Nickel Catalysts For Methanation Research Articles

ChemInform Abstract: Stabilized Magnesia as a Support for Nickel Methanation Catalysts.

AbstractChemInform is a weekly Abstracting Service, delivering concise information at a glance that was extracted from about 100 leading journals. To access a ChemInform Abstract of an article which was published elsewhere, please select a “Full Text” option. The original article is trackable via the “References” option.

Stabilized magnesia as a support for nickel methanation catalysts

Magnesium-aluminium hydroxycarbonate with an Mg/Al ratio of 3, consisting of a single phase only, was used as an additional support in nickel methanation catalysts. This component, when pretreated at 800° C, exhibited very good stability under conditions similar to the actual industrial process.

ChemInform Abstract: Mechanisms of Nickel Catalyst Poisoning

Abstract Poisoning, the strong chemisorption of reactants, products or impurities on active catalytic sites, is an important, difficult deactivation problem in many catalytic processes and particularly in processes involving nickel catalysts. For example, only a few ppm of sulfur impurities can reduce the activity of nickel methanation catalysts by several orders of magnitude within just a few days or weeks; moreover the sulfur thus adsorbed is essentially irreversibly held and cannot be conveniently removed by treatments with air, oxygen, steam, or hydrogen. Catalyst poisons for nickel can be classified according to chemical species, types of reactions poisoned, and selectivity for active catalyst sites. For example, sulfur in the form of H2S and organic sulfides is a highly selective, strongly adsorbing poison for nickel hydrogenation, methanation, and steam reforming catalysts. That surface sulfur-nickel bonds are substantially more stable than the corresponding bulk nickel-sulfur bonds is emphasized by the fact that hydrogen sulfide adsorbs dissociatively with a heat of 250 kJ/mole compared to a heat of bulk formation of 75 kJ/mole. Adsorbed sulfur blocks the adsorption of most other species and generally causes a substantial or complete loss of nickel catalyst activity. Whether this loss of activity is a geometric blocking or a longer range electronic effect is somewhat controversial and probably depends on coverage. The evidence is in favor of a combination of geometric and electronic effects at low sulfur coverages and geometric blocking effects at high coverages. The toxicity of poisons for nickel depends on the stability of the nickel-additive bond as well as the electronegativity of the adsorbing species. Species with a high degree of shielding such as SO3 are less toxic than poorly shielded species such as elemental sulfur and H2S. The toxicity of some poisons, e. g. carbonaceous species, depends not only on their strength of adsorption but also on their reactivity with gasifying agents such as hydrogen or water vapor.

ChemInform Abstract: CHEMICAL MODIFICATION OF CHEMISORPTIVE AND CATALYTIC PROPERTIES OF NICKEL

Abstract Several reactions representing important categories of catalytic systems have been studied on chemically modified single crystal surfaces. These reactions are methanation of CO and CO2, hydrogenolysis of ethane, hydrogenation of ethylene, and cyclopropane ring-opening and hydrogenolysis. Poisoning of the above reactions by ordered, submonolayer coverages of sulfur show large nonlinear effects for sulfur coverages versus reactivity attenuation. These data together with related chemisorption results are reviewed with emphasis on the author's own work. These studies suggest that the dominant effect in poisoning by sulfur is an electronic one and extends over distances larger than the atomic radius. Related studies have addressed the role of potassium promoters in nickel catalysts for methanation. Potassium decreases the rate of methane formation and increases the rate of higher hydrocarbons relative to the clean nickel surface. Similar results have been reported for supported nickel catalysts suggesting that support effects play a small role in catalytic promotion by potassium.

Chemical modification of chemisorptive and catalytic properties of nickel

Several reactions representing important categories of catalytic systems have been studied on chemically modified single crystal surfaces. These reactions are methanation of CO and CO 2, hydrogenolysis of ethane, hydrogenation of ethylene, and cyclopropane ring-opening and hydrogenolysis. Poisoning of the above reactions by ordered, submonolayer coverages of sulfur show large nonlinear effects for sulfur coverages versus reactivity attenuation. These data together with related chemisorption results are reviewed with emphasis on the author's own work. These studies suggest that the dominant effect in poisoning by sulfur is an electronic one and extends over distances larger than the atomic radius. Related studies have addressed the role of potassium promoters in nickel catalysts for methanation. Potassium decreases the rate of methane formation and increases the rate of higher hydrocarbons relative to the clean nickel surface. Similar results have been reported for supported nickel catalysts suggesting that support effects play a small role in catalytic promotion by potassium.

