ISSN 0104-6632 Printed in Brazil
www.abeq.org.br/bjche
Vol. 33, No. 04, pp. 957 - 967, October - December, 2016 dx.doi.org/10.1590/0104-6632.20160334s20150333
*To whom correspondence should be addressed
Brazilian Journal
of Chemical
Engineering
SYNTHESIS OF CUMENE BY
TRANSALKYLATION OVER MODIFIED BETA
ZEOLITE: A KINETIC STUDY
R. Thakur, S. Barman
*and R. Kumar Gupta
Department of Chemical Engineering, Thapar University, Patiala-147004, Punjab, India. Phone: + 91-175-2393437; Fax: + 91-175-239300
E-mail: [email protected]
(Submitted: May 26, 2015 ; Revised: September 25, 2015 ; Accepted: October 29, 2015)
Abstract - In the present study, transalkylation of 1,4-diispropylbenzene (DIPB) with benzene in the presence of modified beta zeolite was performed to produce cumene in a fixed bed reactor. Beta zeolite was exchanged with cerium in order to modify its catalytic activity. Activity of the modified catalyst was evaluated in the range of temperature 493K–593K, space time 4.2 kg h/kmol–9.03 kg h/k mol and benzene/1,4-DIPB molar ratio 1–15 to maximize the reactant conversion and selectivity of cumene. The activity and selectivity of the modified catalyst was found to increase with increase in cerium loading. Maximum selectivity of cumene (83.82%) was achieved at 573 K, benzene/1,4-DIPB 5:1 at one atmosphere pressure. A suitable kinetic model for this reaction was proposed from the product distribution pattern following the Langmuir–Hinshelwood approach. Applying non-linear regression, the model parameters were estimated. The activation energy for the transalkylation reaction was found to be 116.53 kJ/mol.
Keywords: Cerium; Beta zeolite; Kinetic study; Transalkylation; DIPB; Benzene.
INTRODUCTION
Cumene is a colorless liquid, also known as cumol or isopropyl benzene having the boiling-range motor fuel of high antiknock value. It is of industrial demand for the production of high molecular weight hydrocarbons such as cymene and polyalkylated benzene. The main end uses for cumene are for the production of phenolic resins, bisphenol A, and ca-prolactam. However, 5-10 wt% diisopropylbenzene (DIPB) isomers are produced as low value byproduct during the isopropylation of benzene to cumene (Leu
et al., 1990; Sridevi et al., 2001; Reddy et al., 1993). The by-products, DIPB isomers, can be recycled for cumene production, making this process more eco-nomical. With the liquid catalysts, there are inherent problems of product separation, recycling and corro-siveness (Maity and Pradhan, 2006; Barman et al.,
958 R. Thakur, S. Barman and R. Kumar Gupta
Brazilian Journal of Chemical Engineering
out by introducing the feed to a transalkylating zone over beta zeolite/alumina and then feeding to an alkylating zone where MCM-22/alumina catalyst was used (Collins et al., 1999). Transalkylation of DIPB has also been carried out over large pore zeolites, which proved to be very active catalysts (Pradhan and Rao, 1993). In another process, DIPBs were recycled for transalkylation in the reactor containing a single catalyst bed of beta catalyst. The combined alkyla-tion and transalkylaalkyla-tion was performed for alkyl aromatic production to evaluate the performance of different catalysts like MCM-22 and beta zeolite based on their Si/Al ratio, selectivity, and pore size for liquid phase production of cumene (Perego and Ingallina, 2004). The catalysts such as zeolite X, MCM-22, MCM-49, PSH-3, SSZ-25, zeolite Y, beta zeolite (Yeh et al., 2008; Barger et al., 1989; Huang
et al., 1997) were used in transalkylation reaction. These studies show that choice of catalyst, its Si/Al ratio and the acidity of the catalyst highly affect the process.
Kinetics of transalkylation of diisopropylbenzene were studied over Ca modified YH zeolite catalyst which proved to be a good active catalyst (Grigore et al., 2001). Cumene synthesis over beta zeolite has been reported in the literature (Bellussi et al., 1995; Perego et al., 1996; Smirnov et al., 1997; Halgeri and Das, 1999). Therefore, further investigation was necessary to carry out transalkylation of DIPB with benzene over the modified beta zeolite to obtain higher cumene selectivity and reactant conversion. Replacement of sodium ions in zeolites with polyva-lent cations like rare earth metals (La, Ce, etc.) has been reported to produce materials of superior cata-lytic activity (Venuto et al., 1966; Rabo et al., 1968; Hunter and Scherzer, 1971). However, very scarce literature is available on the use of rare earth metal modified beta zeolite for cumene synthesis. It was, therefore, thought desirable to investigate the ki-netics of this commercially important reaction over zeolite H-beta modified by exchanging H+ ions with cerium ions. A further objective of this study was to develop a suitable kinetic model for the synthesis reactions.
