Selective O-alkylation of phenol with methanol

Applied

Catalysis,

21 (1986)

263-271

Elsevier Science Publishers B.V., Amsterdam -Printed

SELECTIVE

0-ALKYLATION

R. PIERANTOZZI*

OF PHENOL

and A.F.

WITH METHANOL

NORDQUIST

Air Products and Chemicals, Inc., P.O. Box 538, Allentown, * to whom correspondence should be addressed.

(Received

4 June

263

in The Netherlands

1985, accepted

21 October

PA 18105, U.S.A.

1985)

ABSTRACT The alkylation of phenol with methanol was studied over La2(HP04)3, BaSO4 and SrS04 catalysts. Studies were conducted in batch liquid phase reactors and in continuous flow reactors. Selectivities for anisole formation were up to 94% over La2(HP04)3 and 907; over BaS04 at 573°K. SrS04 was inactive. In batch liquid phase studies, the high selectivity to anisole was maintained over BaS04 at 86% conversion. La2(HP04)3 showed some decline in selectivity at high conversions. Comparison of these catalysts to A1203, H-ZSM-5 and work reported in the literature is presented.

INTRODUCTION The alkylation anisoles

of phenol with alcohols

over acidic

shown that basic catalysts alkylated

products

the catalyst,

from phenol

products

increased.

the catalysts The increased in a greater

can be correlated acidity

to o-cresol

ratio,

acidic

In a study utilizing faujasites,

Balsama

by reaction

of phenol

cresols

as though

ring alkylation

Tanabe

selectivities

basic

catalysts

and methanol with

catalysts

strongly

acidic

in preference

for

ion [2].

[3] results catalysts

such

MgO gave high

oxide,

Ti02.Mg0

to a combination

such as ZSM-5,

at 250°C

result

of the metal

on the catalyst

that mixtures

the surface

for

or O-alkylated

selectivity

that acidic

of

with

a

than MgO at 400°C with 85% ortho-

was attributed

sites present

zeolite

the acidity

in electronegativity

[If]. The mixed

ring

the selectivity

for anisoles

showed

and

et al. have

predominantly

as high as 82% while

to be more active

et al. showed

was correlated

that the more acidic appears

by the increase

The ortho-selectivity

sites and strong

2,6-xylenol

out that the ring alkylation

or Z,&xylenol

was found

and ZR3(P04)4,

to the electronegativity

afforded

gave anisole

produce

and the selectivity

of ring-alkylation.

selectivities

selectivity.

pointed

o-cresol,

known [I]. Nozaki

[lel. On increasing

BP04, A1P04

decreased

as Si02*A1203

I:1 Ti/Mg

and methanol

using

Moffat

degree

is well

such as MgO and Ca3(P04)2

for example,

ring alkylated products

to produce

and basic catalysts

and cresols

as well as strongly

to 0-alkylation.

are obtained

selectivity

of these materials.

in ring alkylated

[If].

HY and ion exchanged

of anisole

[4]. The maximum

acidity

of weakly

surface

products.

This

to o,pindicates

It therefore

basic catalysts

result

in

264 Our objective interest

in this work was to selectively

in the 0-alkylation

as additives

in gasoline

and sulphate

catalysts

methanol

to produce

alkylate

stems from the report

to boost octane

[5]. We report

that are selective

phenol

to anisole.

Our

that methyl aryl ethersareuseful here our work on phosphate

for the 0-alkylation

of phenol with

anisole.

EXPERIMENTAL Catalyst

testing

Gas phase reactor

reactions

at atmospheric

phenol

and methanol

14-18X He prior to obtain

the mass

Liquid

reactions

conversion

Selectivityi

products,

sieve 5A column

were conducted

The premixed where

were

using a column

tubular feed of

it was diluted

trapped

of 10% SPZIOO

106 column

with

at O"C, weighed on 80/100

gas. The gas phase was analyzed

for CH4,

at 90°C. H2 and CO

at 90°C.

in a 300 ml Parr reactor

using 50 g of

under He.

Moles product i c Moles phenol derived i

products

x

Mass recovery

x ,DD?;

x 1002

calculations

Equilibrium

calculations

free energy

anisole,

He carrier

chamber

[Phenolic derivatives] in Product [Phenol] in Feed

=

=

Thermodynamic

bed. Liquid

using a Chromasorb

and 5 g of catalyst

steel down-flow

using 5.0 cc of catalyst. into a vaporizing

on a molecular

phase

out in a stainless

and analyzed

CO2, C2H6 and CH30H

reactants

Gibb's

recovery

at 90°C with

were determined

Phenol

pressure

was pumped

to the reactor

mesh Supelcaport CH30CH3,

were carried

cresols

ether formation

were made with a computer

of the system

and water.

