CC BY
159
ISSN 2522-1841 (Online)
ISSN 0005-2531 (Print) AZ9RBAYCAN KIMYA JURNALI № 3 2018
UDC 549.67 :544,47 : 542.941.8 A STUDY OF THE KINETICS AND MECHANISM OF THE SELECTIVE OXIDATIVE DEHYDROGENATION REACTiON OF CYCLOPENTANE TO CYCLOPENTADIENE-1,3 OVER MODIFIED ZEOLITE CATALYSTS
A.M.Aliyev, M.Y.Abbasov, Z.A.Shabanova, G.A.Ali-zadeh, M.F.Bahmanov, U.M.Najaf-Guliyev, T.I.Huseynova
M.Nagiyev Institute of Catalysis and Inorganic Chemistry, NAS of Azerbaijan
abbasov. mahir@mail. ru
Received 12.02.2018
The reaction of cyclopentane has been studied on HY zeolite at 380°C. Cyclopentene and cyclopentadiene formed a stable initial product by the dehydrogenation of the raw material, although molecular hydrogen was not found as the primary product. The catalytic activity of the clinoptilolite in the reaction of selective oxidative dehydrogenation of cyclopentane to cyclopentadiene have been measured experimentally and modelled theoretically at several temperatures. It was revealed that when using of clinoptilolite with these cations{ Cu2+ (0.5 mas.%), Zn2+ (0.2 mas.%), Co 2+ (0.1 mas.%), Cr 3+(0.1 mas.%) and CL[Co 2+ (0.5 mas.%)] heterogenic catalysts show the more activity in this reaction and theyare prepared by the ion-exchange method. The theoretical calculation also suggest that catalytic reactions of the process proceed in a highly non-synchronous or even non-consecutive fashion. The experimental data suggest that the active centers containing the components of the catalyst are grouped and the reaction pathways are described by taking into account bonding energies that exchange cations combine with dissociative adsorbed oxygen. The energy barriers and the rate constants of the catalytic systems were accurately modelled by the correlated electronic structure and calculation of the dual-level variational transition state theory.
Keywords: clinoptilolite, cyclopentane, catalytic dehydrogenation, cyclopenten, cyclopentadiene-1,3.
Introduction
The unsubstituted cyclopentane molecule is unique that it is relatively free of ring strain and at the same time does not convert to smaller cyclic structures, or to larger rings as is the case for substituted cyclopentanes and cyclohexanes. Consequently, the dehydrogenation behaviour of cyclopentane at high temperatures is fundamental to an overall understanding of reactions of cycloparaffins on solid acid catalysts. By using clinoptilolite most of our studies of olefins on this catalyst have been carried out in the temperature range of 300-400°C. Natural clinoptilolite can be used as an ion exchanger for removal of heavy metals because it has desirable characteristics of high ion exchange selectivity and resistance to different media [1]. Clinoptilolite is a natural microporous material possessing a versatile range of cation exchange properties that are exploited in many industrial processes. Clinoptilolite hails from the heulandite family of zeolites, which shares the same topology of eight-and ten-membered ring channels running parallel to the c-axis and an intersecting eight-membered ring channel parallel to the a-axis [2]. Clinoptilolite is used in many industrial applications,
due primarily to its abundance and cation exchangeability. We have shown that natural clinoptilolite modified with various non-transition elements and transition cations (Zn, Cu, Co, Cr, Mn, Fe, Mg, Mo, etc.).In this work, we have used a natural clinoptilolite with rich deposits in the territory of the Republic of Azerbaijan and uptake of copper(II), cobalt(II), chrome(III), zinc(II) from their single and mixed ion solutions. The mineralogical and chemical properties of the sorption material were studied by X-ray diffraction, X-ray fluorometry, scanning electron microscopy, and wet analysis. We have applied these cations Cu , Zn , Co and Cr by ion-exchange and indicated that this is the active catalyst for the reaction of oxidative dehydrogenation of cyclopentane. On the basis of experimental kinetic data by using Langmuir-Hinshelwood rate expression we have established that reaction of oxidative dehydrogenation of cyclopentane proceeds with the participation of the dissociative adsorbed oxygen. The purpose of the present work is to determine a role of the components of the catalytic system, in order to simplify kinetic studies of the reaction with conjugated dehydrogenation of cyclo-
pentane with metal-clinoptilolite. including the effect of factors such as raw material volume rates, component ratio, temperature and quartz reactor surface conditions on the process running obtained in our laboratory "Catalysis over zeolites" of the Institute of Catalysis and Inorganic Chemistry NAS of Azerbaijan.