MATERIALS AND METHODS
Materials
Beta zeolite, 1.5 mm extrudates, used in the pre-sent study, was obtained from Sud chemie, Vadodra, India. Ceric ammonium nitrate (99% pure) was pro-cured from CDH chemicals, India. Benzene and
1,4-DIPB of analytical reagent grade ((>99% pure) were obtained from Sigma Aldrich Pvt. Ltd., India. Nitro-gen gas (grade –I, 99.999% pure) was obtained from Sigma gases and services (India).
Catalyst Preparation
The commercially available H-beta zeolite con-taining H+ ions was modified with Ce4+ ions. At first, the zeolite extrudates were calcined for 3 h at 623 K. Calcined zeolite was then refluxed with the required percentage of ceric ammonium nitrate solution at 363 K for 24 h, thereby modifying H-beta zeolite into the Ce-beta form. The catalyst particles were then filtered and washed several times with deion-ized water and then dried at 393 K for 14 h. Finally, they were calcined for 4 h at 723 K to remove the ex-cess ions.The cerium-exchanged zeolite was charac-terized by TPD, XRD and FTIR. Beta zeolite treated with 4%, 6%, 8%, and 10% cerium ammonium ni-trate solution (CeB4, CeB6, CeB8, and CeB10) was used for the present study.
Determination of Cerium in the Exchanged Cata-lysts
The amount of cerium ions exchanged with the H+ ions was calculated analytically (Krishnan et al., 2002). Freshly calcinedcerium modified beta zeolite was taken in a flask and digested for 1 h in concen-trated HCl. The digested catalyst was diluted with distilled water and filtered. The filtrate was trans-ferred to a beaker and its volume was made up to about 250 ml by adding distilled water. 50 ml of saturated oxalic acid solution was mixed with this solution, which produced a white precipitate of ce-rium oxalate. The precipitate was then filtered using a Whatman no.40 ashless filter paper and washed with distilled water. The filter paper was ignited in a previously weighed silica crucible at 1173±10 K to a constant weight. On heating, cerium oxalate was converted to cerium oxide. From the weight of ce-rium oxide the percentage of cece-rium was then calcu-lated. CeB4, CeB6, CeB8 and CeB10 were found to have been loaded with 2.87%, 4.46 wt%, 6.64 wt% and 8.34 wt% of cerium respectively.
Experimental Setup for Transalkylation Reactions
Synthesis of Cumene by Transalkylation Over Modified Beta Zeolite: A Kinetic Study 959
Brazilian Journal of Chemical Engineering Vol. 33, No. 04, pp. 957 - 967, October - December, 2016
in the downstream. A thermowell extending from the top of the reactor to the centre of the bed was used to measure the temperature of the reactor. Typically, 0.002 kg of the catalyst supported on a wire mesh was loaded into the reactor. Before conducting the experiments, catalyst activation was done at a tem-perature 100 K higher than the reaction temtem-perature (maintained according to reaction conditions), for 3 h under the atmosphere of nitrogen. A dosing pump was used to introduce the reactant feed mixture into the reactor. Nitrogen gas was flown through the reac-tor at the rate of 0.565 L/h to activate the catalyst before experimental runs. However during all experi-mental runs, the nitrogen to feed flow rate ratio was kept constant at 0.2. The reactants were vaporized in the preheater, which is maintained at a temperature 30 K lower than the reaction temperature. The vapor-ised reactant feed mixture passes through the catalyst bed in the reactor at proper reaction conditions. The
product vapors, along with the unreacted reactants, were condensed in the condenser (277 K-279 K). The samples were collected and analyzed in a gas chromatograph (Bruker, Model: 436 GC Scion) using a fused silica capillary column having 10 m × 0.53 mm × 1.5 µm dimensions. The sample was introduced through a micro syringe into the injector port of the GC. The temperature of the injector was set at 493 K during the analyses. The column temperature was initially set at 323K, and then increased to 523 K at a rate of 10 K/min. The flow rate of carrier gas (nitro-gen) was maintained at 1.5 L/h. A Flame Ionisation Detector was used at 553 K to detect the products. Peaks were identified by retention time matching with known standards. Various products like aliphatics (propene), benzene, toluene, xylene (C8), cumene, cymene (C10), isomers of DIPB were found. The selectivity of cumene, 1,3 DIPB and conversion of 1,4 DIPB were calculated as:
(1,4 DIPB in feed 1,4 DIPB in exit)
1,4 DIPB conversion 100
(1,4 DIPB in feed)
−
= ×
(Cumene in product mixture)
Cumene selectivity 100
(aromatics in product excluding 1, 4 DIPB and benzene)
= ×
(
)
(
1,3 DIPB in product mixture)
1,3 DIPB selectivity 100
aromatics in product excluding 1, 4 DIPB and benzene
= ×
The mechanism of transalkylation of 1,4 DIPB with benzene is shown in Figure 1.
