Dehydration of 2 3-Butanediol to Mek.2

8/19/2019 Dehydration of 2 3-Butanediol to Mek.2

1/9

The Dehydration

of

Fermentat ive

2,3=Butanediol into Met h y l Ethyl Ketone

A i

V.

Tran and Robert

P.

Chambers

Department of Chemical Engineering, Aubu rn Universi ty,

Auburn, Alabama 36849

Accepted for publ icat ion February 18, 1986

A solid acid catalyst consisted of sulfonic groups cova-

lently bound to an inorganic matrice was developed to

dehydrate 2,3-butanediol into methyl ethyl ketone. Rate

constant and apparent activation energy of the dehydra-

tion reaction were determined. The decay course

of

the

catalyst was

a

two-stage curve. The catalyst was deac-

tivated more rapidly in the first stage than in the second

stage. The strategy of maintaining constant degree of

dehydration was employed to lengthen the lifetime

of

catalyst. Treatment of the 2,3-butanediol containing fer-

mentation broth wi th activated carbon greatly facilitated

the subsequent dehydration reaction.

INTRODUCTION

Recent interest in the utilization of renewable lig-

nocelluloses has intensified research on the fermen-

tation of xylo se and glucose to 2,3-butanedi01'-~(here-

after butanediol). This is because butanediol is the

precursor of a n umber of com pounds.6 Among those

is methyl ethyl ketone (ME K). Com pared to ethanol ,

M EK has a higher heat of combu stion, 584.2 vs. 326.7

kcal/mol. It also gives an octan e num ber of 96.7 when

mixed (25% volume) with gasoline. ' Thu s, ME K is

more effective as a liquid fuel additive than e thanol.

A two-step process from butenes is usually used t o

make MEK.8 Butenes are f i rs t hydrated to give 2-

butanol which is then dehy drogen ated ov er zinc or

copper based catalysts at high temperatures and low

pressures to produce MEK. The conventional con-

version of ferme ntative butanediol into MEK

is

also

a

two-step process. Butanediol

is

first recovered from

ferme ntation broth and purified. It is then dehydra ted

ov er activ ated bentonite9 or sulfuric ac idlo*' to yield

MEK. Sulfuric acid is not able to convert butanediol

in the fermentation broth directly into MEK. This is

due to the preferential reaction of sulfuric acid with

unfermented xylose in the broth to the reaction of sul-

furic acid with butanediol.

In light of the above facts, the present report de-

scribes the direc t dehydratio n of butanediol in the fer-

mentat ion broth into ME K o ver a sol id acid catalyst .

Biotechnology and Bioengineering,

Vol.

XXIX,

Pp. 343-351

1987)

1987 John Wiley & Sons, Inc.

Th e advantag e of this method is the elimination of the

energy-intensive step of reco very and purification of

butanediol from ferm entation broth prior to the sub-

sequen t dehy drat ion react ion.

MATERIALS AND METHODS

Preparat ion of Sol id Acid Catalysts

Alumina and silica-alumina supports were used in

the preparation of catalysts. Alumina support (35-50

mesh) was obtained from Myco, Inc. and sil-

ica-alumina supports were from Davison Chemical and

Cyanamid. The support of Davison Chemical was in

pellet form (3/16 x 3/16 in.). It was then gro und, and

the 8-20 mesh fraction was retained for further use.

Th e su pport from Cyanamid was in fine form (40-60

mesh). Sulfhydryl groups were first covalently at-

tached t o the inorganic supp orts via silane intermedi-

ates.I2 The y were th en transform ed into sulfonic groups

using the procedure of Backer. l 3 The transformation

react ion was carr ied out at

60

? 1 and 90 +_ 1°C.

In

this w ork , the ca talysts A160, D60, and C60 were those

made at 60 1°C from alumina, Divison Chemical,

and Cyanamid suppo rts, respe ctively. Similarly, A190,

D90, and C90 were the catalysts prepared a t

90

1°C

from the co rresponding supports .

