cinetica del etiltolueno.pdf

chemical engineering research and design 9 5 ( 2 0 1 5 ) 3446

Contents lists available at ScienceDirect

Chemical Engineering Research and Design

journa l h om epage: www.elsev ier .com/ locate /cherd

Exper ethyltoluenesprodu ea

Luqman n Sa Center of R hd UnMinerals, Dhb Chemical E rals,

a r t i c

Article histor

Received 31 March 2014

Received in revised form 21 October

2014

Accepted 2

Available on

Keywords:

Ethyltoluen

Alkylation

Toluene

Ethylbenzen

Ethanol

o alky

zene (EB) methylation on ZSM-5 and mordenite (MOR) was studied in a batch uidized-bed

reactor at a temperature range of 200300 C for reaction times of 520 s. Toluene ethylation

with ethanol gave better yield and selectivity to ethyltoluenes on ZSM-5 compared with EB

1. In

Ethyltoluenvariety of industries. synthesis ofood packa1980; Forwtage over transition tial in the(Kaeding etalkylation o

Abbreviao-ET, ortho-

CorresponPetroleum &

E-mail ahttp://dx.do0263-8762/January 2015

line 13 January 2015

es

e

methylation with methanol. A maximum ethyltoluenes yield of 22.0% was achieved during

toluene ethylation whereas 7.3% yield was attained in EB methylation on ZSM-5. To achieve

enhanced para-ethyltoluene selectivity, ZSM-5 was modied by silylation treatment using

tetraethyl orthosilicate (TEOS). While toluene conversion on silylated ZSM-5 (HZ80-6L) was

decreased, 100% para-isomer selectivity was obtained due to the reduction of the effec-

tive pore channel and strength of acid sites. A comprehensive kinetic study of the toluene

ethylation reaction is reported in this paper using the power-law approach for the model

development. A satisfactory correlation between experimental data and the model result

was achieved. The required apparent activation energy for the alkylation step of toluene

ethylation reaction over ZSM-5, HZ80-6L and MOR catalysts was determined to be 70 kJ/mol,

63 kJ/mol and 28 kJ/mol, respectively.

2015 The Institution of Chemical Engineers. Published by Elsevier B.V. All rights reserved.

troduction

es (ETs) are aromatic compounds useful for a wideapplications in the petrochemical and chemicalFor example, p-ethyltoluene (p-ET) is used in thef poly(p-methylstyrene) which are adaptable toges subjected to thermal conditions (Canteniro,ard et al., 1984). Poly(p-methylstyrene) has advan-polystyrene due to its low density, higher glasstemperature, and ash point. It has also poten-

area of ame retardancy or ignition resistance al., 1981). Ethyltoluenes are usually produced viaf toluene with ethanol or ethylene (Walendziewski

tions: DEB, diethylbenzene; EB, ethylbenzene; ET, ethyltoluenes; EtOH, ethanol; m-ET, meta-ethyltoluene; MOR, mordenite;ethyltoluene; TMB, trimethylbenzene; p-ET, para-ethyltoluene.ding author at: Center of Research Excellence in Petroleum Rening & Petrochemicals, P.O. Box 5040, King Fahd University of

Minerals, Dhahran 31261, Saudi Arabia. Tel.: +966 13 860 2029; fax: +966 13 860 4509.ddresses: [email protected] (L.A. Atanda), [email protected] (A.M. Aitani), [email protected] (S.S. Al-Khattaf).

and Trawczynski, 1991; Villareal et al., 2002; Parikh, 2008;Manivannan and Pandurangan, 2010). Most often this reac-tion is conducted on medium pore zeolites especially ZSM-5,because of its shape selective properties favoring para-selectivity. Further improvement of para-selectivity of ZSM-5can be achieved by impregnation of the zeolite channels withmetal or non-metal oxides (Engelhardt et al., 1992; Parikh et al.,1992; Zheng et al., 2003) and/or modication of the externalacid sites with a siliceous material (Hui et al., 2011; Cejka andWichterlov, 2002) or by carbonaceous material in form of cokedeposit (Kaeding et al., 1984; Odedairo and Al-Khattaf, 2010).

The kinetics of toluene alkylation with ethylene hasbeen investigated in a xed bed reactor. Bhandarkar and

i.org/10.1016/j.cherd.2015.01.001 2015 The Institution of Chemical Engineers. Published by Elsevier B.V. All rights reserved.imental and kinetic studies ofction via different alkylation r

A. Atandaa, Abdullah M. Aitania, Sulaimaesearch Excellence in Petroleum Rening & Petrochemicals, King Faahran 31261, Saudi Arabiangineering Department, King Fahd University of Petroleum & Mine

l e i n f o

y:

a b s t r a c t

Ethyltoluenes production via twctions

. Al-Khattafa,b,

iversity of Petroleum &

Dhahran 31261, Saudi Arabia

lation reactions vis: toluene ethylation and ethylben-

chemical engineering research and design 9 5 ( 2 0 1 5 ) 3446 35

Nomenc

Ci

Ei

ki

koi

MWiriR t T ToV WcWhc

yi

Greek lett

Bhatia (19using Langthe EleyRimodel bettface reactiunmodiedtion energyKinetic anaon LHHW (1985) usingthat ethylereaction malkylation ics of the rwas wash-ccates p-ET to-Ethyltoluable quanta result of ET and theActivation ation reactZSM-5 alwacompared tascribed toet al., 1991;

Alkylatihand, has nreaction went catalysbut they prhave undertion reactiomechanismX type zeoring alkylaton basic ze

ion and carbonium ion mechanism governed the alkyl-and nismhylathis pbatc

of izedratiotrating icing cuseematcted

theodel eprenism

Ex

Ma

ms oratiompl+ wiobtaical liensiated

rred h wituatid ates uslature

concentration of specie i in the riser simulator(mol/m3)apparent activation energy of the ith reaction(kJ/mol)apparent rate constant for the ith reaction(m3/kg of catalyst s)pre-exponential factor for the ith reaction afterre-parameterization (m3/kg of catalyst)molecular weight of specie ireaction rateuniversal gas constant (kJ/kmol K)reaction time (s)reaction temperature (K)average temperature of the experimentvolume of the riser (45 cm3)mass of the catalyst (0.81 g)total mass of the hydrocarbon injected the riser(0.162 g)mass fraction of ith component

erscatalyst deactivation constant

94) studied the kinetics of toluene alkylationmuirHinshelwoodHougenWatson (LHHW) anddeal mechanism and demonstrated that the LHHWer represents the reaction mechanism. The sur-on of the co-adsorbed toluene and ethanol on

HZSM-5 required approximately 62 kJ/mol activa- for ET to be formed as reported by the authors.lysis of ethylation of toluene on HZSM-5 basedmechanism was also reported by Lee and Wang

ethylene as the alkylating agent. They concluded

carbanation mechademet

In tidized the useof uidregeneconcenpromisenhanalso foA systconduwell aslaw msions rmecha

2.

