An improved continuous process for alkylation of isoparaffins with olefins to yield a product which includes a large proportion of highly branced paraffins for making gasoline having improved octane is taught. The improved process comprises contacting isoparaffins and olefins with a composite catalyst comprising a Lewis acid and a non-zeolitic inorganic oxide in the presence of a controlled amount of water. The process results in reduced catalyst aging and obviates environmental problems associated with prior art processes.

DESCRIPTION OF THE INVENTION 
The alkylation of isobutane with light olefins plays an important role in 
the manufacture of high octane gasoline blending stocks with alkylate 
typically comprising 10 to 15% of the gasoline pool. Alkylate is a 
particularly valuable portion of the gasoline pool as it has both high 
research and motor octane, contains no olefins or aromatics and little or 
no sulfur, demonstrates excellent stability and is clean burning. 
Applicants have developed a process for producing high octane gasoline. It 
includes a novel isoparaffin/olefin alkylation catalyst. The catalyst 
system includes a Lewis acid, such as BF.sub.3, in combination with a 
non-zeolitic solid inorganic oxide, such as SiO.sub.2, to promote 
paraffin/olefin alkylation, all in the presence of a controlled amount of 
water. The Lewis acid is to be maintained at a level in excess of that 
required to saturate the non-zeolitic solid inorganic oxide. The resulting 
alkylate is of a high quality based on both research and motor octane and 
is particularly suited for blending into a gasoline pool. 
Consider the catalyst comprising the Lewis acid and inorganic oxide. A 
Lewis acid is generally considered to be a molecule which is capable of 
combining with another molecule or ion by forming a covalent chemical bond 
with two electrons from the second molecule or ion, that is to say, the 
Lewis acid is an electron acceptor. Examples of Lewis acids include boron 
trifluoride (BF.sub.3), boron trichloride (BCl.sub.3), antimony 
pentafluoride (SbF.sub.5), and aluminum choloride (AlCl.sub.3). The 
present invention contemplates the use of all Lewis acids, such as those 
set forth in Friedel-Crafts and Related Reactions, Interscience 
Publishers, chapters III and IV (1953), which is incorporated by 
reference. 
The inorganic oxide of this catalyst may be selected from among the diverse 
inorganic oxides including alumina, silica, boria, oxides of phosphorus, 
titanium dioxide, zirconium dioxide, chromia, zinc oxide, magnesia, 
calcium oxide, silica-alumina, silica-magnesia, silica-alumina-magnesia, 
silica-alumina-zirconia, chromia-alumina, alumina-boria, silica-zirconia, 
etc. and the various naturally occuring inorganic oxides of various states 
of purity such as bauxite, clay, diatomaeous earth, etc. The preferred 
inorganic oxides are amorphous silicon dioxide and aluminum oxide. 
The operating temperature of the alkylation process can extend over a 
fairly broad range, for example, from about -40.degree. C. to about 
500.degree. C. and is preferably with the range of from about -40.degree. 
C. to about 250.degree. C. The practical upper operating temperature will 
often be dictated by the need to avoid an undue occurrence of undesirable 
side reactions. 
The pressures used in the present process can extend over a considerably 
wide range, for example, from subatmospheric to about 5000 psig, 
preferably to about 500 psig. 
The amount of catalyst used in the present process can be varied over 
relatively wide limits. In general, the amount of catalyst, as measured by 
the weight hourly space velocity of the olefin, can range from about 0.01 
to about 100. It will be realized by those skilled in the art that the 
amount of catalyst selected for a particular reaction will be determined 
by several variables including the reactants involved as well as the 
nature of the catalyst and the operating conditions used. 
The particular operating conditions used in the present process will depend 
on the specific alkylation reaction being effected. Such conditions as 
temperature, pressure, space velocity and molar ratio of the reactants 
will have important effects on the overall process. Also, the operating 
conditions for the alkylation reaction according to this process may be 
varied so that the same may be conducted in gaseous phase, liquid phase or 
mixed liquid-vapor phase, depending upon product distribution, degree of 
alkylation, as well as the pressures and temperatures at which the 
alkylation is effected. 
The isoparaffin reactant used in the present alkylation process is one 
possessing up to about 20 carbon atoms and preferably one having from 
about 4 to about 8 carbon atoms as, for example, isobutane, 
3-methylhexane, 2-methylbutane, 2,3-dimethylbutane and 2,4-dimethylhexane. 
