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AZ9RBAYCAN KIMYA JURNALI № 1 2016
65
UDC 541.1.17.541.128.43.544.4
GAS-PHASE SELECTIVE OXIDATION OF 2-CHLOROTOLUENE TO CHLORO-MALEIC ANHYDRIDE IN THE PRESENCE OF HETEROGENEOUS
CATALYSTS
A.C.Efendi, E.M.Babayev, F.A.Yunisova, N.F.Aykan, B.A.ismayilova
M.Nagiev Institute of Catalysts and Inorganic Chemistry NAS of Azerbaijan
elmir.magsadoglu@gmail.com Received 12.02.2016
The activities of vanadium oxide catalysts with P, Mo, Sb additions drawn on SiO2 and Al2O3 in the reaction of oxidation of n-chlorotoluene has been iinvestigated. It is shown that the catalytical systems V-Mo-Sb-O/Al2O3 possess higher activities. Effect of the catalyst components activities on the reaction of oxidation mono-chlorotoluene has been determined. At ratio of the active components V:P=1:2—1:3 the catalytical system V-Mo-O/SiO2 display high activity at conversion of 2-chlorotoluenes equal to 85% , the yield of the basic product of oxidation MCMA makes up 24-28%.
Keywords: catalytical oxidation, 2-chlorotoluene, catalysts - vanadium oxide, molybdenum oxide, phosphor, maleic anhydride, chloro-maleic anhydrides.
Introduction
Nowadays, variety of methods is used for the selective decomposition of mono-chloroto-luenes [1, 2]. The methods should be developed not only to dispose of materials that contain these substances, but also to purify the numerous contaminated sites. To protecting environment from the harmful chemical pollutants and minimise their harm to human organism, as well as environment is one of the main purposes of green chemistry [3, 4]. Chloro-aromatic hydrocarbons are toxic, harmful, non-biodegradable compounds. However, they are used as pesticides, herbicides, industrial solvents, dielectric liquids, antimicrobial substances [5]. It should be
noted, infinite-small mole concentration of them
1 2
(10" -10" mol/l) make their counteraction more difficult, it is nearly impossible to effectuate the disposal with available methods. It will be purposeful for both neutralization of them and also the use of rewarding raw materials in chemical industry. Likewise synthesizing necessary inoffensive compounds such as aldehydes, anhydrides, acids and ketenes is too prior issue. The majority of the classical methods to produce those yields from the corresponding chloro-aro-matic hydrocarbons don't follow sustainable chemistry principles [6]. Consequently, in the last decades, the aim of the research in this field was the development of solid catalysts for the selective oxidation of chlorinated alkyl aromatic hydrocarbons in liquid or gas-phase in order to
aforementioned classical methods by other ones which are more simple and cause low environmental pollution. Among them, vanadium based catalysts, as well as those based on Mo, have been reported to be efficient in the partial oxidation of toluenes in gas-phase although values of the yield of substituted benzaldehydes that exceed 20% are rarely attained [7-9]. So, to find novel catalytic systems in order to develop the oxidation processes of chloroaromatic hydrocarbons and change reaction direction is still very interesting. In this respect, we previously studied the catalytic behaviour in the selective oxidation of chloro-hydrocarbons of vanadium oxide catalysts on different carriers [1, 10-12]. We found that oxide based systems supported on SiO2 or Al2O3 were the most active and selective in the mono-chlorotoluene oxidation [1]. Furthermore, the surface properties of vanadia species and, consequently their catalytic behaviour on the support type and vanadia loading have been also determined.
In this context, the present paper reports the results obtained in the gas-phase selective oxidation of 2-substituted toluene derivate of the same vanadium oxide systems previously studied [1, 11].
