Process for the preparation of melonal

Abstract

A process for preparing 2,6-dimethyl-5-heptenal, comprising oxidizing citral of which more than 50% are present as geranial with hydrogen peroxide in the presence of a catalyst comprising a Baeyer-Villiger oxidation catalyst, preferably a tin-containing molecular sieve.

Claims

1. A process for preparing a compound of formula (III) ##STR00043## said process comprising (i) oxidizing a compound of formula (I) ##STR00044## of which more than 50% are present as compound of formula (Ia) ##STR00045## with hydrogen peroxide in the presence of a catalyst comprising a tin-containing molecular sieve, obtaining a reaction mixture comprising a compound of formula (II) ##STR00046## and optionally the compound of formula (III); wherein the process further comprises (ii) optionally separating the catalyst comprising a tin-containing molecular sieve, from the mixture obtained from (i); (iii) hydrolyzing the compound of formula (II), obtaining a mixture containing compound of formula (III); (iv) optionally separating the compound of formula (III) from the mixture obtained from (iii).

2. The process of claim 1, wherein in (i), at least 95% of the compound of formula (I) are present as compound of formula (Ia).

3. The process of claim 1, wherein in (i), the tin-containing molecular sieve is a tin-containing zeolitic material.

4. The process of claim 1, wherein the tin-containing molecular sieve has a tin content in the range of from 0.1 to 20 weight-%, based on the total weight of the tin-containing molecular sieve.

5. The process of claim 1, wherein in (i), the hydrogen peroxide is employed as an aqueous solution containing hydrogen peroxide in an amount in the range of from 25 to 85 weight-%, based on the total weight of the aqueous solution.

6. The process of claim 1, wherein at the beginning of the oxidation in (i), the molar ratio of the compound of formula (I) relative to the hydrogen peroxide is in the range of from 10:1 to 1:1.

7. The process of any claim 1, wherein the oxidizing in (i) is carried out in a solvent.

8. The process of claim 7, wherein the solvent comprises one or more alcohols.

9. The process of claim 7, wherein at the beginning of the oxidizing in (i), the weight ratio of the compound of formula (I) relative to the solvent in the range of from 1:10 to 1:2.

10. The process of claim 1, wherein the oxidizing in (i) is carried out at temperature of the reaction mixture in the range of from 30 to 90 C.

11. The process of claim 1, wherein in (iii), the hydrolyzing is carried out by adding an aqueous base to the reaction mixture obtained from the oxidizing in (i), optionally after separating in (ii), obtaining an organic phase containing the compound of formula (III) and an aqueous phase and wherein in (iv), the separating of the compound of formula (III) from the mixture obtained from (iii) comprises separating the organic phase from the aqueous phase, and wherein the compound of formula (III) is separated from the organic phase.

12. A mixture comprising a compound of formula (I) ##STR00047## wherein more than 50% of the compound of formula (I) are present as compound of formula (Ia) ##STR00048## and a catalyst comprising a tin-containing molecular sieve.

13. A method comprising increasing the selectivity and/or decreasing the reaction time of the Baeyer-Villiger oxidation of the compound of formula (I) ##STR00049## for preparing a compound of formula (III) ##STR00050## compared to the respective Baeyer-Villiger oxidation of the compound of formula (I) of which at most 50% are present as compound of formula (Ia) ##STR00051## at otherwise identical oxidation conditions, the method comprising oxidizing a compound of formula (I) of which more than 50% are present as compound of formula (Ia) to prepare a compound of formula (III).

14. The process of claim 1, wherein in (i), the tin-containing molecular sieve is a tin-containing zeolitic material, wherein the framework structure type of the tin-containing zeolitic material selected from the group consisting of BEA, MWW, MFI, a mixture of two or more thereof, and a mixed type of two or more thereof.

15. The process of claim 1, wherein the tin-containing molecular sieve has a tin content in the range of from 2 to 14 weight-%, based on the total weight of the tin-containing molecular sieve.