Experimental part
We applied catalysts prepared by the ion-exchange method, using Azerbaijan natural cli-noptilolite (crystallinity, 84.0%) and the different metal cations. Modification of zeolites with metal cations was performed by treatment of their initial forms into a solution of chloride salts of the corresponding cations. Before ion exchange, the clinoptilolite was treated by 0.5 N HC1. The number of the cations incorporated into the clinoptilolite was determined by ICP-MS Agilent 7700 and it amounted to (0.1-2)% by weight of the clinoptilolite. The reaction was carried out at 360-400°C and atmospheric pressure. Before the reaction, the catalyst was activated in the air (15 mL/min) at 300°C for 3 h. For Clinoptilolite, the catalysts were typically reduced at 300°C for 2 h in a flow of H2 (10 mL/min). It was noted that H2 was required in this reaction to prevent coke accumulation. At reaction temperature (typically at 380°C), saturated vapour of cyclopentane (Aldrich, 99.5%) was carried by hydrogen (total flow of 15 mL/min) through a fixed bed U-shaped flow reactor made with a quartz tube (outside diameter D - 8 mm). We used the catalysts with particle size in (0.25-0.63) mm. The reactor is placed in an air electric oven with automatic temperature control. Cyclopentane vapours and air mixed with oxygen in the mixer located in a thermostat doven, enter the reactor for the catalysis. The temperature stability is maintained in the oven with a contact thermometer. The temperature in the middle of the catalyst bed is measured with a thermocouple and recorded with the potentiometer. The reaction unit is directly connected to the analysis system through six-way valve what allows the analysis of the reaction mixture without loss. The mixture exiting from the reactor gradually passes through the sample loop and is collected in the cooled
trap. The analyses of the product of the reactions were also performed by gas chromatography using GC "Agilent 7890" with "Agilent 5975" MS and capillary column HP-5MS (length=30 m).
Results and discussion
The obtained cyclopentadiene was determined by chromatography, IR spectroscopy and spectra are shown in Figures 1 and 2.
The selectivities and conversion in the fraction of cyclopentane molecules leading to a given product, are shown explicitly in Table 1. A reaction temperature of 380±20°C was used for
21 3+
the comparison of Cu , Zn , Co , Cr and another transition cations. From the table, we can see natural clinoptilolite and natural clinoptilolite with modified cations, Zn2+ (exp. 1, 2) show lower catalytic activity in the reaction. After we add natural clinoptilolite cations; Cr3+,
2+ 9+
Cu and Co is relatively higher than above mentioned ones (exp. 3-5). Combination of two cations in natural clinoptilolite; Cu2+, Cr3+ and Co , Cr
increase the efficiency of cyclopentadiene from oxidative dehydrogenation of cyclopentane reaction, (exp. 7, 8). When we add third cation Zn2+ in this catalytic system we saw that it causes a considerable increase in the yields of cyclopentadiene (exp. 12, 13).
Deep dehydrogenation is faster on Zn than on the other two metals. After examining more catalysts we have arrived at a conclusion that Cu2+, Cr3+, Co2+ and Zn2+ (exp. 19, 20), cations with modified clinoptilolite system show more catalytic activity and relatively Fe, Mn, Sn, Mo and Ni cations show lower catalytic activity in the reaction of oxidative dehydrogenation of cyclopentane (exp. 9-11, 16-18).
From the data of Table 1, it has been concluded that the natural clinoptilolite containing cations, mas %: Cu2+ - 0.5, Zn2+ - 0.2, Co2+ -
3+
0.1 and Cr -0.1
is the active catalyst for reaction of oxidative dehydrogenation of cyclopentane into cyclopenten and cyclopentadiene.
The activity of the zeolite catalysts in different reactions depends on; crystal structure, nature of cations, method of preparation and distribution of metal cations on a surface of the zeolite.
If'
VM
V-
r, i i f t 1
C 1
I
Jv
i -
i ; r '
■t---M----H
I I
S R 8H
s a
T T T-—h—
S3
H
Fig.l. Chromatography spectramofthe 1,3-cyclopentadiene.
