Beckman rearrangement of cyclohexanone-oxime on HNaY zeolites: kinetic and spectroscopic studies

187

Applied Catalysis, 22 (1986) 187-200 Elsevier Science Publishers B.V., Amsterdam -Printed

BECKMAN

REARRANGEMENT

SPECTROSCOPIC

OF CYCLOHEXANONE-OXIME

A. CORMAb

M.C. BURGUETa, Qufmica,

Facultad

(Valencia),

Spain.

Ingenierfa

50, Burjassot bInstituto

ON HNaY ZEOLITES:

KINETIC

AND

STUDIES

A. AUCEJOa, aDep.

in The Netherlands

de Catalisis

and V. FORNESC

Ciencias

Qufmicas

y Petroleoqufmica,

C.S.I.C.,

de Valencia,

Serrano,

C/Dr. Moliner,

119, 280064adrid,

Spain. 'Institute

de Ffsico-Qufmica

Mineral,

C.S.I.C.,

Serrano,

115 dup. 28006-Madrid,

Spain.

(Received

18 April

1985, accepted

9 December

1985)

ABSTRACT The cyclohexanone-oxime rearrangement catalysed by a series of HNaY zeolites was studied in a fixed-bed reactor with continuous plug flow at atmospheric pressure and 335°C. Selectivity curves for the different reaction products, viz, e-caprolactam,5-cyanopent-I-ene and cyclohexanone, were obtained and from them the reaction mechanism was established. The influence of the level of exchange of Na+ in the HNaY sample on the total conversion of cyclohexanone-oxime, the selectivity for the products and the decay of the catalyst are discussed. It has been found that the formation of E-caprolactam is catalysed by Brllnsted sites of strength pKa 5 1.5, and that 5-cyanopent-l-ene is formed mainly on the Na+ iOnS of the zeolite.

INTRODUCTION E-Caprolactam fibres.

as a catalyst. advantages amount

is important

Its production Although

related

caprolactam

selective,

sulphate.

Owing

in the manufacture

polar acids

investigated

the solid

this process

to these

most

and boron

such as the Beckman the catalytic

the rearrangement

0166-9834/86/$03.50

to their

rearrangement

activity

of various

of oximes

the production

of the operational

used were

silica

the success testing

[9-131. zeolites

to amides.

gel, alumina

and low selectivity.

phosphates

of a large of E-

parameters

Landis

and

Poles

0 1986 Elsevier Science Publishers B.V.

zeolites

acid-catalysed

(mordenite,

Butler

Other catalysts

[l-7].

of synthetic

in other

Thus,

and hetero-

have also been used for the re-

to give caprolactam

From the 1960s until the present, [8] has'led

from some dis-

of heat and the formation limitations,

show low activity

alumina

of cyclohexanone-oxime

lytic cracking

suffers

using oleum

[l-5].

catalysts

[6], but these

such as boron oxide,

of synthetic

out in the liquid phase

in the gas phase and the optimization being

Initially,

arrangement

highly

carried

to the rate of elimination

of ammonium

are still

as an intermediate

is normally

and Venuto

in cata-

reactions, [9] studied

NaX, Lax, HY, etc.,) [tOal used HY and Y

in

188 zeolites highly

containing

exchanged

rearrangement oxime These

to

conclusions

of nitrile

reaction, are also

However,

centration

to our knowledge,

of active

and the decay

TABLE

causes

with the work

showed

that

for the Beckman is responsible

the formation of Ward

for the

of nitriles.

[11,12] who,

verified

that the formation

Li>Na>K>Cs>H+.

a detailed

and selectivity

constants

results

of the catalyst

the metal

study of the cyclohexanone-oxime as a function

sites has not been reported.

of the adsorbed

Their

catalysts

doped with alkali metals,

in the order

of H+ exchange.

nature

whereas

on a series of HNaY zeolites

distribution

levels

of palladium.

and selective

in agreement

Y zeolites

decreases

arrangement

proportions

are active

and that the Brl)nsted acidity

lactam

using decationized

product

various

zeolites

catalysts

for the formation

have been related

re-

and con-

In this work we studied

of four zeolitic

The rate constants

of the nature

to the catalyst

the

with different

of the main

acidity

products

and to the

products.

