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AZ9RBAYCAN KIMYA JURNALI № 2 2017
UDC 541.128 + 542.943 + 544.473 A PROFILE OF CUMENE MODEL AEROBIC OXIDATION IN THE PRESENCE OF 5,10,15,20-TETRAKIS-(2,3,4,5,6-PENTAFLUOROPHENYL)PORPHINE-Fe(III)
CHLORIDE
N.I.Salmanova
Azerbaijan State University of Oil and Industry [email protected] Received 18.02.2016
This article describes primary results of influence of Fe-complex of tetraphenylporphyrin - 5,10,15,20-tetrakis-(2,3,4,5,6-pentafluorophenyl)porphine-Fe(III) chloride on the model reaction of cumene aerobic oxidation in the presence of hydrogen peroxide. The powerful catalytic capacity of the used additives, presumably due to the formed Fenton system, has been found out for the first time.
Keywords: cumene, aerobic oxidation, hydrogen peroxide, complex of tetraphenylporphyrin, Fenton's reagent, free radical mechanism.
Introduction
Oxidation of hydrocarbons is value-enhancing chemical transformation having the goal to make the process manageable, high-yielded, selective and environmentally friendly. Naturally occurring enzymes are excellent suitable examples to reach the criteria: extensive studies have found out the key chemical principles of ferments efficacy as catalysts for aerobic oxidations - important inroads have been made in applying this knowledge to the development of synthetic modeling patterns [1, 2]. Actually, the current industrial catalysts often operate under harsh conditions and produce large amounts of heavy-metal waste while the enzymatic oxidations operate under relatively mild conditions and produce any waste. The enzymes catalyze the chemo-, regio-, and stereoselective oxygenation of hydrocarbons producing alcohols, aldehydes, epoxides, and carboxylic acids [2-4]. The matter is interesting from the scientific point of view, e.g. to contribute more important details to geochemical aspects of genesis of oxygenated petroleum hydrocarbon or to the mechanism of biomimetic catalysis, to make enable new routes for difficult-to-synthesize complex substances of pharmaceutical and agricultural industries as well. Such biologically inspired hydrocarbon oxidation catalysts hold great promise for wide-ranging synthetic applications [5-9].
In the present paper the primary results of Fe-complex of tetraphenyplporphyrin - 5,10,15, 20-tetrakis-(2,3,4,5,6-pentafluorophenyl)porphine-Fe(III) chloride impact on the model oxidation
environment are given. Thereby we have tried to simulate the biomimetic catalysis. Results were appeared very promising since the powerful oxygen uptake has been observed upon addition of hydrogen peroxide. Kinetic measurements as well as deep oxidation outputs are evidences of rational use of catalytic system tested for special purposes related to the challenges of fine synthesis.
Experimental part
The employed cumene was of 99% purity ("Alfa Aesar"). The oxidation of cumene was conducted at 60oC and constant oxygen pressure Po2=20 KPa (air), in the presence of hydrogen peroxide (30% aqueous solution) and 5,10,15,20-tetra-kis-(2,3,4,5,6-pentafluorophenyl)porphine-Fe(III) chloride.
The latter compound was provided by Por-Lab (Porphyrin-Laboratories GmbH, Germany) with the structure:
АЗЕРБАЙДЖАНСКИЙ ХИМИЧЕСКИЙ ЖУРНАЛ № 2 2017
and data:
1. Synonym
2. Part number
3. CAS
4. Molecular formula
5. Molecular weight
6. Melting point
7. Solubility
TPFPP-Fe(III)Cl
PL00192617
36965-71-6
C^ClF^Fe^
1063.8268
no specification
dichlormethan, chloroform
The rate of oxidation was evaluated from the amount of oxygen consumed, which was measured volumetrically with the simple equipment as shown in Figure 1 and described in [10-12]. Oxidation rates were assessed from slopes of a kinetic curve of oxygen consumption. Experiments were carried out at least in triplicate and the correctness of the oxidation rate values determined was within the range of 5-7%.
Fig. 1. Schematic diagram of measuring equipment for oxygen uptake.
Results and Discussion
The results of kinetic experiments are depicted in Figure 2. The Figure shows profile of kinetic dependences of the oxygen uptake for the cumene aerobic oxidation in the presence of
hydrogen peroxide and 5,10,15,20-Tetrakis-(2,3,4,5,6-pentafluorophenyl)-porphine-Fe(III) chloride. The obtained oxygen uptake rates are accumulated in Table 2.
Fig. 2. Profile of kinetic dependences of oxygen oxygen-uptake for aerobic oxidation of cumene in the presence of the 5,10,15,20-tetrakis-(2,3,4,5, 6-pentafluorophenyl)porphine-Fe(III) chloride (PFPhPFeCl) chloride and hydrogen peroxide (H2O2). Reaction mixture volume 10 ml, oxygen pressure: PO2= 20 kPa (air), temperature -600C, [H2O2] = 53 ml/l; [PFPhPFeCl]: 1 - 0.5, 2 - 1.0 g/l, 3 - [H2O2] = 53 ml/l, [PFPhPFeCl] = 0.