Figure 1: Mechanism of transalkylation of 1,4-DIPB with benzene.
+
H
+ Zeol
+
+ H +
H Zeol CH3
H3C
CH3 H3C
CH3
CH3
CH3 H3C
+
H
+
CH3
CH3
CH3 H3C
+
CH3 H3C
C
H
CH3
CH3
H
+
CH3
H3C
CH3
H3C H3C CH3
96 C li S v (2 w p g m sa an o in C fo te tu ca st sa 1 T F p p w w p w sc ch T ar fr ex in a a ta ex w lo d ob th p H p 60 RE Characteriza The powd ite samples w
cattering D alue in the ra 2θ) per min with a Ni-filt reparation f rinding of t mately 0.1-0. ample holder nd tight. Am f the parent n a CHEM-B Catalyst samp
or 1 h with n emperature. ure, was then
atalyst samp tate was atta ample was r 0 K/min. Th Thermal Con FTIR were do
hotometer in les were ana was first grou with KBr salt
owder, whic was then plac
cans were tak Both modi haracterized Typical diffra re observed ramework st xchange. Th ntensity refle typical char
l., 2014). Th al structure o xchange. Th was measured oading of me iffraction lin bserved as a he H+ ions ( ersed in the However, on eaks of meta
ESULTS AND
ation of the M
er X-ray diff were recorde Diffractomete ange of 50-6 nute. The di tered Cu K-for the X-ray the solid int
.2 g of the r with light mmonia Temp and modifie BET 3000 in ple (0.1 g) w nitrogen foll Nitrogen-am n passed thro ple was heate ained; therea raised up to he desorbed a nductivity De one using an n the range alysed by pre und thoroug t and again g ch was then p ced in the F ken for each ified and unm
by XRD an action charac d for both t
tructure is w e CeB10 diffr ection at 2θ = racteristic pe his phenome of beta zeolit he crystallini d from the in etal ions into nes correspon at low loadin (Tang et al., zeolite fram increasing th al oxides pre
D DISCUSS
Modified Ca
ffraction patte d on a Bruke er D8, Germ
00 at a scann ffractometer
α radiation y analysis i o a fine pow sample was compression perature Prog ed catalysts w
nstrument (Q was first deg
lowed by co mmonia gas ough the sam ed to 372 K after the tem 1173 K at a ammonia wa etector analy n Agilant Ca
400 cm-1-40 eparing KBr ghly and then
ground well pressed to m FTIR sample
sample. modified bet nd are shown
cteristics of the zeolites well preserve fractograms e
= 7.80 and 2 ak of beta ze non indicate e was not ch ity of the m ntensity of th o the zeolite nding to met ng, the ceriu 2014) and ework (Garc he metal load esent on the
R. Thakur, S
Brazilian Jou
SION
atalyst
erns of the z er Angle X-R many with ning speed of was equipp source. Sam involved gen
wder. Appro taken into n to make it gram Desorpt were perform Quantachrom gassed at 723 ooling to 273 (1 mol%) m mple for 1 h. T until the stea mperature of
heating rate as detected b yzer. Studies ry-660 spect 000 cm-1. Sa pellets. Sam n it was mix
to make a f make a pellet e holder and
ta zeolites w n in the Fig BEA topolo
indicating ed after ceri exhibited a h 210-220 which
eolite (Zhang es that the cr hanged by me modified sam
e peaks. At l framework, tal species w um ions repl are highly d cia et al., 201 ding, additio catalyst surf
S. Barman and R.
urnal of Chemica
zeo-Ray
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. Kumar Gupta
al Engineering
pear in the X min and Ang gh loading o lated to ceriu und in zeolit milar observ rium (16 w Wang and Zou
gure 2: XR olite.
