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REV. CHIM. (Bucharest) ♦ 61♦ Nr. 12 ♦ 2010 http://www.revistadechimie.ro 1245

Kinetic Investigation on Direct Hydration of n-butenein a Multiphase Reactor

DIANA CURSARU1* ULRICH KUNZ2

1 Universitatea Petrol – Gaze Ploieºti, 39 Bucureºti Blv., 100520, Ploieºti, Romania2 Technische Universität Clausthal-Zellerfeld, Germany

The microkinetics for the liquid phases synthesis of secondary butanol (SBA) from water and n-butenesusing a macroporous sulfonic acid ion exchange resin as catalyst (Amberlyst DT from Rohm & Haas) wasexperimentally measured in a high pressure reactor (an improved version of the Carberry reactor) thatenables the visualization of the phases that occur during the hydration reaction. A first set of experimentswas performed in order to determine the reaction conditions where the surface reaction is the rate limitingstep and where there are no influences of either external or internal mass transfer processes. Followingthese experiments we concluded that kinetic studies should be conducted at 800 rotation per minute stirringspeed, at a temperature between 117 and 130°C on catalyst particle dimensions below 0.71 mm, at 60 barpressure. Under these reaction conditions the surface reaction has been found to be the rate limiting step.The experimental results are well described by a four-parameter model based on Langmuir-Hinshelwoodrate expression, in terms of liquid phase fugacities calculated from the predictive Soave-Redlich-Kwong(PSRK) equation of state with UNIQUAC liquid-liquid equilibrium.

Keywords: secondary butanol synthesis, microkinetic model, multiphase reactor

The hydration of 1-butene to secondary butanolcatalyzed by strong acidic ion exchange resins is analternative route to the conventional homogeneous, indirecthydration process catalyzed by sulfuric acid. Secondarybutanol is a commercially interesting alcohol mainly dueto its use for MEK (methyl ethyl ketone) production.

Both n-butenes hydration processes are licensed onindustrial scale, for many years now, the indirect processsince 1931, and the direct process since 1983. In the lastyears, the tendency is to replace the old, polluting process(i.e. the indirect process) with the environmentally friendlyprocess that is the direct hydration. The indirect process isstill in use due to the following advantages: lowtemperatures and pressures, use of hydrocarbons feeds atlow olefin content, etc. Despite of these advantages, amajor drawback is the use of a highly corrosive reagentthat requires large energy consumption for regeneration.

The major advantage of the direct process is theelimination of the sulfuric acid and of all the consequencesderived from its utilization in the process. However, theconditions used in the direct process are more severebecause of a relatively lower activity of the catalystrequiring higher temperatures in order to obtain reasonablereaction rates, and higher pressures in order to compensatethe effect of higher temperatures on the olefin volatility.Although the direct hydration of butene is an industrial scaleprocess since 1983, very few kinetic data were publishedso far [4, 13]. We have therefore investigated the intrinsicrate of SBA formation accounting for the influence of theexternal and internal mass transport phenomena.

Experimental partThe laboratory plant

A schematic representation of the laboratory plant usedto investigate the kinetics of the hydration of butene ispresented in figure 1.

The laboratory plant consists of two important modules:the reaction system and the analytical system (fig. 3). Thereactant, water, is kept in a tank (B-03) and the olefin is

kept in a bottle (B-02), pressurized by nitrogen (B-01). Thereactor (R-01) is two-phases operated. It is necessary tocontrol the hold-up of both phases independently of theinlet composition. This is realized by two magnetic valves(V-03) and (V-04). Another two magnetic valves (V-01)and (V-02) are installed on the olefin and the water pipesin the suction lines of the HPLC pump (P-01). The magneticvalves can be switched independently [7].

Different volumetric water/olefin ratios can be achievedby this arrangement. The reactants are then combined andfed by means of a high pressure HPLC-pump (P-01) intothe reactor (R-01). Directly in front of the pump a filter (F-01) is connected to protect it against suspended solids.Into reactor the olefin and water are converted to alcohol,whereby the alcohol is extracted by the olefin phase. Thereactor has two outlet lines.

