Ni on alumina

Table 3.9. shows the results of barometric hydrogen chemisorption on Cu/AlaOj, Ni/A Oj, Pt/Al203 and a Ni on alumina-washcoated monolith. 

Acetylene hydrogenation Ni on alumina (sulfided) Pd on alumina (CO-poisoned)... 

Many catalysts used in industry are heterogeneous, e.g. zeolites in the cracking of heavy crude oil. The actual reaction takes place on the surface of the solid, with the substrates and products being in the gas or liquid phase, depending on the type of reaction and reactor being used. Many involve a metal on some kind of support e.g. Pd on charcoal, Ni on alumina. The surface area and porosity of heterogeneous catalysts are important in determining their efficiency. Some of the... 

Wu, Yuan and Xu have studied nonuniform pellets in the hydrogenation of CO over Ni on alumina supports.39 Selectivity is directly related to the CO/H2 ratio inside the pellets. The active Ni particles were deposited as a narrow band in order to approximate a Dirac delta distribution. Experimental data followed theoretical predictions of the researchers regarding enhanced selectivity to... 

The kinetic experiments, activity tests, and poisoning experiments were carried out in a gas-flow isothermal fixed bed reactor [6) at the benzene partial pressure of 7.55 kPa hydro gen partial pressure 99.82 kPa thiophene partial pressure 0.032 kPa and the reaction temperatures 403, 427 and 448 K. The size of the commercial cylindrical catalyst pellet was 5x5mm (21% Ni on alumina, supplied by BASF). The nickel oxide containing precursor was activated by reduction with hydrogen at 743 K for 10 hr. 

Praliaud and Martin (77) proposed the formation of Ni-Si and Ni-Cr alloys on silica and chromia supports, respectively, under H2 at sufficiently high temperatures. They suggested that hydrogen spilt over from Ni to the Cr203 carrier and partially reduced it to Cr°, which was then alloyed with Ni as indicated by magnetic measurements. The same technique in conjunction with IR spectroscopy and volumetric adsorption of H2 was applied to partially reduced Ni-on-alumina and Ni-on-zeolite catalysts by Dalmon et al. (78). These supported Ni systems contained Ni° and Ni+. H2 was found to be activated only when the couple Ni°/Ni+ was present according to... 

Most catalysts, where a metal is an active component, are supported catalysts, because a prime requirement here is the use of a large metal surface area. Examples of supported catalysts are activated-carbon-supported Pt and Pd, and Ni on alumina. 

The selectivity may be oriented toward reduction of the a,)3-unsaturation of conjugated dienones, e.g., hydrogenation of 6-methyl-3,5-heptadien-2-one, 21, over Ni-on-alumina or Ni-on-Zn oxide results in saturation of the S-double bond to give 22, but modification of the catalyst by addition of Cd forms 23 ... 

The catalyst particles were 0.3 x 0.3-cm cylinders, 10% Ni on alumina. Surface area was 30m /g, and the diffusivity of hydrogen within the catalyst at 25 °C was 0.07cm /s. Is there evidence that diffusion was important Assume Knudsen diffusion in the catalyst pore structure. The rate of addition of deuterium to 2-butyne at 25 °C over a 0.03% Pd/ AI2O3 catalyst was reported to be 0.11 gmol/h-cm3 (catalyst). Experimental conditions were feed, D2 saturated with 2-butyne nt 25 °C catalyst dimension, 40 mesh D ff 0.15 of the bulk diffusivity of 2-butyne in hydrogen at 25 °C. Was intraparticle diffusion important in this experiment Note Persevere in obtaining all the exact numbers you need to do this calculation. They come from various sources, and it takes some time. After all, this is real life). 

A mixture of benzene and 3.3 moles of Hg passed at 100-140 through Ni-on-alumina cyclohexane. Conversion ca. 100%.—Of several catalysts investigated... 

Notice in Table XVIII-1 a value for the self-diffusion of Ni on Ni(lll) measured using radioactive Ni. More gross processes can occur. Supported Ni crystallites (on alumina) may show spreading and wetting phenomena due to complex interactions with the substrate [146]. 

Pyrrole can be reduced catalyticaHy to pyrroHdine over a variety of metal catalysts, ie, Pt, Pd, Rh, and Ni. Of these, rhodium on alumina is one of the most active. Less active reducing agents have been used to produce the intermediate 3-pyrroline (36). The 2-pyrrolines are ordinarily obtained by ring-closure reactions. Nonaromatic pyrrolines can be reduced easily with to pyrroHdines. 

To accelerate the polymerization process, some water-soluble salts of heavy metals (Fe, Co, Ni, Pb) are added to the reaction system (0.01-1% with respect to the monomer mass). These additions facilitate the reaction heat removal and allow the reaction to be carried out at lower temperatures. To reduce the coagulate formation and deposits of polymers on the reactor walls, the additions of water-soluble salts (borates, phosphates, and silicates of alkali metals) are introduced into the reaction mixture. The residual monomer content in the emulsion can be decreased by hydrogenizing the double bond in the presence of catalysts (Raney Ni, and salts of Ru, Co, Fe, Pd, Pt, Ir, Ro, and Co on alumina). The same purpose can be achieved by adding amidase to the emulsion. 

