Molecular sieve abstract
The invention relates to an aldehyde conversion method comprising
putting an aldehyde into contact with oxygenated water and with
a catalyst, under oxidation conditions, wherein the catalyst is
a molecular sieve with pores of a diameter of at least 0.52 nm and
has an empirical formula in a calcined and dehydrated form of (Sn.sub.xTi.sub.ySi.sub.1-x-y-zGe.sub.z)O.sub.2
wherein x is a molar fraction of the tin and has a value between
0.001 and 0.1; y is a molar fraction of titanium and has a value
from zero to 0.1; and z is the molar fraction molar of the germanium
and has a value from zero to 0.08.
Molecular sieve claims
The invention claimed is:
1. A method for the conversion of aldehydes comprising putting
an aldehyde into contact with oxygenated water and with a catalyst,
under oxidation conditions, wherein the catalyst is a molecular
sieve with pores of a diameter of at least 0.52 nm and has an empirical
formula in a calcined and dehydrated form of (Sn.sub.xTi.sub.ySi.sub.1-x-y-zGe.sub.z)O.sub.2
wherein x is a molar fraction of the tin and has a value between
0.001 and 0.1; y is a molar fraction of titanium and has a value
from zero to 0.1; and z is the molar fraction of the germanium and
has a value from zero to 0.08.
2. A method according to claim 1 characterized in that the molecular
sieve has a crystalline structure with an X-ray diffractogram corresponding
to a Beta zeolite.
3. A method according to claim 1 characterized in that it is carried
out at a temperature between 20.degree. C. and 150.degree. C. and
during a contact time between 10 minutes and 24 hours.
4. A method according to claim 1 characterized in that it is carried
out at a molar relationship of oxygenated water to aldehyde between
0.1 and 3.
5. A method according to claim 1 characterized in that the aldehyde
is selected from the group formed by 4-methoxybenzaldehyde, 2-methoxybenzaldehyde,
4-propoxybenzaldehyde, 4-methylbenzaldehde, benzaldehyde and 34-dimethoxybenzaldehyde.
6. A method according to claim 1 characterized in that z and y
have a zero value.
7. A method according to claim 1 characterized in that the molecular
sieve is an ordered mesoporous molecular sieve.
8. A method according to claim 1 characterized in that the molecular
sieve is an ordered mesoporous molecular sieve with an MCM-41 structure.
9. A method according to claim 1 characterized in that the molecular
sieve is an ordered mesoporous molecular sieve with an MCM-41 structure,
and the y value as well as the z value is zero.
10. A method according to claim 1 characterized in that the molecular
sieve is an ordered mesoporous molecular sieve with an MCM-48 structure.
11. A method according to claim 1 characterized in that the molecular
sieve is an ordered mesoporous molecular sieve with an HMS structure.
12. A method according to claim 1 characterized in that the molecular
sieve is an ordered mesoporous molecular sieve with an SBA-15 structure.
13. A method to use a molecular sieve with pores of a diameter
of at least 0.52 nm that has an empirical formula in a calcined
and dehydrated form of (Sn.sub.xTi.sub.ySi.sub.1-x-y-zGe.sub.z)O.sub.2
wherein x is a molar fraction of the tin; and it has a value between
0.001 and 0.1; y is a molar fraction of titanium and has a value
from zero to 0.1; and z is the molar fraction of the germanium and
has a value from zero to 0.08; wherein said molecular sieve is used
as catalyst in a conversion reaction of an aldehyde in the presence
of oxygenated water to obtain a reaction product selected among
the esters corresponding to said aldehyde, acids corresponding to
the said aldehyde, and phenols as hydrolysis products of the corresponding
ester.
14. A method according to claim 13 wherein the molecular sieve
is used as catalyst in a reaction of an aldehyde selected from the
group formed by 4-methoxybenzaldehyde, 2-methoxybenzaldehyde, 4-propoxybenzaldehyde,
4-methylbenzaldehyde, benzaldehyde and 34-dimethoxybenzaldehyde.