1

Level of exchange

and unit cell dimensions

Catalyst

of the HNaY catalysts

% exchange

NaY

a/i

0.00

24.69

HNaY-1

23.50

24.67

H;;a'l-2

47.00

24.59

HFia'i3

87.50

24.50

Hfla'l-4

99.07

24.40

EXPERIMENTAL Materials An SK-40 NaY zeolite material.

The HNaY

of the NaY sample

with an Si/Al ratio of 2.4 was used as the starting

samples

The level of exchange the filtrate exchanged

using atomic

Uvasol)

was evaluated absorption

099.5%)

cyclohexanone-oxime and the solution

was dried

by repeated

NH4+ exchange

under vacuum

by determination

spectrometry.

and the unit cell dimensions

The reactant purity

were prepared

and calcination

at 550°C.

are given.

was dissolved

dried with anhydrous

and stored

in

In Table 1 the amount of Na+

of the samples

(Proquimed)

of the Na+ present

in benzene

Na2S04.

over 3fi molecular

Pyridine

sieve.

of high

(Merck,

189 PROCEDURE Catalytic

experiments

All experiments were

were carried

taken at different

the amount condensed

of catalyst

mesh Chromosorb

of a solution

measurements

adsorption

packed

by changing products

which

The reactor The reaction

in benzene

displacement

were

was connected O-ring.

was purged mixture

(17.4 %wt),

pump. The reactor

carried

which was

was glass

Pyrex

infrared

cell fitted

line by means

were evacuated

at room temperature

of a ground-

overnight

and after

at 673 K.

10 min desorbed

1 h at 150 and 350°C. The spectra were recorded at room temperature

by Benesi

tube

out using a grease-free Pyrex -5 Torr could be maintained. of 10

to the vacuum

The samples

(3 Torr) was adsorbed

580 B spectrophotometer

Titration

by

15% Ucon on 80-100-

of 20 mm.

experiments

glass joint with a Viton

Perkin-Elmer

were

and then analysed

with

with oxime.

system, in which a dynamic vacuum -2 were placed in a conventional

The pyridine

(W/F) and samples

Liquid

of experiments.

feeding

of 10 mg cm

with CaF2 windows,

for

constant.

on-stream,

of cyclohexanone-oxime

Catalyst

acidity

before

by a positive

diameter

glass vacuum

a 15 min period

in each series

heating

with an internal

Wafers

time

The W/F ratio was varied

the flow-rate

a 2 m x l/8 in. column

was used

fed into the reactor

Pyridine

contact

at 150-ZOO'C.

N2 for 3 h with

consisted

during

using

Fresh catalyst with

times on-stream. and keeping

and collected

gas chromatography

out at a constant

with n-butylamine

equipped

was carried

in a

with a Data Station.

out following

the procedure

described

[14,15].

RESULTS Kinetic

and product

In preliminary particle

size

by external

distribution

experiments

that,

(0.5 - 1.0 mm) used in this work,

or internal

The chemical

for the flow-rates the process

and catalyst

is not controlled

diffusion.

species

are 5-cyanopent-I-ene,

detected

in a typical

cyclohexanone,

the first

three accounting

the curves

of the yields

version

data

it was found

for more

E-caprolactam,

of the reaction

aniline

than 99% of the total.

at constant

at 335°C are shown

analysis

in Figure

catalyst

to oxime

and methylpyridine,

For these

ratio versus

1 for HNaY zeolites

products

three products, total con-

with different

levels

of exchange. The lines called

in Figure

optimum

obtained

1, which

performance

at a constant

ratio was carried

enclose

envelopes

space velocity

out following

the catalyst/oxime

loops,

(OPE) [16]. The transformation to the data at a constant

a procedure

described

elsewhere

are the soof the results

catalyst [16,17].

