Presentation on theme: "Literature Survey of Two-Step Methane-syngas-methanol Processes"— Presentation transcript:
1 Literature Survey of Two-Step Methane-syngas-methanol Processes Group 4David Bigelow, Sean Coluccio, Luke Rhodes, Peguy TouaniFebruary 5, 2015CHBE
2 Background CH4 + H2O → 3 H2 + CO CO + 2 H2 → CH3OH The production of synthesis gas from methane produces three moles of hydrogen gas for every mole of carbon monoxide, while the methanol synthesis consumes only two moles of hydrogen gas per mole of carbon monoxide.
3 Background cont.To deal with the excess hydrogen, CO2 is injected in the methanol reactor where it forms methanol and waterCO2 + 3 H2 → CH3OH + H2O
4 Reactors and Catalysts There are two types of reactors used today: adiabatic and isothermalCarbon monoxide and hydrogen react over a catalyst to produce methanolCatalyst:Zn/Cr2O3 at high pressure and temperature with impure syngasCu/Zn/Al2O3 are widely use today and is used at lower conditions
5 Step 1: Conversion of Methane to Syngas Preparation of Synthetic gas typically accounts for 50-75% of the total capital cost of a Gas-to-Liquid (GTL) plantSteam Reformation (SR) has been used for decades and forms a hydrogen rich syngasCatalytic Partial Oxidation (CPOX) is a newer technology that oxidizes methane to form syngas
6 Catalytic Partial Oxidation Steam ReformationCatalytic Partial OxidationMethane is contacted with steam over a heated catalyst at high pressures and temperatures to produce a high hydrogen content syngasRequires large heat exchangers and a large initial investmentStrict heat balance requirements which makes it hard to control and difficult to scale down to a small sizeMethane is reacted with oxygen over a catalyst bed to yield syngas at a 2:1 hydrogen ratioOperated at moderate pressures ( MPa) which is compatible with downstream processesEasier to control and manipulate reactor sizingNewer technology that lacks research in comparison to steam reformation
8 Step 2: Methanol Synthesis from Syngas CO + 2H2 ↔ CH3OHThe original methanol synthesis process was operated at high temperature and pressureMethanol is now generally synthesized using a slightly different reaction, which has the addition of CO2 as a reactantModern plants will also use the heat produced from the methanol synthesis for the steam reformation reaction
9 ReactorsTwo main types of reactors are used today, adiabatic and isothermalAdiabatic reactors generally use injection of cooled syngas, whether it is fresh or recycledIsothermal reactors are continuously cooled, though generally from another source, and operate similarly to heat exchangersBoth types of conventional reactors utilize fixed bed catalystsThe Liquid Phase Methanol Synthesis process is used less often and utilizes slurry reactors instead of conventional fixed bed reactorsAdiabatic and isothermal reactors will generally require specific stoichiometric ratio syngas, which may necessitate using the water-gas shift reaction. Multiple passes through the reactor are needed as a single pass is generally unable to convert more than 50% of the syngas.
12 Reactor Examples Cont. Slurry Reactor Slurry reactors are able to convert CO rich syngas, and as such increases the potential for converting methanol from coal or biomass
13 CatalystsThe first catalyst used was Zn/Cr2O3 at high pressure and temperature with impure syngasIn 1966 a Cu/Zn/Al2O3 catalyst began seeing use, and allowed operation at much lower conditionsThis Cu/Zn/Al2O3 catalyst is still used today, and remains the popular choice for methanol synthesis
14 Conclusion Two step process of: Varying forms of operation Conversion Methane to SyngasMethanol Synthesis from SyngasVarying forms of operationMost reactors use similar, using small range of catalystsPreferable for medium to large scale processes
15 ReferencesM. Lyubovsky, S. Roychoudhury, R. LaPierre. “Catalytic partial oxidation of methane to syngas at elevated pressures. Catalysis Letters. Vol. 99, Nos. 3-4, February 2005.Methanol/Default.htm