15. A method according to claim 13 characterized in that at least
one of z and y has a zero value in the molecular sieve.
16. A method according to claim 13 characterized in that the molecular
sieve is used in an oxidation reaction that is carried out at a
temperature between 20.degree. C. and 150.degree. C. during a contact
time between 10 minutes and 24 hours.
17. A method according to claim 13 characterized in that the molecular
sieve is used in a reaction that is carried out at a molar relationship
of oxygenated water to aldehyde between 0.1 and 3.
18. A method according to claim 13 characterized in that the molecular
sieve has a crystalline structure with the X-ray diffractogram corresponding
to a Beta zeolite.
19. A method according to claim 13 characterized in that the molecular
sieve is an ordered mesoporous molecular sieve.
20. A method according to claim 19 characterized in that the ordered
mesoporous molecular sieve is selected from the group formed by
ordered mesoporous molecular sieves with an MCM-41 structure, ordered
mesoporous molecular sieves with an MCM-41 structure where the y
value as well as the z value is zero, ordered mesoporous molecular
sieves with an MCM-48 structure, ordered mesoporous molecular sieves
with an HMS structure, and ordered mesoporous molecular sieves with
an SBA-15 structure.
Molecular sieve description
FIELD OF THE INVENTION
The present invention belongs to the field of conversion processes,
by means of oxidation, of aldehyde into esters, acids and the hydrolysis
products of the esters using a catalyst and aqueous H.sub.2O.sub.2
as oxidizer and the use of molecular sieves in such conversion processes.
BACKGROUND OF THE INVENTION
The substituted phenols, especially the derivatives with a 4-alcoxy
substituent, are important substances in organic chemistry because
they are intermediate products for the manufacture of medicines,
agrochemicals and dyes. They are useful as polymerization inhibitors
for vinyl-type monomers and polyester stabilizers as well as antioxidants
for food and cosmetics also. There is considerable interest due
to the synthesis of such products in industry and academy. See,
for example Caproiu, M. T.; Banciu, A. A.; Olteanu, E. RO 105090
1994; Saito, T.; Hirayama, T.; Sakagushi, S. JP 08151343 1996;
Schwabe, K.; Redslob, J.; Breitfeld, D.; Zeisig, R.; Tschiersch,
B.; Wohlrab, W.; Wozniak, K. D.; Bayer, C.; Nowak, C.; et al. DD
287482 1991. A strategy for the synthesis of these phenols consists
in the Baeyer Villiger reaction with the corresponding aldehydes
(Krow G. Org. React. 1993 43 251).
In general, this reaction is carried out using organic peracids
as oxidizing agents. Meta-chloroperbenzoic acid (Godfrey, I. M.;
Sargent, M. V.; Elix, J. A. J. Chem. Soc. Perkin Trans. 1 1974
1353 1354.), as well as monopersuccinic acid (Anoune, N.; Hannachi,
H.; Lanteri, P.; Longeray, R.; Arnaud, C. J. Chem. Ed. 1998 75
1290 1293.) gave good to excellent yields of the corresponding phenol
in the case of the ortho-anisaldehyde and the para isomer. The meta-anisaldehyde
transforms predominantly into meta-anisic acid. The disadvantage
of an organic peracid like oxidizer is that it implies high costs
and safety measures during its storage and handling, and produces
at least a molecule of acid as waste product.
Oxygenated aqueous water would be a good oxidizing agent since
it is safer and produces only water as sub-product. Nevertheless,
it is not sufficiently reactive and needs activation by a catalyst.
Activation may be achieved by selenium catalysts, and thus 4-methoxyphenol
may be obtained from the corresponding aldehyde with an excellent
yield (Syper, L. Synthesis 1989 167 172). Nevertheless, in this
case considerable quantities of catalyst are necessary, which have
to be recovered and recycled or rejected, since only 12 cycles per
active centre per 30 hours of reaction time are obtained.
