Reaction of ethanol and ammonia to pyridines over zeolite ZSM-5

Applied Elsevier

191

Catalysis, 26 (1986) 191-201 Science Publishers B.V., Amsterdam

REACTION

OF ETHANOL

F.J. VAN DER GAAG, Laboratory

F. LOUTER,

of Organic

'2628 BL Delft, 'Present

AND AMMONIA

in The Netherlands

TO PYRIDINES

OVER ZEOLITE

J.C. OUDEJANS'

and H. VAN BEKKUM

Delft University

Chemistry,

ZSM-5

of Technology,

Julianalaan

136,

The Netherlands.

address:

Unilever

3133 AT Vlaardingen,

(Received

- Printed

Research

Laboratory,

Olivier

van Noortlaan

120,

The Netherlands.

2 December

1985, accepted

10 March

1986)

ABSTRACT Pyridine bases are formed by reacting ethanol and ammonia in the presence of air in a continuous flow microreactor over zeolite ZSM-5. Optimum selectivity to pyridine and optimal conversion are obtained using a HZSM-5 catalyst with Si/Al = 65 at temperatures between 600 and 650 K. Other catalysts i.e., Co-, Fe- or CdHZSM-5, HY, HMordenite or amorphous silica-alumina show lower selectivity and/or activity. When air as a vector gas is replaced by nitrogen, no pyridines are formed. For the ethanol-ammonia reaction to pyridines a mechanism is suggested.

INTRODUCTION Since the discovery been studied. alkylation

of zeolite

The conversion

of benzene

A relatively

amines

ZSM-5

small number

from alcohols,

increase

Cu-H-exchanged

HZSM-5

of the zeolite pyridine

over zeolite

in the patent

of

literature

were

to primary

by

found

to

amines.

reported

to be good catalysts

to the feed had a beneficial

in the

and selectivity. from acetaldehyde

in the patent

literature

of acetonitrile

to be the principal

under similar

and ammonia

[9]. Depending

was observed.

side product

Recently

of phenol

(783 K) [13]. Aniline

conditions

[14,15].

over

on the cation 2-methyl-

amination

to aniline

can also be converted

The conversion

is low and

are found.

zeolite

it is clear that in the absence ZSM-5

is able

to catalyze

o 1986 Elsevier

Science

Publishers

of oxygen

the conversion

to amines.

0166-9834/86/$03.60

catalyzed

The synthesis

of water

From the data available

ammonia

[S-17].

were

ZSM-5 at high temperature

mixture

[63

[17]. The addition

the formation

byproducts

[l-3], the

reported.

and clinoptilolite

of alcohols

have

[5], the alkylation

deal with reactions

was reported

erionite

type zeolites

was reported

to Z-methylpyridine

reactant

or olefins

of (methyl-)pyridines

was found

reactions

to hydrocarbons

of xylenes

papers

of the reaction

ZSM-5

on the activity

zeolite

and ethanol

is one of the reactants

like ZSM-5,

of toluene

The production

many

ethers

Zeolites

ZSM-catalyzed

[7] are the most frequently

of recent

ammonia

the selectivity

ammoxidation effect

of toluene

in which

[8,11,12,16].

of methanol

[4], the isomerization

and disproportionation

zeolite

ZSM-5 numerous

B.V.

in the

of ethanol

and

192 Here we present

data on the reaction

alumina

have been

N-containing

H+-exchanged

of oxygen.

in the presence

For comparison

have been studied.

included.

compounds

of ethanol as well

and ammonia

as metal

also HY, HMordenite,

The influence

(particularly

over zeolite

ion exchanged

zeolites

and an amorphous

of some variables

heteroaromatics)

ZSM-5

silica-

on the formation

of

is shown and a mechanism

is suggested.

EXPERIMENTAL Materials Zeolite

ZSM-5 was prepared

propylammonium

bromide

to the patent

literature

zeolites were

prepared

cedure. 0.05/n

followed

solution

Zeolite

All catalysts of particles

Silicalite

[ZO] using tetra-

was prepared

to the synthesis further

according

mixture.

The

use. H+-exchanged

zeolites

in 0.5 M HCl at ca. 353 K for 0.5 h. (10 g zeolite

zeolites

washing

were

with water

prepared

and repeating

by ion exchange

ion under the conditions

by ion exchange

(IO g zeolite

per

for

of HZSM-5

in a

for H-exchange.

of NaY (SK-40,

1 solution)

the pro-

Union

Carbide)

in an

1 day at room temperature,

at 673 K.

