Liquid-phase heterogeneous oxidation of hydroxypivalaldehyde with oxygen in alkaline aqueous solution in the presence of supported palladium catalyst

Article abstract of DOI:10.1023/A:1020336729589

The kinetics of a model reaction of hydroxypivalaldehyde oxidation with molecular oxygen in alkaline aqueous solution in the presence of 4% Pd/Al ₂O₃ was studied with the aim of searching for promising heterogeneous catalysts for D-g

Full text of DOI:10.1023/A:1020336729589

Russian Journal of Applied Chemistry, Vol. 75, No. 6, 2002, pp. 942 945. Translated from Zhurnal Prikladnoi Khimii, Vol. 75, No. 6, 2002,
pp. 959 962.
Original Russian Text Copyright
2002 by Zhizhkun, Chernaya, Trusov.
CATALYSIS
Liquid-Phase Heterogeneous Oxidation of Hydroxypivalaldehyde
with Oxygen in Alkaline Aqueous Solution
in the Presence of Supported Palladium Catalyst
S. V. Zhizhkun, S. S. Chernaya, and S. R. Trusov
Riga Technical University, Riga, Latvia
Received July 10, 2001; in final form, February 2002
Abstract The kinetics of a model reaction of hydroxypivalaldehyde oxidation with molecular oxygen in
alkaline aqueous solution in the presence of 4% Pd/Al2O3 was studied with the aim of searching for promising
heterogeneous catalysts for D-glucose oxidation.
Previously [1 3] we have shown that D-glucose
can be rapidly and selectively oxidized with molecular
oxygen in the presence of sodium nitrite in strongly
acidic aqueous solutions. D-Gluconic or D-glucaric
acid is formed, depending on the conditions of cata-
lytic oxidation. Although the oxidation in the pres-
ence of sodium nitrite is highly selective, a search
for catalysts allowing this process to be performed
on the industrial scale is a topical problem. Oxida-
tion of organic compounds on supported heteroge-
neous catalysts is widely used in practice. The use of
these catalysts appreciably increases the oxidation
selectivity [4]. It is known [5] that D-glucose deriva-
tives can be oxidized to D-glucuronic acid in weakly
alkaline solutions in the presence of a heterogeneous
catalyst, 1.8% Pd/C. However, this process is slow
and complex, especially in the stage of isolation of the
oxidation products. There are no reports on heteroge-
neous catalytic oxidation of D-glucose to D-gluconic
and D-glucaric acids. Our previous results [1 3, 6]
and published data [5, 7] show that the kinetics of cat-
alytic oxidation of D-glucose with oxygen is complex.
However, the features of chemical transformations of
reaction centers in these reactions can be revealed
using similar model substrates. To simulate D-glucose
oxidation, we studied in this work the oxidation of
hydroxypivalaldehyde (HPA), which, as D-glucose,
contains terminal hydroxy and aldehyde groups:
The presence of hydroxy and aldehyde groups in
an HPA molecule suggests that its oxidation is simi-
lar to that of D-glucose. The absence of internal hy-
droxy groups (which are present in D-glucose) in
HPA has no effect on the reactivity of the terminal
groups being oxidized and does not complicate the ki-
netic study of the catalytic oxidation. The study of
HPA oxidation was also stimulated by the fact that its
oxidation products, hydroxypivalic acid (HPAc) and
dimethylmalonic acid (DMMA)
COOH
CH3 C CH3
CH2OH
COOH
CH3 C CH3
COOH
HPAc
DMMA
are precursors of plasticizers of a new generation.
For HPA oxidation we used the conventional indus-
trial heterogeneous supported catalyst, 4% Pd/Al2O3.
No data on the kinetics of HPA oxidation with oxygen
in the presence of heterogeneous palladium catalysts
have been reported. However, palladium catalysts are
successfully used in oxidation of various alcohols
and aldehydes [8 10].
EXPERIMENTAL
Kinetic experiments on liquid-phase catalytic ox-
idation of HPA were performed in a temperature-con-
trolled gasometric unit in a closed volume under con-
ditions providing kinetic control of the reaction. The
oxidation was performed in alkaline aqueous solutions
in a glass reactor magnetically stirred at 3000 rpm.
The volume of the liquid phase of the system being
CHO
CH3 C CH3
CH2OH
HPA
1070-4272/02/7506-0942 $27.00 2002 MAIK Nauka/Interperiodica

