University of Central Florida STARS

Retrospective Theses and Dissertations

1987

Hydration of Propylene to Isopropanol

Nehemiah Diala University of Central Florida

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STARS Citation Diala, Nehemiah, "Hydration of Propylene to Isopropanol" (1987). Retrospective Theses and Dissertations. 5041. https://stars.library.ucf.edu/rtd/5041 HYDRATION OF PROPYLENE TO ISOPROPANOL

BY Nehemiah Diala B.S., Rust College, 1983

Research Report Submitted in partial fulfillment of the requirements for the Master of Science degree in Industrial Chemistry in the Graduate Studies Program of the College of Arts and Sciences University of Central Florida Orlando, Florida

Spring Term 1987 ABSTRACT

The hydration of propylene to isopropanol was investigated. The first part of this study concerned the direct hydration reaction in various liquid phase systems in the presence of sulfuric acid or p-toluenesulfonic acid. The second part involved a two-stage process in which propylene was contacted with excess acetic acid to form isopropyl acetate; the ester was then hydrolyzed to isopropyl and acetic acid. ACKNOWLEDGEMENTS

I would like to express my appreciation to Dr. Guy Mattson for his excellent contributions. I would also like to express my gratitude to Imo State Government of Nigeria and to my senior brother, Mr. Samuel Diala, for their financial assistance during my undergraduate and graduate studies. Finally, I would like to thank the Department of Chemistry at the University of Central Florida for providing me with all the materials that were used in this study.

i i i TABLE OF CONTENTS

ACKNOWLEDGEMENTS i i i TABLE OF CONTENTS iv LIST OF TABLES v LIST OF FIGURES vi

INTRODUCTION 1 Present technology 1

Reaction mechanism 5

Thermodynamic consideration 5

Kinetic Conversion 9

EXPERIMENTAL 12 Direct hydration 12 Indirect hydration-catalyst screening 14 Indirect hydration-isopropyl acetate formation 17 Indirect hydration-hydrolysis reaction 17

Analytical methods .•...... ••• 20

DISCUSSION OF RESULTS 21

CONCLUSIONS ...... 27

REFERENCES ...... 28

iv LI ST OF TABLES

I. Standard free energies of formation 6

I I. Free energy change and equilibrium constants for the reaction •...••.... 7

I I I. Effect of temperature on equilibrium yield 8

IV. Effect of pressure on equilibrium yield 8

v. Effect of molar ratio on equilibrium yield 9

VI. Direct hydration of propylene 13

VI I. Direct hydration of cyclohexene 15

VIII. Reaction conditions for catalyst screening 16

IX. Formation of isopropyl acetate ...... 18

x. Hydrolysis of isopropyl acetate ...... 19

v LIST OF FIGURES

1. Relation of yield and reaction temperature formation of isopropyl acetate • . . • . • • . • . . 24

2. Relation of yield and reaction time formation of isopropyl acetate ...... • 25

vi INTRODUCTION

Present Technology The hydration of propylene to isopropanol has been the topic of many experimental studies. The introduction of the first commercial process for the manufacture of isopropanol in 1920 is considered to be the origin of the modern synthetic industry. Berthelot discovered in 1855 that concentrated sulfuric acid consumes a substantial amount of propylene.1,2 He observed that the resulting solution when reacted with water produces an alcohol which distills at 82°C. The configuration of the new compound was not known until 1882. At that time, Kolbe proposed a structure for the alcohol produced from reducing over sodium amalgam. He observed that this alcohol had similar properties to the alcohol Berthelot patented in 1855. Since 1855, many patents have described different processes for producing isopropanol.3,4

~ (2) H2~

( 1) CH 3CH(OH)CH 3 ~)

