FIELD OF THE INVENTION
The present invention relates to an improved process for the production of
gamma-butyrolactone (GBL). Particularly, the present invention relates to a
process for preparing gamma-butyrolactone by the liquid phase oxidation of
tetrahydrofuran (THF) with hydrogen peroxide in the presence of catalytic
amount of a selenium (IV) oxide in the temperature range ambient to 50 °C.
BACK-GROUND OF THE PRESENT INVENTION
gamma-Butyrolactone is a highly useful commodity of great industrial interest
which find extensive applications, for example, as a dye solvent, as a spinning
solvent for synthetic fibers, and as intermediate for the synthesis of solvents like
pyrrolidone and N-methylpyrrolidone, which have lower environmental impact
than chlorinated ones. The first GBL synthesis was appeared in 1940's by Reppas,
form acetylene and formaldehyde to give 1 ,4-butanediol (BOO) and then GBL
by dehydrogenation. However, this process is associated with the draw-backs of
the fluctuating prices of the raw materials as well as hazard and the
environmental impact of the use of both acetylene and formaldehyde. The
commercial process for the synthesis of GBL involves the liquid phase
hydrogenation of maleic acid/anhydride or succinic acid/anhydride with
hydrogen over a metallic catalyst. The major limitations of the process are
limited product yield, deactivation of the catalyst due to the coke formation
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and higher reaction temperature and pressure. Subsequently, a number of
catalysts have been developed for the hydrogenation of maleic
acid/anhydride to GBL. However, none of the catalyst is reached great
industrial importance In practice due to the deactivation of the catalyst through
tar and coke formation within a relatively short time. Many patents describe the
vapor phase hydrogenation of maleic anhydride or its esters, but mainly for the
production of 1 ,4-butanediol; for instance WO 86/03189 describe the vapor
phase hydrogenation of diethyl maleate to BDO. But most of the processes
suffered from the drawback of the lower yield and formation of by-products.
Another approach for the synthesis of GBL involves the cyclization of 1 ,4-
butanediol, which have been known for a long time. K. Weissermel, H.-J. Arpe,
lndustrielle organische Chemie, VCH Verlagsgesellschaft, D 69451 Weinheim,
1994, page 112, describes the dehydrocyclization of 1 ,4-butanediol over copper
catalysts at from 200-250 °C. A disadvantage of this process is that the 1 ,4-
butanediol used has to be purified before use. The purification of 1 ,4-butandiol is
usually carried out by means of a complicated multistage distillation in which
undesired low- and/or high-boiling constituents, including water, are removed.
This water-free pure butanediol is subsequently cyclized to form GBL, with
undesirable by-products being formed. For this reason, the cooled GBL again
has to be purified by distillation after the reaction. It is thus necessary to carry out
two comparable, complicated purification and separation steps.
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Another Industrial process for the GBL synthesis involves the oxidation of THF with
brominated oxidizing agents. Subsequently, a process for the production of GBL
involves the oxidation of tetrahydrofuran, by ruthenium tetraoxide at 0 °C
(Synth.Commun.; EN; 1 0; 3; 1980; 205-212). The expensive nature and lower yield
are the main drawbacks of this process. Further, a number of oxidizing agents
involving peroxo-phosphoric acid (J. Org. Chem. 1980, 45(7), 1320-1322),
brominated agents (Buii.Chem.Soc. Jpn. 1986, 3, 747-750), Zinc dichromate
trihydrate (Microgram, 2000, XXXIII(11 ), 321-324)and calcium hypochlorite (let.
Lett. 1982, 23(1), 35-38) have been used in stoichiometric amounts for the
oxidation of THF to GBL. The major drawback of these methods is the production
of huge amounts of metallic wastes, which is very difficult to dispose of and
therefore is not desirable from environmental viewpoints. Owing to the growing
environmental consideration, the use of environmentally benign oxidants such
as hydrogen peroxide is gaining considerable interest in recent years. A recent
literature report describes the oxidation of THF to GBL by using TS-1 as catalyst
and hydrogen peroxide as oxidant (J. Mol. Catal. 2011, 338, 105-110). However,
the poor selectivity and lower product yield are the notable drawbacks of this
method. In references lnorg. Chem. Comm. 2006, 9, 628-633, oxidation of THF to
GBL has been described by using zeolite Y-encapsulated hexaaza macrocyclic
complex of copper (II) as catalyst and hydrogen peroxide as oxidant. All the the
reactions were carried out under reflux and provided 100 % conversion of THF
with the selectivity ( 1 7.3 %) for GBL synthesis. The reported process revealed the
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advantages of heterogeneous catalyst such as facile recovery and recycling of
the catalyst. However with each subsequent run the efficiency of the catalyst
was found to be decreased, probably due to the leaching of the active metal
species during the reaction. Furthermore, authors have shown the oxidation of
THF by using corresponding homogeneous 16-membered hexaaza macrocyclic
copper{ll) {CI04)2 as catalyst and hydrogen peroxide as oxidant under reflux
condition. The conversion of the THF was achieved l 00 % with selectivity 100 %
for the gamma-butyrolactone. However the synthesis of reported copper
complex was a very tedious multi-step synthesis involving the use of several
expensive chemicals. Therefore the reported method might be not suitable for
the large scale synthesis of the said compound. Furthermore high reaction
temperature and difficult synthesis of macrocyclic copper complex limited the
utility of the process.