Reactors and th e Dehydrat ion

of

Butanedio l

Tubing Bomb

The dehydrat ion of butanediol into ME K was f irst

made in

a

21-cm-long, I-cm-I.D., stainless-steel tubing

bomb. After charging with A190 and butanediol (50

g/L), the tubing bomb was placed in an oil bath pre-

viously heated to a given temperature. It was then

cooled in a stream of water and filtered. The filtrate

was used for determinat ion of butanediol and M EK .

CCC

0006-3592/87/030343-09 04.00


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Batch Autoc lave

A 600-ml Parr batch autoclave reactor was em-

ployed. About 13.5 g catalyst and 300 mL of

50

g/L

butanediol solution (Sigma Chemical) were used for

each run. T he st i r rer speed was 15 rpm. Tim e zero

(initial time) was the time at wh ich the rea ctor reached

the given tem perature. Sam ples were taken a t intervals

after passing a sampling coil (1 m) imm ersed in an ice-

water bath. After the dehydrat ion react ion, the reactor

was cooled and f il tered. T he catalyst was washed w ith

4 L distilled wate r and allowed to air-dry overnight. It

was used recurrently in three succe ssive runs a t iden-

tical conditions.

Packed Bed Reactor

Figure 1 depicts the packed bed reactor system used

in this work. A minipump (Milton Roy) pumped the

aqueous butanediol solution (50 g/L) through the sys-

tem. A fter passing 40 mL , the packed bed reactor was

immersed in an oil bath which was previously heated

to

a

given temperature. In or der to ensure equilibrium

condit ions, a foreru n of 40 mL w as passed before col-

lecting the liquid products for analysis. The pressure

of the system was 300 psi (gauge pressure).

Regeneration of Catalyst

The catalyst was washed by pumping water (500 ml)

through the packed bed reactor . Water was then re-

placed by hydrochloric acid [5% ( v h ) , 400 mL1. The

water-hydrochloric acid cycle was repeated three times.

Finally, the reactor was washed with water until no

trac e of hydrochloric acid was dete cted (the indicator

was methyl orange).

Preparation of Fermentation Broth

A

solution

(5

L) composed of NaCl (1 g/L),

M gS 047 H2 0 (0.2 g/L), NH4CI (2 g/L), yeast extract

(6

g/L),

and xylose (100 g/L) was sterilized at 120°C

fo r 15 min in

a

16-L fermentor (New Brunswick, type

SF-116). Inoculation (1

L)

of Klebsiella pneumoniae

AU-1-d3 was added to the medium. The butanediol

fermentat ion was then proceeded a t 32°C for 15 h. Th e

pH was maintained at 5.4 with

5N

NaO H. The source ,

grow th conditions, and inoculum composition of Kleb-

siella pneumoniae AU-l-d3 were described else-

where.I4 The fermentation broth was withdrawn from

the fermentor , centr i fuged (15 x lo3 rpm x 15 min,

at 4 C),

and

stored

in

a

cold

room (4°C).

Fermentation

products in

the broth

were butanediol(27.5

a ,

thanol

(4.2

g/L),

acetic

acid (2.1

g/L), and

acetoin

(5.7

g/L).

Figure

1. Scheme

of

the packed bed reactor system:

1 ) reservoir of butanediol solutio n, (2) minipump, (3) pressure gauge,

(4) relief valve,

(5)

filters, (6) quick-fix connector,

(7)

oil bath,

(8)

packed bed reactor,

(9)

coil 1 m), (1 0) ice-water bath, 1

1)

fraction

collector, (12) thermometer, 13) stainless-steel ubing, (14)200 mesh

screen, (15)glass wool, (16)glass bead

(3

mm

O.D.),

and

(17)

catalyst.

Treatment of Fermentation Broth

Since butanediol in the fermentation broth wa s not

efficiently dehydrated to

M E K

over the ca ta lys t s as

will be described later, two treatments were used for

the broth prior to th e subseq uent dehydrat ion react ion.

In the first treatm ent, the broth w as run through

a

glass

column (25 cm long

x

1.2 cm I.D.) packed w ith Am-

berlite IR-120, H+ orm. The treated broth was col-

lected after passing a forerun of 35 mL. In th e second

treatment , the broth w as t reated with act ivated carbon

(50

g/L, Darco grade

MD

3000) at 60°C

for

40 min. It

was then filtered (Whatman filter paper No. 3) and

centrifuged (12 x lo3 rpm x 10 min, a t 4°C).

