Combination alkylation-reforming process

High octane number motor fuel is produced by a combination process comprising alkylating isobutane with an olefin to produce an alkylate, fractionating the alkylate to remove isobutane, C.sub.3 hydrocarbons and lighter, and subjecting the total alkylate to reforming to increase aromatic content thereof and yield a reformed alkylate product of improved gasoline characteristics.

This invention relates to the production of high octane gasoline. In 
accordance with one aspect, this invention relates to a combination 
process involving alkylation and reforming wherein the total alkylate 
product obtained from alkylation is reformed to increase the aromatic 
content. In accordance with another aspect, this invention relates to a 
combination process comprising alkylating isobutane with an olefin, 
fractionating the alkylate product to remove materials having lower 
boiling points than normal butane, and subjecting the total alkylate, 
including at least a portion of the normal butane, to reforming to 
increase the aromatic content of the alkylate, as well as isomerize the 
normal butane to isobutane which can be recycled to alkylation. In 
accordance with a further aspect, this invention relates to a process of 
upgrading alkylate gasoline having a (TEL) tetraethyl lead-free Research 
Octane Number (RON) of about 92-94 to a highly aromatic gasoline having a 
TEL-free RON of at least about 100 by reforming the total produced 
alkylate which alkylate includes at least a portion of normal butane and 
includes higher boiling materials and recovering a reformed alkylate 
product of improved gasoline characteristics having an increased aromatic 
content and octane number. 
The production of motor fuels having high octane numbers and antiknock 
properties suitable for use in automotive and aviation fuels is of 
considerable importance to the refinery industry. In addition, there is an 
everincreasing need of TEL-free high octane number motor fuel. A common 
source of high octane number motor fuels is the catalytic alkylation of 
isoparaffin with olefin. These processes typically produce a motor fuel 
alkylate having a research clear octane rating of 92-94. It is also known 
that various refinery streams can be subjected to reforming in order to 
increase the aromatic content of the treated stream. We have now conceived 
that by combining alkylation and reforming, as is done herein, it is 
possible to upgrade alkylate gasoline to at least about 100 RON TEL-free 
by subjecting the total alkylate to reforming. 
Accordingly, an object of this invention is to provide an improved 
alkylation operation. 
It is a further object of this invention to provide an improved reforming 
operation. 
It is a further object of this invention to provide a combination 
alkylation-reforming process. 
A further object of this invention is to provide an improved process 
whereby high octane TEL-free gasoline is produced. 
Other objects, aspects, and the several advantages of the invention will 
become apparent to those skilled in the art upon a study of the 
disclosure, the drawing, and the appended claims. 
In accordance with the invention, the hydrocarbon effluent phase removed 
from an alkylation is fractionated at to remove isobutane and lower 
boiling materials, and the total alkylate obtained from the effluent is 
subjected to reforming to increase the aromatic content thereof, and 
thereby yield a product of improved gasoline characteristics. 
In accordance with one embodiment, high octane motor fuel is produced by 
alkylating isobutane with an olefin to produce an alkylate, fractionating 
the alkylate to remove isobutane and lower boiling materials, and 
subjecting the remainder or total alkylate to reforming to increase 
aromatic content and increase the TEL-free Research Octane Number of the 
produced alkylate to at least about 100. 
In accordance with one specific embodiment of the invention, isobutane is 
alkylated with a C.sub.3 -C.sub.4 mixture of olefins to produce an 
alkylate product followed by fractionation of the alkylate product to 
remove isobutane and lower boiling material and then subjecting the 
remainder of the produced alkylate, including normal butane, to reforming 
under conditions of dehydrocyclization and isomerization to increase the 
aromatic content of the produced alkylate and isomerize normal butane to 
isobutane, and recovering a reformed alkylate product of improved gasoline 
characteristics. 
In further embodiments, isobutane separated from the alkylation zone 
effluent and isobutane produced during reforming can be recycled to the 
alkylation as at least part of the feed therefor. 
In a further embodiment, the reforming zone effluent is subjected to 
fractionation and solvent extraction to produce a superaromatic high 
octane gasoline which can have a TEL-free Research Octane Number of about 
110. 
The alkylation step of the present invention can be any one of a number of 
alkylation processes well known in the art. The alkylation can be carried 
out at a temperature in the range of about 0.degree. F to about 
200.degree. F, a pressure ranging from atmospheric to about 50 
atmospheres, a catalyst to hydrocarbon volume ratio of 0.5:1 to 10:1, an 
isobutane to olefin mole ratio of 2:1 to 20:1, and an acid-type alkylation 
catalyst such as sulfuric acid or hydrofluoric acid. Hydrogen fluoride is 
generally preferred as the catalyst. 