Thus, the drawbacks of the hitherto known processes as mentioned above
evident the necessity for development of an improved process for the
production of GBL.
OBJECTIVE OF THE PRESENT INVESTIGATION
The main object of the present invention is to provide an improved process for
the selective synthesis of GBL by the liquid phase oxidation of TH F which obviates
the drawbacks of hitherto known methods as detailed above.
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Another object of the present invention is to provide a process for the liquid
phase oxidation of THF to GBL by using hydrogen peroxide as environmentally
benign oxidant.
Yet another objective of the present invention is to provide a process for the
liquid phase oxidation of THF to GBL with hydrogen peroxide by using selenium
compound particularly selenium (IV) oxide as catalyst.
Yet another objective of the present invention is to provide a process for the
production of GBL via oxidation of THF at room temperature (35 °C) and
atmospheric pressure.
SUMMARY OF THE INVENTION
Accordingly the present invention relates to an improved process for the
production of GBL (gamma-butyrolactone) by the liquid phase oxidation of
tetrahydrofuran (THF) in the presence of a selenium compound as a catalyst,
wherein the said process comprises the steps of;
(a) adding cyclic ether and hydrogen peroxide in a molar ratio of cyclic
ether to hydrogen peroxide in the range 1 :1 to 1 :1 0 in the presence of a
selenium compound at a temperature in the range of 20-1 00 oc at
atmospheric pressure for a period 5-50 hrs in a batch or continuous
manner,
(b) removing catalyst from the reaction mixture as obtained in step (a) by
filtarton followed by fractional distillation of the filtrate to obtain GBL.
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In an embodiment of the present invention the cyclic ether used in step (a) is
selected from the group consisting of tetrahydrofuran, tetrahydropyran, 2-
methyl tetrahydrofuran, 2-methyl tetrahydropyran, and dioxane.
In one embodiment of the present invention the hydrogen peroxide used in step
(a) is selected from the group consisting of 5-60 wt% aqueous H202. urea-H202
adduct, H202-alkali metal borate adduct and H202-alkali carbonate adduct.
In another embodiment of the present invention a selenium compound used in
step (a) having a valence of +4 is selected from the group consisting of selenium
dioxide, selenious acid, alkali metal salts of selenious acid, selenium halides and
selenium oxyhalides.
In yet another embodiment of the present invention the mole ratio of cyclic
ether to hydrogen peroxide used in step (a) is preferably in the range of 1:1 to
1 :6.
In yet another embodiment of the present invention the mole ratio of selenium
catalyst to cyclic ether is in the range of 2-5 mol%.
In still another embodiment of the present invention reaction time is in the range
of preferably 1 0-30 hrs.
In still another embodiment of the present invention the conversion of THF is in
the range 20-90 %.
In still another embodiment of the present invention the selectivity of GBL is 1 00
% without any side product.
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DETAILED DESCRIPTION OF THE INVESTIGATION
In the present invention, 30 I 50 % aqueous solution of hydrogen peroxide ( 1 0 to
60 mmol) was added to the stirred mixture of THF and selenium compound (2 to
5 mol %) contained in a 1 00 ml round bottomed flask at ambient temperature
(20-50 °C) and atmospheric pressure. The resulting reaction mixture was
continuously stirred at the same temperature for 5-50 h followed by the removal
of catalyst by passing the reaction mixture through a small silica gel column. The
reaction mixture thus obtained was analyzed by high resolution GCMSD El,
quadrapole mass analyzer, EM detector. The conversion of THF as determined
by GCMSD remained 1 0-90 %. The product selectivity remained 1 00 % without
any evidence for the formation of any by-product.
Following are the examples given to further illustrate the invention and should
not be construed to limit the scope of the present invention.
