I
5. K. BHATTACHARYYA and DHARAM VIR Department of Applied Chemistry, Indian Institute of Technology, Kharagpur, India
Synthesis of Methyl and Ethyl Glycolates The three-step method of making ethylene glycol commercially may be reduced to two steps by using catalysts of supported metal halides
BECAUSE
THEY are reducible to ethylene glycol (5, 9 ) , methyl and ethyl glycolates have considerable commercial importance. Except for a few patent claims (5, 3 ) , however, few data on these compounds have been reported. E. I. du Pont de Nemours S: Co. synthesizes under high pressure commercial ethylene glycol from formaldehyde in three steps-Le., synthesis of glycolic acid from formaldehyde, carbon monoxide, and water; esterification of the acid; and then reduction of the ester (7). I n the work reported here, the possibility of combining the first t w o steps has been explored by studying methyl and ethyl glycolate synthesis using as catalysts, nickel, cobalt, and iron iodides. These catalysts are efficient for synthesizing glycolic acid by this method ( 3 , 4 , 72),and also have been used for analogous carboxylic acid syntheses (7, 70).
--__ - 0
METHYL ESTER ETHYL ESTER
NIIz-Si02 0 CoI,-SiO,
24
x Fe12-SiOz
,A
/
Lz2
.’/
----_.
W
t-
v)
W
0 +
I&
I--
z
W
u Lz
If
w
a 2-
2 12 v) [r
w
> z
0
0
9
Experimental T h e high pressure bomb (164- and 342-ml. capacity for the methyl and ethyl ester synthesis, respectively), made of nickel-chromium-molybdenum steel, is similar in design and construction to one previously described ( 2 ) . Before use, it was hydraulically tested to withstand a pressure of 30,000 p.s.i. at room temperature for 24 hours. T h e reactants were dehydrated ethyl alcohol, 99.9% pure, methanol 98.5y0 pure, and paraformaldehyde which assayed 96.0Yo HCHO. Also, carbon
6
3
/
/
I
I 2000
I 4000
I
I
I 8 C 10
6300
REACTION PRESSURE, psi. Figure 1.
Yields of esters increase with reaction pressure VOL. 51, NO. 2
FEBRUARY 1959
139
.
24 0
IL
21
-
18
-
w + cn W
0
X
CoIz-~iO;! feI2-SLO7
I'-t
z
15-
IL
w
a 2G cn
12-
LT W
> z 9-
0
0
6-
3t I
Figure 2.
I
I
I
3
I 2 RESIDENCE PERIOD, HRS.
Yields of esters increase with residence time
monoxide was prepared from sulfuric and commercial formic acid, and then purified by washing with solutions of potassium hydroxide and pyrogallol. The catalysts, reduced nickel, cobalt, iron, and their iodides supported on kieselguhr or silica gel, had a metal support ratio of 50:50 ( 3 ) . A static method was used. After charging the bomb with the catalyst and reactants, the Sunvic regulator which controlled external heating of the bomb was switched on. When the required temperature was reached, pressure, maintained under isothermal conditions, first rose to a maximum and then decreased slightly to a steady value. When the residence period had expired, the products were released, usually at the temperature of the reaction itself, and cooled. The condensable and noncondensable portions were collected separately. T o evaluate the effect of low temperature release, the bomb was sometimes cooled before its contents were released. The liquid product containing the ester, acid, and unreacted alcohol was analyzed by usual methods (77). The acid was estimated by direct titration
140
