UDC 541.124.2

N.R. BUKEIKHANOV², P.B. VOROBYEV¹, I.M. CHMIR’², L.V. LI¹,

A.S. ZULKASHEVA¹, T.P. MIKHAILOVSKAYA¹

¹JSC «Institute of chemical sciences named after A.B. Bekturov», Almaty

²FSBEI HPE Moscow State Technological University “STANKIN”,

Russian Federation, Moscow

CONJUGATED AND COMBINED CHEMICAL PROCESSES

Abstract. Сombined chemical reactions include such leading industrial processes as oxidative chlorination, oxidative ammonolysis, oxidative esterification whereby modern bulk products - vinyl chloride, acrylonitrile, and terephthalo- and isophthalonitrile, vinyl acetate are produced. Such well-known polymeric materials as polyvinyl chloride (manufacture of double-glazing windows, linoleum, packaging materials), polyacrylonitrile (manufacture of "nitrone" fiber, carbon fiber-reinforced plastic), polyesters, polyamides, polyurethanes (synthetic fibers, rubbers, adhesives), polyvinyl acetate (PVA building adhesive, the starting material for the polyvinyl alcohol used to prepare the high modulus fibers and others) are obtained from these monomers. A number of processes based on the coupled reactions such as oxidative ammonolysis, oxidative dealkylation, producing of terephthalic acid by liquid phase oxidation of p-xylene have been developed in Kazakhstan under the supervision of academician of NAS RK - B.V. Suvorov.

Academician Boris Viktorovich Suvorov defined a coupling as a key step of the complex reactions’ mechanism [1-3]. Consistently [4, 5], acceleration (and deceleration) reactions by combining two or more components in a reaction mixture are typical for the conjugated complex reaction mechanism. Suvorov and co-workers [6] proposed a methodological procedure of defining conjugation stages in complex catalytic process, which lies in a proof of the transfer of starting material fragments from one direction of chemical process to another parallel direction by identifying the corresponding reaction products. Thus, the transfer of fragments was detected by using heteroatomic compounds as starting materials. For example, cyanopyridines are formed in small amounts in the process of oxidation of methylpyridine (picoline) on the vanadium oxide catalysts, along with the products of partial oxidation - pyridine carboxylic acid and pyridine aldehyde. The efficiency of donor nitrogen (nitrogen-containing fragments) transfer was determined by calculation of the experimental data of catalytic oxidation of alkylpyridines by equation S = (A * 100) / [100 - (B + C)] where: S – selectivity of nitrile formation, in%, A - nitrile yield, in %, from the theoretically possible, B - the amount of unreacted starting material, C - total yield of the defined reaction products, in%, from the theoretically possible. According to calculations the selectivity of cyanopyridine formation can reach 81% in the process of 2-methylpyridine oxidation [6].

Studying kinetics of heterogeneous catalytic oxidation of 4-methylpyridine into isonicotinic acid, the raw material for antituberculous drugs, it was able to detect the presence of coupling between the stages of pyridine-4-aldehyde formation and deep oxidation of raw and desired reaction product, carrying with nitrogen-containing fragments, which play a role of the nitrogen donor for cyano group formation [7]. The kinetic model of this reaction, carrying in the flow integral reactor, represents a system of ordinary differential equations, numerical solution of which was performed by the Gear method [8]:

-dC_4-Pic/dt = (k₁ + k₄ ) · C_4-Pic;

dC_4-PyCHO /dt = k₁ · C_4-Pic - (k₂ + k₆) · C_4-PyCHO;

dC_4-PyCOOH /dt = k₂ · C_4-PyCHO - (k₃ + k₅) · C_4-PyCOOH ;

dC_Py /dt = k₃ · C_4-PyCOOH;

dC_CO2 /dt = k₄ · C_4-Pic + k₅ · C_4-PyCOOH;

dC_4-PyCN /dt = k₆ · C_4-PyCHO.

The optimum values of kinetic stages’ constants were defined from the conditions of minimizing the sum of squared deviations between experimental and calculated reagents’ concentrations by using Powell’s method [9]. The standard deviation for each product does not exceed 8%. Table 1 shows the calculated kinetic stages’ constants (kj) of 4-picoline oxidation over the V-Ti-Zr-oxide catalyst at the temperature of 245^оС and different ways of water supply into the contact area. The observed increase of the kinetic stages’ constants of initial 4-picoline and intermediate isonicotinic aldehyde conversion on increasing concentration of water vapor in the reaction mixture, presumably, is connected with the increase in the surface catalyst acidity and enhancement of its adsorption ability with respect to pyridine derivatives. It is known that Bronsted acidic sites are formed as a result of the dissociative adsorption of water molecules on the surface of oxide catalysts [10].

