I= METHANATION-BIMETALLIC CATALYSTS
Pakistan Research Repository Home
 

Title of Thesis
METHANATION-BIMETALLIC CATALYSTS

Author(s)
A.Hamid Khan Tahir
Institute/University/Department Details
Institute of Chemical Engineering & Technology University of the Punjab
Session
1992
Subject
Chemical Engineering & Technology
Number of Pages
260
Keywords (Extracted from title, table of contents and abstract of thesis)
METHANATION-BIMETALLIC CATALYSTS, methanation reaction, bimetallics, nickel

Abstract
The bimetallics of nickel with calcium, cadmium, chromium, cobalt, iridium, magnesium, manganese, mercury, molybdenum, palladium. Platinum. Rhodium,. ruthenium, strontium, titanium, tungsten or zirconium, supported on gamma alumina have been investigated for methanation reaction. The catalyst was prepared by impregnation the mixed solution of nickel nitrate and soluble salt of the additive on gamma alumina pellets. The parameters studied include minimum methanation temperature, the apparent activation energy, the reaction order, surface area, the catalytic activity, concentration profile and the extent of sulphur poisoning. The correlations between the observed values of these parameters and measurable characteristics like intermetal heat of adsorption, ionic radius, electron density and metallic radius of the additive suggest that the catalytic behaviour of the nickel-bimetallic system is, under the influence of electron effects. However, geo-metric factors are also playing some part, It has been demonstrated that reducible oxides behave better than irreducible in maintaining catalytic activity, The addition of palladium, platinum, tungsten and chromium metals, famous for hydrogen spillover, improved the performance of the catalyst, supporting the fact that local concentration of hydrogen plays some part, The kinetic data indicates that reaction orders are strongly negative for all catalysts except Ni-pt /Al2O3; in this case it becomes positive at higher temperatures. The reaction orders for catalysts except Ni-Ca/al2o3 become less negative with increasing temperature, suggesting a competitive adsorption of co.

The impregnation profiles of Zr, Co, Rh, Ir and Mo ions on alumina pellets relative to Ni ions suggest that ions of Co, Rh, Ir and Mo, because of higher charge density and ions of Zr, for larger ionic radius as compared to Ni ions, are preferentially adsorbed of restricted at the periphery. This study establishes that with longer soaking time of increasing solution concentration, ions travel deep into pellets.

The bimetallics of nickel with calcium, chromium, cobalt, titanium, strontium, magnesium, manganese, palladium and ruthenium, leach supported on gamma alumina, deactivated with treatment of 50ml H2S slug. The effect of sulphur poisoning , The loss of activity or slow deactivation of catalysts with additives W, Zr, Pt, Hg, Rh, Ir, Cd, Mo and Ni itself due to H2S in the mixture is ascribed to the partial dissociation of hydrogen sulphide and formation of irreducible surface sulphide. Increase in rate if deactivation with increase in temperature, observed in this study, is due to temperature dependency of the site specificity, The sulphur poisoning of various promoters in this study was predominantly geometric, the extent of loss of activity being dependent upon the structural changes involved.

Download Full Thesis
1486.98 KB
S. No. Chapter Title of the Chapters Page Size (KB)
1 0 Contents
83.05 KB
2 1 Literature Review 2-101
582.26 KB
  1.1 General
  1.2 Thermodynamics
  1.3 Kinetics
  1.4 Mechanism of reaction
  1.5 Summary
  1.6 Factors €“ designing of methanation catalyst
  1.7 Adsorption if reactants
  1.8 Breakage of c€”bond
  1.9 Supply of hydrogen
  1.10 Removal of water
  1.11 Support
  1.12 Bimetallic system
  1.13 Sulphur poisoning
3 2 Experimental 102-125
146.31 KB
  2.1 General
  2.2 Materials
  2.3 Apparatus
  2.4 Calibration of gas chromatograph
  2.5 Preparation of catalyst
  2.6 Determination of surface area
  2.7 Concentration profile
  2.8 Methanation procedure
  2.9 Kinetic measurements
  2.10 Effect of hydrogen sulphide
4 3 Results 126-175
251.12 KB
  3.1 General
  3.2 Minimum methanation temperature
  3.3 Catalytic activity
  3.4 Apparent activation energy
  3.5 Rate equation
  3.6 Total surface area
  3.7 Concentration profile
  3.8 Effect of 50ml H 2 S slug
  3.9 Effect of continuous flow of H 2 S
5 4 Discussion 176-227
285.54 KB
  4.1 General
  4.2 Activation energy
  4.3 Catalytic activity
  4.4 Minimum methanation temperature
  4.5 Rate equation
  4.6 Reaction mechanism
  4.7 Concentration profile
6 5 References
98.14 KB