Cycloalkane oxidation catalysts and method to produce alcohols and ketones

Abstract

The present invention concerns a method of oxidizing a cycloalkane to form a product mixture containing a corresponding alcohol and ketone, said method comprising contacting a cycloalkane with a hydroperoxide compound in the presence of a catalytic effective amount of a cerium oxide based catalyst.

Claims

1. A method of oxidizing a cycloalkane to form a product mixture containing a corresponding alcohol and ketone, said method comprising contacting a cycloalkane with a cyclohexyl hydroperoxide compound in the presence of at least a cerium oxide based catalyst that has a cerium oxide content of at least 60 wt %, wherein the cerium oxide based catalyst is at least one catalyst selected from the group consisting of: a composition comprising cerium oxide and at least one oxide of another rare earth, a composition comprising cerium oxide and at least one compound of another rare earth, a cerium composite oxide comprising at least cerium oxide, silicon oxide, titanium oxide and at least one oxide of another rare earth, and/or a composition comprising cerium oxide, zirconium oxide and at least one oxide of another rare earth; and wherein the cerium oxide based catalyst at least includes an oxide of a rare earth of one of praseodymium oxide and/or lanthanum oxide, wherein the cerium oxide based catalyst is used as such.

2. A method according to claim 1, wherein cycloalkane is selected from the group consisting of cyclopentane, cyclohexane, cycloheptane, and cyclooctane.

3. A method according to claim 2, wherein the cycloalkane is cyclohexane, the alcohol is cyclohexanol and the ketone is cyclohexanone.

4. A method according to claim 1, wherein the amount of catalyst is from 0.01 wt % to 10 wt. based on the total weight of the reaction medium.

5. A method to produce adipic acid, comprising: oxidizing liquid cyclohexane by reaction with oxygen gas to produce cyclohexane hydroperoxide, decomposing the cyclohexane hydroperoxide into a mixture of cyclohexanol and cyclohexanone, by using the cyclohexane hydroperoxide as the hydroperoxide compound in a method according to claim 1, oxidizing, with nitric acid, the mixture of cyclohexanol and cyclohexanone to adipic acid, and extracting and purifying the adipic acid.

6. A method of producing polyamide, obtained by polycondensation from adipic acid produced by the method of claim 5, and hexamethylenediamine, comprising the following steps: mixing adipic acid produced by the method of claim 5 with hexamethylenediamine, to produce hexamethylenediammonium adipate, and heatingan aqueous solution of the hexamethylenediammonium adipate.

7. The method according to claim 1, wherein the cerium oxide based catalyst has a nano-rod nanostructure.

8. The method according to claim 1, wherein the cerium oxide based catalyst is a composition comprising cerium oxide and at least one oxide of another rare earth.

9. The method according to claim 1, wherein the cerium oxide based catalyst is a composition comprising cerium oxide and at least one compound of another rare earth.

10. The method according to claim 1, wherein the cerium oxide based catalyst is a cerium composite oxide comprising at least cerium oxide, silicon oxide, titanium oxide and at least one oxide of another rare earth.

11. The method according to claim 1, wherein the contacting of the cycloalkane with the cyclohexyl hydroperoxide compound in the presence of at least the cerium oxide based catalyst does not include an addition of any additional oxidizing agent selected from group consisting of pure oxygen, air, oxygen-enriched air, oxygen-depleted air, oxygen diluted with an inert gas, or a combination thereof.

12. The method according to claim 11, wherein the contacting of the cycloalkane with the cyclohexyl hydroperoxide compound in the presence of at least the cerium oxide based catalyst is conducted in the presence of a nitrogen overpressure.

Description

EXPERIMENTAL PART

Abbreviations

(1) .sup.tBuOOH: tert-butyl hydroperoxide CyOH: cyclohexanol CyO: cyclohexanone CyOOH: cyclohexyl hydroperoxide

Definition of Terms

(2) Conversion is defined as the ratio between the number of moles of hydroperoxide ROOH consumed divided by the number of initial moles of ROOH.

(3) $\mathrm{Conversion}\left(\%\right)=100\times \frac{n\mathrm{ROOH}\left(\mathrm{consumed}\right)}{n\mathrm{ROOH}\left(\mathrm{initial}\right)}$

(4) In the case of tBuOOH decomposition, selectivity is defined as the number of moles of Cyclohexanol (CyOH) and cyclohexanone (CyO) produced divided by the number of moles of tBuOOH consumed.

(5) $\mathrm{Selectivity}\left(\%\right)=100\times \frac{n\mathrm{CyO}\left(\mathrm{produced}\right)+n\mathrm{CyOH}\left(\mathrm{produced}\right)}{nt\mathrm{BuOOH}\left(\mathrm{consumed}\right)}$

(6) If selectivity is 0, catalyst decomposes tBuOOH without oxidizing cyclohexane. If selectivity is higher than 0, catalyst is able to decompose the peroxide and oxidize cyclohexane at the same time

(7) In the case of CyOOH decomposition, selectivity is defined as the number of moles of Cyclohexanol (CyOH) and cyclohexanone (CyO) produced divided by the number of moles of CyOOH consumed.