In both lines two filters (F-02) and (F-03) are inserted toprotect the downstream equipment against catalystparticles. Small but representative samples are taken outoff the reactor outlet line by a sample injector (ROLSI-RapidOn-Line Sample Injector). The rest of the products is sentto a phase-separation vessel (A-01) and the not consumedbutene is fed to a burner. Qualitative analyses of thereaction products are finally made by a gas chromatographHP 5890 series II model.

The experimental reactorThe central part of the reaction system is the chemical

reactor. In this work a newly developed reactor designedfor liquid-liquid reactions was tested and operated toreceive kinetic data [8].

The chemical reaction of butene with water is a reactionbetween two reactants with a low solubility. To increasethe solubility of butene in water it is obviously necessary tochose reaction conditions to keep the reactants in liquidphase. The reactants have a partial miscibility due to theirlow solubility. Therefore the reactor has two liquid phases:the olefin phase (as the upper one) and the water phase(as the lower one).

* email: [email protected]; Tel.: 0244556445

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Because in the industrial reactor the status of the catalystis not well defined (it is not known to what extend thecatalyst is contacted by water or olefin) and taking intoaccount all these drawbacks of the butene hydrationsystem, it was necessary to design a laboratory reactorthat enables a visible control of the two-phases separationline, of the attachment of the catalyst in a well definedplace and adjustment of hold-up independently from thefeed ratio and the progress of the chemical reaction aswell [8, 9, 20]. In addition, our study was focused ondetermining the kinetics for butene hydration reactions,but for kinetic investigations a gradientless reactor seemsto be more attractive due to its features: a constant reactionrate in all the reaction volume and the absence ofconcentration and temperature gradients due to itshydrodynamics [1, 8].

A laboratory reactor able to fulfill all these requirementsis the basket-type mixed flow reactor also known asCarberry reactor. This reactor is designed for heterogeneouscatalyzed gas phase reactions or liquid reactions in onehomogeneous phase.

Own reactor is a development of the Carberry reactordue to its suitability for more complicated reaction systemslike heterogeneous liquid/liquid/solid reaction. Each of eightcages, containing one layer of pellets, behaves like adifferential reactor which is swept through the fluidenvironment some thousand times per minute.

The laboratory reactor used in this work has twowindows made of high pressure resistant glass, allowingthe observation of the mixing behaviour inside the reactor.In addition, the windows allow the control of the hold-upand if necessary the windows can be also dismantled and

replaced with a measuring sensor for FTIR spectrometer(Fourrier Transformed Infra Red spectrometer) used tomeasure the changes of the reactants and productsconcentrations in time. This reactor has one feeding tubenear to the separation line level and two outlet tubes,arranged at different heights. One is on top of the organicphase the other is located at the bottom of the water phase.

The stirrer of the reactor is divided in two identicalsections, one rotating in the organic phase, the other in thewater phase. This ensures well defined conditions for thecatalyst.

The reactor can be operated up to 200 bar andtemperatures up to 200°C and has a free volume of 100 mLand the reaction volume is approximately 80 mL. Thematerial for gaskets of the windows is made of fluorinatedelastomer (Kalrez) while the material for the sealing ofthe reactor cover is Teflon.

The operation of this reactor requires an adapted feedratio control and simultaneously a control of the reactoroutlet flow, independently from each other. This can beachieved with a pulse-width modulation of the tworeactants [7]. A high pressure HPLC-pump was used tofeed the reactants into the reactor. To achieve the desiredfeed ratio the inlet side of the pump is separated in twotubes, the first is connected to the butene bottle, the secondto the water tank. To ensure the same pressure inside thetwo liquid reservoirs, the water tank and the butene bottleare connected to a cylinder with pressurized nitrogen. Thebutene bottle is under pressure keeping the butene in theliquid state, avoiding cavitation problems in the pumpduring suction. In figure 2 the method of the reactor feedingand the reactor outlet control are depicted.

Fig. 1. Schematic representation of the laboratory plant for olefin hydration [10]

Fig. 2. Method of feed control andoutlet flow control by independentpulse-width modulation of the twostreams [7] (1 - color-olefin stream,

2 - color-water stream)

olef

in/w

ater

1 11 1 12222 2

5:11:1


Two magnetic valves, alternately switched allow thecontrol of the desired feed ratio just by setting the on/off-ratio to an electronic device. A similar arrangement of twomagnetic valves is used to set the reactor outlet flow ratioof the two phases. This arrangement allows feed ratiocontrol independent by hold-up and progress of thechemical reaction during the residence time in the reactorwith only one single high pressure pump.

