History
From 1932 to 1936, alkylation was independently discovered by Universal Oil
Products (Ipatieff and Grosse 1935) (now UOP a Honeywell Company), Shell, the
Anglo-Iranian Oil Company (now BP), and Texaco whose first publications issue in
that order.
Herman Pines told the story of UOP’s discovery of the alkylation of ethylene
by pentanes in 1932 (Pines 1982). At that time, leading universities taught that
isoparaffins were inert except at high temperatures and pressures. After finding
anomalies in an olefin assay based upon H 2 SO 4 extraction, Pines and his mentor
Vladimir Ipatieff hypothesized that paraffins may not be inert to acids. Despite
the ridicule, they tested that hypothesis by bubbling ethylene into chilled pentanes
over AlCl 3 and found that all the ethylene was converted into saturated hydrocarbons.
Over the next few years, they tested AlCl 3 -HCl, H 2 SO 4 , HF, and HF-BF 3 as alkylation
catalysts.
Alkylate derived from butenes and isobutane was found to have excellent
aviation gasoline properties. It was the highest octane fuel component then
known, with high motor octane and excellent lead response. All of these properties
are derived from the highly branched paraffins that form its composition.
Humble Oil (now ExxonMobil) built the first commercial H 2 SO 4 alkylation
unit in 1938 at Baytown, Texas (Hooper 1986). Alkylation for aviation gasoline
grew rapidly with the Allies’ war effort. In 1939, six petroleum companies
formed a consortium to pool their alkylation technology and develop both
sulfuric acid and HF acid processes for 100 octane aviation fuel. As a result
of this effort, the first commercial HF alkylation unit started up in 1942 at
Phillips Petroleum’s Borger, Texas refinery, broadening the feedstock to include
propylene and pentene along with butenes (Phillips 1946). During the war, a total
of 60 alkylation units were built for the Allies’ war effort. Half were built
with sulfuric acid as the catalyst and half with hydrofluoric acid. Following
World War II, most alkylation operations were discontinued although a few
refiners continued to use the process for the production of aviation and premium
automobile gasolines.
In the mid-1950s, the use of higher-performance automotive engines required
the refining industry to increase both gasoline production and quality. The development of catalytic reforming, such as the UOP Platforming™ process, provided
refiners with an important refining tool for the production of high-octane gasolines.
However, the motor fuel produced in such operations, called reformate, is highly
aromatic with a higher sensitivity (the spread between research and motor octane)
and a lower lead response than alkylate. Many refiners expanded their alkylation
operations and use of propylene, and even some pentenes in the alky unit feed in
addition to butenes became more widespread.
With the phaseout of leaded gasoline and the advent of environmental gasolines,
the lead response of alkylate is no longer valued, but the importance of alkylate and
its production have both grown because of its other properties. Its high unleaded
motor octane, low volatility, low sulfur, and nearly zero olefins and aromatics make
Alkylation in Petroleum Processing
437
From 1932 to 1936, alkylation was independently discovered by Universal Oil
Products (Ipatieff and Grosse 1935) (now UOP a Honeywell Company), Shell, the
Anglo-Iranian Oil Company (now BP), and Texaco whose first publications issue in
that order.
Herman Pines told the story of UOP’s discovery of the alkylation of ethylene
by pentanes in 1932 (Pines 1982). At that time, leading universities taught that
isoparaffins were inert except at high temperatures and pressures. After finding
anomalies in an olefin assay based upon H 2 SO 4 extraction, Pines and his mentor
Vladimir Ipatieff hypothesized that paraffins may not be inert to acids. Despite
the ridicule, they tested that hypothesis by bubbling ethylene into chilled pentanes
over AlCl 3 and found that all the ethylene was converted into saturated hydrocarbons.
Over the next few years, they tested AlCl 3 -HCl, H 2 SO 4 , HF, and HF-BF 3 as alkylation
catalysts.
Alkylate derived from butenes and isobutane was found to have excellent
aviation gasoline properties. It was the highest octane fuel component then
known, with high motor octane and excellent lead response. All of these properties
are derived from the highly branched paraffins that form its composition.
Humble Oil (now ExxonMobil) built the first commercial H 2 SO 4 alkylation
unit in 1938 at Baytown, Texas (Hooper 1986). Alkylation for aviation gasoline
grew rapidly with the Allies’ war effort. In 1939, six petroleum companies
formed a consortium to pool their alkylation technology and develop both
sulfuric acid and HF acid processes for 100 octane aviation fuel. As a result
of this effort, the first commercial HF alkylation unit started up in 1942 at
Phillips Petroleum’s Borger, Texas refinery, broadening the feedstock to include
propylene and pentene along with butenes (Phillips 1946). During the war, a total
of 60 alkylation units were built for the Allies’ war effort. Half were built
with sulfuric acid as the catalyst and half with hydrofluoric acid. Following
World War II, most alkylation operations were discontinued although a few
refiners continued to use the process for the production of aviation and premium
automobile gasolines.
In the mid-1950s, the use of higher-performance automotive engines required
the refining industry to increase both gasoline production and quality. The development of catalytic reforming, such as the UOP Platforming™ process, provided
refiners with an important refining tool for the production of high-octane gasolines.
However, the motor fuel produced in such operations, called reformate, is highly
aromatic with a higher sensitivity (the spread between research and motor octane)
and a lower lead response than alkylate. Many refiners expanded their alkylation
operations and use of propylene, and even some pentenes in the alky unit feed in
addition to butenes became more widespread.
With the phaseout of leaded gasoline and the advent of environmental gasolines,
the lead response of alkylate is no longer valued, but the importance of alkylate and
its production have both grown because of its other properties. Its high unleaded
motor octane, low volatility, low sulfur, and nearly zero olefins and aromatics make
Alkylation in Petroleum Processing
437