Process for the hydration olefins

A process for converting propylene to isopropyl alcohol by contacting water with a propylene-containing feed at a mole ratio of water to propylene of at least about 0.5:1 (water:olefin), usually about 1:1-10:1 in the vapor and/or liquid phase under propylene hydration conditions. The hydration is carried out in the presence of a relatively constrained intermediate pore size zeolite such as ZSM-35 or ferrierite as the hydration catalyst. The zeolite is used in the acid form and with a crystal size of not more than 0.2.mu. to give high activity for conversion to isopropyl alcohol.

FIELD OF THE INVENTION 
This invention relates to a process for the catalytic hydration of 
propylene to provide isopropyl alcohol in enhanced amounts. The process 
employs the acidic form of certain natural or synthetic porous crystalline 
materials or zeolites, especially the constrained intermediate pore size 
zeolites such as ferrierite and the synthetic zeoites such as ZSM-22, 
ZSM-23 and ZSM-35 as the catalyst. The product isopropyl alcohol is useful 
as a solvent, a chemical intermediate and as a high octane blending 
component for gasoline. 
BACKGROUND OF THE INVENTION 
There is a need for an efficient catalytic process to manufacture alcohols 
from light olefins to augment the supply of high octane blending stocks 
for gasoline. Lower molecular weight alcohols such as isopropyl alcohol 
(IPA) are in the gasoline boiling range and are known to have a high 
blending octane number. In addition, by-product propylene from which IPA 
can be made is usually available at low cost in a petroleum refinery. 
The catalytic hydration of olefins to provide alcohols is a 
well-established art and is of significant commercial importance. 
Representative olefin hydration processes are disclosed in U.S. Pat. Nos. 
2,162,913; 2,477,380; 2,797,247; 3,798,097; 2,805,260; 2,830,090; 
2,861,045; 2,891,999; 3,006,970; 3,198,752; 3,810,849; 3,989,762, among 
others. 
Olefin hydration employing zeolite catalysts is known. As disclosed in U.S. 
Pat. No. 4,214,107, monoolefins in the C.sub.2-4 range, specifically, 
ethylene, propylene, n-butene-1 and cis and trans n-butene-2, are reacted 
with water at olefin:water mole ratios of from about 0.1:1 to 2:1, 
preferably from about 0.5:1 to 1.5:1 (equivalent to water:olefin mole 
ratios of from about 10:1 to about 0.5:1 and preferably from about 2:1 to 
about 0.67:1) to provide the corresponding alcohol, essentially free of 
ether and hydrocarbon by-product, employing as olefin hydration catalyst a 
zeolite having a Constraint Index of 1 to 12 as exemplified by ZSM-5, 
ZSM-11, ZSM-12, ZSM-35 and ZSM-38. Of the foregoing zeolites, only acidic 
ZSM-5 is illustrated in a working example. 
According to U.S. Pat. No. 4,499,313, an olefin is hydrated to the 
corresponding alcohol in the presence of hydrogen-type mordenite or 
hydrogen-type zeolite Y each having a silica-alumina molar ratio of 20 to 
500. The use of such a catalyst is said to result in higher yields of 
alcohol than olefin hydration processes which employ conventional solid 
acid catalysts. Use of the catalyst is said to offer the advantage over 
ion-exchange type olefin hydration catalysts of not being restricted by 
the hydration temperature. Reaction conditions employed in the process 
include a temperature of from 50.degree.-300.degree. C., preferably 
100.degree.-250.degree. C., a pressure of 5 to 200 kg/cm.sup.2 to maintain 
liquid phase or gas-liquid multi-phase conditions and a mole ratio of 
water to olefin of from 1 to 20. The reaction time can be 20 minutes to 20 
hours when operating batchwise and the liquid hourly space velocity (LHSV) 
is usually 0.1 to 10 in the case of continuous operation. 
European Patent Application 210,793 describes an olefin hydration process 
employing a medium pore zeolite as hydration catalyst. Specific catalysts 
mentioned are Theta-1, said to be preferred, ferrierite, ZSM-22, ZSM-23 
and NU-10. 
SUMMARY OF THE INVENTION 
We have now found that the activity of the more highly constrained 
intermediate pore size zeolites such as ferrierite and the synthetic 
ferrierite ZSM-35 for the production of alcohols may be enhanced by the 
use of the zeolite with a particular and specific crystal size. According 
to the present invention, the zeolite is used with a crystal size of not 
more than 0.2(microns). The improved activity of the small crystal size 
zeolite is especially notable at water:olefin ratios of 0.5:1 or higher, 
e.g. from 1:1 to about 10:1 (water:olefin). 
