Catalytic derichment (CDR) is a development of a process to convert the higher hydrocarbons into substitute natural gas (SNG). This process was developed to allow the manufacture of pipeline gas from naphtha but is even better suited for the conversion of low molecular weight hydrocarbons to methane.
The process starts with the steam reforming of the hydrocarbon to give hydrogen and carbon monoxide which coupled with the shift reaction gives hydrogen and carbon dioxide. Hydrogen is then reacted with carbon monoxide to give methane and water. The CDR reactor is a simple, fixed bed adiabatic vessel.
Ethane is the most efficient hydrocarbon for methane conversion with a reforming temperature of 300-350OC. Not only does the process allow for the de-richment of LNG but also increases the methane yield.
The operation of a plant supplied with a CDR conversion unit has considerable flexibility. Thus the quality of the LNG produced can be adjusted by tuning the fraction of the de-ethaniser overhead stream sent for conversion and given segregated storage tanks, can supply different markets.