EXAMPLE 1
In to a 100 ml round-bottomed double necked flask containing, THF (0.02 mol,
l.44g), 50% aq. hydrogen peroxide (0.02 mol, l.36g) and Se02 ( 1 0 mol%, 0.22g).
The reaction was continued with vigorous stirring at 35 oc for 15h. The reaction
mixture was then filtered through a Buckner funnel, passed through a short
column of silica gel to remove the catalyst and concentrated under reduced
pressure. The resulting residue was analyzed by high resolution GCMSD, El,
quadrapole mass analyzer, EM detector to determine the selectivity for the
formation of GBL. The conversion of THF to GBL was determined on the basis of
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the weight of the residue left after evaporation. Based on these analyses, the
conversion of THF was found to be 25.4 % with the 100 % selectivity for the
formation of GBL.
EXAMPLE 2
In to a 100 ml round-bottomed double necked flask containing, THF (0.02 mol,
1.44g), 50% aq. hydrogen peroxide (0.04 mol, 2.72g) and Se02 (10mol%, 0.22g).
The reaction was continued with vigorous stirring at 35 oc for 15h. The reaction
mixture was then filtered through a Buckner funnel, passed through a short
column of silica gel to remove the catalyst and concentrated under reduced
pressure. The resulting residue was analyzed by high resolution GCMSD, El,
quadrapole mass analyzer, EM detector. The conversion of THF to GBL was
determined on the basis of the weight of the residue left after evaporation and
selectivity for GBL formation was determined by GC. Based on these analyses,
the conversion of TH F was found to be 7 5 % with the 1 00 % selectivity for the
formation of GBL.
EXAMPLE 3
In to a 100 ml round-bottomed double necked flask containing, THF (0.02 mol,
1.44g), 50% aq. hydrogen peroxide (0.06 mol, 4.08g) and Se02 ( 15mol%, 0.22g).
The reaction was continued with vigorous stirring at 35 oc for 15h. The reaction
mixture was then filtered through a Buckner funnel, passed through a short
column of silica gel to remove the catalyst and concentrated under reduced
pressure. The resulting residue was analyzed by high resolution GCMSD, El,
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quadrapole mass analyzer, EM detector. The conversion of THF to GBL was
determined on the basis of the weight of the residue left after evaporation and
selectivity for GBL formation was determined by GC. Based on these analyses,
the conversion of THF was found to be 88 % with the 100 % selectivity for the
formation of GBL.
EXAMPLE 4
In to a 100 ml round-bottomed double necked flask containing, THF (0.04 mol,
2.88g), 50% aq. hydrogen peroxide (0.02 mol, 1.36g) and Se02 (10mol%, 0.22g).
The reaction was continued with vigorous stirring at 35 oc for 15h. The reaction
mixture was then filtered through a Buckner funnel, passed through a short
column of silica gel to remove the catalyst and concentrated under reduced
pressure. The resulting residue was analyzed by high resolution GCMSD, El,
quadrapole mass analyzer, EM detector. The conversion of THF to GBL was
determined on the basis of the weight of the residue left after evaporation and
selectivity for GBL formation was determined by GC. Based on these analyses,
the conversion of THF was found to be 28 % with the 100 % selectivity for the
formation of GBL.
EXAMPLE 5
In to a 100 ml round-bottomed double necked flask containing, THF (0.02 mol,
1.44g), 50% aq. hydrogen peroxide (0.06 mol, 4.08g) and Se02 ( 1 Omol%, 0.22g).
The reaction was continued with vigorous stirring at 50 oc for 15h. The reaction
mixture was then filtered through a Buckner funnel, passed through a short
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column of silica gel to remove the catalyst and concentrated under reduced
pressure. The resulting residue was analyzed by high resolution GCMSD, El,
quadrapole mass analyzer, EM detector. The conversion of THF to GBL was
determined on the basis of the weight of the residue left after evaporation and
selectivity for GBL formation was determined by GC. Based on these analyses,
the conversion of TH F was found to be 7 5 % with the 1 00 % selectivity for the
formation of GBL.
EXAMPLE 6
In to a 100 ml round-bottomed double necked flask containing, THF (0.02 mol,
1 .44g), 50% aq. hydrogen peroxide (0.02 mol, 1 .36g) and Se02 (20 mol%, 0.44g).