(8) $\mathrm{Selectivity}\left(\%\right)=100\times \frac{n\mathrm{CyO}\left(\mathrm{produced}\right)+n\mathrm{CyOH}\left(\mathrm{produced}\right)}{n\mathrm{CyOOH}\left(\mathrm{consumed}\right)}$

(9) When selectivity is lower or equal to 100%, catalyst only decomposes CyOOH without oxidizing cyclohexane.

(10) When selectivity is higher than 100%, catalyst is able to decompose the peroxide and oxidize cyclohexane at the same time.

(11) Analysis

(12) Iodometry

(13) Cyclohexyl hydroperoxide (CyOOH) is quantified by iodometry which consists in reacting CyOOH with KI to yield cyclohexanol and I.sub.2. The amount of I.sub.2 formed is estimated by potentiometry by reaction of I.sub.2 with Na.sub.2S.sub.2O.sub.3.

(14) About 1 g of the solution containing CyOOH is weighed in an Erlenmeyer flask. Then, 20 mL of 80% acetic acid, about 1 g of sodium hydrogenocarbonate (NaHCO.sub.3) and about 1 g of potassium iodide (KI) are introduced. NaHCO.sub.3 is a weak base and reacts with acetic acid to produce CO.sub.2, so that O.sub.2 is pushed away. Indeed, the presence of O.sub.2 would induce error on the evaluation of CyOOH quantity.

(15) After mixing, the Erlenmeyer flask is stored 20 minutes in the dark. The Erlenmeyer flask is washed with distilled water and acetonitrile (which avoid the formation of foam). The solution is dosed with a solution of sodium thiosulfate Na.sub.2S.sub.2O.sub.3 (0.1 N). The same method is used to quantify tert-butyl hydroperoxide (tBuOOH).

(16) GC (gas chromatography)

(17) GC Used to Quantify Cyclohexanol and Cyclohexanone Formed after tBuOOH Decomposition

(18) The reaction mixture contains cyclohexane, tert-butyl hydroperoxide, cyclohexanol, cyclohexanone, tert-butanol and small amounts of other byproducts, like carboxylic acids or diols.

(19) Tert-butyl hydroperoxide is quantified by iodometry, while cyclohexanol and cyclohexanone formed during the reaction are quantified by GC using a Varian CP-3800 chromatograph with a HP-5 column (0.25 μm film thickness, length 25 m, inner diameter 0.25 mm). For each sample, 30 μL are extracted from the glass reactor vessel using a syringe and introduced in a vial containing cyclohexane. The amount of tBuOOH is measured by iodometry.

(20) GC Used to Quantify Cyclohexanol, Cyclohexanone and CyOOH after CyOOH Decomposition

(21) The reaction mixture contains cyclohexane, cyclohexyl hydroperoxide, cyclohexanol, cyclohexanone, and small amounts of other byproducts (carboxylic acids, diols, lactones, peroxide) which are quantified by GC using a specific polar column (Permabond FFAP 0.10 μm film thickness, length 20 m). The amount of CyOOH of calibration solution is measured by iodometry.

(22) Dinitrogen physisorption for BET area quantification was performed on a Micromeritics ASAP®2420 Accelerated Surface Area and Porosimetry System at 77 K. BET analyses allowed to determine the surface area of the catalysts.

(23) Materials:

(24) Cyclohexyl Hydroperoxide (CyOOH) Solution in Cyclohexane

(25) CyOOH was extracted from a cyclohexane oxidate resulting from the thermal oxidation of cyclohexane by oxygen in an industrial unit. The oxidate was washed with water first then it was extracted with 1 M NaOH. The water phase was then extracted with ether and was neutralized with a chilled aqueous 4 M HCl. solution until slightly acidic. The water phase was subsequently extracted 3 times with cyclohexane and dried over Na.sub.2SO.sub.4 or MgSO.sub.4. The solution was concentrated to reach a concentration of 4.7 wt % or 5.6 wt % CyOOH.

(26) Tert-Butyl Hydroperoxide (tBuOOH) Solution in Cyclohexane

(27) The reaction mixture is prepared from a commercial solution of .sup.tBuOOH diluted in water (3:2 .sup.tBuOOH: water, ie 80% in mass percentage) from Fluka, and cyclohexane (>99% purity). The proper amount of .sup.tBuOOH solution and cyclohexane is mixed. Molecular sieves are added to the solution in order to absorb the water and make the mixture anhydrous. The exact amount of .sup.tBuOOH in the final mixture is analyzed by iodometry. The mixture is then stored in darkness at low temperature (10° C.) until it is used for reaction.