2.1.

Na formolar The sathe Na2 h to chemiA suspwas hethe stiat 70 Cby evaccalcinesix timne adsorption was the rate determining step of theechanism and the estimated activation energy forwas 75.4 kJ/mol. Parikh (2008) reported the kinet-eaction using a monolith reactor on which ZSM-5oated. He proposed a rate expression which indi-o be the primary product of the alkylation reaction.ene was not accounted for due to negligible observ-ities while the net rate of m-ET formation was asthe total rate of toluene consumption to form p-

subsequent isomerization rate of p-ET to m-ET.energy of 64 kJ/mol was estimated for the alkyl-ion. It is noteworthy to point out that modiedys has higher activation energy for alkylation wheno the unmodied ZSM-5. This variation has been

lowering of acid strength after modication (Lnyi Bhandarkar and Bhatia, 1994).on of ethylbenzene (EB) with methanol on the otherot been extensively reported in the literature. Thisas studied by Ko and Huang (1993) using differ-ts. The kinetics of the reaction was not studiedoposed a reaction network of EB on HY zeolite togone alkylation, disproportionation and dealkyla-ns. Inuence of acidity and basicity on the reaction

of methylation of EB was also investigated usinglites (Huang and Ko, 1993). Acidic zeolite favoredion whereas side-chain alkylation was promotedolite. On KX zeolite which has mainly basic sites,

deposition Toluene

(100.0%) wattempt wa

2.2. Ca

Powder X-ra Shimadztion ( = 0.1recorded indetector an

The texacterized bQuantachrogassed at 2physisorptimined from0.060.3, asarea of th(PSD) was BarrettJoythe PSD waysis was uspore volum

Temperawas condudealkylation reactions, respectively. Free radical leading to the formation of dehydrogenation andion products also took place.aper, we report the ethylation of toluene using a u-h reactor whereas previous studies have reportedxed bed reactor. We seek to exploit the advantages

bed over xed bed such as the ease of catalystn as well as the elimination of temperature andion gradients. p-Ethyltoluene is considered to be ofndustrial interest, hence, the effect of silylation inpara-selectivity of ZSM-5 was examined. This studyd on detailed kinetic investigation of the reaction.ic kinetic analysis of the alkylation reaction wasto account for the toluene ethylation reaction as

concomitant isomerization taking place. A poweris employed to develop the mathematical expres-senting the reaction rates for the proposed reactions.

perimental

terials

f ZSM-5 (Si/Al molar ratio 80) and mordenite (Si/Al 180) were obtained from Tosoh chemicals, Japan.es were ion exchanged with NH4NO3 to replaceth NH4+, then followed by calcination at 600 C forn the proton (H+) form. HZ80-6L was prepared byquid deposition as reported by Zheng et al. (2006).on of parent ZSM-5 zeolite (Si/Al = 80) in n-hexane

until reux at 70 C. TEOS solution was added toeated mixture and silylation was continued for 2 h

h reux and stirring. Excess n-hexane was removedon. The sample was dried at 100 C for 24 h and then

550 C for 4 h. Silylation treatment was conducteding the same procedure to obtain six layers of TEOS(4 wt% SiO2) on the parent zeolite.

(99.6%), ethanol (99.9%), EB (99.8%) and methanolere obtained from SigmaAldrich and no furthers made to purify the chemicals.

talyst characterization

ay diffraction (XRD) patterns were recorded onu powder diffraction system using Cu K radia-54 nm, 45 kV and 35 mA). The XRD patterns were

the static scanning mode from 1.2 to 60 (2) at agular speed of 0.01/s and step size of 0.02.tural properties of the zeolite samples were char-y N2 adsorption measurements at 196 C usingme Autosorb 1-C analyzer. Samples were out-20 C under vacuum (105 torr) for 3 h before N2on. The BET specic surface areas were deter-

the desorption data in the relative P/P0 range fromsuming a value of 0.164 nm2 for the cross-sectione nitrogen molecule. The pore size distributioncalculated from the adsorption branch using thenerHalenda (BJH) method, and the maximum ofs considered as the average pore size. t-Plot anal-ed to determine the micropore surface area ande.ture-programmed desorption of NH3 (NH3-TPD)cted using Quantachrome Autosorb 1-C/TCD to

36 chemical engineering research and design 9 5 ( 2 0 1 5 ) 3446

determine total acid sites on the catalyst samples. Sampleswere pretre2 h. This win helium) a helium sbound ammThe sampla heating rwhile mon

Infrareddetermine and/or Lewducted usiFTIR spectform of a 20 mm in form layermounted iwindows (Mheated undadsorptiontitative chaabsorption1545 cm1,and 1454 cet al., 2009)

2.3. Ca

Experimenscale uidioperated ition rates apre-determlocations oiment, 0.8 gcrushed anbasket of tmal activatat 620 C foand ethanofor methylais of 1:1 mo

All exppressure anwas analyzwith a aInnowax, 6diameter otal runs wthe range product yiefollows:

% toluene (

= T (or EB

% yieldi = w

% selectivit

1

FTI80-6L

-sele

Re

Tex

al pr1. Bytionolumibite. Themeth

mayels bystalion thous

Acidity results

2 shows the acid properties of the catalyst samples.tal concentration of acid sites measured by NH3-TPDdied zeolite (HZ80-6L) was lower compared to the par-olite (ZSM-5). In addition, FTIR of chemisorbed pyridined reduced peak intensities (Fig. 1) as well as reduction inantied Brnsted and Lewis acidities (Table 2) after sily-treatment. It can thus be concluded that the introducedas partly deposited onto the acid sites of the zeolite

e, reducing the number of available acid sites that cant with the probe gases (ammonia and pyridine).

