Nickel sulfide catalysts preparation

Nickel sulfide catalysts may be prepared by any of the following reactions ... 

The first step in regenerating the coated, inactive nickel sulfide catalysts is to remove the reactants and products of the catalytic reaction aloi with the extraneous material coating the catalyst. In most cases, extraction of the catalytic mass with solvents, or purging with steam is adequate for this clean-up. The more resistant film of coke or tar is then removed by oxidation with air under carefully controlled conditions to avoid over-heating the catalyst. During this oxidation, the nickel sulfide is usually oxidized to NiO. This NiO is then reduced and sulfided in the same manner as in the initial preparation of the catalyst. 

Nickel sulfide, NiS, can be prepared by the fusion of nickel powder with molten sulfur or by precipitation usiag hydrogen sulfide treatment of a buffered solution of a nickel(II) salt. The behavior of nickel sulfides ia the pure state and ia mixtures with other sulfides is of iaterest ia the recovery of nickel from ores, ia the high temperature sulfide corrosion of nickel alloys, and ia the behavior of nickel-containing catalysts. 

A cationic molybdenum sulfide cluster [Mo3S4(H20)9] " with incomplete cubane-type structure and a cationic nickel-molybdenum mixed sulfide cluster [Mo3NiS4Cl(H20)9p " with complete cubane-type structure were introduced into zeolites NaY, HUSY and KL by ion exchange. Stoichiometry of the ion exchange was well established by elemental analyses. The UV-visible spectra and EXAFS analysis data exhibited that the structure of the molybdenum cluster remained virtually intact after ion exchange. MoNi/NaY catalyst prepared using the molybdenum-nickel sulfide cluster was found to be active and selective for benzothiophene hydrodesulfurization. 

Another SIMS study on model systems concerns molybdenum sulfide catalysts. The removal of sulfur from heavy oil fractions is carried out over molybdenum catalysts promoted with cobalt or nickel, in processes called hydrodesulfurization (HDS) [17]. Catalysts are prepared in the oxidic state but have to be sulfided in a mixture of H2S and H2 in order to be active. SIMS sensitively reveals the conversion of Mo03 into MoSi, in model systems of MoCf supported on a thin layer of Si02 [21]. 

Nickel silicate, as catalyst, 20 106-109 differential thermogram of xerogel, 20 107 infrared spectra of, 20 108 preparation by SHCP method, 20 106 properties and structure of, 20 107-109 X-ray diffraction pattern of, 20 109 Nickel sulfate hexahydrate, dehydration of, dislocations and, 19 389 Nickel sulfides... 

Theories and principles of the characterization techniques are not described here. For consistenc), all the catatysts described in this review are referred to with the same nomenclature, although a different nomenclature is sometimes used in the cited publications. Each catalyst component (element) separated by the symbol indicates the sequence of its introduction into the catalyst formulation from right to left. Those separated by the symbol 7 between right and left belong to the support material and the elements on the support, respectively. For example, NiMo-P/Al refers to a catalyst prepared such that the phosphorus-containing precursor is loaded on the alumina support first, followed by nickel and molybdenum, which are introduced simultaneously. CoMo/Al — P refers to a catalyst in which cobalt and molybdenum are introduced simultaneously onto an alumina support doped with phosphorus-containing species. Each element may represent its oxide or sulfide forms. In all cases, A1 refers to the alumina-based support or to its hydroxide precursor. 

The supported Ni catalysts (5 wt.%) for H2S oxidation were prepared by incipient wetness impregnation of the two supports, i.e. SiC grains and graphite felt coated with carbon nanofibers, with an aqueous solution of Ni(N03)2.6H20 (Merck). After drying overnight at 120°C, the catalysts were calcined at 350°C for 2h in order to decompose the nitrate salt and to form the nickel oxide. The corresponding sulfidic catalysts were obtained by sulfidation of NiO by reaction with a H2S/He flow at 300°C. 

Silanes normally reduce aldehydes or ketones under catalytic conditions to the silyl ethers. However, with certain catalysts such as nickel sulfide,Co2(CO)8, or (Ph3P)3RhCl, carbonyl compounds react with silanes to yield an equilibrium mixture of enol silyl ethers (Scheme 17). In a similar vein, the silyl-hydroformylation reaction of cycloalkenes with CO and silanes may be a practical way to prepare enol silyl ethers. An example is the preparation of compound (49). Catalytic 1,4-hydrosilation of a, -un-saturated ketones or aldehydes gives the corresponding enol silyl ethers. The reaction is similar to the reductive silylation referred to previously, but the reaction conditions are neutral and milder. The formation of the enol silyl ether (50) is outlined below. ... 

Catalysts used in this work had a composition of 3 wt% nickel, 8 wt% molybdenum and 0 or 2 wt% phosphorus. They were prepared by incipient wetness impregnation, followed by drying at 393 K and calcination at 773 K. Details of the catalyst preparation can be found elsewhere [2], The HDN reactions were carried out in a continuous-flow microreactor. A sample of 0.1 g catalyst diluted with 9.5 g SiC was used for each reaction. The catalyst was sulfided in situ with a mixture of 10% (mol) H2S and H2 at 643 K and 1.5 MPa for 4 h. After sulfidation, the pressure was increased to 3.0 MPa and liquid reactant was fed to the reactor by means of a high pressure pump, with n-octane as the solvent. The catalyst was stabilised at 643 K and 3.0 MPa for 100 h before samples were taken. The initial reactant partial pressure (P°) of Q, THQ5 and OPA was usually 4.76 kPa, and that of H2S was 6.5 kPa by adding dimethyldisulfide to the liquid reactant. n-Nonane as well as n-dodecane were used as internal standards. 

In the hydrogenation of fatty oils such as cottonseed or peanut oil, it is often desirable to saturate only one double bond of the doubly unsaturated esters present. If such hydrogenations are carried out in the presence of a nickel catalyst containing even traces of nickel sulfide, an isomerization takes place so that the product contains isooleates (elaidates). Paterson (14) observed that this so-called elaidinization does not take place in the presence of nickel catalysts free of sulfur. Bailey, Fuege, and Smith (15) found that a nickel catalyst prepared from nickel sulfate catalyzed elaidinization." Ziels and Schmidt (16) recom-... 

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