Conversion of olefins to low pour point distillates and lubes

A process for the conversion of olefins to distillate range hydrocarbons comprising contacting olefins with large pore zeolites.

BACKGROUND OF THE INVENTION 
This invention relates to a process for effecting the conversion of olefins 
to distillate range hydrocarbons and more particularly to improvements in 
the zeolite catalytic conversion of olefins to produce C.sub.10 + 
hydrocarbons. 
With the advent of fossil fuel shortages and the accelerated demand for 
petroleum derived products, there has been an ever increasing demand for 
synthetic means of providing hydrocarbons, useful as fuel components. 
Recently, much effort has been devoted to the synthetic conversion of 
alcohols, such as methanol, to gasoline range hydrocarbons. One means 
which has proven successful involves the use of zeolites as catalysts for 
such conversion reactions. Among these processes are those disclosed in 
U.S. Pat. Nos. 3,928,483, 4,138,442, 4,013,732, 4,138,440, 3,979,472, and 
4,035,430. Others include U.S. Pat. No. 4,156,698 which discloses 
employing an improved zeolite catalyst in a rare-earth matrix in the 
conversion process. Moreover, U.S. Pat. No. 4,058,576 discloses a method 
wherein alcohols are converted to olefins in the presence of zeolite 
catalysts and subsequently wherein these olefins are converted to gasoline 
boiling range components in the presence of certain zeolites. 
Concomitant with the shortage of fossil fuel and the rising costs of 
gasoline, utilization of low pour point distillates, i.e. diesel fuels and 
lubricating oils, has been ever increasing too. Accordingly, recent 
efforts have been given to the development of improved processes for the 
production and upgrading of diesel fuel and lube products. While definite 
advances have been made in the production and upgrading of these type 
products, further processes are obviously welcome. 
SUMMARY OF THE INVENTION 
Accordingly, it is one object of the present invention to provide a process 
for the production of distillate and lube range (C.sub.10 +) hydrocarbons. 
Another object of this invention to provide a novel process for the 
conversion of olefins to distillate and lube range hydrocarbons. 
A further object of this invention is to provide a simple and direct 
one-step process for the production of distillate and lube range 
hydrocarbons from olefins. 
A still further object of the present invention is to provide a process for 
the production of distillate and lube range hydrocarbon products which are 
suitable as diesel fuel, jet fuels and lubricating oils. 
These and other objects are achieved herein by a process which comprises 
contacting a feed comprising an olefin, a mixture of olefins or a mixture 
of olefins and other hydrocarbon types, such as paraffins, with a high 
SiO.sub.2 /Al.sub.2 O.sub.3 ratio large pore zeolite catalyst, under 
conditions of temperature and pressure sufficient to product C.sub.10 + 
hydrocarbons. 
DETAILED DESCRIPTION OF THE INVENTION 
In accordance with the present invention, it has been surprisingly 
discovered that olefins can be converted to distillate range (C.sub.10 +) 
hydrocarbons by contact with large pore zeolite catalysts under certain 
conditions of temperature and pressure. 
Thus, for the purpose of this invention, olefin rich feeds comprising light 
olefins, for example C.sub.2 -C.sub.10 may be used as starting material to 
be converted by the process herein. More specifically, among the olefins 
contemplated as feed herein are included olefins having from C.sub.2 to 
about C.sub.10 carbon atoms. Moreover, mixtures of these olefins may be 
used as well as mixtures of these olefins and paraffins. Particularly 
preferred olefin feeds are comprised of olefins having from C.sub.2 to 
about C.sub.6 carbon atoms. 
The zeolite catalysts which are employed in the present process are 
generally defined as large pore zeolites having pore dimensions greater 
than about 6 angstrom units and pore windows of about a size such as would 
be provided by 12-membered rings of oxygen atoms. 
The zeolites useful in the present process have a structure which provides 
access to larger molecules. Rather than attempt to judge from crystal 
structure whether or not a catalyst possesses the necessary access, a 
simple determination of the "constraint index" may be made by continuously 
passing a mixture of an equal weight of normal hexane and 3-methylpentane 
over a small sample, approximately 1 gram or less, of catalyst at 
atmospheric pressure according to the following procedure. A sample of the 
catalyst, in the form of pellets or extrudate, is crushed to a particle 
size about that of coarse sand and mounted in a glass tube. Prior to 
testing, the catalyst is treated with a stream of air at 1000.degree. F. 
for at least 15 minutes. The catalyst is then flushed with helium and the 
temperature adjusted between 550.degree. F. and 950.degree. F. to give an 
overall conversion between 10% and 60%. The mixture of hydrocarbons is 
passed at 1 liquid hourly space velocity (i.e. 1 volume of liquid 
hydrocarbon per volume of catalyst per hour) over the catalyst with a 
helium dilution to give a helium to total hydrocarbon mole ratio of 4:1. 
