Poisoning of nickel catalysts

Sulfur. It is not readily predictable from existing thermodynamic data that sulfur would be a poison of nickel catalysts. The action of sulfur is undoubtedly through the reaction of hydrogen sulfide with nickel, according to ... 

Steam. Steam is a potential poison of nickel catalysts under extremely high steam concentrations and low hydrogen concentrations. This is apparent in Figure 11 where the equilibrium ratio of Ph2/Fh2o over Ni and over Ni(active) is plotted as a function of temperature for the following reactions ... 

Sulphur poisoning of nickel catalysts in catalytic hot gas cleaning conditions of biomass gasification... 

Riesz, C. H., Dirksen, H. A., and Kirkpatrick, W. J Sulfur Poisoning of Nickel Catalysts. Institute of Gas Technology Research Bulletin No. 10, September, 1951. 

Reversibility of these poisons depends on process conditions. Sulfur-poisoning of nickel catalysts, for example, is irreversible at lower temperatures. Methanation catalysts beds cannot be regenerated even with... 

It is evident that many of the older ideas about the poisoning of nickel catalysts must be re-examined in the light of data now available. The two nickel sulfides, NisSa and NiS, which can exist under the conditions prevailing in some catalytic systems, are catalysts for some reactions also catalyzed by metallic nickel and for other reactions not yet found to be catalyzed by the metal. Explanations of this behaAuor in terms of band theory (or Brillouin zones) can be expected in the near future. 

The incorporation of promoters can also neutralize catalyst poisons. Thus the sulfur poisoning of nickel catalysts is reduced by the presence of copper chromite since copper ions readily form sulfides. 

Figure 8.3.1 is a typical process diagram for tlie production of ammonia by steam reforming. Tlie first step in tlie preparation of tlie synthesis gas is desulfurization of the hydrocarbon feed. Tliis is necessary because sulfur poisons tlie nickel catalyst (albeit reversibly) in tlie reformers, even at very low concentrations. Steam reforming of hydrocarbon feedstock is carried out in tlie priiiiiiry and secondary reformers. 

Catalyst Poisons. It is well known that sulfur, chlorine, etc. are strong poisons for nickel catalyst. Chlorine was not detectable in the synthesis gas downstream of the Rectisol in the SASOL plant. The total sulfur content of this gas—in the form of H2S, COS, and organic sulfur components—averaged 0.08 mg/m3 with maximum values of 0.2 mg total sulfur/m3. 

In studies on the para-hydrogen conversion rate on nickel and its alloys with copper other authors also noted the poisoning effect of the sorbed hydrogen. Singleton (53) mentioned the poisoning of nickel film catalysts by the slow-sorbed hydrogen. Shallcross and Russell (54) observed a similar phenomenon for nickel and its alloys with copper at — 196°C. At higher... 

Kalibaeva G, Vuilleumier R, Meloni S, Alavi A, Ciccotti G, and Rosei R. Ab initio simulation of carbon clustering on an Ni (111) Surface A model of the poisoning of nickel-based catalysts. J Phys Chem B 2006 110 3638-3646. 

The poisoning of metallic catalysts by sulfur has been extensively studied, essentially on nickel, palladium, and platinum, for numerous reactions and consequently under very different experimental conditions, particularly for temperatures ranging from 300 to 1300 K. Experiments carried out at high temperatures (1-4) have shown that poisoning can be balanced by the following reaction ... 

The addition of 0.5 to 10 percent by volume of H2 to the natural gas feed has been shown to keep the nickel in the reduced state, which makes it more active. Also, the hydrogen will retard the formation of nickel sulfide, which will prevent or minimize poisoning of the catalyst ... 

Sulphur-poisoning studies of nickel catalysts have been performed with fixed-bed tube reactors at 800 - 950 °C under 1 - 20 bar total pressure with real and simulated gasification gas mixtures containing H2S (50 - 1000 ppmv). The effect of sulphur concentration of the gas and the operation conditions will be presented and discussed in this paper. 

Deactivation by sulfur has been explained by the withdrawing of electrons from the catalyst surface. It has also been shown that sulfur inhibits the dissociation of CO on iron surfaces l]. The deliberate partial poisoning of iron/manganese cataly.sts with sulfur has been used to shift the product selectivity towards short-chain hydrocarbons. At higher sulfur concentrations (0.7 mg S/g catalyst) the activity is significantly decreased and the olefin selectivity increased [82]. Sulfur poisoning of nickel catalysis has recently been shown to inhibit the chemisorption of hydrogen 83.84). 

The colloidal nickel catalyst cannot be removed by conventional filtration techniques nor have effective means of deactivation by poisoning been found. Ziegler claims that addition of colloidal iron will poison the nickel catalyst. The use of iron and other potential nickel poisons has been studied in some detail. Salts of Cd, Cu, Cr, Fe, Hg, Se, V, and Zn along with phenylacetylene and sulfur dichloride have been tested as nickel deaotivators. Iron, cadmium, and copper salts seemed effective in limiting alkylation between olefins and triethylaluminum... 

Poisoning of metal catalysts may provide a tool for improving selec> tivity by affecting the concentrations of ensembles required by different reaction paths. This is illustrated by steam reforming on sulfur passivated nickel catalysts and the results are compared with observations for sulfided platinum-rhenium catalysts for catalytic reforming and for a chlorine poisoned palladium catalyst for partial oxidation of methane. 

Sulfur Poisoning of Nickel-based Hot Gas Cleaning Catalysts in Synthetic Gasification Gas... 

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