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Catalytic Removal of Oxygen from a Hydrocarbon Stream

IP.com Disclosure Number: IPCOM000021865D
Publication Date: 2004-Feb-13
Document File: 2 page(s) / 31K

Publishing Venue

The IP.com Prior Art Database

Related People

A. Dale Harley: INVENTOR [+3]

Abstract

Processes that react a source of oxygen with a hydrocarbon often produce a vent or recycle stream that contains oxygen, which represents a safety hazard in further utilization. This study pertains to removal of oxygen from a propylene vent stream for recovery and recycle of propylene. Removal of the oxygen via combustion over a variety of supported catalysts is reported. Preferentially, the vent stream is contacted with a catalyst comprising silver, and optionally palladium, supported on carbon, in the presence of added hydrogen for essentially complete oxygen removal.

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Catalytic Removal of Oxygen from a Hydrocarbon Stream

A. Dale Harley and Michael T. Holbrook

Dow Global Technologies Inc.

Introduction and Results

Processes that react a source of oxygen with a hydrocarbon often produce a vent or recycle stream that contains oxygen, which represents a safety hazard in further utilization. Distillation or solvent extraction both cross the flammability limit. This is especially true when working with a light olefin, such as, ethylene or propylene. One manner in which the oxygen may be removed is to catalytically combust the oxygen using a sacrificial portion of the hydrocarbon stream to produce carbon dioxide and water. Depending on the catalyst system employed, it may be advantageous to add hydrogen to react with the oxygen rather than the hydrocarbon. This study presents the removal of oxygen from a propylene vent stream for recovery and recycle.

Initial studies concentrated on the use of a catalyst comprising palladium (Pd) or platinum (Pt) supported on alumina or silica. Oxygen was present at 1 percent of the stream. It was found that propylene tended to coke on these supports at the temperatures required to combust the oxygen. Moreover, the addition of hydrogen tended to reacted preferentially with the propylene leaving the oxygen concentration unchanged. A variety of other supports were also investigated including titania, zirconia, magnesium oxide, and carbon. Graphitic carbon, preferably heat treated at a temperature from about 800 to about 1,000 degrees Centigrade, did not evidence coking.

Silver is known to be an active oxidation catalyst while possessing no hydrogenation activity. Thus, we investigated the use of a catalyst comprising silver supported on carbon for use in the removal of oxygen from a propylene vent stream. Hydrogen was added to the feed in a range from about 5 percent to about 20 percent, preferably, at about 10 mole percent. The temperature required for activity was about 300 degrees Centigrade. From previous work on another process it was known that palladium could be added to silver without extensive hydrogenation of propylene. We therefore studied mixtures of silver and palladium supported on carbon for use in removing oxygen from a propylene vent stream. Silver loading on the support typically ranged from about 1 percent to about 15 percent by weight. Palladium loading on the support typically ranged from about 0.05 to about 0.5 weight percent. An optimal ratio or loading was 5 percent by weight silver and 0.1 percent by weight palladium. The catalyst was active enough to remove 100 percent of the oxygen at 235 degrees Centigrade. From about 3 percent to about 5 percent hydrogenation of propylene was observed, presumably due to the presence of palladium. R...