Catalyst – solid sorbent – or support therefor: product or process – Regenerating or rehabilitating catalyst or sorbent – Treating with a liquid or treating in a liquid phase,...
Reexamination Certificate
1998-04-29
2001-06-12
Bell, Mark L. (Department: 1755)
Catalyst, solid sorbent, or support therefor: product or process
Regenerating or rehabilitating catalyst or sorbent
Treating with a liquid or treating in a liquid phase,...
C502S038000, C502S051000, C502S055000, C585S638000, C585S639000, C585S640000
Reexamination Certificate
active
06245703
ABSTRACT:
FIELD OF THE INVENTION
The present invention relates to a method in which water and air are used to regenerate oxygenate to olefin catalysts. The regeneration process results in hydrothermal treatment of small pore molecular sieve catalysts in situ to improve selectivity of the catalysts to desired light olefins. The method also may eliminate the need for a separate catalyst cooler.
BACKGROUND OF THE INVENTION
Light olefins, defined herein as ethylene, propylene, and butylene, serve as feeds for the production of numerous chemicals. Olefins traditionally are produced by petroleum cracking. Because of the limited supply and/or the high cost of petroleum sources, the cost of producing olefins from petroleum sources has increased steadily.
Alternative feedstocks for the production of light olefins are oxygenates, such as alcohols, particularly methanol, dimethyl ether, and ethanol. Alcohols may be produced by fermentation, or from synthesis gas derived from natural gas, petroleum liquids, carbonaceous materials, including coal, recycled plastics, municipal wastes, or any organic material. Because of the wide variety of sources, alcohol, alcohol derivatives, and other oxygenates have promise as an economical, non-petroleum source for olefin production.
The catalysts used to promote the conversion of oxygenates to olefins are molecular sieve catalysts. Because ethylene and propylene are the most sought after products of such a reaction, research has focused on what catalysts are most selective to ethylene and/or propylene, and on methods for increasing the life and selectivity of the catalysts to ethylene and/or propylene.
The conversion of oxygenates to olefins generates and deposits carbonaceous material (coke) on the molecular sieve catalysts used to catalyze the conversion process. Over accumulation of these carbonaceous deposits will interfere with the catalyst's ability to promote the reaction. In order to avoid unwanted build-up of coke on the molecular sieve catalyst, the oxygenate to olefin process incorporates a second step comprising catalyst regeneration. During regeneration, the coke is removed from the catalyst by combustion with oxygen, which restores the catalytic activity of the catalyst. The regenerated catalyst then may be reused to catalyze the conversion of oxygenates to olefins.
Typically, oxygenate to olefin conversion and regeneration are conducted in two separate vessels. The coked catalyst is continuously withdrawn from the reaction vessel used for conversion to a regeneration vessel and regenerated catalyst is continuously withdrawn from the regeneration vessel and returned to the reaction vessel for conversion. Steam has been used to absorb the exothermic heat of reaction in the regenerator; however, the steam typically must be generated using a catalyst cooler/heat exchanger. The catalyst cooler is an expensive item of equipment which is limited in size. Because of size limitations, it often is necessary to use more than one catalyst cooler to remove the amount of heat generated by a given regenerator. The use of more than one catalyst cooler is undesirable because every piece of equipment through which the catalyst must travel increases catalyst attrition and catalyst make-up cost.
More economical methods are needed to absorb the heat from the combustion of coke during the regeneration of oxygenate to olefin catalysts.
SUMMARY OF THE INVENTION
The present invention provides a method for regenerating an oxygenate to olefin catalyst comprising: contacting a feed comprising oxygenates with a total reaction volume of a molecular sieve catalyst in a reaction zone under conditions effective to produce a stream comprising C
2
-C
3
olefins and to form an initial amount of carbonaceous deposits on the catalyst; transferring a portion of the catalyst to a regeneration zone, leaving a remainder of the catalyst in the reaction zone; treating the portion of catalyst in the regeneration zone by injecting a stream comprising oxygen and a quantity of liquid water under regenerator conditions effective to regenerate the portion of catalyst, forming a regenerated portion, wherein the quantity of liquid water is sufficient to maintain a temperature effective to regenerate the catalyst without destroying structural integrity of the catalyst.
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Kuechler Keith H.
Vaughn Stephen N.
Bell Mark L.
Exxon Mobil Chemical Patents Inc.
Hailey Patricia L.
Keller Bradley
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