Both outlet streams lead to the analytical equipment;the main stream passes a back pressure regulator thatallows adjusting the desired operation pressure of thereactor [20].

The analytical systemFor the measurement of the composition of the reaction

mixture a Hewlett-Packard 5890 Series II gaschromatograph was used. This gas chromatograph isequipped with a separation column SPB-1 type of theSupelco Company, suitable to separate the olefins and thecorresponding alcohols. A heat conductivity detector (TCD)able to detect not only alcohols and olefins but also waterwas applied. The temperature program of the gaschromatograph for the olefin hydration and more detailsabout the separation column are presented in table 1.

To investigate the kinetics in the olefin hydration systemswas mandatory to have a very good reproducibility of theoutlet composition analyses with relative errors smallerthan 3%.

Because the reaction mixture contains compounds withdifferent boiling temperatures the compound with thelowest boiling point starts to boil before the others,producing bubbles on the liquid phase that is beingvaporized, and as a result a random fluctuation of thepressure and a small substance separation effect occur.This effect is a consequence of low reproducibility of theanalyses [14].

The solution for these drawbacks was a rapid on-linesample injector (ROLSI) (a detalied description of ROLSIis given in [10]), able to take a small sample under reactionconditions and to evaporate it in a flow carrier gas for thegas chromatograph [19]. By applying ROLSI thereproducibility was significantly improved. The average ofthe relative error concerning the concentrationmeasurement of the sec-butyl-alcohol was about 1 %.

A flow sheet of the analytic system is depicted in figure3.

The sample injector is inserted directly behind the reactoron the olefin phase outlet, due to the bigger quantity of themain product concentrated into this phase (the alcohol isextracted from the water phase by supercritical butene).

The water used in our investigation was distillated waterproduced in our laboratories, the butene bottle was suppliedby our industrial partner SASOL Germany, the compositionof this bottle is given in table 2 (we used for kineticinvestigation the same butene as used in the industrial

Table 1THE TEMPERATURE PROGRAM OF THE GC

Fig. 3. Schematic of the analytic system for the olefin hydration laboratory plant [14]


plant), and the secondary butanol (99.8%) was providedby Sigma-Aldrich.

The chemical reaction between water and butene takesplace on the internal surface area of the catalyst on itsactive sites. The chemical reaction is promoted by thetransport steps: the mass transfer of the butene from theorganic phase, through the boundary between the phases,to the water phase and further to the external and then tothe internal surface area of the catalyst. The main product,secondary butanol, formed in the hydration reaction isdesorbed and then transported into the water phase.Secondary butanol is extracted from the water phase bysupercritical butene.

The experimental evaluation of the performance inbutene hydration was conducted at three differenttemperatures (120, 140 and 155°C), at constant pressure(60 bar), using the same amount of catalyst (3 g), workingat constant space time (47.9 gcat/mol/min), but 5 differentstirring speeds (250, 400, 550, 700, 850 RPM). Thebutene:water mixtures (80:20 volumetric ratio) were fedinto the reactor. Stirring started after achieving the reactiontemperature and pressure. For each stirring speed 4 or 5significant measurements were recorded with the meanrelative error less than 3%. The average value of theseresults was considered the valid experimental pointcorresponding to the reaction parameters tested.

The experimental results show that the rate of theforward reaction is independent of the stirring speed above700 RPM. These results are in agreement with thoseobtained on a similar catalyst [15-18].

Therefore, all further experiments were performed at800 RPM to make sure they are conducted in a domainfree of external diffusion influence.

Internal mass transport experimentsThe internal diffusion influence on process kinetics

depends on the catalyst particle size, the intrinsic activityof the catalyst, the reaction temperature and the catalysttexture [5, 6, 9]. Because the influence of the intrinsicactivity of the catalyst and of its texture exceeds thepurpose of our investigation we focused on the influenceof the size distribution of the catalyst particles and thereaction temperature.

With increasing temperature, intraparticle masstransport limitations are expected to grow due to itsstronger influence on the surface reaction as comparedwith the influence on effective diffusion coefficients insidethe pores network.

