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AZERBAIJAN CHEMICAL JOURNAL № 1 2019
UDC 544:544,344
ACTIVATION INFLUENCE ON CATALYTIC ACTIVITY OF MODIFIED BY METALS CATIONS SYNTHETIC ZEOLITE - MORDENITE IN TOLUENE DISPROPORTIONATION REACTION
A.M.Aliev, V.Sh.Aghayev, A.A.Sarijanov, R.Y.Mirzaeva, S.R.Mammedova
M.Nagiev Institute of Catalysis and Inorganic Chemistry, NAS of Azerbaijan
[email protected] Received 13.09.2018
Catalytic activities of synthetic zeolite (SiO2/Al2O3=18) - mordenite, modified by metal cations (Pd2+, Ni2+, Co2+, Nd3+, Mo3+, Zr4+, Nb5+) activated under different air stream conditions in the temperature range of 300-4200C in disproportionation reaction of toluene to benzene and xylenes were studied. It was found that synthetic zeolite - mordenite comprising Pd2+, Ni2+ and Nd3+ cations are more active than the catalysts containing Co2+, Mo3+, Zr4+, Nb5+. It has been established that in conditions under study the samples activated in dry-wet air media (by joint yield of toulene and xylene) display the most activity and selectivity.
Keywords: disproportionation, toluene, zeolite, mordenite, benzene, xylenes, cation, calcination, modification.
https://doi.org/10.32737/0005-2531-2019-1-14-18
Zeolite mordenite catalyst exhibits more activity and selectivity than faujasite type zeolites in disproportionation reaction of toluene [1, 2]. For toluene disproportionation reaction it is possible to receive highly active and highly selective catalyst at molar ratio in zeolite mor-denite catalyst SiO2:Al2O3 within frame of 1730 and introducing metal cations into it [3-5].
One of the important prospective methods of regulating activity and selectivity of zeolite catalysts is their calcination under various conditions. But, influence of calcination on the activity of a metal-containing mordenite zeolite catalyst in this reaction has not been studied sufficiently [3].
The main goal of the work is to study the effect of calcination of zeolite mordenite catalysts modified by different metal cations on their activity in toluene disproportionation reaction.
Experimental part
Modification of zeolite H-mordenite (SiO2:Al2O3=a=18) with cations of different elements (Pd2+, Ni2+, Co2+, Mo3+, Nd3+, Zr4+, Nb5+) was performed in their sold of chloride and nitrate solution using ion-exchange technique. Preparation of zeolite H-mordenite (a=18) is given in the work [4]. Modification by Pd+2 ions was performed in the solution of [Pd(NH3)4]Cl2 complex salt. Mo H-mordenite
catalyst was prepared with using paraammonium molybdate salt solution by absorption method. The content of metal cations in zeolite is about 1.0% of a zeolite mass.
In the present work after drying synthesized catalysts (100-1200C, 8-10 h) they are thermally treated at 3500C (5 h) and 5000C (3 h). Prepared catalyst samples are pressed, then granules with sizes of 0.25-0.7 mm are separated into fractions. The process is carried out in U-shaped flow type reactor, in the temperature range of 3 00-4200C, in flow rate of 3.1 h-1, H2:CH(toluene)=3:1 molar ratio, under atmospheric pressure. Volume of catalyst samples in the reactor is 3 cm3, sizes of granules are 0.250.63 mm. The reactor is placed into a thermostat equipped with an electric ventilator and after treating the catalyst at
4000C for 10 l/h in dry (d) (dried before in silicagel then NaX zeolite for 3 h), wet (w) (in 50% of water steam with air for 3 h), wet-dry (wd) (50% of water steam air mixture for 2 h, on dry air for 1 h) and dry-wet (dw) (on dry air for 1 h, wet air for 2 h) air stream conditions argon gas is supplied into the system for 5-10 min (1.0 l/h) and at the same temperature it is reduced with hydrogen (8.0 l/h) for 3 hours and the temperature is regulated according to the temperature of the experiment, and using NE-1600 microdosator toluene is passed with a volume rate to a mixer regula-
A3EPEAH#^AHCKHH XHMHHECKHH ^YPHAH № 1 2019
ted with thermoregulator XMDT-6000 placed in a thermostatic chamber heated with electric spirals.