Analytical

Butanediol and M EK from th e dehydrat ion reaction

were analyzed on a Varian gas c hromatog raph 3700

using a 1-m glass column packed w ith Chrom osorb 101

(60/80 mesh). The gas chromatograph was equipped

with a flame ionization dete ctor , a Varian autosam pler

5000, and a V arian integrater CDS-1 11C. Ferm entatio n

products w ere analyzed on the sam e equipment. Sulfonic

groups of the catalyst were determined by treating

the catalyst

(0.5

g) with 0 .1N NaO H

(50

mL ) overnight

with stirring. Th e residual Na OH was the n titrated with

0.

lNHC1. pH cur ve of the catalyst w as carried out with

a glass-electrode Ho rizon p H Controller 5997-20.

RESULTS AND DISCUSSION

Properties

of

Catalyst

Table I indicates that the catalys ts made at 90 ? 1°C

contained more sulfonic groups than did the

corre-

sponding ones prepared at

60

1°C. As seen in Figure

2, the initial pH of

A190,

D90, and C90 was higher than

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BIOTECHNOLOGY AN D BIOENGINEERING, VOL.

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1987


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Table I. Sulfonic groups content and the dehydration

of

butanediol over various

catalysts in batch reactor.

Catalyst

A190

Run 1

Run 2

Run 3

A160

Run 1

Run

2

Run

3

D90

Run 1

Run 2

Run

3

6

Run

I

Run

2

Run 3

C90

Run

1

R un 2

Run 3

C60

Run 1

Run 2

Run 3

Rate constant

[min-

g-I ( x

Degree of

First Second butanediol

O,H

(meq/g) Overall stage stage dehydration ( )

1.31 32.97 100

18.48

12.55 26.02 98.6

13.45

9.79 16.13 89.2

1.28 28.47

100

16.55

13.73 21.04 93.4

9.80

8.08 10.84 81.5

1.44 53.37

100

18.67 16.84 23.11 97.3

1.22 9.13 7.03 11.10 91.7

1.41 44.77 100

18.06

14.67

22.46

96.5

7.66

5.42 9.07 87.0

1.81 39.85

100

9.62 7.92 10.65 94.4

I .05 2.61

2.24 2.74 86.7

1.59 32.92

100

11.10

10.53

11.84 90.7

4.33

3.36 5.00 84.3

that of A160, D60, and C60, respectively. Also, the pH

curves (Fig. 2) show that after ca. 0.75 mL of 0.1N

NaOH was consumed, the former catalysts had lower

pH than did the later catalysts. These results suggest

that

AIW, DW,

and C90may have lower external but

higher internal sulfonic groups than do the respective

catalysts

A160, D60,

and

C60.

Dehydrationof Butanediol into

MEK

Tubing

B o m b

In order to establish the reaction conditions of bu-

tanediol dehydration, tubing bomb was used. Results

in Figure 3 indicate that the dehydration reaction was

depended on the temperature and quantity of catalyst.

As temperature increased from 150 to 220 C, ca. 100%

increase in the degree of butanediol dehydration was

obtained. On the other hand, ca. 15 increase in the

degree of butanediol dehydration was observed for a

quadruple in catalyst quantity. Thus, the effect of tem-

perature on the butanediol dehydration was more pro-

nounced than that of catalyst quantity. From these

data, 2 10°C was arbitrarily selected as the dehydration

temperature for subsequent experiments.

2

A l 60

A l 90

D

60

D 90

C

60

c 90

- -

-. -

.

_---

_ . -

1 2

1

2 3

4 5

0 . N NaOH

( m l )

Figure 2. Titration curves with

0.1N

NaOH of various catalysts.

345

RAN AND CHAMBERS: DEHYDRATION

OF

2,3-BUTANEDIOL


4/9

T e m p e r a t u r e

( C)

C

0

0

L

V

>

JZ

W

.-

e

n

-

0

-0

W

t

0

.-

rn

w

0

W

W

L

0

W

n

0

0.5

1

o

1.5

2 . 0

A l 9 0 ( g )

Figure

3. Degree of butanediol dehydration a s a function of tem-

perature and cata lys t quantity.

