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Alkylation unit
An alkylation unit (alky) is one of the conversion processes used in petroleum refineries. It is used to convert isobutane and low-molecular-weight alkenes (primarily a mixture of propene and butene) into alkylate, a high octane gasoline component. The process occurs in the presence of an acid such as sulfuric acid (H2SO4) or hydrofluoric acid (HF) as catalyst. Depending on the acid used, the unit is called a sulfuric acid alkylation unit (SAAU) or hydrofluoric acid alkylation unit (HFAU). In short, the alky produces a high-quality gasoline blending stock by combining two shorter hydrocarbon molecules into one longer chain gasoline-range molecule by mixing isobutane with a light olefin such as propylene or butylene from the refinery's fluid catalytic cracking unit (FCCU) in the presence of an acid catalyst.
Since crude oil generally contains only 10–40% of hydrocarbon constituents in the gasoline range, refineries typically use an FCCU to convert high molecular weight hydrocarbons into smaller and more volatile compounds, which are then converted into liquid gasoline-size hydrocarbons. Byproducts of the FCC process also include other low molecular-weight alkenes and iso-paraffin molecules which are not desirable. Alkylation transforms these byproducts into larger iso-paraffins molecules with a high octane number.
The product of the unit, the alkylate, is composed of a mixture of high-octane, branched-chain paraffinic hydrocarbons (mostly isoheptane and isooctane). Alkylate is a premium gasoline blending stock because it has exceptional antiknock properties and is clean burning. The octane number of the alkylate depends mainly upon the kind of alkenes used and upon operating conditions. For example, isooctane results from combining butylene with isobutane and has an octane rating of 100 by definition. There are other products in the alkylate effluent, however, so the octane rating will vary accordingly.
The first alkylation units entered in service in 1940. In 2009 around 1,600,000 barrels per day of capacity were installed worldwide, with an equal share of 800,000 barrels per day for SAAU and HFAU technologies. On the 1st January 2016 according to the Oil & Gas Journal the worldwide installed alkylation capacity was 2,056,035 barrels per day. Since 2009 over 90% of the additional installed capacity was based on SAAU technology.
According to the Oil & Gas Journal on the 1st January 2016 there were 121 refineries operated in US with an overall capacity of 18,096,987 barrels per day. These refineries had 1,138,460 barrels per day of alkylation capacity.
Alkylate is a component of choice in gasoline, because it is free of aromatics and olefins. About 11% of the gasoline winter pool in the U.S. is made up of alkylate. In the gasoline summer pool, the content of alkylate can be as high as 15% because lower Reid vapor pressure (RVP) reduces the possibility to blend butane.
For safety reasons, SAAU is the prevalent current technology of choice. Indeed, in 1996 around 60% of the installed capacity was based on HF, but since then this ratio has been reducing because during the last decade on 10 new alkylation units commissioned, more than 8 of them were SAAU.
The two major licensors (sharing a similar share of the market) of the HFAU process were UOP and ConocoPhillips, which have been combined as UOP under the ownership of Honeywell. The main technology used for the SAAU is the STRATCO process licensed by DuPont, recently divested into privately held Elessent Clean Technologies. This is followed by the EMRE technology owned by ExxonMobil. From the mid-2000s to the mid-2010s, in excess of 85% of the SAAU capacity added worldwide has utilized Elessent's STRATCO technology.
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Alkylation unit
An alkylation unit (alky) is one of the conversion processes used in petroleum refineries. It is used to convert isobutane and low-molecular-weight alkenes (primarily a mixture of propene and butene) into alkylate, a high octane gasoline component. The process occurs in the presence of an acid such as sulfuric acid (H2SO4) or hydrofluoric acid (HF) as catalyst. Depending on the acid used, the unit is called a sulfuric acid alkylation unit (SAAU) or hydrofluoric acid alkylation unit (HFAU). In short, the alky produces a high-quality gasoline blending stock by combining two shorter hydrocarbon molecules into one longer chain gasoline-range molecule by mixing isobutane with a light olefin such as propylene or butylene from the refinery's fluid catalytic cracking unit (FCCU) in the presence of an acid catalyst.
Since crude oil generally contains only 10–40% of hydrocarbon constituents in the gasoline range, refineries typically use an FCCU to convert high molecular weight hydrocarbons into smaller and more volatile compounds, which are then converted into liquid gasoline-size hydrocarbons. Byproducts of the FCC process also include other low molecular-weight alkenes and iso-paraffin molecules which are not desirable. Alkylation transforms these byproducts into larger iso-paraffins molecules with a high octane number.
The product of the unit, the alkylate, is composed of a mixture of high-octane, branched-chain paraffinic hydrocarbons (mostly isoheptane and isooctane). Alkylate is a premium gasoline blending stock because it has exceptional antiknock properties and is clean burning. The octane number of the alkylate depends mainly upon the kind of alkenes used and upon operating conditions. For example, isooctane results from combining butylene with isobutane and has an octane rating of 100 by definition. There are other products in the alkylate effluent, however, so the octane rating will vary accordingly.
The first alkylation units entered in service in 1940. In 2009 around 1,600,000 barrels per day of capacity were installed worldwide, with an equal share of 800,000 barrels per day for SAAU and HFAU technologies. On the 1st January 2016 according to the Oil & Gas Journal the worldwide installed alkylation capacity was 2,056,035 barrels per day. Since 2009 over 90% of the additional installed capacity was based on SAAU technology.
According to the Oil & Gas Journal on the 1st January 2016 there were 121 refineries operated in US with an overall capacity of 18,096,987 barrels per day. These refineries had 1,138,460 barrels per day of alkylation capacity.
Alkylate is a component of choice in gasoline, because it is free of aromatics and olefins. About 11% of the gasoline winter pool in the U.S. is made up of alkylate. In the gasoline summer pool, the content of alkylate can be as high as 15% because lower Reid vapor pressure (RVP) reduces the possibility to blend butane.
For safety reasons, SAAU is the prevalent current technology of choice. Indeed, in 1996 around 60% of the installed capacity was based on HF, but since then this ratio has been reducing because during the last decade on 10 new alkylation units commissioned, more than 8 of them were SAAU.
The two major licensors (sharing a similar share of the market) of the HFAU process were UOP and ConocoPhillips, which have been combined as UOP under the ownership of Honeywell. The main technology used for the SAAU is the STRATCO process licensed by DuPont, recently divested into privately held Elessent Clean Technologies. This is followed by the EMRE technology owned by ExxonMobil. From the mid-2000s to the mid-2010s, in excess of 85% of the SAAU capacity added worldwide has utilized Elessent's STRATCO technology.