After 20 minutes on stream, a sample of the effluent is taken and 
analyzed, most conveniently by gas chromatography, to determine the 
fraction remaining unchanged for each of the two hydrocarbons. 
The "constraint index" is calculated as follows: 
##EQU1## 
The constraint index approximates the ratio of the cracking rate constants 
for the two hydrocarbons. 
Catalysts suitable for the present invention are those having a constraint 
index of about 0.5 to less than 2. 
Representative crystalline aluminosilicates suitable for the present 
invention include those natural and synthetic crystalline aluminosilicates 
having uniform pores of a diameter preferably greater than about 6 
angstrom units. Such crystalline aluminosilicates include zeolites Y, X, 
beta, L, ZSM-4, ZSM-20, as well as naturally occuring zeolites including 
faujasite, mordenite, offretite, gmelinite, and the like. Preferred 
crystalline aluminosilicates include those having a high SiO.sub.2 
/Al.sub.2 O.sub.3 ratio, typified by zeolite Beta and dealuminized Y and 
mordenite. High SiO.sub.2 /Al.sub.2 O.sub.3 ratio large pore zeolites are 
preferred since they reduce catalyst aging. Ratios of from about 7:1 to 
about 1000:1 are contemplated. 
The crystalline aluminosilicates employed herein are essentially 
characterized by a high catalytic activity. This high catalytic activity 
may be imparted to the catalyst particles by base exchanging alkali metal 
aluminosilicate particles with a base-exchange solution containing ions 
selected from the group consisting of cations of elements of Group IB-VIII 
of the Periodic Table, hydrogen, and hydrogen precursors, including 
mixtures thereof with one another. Hydrogen precursors, such as ammonia 
and ammonium salts, typically undergo, upon heating, degradation to 
hydrogen cations in contact with aluminosilicates. Suitable methods of 
base exchange are described in U.S. Pat. Nos. 3,140,249 and 3,140,253. 
Where an alkali metal aluminosilicate is employed initially, it is 
essential to base exchange either the aluminosilicate particles to reduce 
the sodium content of the final product to less than about 4% by weight 
and preferably less than 1% by weight. 
As previously discussed, base exchange may be accomplished by one or more 
contacts with a solution containing ions selected from the group 
consisting of cations of the elements of Groups IB-VIII, hydrogen and 
hydrogen precursors, including mixtures thereof with one another. 
Water is the preferred solvent for the cationic salt for reasons of economy 
and ease of preparation in large scale operations involving continuous or 
batchwise treatment. Similarly, for this reason, organic solvents are less 
preferred but can be employed providing the solvent permits ionization of 
the cationic salt. Typical solvents include cyclic and acylic ethers such 
as dioxane, tetrahydrofuran, diethyl ether, diisopropyl ether, and the 
like; ketones, such as acetone and methyl ethyl ketone; esters such as 
ethyl acetate; alcohols such as ethanol, propanol, butanol, etc.; and 
miscellaneous solvents such as dimethylformamide, and the like. 
In carrying out the treatment with the fluid medium, the procedure employed 
varies depending upon the particular aluminosilicate which is treated. If 
the aluminosilicate which is treated has alkali metal cations associated 
therewith, then the treatment with the fluid medium or media should be 
carried out until such time as the alkali metal cations originally present 
are substantially exhausted. Alkali metal cations, if present in the 
treated aluminosilicate, tend to suppress or limit catalytic properties, 
the activity of which, as a general rule, decreases with increasing 
content of these metallic cations. On the other hand, if the 
aluminosilicate which is treated with the desired fluid medium is 
substantially free of alkali metal cations, i.e., a calcium 
aluminosilicate, then the treatment need not be carried out until such 
time as the metal is exhausted since the presence of metals other than 
alkali metals does not seriously limit catalytic properties. Effective 
treatment with the fluid medium to obtain a modified aluminosilicate 
having high catalytic activity will vary, of course, with the duration of 
the treatment and the temperature at which the treatment is carried out. 
Elevated temperatures tend to hasten the speed of treatment whereas the 
duration thereof varies inversely with the general concentration of ions 
in the fluid medium. In general, the temperatures employed range from 
below ambient room temperature of 24.degree. C. up to temperatures below 
the decomposition temperature of the aluminosilicate. Following the fluid 
treatment, the treated aluminosilicate is washed with water, preferably 
distilled water, until the effluent wash water has a pH value of wash 
water, i.e., between 5 and 8. The aluminosilicate materials is thereafter 
analyzed for metallic content by methods well known in the art. Analysis 
also involves analyzing the effluent wash for anions obtained in the wash 
as a result of the treatment, as well as determination of and correction 
for anions that pass into the effluent wash from soluble substances, or 
decomposition products of insoluble substances, which are otherwise 
present in the aluminosilicate as impurities. 