16. The process of claim 1, wherein in (i), the hydrogen peroxide is employed as an aqueous solution containing hydrogen peroxide in an amount in the range of from 65 to 75 weight-%, based on the total weight of the aqueous solution.

17. The process of claim 1, wherein at the beginning of the oxidation in (i), the molar ratio of the compound of formula (I) relative to the hydrogen peroxide is in the range of from 5:1 to 1:1.

18. The process of claim 7, wherein the solvent one or more of tert-butanol, 2-methyl-2-butanol, n-pentanol, 3-methyl-1-butanol, n-hexanol, 2-methyl-1-pentanol, 3-heptanol, 2-ethyl-1-hexanol, 2-octanol, 1-octanol, 2,4,4-trimethyl-1-hexanol, 2,6-dimethyl-4-heptanol, 2-propyl-1-heptanol, and 2-propyl-5-methyl-1-hexanol, or wherein the solvent comprises one or more ethers.

Description

EXAMPLES

Reference Example 1: Determination of the Water Uptake

(1) Water adsorption/desorption isotherms were performed on a VTI SA instrument from TA Instruments following a step-isotherm program. The experiment consisted of a run or a series of runs performed on a sample material that has been placed on the microbalance pan inside of the instrument. Before the measurement was started, the residual moisture of the sample was removed by heating the sample to 100 C. (heating ramp of 5 C./min) and holding it for 6 h under a nitrogen flow. After the drying program, the temperature in the cell was decreased to 25 C. and kept isothermal during the measurement. The microbalance was calibrated, and the weight of the dried sample was balanced (maximum mass deviation 0.01 weight-%). Water uptake by the sample was measured as the increase in weight over that of the dry sample. First, as adsorption curve was measured by increasing the relative humidity (RH) (expressed as weight-% water in the atmosphere inside of the cell) to which the sample was exposed and measuring the water uptake by the sample as equilibrium. The RH was increased with a step of 10 weight-% from 5% to 85% and at each step the system controlled the RH and monitored the sample weight until reaching the equilibrium conditions after the sample was exposed from 85 weight-% to 5 weight-% with a step of 10% and the change in the weight of the sample (water uptake) was monitored and recorded.

Reference Example 2: Determination of the Crystallinity

(2) The crystallinity of the zeolitic materials according to the present invention was determined by XRD analysis using the EVA method as described in the User Manual DIF-FRAC.EVA Version 3, page 105, from Bruker AXS GmbH, Karlsruhe. The respective data were collected on a standard Bruker D8 Advance Diffractometer Series II using a Sol-X detector, from 2 to 50 2theta, using variable slits (V20), a step size of 0.02 2theta and a scan speed of 2.4 s/step. Default parameters were used for estimating the background/amorphous content (Curvature=1, Threshold=1).

Reference Example 3: FT-IR Measurements

(3) The FT-IR (Fourier-Transformed-Infrared) measurements were performed on a Nicolet 6700 spectrometer. The powdered material was pressed into a self-supporting pellet without the use of any additives. The pellet was introduced into a high vacuum (HV) cell placed into the FT-IR instrument. Prior to the measurement the sample was pretreated in high vacuum (10.sup.5 mbar) for 3 h at 300 C. The spectra were collected after cooling the cell to 50 C. The spectra were recorded in the range of 4000 to 800 cm.sup.1 at a resolution of 2 cm.sup.1. The obtained spectra are represented in a plot having on the x axis the wavenumber (cm.sup.1) and on the y axis the absorbance (arbitrary units, a.u.). For the quantitative determination of the peak heights and the ratio between these peaks a baseline correction was carried out. Changes in the 3000-3900 cm.sup.1 region were analyzed and for comparing multiple samples, as reference the band at 18805 cm-.sup.1 was taken.