The preferred hydrocarbon feed charged to alkylation is an 
olefinisoparaffin (e.g., isobutane and/or isopentane) hydrocarbon stream, 
preferably butylenes-isobutane. However, other olefins including mixtures 
of olefins can be used, such as C.sub.3 -C.sub.4 olefin mixtures. The 
alkylation step of the process of this invention comprises contacting a 
hydrocarbon feedstock containing isobutane and olefin, preferably with an 
acid-acting alkylation catalyst in an alkylation zone. The isobutane and 
olefin(s) can be introduced as separate feedstreams or in admixture with 
one another. The contacting is preferably effected by intimately mixing 
the hydrocarbons with a catalyst, preferably a strong acid catalyst, and 
then passing the alkylation effluent to a phase separation zone to 
separate an acid phase and a hydrocarbon phase. A typical HF alkylation is 
disclosed in U.S. Pat. No. 3,213,157. 
The reforming step of the present invention can be any one of a number of 
reforming processes well known in the art. Reforming can be effected at 
temperatures in the range of 700.degree. F to 1100.degree. F, a pressure 
of atmospheric to 1,000 psig, a liquid hourly space velocity, LHSV 
(volumes/volume catalyst/hr.), of 0.1 to 10, a hydrogen to hydrocarbon 
mole ratio of 1:1 to 20:1, in the presence of a noble metal catalyst. In 
actual operation, the produced alkylate preferably including normal butane 
obtained from the effluent of the alkylation zone is passed through a 
reforming zone wherein the lower octane constituents in the alkylate are 
converted to higher octane components by dehydrocyclization, 
isomerization, and the like, and other various reactions which occur in a 
reforming zone. 
Suitable reforming catalysts can include noble metal catalysts, 
particularly platinum-containing catalysts, as is well known in the art. 
Other catalysts that can be employed include (such as those disclosed in 
U.S. Pat. No. 3,957,688; U.S. Pat. No. 3,894,110; U.S. Pat. No. 3,844,935; 
U.S. Pat. No. 3,434,960; U.S. Pat. No. 3,415,737; U.S. Pat. No. 3,558,477; 
U.S. Pat. No. 3,578,582; U.S. Pat. No. 3,679,578): platinum-rhenium on 
alumina; platinum-iridium-gold on alumina; platinum-tin on zinc aluminate; 
and the like. 
The drawing illustrates one embodiment of the present invention. In the 
drawing, fresh isobutane in line 12 and a mixture of C.sub.3 and C.sub.4 
olefins in line 11 are passed as feed to alkylation zone 10 which contains 
HF acid as catalyst. In zone 10, feed isobutane and olefins are intimately 
contacted with HF to produce an alkylate product, and the total reaction 
mixture including catalyst is ordinarily passed to a phase separation zone 
(not shown) wherein an acid phase is separated from a hydrocarbon phase by 
gravity. The acid phase can be returned to the alkylation zone or passed 
to a return unit and then returned to the alkylation zone. 
The hydrocarbon phase separated from the alkylation effluent in line 16 is 
passed to fractionation zone 20 wherein the hydrocarbon phase is subjected 
to fractionation conditions such that isobutane, propane, and lighter 
materials are removed from an upper portion of the fractionation zone, the 
remainder of the hydrocarbon phase being removed as bottoms. Isobutane is 
removed from an upper portion of zone 20 by line 14 and recycled via line 
13 and 12 for introduction into alkylation zone 10 as at least a portion 
of the feed. Propane and lighter materials are removed overhead by line 17 
and passed to further processing as desired. 
Fractionation zone 20 is operated under conditions including an upper 
temperature of about 113.degree. F and a bottoms temperature of about 
402.degree. F under suitable conditions of pressure, e.g., 250 psia. It is 
to be understood that zone 20 can be one or more fractionation columns, as 
is known in the art. 
The produced or total alkylate including normal butane is removed as 
bottoms from fractionation zone 20 by line 18 and passed directly via line 
19 to reforming zone 30 wherein the total alkylate is subjected to 
reforming conditions in the presence of a suitable catalyst to increase 
the aromatic content of the total alkylate, as well as convert the normal 
butane to isobutane. Hydrogen (recycle) is also introduced into reforming 
zone 30 along with hydrocarbon feed introduced by line 21. Normal butane 
(vapor) can be withdrawn from zone 20 via line 20'; however, it is 
presently preferred that at least a portion of the normal butane in the 
alkylation effluent 16, which is charged to zone 20, be removed along with 
the total alkylate in line 18, and charged to zone 30 in order to produce 
isobutane therefrom in zone 30, and to charge this isobutane to alkylation 
10. 