The oxidation of aldehydes with H.sub.2O.sub.2 may also be catalyzed
by Bronsted acids. The oxygenated water, activated by the sulphuric
acid in methanol as solvent produces 4-methoxyphenol with an excellent
yield. Nevertheless, anhydrous conditions and highly concentrated
oxygenated water are necessary for this since it is considered that
the reaction goes ahead via the peroxyhemiacetal that is unstable
in the presence or water (Matsumoto, M.; Kobayashi, H.; Hotta, Y.
J. Org. Chem. 1984 49 4740 4741). These anhydrous conditions of
the reaction lead to extra costs in safety measures since the concentrated
oxygenated water is potentially explosive.
On the other hand, the oxidation of Baeyer Villiger with oxygenated
water in formic acid is less suitable for the production of phenols
since it has been developed for the general oxidation of aldehydes
to carboxylic acids (Dodd, R. H.; Le Hyaric, M. Synthesis 1993
295 297). The present invention has as its main aim to overcome
the disadvantages of the above-mentioned method by means of a method
wherein the use of oxygenated water as oxidizing agent and the use
of catalysts that give high conversions and are easily recyclable
is permitted and that, besides, allows by simply changing the conditions
of reaction, the possibility to choose as main final product different
products as for example aryl formiate or substituted phenol.
DESCRIPTION OF THE INVENTION
The present invention achieves the above-mentioned objects by means
of a method for the conversion of aldehydes that comprises putting
an aldehyde, such as 4-methoxybenzaldehyde, 2-methoxybenzaldehyde,
4-propoxybenzaldehyde, 4-methylbenzaldehyde, benzaldehyde and 34-dimethoxybenzaldehyde,
into contact with oxygenated water and with a catalyst under oxidation
conditions, the method being characterized in that the catalyst
is a molecular sieve with pores of a diameter of at least 0.52 nm
and has an empirical formula in a calcined and dehydrated form of
(Sn.sub.xTi.sub.ySi.sub.1-x-y-zGe.sub.z)O.sub.2 wherein
x is a molar fraction of the tin and has a value between 0.001
and 0.1;
y is a molar fraction of titanium and has a value from zero to
0.1; and
z is the molar fraction of the germanium and has a value from zero
to 0.08.
This method can be carried out at a temperature between 20.degree.
C. and 150.degree. C. and during a contact time between 10 minutes
and 24 hours. The molar relationship of oxygenated water to aldehyde
can be considered at between 0.1 and 3.
In accordance with the method of the present invention, aldehydes
may be converted into formiates or acids. In particular, the method
allows aromatic aldehydes to be converted into aryl formiates and/or
directly into the hydrolysis products that are formic acid and a
phenol with substituents. Changing the conditions of the reaction,
the ester may be saponified during the process into the corresponding
alcohol.
Suitable molecular sieves that can be used as catalysts in the
method are molecular sieves corresponding to the general formula
specified above wherein z and y have the value zero. In the same
way, molecular sieves may be used that correspond to the above mentioned
general formula, which show an X-ray diffractogram corresponding
to a Beta zeolite.
Molecular sieves based on zeolites with pores, made up by rings
with 12 or more tetrahedrons, as for example Beta zeolite and that
contain tin are especially suitable as catalysts in the reaction
described above. These molecular sieves have a three-dimensional
microporous structure with at least tetrahedral units of SiO.sub.2
and SnO.sub.2 and from the crystallographic point of view have
a regular system of pore or pores.
Also ordered mesoporous molecular sieves encompassed by the general
formula defined above, as for example those with an MCM-41 structure
are usable, wherein the y value as well as the z value may be zero
or with an MCM-48 structure, or HMS or SBA-15 structure.