Reference Example 4: Determination of the Crush Strength of Moldings

(4) The crush strength as referred to in the context of the present invention is to be understood as determined via a crush strength test machine Z2.5/TS1S, supplier Zwick GmbH & Co., D-89079 Ulm, Germany. As to fundamentals of this machine and its operation, reference is made to the respective instructions handbook Register 1: Betriebsanleitung/Sicherheitshandbuch fr die Material-Prfmaschine Z2.5/TS1 S, version 1.5, December 2001 by Zwick GmbH & Co. Technische Dokumentation, August-Nagel-Strasse 11, D-89079 Ulm, Germany. With said machine, a given strand as described in Example 5, having a diameter of 1.5 mm, is subjected to an increasing force via a plunger having a diameter of 3 mm until the strand is crushed. The force at which the strand crushes is referred to as the crushing strength of the strand. The machine is equipped with a fixed horizontal table on which the strand is positioned. A plunger which is freely movable in vertical direction actuates the strand against the fixed table. The apparatus was operated with a preliminary force of 0.5 N, a shear rate under preliminary force of 10 mm/min and a subsequent testing rate of 1.6 mm/min. The vertically movable plunger was connected to a load cell for force pick-up and, during the measurement, moved toward the fixed turntable on which the molding (strand) to be investigated is positioned, thus actuating the strand against the table. The plunger was applied to the stands perpendicularly to their longitudinal axis. Controlling the experiment was carried out by means of a computer which registered and evaluated the results of the measurements. The values obtained are the mean value of the measurements for 10 strands in each case.

Reference Example 5: Preparation of Tin-Containing Molecular Sieves (Tin-Containing Zeolitic Materials Having a BEA Framework Structure) Via Solid-State Ion-Exchange

Reference Example 5.1: Tin-Containing Zeolitic Materials Having a BEA Framework Structure Having a Tin Content of 12.4 Weight-%

(5) 50.0 g of the deboronated zeolitic material having a BEA framework structure described in Reference Example 5.3.2 below were added to a kneader together with 14.2 g of tin(II) acetate (Sn(OAc).sub.2 [CAS-No: 638-39-1]), and the mixture was first dry-mixed, then the mixture was mashed with 50 ml of de-ionized water using a kneader, and the resulting mixture was kneaded for 15 minutes. After the kneading, the mixture was dried overnight at 60 C. Subsequently, the dried mixture was heated to a temperature of 500 C. under nitrogen (heating ramp: 2 K/min) and kept at 500 C. for 3 h, followed by calcination at 500 C. for 3 h under air. The obtained powder material had a Sn content of 12.4 weight-%, a silicon (Si) content of 35 weight-%, a B content of less than 0.03 weight-%, and a TOC of less than 0.1 weight-%. The BET specific surface area measured by DIN 66131 was 443 m.sup.2/g, the crystallinity was 45% determined by XRD, and the water uptake was 12 weight-%.

Reference Example 5.2: Tin-Containing Zeolitic Materials Having a BEA Framework Structure Having a Tin Content of 1.1 Weight-%

(6) 5.2.1 Preparing a Boron-Containing Zeolitic Material Having a BEA Framework Structure

(7) 259 g de-ionized water were provided in a vessel. Under stirring at 120 rpm (rounds per minute), 440 g tetraethylammonium hydroxide were added and the suspension was stirred for 10 minutes at room temperature. Thereafter, 75.6 g boric acid were suspended and the suspension was stirred for another 30 minutes at room temperature. Subsequently, 687.9 g Ludox AS-40 were added, and the resulting mixture was stirred for another hour at room temperature. The finally obtained mixture was transferred to a crystallization vessel and heated to 160 C. and stirred at 140 rpm for 120 h. The mixture was cooled to room temperature and subsequently. De-ionized water (twice the amount of the mixture) was added, resulting in a mixture having a pH of 10.0. This mixture was adjusted to a pH of 7-8 by adding aqueous HNO.sub.3 (10 weight-% HNO.sub.3). The mixture was subjected to filtration and the filter cake was washed with de-ionized water until the washing water had a conductivity of less than 150 microSiemens. The thus obtained filter cake was subjected to drying at 120 C. for 2 h under air, followed by calcination at 490 C. for 5 h under air (heating ramp: 2 K/min). The calcined material had a B content of 0.89 weight-%, a Si content of 47 weight-%, a total carbon content of (TOC) of less than 0.1 weight-%, a crystallinity determined by XRD of 42%, and a BET specific surface area determined by DIN 66131 of 257 m.sup.2/g.