to oxime

190

5-CYANO-1

CAPROLACTAM

0

10

CYCLOHEXANONE

FIGURE

1

Yields

were

primary

calculated

given

in Figure

The kinetic [I71 with

which

products

by measuring

30

LO

O-HNaY-1 O=HNaY-2 O-H NaY-3 @-HNaY -L

of the three main reaction

The types of products of the major

20

PENTENE

products

these OPEs represent are given

in Table

(Gi) versus

total conversion

and the initial

2. These

the slope of the tangent

selectivities

in tial selectivities

to the OPEs for the products

1 at zero conversion. rate and decay

the different

constants

catalyst

samples

for the total disappearance given

in Table

of reactant

3 were calculated

by fitting

the data from Figure 6 to the equation

x = 1 - exp

where global

-KT

[So]

(1 + Gt)-N P.b.tf

x is the instantaneous rate constant,

decay constant,

conversion

So is the initial

I

for the cyclohexanone-oxime, concentration

tf is the final time on-stream

ratio; G and N are the decay

parameters,

which

of active

and P is the catalyst take

into account

KT is the

sites,

Kd is the

to oxime

the decrease

in

193 TABLE

2

Initial

selectivities

S = secondary)

and behaviour

of the three main

(PS = primary

reaction

stable;

PI = primary

Initial

selectivity

Catalyst

Product

Type

HNaY-1 II

Caprolactam

PS + s

0.13

Cyanopentene

PI

0.53

Cyclohexanone

PI

0.29

Caprolactam

PS + s

0.58

Cyanopentene

PI

0.21

Cyclohexanone

PI

0.17

Caprolactam

PS

0.75

Cyanopentene

PS

0.07

Cyclohexanone

PI

0.16

Caprolactam

PS

0.77

Cyanopentene

PS + s

0.07

Cyclohexanone

PI

0.15

HNaY-2 II

HNaY-3 II II HNaY-4

TABLE

3

Kinetic

and decay

parameters

for the cyclohexanone-oxime

Catalyst

KT/min-'

G/min

HNaY-1

124.0

0.143

HNaY-2

125.0

HNaY-3

132.0

HNaY-4

139.5

0.050

conversion

with

-1

experimentally

m

Kd/min-'

1

2

0.143

0.114

1

2

0.114

0.081

1

2

0.081

1

2

0.050

time on-stream,

x = 1/t

is related

reaction

N

and are related

to the order

(Kd) by G = (m - 1) Kd and N = l/m-l. The average to the instantaneous

conversion,

conversion

(m) and decay constant x, measured

given

in equation

(I) by

tf f

x dt

(2)

s 0

With the global given

unstable;

products.

in Tables

rate constants

kinetic

rate constant

2 and 3, and taking for the formation

(Ki) can be calculated.

and initial

into account

E-caprolactam,

The results

are given

selectivity

(ISi) values

that ISi = Ki/KT, 5-cyanopent-I-ene

in Table

4.

the kinetic and cyclohexanone

192

TABLE

4

Rate constants

for the main reactions Ki/min -1

Catalyst E-Caprolactam

Cyclohexanone

5-Cyanopent-I-ene

HNaY-1

17.70

65.70

35.96

HNaY-2

72.50

26.00

21.00

HNaY-3

99.0

9.24

21.10

107.41

9.21

21.50

HNaY-4

I

i I

1500

1

I

1400

1600

I

I

1500

I

1400

2

IR spectra

of pyridine

1500

1400

HNaY-3

Wavenumber FIGURE

1600

HNaY-2

HNaY-1

I

I

I

1600

I

I

1500

1401

HNaY-4

(Cm-‘)

adsorbed

on the zeolite

catalysts

after

evacuation

at 150°C.

Catalyst

acidity

The infrared evacuation After

of pyridine

at 150°C are shown evacuation

characteristic entiated

data spectra

on the HNaY zeolites

at 20°C after

2.

at 150°C all the samples

exhibit

the band near 1545 cm-'

of the pyridinium ion (Brbnsted acidity) and two clearly differ-1 , which are associated with pyridine coordinated with

bands at 1455 cm

Na+ ion and true Lewis acid sites with Brbnsted in Table

adsorbed

in Figure

5.

and true Lewis

[11,18,19].