The emp ty c ircles show 0.5 g A190,

12

m L 50 g/L butanediol, de-

hydrated for 150 min in the tubing bomb ; the solid circles show 12

m L 50 g/L butanediol, at 2WC, dehydrated for 150 min in the tubing

bomb.

Batch Autoclave Reactor

Shown in Figure 4 is the typical relationship of In

C/Co with reaction time for the catalysts D90 and C90.

Parameters

C o

and

C

were butanediol concentrations

at initial and different reaction times, respectively; the

slopes of the lines were the rate constants of the re-

action. Apparently, the dehydration reaction was first

- 1

0

\

c

2

- .

order in butanediol concentration. Both D90 and C90

completely dehydrated butanediol in the first run.

However, their activity was somewhat decreased in

the second and third recurrent runs as indicated by the

decreases in the reaction rate constant and degree of

butanediol dehydration of these runs (Table

I).

This

implies that both catalysts were deactivated. The de-

hydration reaction in the second and third runs fol-

lowed a two-stage path (Fig.

4).

Compared to the re-

action rate constant of the first stage, that of the second

stage was higher (Table I ) . Thus, the dehydration re-

action was faster in the second stage than in the first

stage. The reason of these facts will be elaborated later.

The behavior of other catalysts was similar to that

of D90 and C90. The catalysts made at

60

1°C had

lower reaction rate constants than did the correspond-

ing ones prepared at 90 ? 1°C. This is due to the lower

sulfonic groups of the former catalysts (Table I).

The apparent activation energy of the dehydration

reaction over the catalysts was 2.9

x

lo4 cal/mol, cal-

culated from their Arrhenius plots (not shown here).

This value is lower than that found for the dehydration

of butanediol by sulfuric acid

(3.6 x

lo4 cal/mol).

Packed Bed Reactor

Typical packed bed reactor profiles at 210°C are il-

lustrated in Figure 5 for the catalysts D90 and C90.

The butanediol concentration decreased to a minimal

point then increased gradually. This indicates that the

catalysts were deactivated after the maximal dehydra-

tion of butanediol occurred. Assuming that the dehy-

dration reaction was in the steady state, i.e., the bu-

tanediol concentration after the minimal point was

unchanged, the rate constant of the reaction was eval-

uated from the equation: In

C J C i

= - k ~ here

C i

- 1

- 2

-3

1 ' 1 . l . I . l . ~

40

80 1 2 0

160 2 0 0

0 4

8

120

160

2 0 0

T i m e ( m i n )

Figure 4.

2)

second run, and

(3)

third

run.

Correlation of In C/Co) with time for batch rea ctor at 210°C: A) catalyst D90,

(B)

catalyst C90, (1) first run,

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BIOTECHNOLOGY AND BIOENGINEERING, VOL.

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1987


5/9

L

c

50

c

0

V

-

4 0

0

v

0

.-

30

m

20

- 1

T i m e (m in )

Figure

5.

in packed bed reactor at

210°C:

(A) catalyst D90, 15.4 g T

=

7. 7 rnin;

(B) catalyst C90, 27.5 g, T = 19.9 rnin;

( I ) run prior to the regenera tion of catalyst;

(2)

run a fter the first regen eration; and

(3) run after the second regeneration.

Profiles

of

butanediol dehyd ration over different catalysts

and

C

are butanediol concentrations at time zero and

at

the point of maximal dehydration, respectively. The

residence time, T was computed using the feed rate

(mL/min) and void volume of the catalyst bed (mL).

The void volume was assumed to be 70% of the total

volume of catalysts bed.I5

Again, the dehydration reaction rate constants of the

catalysts made at 90 1°C were higher than those of

the counterparts made at 60

?