[6,7], assuming

program

that minimized

that the only products

This was a fair approximation

the

are

since methane

and dimethyl

was minimal.

Catalysts A1203

was Alcoa

was prepared

F-20, 80-200

by precipitation

stoichiometric

amount

mesh, with

surface

from a 2M aqueous

of (NH4)2HP04.

La = 29.0%,

P = 7.44%.

the major

crystalline

phase as La(P04).

or Sr(N03)2

Surface

HZSM-5

was prepared in a manner

and NH4HS04.

Ba catalyst

analysis:

8a = 53.13%; S = 12.7%. Surface

Sr catalyst

analysis:

Sr = 40.1%;

The

major

crystalline

phase

with

a

was washed and dried at 110°C. -1 area = 47.27 m2 g _ XRD analysis described

[El]. BaSD4 and SrS04 were prepared

literature

of [La(N03)3]

The precipitate

Analysis:

from Ba(N03)2

area of 210 m2 g-l. La2(HP04)3

solution

S = 18.8%. Surface

in the Sr catalyst

as described

analogous

in the

to La2(HP04)3

2 -1 area = 3.73 m2 g . -1 area = 1.38 m g .

was SrSO4.

RESULTS

AND DISCUSSION

Catalysts pressure

were

tested

in either

or in a continuous

a stirred

flow reactor

batch

at

reactor

under autogeneous

1 atm.

Table 1 summarizes the results obtained with Al203 and HZSM-5 in continuous gas phase were

reactions.

l&24%.

Molar

the reaction

rates were

methylanisoles products phenol

to aniSOle

was

1:1 to 5:1. On HZSM-5, 1:1, the rates were selectivity

HZSM-5

was the most active

to agree with alkylation.

Balsama's

hydrocarbons

reported

the CH30H/phenol

Table

results

to anisole

a drop in anisole

selectivity

from the increased

formation

increased

to 11.25.

product tested

Higher

and anisole

is obtained. the product

Comparing negativity

temperatures

At thermodynamic

cresol

range 573-674

Selectivity

aniSOle

in this selectivity

dropped

product,

equilibrium

NO

catalyst

K.

but

arises

of ring alkylated

to 60% and the methylanisoles

rather

of both

than the kinetic

under any

the conditions

Of

at greater

CreSOlS

deactivation

than

was observed

with

over an 8 hour period. this result

argument

to that reported

for comparison

seem to fit this case. La2(HP04)3 Ca3(P04)2

LaP04.

and the selectivity

= 5:1, the

mix would contain

concentration.

The La2(HP04)3

tend to favor the ring alkylation

as the thermodynamic

H2

in four fold rate increase

loss

of

conversion.

and 23.61%

increased,

and the appearance

for anisole

of this reaction

IO4 times the anisole this catalyst

to 622 K results

of cresol

At 674 K the selectivity

and BaSO4.

to

traces

co-fed

for CH3DH

28.8 wt% La2(HP04)3

to 8O?i. The major

anisoles.

the phenol

is that Balsama

At 573 K with methanol/phenol

the temperature

tends

ring

in the activity

only detected

the catalyst

the conversion

higher

was converted

of 12-71X over the temperature

was increased,

decreased.

observed

for La2(HP04)3

:

and

selectivity

gives

studies

We, however,

obtained

containing

in conversions

When the temperature

was 947I. Raising

mixture

from

et al. reported

acidity

in the reactions

but the

[4]. In our hands,

Our ring alkylation

may have activated

The methanol/

ratio was raised

Balsama

in their

and

i.e. at methanol/phenol

at 250°C

that higher

phenols.

difference

species.

but

aromatic

rate for A1203,

the 5:1 feed ratio,

for the discrepancies

the results

is a hydrated

La2(HP04)3

tested.

that the methanol

which

2 summarizes

catalyst

was observed,

than with

over HZSM-5

showing

and not to alkylated

CH4 and C2H4. The major with

catalyst

We have no explanation

of HZSFI-5. Balsama

alkylated

Interestingly,

alkylation

results

were cresols

low. The other

on the reaction

effect

higher

unaffected.

for phenol

was

when the methanol/phenol

the opposite

significantly

was virtually

little activity

effect

improved

produced

selectivity

and other multiply

to have little

1 atm, phenol conversions

were as high as 76% with Al203

by-products

the methylanisole

2,6-xylenol

seemed

3OO"C,

to anisole

low. The major

although

included

ratio

selectivity

Under these conditions, selectivities

(ring alkylation

selectivity

by rloffat [21,

shows that

of the ring and O-alkylation has an electronegativity

= 882) and A1P04

the electro-

activity

intermediate

(ring alkylation

at 674 K is still only 40X. The reactions

does not between

= 56%), Yet the over Ca3(P04)2.