HMordenite

and LA-LPV

template.

at 823 K before

of the desired

by calcination

in the literature

NH4F added

by thorough

HY was prepared

0.1 M NH4Cl

with

overnight

M("+)-exchanged

followed

[21]

by ion exchange

M solution

Zeolite

HA-HPV

as the organic

were calcined

per 1 solution),

as described

(Zeolon

cracking were

IOOH, Norton)

catalysts

dry pressed,

and amorphous

(Ketjen),

crushed

were

silica-alumina

used without

and sieved

to obtain

catalysts,

exchange. a sieve fraction

of 1.4-2.0 mm.

Procedure The apparatus described

used in the catalytic

by Oudejans

The catalyst 8 mm internal

(3 g) was placed

diameter.

saturators

containing

H20:02

ethanol

of the saturators were chosen

is essentially

the same as

continuous

and an aqueous

flow glass

in an electronically

air) was passed

through

0.5 M ammonia

were obtained

reactor

of

controlled

two thermostatted

solution,

by adjusting

respectively.

and controlling

and the two flows of the carrier

such that the molar

the

gas. Standard

ratio of the reactants

was: NH3:C2H50H:

= 1:3:6:9.

The saturated

gas streams

0.17 h-l. The gas mixture graphy

was placed

gas (usually

flows of the reactants

temperature conditions

in a fixed-bed

The reactor

fluid bed oven. The carrier

The desired

experiments

[19].

were mixed

leaving

using a 3 m 10% PEG on Chromosorb

(temperature inorganic

programmed

components

operation)

was analyzed

column

with

and a 1 m PORAPAK

(e.g., CO and C02, isothermal

was performed

by a computer

products

identified

were

and fed to the reactor

the reactor

connected

by GC-MS

at WHSV

by online

FID for organic Q column

components

with TCO for

operation).

to the gas chromatographs.

using a Varian

(ethanol)

Peak integration

If

=

gas chromato-

necessary

44 S mass spectrometer.

193 100 %

T 80

6C

4c

2(

(

FIGURE

1

Conversion

and selectivity

the ethanol-ammonia to pyridine; 0,)

v

4

2

0

reaction

8

-

AI/UC

(wt%) plotted

vs. Al atoms

over HZSM-5.@,Oconversion;

selectivity

, A

and 633 K (O,Cl,n

6

to ethene;

reaction

w

per unit cell in selectivity

, 0

613K(.,w,

temperature:

).

RESULTS Several

catalysts

to pyridine

bases.

have been tested

The results

in terms of the influence

in the conversion

of these experiments

of single

catalyst

of ethanol

will

and ammonia

be presented

and reaction

parameters

and discussed on conversion

and selectivity.

Effect

of Si/Al

ratio of ZSM-5 zeolites

Data of experiments Major

products

using air as the vector components

with HZSM-5

mixture

Ethyl acetate

< 0.5%. Oxidation (wt%) respectively

to carbon

ratios.

include

diethyl

ether

acetaldehyde,

and 3- and 4-picoline dioxide

in Table

- in the presence

is substantial

1 and Figure 1.

of water

and pyridine. ethylamine,

are generally

acetonitrile

present

but in general

and

Other

in amounts

lower than 20%

8.5% on carbon.

The data show that there high Si/Al

are presented

reaction

gas - are ethene,

in the product

and toluene.

zeolites

in the ethanol-ammonia

is an optimum

in pyridine

selectivity

at relatively

194 TABLE

1

Effect

of Si/Al

Si/Al

ratio

Al/uc

in the ethanol-ammonia

reactiona

Temp.

Conv.

Selectivity

/K

/:;

