Organic compounds -- part of the class 532-570 series – Organic compounds – Oxygen containing
Reexamination Certificate
2001-04-30
2003-09-16
Keys, Rosalynd (Department: 1621)
Organic compounds -- part of the class 532-570 series
Organic compounds
Oxygen containing
C568S678000, C568S679000
Reexamination Certificate
active
06620975
ABSTRACT:
The present invention relates to a process for making butyl ethers of glycols by hydrogenation of the corresponding butenyl ethers. These can be made by reacting butadiene with a glycol in the presence of a Bronsted or a Lewis acid catalyst.
n-Butyl glycol ethers are valuable chemical commodities. Hitherto such glycol ethers have been produced by the reaction of n-butanol with an olefin oxide such as ethylene oxide. However, the selectivity of such a process is limited by the formation of a significant amounts of unwanted by-products such as diglycol- and triglycol ethers. The presence of these by-products adds complexity to the separation of the desired n-butyl mono glycol ethers. The loss of selectivity and the resultant complexity of separation can adversely affect the process economics.
It is also known that butadiene can be reacted with an alcohol to form a mixture of isomeric unsaturated ethers (e.g. DE2550902, U.S. Pat. No. 2,922,822, U.S. Pat. No. 4,843,180, EP0025240 and DE19637895).
U.S. Pat. No. 2,922,822, for example, discloses a method for making unsaturated ethers by reacting butadiene with an alcohol, in the presence of an active acid catalyst, e.g. a strongly acidic ion-exchange resin. The alcohol employed is preferably, a primary aliphatic monohydric alcohol. For example, when methanol is employed, the reaction produces two mono methyl ether isomers, which are separable by distillation. The patent recites that if one of these isomers is recycled to give an equilibrium mixture with the other and again separated, it is possible to produce predominantly one or the other isomer (col 2, lines 53 to 58).
More recently, U.S. Pat. No. 5,705,707 describes an application of this addition chemistry for making butyraldehyde and n-butanol. Butadiene is reacted with an alcohol in the presence of an acidic catalyst to form a mixture of isomeric unsaturated ethers. Thus the reaction of an alcohol with butadiene yields a mixture of isomeric adducts of formulae (a) and (b) as shown below:
CH
3
.CH═CH.CH
2
.OR (a)
CH
2
═CHCH(OR).CH
3
(b)
Under acidic conditions, compound (b) (3-alkoxybut-1-ene, also known as sec-butenyl ether) is in equilibrium with compound (a) (1-alkoxybut-2-ene, also known as n-butenyl ether or crotyl ether). For the production of n-butyraldehyde (a) is further isomerised by a transition metal catalyst to a vinyl ether compound (c) of the formula:
CH
3
—CH
2
—CH═CH.OR (c)
Compound (c) is then converted to the butyraldehyde in the liquid phase in the presence of a catalyst by hydrolysis. Hydrogenation of butyraldehyde results in the formation of butanol.
DE19637895(equivalent WO 98/12164) describes a process for preparing n-butyl alkyl ethers by I) reacting butadiene with a glycol to give a mixture of n-butenyl ether and secondary butenyl ether, II) separating the ether adducts produced, III) isomerising the secondary butenyl ether into the n-butenyl ether, and IV) hydrogenating the n-butenyl ether produced. The isomerisation step (III) maybe carried out in the same process stage as the initial reaction between the butadiene and the glycol (step I). Alternatively, the secondary butenyl ether adduct separated in step II may be isomerised in a separate isomerisation stage by contacting the adduct with an isomerisation catalyst. This reaction produces a mixture of the n-butenyl and secondary butenyl adducts. The n-butenyl adduct produced is isolated by fractional distillation and hydrogenated into the desired product.
We have now found that we can improve the productivity and selectivity of the butyl glycol ether production process by A) using a modified catalyst to catalyse the addition of butadiene to a saturated aliphatic glycol, and/or B) converting any unwanted ether adduct into the starting butadiene and glycol in a separate reaction zone.