The present invention also refers to a method to use a molecular
sieve with pores of a diameter of at least 0.52 nm and has an empirical
formula in a calcined and dehydrated form of (Sn.sub.xTi.sub.ySi.sub.1-x-y-zGe.sub.z)O.sub.2
wherein
x is a molar fraction of the tin and has a value between 0.001
and 0.1;
y is a molar fraction of titanium and has a value from zero to
0.1; and
z is the molar fraction of the germanium and has a value from zero
to 0.08;
in which method the above mentioned molecular sieve is used as
catalyst in a conversion reaction of an aldehyde in the presence
of oxygenated water to obtain a reaction product selected among
the esters corresponding to the above mentioned aldehyde, acids
corresponding to said aldehyde and phenols as hydrolysis products
of the corresponding ester. The conditions of the method and the
specific molecular sieves used in accordance with this method may
be those previously described in relation to the characteristics
of the method of the present invention.
The molecular sieves that may be used in accordance with the present
invention can be prepared by means of a hydrothermal crystallization
process in which a reaction mixture is prepared combining the sources
of tin, silicon, a organic structure directing agent, optionally
germanium, optionally titanium, optionally oxygenated water and
water. Silicon sources include, though they are not limiting, colloidal
silica, amorphous silica, pyrogenic silica, silica gel and tetraalkylorthosilicate.
Tin sources include tin halides, tin alcoxides, tin oxides, metallic
tin, alkaline stannates, alkaline-terreous stannates and organometallic
tin compounds, without these being limiting examples. A preferred
source is tin tetrachloride. Examples of tin alkoxides include tin
buthoxide, tin ethoxide and tin propoxide. The organic structure
directing agents include tetraalkylammonium ions such as the tetraethylamonium
ion, aza-polycyclic compounds such as 14-diazabicyclo-[222]-octane;
dialkyldibenzylammonium ions such as the dimethyl-dibenzylammonium
ion and bispiperidinium ions, such as the 44'-trimethylene-bis-(N-benzyl-N-methylpiperidinium),
without these being limiting. These ions may be used as hydroxides
or halides. Germanium sources include germanium halides, germanium
alkoxides and germanium oxides, without these being limiting. Finally,
the sources of titanium include titanium alkoxides and titanium
halides. The titanium alkoxides preferred are titanium tetraethoxide,
titanium isopropoxide and titanium tetrabuthoxide.
Hydroxide or fluoride ions are used as SiO.sub.2 mobilizing agents.
The synthesis is carried out in a hydrothermal system at temperatures
between 120 and 195.degree. C. and during times between 12 hours
and 25 days. Once the material has crystallized, the solids are
separated from the liquids, and the solids are washed with water
up to around 9 pH. Finally the dry solid is calcined in air or in
N.sub.2 followed by air at temperatures between 400 and 700.degree.
C. in order to eliminate the organic component.
A molecular sieve preferred corresponds to that of the Beta zeolite
and its possible individual or combined polymorphs. In the case
of the Beta zeolite, the X-ray diffractogram shows at least the
peaks and intensities presented in Table A. The intensities shown
in Table A are relative intensities that are obtained relating the
intensity of each peak (1) with that of the darkest line (1.sub.0).
The intensity is calculated by means of the equation 100.times.1/1.sub.0
and is represented by vs, s, m and w, where these are defined as:
vs=80 100; s=60 80; m=15 60 and w=0 15.
TABLE-US-00001 TABLE A Relative .theta. d (.ANG.) intensity 7.22
12.23 m 7.76 11.38 s 21.54 4.12 m 22.57 3.94 vs 22.96 3.87 w 25.45
3.50 w 27.00 3.30 w 29.00 3.08 w 29.65 3.01 m 30.60 2.92 w
The synthesized zeolite is activated for adsorption or catalytic
reactions generally through calcination of the molecular sieve at
a temperature between 300.degree. C. and 1000.degree. C. during
a time generally between 1 and 10 hours. As has been said, the molecular
sieves described above perform very well as catalysts for the oxidation
of aldehydes to formiates or acids, or to ester hydrolysis products.