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H-beta zeoli e case of Ce-the higher t e presence o
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XRD pattern ggoro, 2003 of cerium (1 um oxide (2θ te XRD patt vation was re t%) into the u, 2003).
RD of beta a
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and cerium
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orption peak mperatures w rman et al., 2 sites also inc Ce exchange that cerium e antity and s kur et al., 20 f H–beta zeo that of cerium
d Amin, 200
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2005). More creases as th e. Thus, it ca exchange lea
trength of th 14; Wang an lite was foun m beta zeoli
F ze b b 1 cm at T (K 4 b O O ca sh ab th o h b v ar g af o A b st sh m v d w th in
Figure 3: Am eolites.
The FTIR eta zeolite ar eta and CeB 650 cm−1 re m−1 region. B t 460, 520, 7 The peak at 5
Kiri et al., 1 60, 785, 106 ending mode O-T-O interna O-T-O extern
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Activity of Ca
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Syn
Brazilian
mmonia-TPD
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exchange pr e.
atalyst in the
ty of Ce-beta were tested
3 K and atm maximum o tained over C 09% after 3.5
vation of ze the catalyst y of cumene ontent of zeo
nthesis of Cumen
Journal of Chem
D profile of
H-beta and cer Fig. 4. The I ow major ba dditional ban
shows bands 1212, 1625 a characteristic major charact cm−1 are attr ternal symme ric stretching tric stretch, r
beta zeolite ak positions. number 553
et al., 2009). ied zeolite a ds observed m−1 are due to
oups, and tho les, respectiv mework rem
ocess and ce
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a zeolites an for a 3.5 h mospheric p of 83.82% se CeB10, which 5 h on stream
olite by form t surface. It i e decreases w
olite and wa
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mical Engineering
f different b
rium exchang IR spectra of ands in the 45 nds at the 34 s approximat and 3440 cm c of beta zeo teristic bands ributed to a T etric stretch a g vibrations a respectively. e all the pe The additio cm-1 represe . The intensit are greatly
in the case o the stretch ose at 1635 cm
vely. This su mains unaffec
erium exchan
lation Reacti
nd the parent time period pressure. Fig electivity of h decreases t m. This may mation of co is observed t with a decre as found to
ation Over Modifi
g Vol. 33, No. 04,
beta ged f H-50– 450 tely m−1. olite s at T-O and and . In aks onal ents ties of hing
m−1 ug-cted nge ion t H-on g. 5 cu-to a y be oke, that ease be 81 res (73 Fig zeo Fig on per tim lys Ef Pr sho 59 per an thi du tem DI 57
fied Beta Zeolite:
, pp. 957 - 967,
.33% and 7 spectively. S 3.23%) in the
gure 4: FTIR olites.
gure 5: Cum n-stream. Rea
rature = 573 me = 9.03 kg
st amount = 0
ffect of Tem roduct Selec
The effect o own in Fig. 3 K over Ce rature, the c d reaches a m is temperatur ue to the form The produ mperatures is IPB was ma
3 K and the
A Kinetic Study
October - Decem
77.87% over Selectivity of e case of unm
R of H-beta
mene selectiv ction Conditi 3 K, benzen g h/ kmol, N
0.002 kg.
mperature on tivity
of temperatur 6 in the tem eB10 catalyst. cumene selec maximum (83 re the cumen mation of the
ct distributi s shown in T aximum (94.
en decreased
mber, 2016
r CeB8 and f cumene be modified bet
and Cerium
vity as a fun tions: Pressur ne/1,4-DIPB N2 to feed rat
n DIPB Co
re on produc mperature ran
. With the in ctivity increa 3.82%) at 57 ne selectivity
side product ion at diffe Table 1. The 69%) at a t d to 85.12%
9
CeB6 zeolite ecomes lowe ta zeolite.
modified be
nction of tim re =1 atm, tem
= 5:1, spa io = 0.2, cat
onversion an
ct selectivity nge of 493 K ncrease in tem ases gradual 73 K but abov
y is decrease t xylene. erent reactio
conversion temperature
at 613 K. A
96
h to o
F
it 1 N ly
T p
R s m
E P
D p F o ra 1 cu
62
igher temper o deactivatio n the catalys
Figure 6: Eff ty (Reaction ,4-DIPB rati N2 to feed rat yst (CeB10) a
Table 1: Pro eratures.