(8) 5.2.2 Deboronation and Forming Vacant Tetrahedral Sites

(9) 2,100 g de-ionized water were passed in a 4 l stirred vessel. Under stirring, 140 g of the material obtained from Reference Example 5.2.1 above were added, and the resulting mixture heated to 100 C. The mixture was kept at this temperature under reflux for 10 h. Then, the mixture was cooled to room temperature. The cooled mixture was subjected to filtration and the filter cake was washed with de-ionized water. The thus obtained filter cake was subjected to drying at 120 C. for 12 h under air (heating ramp: 3 K/min), followed by calcination at 550 C. for 5 h under air (heating ramp: 2 K/min). The calcined material had a B content of 0.15 weight-%, a Si content of 49 weight-%, a total carbon content of (TOC) of less than 0.1 weight-%.

(10) 5.2.3 Incorporating Tin Via Solid-State Ion-Exchange

(11) 25 g of the deboronated zeolitic material having a BEA framework structure described in Reference Example 5.2.2 above were added to a mixer (mill type Microton MB550) together with 1.02 g of tin(II) acetate (Sn(OAc).sub.2 [CAS-No: 638-39-1]), and the mixture was milled for 15 minutes with 14,000 r.p.m. (rounds per minute). After the milling, the mixture was transferred to a porcelain basket and calcined in air at 500 C. for 3 h under N.sub.2 followed by 3 h under air, with a heating ramp of 2 K/min. The obtained powder material had a Sn content of 1.1 weight-%, a silicon (Si) content of 47 weight-%, a B content of less than 0.1 weight-%, and a TOC of less than 0.1 weight-%. The BET specific surface area measured by DIN 66131 was 170 m.sup.2/g.

Reference Example 5.3: Tin-Containing Zeolitic Materials Having a BEA Framework Structure Having a Tin Content of 13.1 Weight-%

(12) 5.3.1 Preparing a Boron-Containing Zeolitic Material Having a BEA Framework Structure

(13) 209 kg de-ionized water were provided in a vessel. Under stirring at 120 rpm (rounds per minute), 355 kg tetraethylammonium hydroxide were added and the suspension was stirred for 10 minutes at room temperature. Thereafter, 61 kg boric acid were suspended in the water and the suspension was stirred for another 30 minutes at room temperature. Subsequently, 555 kg Ludox AS-40 were added, and the resulting mixture was stirred at 70 rpm for another hour at room temperature. The liquid gel had a pH of 11.8 as determined via measurement with a pH electrode. The finally obtained mixture was transferred to a crystallization vessel and heated to 160 C. within 6 h under a pressure of 7.2 bar and under stirring (140 rpm). Subsequently, the mixture was cooled to room temperature. The mixture was again heated to 160 C. within 6 h and stirred at 140 rpm for additional 55 h. The mixture was cooled to room temperature and subsequently, the mixture was heated for additional 45 h at a temperature of 160 C. under stirring at 140 rpm. 7800 kg de ionized water were added to 380 kg of this suspension. The suspension was stirred at 70 rpm and 100 kg of a 10 weight-% HNO.sub.3 aqueous solution was added. From this suspension the boron containing zeolitic material having a BEA framework structure was separated by filtration. The filter cake was then washed with de-ionized water at room temperature until the washing water had a conductivity of less than 150 microSiemens/cm. The thus obtained filter cake was subjected to pre-drying in a nitrogen stream. The thus obtained zeolitic material was subjected, after having prepared an aqueous suspension having a solids content of 15 weight-%, based on the total weight of the suspension, using de-ionized water, to spray-drying in a spray-tower with the following spray-drying conditions:

(14) drying gas, nozzle gas: technical nitrogen

(15) temperature drying gas:

(16) temperature spray tower (in): 235 C. temperature spray tower (out): 140 C.
nozzle: top-component nozzle supplier Gerig; size 0 nozzle gas temperature: room temperature nozzle gas pressure: 1 bar
operation mode: nitrogen straight
apparatus used: spray tower with one nozzle
configuration: spray towerfilterscrubber
gas flow: 1,500 kg/h
filter material: Nomex needle-felt 20 m.sup.2
dosage via flexible tube pump: SP VF 15 (supplier: Verder)

(17) The spray tower was comprised of a vertically arranged cylinder having a length of 2,650 mm, a diameter of 1,200 mm, which cylinder was conically narrowed at the bottom. The length of the conus was 600 mm. At the head of the cylinder, the atomizing means (a two-component nozzle) were arranged. The spray-dried material was separated from the drying gas in a filter downstream of the spray tower, and the drying gas was then passed through a scrubber. The suspension was passed through the inner opening of the nozzle, and the nozzle gas was passed through the ring-shaped slit encircling the opening. The spray-dried material was then subjected to calcination at 500 C. for 5 h. The calcined material had a B.sub.2O.sub.3: SiO.sub.2 molar ratio of 0.045, a total carbon content of (TOC) 0.08 weight-%, a crystallinity determined by XRD of 56%, and a BET specific surface area determined by DIN 66131 of 498 m.sup.2/g.

(18) 5.3.2 Deboronation and Forming Vacant Tetrahedral Sites

(19) 840 kg de-ionized water were provided in a vessel equipped with a reflux condenser. Under stirring at 40 rpm, 28 kg of the spray-dried and calcined zeolitic material described above in 5.1 were employed. Subsequently, the vessel was closed and the reflux condenser put into operation. The stirring rate was increased to 70 rpm. Under stirring at 70 rpm, the content of the vessel was heated to 100 C. within 1 h and kept at this temperature for 20 h. Then, the content of the vessel was cooled to a temperature of less than 50 C. The resulting deboronated zeolitic material having a BEA framework structure was separated from the suspension by filtration under a nitrogen pressure of 2.5 bar and washed four times with deionized water at room temperature. After the filtration, the filter cake was dried in a nitrogen stream for 6 h. The obtained deboronated zeolitic material was subjected, after having re-suspended the zeolitic material in de-ionized water, to spray-drying under the conditions as described in 5.3.1. The solid content of the aqueous suspension was 15 weight-%, based on the total weight of the suspension. The obtained zeolitic material had a B.sub.2O.sub.3:SiO.sub.2 molar ratio of less than 0.002, a water uptake of 15 weight-%, a crystallinity determined by XRD of 48% and a BET specific surface area determined by DIN 66131 of 489 m.sup.2/g.

(20) 5.3.3 Incorporating Tin Via Solid-State Ion-Exchange

(21) 50 g of the deboronated zeolitic material having a BEA framework structure described in Reference Example 5, section 5.3.2, were added to a mixer (mill type Microton MB550) together with 14.2 g of tin(II) acetate (Sn(OAc).sub.2 [CAS-No: 638-39-1]), and the mixture was milled for 15 minutes with 14,000 r.p.m. (rounds per minute). After the milling, the mixture was transferred to a porcelain basket and calcined in air at 500 C. for 3 h under N.sub.2 followed by 3 h under air, with a heating ramp of 2 K/min. The obtained powder material had a Sn content of 13.1 weight-%, a silicon (Si) content of 38 weight-%, and a TOC of less than 0.1 weight-%. The BET specific surface area measured by DIN 66131 was 442 m.sup.2/g, the crystallinity determined by XRD was 44%, and the water uptake was 11.5 weight-%. The UV/Vis spectrum showed two maxima, one at wavelength of 200 nm with a shoulder around 250 nm. In the FT-IR spectrum the intensity ratio between a first adsorption band with a maximum between 3701 to 3741 cm.sup.1 and a second adsorption with the maximum between 3600 to 3690 cm.sup.1 was 1.62.