Examples of aldehydes that can be used in the process include aliphatic
aldehydes, .alpha.,.beta.-unsaturated aldehydes, and aromatic aldehydes,
without being limiting. Specific examples are 2-methoxybenzaldehyde,
4-methoxybenzaldehyde, 4-methylbenzaldehyde, benzaldehyde, 4-npropoxybenzaldehyde
and 34-dimethoxybenzaldehyde.
The process implies putting the aldehyde in contact with a catalyst
(as is described above) and oxygenated water under oxidation conditions.
The oxidation conditions for the instantaneous process include a
temperature between 20 and 150.degree. C. and a contact time between
10 min. and 24 hours. As has been pointed out previously, oxygenated
water is used as oxidizing agent in a solution in water of 3% to
70% in weight, preferably a solution at 35% in weight. This reaction
may be carried out with or without solvent. In the case where the
use of a solvent is desired, preferred solvents are acetonitrile,
dioxane, and toluene. Likewise, the process may be carried out in
a batch type or continuous reactor. When operating in batch mode,
the catalyst, the aldehyde, optionally a solvent, and the H.sub.2O.sub.2
are mixed in a suitable reactor preferably stirring the mixture
at the desired temperature during a time between 10 minutes and
24 hours. The H.sub.2O.sub.2/aldehyde molar relationship may vary
between 3 and 0.1 and preferably between 1 and 0.3. In continuous
mode, the catalyst may be used on a fixed bed, boiling bed, mobile
bed, or in any other known configuration. When a fixed bed is used,
the aldehyde and oxygenated water may pass from a downwards to upwards
direction or vice versa with regard to the catalytic bed. The H.sub.2O.sub.2
and the aldehyde can be injected separately, or they can be mixed
before, and afterwards injected into the reactor.
Regardless of the way the reagents are introduced and the type
of bed used, the reagents flow through the reactor at a spatial
speed between 0.01 and 50 h.sup.-1 to ensure the suitable contact
time between the reagents and the catalyst. Finally, regardless
of whether batch mode or a continuous process is used, the products,
the reagents and any formed by-product are separated by methods
well known in the art.
EMBODIMENTS OF THE INVENTION
The following examples intend to illustrate characteristics related
to the invention.
EXAMPLES
Example 1
Preparation of Seeds for the Beta Zeolite Used for the Preparation
of a Beta Zeolite with Sn
In a reactor, 1.85 grams of AlCl.sub.3.6H.sub.2O were dissolved
in 4.33 grams of water. 45.24 grams of tetraethylamonium hydroxide
(TEAOH) (aqueous solution of 35% in weight) were added to this solution.
Afterwards, 40 grams of tetraethylortosilicate (TEOS) were added
and the mixture was stirred until the ethanol formed by the hydrolysis
of the TEOS had evaporated. The final composition of the gel was
the following: SiO.sub.2:0.28TEA.sub.2O:0.02Al.sub.2O.sub.3:6.5H.sub.2O
The obtained solution was transferred to a stainless steel autoclave
with inner walls protected by Teflon.COPYRGT., heated to 140.degree.
C. and left to react for 3 days with stirring. The product was recovered
by centrifugation, washed with distilled water and dried to 100.degree.
C. The product showed the Beta zeolite structure with crystallinity
near to 90%.
The sample of the Beta zeolite in the previous paragraph was dealuminated
by treating 1 gram of the zeolite with 60 grams of HNO.sub.3 (60%
in weight) at 80.degree. C. for 24 hours. The solid was recovered
by filtration, washed with water and dried at 100.degree. C. The
crystallinity of this product was 70% and the Si/Al relationship
was determined by elementary analysis and was larger than 2000.
Example 2
Synthesis of a Tin Silicate with the Structure of a Beta Zeolite
30 grams of TEOS and 32.99 grams of TEAOH (35% in weight) were
mixed in a reactor. After 90 minutes, a solution of 0.43 grams of
SnCl.sub.4.5H.sub.2O (98%) was added in 2.75 grams of water and
the mixture was stirred until evaporation of the ethanol formed
by the hydrolysis of the TEOS. 3.2 grams of fluorhydric acid were
added to the bleached solution (48% in weight) and a viscous paste
was obtained. Finally, a suspension of 0.36 grams of Beta zeolite
dealuminated seeds, prepared according to Example 1 was added to
1.75 grams of water. The final composition of the gel is shown by
the following formula: SiO.sub.2:0.27TEAO:0.008SnO.sub.2:0.54HF:7.5H.sub.2O
The paste was transferred to an autoclave of stainless steel with
inner walls protected by Teflon.COPYRGT., heated to 140.degree.