1 2 The need for isopropanol during and after World War II created a market demand which increased rapidly. Isopropanol is used as a solvent and a basic intermediate in the manufacture of other compounds. It can also be used as a deicing agent, a rubbing agent and in the formulation of shampoos, detergents and cosmetics. The increase in demand for isopropanol has stimulated improvement in the technology of production. Processes for the manufacture of isopropanol are based upon direct or indirect hydration of propylene. Standard Oil of New Jersey commercialized the first indirect, liquid phase hydration process.1,5,6 Propylene was reacted with concentrated sulfuric acid to form a sulfate ester which was then hydrolized with water to isopropanol and dilute sulfuric acid. This process is still in use today, but it has the disadvantages of high energy costs, very corrosive conditions and pollution problems. The hydrolysis step yields a dilute aqueous sulfuric acid solution, which is regenerated by submerged combustion. The high temperatures involved in this process result in high energy costs as well as corrosive damage. Materials such as silicon, iron, teflon and graphite have been used for plant construction to minimize damage. During the regeneration of the sulfuric acid, large amounts of so 2 are given off. This compound is an environmental nuisance from the standpoint of air pollution. Also, large amounts of waste water are generated which must be treated before disposal. These factors add to the capital and operating costs. Despite these problems this process is still being used by a number of producers because it gives a reasonable conversion and efficiency and because it can utilize a rather low purity propylene feed. 3 In 1947 the Shell Development Company developed the first direct hydration process. 1 Propylene gas was contacted with steam to produce isopropanol. Phosphoric acid catalyst on an inert support was used. This is an equilibrium reaction. Improved equilibrium yields are favored by low temperatures, high pressures and high water concentration. However, there are a number of other factors which determine the process conditions. The catalyst is not sufficiently active to give useful reaction rates at low temperatures. Increases in the water/propylene feed ratio decrease the formation of the two major by-products, isopropyl ether and propylene polymers, as well as having a favorable effect upon the equilibrium. Increasing the operating pressure increases the equilibrium yield but increases polymer formation and increases the capital cost of the plant. Large excesses of water, combined with high pressures lead to catalyst deactivation by accelerated depletion of the phosphoric acid from the catalyst support. Other vapor phase processes include the ICI process.6 This process uses acidic oxide catalysts such as tungsten oxides which allow high water/propylene feed ratios. These catalysts however are not impressively active, so conversion rates are low and the high temperatures required lead to decreased equilibrium yields. More recently, a direct hydration process using a gas/liquid phase in a trickle bed reactor was developed by Deutsche Texaco. It utilizes a strong acid ion exchange resin as the catalyst.7 It allows high water concentrations which favor higher equilibrium yields and suppress by­ product formation. High pressures are necessary to increase the solubility of the gaseous propylene in the liquid water. 4 In 1978, Tokyuama Soda announced the development of a liquid phase direct hydration process. 7 The acidic catalyst system was described as containing an "inorganic polyacid anion" and was said to resist hydrolytic degradation. The principal advantages claimed are - high conversions; improved catalyst life; and the elimination of corrosion and pollution problems.

Direct hydration processes utilizing H3Po3, H2so4 and HCl at high pressures and temperatures have also been reported.8,9 Although the direct hydration processes generally require high pressures and a high purity propylene feed, a number of commercial plants utilize direct hydration. This study concerns a search for alternate schemes to affect the hydration of propylene. The first part of the work is based upon direct hydration and is an investigation of various liquid phase systems containing a strong acid catalyst and an agent to dissolve sufficient propylene to achieve acceptable reaction rates at modest temperatures and pressures. The second part of the work concerns the investigation of an indirect process in which propylene is first reacted, in the liquid phase, with acetic acid to form isopropyl acetate. The ester is then hydrolyzed to isopropanol and acetic acid. After separation, the dilute acetic acid would be concentrated and recycled. Such a process could avoid the severe corrosion and pollution problems of the sulfuric acid based indirect process. It could offer advantages over the vapor phase processes in terms of conversion rates and over the direct processes in propylene purity requirements. 5 Reaction Mechanism All of the direct hydration processes utilize acidic catalysts. Based upon fundamental studies on the reaction of other , such as isobutylene, 10 it is commonly accepted that the mechanism involves a carbocation intermediate and the overall reaction rate is proportional to the acidity factor of the system.