The olefin reactant used generally contains from 2 to about 12 carbon 
atoms. Representative examples are ethylene, propylene, butene-1, 
butene-2, isobutylene, and pentenes, etc. Particularly preferred are 
C.sub.3 and C.sub.4 olefins and mixtures thereof. 
In general, the relative molar ratio between the isoparaffin reactant and 
the olefin alkylating agent can be from about 0.5:1 to about 200:1 and is 
preferably in the range of from about 5:1 to about 25:1. However, in one 
embodiment the molar ratio is from about 0.5:1 to about 5:1. 
A critical requirement of the improved alkylation process herein is that 
water be added continuously to the alkylation reactor, that is, at a rate 
on average of from about 0.1 ppmw to about 1 wt. % based upon total 
hydrocarbon feed rate, preferably at a rate from about 0.1 to about 500 
ppmw. The water can be supplied as such or be a feed material which 
provides water under the alkylation condition selected. Suitable 
water-forming materials which can be introduced into the reactor without 
interfering with the desired alkylation include monohydric and dihydric 
alcohols which yield water upon undergoing dehydration. Of this group, 
particular preference is accorded the aliphatic alcohols, especially those 
containing 1 to 6 carbon atoms, for example, methanol, ethanol, 
isopropanol, t-butyl alcohol and isopentyl alcohol. 
EXPERIMENTATION 
The following examples will serve to illustrate the process of the 
invention without limiting it. The data presented below in Examples 1 and 
2 demonstrate the improved octane and reduced catalyst aging which result 
from the addition of water to the composite catalyst system comprising a 
Lewis acid in combination with a non-zeolitic solid inorganic oxide. 
EXAMPLE 1 
This examples illustrates the effect of continuous H.sub.2 O addition on 
the resulting alkylate quality. The specific alkylation operating 
conditions used in the examples are set forth in Table 1. 
TABLE 1 
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BF.sub.3 PROMOTED ALKYLATION OPERATING CONDITIONS 
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Temperature, .degree.C. 20 
Pressure, psig 150 
Stirring Rate, rpm 1900 
BF.sub.3 Feed Rate, wt % of HC Feed 
3.0 
HC Feed, i-C.sub.4 /olefin ratio 
10/1 
Olefin WHSV, hr.sup.-1 1.2 
MIXED C.sub.3 /C.sub.4 OLEFIN DISTRIBUTION, WT % 
Propylene 42.5 
1-Butene 13.7 
Cis + Trans-2-Butene 28.2 
Isobutylene 15.6 
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The non-zeolitic solid inorganic oxide used in this example is a 
commercially available amorphous SiO.sub.2 (0.5 weight % Al.sub.2 
O.sub.3). The as-received material is calcined at 1000.degree. F. and 
sized to 100/200 mesh before use in the alkylation reactor. 
In a standard start-up procedure, 10 grams of catalyst is placed in the 300 
ml autoclave reactor, and about 300 ml of isobutane is charged to fill the 
reactor. The resulting mixture is cooled to the desired temperature with 
constant stirring at 1900 rpm and BF.sub.3 gas is introduced continuously 
into the reactor. After BF.sub.3 breakthrough is observed, the BF.sub.3 
flow rate is then reduced to a level equivalent to 3 wt % of total 
hydrocarbon feed rate. At this point, the isobutane/olefin mixture is 
continuously fed into the reactor to initiate the catalytic alkylation. 
The feed is a simulated commercial feed (approximately 10/1 i--C.sub.4 
/mixed olefins) approximating the C.sub.3.sup..dbd. /C.sub.4.sup..dbd. 
fraction produced from an FCC. The operating conditions as set forth in 
Table 1 are 150 psig, 20.degree. C., 1900 RPM, 1.2 WHSV based on olefin 
and 3.0 wt % BF.sub.3 based on total hydrocarbon feed rate. The product is 
continuously withdrawn from the reactor and is weathered to atmospheric 
pressure via a back pressure regulator and then sent to a receiver which 
is kept at 0.degree. C. Periodically, the product is drained from the 
receiver and weathered at room temperature prior to analysis. 
An on-line gas chromatograph coupled with an automatic sampling device is 
used to monitor the course of the alkylation reaction. All reported octane 
numbers are measured. The isobutane (C.P. grade), isobutane/mixed C.sub.3 
+C.sub.4 olefins and BF.sub.3 (C.P. grade) are used without further 
purification. 