It was predicted that, for a common resin (XE-307) usedin the butene hydration, at a particle size of 0.8 mm (typicalsize of commercial ion exchangers) intraparticle diffusionlimitations have to be taken into account at temperaturesabove 115°C [13].

In the literature only few data are available to predictthe diffusional resistances in ion exchange resin particles.

The region where the internal mass transport is the ratelimiting step was determined by varying the catalystparticle size. The experiments were performed under thesame conditions of temperature (120, 140 and 155°C),pressure (60 bar), space time (47.9 gcat/mol/min) andvolumetric butene to water ratio (80:20) as those chosenfor the external diffusion tests.

For the internal diffusion tests, 4 particle sizes of thecatalyst were used. The same investigations wereconducted for the whole distribution of catalyst particlesizes used in industrial reactors.

The results of the internal mass transport investigationsproved that the observed reaction rates depend on theparticle size of the catalyst. Since the temperature wasconstant during the investigations, only internal mass

Table 2THE MASS COMPOSITION OF THE BUTENE FEED

The catalyst used in our investigation is a strong acid ionexchanger, its matrix is built of polystyrene divinylbenzenecopolymer and the functional groups (-SO3H) areintroduced in a sulfonation step. The catalyst has thecommercial name Amberlyst DT and was provided bySASOL Germany and it was delivered in swollen form.

A first set of experiments were performed aiming toidentify a window of operating parameters where thesurface reaction is the rate limiting step, that is where thereare not external, nor internal diffusion limitations of thereaction kinetics.

Table 3AMBERLYST DT-TECHNICAL DATA*

the technical data are given by the Amberlyst DT suppliers-Rohm & Haas

External mass transfer experimentsIn order to measure the rate of the external mass

transport processes the stirring speed was varied. It is wellknown that increasing the stirring speed leads to a fastertransport of the reactants to the outer surface of the catalystand, thus to the active sites of the catalysts, and alsoaccelerates the diffusion of the products from the activesites to the bulk fluid.

The experimental tests of secondary butanol synthesiswere investigated in a gradientless reactor with a volumeof 77 mL. The solid catalyst - Amberlyst DT (3 g) - wasplaced into the baskets attached to a rotating shaft stirredmagnetically.

As demonstrated elsewhere [10] a steady-state catalyticactivity of the Amberlyst DT is obtained only after 1000 h ofoperation. We have therefore used in our experiments acatalyst that was previously aged for 1200 h. Thecharacteristics of the catalyst used in our investigationsare presented in table 3.

The experiments performed previously with the catalystlocated in the upper basket placed into the organic phase,lead to an undesirable by-product di-secondary-butyl-ether(DSBE); therefore, in order to avoid the side reaction, thecatalyst was placed only in the baskets located into thewater phase.


transfer by diffusion in macroporous catalyst affects theobserved rates of reaction. The goal of the followingexperiments was to eliminate the influence of diffusion bydecreasing the size of resin particles.

Therefore, all diffusions experiments proved that forstirring speeds higher than 800 RPM we are in a domainfree of external diffusion and all the kinetic experimentswere performed at 800 RPM. The experimental resultsdepicted in figure 4 proved that we are in a domain free ofexternal diffusion and the effect of internal diffusion canbe neglected for catalyst particle dimensions below 0.71mm and temperatures lower than 155°C.

between the phases reaches the middle of the reactor.After the volumetric butane to water ratio was set andcorresponding volumetric flow rate was adjusted, the stirrerwas started. The operating parameters are given in table4.

Fig. 4. Effect of the catalyst particle size on reaction rates in SBAsynthesis on Amberlyst DT (T=120, 140, 155°C, p=60 bar, 80:20 vol.

butene:water)

Determination of the reaction rateThe reaction between butene and water is slow and the

conversion level in industrial reactors is approximately 8%. The conversion is related to the amount of thestoechiometric limiting reactant – butene in our case - thus,higher conversion levels in the laboratory reactor are notexpected [2, 3].

The system we studied involves two reactions in series,the hydration of the butene to secondary butanol and theetherification of the secondary butanol to di-secondary-butyl-ether, with both reactions reversible. The reversereaction –etherification- can be neglected for the hydrationprocess carried on under the operation conditionscorresponding to temperatures between 117 and 130°C,60 bar pressure and the catalyst particle dimensions below0.71 mm. By carring on the hydration under conditionspresented above, no etherification reaction product wasdetected because the reaction was carried on in such wayto avoid the formation of byproducts by placing the catalystin the baskets located into the water phase, thus limitingthe concentration of butene at the catalyst surface.