with a standard solution of sodium hydroxide, using thymolphthalein as an indicator. The ester was determined by increase in acidity after alkaline hydrolysis. The gas consisting of carbon monoxide and dioxide, hydrogen, and hydrocarbons was assayed by standard methods. Hydrocarbons were expressed as methane, even though ethane was certainly present, especially in the synthesis of ethyl glycolate. Except where otherwise indicated, operating conditions are the optimum reaction temperature of 200' C., 3000 p.s.i. initial pressure, 3 hours' residence period, 10-ml. catalyst volume, 5 grams of paraformaldehyde, and 6.5 ml. of alcohol. The reactant gas contained 94.0% carbon monoxide and 6.0% of nitrogen. Discussion As shown in Table I, the activity of reduced metal catalysts was negligible. Nickel, cobalt, or iron iodides caused a remarkable increase in the yields of esters, but yield of glycolic acid was also substantially increased. The order of
INDUSTRIAL AND ENGINEERING CHEMISTRY
activity for the iodide catalysts was nickel > cobalt > iron; this conforms with that for synthesis of glycolic acid from formaldehyde, carbon monoxide, and water ( 3 ) . Silica gel-supported catalysts were more efficicnt than the corresponding kieselguhr-supported catalysts. At 200' C. nickel iodide on silica gel produced better conversion to ethyl glycolate than to methyl glycolate, but for cobalt and iron iodides, the conversions were nearly the same. The use of water instead of alcohols gave yields of glycolic acid higher than those for esters under corresponding conditions. When four reaction bombs of volumes 141, 164, 187, and 342 ml. were used, conversion to methyl glycolate varied in the range 20.0 f 0.5y0 at 200' C., and for ethyl glycolate the range was 23.4 i 0.6'%. Therefore, volume of the reaction bomb did not seem to affect ester yield. With an initial carbon monoxide pressure of 3000 p.s.i. and a residence period of 3 hours, the optimum temperature of reaction was 200' C.' For methyl glycolate with nickel iodide on silica gel, however, the optimum temperature was 180' C. (Table I). Yields of both esters increased with increased reaction pressure (Figure 1). Yields of the acid formed as a by-product in both reactions varied similarly but as before continued to be low. A sesidence period-conversion relationship curve was similar to that for reaction pressureconversion curve, both tending toward a maximum steady value (Figure 2). The samples of formaldehyde employed contained 4% of water, and this probably accounted for the conversion to glycolic acid in both systems, because when more water was added glycolic acid yield increased rapidly and ester yield decreased (Table 11). Thus a sufficiently large water-alcohol ratio might reduce ester yield to nearly zero. This also conforms with previous results for glycolic acid synthesis (72). In second runs, the activity of nickel iodide as a catalyst was substantially less than that in the first runs (Table 111). Similar results were reported for the synthesis of acetic acid from methanol and carbon monoxide (7). However differential thermal analysis indicated that activity could be restored if the catalyst was pretreated with water before re-use. This was verified by experimental results (Table 111). Releasing spent nickel iodide catalysts at a temperature below 95' C. should maintain catalytic activity (7). Experiments on conversions to glycolic acid of formaldehyde, carbon monoxide, and water later proved that the behavior of cobalt iodide and iron iodide catalysts was similar. Iodide catalysts probably behave in
'
METHYL AND ETHYL GLYCOLATE SYNTHESIS Comparative Activity of Catalysts and Effect of Temperature Methyl Glycolate Ethyl Glycolate Reaction % Total C Convxo 5% Total C Conv. to % HCHO Conv. to press., % HCHO Conv. to coz CH4 Ester Acid con CHI P.S.I. Ester Acid Catalyst Activity. Reaction Temp., 200° C.; Reaction Press., 5600 P.S.I.
Table 1.
Temp.,
c.