Catalytic activity

Ethylation of toluenerature and time dependence of toluene conversion is

in Fig. 2A and B for the alkylation of toluene withl on both ZSM-5 and MOR. Expectedly, conversionene rose with increase in temperature and time. Atn conditions of 300 C and 20 s, toluene conversion ofated at 450 C in a ow of helium (25 ml min1) foras followed by the adsorption of ammonia (5 vol.%at 100 C for 30 min. Samples were then purged intream for 2 h at 120 C in order to remove looselyonia (i.e. physisorbed and H-bonded ammonia).

es were then heated linearly from 100 to 700 C atate of 10 C/min in a ow of helium (25 ml min1)itoring the evolved ammonia using TCD.

spectroscopy of adsorbed pyridine was used tothe types of available acid sites (i.e. Brnstedis acid sites). The measurements were con-

ng a Fourier transform infrared using Nicoletrometer (Magna 500 model). The samples in theself-supporting wafer (ca. 60 mg in weight anddiameter) were obtained by compressing a uni-

of the powdered samples. The wafer was thenn an infrared vacuum cell equipped with KBrakuhari Rikagaku Garasu Inc., Japan), and pre-er vacuum (ca. 103 torr) at 450 C for 2 h. The

temperature of pyridine was 150 C. For a quan-racterization of acid sites, the following bands and

coefcients were used: pyridine (PyH+) band at = 0.078 cm mol1; pyridine (PyL) bands at 1461m1, = 0.165 cm mol1 (Gil et al., 2008; Zilkov.

talytic test

ts were conducted on a riser simulator, a benchzed bed reactor invented by de Lasa (1991). It isn a batch mode under high gas phase circula-s well as intense catalyst mixing conditions andined reaction times, thereby simulating variousf riser/downer type reactor units. In a typical exper-

of the catalyst sample which has already beend sieved to 60 m was loaded into the catalysthe reactor. Before the catalytic activity test, ther-ion of the catalyst was done in the presence of Arr 15 min. The reactant feed is a mixture of toluenel (1:1) for ethylation reaction, EB and methanol (1:1)tion reaction. For both reactions, the feed mixturelar ratio.erimental runs were conducted at atmosphericd under isothermal condition. The reactor efuented in an Agilent model 6890N gas chromatographme ionization detector and a capillary column0 m cross-linked methyl silicone with an internalf 0.32 mm. Reproducibility check of the experimen-as performed. Typical errors were found to be inof 2%. The terms for toluene or EB conversion,ld, ET selectivity and p-ET selectivity are dened as

T) or EB conversion

) in feed T (or EB) in productT (or EB) in feed

100

wt% of product it% of toluene in feed

100%

y = wt% of ethyltouene (ET) in productwt% of aromatic in product

100

Fig. 1 (B) HZ

% para

3.

3.1.

TexturTable adsorppore v6L exhZSM-5t-plot whichchanntive crsilylatamorp

3.2.

Table The toon moent zeshowethe qulation silica wsamplinterac

3.3.

3.3.1. Tempeshownethanoof tolureactiowavenu mber (c m-1)

(A)

(B)

140015001600700

R of chemisorbed pyridine onto (A) ZSM-5 and.

ctivity = wt% of p-ET in productwt% of ET in product

100

sults and discussion

tural properties of catalysts

operties of the catalyst samples are presented in applying the multiple-point BET model on the

branches of the N2-isotherm, the BET areas andes were calculated. As shown in Table 1, HZ80-d lower BET area and pore volume compared to

estimated micropore volume obtained from theod also show reduction for the modied ZSM-5

be due to partial pore blockage of the zeolite porey the deposited silica. From the XRD results, rela-linity of ZSM-5 reduces from 100% to 85% after thereatment indicating that the incorporated silica is.


Table 1 Textural properties of the catalysts.

Catalyst SBET (m2 g1) Smeso (m2 g1)a Vmicro (cm3/g)a Vmeso,N2 (cm3/g)b RC (%)c

ZSM-5 451 51.0 0.19 0.09 100HZ80-6L 424 45.0 0.17 0.08 85MOR 514 0.24 0.05 100

a Obtained from t-plot.b Pore volume in the range of 4100 nm derived from N2 adsorption.c Relative crystallinity derived from XRD measurements.

Table 2 Acid sites properties of the catalysts.

Catalyst NH3-TPD (mmol g1)a FTIR-chemisorbed Pyr. (mmol g1)

Tb L.T. (weak) H.T. (mediumstrong) T B L

450 Cc

ZSM-5 0.354 1.00 0.194 0.16 0.205 0.165 0.040HZ80-6L 0.307 0.95 0.187 0.12 0.158 0.131 0.027MOR 0.04 0.270 0.05 0.22

a L.T. and H.T. correspond to low- and high-temperature NH3 desorption peak, respectively.b Total number of acid sites is based on the amount of NH3 desorbed above 300 C (i.e. H.T. region).c Strong ac

approximaMOR, respetion tempewhich was all tempera200 C whefact that etsion. This iboth alkylaalso increasand B) on value of totand 20 s for

Activityover ZSM-5reaction prto insignialkylation carbenium

paraollowannaeactil is p

e to fyl cahe oT. Thethylphilns.

isom in hampland ution

Table 3

Reaction te

Reaction ti

Toluene coEthanol coProduct yie

p-ET m-ET o-ET Total ETGases BenzeneEB Xylenes TMBs DEBs ET select

ET composp-ET m-ET o-ET id sites of Brnsted and Lewis nature, respectively.

tely 30.8% and 33.3% was achieved on ZSM-5 andctively. In contrast to toluene conversion, reac-rature has negligible effect on ethanol conversionin the range of 8087% after 20 s of reaction time fortures. The only exception is with MOR catalyst atre ethanol conversion is 52.6%. Noteworthy is thehanol conversion is higher than toluene conver-s because of the reactivity of ethanol to undergotion and dehydration reactions. The total ET yielded with toluene conversion or temperature (Fig. 3Aboth catalysts but selectivity reduced. Maximumal ET yields of 22% and 14.6% was recorded at 300 C

ZSM-5 and MOR, respectively. results of the alkylation of toluene with ethanol

and MOR are detailed in Tables 3 and 4. Theoduct comprises mainly of ET isomers and smallcant amount of other observed products. Typical

orthoring fManivsible rEthanosamplto ethboth tform Ethe melectropositio

Them-ETsFor exm-ET distribreaction of aromatic compounds is governed by ion type mechanism involving the direct

49.9% (m-Eand Wang

Catalytic performance of ZSM-5 in toluene alkylation with ethan

mp. (C) 200 225

me (s) 10 20 10 20

nversion (%) 5.8 13.7 7.4 18.8 nversion (%) 65.9 79.7 67.6 81.8 ld (%)

2.4 4.3 2.8 5.4 3.3 7.2 3.9 10.4 0.2 0.5 0.2 1.0 5.9 12.0 6.8 16.8

14.4 13.4 14.7 10.5 0.1 0.1

0.1 0.2 0.1 0.4 0.2 0.4 0.2 0.4 0.2 0.6

ivity (%) 95.2 96.0 95.8 91.8 ition (%)