The reaction was continued with vigorous stirring at 35 oc for 15h. The reaction
mixture was then filtered through a Buckner funnel, passed through a short
column of silica gel to remove the catalyst and concentrated under reduced
pressure. The resulting residue was analyzed by high resolution GCMSD, El,
quadrapole mass analyzer, EM detector. The conversion of THF to GBL was
determined on the basis of the weight of the residue left after evaporation and
selectivity for GBL formation was determined by GC. Based on these analyses,
the conversion of THF was found to be 35 % with the 100 % selectivity for the
formation of GBL.
EXAMPLE 7
In to a 100 ml round-bottomed double necked flask containing, THF (0.01 mol,
0.72g), sodium percarbonate (0.005 mol, 1.57 g), Se02 ( 1 0 mol%, 0.22g) and
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dichloromethane (5 ml). The reaction mixture was vigorous stirred at 25 °C for
15h. The reaction mixture was then filtered through a Buckner funnel, passed
through a short column of silica gel to remove the catalyst, sodium salt and
concentrated under reduced pressure. The resulting residue was analyzed by
high resolution GCMSD, El, quadrapole mass analyzer, EM detector. The
conversion of TH F to GBL was determined on the basis of the weight of the
residue left after evaporation and selectivity for GBL formation was determined
by GC. Based on these analyses, the conversion of THF was found to be 20%
with the 1 00 % selectivity for the formation of GBL.
EXAMPLE 8
In to a 100 ml round-bottomed double necked flask containing, THF (0.02 mol,
1.44g), TBHP (70 wt %solution, 0.04 mol) and Se02 ( 10 mol%, 0.22g). The reaction
mixture was vigorous stirred at 35 oc for 15h. The reaction mixture was then
filtered through a Buckner funnel, passed through a short column of silica gel to
remove the catalyst, sodium salt and concentrated under reduced pressure.
The resulting residue was analyzed by high resolution GCMSD, El, quadrapole
mass analyzer, EM detector. The conversion of THF to GBL was determined on
the basis of the weight of the residue left after evaporation and selectivity for
GBL formation was determined by GC. Based on these analyses, the conversion
of THF was found to be 20% with the 80% selectivity for the formation of GBL.
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Advantages of the present invention
• The present process is uniformly applicable for a wide variety of cyclic
ethers such as 2-methyl tetrahydrofuran, tetrahydropyran, 2-methyl
tetrahydropyran, dioxane etc,
• The present process involves the use of environmentally benign oxidant
under mild reaction conditions.
• The present process does not require the pre-purification of the THF prior
to the reaction and avoids the formation of undesirable by-products.
• The present process provides higher conversion of THF with excellent
selectivity for the GBL synthesis.

We claim:
1. An improved process for the production of GBL (gamnna-butyrolactone) by
the liquid phase oxidation of tetrahydrofuran (THF) in the presence of a
seleniunn compound as a catalyst, wherein the said process comprises the
steps of;
a) adding cyclic ether and hydrogen peroxide in a molar ratio of cyclic
ether to hydrogen peroxide in the range 1:1 to 1:10 in the presence of a
selenium compound at a temperature in the range of 20-100 °C at
atmospheric pressure for a period 5-50 hrs in a batch or continuous
manner,
b) removing catalyst from the reaction mixture as obtained in step (a) by
filtration followed by fractional distillation of the filtrate to obtain GBL.
2. An improved process as claimed in claim 1, wherein the cyclic ether used in
step (a) is selected from the group consisting of tetrahydrofuran,
tetrahydropyran, 2-methyl tetrahydrofuran, 2-methyl tetrahydropyran, and
dioxane.
3. An improved process as claimed in claim 1, wherein the hydrogen peroxide
used in step (a) is selected from the group consisting of 5-60 wt % aqueous
H2O2, urea-H202 adduct, H202-alkali metal borate adduct and H202-alkali
carbonate adduct.
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4. An improved process as claimed in claim 1, wherein a selenium compound
used in step (a) having a valence of +4 is selected from the group consisting
of selenium dioxide, selenious acid, alkali metal salts of selenious acid,
selenium halides and selenium oxyhalides.
5. An improved process as claimed in claim 1, wherein the mole ratio of cyclic
ether to hydrogen peroxide used in step (a) is preferably in the range of 1:1
to 1:6.
6. An improved process as claimed in claim 1, wherein the mole ratio of
selenium catalyst to cyclic ether is in the range of 2-5 mol%.
7. An improved process as claimed in claim 1, wherein reaction time is in the
range of preferably 10-30 hrs.
8. An improved process as claimed in claim 1, wherein the conversion of THF is
in the range 20-90 %.
9. An improved process as claimed in claim 1, wherein the selectivity of GBL is
100 % without any side product.