cinetica del

  • View

  • Download

Embed Size (px)

Text of cinetica del

  • 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


    Accepted 2

    Available on







    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



    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.


    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: (L.A. Atanda), (A.M. Aitani), (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 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


    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






    MWiriR t T ToV WcWhc


    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



    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



    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 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.



    f ZSM-5 (Si/Al molar ratio 80) and mordenite (Si/Al 180) were obtained from Tosoh chemicals, 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 f