41.0 35.9 40.4 32.1 55.9 60.0 56.6 62.3 3.10 4.10 3.10 5.60 attack of the alkylation agent on the benzeneed by positional isomerization (Perez, 1978;n and Pandurangan, 2009). Fig. 4 presents a plau-on pathway for toluene alkylation with ethanol.rotonated by the Brnsted acid site of the zeolite

orm ethyl oxonium ion which is then transformedtion. This subsequently reacts with toluene atrtho- and para-positions of the benzene ring toe reaction takes place at these positions because

group of toluene is an orthopara director andic attack of ethyl cation occurs at ortho and para

er distribution of ET on ZSM-5 favors both p- andigher quantities than o-ET as shown in Fig. 5A.e, ET isomers distribution at 300 C, 20 s for p-ET,o-ET is 27.5%, 61.4% and 11.1%, respectively. This

is near equilibrium concentration of 33.7% (p-ET),

T) and 16.3% (o-ET) at 330 C as reported by Lee(1985). The excess concentration of m-ET above

ol.

250 300

10 20 10 20

17.3 25.9 24.2 30.866.6 84.2 68.6 80.2

4.6 6.2 5.3 6.19.4 12.9 11.7 13.50.9 1.5 1.8 2.4

14.9 20.6 18.8 22.08.7 10.3 8.2 10.50.1 0.2 0.3 0.50.4 0.7 0.8 1.20.3 0.6 0.8 1.2 0.1 0.1 0.20.4 0.6 0.5 0.7

92.5 90.4 88.3 85.3

31.2 30.3 28.4 27.563.0 62.5 61.9 61.45.80 7.20 9.70 11.1


Table 4 Catalytic performance of MOR in toluene alkylation with ethanol.

Reaction temp. (C) 200 225 250 300

Reaction time (s) 10 20 10 20 10 20 10 20

Toluene conversion (%) 6.9 22.2 14.0 23.7 10.6 24.5 22.4 33.3Ethanol conversion (%) 47.7 52.6 69.4 85.2 57.7 79.0 64.6 84.3Product yield (%)

p-ET 0.7 1.0 1.1 2.1 1.1 2.5 2.3 3.6m-ET 1.4 2.5 3.1 6.1 3.5 7.3 5.9 8.7o-ET 3.3 5.1 4.6 4.6 2.8 2.9 1.7 2.4Total ET 5.4 8.6 8.8 12.8 7.4 12.5 9.9 14.7Gases 9.5 16.3 10.5 10.8 8.4 7.6 6.9 6.8Benzene 0.1 0.1 0.3 0.4 0.8EB 0.2 0.2 0.9 1.2 2.0Xylenes 0.1 0.2 1.0 1.6 2.8TMBs 0.1DEBs 0.2 0.4 0.8ET selectivity (%) 100 100 100 96.9 93.6 83.9 73.3 69.3

ET composition (%)p-ET 12.9 12.0 12.8 16.4 14.3 19.9 23.2 24.4m-ET 26.0 29.1 34.9 47.8 47.7 56.6 59.4 59.4o-ET 61.1 58.9 52.3 36.1 38.0 23.5 17.4 16.2

0 4 8 12 16 200

5

10

15

20

25

30

35

40 200 C 225 C 250 C 300 C

Tolu

ene

conv

ersi

on /

%

Reaction time / s

A

0 4 8 12 16 200

5

10

15

20

25

30

35

40B 200 C

225 C 250 C 300 C

Tolu

ene

conv

ersi

on /

%

Reaction time / s

Fig. 2 Catalytic activity of (A) HZSM-5 and (B) MOR, foralkylation of toluene with ethanol. Reaction conditions:temperature = 200300 C, reaction time = 520 s,toluene/EtOH molar ratio = 1:1. Experimental data (datapoints), model predicted values (solid lines).

100 200 30 0 4000

20

40

60

80

100

0

20

40

60

80

100

Sel

ectiv

ity /

%

Con

vers

ion

& Y

ield

/ %

Reaction tem perature / C

A

100 20 0 30 0 40 00

20

40

60

80

100

0

20

40

60

80

100B

Sel

ectiv

ity /

%

Con

vers

ion

& Y

ield

/ %

Reaction tempe rature / C

Fig. 3 Temperature effect on the activity of (A) ZSM-5 and(B) MOR at 20 s reaction time. () toluene conversion, ()ethyltoluene selectivity, () ethyltoluene yield.


Fig. 4 Reaction pathway for toluene ethyla

100 20 0 30 0 40 010

20

30

40

50

60 B

Eth

ylto

luen

e se

lect

ivity

/ %

Reaction tempe rature / 0C

100 20 0 30 0 40 00

10

20

30

40

50

60

Eth

ylto

luen

e se

lect

ivity

/ %

Reaction temperature / C

A

Fig. 5 Ethyltoluene selectivity as a function of temperatureon (A) ZSM-5 and (B) MOR at 20 s reaction time. () para, ()ortho, () meta.

equilibriumon the exteshows thatthat obtain200 C, isomof o-ET (6with rise inat 300 C. Woccurs to acentration be assumeization of omainly formalkylation oThe yield ofrom directsolid acid cortho-positof alkylatioManivanna

0

20

40

60

80

100

Xyl

ene

isom

er d

istri

butio

n / %

Fig. 6 Xylat 300 C antion with ethanol.

value is ascribed to the isomerization of p-ETrnal surface of the crystal (Parikh, 2008). Fig. 5B

the ET isomer distribution on MOR differs fromed on ZSM-5, especially at low temperatures. Aterization is slow, and therefore a high selectivity

0%) was observed. However, o-ET selectivity drops temperature to a near equilibrium value of 16%ith increase in temperature, isomerization rate

great extent, thereby resulting in increased con-of m-ET in the ET isomer distribution. Thus, it cand that m-ET is produced mainly from the isomer--ET. Cejka et al. (1991) also reported that m-ET ised from o-ET previously generated by preferential

f toluene with ethylene on a H-Y zeolite catalyst.f p-ET also increases with temperature, arising

alkylation of toluene with ethanol. Therefore, overatalysts where no shape selectivity are expected,ion is preferentially attacked, and the initial stagen involves o-ET formation (Coughlan et al., 1982;n and Pandurangan, 2010).

MOR ZSM-5 HZ80-6L

m-xylene o-x ylene p-xylene

ene isomer distribution over the zeolite catalystsd 20 s.