Product distribution (wt%) Aliphatics Benzene Toluene Xylene Cumene n-PB C10 1,3-DIPB 1,4-DIPB Cumene yield (%) 1,4-DIPB conv(wt%)
Reaction Conditio space time = 9.03 min, catalyst (CeB
Effect of Be Product Sele
In the tran DIPB ratio wa
erature of 57 Fig. 7 shows f cumene w atio of 5:1, ,4-DIPB see umene select
rature the de on of the cat
st surface.
fect of tempe Conditions: io = 5:1, spa tio = 0.2, tim amount = 0.0
oduct distri
T 493 513 0.76 0.79 67.15 67.07
0.12 0.20 0.17 0.23 2.96 10.60 0.29 0.35 1.39 2.41 6.10 5.89 21.06 12.46
2.96 10.60
29.01 51.69
ons: Pressure =1 kg h/ kmol, N2 to
B10) amount =0.0
enzene to 1 ctivity
nsalkylation r as varied fro 73 K and spa
that the max was obtained beyond this ems to increa
tivity was ob
ecrease in co alyst by dep
erature on pr Pressure =1 ace time = 9. me on stream
002 kg).
ibution at
Temperature ( 533 553 0.72 0.40 66.91 63.27 0.22 0.30 0.31 0.74 15.03 20.18 0.41 0.50 5.31 5.16 5.72 5.66 5.40 3.79 15.03 20.18
81.78 87.20
1 atm, benzene/1 o feed ratio = 0.2
02 kg.
1,4-DIPB M
reaction, the m 1 to 15 at ace time of 9
ximum selec at a benzen ratio, the is ase and henc bserved.
R. Thakur, S
Brazilian Jou
onversion is d position of co
roduct select 1 atm, benze 03 kg h/ k m
= 30 min, ca
different te
(K)
573 59 0 0.07 0.0
7 47.21 56. 0 0.35 0.6 4 1.14 1.5 8 42.94 32.5 0 0.58 1.5 6 0.97 0.5 6 5.17 3.3 9 1.57 3.3 8 42.94 32.5
0 94.69 88.
,4-DIPB ratio = , time on stream
Mole Ratio
benzene to a reaction te 9.03 kg h/k m ctivity (83.82
ne to 1,4-DI somerisation ce a decrease
S. Barman and R.
urnal of Chemica
due oke
tiv-ene/ mol,
ata-
em-93 03 .40 69 55 54 56 53 33 37 54
.63
5:1, = 30
on
1,4 em-mol.
2%) IPB n of
e in
Fig
sel tem N2 lys
Ef Co
of sel rea 9.0 tan cat the an fun
Fig
(R = rat am
. Kumar Gupta
al Engineering
gure 7: Effe lectivity (Re mperature = 2 to feed ratio st (CeB10) am
ffect of Spac onversion of
The effect o 4.21 kg h/k lectivity incr ached its ma 03 kg h/kmo nts to remain
talyst surfac e transalkyla
d disproport nction of spa
gure 8: Effe Reaction Con 573 K, benz tio = 0.2, tim mount = 0.002
ect of reacta eaction Cond
573 K, spac o = 0.2, time mount = 0.00
e Time on S f 1,4 DIPB
of space-time k mol–9.03 reased with i aximum of 8 l. Higher con n in the vicin e for longer ation reaction
tionation. Se ace time is sh
ect of space t nditions: Pres
zene/1,4-DIP me on stream
2 kg).
ant mole rat ditions: Pres ce time = 9.0 e on stream = 02 kg).