(JtCSfO "AJ^I] Id ^JV
x>
91 № o < u> |
-xo
i a
B
i 0 S
a
s
_L
S
I
fi IS s 8 li i?
I i
a g
f' H x 1 1
R t'
a
Sj 4 B ill
1% * • *
e
Fig.2. Infrared spectrum of the 1,3-cyclopentadiene.
Table 1. The results of the activity of modified natural clinoptilolite (CL) catalyst in the reaction of oxidative dehydro-genationof cyclopentane (T= 380':'C, i = 2000 If'. C5H10:O2:N2= 2:1:3.7) _"
No Catalyst Conversion of C\H,0, x,% Selectivity s,% Yield, ,4, %
C5H8 C5H6 CO.
1 CL 8.2 7.3 7.5 0.6 0.1
2 CLZn (0.2*) 1.7 17.7 0.9 0.3 0.5
3 CLCr (0.1) 15.4 19.5 6.7 3.0 5.7
4 CLCu (0.5) 7.1 22.5 3.1 1.6 2.4
5 CLCo (0.1) 16.4 19.5 7.6 3.2 5.6
6 CLZnNi (0.2:0.2) 10.2 17.6 4.9 1.8 3.5
7 CLCuCr (0.5:0.1) 13.4 16.4 3.6 2.2 7.6
8 CLCoCr (0.1:0.1) 22.3 23.8 8.8 5.3 8.2
9 CLCuSn (0.5:0.5) 8.8 21.6 2.6 1.9 4.3
10 CLCuMn (0.5:0.5) 13.7 21.2 4.2 3.0 6.5
11 CLCuFe (0.5:0.5) 10.9 22.9 1.8 2.5 6.6
12 CLZnCoCr (0.2:0.1:0.1) 24.7 24.3 9.9 6.0 8.8
13 CLZnCuCr (0.2:0.5:0.1) 20.5 27.3 9.3 5.6 6.6
14 CLCuCoCr (0.5:0.1:0.1) 20.8 27.9 7.9 5.8 7.1
15 CLCuZnCo (0.5:0.2:0.1) 22.2 28.3 10.1 6.3 5.8
16 CLCoMnCu (0.1:0.1:0.5) 22 25 8.9 5.5 7.6
17 CLCoMnCr (0.1:0.5:0.1) 18.4 25.5 9.9 4.7 3.8
18 CLCoMnCr (0.1:0.1:0.1) 16.5 21.8 8.5 3.6 4.4
19 CLCuZnCoCr (0.5:0.2:0.1:0.1) 25.3 34.8 2.5 8.8 14.0
20 CLCuZnCoCr (2:2:1:0.5) 20.6 33.0 10.9 6.8 2.9
* - the Figures in brackets indicate the containing exchange cations in mas.%
The naturally occurring Heulandite-type zeolites, including heulandite (Heu) and clinoptilolite (CPT), are the most abundant minerals on earth, exhibiting a zeolite structure. Large, easily accessible surface deposits mainly of volcanoclastic origin, enables clinoptilolite low-cost production by simple excavation [3, 4]. The crystal structure shows the existence of three types of structural channels confined by ten- and eight-membered tetrahedral ring systems (Figure 1). From the crystal-chemistry point of view, alumosilicate framework possesses a negative charge that is equilibrated by cations located in the channels (simplified formula: ([Me+, Me2+, N,H20]6+[Al6Si3o072]6l. Detailed structural investigations on complete and partially ion-exchanged on Na, K, Rb, Cs, Cd, Ag, Mn. Cu, Pb, Sr, Er, La clinoptilolite have been carried out and summarizing the results some typical positions for cation placement in the channels have been assigned [5, 6]. However, no detailed single crystal structural studies for Zn ion-exchanged clinoptilolite (ZnCL) have been undertaken. The studies conducted by us revealed that CL tolerates li-
mited to complete Zn ion-exchange. The ion-exchange and reduction processes for Co reduction mechanism is complex, indirect and sensitive to reduction temperature; consequently, Co,, states intermediate between Co" and
Co should be present in the reduced samples. We know from the literature a crystal lattice of clinoptilolite consist of three open channels; A, B and C. In Figure 3 the polyhedron model of clinoptilolite, has a fragment of the structure with exchange cations is shown. A and B channels are parallel to axis, C and consist of tencyclic and octocyclic rings.
с с с
Fig.3. Polyhedron model of clinoptilolite reflected of structure with exchange cations.