Hydrogen is supplied into a mixer from a separate line. Stable temperature is regulated using microelectronic thermoregulator in a thermostat. After toluene and hydrogen are supplied to a mixer toluene passes to a gas phase and toluene-hydrogen mixture enters to the reaction zone through the entrance of the reactor.
Analysis methods of primary reagents and products are given in the work [4]. After the experiment is finished argon gas is supplied with 2-3 l/h rate for 10-15 min and calcinated in air flow at 5000C for an hour to extract the reaction products from the reactor.
Results and discussion
First the effect of thermal treatment of mordenite zeolite catalysts modified with different metal cations (Pd2+, Ni2+, Co2+, Nd3+) in dry, wet, dry-wet air stream condition on their catalytic activity in disproportionation of toluene at 3500C in V=3.1 h-1, H2:CH=3:1 was studied (Table 1).
As Table 1 shows, mordenite zeolite catalysts modified with different metal cations exhibit various activity in disproportionation of toluene depending on calcination method. It
was determined that catalyst samples treated in dry-wet air stream condition exhibit higher activity and selectivity than catalyst samples treated in dry, wet, wet-dry air stream conditions. As a result of the reaction trimetylben-zenes (TMB) and non-aromatic (Non-ar) hydrocarbons are formed together with the target products - benzene and xylenes. Thus, conversion of toluene in the samples treated in dry-wet air stream condition is 41.2-44.2%, joint yield of benzenes and xylenes is in the range of 37.242.5% (selectivity of the process - 90.396.2%), conversion of toluene in samples treated in dry air stream condition is 30.4-35.2%, joint yield of benzenes and xylenes is 11.318.8% (selectivity of the process - 37.2-56%).
It should be noted that the yield and selectivity of benzene and xylenes in the samples calcinated in wet-dry air stream condition are higher than in the samples treated in dry and wet air stream conditions. If the selectivity is in the range of 85.5-89.2% and the joint yield of benzenes and xylenes is in the range of 33.9-37.3% in the samples treated in wet-dry air stream condition, these indicators are 62.1-81.3% and 23.1-30.5% in the samples treated in wet air stream condition, correspondingly.
Table 1. Catalytic activity of the catalysts calcinated in dry, wet, wet-dry and dry-wet air stream condition at 4000C in disproportionation of toluene; y=350°C, V=3.1 h-1, H2/C'H=3:1___
Catalysts Yield of reaction products, % Conversion, % Selectivity, % Yield of IXy+b, % Selectivity for IXy+b, %
benzene xylenes TMB non-ar hc benzene xylenes TMB non-ar hc
K1 d 10.2 8.6 11.3 3.5 33.6 30.4 25.6 33.6 10.4 18.8 56.0
K2 d 8.1 6.8 15.2 4.1 34.2 23.7 19.9 44.4 12.0 14.9 43.6
K3 d 6.2 5.1 14.5 4.6 30.4 20.4 16.8 47.7 15.1 11.3 37.2
K4 d 8.3 8.1 14.6 4.2 35.2 23.6 23.0 41.5 11.9 16.4 46.6
K1 w 15.7 14.8 5.1 1.9 37.5 41.9 39.5 13.6 5.1 30.5 81.3
K2 w 14.1 12.6 8.2 3.5 38.4 36.7 32.8 21.4 9.1 26.7 69.5
K3 w 12.9 10.2 10.3 3.8 37.2 34.7 27.4 27.7 10.2 23.1 62.1
K4 w 14.7 11.6 8.3 3.5 38.1 38.6 30.4 21.8 9.2 26.3 69.0
K1 wd 19.5 17.8 3.3 1.2 41.8 46.7 42.6 7.9 2.9 37.3 89.2
K2 wd 18.3 16.4 4.0 1.9 40.6 45.1 40.4 9.9 4.7 34.7 85.5
K3 wd 18.1 15.8 4.1 1.1 39.1 46.3 40.4 10.5 2.8 33.9 86.7
K4 wd 19.1 16.1 3.5 0.9 39.6 48.2 40.7 8.8 2.3 35.2 88.9
K1 dw 23.1 19.4 1.5 0.2 44.2 52.3 43.9 3.4 0.5 42.5 96.2
K2 dw 20.9 18.2 3.7 0.3 43.1 48.5 42.2 8.6 0.7 39.1 90.7
K3 dw 19.4 17.8 3.6 0.4 41.2 47.1 43.2 8.7 1.0 37.2 90.3
K4 dw 20.8 17.6 3.2 0.2 41.8 49.8 42.1 7.7 0.5 38.4 91.9
K1 - Pd Hm, K2 - Ni Hm, K3 - Co Hm, K4 - Nd Hm
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A.M.ALIEV et al.
