INTRODUCTION:

Oxidation reaction constitutes core technologies for converting bulk chemicals to useful products of a higher oxidation state. The selective oxidation of alcohol is one of the most challenging reactions in green chemistry.

While the current chemical industry uses organic and inorganic oxidants to produce carbonyl compounds, it is highly desirable to use a heterogeneous catalyst for the efficient oxidation of alcohols. The present research is focused on increasing the activity and selectivity towards the corresponding carbonyl of the heterogeneous oxidation for alcohols^1,2.

Cyclohexanone is an important intermediate because of its use in the manufacture of ε-caprolactam (via Cyclohexenon oxime route) which is used as lactam for nylon 6.

It also finds application as a solvent for cellulose acetate, nitro cellulose and natural and vinyl resins. Cyclohexene is used as an alkylating component and as a stabilizer for high octane gasoline. It also finds application in the manufacture of maleic acid, hexahydrobenzoic acid and cyclohexanecarbaldehyde¹. Cyclohexenon is manufactured by two processes –

i. Cyclohexane oxidation to cyclohexanone/cyclohexenol followed by dehydrogenation of cyclohexenol at 400-500°C and atmospheric pressure over Zn or Cu catalysts.

ii. Conversion of phenol into cyclohexanone via two step process after ring hydrogenation with nickel catalyst at 140-160°C and 15 bar pressure followed by hydrogenation².

Mechanism of oxidation:

Preparation of catalyst:

All the chemicals employed were of analytical grade and used As such without further purification . Aluminum nitrate (LOBA Chemie Pvt. Ltd.) as Al2O3 precursor, ammonium metavanadate (Sigma–Aldrich) as vanadium precursor, and citric acid (Merck) as a fuel were used as received. To prepare alumina-supportedV2O5 (AV) in molar ratio 90:10, a solution of 16.55 g of aluminum nitrate in 100 ml of water was mixed with another solution prepared by mixing 0.64 g of NH4VO4 in 50 ml of water. The final solution was mixed with 17.19 g of citric acid and fired in a microwave oven for 2 min. The material swelled into a green-colored gel. The gel was powdered and Calcine in a muffle furnace at 500 _C for4 h. A dark-green-colored residue was obtained, which was grounding a motor pestle to a fine powder. A series of catalysts were prepared by changing the vanadium content from 5 to 25%. A similar procedure was adopted for preparation of ZrV2O7 (ZV) and TiV2O7TV). The catalysts were designated as MVX, where M = Al/Zr/Ti,V = vanadium, and X is the vanadium percentage in the catalyst.

EXPERIMENTAL:

The reaction was done 107 atmospheric pressure in a fixed bed, vertical, down-flow, reactor placed inside a double-zone furnace. The catalysts were pressed, pelletized and broken into uniform pieces and sieved to obtain catalyst particles of size 10–20 mesh. Exactly 3 g catalyst was charged each time in the centre of the reactor in such a way that the catalyst was sandwiched between the layers of inert porcelain beads. The upper portion of the reactor served as a vaporizer cum pre-heater. All heating and temperature measurements were carried out using ‘Aplab’ temperature controller and indicator instruments. A thermocouple was positioned at the centre of the catalyst bed to monitor the exact temperature of the catalyst bed.

The catalysts were activated in the reactor itself at 573 K in a sufficient flow of dry air for at least 3 h before each run. The liquid reactant was fed by a syringe. The products of the reaction were collected downstream from the reactor in a receiver connected through a cold water circulating condenser. Products were collected at various time intervals and analyzed by gas chromatography. Identification of products was done by comparing the GC retention times of expected products with those of standard samples.

Fig. 1 Experimental set up for study of the reaction. arise due to closed shell calculations

Computational methods:

All the DFT calculations were performed using Gaussian 09Wsuite19 and B3LYP functionals.²⁰ We had used LANL effective core potential (ECP) with double zeta potential (Lanl2dz) for optimization of reactants, products, and transition state. This basis set has overall combination of ECP and valence basisset.²¹ The ECP parameters for vanadium atom have been derived from atomic wave functions obtained by all-electronnon-relativistic Hartree–Fock calculations. The light atoms (carbon, hydrogen and oxygen) were optimized using 6-311G(d, p) basis set while for heavy atoms (vanadium and titanium atom) we had used lanl2dz basis set. Modeling of transition state structure calculation QST2/QST3 keyword has been used.²⁰ At many places the optimization of transition state was achieved directly also.²² Vibrational frequencies were calculated for the optimized geometries to identify the nature of the reactant or product (no imaginary frequency) and TS structure (one imaginary frequency). RB3LYP was used for singlets and UB3LYP for higher multiplicities. In UB3LYPcalculations separate a and b orbitals are computed.¹⁹ The calculation for singlet diradical system has been performed using “guess ¼(mix, always, density mix)” keywords. This keyword helps to predict atomic spin density(Unpaired electron density), if alpha and beta electron densities were situated over different atoms i.e. singlet diradical system. We had also calculated the “open shell vs. closed shell correction term” over 6-311G(d, p) basis set as it includes all electron calculation. This term is used to eliminate the error which may arise due to closed shell calculations.

The enthalpy and the activation energies were calculated at the reaction temperature as described by J. W. Ochterski.²³ The Adsorption energy (Eads) was calculated

E_ads=E_(adsorbate_{_-}_substrate)_(E_A_{dsorbate +}_S_ubstrate)_.

The chemical reactivity of various oxygen atoms has been described in the form of Fukui functions. We have also calculated the Fukui functions for the different type of oxygen atoms present in our catalyst

Evaluation of kinetic data:

Most studies on kinetics and mechanism of oxidations, ammoximation and oxidative dehydrogenation over V₂O₅catalyst are based on Mars-Van-Krevelen mechanism. According to this mechanism the catalyst is Ist reduced by the hydrocarbon (EB) and then the reduced catalyst is re-oxidize by the molecular oxygen. We considered a two stage as well as three state redox mechanisms for the reaction and are listed here-.

Two step mechanism.

Cl+ S_ox--------cn +S_red

k₂

S_red + 1/2O₂----- S_ox

Rate of reduction of surface =k₁S_oxP_cl

Rate of oxidation of surface = k₂(1S_ox)P_O

Here, k₁ and k₂ are constants.

At steady state condition,

k₂(1 S_ox)P_O = k₁S_oxP_cl

k₂P_O = (k₂P_O + k₁P_cl)S_ox

k₂P_O

S_ox=-------------

[k₂P_O + k₁P_cl]

Rate of reaction = k₁P_clS_ox (1)

^k1^Pcl^k2^PO

Rate =---------------------- (2)

k₂P_O + k₁P_cl

Redox models tested for oxidative dehydrogenation of cyclohexenol to Cyclohexenon.

R =rate of formation of cyclohenone,

k₁, k₂ or k₃= rate constants,

P_O= partial pressure of oxidant,

P_cl= partial pressure cyclohexenol,

cn=Cyclohexenon,

S_red=reduced surface,

S_ox= oxidized surface.

The rate law for these two mechanisms can be derived as follows.

Applying steady state approximation for

TS -S_red and S_red

k₁P_clS_ox = k₂[TS -S_red]

[TS - S_red] = k1PclSox

-----------------

k₂

k₂ [TS - S_red] = k₃P_OS_red

S_red=k_2½ [TS-S_red]

------------------

k₃P_O

1 = S_ox + S_red + [TS - S_red]

ox +

k₂[TS -S_red]

^k1^Pcl^Sox

k₃P_O

k₂

1 = S_ox+

k2k1PclSox

^k1^Pcl^Sox

k₂k₃P_O

k₂

1 = S_ox

^k1^Pcl^Sox

k₃P_O

k₂

Sox

¹k₃P_O

k₂

KPclSox

k1pclox

Rate

K1PclSox

k1pcl

)

^{k P}cl^Sox

^k1^Pcl^Sox

k₃P_O

k₂

RESULT AND DISCUSSION:

Table1. Decomposition of cyclohexenol over alumina supported zirconium at various temperature

Reaction temperature	Cyclohexenol conversion	% selectivity of Cyclohexenon
200	42%	82%
250	42%	82%
275	48%	82%
290	52%	82%
300	61%	82%
325	76%	82%
350	76%	82%

Reaction condition: wt of the catalyst=1.0 g

feed rate- 0.1 ml/min

CONCLUSION:

In this paper we have explored oxidation over catalyst zirconium vanadate, and there preparation method is also described here made by solution combustion method. We done oxidation reaction with the help of fix bed t reactor in vapor phase on different temperatures i n a fix air pressure them amount of catalyst is also specified for particular temperature. And the result of gas chromatography in the form of Conversion and selectivity table of samples are also given here.

