The MaxEne process increases the ethylene yield from naphtha crackers by raising the concentration of normal paraffins (nparaffins) in the naphtha-cracker feed. The MaxEne process is the newest application of UOP’s Sorbex technology. The process uses adsorptive separation to separate C5 – C11 naphtha into a n-paraffins rich stream and a stream depleted of n-paraffins.
The separation takes place in an adsorption chamber (2) that is divided into a number of beds. Each bed contains proprietary shape-selective adsorbent. Also, each bed in the chamber is connected to a rotary valve (1). The rotary valve is used along with the shape-selective adsorbent to simulate a counter-current moving bed adsorptive separation. Four streams are distributed by the rotary valve to and from the adsorbent chamber. The streams are as follows:
• Feed: The naphtha feed contains a mixture of hydrocarbons.
• Extract: This stream contains n-paraffin and a liquid desorbent. Naphtha, rich in n-paraffin, is recovered by fractionation (3) and is sent to the naphtha cracker.
• Raffinate: This stream contains non-normal paraffin and a liquid desorbent. Naphtha, depleted in n-paraffins, is recovered by fractionation (4) and is sent to a refinery or an aromatics complex.
• Desorbent: This stream contains a liquid desorbent that is recycled from the fractionation section to the chamber.
The rotary valve is used to periodically switch the position of the liquid feed and withdrawal points in the adsorbent chamber. The process operates in a continuous mode at low temperatures in a liquid phase. Yields: Ethylene yields from a naphtha cracker can be increased by over 30% using MaxEne extract as feedstock and the MaxEne raffinate can provide a 6% increase in octane-barrels from a refiner’s catalytic naphtha reforming unit.
Economics: Capital costs and economics depend on feed composition as well as the desired increase in ethylene and propylene production in the steam cracker.
Licensor: UOP LLC, A Honeywell Company