(2)

With the exception of the work reported by Onoue et al. at Tokyuama Soda, 7 there is no indication that the anion of the acidic catalyst plays a direct role in the kinetics of the reaction.

Thermodynamic Considerations Free energy calculations are a powerful tool that can be employed to predict the equilibrium yield of a reaction. By definition the free energy of a reaction is the energy change occurring when the reactants, in their standard states, are converted to the products in their standard states.11

tiGreaction = EtiGproducts - EtiGreactants (3) 6 Table I Standard free energies of formation

TemEerature OK 298 400 500 700 1000 CH3-CH=CH2 14.99 17.62 22.45 30.60 43.43

H2o -54.64 -53.52 -52.36 -49.92 -46.04

CH3-yH-CH3 -41.49 -33.17 -24.66 -7.07 19.93 OH

Using equation (3) and the values in Table I, it is possible to calculate the free energy change for the following reaction:

(4)

Using these values for the free energy change of the reaction, and the following relation:

6G reaction = -RT ln Kp (5) the equilibrium constants can be calculated. For example, at 298°K

6 Greaction = ( 6GC3HgO)-( 6GH20 +

= (-41,49)-(-54.64 + 14.99)

= -1.84 Kcal/mole

6Greaction = -RT ln Kp (6) 6Greaction log KP = 2.303·1.987 cal/mole/°K·298°K Kp = 22.36 7 Table II Free energy change and equilibrium constants for the reaction

Tem~erature °K 298 400 500 700

~GreactionKCal -1.84 +1.73 +5.25 +12.25 Kp 22.36 0.113 0.005 0.0015

It is noted in Table II that the equilibrium constant Kp decreases rapidly as the temperature increases. These values of KP can be used to calculate the equilibrium yield of isopropanol at various temperatures as follows:

(7)

(8)

Pto ta 1 Kp = K ~ v n ntota 1

at P total = 1 atm

nc3H80 -1 KP = . ( 1 ) n -n ntota 1 c3H8 · H20 8 assuming an initial charge of 1 mole C3H5 and 1 mole H20 forming X moles of C3H 80 at 298°K - x 2-X 22.36 =~-~-~(1-X)(l-X) -1-

X = 0.793 (79.3% yield) In a similar manner the theoretical equilibrium yields at other temperatures can be calculated. Also the effects of changes in total pressure and the mole ratio of water and propylene can be determined. The results are presented in Tables III, IV and V.

Table III Effect of temperature on equilibrium yield (1 atmosphere, 1:1 mole ratio) TEMPERATURE EQUILIBRIUM YIELD %

298 25 79.3 373 100 13.8 400 127 5.2 500 227 0.2

Table IV Effect of pressure on equilibrium yield (25°c, 1:1 mole ratio) PRESSURE EQUILIBRIUM YIELD % Atm PSIA 1 14.7 79.3 2 29.4 85.2 5 73.5 90.6 9 Table V Effect of molar ratio on equilibrium yield (loo 0 c, 1 atm) MOL RATIO EQUILIBRIUM YIELD % C3H5/H 20 1/1 13.8 1/10 24.0 1/100 25.6

These calculations, which do not consider reaction rates, by-product formation or the problems of achieving the required concentrations of reactants in the same phase with the catalyst, indicate the benefits of a reaction system which has reasonable conversion rates at low temperatures.

Kinetic Conversion This approach to a consideration of the kinetics of this reaction is based upon the following mechanism: kl ___::::..... (a) ~

k - ~ ~4

It is assumed that the cation C3H7+ is very reactive; its concentration is indeterminate but very small. The net rate of formation is assumed to be zero. 10

(10)

The rate of formation of product is

(11)

