ー 論文ー●One-step synthesis of ester from alkene
Madoka Furuta
UFO Project

M.C.Kung and H.H.Kung
Northwestern UniversityAbstract
A one-step synthesis of ethylacetate from a feed mixture of ethene, oxygen, and water using a supported Pdand silicotungstic acid catalyst was demonstrated. At about 180℃ and 25% ethene conversion, ethylacetate could
be produced with to 46% selectivity, with 34% acetic acid and ethanol that could be recycled. The catalyst wasbelieved to be bifunctional, with Pd providing the oxidation function and the silicotungstic acid providing theacidic function. And this catalyst system had an activity that could produce isopropylacrylate from a feed mixtureof propene, oxygen, and water.

1 Introduction
C2H5OH + O2 = CH3COOH + H2O

Carboxylic acid esters are used in a wide range of applications.

(2)

They are used, for example, as plasticizers, solvents, surface-active

Finally, ethyl acetate is produced by the esterification of ethanolagents, and flavor and perfume materials. There are many knownwith acetic acid over a catalyst.

methods to produce esters. The most common method is theC2H5OH + CH3COOH = CH3COOC2H5 + H2O

esterification, which is a reaction of alcohol with carboxylic acid1,2）.

(3)

Thus the overall reaction isFor example, ethyl acrylate is synthesized from ethyl alcohol andacrylic acid, and ethyl acetate from ethyl alcohol and acetic acid. An

2C2H4 + O2 = CH3COOC2H5acidic catalyst, which can be a mineral acid, or polymeric material(4)

containing chemically-bound acid groups, such as sulfonatedSuch a one-step process has the advantage of starting with reactants,polystyrene, is commonly used in the esterification. Other methods

which are much less expensive than corresponding alcohols andare also available such as acylation with acryl halides, carboxylicacids, or anhydrides, halides, and nitriles. If the reactions occur

anhydrides or ketenes, carbonylation of alkenes in an alcoholic

selectively, the produced mixture coming out of a reactor consists ofsolution, alcoholysis of nitriles, and acylation of alkenes withdesired products and recyclable intermediates.

1,2)

carboxylic acid . The synthesis of ethyl acetate by gas phase

According to the conceptual reaction scheme described in thisreaction of ethene and acetic acid over a solid acid catalyst waspaper, in order for this one-step synthesis to be successful, a multi-

reported, such as supported heteropoly acid and Amberlyst3).

functional catalyst is required. The catalyst needs to contain a

It is interesting to note that a Pd-M-H 3 PO 4 /SiO 2 catalyst

selective oxidation function for the oxidation of ethanol to acetic(M=V,Mo,W, and Cr) was reported not to produce any ethyl acetate

acid, and an acid function for hydration and esterification. Ideally,

but only acetaldehyde at 150℃ , using a feed containing

the reaction condition would be such that all three reactions occur4)

C2H4/O2/H2O/N2=50/7/30/13 . The oxidation of ethene to acetic acidsimultaneously at about the same rate. For example, highusing a heteropolyacid-Pd/SiO2 catalyst was also reported5).

temperature might be unfavorable because the equilibrium constant

We have recently studied a one-step synthesis of ethyl acetate byof ethene to ethanol in the hydration reaction decreases asreaction of ethene, water and oxygen over a catalyst. Here we reporttemperature rises. In these experiments, the acid function was

the results of this study. A conceptual scheme of the one-stepprovided by a heteropolyacid, and the oxidation function wassynthesis can be accomplished is as follows:

provided by palladium. Such a bifunctional-bicomponent system isadvantageous over a single component system(e.g. heteropolyacid)that requires separate reaction conditions to activate each function 6).

A catalyst induces the hydration of ethene to ethanol
C2H4 + H2O = C2H5OH(1)

2 Experimental

Some of ethanol is then selectively oxidized to acetic acid.

東亞合成研究年報

The catalysts were prepared using a silica support (Davison 62,16TREND 2001 第4号

60/80mesh, 250m2/g) which had been washed with 1 M nitric acid at

ml/min. Reaction products were analyzed by on-line gas

80℃ and deionized water to remove mineral impurities, and thenchromatography using a Parapak Q column. Typically, the reaction

dried and calcined at 520℃ for 6h. Pd was introduced into silica as

was carried out for 4 to 6 h.

Pd chloride (Aldrich) dissolved in 1 M HCl using the incipient

3 Results and Discussion

wetness technique. The impregnated samples were calcined in aflow of O2 in He (2/8 molar ratio) at 350℃ for 2h and then in H2 atTable 1 shows the results using catalysts of different Pd and300℃ for 3h. Silicotungstic acid (H4SiW12O40, Nippon Inorganic

H4SiW12O40(SiW) contents. Each datum represents an average of atColor and Chemical Co., Ltd.) was impregnated onto the Pd/SiO2

least three separate product analyses.

samples by incipient wetness using its aqueous solution, and dried inUnder similar conditions, a 5wt.% Pd/SiO2 catalyst produced acetic

air at 110℃ overnight. All the catalysts were treated at 180℃ inacid with only 0.5% yield and 2.5% CO 2, whereas a 44 wt.%

helium stream (or atomospere) for 1h before reaction. Reactions

SiW/SiO2 sample produced <2% yield acetic acid, 2.5% ethanol, andwere conducted in a 6.3mm i.d. stainless tubular reactor. The reactor<1% acetaldehyde. No ethyl acetate was obtained from the above

pressure was between 200 to 330 kPa, and 5ml of catalyst was used.

two catalysts. The low yield of acetic acid from the Pd/SiO2 catalystThe reactor was heated by an electrical furnace equipped withmakes it unlikely that the function of Pd is to oxidize ethylene totemperature controllers. The flow rates of ethene, oxygen andacetic acid(Eq.(5)), which then reacts with ethene over SiW to form

helium were controlled by mass flow controllers. Liquid water was

ethyl acetate. This low yield cannot account for the yields of ethyl

introduced by a syringe pump and then vaporized in a heated zone.

acetate over the SiW/Pd-SiO2 catalysts.

