reactions kinetics

Report
Reaction Kinetics of
Methanol Synthesis
Jill DeTroye, Brandon Hurn,
Kyle Ludwig, and Isaac Zaydens
Overview
● Review the Reactions
● Brief Introduction of Catalytic Kinetics
● Discussion of Reaction Kinetics
● Summary and Conclusions
● Questions
Reactions
● Our proposed process reactions include:
○ Methane-Steam Reforming (MSR)
○ Water-Gas Shift (WGS)
○ Methane Oxidation (MO)
○ Methanol Synthesis (MS)
Reactions
Reaction Name
Reaction’s Chemical Formula
Methane Steam Reforming
CH4 + H2O
CO + 3H2
Water Gas Shift
CO2 + H2O
CO + H2
Methane Oxidation
Methanol Synthesis #1 (Syngas)
Methanol Synthesis #2 (CO2)
CH4 + 2O2
CO + 2H2
CO2 + 3H2
CO2 + 2H2O
CH3OH
CH3OH + H2O
Catalytic Reaction Rates
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Homogeneous - Reactants/Catalysts in same phase
Heterogeneous - Reactants/Catalysts in different phase
Our purposes: Solid-Phase Catalyst w/ Gas/Vapor Phase
Reactants
Adsorption Constants (generally K)
Rate Constants (generally k)
Partial Pressures (pi)
Methane Steam Reforming
● Main process for the production
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of syngas using nickel-alumina
catalysts
High ratio of steam to methane
Moderate temperature
Low/moderate pressure
Methane Steam Reforming
Steam Methane Reforming
● Coefficients change depending
on temperature, pressure, and
steam-to-methane ratio
● Rates use partial pressures,
typical of catalytic kinetics
Steam Methane Reforming
Steam Methane Reforming
Steam Methane Reforming
● Activation Energies, Adsorption Enthalpies, PreExponential Factors
Water-Gas Shift
● Moderately exothermic
● K decreases with increasing T
● Kinetically favored at high T, but Thermodynamically
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favored at low T
Catalyzed by metals and metal-oxides
ΔHfo = -41.09 kJ/mol
Water-Gas Shift
Regenerative Mechanism
Associative Mechanism
Water-Gas Shift
Water-Gas Shift
● Reaction rate based on Langmuir:
Methane Oxidation
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ΔGo= -801.06 kJ/mol
ΔHfo= -802.64 kJ/mol
Highly exothermic - Increase in heat shifts
reaction to the left
Pressure - No change
Methane Oxidation
Figures adapted from Veldsink et al.
Methane Oxidation
Catalyst: CuO-γ-Al2O3
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k0 = 1.08 (kmol kgcat-1 Pa-1 s-1)
EA = 1.25 x 105 (J mol-1)
K02 = 1.2 x 10-2 (Pa-1)
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KH2O = 1.2 x 10-2 (Pa-1)
KCO2 = 5.0 x 10-3 (Pa-1)
Figures adapted from Veldsink
et al.
Methane Oxidation
Methane Oxidation
Optimal operating conditions:
• pCH4≤ 6 kPa
• pH2O≤ 8 kPa
• pCO2≤ 20 kPa
• 0.06 kPa ≤ pCO2 ≤ 22 kPa
• 723 K ≤ T ≤ 923 K
Methanol Synthesis
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ΔHfo = -90.55 kJ/mol at 298K
ΔGo = -25.34 kJ/mol
Exothermic: higher methanol yields are obtained at
lower temperatures and higher pressures
Methanol Synthesis
● ZnO/Cr2O3 catalyst with copper dispersed on the zincbased catalysts.
Methanol Synthesis
● ΔHfo = -49.43 kJ/mol
● ΔGo = 3.30 kJ/mol
● Exothermic: higher methanol yields are obtained at
lower temperatures and higher pressures
Methanol Synthesis
● ZnO/Cr2O3 catalyst with copper dispersed on the zincbased catalysts
Sources
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Hou, Kaihu, and Ronald Hughes. "The Kinetics of Methane Steam Reforming over a Ni/alpha-Al2O
Catalyst." Chemical Engineering Journal 82 (2001): 311-28. Web. 10 Feb. 2015.
Smith, Byron, RJ, Muruganandam Loganathan, and Murthy S. Shantha. "A Review of the Water Gas Shift
Reaction Kinetics." INTERNATIONAL JOURNAL OF CHEMICAL REACTOR ENGINEERING R4 8
(2010): 1-32. Web. 10 Feb. 2015.
Veldsink, J.W., G.F. Versteeg, and W.P.M. Van Swaaij. "Intrinsic Kinetics of the Oxidation of Methane
Over an Industrial Copper(II) Oxide Catalyst on a Gamma-Alumina Support." The Chemical Engineering
Journal 57 (1995): 273-83. Print.
"Industrial Methanol from Syngas: Kinetic Study and Process Simulation : International Journal of
Chemical Reactor Engineering." Industrial Methanol from Syngas: Kinetic Study and Process Simulation
: International Journal of Chemical Reactor Engineering. N.p., 27 Aug. 2013. Web. 12 Feb. 2015.

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