0

10

20

30

40

50

60To

luen

e co

nver

sion

& p

rodu

ct y

ield

/ %

Fig. 7 Information

Silylatiothe silica sTable 5 sho5 (HZ80-6Lof silica gretoluene conditions of 3selectivity whereas ontoluene cowere achievdistributionpore mouthnal surfacepore mouthand coveraerization oalso be exteproduced frHZ80-6L as

The molthe effect otoluene forratio of toluthrough a mreactivity otion whichother handtionation oethylbenzeof toluene:

3.3.2. MeIn order tomethylatiosimultaneoaromatic rcomparisoncatalytic aproducts oproducts a

0

5

0

5

0

Comtion tic co

(199nol e thre m

EB/bense

is inethahat tropoeadin rou

studeth

actiylbe

toluses wnol thylb3:11:11:3

Toluene:EtOH molar ratio

Toluene conv. gases EB Bz Total ET

uence of toluene:EtOH molar ratio on theof ethyltoluenes over MOR at 300 C and 20 s.

n treatment of ZSM-5 was conducted using TEOS asource, in order to improve para-isomer selectivity.ws the catalytic performance of the modied ZSM-) for alkylation of toluene with ethanol. Additionatly enhanced p-ET selectivity and yield, however,version was reduced. For example, at reaction con-00 C and 20 s, toluene conversion, p-ET yield andon ZSM-5 are 30.8%, 6.1% and 27.5%, respectively,

HZ80-6L, values of 18.8%, 13.5% and 77.1% fornversion, p-ET yield and selectivity, respectively,ed. It is suggested that 100% p-ET in the ET isomer

is caused by two reasons: one is the reduction of and the other is coverage of acid sites on the exter-

of zeolite (Kaeding et al., 1984). The reduction of prevents diffusion of m- and o-ET out of the pores,ge of outer surface acid sites suppresses the isom-f p-ET on the external surface. These reasons cannded to why p-xylene is the only isomer of xylene

1

1

2

Tota

l eth

ylto

luen

e yi

eld

/ %

Fig. 8 ethylaaroma

Huangmethadescribsteps aand Das a cowhichwith mgests tor dispplace lreactioof thisof EB-m

Thethe eththat ofincreamethature. E

om the disproportionation reaction of toluene over shown in Fig. 6.ar ratio of toluene:ethanol was varied to investigatef concentration of the alkylating agent on ethyl-

mation. Fig. 7 shows that with the increase in molarene to ethanol, total ethyltoluene formation goesaximum at 1:1. At low toluene:ethanol ratio, high

f ethanol led to huge gaseous hydrocarbon forma- include ethylene, ethane and diethyl ether. On the, high toluene:ethanol ratio promotes dispropor-f toluene to benzene and its successive alkylation tone. From this result, the most suitable molar ratioethanol appears to be 1:1.

thylation of ethylbenzene investigate an alternate route to producing ETs,n of EB is conducted. The idea is to look at theus effect of increasing the alkyl substituent on theing and reduction of the alkylating agent size in

with toluene ethylation. It was found that thelkylation of EB with methanol gave a variety ofn both ZSM-5 and MOR. Most signicant of there DEB, ET, toluene and benzene (Table 6). Ko and

300 C and correspondFig. 8 comptemperaturethylation an exampltoluene ethproduced ialkylation rzeolite samthe stabilitble than mcation frommethanol. from alkylaof EB withat 300 C ansented in Fis much hicatalyst sativity is simThis meanmuch variaZSM-5 MOR HZ80-6L

Tol + EtOH EB + MeOH

parison of total ethyltoluene yield via tolueneand EB methylation reactions at 300 C and 20%nversion.

3) has proposed the reaction paths for the EB-reaction which can be adapted in this study toe observed product mixture. The primary reactionethylation and disproportionation of EB to give ETnzene, respectively. Benzene and toluene may be

quence of dealkylation of EB and ET, respectively,uenced by temperature. Benzene can further reactnol to give toluene and the presence of xylene sug-oluene subsequently undergoes either methylationrtionation reaction. The multiple reactions takingng to a wide range of alkyl aromatics suggest thiste is non-selective toward ET formation. The scopey therefore will not include detailed investigationanol reaction mechanism.vity of all the catalysts in terms of conversion fornzene methylation reaction (Table 6) is similar toene ethylation reaction. Ethylbenzene conversionith both reaction time and temperature whereas

conversion seems to be unaffected by tempera-enzene conversion on ZSM-5, MOR and HZ80-6L at20 s is 40.4%, 54.5% and 26.6%, respectively with aing methanol conversion of 85.9%, 86.3% and 85%.

ares the yield of total ET produced at 300 C reactione and 20% aromatic conversion via both tolueneand EB methylation reactions. Taking ZSM-5 ase, approximately 20% ET yield was formed duringylation reaction while about 4.4% yield of ET wasn the methylation reaction of EB. Similar trend ofeaction inuencing ET yield was observed in otherples as well. This is caused by the difference in

y of attacking carbocation. Ethyl cation is more sta-ethyl cation. Accordingly, the formation of ethyl

ethanol is easier than that of methyl cation fromThis can explain why the total yield of ET is highertion of toluene with ethanol than from alkylation

methanol. The selectivity to total ETs and p-ETd 20% aromatic conversion are plotted and pre-

ig. 9A,B. Fig. 9A clearly shows that selectivity to ETgher in the toluene ethylation reaction on all themples. It was however found out that p-ET selec-ilar irrespective of the type of alkylation reaction.

s that the choice of alkylating route does not havetion on para-isomer distribution. A look at the p-ET


Table 5 Catalytic performance of HZ80-6L in toluene alkylation with ethanol.

Reaction temp. (C) 200 225 250 300

Reaction time (s) 10 20 10 20 10 20 10 20

Toluene conversion (%) 3.3 3.8 3.7 9.5 6.2 10.3 13.5 18.8Ethanol conversion (%) 64.3 85.3 65.8 85.5 68.8 83.8 71.8 86.7Product yield (%)

p-ET 3.8 5.3 5.7 10.4 7.7 11.4 11.0 13.5m-ET o-ET Total ET 3.8 5.3 5.7 10.4 7.7 11.4 11.0 13.5Gases 16.0 20.6 12.5 14.5 11.3 11.7 12.0 14.7Benzene 0.1 0.1 0.2 0.4 0.7EB 0.1 0.2 0.2 0.6 0.5 0.8 1.3 2.0Xylenes 0.1 0.1 0.2 0.4 0.3 0.6 0.8 1.3TMBs DEBs ET selectivity (%) 95.0 94.6 93.4 90.4 89.5 87.7 82.1 77.1

ET composition (%)p-ET 100 100 100 100 100 100 100 100m-ET o-ET

selectivity on ZSM-5 for example for both alkylation reactionswas approxrium value