This expression relates to a homogeneous reaction system. In a heterogeneous system, where the reaction takes place on the surface of a solid catalyst, the effective concentrations are not equal to the concentrations in the bulk liquid or vapor. In such systems [H 20J, [C 3H6] and [C 3H70H] may be replaced by aw[H20J, ap[C 3H6] and aa[C3H70H] where the a represents a suitable distribution coefficient. 11 In a liquid phase system the problems of achieving effective reaction rates at low temperatures and pressures involve the vastly different solubility characteristics of propylene and water. In the first part of this work, we have evaluated several unique solvent systems such as toluenesulfonic acid/water, toluene/sulfuric acid/water, toluene/sulfuric acid/water/surfactant and toluene/sulfuric acid/water/phase transfer catalyst. EXPERIMENTAL

The experimental work described in this section includes fourteen runs to evaluate various catalysts for the direct hydration of propylene in liquid phase systems. In order to more easily quantify the extent of reaction four runs were made using cyclohexene as the . Five candidate catalysts for the acylation step of the indirect hydration were screened using cyclohexene. Thirteen runs were made reacting propylene with acetic acid and eight runs were made hydrolyzing isopropyl acetate.

Direct hydration-catalyst screening A preliminary series of runs were made at atmospheric pressure, passing propylene gas through a p-toluenesulfonic acid/water (2/1) system at 110° and 150°. No propylene was absorbed under these conditions and these runs are not discussed further. The runs made at pressures above atmospheric recorded in Table VI were carried out in a Parr Model 4521 stirred Reactor. This stainless steel reactor is equipped with three inlet valves, a rupture disc, a pressure gage, two 6-blade impellers on the stirrer shaft and a Type J thermocouple in a thermocouple well. The temperature was controlled by a Parr Model 4831 automatic temperature controller. At the start of each run the reactor was .charged with the water, candidate catalyst and any solvent or surfactant. The reactor was then sealed, evacuated under house vacuum and purged with propylene three times to displace air. The reactor was then raised to the designated temperature and propylene Table VI Direct hydration of propylene

Water Catallst Propylene Residence Temperature Pressure IPA Run (grams} T~~e Amount {grams} Time {Hrs) {oq ~Si formed 1 200 toluene-sulfonic acid 200 30.6 30 25 0-50 no 2 200 toluene-sulfonic acid 200 30.86 30.5 75-85 10-50 yes 3 200 toluene-sulfonic acid 200 30.1 18.5 100 60-100 yes 4 320 toluene-sulfonic acid 80 1.76 5 150 90-100 no 5 200 toluene-sulfonic acid 200 9.2 37 150 90-100 no 6 200 dodecylbenzene- 200 2.6 10 100 90-100 no sulfonic acid 7 200 toluene 97 11.5 21 100 80-100 yes sulfuric acid 103 8 200 toluene 297 41.33 5 90 70-100 no sulfuric acid 103 9 70 toluene 300 15.25 8 100 70-100 no sulfuric acid 30 10 70 toluene 250 11.5 34 100 140 yes toluene sulfonic acid 95.5 11 70 toluene 250 45.8 26.5 25 140 no toluene sulfonic acid 95.5 12 70 toluene 250 13.2 24 100 140 no sulfuric acid 95.5 13 200 toluene 97 11.5 24 100 140 yes tetraphenyl boron sodium 2 sulfuric acid 103 14 140 toluene 160 32.2 48 100 135 yes phosphoric acid 200 (48% yield) tetraphylboron sodium 2 ....., w 4 passed into t e reactor at the designated press re.. Pro ylene

absorption or reaction was indicated by a drop ·n press~ e. Under t ese condit"ons tbe v lu e of propylene re ated to a pressu e d o o SI

to PSIG as asured y wet tes eter to e 2.35 • H e e , se of t e d "ff ·c lt ·es and "nhererot errors in m1eas11Jr • g pro yle e act a.illl y

fed to t e reactor,, these rn.ms were co s "dered to be qual "tativ1e a:t 1e

ua t· a ive. t thte end of the 11react i o pe i od the e.ac c o]e to o um t erat re and t e co te ts t sfe ed .o a

d"stil]iatiion set p. Dist"llatilll11 was. ieontimJ1ed u 1rt"l thie head

t erat re reac e 10 °c. T e d"sti ate ~s t e a al zecl y Jas

r at ra y as esc e le 0 .