Catalyst
0.0 0.0
Ni-S co-s Fe-S NiIz-K COIZ-K FeL-K Nih-S CoIz-s FeL-S
0.2 0.0 14.8 13.7 7.4 20.0 20.1 12.2
1.3 4.7 4.0 3.1 8.0 7.6 6.4 8.6 8.5 8.0
0.2 0.3 0.3 0.2 1.9 1.8 1.8 2.1 2.5 2.3
12.1 11.1 6.3 24.0 20.5 11.8
0.3 0.3 0.2 0.3 1.8 1.4 1.3 2.0 1.7 1.5
1.4 4.7 4.7 3.6 9.2 8.8 7.7 9.5 9.2 8.3
0.1 0.2 0.1 0.2 0.3 0.3 0.2 0.5 0.4 0.3
0.5 0.6 0.6
9.7 15.3 19.4 24.0 16.8
1.5 1.8 2.0 2.0 1.8
6.3 7.8 8.6 0.5 10.6
0.3 0.4 0.4 0.5 0.4
0.2 0.4 0.4 0.3 0.5 0.4 0.4 0.6 0.5 0.5
0.0 0.0 0.0 0.0
Effect of Temp., Initial Press., 3000 P.S.I. Nib-S
0.3
140 160 180 200 220
4350 4600 5100 5600 6000
10.0 18.3 25.3 20.0 13.3
1.2 1.8 1.9 2.1 2.0
5.9 7.1 7.6 8.6 9.5
COI2-s
140 160 180 200 220
4300 4500 5000 5600 6000
8.0 12.2 16.8 20.1 17.1
1.2 1.8 2.2 2.5 2.8
6.0 7.0 7.5 8.5 9.2
0.3 0.4 0.4 0.5 0.6
7.6 12.1 16.9 20.5 15.1
1.3 1.5 1.6 1.7 1.8
6.1 7.3 8.3 9.2 10.1
0.3 0.4 0.4 0.4 0.5
FeIz-S
140 160 180 200 220
43 50 4600 5200 5600 6000
7.0 8.7 10.1 12.2 10.4
1.4 1.8 2.0 2.3 2.5
5.4 6.4 7.0 8.0 8.9
0.2 0.3 0.4 0.5 0.5
3.4 5.9 8.6 11.8 8.5
0.8 1.4 1.4 1.5 1.7
5.7 1.3 7.2 8.3 9.5
0.2 0.3 0.3 0.3 0.4
0. T
K = kieselguhr; S = silica.
~
Table II.
Catalyst Ni12-Sb
Water Added, M1.
~
~~~
~
~
Effect of W a t e r and Release Temperatures
Methyl Ethyl Glycolate - Glycolate % ' Total C Conv.to % ' Total C. Conv. to % HCHO Conv. to Ester Acid con CH4 Ester Acid coz CHI Reaction Temp., 200' C.; Reaction Press., 5600 P.S.I." "
Temp.,O O
c.
0.0 0.2 0.5 1.0
3.0
~~
I
Yo HCHO Conv. to
25.3 24.1 22.6 20.5 13.0
1.9 2.6 3.8 7.5 10.7
.
7.6 7.8 8.0 7.9 7.8
0.5 0.6 0.6 0.5 0.6
24.0 22.5 20.7 18.1 12.9
2.0 2.2 2.6 4.9 8.1
9.5 9.4 9.5 9.6 9.6
0.5 0.4 0.4 0.5 0.5
8.5 8.2 8.6 8.3
0.5 0.5 0.6 0.6
20.5 19.3 17.7 15.8 10.5
1.7 1.9 2.5 5.1 7.5
9.2 9.2 9.2 9.2 9.4
0.4 0.4 0.4 0.4 0.5
COI2-s
0.0 0.2 0.5 1.0 3.0
20.1 18.2 17.1 15.7
2.5 2.7 3.4 6.6
FeL-S
0.0 0.2 0.5 1.0 3.0
12.2 8.4 7.7 6.1
2.3 2.6 3.2 3.4
8.0 8.1 7.9 7.9
0.5 0.5 0.4 0.5
...
11.8 10.9 9.6 7.2 5.2
1.5 2.3 3.4 5.1 7.0
8.3 8.4 8.4 8.3 8.2
0.3 0.4 0.4 0.4 0.4
25.3 20.9 24.3 24.1
1.9 1.7 1.8 1.7
7.6 8.2 7.6 7.7
0.5 0.6 0.3 0.4
24.0 16.4 22.6 21.9
2.0 1.6 1.8 1.7
9.5 9.8 9.2 9.3
0.5 0.4 0.3 0.3
20.1 12.1 18.9 18.0
2.5 1.8 2.0 1.8
8.5 9.0 7.6 7.7
0.5 0.5 0.3 0.4
20.5 15.3 20.2 19.1
1.7 1.4 1.3 1.3
9.2 9.5 8.9 9.2
0.4 0.4 0.3 0.3
12.2 6.0 10.7 10.0
2.3 2.0 1.8 1.7
8.0 8.8 8.1 8.3
0.5 0.5 0.3 0.4
11.8 6.8 11.3 10.3
1.5 1.2 1.4 1.3
8.3 8.5 8.3 8.5
0.3 0.2 0.2 0.2
NiI2-S
...