Similarly, the reaction of AsPha, under H2, on Ni surfaces can be monitored by measuring the variation of the arsine concentration with time at various temperatures [139]. In the presence of Ni/Al203 (alumina 250m /g Ni loading 25wt%, average diameter of the metallic particles 6nm 18% of dispersion) and H2 (12 bars), AsPha concentration decreases (Fig. 8a), and... 

Scheme 12 Total synthesis of (-)-xestospongin A (116), (+)-araguspongine B (129), and (+)-xestospongin C (130) [41]. Experimental conditions i. (a) NaH, THE, (b) -BuLi, (c) 132 a. Ru(II)-S-BINAP, H2, EtOH Hi. LiBH4, Et20 iv. PPTS, 2,2-dimethoxypropane, acetone v. Nal, acetone, reflux vi. 3-picoline, EDA, THE vii. HCl(aq.), EtOH viii. TsCl, EtsN, CH2CI2 ix. Nal, butanone, reflux x. LiBH4, MeOH, i-PrOH xi. DEAD, CH2CI2 xii. H2, Ni (Raney), MeOH xiii. Rh on alumina, MeOH, H2, then add alumina, reflux...

Supported Co, Ni, Ru, Rh, Pd and Pt as well as Raney Ni and Co catalysts were used for the hydrogenation of dodecanenitrile to amines in stirred SS autoclaves both in cyclohexane and without a solvent. The reaction temperature and the hydrogen pressure were varied between 90-140 °C and 10-80 bar, respectively. Over Ni catalysts NH3 and/or a base modifier suppressed the formation of secondary amine. High selectivity (93-98 %) to primary amine was obtained on Raney nickel, Ni/Al203 and Ru/A1203 catalysts at complete nitrile conversion. With respect to the effect of metal supported on alumina the selectivity of dodecylamine decreased in the order Co Ni Ru>Rh>Pd>Pt. The difference between Group VIII metals in selectivity can be explained by the electronic properties of d-band of metals. High selectivity to primary amine was achieved on base modified Raney Ni even in the absence of NH3. 

Ancheyta-Iuarez, J. Maity, S. K. Betancourt-Rivera, G., et al., Comparison of different Ni-Mo/alumina catalysts on hydrodemetallization of Maya crude oil. Applied Catalysis, A General, 2001. 216(1-2) pp. 195-208. 

Figure 4. Differential spectra of CO chemisorbed on alumina-supported Ni particles both before and after heating to 425 K. Very little surface hydrocarbon is seen to form on the Ni particles. This lack of surface hydrocarbon reflects the selectivity of such catalysts for methanation over Fisher-Tropsch synthesis.

Catalysts were prepared by chemically depositing Cu, Ni and Cr on alumina. SRE reaction produces a mixture of H2 and CO. Ni was thought to help breaking C-C bond while Cu and Cr for oxidation of Cl species into CO and H2... 

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). 

In fact, there are only two heterogeneous catalysts that reliably give high enantioselectivities (e.s. s) (90% e.e. or above). These are Raney nickel (or Ni/Si02) system modified with tartaric acid (TA) or alanine for hydrogenation of /(-kctocstcrs [12-30], and platinum-on-charcoal or platinum-on-alumina modified with cinchona alkaloids for the hydrogenation of a-ketoesters [31-73],... 

Fast reactions between pure metal powders (A1 + Ni, A1 + Ti and A1 + Ni + Ti) have been studied by Javel etal. (1997) by using time-resolved X-ray diffraction with the help of synchrotron radiation. The sample (20 X 10 X 2 to 3 mm3 was prepared under purified argon by cold pressing the metal powders mixed in the required proportion. It was then placed in a reaction chamber kept under He gas. A mylar window allows the incident and diffracted X-ray beams to pass in and out. Two small heating devices (tungsten coils on alumina supports) were included. The first one was used to keep the sample at a uniform temperature before ignition and the second one to start the self-propagating reaction at one end of the sample. X-rays irradiated the centre of the specimen. 

One would expect the presence of trapped electrons in the oxidized samples to give rise to n-type conductivity, conduction possibly taking place by jump migration of the odd electron in the lattice of Cr + ions in a somewhat similar manner to the mechanism discussed by Heikes 174) for the migration of Ni + holes in lithia-doped NiO. The observed p-type conductivity of chromia in an oxygen atmosphere is presumably due to electron holes in a solid which is predominantly CraOs for the low concentrations of chromia-on-alumina where the 7-phase resonance intensity is maximum, the chromium is predominantly in the d-6 valence state 167). 

The coals used were PSOC 1098 Illinois 6 and Beulah-Zap North Dakota lignite from the Argonne coal bank. The analytical data of these coals are shown in Table I. The ratio of catalyst to coal was approximately 0.6 mmoles of metal per gram of coal. The organometallic catalysts were molybdenum(II) acetate dimer, Mo2(OAc)4, obtained from Strem, molybdenum(II) allyl dimer Mo2(OAc)4, was prepared by die method of Cotton and Pipal (25). The NiMo supported catalyst was prepared by addition of bis(l,5-cyclooctadiene) Ni(0) (Strem) to sulfided Mo on alumina (. Cp2Mo2( l-SH)2(p.-S)2, referred to as MoS2(OM), was prepared by modification of method of Dubois et al. (26), and Cp2Mo2Co2( i3-S)2(li4-S)(CO)4, CoMo(OM) was prepared by the method of Curtis et al. (27). Pentacarbonyl iron was obtained from Aldrich,... 

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