Dimerization of formaldehyde to methyl formate on SnO2-Wo3 catalysts

Applied Catalysis, 9 (1984) 3’7-377 Elsevier Science Publishers B.V., Amsterdam

DIMERIZATION

OF FORMALDEHYDE

371 - Printed in The Netherlands

TO METHYL

FORMATE

ON Sn02-W03

CATALYSTS

M. AI Research

Laboratory

4259 Naaatsuta,

(Received

of Resources

Midori-ku,

5 October

Tokyo

Utilization,

Yokohama

1983, accepted

Institute

of Technology,

227, Japan.

21 November

1983)

ABSTRACl The catalytic performance of SnO2-WO3 oxides for the dimerization of formaldehyde to methyl formate (Tischenko reaction) was investigated. The Sri///(atomic ratio) = 67/33 catalyst showed the highest activity amongst a series of catalysts different in Sri///ratio. The acidity and basicity data proved that the possession of both acidic and basic properties are required to promote the reaction. The Sri/// = 67/33 catalyst showed a high activity just as the Sn/Mo = 70/30 catalyst and, a much better selectivity to methyl formate. The activity of the Sri///= 67/33 was found to be very stable, even in the absence of oxygen whose participation in the reaction is not desirable.

INTRODUCTION It was shown in the previous to methyl

formate with a Sn/Mo

lytic property

is attributable

properties

required

(Tischenko

reaction).

Actually, formate

considerable

by the dimerization

Yamamoto already

to catalyze

paper [l] that methanol (atomic ratio)

to the possession the dimerization

attention

reported

as active

reaction

of both the acidic and the basic of formaldehyde

to methyl

as has been reviewed of benzaldehyde,

sites in the case of the reaction

binary oxide catalysts

in an oxidizing

for the formation

of methyl

on heterogeneous

by Chono and

Tanabe

et al. have

formate

catalysts

was passed over various

atmosphere.

It was concluded

are obtained

formate

of methyl

that a Lewis acid site and a basic site play important

In the preceding study [6], formaldehyde results

selectively

and that this cata-

has been given to the production

of formaldehyde,

[23. As for the Tischenko

is oxidized

= 70/30 catalyst

[3-53.

single and that the best

with SnO,-WO, L

roles

.3

and SnO,L

Moo3 catalysts. Since the catalytic formate

activity

from both methanol

of the Sn02-Moo3

and formaldehyde

ious work Cl], in this study, attention the Sn02-W03

system for the formation

has already

system.

0166-9834/84/$03.00

been studied

is drawn to the catalytic

0 1984 Elsevier Science Publishers B.V.

of methyl

in the prev-

performance

of

372

Atomic

FIGURE

1

surface

Effect of the catalyst

area.

(0):

ratio

W/(Sn+W)

composition

rate of methyl

on the catalytic

formate formation

activity

at 403 K, (0):

and the surface

area

EXPERIMENTAL Catalysts The Sn02-Moo3 The Sn02-W03 required aqueous

catalyst

catalysts

quantities ammonia

and washing,

solution

(NH~),~w,~~,.H~~. Hz0 dissolved

Since

completely.

The amount

The reaction

in water. To this solution,

was added to precipitate hydroxide

the hydroxide.

was added to an aqueous

(NH4)10w12041. H020 is scarcely Then,

soluble

solution

The

a dilute

After filtering

solution

of

in water,

oxalic

until the (NH4),oW,204,.

IO/20 mesh size natural pumice was mixed with the

of pumice was about 500 ml per g atom of (Sn + W). The cata-

under flowing

oxygen at 773 K for 4 to 5 h.

of formaldehyde

The reactor

in earlier

works

was carried

and the experimental [1,6,71.

in from the top of the reactor was introduced feeder.

dissolved

study Cl].

as follows.

procedures

flow system. employed

Sri/W ratio, were prepared

little by little to the aqueous

lyst was calcined

Reaction

of SnC12were

the paste-like

acid was added

solution.

was the same as that used in the previous

with different

and

into a preheating

The amount

were: formaldehyde

of catalyst - oxygen

Nitrogen

out with a conventional procedures

or nitrogen-oxygen

about 33 wt% formaldehyde

section of the reactor

continuous

were the same as those mixtures aqueous

were fed

solution

by using a micro

liquid

used was IO to 40 g. The feed rates of reactants

- nitrogen - steam = 7.5 x IO-' - 4.0 x 1o-2 - 91 x -2 - 0 - 91 x 10-z - 25 x low2 mol h-l.