ethene

over HZSM-5

/ wt% to:b

diethyl

acetal-

ethyl-

ether

dehyde

amine

12.3

7.2

613

59.9

51.4

8.0

3.0

< 0.1

12.3

7.2

628

93.4

72.6

0.8

0.5

< 0.1

12.5

7.1

613

21.6

29.7

12.0

4.7

0.8

15.4

5.8

613

19.3

40.9

4.4

1.9

0.3

15.4

5.8

633

40.8

71.3

4.9

2.8

0.3

90.5

0.6

< 0.1

< 0.1

1.7

0.4

20.3

4.5

653

83.9

26.3

3.5

613

46.8

26.3

5.4

26.3

3.5

633

88.0

63.1

0.3

0.4

< 0.1

26.3

3.5

653

98.1

76.3

1.6

< 0.1

< 0.1

27.3

3.4

623

53.0

56.9

3.4

1.7

0.4

27.3

3.4

643

97.7

72.5

< 0.1

< 0.1

< 0.1

55.5

1.7

613

34.0

23.4

7.1

3.0

2.2

55.5

1.7

633

22.9

24.0

13.1

5.0

3.5

36.0

9.0

2.9

1.7

32.9

55.5

1.7

653

35.8

55Y

I,7

613

18.0

9.5

15.4

< 0.1

131.1

0.7

593

11.3

10.0

7.8

5.7

6.8

131.1

0.7

633

29.3

27.3

6.9

3.6

3.5

131.1

0.7

653

50.8

51.0

2.7

2.8

1.2

m

0

608

8.1

2.2

1.2

m

0

638

14.4

6.1

m

0

663

32.8

9.6

19.3

6.4

0.6

22.6

3.0

0.4

31.7

2.7

aMolar ratio NH3:C2H50H:H20:02 = 1:3:6:9, WHSV (ethanol) b Composition of product mixture after 4 h on stream. 'Experiment

with

1% O2 in N2 vector

It is also observed

that with

as the number

version

increases,

content

show an increased

In general,

deactivation

the conditions

used; after

reached,

in which

increasing

of Al atoms

increases.

per UC the con-

Zeolites

with a high Al

to ethene.

of the HZSM-5 an initial

of air.

number

of acid sites

selectivity

conversion

of at least 48 hours.

gas instead

= 0.17 h-'.

catalysts

period

and selectivity

is hardly

observed

of a few hours a steady stay almost

constant

under

state

is

over a period

195

acetonitrile

toluene

pyridine

3.7

< 0.1

13.4

2.7

<

5.2

< 0.1

Z-picoline

cop

4.6

14.3

< 0.1

17.3

11.7

6.8

11.6

6.1

0.1

4.1

3.4

10.2

5.1

20.8

< 0.1

3.7

5.5

1.6

7.3

< 0.1

2.1

1.4

0.3

4.9

8.1

< 0.1

36.2

8.0

11.7

3.5

2.1

12.4

0.5

17.3

1.6

0.4

7.5

< 0.1

14.0

4.6

< 0.1

18.8

2.8

< 0.1

14.5

< 0.1

10.2

3.0

< 0.1

47.6

2.5

8.9

2.1

< 0.1

33.6

2.4

13.3

2.5

< 0.1

31.5

1.8

12.0

6.4

4.4

23.4

4.9

0.1

3.3

< 0.1

43.8

2.5

20.0

3.1

< 0.1

33.5

0.8

21.2

2.4

< 0.1

27.9

0.4

11.7

12.6

16.0

< 0.1

38.1

2.6

11.9

7.0

< 0.1

39.7

5.6

0.5

2.6

< 0.1

44.3

< 0.1

Effect

of metal

Table metal

exchange

conversion

and/or

to pyridine.

ZSM-5

data of catalytic

zeolites.

shows hardly

experiments

performed

In general, HZSM-5 catalysts

to pyridine

high activity

NaZSM-5

than the MHZSM-5

for deep oxidation

zeolites.

and therefore

with

some

show better FeHZSM-5

a low selectivity

any activity.

of the type of Si-Al-catalyst

The results catalysts

HZSM-5

selectivity

shows a relatively

Influence

in zeolite

2 shows the analysis

ion exchanged

10.2

3.9

of experiments

are given

All catalysts

in Table

in Table

with different

types of zeolite

and with amorphous

3.

3 are, more or less, capable

of forming

pyridines

from

TABLE 2

Si/Al

28.5

17.9

16.5

16.5

Catalyst

CdHZSM-5

FeHZSM-5

CoHZSM-5

CoHZSM-5

Ethanol-ammonia

0.25

0.25

0.38

0.11

M/UC

reaction

633

613

598

46.7

19.9

75.2

39.7

/K

623

Conv.

1%

Temp.

using MHZSM-5

56.9

33.4

10.6

48.0

ethene

7.8

17.1

5.3

4.0

8.7

5.1

1.9

dehyde

ether 7.5

acetal-

to:

diethyl

Selectivities/wt%

catalysts.