Selectivity of
me was studie kg h/k mol increase in s 83.82% at a
ntact time al nity of each time, theref n instead of electivity of hown in Figu
time on prod ssure =1 atm PB ratio = 5
= 30 min, ca
tio on produ ssure =1 atm 03 kg h/ kmo = 30 min, cat
f Products an
ed in the rang . The cumen space time an space time llows the rea other and th fore enhancin f isomerisatio products as ure 8.
duct selectivi m, temperatu 5:1, N2 to fee
atalyst (CeB1 uct
m, ol,
ta-nd
ge ne nd of
ac-he ng on a
g co sp ti 1 9 T R 1 c F si P to (C ex si im The produ iven in Tabl onversion of pace time; w ime between ,4-DIPB was .03 kg h/kmo
Table 2: Prod
Product distribution (wt%) Aliphatics Benzene Toluene Xylene Cumene n-PB C10 1,3-DIPB 1,4-DIPB Cumene yield (%) 1,4-DIPB conv.(wt%) Reaction Conditio 1,4-DIPB ratio = catalyst (CeB10) a
Figure 9: Eff ion at differ Pressure = 1 o feed ratio = CeB10) amou
MASS T
In solid ca xternal and i ignificant. E mportance of
Syn
Brazilian
uct distributio le 2. As can f 1,4-DIPB in which may b n reactants a s increased t ol. duct distribu Spa 4.2 4.8 0.71 0.49 68.82 68.25 0.94 0.58 0.32 0.39 16.96 18.78 0.11 0.16 3.34 2.42 2.08 4.01 6.72 4.92 16.96 18.78 77.34 83.41
ons: Pressure =1 5:1, N2 to feed r
amount = 0.002 kg
fect of space ent temperat atm, benzen = 0.2, time o unt = 0.002 k
TRANSFER
atalyzed gas p internal mass
xperiments w f external dif
nthesis of Cumen
Journal of Chem
on at various n be seen fr ncreased with be due to the and catalyst.
o 94.69% at
ution at vario
ce Time (kg h/ 5.75 7.02 0.48 0.04 67.91 62.4 0.29 0.48 0.42 1.03 21.02 28.6 0.23 0.36 1.14 0.14 4.29 4.49 4.22 2.39 21.02 28.6 85.77 92.3 atm, temperatur ratio = 0.2, time g.
e time on 1,4 tures. Reacti ne/1,4-DIPB on stream = 3 kg.
CONSIDER
phase reactio s transfer resi were carried ffusional resi
ne by Transalkyla
mical Engineering
s space times rom Fig. 9,
h an increase e higher cont
Conversion a space time
ous space tim
/ k mol) 2 7.9 9.0
4 0.10 0.0 2 53.97 47. 8 0.22 0.3 3 0.56 1.
5 37.39 42. 6 0.52 0.5 4 0.70 0.9 9 4.66 5. 9 1.88 1.5
5 37.39 42.
9 93.69 94.
re = 573 K, benz on stream = 30
4-DIPB conv ion Conditio ratio = 5:1, 30 min, catal
RATIONS
ons, the effect istances may d out to find istance by va
ation Over Modifi
g Vol. 33, No. 04,
s is the e in tact n of e of mes. 03 06 .26 35 14 .93 57 96 16 57 .93 .69 zene/ min, ver-ons: N2 lyst t of y be the ary-ing Ta con Th ne dif spa siz cat wi par ran Ta on S (k Re 1,4 Ta on P d Re 1,4 tem the ble mo con Hi wi reg ram rea ne tio fit
fied Beta Zeolite:
, pp. 957 - 967,
g feed rates a able 3 shows nstant space herefore, the gligible. To ffusion the e ace-time con ze. The expe te that the c ith catalyst s rticle mass t nge studied.
able 3: Effec n conversion pace-time kg h/kmol) 4.2 4.8 5.75 eaction Condition 4-DIPB ratio = 5:
able 4: Effect n DIPB conv
Particle size p (mm) s (k 0.50 1.00 1.50 eaction Condition 4-DIPB ratio = 5:
K
The kinetic mperatures. e zone in wh e. Based on t odels (adsorp
ntrol) were inshelwood ith the help o gression alg meter estima action contro
gative kineti on based on the experim
A Kinetic Study
October - Decem
and catalyst s s that the co e time are i e external m investigate experiments nstant but va erimental dat conversion o size which i transfer resis
ct of extern of 1,4-DIPB
Conv Catalyst we = 0.002 k 64.34 69.80 74.03 ns: Pressure = 1 a 1, N2 to feed ratio
t of intrapar version over Conv space-time kg h/kmol) =4.2 65.87 65.35 64.34 ns: Pressure =1 a
1, N2 to feed ratio
KINETIC M
runs were c The experim hich mass tra
the product d ption, desorp formulated approach. T of the experi orithm was ation. All mo ol, were rej ic constants. surface reac mental data s
mber, 2016
size at consta onversions o
independent mass transfer the effect o were carrie arying the ca
ta shown in of 1,4-DIPB indicates ne stance in th
al diffusion B over CeB1
version of 1,4-D (%) eight kg
C
atm, temperature o = 0.2, time on s
rticle diffusio CeB10.