Taking into account that the butene hydration, underlaboratory reactor conditions, is a multiphase reaction, andtwo liquid phases occur in the reactor, it is mandatory towrite a suitable mass balance equation for this system.

Because in our experimental set up the effect of theadsorption of the reactants on the inner surface andchemical reaction on specific active sites cannot beseparated; the cumulated effect of these steps will bestudied together; therefore three 2-butanol concentrationlevels were used in these experiments: 5, 8 and 20 wt%. Atthe beginning, the reactor was filled with water-SBAmixtures and the operating pressure was set. The reactorwas heated to the desired reaction temperature, between117-130°C. After reaching the desired temperature, thebutene was fed to the reactor, until the separation line

Table 4THE EXPERIMENTAL PARAMETERS FOR KINETIC INVESTIGATIONS

After a certain time, long enough to reach the steadystate (1 hour after temperature and pressure becomeconstant), samples from the olefin phase were collectedand analyzed by GC. The main product - secondary butanol- is the result of the chemical reaction between theadsorbed reactants on the active sites of the catalyst. Afterdesorption, secondary butanol migrates into the waterphase. The supercritical butene also extracts the secondarybutanol and, for this reason, the alcohol will be distributedin both phases, mostly being concentrated in the olefinphase [11, 12]. For each set of operating parameters, atleast three samples were analyzed, the mean value beingused for the calculation of the reaction rates.

The observed reaction rate ( SBAr ) was calculated withthe equation (1).

(1)

with

(2)

where:FC4 represents the molar flow rate of butene;xSBA,C4prod - the molar fraction of SBA (produced in the

hydration) located into the butene phase;xSBA,C4out; xSBA,C4in - the molar fraction of SBA in the butene

phase from outlet and inlet.Equation (2) gives the increase of SBA concentration

(found in the organic phase) as result of chemical reaction.The SBA quantity produced is calculated as a differencebetween the SBA quantity in the outlet and the SBA quantityin the feed.

The reaction rates were calculated with equation (1),the numeric values could be found in the tables from 5 to8. In figure 5 the steady state rates for 5wt % 2-butanolconcentration level versus 1/T is given.

The reaction rate was found to increase with increasingtemperature and with the decreasing of the volumetricbutene to water ratio in the inlet. Low (1, 2 and 5 wt%)concentrations of secondary alcohol in the feed arebeneficial for the process; secondary butanol acts as acosolvent and improves the solubility of butene in water,consequently the apparent reaction rates increase [11].

Microkinetic modelThe butene-water-2 butanol mixture under reaction

conditions causes some difficulties in the prediction of thephase behavior due to the supercritical state of butene andalso due to a very low mutual solubility between buteneand water. More than that, water and 2-butanol are strongly


Table 5THE EXPERIMENTAL PARAMETERS AND THE REACTION RATES IN SBA SYNTHESIS AT 117°C


polar species and form an azeotrop with maximumtemperature.

The operating conditions for the hydration of butene werechosen to correspond to the supercritical butene. Theliquid-liquid equilibrium (LLE) is of essential importance inthis work, since the reaction between water and butene isoperated under such conditions that a homogeneous regionis expected therefore, LLE must be investigated for acomplete overview of the phase equilibrium.

Because of the problems presented above, only modifiedcubic equation of state as the Predictive Soave-Redlich-Kwong (PSRK), which incorporate temperature-dependentterms, together with UNIQUAC are reliable to predict thereal behavior of high non-ideal mixture with polarcompounds such our multicomponent fluid mixture.

Based on equilibrium composition (the composition ofboth liquid phases in equilibrium at 160°C was measured


by LTP Oldenburg) at a certain temperature and with helpof PSRK equation of state and UNIQUAC it was possible topredict the thermodynamic behaviour of themulticomponent system at different temperatures as wellas the calculation of fugacities corresponding to the butenephase [10, 12].

The general condition for two phases to be inthermodynamic equilibrium can be described in terms offugacity with the equation (3).