The reformed alkylate product is removed from reforming zone 30 by way of 
line 22 and passed to the fractionation zone 40. At least a portion of the 
reforming zone effluent can be passed by way of line 31 as an indirect 
source of reboiler heat to fractionation zone 20 and then returned by line 
32 for passage on to fractionation zone 40. 
The reformed product introduced into fractionation zone 40 is subjected to 
fractionation conditions such that isobutane is removed from an upper 
portion of zone 40 by way of line 15 and recycled to alkylation zone 10 by 
way of lines 12 and 13. Light hydrocarbons lower boiling than isobutane 
are also removed from an upper portion of fractionation zone 40 by way of 
line 23 and passed to further processing as desired. Hydrogen and other 
light components are removed overhead from zone 40 by way of line 42 and a 
portion is recycled by way of line 21 to reforming zone 30. Net hydrogen 
produced can be removed by way of line 43 and passed to further use as 
desired. 
The upgraded alkylate that has been subjected to reforming, freed of 
isobutane and lighter materials, is removed from a lower portion of zone 
40 by line 41. If desired, the total aromatic gasoline removed from a 
lower portion of zone 40 can be removed by line 44 for final usage. 
Fractionation zone 40 is operated at conditions of temperature and pressure 
such that isobutane is taken from an upper portion of the zone and higher 
boiling materials as bottoms. The temperature in the upper portion of the 
column will ordinarily be about 150.degree. F and at the bottom of the 
column will be about 500.degree. F. Suitable pressures include 100 to 200 
psig. It is to be understood that zone 40 can be one or more separation 
vessels and fractionation columns, as is known in the art. 
In a further embodiment of the invention, the aromatic gasoline removed 
from the bottom of fractionation zone 40 can be passed via line 45 to 
solvent extraction zone 50 wherein the aromatic gasoline is contacted with 
a suitable solvent, e.g., sulfolane, tetraethylene glycol, triethylene 
glycol, phenol, etc., to remove paraffinic materials therefrom. The 
paraffinic materials after being freed from solvent can be passed by way 
of line 46 and combined with the total alkylate and passed to reforming 
zone 30 by way of line 19. The superaromatic gasoline is removed by line 
47. This gasoline can have an octane number of 110 RON clear.

The following example illustrates the invention. 
EXAMPLE 
An olefin mixture containing propylene and butylenes, the majority of which 
are butylenes, alkylates isobutane in a conventional commercial alkylation 
system 10, utilizing hydrogen fluoride as a catalyst. The system is 
maintained at alkylation conditions as follows: 
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Temperature 100.degree. F 
Pressure, psia 150 (for liquid phase operation) 
iC.sub.4 /olefin vol. ratio 
11.2/1 
HF/hydrocarbon volume 
ratio 4/1 
Residence time, sec. 
30 
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The hydrocarbon phase 16 separated from the alkylation effluent is 
fractionated in 20 as described in connection with the drawing so as to 
remove propane and lighter 17 as overhead and an upper sidestream 14 of 
isobutane. The total alkylate, including normal butane removed as bottoms 
from the fractionation, is passed via 18 to a reforming zone 30. 
The reforming zone is operated as set forth below: 
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Temperature 970.degree. F 
Pressure, psia 150 
H.sub.2 /hydrocarbon mole ratio 
5 
V/V/Hr. (Hydrocarbon/catalyst) 
1 
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The catalyst is fixed bed platinum-rhenium on alumina (0.35 weight percen 
of each catalyst component). 
The total alkylate 18 (after denormal butanization) removed as bottoms from 
fractionation zone 20 has a TEL-free Research Octane Number of 94 (RON 
clear). The aromatic gasoline 41 separated from the reforming zone 
effluent has a TEL-free Research Octane Number of 100 (RON clear). 
The compositions of the various streams are given in Table I wherein the 
stream numbers correspond to the conduit numbers in the drawing described 
hereinbefore. 
TABLE I 
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Volume, Gal./Hr. 
Stream: 11 12 13 14 15 18 41 
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Propane -- 50 200 200 -- -- -- 
Normal Butane 
-- 50 100 100 -- 50 -- 
Isobutane -- 810 10090 10000 90 -- -- 
Propylene 400 -- -- -- -- -- -- 
Butylenes 500 -- -- -- -- -- -- 
Alkylate -- -- -- -- -- 1500 -- 
Reformate -- -- -- -- -- -- 1200 
Total 900 910 10390 10300 90 1550 1200 
RON Clear -- -- -- -- -- 94 100 
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