Organic non-quaternary clathrate salts for petroleum separation

Organic non-quaternary clathrate salts are useful for separating hydrocarbon feed streams into aromatics rich fraction and aromatics lean fraction. The organic non-quaternary clathrate salts are characterized by having cations containing less than 16 carbon atoms. Preferred salts are collidinium triflate and triethylammonium dihydroxybenzoate.

BACKGROUND OF THE INVENTION 
1. Field of the Invention 
Hydrocarbon feed streams containing mixtures of aromatic hydrocarbons and 
non-aromatic hydrocarbons are separated into aromatics lean streams and 
aromatics rich streams by contacting the hydrocarbon stream with an 
organic non-quaternary clathrate salt having a cation containing less than 
16 carbon atoms. The clathrate salts selectively interact with the 
aromatic components of the hydrocarbon feed mixture. The organic 
non-quaternary clathrate salt possess non-quaternary cations such as 
phosphonium, ammonium, imidazolium, pyridinium and piperidinium and a 
monovalent or polyvalent anion. They can be represented by formula: 
##STR1## 
wherein 
R is a radical independently selected from the group consisting of 
hydrogen, linear or branched C.sub.1 -C.sub.12 alkyl, C.sub.5 -C.sub.12 
cycloalkyl, C.sub.7 -C.sub.12 aralkyl and alkaryl and C.sub.6 -C.sub.10 
aryl, including inert or unreactive substitutes therein and mixtures 
thereof, wherein the total number of carbon atoms in the total of the R 
radicals in the cation is less than 16; 
n is 1-3; 
m is 1-5; 
Q is N or P; 
A is a monovalent or polyvalent anion. 
The separation is conducted either above the melting point of the clathrate 
salt but below the decomposition temperature of either the salt or the 
hydrocarbon feed or under conditions such that the salt goes into solution 
in the hydrocarbon feed. The clathrate salt is separated from the aromatic 
hydrocarbon with which it combines by e.g. washing with water. 
2. Description of the Related Art 
U.S. Pat. No. 4,359,596 describes the separation of aromatics from mixed 
aromatics/aliphatics hydrocarbon streams by liquid salt extraction. The 
liquid salts used are of the formula 
EQU [R.sub.4 Q][A] 
wherein 
Q is nitrogen, phosphorous or arsenic; 
A is a monovalent or polyvalent anion; 
R.sub.4 Q is a monovalent or polyvalent cation in sufficient numbers to 
render the salt electrically neutral; 
R is a hydrocarbon radical independently selected from the group consisting 
of linear or branched C.sub.1- C.sub.20 alkyl, C.sub.5 -C.sub.10 
cycloalkyl, C.sub.7 -C.sub.20 aralkyl and alkaryl, and C.sub.6 -C.sub.10 
aryl, concluding inert or unreactive substitutes therein and mixtures 
thereof, wherein the total number of carbon atoms in the four R radicals 
totals at least 16 and wherein not more than one R radical is methyl. The 
separation is performed by contacting the hydrocarbon feed with the salt 
above the melting point but below the decomposition point of the liquid 
salt. The salt is seen to possess a cation which is quaternary and 
contains at least 16 carbon atoms. 
SUMMARY OF THE INVENTION 
Aromatic hydrocarbons are separated from hydrocarbon feed streams 
comprising mixtures of aromatic hydrocarbons and non-aromatic hydrocarbons 
by contacting the hydrocarbon feed with an organic nonquaternary clathrate 
salt having a cation containing less than 16 carbon atoms. The organic 
non-quaternary clathrate salt selectively combines with the aromatic 
hydrocarbons in the feed and produces a binary liquid-liquid phase system, 
i.e., a raffinate phase of reduced aromatic content and an extract phase 
of increased aromatic content containing the aromatic hydrocarbon combined 
with the clathrate salt. The raffinate and extract phases are separated, 
then the aromatic hydrocarbon-clathrate salt combination is itself 
separated into an aromatics rich stream and a recovered organic 
non-quaternary clathrate salt stream, which is recycled to the separation. 
The organic non-quaternary clathrate salt possesses as non-quaternary 
cations such cations as ammonium, phosphonium, pyridinium, imidazolium, 
and piperdinium, preferably ammonium and pyridinium, and a monovalent or 
polyvalent anion. 