(28) CeO.sub.2 Based Catalyst from the Invention CeO.sub.2: this catalyst can be produced according to a process described in EP 300852 or EP 388567 CeO.sub.2 Aldrich: cerium oxide commercialized by Aldrich. CeO.sub.2 nano-structures (rods, octahedral, cubes): these catalysts can be produced according to a process described in references [1] or [2] ([1] S. Laursen, D. Combita, M. Boronat, A. Corma, Angew. Chem. Int. Ed. 2012, 51, 4190-4193 and [2] H. Mai, L. Sun, Y. Zhang, R. Si, W. Feng, H. Zhang, H. Liu, C. Yan, J. Phys. Chem. B 2005, 109, 24380-24385). A solution of NaOH was added under vigorous stirring to a solution of Ce(NO.sub.3).sub.3.6H.sub.2O (Aldrich, Analytical grade). The formed suspension was kept stirring for 30 minutes. This step produces seeds for the hydrothermal growth. This milky slurry was transferred to a Teflon liner autoclave and the autoclave was sealed tightly. The autoclave was transferred to an oven for the hydrothermal treatment during 24 hours. Table 1 shows the conditions for each type of CeO.sub.2 nano-structure. After cooling down at room temperature, the precipitated yellow-white solids were filtrated and washed thoroughly with distillated water, controlling the pH of the filtrates. After that, the samples were dried at 120° C., under flowing air for 12 hours.

(29) TABLE-US-00001 TABLE 1 Synthesis parameters for the production of the CeO.sub.2 nano-structures. SHAPE V.sub.Sol. NaOH/V.sub.Sol. Ce+3 [NaOH] (M) [Ce.sup.+3] (M) T (° C.) Cubes 7 9 5 200 Octahedra 7 1 5 175 Rods 7 9 5 100 Doped CeO.sub.2 nano-rods: The procedure is essentially the same as described above for CeO.sub.2 nano-structures, with an additional step in which the proper amount of X(NO.sub.3).sub.3.6H.sub.2O (Sigma-Aldrich, Analytical grade, X=La,Pr,Y, CAS: 10277-43-7, 15878-77-0, 13773-69-8 respectively) is added to the Ce(NO.sub.3).sub.3.6H.sub.2O solution before addition of NaOH. The content of X in the catalyst is 1 wt %. Ce—Zr: mixture of CeO.sub.2 and ZrO.sub.2 Ce—Zr—La: mixture of CeO.sub.2, ZrO.sub.2 and La.sub.2O.sub.3 Ce—Zr—Pr: mixture of CeO.sub.2, ZrO.sub.2 and Pr.sub.6O.sub.11 Ce—La—Pr: mixture of CeO.sub.2, La.sub.2O.sub.3 and Pr.sub.6O.sub.11 Ce—Pr: mixture of CeO.sub.2 and Pr.sub.6O.sub.11 Ce—Si: mixture of CeO.sub.2 and SiO.sub.2 Ce—Si—Ti: mixture of CeO.sub.2, SiO.sub.2 and TiO.sub.2 Ce—Si—Ti—La: mixture of CeO.sub.2, SiO.sub.2, TiO.sub.2 and La.sub.2O.sub.3

(30) The numbers mentioned in the “composition” columns of the tables below correspond to the weight percentage of the different oxides (CeO.sub.2, ZrO.sub.2, La.sub.2O.sub.3 and/or Pr.sub.6O.sub.11) present in the catalysts.

(31) Some of these catalysts are commercial products from Solvay.

(32) Other Catalysts (for Comparison)

(33) Titanium dioxide (TiO.sub.2): commercial product from Aldrich Zirconium dioxide (ZrO.sub.2): commercial product from Aldrich Molybdenum oxide (MoO.sub.2): commercial product from Aldrich Praseodymium oxide (Pr.sub.6O.sub.ii): commercial product from Aldrich Calcium oxide (CaO): commercial product from Aldrich Gallium oxide (Ga.sub.2O.sub.3): commercial product from Aldrich Germanium oxide (GeO.sub.2): commercial product from Aldrich Yttrium oxide (Y.sub.2O.sub.3): commercial product from Aldrich Tin oxide (SnO and SnO.sub.2): commercial products from Aldrich Hafnium oxide (HfO.sub.2): commercial product from Aldrich Tantalum oxide (Ta.sub.2O.sub.5): commercial product from Aldrich Neodymium oxide (Nd.sub.2O.sub.3): commercial product from Aldrich Samarium oxide (Sm.sub.2O.sub.3): commercial product from Aldrich Europium oxide (Eu.sub.2O.sub.3): commercial product from Aldrich Erbium oxide (Er.sub.2O.sub.3): commercial product from Aldrich Zinc oxide (ZnO): commercial product from Fluka Tungsten oxide (W.sub.2O.sub.3); commercial product from Fluka High surface area titanium dioxide (TiO.sub.2 HSA): commercial product from Mirkat Magnesium oxide (MgO 600 m.sup.2/g): commercial product from Nanoactive Alumina (Al.sub.2O.sub.3 550 m.sup.2/g): commercial product from Nanoactive Niobium oxide (Nb.sub.2O.sub.5): commercial product from Alfa Aesar Lanthanum oxide (La.sub.2O.sub.3): commercial product from Merck
Catalyst Pre-Treatment.