Chemical modification of chemisorptive and catalytic properties of nickel☆

Several reactions representing important categories of catalytic systems have been studied on chemically modified single crystal surfaces. These reactions are methanation of CO and CO 2 , hydrogenolysis of ethane, hydrogenation of ethylene, and cyclopropane ring-opening and hydrogenolysis. Poisoning of the above reactions by ordered, submonolayer coverages of sulfur show large nonlinear effects for sulfur coverages versus reactivity attenuation. These data together with related chemisorption results are reviewed with emphasis on the author's own work. These studies suggest that the dominant effect in poisoning by sulfur is an electronic one and extends over distances larger than the atomic radius. Related studies have addressed the role of potassium promoters in nickel catalysts for methanation. Potassium decreases the rate of methane formation and increases the rate of higher hydrocarbons relative to the clean nickel surface. Similar results have been reported for supported nickel catalysts suggesting that support effects play a small role in catalytic promotion by potassium.

Deactivation of nonuniform nickel/alumina methanation catalysts

The effect of metal distribution on the deactivation behavior of alumina-supported nickel methanation catalysts prepared with nickel that was uniformly distributed over the cross section of the pellet, concentrated in a central core, and concentrated in an outer shell was studied. Unavoidably low nickel loadings for the core and shell catalysts made it difficult to distinguish radial distribution effects from nickel dispersion or metal-support interactions effects during studies of low-pressure methanation in a constant-flow stirred reactor at 698/sup 0/F. Results indicate that the absolute deactivation rates for the uniform and core nickel catalysts are nearly equal, but the selectivity differences are appreciable. When investigators tested a zinc shell/nickel core composite catalyst to determine if the zinc shell would serve as a sulfur-getter and protect the nickel core when operating on H/sub 2/S-containing feed, the composite catalyst demonstrated a much lower H/sub 2/S-induced deactivation rate than a uniform nickel catalyst.

ChemInform Abstract: Deactivation of Nickel Methanation Catalysts Induced by the Decomposition of Iron Carbonyl. Part l. Deactivation via Pore‐Mouth Blocking. Part 2. Interactions Between Iron and Nickel.

ChemInform Abstract: Deactivation of Nickel Methanation Catalysts Induced by the Decomposition of Iron Carbonyl. Part l. Deactivation via Pore‐Mouth Blocking. Part 2. Interactions Between Iron and Nickel.

Deactivation of nickel methanation catalysts induced by the decomposition of iron carbonyl: I. Deactivation via pore-mouth blocking

The deactivation of alumina-supported nickel methanation catalysts due to decomposition of Fe(CO) 5 was studied using both reaction kinetics measurements and in situ Mössbauer spectroscopy. Iron carbonyl, enriched in 57Fe for Mössbauer spectroscopy studies, was produced in situ and entrained with the carbon monoxide feed to a methanation reactor operating at temperatures of 620–650 K and H 2 CO ratios near 7. This incorporation of Fe into the nickel catalyst via the decomposition of Fe(CO) 5 resulted in significant catalyst deactivation as well as changes in the parameters of a power law rate expression describing the methanation kinetics. With increasing amounts of Fe deposited on the catalyst, the kinetic parameters were shifted toward those of iron catalysts. These iron-induced phenomena are due to (1) pore-mouth blocking of the Al 2O 3 micropore structure by iron particles formed during the diffusion-limited decomposition of Fe(CO) 5, and (2) interactions between iron and nickel in the macropores of the support. Specifically, the loss of catalyst activity is primarily caused by pore-mouth blocking, while shifts in kinetic parameters are the consequence of both pore-mouth blocking and interactions between iron and nickel. The majority of the iron deposited under methanation reaction conditions has been identified as χ-carbide (Hägg carbide) using Mössbauer spectroscopy at liquid helium temperature.