C. and left to react during 11 days with stirring. After 11 days
the product was recovered by filtration. By means of X-ray diffraction,
it was demonstrated that the product had the structure of a Beta
zeolite with crystallinity near to 95%. The elementary analysis
gave a tin content with 1.62% by weight. The product was calcined
at 580.degree. C. for 3 hours and maintained its crystallinity.
The empirical formula of the calcined, anhydrous material was the
following: (Si.sub.0.992Sn.sub.0.008)O.sub.2 This product was named
sample A.
Example 3
Synthesis of a Pure Beta Zeolite Silica
30 grams of TEOS and 32.99 grams of TEAOH (35% in weight) were
mixed in a reactor. The mixture was stirred until the evaporation
of the ethanol formed by the hydrolysis of the TEOS. 3.2 grams of
fluorhydric acid (48% in weight) were added to the solution and
a viscous paste was obtained. Finally, a suspension of 0.36 grams
of Beta zeolite dealuminated seeds prepared according to Example
1 was added to 1.75 grams of water. The final composition of the
gel is shown by the following formula: SiO.sub.2:0.27TEA.sub.2O:0.54HF:7.5H.sub.2O
The paste was transferred to an autoclave of stainless steel with
inner walls protected by Teflon.COPYRGT., heated to 140.degree.
C. and left to react during 24 hours with stirring. After 24 hours
the product was recovered by filtration. By means of X-ray diffraction,
it was demonstrated that the product had the structure of a Beta
zeolite with a crystallinity near to 100%. The product was calcined
at 580.degree. C. for 3 hours and maintained its crystallinity.
This product was named sample C.
Example 4
Synthesis of a Tin Silicate Mesoporous Molecular Sieve
A hexa-decyl-trimethylamonium hydroxide (C.sub.16TAOH) aqueous
solution, a tetramethylamonium hydroxide solution and an aqueous
SnCl.sub.4.5H.sub.2O solution were mixed in a reactor. After obtaining
a homogeneous solution the silica was added by constant stirring.
The final composition was the following: 1SiO.sub.2:0.16C.sub.16TAOH:0.26TMAOH:0.04SnCl.sub.4:24.3H.sub.2O
The homogeneous gel was transferred to an autoclave of stainless
steel with inner walls protected by Teflon.COPYRGT., heated to 135.degree.
C. and left to react during 24 hours without stirring. The resultant
product was recovered by filtration, washed and dried for 24 hours
at 60.degree. C. The occluded organic was eliminated by heating
the solid at 540.degree. C. during an hour in nitrogen flow and
afterwards for 6 hours in air. The obtained solid shows a typical
MCM-41 structure model in X-ray diffraction. Elementary analysis
gave a tin content of 7.1% in weight. The empirical formula of the
calcined, anhydrous material was: (Si.sub.0.96Sn.sub.0.04)O.sub.2
This product was named sample D.
Example 5
Sample B is a commercial zeolite supplied by Zeolyst with the VALFOR
CP811BL-25 (Si/Al=13)code. The samples of A to D were tested for
the selective oxidation of 4-methoxybenzaldehyde to 4-methoxyphenyl
formiate and the corresponding hydrolysis products 4-methoxyphenol
and formic acid according to the following procedure. In a flask,
50 mg of catalyst were added to a 0.5 g aldehyde solution, aqueous
oxygenated water (35% in weight) in small excess (1.5 equivalents)
and dioxane (3.0 g) as solvent. The flask was heated to 80.degree.