According to the present invention, therefore, propylene is converted to 
isopropyl alcohol by contacting water with a propylene feed in a mole 
ratio of water to propylene of at least 0.5:1 in the vapor and/or liquid 
phase under propylene hydration conditions. The reaction is carried out in 
the presence of ferrierite or ZSM-35 which is at least partially in the 
acid or hydrogen form as the propylene hydration catalyst. The zeolite 
which is used has a crystal size of not more than 0.2.mu.. The product of 
the hydration is isopropyl alcohol and is obtained with relatively high 
selectivity and with high conversion levels of the propylene feed. 
At water:propylene mole ratio of at least 0.5:1,e.g. 1:1 to 10:1, these 
zeolite hydration catalysts, especially ZSM-35 have been found to be far 
more effective as catalysts for the conversion of propylene to isopropyl 
alcohol than other acidic zeolites. 
The isopropyl alcohol resulting from the propylene hydration process of 
this invention is advantageously employed as a blending component for 
gasoline, as a solvent and an as intermediate for a variety of industrial 
chemical syntheses. 
DETAILED DESCRIPTION 
The present invention is applicable to the hydration of essentially pure 
propylene or propylene in admixture with one or more materials which may 
or may not contain other hydratable olefins. Examples of 
propylene-containing streams which are particularly advantageous herein 
due to their low cost and ready availability where petroleum refineries 
are concerned include gas plant off-gas containing ethylene and propylene 
and refinery FCC propane/propylene streams. For example, a typical FCC 
light olefin stream possesses the composition shown in Table 1 below. 
TABLE 1 
______________________________________ 
Typical Refinery FCC Light Olefin Composition 
Wt. % Mole % 
______________________________________ 
Ethane 3.3 5.1 
Ethylene 0.7 1.2 
Propane 14.5 15.3 
Propylene 42.5 46.8 
Isobutane 12.9 10.3 
n-Butane 3.3 2.6 
Butenes 22.1 18.3 
Pentanes 0.7 0.4 
______________________________________ 
In order to achieve high conversion of the propylene to the corresponding 
alcohol, the hydration is carried out at water:propylene mole ratios of at 
least 0.5:1 and preferably higher e.g. 2:1. Ratios of up to 10:1, usually 
not more than 5:1 are preferred. 
The other operating conditions of the propylene hydration process are not 
especially critical and include a preferred temperature range of from 
about 200.degree. to about 400.degree. F., preferably from about 
250.degree. to about 350.degree. F. and most preferably from about 
280.degree. to about 350.degree. F. Total system pressure will normally be 
from at least about 5 atm, preferably at least about 20 atm and still more 
preferably at least about 40 atmospheres. 
The hydration can be carried out under liquid phase, vapor phase or mixed 
vapor-liquid phase conditions in batch or continuous manner using a 
stirred tank reactor or fixed bed flow reactor, e.g., trickle-bed, 
liquid-up-flow, liquid-down-flow, counter-current, co-current, etc. 
Reaction times of from about 20 minutes to about 20 hours when operating 
in batch and an LHSV of from about 0.1 to about 10 when operating 
continuously are suitable. It is generally preferable to recover any 
unreacted propylene and recycle it to the reactor. 
The catalyst employed in the propylene hydration process is a relatively 
constrained intermediate pore size zeolite, that is the zeolite has a 
Constraint Index in the range of 1-12, as determined by the method 
described in U.S. Pat. No. 4,016,218. The zeolites which are actually used 
in the present process, however, are also characterised by specific 
sorption properties related to their relatively constrained diffusion 
characteristics. These sorption characteristics are those which are set 
out in U.S. Pat. No. 4,810,357 for the zeolites such as zeolite ZSM-22, 
ZSM-23, ZSM-35 and ferrierite. 
The zeolite hydration catalysts used in the present process are zeolites 
which have pore openings defined by: (1) a ratio of sorption of n-hexane 
to o-xylene, on a volume percent basis, of greater than about 3, which 
sorption is determined at a P/P.sub.o of 0.1 and at a temperature of 
50.degree. C. for n-hexane and 80.degree. C. for o-xylene and (2) by the 
ability of selectively cracking 3-methylpentane (3MP) in preference to the 
doubly branched 2,3-dimethylbutane (DMB) at 1000.degree. F. and 1 
atmosphere pressure from a 1/1/1 weight ratio mixture of 
n-hexane/3-methyl-pentane/2,3-dimethylbutane, with the ratio of rate 
constants k.sub.3MP /k.sub.DMB determined at a temperature of 1000.degree. 
