Application: The CD-Isotame process combines skeletal isomerization and etherification steps to maximize the production of tertiary amyl methyl ether (TAME) from refinery and steam-cracker C5 streams.
Description: TAME is formed by the catalytic etherification of reactive isoamylenes with methanol. Skeletal isomerization increases TAME production from an olefinic C5 stream by converting normal amylenes to isoamylenes. The combination significantly reduces olefin content while also increasing octane.
This process provides the minimum capital cost at about 80% C5 olefin reduction. The olefinic C5 stream is fed to a selective hydrogenation step where dienes are converted to olefins. Removal of dienes reduces color and gum formation in the TAME product. In addition, unreactive 3 methyl 1-butene (3MB1) is converted to reactive isoamylene via hydroisomerization, thus increasing the TAME yield.
The primary TAME product is made in the first CDTame unit where greater than 90% conversion of isoamylene is achieved. Raffinate 1 from this unit is fed to a skeletal isomerization unit (ISOMPLUS) where n-pentenes are converted to isoamylenes at high yield and selectivity. The vapor-phase reaction takes place over a robust catalyst with long cycles between regenerations.
The isomerate is then fed to a second CDTame unit where additional TAME is produced at greater than 95% conversion of isoamylenes. Even higher conversion of normal pentenes to TAME can be achieved by an optional raffinate 2 recycle to the skeletal isomerization unit. A purge stream removes the saturated C5s from the recycle stream. A common methanol recovery unit serves both CDTame units.
Process advantages include:
• Selective hydrogenation of diolefins at minimum capital cost
• High conversion of isoamylenes (> 95%)
• High conversion of normal pentenes (> 70%)
• High selectivity of isomerization (> 90%)
• Isomerization of 3MB1 to reactive isoamylene
• Improved C5 raffinate as gasoline feedstock due to reduced, color, gum formation and olefin content
• Increased TAME production
• Increased gasoline pool octane
• Decreased gasoline pool Rvp and olefins
• Low capital and operating cost
• Superior economics and performance over C5 alkylation
• High-quality TAME product without objectionable odor or color.