version of 1,4-D (%) space-time (kg h/kmol) = 4.8 70.23 69.98 69.80 atm, temperature
o = 0.2, time on s
MODELLING
carried out at ments were ansfer effects
distribution v ption, and su following t These model rimental data used for th odels, excep ected as the . The follow ction-control satisfactorily
9
ant space-tim f 1,4-DIPB of feed rat r resistance of intrapartic d out keepin atalyst partic
Table 4 ind remain sam egligible intr
e particle si
nal resistanc 10. DIPB Catalyst weight =0.004 kg 65.11 70.87 75.12 = 573 K, benzen stream = 30 min.
onal resistan DIPB space-time (kg h/kmol = 5.75 75.34 74.76 74.03 = 573 K, benzen stream = 30 min.
G
t four differe conducted s were neglig
various kinet urface reactio the Langmui ls were teste a. A non-line
la-964 R. Thakur, S. Barman and R. Kumar Gupta
Brazilian Journal of Chemical Engineering
tion of 1,4 DIPB with benzene is a complex reaction which is followed by isomerization and dispropor-tionation reactions.
i) 1,4-DIPB transalkylation:
+
CH3
H3C
CH3
H3C H3C CH3
2 k1
1,4 DIPB Benzene Cumene
(1) ii) Isomerisation:
CH3
H3C
CH3
H3C
1,4 DIPB k2
CH3
H3C
CH3
CH3
1,3 DIPB
(2) iii) Dispropotionation:
CH3 H3C
CH3
H3C
1,4 DIPB
+
Aliphatics k3Benzene
(3) iv)
Benzene
+
Alipathics k4 C8+
C10(4)
For the above reactions, the possible rate equa-tions based on different mechanisms are presented below. k4 is not considered while developing the model because the model is in terms of conversion of 1,4-DIPB and this reaction does not involves DIPB.
k3 is also not considered since only those reactions whose product yield is significant are taken into con-siderations.
Dual-site mechanism:
2 2
1
⎡ ⎛ ⎞ ⎤
− = ⎢ +⎜ ⎟ ⎥
⎝ ⎠
⎣ ⎦
DIPB v B B DIPB DIPB DIPB DIPB v
k
r C k k p k p k p
C (5)
where,
1
(1 )
=
+ +
v
B B DIPB DIPB C
k p k p (6)
Single-site mechanism:
1 2
[ ]
−rDIPB =C k p kv B DIPB pDIPB +k kDIPB pDIPB (7)
where, 1 (1 )
= +
v
B B C
k p (8)
Stoichiometric model:
[
1 2]
−rDIPB = k pB pDIPB+k pDIPB (9)
The partial pressure of 1,4 DIPB and benzene are related to the fractional conversions and the total pressure (P) by these following equations:
(
1 /)
7.2= −
DIPB DIPB
p X P (10)
(
5)
/ 7.2= −
B B
p X P (11)
( ) / 7.2
=
c c
p X (12)
The optimum values of the parameters were ob-tained by minimizing the objective function given by the equation:
(
)
2(
⎡ – ) ⎤
=
∑
⎣ pred exp ⎦f X i X i (13)
Model Selection
u d fo T ex q an an u sy 1 ac th ln F T fe T co ze an op F u c r nder investi icted 1,4 DI our different The figure s
xpression p uite compara n R2 value o nd tabulated sed to determ ynthesis (tran 16.53 kJ/mo ctivation ene he following
nk=lnA− E R
Figure 10: Ex
Table 5: Kin erent tempe
Kinetic and a parame k1 (k mo
k2 (k mo
K Dipb (at
K B (atm
The plot o The activatio
ompare well eolites obtain nd Upadhya ped was ab Formation of cts, is derive Rate of for
1
=
c B B
r k k p
Syn
Brazilian
gation. The IPB convers t temperatur shows that t predicts 1,4
able to the e of 0.99. The d at various t
mine the act nsalkylation) ol; for the ergy was fou equation:
a E RT
xperimental v
netic and ad rature.
