UOP OFFERS C5 OLEFIN ISOMERIZATION PROCESS

Refiners now have access to olefin isomerization technology that will help them meet U.S. reformulated gasoline requirements.

UOP, Des Plaines, Ill., offered for license a new C5 olefin isomerization process at its petrochemical technology conference in Houston.

Robert Denny, UOP director of marketing services, said the company is prepared to design and guarantee the process, called Pentesom.

UOP plans to offer a similar C4 olefin isomerization process, Butesom, in 1993.

MTBE, TAME

U.S. refiners will soon blend ethers into gasoline to meet the minimum oxygen requirements of the 1990 Clean Air Act amendments.

Main suppliers of this oxygen will be ethers--mainly methyl tertiary butyl ether (MTBE), produced by reacting isobutylene with methanol, but also tertiary amyl methyl ether (TAME), the product of a similar isoamylene/methanol reaction.

Reactive iso-olefins are present in fluid catalytic cracking (FCC) and steam cracker C4-C5 streams. These streams also contain large concentrations of nonreactive normal olefins that can be isomerized to reactive iso-olefins to increase ether production.

David Martindale, business manager of light ends technology for UOP, said a typical refinery with an FCC unit can produce gasoline with an oxygen concentration of about 0.3 wt % by converting all available isobutylene to MTBE. Producing TAME in addition to MTBE can increase the total oxygen content of the gasoline pool to about 0.6 wt %, depending on FCC operating conditions.

This is clearly a significant shortfall when compared with the 2 wt % oxygen specification for U.S. reformulated gasoline.

Martindale said Pentesom can help meet this shortfall by increasing TAME production.

Alternatively, steam cracker C5s can be upgraded after either isoprene extraction or selective hydrogenation. If C5 raffinate-1 is processed after isoprene extraction, followed by selective hydrogenation of the remaining diolefins, the integration of normal pentene skeletal isomerization can theoretically double TAME yields, Martindale said.

And if all the C4-C5 diolefins and normal olefins are upgraded by selective hydrogenation and skeletal isomerization, a steam cracker complex producing 400,000 metric tons/year of ethylene theoretically could produce 280,000 metric tons/year (7,250 b/d) of ethers.

Calculated variable costs of TAME production are 690/gal without Pentesom and 660/gal with the process.

NEW CATALYST

Also at the conference, UOP introduced a new catalyst, R-132, for use in existing and new CCR Platforming units. Robert Rachford, marketing engineer for Platforming process technology, said R-132 represents a significant improvement in CCR Platforming catalysts.

The new catalyst provides aromatics producers with existing Platformers increased flexibility to operate at higher severities or lower pressure. The catalyst also enhances the profitability of new installations, Rachford said.

Pilot plant tests and commercial demonstrations show that the new catalyst is at least 5 C. higher in activity than the R-32 and R-34 catalysts it replaces. The new catalyst also retains the selectivity of those catalysts over the entire catalyst life.

The activity advantage can be used to increase either capacity--by at least 20%--or conversion, by at least 1.2 wt % aromatics.

R-132 is characterized by a significant improvement in surface area stability relative to R-32 and R-34. The catalyst also has greatly improved chloride retention characteristics, reducing the required chloride injection rate during its life.

This reduces vent gas scrubber requirements and improves the life of the net hydrogen and LPG treaters. UOP estimates chloride use to be less than 50% that of R-32 and R-34, saving an average $101,000/year for a typical 840,000 metric ton/year ultralow pressure Platformer.