(34) Calcination:

(35) Catalysts can be calcined before reaction under the following classical conditions. The catalyst is placed into a porcelain evaporating dish, it is introduced in the oven and calcined in static air with the following temperature program: 4 hours gradient from room temperature to 400° C., and then an isotherm of 400° C. for 4 hours. The catalyst is kept inside the oven until the reaction is to be performed.

(36) Gas Flow.

(37) The catalyst can also be treated under different gas flow. The catalyst is placed into the batch reactor, and a stirrer is also introduced in the system. Then, a flow of the desired gas for the treatment (N.sub.2, H.sub.2, or O.sub.2) is introduced through the vent valve, and the flow is controlled with a flowmeter (15-20 mL/min). While the gas is passing through the system, stirring is active to ensure that the gas reaches all catalyst mass. Temperature is kept constant at the desired value (135° C. or 85° C. for N.sub.2 and 85° C. for H.sub.2 and O.sub.2) during the treatment that takes 45 min.

(38) General Conditions of tBuOOH Deperoxidation Reaction:

(39) Reactor.

(40) The reaction is performed in a batch reactor consisting of: a glass reactor vessel (chemical and thermal shock resistant, 2 mL Volume capacity, Duran Manufacturer). a vent valve (Gas inlet, for pressurizing/depressurizing the system with nitrogen). an outlet micro valve for sample taking. a pressure gauge (Pressure range: 1-16 bar). a magnetic stirring bar, which is stored inside the reaction media in the reactor vessel.

(41) To ensure that the reactor is completely clean and no traces of contaminants are present, it is first washed with acetone, then with cyclohexane, and after that dry air is passed through.

(42) Reaction Procedure.

(43) The proper amount (16 mg) of catalyst is introduced in the reactor. Then, 200 μL of internal standard Undecane (99% purity, from Sigma-Aldrich) are introduced in the glass reactor vessel and its exact mass weighted.

(44) Next, the reactor is opened, 2 mL of the tert-butyl hydroperoxide/cyclohexane solution is introduced, and its exact mass weighted. Finally, a magnetic stir bar is introduced and the reactor is closed. An overpressure of nitrogen is then added in order to increase the boiling point of cyclohexane and keep reaction media at liquid state. The gas is introduced through the vent valve until an internal pressure in the reactor within 4 to 6 atmosphere is reached.

(45) An aluminium container for reactors, at the desired reaction temperature (100° C.), is kept on a hot-stirring plate. The stirring is set to 1400 rpm. The glass reactor vessel is introduced in the container, and the reaction starts.

(46) To follow the reaction progress, samples are taken at different times and their composition analyzed by iodometry (t-butyl hydroperoxide) and Gas Chromatography (cyclohexanol and cyclohexanone). At each time, the reactor is first taken off the container and stored in a water bath at room temperature, in order to cool down the reaction media. Once the reactor is at room temperature, three different samples are taken from it through the outlet micro valve and analyzed.

Examples 1 to 20 (According to the Invention)

(47) It is observed that pretreatment has an influence on activity and selectivity of CeO.sub.2. The CeO.sub.2 catalyst has been treated under different gas flows as described in the “catalyst pre-treatment” section above or calcined at 500° C. according to the following procedure: The CeO.sub.2 catalyst (16 mg) is placed into a porcelain evaporating dish, it is introduced in the oven and calcined in static air with the following temperature program: 3 hours gradient from room temperature to 500°, and then an isotherm of 500° for 5 hours. The catalyst is kept inside the oven until the reaction is to be performed.

(48) The CeO.sub.2 Aldrich catalyst (16 mg) is calcined under classical conditions before test as described in the “catalyst pre-treatment” section above.

(49) The catalyst was tested under the conditions specified above (see “reaction procedure” section above) at 100° C.

(50) In all cases, selectivity is positive, meaning CeO.sub.2 is able to oxidize cyclohexane in the presence of tBuOOH.

(51) The catalyst of example 20 has a surface area of 12.7 m.sup.2/g.