I 0 1 1 r1 :ns ere a e si g eye 0 exet111e as thie a ke :e ii I a · a:1 e.1pt 1 21 t '. antiify t ie f o 1at i oni of alcoiho I1 t ese 1r1 I S t 'E: li

a:s c a e the eaicto ith t 1e ()I er co o e· "ts. e ·a'....

·e sea e e ac ate a ro g t to t 1e 1es g ate t e "

. :0 es g1·. ated ti e c. I it iio s fo·ir t ese r s a. e s 0 'I i a le \fII.

a se es o Ul ~ S off a a· .e , · c ac 1d to fio1 m a · 1Gy1 .ace·tates

1 Cj ""1 o 1ex.ene ic I i s ore corrvi en1 · e1 ·t1:y easure t a ga'Seo. s

e a .. 5> a 1 e· ""' , cat.a yst a d so · e e ] I ifi.

las fitte it a efl a 1

i1]ij .1 ; s: .as ifi, :i::.i · b , Q. g t to t e d.e~ i g ated temper·"@.tur e f t e

es i g a·terl e.a'"'··t i. o i 1e. e.a·-·t 1 I co itio· ii e

. e a .... t e: i s.o 1 a .. e fi e- ti fr·a t.10. .aJ ati m ~· i 8 I g of ice,

ex·tra:ct i i0 n t. ·~ e:e t.; I 1 es \11.dt. 51 I m1 0 ti on o·f e ·afll1e .. A.I aljsies 0 t e Table VII Direct hydration of cyclohexene

Run Water Temperature Residence Cyclohexene Alcohol Number {grams) Catal~st Solvent (oq Time {Hrs} {grams} formed 1 7 phosphoric acid, toluene, 8 g 100 4 5 no 10 g 2 25 phosphomolybdic 180 4 10 no acid, 0.25 g 3 200 phosphomolybdic 180 3 80 no acid, 1.52 g Cr(N03)3, 0.56 g 4 7 phosphoric acid, toluene, 8 g 180 4 5 no 10 g Dow Expeimental Surfactant XDS 8390, 0.35 g Table VIII Reaction conditions for catalyst screening

Acetic Acid Acetic Anhydride Catalyst Cyclohene Temp. Run (grams) (grams) Type (grams) (grams) (OC) Yield 1 120 2 sulfuric acid 10 8.2 25 none 2 120 2 polyphosphoric acid 100 8.2 25 none 3 120 2 SnCl4 15 8.2 55 6% 4 120 2 sulfuric acid 10 8.2 55 12% 5 120 2 polyphosphoric acid 100 8.2 55 49% 6 120 2 SnC1 4 15 8.2 55 42% 7 120 2 toluenesulfonic acid 20 8.2 55 7.8% 8 120 2 sulfuric acid 10 8.2 55 96% 9 120 2 P205 (66.43 g) and 85% H3Po4 8.2 55 none 17

extract, after washing with water, 10% NaHC03 solution and saturated NaCl solution, and drying over anhydrous calcium sulfate is described below.

Indirect hydration-isopropyl acetate formation Gaseous propylene was reacted with acetic acid with a sulfuric acid catalyst in a Parr Model 3911 shaker type reactor, equipped with a heater. The 500 ml pressure bottle was charged with 120 g of glacial acetic acid, 2 g of acetic anhydride and 10 g of sulfuric acid. The bottle was connected to the gas inlet tube. The bottle was then evacuated and purged with propylene three times. The pressure was then adjusted to the designated amount, the shaker started and the temperature adjusted to the designated value. Shaking was continued for the designated reaction time with periodic recording of the drop in propylene pressure and readjustment of the bottle pressure from the gas reservoir. At the end of the reaction period the pressure was released and the contents of the bottle transferred to a simple distillation setup. The reaction was distilled to a head temperature of 98°c. The isopropyl acetate content of the distillate was measured as described below. The reaction conditions are recorded in Table IX.