Reference Example 5.4: Tin-Containing Zeolitic Materials Having a BEA Framework Structure Having a Tin Content of 12.0 Weight-%

(22) 50 g of the deboronated zeolitic material having a BEA framework structure described in Reference Example 5.3.2 above were added to a mixer (mill type Microton MB550) together with 14.2 g of tin(II) acetate (Sn(OAc).sub.2 [CAS-Nr: 638-39-1]), and the mixture was milled for 15 minutes with 14,000 r.p.m. (rounds per minute). After the milling, the mixture was transferred to a porcelain basket and calcined in air at 500 C. for 3 h, with a heating ramp of 2 K/min.

(23) The obtained powder material had a Sn content of 12.0 weight-%, a silicon (Si) content of 35 wt. % and a TOC of less than 0.1 weight-%. The BET specific surface area measured by DIN 66131 was 391 m.sup.2/g, the crystallinity determined by XRD 44%, and the water uptake 15 weight-%. The UV/Vs spectrum showed two maxima, one at wavelength of 200 nm with a shoulder around 250 nm. In the FT-IR spectrum the intensity ratio between a first adsorption band with a maximum between 3701 to 3741 cm.sup.1 and a second adsorption with the maximum between 3600 to 3690 cm.sup.1 was 1.32.

Reference Example 5.5: Tin-Containing Zeolitic Materials Having a BEA Framework Structure Having a Tin Content of 12.4 Weight-%

(24) 50 g of the deboronated zeolitic material having a BEA framework structure described in Reference Example 5.3.2 above were added to a ball mill (17 balls with a total weight of 904 g) placed in an oven, together with 14.2 g of tin(II) acetate (Sn(OAc).sub.2 [CAS-No: 638-39-1]), and the mixture was ball-milled for 15 minutes at 80 r.p.m. After the ball-milling, the mixture heated in said oven to a temperature of 500 C. at a heating ramp of 2 K/min and kept at 500 C. for 3 h.

(25) The obtained powder material had a Sn content of 12.4 weight-%, a silicon (Si) content of 35.5 wt. %, a B content of less than 0.03 weight-%, and a TOC of 0.01 weight-%. The BET specific surface area measured by DIN 66131 was 426 m.sup.2/g.

Example 1: Baeyer-Villiger Oxidation of Citral (Compound of Formula (I)) with Hydrogen Peroxide in Tert-Butanol as Solvent Using a Zeolitic Material Having a BEA Framework Structure and a Tin Loading of 12.4 Weight-%

(26) A 1 L glass flask was charged with citral (122.5 g) as indicated in Table 1 below, the zeolitic material according to Reference Example 5. 1 above (8.75 g, Sn loading=12.4 weight-%) and tert-butanol (367.5 g) and heated to 65 C. An aqueous solution of hydrogen peroxide 70 w/w %, 29.75 g) was then added and the reaction mixture was stirred. After cooling to room temperature, the resulting solution was filtered and the filtrate was analyzed by GC using dioxane as internal standard.

(27) The results are shown in Table 1 below.

(28) TABLE-US-00001 TABLE 1 Results of Example 1 Example (E) and Citral Citral Selectivity.sup.1) Comparative Reaction Type/ Con- based on Selectivity.sup.2) Example Time/ % trans- ver- hydrogen based on (CE)/# min citral sion/% peroxide/% citral/% CE1.1 55 50 25 46 68 CE1.2 30 7 18 51 50 CE1.3 40 7 22 48 45 CE1.4 50 7 24 45 44 CE1.5 60 7 27 43 47 E1.1 3 98 11 80 99 E1.2 6 98 20 71 88 E1.3 10 98 28 67 78 E1.4 15 98 33 67 77 .sup.1)molar amount of melonal (compound of formula III)) + molar amount of enol formate (compound of formula (II)) obtained from the reaction divided by the molar amount of hydrogen peroxide employed in the reaction .sup.2)molar amount of melonal (compound of formula III)) + molar amount of enol formate (compound of formula (II)) obtained from the reaction divided by the molar amount of citral (compound of formula (I)) employed in the reaction

