University of Central Florida University of Central Florida

STARS STARS

Retrospective Theses and Dissertations

1987

Hydration of Propylene to Isopropanol Hydration of Propylene to Isopropanol

Nehemiah Diala University of Central Florida

Part of the Other Chemistry Commons

Find similar works at: https://stars.library.ucf.edu/rtd

University of Central Florida Libraries http://library.ucf.edu

This Masters Thesis (Open Access) is brought to you for free and open access by STARS. It has been accepted for

inclusion in Retrospective Theses and Dissertations by an authorized administrator of STARS. For more information,

please contact STARS@ucf.edu.

STARS Citation 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 alcohol 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

TABLE OF CONTENTS

LIST OF TABLES

LIST OF FIGURES

INTRODUCTION

Present technology

Reaction mechanism

Thermodynamic consideration

Kinetic Conversion

EXPERIMENTAL

Direct hydration

Indirect hydration-catalyst screening

Indirect hydration-isopropyl acetate formation

Indirect hydration-hydrolysis reaction

Analytical methods .•......•••

DISCUSSION OF RESULTS

CONCLUSIONS . . . . . . . . . . . . . . . . . . . . . . . .

REFERENCES . . . . . . . . . . . . . . . . . . . . . . . . .

iv

i i i

iv

v

vi

1

1

5

5

9

12

12

14

17

17

20

21

27

28

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 ...........•

vi

25

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 petrochemical 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 acetone 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

1

~ (2)

H2~ CH3CH(OH)CH3

~) ( 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

so2 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.

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.

4

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 alkenes, 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.

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

(2)

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

G ( 6GC3HgO)-( 6GH20 + 6 reaction =

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

= -1.84 Kcal/mole

6Greaction = -RT ln Kp (6)

log KP = 6Greaction

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)

K = K P to ta 1 ~v p n ntota 1

at P total = 1 atm

nc3H80 ( 1 )

-1 KP = .

n -n ntota 1 c3H8 · H20

assuming an initial charge of 1 mole C3H5 and 1 mole H20 forming X moles

of C3H80 at 298°K -

22.36 x =~-~-~ (1-X)(l-X)

2-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

373

400 500

25

100

127 227

Effect

PRESSURE Atm PSIA

1 14.7

2 29.4

5 73.5

Table IV

79.3

13.8 5.2 0.2

of pressure on equilibrium yield (25°c, 1:1 mole ratio)

EQUILIBRIUM YIELD

79.3 85.2 90.6

%

8

Table V Effect of molar ratio on equilibrium yield

(loo0 c, 1 atm)

MOL RATIO C3H5/H20

1/1 1/10

1/100

EQUILIBRIUM YIELD %

13.8

24.0 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 ___::::.....

~

k -~ ~ 4

(a)

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.

9

(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 [H20J,

[C3H6] and [C3H70H] may be replaced by aw[H20J, ap[C 3H6] and aa[C 3H70H]

where the a represents a suitable distribution coefficient.

10

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 alkene. 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

Tabl

e VI

D

irec

t hy

drat

ion

of p

ropy

lene

Res

iden

ce

Pres

sure

W

ater

C

atal

lst

Prop

ylen

e Te

mpe

ratu

re

IPA

Run

(gra

ms}

T~

~e

Amou

nt {g

ram

s}

Tim

e {H

rs)

{oq

~Si

form

ed

1 20

0 to

luen

e-su

lfon

ic a

cid

200

30.6

30

25

0-

50

no

2 20

0 to

luen

e-su

lfon

ic a

cid

200

30.8

6 30

.5

75-8

5 10

-50

yes

3 20

0 to

luen

e-su

lfon

ic a

cid

200

30.1

18

.5

100

60-1

00

yes

4 32

0 to

luen

e-su

lfon

ic a

cid

80

1.76

5

150

90-1

00

no

5 20

0 to

luen

e-su

lfon

ic a

cid

200

9.2

37

150

90-1

00

no

6 20

0 do

decy

lben

zene

-20

0 2.

