2 ISOALKY ™ Technology: Next-Generation Alkylate Gasoline …
39
Refinery-standard personal protective equipment (PPE) gives adequate protection
for the operation of the ISOALKY Technology. This is a significant advantage of
the ISOALKY Technology compared with HF technology where extensive PPE is
required due to high volatility and toxicity of HF.
2.6 ISOALKY Technology Performance Advantages
The trace HCl added to the ionic liquid catalyst leads to coordination of the HCl with
[Al 2 Cl 7 ]
− anions and formation of “free” superacidic protons [8, 9] per the following
equation where B is a base or a proton acceptor, which could be an olefinic species
for our alkylation process.
HCl + B + [Al 2 Cl 7 ]
−
→ BH
+
+ 2 [AlCl 4 ]
−
To compare Brønsted acidities in non-aqueous media, Hammett and Deyrup developed the concept of Hammett acidity H o (pK BH+ at infinite dilution) where a more
negative number indicates stronger acidity using a log10 exponential scale [17].
Smith et al. [9] and Ma and Johnson [7] each measured the Hammett acidity of
the protons in ethylmethylimidazolium chloroaluminate ionic liquids with 0.55 mol
fraction of AlCl 3 (x(AlCl 3 )) in the ionic liquid. Johnson reported a H o of −14 [7],
while Smith reported −18 [9]. Concentrated sulfuric acid has a H o of −10.6 [17]
and concentrated HF a H o of −10.7 [7]. These results suggest that the acidity of HCl
dissolved in ionic liquid is at least 3 orders of magnitude greater than the acidity of
conventional alkylation catalysts.
Due to a significantly higher activity of the ISOALKY Catalyst than the conventional acid catalysts, a much smaller catalyst volume and a shorter residence time
are used in the ISOALKY Alkylation sub-process. Our alkylation reactor runs with
droplets of the ionic liquid catalyst (3–6 vol%) dispersed in a continuous phase of
hydrocarbon. This contrasts with the conventional mineral acid-based alkylation process where the continuous phase is the acid. The acid occupies over 50 vol% in the
sulfuric acid alkylation reactor and 60–75 vol% in the HF acid alkylation reactor.
Based on the catalyst volume and residence time, the ionic liquid catalyst is about
60 times more active than the H 2 SO 4 catalyst.
In addition to the higher activity, the ISOALKY Ionic Liquid Catalyst has several
other performance advantages.
The ionic liquid catalyst has a very wide operational temperature window of
30–120 °F, unlike the other conventional alkylation processes.
The ISOALKY Technology shows about a two (2) research octane number (RON)
advantage in alkylate gasoline product over the H 2 SO 4 processes [18] at comparable
reactor temperature with a mixed C 4 olefin feed as shown in Fig. 2.4. A higher
RON of 98 can be achieved with the ISOALKY Technology at 40 °F alkylation
reactor temperature with a typical mixed C 4 olefin feed from a refinery fluid catalytic
cracking (FCC) unit. For the ISOALKY Technology, a selective hydroisomerization
39
Refinery-standard personal protective equipment (PPE) gives adequate protection
for the operation of the ISOALKY Technology. This is a significant advantage of
the ISOALKY Technology compared with HF technology where extensive PPE is
required due to high volatility and toxicity of HF.
2.6 ISOALKY Technology Performance Advantages
The trace HCl added to the ionic liquid catalyst leads to coordination of the HCl with
[Al 2 Cl 7 ]
− anions and formation of “free” superacidic protons [8, 9] per the following
equation where B is a base or a proton acceptor, which could be an olefinic species
for our alkylation process.
HCl + B + [Al 2 Cl 7 ]
−
→ BH
+
+ 2 [AlCl 4 ]
−
To compare Brønsted acidities in non-aqueous media, Hammett and Deyrup developed the concept of Hammett acidity H o (pK BH+ at infinite dilution) where a more
negative number indicates stronger acidity using a log10 exponential scale [17].
Smith et al. [9] and Ma and Johnson [7] each measured the Hammett acidity of
the protons in ethylmethylimidazolium chloroaluminate ionic liquids with 0.55 mol
fraction of AlCl 3 (x(AlCl 3 )) in the ionic liquid. Johnson reported a H o of −14 [7],
while Smith reported −18 [9]. Concentrated sulfuric acid has a H o of −10.6 [17]
and concentrated HF a H o of −10.7 [7]. These results suggest that the acidity of HCl
dissolved in ionic liquid is at least 3 orders of magnitude greater than the acidity of
conventional alkylation catalysts.
Due to a significantly higher activity of the ISOALKY Catalyst than the conventional acid catalysts, a much smaller catalyst volume and a shorter residence time
are used in the ISOALKY Alkylation sub-process. Our alkylation reactor runs with
droplets of the ionic liquid catalyst (3–6 vol%) dispersed in a continuous phase of
hydrocarbon. This contrasts with the conventional mineral acid-based alkylation process where the continuous phase is the acid. The acid occupies over 50 vol% in the
sulfuric acid alkylation reactor and 60–75 vol% in the HF acid alkylation reactor.
Based on the catalyst volume and residence time, the ionic liquid catalyst is about
60 times more active than the H 2 SO 4 catalyst.
In addition to the higher activity, the ISOALKY Ionic Liquid Catalyst has several
other performance advantages.
The ionic liquid catalyst has a very wide operational temperature window of
30–120 °F, unlike the other conventional alkylation processes.
The ISOALKY Technology shows about a two (2) research octane number (RON)
advantage in alkylate gasoline product over the H 2 SO 4 processes [18] at comparable
reactor temperature with a mixed C 4 olefin feed as shown in Fig. 2.4. A higher
RON of 98 can be achieved with the ISOALKY Technology at 40 °F alkylation
reactor temperature with a typical mixed C 4 olefin feed from a refinery fluid catalytic
cracking (FCC) unit. For the ISOALKY Technology, a selective hydroisomerization