Accordingly, a first aspect of the present invention provides a process for the production of a butyl glycol ether which comprises:
i. forming a mixture of n-butenyl glycol ether and secondary butenyl glycol ether by reacting butadiene with a saturated aliphatic glycol in the presence of a heterogeneous catalyst which is modified by the addition of at least one counterion selected from the group consisting of: an alkyl pyridinium, quaternary ammonium, quaternary arsonium and quaternary phosphonium;
ii. separating the n-butenyl ether and secondary butenyl glycol ether formed in step i), and
iii. hydrogenating the n-butenyl ether separated in step ii) in the presence of a catalyst to the corresponding n-butyl ether.
Suitable counterions for the present invention are described in, for example, U.S. Pat. No. 4,450,287, U.S. Pat. No. 4,450,288 and U.S. Pat. No. 4,450,289. For instance, suitable pyridinium counterions have the formula C
5
H
5
N
+
R, wherein R is a hydrocarbyl (e.g. an alkyl) having 1 to 30 carbon atoms, preferably more than 5 carbon atoms. Most preferably, the alkyl group is a straight chain alkyl group. One or more of the 5H's on the pyridinium ring may be substituted with an alkyl group, for example, a methyl or ethyl group.
Suitable quaternary ammonium counterions have the formula NR
1
R
2
R
3
R4, where each of R
1
, R
2
, R
3
R
4
is a hydrocarbyl group having 1 to 30 carbon atoms. R
1
, R
2
, R
3
R
4
may be the same or different. Preferably the sum of the total number of carbon atoms is more than 15. Specific examples include:
N
+
[(C
4
H
9
)]
4
, N
+
(CH
3
)
3
(C
16
H
33
), N
+
(C
12
H
25
)(CH
3
)
3
.
Suitable quaternary phosphonium counterions have the formula PR
1
R
2
R
3
R
4
, where each of R
1
, R
2
, R
3
R
4
is a hydrocarbyl group having 1 to 30 carbon atoms. Preferably, the sum of the number of carbon atoms in the phosphonium counterion is greater than 15. R
1
, R
2
, R
3
R
4
may be the same or different. Specific examples of such a quaternary phosphonium counterion include: P
+
(CH
3
)
3
(C
16
H
33
), tetraphenyl phosphonium, and methyl triphenyl phosphonium ions.
Quaternary ammonium or quaternary phosphonium substituted ferrocene may also be employed as a counterion. Such counterions have the general formula:
where X is a quaternary ammonium or quaternary phosphonium cation.
Specific examples of such counterions include:
Such counterions are employed to modify heterogeneous catalysts. Suitable heterogeneous catalysts include sulphonic acid substituted polymers such as strong acid ion-exchange resins. Examples of such catalysts include sulphonic acid functionalised polymers of macrorecticular and gel type (e.g. ion exchange resins such as Amberlyst 15H®, Amberlyst IR120®, Amberjet 1500H®, Nafion®), phosphoric acid fuinctionalised polymers, supported heteropolyacids of tungsten or molybdenum and acidic oxides (such as HY zeolites). To modify these catalysts, the quaternary cations are ion exchanged. The starting salts may contain as counter anions halides, sulphates or carboxylates. The proportion of acid sites exchanged by these bulky counterions may be 1-40%, preferably 1-10%.
One advantage of using a heterogeneous catalysts is that it allows reaction products to be separated relatively easily from the reaction mixture. The heterogeneous catalyst phase can be liquid (e.g. liquid acidic polymers and partially solvated polymers) or a solid (e.g. HY zeolites, strong acid macrorecticular and gel type ion-exchange resins and heteropolyacids of tungsten or molybdenum which have been ion-exchanged and/or supported on a carrier material).
The secondary butenyl glycol ether (3-alkoxybut-1-ene) separated from the mixture of butenyl ethers may be recycled back to step i). This allows isomerisation to be suitably combined with the initial addition reaction stage.
In an alternative embodiment, the secondary butenyl glycol ether separated from the mixture of butenyl ethers may be catalytically isomerised to the n-butenyl glycol ether in a separate reaction step. An acid catalyst may be employed to catalyse this isomerisation. Suitable catalysts include Bronsted acids which are non-oxidising; complexes of Group Ib,
BP Chemicals Limited
Keys Rosalynd
Nixon & Vanderhye
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