...
2005 80
cor*-s
200 80
FeIz-S
200 80
Release.
e . .
...
...
...
...
For methyl ester, reaction temp. is 180' C.; reaction press., 5200 p.8.i.
VOL. 51, NO. 2
FEBRUARY 1959
141
this manner because the iodides form complexes with carbon monoxide and water a t elevated temperatures and pressures. These complexes, unstable at high temperatures at atmospheric pressure, probably act as catalysts during the reaction. However when the products are released at temperatures higher than 95’ C., the pressure release decomposes the complexes. At atmospheric pressure, the decomposition does not take place below this temperature. After the gas pressure has been removed from the system a t a temperature above 95’ C., catalytic activity is maintained only if the catalyst has been pretreated with water-e.g., in the synthesis of the esters of glycolic acid from formaldehyde, carbon monoxide, and alcohols, or of acetic acid from methanol and carbon monoxideor if water is utilized as a reactant. Thus, in the synthesis of glycolic acid from formaldehyde, carbon monoxide. and water, no pretreatment with water was needed. In five runs, the activity of the iodide catalysts did not decrease significantly. These conclusions conform with previous studies (7, 73). In the work reported here, low temperature release arrested the fall in catalytic activity on re-use (Table 11). Initial conversions to esters were somewhat less a t a release temperature of
Table 111.
Reactivation of Spent Catalyst (NiI2-silica)
Water, ReactiCatalyst Fresh Spent vated Ethyl Glycolate: 200° C., 5600 P.S.I. HCHO to ester, % 24.0 16.4 22.8 HCHOtoacid, % ’ 2.0 1.6 1.6 Total carbon to con, % 9.5 9.8 9.7 Total carbon to CH4, % 0.5 0.4 0.4 Methyl Glycolate: 180’ C.; 5200 HCHO to ester, % 25.3 20.9 HCHO toacid, 1.9 1.7 Total carbon to co2, % 7.6 8.2 Total carbon to CH4, % 0.5 0.6
P.S.I. 24.4 1.7 8.2
c.
3000 3000 3000 1000 2000 3000
4850 5550 6000 1600 3400 5550
0.9 1.4 1.7 2.1 1.7 1.4
0.2 0.3 0.4 0.6 0.5 0.3
150 200 230 200 200 200
3000 3000 3000 1000 2000 3000
4800 5550 6000 1600 3450 5550
0.9 1.3 1.6 2.0 1.7 1.3
0.2
180’ C., but with this technique average conversions were higher. I n ethyl glycolate synthesis, carbon monoxide, carbon dioxide, methane. ethanol, formaldehyde, glycolic acid, and hydrogen were formed by hydrolysis into the alcohol and the acid; other products were possibly formed by the decomposition of these primary products. Higher temperatures increased de-
150 200 230 200 200 200
3000 3000 3000 1000 2000 3000
4800 ,5600 6000 1650 3400 5600
0.6
150 200 230 200 200 200
3000
4850 5600 6000 1650 3450 5600
0.2 0.3
0.1 0.2 0.2 0.3 0.3 0.2
5.9 7.2 8.4 10.2 8.7 7.2
2.7 3.3 4.0 4.9 4.1 3.3
5.4 6.6 8.2 8.9 8.2 6.6
0.802 0.754 0.723 0.821 0.785 0.723
5.4 7.0 8.3 8.7 7.0
2.6 3.1 3.6 4.5 3.8 3.1
5.2 6.6 8.1 9.0 8.3 8.1
0.781 0.753 0.710 0.800 0.769 0.753
5.2 6.8 8.3 10.1 8.8 6.8
2.1 2.5 2.8 3.6 3.0 2.5
5.0 6.0 7.7 8.7 7.8 6.0
0.768 0.746 0.701 0.804 0.768 0.746
4.5 5.7 6.9 8.8 7.2 5.7
1.2 1.5 1.9 2.7
4.0 5.0 6.5 6.9 6.6 5.0
0.756 0.732 0.701 0.789 0.757 0.732
CoIrSilica 0.1 0.1 0.2 0.3 0.2 0.1
0.3
0.3 0.6 0.4
0.3
10.0
FeIn-Silica 1.0
1.3 1.7 1.4 1.0
0.1 0.2 0.3 0.6 0.4 0.2
0.0 0.1
0.1 0.2 0.2 0.1
No Catalyst
O
3000 3000 1000 2000 3000
0.3
0.6 0.4 0.3
0.0
0.1 0.1 0.5 0.3 0.1
0.0 0.0 0.1 0.3 0.2 0.0
Total alcohol present estimated as ethyl alcohol.