The salts can be represented by the following formula: 
##STR2## 
wherein 
Q is nitrogen, phosphorus, or arsenic; 
R is hydrogen, C.sub.1 -C.sub.12 linear or branched alkyl, C.sub.5 
-C.sub.12 cycloalkyl, C.sub.7 -C.sub.12 aralkyl or alkaryl, and C.sub.6 
-C.sub.10 aryl, including inert or unreactive substances including 
heteroatom containing species such as alkoxy, and mixtures thereof, 
wherein the total number of carbon atoms in the sum of the R radical 
groups in the cation is less than 16; 
n is an integer ranging from 1-3; 
A is a monovalent or polyvalent anion. 
The separation of aromatic hydrocarbons from the hydrocarbon feeds is 
performed by contacting the hydrocarbon feed with the organic 
non-quaternary clathrate salt either above the melting point of the salt 
but below the decomposition temperature of either the salt or the 
hydrocarbon feed or under conditions such that the solid salt goes into 
solution in the hydrocarbon feed. 
DETAILED DESCRIPTION OF THE INVENTION 
Aromatic hydrocarbons may be selectively separated from hydrocarbon feeds 
comprising mixtures of aromatic hydrocarbons and non-aromatic hydrocarbons 
by contacting hydrocarbon feed with an organic clathrate salt having a 
non-quaternary cation possessing less than 16 carbon atoms. 
The process is useful in treating lube stocks for the removal of aromatics 
to produce aromatics lean raffinates or for the recovery of aromatics such 
as benzene, toluene and xylene in chemical feed streams. 
The separation employs a organic clathrate salt having a non-quaternary 
cation possessing fewer than 16 cation atoms. The salt may be a "liquid 
salt" by which is meant a molten fluid at the temperature of extraction, 
from about room temperature (approximately 20.degree. C.) to about 
400.degree. C., preferably about 20.degree. C. to 200.degree. C., in which 
the solvent is present above its melting point but below the decomposition 
temperature of either the salt or the hydrocarbon feed. 
When used as a liquid salt the liquid salt can be a clear, pourable fluid 
or a melt. The salt can be a solid provided it goes into solution in the 
hydrocarbon feed under the conditions employed. 
Contacting the salt with the hydrocarbon feed permits the salt to combine 
with the aromatic hydrocarbons present in the feed to produce a binary 
liquid-liquid phase system. The extract phase of salt plus aromatics is 
usually the more dense phase and exists either as a separate distinct 
lower phase or as suspended droplets in a continuous lighter phase (the 
raffinate). 
The process of the present invention employs organic nonquaternary salts 
which may be represented by the following formula: 
##STR3## 
wherein 
Q is nitrogen, phosphorus, or arsenic; 
R is hydrogen, C.sub.1 -C.sub.12 linear or branched alkyl, C.sub.5 
-C.sub.12 cycloalkyl, C.sub.7 -C.sub.12 aralkyl or alkaryl, and C.sub.6 
-C.sub.10 aryl, including inert or unreactive substances including 
heteroatom containing species such as alkoxy, and mixtures thereof, 
wherein the total number of carbon atoms in the sum of the R radical 
groups in the cation is less than 16; 
n is an integer ranging from 1-3; 
A is a monovalent or polyvalent anion present in sufficient number to 
balance the electrical charge of the cation. 
Representative R radicals in the cation include methyl. ethyl, propyl, 
n-butyl, sec-butyl, t-butyl, n-pentyl, 2 methylbutyl, 3-methylbutyl, 
n-hexyl, n-octyl, 2-ethylhexyl, decyl, stearyl, cyclohexyl, p-chlorobenyl, 
benzyl, p-methylbenzyl, 2-phenethyl, tolyl, p-xylyl, phenyl, chlorophenyl, 
dodecyl, trifluorobutyl, n-eicosonyl, cyclohexylbutyl, phenylbutyl, 
butylphenyl, naphthyl and the like. The R radical may also be substituted 
with substituents inert under the process condition such as C.sub.1 
-C.sub.12 alkoxy, C.sub.6 -C.sub.10 aryloxy and the less reactive halogens 
fluorine and chlorine. 
Representative cations include triethylammonium, lutidinium, collidinium, 
2-ethyl pyridinium, 2-ethoxy pyridinium, 1-methyl piperidinium, 
piperidinium, 1-ethylcollidinium, 1-methyl, 3-ethylimidazolium, 
1-methylimidazolium. 
Anions may be any of the typical anions common to salt formation including 
carboxylates, benzoates, sulfonates and derivatives thereof, e.g.: 
##STR4## 
where R is OH, C.sub.1 -C.sub.10 alkyl, C.sub.1 -C.sub.10 alkoxy, n=0.5. 
wherein R is OH, C.sub.1 -C.sub.10 alkyl, C.sub.1 -C.sub.10 alkoxy, n=0.5. 