1.0

2.2

0.8

0.6

amine

ethyl-

3.0

2.2

13.8

2.1

nitrile

aceto-

5.0

7.4

10.6

16.5

pyridine

1.9

3.7

< 0.1

4.1

2-piCOliW

x/4-

2.2

3.5

< 0.1

2.4

picoline

18.2

18.4

53.7

16.8

co2

z 0,

3

2.5

2.5

a

b

HY

HY

HA-HPV

LA-LPV

b13 wtX A1203

a25 wt% A1203

5

5

HMordenite

Si/Al

HMordenite

Catalyst

Other Si-Al catalyst

TABLE

598

613

613

623

598

623

56.6

44.1

43.7

86.2

34.1

97.2

88.8

36.6

16.3

61.7

49.2

87.4

6.5

2.1

2.7

4.8

0.4

1.6

2.2

1.5

0.6

4.0

0.6

< 0.1

acetaldehyde

/K

to:

ether

ethene

1% diethyl

Selectivities/wt%

Conv.

Temp.

types

ethyl-

7.5

41.7

< 0.1

0.7

< 0.1

< 0.1

amine

aceto-

8.5

4.4

8.3

6.4

1.6

1.5

nitrile

pyri-

6.2

1.7

1.6

2.0

< 0.1

< 0.1

dine

32.5

29.9

25.0

32.6

10.5

8.1

COP

198 ethanol

and ammonia

that HZSM-5 especially

in the presence

is a superior Si-rich

catalyst

preparations

in contrast

to other Si-Al

some coking

is observed

whereas

other

Influence

of reaction

From Table

of the catalysts

In addition,

in this reaction.

(Si/Al > 23, Al/uc

but the activity

HZSM-5

shows

catalysts,

< 4), show a low rate of coking,

e.g., HY. With Al-rich

catalysts,

Si-Al catalysts

Comparison

of oxygen.

is hardly

HZSM-5

affected

catalysts

after 48 h on stream

deactivate.

temperature

1 the following

effects

of increasing

reaction

temperature

can be

observed: (i)

The conversion

of ethanol

(ii)

The selectivity vity to ethene

Effect

of the reaction

to pyridine

bases decreases

and the selecti-

(and CO2) increases.

(iii) The selectivity substituted

increases.

within

the group of pyridine

bases shifts

towards

the un-

product.

of feed composition

Oxygen carrier

content

of the vector

gas from 20 ~01%

The yields

of diethyl

as a carrier ethylamine oxidized

On decreasing

ether and substituted

gas a product

is obtained. products

gas.

the oxygen

(air) to ca. 1 ~01% the yield pyridines

mixture

comprised

mainly

A decrease

in oxygen

content

(substituted

pyridines

content

of pyridine increase.

of ethene,

of the

decreases.

When using nitrogen diethyl

ether and

thus leads to a decrease

are less dehydrogenated

in

than pyridine

itself). Ammonia

and water

content.

no nitrogen-containing ethanol

is almost

deep oxidation

completely

reactions

When no water

is observed.

formation

and keeping

when no ammonia

can be formed,

oxidized

on HZSM-5

is present

formation

Obviously,

compounds

in the absence

to CO2 and H2D. Ammonia

of ammonia,

therefore

inhibits

deactivates

and coke

catalysts.

in the feed the HZSM-5

It may be concluded the zeolite

is fed to the reactor

Moreover,

surface

catalyst

that water

assists

in preventing

coke

clean.

DISCUSSION A comparison obtained

of the optimum

in the conversion

considerably Obviously

higher

poisoned

to aromatics. HZSM-5

acid sites.

These

by partial

poison

without

sites

ammonia

here with

for HZSM-5

of the catalytically

coke by cracking

of conversion. active

[223 found

in the conversion

an increased

the results

[3] shows that here a a good degree

Nayak and Choudhary

(Si/Al = 17), probably

remove

reported

to obtain

poisoning

bases.

They also reported

catalysts

conditions

is required

and the product

to be the most effective olefins

of ethanol

temperature

this is caused

sites by ammonia

reaction

of alcohols

rate of coking

(acid)

pyridine and

on pyridine

caused

by the lack of strong

reactions.

We also find coke

199 formation

on Al-rich

Water Water

to keep the catalyst

has a positive

vapor

effect

can assist

For the conversion

and aromatization

Because

zation.

non -acid sites

NH3

H'

-

H'

-

SCHEME

supposed

+

Pyridines

NH3

CH,CHO

acid

sites

CH,CN

CHj=CH,

CH,COOH

can be

ring closure

to acetaldehyde, and aromati-

instead

the second mechanism in Scheme

Also

to the feed.

cyclization

way

CH3CH2NH,

Possible

The first

ammonia

.

in a simplified

vapor

amination,

as a feedstock

formation,

of the catalys

two mechanisms

of ethanol

with ammonia,

or propene

in pyridine

activity

of ethanol is preferred.