10-z - 25 x IO-' mol h-l or 7.5 x 10

373

3

0

0

0.2

0.4

Atomic

FIGURE 2

Acidity

adsorption rp,

of Sn02-W03

activity

0.8

1.0

W/(Sn+W)

as a function

of NH3 at 473 K, (0):

(A):catalytic

ratio

0.6

of the W03-content.

dehydration

activity

for decomposition

(0):

irreversible

for Z-propanol

of formic

at 453 K,

acid to CO at 473 K, rf.

RESULTS Activity

of SnO2_WO

The effects

catalysts

of composition

were studied

in the Sri///ratio. The surface 77 K, is shown in Figure W) atomic

(4 ~01%) of oxygen,

plotted

in Figure

activity

sharply

Acidity

of Sn02z3

The acidity

much as

work

rate of methyl

1 (solid line). With an increase increases

and then passes through

of catalysts

a proper conversion at 403 K is also

in the content a maximum

+

of W03, the

at W/(Sn + W) = 0.33.

system

are shown

In order to confirm

adsorption

was measured

in Figure 2.

the values of the acidity,

reactions,

catalysts

of NH3 at 473 K using the static method

such as dehydration

and formic acid concentrations

the catalytic

of 2-propanol

of formic acid to CO [8], was studied.

at P-propanol

to achieve formation

at

near W/(Sn

of a small amount

[6] and the amounts

formate

different

using nitrogen

is present

out in the presence

(number of acidic sites) of the Sn02-W03

[7]. The results

composition

was carried

the previous

by the irreversible

acid catalyzed

by the BET method

in the range of 5 to 20 g, in order

(less than 16%). The specific

directly

area obtained

1 (dotted line). A sharp maximum

ratio = 0.2. Reaction

used were varied

using a series of catalysts

activity

for two

to propylene

and de-

The reactions

were carried

out

of 1.7 and 2.3 ~01% in air, respect-

374

5.0-‘” 4

0.35 y 0.10 f : L >. z

-0.05 x d

0

0.1 Atomic

FIGURE

Basicity

3

adsorption

of Sn02-W03

0.2

ralio

W/(Sn+W)

as a function

of CO2 at 293 K, (0):

0.3

. &o

catalytic

of the W03-content. activity

(a):

for decomposition

irreversible of formic

acid to CO2 at 533 K and 2.3 mol% formic acid in air.

0’0

’

’

4 Reaction

FIGURE 4 67/33,

Stability

(a,:

of catalytic

a time

activity

Sn/Mo = 70/30, catalyst

ively, and the total flow rate of 1.0

’

’

I

’ 12

’

Ih

in the absence

= 20 g,

together

(0):

Sri///=

1 min -1 with various amounts of catalyst

, and the rate of formic acid decomposition

plotted

of oxygen.

T = 433 K.

in the range of 1 to 20 g. The initial rate of 2-propanol r

’ _I II 6

with the amount of adsorbed

dehydration at 453 K, -1 mV2) , are

at 473 K, rf (mol h NH3 in Figure 2.

375

Conversion

FIGURE

5

(A,&:

of

HCHO

Effect of oxygen on the product methanol

gas, (@,A):

+ formic acid,

in the presence

distribution.

(O,A):

of oxygen

I %

in the absence

(O,@):

methyl

of oxygen

(about 4 vol%), catalyst:

formate,

in the feed Sri///= 67/33

(20 g), T = 375 to 423 K.

420

440

Reaction

FIGURE 6 reacted (0):

Product distribution formaldehyde,

CO, catalyst:

(0):

460

480

temperature

500 I K

in the reaction

methyl formate,

Sri///= 67/33

520

at higher temperatures,

(A):

methanol,

(40 g), in the absence

(0,:

of oxygen.

(0):

formic

un-

acid,

The catalytic direction

activities

for the two acid catalyzed

as do the amount of adsorbed

It is found that a maximum

in the acidity

generation

W/(Sn + W) = 0.67, unlike the case of Sn02-Moo3 occurs

in the Mo03-lean

Basicity

of Sn02_W03

eversibly

adsorbed

the decomposition catalyzed

region, Mo/(Sn

of the results.

in the W03-rich

system where a maximum

region,

in acidity

+ MO) = 0.3 to 0.4 [1,71.

system

at 293 K, is plotted

by the amount of CO2 irr-

in Figure 3. The catalytic

of formic acid to CO2 at 533 K, which

reaction

vary in the same

the validity

occurs

per unit surface area, as determined

The basicity

reactions

NH3. indicating

[83, is also plotted

activity

is considered

for

as a base-

in Figure 3. As may be seen in Figure

SnOe by itself is fairly basic, but the basicity

decreases

upon the addition

3, of

wo3.