Experimental part
Preparation of oxide based catalytic systems supported on SiO2 or Al2O3 have been previously reported [1]. The systems were mainly received by the diluting ammonia vanadates, so-
dium phosphates in the oxalate or hydrochloric acid. Solid solution was evaporated for the short time and permeated on the SiO2 or Al2O3. Then subsequent desiccated on air at 180-23 00C for an hour, further step calcined in the fume cupboard 270-3800C for two hours, at last calcined for an hour at 5 000C. Before the reaction the reagents were heated above than 1000C, and then oxidation process was carried out.
Surface area and pore size information of the catalysts were obtained from the adsorption-desorption isotherm of nitrogen at its liquid temperature, using a Gas Adsorption Surface Porosymeter. Prior to measurements, all samples were degassed to 0.1 Pa. B.E.T surface areas were calculated assuming a cross-sectional as 0.164 nm2 for nitrogen molecule. The values for surface area, porous radius and radius diameter were established [1].
Phase identification and quantification: phase properties (cell parameters, crystallite size, and lattice strain), is offered. Crystal structure of synthesized catalytic systems was determined by the Bruker manufactured D2 Phase X-ray powder Diffraction analyzer.
Selective oxidation of 2-chlorotoluene (2-CT) was carried out in a continuous flow fixed-bed reactor at an atmospheric pressure and in the temperature range of 3 70-4800C. 2-CT was fed by means of microfeeder at 1.0 mL/h for an hour.
Results and discussion
The activities of the catalytic systems based on oxide synthesized and participated on the variety of suppliers were determined in the oxidation reaction of mono-chlorotoluene (p-CT and m-CT). The conversion of 2-substituted toluene in the presence of these catalytic systems at 3400C temperature and 0.8 sec-1 contact time was 70-85%. The results are given in Table. According to the Table the activities of none participated on the suppliers oxide catalysts in contrast to catalytic systems based on SiO2 or Al2O3 aren't high. V-P-O/SiO2 and V-Mo-Sb/Al2O3 systems showed high results among the attained catalytic ones.
An effect of active components of these catalysts on the oxidation reaction was also studied.
Activity changes of catalytic systems in the 2-chlorotoluene oxidation reaction at 713 K, 2-CT:O2=1:15_
Й .g
in Yields of reaction, %
Catalytic systems О О
2-CT MCMA MA 2-CB 2-CB acid <N О О
V-P-O 68 8 6 - - 34
V-Mo-O 72 10 8 2 2 32
V-Sb-O 70 14 10 6 6 30
V-P-O/SiO2 78 24 22 12 14 16
V-Mo-O/Al2O3 82 26 21 14 17 10
V-Sb-O/Al2O3 82 24 20 14 18 11
V-Mo-O/SiO2 78 22 18 10 13 14
V-Mo-Sb/Al2O3 80 26 22 11 10 12
MA - maleic anhydride, 2-CB - 2-chlorobenzaldehyde, 2-CB acid - 2-chlorobenzoic acid.
Influence of the mole ratio of active components V:Mo to the oxidation reaction at 4400C is given (Fig. 1). As it is seen in Fig. 1 at a V:Mo=1:2-1:3 ratios the conversion of 2-CT performs 75-78%, the yields of mono-chloromaleic anhydride (MCMA) were 24-27%. Yield of 2-CB begins to increase at V:P=1:4-1:5 ratios. According to the obtained results usage of the catalytic systems based on V:Mo=1:2-1:3 are considered purposeful for our further researches.
Temperature dependence of the 2-chlo-rotoluene oxidation reaction yields on the synthesized V-Mo-O systems supported Al2O3 was established. Although the oxidation reaction begins from the 3800C and conversion of 2-chlorotoluene 50%, determined that the yields of main products are negligible (Fig.2). By increasing temperature both the conversion of the 2-CT and yield of MCMA begins to rise, and at the 4200C temperature it showed the maximum (24-27%). Simultaneously, the yields of maleic anhydride (MA), 2-chlorobenzaldehyde and 2-chlorobenzoic acid (2-CB acid) decreased. By the further rise of temperature 2-CT conversion continues to increase, but also yields of the main products at its maximum begin to decrease and this happens by way of their exposing deep oxidation process that verified by increasing of CO2 yield.