F. being in excess of about 2. 
The expression, "P/P.sub.o ", is accorded its usual significance as 
described in the literature, for example, in "The Dynamical Character of 
Adsorption" by J.H. deBoer, 2nd Edition, Oxford University Press (1968) 
and is the relative pressure defined as the ratio of the partial pressure 
of sorbate to the vapor pressure of sorbate at the temperature of 
sorption. The ratio of the rate constants, k.sub.3MP /k.sub.DMB, is 
determined from 1st order kinetics, in the usual manner, by the following 
equation: 
EQU k=(1/T.sub.c) 1n (1/1-.epsilon.) 
where k is the rate constant for each component, T.sub.c is the contact 
time and .epsilon. is the fractional conversion of each component. 
Zeolites conforming to these sorption requirements include the naturally 
occurring zeolite ferrierite as well as the synthetic zeolites ZSM-22, 
ZSM-23 and ZSM-35. ZSM-35 is the preferred catalytic material for the 
present purposes. These zeolites are at least partly in the acid or 
hydrogen form when they are used in the present hydration process. 
The preparation and properties of zeolite ZSM-22 are described in U.S. Pat. 
No.4,810,357 (Chester) to which reference is made for such a description. 
The synthetic zeolite ZSM-23 is described in U.S. Pat. Nos. 4,076,842 and 
4,104,151 to which reference is made for a description of this zeolite, 
its preparation and properties. 
The intermediate pore-size synthetic crystalline material designated ZSM-35 
("zeolite ZSM-35" or simply "ZSM-35"), is described in U.S. Pat. No. 
4,016,245, to which reference is made for a description of this zeolite 
and its preparation. 
Ferrierite is a naturally-occurring mineral, described in the literature, 
see, e.g., D.W. Breck, ZEOLITE MOLECULAR SIEVES, John Wiley and Sons 
(1974), pages 125-127, 146, 219 and 625, to which reference is made for a 
description of this zeolite. 
In general, the zeolitic propylene hydration catalyst employed in the 
present process will possess a silica to alumina ratio of at least about 
10. In place of all or a part of the aluminum present in the framework 
structure of the zeolite, other trivalent acidic metals can be present 
such as gallium, iron, boron, etc. 
The zeolite hydration catalyst used in the process will generally possess 
an alpha value of at least about 1, and preferably at least about 10. 
"Alpha value", or "alpha number", is a measure of zeolite acidic 
functionality and is more fully described together with details of its 
measurement in U.S. Pat. No. 4,016,218 J. Catalysis, 6, pp. 278-287 (1966) 
and J. Catalysis, 61, pp. 390-396 (1980). Low acidity values (alpha values 
of less than about 200) can be achieved by a variety of techniques 
including (a) synthesizing the zeolite with a high silica/alumina ratio, 
(b) steaming, (c) steaming followed by dealuminization and (d) 
substituting aluminum with one or more other species. For example, in the 
case of steaming, the zeolite can be exposed to steam at elevated 
temperatures ranging from about 500.degree. to about 1200.degree. F. and 
preferably from about 750.degree. to about 1000.degree. F. This treatment 
can be accomplished in an atmosphere of 100% steam or an atmosphere 
consisting of steam and a gas which is substantially inert to the zeolite. 
A similar treatment can be accomplished at lower temperatures employing 
elevated pressure, e.g., at from about 350.degree. to about 700.degree. F. 
with from about 10 to about 200 atmospheres. Specific details of several 
steaming procedures may be gained from the disclosures of U.S. Pat. Nos. 
4,326,994, 4,374,296 and 4,418,235, the contents of which are incorporated 
by reference herein. Aside from or in addition to any of the foregoing 
procedures, the surface acidity of the zeolite can be eliminated or 
reduced by treatment with bulky reagents as described in U.S. Pat. No. 
4,520,221, the contents of which are incorporated by reference herein. 
The use of these zeolites, especially ZSM-35, as the propylene hydration 
catalyst results in high selectivity for isopropyl alcohol, especially at 
water:olefin ratios of 0.5:1 or higher and with zeolite crystal sizes of 
not more than 0.2.mu.. At temperatures from about 320.degree. to 
370.degree. F. propylene conversion increases from about 33 to 41% at 
about 1500 psig system pressure but IPA selectivity remains high. This 
result contrasts with that obtained using zeolite Beta as hydration 
catalyst where high olefin oligomerisation selectivity limits the upper 
temperature of the process to about 360.degree. to 380.degree. F. 