Table 1 - Influence of water vapor concentration in the contact area on the kinetic stages’ constants of 4-picoline oxidation over the V-Ti-Zr-oxide catalyst at a temperature of 245^оС. The initial concentrations: [4-picoline] = 1,1·10^-4,

[O₂] = 9,4·10^-3 mol·L^-1.

Stages		kj , с^-1
	Mechanism stages	[H2O] ·10^3, mol·L^-1
		0	1,3	2,45	5,1	8,9	15,2
1	4-Pic ® 4-PyCHO	1,788	1,970	2,799	3,891	4,269	4,241
2	4-PyCHO ® 4-PyCOOH	1,713	1,968	3,790	6,249	6,389	9,571
3	4-PyCOOH ® Py	0,290	0,126	0,080	0,088	0,078	0,056
4	4-Pic ® CO2 + NOx	0,084	0,276	0,485	0,316	0,118	0,161
5	4-PyCOOH®CO2+ NOx	0	0	0	0,667	0,434	0,514
6	4-PyCHO ® 4-PyCN	0,164	0,597	0,814	1,079	0,862	0,650

According to calculations, the isonicotinic acid is composed from 4-picoline through the stage of isonicotinic aldehyde formation and partially decarboxylated at the stage № 3 with pyridine formation. The presence of 4-cyanopyridine in catalyzates’ experiments indicates that generated nitrogen-containing fragments at the stage of deep oxidation of initial 4-picoline (stage № 4) and isonicotinic acid (stage № 5) play the role of a nitrogen donor in relation to aldehyde at the stage № 6 [11].

Experiments for p-nitrotoluene and 3-cyanotoluene oxidation over V-Ti-catalyst showed that p-nitrobenzonitrile and isophthalodinitril are formed along with the p-nitrobenzoic acid and m-cyanobenzoic acid, the formation selectivity of which was 4-10 % per taken starting material [12]. According to the process scheme (Figure 1), the starting and intermediate materials are converted towards partial oxidation with aldehydes’ and acids’ formation and towards destructive oxidation, furnishing nitrogen-containing fragments (potential nitrogen donors) and carbon oxides. Nitrogen donor transfer from one reaction direction to another in coordination with n-nitrobenaldehyde and p-nitrobenzoic acid leads to the formation of p-nitrobenzonitrile, which is an absolute proof of the conjugated process nature. However, the examples of obvious conjugation are likely special cases. In general terms, conjugation is more widespread, but usually in an implicit form.

A number of processes based on the coupled reactions such as oxidative ammonolysis, oxidative dealkylation, obtaining of terephthalic acid by liquid phase oxidation of p-xylene have been developed in Kazakhstan under the supervision of academician of NAS RK - B.V. Suvorov.

A number of processes based on the coupled reactions [13], such as continuous method of producing terephthalic acid by liquid phase oxidation of p-xylene; process of producing propylene by conjugated liquid phase oxidation of propylene together with acetaldehyde [14]; conjugated reactions of hexamethylene dehydrogenation and toluene or o-xylene hydrodealkylation on palladium membranes [15] have been developed and proposed by B.V. Suvorov and co-workers.

Fig.1. The p-nitrotoluene oxidation process scheme over V-Ti-catalyst

One of the methods of chemical processes’ formation lies in ammonia substitution in the reaction of catalytical oxidative ammonolysis for another nitrogen donor and air substitution for another oxidant. Thus, the process of producing benzonitrile by toluene and ammonia oxidation of sulfur dioxide on aluminum oxide and other catalysts (the yield of nitrile is 62%, the selectivity is 92%) was developed, and called similarly with oxidative ammonolysis «ammonsulfooxidaton» [16].

The ammonolysis processes have been implemented into industry for the purpose of producing benzonitrile from toluene, phthalodinitril from o-xylene, nicotinonitrile from β-picoline, wherein the movable catalyst oxygen was an oxidizing agent, the reduced form of which was activated by air in the auxiliary reactor [17]. The process of «nitrooxydation», wherein benzonitrile is synthesized from Te, Fe, Pb, Sn oxides on the catalyst, with the yield of 67% by reacting 1 mole of toluene with 2 moles of NO, have been investigested. The latter acts both as oxidant, and nitrogen donor [18].

Based on analysis of literature data array on catalytic oxidation reactions we made a conclusion that it is possible to isolate group reactions, which on its phenomenological characteristics approach to the reaction of oxidative ammonolysis mentioned above. They all take place by a single scheme: the starting material + coreactant + oxidizing agent + catalyst → reaction product (usually not containing oxidizing agent in its compound). Examples of such reactions are shown in Table 2. A lot of them have analogues carried out in the liquid phase, for example, the catalytic and non-catalytic oxidative ammonolysis [11], oxidative chlorination, oxidative etherification [11].

