1. Direct Oxidation of Methane to Methanol
Group 7
Joey Saah, Richard Graver, Shekhar shah, Josh Condon

2. Methanol Applications 21 million tons produced per year
Solvent
Gasoline additive
Feedstock for many chemical processes
21 million tons produced per year
Primary component of natural gas
Currently an abundant fuel source
Difficult and uneconomical to transport
Simple and cost effective on-site process required
wikimedia.org

3. Standard Methanol Synthesis
Conversion of natural gas into syngas
Steam reforming reactor with catalyst
Creates carbon monoxide and hydrogen from methane
Syngas to Methanol
H2 and CO react in 2:1 ratio to form methanol
Catalyst selectively forms methanol
Haldor Topsoe

4. One-Step Methanol Process
Advantages
Steam in steam reformer is expensive to produce
Less capital costs required to build one-step plant
May be created near more remote methanol sources
Remote methanol sources more profitable, attractive
Challenges
Past one-step reactions showed low yield or selectivity with homogeneous and heterogeneous catalysts
Other methods did not produce methanol levels required for commercialization
Liquid phase or Supercritical reactor methods

5. History of Methanol 1661 – Methanol discovered by Robert Boyle
1834 – The chemical structure and identity of methanol was identified by Dumas and Peligrot
Destructive distillation of wood was the first method to produce methanol
Pyrolysis in a distillation apparatus

6. History of Industrial Methanol Production
First synthetic methanol production route discovered in 1905
BASF commercialized the process in 1934
Zinc-Chromium Oxide Catalyst
300 °C and 200 atm
This process was used until 1966 when a lower pressure, higher efficiency method was discovered

7. History of Industrial Methanol Production cont.
Imperial Chemical Industries, Ltd. discovered a new process in 1966
Copper-Zinc Oxide catalyst °C
atm
Poisoning of catalyst was a problem for this method
Lifetime of catalyst is about 4 years
Only if there is good control of temperature and feedstock purity

8. Thermodynamic Analysis
Reaction
ΔG reaction (KJ/mol)
298
650
700
750
800
1000
Direct
CH4+1/2O2 è CH3OH
-111
-93
-91
-88
-86
-76 SR
CH4 + 1/2O2 è CO + 2H2
-152
-162
-172
-182
-222
CH4 + H2O è CO + 3H2
142 60 48 36 23
-27

9. Optimal Conditions
Traditional steam reforming requires 1000 K or higher
Direct oxidation (direct synthesis) favorable at lower temperatures thermodynamically
Theoretically, 33% equilibrium conversion at 298 K for direct synthesis
Maximum of 5 % equilibrium conversion in direct synthesis actually obtained due to high activation energy

10. Thermodynamic Requirements
Direct synthesis would be economically feasible (compared to traditional method) if 5.5% conversion and 80% selectivity to methanol is obtained in the reaction
Low conversion requirement is indicative of the high cost of current methanol production
CO2 and CO are thermodynamically the most favorable products of direct oxidation (selectivity to methanol is a challenge)

11. Why do we need a catalyst?
Methane is a more stable molecule than methanol
Reaction equilibrium favors methane at operating conditions
Low conversion
Large activation energy
Complete oxidation to carbon monoxide and carbon dioxide is thermodynamically favored
Low selectivity for the partially oxidized product
Harsh operating conditions
Requires 440 kJ/mol to break the first C—H bond
bar and K
Energy intensive step would be eliminated
The first question you might ask is: why do we even need a catalyst? Is a catalyst absolutely necessary? YES! Methane is a very stable molecule and it is very difficult to abstract a hydrogen atom from methane (roughly … kJ/mol). This reaction will not proceed in the forward reaction due to thermodynamic restrictions on the equilibrium. In order to make this reaction happen we need to lower the activation energy that is necessary for the reaction to occur. The first step is the creation of a free radial methyl group and is followed by subsequent attack of a water molecule to get the remaining OH group attached.

12. Important Catalytic Parameters
Temperature
Pressure
Oxygen concentration in the feed gas
Gas flow rate
Additives
These parameters are critical to optimizing the conversion of methane and selectivity toward the methanol product.
As shown in the thermodynamic table a couple slides ago, as temperature increases the change in gibbs free energy becomes increasingly negative for the complete oxidation, while, for the partial oxidation, the opposite is true. This indicates that the reaction should be run at lower temperatures, and we see from the table that the partial oxidation becomes the dominating reaction at 298 K. This is one of the biggest reasons why this process is of such interest to researchers, the energy intensive reforming to syngas can be completely bypassed!

13. Heterogeneous Catalytic Partial Oxidation
Direct conversion of methane and oxygen to methanol
Conversion of methane and selectivity to desired product are limiting factors
Activation energy for the reaction is extremely large and limits the conversion of methane to products
Involves the abstraction of a hydrogen from methane to create a methyl radical followed by subsequent reaction to form methoxide ions
Solid catalysts containing metal oxide catalysts have been effective at removing hydrogen
CH4 + ½ O CH3OH Direct Oxidation Reaction

14. References
Khirsariya, P., Mewada, R. “Single Step Oxidation of Methane to Methanol – Towards Better Understanding”. Procedia Engineering