Sulfuric Acid Alkylation Process by ExxonMobil Research & Engineering Co

ExxonMobil’s Research & Engineering (EMRE’s) autorefrigerated sulfuric-acid catalyzed process that combines butylene (and propylene or pentylene if desired) with isobutane to produce high-octane gasoline components that are particularly attractive in locations that are MON limited. Technology can be installed rassroots or retrofit into existing alkylation facilities.

Olefin feed and recycled isobutane are introduced into the stirred, autorefrigerated reactor (1). Mixers provide intimate contact between the reactants and acid catalyst. Highly efficient autorefrigeration removes heat of reaction heat from the reactor. Hydrocarbons, vaporized from the reactor to provide cooling, are compressed (2) and returned to the reactor. A depropanizer (3), which is fed by a slipstream from the refrigeration section, is designed to remove any propane introduced to the plant with the feeds.

Hydrocarbon products are separated from the acid in the settler containing proprietary internals (4). In the deisobutanizer (5), isobutane is recovered and recycled along with makeup isobutane to the reactor.

Butane is removed from alkylate in the debutanizer (6) to produce a low-Rvp, high-octane alkylate product. A small acid stream containing acid soluble oil byproducts is removed from the unit and is either regenerated on site or sent to an off-site sulfuric acid regeneration facility to recover acid strength.

Products: A low-sulfur, low-Rvp, highly isoparaffinic, high-octane (especially MON) gasoline blendstock is produced from this alkylation process.

Yields:
Alkylate yield 1.8 bbl C5+ / bbl butylene feed
Isobutane required 1.2 bbl / bbl butylene feed
Alkylate quality 97 RON / 94 MON
Rvp, psi 3

Utilities: typical per barrel of alkylate produced:
Water, cooling, M gal 2
Power, kWH 9
Steam, lb 200
H2SO4, lb 19
NaOH, 100%, lb 0.1

Operating experience: Extensive commercial experience in both ExxonMobil and licensee refineries, with a total operating capacity of 137 bpsd at 13 locations worldwide. Unit capacities currently range from 2,000 bpsd to 30,000 bpsd. In addition, the world’s largest alkylation unit, with a capacity of 83,000 bpsd will be starting up in 2008 at Reliance ’Petroleum Limited’s Export Refinery in Jamnagar, India. Another licensed unit is in the design phase with a capacity of 16,000 bpsd. The larger units take advantage of the single reactor/settler trains with capacities up to 10,000 bpsd.

Technical advantages:
• Autorefridgeration is thermodynamically more efficient, allows lower reactor temperatures, which favor better product quality, and lowers energy usage.
• Staged reactor results in a high average isobutane concentration, which favors high product quality.
• Low space velocity results in high product quality and reduced ester formation eliminating corrosion problems in fractionation equipment.
• Low reactor operating pressure translates into high reliability for the mechanical seals for the mixers, which operate in the vapor phase.

fig 1 7 - Sulfuric Acid Alkylation Process by ExxonMobil Research & Engineering Co


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