Reaction

in the absence

of oxygen

Since oxygen does not take part in the Tischenko that the reaction

reaction,

in the absence of oxygen

in the feed gas, the catalytic

70/30 catalyst

decreases

The catalyst

gradually

is reduced

its activity. activity

with the reaction

by the reactant

during the reaction

or absence

of oxygen

and, as a result,

absence of oxygen, when the temperature served and methyl

formate,

together

the Sri///= 67/33 catalyst 70/30 catalyst

the

in the feed gas on the product

is independent

As may

of the presence

or

is lower than 423 K. No CO and CO2 is ob-

with small and equal amounts

formic acid, are the sole products.

loses

of oxygen.

was then studied with regard to the Sri///= 67/33 catalyst.

be seen in Figure 5, the product distribution

of methanol

It should be noted that the selectivity

to methyl formate

and of

is much higher than that of the Sn/Mo =

Cl].

With a further

elevation

formate

of the reaction

and the consumption

6). At temperatures the expense

of the Sn/Mo =

time, as shown in Figure 4.

stable for a long time even in the absence

The effect of the presence

of methyl

activity

However,

On the other hand, in the case of the Sri///= 67/33 catalyst,

is almost

distribution

it is predictable

is zero order with respect to the oxygen concentration.

above453

of a decrease

temperature

to 453 K, the formation

vary only a little

of formaldehyde

K an equal amount of methanol

in the amount of methyl

(Figure

and CO are formed at

for-mate.

DISCUSSION The specific

activity

for the Tischenko

W/(Sn + W) = 0.33, whereas W/(Sn + W) = 0.67, W03-rich with an increase

the maximum

region. On the other

in the W03 content.

view that the Tischenko

reaction

attains

in the specific

occurs

hand, the basicity

These findings

reaction on heterogeneous

a maximum

acidity

requires

at around

decreases

are in conformity

catalysts

value at

with the the possession

311 of both acidic and basic sites [1,3-51. the highest

activity

because

just the appropriate are deficient the acidic

proportion

It should

be noted that the largest

combination

the reaction;

the W03-rich

catalysts

are

in

catalysts

deficient

in

amount of acidic sites is generated

shows the highest

catalysts

of a pure acid and/or ing function:

function

activity,

catalysts,

than Mo03-based

base catalyzed

for example,

reaction

the Tischenko

much as Mo03-based

With regard to selectivity, Sn/Mo = 70,'30 catalyst

acidity

[l], because

reaction,

has a significant

oxidizing

the formation

because

The yield of methyl in this study.

[ll]. However,

W03-based

formate

oxides

show a high

is much better than the

of formic acid is largely

cannot

in the oxidizing

cannot exceed

in

function, catalyst

is oxidized

take place over the Sn02-W03

in the oxidizing

that the yield

supp-

(Figure 5). This difference

a great part of formaldehyde

is lacking

It is believed

in the case

of the oxidiz-

study [6]. Since the Sn02-Moo3

this side reaction

the catalyst

oxides are much

is independent

to the difference

function,

binary oxides dehydrogen-

oxides.

out in the preceding

to formic acid. However,

oxides

W03-based

the Sri///= 67/33 catalyst

should be ascribed

as has been pointed

for the oxidative

because

by the

[9], just as the

among the Mo03-based

which

in the case of the Sri///= 67/33 catalyst

the selectivity

binary oxides

are much less active

than the Sn02-Moo3

lower in the oxidizing

catalyst

shows

and basic properties

and the Sn02-rich

of Sn02 with W03 among the W03-based

ation of methanol

ressed

to promote

in the basic property

[IO]. The Sn02-W03

catalytic

both acidic

property.

combination SnO2-Moo3

That is, the Sri///= 67133 catalyst

it possesses

function.

57 mol% under the conditions is limited

by the reaction

used

equili-

brium. From the tests for methyl was found that methyl temperature

formate

formate

decomposition

is gradually

higher than 453 K. This finding

in the reaction

of formaldehyde

in the absence

decomposed

to methanol

is consistent

of oxygen,

with the results

(Figure 6).

REFERENCES 1 2 3 4 5 6 7 8 9 10 11

M. M. K. K. K. M. M. M. M. M. M.

it

and CO at a

Ai, J. Catal., 77 (1982) 279. Chono and T. Yamamoto, Shokubai, 23 (1981) 3. Saito and K. Tanabe, Nippon Kagaku Kaishi, (1973) 1845. Saito and K. Tanabe, Nippon Kagaku Kaishi, (1974) 1014. Tanabe and K. Saito, J. Catal., 35 (1974) 247. Ai, J. Catal., 83 (1983) 141. Ai, J. Catal., 40 (1975) 327. Ai, J. Catal., 50 (1977) 291. Ai, Preprint of 48th Symp. Catal. Sot. Japan, 2W15, Okayama, Ai and A. Ozaki, Bull. Chem. Sot. Jpn., 52 (1979) 1454. Ai, J. Catal., 49 (1977) 313.

(1981).

obtained