A.C.EFENDI et al.
67
70
^ 60
ГЛ
a so
40 -
S 30 >
ö о О
20
10 ■
1:1
1:2
1:3
1:4
V:Mo
1:5
Figure 1. Effect of mole ratio of V:Mo components on the 2-chlorotoluene oxidation reaction activity; 1 - conversion of 2-CT, 2 - yield of MCMA, 3 - yield of 2-CB.
1
%
653
673
693
713
733
Figure 2.Temperature dependence of the 2-chlorotoluene oxidation reaction yields on the synthesized V-Mo-O systems supported Al2O3; 1 - 2-CT; 2 - CO2; 3 -MCMA; 4 - MA; 5 - 2CB; 6 - 2CB acid.
753 "C
Conclusions
In conclusion it has been determined that V-P-O/SiÜ2 and V-Mo-Sb/Al2Ö3 are the most active and selective catalytic systems in the oxidation reaction of mono-chlorotoluenes. The optimum reaction condition for the activity and selectivity for received catalysts was designated, so under this condition the conversion of mono-chlorotoluene reached 70-90%. Consequently, the p-chlorosubstituted substrate, p-chlorotoluene, is much more reactive than the да-chlorosub-stituted counterpart.
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HETEROGEN KATALiZATORLARIN i^TiRAKINDA QAZ FAZADA 2-XLORTOLUOLUN XLORMALEIN ANHiDRlDiNO SELEKTIV OKSiDLO^MOSi
A.C.Ofandi, E.M.Babayev, F.A.Yunisova, N.F.Ayxan, B.A.ismayilova
Osasi vanadium oksid va bir sira alavalarla P, Mo,Sb ahnmi§ va SiO2, Al2O3 üzarina gökdürülmüij katalitik sistemlarin mono-xlortoluolun oksidla§masi reaksiyasinda aktivliklari tadqiq edilmi§dir. Göstarilmi§dir ki, tadqiq olunan sistemlar igarisinda daha yüksak aktivliya V-P-O/SiO2 va V-Mo-Sb-O/Al2O3 katalizatorlari nümayi§ etdiriblar. Katalizatorlann aktiv kompo-nentlarinin V:P=1:2-1:3 nisbatlarinda reaksiyanin konversiyasi (85%) va MXMA-nin giximinin daha yüksak olmasi 24-28% müayyan edilmi§dir.
Agar sözlzr: katalitk oksidh§m3, mono-xlortoluol; vanadium, molibden, fosfor oksid 3sasli katalizatorlar, malein anhidridi, xlormalein anhidridi.
ГАЗОФАЗНОЕ СЕЛЕКТИВНОЕ ОКИСЛЕНИЕ 2-ХЛОРТОЛУОЛОВ В ХЛОРМАЛЕИНОВЫЙ АНГИДРИД В ПРИСУТСТВИИ ГЕТЕРОГЕННЫХ КАТАЛИЗАТОРОВ
А.Д.Эфeнди, Е.М.Бабаев, Ф.А.Юнисова, Н.Ф.Айкан, Б.А.Исмайилова
Исследована активность оксиванадиевых катализаторов с добавками P, Mo, Sb и нанесенных на SiO2 и Al2O3 в реакции окисления моно-хлортолуола. Показано, что более высокой активностью обладают V-P-O/SiO2 и V-Mo-Sb-O/Al2O3 каталитические системы. Определено влияние активности компонентов катализатора на реакцию окисления п-хлортолуола. При соотношении активных компонентов V:P=1:2-1:3 каталитическая система V-Mo-O/SiO2 показывает высокую активность, при конверсии 2-хлортолуола, равной 85 %, выход основного продукта окисления МХМА составляет 24-28%.
Ключевые слова: каталитическое окисление, 2-хлортолуол, катализаторы - оксиды ванадия, молибдена, фосфора, малеиновый ангидрид, хлоромалеиновые ангидриды.