(52) TABLE-US-00002 TABLE 2 Catalytic performance of CeO.sub.2 after test in tBuOOH/cylohexane solution Wt % Catalyst Pre- Reaction Example tBuOOH Catalyst treatment T (° C.) t (h) Conversion % Selectivity % 1 11.9 CeO.sub.2 — 80 8 43 53 2 11.9 CeO.sub.2 N.sub.2 at 135° C. 80 8 49 35 3 11.9 CeO.sub.2 N.sub.2 at 135° C. 80 11 57 34 4 11.9 CeO.sub.2 N.sub.2 at 85° C. 80 8 41 29 5 11.9 CeO.sub.2 N.sub.2:O.sub.2 95:5 in 80 8 38 34 volume at 85° C. 6 11.9 CeO.sub.2 O.sub.2 at 85° C. 80 8 44 40 7 11.9 CeO.sub.2 H.sub.2 at 85° C. 80 8 28 26 8 11.9 CeO.sub.2 calcined 80 8 33 60 at 500° C. 9 11.3 CeO.sub.2 N.sub.2 at 85° C. 85 4 33 39 10 11.3 CeO.sub.2 N.sub.2 at 85° C. 85 8 46 39 11 11.3 CeO.sub.2 N.sub.2 at 85° C.c 100 4 39 61 12 11.3 CeO.sub.2 N.sub.2 at 85° C. 100 8 73 36 13 11.3 CeO.sub.2 N.sub.2 at 85° C. 120 4 48 54 14 11.3 CeO.sub.2 N.sub.2 at 85° C. 120 8 83 31 15 11.3 CeO.sub.2 calcined 85 4 24 48 at 500° C. 17 11.3 CeO.sub.2 calcined 85 8 34 60 at 500° C. 18 11.3 CeO.sub.2 calcined 100 4 44 43 at 500° C. 19 11.3 CeO.sub.2 calcined 100 8 74 34 at 500° C. 20 6.0 CeO.sub.2 Aldrich calcined at 100 9 33 21 400° C.

Examples 21 to 29 (According to the Invention)

(53) CeO.sub.2 was calcined at 600° C., 700° C. and 900° C. according to the following procedure: They were placed into a porcelain evaporating dish, introduced in the oven and calcined in static air with the following temperature program: from room temperature to final temperature at 0.5° C./min, and then an isotherm at the desired temperature for 4 hours.

(54) They were tested under the conditions specified above (see “reaction procedure” section above) at 100° C. in a 7.37 wt % tBuOOH/cyclohexane solution. It is observed that selectivity is positive in all cases meaning that these catalysts are able to oxidize cyclohexane. However, increasing calcination temperature resulted in the decrease of activity and selectivity.

(55) The catalyst of examples 21 to 23 has a surface area of 159.8 m.sup.2/g, and the catalyst of examples 24 to 26 has a surface area of 115.9 m.sup.2/g.

(56) TABLE-US-00003 TABLE 3 Catalytic performance of CeO.sub.2 calcined between 600° C. and 800° C. after test in 7.37 wt % tBuOOH/cyclohexane solution at 100° C. Conversion Selectivity Example Catalyst t(h) % (%) 21 CeO.sub.2 calcined at 600° C. 3 58 34 22 CeO.sub.2 calcined at 600° C. 6 77 33 23 CeO.sub.2 calcined at 600° C. 9 81 29 24 CeO.sub.2 calcined at 700° C. 3 48 40 25 CeO.sub.2 calcined at 700° C. 6 67 33 26 CeO.sub.2 calcined at 700° C. 9 78 29 27 CeO.sub.2 calcined at 900° C. 3 18 29 28 CeO.sub.2 calcined at 900° C. 6 36 27 29 CeO.sub.2 calcined at 900° C. 9 42 27

Examples 30 to 37 (According to the Invention)

(57) CeO.sub.2 doped with La and/or Pr, ZrO.sub.2—CeO.sub.2 mixed oxides and CeO.sub.2—ZrO.sub.2 mixed oxides doped with La or Pr were calcined under classical conditions before test as described in the “catalyst pre-treatment” section.

(58) They were tested under the conditions specified above at 100° C. in a 7.57 wt % tBuOOH/cyclohexane solution. Selectivity is positive in each cases meaning all catalysts are able to oxidize cyclohexane.

(59) The catalyst of example 30 has a surface area of 221.9 m.sup.2/g.

(60) TABLE-US-00004 TABLE 4 Catalytic performance of CeO.sub.2 doped with La and/or Pr, ZrO.sub.2—CeO.sub.2 mixed oxides and CeO.sub.2—ZrO.sub.2 mixed oxides doped with La or Pr after 9 h in 7.57 wt % tBuOOH/cyclohexane solution at 100° C. (see “reaction procedure” section above) Conversion Selectivity Example Catalyst Composition (%) (%) 30 CeO.sub.2 (100) 88 34 31 Ce—Pr (90-10) 86 36 32 Ce—Zr—Pr (90-5-5) 85 31 33 Ce—La—Pr (90-5-5) 76 34 34 Ce—Zr—La (86-10-4) 59 35 35 Ce—Zr—La (20-75-5) 47 26 36 Ce—Zr (70-30) 69 37 37 Ce—Zr (57-43) 64 37

Examples 38 to 40 (According to the Invention)

(61) CeO.sub.2—SiO.sub.2 mixed oxides, CeO.sub.2—SiO.sub.2—TiO.sub.2 mixed oxides or CeO.sub.2—SiO.sub.2—TiO.sub.2 mixed oxides doped with La, were calcined under classical conditions before test as described in the “catalyst pre-treatment” section.

