 

Two series of 20-40 mesh y-alumina and silica supported Ni-based catalysts were prepared by the incipient wetness impregnation with nitrate as the metal precursors. The solids were dried overnight in air at 393 K, then calcined at 773 K in air for 6 hrs for complete decomposition of the precursors. For the promoted catalysts, magnesium nitrate and cerous nitrate were added to the support by the same method. Before the reaction, the catalyst was reduced at 973 K in a stream of H2 (99.995%) for at least 2 hrs. 

Under the conditions studied it was found that the supported Ni catalysts also produced low enantioselectivities, and changing the silica support for alumina completely inhibited enantioselectivities. 

Nakagawa Y, Tomishige K (2010) Total hydrogenation of furan derivatives over silica-supported Ni-Pd alloy catalyst. Catal Commun 12 154-156... 

The Dumesic group at the University of Wisconsin has developed a method to upgrade the aqueous-phase sugars and alcohols derived from biomass into either H or alkanes [7, 55-61]. For the production of H from biomass, aqueous-phase reforming of the sugar solution over many different catalysts has been studied [56]. Silica-supported Ni (19.1 wt %), Pt (5.85 wt %), Pd (4.78 wt %), Rh (9.37 wt %), Ru... 

Proven, industrially used catalysts are mostly based on either iron or cobalt. Ruthenium is an active F-T catalyst but is too expensive for industrial use. Both Fe and Co are prepared by several techniques including both precipitation and impregnation of (e.g. alumina or silica) supports. The more noble Ni catalyst produces nearly exclusively methane and is used for the removal of trace of CO in H2. 

The Ni and S contents on the catalyst series were determined after calcination at 600°C. As shown in Table 1, sulfate was only retained on the silica support when Ni was present. Infrared studies have previously shown that sulfate groups impregnated on pure silica are thermally unstable [13], Therefore, the S04/Ni molar ratios, close to unity, together with the colors resulting after calcining the silica-supported samples made us conclude that Ni was in the form of NiS04 On zirconia, the S04/Ni ratios were larger than one because the sulfate can be associated with both, Ni and the support. 

Alstrup, I. and Tavares, T., Kinetics of carbon formation from CH4-H2 on silica-supported nickel and Ni-Cu catalysts, /. Catal., 139, 513,1993. 

Ethanol can be derived from biomass by means of acidic/enzymatic hydrolysis or also by thermochemical conversion and subsequent enzymatic ethanol formation. Likewise for methanol, hydrogen can be produced from ethanol with the ease of storage/transportation and an additional advantage of its nontoxicity. Apart from thermodynamic studies on hydrogen from ethanol steam reforming,117-119 catalytic reaction studies were also performed on this reaction using Ni-Cu-Cr catalysts,120 Ni-Cu-K alumina-supported catalysts,121 Cu-Zn alumina-supported catalysts,122,123 Ca-Zn alumina-supported catalysts,122 and Ni-Cu silica-supported catalysts.123... 

Grenoble and coworkers229 reported an important influence of the support on the water-gas shift activity of various metal catalysts. For example, the rate increased an order of magnitude when Pt was supported on alumina versus silica. Turnover numbers for alumina-supported metal catalysts decreased in the order Cu, Re, Co, Ru, Ni, Pt, Os, Au, Fe, Pd, Rh, and Ir, whereby the activity varied by 3 orders of magnitude, suggesting a correlation between activity of the metal and the heat of adsorption. To describe these differences in activity, the authors used a bifunctional model, involving chemisorption of water on alumina and CO on the metal, followed by association of the CO with the water to form a formic acid-like formate species, with subsequent decomposition via dehydrogenation on the metal sites (Scheme 55). 

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