142
+ CO + CHaOH e
HCHO
+ C O + H?O s
INPUSTRIAL AND ENGINEERING CHEMISTRY
2.1
1.5
Metal-support ratio, 60:40.
CH?OHi‘OOCH1
CHZOHCOOH HCHO
CHZOHCOOH
+
CHiOH G CH20HCOOCH,
+ H.0
+ C O + CzHbOH e
CHzOHCOOCzH j
HCHO
Decomposition of Ethyl Glycolate under Nitrogen Pressure (Catalyst and ester vol., 5 ml. each; residence time, 2 hr.) React. Press., P.S.I. %CH20HCOOC2HsConv. to HJCO CO Con CHI CnHaOH“ HCHO CHnOHCOOH Ratio Init. Max. Nib-Silicab
150 200 230 200 200 200
HCHO
0.5
Table IV.
Temp.,
composition, and all the products were formed in larger amounts. The hydrogen-carbon monoxide ratio, however, decreased although absolute amount of hydrogen formed increased. When pressure was increased the opposite trend occurred, except that the hydrogen carbon monoxide ratio also decreased. Some or all of the following reactions may occur in the reaction systems:
+ C O + HzO e +
CHZOHCOOH
CHrOHCOOH CzIljOH 2 CHzOHCOOCr H j
+ HzO
Side reactions:
+c HCHO S C O + H ? COP + H f CO + H z O CO + 2H2 CHaOH HCHO + Hz e CHaOH C O + 3Hz e CHI + HzO 2CO
coz
F?
Glycolic acid and alcohol, produced in some of the reactions, probably further decomposed into some or all of the decomposition products. literature Cited (1) Bhattacharyya, S. K., Sourirajan, S., J . Appl. Chem. (London) 6, 442 (1956). (2) Bhattacharyya, S. K., Sourirajan, S., J . Sri. Znd. Research (India) 13B, 609
(1954). (3) Bhattacharyya, S. K., Vir, D., “Advances in Catalysis,” vol. IX, pp. 62535, Academic Press, New York, 1957. (4) Bhattacharyya, S. K., Vir, D., Proc. Intern. Congress on Catalysis, Philadelphia, 1956. (5) Cockerill, R. F., U. S. Patent 2,258,444 (1941). (6) E. I. du Pont de Nemours & Co., Brit. Patent 534,197 (1941). ( 7 ) Faith, W. L., Keyes, D. B., Clark, R. L., “Industrial Chemicals,” Wiley, New York, 1950. (8) Loder, D. J., U. S. Patent 2,211,625 (1940). (9) Zbid., 2,285,448 (1942). (10) Sen Gupta, S. P., Bhattacharyya, S . K., Bull. Natl. Znst. Sci. (India), Proc. of Symposium on Contact Catalysis, 1956. (11) Siggia, S., “Quantitative Organic Analysis via Functional Groups,” Wiley, New York, 1949. (12) Vir, D., Bhattacharyya, S. K., Bull. Natl. Inst. Sci. (India), Proc. of Symposium on Contact Catalysis, 1956. (13) Vir, D., Bhattacharyya, S. K., unpublished data.
RECEIVED for review January 29, 1958 ACCEPTED May 24, 1958