The treatment of the aluminosilicate with the fluid medium or media may be 
accomplished in a batchwise or continuous method under atmospheric, 
superatmospheric or subatmospheric pressures. A solution of rare earth 
metal cations in the form of a molten material, vapor, aqueous or 
non-aqueous solution may be passed slowly through a fixed bed of 
aluminosilicate. If desired, hydrothermal treatment or corresponding 
non-aqueous treatment with polar solvents may be effected by introducing 
the aluminosilicate and fluid medium into a closed vessel maintained under 
autogeneous pressure. Similarly, treatments involving fusion or vapor 
phase contact may be employed. 
Aluminosilicates which are treated with a fluid medium or media in the 
manner above described include a wide variety of aluminosilicates both 
natural and synthetic which have a crystalline or combination of 
crystalline and amorphous structure. 
The aluminosilicates can be described as a three-dimensional framework of 
SiO.sub.4 and AlO.sub.4 tetrahedra in which the tetrahedra are 
cross-linked by the sharing of oxygen atoms whereby the ratio of total 
aluminum and silicon atoms to oxygen atoms is 1:2. In their hydrated form, 
the aluminosilicates may be represented by the formula: 
EQU M.sub.2/n O:Al.sub.2 O.sub.3 :wSiO.sub.2 :YH.sub.2 O 
wherein M represents at least one cation which balances the electrovalence 
of the tetrahedra, n represents the valence of the cation, w the moles of 
SiO.sub.2 and Y the moles of H.sub.2 O. The cations can be any or more of 
a number of metal ions, depending upon whether the aluminosilicate is 
synthesized or occurs naturally. Typical cations include sodium, lithium, 
potassium, silver, magnesium, calcium, zinc, barium, iron, nickel, cobalt 
and manganese. Although the proportions of inorganic oxides in the 
silicates and their spatial arrangements may vary affecting distinct 
properties in the aluminosilicate, the main characteristic of these 
materials is their ability to undergo dehydration without substantially 
affecting the SiO.sub.4 and AlO.sub.4 framework. 
Aluminosilicates falling within the above formula are well known and, as 
noted, include synthesized aluminosilicates, natural aluminosilicates, and 
certain caustic treated clays. Among the aluninosilicates are included 
zeolites, Y, L, S, X, levynite, erionite, faujasite, analcite, paulingite, 
noselite, phillipsite, datolite, gmelinite leucite, scapolite, mordenite 
as well as certain caustic treated clays such as montmorillonite and 
kaolin families. The preferred aluminosilicates are those having pore 
diameters of greater than about 6 angstroms. 
It has been discovered herein that certain conditions of temperature and 
pressure are essential to the conversion of the olefin feed to distillate 
range hydrocarbons. That is, it has been found herein that the conversion 
to distillate range hydrocarbons takes place under conditions of elevated 
pressure and relatively low temperature. More particularly, the elevated 
pressures contemplated within the scope of the present invention are 
within the range of from about 200 psig to about 2000 psig, preferably 
from about 500 to about 1500 psig, while the temperatures found essential 
to the conversion are from about 200.degree.-750.degree. F. and preferably 
from about 300.degree. to about 650.degree. F. 
Typically, in carrying out the process of the present invention, the olefin 
feed is brought into contact with the hereinbefore described large pore 
zeolite catalysts at a temperature in the range of from about 
300.degree.-650.degree. F. for a contact time equivalent to or the same as 
a weight hourly space velocity (WHSV) of about 20 to about 0.1, preferably 
about 5 to about 0.5, it being understood that WSHV signifies pounds of 
feed per pound of zeolite per hour; and at a pressure as recited above. 
The conversion can be carried out with or without a diluent gas (such as 
hydrogen or nitrogen). 
The distillate range products resulting from the present process comprise 
330.degree. F. to about 650.degree. F. distillate products ranging from 
kerosene to diesel fuels, jet fuels and the like as well as 650.degree. 
F..sup.+ lube products.

In order that those skilled in the art may better understand how the 
present invention may be practiced, the following examples are given by 
way of illustration and not by way of limitation. 
EXAMPLE 
Propylene is converted over a dealuminized Y(SiO.sub.2 /Al.sub.2 O.sub.3 
=75) zeolite at 510.degree. F., 1000 psig, 1 WHSV and N.sub.2 /HC ratio of 
1. The results are tabulated below: 
TABLE 
______________________________________ 
Wt. % in Liquid Product 
______________________________________ 
IBP to about 330.degree. F. Naphtha 
19.8 
330.degree. to about 650.degree. F. distillate 
68.3 
650.degree. F..sup.+ lube 
9.1 
______________________________________ 
Substituting other large pore zeolite catalysts and other olefins, such as 
Beta and hexene respectively, provides similar conversion results. 
The process of the present invention provides a particularly desirable 
alternative to refiners for the increased production of distillates and 
lubes, especially in the situation where increased amounts of light 
olefins are produced as a result of more severe FCC operations.