Indirect hydration-hydrolysis reaction The hydrolysis of isopropyl acetate or the reaction mixture to and acetic acid was carried out by refluxing the ester and water for the designated time. The hydrolysis product was then distilled to a head temperature of 100°c, the distillate weighed and analyzed as described below. Conditions for the hydrolysis are recorded in Table X. 18 Table IX

Formation of isopropyl acetate

Temperature Pressure Reaction Run {oC} {~si} Time {Hrs} Yield 1 25 25 4 none 2 25 50 4 none 3 25 100 4 none 4 55 50 4 1.04 g distillate 5 40 100 4 2.36 g distillate 6 55 100 4 10% 7 75 100 4 25% 8 75 100 1 41.5%

9 75 100 2 64% 10 75 100 3 66% 11 75 100 4 67% 12 85 100 2 71% 13 82 55 4 80%

Note: 17.6 grams of propylene was used in runs 1-12. 8.4 grams of propylene was used in run 13. 19

Table X Hydrolysis of isopropyl acetate

Isopropyl Sulfuric Acetic Reaction Run Acetate* Water* Acid* Acid* Time-hrs Yield 1 10.2 100 1 3 19% 2 10.2 30 1 3 19.8% 3 10.2 100 5 60 3 64% 4 10.2 30 1 30 3 47% 5 10.2 30 1 30 5 47% 6 7.8 200 5 60 3 63% 7 28.1 600 2 61% 8 29.l 600 2 75%

*grams Note - In run 7, the isopropyl acetate was the reaction product from run 12 in Table IX. Similary, in run 8, the reaction product from run 13 in Table IX was used. Analytical methods Isopropyl alcohol and isopropyl acetate samples were analyzed on a Barber-Coleman gas chromatograph equipped with a thermal conductivity detector. Conditions were as follows. A 30 meter column was packed with Porr Pack Q with inlet temperature at 15o0 c and 1aooc for the detector. The column temperature was held isothermal at 19ooc. Helium was used as a carrier gas at a flow rate of 20 ml/min. The internal standard used was n-. A 1.0 µl syringe was used. Pure samples of isopropyl alcohol, n-butanol, water and toluene were injected separately into the gas chromatograph and each elution time was observed. To quantify the product, a mixture of isopropyl alcohol and n-butanol was injected into the gas chromatograph and each response was observed. A quantity (O.l g) of the internal standard was dissolved in 2 g of sample and 0.2 µl of the mixture was injected into the gas chromatograph. The amount of isopropyl alcohol present in the 2 g of sample was determined by dividing 0.1 g by the calculated area of the internal standard signal multiplying the result by the area of the isopropanol signal. Analysis of the cyclohexylacetate samples was performed on a Sigma 300 Perkin Elmer gas chromatograph equipped with flame ionization detector, a laboratory data system (Sigma 3600) and an auto sampler. A Durabond 5 capillary column was used. Durabond 5 is a non-polar stationery phase consisting of 95% dimethyl-(5%) diphenyl polysiloxane, with a temperature range of -60° to 3500c. The capillary column was 30 meters long with an inner diameter of 0.25 mm and a standard film thickness of 0.25 µm. The inlet temperature was kept at 325°C and the detector at 2so0 c. Column temperature was held isothermal at so0 c for 21 one minute, then programmed at 8°C/minute to 16o 0 c for one minute, then 30°C/minute to 270°C for 30 minutes. Hydrogen and breathing air were used for flame ignition. Helium was used as carrier gas. A stock standard solution was prepared by transferring exactly 50 mg of pure cyclohexyl acetate to a 50 ml volumetric flask and diluting with hexane. One ml of this solution was further diluted to 50 ml in hexane to give 20 g/ml concentration. About 0.5 ml of this solution was placed into an auto sampler vial and injected into the gas chromatograph. The calculated area of the standard peak was observed. About 50 mg of each sample was treated the same way. The auto sampler tray was loaded with sample vials in the even number position while odd- numbered vials were loaded with hexane. The auto sampler was set such that it sampled even numbered vials and flushed the syringe with odd numbered vials. The syringe assembly had a nominal volume of 5 µl. The syringe barrel was graduated and the distance travelled by the syringe was adjusted to 2 µl by means of a knurled stop screw. The amount of cyclohexyl acetate was calculated as follows: 1 standard x cone. standard x sample response x final volume standard response 1 sample injected sample size DISCUSSION OF RESULTS

