Nickel silicate

The temperature profiles for each catalyst at two different space velocities are plotted in Figure 1. The catalysts with lower nickel content had reasonable activity, but the activity obviously decreased with nickel content. At 25,000/hr space velocity, the 30% nickel-on-alumina catalyst used 50% of the bed to obtain the maximum temperature whereas with 50% nickel the reaction used only 30% or the bed. The method used to prepare the C150-3-02 catalyst resulted in a non-reduceable nickel silicate... 

Nickel selenide, 22 87 Nickel-selenium, 22 73t Nickel sensitization, 17 119 Nickel silicate, 17 89 Nickel silicate green olivine, formula and DCMA number, 7 347t Nickel silicides, 17 121 uses for, 17 123 Nickel-silver, 7 759... 

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... 

Nickel ores are of two general types magmatic sulfide ores, which are mined underground, and lateritic hydrous nickel silicates or gamierites, which are surface mined (Duke 1980a Warner 1984). 

The lateritic hydrous nickel silicate ores are formed by the weathering of rocks rich in iron and magnesium in humid tropical areas. The repeated processes of dissolution and precipitation lead to a uniform dispersal of the nickel that is not amenable to concentration by physical means therefore, these ores are concentrated by chemical means such as leaching. Fateritic ores are less well defined than sulfide ores. The nickel content of lateritic ores is similar to that of sulfide ore and typically ranges from 1% to 3% nickel. Important lateritic deposits of nickel are located in Cuba, New Caledonia, Indonesia, Guatemala, the Dominican Republic, the Philippines, and Brazil. Fossil nickeliferous laterite... 

The form of nickel emitted to the atmosphere varies according to the type of source. Species associated with combustion, incineration, and metals smelting and refining are often complex nickel oxides, nickel sulfate, metallic nickel, and in more specialized industries, nickel silicate, nickel subsulfide, and nickel chloride (EPA 1985a). 

The reduction of samples impregnated with nickel hexammine [Ni(NH3)6]2+ also shows a dramatic decrease in the reduction rate and ultimate degree of reduction, compared to the nitrate-impregnated catalysts [79]. The explanation in that case must take into account two factors which have a parallel influence, namely the formation of a small amount of nickel silicate (or hydroxysilicate) and a much higher dispersion for a NiO loading of 9.43%, the ratio of the Ni2P to Si2P XPS bands is multiplied by a factor of about 14 [79]. 

Smuda A process for pyrolyzing waste plastics (preferably polyolefins) with the production of diesel fuel and gasoline. A disposable catalyst is used, preferably nickel silicate. Developed by H.W. Smuda (also spelled Zmuda). A large plant has operated in Zabrze, Poland, since 1997. 

Nickel silicate and ferrous silicate are the preferred catalysts in the Smuda process. The Smuda catalyst is a layered silicate clay framework with ordered nickel (or iron) atoms inside. The catalyst is charged at 10 wt% ratio of the plastic feedstock. The catalysts are based on layered silicates with Lewis acid activity [24]. Catalytic cracking results in very little noncondensable gas (<1%) and minimal carbonaceous char. The hfe of the Smuda catalyst is approximately 1 month [24]. 

Ni204Si (s) 2NiO Si02 (s) Nickel Silicate Ni204Si (s) 2NiO Si02 (s)... 

Calcining a silica supported nickel ammine complex gave a nickel silicate like material with nickel ions present in an octahedral coordination surrounded by oxygens. Heating the titania supported species, however, resulted in the formation of Ni 2 d Ni cations present in small patches of nickel oxide on the... 

Nickel hydroxide combines easily with aluminum hydroxide hydrogel, as mentioned above, but hardly with silica hydrogel in the course of ordinary precipitation and drying. The formation of nickel silicate from the two-component precipitates necessitates the heating of these mixtures with hot water in an autoclave at 250° over 24 hours. 

Fig. 7. Thermograms of nickel silicate xerogels. Rate of raising temperature 10°/ minute a and b, for the samples prepared by the SHOP method at final pH s of 6.6 and 8.4, respectively c, for the sample prepared by mixing of individual precipitates.

Figure 8 shows infrared (IR) spectra of the various gels obtained by drying at 100°. Gel of nickel silicate prepared by the SHOP method gave quite different IR spectra profiles from that of either the dried nickel hydroxide or the silica gel, thus supporting the conclusion obtained from the DTA data. 

Figure 9 gives the X-ray diifraction patterns of the nickel silicate xerogels prepared by the SHOP method and that of the mechanical mixture of the two components. The ai and bi patterns indicate the difficulty of reduction of the precipitate from SHOP. Decomposition and reduction to metallic nickel started very slowly only above 600°. The calcination of these dried gels at 900° increased the rate of decomposition and reduction of nickel silicate at 600°. The higher value of pH of the mother solution also induced easier decomposition and reduction. 

Nickel silicate prepared by the SHOP method has little activity for hydrogenation in general, but exhibits a high selective activity for the hydrogenation of the benzene nucleus when heated above 500° for 1 hour in hydrogen. It is noticeable that this catalyst has no ability to hydrosplit the C—C bond. 

The thermal and chemical stability of the cations exchanged on the catalyst depend on the chemical species of the cations. NiSA decomposed to a slight extent even at 450-500° in a stream of hydrogen, indicating less stability than that of the nickel silicate obtained by SHOP. 

Catalyst deactivation and resistance to coking are two important issues of the methane reforming reaction with CO2 over Ni based catalysts because of their potential industrial application. Chen and Wren (9) and Bhattacharya and Chang (10) have recently proposed that the nickel aluminate spinel produced by interaction between nickel and alumina has a positive effect on the suppression of carbon deposition in CO2 reforming of methane. On the other hand, the formation of various types of nickel silicate species between the nickel and the support, attributed to the strong metal-support interaction, has been reported in Ni-silica catalysts (11,12). From these conclusions, it seems interesting to study the influence of Ni-silica interaction on carbon deposition. 

The structure and chemistry of the hydrous nickel silicate and aluminate minerals. 1282 ... 

---