They cross with the third octocyclic channel parallel to the, a. Hexagonal planers in the structure of clinoptilolite are surrounded by channels A, B and C in which the exchange cations are localized. A planar molecule of cyclo-pentane is pentagonal planers surrounded exchange cations in the structure of clinoptilolite.
In clinoptilolite there are four types of places in the localization of exchange cations; they are Mi in channel A, M2 in channel B, M3 in C arranged along axis of a near center of the hexacyclic ring and M4 - place arranged in channel A in center of inversion. Their quantity is not great. M3 is arranged near Mi [7, 8].
A role of components of the catalytic system in the reaction of oxidative dehydrogena-tion of cyclopentane can be explained by analysis of surrounding of the adsorbed molecules of cyclopentane with the exchange cations bonded with dissociative adsorbed oxygen, taking into account their bonding energies which can be found by expression [9].
% = "(^ads + 500),
where 500 kJ/mole - energy of dissociation of molecule oxygen, qilL\s - heat of adsorption of oxygen the pure surfaces of the polycrystal specimens of transient metals, qads, kJ/mole for [10]; Cu=478 Zn=240, Co=418, Cr=753. Bonding energies of the components of catalyst with oxygen can be calculated by using cited above formula; c/0(Cu)=489 kJ/mole, c/0(Zn)=370 kJ/g-atom, <7o(Co)=459 kJ/g-atom, <y0(Cr)=612 kJ/g-atom.
The maximum propellant force of hydrogen atoms of cyclopentane is indicated by the oxygen atoms bonded with the component of the catalyst.
The source of the cyclopentane oxidative decomposition reaction products depends on the amounts and the concentration of effective centres for the reaction and the combination of ion exchange cations. On obtaining 1,3-cyclopen-tadien the optimum succession incorporating of cation in clinoptilolite is Cu2+ (0.5 mas %) —»■ Zn2+ (0.2 mas % ) -> Co2+ (0.2 mas %) -> Cr3+ (0.2 mas %) —► CL. From experimental data it
was confirmed that the kinetic scheme of the considered reactions over the active catalytic system does not proceed on a consecutive mechanism. As well from these experimental data, it can be concluded that on the surface of the catalyst there are different active centres obtained, which are responsible for the formation of the products of the reaction. The mechanism of oxidative dehydrogenation cyclopentane on above mentioned active centres may be presented as following stage scheme:
02+2Zr 02+2Z2
K
■>2ZjO|l/2|
^—> 2Z20 |l/2| (Z,0 + Z20) + C5H10 —^->(Z,0 + Z20) C5H
10
(Z,0 + Z20) C5H10 —^C5H6 + 2H20 + Z, +Z2 C5H10 + O2=C5H6+2H2O
The following expression can be written for rates of the stages:
r4=k4e4.
r2 ^2^2-^Q, '
e1+e2+e3+e4 =\.
f% - IC-yQ-yfr
C,H,n J
\k P
v 3 2 vk^
64 =
where 9i, 02, 63 and 64 are fractions of catalyst surface; the sites with two near arranged adsorbed atom oxygen on different exchange cations and the sites with adsorbed molecules of cyclopentane.
In stationary conditions
r = rl=r2=ri=rA.
k P
3 C5H'° 63+63 +
<767-1=0.
\hPr
'3 C,H,,
\hPr
'3 C,Hlr
k1 P,
y
Assuming:
(
3 C5H10 _ J^
\k P
,K3rc5uK
KPo,
\k P
IK3rC5Uu
= B.
03=x2, yj%=x, Ax2+Bx-1 = 0.
We'll receive:
-B±«JB2 + 4A ~2A '
r-B±slB2+4A ^2
03=x2 =
2 A
J
Then the equation of rate of the formation 1,3-cyclopentadiene appears as:
f -B±^B2+4A V
r = rl = к P
' 'c5H6 C5HK
2A
(1)
f (
v — it — и
4H6 3 5 10
/ к P K3rc5Kw kp
[i KPo2 i
к P
/Vo-i f^ TT
2 J 5 10
V
к P
hPo2 V
к P
"з^СзНю
к P
Ло-i f^ TT _ ^ J ^5-H-lO
к P
Ло-i f^ TT
Q J ^5-H-lO
(2)
Stage scheme of oxidative dehydrogena-tion of cyclopentane into cyclopentene may be presented as
02 + 2Z6 2Z60 + C5H10
Z6OC5H10
->2Z60|l/2
к
k7
>Z6OC5H10|1| ->C5H8+H20 + Z6|l|
C5H10+^O2=C5H8+H2O
The following expression can be written for rates of the stages:
rs = , r6 = k6Q6PC Bs, r7 = k7Q7.