1°C (Table 11 . Com-

pared to the reaction rate constants measured for batch

reactor, those determined for packed bed reactor were

slightly higher except for A160. Thus, the physical

properties, i.e., the differences in the void and pore

structures of the supports used, of the catalysts have

probably affected their behaviors in packed bed re-

actor. The degree of butanediol dehydration of the cat-

alysts made at 90

*

1°C was also higher than that of

the catalysts prepared at 60 1 C, thus corresponding

to the higher reaction rate constants (Table 11 and

higher sulfonic groups (Table

I

of the former catalysts.

Since the amount of

D90

used was small (Fig. 5 , its

degree of butanediol dehydration was expectedly low

(Table 11 .

The deactivation constant of the catalysts in packed

bed reactor was calculated using the equation

k, =

ke

- k d f , 1 6 where k, is the dehydration reaction rate con-

stant at time t after the maximal dehydration point; k

is the rate constant at the maximal dehydration point;

and kd is the deactivation constant. The deactivation

constant of the catalysts made at

90

1°C was slightly

lower than those of the counterparts made at 60 *

1°C

(Table 11 . As Figure 6 shows, the deactivation of the

catalysts was a two-stage curve. The catalysts were

deactivated faster in the first stage than in the second

stage (Table

11 .

These results will be discussed in de-

tail later.

Improvement

of

Catalyst A ct iv i ty

Batch Au toclave Reactor

One reason of the catalyst deactivation is due to

poisons which block the active sites, i.e. sulfonic groups,

of the ~at a1y st.l ~he dehydration in batch reactor was

then proceeded with the addition of

0.5%

(w/w, cata-

Table

11. Characteristics of the dehydration

of

butanediol over different catalysts in packed b ed reacto r.

Deactivation constant

[min-'

( x

lo- ]

Rate constant First Second Degree of butanediol

Catalyst [min-'

g- l

( x

Overall stage stage dehydration

( )

A190

33.59 33.65 52.17 10.57 87.7

First regeneration 15.21 27.67 40.56 21.96 60.7

Second regeneration

8.01 3 1.47 83.99 29.26 40.9

A160

30.08 34.07 54.07 16.35 79.4

D90

73.06 39.62 63.16 21.21 58.0

First regeneration 27.13 54.45 77.23 29.57 29.9

0 6 0

50.58 39.89 62.92 18.48 71.7

C90

67.06 35.57 52.69 29.37 97.4

First regeneration 16.76 43.79 69.04 27.02 50 0

Second regeneration 12.50 15.98

10.95

12.02 38.8

C60

46.30 39.16 59.46 14.13 83.3

Conditions of the dehydration reaction are given in Figure 5

TRAN AND CHAMBERS: DEHYDRATION

OF

2.3-BUTANEDIOL

347


6/9

A

T i m e (m i n )

Figure

6.

Deactivation curves

of

different catalysts used in packed bed reactor; see Figure

5

for

Codes.

lyst basis) of

0.5%

platinum on alumina

(40-60

mesh).

Prior

to

heating

,

he batch reactor was pressurized to

100 psi with hydrogen. As data in Tables I and I11

indicate, a lthough the p at tern of th e dehyd rat ion re-

action s with and without platinum w as the sam e, i.e.,

one stage in the first run and two-stage path in the

second and third recurrent runs, th e rate constants of

the former reaction (with platinum) were lower than

those of the latter reaction (without platinum). These

results imply that

a

part of sulfonic grou ps was blocked

by platinum containing alumina, thus resulting in lowe r

rate constants of the dehydration reaction with plati-

num. This, in turn, suggests that the deactivation of

catalyst was not caused by poisons but rather by the

decre ase in sulfonic groups. A

case

in point is the low er

sulfonic groups of

D90

and

C90

after the third run

(Table

I).

Due to the decrease in sulfonic groups, and

since the catalyst contained m ore internal than ex ternal

sulfonic groups a s mentioned earlier, i t may th en con-

ceive that afte r the first run the exte rnal sulfonic grou ps

were depleted at

a

much faster rate than were the in-

ternal sulfonic gr oup s. This will explain th e higher re-

Table

111.

Rate constant and degree

of

the butanediol dehydration in batch re-

actor with the addition of 0.5 w/w) platinum.