The intensity

acid sites were measured,

of the bands

and the values

associated

are given

193 TABLE

5

Pyridine

adsorption

IR associated

Intensity

experiments.

bands,

in arbitrary

units,

of Brllnsted (B) and Lewis acid

at 150°C.

Catalyst

B

L

HNaY-1

30

22

HNaY-2

66

54

HNaY-3

126

194

HNaY-4

123

148

TABLE

6

Acidity

of the catalysts

measured

by n-butylamine

titration.

m equiv. No.

Indicator

1

Anthraquinone

-8.2

2

Benzylacetophenone

-5.6

3

Dicinnamylacetone

-3.0

4

Benzeneazodiphenylamine

5

Butter yellow

6

Natural

In Table method

(L)

6 the acid strength

-1

cat

HNaY-2

HNaY-3

0.00

0.00

0.00

0.00

0.00

0.00

0.14

0.20

0.07

0.30

1.42

1.23

+1.5

0.18

0.86

1.23

1.23

+3.3

0.42

0.86

1.23

1.23

+6.8

1.25

1.75

1.57

1.40

pKa

red

HNaY-1

g

distributions

of the catalysts

measured

HNaY-4

by Benesi's

are reported.

DISCUSSION From the behaviour with all the catalysts 5-cyanopent-I-ene rearrangement, oxime.

of the OPE curves studied,

the three major

and cyclohexanone,

fragmentation

in the Figure

are primary

and hydrolysis,

1 it can be seen that

products, products,

respectively,

i.e., E-caprolactam, which

are produced

of cyclohexanone-

by

194

NOH

0 NH Beckman

rearrangement

’

CSN CH2 +H20

0

/

Fragmentation

E-caprolactam

G

I

0

5-cyanopentl-ene

+ NH20H Hydrolysis Nature

of the active

cyclohexanone

sites

We have seen that there are changes products

when

indicates

the level of exchange

that the active

rearrangement,

hydrolysis

In fragmentation selectivity decrease

sites

in the selectivity

of the zeolite

involved

when

in the three main

and fragmentation,

of cyclohexanone-oxime

and the kinetic rate constant the level of exchange

cannot

of the zeolite

the Briinsted or the total acidity

it is clear that the acid sites cannot in agreement

Na+ ions can also be active correlation

between

in the supercavity

with

in catalysing

i.e.,

with

the initial

of this product

catalyst

increases

Butler

increases increasing

(Table 2). level of

be the only ones responsible and Poles

such reaction,

the kinetic rate constant of the zeolite,

reactions,

This

be the same.

to give 5-cyanopent-I-ene,

exchange,

If,

is varied.

for the formation

As either

for this reaction.

of the three major

catalyst

[IO], we assume there should

and the amount

as can be observed

that

be a direct

of Na+ ions located

in Figure

3.

K2 (min-l)

‘O 60..

0' FIGURE

3

Rate constant

of the zeolites.

10

8

6

for the formation

4

2

0

5-cyanopent-I-ene

Na+ versus

Na+ content

195

Kl 160 (mine*)

t

12cb

FIGURE

4

Rate constant

Brt)nsted sites retaining

for the formation pyridine

after

of E-caprolactam

evacuation

vs. the intensity

of

at 150°C.

Kl 180 SO-

0

0 0

0.2

0.4

0.6

0.8

1.0

1.2

mequiv FIGURE

5

Rate constant

sites of different

In any case, total absence

for the formation

1.4

butylamine

of E-caprolactam

I 1.6 1.8 @.a] -1 cat. g vs. the amount

of acid

acid strength.

the existence

of 5-cyanopent-l-ene

of Na+ indicates

as a primary

that the acid centres

should

product

in the

also catalyse

this

reaction. In the case of the qualitatively E-caprolactam,

it is generally

Brt)nsted acid sites. rate constant medium

there

for this reaction

strength

of Figure

More specifically, rearrangement

C9,lOl

is a direct

and the amount

(those retaining

seen on inspection

Beckman

Indeed,

and quantitatively

accepted

pyridine

after

most

important

that the catalytic relationship

product,

sites are the

between

the kinetic

of BrClnsted sites of strong desorption

at 15O"C),

and

as can be

4.