Deactivation of nickel methanation catalysts induced by the decomposition of iron carbonyl: II. Interactions between iron and nickel

Catalysts prepared by thermally decomposing Fe(CO) 5 on Al 2O 3 powder or Ni Al 2 O 3 catalysts were studied using both methanation reaction kinetics measurements and in situ Mössbauer spectroscopy. Iron-induced shifts in the kinetic parameters of the methanation reaction over supported nickel catalysts are the consequence of both pore-mouth blocking of the alumina micropores by iron particles and the interaction of iron with nickel particles in the macropores of the support. The presence of nickel appears to facilitate the formation of zero-valent iron during the decomposition of Fe(CO) 5. In addition, Auger electron spectroscopy (AES) studies of model Ni Al 2 O 3 samples composed of nickel evaporated onto thin films of alumina demonstrated that, at low partial pressures, Fe(CO) 5 decomposes preferentially on nickel surfaces rather than on Al 2O 3. Besides poremouth blocking, iron-induced deactivation of nickel methanation catalysts can also be attributed to the deposition of carbon on the catalyst.

Sulfur poisoning of nickel methanation catalysts: II. Effects of H 2S concentration, CO and H 2O partial pressures and temperature on reactivation rates

Poisoning of unsupported and supported nickel methanation catalysts was investigated in Pyrex, fixed-bed and quartz, mixed-flow microreactors over a range of reaction conditions and H 2S concentrations. The results indicate that poisoning rates are complex functions of H 2S concentration, temperature and partial pressures of CO and H 2O. In general, deactivation rates decrease with increasing H 2S concentration, due to formation of multilayer sulfides, and increase with increasing CO and H 2O partial pressures. The application of deactivation models to poisoning of nickel by sulfur is discussed.

ChemInform Abstract: SULFUR DEACTIVATION OF NICKEL METHANATION CATALYSTS

Chemischer InformationsdienstVolume 13, Issue 45 Preparative Organic Chemistry ChemInform Abstract: SULFUR DEACTIVATION OF NICKEL METHANATION CATALYSTS W. D. FITZHARRIS, W. D. FITZHARRISSearch for more papers by this authorJ. R. KATZER, J. R. KATZERSearch for more papers by this authorW. H. MANOGUE, W. H. MANOGUESearch for more papers by this author W. D. FITZHARRIS, W. D. FITZHARRISSearch for more papers by this authorJ. R. KATZER, J. R. KATZERSearch for more papers by this authorW. H. MANOGUE, W. H. MANOGUESearch for more papers by this author First published: November 9, 1982 https://doi.org/10.1002/chin.198245081Read the full textAboutPDF ToolsRequest permissionExport citationAdd to favoritesTrack citation ShareShare Give accessShare full text accessShare full-text accessPlease review our Terms and Conditions of Use and check box below to share full-text version of article.I have read and accept the Wiley Online Library Terms and Conditions of UseShareable LinkUse the link below to share a full-text version of this article with your friends and colleagues. Learn more.Copy URL Share a linkShare onFacebookTwitterLinkedInRedditWechat No abstract is available for this article. Volume13, Issue45November 9, 1982 RelatedInformation

Sulfur deactivation of nickel methanation catalysts

Sulfur deactivation of supported Ni in CO hydrogenation was studied in an all-quartz internalrecycle reactor with a feed containing 4% CO in H 2. Thirteen ppb H 2S reduced the steady-state methanation activity of Ni γ- Al 2 O 3 about 200-fold at 661 K; 100 ppb H 2S reduced the activity 5000-fold. A dual site Langmuir-Hinshelwood rate expression predicts both the CO partial pressure dependence and the S poisoning. Poisoning and chemisorption data indicate formation of a stable two-dimensional, surface sulfide with a S: Ni surface atom ratio of 1: 2 for 13 ppb H 2S in H 2 at 661 K. The surface sulfide has a free energy of formation of at least −26 kcal/mole which is 15 kcal/mole more stable than bulk Ni 2S 3. Sulfur poisoning is due to geometric effects, i.e., site blockage, rather than electronic effects since the activation energy for methanation over S-poisoned Ni was the same as that over unpoisoned Ni, 24 kcal/mole.

Effect of hydrogen sulfide on the activity of nickel catalysts for methanation

The resistance of 14 different nickel catalysts to H2S poisoning in CO2 methanation was examined. Experiments were carried out in a quartz reactor of special design, utilizing the methods of temperature difference measurement (DTA) and chromatographic analysis of outlet gases.