62
N.I.SALMANOVA
Table 2. Oxidation rates of the liquid-phase oxidation of cumene. Reaction mixture volume: 10ml, oxygen pressure: Po2 = 20 kPa (air), temperature = 600C, [H2O2] = 53 ml/l
The data obtained give the evidence concerning extremely high catalytic activity of the system 5,10,15,20-tetrakis-(2,3,4,5,6-pentaflu-orophenyl)porphine-Fe(III) chloride + hydrogen peroxide" which can be considered as analogue of the Fenton's reagent in the oxidation of hydrocarbons - the reaction rate is increased hundred fold in the presence of the system.
General mechanism of the oxidation may be represented as follows:
[Catalyst], g/l Й - 1 , Г/ i - 'сл о s 9 В
without H2O2 and with PFPhPFeCl (0.5 g/l) 0 0
without PFPhPFeCl and H2O2 2 0.14
without PFPhPFeCl and with H2O2 5 0.34
[PFPhPFeCl] = 0.5 198 13.5
[PFPhPFeCl] = 1.0 271 18.4
I. Generation of oxidation chains:
+ H2O2 ^ Fe + HOO^ + H+ Fe2+ + H2O2 ^ Fe3+ + HO^ + OH-
II. Chain propagation: HOO^ +RH ^ R^ + H2O2,
HO+RH ^ R^ + H2O, R^ + O2 ^ R ó + RH ^ ROOH + R\
2
III. Chain termination:
Ró + Ró ^ molecular products of oxidation.
Scheme 1. The aerobic oxidation of the hydrocarbon (RH, cumene) in the simultaneous presence of 5,10,15,20-tetrakis-(2,3,4,5,6-pentafluorophenyl)porphine-Fe(III) chloride and hydrogen peroxide at moderate temperatures (60+20)°C.
Conclusions
The extremely high catalytic activity of the Fenton like system 5,10,15,20-tetrakis-(2,3,4,5,6-pentafluorophenyl)porphine-Fe(III)chloride+hydrogen peroxide in the model oxidation of cumene has been revealed for the first time.
Note
The work has been carried out within the framework of the agreement dated (02.07-02.09) 2015 between Institute of Catalysis and Inorganic Chemistry of ANAS and Azerbaijan State University of Oil and Industry.
Acknowledgement
The author thanks Professor Eldar Zeynalov for the tutelage and management.
АЗЕРБАЙДЖАНСКИМ ХИМИЧЕСКИМ ЖУРНАЛ № 2 2017
References
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5,10,15,20-TETRAKiS-(2,3,4,5,6-PENTAFLÜORFENIL)PORiIN-Fe(In)XLORiDiN i§TIRAKI iLO KUMOLUN OKSiDLOSMOSiNiN MODEL REAKSiYASININ PROFiLi
N.i.Salmanova
Kompleks birla§ma - 5,10,15,20-tetrakis-(2,3,4,5,6-pentaflüorfenil)porfin-Fe(III) xloridin hidrogen peroksidin i§tirakinda kumolun aerob oksidla§ma model reaksiyasina tasirinin naticalari verilmi§dir Müayyan olunmu§dur ki, göstarilan kompleks hidrogen peroksidin i§tirakinda guclu katalitik effekta malikdir ki, bu da Fenton reagenti tasirina analoji olaraq aktiv reaksiya markazlarinin yaranmasi naticasinda ba§ verir.
Acar sözlar: kumol, havanin oksigeni ila oksidbgma, hidrogen peroksid, tetrafenilporfirin kompleksi, Fenton reagenti, sarbast radikal mexanizmi.
ПРОФИЛЬ МОДЕЛЬНОЙ РЕАКЦИИ ОКИСЛЕНИЯ КУМОЛА В ПРИСУТСТВИИ 5,10,15,20-ТЕТРАКИС-(2,3,4,5,6-ПЕНТАФTOРФЕНИЛ)ПОРФИН-Fe(ЩlХЛОРИДА
Н.И.Салманова
Описаны результаты действия комплексного соединения порфирина - 5,10,15,20-тетракис-(2,3,4,5,6-пента-фторфенил)порфин-Fe(III)хлорида на модельную реакцию аэробного окисления кумола в присутствии перокси-да водорода. Установлено, что указанный комплекс в присутствии H2O2 оказывает сильнейший каталитический эффект вследствие генерирования активных реакционных центров по аналогии с действием реактива Фентона.
Ключевые слова: кумол, окисление воздухом, пероксид водорода, комплекс тетрафенилпорфирина, реагент Фентона, свободно-радикальный механизм.