The resulting yield and octane data for the BF.sub.3 /SiO.sub.2 catalyst 
system, summarized in Table 2, shows a comparison between alkylation with 
and without added water. These two runs are designated in Table 2 as 
Examples 1B and 1A, respectively. In case of water addition (Example 1B), 
water is added intermittently throughout the run at an average rate of 
about 100 ppmw based upon total hydrocarbon feed rate. 
TABLE 2 
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THE EFFECT OF WATER ADDITION ON 
BF.sub.3 -PROMOTED ALKYLATION 
1A 1B 
Example BF.sub.3 /SiO.sub.2 
BF.sub.3 /SiO.sub.2 /H.sub.2 O 
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Catalyst System 2.1 2.1 
Yield, g C.sub.5 +/g 
Olefin Converted 
Yields in C.sub.5 +, Wt % 
C.sub.5 3.4 2.7 
C.sub.6 3.3 2.3 
C.sub.7 29.1 27.1 
C.sub.8 54.7 61.4 
C.sub.9 + 9.6 6.4 
RON + O 91 93 
MON + O 89 90 
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The results show that aklylation is essentially complete in both cases 
based upon the high C.sub.5 + yield per g of olefin converted. However, 
low level H.sub.2 O addition substantially improves alkylate quality over 
BF.sub.3 /silica catalyst alone as seen by the increased research and 
motor octanes and reduced C.sub.9 + yield. 
EXAMPLE 2 
Example 1 is repeated except that the reaction temperature is 0.degree. C. 
and the catalyst is different: BF.sub.3 / SiO.sub.2 (0.2 wt. percent 
Al.sub.2 O.sub.3). The purpose of this experiment is to show the effect of 
intermittent H.sub.2 O addition on catalyst aging. The experiment is 
conducted without H.sub.2 O addition until time onstream is about 75 
hours. At that point, 2 cc H.sub.2 O are added. Thereafter, 1 cc of 
H.sub.2 O is added at about 155 hours. During the reaction the C.sub.5 + 
and C.sub.9 + yields are measured and the results are shown in FIGS. 1 and 
2, respectively. In FIG. 1, the C.sub.5 + yield progressively degrades to 
about 1 g C.sub.5 +/g olefin converted until 2.0 cc of water is added at 
about 75 hours into the reaction. At this point, the C.sub.5 + yield 
increases dramatically to 2.1 g C.sub.5 +/g olefin converted, indicating 
complete alkylation is restored. At about 155 hours into the reaction, an 
additional 1 cc of H.sub.2 O is added to further extend the cycle length. 
FIG. 2 shows that the addition of H.sub.2 O inhibits C.sub.9 + formation, 
presumably by minimizing undesireable side reactions, e.g. polymerization. 
Thus, addition of H.sub.2 O in an alkylation reaction using a BF.sub.3 / 
SiO.sub.2 catalyst system significantly reduces catalyst aging. 
Commerical processes for alkylation of isobutane with propene and butenes 
require high isobutane to olefin feed ratios (I/O) to maintain high octane 
products. Low isobutane to olefin ratios, that is, between about 0.5:1 to 
about 5:1, produce high levels of C.sub.9 + fraction with octanes around 
70 while high I/O ratios, that is, from about 5:1 to 25:1 and above, 
suppress the formation of the undesirable C.sub.9 + material. Quite 
unexpectedly, applicants have found that the C.sub.9 + fraction produced 
from isobutane/olefin alkylation using BF.sub.3 -promoted silica catalysts 
has octanes above about 85. This permits operation at heretofore 
unacceptably low isobutane to olefin ratios. Because the C.sub.9 + 
fraction is formed from less than one mole of isobutane per mole of 
olefin, this system also permits complete olefin conversion to gasoline 
when stoichiometric amounts of isobutane are not available. This offers 
the refiner a process with significantly improved flexibility when 
isobutane availability is limited. 
The discovery of high octane C.sub.9.sup.+ products from alkylation of 
isobutane with olefins using a BF.sub.3 -promoted silica catalyst is both 
new and unexpected. The C.sub.9.sup.+ fraction produced from alkylation 
with hydrofluoric acid or sulfuric acid, the two existing commercial 
processes, are low octane and therefore detrimental to the alkylate 
quality. 