if one tries to relate reaction

with

the kinetic

the amount

of acid

rate constant

for the

sites of different

acid

196 strength, (Figure

a straight

line is obtained

5). We can therefore

acid strength

Mechanistic

corresponding

The shape of the curves is a primary

level exchanged of exchange

Y zeolite,

e-caprolactam

zeolites,

exchanged

zeolites

These assume

results,

at high levels

of conversion stable

whereas

for those

which

appears

as a primary

by Na+ ions [lOa], which would the less exchanged

reversible

exchanged

cyanopent-I-ene as a primary

the opposite, although

would

product.

product

plus secondary

in Table

can be formed

low levels

On the other

on 23.5 and 47.0%

stable

product

when further

2, can be explained

in two possible

the e-caprolactam,

be responsible

intermediate

ways,

if we

one

and the other

for the high values

in the acid catalysis

5-cyanopent-I-ene

elsewhere

zeolites,

catalysed

obtained

with

[ZO,

product,

With a higher

5-cyanopent-I-ene

the small amount

proportion appearing

of transformed

the

This

73. high concentration

of E-caprolactam,

whereas

can explain

and E-caprolactam.

the relatively

cause the formation

plus secondary

product.

with

with 87.5 and 99.0%

stable

unstable

given

with

between

has been reported

In the less

zeolites

1) shows that

when working

zeolite.

of a common

transformation

possibility

unstable

E-caprolactam.

are used as catalysts. and also the values

by HC [9], competitive

The existence

(Figure

product

to be a primary

is a primary

that the 5-cyanopent-1-ene

catalysed

Brt)nsted sites with an

in producing

plus secondary

appears

5-cyanopent-I-ene,

exchanged

that only those

to pK, 2 1.5 are active

considerations

E-caprolactam

hand,

only when sites of pKa I 1.5 are considered

conclude

which would

5-cyanopent-l-ene

of e-caprolactam as a primary

E-caprolactam

of 5-

would

the process

plus secondary makes

appear

behave

as

can be

product,

this instability

negligible. The third major unstable explain traces

product.

compound,

cyclohexanone,

The presence

the primary

character

of water

of the cyclohexanone.

in the feed or as residual

possible

to explain

with nitrogenated

+

NH2R

water

the instability

bases

to give E-caprolactam

appears

adsorbed

unstable

media

This water

to

can be present

as

[21]. It is

by assuming

intermediate

as a primary,

is necessary

on the zeolite

of cyclohexanone

to give a highly

on all catalysts

in the reaction

that

it can react

that will decompose

[22]:

_

(3)

197 We checked by feeding

the possibility

cyclohexanone

HNaY zeolite were

take place

and cracked

and the formation

the instability

observed

under our experimental

with the ketoxime

temperature

of 335°C.

of 5-cyanopent-I-ene

for cyclohexanone

would

using an

products

reaction

Nevertheless,

conditions.

conditions

into the reactor,

The main reaction

Consequently,

products.

under our experimental

cyclohexanone with

together

at a reaction

5-cyanopent-I-ene

of such a reaction

detected

(3) does not

the disappearance

of

also be consistent

and the secondary

character

for the processes

taking

of

5-cyanopent-I-ene.

In conclusion, during

a possible

the Beckman

reaction

rearrangement

mechanism

on HNaY zeolites

place

is

Ni’H

3,3

Cyclohexanone

Pentametilw-

5-Cyanopent-l-ene

oxaziridine

Catalyst

decay

From Figure

6, where

seen that the activity

the conversion

vs. time on-stream

of the catalysts

decays

The decay may be due to the formation formation

during

methylpyridine

the reaction

and aniline.

the decay of the catalyst

products.