Reducibility and surface area of coprecipitated supported nickel methanation catalysts

A study on the effect of reducing temperature and time on the N2 BET surface area and the H2 chemisorption metal surface area of a range of alumina and silica supported nickel methanation catalysts is described. Increasing the reduction temperature from 400 to 600 °C generally decreases the N2 BET surface area. The effect is more marked in the silica supported catalysts. The reduced metal surface area increases in the silica supported catalysts as the temperature increases from 400 to 600 °C. In the alumina supported catalysts the metal surf ace area increases from 400 to 500 °C, but decreases from 500 to 600 °C. The fraction of nickel that is reduced increases as the reduction temperature increases.

Magnetic susceptibility: instrumentation and analytical applications including bioscience, catalysis, and amorphous materials

A review of the Jan. 1978-Dec. 1979 literature covers applications in catalyst studies, including nickel methanation catalysts, iron-doped sodium-A-type zeolites, highly dispersed iron oxides, silica-supported Ni/Cu catalysts, hydrogen activation on Fe/MgO catalysts, the dispersion of iron species in Linde 13X zeolites, silica gel, and alumina-supported Pd particles, and olefin hydrogenation over CrO/sub x//SiO/sub 2/ catalysts.

Studies of the metal–support interaction in coprecipitated nickel on alumina methanation catalysts using X‐ray photoelectron spectroscopy (XPS)

AbstractCharacterization studies on a series of coprecipitated alumina‐supported nickel methanation catalysts by X‐ray photoelectron spectroscopy are described. Binding energies and spectral shapes have been determined for several standard compounds (Ni, NiO, Ni(OH)2, NiAl2O4, Al2O3) to provide background information for interpreting the catalyst spectra. The results indicate that the surface regions of the fresh (unreduced) catalysts are composed primarily of amorphous NiAl2O4 with some NiO particles present either within the pores of the support or covered by a NiAl2O4 layer. In comparison with similarly prepared silica‐supported catalysts, reducibility is more difficult indicating the presence of stronger support interactions.

Sulfur poisoning of nickel methanation catalysts: I. in situ deactivation by H 2S of nickel and nickel bimetallics

The effects of exposure to dilute H 2S during reaction on the methanation activity of alumina-supported nickel, cobalt, and nickel bimetallic catalysts in powder, pellet, and monolith form were investigated. Results of activity tests at 525 °K, 1 atm, and a space velocity of 30,000 hr −1 with 10 ppm H 2S in the reactant stream show that cobalt and most nickel bimetallic catalysts are not significantly more or less sulfur tolerant than nickel; Ni-MoO 3, however, is more active before, during, and after exposure to H 2S. The data also indicate that monolithic catalysts are significantly more sulfur resistant than either powder or pellet catalysts. All of these catalysts, however, are completely deactivated within a period of 2–3 days under the conditions investigated. During reaction in the presence of H 2S, there is an exponential decrease in activity accompanied by a gradual breakthrough of the poison. Less sulfur is adsorbed on the catalyst during reaction than would be if equilibrium adsorption occurred. Data showing the roles of temperature, gas composition, and catalyst geometry in the poisoning process and the results of regeneration experiments are presented and discussed.

Characterization of coprecipitated nickel on silica methanation catalysts by X-ray photoelectron spectroscopy

An X-ray photoemission spectroscopy study of a series of standard nickel compounds (Ni, NiO, Ni(OH) 2, NiSiO 3) and silica-supported nickel methanation catalysts has been conducted. The binding energies and spectral shapes of the standard samples provide a data base which has been used to understand the catalyst spectra. The activity and thermal stability of coprecipitated nickel catalysts has been attributed to the metal-support interaction. This interaction has been observed in two coprecipitated nickel-on-silica catalysts. The nickel spectra closely resemble those of amorphous NiSiO 3. The interaction varies somewhat between the two catalysts studied as evidenced by differences in their reducibility.

Some Crystal Field Surface Orbital-Bond Energy Bond Order (CFSO-BEBO) Calculations of Heats of Adsorption of Hydrogen on Nickel Methanation Catalysts

Some Crystal Field Surface Orbital-Bond Energy Bond Order (CFSO-BEBO) Calculations of Heats of Adsorption of Hydrogen on Nickel Methanation Catalysts