Of course, such different reactions do not proceed by the same mechanism. However, common phenomenological characteristics (performing reactions in the presence of oxidizing agents and as a rule, semiconductor catalysts, dependence of speed and processes’ selectivity on additions of various substances in the starting reaction mixture, producing the desired product which does not have oxidizing agents in its compound) were used as a reason to define the generality in the regularities of these processes [11, 19, 20].

Table 2 - Complex gas-phase oxidation processes.

Starting materials	Catalyst, temperature		Basic process product	References
1. Oxidative alkylation
Benzene, ethylene, О2	Pt, 200^0C	Styrole С6Н5СН=СН2		11, p. 97
Benzene, methane, О2	FeOX,TiOX, 600^0C	Ethylbenzene + Styrole
2.Oxidative hydroxylation
Benzene methanol, О2	Silica, В2О3, 640^0C	Phenol		22
3. Oxidative chlorination
Ethylene, 2HCI, 0,5 О2	CuCl2 ,200^0C	Dichloroethane		11, ch.8
Benzene, HCI, 0,5 О2	Cu, Fe chlorides, 215^0C	Chlorbenzene
4. Oxidative etherification
Ethylene, СH3COOH, О2	PdCl2 , 160-200^0C	Vinyl acetate CH2=СН-OСO-CH3		11,ch.5
С6Н5СOOН, СН3OН, О2	VXOY	С6Н5СOOCH3
5. Oxidative cyanation
Methane, acetonitrile, О2	Silica, 600^0C	CH3СН2СN + CH2=СНСN		11, ch.4
Styrole, HCN, О2	PdCl2, KCl, 250^0C	С6Н5СН=СНCN
6. Oxidative heterocyclization
CH2=СНСНО, NH3, О2	Cu, Zn, Pb, Ag oxides, 350-400^0C	Pyridine, 3-methylpyridine (β-picoline)		11, p. 99
7. Oxidative ammonolysis
CH2=СНСN, NH3, О2	Bi, Mo oxides, 250-450^0C	CH2=СНСN, acrylonitrile		11, ch. 6, 23
Substituted alkylbenzenes (substitutes – haloids, oxy-, alkoxy-, nitro group), NH3 , О2	V,Ti, Mo, B, P oxides, 350-400^0C	Benzonitrile, di-, tri-cyanbenzenes and corresponding derivatives with haloids, oxy-, alkoxy-, nitro groups
Pyridine, 2-, 3- и 4- methylpyridines	V,Ti, Mo, Bi oxides, 350-400^0C	2-, 3-, 4- cyanpyridines
8. Ammonsulfooxidation
Toluene, NH3 ,SО2	Al, Si, Zr, V oxides, 400^0C	Benzonitrile		11, p. 136
9. «Lammas»-process
Substituted alkylbenzenes, NH3	V superoxides, 400^0C	Benzonitrile and corresponding derivatives		11, p. 132,155-157
10. Oxidative nitrilling
Toluene, HCN or CH3CN, О2	Cu,V,Ti oxides, 400-450^0C	Benzonitrile		11, p. 110, 422
Toluene, nitrobenzene or aniline, О2	V,Ti oxides, 400-600^0C

It can be concluded that a significant number of complex reactions mentioned above are genetically connected with heterogeneous oxidation reactions conducted in various extreme conditions. Also reactions, in which the main direction of the process is caused by non-oxidative conversions, can be associated, for example, the reaction of oxidative etherification. However, here too the oxidizing agent is required for the total process. In most considered reactions the catalyst operates according to reductive-oxidative mechanism, where the oxidizing agent performs the function of reoxidation of reductive active catalyst sites by organic matter and co-reactant. The conjugated process character have been proven for a number of processes such as oxidative ammonolysis, ammonsulfooxidation, conjugated oxidative dehydrogenation, oxidative chlorination [11]. However, the conjugation role is still an open question, therefore, all processes shown in the table should be primarily attributed to a complex combined processes including stages of different consecutive, parallel and coupled reactions.

The method of chemical processes’ formation by introducing an oxidizing agent into a mixture of basic co-reactants, the components of which are part of the desired product, was quite productive. It allowed to create such leading industrial processes as oxidative chlorination, oxidative ammonolysis, oxidative etherification, according to which modern bulk products - vinyl chloride, acrylonitrile and vinyl acetate have been produced [21]. Such well-known polymeric materials as polyvinyl chloride (manufacture of double-glazing windows, linoleum, packaging materials), polyacrylonitrile (manufacture of "nitrone" fiber, carbon fiber-reinforced plastic), polyvinyl acetate (PVA building adhesive, the starting material for the polyvinyl alcohol used to prepare the high modulus fibers and others) are obtained from these monomers. Other examples of complex reactions are given in works [22, 23].