Typically, the gas flow rates at atmospheric pressure and roomC2H4 + O2 = CH3COOH

temperature were 10(ethene), 2.5(O 2), 2.0(He), and ≦6.0(H 2O)

東亞合成研究年報

17TREND 2001 第4号(5)Better activity of SiW/Pd-SiO2 at higher reaction temperature isappropriate alkenes. For example, when a mixture of C3H6, O2, H2O,

shown in table 2. Although optimal reaction temperature ofand He, in a volume ratio of 10/5.5/1.6/1, was passed over a catalyst

hydration of ethene was around 150℃ over heteropolyacid

bed at 120℃ containing H3PW12O40, Pd and SiO2, at a total pressure4)

catalysts , yield of acetic acid was obviously increased atof 500kPa, 37% conversion of propene was obtained. The carbon

temperatures over 170℃. These data indicate that oxidation activity

selectivity of various products were isopropylacrylate 36% (11.9%of SiW/Pd-SiO2 is enhanced at the temperature.

yield), acrylic acid 13% (4.2% yield), 2-propanol 11% (3.7% yield),

As shown in Table 3, evidently, acetic acid was produced more at

isopropylacetate 7% (2.2% yield), acetone 26% (8.8% yield), andhigher reaction pressure. Higher reaction pressure was advantageous

diisopropylether 7% (2.3% yield).

for desired element reactions, hydration and oxidation of ethene,

4 Conclusion

stoichiometrically (Eq.(4)) .
The data show that, under these conditions, ethyl acetate could be

A one-step synthesis of ethyl acetate from a feed mixture of ethene,

produced with almost 50% selectivity. Very importantly, the total

oxygen, and water using a supported Pd and silicotungstic acidselectivity for the desired product and the intermediates that can becatalyst was reported. At about 180℃, 25% ethene conversion wasrecycled ( ethanol and acetic acid) was as high as 80%. Carbon (≦obtained and ethyl acetate could be produced with as high as 46%20%) was wasted mostly as CO2.

selectivity, together with 34% acetic acid and ethanol that could be

An optimal Pd/SiW ratio appears to be about 1/15 to 1/60 for highrecycled. The catalyst was believed to be bifunctional, with Pd

yields of ethyl acetate. Since the overall yield comes from theproviding oxydation function and silicotungstic acid providing

combination of Eq.(1) to Eq.(3), both catalytic functions (Pd andacidic function.

SiW) are required. Small Pd/SiW ratio is probably a result of higher

Acknowledgements

dispersion of Pd on SiO2 and its higher catalytic activity per unit

Support of this work by Prof. H.H. Kung and Dr. M.C. Kung of

surface area.

Northwestern University is gratefully acknowledged.

Other supports were also tested, including alumina and activatedcarbon. For example, with a carbon-supported catalyst that
contained SiW, Pd, and carbon in a weight ratio of 0.8, 0.05 and 1,

References

an ethene conversion of 25% was obtained, with selectivity for ethyl1) Kirk Othmer Encyclopedia of Chemical Technology, Wiley, Vol.

acetate, acetic acid, and ethanol of 36, 35, and 7%, respectively.

9, 1994.

Thus, we have demonstrated that it is possible to synthesize ethyl2) Ullmann's Encyclopedia of Industrial Chemistry, VCH

acetate from rather inexpensive reactants in a one-step, catalytic

Verlagsgesellschaft mbH, Vol. 9, 1987.

process reaction. The reaction yields only a small amount of3) Y. Murakami, T. Hattori, H. Uchida, Kagaku Kogyo Zasshi, 72,unwanted byproducts. It is quite possible that with further1945(1969).

optimization of catalyst composition and reaction conditions, such astemperature, feed composition, and pressure, can increase the yield

4) Y. Ishii, Catalts Catal. (Japan) 39, 2(1997).

and selectivity for ethyl acetate.

5) T. Suzuki, US Patent 5405996 (1995).
6) T.Okuhara, N. Mizuno, M. Misono, Adv. Catal. 41, 113(1996).

In addition to ethyl acetate, other esters can be produced from

●アルケンを原料としたエステルの一段合成
UFOプロジェクト

古田 円

ノースウエスタン大学

M.C.Kung、 H.H.Kung

Pdとシリコタングステン酸を担持したシリカを触媒として、エチレン、酸素、水を原料とした酢酸エチルの一段合成を試みた。この触媒は、Pdの酸化活性とシリコタングステン酸の強酸性との複合活性により、それぞれエチレンの酸化及び水和、そしてエステル化反応に必要な機能を併せ持っている。反応温度180℃でエチレンの転換率が25％ととなり、その時の酢酸エチルの選択率は46％以上であった。同時に酢酸とエタノールが合わせて34％の選択率で得られ、これらをリサイクルすれば、更なる高収率が期待される。また、プロピレン、酸素、水を原料とした反応から、アクリル酸イソプロピルの生成が確認された。

東亞合成研究年報

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