REFERENCES:

1. Tamasmallat and Alfonsbaiker, Chem.Rev.2004, 104, 3037-3058.

2. Wenshuaizhu, Huamimg Li, Xiaoying He, Qi Zhang, Huomingshu, Yongshengyan, catalyst communication 2008, 551-555.

3. Choudhari S.M., Waghulde A.S. Samuel V. Bari M. L. and Chumbhale V.R. Vol.3 (7, 38-44, July (2013).

4. Sonali Sengupta, Debarpita Ghoshal, Jayanta K. Basu. Bulletin of chemical reaction engineering and catalysis, 8(2, 2013, 167-177).

5. Manish M Shinde and Manohar R Sawant. Vol. 42A. March 2003, pp 510-512.

6. Gyungsoojeon, Gonseo and Jongshik Chung, Korean j. of chem. Eng, 13(4), 412-414(1996).

7. Tassaditmazarisihambenadji, Adanetahar, J. of material science and engg. B 3(3 2013) Vol. (146-152).

8. Method of producing cyclohexenone from cyclohexenol through oxidative dehydrogenation US 4918239 A patent.

9. K. G. Sekar and R. V. Sakthivel J. of chem. And pharmaceutical research, 2012, 4(7):3391-3395.

10. Praveen K. tendon Mamtadhusia Alok K. Singh and Santosh B. Singh the open catalysis j. 2013, 6-29-36.

11. Ying he, Xiaoyun ma and Minglu Arkivoc 2012(VIII) 187-197.

12. Dana Gasparovicova, Zuzunacvenggrosova M Ilanhronse Sept. vol. 21 -22 2009.

13. Mohammad sadiq, Gull Zamin, Razia, Mohammad Iilyas modern research in catalysis, 2014 vol.3 (12-17).

14. Y K Vyawahare, V R Chumbhale, S A Pardhy, V Samuel and A S Aswar, Indian journal of chem. Techn. Vol 17, Jan 2010 (43-49).

15. Camilla Parmeggiani and Francesca Cadona Green chem.., 2012 vol. 14, 574.

16. Jellebrinksma, Minza T. Rispense, Ronald H uge, Ben L. Feringa, inorg. chem., act 337(2002) 75-82.

17. Benjamin Beck Manuel Harth Neil G. Hamilton Carlos Carrero John J. Uhlrich Annette Trunschke Shamil Shaikhutdinov Helmut Schubert Hans-Joachim Freund Robert Schlögl Joachim Sauer Reinhard Schumacher journal of catalysis 296(2012) vol. 120-131.

18. Christopher J. Cramer and Donald G. Truhlar

19. Lee, C. T.; Yang, W. T.; Parr, R. G. Phys. Rev. B 1988, 37, 785.

20. London, F. Z. Phys. Chem. 1930, 11, 222.

21. Yang, W. T.; Ayers, P. W.; Wu, Q. Phys. Rev. Lett. 2004, 92, 146404.

22. Perdew, J. P.; Zunger, A. Phys. Rev. B 1981, 23, 5048.

23. Heitler, W.; London, F. Z. Phys. 1927, 44, 455.

24. Thomas, L. H. Proc. Cambridge Philos. Soc. 1927, 23, 542.

25. Fermi, E. Z. Phys. 1928, 48, 73.

26. Slater, J. C. Phys. Rev. 1951, 81, 385.

27. Dirac, P. A. M. Proc. Cambridge Philos. Soc. 1930, 26, 376.

28. Ceperley, D. M.; Alder, B. J. Phys. Rev. Lett. 1980, 45, 566.

29. Vosko, S. H.; Wilk, L.; Nusair, M. Can. J. Phys. 1980, 58, 1200.

30. Perdew, J. P.; Wang, Y. Phys. Rev. B 1992, 45, 13244.

31. Bright-Wilson, E. In Structural Chemistry and Molecular Biology; Rich, A., Davidson, N., Eds.;W. H. Freeman, San Francisco, 1968; pp 753_760.