LIQUID-PHASE HETEROGENEOUS OXIDATION OF HYDROXYPIVALALDEHYDE
oxidized was 3 ml. The process was initiated by
943
adding NaOH. The oxidation rate was monitored by
the rates of oxygen uptake and accumulation of the
oxidation products. The oxidation products were ana-
lyzed by GLC on a Tsvet-500 chromatograph equipped
with a 5-m steel column, 2.2 mm i.d., packed with
5% OV-17 on Chromaton N-AW-DMCS. The column
1
was heated to 60 150 C at a rate of 10 deg min ;
the vaporizer temperature was 200 C. Nitrogen was
the carrier gas.
Since these are no published data on use of 4%
Pd/Al2O3 supported catalysts in HPA oxidation with
molecular oxygen, we optimized the oxidation con-
ditions by the Box-Wilson procedure [11]. We found
that the most important parameters affecting the HPA
oxidation were the amount of catalyst, temperature,
and NaOH concentration. The experimental results
were fitted by the equation
Y = 13.590 + 0.848X1 + 1.768X2 + 2.025X3, (1)
where Y is the volume (ml) of oxygen taken up within
30 min; X1 is the catalyst concentration (wt %), X1 =
100%, where
= m1/m2 is the content of
cat
heterogeneous catalystca(twt %), m1 is the weight of
4% Pd/Al2O3 (g), and m2 is the weight of the system
being oxidized (g); X2 is the NaOH concentration (M);
and X3 is temperature (K).
A kinetic study of the catalytic oxidation of HPA
was performed under conditions optimized by exper-
imental design. The concentrations of HPA and NaOH
were varied from 0.2 to 1.2 and 0 to 1.2 M, respec-
tively; T = 293 323 K; PO = 0.21 1 atm; cat = (0.1
1.8) 10 wt %. The total pressure in the system
was maintained constant (1 atm).
Fig. 1. Kinetic curves of HPA oxidation with oxygen:
2
(a) at weight fraction of the catalyst
(2) 0.2, (3) 0.4, (4) 0.6, (5) 0.7, (6) 0.8, (7) 1.0, (8) 1.2,
10 : (1) 0.1,
cat
(9) 1.5, and (10) 1.8, T = 313 K; (b) (1) at 293, (2) 303,
2
(3) 308, (4) 313, (5) 318, and (6) 323 K,
= 1 10
.
cat
2
2
Initial HPA and NaOH concentration 0.4 and 0.7 M, re-
spectively, p = 1 atm.
O2
As determined by both gas volumetric analysis and
GLC, the HPA oxidation occurs in two consecutive
steps. The first step is formation of hydroxypivalic
acid by the reaction
is too fast for the aldehyde to be detected in the ox-
idation products.
In this work, we studied in detail the kinetics of
the first step of HPA oxidation [reaction (I)]. All res-
ults of gas-volumetric measurements were recalculated
in accordance with the stoichiometry of reaction (I)
to the current HPA concentration cHPA (M).
2C(CH3)2(CH2OH)(CHO) + O2
4% Pd/Al2O3
(I)
2C(CH3)2(CH2OH)(CHOH).
NaOH
A mathematical treatment of the kinetic data showed
that the reaction is first-order with respect to HPA
in the whole range of HPA concentrations, i.e., at
Hydroxypivalic acid is oxidized further to dimeth-
ylmalonic acid
= const
cat
C(CH3)2(COOH)(CH2OH) + O2
(2)
W = k1cHPA
,
4% Pd/Al2O3
(II)
C(CH3)2(COOH)2 + H2O.
NaOH
(3)
k1 = k2 pO ,
2
1
where W is the rate of HPA oxidation (mol l 1 s ),
This step obviously involves formation of dimeth-
1
ylmalonic acid monoaldehyde. However, this reaction and k1 and k2 are the rate constants of oxidation (s ).
RUSSIAN JOURNAL OF APPLIED CHEMISTRY Vol. 75 No. 6 2002