In the process of this embodiment of the present invention, applicants 
propose using a BF.sub.3 -promoted solid catalyst system with the I/O 
ratios well below that of current commercial processes. The resulting 
product has a substantial fraction of C.sub.9 + components and yet quite 
unexpectedly has a high octane. 
EXAMPLES 3& 4 
Example 1 is repeated with the exceptions noted below. Table 3 shows the 
resulting octane/boiling point distributions for alkylate samples from 
continuous pilot unit runs using BF.sub.3 promoted silica in both a slurry 
unit (Example 3) and a fixed bed unit (Example 4). Both examples were 
carried out at 0.degree. C. and 150 psig using a 10/1 isobutane/2-butene 
feed. The slurry unit evaluation of Example 3 also included intermittent 
H.sub.2 O addition at an equivalent of approximately 100 ppmw based on 
total hydrocarbon feed rate. The results show that as the C.sub.9.sup.+ 
fraction of the alkylate increases from 11.5 to 67.6 wt % in going from 
Example 3 to Example 4, the research octane number (RON) of the full range 
gasoline is uneffected while the motor octane number (MON) decreases only 
slightly. In both cases, the full range gasoline octanes are above 90. 
Furthermore, the RON of the C.sub.9.sup.+ fraction is nearly 85 in the 
case of Example 3 and over 95 for Example 4. The relatively high octanes 
of the C.sub.9.sup.+ fractions indicate that operation at heretofore 
unacceptably low I/O ratios is possible with the catalyst system of the 
present invention. Low I/O ratio operation favors high C.sub.9.sup.+ 
yields with low isobutane consumption. By comparison, Table 3 also shows 
the octane/boiling point distribution for several commercial alkylates. 
The octane of the C.sub.9.sup.+ fractions are all quite low for the 
commercial alkylates. These low octanes make operation of a commercial HF 
unit at low I/O ratios unattractive since these conditions favor 
production of the low octane C.sub.9.sup.+ fraction. 
TABLE 3 
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OCTANE/BOILING POINT DISTRIBUTIONS FOR 
VARIOUS ALKYLATE SAMPLES 
Boiling Point 
Distribution, wt 
Octanes 
% RON MON 
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Example 3 Alkylate 
Full Range Alkylate 
100.0 97.0 94.0 
IBP - 265.degree. F. 
85.8 97.3 -- 
265 - 350.degree. F. 
2.7 88.8 -- 
350.degree. F..sup.+ (C.sub.9.sup.+) 
11.5 84.5 88.1 
Example 4 Alkylate 
Full Range Alkylate 
100.0 97.2 91.1 
IBP - 265.degree. F. 
24.0 -- -- 
265 - 350.degree. F. 
8.4 87.4 -- 
350.degree. F..sup.+ (C.sub.9.sup.+) 
67.6 96.7 92.6 
Commercial HF Alkylate 1 
Full Range Alkylate 
100.0 93.7 92.0 
IBP - 265.degree. F. 
87.4 95.0 -- 
265 - 350.degree. F. 
7.4 78.6 -- 
350.degree. F..sup.+ (C.sub.9.sup.+) 
5.2 66.5 -- 
Commercial HF Alkylate 2 
Full Range Alkylate 
100.0 90.3 89.9 
IBP - 265.degree. F. 
85.0 93.2 92.0 
265.degree. F..sup.+ (C.sub.9.sup.+) 
15.0 68.0 68.0 
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In a commercial plant, the flexibility to operate at reduced isobutane 
consumption can be obtained automatically. As the isobutane to olefin 
ratio drops below the stoichiometric amount, the isobutane consumption 
will initially exceed the isobutane makeup. This will decrease the 
isobutane available for recycle, resulting in a reduced isobutane to 
olefin ratio. The low isobutane to olefin ratio causes C.sub.9.sup.+ 
oligomer yield to increase, thereby decreasing the isobutane consumption. 
The whole system will reach a new equilibrium where the isobutane 
consumption equals the isobutane makeup. 
Although the invention has been described in conjunction with specific 
embodiments, it is evidence that many alternatives and variations will be 
apparent to those skilled in the art in light of the foregoing 
description. Accordingly, the invention is intended to embrace all of the 
alternatives and variations that fall within the spirit and scope of the 
appended claims.