4. Kinreaction

The reactiostudied uslar to a urepresentinbased on tthe model,the design amount of was assumpseudo-rsinvolved ina function o

was dened for all reactions. Using the rst order rate reactiontch re of

i = ri

ri an speis tht) is

accoalysle conn of ehe ch

iWhcWiV

Table 6

Reaction te

Catalyst sa

EB conversMethanol cProduct yie

p-ET m-ET o-ET Total ET Gases BenzeneTolueneXylenes TMBs DEBs ET select

ET composp-ET m-ET o-ET imately 27% and this value is close to the equilib- (Kaeding et al., 1984).

etics of the toluene ethylation

n kinetics for the toluene ethylation reaction ising a riser simulator whose operation is simi-idized bed batch reactor. Mathematical modelsg the rates of chemical reactions are developedhe observed product distribution. In formulating

isothermal operating condition is assumed givenof the riser simulator unit and the relatively smallreacting species. The rate of reaction for alkylationed to follow simple second-order kinetics and at order reaction kinetic was assumed for all species

the reactions. Catalyst deactivation is taken to bef reaction time, and a single deactivation function

for a bathe rat

V

Wc

dC

dt

whereof eachtor, Wcexp(whichthe cat

Mofractiofrom t

Ci =y

MCatalytic performance of EB alkylation with methanol at 20 s rea

mp. (C) 250

mples ZSM-5 MOR HZ80-6L

ion (%) 29.5 40.9 13.7 onversion (%) 84.5 72.3 82.3 ld (%)

2.1 2.1 2.6 4.7 5.6 0.6 2.3 7.3 9.8 2.6 6.8 3.1 9.5

2.1 4.4 1.6 1.5 3.1 1.4 1.6 1.7 0.8 1.6 1.0 9.3 3.4 6.1

ivity (%) 31.2 41.9 20.8 ition (%)

28.6 21.0 100 63.7 55.8 7.7 23.2 eactor and employing the power law rate equation,reaction can be written as:

exp(t) (1)

d Ci are the reaction rate and mole concentrationcies in the system, V is the volume of the reac-e mass of the catalyst, t is time in seconds, while

the reaction time catalyst deactivation functionunts for catalytic activity loss and is known ast.centration, Ci, can be expressed in terms of weightach species yi, which are the measurable variablesromatographic analysis, we have:

(2)ction time.

300

ZSM-5 MOR HZ80-6L

40.4 54.5 26.685.9 86.3 85.0

2.0 2.8 2.64.7 6.5 0.7 1.7 7.4 10.9 2.69.2 5.9 15.55.5 3.8 5.44.5 4.1 4.13.1 3.4 1.61.9 2.0

11.1 6.9 6.922.1 35.1 12.6

27.0 25.4 10063.3 59.4 9.7 15.2


0

10

20

30

40

50

60

70

80

90

100

Tota

l eth

ylto

luen

e se

lect

ivity

/ %

A

0

10

20

30

40

50

60

70

80

90

100B

Par

a-et

hylto

luen

e se

lect

ivity

/ %

Fig. 9 Com(B) para-ethEB methylaconversion

where WhcMWi is the

The reathe concenki, can be exnius equati

ki = ki0 exp

where kEi is the ento as the cthe temperreduce parBrisk (1985

Two reaation of toformation ethanol; Scwith succeelementarycussed belo

e 1

Alk

ain rekylatd asroduactiorefo

CTCE

the r

CT =ZSM-5 MOR HZ80-6L



Schem

4.1.

The mis to algroupeother pside re

The

r1 = k1

For

V dZSM-5 MOR HZ80 -6L

parison of (A) total ethyltoluene selectivity andyltoluene selectivity, via toluene ethylation andtion reactions at 300 C and 20% aromatic.

is the weight of feedstock injected into the reactor,molecular weights of the species.ction rate, ri, is a function of the rate constant andtration of the reacting species. The rate constant,pressed in terms of temperature dependent Arrhe-on as:

[Ei

R

(1T

1T0

)](3)

i0 is the pre-exponential factor of reaction i andergy of activation of the reaction i. T0 is referredentering temperature which is the average of allatures for the experiment. This was introduced toameter interaction as postulated by Agarwal and).ction schemes have been proposed for the alkyl-luene with ethanol: Scheme 1 involves the directof ethyltoluenes by alkylation of toluene withheme 2 involves a two step reaction of alkylationssive isomerization. The rate equations for the

reactions are derived using these schemes as dis-w:

Wc dt

rate of ETs

V

Wc

dCEToldt

=

4.2. Alk

This schemformation The rst sterization rethe channeation step (of the zeoliwith acid s1987). Furththe m-ET cor ortho poalso propos

The ratreactions c

r1 = k1CTCE

r2 = k2(

CP

r3 = k3(

CM

where Keq1erization ocalculated

The ratewritten as:

rate of tol

VWc

dCTdt Toluene ethylation reaction to ethyltoluenes.

ylation only

action pathway of toluene alklylation with ethanoled products, i.e. the ET isomers. The ET isomers are

a single product represented with Scheme 1. Allcts were neglected as a result of the insignicantn effects.re, reaction rate for the alkylation reaction is:

(4)

eacting species, rate of toluene consumption is:

r1 exp(t) (5)

formation

r1 exp(t) (6)

ylation with isomerization

e considers a two-step reaction pathway for theof the ET isomers, neglecting other side reactions.ep of the reaction is alkylation followed by isom-action. For ZSM-5, p-ET is preferentially formed inl intersections of the zeolite during the initial alkyl-Cejka et al., 1991). The p-isomer then diffuses outte pores and isomerizes toward m-ET upon contactites on the zeolite external surface (Paparatto et al.,ermore, a rearrangement of the methyl group on

an simultaneously occur, shifting either to the parasition to give p-ET or o-ET as shown in Scheme 2a,ed by Cejka et al. (1991).e equations for the alkylation and isomerizationan then be written as:

(4)

ET CMETKeq1

)(7)

ET COETKeq2

)(8)

and Keq2 are the equilibrium constants for isom-

f p-ET to m-ET and m-ET to o-ET, respectively,from Alberty (1985).

of reaction for each reacting species can then be

uene consumption

= r1 exp (t) (9)


(a)

(b

Scheme 2 M-5.isomerizat

Table 7 ethylation

Catalyst

ZSM-5 MOR

Table 8 ethylation

Pre-exponenk1 (m6/kgcak2 (m3/kgcak3 (m3/kgcaActivation eE1E2E3Deactivation

rate of p-E

V

Wc

dCPETdt

rate of m-

V

Wc

dCMETdt

rate of o-E

V

Wc

dCMETdt

Table 9 ethylation

Kinetic par

k1 (m6/kgca

E1 (kJ/mol) )