##STR5## 
wherein R is H, CF.sub.3, C.sub.1 -C.sub.10 alkyl. Other typical anions 
include (fluoride, chloride, bromide, iodide, sulfate, naphthenate, 
bicarbonate, bisulfide, nitrate, halometallate (e.g., tetrafluoro-borate) 
methanesulfonate, trifluorormethanesulfonate, dodecylsulfonate, 
phosphonate, benzenephosphonate, tetra-n-butylboranate, acetate and 
2-ethylthexanoate, benzenesulfonate, p-toluenesulfonate, 
p-chlorobenzenesulfonate, phenoxybenzenesulfonate, benzenephosphinate, 
benzoate, tetrachloroaluminate, tetrafluoroborate, hydroxide, methoxide, 
phenoxide, 2,4,6-tri-t-butylphenoxide, tris(2-methoxyethoxy)acetate, 
tetra-2-ethylhexylboranate, tetra-sec-butylboranate, 
triethyl-2-ethylhexylboronate, and the like. Particular examples include 
salicylate, triflate, 2,6-dihydroxy benzoate. 
The organic non-quaternary clathrate salts useful in the present invention 
are synthesized by techniques common to the art. The appropriate organic 
base is reacted with the appropriate organic acid in a suitable solvent 
such as tetrahydrofuran (THF), or the reaction can be run neat (in the 
absence of solvent) if one or both of the acid or base is liquid. 
Preferred organic non-quaternary clathrate salt include triethylammonium 
salicylate, lutidinum triflate, collidinium triflate 
##STR6## 
2-ethylpyridinium triflate, 2 ethoxypyridinium triflate, 
1-methylpiperidinium triflate, triethylammonium 2,6dihydroxybenzoate, 
piperidinium triflate, tripropyl ammonium formate, 1-methyl piperidinium 
phenylacetate, triethyl ammonium m-nitrobenzoate, quinolinium triflate. 
The extracting solvent in this process comprises an organic non-quaternary 
salt and can also include a small quantity of cosolvent or cosolvents for 
the liquid salt, such as water, acid, alcohol, or the corresponding acid 
of the anion radical. Water is especially useful because it is 
inexpensive, relatively non-corrosive and can increase selectivity in the 
extraction; however, the use of water does diminish extraction capacity. 
The extraction process of the present invention is typically conducted at 
between about 20.degree. C. to about 400.degree. C., preferably about 
20.degree. C. to 200.degree. C. Pressures employed are preferably 
atmospheric, but elevated pressure may be employed, if necessary, to 
maintain the hydrocarbon feed in the liquid state. 
The amount of salt used in the extraction process is flexible and amounts 
ranging from about 50 to 400 mass % salt/feed can be employed, preferably 
50 to 100 mass %. The actual amounts of salt employed will depend on the 
amount of aromatics in the feed, the degree of separation desired, the 
particular characteristics of the salt employed. 
The extraction process can be run on a batch or continuous basis, including 
countercurrent extraction. Procedures such as liquid membrane suspension 
of the salt can also be employed. 
The separation process produces a binary two liquid phase system. The 
upper, lighter phase is typically the raffinate, of reduced aromatics 
content and very low salt content. The lower, heavier phase is the extract 
containing the aromatics-salt clathrate. 
Following physical separation of these two liquid phases one from the other 
by typical techniques such as centrifugation or simple decantation, the 
salts are released from the aromatics-salt clathrate by the addition of a 
polar, protic substitution agent such as water, which breaks the clathrate 
forming a new binary liquid-liquid phase comprising a light-upper phase of 
hydrocarbon and a heavier, lower phase of salt-water. These phases can be 
separated by typical liquid-liquid separation procedures again such as 
centrifugation or decantation. The salt can be recovered from the 
salt-water phase by distillation or flashing to remove the water. The 
recovered salt can then be recycled to use. Alternatively, some 
aromatic-salt clathrates can be declathrated by simply reducing the 
temperature of the aromatic-salt clathrate from the formation temperature 
to a reduced temperature, e.g., by cooling from 50.degree. C. down to 
ambient. As another alternative the araomtic hydrocarbon salt clathrate 
can be heated to recover the hydrocarbon with the salt being recycled. 
The present invention is described and demonstrated in the following 
non-limiting examples.