REFERENCES

1. B.V. Suvorov, S.R. Rafikov, A.D. Kagarlitskiy. The oxidative ammonolysis of organic compounds // Usp. - 1965. - T.35, №9. - p. 1526-1549;

2. B.V. Suvorov. The oxidative ammonolysis of organic compounds. - Almaty, Science of the Kazakh SSR, 1971. – p. 146;

3. B.V. Suvorov in the book; V.A. Volkov, E.V. Vonskiy, G.I. Kuznetsova. Outstanding chemists of the world. Edited by G.I. Kuznetsova - M.: High School, 1991. – p. 656;

4. N.N. Shilov. Conjugate oxidation reactions. - M., 1905. - p.304;

5. N.M. Emanuel, D.G. Knorre. Course of chemical kinetics, 4th ed. - M., High School, 1984. - p. 463;

6. N.R. Bukeikhanov, B.V. Suvorov, B.T. Dzhusupov and others. The conjugated character of contact oxidation of some nitrogen-containing organic compounds // Math. Academy of Sciences of the Kazakh SSR, Ser. chem. - 1977, №3. - p.48-52;

7. P.B. Vorobyev, T.P. Mikhailovskaya, R. Kurmakyzy, A.B. Dikhanbayev, D.H. Sembaev. Partial oxidation of 4-picoline on V₂O₅ and promoted vanadium oxide catalysts // Chem. Journal. of Kazakhstan. - 2010, № 4. - p. 58-66;

8. L.S. Polak, M.J. Goldenberg, A.A. Levitskyi. Computational methods in chemical kinetics. - M., 1984. - p. 280;

9. D. Himmelblau. Experimental nonlinear programming. - M., 1975. - p.536;

10. V.F. Kiselev, O.V. Krylov. Electronic effects in adsorption and catalysis on semiconductors and dielectrics. - M., 1979. - p.236;

11. B.V. Suvorov, N.R. Bukeikhanov. Oxidation reactions in organic synthesis. - M. Chemistry, 1978. - p.197;

12. B.T. Dzhusupov, N.R. Bukeikhanov, B.V. Suvorov. Synthesis of aromatic nitriles by oxidation of alkylbenzenes with organic nitrogen-containing compounds // Math. Academy of Sciences of the Kazakh SSR, Ser. chem. - 1977, № 4. - p. 66-70;

13. L.G. Manukovskaya, A.V. Solomin, B.V. Suvorov, S.R. Rafikov. Continuous method of producing terephthalic acid by liquid phase oxidation of p-xylene // Petrochemistry. - 1962. - B. 2, №4. - p. 531-535;

14. N.M. Emanuel, O.N. Dyment, E.A. Blumberg. Modern methods of ethylene oxide and propylene oxide production // Journal. WMO named after D.I. Mendeleev. - 1969. - B.14, №3. - p. 238-262;

15. V.M. Gryaznov. Reaction conjugation by using membrane catalysts // Kinetics and catalysis. -1971. - B.12, issue 3. - p. 640-645;

16. H. Hoffmann. Ammonsulfooxidation // Chem. Zeit., Chem.Apparat. - 1967, №12. - P. 392-398;

17. J.E. Paustian, F. Pustio, N. Stavropouls, M. Sce. A lesson inflow sheet design nicotinamide and acid // Chem.Techn. –1981. – V.11, № 3. – p. 174-178;

18. E. Fisher. Preparation of aromatic nitriles by means of a new vapor phase reaction // Chem.Ind.Techn. – 1966. – Bd.38. – p. 35-37;

19. V.S. Zulkasheva, N.R. Bukeikhanov, B.V. Suvorov. The oxidative ammonolysis of mixtures of some methylbenzenes // Iss. Academy of Sciences of the Kazakh SSR, Ser. chem. - 1980, №5. – p. 48-51;

20. B.V. Suvorov, N.R. Bukeikhanov, L.V. Li. Ways of processes intensification of nitriles production on the basis of oxidative ammonolysis reaction of organic substances // In book.: Synthesis and study of monomers and polymers. - Alma-Ata, Science. - 1983. - p. 3-23;

21. L. Berdick Donald, William L. Leffler Petrochemistry/ trans. from English. - M .: CJSC "Olymp-Business." - 2001. - p. 416;

22. D.R. Ashmead Brit. Pat. № 1274653, 1972. Oxydation of Hydrocarbons.

23. N.R. Bukeikhanov, B.V. Suvorov. Synthesis of substituted aromatic nitriles. - In coll.: Chemistry of monomers and polymers. - Alma-Ata, Science, 1980. - p. 3-15.