Here 05,06,07 are fractions of catalyst
surface; sites with the ability to adsorb atom oxygen sites with atom oxygen and sites adsorbed molecules of cyclopentane. In stationary conditions
r = r5=r6=r7
05 +06 +07 =l,
A _ ^6^c5H8 А л _
f-7 —-D- —
7 ' 6 5 ML
k^R,
-06 +06 +
Assuming:
к P Ik P
-— + 1 = С,
= x.
We'll obtain
cx2 +ifc-l = 0,
Г
06=x2 =
-d + лId2 + 4 с
2c
Then equation of formation rate of cyclopentene appears as
r гс5н8 ^б0з^с5н1О
r = rl =k P
C5H8 6 C5H10
-d + 4d2 + 4c
2c
,(3)
£ P
б C5HK
к, I ]
■6 c5Hlt
+1
6 C5H10 2
6 C5H10 2
V
(4)
Results of experimental investigation of kinetic regularities of the reaction of oxidative dehydrogenation of cyclopentane over metal-clinoptilolite catalyst CL-CuCrCoZn are given in Table 2. Kinetic tests were performed in the temperature range of 350-390°C, at a space velocity of 500-2500 h"1, partial pressure of reagents PrH = 0.273-0.5641 atm, Pn = 0.0768-0.1540
5 10 ' °2
atm, Gcat =1.78 g, KM =3 cm3.
Table 2. The results of kinetic runs
Partial pressure of reagents, atm Moles of substance, mol/h Moles of substance, mol/h Moles of substance, mol/h Space velocity, v, h"1 Temperature, T, °C Conversion, X,% Yields of products of reaction, A, %
p CSH10 Po2 n° C5H10 «0 < Al (C5H8) A2 (C5H6) A3 (C02)
0.2738 0.1540 0.0654 0.0368 0.1367 2000 320 6.6 1.8 3.9 0.9
0.2738 0.1540 0.0654 0.0368 0.1367 2000 340 8.2 0.7 5.1 2.4
0.2738 0.1540 0.0654 0.0368 0.1367 2000 360 11.9 3.2 5.5 3.2
0.2738 0.1540 0.0654 0.0368 0.1367 2000 380 13.6 3.7 6.3 3.6
0.2738 0.1540 0.0654 0.0368 0.1367 2000 390 25.3 2.5 8.8 14.0
0.2980 0.1489 0.0368 0.0184 0.0683 1000 320 19.8 14.7 3.2 1.9
0.2980 0.1489 0.0368 0.0184 0.0683 1000 400 11.7 2.1 7.0 2.6
0.2980 0.1489 0.0368 0.0184 0.0683 1000 350 11.0 1.1 3.3 6.6
0.2980 0.1489 0.0368 0.0184 0.0683 1000 370 12.3 2.8 5.1 4.4
0.2980 0.1489 0.0368 0.0184 0.0683 1000 390 13.4 3.8 6.6 3.0
0.2980 0.1489 0.0368 0.0184 0.0683 1000 380 9.4 2.5 5.7 1.2
0.3225 0.0768 0.0189 0.0045 0.0352 500 390 14.8 0.8 5.6 8.4
0.5641 0.1491 0.0841 0.0421 0.1561 2500 370 13.1 6.6 4.9 1.6
0.5641 0.1491 0.0841 0.0421 0.1561 2500 390 15.4 15.4 7.3 3.1
1 2 3
Г = r +r +Г
'со, 'со, ^ 'со, 'со,
Assuming that carbon dioxide is formed as a result of interaction of adsorbed molecules; cyclopentane, cyclopentene and cyclopentadi-
ene with adsorbed molecules of oxygen it can ... ..... ,
u , i r- ,, • , • the adsorption equilibrium constant, k, - the re-
be written the following kinetic equations cor- J ^ ^
responding to these mechanisms.