adsorption eters
l/kg h)
l/kg h) 0
tm-1)
m-1) 2
of ln k vs 1/T on energy va
l with the va ned by other ayula, 2008). ble to predic f cumene and ed from the e
rmation of cu
DIPB DIPB
k p
nthesis of Cumen
Journal of Chem
experimenta sions from E res are plott the proposed -DIPB conv experimental kinetic cons emperatures tivation ener ) which was isomerisatio und to be 17
vs predicted r
dsorption co Temper 493 513 1.11 2.34 0.097 0.534 1.223 0.839 2.345 2.00
T is represen alues for va alues of simil r investigato . The kinetic ct the produ d 1,3-DIPB, equations bel
umene:
B
ne by Transalkyla
mical Engineering
al and the p Equation (5) ted in Fig. d reaction r version valu
values, hav stants evalua (Table 5) w rgy for cume
estimated to on reaction 76.01 kJ/mol
(1
rate of reactio
onstants at d
rature (K) 533 55 10.49 20. 4.54 10. 0.689 0.4 1.80 1.
nted in Fig. arious reactio
lar reactions ors (Kondam c model dev uct distributi
the main pr low.
(1
ation Over Modifi
g Vol. 33, No. 04,
pre-) at 10. rate lues ving ated were ene o be the l by 14) on. dif-53 53 54 59 50 11. ons s on mudi vel-ion. rod-15) Ra 1,3 r k1, gre an (10
kB,
for of Fig the bet po ces act lite en 94 Ce a cu Ba mo we alk be ind be the tio
fied Beta Zeolite:
, pp. 957 - 967,
ate of format
2
3 =⎛⎜ ⎞
⎝ ⎠
DIPB v k C
k2,kB,kDIPB
ession analy d pDIPB valu
0) and (11). , kDIPB, pB, a
rmation of cu 1,3-DIPB ca
gure 11: A p e activation e
The catalyt ta zeolite wa ortant cumen
ssfully modi tivity and se e was higher ce of strong 4.69% conve eB10 zeolite w
benzene to mene select ased on the p
odel was pro ere estimated kylation and 116.53 kJ/m dustry, using increased, w e operating on, reactor vo
A Kinetic Study
October - Decem
ion of 1,3-DI
⎞ ⎟
⎠ kDIPB pDIP
were estima sis using the es can be ca By using the and pDIPB, in
umene and, i an be predict
plot of ln k v energy.
CONCL
tic performa as evaluated ne synthesis.
fied with cer electivity of than the par g acid sites rsion of 1,4 with 8.3 wt%
1,4-DIPB r tivity in this
product distr posed and th d. The activat isomerisatio mol and 176. g this catalys which can sav
cost by min olume, and re
mber, 2016
IPB:
PB
ated by using e least squar alculated by e known par n Equations in Equation ted.
vs 1/T for de
LUSION
ance of ceriu d for the com . H-beta zeo rium and it w
the cerium-rent zeolite d in the exch 4-DIPB was % Ce content reactant ratio s condition ribution patt he parameter ation energies on reactions .01 kJ/mol re st, the rate o
ve the fixed nimizing ene reaction time
9
(16
g nonlinear r re criterion. p
the Equation rameters k1, k
(15) and (16 (2), formatio
etermination
um exchange mmercially im olite was su was found th -modified ze due to the pre
anged zeolit obtained ov , at 573 K an o of 5:1. Th was 83.82% erns, a kinet rs of the mod s for the tran were found espectively. of reaction ca
cost as well ergy consum e and make th
965
6)
re-pB
ns
966 R. Thakur, S. Barman and R. Kumar Gupta
Brazilian Journal of Chemical Engineering
process more economic. The kinetic model derived for the reactions can provide the necessary infor-mation to scale up the reactor for large scale produc-tion in industry.
NOMENCLATURE
B benzene C cumene DIPB diisopropyl benzene k1, k2,
k3, k 4
kinetic constant (kmol/kg atm2 h) KB adsorption constant for benzene (atm-1) KDIPB adsorption constant for DIPB (atm-1) KC adsorption constant for cumene (atm-1) P total pressure (atm)
PDIPB partial pressure of DIPB (atm) pB partial pressure of benzene (atm) pC partial pressure of cumene (atm)
τ space-time (kg h/kmol) XDIPB fractional conversion of DIPB XB moles of benzene reacted (kmol) XC moles of cumene formed (kmol) Xexpt experimentally measured fractional
conversion of DIPB
Xpred model predicted fractional conversion of DIPB
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