Cycloalkane oxidation catalysts and method to produce alcohols and ketones

Abstract

Disclosed is 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 in the presence of a catalytic effective amount of a crystalline MWW-type titanosilicate catalyst. Hydroperoxides may notably be tert-butyl hydroperoxide, tert-amyl hydroperoxide, cumene hydroperoxide, ethylbenzene hydroperoxide, cyclohexyl hydroperoxide, methylcyclohexyl hydroperoxide, tetralin hydroperoxide, isobutylbenzene hydroperoxide, and ethylnaphthalene hydroperoxide.

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 hydroperoxide in the presence of a catalytically effective amount of a crystalline MWW-type titanosilicate catalyst.

2. A method according to claim 1, in which the hydroperoxide is chosen in the group consisting of: tert-butyl hydroperoxide, tert-amyl hydroperoxide, cumene hydroperoxide, ethylbenzene hydroperoxide, cyclohexyl hydroperoxide, methylcyclohexyl hydroperoxide, tetralin hydroperoxide, isobutylbenzene hydroperoxide, and ethylnaphthalene hydroperoxide.

3. A method according to claim 1, in which the hydroperoxide is added to the cycloalkane at the start of the step of contacting.

4. A method according to claim 1, in which the hydroperoxide is generated in situ by reaction of a cycloalkane with oxygen or an oxygen generator.

5. A method according to claim 1, in which the MWW structure is represented by the following chemical composition formula:
xTiO.sub.2.(1x)SiO.sub.2, wherein x is between 0.0001 and 0.5.

6. A method according to claim 1, in which the catalyst further comprises one or more heteroatoms from the group consisting of the elements of Periods IB, IVB, VB, VIB, VIIB, VIIIB and VA.

7. A method according to claim 1, in which the contacting is at a temperature of between 20 and 200 C.

8. A method according to claim 1, in which pure oxygen, air, oxygen-enriched air, oxygen-depleted air, or oxygen diluted with an inert gas is used in a reaction medium.

9. A method according to claim 1, in which the catalyst is used in a range of between 1 and 10 wt. %, in relation to the total weight of the reaction medium.

Description

EXPERIMENTAL PART

Example 1

Synthesis of Ti-MWW Zeolite

(1) Ti-MWW was synthesized using two steps according to the report of Prof. Wu's group (Wu P., J. Phys. Chem. B 2002, 106, 748-753). First, Ti-containing MWW was synthesized from fume silica (Cab-o-sil M7D), tetrabutyl orthotitanate, boric acid, piperidine (PI) and distilled water. Secondly, the Ti-containing precursors were then refluxed with 2M HNO.sub.3 aqueous solution to remove extraframework Ti species and a part of framework boron. The solid product was filtered, washed, dried, and finally calcined at 550 C. for 10 h.

Example 2

Comparison of the Catalytic Property of Ti-MWW with Other Catalysts for the Oxidation of Cyclohexane

(2) Transition metal-implemented zeolites have been used to catalyze the oxidation of cylcohexane using t-butyl hydroperoxide (TBHP) at 80 C. for 1.0 h with 0.10 g catalyst and 6.0 wt. % TBHP in cyclohexane. Results are mentioned in Table 1.

(3) TABLE-US-00001 TABLE 1 TBHP KA KA Conversion Selectivity Yield Trials Catalyst (%) (%) (%) C1 None 0.7 98.0 0.7 C2 Beta 92.4 5.25 4.86 C3 Si-Beta 1.09 98 1.07 C4 Cu-Beta 51.6 26.8 13.82 C5 FeCr-Beta 98.9 15.6 15.43 C6 Co-Beta 66.2 15.6 10.33 C7 Cr-Beta 97.9 23.4 22.91 C8 Fe-MCM-22 70.2 15.6 10.95 C9 NaFe-MCM-22 41.2 13.6 5.60 C10 Fe-Beta 99.5 12.6 12.54 C11 TS-1 10.1 28.5 2.88 C12 Ti MCM-41 16.9 43.5 7.1 1 Ti-MWW 10.7 90.1 9.64

(4) It appears then that without any catalysts, TBHP conversion and KA yield are less than 1%. Beta with Al.sup.3+ zeolite showed high TBHP conversion (92.4%) but poor KA selectivity. Without any Al.sup.3+, pure silica beta zeolite had barely TBHP conversion and KA selectivity. After incorporation with transition metals (Cu.sup.2+, Fe.sup.3+, Cr.sup.3+, Co.sup.2+) into zeolites, the selectivity to KA oil and KA yield all increased compared to without transition metals. While all these catalysts had the problem of leaching active sites after first run, the best results in conversion, selectivity and yield are only obtained with the Ti-MWW zeolite catalyst.

(5) It also appears here that the catalytic activity of zeolites on the oxidation of cyclohexane using TBHP as oxidant is not directly correlated with the effective pore size. It is more related to the structure of molecular sieves itself and the coordination state of titanium in molecular sieves. Here Ti-MWW showed the best selectivity to KA oil (90.1%) and the highest yield of KA oil (9.64%). Due to the limit of pore size, the catalytic activity of Ti-MWW on oxidation of cyclohexane mainly occurred in the half cage on the surface of zeolite.