US 6,080,226 AGranted

Nitrous oxide purification by pressure swing adsorption

AssigneeUop LLC

InventorsWilliam B. Dolan, Andrew S. Zarchy, Kirit M. Patel, Timothy M. Cowan, Mark M. Davis

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Abstract

A feedstream comprising nitrous oxide is purified by a pressure swing adsorption process employing a copurge with an oxygen-lean stream to produce a high purity nitrous oxide stream. The high purity nitrous oxide stream can be incorporated in a complex for the production of adipic acid to recover nitrous oxide from a dilute waste stream and pass the recovered nitrous oxide to a process for the production of phenol from an aromatic hydrocarbon. Unreacted nitrous oxide from the phenol production step acid can be recovered in a second, or vent PSA step, and combined with the recovery of byproduct nitrous oxide waste streams from the production of adipic for the overall recovery of nitrous oxide, thereby significantly reducing nitrous oxide emissions from the production of adipic acid.

Claims30

Dependent claims

A pressure swing adsorption process for the separation of nitrous oxide from a waste stream comprising nitrous oxide, nitrogen, and oxygen, said process comprising the following steps:

a) passing the waste stream at effective conditions including an adsorption pressure and an adsorption temperature to a first adsorbent bed of at least two adsorbent beds in a pressure swing adsorption zone, each of said adsorbent beds containing an adsorbent selective for the adsorption of nitrous oxide relative to nitrogen and oxygen to provide a first adsorption effluent stream comprising oxygen and nitrogen;
b) terminating the passing of said waste stream to the first adsorbent bed prior to the breakthrough of nitrous oxide from said first adsorbent bed;
c) cocurrently depressurizing the first adsorbent bed to a first reduced pressure that is lower than the adsorption pressure and to provide a first vent stream comprising oxygen and nitrogen;
d) further cocurrently depressurizing said first adsorbent bed to an equalization pressure that is lower than the first reduced pressure and passing an equalization effluent to a second adsorbent bed being repressurized;
e) countercurrently depressurizing the first adsorbent bed to a desorption pressure that is lower than the equalization pressure and effective to desorb nitrous oxide and withdrawing a first desorption effluent stream comprising nitrous oxide;
f) countercurrently purging the first adsorbent bed with an oxygen-lean stream to provide a second desorption effluent stream comprising nitrous oxide;
g) combining the first desorption effluent stream and the second desorption effluent stream to provide a nitrous oxide stream and repressurizing the first adsorbent bed to the adsorption pressure and,
h) repeating steps (a)-(g) to provide a continuous process.

5 more elements

A pressure swing adsorption process for the separation of nitrous oxide from a waste stream comprising nitrous oxide, nitrogen, and oxygen, said process comprising the following steps:

a) passing the waste stream at an adsorption pressure to a first adsorbent bed of a first pressure swing adsorption zone comprising a plurality of adsorbent beds, each adsorbent bed containing a nitrous oxide selective adsorbent selected from the group consisting of silica gel, calcium Y zeolite, zinc X zeolite, and mixtures thereof to provide an adsorption effluent comprising oxygen and nitrogen;
b) cocurrently purging the first adsorbent bed at a purge pressure equal to or lower than the adsorption pressure with an oxygen-lean stream to provide an additional adsorption effluent stream;
c) cocurrently depressurizing the first adsorbent bed to a first reduced pressure that is lower than the adsorption pressure and to provide a provide purge stream comprising oxygen and nitrogen;
d) further cocurrently depressurizing said first adsorbent bed to an equalization pressure that is lower than the first reduced pressure and passing an equalization effluent to a second adsorbent bed being repressurized;
e) countercurrently depressurizing the first adsorbent bed to provide a desorption effluent stream comprising high purity nitrous oxide comprising less than about 2 mol-% oxygen;
f) countercurrently purging the first adsorbent bed with an oxygen lean stream to provide an additional high purity nitrous oxide stream;
g) repressurizing the first adsorbent bed with a portion of the adsorption effluent;
and
h) repeating steps (a)-(g) to provide a continuous process.

6 more elements

Dependencies are inferred from the claim text.