Direct Hydration The initial runs (runs 1-5) evaluated the reaction of propylene gas with one phase toluene/sulfonic acid/water systems at pressures from o to 100 PSIG and temperatures from 25 to 150°c. At 25°c no product was formed. At temperatures from 75 to 100°c traces of isopropyl alcohol were formed. There was no evidence of product formation at 15o 0 c. It appears that, with this system, the reaction rate increases with temperature but passes through an optimum. At high temperatures (150°C) the solubility of propylene is too low for reaction to occur. In run 6, the toluene sulfonic acid was replaced with a long chain alkyl aryl sulfonic acid to increase the solubility of the propylene, but no isopropyl alcohol was formed. In runs 7-12 the one phase system was replaced with a two phase toluene/water/acid system. This increased the solubility of propylene, but did not have a significant effect on the rate of reaction. At low temperature (25°C) a large amount of propylene was absorbed but no product was formed. At 100°c and 140 PSI the propylene absorption was lower but a small amount of product was formed. In runs 13 and 14 tetraphenyl boron sodium was added as a proton phase transfer catalyst. The yield of product increased significantly. The results of these direct hydration runs confirmed that the inhomogeniety of the reaction system is a major obstacle to reaction. Reaction was not observed at 25oc. As the temperature is increased 23 reaction does occur but the rate is limited by the decreased solubility of propylene. Four runs, recorded in Table VII, were made using cyclohexene as the alkene. Two runs utilized toluene/water systems with phosphoric acid as the catalyst. In one of these runs hexadecyl diphenyl oxide sulfonic acid, a surfactant active in strong acid systems was used. Two runs were aqueous systems containing phosphomolybdic acid. No cylo­ hexanol was detected in this series.

Indirect hydration In the second phase of the work an indirect hydration process was evaluated. In this approach the propylene would be reacted with acetic acid to form isopropyl acetate. This ester would then be hydrolyzed to isopropyl alcohol and acetic acid which would be dried and recycled. It was thought that the solubility of the alkene and strong acid catalysts in the acetic acid would eliminate the problems of inhomogeniety which hampered the reaction in aqueous systems. In the first stage of this phase catalysts for the acylation reaction were evaluated using cyclohexene as the alkene. These runs are recorded in Table VIII. There were some initial difficulties in the separation and analysis of the product. The best results were obtained by dilution of the reaction product with ice water, extraction with hexane and GC analysis of the extract. This required a gas chromatograph with a more sensitive detector. The analytical procedure has been described in the Experimental section. The results indicated that sulfuric acid is an active and selective catalyst for the acylation reaction. Toluene sulfonic acid was less active. Stannous chloride and polyphosphoric acid were less selective. The analysis of runs using 24 these catalysts was marked by peaks of several coproducts which were not isolated or identified. Table IX records the runs made evaluating the reaction of propylene and acetic acid with a sulfuric acid catalyst. Again it was found that the reaction rate at 25°C was too slow to be practical. The relation of yield to product to temperature is illustrated in Figure 1. The data from runs 8 through 11 indicate that at 75°c the reaction is essentially complete within two hours. This is illustrated in Figure 2. The runs made to evaluate the acid catalyzed hydration of isopropyl acetate are recorded in Table X. The results indicate that an increase in catalyst concentration from 0.01 moles/mole ester to 0.05 moles/mole of ester increases the reaction rate. The equilibrium is displaced towards product by a large excess of water. The yield of product is increased by the presence of acetic acid, probably by increasing the solubility of the ester in the reaction mixture. Under these conditions the reaction is essentially complete within three hours. 25

100

80

60

.,.... 40 >-

20

25 50 75 100 Temperature (0 c)

Figure 1. Relation of yield and reaction temperature formation of isopropyl acetate. 26