Results of Example 1

(29) Example 1 clearly shows that when using the compound of formula (I) with a content of the compound of formula (Ia) of more than 50%, both the selectivity based on hydrogen peroxide and the selectivity based on the compound of formula (I) were significantly increased and the conversion of the compound of formula (I) remained in the range of the comparative examples where the compound of formula (I) was employed either with a content of the compound of formula (Ia) of more 50% or less than 50%.

(30) With respect to Example E1.1, it is noted that while the conversion of the compound of formula (I) was lower than the conversions of the Comparative Examples, the selectivities exhibited by far the highest values; in particular, it is noted that it is these selectivity values which represent a decisive parameter for the industrial application of a reaction.

Example 2: Baeyer-Villiger Oxidation of Trans-Citral (Compound of Formula (Ia)) with Hydrogen Peroxide in Methyl Tert-Butyl Ether as Solvent Using Different Tin-Containing Zeolitic Materials Having a BEA Framework Structure

(31) For each run catalyst, a 1 L glass flask was charged with 122.5 g citral (compound of formula (I)), having a content of trans-citral (compound of formula (Ia)) of 98%), a catalyst as indicated in Table 2 below, and methyl tert-butyl ether a solvent, and heated to 50 C. An aqueous solution of hydrogen peroxide (70 w/w %,) was then added so that in the mixture, 1.3 molar equivalents of the compound of formula (Ia) relative to hydrogen peroxide were present. The amount of catalyst was, in each experiment, 6.6 weight-% relative to the compound of formula (I). The reaction mixture stirred, and the reaction was carried out for 150 min in each experiment. After cooling down to room temperature, the solution was filtered and the filtrate was analyzed by GC using dioxane as internal standard.

(32) The results are shown in Table 2 below.

(33) TABLE-US-00002 TABLE 2 Results of Example 2 Sn Catalyst Citral Selectivity Ex- Content of from Con- to melonal.sup.1) ample catalyst/ Reference ver- based on (E)/# weight % Example/# sion/% citral/% E2.1 1.1 5.2 11 63 E2.2 13.1 5.3 18 66 E2.3 12.7 5.4 10 73 E2.4 12.4 5.5 22 55 .sup.1)molar amount of melonal (compound of formula III)) + molar amount of enol formate (compound of formula (II)) obtained from the reaction divided by the molar amount of citral (compound of formula (I)) employed in the reaction

Results of Example 2

(34) Example 2 shows that all tin-containing molecular sieves employed in the Baeyer-Villiger oxidation which were prepared according to simple methods avoiding the disadvantages of the preparation process according to Corma et al., Journal of Catalysis 234 (2005) 96-100 lead to advantageous selectivities to the valuable product melonal. It has to be noted that although some selectivity values according to Table may appear to be lower than some selective values according to Table 1, the selectivity values of Tables 1 and 2 cannot be compared with each other because different solvents and different catalysts at different process conditions are used. While Example 1 allows a direct comparison and thus illustrates the advantage of the use of the trans-form of citral as starting material compared to the use of the 1:1 mixture taught in the art, Example 2 shows the general validity of the inventive concept illustrated by a variety of catalysts.

CITED LITERATURE

(35) Corma et al., Journal of Catalysis 234 (2005) 96-100 WO 2014/068134 A Baerlocher et al., Atlas of Zeolite Framework Structures, Sixth Revised Edition, Elsevier, Amsterdam (2007) pp 72-73 K. S. W. Sing, D. H. Everett, R. A. W. Haul, L. Moscou, R. A. Plerotti, J. Rouquerol, T. Siemieniewska, Reporting Physisorption Data for Gas/Solid Systems with Special Reference to the Determination of Surface Area and Porosity (Recommendations 1984) Pure & Appl. Chem. 57 (1985) 603-619