The effect of zeolite crystal size is shown in Table 2 below which shows 
the extent of propylene conversion at two different water:olefin ratios 
for three differently sized ZSM-35 and ferrierite crystals. The olefin 
hydration was carried out at 330.degree. F., 1000 psig, 0.6 WHSV C.sub.3 
=. 
TABLE 2 
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Percent C.sub.3 = conv. 
at H.sub.2 O:C.sub.3 ratio 
Zeolite, crystal Size, .mu.. 
2:1 0.5:1 
______________________________________ 
ZSM-35, &lt;0.1 55 28 
ZSM-35, 0.1-0.2 45 27 
Ferrierite, 0.2-1.0 
9 6 
______________________________________ 
Thus, the smaller crystal size shows higher conversion, indicating that the 
reaction is crystal size dependant at water:olefin ratios above 0.5:1 and 
that pore diffusion limitations exist under these conditions. 
In practicing the propylene hydration process of the present invention, it 
is usually advantageous to incorporate the zeolite with a matrix or binder 
material which is resistant to the temperature and other conditions 
employed in the process. Useful matrix materials include both synthetic 
and naturally-occurring substances, e.g., inorganic materials such as 
clay, silica and/or metal oxides. The latter can be either 
naturally-occurring or can be provided in the form of gelatinous 
precipitates or gels including mixtures of silica and metal oxides. 
Naturally-occurring clays may also be used as the binder or matrix 
material. 
Among the synthetic oxides with which the zeolite can be composited with 
are porous matrix materials such as alumina, silica, titania, zirconia, 
silica-alumina, silica-magnesia, silica-zirconia, silica-thoria, 
silica-beryllia and silica-titania etc., as well as ternary oxide 
compositions such as silica-alumina-thoria, silica-alumina-zirconia, 
silica-alumina-magnesia and silica-magnesia-zirconia. The matrix can be in 
the form of a cogel. The relative proportions of zeolite and matrix 
material, on an anhydrous basis, can vary widely with the zeolite content 
ranging from between about 1 to about 99 wt%, and more usually in the 
range of about 5 to about 90 wt%, of the dry composite. 
In some cases, it may be advantageous to formulate the zeolite hydration 
catalyst as an extrudate bound with a low acidity refractory oxide binder 
such as titania or silica since catalysts made with these low-acidity 
binders have been found to exhibit higher activity than similar catalysts 
bound with alumina or other more acidic type binders. Table 3 below shows 
the improved conversion of the propylene feed at 330.degree. F., 1000 
psig, 0.6 WHSV C.sub.3 =, 2:1 water:olefin. 
TABLE 3 
______________________________________ 
Binder TOS, hr Percent C.sub.3 Conv. 
______________________________________ 
Al.sub.2 O.sub.3 
24 55 
SiO.sub.2 54 70 
TiO.sub.2 24 73 
______________________________________ 
Under most conditions it has been found that selectivity for IPA is greater 
than 99%, regardless of binder type with small amounts of di-isopropyl 
ether and olefin oligomer, primarily hexene, being the only detectable 
by-products. 
The catalysts made using the low acidity binders such as silica or titania 
can be made by the method described in commonly assigned U.S. patent 
applications Ser. No. 07/44,639, filed May 1, 1987 now abandoned and 
Serial No. 07/140,357, filed Jan. 4 1988, to which reference is made for a 
description of the method. In the method described in those applications, 
a homogeneous mixture of zeolite, water and a low acidity refractory oxide 
binder, e.g., silica, which contains at least an extrusion-facilitating 
amount of the binder in a colloidal state and which is substantially free 
of added alkali metal base and/or basic salt, is formed into an extrudable 
mass, the mass is extruded and the resulting extrudate is dried and 
calcined. 
The original cations associated with the zeolite can be replaced by a wide 
variety of other cations employing techniques well known in the art, e.g., 
by ion-exchange. Typical replacing cations include hydrogen, ammonium, 
alkyl ammonium and metal cations, and their mixtures Metal cations can 
also be introduced into the zeolite. In the case of metal cations, 
particular preference is given to metals of Groups IB to VIII of the 
Periodic Table, including, by way of example, iron, nickel, cobalt, 
copper, zinc, palladium, calcium, chromium, tungsten, molybdenum, rare 
earth metals, etc. These metals can also be present in the form of their 
oxides. 
A typical ion-exchange technique involves contacting the zeolite with a 
salt of the desired replacing cation. Although a wide variety of salts can 
be employed, particular preference is given to chlorides, nitrates and 
sulfates. Representative ion-exchange techniques are disclosed in a number 
of patents including U.S. Pat. Nos. 3,140,249, 3,140,251 and 3,140,253.