C. and after 7 hours the conversion and the selectivity to 4-methoxyphenyl
formiate (1a) and 4-methoxyphenol (2a) were determined. The activities
and selectivities obtained for the conversion of 4-methoxybenzaldehyde
with several catalysts are shown in Table 1.
TABLE-US-00002 TABLE 1 Oxidation of 4-methoxybenzaldehyde with
several catalysts distribution conv. of products Catalyst [%] 1a
2a other A (Sn-Beta) 2% SnO.sub.2 49 63 35 2 B (Al-Beta) 3% Al.sub.2O.sub.3
17 77 23 0 C (Beta) SiO.sub.2 0 -- -- -- 0 -- D (Sn-MCM-41) 25 45
42 13 9% SnO.sub.2
Example 6
Catalyst A was tested by means of the procedure described in Example
5 with 4-methoxybenzaldehyde and aqueous oxygenated water with 50%
by weight (1.4 equivalents) in dioxane (3.0 g) or in acetonitrile
(3.0 g) as solvent. The obtained results are shown in Table 2.
TABLE-US-00003 TABLE 2 Oxidation of 4-methoxybenzaldehyde in dioxane
and acetonitrile using a Sn-Beta zeolite as catalyst (sample A)
distribution conv. of products solvent [%] 1a 2a other dioxane 43
77 23 0 MeCN 57 4 96 0
Example 7
Catalyst A was tested by means of the procedure described in Example
6 with 4-n-propoxybenzaldehyde, with 4-methylbenzaldehyde and with
benzaldehyde. After 7 hours the conversion and selectivity to the
corresponding arylic formiate (1) and substituted phenol (2) and
to the corresponding aromatic acid (3) were determined. These results
are shown in Table 3.
TABLE-US-00004 TABLE 3 Oxidation of various aldehydes using an
Sn-Beta zeolite as catalyst (sample A) Distribution of conv. products
substrate solvent [%] 1 2 3 others 4-methoxy- dioxane 43 77 23 0
0 4-methoxy- MeCN 57 4 96 0 0 4-n-propoxybenzaldehyde dioxane 62
77 23 0 0 4-n-propoxybenzaldehyde MeCN 82 13 87 0 0 4-methyl- dioxane
26 29 44 23 4 4-methyl- MeCN 22 2 18 35 16 benzaldehyde dioxane
8 0 0 100 0 benzaldehyde MeCN 19 0 0 100 0
Example 8
Catalyst A was tested by means of the procedure described in Example
5 with 2-methoxybenzaldehyde at 90.degree. C. After 7 hours, a conversion
of 24% and a selectivity of 60% for 2-methoxyphenyl formiate (1e)
was observed and a selectivity of 25% for 2-methoxyphenol (2e).
Example 9
Catalysts A y D were tested by means of the procedure explained
in Example 5 with 34-dimethoxybenzaldehyde at 90.degree. C. The
activity and selectivity of both catalysts for the conversion of
the 34 dimethoxybenzaldehyde into 34-dimethoxyphenyl formiate
(1f) and 34-dimethoxyphenol (2f) are shown in Table 4.
TABLE-US-00005 TABLE 4 Oxidation of 34-dimethoxybenzaldehyde using
samples A y D as catalysts Distribution conversion of products Catalyst
[%] 1f 2f others A (Sn-Beta) 2% SnO.sub.2 9 92 0 8 D (Sn-MCM-41)
9% SnO.sub.2 22 97 0 3
Example 10
Catalyst A for the selective oxidation of 4-methoxybenzaldehyde
without solvent was tested according to the following procedure.
In a flask, 50 mg of catalyst were added to 3.0 g of aldehyde solution
and 0.29 grams of aqueous oxygenated water (35% in weight). The
flask was heated to 80.degree. C. and after an hour a 91% conversion
with regard to the oxygenated water and a selectivity of 97% for
the 4-methoxyphenyl formiate (1a) and a selectivity of 2% for the
4-methoxyphenol (2a) was observed. |