(11) (12)
'со,
KKA
r2 =
'CO,
r =
'со,
(l + KXPX + ^К+ КЪРЪ + K4P4 + К5Р5 ) __
(l + кхрх + + КЪРЪ + К4Р4 + К5Р5 )2
(i+Кхрх+ + Къръ + К4р4 + К5р5 )
_ 1 2
СгНо СгНо со,
1 з г = г —Г
' г^ и ' г^ и 'г
С5Н6 С5Н6
со2 '
,(5) ,(6)
,(7)
(8) (9)
(10)
Equations (8)—(10) make up the kinetic model of the considered reaction, where Ki -
action rate constant.
i Ql\
Kt=Kf-eRr
E
k, = k" • e liT .
We can show the rate of formation of carbon dioxide can be represented by the following differential equation: d4
9 cL4-y -> cL4>
'CO, q 5 'CO, r i ■> 'CO.
d—— n°
d—
n°
C<H,„
f
d—^ n°
ОДл
(13)
= KP
V
k P
d^
n,
11 г
k P
б с5н10 ^7<> у
f k P
f k P
V
kgK^P^
(1+ад + Jkë+ад + ад + ад )2 '
(14)
kP
Q ^з1 C,H,r
/ k P 3 с5н10 ! kP 3 C5H10 f k P 3 с5н10 kP 3 C5H10
N k2PQ2 j W N KPo2 i КР02 /
k P
. 4 3 C5H1CI
k P
2 3 С5Н10
k10K4P4
(l + ад + ^ад + K3P3 + K4P4 + K5P5 )
(15)
<LI
ksKxPx
k9K3P3
G„
d^*. (1+kxpx+Jkj2+k3p3+k4p4+k5p5) (i+kxpx+Jkj2+k3p3+k4p4+k5p5)
K0K4P4
(l + KXPX+^P2+K3P3+K4P4+K5P5)2 '
The suitable stoichiometric equations for forming of the reaction products are
1) C5Hio+f02=C5H8+H20,
2) C5HIO+02=C5H6+2H20,
3) C5H10+7.5O2=5CO2+5H2O,
4) C5H8+702=5C02+4H20,
5) C5H6+6.502=5C02+3H20.
By using these equations, the reaction yield and the initial molar amounts of the reac-tants we can determine the current velocity in the molar flow of cyclopentane, cyclopentene, cyclopentadiene, carbon dioxide, oxygen and water accordingly by the following equations:
■VH -(4wrn +Ancw + AjB. o yioo
Lstlm ^ 1 L,H1n 1 L,H1n 1 L,H1n f
CA
= At\
C5HI0
/100
C^LLin
"co2 =5M°5h/00
%o =(4"c,Hin +H«c(Hin +54«°)/! 00
,(17)
The partial pressure of the reactants expressed by the equation:
P. =
ti.
p.
(18)
Here Ai, Ai, A3 - yield of cyclopentene, cyclopentadiene and carbon dioxide respectively. P\, Pi, P% P4, P5 ~ partial pressure of cyclopentane, oxygen, cyclopentene, cyclopentadiene and water, accordingly.
A kinetic model of the reaction subjected to statistical analysis on the basis of kinetic data. Calculation of pre-exponential factors of the reaction constants, activation energies and heats of adsorption conducted by methods of "rolling admission" and Pauelusing software system "Search" [11], where the objective function has the form:
/,=minZZ
H >'='
^exp _
AQxp
(19)
-the experimental and calculated values of outputs 7-th component in the /-experiment, m - the number of experiments, n -the number of components.
Numerical values of the constants of a kinetic model presented in the Table 3. Calculations showed that the relative error of experimental and calculated data did not exceed 10-15%.