32. Gross, E. K. U.; Dreizler, R. M. Z. Phys. A: Hadrons Nucl. 1981, 302, 103.

33. Becke, A. D. Phys. Rev. A 1988, 38, 3098.

34. Perdew, J. P.; Burke, K.; Ernzerhof, M. Phys. Rev. Lett. 1996,

35. Levy, M.; Perdew, J. P. Phys. Rev. A 1985, 32, 2010.

36. Levy, M. Coordinate scaling requirements for approximating exchange and correlation. In Density Functional Theory; Gross, E. K. U., Dreizler, R. M., Eds.; 1995; Vol. 337, pp 11_31.

37. Langreth, D. C.; Perdew, J. P. Solid State Commun. 1979, 31, 567.

38. Langreth, D. C.; Perdew, J. P. Phys. Rev. B 1980, 21, 5469.

39. Perdew, J. P.; Ruzsinszky, A.; Csonka, G. I.; Vydrov, O. A.; Scuseria, G. E.; Constantin, L. A.; Zhou, X. L.; Burke, K. Phys. Rev. Lett. 2008, 100, 136406.

40. Perdew, J. P.; Yue, W. Phys. Rev. B 1986, 33, 8800.

41. Perdew, J. P. Phys. Rev. B 1986, 33, 8822.

42. Becke, A. D. J. Chem. Phys. 1986, 84, 4524.

43. Perdew, J. P.; Chevary, J. A.; Vosko, S. H.; Jackson, K. A.; Pederson, M. R.; Singh, D. J.; Fiolhais, C. Phys. Rev. B 1992, 46, 6671.

44. Hamprecht, F. A.; Cohen, A. J.; Tozer, D. J.; Handy, N. C. J. Chem. Phys. 1998, 109, 6264.

45. Tsuneda, T.; Suzumura, T.; Hirao, K. J. Chem. Phys. 1999, 110, 10664.

46. Boese, A. D.; Doltsinis, N. L.; Handy, N. C.; Sprik, M. J. Chem. Phys. 2000, 112, 1670.

47. Boese, A. D.; Handy, N. C. J. Chem. Phys. 2001, 114, 5497.

48. Handy, N. C.; Cohen, A. J. Mol. Phys. 2001, 99, 403.

49. Handy, N. C.; Cohen, A. J. J. Chem. Phys. 2002, 116, 5411.

50. Keal, T. W.; Tozer, D. J. J. Chem. Phys. 2004, 121, 5654.

51. Zhao, Y.; Truhlar, D. G. J. Chem. Phys. 2008, 128, 184109.

52. Perdew, J. P.; Schmidt, K. Jacob’s ladder of density functional approximations for the exchange_correlation energy. In Density Functional Theory and Its Application to Materials; VanDoren, V., Van Alsenoy, C., Geerlings, P., Eds.; 2001; Vol. 577, pp 1_20.

53. Becke, A. D. J. Chem. Phys. 1988, 88, 1053.

54. Becke, A. D. Int. J. Quantum Chem. 1994, 625.

55. Becke, A. D.; Roussel, M. R. Phys. Rev. A 1989, 39, 3761.

56. Perdew, J. P.; Kurth, S.; Zupan, A.; Blaha, P. Phys. Rev. Lett. 1999, 82, 2544.

57. Perdew, J. P.; Constantin, L. A. Phys. Rev. B 2007, 75, 155109.

58. Perdew, J. P.; Ruzsinszky, A.; Tao, J.; Csonka, G. I.; Scuseria, G. E. Phys. Rev. A 2007, 76, 042506.

59. Perdew, J. P.; Ruzsinszky, A.; Csonka, G. I.; Constantin, L. A.; Sun, J. W. Phys. Rev. Lett. 2009, 103, 026403.

60. Tao, J. M.; Perdew, J. P.; Staroverov, V. N.; Scuseria, G. E. Phys. Rev. Lett. 2003, 91, 146401.

61. Lee, C. T.; Parr, R. G. Phys. Rev. A 1987, 35, 2377.

62. Becke, A. D. J. Chem. Phys. 1996, 104, 1040.

63. Becke, A. D. J. Chem. Phys. 1998, 109, 2092.

64. Van Voorhis, T.; Scuseria, G. E. J. Chem. Phys. 1998

Received on 03.04.2019 Modified on 06.05.2019

Asian J. Research Chem. 2019; 12(3):165-168.

DOI: 10.5958/0974-4150.2019.00033.6