(a) Toluene ethylation and concurrent isomerization on ZSion on MOR.Estimated kinetic parameters for toluene using Scheme 1.

k1 (m6/kgcat s) 102 E1 (kJ/mol)

2.76 0.4 56.4 4.9 0.102 0.0022.41 0.7 21.2 6.4 0.040 0.034

Estimated kinetic parameters for toluene on ZSM-5 using Scheme 2a.

tial factor

t s) 102 2.24 0.4t s) 101 1.06 0.4t s) 104 5.95 3.8nergy (kJ/mol)

69.9 6.444.7 16.781.5 45.1

constant0.16 0.023

T formation

= (r1 r2) exp(t) (10)

ET formation

(r2 r3) exp(t) (11)

T formation

r3 exp(t) (12)

Estimated kinetic parameters for toluene on HZ80-6L using Scheme 2a.

ameters Values

t s) 102 1.33 0.562.7 14.90.12 0.06

Table 10 ethylation

Pre-exponenk1 (m6/kgcak2 (m3/kgcak2 (m3/kgcActivation eE1E2E2Deactivation

In the caformation tion proceeof toluene.and p-ETs ation and mreaction. Tproducts ofshown belo

The ratereactions c

r1 = k1CTCE

r2 = k2(

Ca

where Calkdirect alkylconstant foUnlike in ZSreaction teof temperatheir non-e

The ratewritten as: (b) Toluene ethylation and concurrent

Estimated kinetic parameters for toluene on MOR using Scheme 2b.

tial factor

t s) 102 2.10 0.5t s) 102 4.44 2.9

2

at s) 10 4.40 3.3nergy (kJ/mol)

27.9 5.8133.3 34.7123.3 32.6

constant0.08 0.02

se of MOR, the reaction scheme for the ET isomeris represented by Scheme 2b. The alkylation reac-ds by direct attack on both the paraortho positions

Due to the non-selective nature of MOR, both o-re produced primarily from direct alkylation reac--ET was formed through successive isomerizationherefore, o-ET and p-ET are grouped together as

direct alkylation reaction in the reaction schemew:

equations for the alkylation and isomerizationan then be written as:

(13)

lk CMETKeq3

)(14)

is the combined concentrations of the product ofation (i.e. CPET and COET) and Keq3 is the equilibriumr the isomerization of alkylated products to m-ET.M-5, the equilibrium constant is estimated at each

mperature. This is because of the strong inuenceture on the ET isomer distribution in relation toquilibrium composition.

of reaction for each reacting species can then be


Table 11 Rate constants as a function of temperature evaluated for the ethylation of toluene ethylation over MOR basedon Scheme2b.

Temp C k1 (m6/kgcat s) 102 k2 (m3/kgcat s) 102 k2 (m3/kgcat s) 102 Keq3(k2/k2)

200 1.15 0.25 0.31 0.81225 1.64 1.38 1.49 0.92250 2.27 6.43 6.20 1.04300 3.97 93.2 73.5 1.27

Table 12 Correlation matrix for parameters of tolueneethylation over ZSM-5 based on Scheme 1.

k1 E1

k1 1.0000 0.4948 0.9196E1 0.4948 1.0000 0.6338 0.9196 0.6338 1.0000

rate of toluene consumption

VWc

dCTdt

= r1 exp(t) (15)

rate of alk

V

Wc

dCalkdt

rate of m-

V

Wc

dCMETdt

Adaptinsition consfor the tolucan be writ

rate of tol

VWc

dCTdt

rate of p-E

V

Wc

dCPETdt

Table 15 Comparison of activation energy obtainedwith reported values in literature.

Authors Catalyst Activationenergy (kJ/mol)

Lee and Wang (1985) ZSM-5 75Bhandarkar and Bhatia

(1994)ZSM-5 62

Parikh (2008) ZSM-5 supportedon monolith

64

Present work ZSM-5 70

4.3. Model parameter evaluation

intries 1is toeric

s preterstiones 12le 14ith varam

paraisk, nd ptionThis.m Sc

for t/mol7). T

Table 13 r ZSM-5 based on Scheme 2a.

k3 E3

k1E1k2E2k3E3

Table 14

k1E1k2E2k2E2 ylated products formation

= (r1 r2) exp(t) (16)

ET formation

= r3 exp(t) (17)

g Scheme 2a to HZ80-6L, whose ET isomer compo-ists solely p-ET, k2 and k3 0. The rate equationsene consumption and p-ET formation respectivelyten as:

uene consumption

= r1 exp(t) (9)

T formation

= r1 exp(t) (18)

The Schemanalysto nummodelparamcorrelain Tablin Tablevel wlevel pkineticand Brdata acorrela(0.99). model

Fromated26.1 kJ(Table

Correlation matrix for parameters of toluene ethylation ove

k1 E1 k2 E21.0000 0.4736 0.8552 0.1614 0.4736 1.0000 0.6254 0.1196 0.8552 0.6254 1.0000 0.2571

0.1614 0.1196 0.2571 1.0000 0.3186 0.1124 0.2293 0.0626

0.0359 0.2305 0.0658 0.0009 0.9116 0.6649 0.9395 0.1791

Correlation matrix for parameters of toluene ethylation over MO

k1 E1 k2 E2

1.0000 0.3137 0.3683 0.1234 0.3137 1.0000 0.2365 0.1244 0.3683 0.2365 1.0000 0.5847

0.1234 0.1244 0.5847 1.0000 0.3284 0.2114 0.9748 0.6111

0.0839 0.1119 0.6111 0.9521 0.9385 0.3485 0.3710 0.1019 nsic kinetic parameters for both reaction and 2 were estimated using non-linear regressiongether with fourth order RungeKutta routineally integrate the rate equations. The developedovide approximate estimates of all the kinetic

which are reported in Tables 711. The cross- matrices of Schemes 1 and 2a for ZSM-5 are given

and 13, and that of Scheme 2b for MOR is reported. Most of the correlation coefcients are at lowery few at moderate level. This is indicative of loweter interaction, which implies that the estimatedmeters are statistically valid and reliable (Agarwal

1985). In addition, parity plot of the experimentalredicted values shown in Fig. 10AC gives a good

with a R2 value of the regression close to unity also conrms the suitability of the proposed

heme 1, activation energy of 56.4 kJ/mol was esti-he alkylation of toluene to ETs on ZSM-5 whereas,

of energy is required for the same reaction on MORhe huge difference in the activation energy can be0.3186 0.0359 0.91160.1124 0.2305 0.66490.2293 0.0658 0.9395

