Natural Gas To Diesel

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How to Create a Fuel like Diesel from Natural Gas

From Wiki
Gas to liquids (GTL) is a refinery process to convert natural gas or other gaseous hydrocarbons into longer-chain hydrocarbons such as gasoline or diesel fuel. Methane-rich gases are converted into liquid synthetic fuels either via direct conversion or via syngas as an intermediate, for example using the Fischer Tropsch or Mobil processes

Fischer-Tropsch process
GTL process using the Fischer Tropsch method This method starts with partial oxidation of methane (a component in natural gas) to carbon dioxide, carbon monoxide, hydrogen and water, the carbon monoxide to hydrogen (H2) ratio is adjusted using the water gas shift reaction) and the excess carbon dioxide removal by aqueous solutions of alkanolamine (or physical solvents) the water is removed yielding synthesis gas (syngas) that is chemically reacted over an iron or cobalt catalyst to produce liquid hydrocarbons and other byproducts

Mobil process
An alternative path starts by conversion of the natural gas to syngas, conversion of the syngas to methanol which is subsequently polymerized into alkanes over a zeolite catalyst. It was developed by Mobil in early 1970s.

Methanol is made from methane (natural gas) in a series of three reactions:

1. Steam reforming: CH4 + H2O → CO + 3 H2 ΔrH = +206 kJ mol-1
2. Water shift reaction CO + H2O → CO2 + H2 ΔrH = +206 kJ mol-1
3. Synthesis 2 H2 + CO → CH3OH ΔrH = -92 kJ mol-1
The methanol thus formed may be converted to gasoline by the Mobil process. First methanol is dehydrated to give dimethyl ether:

2 CH3OH → CH3OCH3 + H2O

This is then further dehydrated over a zeolite catalyst, ZSM-5, to give a gasoline with 80% (by weight based on the organics in the product stream) C5+ hydrocarbon products.

ZSM-5 is deactivated by a carbon build-up ("coking") over time in converting methanol to gasoline. The catalyst can be re-activated by burning off the coke in a stream of hot (500 °C (930 °F)) air; however, the number of re-activation cycles is limited.

Pearl GTL Overview
Pearl Gas-to-Liquids (GTL) Plant, Quatar



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