Table 8THE EXPERIMENTAL PARAMETERS AND

THE REACTION RATES IN SBASYNTHESIS AT 130°C

(3)

Langmuir-Hinshelwood isotherms are assumed fordescribing the sorption behaviour of the components ofthe reaction mixture (1-butene, water and secondarybutanol) in the catalytic active gel phase of the resin [13,18]. Therefore the sorption equilibria of 1-butene, waterand secondary butanol on one active site s is given by theequations (4-6) and the fraction of the actives sites

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Fig. 6. Observed reaction rates as function of temperature

occupied by component i can be written as equation (7)with the observation that the liquid phase concentration ofthe species i (Ci) can be replaced by the activities ai (ai =xi. yi) or by the fugacities if ( iii xpf ⋅⋅= ϕ ). Since ourreaction system is strongly nonideal and the operatingpressure is very high, the behaviour of this system can bebetter described in terms of fugacities.

Due of this reason the fraction of the active sitesoccupied by the component i and the reaction rate equationare formulated in terms of fugacities.

(8)

The rate-determining step, the chemical reaction ofsorbed molecules, was formulated according to thehomogeneous catalysis as first order in all species (as it ispresented in equation 10) [16, 17].

According to the equation (9) and (10) the rate of thechemical reaction can be written as:

Fig. 5. Observed reaction rate, ri, of the butene hydration reactionversus 1/T [10]

(4)

(5)

(6)

(7)

Inserting equation (11) into equation (12) leads to anexpression for the reaction rate, where the fractions ofoccupied sites are controlled by the fugacities of thecomponents:

(13)

The kinetics for the forward reaction between buteneand water was very well described by a model equationwith four adjustable parameters based on Langmuir-Hinshelwood kinetics.

As previously described, two liquid phases occur duringthe direct hydration of liquid butene in the laboratory reactor.The main product, the secondary butanol, is formed in thewater phase and it is extracted by supercritical butene intothe organic phase. Due to the bigger quantity of the mainproduct concentrated into the organic phase, the fugacitiesare related to this phase.

The expression for the reaction rate equation that fit ourexperimental results is given bellow.

(14)

with:

(15)

The calculated values for the kinetic parameters, Kb andKw are given in table 9.

The Arrhenius equations (15) together with Arrheniusplot (fig. 6) were used for the calculation of the Arrheniusparameters (Ea and k0).

The activation energy calculated for the butenehydration on Amberlyst DT, in temperature range of 117-130°C is about 110 kJ/mole and the preexponential factork0 is 1.14 mole/eq/s.

In order to correlate our experimental data with thereaction rate equation proposed (14), we used a powerfulsimulation program (MathLab). For MathLab simulationswe utilized the activation energy resulting fromcalculations, respectively 110 kJ/mole, while thepreexponential factor was fitted.

The value for the preexponential factor obtained aftersimulation in MathLab, which verify the expression of thereaction rate proposed, was found to be 1.466 mole/eq/s.

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(9)

(10)

(12)

(11)

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The objective function F(x) calculated with equation (16)is 5 . 7 . 10-03, suggesting a very good agreement betweenthe rate expression and the experimental data.

(16)

The model parameters for equation 14 are shown intable 9.

ConclusionsSince reliable kinetic data are only obtained in a domain

unaffected by transport phenomena preliminar yexperiments were done to check the influence of the filmdiffusion and the internal mass transfer. It was found thatfor stirring speeds higher than 800 RPM we are in a domainfree of external diffusion and for the catalyst particledimensions below 0.71 mm and temperature range 117 to130°C the effect of the internal diffusion can be neglected.Therefore, the kinetic investigations were done underconditions previously presented.

Based on our experimental data we propose anexpression for the rate equation of the forward reactionbetween butene and water described by a model equationwith four adjustable parameters based on Langmuir-Hinshelwood kinetics expressed in terms of fugacities.

The expression of the rate equation proposed fits verywell the experimental data and results in apparentactivation energy value consistent with those reported byother authors. The MathLab simulations performed in orderto correlate our experimental data with the reaction rateequation proposed, lead to a value for preexponential factorsimilar with that calculated based on the Arrhenius equationand Arrhenius plot.

