PROCESS FOR THE LIQUID PHASE OXIDATION OF TOLUENE TO BENZALDEHYDE

Abstract

The present invention provides a liquid phase oxidation of toluene by using catalyst containing manganese (Manganese II acetate) in presence of Lewis acid (Stannous (II) chloride) and a bromide promoter (NaBr), at a temperature of 120° C. and at a pressure of air in the range of 70-400 psig, in presence of carboxylic acid (acetic acid), as a solvent, to obtain high selectivity to benzaldehyde (76%). High activity was obtained with minimum byproducts such as benzoic acid, benzyl alcohol and benzyl acetate.

Description

Claims

1. An improved process for the oxidation of toluene to benzaldehyde, which comprises reacting toluene with lean oxygen in presence of a composite catalyst system comprising a catalyst containing manganese, a Lewis acid and an organic or an inorganic halide, as promoter, in presence of an organic acid, as a solvent, at a temperature in the range of 50-150° C., at pressure in the range of 20-1000 psig, for a period of 3-5 hrs to obtained the desired product of benzaldehyde, separating the resultant benzaldehyde product either by distillation or solvent extraction and leaving behind the manganese catalyst, Lewis acid and halide promoters for being reused for another cycle of oxidation process.

2. An improved process according to claim 1, wherein the catalyst containing manganese used is a salt of manganese selected from the group consisting of manganese acetate, manganese chloride, manganese bromide, manganese iodide, manganese nitrate, manganese carbonate, manganese sulfate, manganese oxide and manganese phosphate.

3. An improved process according to claim 1, wherein the Lewis acid promoter used is a carbonate, halide, acetate, phosphate, nitrate or sulphate salt of Na+, K+, Be2+, Mg2+, Ca2+, Al3+, Sc3+, In3+, Ti4+, Zr4+, U4+, Sn4+, Sn2+, Sb3+, Bi3+, Ir3+, Ru2+, Ag+, Au+, Tl+, Hg2+, Pd2+, Cd2+, Pt2+, or Tl3+.

4. An improved process according to claim 1, wherein the inorganic halide promoter used is chloride, bromide or iodide salt, preferably a bromide salt of Li, Na, K, Cs, Be, Ca, Mg, Sr or Ba.

5. An improved process according to claim 1, where the organic halide promoter used is a compound having a general formula R1R2R3R4NX or R1R2R3R4PX wherein R1, R2, R3 and R4 are same or different and are/is H or an alkyl group containing 1-5 carbon and X is a halogen atom selected from the group consisting of F, Cl, Br and I.

6. An improved process according to claim 1, wherein the molar ratio of manganese to Lewis acid promoter used is in the range of 0.1 to 10, preferably 0.3 to 0.6.

7. An improved process according to claim 1, wherein the molar ratio of manganese to inorganic or an organic halide promoter used is in the range of 0.1 to 10, preferably 0.1 to 0.2.

8. An improved process according to claim 1, where the molar ratio of manganese to toluene used is in the range of 0.1 to 10, preferably 0.3 to 5%.

9. An improved process according to claim 1, wherein the organic acid used as a solvent is a carboxylic acid selected from the group consisting of acetic acid, propionic acid, butanoic acid, pentanoic acid and benzoic acid.

10. An improved process according to claim 1, wherein the concentration of oxygen in gas phase used is in the range of 1-30% in an inert gas selected from nitrogen, helium and argon

11. An improved process according to claim 1, where the lean oxygen used is compressed air.

12. An improved process according to claim 1, wherein the temperature used for the oxidation of toluene is in the range of 70-140° C.

13. An improved process according to claim 1, wherein the pressure of lean oxygen used is in the range of 70-400 psig.

14. An improved process according to claim 1, wherein the product benzaldehyde is separated from the reaction mixture by distillation.

15. An improved process according to claim 1, wherein the manganese catalyst, Lewis acid and organic or inorganic halide promoters used in the oxidation reaction are reused for further cycles of oxidation of toluene.

16. An improved process according to claim 1, where the selectivity to benzaldehyde obtained is in the range of 50-76%.