100

80 -

60

r-- 40 Q) •r-

20

0 1 2 3 4 Time (hrs)

igure 2. Relation of yield and reaction time formation of isopropyl cetate at 75°C. CONCLUSIONS

The goal of finding a solvent/catalyst system in which propylene could be directly hydrated in high conversions at low temperatures and pressures was not realized. The best results for direct hydration utilized a toluene/water/sulfuric acid system with tetraphenylboron anion as a phase transfer catalyst. Since this catalyst is fairly expensive and is reported to have limited stability in aqueous solutions, it does not appear to be a practical solution to the inhomogeniety problem. Any future studies of the direct hydration process should be conducted in equipment which is capable of operating at higher pressures and with more efficient mixing of the two phase liquid system. The results of the investigation of the two-step, indirect hydration indicate that it has the potential for an economically practical route to isopropanol. Sulfuric acid is an active and selective catalyst for the acylation step at relatively low temperature and pressures. The results of the investigation of the hydrolysis step indicate that this reaction takes place at a reasonable rate and in good yield. Optimum reaction conditions would be determined by economic and engineering considerations. REFERENCES

1. Handcock, E.G. "Propylene and its Industrial Derivatives", John Wiley & Sons: New York, 1973, p 214-234. 2. Katuno, Masahuru. J. Soc. Chem. Ind. Japan, (Supplement binding), 1940, 43, 5-8. 3. Davis, H.S.; Quiggle, D. Ind. Eng. Ch. Anal. Ed., 1930, 2, 39 4. Clough, W.W.; Johns, C.O. Ind. Eng. Chem., 1923, 15, 1030. 5. Weissermel, Klaus; Arpe, Jurgen Hans. "Industrial Organic Chemistry"; Verlag Chemie: New York, 1978, p 175. 6. Wiseman, Peter. "An Introduction to Industrial Organic Chemistry"; John Wiley & Sons: New York, 1972, p 192-3. 7. Onoue, Yasuharu; Mizutani, Yukio; Akiyama, Sumio; Izumi, Yusuke. CHEM TECH, 1978, 8, 432-435. 8. Bunton, C.A.; Crabtree, H.G; Robinson, L. J. Am. Chem. Soc. 1968, 90, 1258. 9. Radhakrishnamurt, P.S.; Patro, Chandra Prakash. J. Indian Chem. Soc., 1969, 46, 907-908. 10. Levy, J.B.; Taft, R.W.; Aaron, D.; Hammett, L.P. J. Am. Chem. Soc., 73, 3792. 11. Klotz, M. Irving. "Chemical Thermodynamics"; Prentice Hall, Inc.: New York, 1950, p 122-125. 12. Stu 11, Dani a 1 R. "The Chemi ca 1 Thermodynamics of Organic Compounds'', Academic Press: London (1970) 512-513. 13. Cox, J.D.; Pilcher, G. "Thermochemistry of Organic and Organometallic Compounds", Academic Press: London, 1970, 512-513. 14. Neier, W; Woellner, J. CHEM TECH, 1973, 95-99. 15. Ogura, Tatsushi. Japan patent 7 436 305, 1974. 16. Onoue, Yasuharu. Kagaku Kogyo, 1975, 26, (4), 355-8. 17. Taft, Jr., W. J. Am. Chem. Soc., 1952, 74, 5372. 29 18. Day, J.D.E.; Ingold, C.K. Trans Faraday Soc., 1941, 37, 686. 19. Ingold, C.K. "Structure and Mechanism in Organic Chemistry", Cornell University Press: Ithaca, N.Y., 1953, p 767. 20. Tabe, Kazo; Matsuzaki, Isumio. Japan patent 7 223 523, 1972. 21. Kulkarni, S.B.; Dev, Sukh. Tetrahedron, 1968, 24, 561-563. 22. Nevitt, T.D.; Hammond, G.S. J. Am. Chem. Soc., 1954, 76, 4124. 23. Mousseron, M.; Jacquier, R. Bull. Soc. Chim. Fr., ,1950, 698.