(62) They were tested under the conditions specified above at 100° C. in a 7.85 wt % tBuOOH/cyclohexane solution. Selectivity is positive in each cases meaning all catalysts are able to oxidize cyclohexane.

(63) TABLE-US-00005 TABLE 5 Catalytic performance of CeO.sub.2 mixed oxides alone or doped with La after 9 h in 7.85 wt % tBuOOH/cyclohexane solution at 100° C. (see “reaction procedure” section above) Conversion Selectivity Example Catalyst Composition (%) (%) 38 Ce—Si (98-2) 91 24 39 Ce—Si—Ti (90-5-5) 99 26 40 Ce—Si—Ti—La (80-10-5-5) 99 25

Examples 41 to 43 (According to the Invention)

(64) CeO.sub.2 nanostructures were calcined under classical conditions before test as described in the “catalyst pre-treatment” section.

(65) They were tested under the conditions specified above at 100° C. in a 7.57 wt % tBuOOH/cyclohexane solution. Selectivity is positive in each cases meaning all catalysts are able to oxidize cyclohexane. Cubes were found less active and selective than octahedra, and the best performance was obtained for rods.

(66) TABLE-US-00006 TABLE 6 Catalytic performance of nanostructures of CeO.sub.2 after 9 h in 7.57 wt % tBuOOH/cyclohexane solution at 100° C. (see “reaction procedure” section above) Surface area Conversion Selectivity Example Morphology (m.sup.2/g) (%) (%) 41 Rods 111.0 86 29 42 Octahedra 64.9 67 26 43 Cubes 31.2 31 25

Examples 44 to 67 (Comparative Examples)

(67) Different oxides were calcined before test under classical conditions as described in “catalyst pretreatment” section above. In some cases, they were treated under N.sub.2. They were tested in tBuOOH/cyclohexane solution at 80° C. and 100° C. (see “reaction procedure” section above). Results are presented in Table 7.

(68) TiO.sub.2 and Sm.sub.2O.sub.3 oxides are inactive.

(69) CaO, MgO, ZnO, TiO.sub.2 HSA, La.sub.2O.sub.3, Ga.sub.2O.sub.3, GeO.sub.2, Y.sub.2O.sub.3, Nb.sub.2O.sub.5, SnO, SnO.sub.2, HfO.sub.2, Ta.sub.2O.sub.5, Nd.sub.2O.sub.3, Eu.sub.2O.sub.3 and Er.sub.2O.sub.3 oxides are weakly active with a conversion lower than 24% but able to oxidize cyclohexane.

(70) Pr.sub.6O.sub.11, W.sub.2O.sub.3 and ZrO.sub.2 decompose tBuOOH with a low conversion and do not oxidize cyclohexane.

(71) MoO.sub.2 oxide is active with a high conversion but selectivity is low (17%). Catalyst of the invention represents the best compromise with a high activity (conversion 88%) and the highest selectivity obtained (34%). Hence, catalyst of the invention is the best oxide to decompose tBuOOH and oxidize cyclohexane.

(72) TABLE-US-00007 TABLE 7 Catalytic performance of oxides after 9 h in tBuOOH/cyclohexane Catalyst Wt % pre- Example Catalyst tBuOOH T° C. treatment Conversion % Selectivity % 44 CaO 7 100 Calcined 11 14 45 TiO.sub.2 5 80 N.sub.2 at 135° C. <5% 0 46 ZrO.sub.2 5 80 N.sub.2 at 135° C. <5% 0 47 ZrO.sub.2 7 100 Calcined 12 2 48 MgO 7 100 Calcined 10.8 28 49 ZnO 7 100 Calcined 10 25 50 W.sub.2O.sub.3 7 100 Calcined 8 0 51 TiO.sub.2 7 100 Calcined 18 25 HSA 52 MoO.sub.2 7 100 — 70 15 53 MoO.sub.2 7 100 Calcined 98.5 17 54 La.sub.2O.sub.3 7 100 Calcined 16.6 27 55 Pr.sub.6O.sub.11 7 100 Calcined 11 0 56 Ga.sub.2O.sub.3 7 100 Calcined 12 18 57 GeO.sub.2 7 100 Calcined 10 14 58 Y.sub.2O.sub.3 7 100 Calcined 13 16 59 Nb.sub.2O.sub.5 7 100 Calcined 22 15 60 SnO 7 100 Calcined 15 17 61 SnO.sub.2 7 100 Calcined 14 15 62 HfO.sub.2 7 100 Calcined 7 19 63 Ta.sub.2O.sub.5 7 100 Calcined 9 12 64 Nd.sub.2O.sub.3 7 100 Calcined 12 20 65 Sm.sub.2O.sub.3 7 100 Calcined 0 0 66 Eu.sub.2O.sub.3 7 100 Calcined 23 14 67 Er.sub.2O.sub.3 7 100 Calcined 16 17
General Conditions of CyOOH Deperoxidation Reaction:
Reactor