Indeed,

catalyst,

as is indicated

the increase

sample

in the reaction After

reaction, cm-').

work by elimination

centred

surface

with

several Because

infrared

bands appear

in HNaY-4

important

of basic

colour

factor

nitrogenated

level of exchange. after

on the and

Furthermore, being used

can be made.

catalyst

of interpreting

on hydrogen-Y

to the

of the catalyst

spectroscopy

possibilities.

adsorbed

and/or

of coke is deposited

observations

of the difficulty

of the different

white

increasing

by

it can be

such as hydroxylamine,

that the most

is the adsorption

7), the following

ClObJ, _":e cyclohexanone-oxime 3640 cm

indicate

by the still almost

is analysed

(Figure

of coke on the catalyst

a very small amount

of the decay constant

if the zeolite

(4000-1350

reaction

is plotted,

time on-stream.

of very basic products,

Two facts

producing

after

with

in the region the spectra

studied

we must

According

to Butler

and Poles

zeolite

interacts

with the

hydroxyl band of the zeolite, and its spectrum shows two bands -1 -1 at 1700 cm and 2700 cm assigned to v(C=N+) and v(N+-H), respectively.

.

,.

, _

~, ,_ ^

FIGURE 6

-

g

Total

0

, 60

_^

,

__.-

,

,

,

, T.0.S (min)

loo 120 140 160

-

(CT) vs. time on-stream

60

HNaY-3

conversion

,

40

,

20

(T.O.S.)

I

’

’

’

for the different

I

zeolite

Catalysts.

199

Wavenumber FIGURE 7

(Cm-l)

IR spectrum of HNaY-4 catalyst

after

reaction.

As both the 1700 and 2700 cm-' stretching

bands are absent

(Figure

oxime must

7), the presence

On the other hand, with

the presence

of cyclohexanone

of a band at about

[lob], and therefore

and water, at1650cm adsorbed

The v(NH)

it is masked

band at 1540 cm-'

by the v(CO)

(amide

and &(HOH)

II)

is very

of &-caprolactam

&-caprolactam. the band appearing

to NH stretching consequently

vibrations

The presence

at about

of amines

infer the probable

on the surface

in the spectrum Only a weak

3300, 3150 and 3050 cm

and u(=C-H)

presence

-1

can be assigned

of the aromatic

of aniline

ring. We can

and methylpyridine

adsorbed

of the zeolite. of 5-cyanopent-I-ene

ruled out, as the characteristic

band in this region

on the highly

band of nitriles

of 5-cyanopent-1-ene

adsorbed

is detected

exchanged at about

zeolites must be -1 2280 cm that appears

on HY zeolites

in the zeolites

[23] is not visible. with a high sodium

(Nay and HNaY-1).

On the other hand, (Table 3), decreases by considering nitroqenated amount

of E-caprolactam must be associated -1 [v(CO)] and a complex band centred 1650 cm

respectively. In the spectrum we observe a very strong band centred -1 -1 that may correspond to the , and a more complex band at 1450 cm

Finally,

content

be ruled out.

the IR absorption

at 1450 cm -' (uCH, CH2 scissor). weak

in the catalyst

the decay of the catalysts, with

compounds,

of these products

exchange

increasing

that aniline,

of the zeolite

level of exchange.

methylpyridine,

are responsible formed

measured

increases.

These

hydroxylamine

for the catalyst

per gram of catalyst

by their decay results

constants

are explained

and, in general, poisoning,

decreases

basic

and that the

when the level of

200 it can be said that the Beckman

In conclusion,

oxime on HNaY zeolites to this reaction, the active

5-cyanopent-l-ene

sites of this reaction

Na+ ions located is increased to primary

the behaviour

stable.

decay

(hydroxylamine,

is formed

which

is explained

aniline

coke on the catalyst

by fragmentation

changes

of the reactant, but also the of the zeolite

from primary

by considering

takes place at low levels

is due to poisoning

of cyclohexanone

When the level of exchange

of c-caprolactam

This result

rearrangement

by Brllnsted acid sites of pKa 5 1.5, Parallel

being not only the acid sites,

in the supercavity.

of 5-cyanopent-I-ene catalyst

is catalysed

plus secondary

a consecutive

of exchange.

reaction

Finally,

of the acid sites by the basic products

and methylpyridine),

rather

than to the deposition

the formed of

surface.

REFERENCES 1

9 10

1: 13 14 15 1; 18 :: 21 22 23

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