1.

CH3CH20H H+

w

CH!!-0-CHCH 3

2

3

CH,CH,-0-CH,CH,

H'

1

of ethene

are depicted

02

CH,CH,OH

-

the use

of water

to pyridines

and the other via dehydrogenation

not to result

Some pathways

and the stability

ions, oligomerization,

reaction

Here cracking

clean.

bases from the catalyst.

by addition

and ammonia

carbenium

aldolization/retroaldolization,

was found

the product

is decreased

of ethanol

one involving

zeolites.

surface

on the selectivity

in desorbing

the rate of coke formation

envisaged:

but not on Si-rich

zeolites,

seems to be high enough

mechanism

for reaction

step for the formation

to be the dehydrogenation are then converted

of C2H50H

of pyridines of ethanol

to pyridines.

and NH3 to pyridines.

from ethanol

to acetaldehyde.

and ammonia

is

Acetaldehyde

Both steps have been separately

and

reported

in the literature. Matsumura

et al. [24] showed

over ZSM-5 zeolites

containing

catalyze

the dehydration

the most

part poisoned

could be catalyzed picture reaction

of ethanol.

temperature.

Matsumura Adding

temperature

can be produced

In our experiments

by NH3 and the product

by the resulting

is lacking.

the reaction

that acetaldehyde

little or no acid sites.

non-acidic

bases. sites

needed.

as a hydrogen

Shabtai

from ethanol ZSM-5 zeolites

the acid sites are for

The dehydrogenation though

et al. use an oxygen-free oxygen

Protonated

a detailed

reaction molecular

feed and a somewhat

acceptor

to the feed might

higher lower

et al. [25] found that type X zeolites

t.

200 are able

to catalyze

as hydrogen

acceptor

show that zeolites acetaldehyde of proton

the dehydrogenation at temperatures

with

to ethene.

sites

increasing

between

being in equilibrium

reaction

selectivity

acetaldehyde the number pyridine

to pyridines

production of acidic

formation

and low enough temperature

temperature

pyridines

is found

to assure

Further

reactions

(i)

conversion

(ii)

ammoxidation

(iii) oxidation (iv)

on the zeolite

to ethene

of ethanol

to acetic

total oxidation

caused

As a result,

catalysts

At this point

enough

reaction

activity

for

over non-acidic

increases

by a lower fraction

optimum

of

selectivity

more of

to

temperatures.

comprise:

ether over the acid sites,

or acetaldehyde

acid, followed

of reactants

to

where catalysis

dehydrogenation

ratio at higher

and diethyl

sites.

and ammonia

is balanced.

to assure

ethanol

(possibly

Si/Al

number

(ca. 725 K) and feed rate

to pyridines

by N-compounds).

at a higher

1

from

conditions.

the rate of the former

than the rate of the dehydrogenation acidic sites poisoned

and ammonium

of acetaldehyde

sites has to be high enough

sites. At increasing

1 and Figure

in selectivity

is found at an Al content

and conversion

of aldehydes

in terms of an increasing

with pyridinium

(LHSV = 1) are used here under oxygen-free Optimum

show a shift

the conversion

over HZSM-5. A higher

in the presence

373 and 453 K. Table

A? content

This can be explained

Chang and Lang [9] described pyridines

of alcohols

to acetonitrile.

by esterification

or products

to carbon

to ethyl acetate. dioxide

and water.

CONCLUSIONS Pyridine oxygen,

bases can be produced

using HZSM-5

positive

effect

direct processing possible.

by stepwise

activity

in the presence

of water in the feed mixture

and stability

as obtained

of the catalyst,

by fermentation to pyridines

between

of has a

therefore

processes,

under standard

is flow

600 and 650 K and a HZSM-5

be selected.

with the partial

conversion

and ammonia

and selectivity

temperatures

= 65 should

starting

The presence

ethanol,

conversion

conditions

with Si/Al

A mechanism followed

of aqueous

For optimum

and concentration catalyst

catalysts.

on selectivity,

from ethanol

oxidation

to pyridine

bases,

of ethanol

to acetaldehyde,

is suggested.

REFERENCES 1 2 3 4 5 6 7

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