Rate constant

[rnin-' g-' ( x

Degree of

First Second butanediol

Catalyst Overall stage stage dehydration ( )

090

Run 1

35.39

100

Run

2 15.80 13.91 17.02 98. 2

Run

3 7.04 6.57 7.71 83.5

6

Run

1

34.32

100

Run

2 13.00 12.88 13.17 96.5

Run

3 5.49 3.50 7.82 84.0

C90

Run 1

35.22 100

Run 2 16.45 13.71 17.75 95.9

Run

3 7.82 7.39

8.06

85.7

C60

Run I 23.50 100

Run 2

10.55 9.47

11.10

86.5

Run 3 4.66 3.29 5.12 79.7

348

BIOTECHNOLOGY AND BIOENGINEERING, VOL. 29, FEBRUARY 1987


7/9

- 5 0 -

-

\

0

-

C 4 0 -

0

0

L

0

0

0

.-

2 3 0 -

20-

-

0

-0

0

0

.-

c 1 0 -

a

m

c

I

1

24

10 12 14

16 18

2 0 2 2

;,

2

4 6

T i m e

(hr)

Figure 7.

I ) catalyst D90, 185 C, 45 .9 g, = 74.1 min;

(2) catalyst D60, 192 C, 44.5 g,

=

72.3 min;

(3) ca ta lyst C60 , IW C , 40.6 g, = 83.6 min; and

(4) ca ta lys t C90, I W C , 38.4

g

7

=

87.7 min.

Profiles

of

butandiol dehydration over different catalysts in packed bed reactor at lower reaction temperatures:

action rate constants

of

the second stage compared to

those of the first stage in the second and third recurrent

runs (Tables I and 111).

Packed Bed Reactor

Regeneration of Catalyst.

It

is likely that the de-

hydration of butanediol proceeds with protons derived

from the sulfonic groups of the catalyst. Thus, the

mechanism of the reaction can be written as follows:

H O O H H O O H + *

I I H I I

I

CH3-C-C-CH3 - C H 3 - C - C - ~ ~ 3 ---

H H

H

(butanediol)

HO H + O

H

I II I

I

CH3-C-C-CH3 -- CH3-C-C-CH3

--

H

H

carbonium ion)

(secondary (oxonium ion)

The protons, in ideal state, will be recycled

in

the

dehydration reaction. Since the catalyst was deacti-

vated as proven above, the sulfonic groups might lose

Table

IV.

Rate constant, deactivation constant, and degree

of

butanediol dehydration

of

various catalysts

in packed bed reactor.

Deactivation constant

[rnin-I

(

x

10-91

Rate constant First Second Degree

of

butanediol

Catalyst [min-'

g-I

( X Overall stage stage dehydration ( )

D9

2.35

2.12 6.27 I .67 55.0

D60 3.18

3.85 11.97 2.89 63 .2

C90 8.14

4.60 9.84 3.45 93.6

C60

6.78

4.67 7.13 3.82 89.9

Conditions of the dehydration reaction are given in Figure 7 .

TRAN AND CHAMBERS: DEHYDRATION OF 2,BBUTANEDIOL

349


8/9

Table V.

of the dehydration reaction

of butanediol in simulated fermentation broth over the catalyst D90 in batch

reactor using conditions of Figure 4.

Rate constant [min-l g- ' ( X

Feed composition Run

I

Run

2

Run

3

Butanediol

(50

g/L)

53.37 18.67 9.13

Simulated fermentation broth (SFB)

12.58 3.50 0.03

SFB without yeast extract

53.31 17.31 9.31

a

Composition of SBF (g/L): ethanol,

11.5;

acetic acid, 4.5; acetoin, 2.3;

butanediol,

30;

NaCI, 1; MgSO4.7H2O,

0.2;

NH,CI,

2;

yeast extract,

6;

and

xylose,

100.

their protons. HC1 was then used to regenerate the

catalyst. Figure illustrates the profiles of the dehy-

dration over the regenerated catalysts. The regenera-

tion process did not improve the catalyst activity. The

rate constant and degree of butanediol dehydration of

the reaction over the regenerated catalyst were lower

than those of the reaction over the fresh catalyst (Table

11). These results imply that the deactivation of catalyst

was due to the

loss

of sulfonic groups in the reaction,

thus supporting the above conclusion on the catalyst

deactivation in batch autoclave reactor.