Table 3. The kinetic parameters of kinetic models
For kinetic model of reaction of oxidative dehydrogenation of cyclopentane
in /if (in k;) Ej(07), kcal/mole
In k° 53.89 Et 20.62
111 k° 86.76 e2 19.76
In k° 3.62 E3 23.48
hi k\ 20.81 e4 20.56
ln/f° 61.88 e5 19.88
in a:,0 -16.43 Ol 5.05
in a:,0 -49.30 Q2 4.50
in k; -21.34 Qs 7.25
\nKl -61.23 04 10.0
In Kt -33.49 05 2.26
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TSiKLOPENTANIN 1,3-TSiKLOPENTADiENO SELEKTIV OKSiDLO§DiRiCi DEHiDROGENLO§MOSi REAKSiYASININ MEXANiZM VO KINETIKASININ IMODiFIKASIYA OLUNMU§ SEOLiT KATALiZATORU ÜZORINDO ÖYRONiLMOSi
A.M.01iyev, M.Y.Abbasov, Z.A.§abanova, G.O.Olizada, M.F.Bohmonov, U.M.Nacaf-Quliyev, T.i.Hüseynova
Tsiklopentanin 380uC-do HY scolitlor ii/orindo reaksiyasi ovronilmisdir. Osas xammalin dcliidrogcnlosmosinin ilkin morholosindo davamli tsiklopenten vo tsiklopentadien molekulu этэ1э golmisdir. lakin osas mohsul kimi molekulyar hidrogcno rast golinmomisdir. Klinoptilolitin katalitik aktivliyi tsiklopentandan tsikllopentadienin alinmasi istiqamotindo tocriibi olaraq ovronilmis vo bir ncco temperaturda no/ori olaraq modcllosdirilmisdir. Мйэууэп olunmusdur ki, klinoptilolt bu kationlarla {Cu2+ (0.5 küt.%), Zn2+ (0.2 küt.%), Co 2+ (0.1 küt.%), Cr 3+(0.1 küt.%) va CL{Co2+ (0.5 küt.%)} daha дох katalitik aktivlik göstorir va bu katalizatorlar ion-miibadilosi üsulu ilo lia/irlanmisdir. No/ori hesablamalar ho mein in sübut etdi ki, bu reaksiyalar qeyri-sinxron, voni ardicil olamayan sokildo gedir. Tocriibi molumatlarda katalizatorun torkib hissolorini ohato cdon aktiv morko/lorin qniplasdirildigi vo kationlorin dissosiativ adsorbsiyali oksigen ilo birlosmosini to mi n cdon rabito cncrjilori пэгэгэ alinmaqla reaksiya yollanmn tasvir olundugu bildirilir. Eneiji bancrlori vo katali/o olunan sistcmlorin elektron qimilusla olaqoli siirot sabitlori va ikili saviyyali varyasyon kccid no/oriwosi hesablamanin kömayi ilo doqiqliklo modcllosdirilmisdir.
Agar sözfor: klinoptilolit, tsiklopentan, katalitik dehidrogenh§m3, tsiklopenten, tsiklopentadien-1,3.
ИЗУЧЕНИЕ КИНЕТИКИ И МЕХАНИЗМА РЕАКЦИИ СЕЛЕКТИВНОГО ОКИСЛИТЕЛЬНОГО ДЕГИДРИРОВАНИЯ ЦИКЛОПЕНТАНА В ЦИКЛОПЕНТАДИЕН-1,3 НА МОДИФИЦИРОВАННОМ
ЦЕОЛИТНОМ КАТАЛИЗАТОРЕ
А.М.Алиев, М.Я.Аббасов, З.А.Шабанова, Г.А.Ализаде, М.Ф.Бахманов, У.М.Наджаф-Гулиев,
Т.И.Гусейнова
Реакция окислительного дегидрирования циклопентана издалась на цеолите HY при 380°С. Циклопентен и циклопентадиен образуются в виде стабильного исходного продукта путем дегидрирования сырья, хотя молекулярный водород не был обнаружен в качестве первичного продукта. Каталитическая активность клиноптилолита в реакции селективного окислительного дегидрирования циклопентана в циклопентадиен-1,3 была измерена экспериментально и теоретически смоделирована при нескольких температурах. Выяснено, что клиноптилолит, модифицированный катионами {Си2+ (0.5 мае. %), Zn2+ (0.2 мас.%), Со2+ (0.1 мас.%), Cr1 (0.1 мас.%) и CL{Co2+ (0.5 мас.%)}, показывает наибольшую активность. Катализатор получали ионообменным методом. Теоретический расчет показал, что катализируемые реакции протекали не синхронно и не последовательно. Экспериментальные данные выявили, что активные центры катализатора сгруппированы. Описаны пути реакции с учетом энергии связи, которые обмениваются катионами в сочетании с диссоциативным адсорбированным кислородом. Энергетические барьеры и константы скорости катализируемых систем были точно моделированы коррелированной электронной структурой и двухуровневым изменением теории состояния вариационного перехода. Ключевые слова: клиноптилолит, циклопентан, каталитическое дегидрирование, циклопентен, циклопентадиен-1,3.