The yield of TMB and Non-ar hydrocarbons decreases in reaction products in the samples calcinaned in wet-dry and dry-wet air stream conditions and the selectivity of the reaction increases (Table 1).
Regardless of calcination condition the
2+ 2+
samples modified with Pd and Ni cations exhibit higher activity and selectivity in disproportionation reaction of toluene than other MeHm (Nd, Co) samples (Table 1).
In the following studies the influence of temperature on catalytic activity of H-mordenite zeolite catalysts modified with different metal cations calcinated in dry-wet air stream condition in disproportionation of toluene was studied. The results are shown in Table 1 and 2.
As Table 1 and 2 show, when the temperature increases from 300 to 4000C in metal-containing H-mordenite zeolite samples conversion of toluene and joint yield of benzene and xylenes increase (Figure).
The subsequent increase (4200C) of temperature does not essentially influence on joint yield of benzene and xylenes (Table 1). But zirconium- and niobium-containing zeolite mordenite catalysts exhibit a high activity at 4000C in disproportionation reaction of toluene and due to joint yield of benzene and xylenes and selectivity of the reaction it is found to be higher than cobalt- and molybdenum-containing samples (Table 2).
Table 2. The influence of temperature on activity of H-mordenite zeolite catalysts, modified with transition element cations calcinated in dry-wet air stream condition in disproportionation of toluene. V=3.1 h'1, H2/CH=3:1_
Element cations Temperature, 0C Yield of reaction products, % Selectivity for XKs+B, %
benzene xylenes TMB non-ar hc
Pd2+ 300 16.5 20.1 0.5 0.0 98.7
350 19.4 23.1 1.5 0.2 96.2
400 21.4 23.7 3.1 0.4 92.8
Ni2+ 300 14.8 18.7 0.9 0.0 97.4
350 18.2 20.9 3.7 0.3 90.4
400 20.6 23.7 5.3 0.5 88.4
Co2+ 300 13.6 17.8 0.8 0.0 97.5
350 17.8 19.4 3.6 0.4 90.3
400 19.5 20.3 5.2 0.8 86.9
Mo3+ 300 12.8 17.7 0.7 0.0 97.8
350 16.6 19.8 3.4 0.3 90.8
400 18.4 21.1 4.8 0.5 88.2
Nd3+ 300 14.1 18.1 0.6 0.0 98.2
350 17.6 20.8 3.2 0.2 91.9
400 19.7 22.7 4.1 0.5 90.2
Zr4+ 350 10.4 13.1 1.6 1.0 93.3
400 20 .2 22.4 3.8 0.3 91.2
Nb5+ 350 8. 9 12.6 1.7 0.2 91.9
400 18.3 21.8 4.2 0.3 89.9
30 -
Dependence of toluene conversion (a, x) and joint yield of benzene and xylenes (b, A) on the temperature in disproportionate of toluene on metal zeolite catalysts; Ft= 3.1
li\H2/CH=3:l. ♦-Pd;n -Ni; A -Nd ; A -Co : D-Mo
But increase of reaction temperature causes the high yield of by-products (TMB and Non-ar hydrocarbons) and the selectivity of reaction decreases.
Thus, the results suggest that the activity and selectivity of a metal zeolite catalyst in disproportionation reaction of toluene can be regulated by calcinating them in dry-wet and wet-dry air stream conditions.
