The NExOCTANE™ process developed by Fortum's Neste Engineering Oy and
licensed exclusively in the Americas through Kellogg Brown & Root selectively
converts isobutylene to mainly di-isobutylene (isooctene) that is optionally
hydrogenated to paraffinic isooctane. Both di-isobutylene and isooctane are
high octane number, high quality gasoline blending stocks. The process is
especially attractive for refiners wishing to discontinue methyl tertiary
butyl ether (MTBE) production since usually the fixed bed reactors, the fractionator
and much of the MTBE unit can be utilized in the conversion into a NExOCTANE
plant.
California and some 16 other states banned or limited the use of MTBE due
to contamination of underground water by MTBE contained in gasoline leaking
from underground storage tanks. The bans in California (31.7% of U.S. MTBE
consumption), New York (7.5%) and Connecticut (3.1%) are effective by January
1, 2004. The future use in the rest of the U.S. is in doubt.
In the U.S., 29 refiners have MTBE units. Capacities range from 660 to 20,000
BPCD with the average plant producing 3,000 BPCD. Total North American production
at refineries is 114,017 BPCD. Outside North America, 58 refineries produce
95,230 BPCD of MTBE, averaging 1642 BPCD. Worldwide, 91 refiners produce 209,250
BPCD of MTBE with a portion exported to the U.S. market. Already, one Canadian
MTBE unit has been converted into a NExOCTANE unit.
Pure isooctane (2,2,4 trimethylpentane) has both a high research octane
number (RON) and a high motor octane number (MON): 100 RON and 100 MON. Isooctane's
low Reid vapor pressure of 1.8 psi is also attractive for bending into reformulated
gasoline. Of course, isooctane is sulfur and aromatic free. The octane number
is higher than alkylate or polymerate, two alternate blending stocks that
are also made from isobutylene. The low density of isooctane results in more
barrels of gasoline per pound of blendstock. In many cases when the olefins
can be accommodated in the gasoline pool, blending the di-isobutylene is an
attractive option for increasing octane number. The blending octane numbers
of isooctene at 10 vol% in CARB base gasoline (from fluid catalytic cracking)
are 124 RON and 99 MON.
We review the NExOCTANE process. We develop the economics for a generic grassroots,
1,801 BPSD (69,510 mt/yr or 286.4 m3/SD) NExOCTANE unit producing isooctane
at an on stream factor of 0.95. The economics of retrofitting a MTBE unit
depend greatly on the specificapplication. These grassroots economics may
serve as a starting point and benchmark when considering retrofitting.
By: Richard H. Nielsen