(73) The reaction is performed in a Teflon batch reactor consisting of: a teflon reactor vessel (40 mL Volume capacity, Bola Manufacturer) an outlet micro valve for sample taking. a pressure gauge. a thermocouple a magnetic stirring bar, which is stored inside the reaction media in the reactor vessel.

(74) To ensure that the reactor is completely clean and no traces of contaminants are present, it is first washed with acetone, then with water. In case some trace of metal remains on the reactor wall, it is washed with diluted HCl.

(75) Reaction Procedure

(76) The proper amount (160 mg) of catalyst is introduced in the reactor. Then, 0.6 g of internal standard orthodichlorobenzene (99% purity, from Sigma-Aldrich) are introduced in the teflon reactor.

(77) Next, the reactor is opened, about 16 g of the CyOOH purified solution are introduced and its exact mass weighted. Finally, a magnetic stir bar is introduced and the reactor is closed.

(78) A silicon bath at the desired reaction temperature (typically 100° C.) is kept on a hot-stirring plate. The glass reactor vessel is introduced in the silicon bath. It takes about 30 minutes to reach 100° C. inside the reactor. During this transition period of heat, the stirring is off to slow down reaction between room temperature and 100° C.

(79) The follow up of reaction and stirring of the mixture begin when temperature reaches 100° C. To follow the reaction progress, samples are taken at different times and their composition analyzed by Gas Chromatography. The medium is sampled through a syringe and put in a GC vial when it is cold.

Examples 68 to 69 (According to the Invention)

(80) The CeO.sub.2 catalyst is calcined in a static air oven at 500° C. prior to reaction. The CeO.sub.2 catalyst (160 mg) is placed into a porcelain evaporating dish, it is introduced in the oven and calcined in static air at 500° C. during 13 h. Reaction is performed as described above. Selectivities higher than 100% are obtained meaning CeO.sub.2 is able to oxidize cyclohexane in the presence of CyOOH (Table 8).

(81) TABLE-US-00008 TABLE 8 Catalytic performance of CeO.sub.2 after test in 4.7 wt % CyOOH/cyclohexane solution at 100° C. Example t(h) Conversion % Selectivity % 68  5 h 30 92.8 113 69 21 h 30 99.8 113

Examples 70 to 76 (According to the Invention)

(82) CeO.sub.2 doped with La and/or Pr, ZrO.sub.2—CeO.sub.2 mixed oxides and CeO.sub.2—ZrO.sub.2 mixed oxides doped with La or Pr were used without calcination. Results are presented in Table 9. It can be observed that selectivities higher than 100% are obtained, meaning these catalysts are able to oxidize cyclohexane.

(83) TABLE-US-00009 TABLE 9 Catalytic performance of doped CeO.sub.2 and mixed oxides after test in 4.7 wt % CyOOH/cyclohexane solution at 100° C. (see “reaction procedure” section above) Compo- Conversion Selectivity Example Catalyst sition T(h) % % 70 Ce—Zr 70-30 5 h 30 97 108 71 Ce—Zr 57-43 5 h 30 88 108 72 Ce—Zr—La 86-10-4 5 h 30 95 113 73 Ce—Zr—La 20-75-5 6 h   41 107 74 Ce—Zr—Pr 90-5-5 6 h   100 107 75 Ce—La—Pr 90-5-5 5 h 30 99 104 76 Ce—Pr 90-10 5 h 50 100 106

Examples 77 to 85 (According to the Invention)

(84) CeO.sub.2—SiO.sub.2 mixed oxides, CeO.sub.2—SiO.sub.2—TiO.sub.2 mixed oxides or CeO.sub.2—SiO.sub.2—TiO.sub.2 mixed oxides doped with La, were used without calcination. Results are presented in Table 10. It can be observed that selectivities higher than 100% are obtained, meaning these catalysts are able to oxidize cyclohexane.