References
1. Tcybulevskii A.M., Pak P.M., Zolotareva Z.V.
Disproportcionirovanie toluola na nikel dealiumi-
nirovannom mordenite // Neftehimiia. 1990. T. 20. № 3. S. 372-380.
2. Butler I. R., Xiao X., Hall Rosa. Toluene disproportionate catalyst, Pat. US 20100041934 A1. 2010.
3. Pat. 4956511 US. Toluene disproportionation process / Butler I. R., Randall J. Curtis. 1990 .
4. Oliyev A.M, Agayev V.§, Sancanov O.O. Müx-talif silikat modullu H-mordenit seoliti üzarinda toluolun benzol va ksilollara disproporsionla§masi //Chemical Problems. 2018. № 2. S. 239-244.
5. Hak Sung LEE, Byung Kyu Kim. Bok Soo Park. Toluene disproportionation over metal loaded mordenites // Korean J. Chem. Eng. 1990. No 4. P. 243-249.
TOLUOLUN DiSPROPORSiONLA§MA REAKSiYASINDA SiNTETiK SEOLITiN - METAL KATiONLARI iLO MODiFiKASiYA OLUNMU§ MORDENiTiN KATALiTiK FOALLIQLARINA
AKTiVLO^MONiN TOSiRi
A.M.Oliyev, V.§.Agayev, O.O.Saricanov, RY.Mirzayeva, S.RMammadova
Toluolun benzol va ksilollara disproporsionla§ma reaksiyasinda müxtalif hava mühitinda aktivla§mi§ metal katalionlari ila (Pd2+, Ni2+, Co2+, Nd3+, Mo3+, Zr4+, Nb5+) modifikasiya olunmu§ sintetik mordenit seolit (SiO2/Al2Os=18) -katalizatorlarinm 300-4200C temperatur intervalinda katalitik faalliqlari tadqiq edilmi§dir. Göstarilmi§dir ki, tarkibinda Pd2+, Ni2+ va Nd3+ kationlan saxlayan seolit mordenit katalizatorlari Co2+, Mo3+, Zr4+, Nb5+ tarkibli katalizatorlara nisbatan yüksak faalliga malikdirlar. Müayyan olunmu§dur ki, tadqiq olunan reaksiyada benzol va ksilollarin birga Qiximi va selektivliyi quru-nam hava mühitinda aktivla§mi§ katalizatorlarda maksimum olur.
Agar sözlar: disproporsionla§ma, toluol, seolit, mordenit, benzol, ksilollar, kation, aktivte§m3, modifikasiya.
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ЛМЛЬТБУ й а1.
ВЛИЯНИЕ АКТИВАЦИИ НА КАТАЛИТИЧЕСКУЮ АКТИВНОСТЬ СИНТЕТИЧЕСКОГО ЦЕОЛИТА - МОРДЕНИТА, МОДИФИЦИРОВАННОГО КАТИОНАМИ МЕТАЛЛОВ, В РЕАКЦИИ
ДИСПРОПОРЦИОНИРОВАНИЯ ТОЛУОЛА
А.М.Алиев, В.Ш.Агаев, А.А.Сарыджанов, Р.Ю.Мирзоева, С.Р.Мамедова
Исследовано влияние активации на каталитические свойства модифицированного катионами металлов (Р^2, №2+, Со2+, Nd3+, Мо3+, 2г4+, №5+) синтетического цеолита - морденита ^Ю2/А1203=18) - в реакции диспропорционирования толуола в бензол и ксилолы в интервале температур 300-4200С. Найдено, что катализаторы, модифицированные катионами Pd+2, Ni2+ и Nd , проявляют относительно более высокую активность и селективность по сравнению с образцом морденита, содержащего катионы Со2+ , Мо3+, 2г4+, №5+. Установлено, что в изученных условиях наибольшей активностью (по выходу суммы бензол и ксилолы) и селективностью обладают образцы, активированные в сухо-влажной среде воздуха.
Ключевые слова: диспропорционирование, толуол, цеолит, морденит, бензол, ксилолы, катион, активация, модификация.