6 10

10

0 90

-100

no

su

lfon

ic a

cid

7 20

0 to

luen

e 97

11

.5

21

100

80-1

00

yes

sulf

uric

aci

d 10

3 8

200

tolu

ene

297

41.3

3 5

90

70-1

00

no

sulf

uric

aci

d 10

3

9 70

to

luen

e 30

0 15

.25

8 10

0 70

-100

no

su

lfur

ic a

cid

30

10

70

tolu

ene

250

11.5

34

10

0 14

0 ye

s to

luen

e su

lfon

ic a

cid

95.5

11

70

tolu

ene

250

45.8

26

.5

25

140

no

tolu

ene

sulf

onic

aci

d 95

.5

12

70

tolu

ene

250

13.2

24

10

0 14

0 no

su

lfur

ic a

cid

95.5

13

200

tolu

ene

97

11.5

24

10

0 14

0 ye

s te

trap

heny

l bo

ron

sodi

um

2 su

lfur

ic a

cid

103

14

140

tolu

ene

160

32.2

48

10

0 13

5 ye

s ph

osph

oric

aci

d 20

0 (4

8% y

ield

) te

trap

hylb

oron

sod

ium

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 r1 :ns ere a e si g eye 0 1exet111e as thie a ke :e ii I a · a:1 e.1pt

t 1'. antiify t ie f o 1at i oni of alcoiho 21 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

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

a se es o Ul ~S

off a a · .e , · c ac 1 d to fio1 m a · 1Gy1 .ace·tates

Cj ""1 o 1ex.ene ic I i s ore corrvi 1en1 · 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 ef l 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

Tabl

e V

II

Dir

ect

hydr

atio

n of

cyc

lohe

xene

Run

Wate

r Te

mpe

ratu

re

Res

iden

ce

Cyc

lohe

xene

A

lcoh

ol

Num

ber

{gra

ms)

Ca

tal~

st

Solv

ent

(oq

Tim

e {H

rs}

{gra

ms}

fo

rmed

1

7 ph

osph

oric

aci

d,

tolu

ene,

8 g

10

0 4

5 no

10

g

2 25

ph

osph

omol

ybdi

c 18

0 4

10

no

acid

, 0.

25 g

3 20

0 ph

osph

omol

ybdi

c 18

0 3

80

no

acid

, 1.

52 g

C

r(N03

)3,

0.56

g

4 7

phos

phor

ic a

cid,

to

luen

e, 8

g

180

4 5

no

10 g

Do

w Ex

peim

enta

l Su

rfac

tant

XDS

839

0,

0.35

g

Tabl

e V

III

Rea

ctio

n co

nditi

ons

for

cata

lyst

scr

eeni

ng

Ace

tic A

cid

Ace

tic A

nhyd

ride

Cat

alys

t C

yclo

hene

Te

mp.

Run

(gra

ms)

(g

ram

s)

Type

(g

ram

s)

(gra

ms)

(O

C)

Yie

ld

1 12

0 2

sulf

uric

aci

d 10

8.

2 25

no

ne

2 12

0 2

poly

phos

phor

ic

acid

10

0 8.

2 25

no

ne

3 12

0 2

SnCl

4 15

8.

2 55

6%

4

120

2 su

lfur

ic a

cid

10

8.2

55

12%

5 12

0 2

poly

phos

phor

ic

acid

10

0 8.

2 55

49

% 6

120

2 Sn

C14

15

8.2

55

42%

7 12

0 2

tolu

enes

ulfo

nic

acid

20

8.

2 55

7.8

%

8 12

0 2

sulf

uric

aci

d 10

8.

2 55

96

% 9

120

2 P2

05

(66.

43 g

) an

d 85

% H 3

Po4

8.2

55

none

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

17

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

isopropyl alcohol 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.

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

5 40 100 4 2.36

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.

g

18

distillate

distillate

Isopropyl Run Acetate*

1 10.2

2 10.2

3 10.2

4 10.2

5 10.2

6 7.8

7 28.1

8 29.l

*grams

Table X Hydrolysis of isopropyl acetate

Sulfuric Water* Acid*

100 1

30 1

100 5

30 1

30 1

200 5

600

600

Acetic Acid*

60

30

30

60

Reaction Time-hrs

3

3

3

3

5

3

2

2

19

Yield 19%

19.8%

64%

47%

47%

63%

61%

75%

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-butanol. 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 so 0 c for

21

one minute, then programmed at 8°C/minute to 16o0 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 standard response

x sample response x 1 sample injected

final volume 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 15o0 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

reaction does occur but the rate is limited by the decreased solubility

of propylene.

23

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.

100

80

60

.,.... 40 >-

20

25 50 75 100

Temperature (0 c)

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

25

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.

26

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.

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.

29