1

1

1

5

HZSM-5

HZSM-Sd

HZSM-5

22.0

11.3

19.8

10.7

23.9

conversion

'Feed stream contains d After 24 h on stream

14-18% He

540

496

503

503

521

GHSVC

0.77

1.16

1.8

0.70

0.64

anisole

g cat

-1 h-'

58.1

64.2

57.8

65.9

76.5

Anisole

36.9

34.0

37.7

32.3

17.7

Cresols

1.67

0.86

2.56

0

0.5

anisoles

Methyl

3.34

1.01

1.78

1.8

5.3

aromatics

Other

in the gas phasea

selectivities

and ZSM-5

Product

of phenol with CH30H over A1203

Rate/mmol

results for alkylation

% Phenol

testing

aReactor conditions: 570-576°K. b Methanol/phenol feed ratio

5

A'203

m/pb

Catalyst

A1203

of catalyst

1

Summary

TABLE

2

aReactor

conditions:

0.05

0.19

1.20

0.82

0.25

h-'

91.1

90.9

60.1

80.0

94.3 5.5

8.1

9.1

20.4

11.4

0

0

11.2

3.E

0

anisoles

Methyl-

selectivities

over La2(HP04)3

Cresols

Product

with methanol

Anisole

of phenol

n -I, P = 1 atm.

g cat

= 5:1, GHSV = 450-650

1.9

624

methanol/phenol

7.4

73

674

573

42.3

622

BaS04

12.6

573

anisole

conversion

-1

alkylation

Rate/mm01

for the gas phase

Phenol

results

La2(HP0413

T

testing

/"K

of catalyst

Catalyst

Summary

TABLE

0.20

C

8 .4

4.8

C

aromatics

Other

and BaS04"

of catalyst

5

19

1

4

5

5

19

4

5

m/pb

86.6

30.3

45.0

85.3

50.2

conversion

" 6 Phenol

97.2

98.9

98.9

87.0

96.6

Anisole

2.07

1.11

0.8

6.7

2.7

Cresols

0

0

0.2

3.0

0.6

anisoles

Methyl-

selectivities/X

of phenol with methanol

Product

results for the liquid phase alkylation

4

/h

Time

testing

aReactor conditions: 573°C; 600 psi for m/p = 1; 1200 psi for m/p = 5. b m/p = methanol/phenol ratio.

BaSO4

La2(HP0413

Catalyst

Summary

TABLE 3

0

0

0

3.3

0

Other

over La2(HP04)3

and BaS04a

z

269

however,

were conducted

at 733 K so a valid

be noted that CaHP04

results

the use of an HP042-

anion

PO 3- anion. 4 The BaS04 catalyst, catalyst

anisole.

selectivity

deactivation

The sulfate,

arguments)

problems

autoclaves

decomposes

at autogeneous

phenol

19 h, phenol

conversion

the formation products

the anisole BaS04

selectivity

behaved

similarly

and rates.

of phenol were obtained

of 600-1200

were

cresols

in

psig. When the methanol/

and cresol

increasing.

5 g

selectivity

and methyl-anisoles.

to anisole

With a methanol/phenol

to La2(HP04)3

of 87% were

were obtained.

for La2(HP04)3

but

in severe

was 1200 psig at 573 K. Utilizing

dropped

was

After

to 87% with

Other multiple

alkylation

ratio of I:1 at 600 psig

Unlike

in liquid

obtained

anisole

phase

after

activity,

selectivity

studies.

At methanol/

19 h and selectivities

the La2(HP04)3,

BaS04 gave little or no ring alkylation while

resulted

was 992, at 45% conversion.