(85) TABLE-US-00010 TABLE 10 Catalytic performance of CeO.sub.2 mixed oxides alone or doped with La after test in 4.9 wt % CyOOH/cyclohexane solution at 100° C. (see “reaction procedure” section above) Conver- Selec- Exam- Compo- sion tivity ple Catalyst sition Time (%) (%) 77 Ce—Si (95-5) 2 h 93 104 78 Ce—Si (95-5) 4 h 99 104 79 Ce—Si (98-2)   1 h 45 60 104 80 Ce—Si (98-2)   4 h 30 93 104 81 Ce—Si (98-2)   5 h 45 98 102 82 Ce—Si—Ti (90-5-5) 2 h 92 106 83 Ce—Si—Ti (90-5-5) 4 h 99 105 84 Ce—Si—Ti—La (80-10-5- 2 h 62 108 5) 85 Ce—Si—Ti—La (80-10-5- 4 h 99 108 5)

Examples 86 to 102 (According to the Invention)

(86) CeO.sub.2 nanostructures with rod, cube or oroctahedra morphology were tested as such or after doping with La, Pr, or Y. Selectivity is higher than 100% in each cases meaning all catalysts are able to oxidize cyclohexane.

(87) TABLE-US-00011 TABLE 11 Catalytic performance of CeO.sub.2 nanostructures and CeO.sub.2 rods doped with La, Pr, or Y after test in 5.0 wt % CyOOH/cyclohexane solution at 100° C. (see “reaction procedure” section above) Conversion Selectivity Example Catalyst t(h) % (%) 86 CeO.sub.2 rods 3 97 107 87 CeO.sub.2 rods 6 100 104 88 CeO.sub.2 rods 9 100 104 89 CeO.sub.2 cubes 3 26 105 90 CeO.sub.2 cubes 6 44 115 91 CeO.sub.2 cubes 9 58 111 92 CeO.sub.2 octahedra 3 22 127 93 CeO.sub.2 octahedra 6 51 113 94 CeO.sub.2 octahedra 9 75 104 95 CeO.sub.2 rods La-doped 6 100 104 96 CeO.sub.2 rods La-doped 9 100 101 97 CeO.sub.2 rods Pr-doped 3 92 107 98 CeO.sub.2 rods Pr-doped 6 99 108 99 CeO.sub.2 rods Pr-doped 9 100 110 100 CeO.sub.2 rods Y-doped 3 80 109 101 CeO.sub.2 rods Y-doped 6 96 107 102 CeO.sub.2 rods Y-doped 9 100 108

Examples 103 to 104 (Comparative Examples)

(88) Al.sub.2O.sub.3 and MgO were calcined under classical conditions (see “catalyst pre-treatment section” above) before reaction with 5.6 wt % CyOOH/cyclohexane solution. 16 mg of catalyst and 2 mL of CyOOH/cyclohexane solution were placed in the reactor and heated to 100° C. (see “reaction procedure” section above). Results are presented in Table 12. After 6 hours, no reaction took place, so these oxides are not active to decompose CyOOH.

(89) TABLE-US-00012 TABLE 12 Catalytic performance of different oxides after test in 5.6% CyOOH/cyclohexane solution at 100° C. Conversion Selectivity Example Catalyst Treatment t (h) (%) (%) 103 Al.sub.2O.sub.3 Calcined. 8 <5% 0 at 500° C. 104 MgO Calcined at 8 <5% 0 500° C.

Example 105 (Comparative Example)

(90) Reactor

(91) The reaction is performed in a Teflon batch reactor consisting of: a teflon reactor vessel (40 mL Volume capacity, Bola Manufacturer) an outlet micro valve for sample taking. a pressure gauge. a thermocouple a magnetic stirring bar, which is stored inside the reaction media in the reactor vessel.

(92) To ensure that the reactor is completely clean and no traces of contaminants are present, it is first washed with acetone, then with water. In case some trace of metal remains on the reactor wall, it is washed with diluted HCl.

(93) Reaction Procedure

(94) The proper amount (160 mg) of CeO.sub.2 (without pretreatment) is introduced in the reactor. Then, 0.6 g of internal standard undecane (99% purity, from Sigma-Aldrich) are introduced in the teflon reactor.

(95) Next, the reactor is opened, about 16 g of cyclohexane (99.8% purity, from Sigma-Aldrich) are introduced and its exact mass weighted. Finally, a magnetic stir bar is introduced and the reactor is closed. The reactor is kept in an air atmosphere. No nitrogen overpressure is added.

(96) A silicon bath at the desired reaction temperature (typically 100° C.) is kept on a hot-stirring plate. The glass reactor vessel is introduced in the silicon bath. It takes about 30 minutes to reach 100° C. inside the reactor. During this transition period of heat, the stirring is off to slow down reaction between room temperature and 100° C.

(97) The follow up of reaction and stirring of the mixture begin when temperature reaches 100° C. To follow the reaction progress, samples are taken at different times and their composition analyzed by Gas Chromatography. The medium is sampled through a syringe and put in a GC vial when it is cold.

(98) No conversion of cyclohexane was obtained after 24 hours.

(99) So CeO.sub.2 is not able to oxidize cyclohexane with air.