List of notationsSymbol Unity Meaninga [-] activityf [bar] fugacityk [s-1] reaction rate constantk0 [s-1] Arrhenius parameterr [mol/eq/h][-] reaction ratex [-] molar fractionC [mol/l] liquid phase concentrationCAP [eq/g] catalyst capacityEa [J/mol/K] activation energyF [mol/min] molar flowK [-] adsorption rate constantR [dm³bar/mol/K] general gas constantT [K] absolute temperatureW [g] catalyst weightϕ [-] fugacity coefficientγ [-] activity coefficientΘi [-] fraction of actives

sites occupied by component i

Θν [-] fraction of vacant sites

Table 9MODEL PARAMETERS FOR EQUATION (14)

Indicescal calculatedexp experimentalin inletout outletC4 butene phase1 direct reaction-1 reverse reactiona alcoholb buteneAbbreviationxSBA Secondary butanol

RPM Rotation per minute

References1. BOHÎLÞEA, I., Reactoare chimice, Universitatea Petrol-Gaze Poieºti,Romania, 1996,2. *** BP CHEMICALS, German patent, 1972, 2 340 8163.*** DEUTSCHE TEXACO AKTIENGESELLSCHAFT CHEMIE,“Development of a process for direct hydration of n-butenes basisIsopropanol process Know How. Kinetic studies in the batch reactor”,1978, report no. 104. DOUGLAS, W.J.M., “Hydration of n-butene with cation exchangeresins”, PhD Thesis, University of Michigan, 1958, USA5. FOGLER, H.S., “Elements of chemical reaction engineering”, 1999,Prentice-Hall International, 3rd edition6. HELFFERICH, F., “Ion Exchange”, 1962, McGraw-Hill, New York7. KUNZ, U., Versatile pulse-width-modulator, 1991, ElektorElectronics, 5, 488. KUNZ, U., HOFFMANN, U., Design of a high pressure liquid/liquid/solid catalyst reactor, work report, 2003, TU Clausthal, ICVT, Germany9. LEVENSPIEL, O., „Chemical reaction engineering”, 1999, Wiley&Sons, New York10. PETRE, D., Kinetic investigations on direct hydration of n-butenesin a multiphase reactor, 2006, PhD Thesis, TU Clausthal, germany11. PETRE, D.,Rev. Chim. (Bucharest), 58, no. 8, 2007, p. 83312. PETRE, D., „An inferential method for VLLE prediction- applicationfor n-butene-water-secondary butanol mixtures”, 2006, Buletinul UPGPloiesti, LVIII, 2006, p. 21313. PETRUS, L., „Hydration of lower alkenes catalyzed by strong acidion exchangers”, 1982, PhD Thesis, University of Groningen, TheNetherlands14. PFEUFFER, B., Verbesserung des Analysesystems und kinetischeUntersuchungen zur heterogenkatalytischen Direkthydratisierung vonn-Butenen, 2005, Diplomarbeit, TU Clausthal, Germany15. REHFINGER, A., „Reaktionstechnische Untersuchungen zurFlüssigphasesynthese von Methyl-tert.-butylether (MTBE) an einemstarksauren makroporösen Ionenaustauscherharz als Katalysator”,1988, PhD Thesis, TU Clausthal, Germany16. REHFINGER, A., HOFFMANN, U., „Kinetics of methyl tertiary butylether liquid phase synthesis catalyzed by ion exchange resin. Intrinsicrate expression in liquid phase activities”, Chemical EngineeringScience, 45, 6, 1990, p. 160517. REHFINGER, A., HOFFMANN, U., “Kinetics of methyl tertiary butylether liquid phase synthesis catalyzed by ion exchange resin.Macropores diffusion of methanol as rate controlling step”,ChemicalEngineering Science, 45, 6, 1990, p. 161918. REHFINGER, A., “Reaktionstechnische Untersuchungen zurFlüssigphase-synthese von Methyl-tert.-butylether (MTBE) an einemstarksauren makroporösen Ionenaustauscherharz”, PhD Thesis, TUClausthal, 1988, Germany19. RICHON, D., Procede et dispositif pour prelever des micro-echantillons d’un fluide sous pression contenu dans un container,2003, EP 1105722 B120. SAJDOK, J., Entwurf eines Reaktors für die heterogen-katalytischeDirekthydratisierung von n-Butenen zu 2-Butanol, 2004, Studienarbeit,TU Clausthal, Germany

Manuscript received: 3.11.2009

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