944
ZHIZHKUN et al.
k1
cNaOH
k1
k1
T
= 0;
,
> 0.
(4)
cat
The dependence of the oxidation rate on the cata-
lyst content is shown in Fig. 2. The results presented
in Fig. 2 and the table can be described by the equa-
tion
2
k = a + b
,
(5)
cat
3
where a and b are constants equal to 0.17 10 and
3
1
1.35 10 s , respectively.
As seen from Eq. (5), the reaction is second-order
with respect to the content of 4% Pd/Al2O3 supported
heterogeneous catalysts.
Fig. 2. Rate constant k vs. the initial content of the cat-
A mathematical treatment of the temperature de-
pendence of the rate constant of catalytic oxidation at
= 1 102, cNaOH = 0.7 M, and pO = 1 atm gave
1
alyst,
. T = 313 K and p
= 1 atm.
cat
O2
cat
2
Figures 1a and 1b show how the rate of catalytic
oxidation of HPA with oxygen depends on the cata-
lyst content and temperature, respectively. We found
that, under the above conditions, HPA oxidation starts
at NaOH concentration of 0.3 M and higher. The re-
sults of a treatment of the kinetic data on HPA ox-
idation with oxygen in the presence of 4% Pd/Al2O3
are presented in the table.
the following Arrhenius equation:
k1 = 1.2 108exp( 66510/RT),
(6)
with activation energy of the process equal to
1
66 510 J mol .
On the basis of the above relationships, the kinetic
1
equation for W (mol l 1 s ) of HPA oxidation to
hydroxypivalic acid in the presence of 4% Pd/Al2O3
in alkaline aqueous solution (cNaOH 0.3 M) can be
described by the equation
These data show that at cNaOH 0.3 M and pO
1 atm.
=
2
2
Oxidation of HPA with oxygen in the presence of 4%
W = kcHPA pO
.
(7)
cat
2
Pd/Al2O3 at pO = 1 atm
2
It is known [12] that liquid-phase oxidation of hy-
drocarbons with molecular oxygen in the presence
of heterogeneous supported catalysts may involve the
step of oxygen activation by the reaction
cHPA
cNaOH
k1 103,
102
T, K
1
cat
s
M
S...S + O2
[S S...O2 ],
(III)
0.2 0.7
0.4
0.4
0.4
0.4
0.4
0.4
0.4
0.4
0.4
0.4
0.4
0.4
0.4
0.4
0.4
0.7
0.3 1.2
0.7
0.7
0.7
0.7
0.7
0.7
0.7
0.7
0.7
0.7
0.7
0.7
0.7
0.7
1
1
313
313
313
313
313
313
313
313
313
313
313
293
303
308
318
323
1.55
1.55
where S is a catalyst.
0.1
0.2
0.4
0.6
0.7
0.8
1.2
1.5
1.8
1
0.313
0.333
0.351
0.521
0.769
0.909
2.00
3.67
4.33
0.521
1.39
1.50
Since water is a polar electron-donor solvent, it
favors charge transfer to an electron-acceptor oxygen
molecule when both are sorbed on the catalyst surface
[13]:
+
--
H2O
S
O2.
As a result, molecular oxygen is intensively acti-
vated, with generation of radicals by a heterogeneous
reaction, which do not escape into the liquid phase.
As a results, nonchain intraspheric or purely hetero-
geneous selective catalytic oxidation occurs. Clearly,
the mechanism of HPA oxidation with molecular oxy-
gen in the presence of 4% Pd/Al2O3 is similar, which
1
1
1
1
1.67
2.22
RUSSIAN JOURNAL OF APPLIED CHEMISTRY Vol. 75 No. 6 2002

LIQUID-PHASE HETEROGENEOUS OXIDATION OF HYDROXYPIVALALDEHYDE
945
is confirmed by the experimental dependence (7).
The features of HPA oxidation with oxygen in the
presence of 4% Pd/Al2O3 suggest that the kinetics
of D-glucose oxidation under similar conditions will
be similar. The process will also occur in two steps.
In the first step, formation of D-gluconic acid is possi-
ble, which will be further oxidized to D-glucaric acid.
4. Blyumberg, E.A. and Norikov, Yu.D., Itogi Nauki
Tekh., Ser: Kient. Katal., 1984, vol. 12, pp. 103 109.
5. Fel’dman, D.P., Voitenko, A.D., Shimanskaya, M.V.,
et al., Khim.-Farm. Zh., 1984, vol. 18, no. 11,
pp. 1356 1360.
6. Borovko, N.A., Chernaya, S.S., and Trusov, S.R.,
Zh. Prikl. Khim., 1999, vol. 72, no. 11, pp. 1842 1846.
7. Fel’dman, D.P., Voitenko, A.D., Shimanskaya, M.V.,
et al., Khim.-Farm. Zh., 1983, vol. 17, no. 2,
pp. 61 68.
CONCLUSIONS
(1) A kinetic study of liquid-phase oxidation of
hydroxypivalaldehyde with molecular oxygen in the
presence of a heterogeneous catalyst, 4% Pd/Al2O3,
showed that the oxidation occurs in two steps. Hy-
droxypivalic acid formed in the first step is oxidized
to dimethylmalonic acid in the second step.
8. Hiroshi, K., Akio, K., Isao, K., et al., Appl. Catal.
A: General, 1993, vol. 95, no. 2, pp. 143 169.
9. Mitsuo, A., Shinji, N., Toshiyuki, S., et al., Bull.
Chem. Soc. Jpn., 1993, vol. 66, no. 5, pp. 1511 1515.
10. Shlangen, I.W.A., Neuhaus, G.W., Mandani, M.,
et al., Allgem. Praktt. Chem., 1992, vol. 334, no. 6,
pp. 465 473.
11. Adler, Yu.P., Markova, E.V., and Granovskii, Yu.V.,
Planirovanie eksperimenta pri poiske optimal’mykh
uslovii (Experimental Design in Searching for Optimal
Conditions), Moscow: Nauka, 1976.
(2) A kinetic equation of hydroxypivalaldehyde
oxidation to hydroxypivalic acid was derived. The
activation energy of this process was determined.
REFERENCES
12. Norikov, Yu.D., Blyumberg, E.A., Bochorshvili, Sh.K.,
et al., Dokl. Akad. Nauk SSSR, 1975, vol. 223, no. 5,
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