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 CH4 + 2O2 CO2 + 2H2O

Methanol Synthesis #1 (Syngas)

CO + 2H2 CH3OH

Methanol Synthesis #2 (CO2) CO2 + 3H2 CH3OH + H2O

Catalytic Reaction Rates● 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 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, Pre-

Exponential Factors

Water-Gas Shift

● Moderately exothermic● K decreases with increasing T● Kinetically favored at high T, but Thermodynamically

favored at low T● Catalyzed by metals and metal-oxides● ΔHf

o = -41.09 kJ/mol

Water-Gas ShiftRegenerative Mechanism Associative Mechanism

Water-Gas Shift

Water-Gas Shift● Reaction rate based on Langmuir:

Methane Oxidation

• ΔGo= -801.06 kJ/mol• ΔHf

o= -802.64 kJ/mol

• Highly exothermic - Increase in heat shifts reaction to the left

• Pressure - No change

Methane OxidationFigures adapted from Veldsink et al.

Methane Oxidation

Catalyst: CuO-γ-Al2O3

● 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)

● KH2O = 1.2 x 10-2 (Pa-1)

● KCO2 = 5.0 x 10-3 (Pa-1)

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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

• 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 zinc-based 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 zinc-based catalysts

Sources● 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.