The above suggestion that during the dehydration

reaction the catalyst lost more external than internal

sulfonic groups can also be used to account for the

two-stage deactivation curve of the catalyst (Fig.

6).

It may envisage that the dehydration reaction in packed

bed reactor proceeded first with the external, then with

the internal sulfonic groups. Consequently, the deac-

tivation of the catalyst was a two-stage curve. Since

the remaining external sulfonic groups were lower as

already suggested, it is understandable that the deac-

tivation constant in the second stage was lower than

that of the first stage.

Maintenance of Constant Degree of Butanediol De -

hydration. One of the strategies to lengthen the catalyst

lifetime in packed bed reactor is to maintain a constant

degree of conver~ion.'~his can be done by either

varying the reaction temperature with time while keep-

ing the feed rate constant or changing the feed rate

while holding the reaction temperature constant. The

latter method was selected for the present catalyst. The

reaction temperature, however, was maintained a t ca.

190°C. This is because the temperature of the oil bath

could not be raised to 210°C. This fact, in turn, de-

manded

an

increase in the catalyst quantity. The pro-

files of this experiment is shown in Figure 7. The de-

grees of butanediol dehydration were almost the same

for the reactions at 210 and 190°C (Tables I1 and IV).

However, the lifetime of the catalyst was maintained

longer,

24

h vs.

6

h (Figs.

5

and

7),

although this re-

sulted in lower deactivation constant and reaction rate

constant.

Also,

the deactivation course of the catalyst

was unchanged. That is the catalyst was deactivated

more rapidly in the first stage than in the second stage

(Table IV).

Dehydration of Fermentative Butanediol

The catalyst D90 was first employed to examine the

effect of different components in the simulated fer-

mentation broth on the dehydration of butanediol in

batch reactor. Data in Table V indicate that xylose,

mineral salts, and fermentation products, i.e. butane-

diol, ethanol, acetic acid, and acetoin, did not hinder

the dehydration reaction. Yeast extract, however, in-

hibited the dehydration of butanediol, presumably

through the blockage of sulfonic groups. This is

fur-

thered by the fact that butanediol in the actual fer-

Table VI.

Dehydration of butanediol in actual fermentation broth in packed bed reactor using conditions of Figure

7.

Weight Temperature

Cataly st (g) ( C)

Feed

Rate const ant Degree of butanediol

[m in- ' g - ' ( x lo- )]

dehydration ( )

D90 35.2 185

butanediol

(27.5

g/L)

2.84

D90

35.5 185 actual fermentation broth

I

.27

D90 35.3 185 actual fermentation bro th 2.71

C90 38.4 190 butanediol (50

g/L)

8.14

C90 35.4 190 actual fermentation brotha 3.57

C90 34.7 190 actual fermentation broth 3.96

C90 35.2 190 actual fermentation broth

7.01

treated with activated carbon

treated with IR-120, H'

treated with activated carbon

57.5

21.2

44.4

93.6

60.6

65.7

80.7

a

See the Materials and Methods section.

350

BIOTECHNOLOGY AND BIOENGINEERING, VOL. 29, FEBRUARY 1987


9/9

mentation broth could not be effectively dehydrated

(Table

VI).

Again, the color bodies deposited on the

catalyst were the cause. Removal of the color bodies

by treating the actual fermentation broth with activated

carbon greatly facilitated the subsequent dehydration

reaction. On the other hand, treatment with Amberlite

IR-120, H did not affect much the dehydration over

the catalyst of the treated broth (Table VI). Similar

results were also obtained for the treatments with Am-

berlite

IR-45,

H-,

and trichloroacetic acid.

This research was financed by grants from the Advanced

Manufacturing Technology Center and the Pulp and Paper

Research and Engineering Center, Auburn University.

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35

RAN AND CHAMBERS: DEHYDRATION OF 2.3-BUTANEDIOL

Documents

Dehydration of 2 3-Butanediol to Mek.2