0.0626 0.0009 0.17911.0000 0.1238 0.24250.1238 1.0000 0.0675

0.2425 0.0675 1.0000

R based on Scheme 2b.

k2 E2

0.3284 0.0839 0.93850.2114 0.1119 0.34850.9748 0.6111 0.3710

0.6111 0.9521 0.10191.0000 0.6677 0.3300

0.6677 1.0000 0.06690.3300 0.0669 1.0000


0 0

10

20

30

40P

redi

cted

val

ue

0 0

10

20

30

40

Pre

dict

ed v

alue

0 0

10

20

30

40

Pre

dict

ed v

alue

Fig. 10 Pa(Scheme 1)

related to thsizes whosof the aromMeanwhileble mobilityconstants abeen dedu

is of sorption accompanied by chemical reactions ons. ThationEi + Endehavelecu 200 C 225 C 250 C 300 C

analyszeolitesummEapp = (is depealysts the mo10 20 30 40

Experimental data

A

10 20 30 40

B

Experimental data

200 C 225 C 250 C 300 C

10 20 30 40

C

Experimental data

200 C 225 C 250 C 300 C

rity plot of toluene conversion on (A) ZSM-5, (B) ZSM-5 (Scheme 2a) and (C) MOR (Scheme 2b).

e channel size of the zeolite pores. ZSM-5 has poree channel diameter is close to kinetic diametersatic molecules, thereby hindering free mobility.

, MOR is a large pore size zeolite with apprecia- of the reacting molecules. Hence, reaction kineticre inuenced by diffusion. Similar conclusion hasced by Palekar and Rajadhyaksha (1986) in their

inuencingenergy of a(Table 8) w62.7 kJ/molET and m-E44.7 kJ/molisomerizatipared to this thermodrequired totion. Table alkylation close in ma

Schemethe ET isomactivation ethe product27.9 kJ/molated produfor the bacalso determdistributionthe rate cotion (k2/k

as a functioTable 11.

5. Co

Alkylation oa uidized tiveness ofto MOR. Fuwas achievdeposition.ZSM-5 provselectivity, of the pyridica resultedsurface, whReduction ifrom the Ncontributed

Methylaunder the strum of proand xylenethat in tanddue to alkyis not selec

Kineticspower law anism. Theand silylaterespectivelsary for this is because apparent activation energy is half the of intrinsic and diffusion activation energies, i.e.

d)/2 (Levenspiel, 1999). Intrinsic activation energynt on acid strength of the catalyst. Since both cat-

similar acid content, the energy requirement ofles to freely move, Ed, is therefore the main factor

the Eapp. According to Scheme 2a, the activationlkylating toluene to p-ET over ZSM-5 is 69.9 kJ/molhereas HZ80-6L (silylated ZSM-5) gives a value of

as shown in Table 9. Isomerization of p-ET to m-T to o-ET require apparent activation energies of

and 81.5 kJ/mol, respectively. This suggests thaton of p-ET to m-ET occurs with relative ease com-at of m-ET to o-ET. This is may be because m-ETynamically more stable, hence, higher energy is

shift the methyl group from meta to ortho posi-15 shows a comparison of activation energy for thestep reported by some authors. These values aregnitude to that calculated in our present study.

2b represents the proposed reaction pathway forer distribution over MOR. The estimated apparentnergies are given in Table 10. p- and o-ETs, being

of the alkylation step, requires activation energy of. Meanwhile, successive isomerization of the alkyl-cts requires 133.3 kJ/mol of energy. The parameterskward isomerization reaction (k2 and E2) wereined and given in Table 10. Since the ET isomer

over MOR is temperature dependent, the ratio ofnstants of the forward and backward isomeriza-

2) was used to compute the equilibrium constantn of temperature and the values are tabulated in

nclusion

f toluene with ethanol has been investigated usingbed reactor operated in batch mode. Shape selec-

ZSM-5 favored more yield of p-ET as comparedrther improvement of p-ET selectivity on ZSM-5ed via silylation treatment which involves silica

The use of TEOS as the silica source to modifyed to be an effective way of enhancing para-isomereliminating undesired isomer yields. The resultsine FTIR and NH3-TPD showed that deposited sil-

in partial coverage of acid sites on the externalich are responsible for para-isomer isomerization.n the pore openings of ZSM-5 channels was evident

2 adsorption analysis. These two factors combined to the enhanced para-isomer selectivity.tion of EB in comparison with ethylation of tolueneame reaction conditions resulted in a wide spec-ducts. Side products such as DEB, benzene, toluene

are found in higher amounts. This is an indicationem with EB methylation, disproportionation of EB

l side chain cracking is occurring, hence, this routetive toward ET formation.

of the toluene alkylation reaction modeled byis well represented by the two-step reaction mech-

activation energy for p-ET formation on ZSM-5d ZSM-5 (HZ80-6L) is 70 kJ/mol and 63 kJ/mol,

y whereas, lower energy of 28 kJ/mol is neces-e alkylation of toluene with ethanol over MOR.


Zeolites with MFI structure (ZSM-5 and HZ80-6L) requirehigher activation energy for the initial alkylation step com-pared to MOR, which can be ascribed to diffusional constraintarising from pore channel dimension.

Acknowledgment

The authors are grateful to King Abdulaziz City for Science& Technology (KACST) for nancial support of this researchthrough Project No. AR-34-22. The authors also appreciate thesupport from the Ministry of Higher Education, Saudi Ara-bia in establishment of the Center of Research Excellence inPetroleum Rening & Petrochemicals at KFUPM. The authorsare also grateful to the advice of Professor Hideshi Hattoriand to Mr. Mariano Gica for his assistance in catalyst activitytesting.

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Lnyi, eth

Manivaethtolu

ManivatoluKin

Odedaiethreac

Palekache371

Paparaeth

Parikh,Tolustud

Parikh,ethEng

Perez, Phy

VillareOptpen

Walendwit

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Experimental and kinetic studies of ethyltoluenes production via different alkylation reactions1 Introduction2 Experimental2.1 Materials2.2 Catalyst characterization2.3 Catalytic test

3 Results and discussion3.1 Textural properties of catalysts3.2 Acidity results3.3 Catalytic activity3.3.1 Ethylation of toluene3.3.2 Methylation of ethylbenzene

4 Kinetics of the toluene ethylation reaction4.1 Alkylation only4.2 Alkylation with isomerization4.3 Model parameter evaluation

5 ConclusionAcknowledgmentReferences

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