= 5:l conversions

97% to anisole

pressures

products

of methylanisoles

to

for La2(HP04)3

by the low conversions

was 85:; and selectivity

were also observed.

is a less acidic BaS04 gave

after 4 h was 50.2% and anisole

96.670. The only other observed

than a

but high selectivities

the temperature

conversions

pressure

conversion

that

at these temperatures.

higher

ratio was 5:1, reaction

of La2(HP04)3

Raising

as evidenced

and BaS04,

chemistry

than La2(HP04)3.

rates than La2(HP04)3,

It should

suggesting

87.6% BaS04 and 3.5% Ba(HS04),

was 91.7%.

presumably,

Using La2(HP04)3

phenol

different

At 573 K the rate was 27% less than that observed

catalyst

stirred

is not possible. to cresols

in significantly

containing

lower reaction

the anisole

phenol

results

(based on electronegativity

significantly

comparison

in only 28% selectivity

however,

of

the less acidic

even at high conversions,

falls off due to cresol

and methylanisole

formation. With the idea that weakly vity, a SrS04

catalyst

At temperatures The activity

dependent

patterns

observed

surface

The selectivity

on the catalyst

in some ring alkylation high. BaS04,

conversion

and ZSM-5 show a similar

observed,

behavior

while

little

was carried

with

the

degree

in greater batch

was observed. correlated

of

the most water

for La2(HP04)3 acidic

in the stirred

selecti-

was also studied.

of phenol

containing

however,

results

and ZSM-5 give significant

0-alkylation

and La2(HP04)3

The more strongly

in the stirred

A1203

over Lap(HP04)3

and

when conversions

ring alkylation

BaS04

for SrS04,

acidity.

In an effort to understand

no conversion

area La2(HP04)3

onthe other hand,

at 86% phenol

give greater

60.01 SrS04 and 36.9X Sr(HS04)2

area of the catalysts

The higher

most active.

containing

catalysts

as high as 622 K, however,

with the surface hydration.

acidic

and BaS04

La2(HP04)3

batch reactor

0-alkylation

is the is

results are fairly

selectivity

even

In line with this, Al 0 23 in gas phase studies. The more acidic

pattern

reactor.

amounts

of ring alkylated

products

is observed

for the phosphate

or sulfate

the reaction

out in a batch

mechanism reactor

and sequence,

with CH30H/phenol

at 573°K catalysts.

the reaction = 5:l at 300°C

270

6

2

A

anisole

X

o-cresol

0

m,p-cresol

m

methylanisoles

--

0 0

2

4

6

a

TIME hours FIGURE

1

Product

profile

for phenol

alkylation

with methanol

over La2(HP04)3

at

573 K.

to essentially

quantitative

shows that the anisole by an isomerization This is consistent cresols formed

mechanism,

however,

may isomerize

significant

amount

dynamically

most

initially

pointed

for formation

significantly

Ca3(P04)2

out by Nozaki shown

of reaction.

are also The o-cresol,

form only when a

in the reaction.

[7]. Methylanisoles

formation

1,

Likewise

that the cresols

The thermo-

are formed most

of the cresol

than anisole

Figure and not

activation.

substantiates

by the catalyst The fact that

this. This was

et al. [lel. in Scheme

1 is what

is envisioned

as the sequence

of products,

The La2(HP04)3

no xylenols

anisole

the onset

of the anisole.

since the activation

more favorable

favors

from

since those products present

profile,

of the oxygen

of the products.

indicating

is m-cresol

of cresol

sequence

is present

stability

is already

product

shouldbe

alkylation

The reaction

to m,p-cresols

stable

alkylation

and not by isomerization

of o-cresol

likely by 0-alkylation

the initial

since anisole

of the reaction

alkylation

throughtheOHgroup

over 18 h. The product

by the direct

with the thermodynamic

farm at the onset by direct

conversions

is formed

and BaSOq catalysts

higher

described

than those described

are formed over La2(HP04)3

the xylenols

to the lack of strong

are a significant

here have 0-alkylation

in previous

or BaS04 while

literature.

basic sites on La,(HPO,),

SWPriSinglY,

over catalysts

part of the product.

- and BaSO,.

selectivities

such as

This may be due

271 OH

OCH3

0 0

t CH30H

@

p

+

&CH3

0CH3

OH

t CH30H

-

OH

OH

CH3

SCHEME

1

In conclusion,

we have reported

for the 0-alkylation a result

of the weak acidity

alkylation

that La2(HP04)3

of phenol with

CH30H.

and BaSO4 are selective

We suggest

of these catalysts

which

that this selectivity prevents

substantial

catalysts is ring

from occurring.

ACKNOWLEDGEMENTS We thank Jane Zmuida Eskanazi permission

for her expert

for the catalyst to publish

samples

technical

assistance.

used and Air Products

We also thank V.

and Chemicals

for their

this work.

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