methyl al

chemical engineering research and design 9 0 ( 2 0 1 2 ) 696703

Contents lists available at SciVerse ScienceDirect

Chemical Engineering Research and Design

journa l h o me pa ge: www.elsev ier .com/ locate /cherd

Exper acof het la

Jan-Oliva Laboratory in-ScGermanyb Ineos Para

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2011 The Institution of Chemical Engineers. Published by Elsevier B.V. All rights reserved.

Keywords: Methylal; Reaction kinetics; Formaldehyde; Acetals

1. In

Methylal isvent or for(Lojewska might also fuel additivmethanolictain water common parrangemea heterogensequence wunreacted Gring et adisadvantacal equilibrthe reactorone apparalimitation. tion has be

CorresponE-mail aURL: httpReceived

0263-8762/$doi:10.1016/troduction

an important chemical which can be used as a sol- producing concentrated formaldehyde-solutionset al., 2008). Recent studies have shown that itbecome an important resource in the production ofes (Burger et al., 2010). Methylal is produced from

formaldehyde solutions which typically also con-from the formaldehyde-production process. Therocess of methylal synthesis consists of a serialnt of a reactor in which the feed is converted usingeous acidic catalyst and a downstream separationhich is needed to separate the product from the

educts and eventually from byproducts (see e.g.l., 2004; Kaufhold and Mller, 1982). One majorge of that conguration results from the chemi-ium which limits the formaldehyde-conversion in. Realizing chemical reaction and separation withintus using reactive distillation can overcome thisTherefore, producing methylal by reactive distilla-en focus of research of different groups over the

ding author. Tel.: +49 631 205 3464; fax: +49 631 205 3835.ddress: [email protected] (H. Hasse).://thermo.mv.uni-kl.de (H. Hasse).

23 March 2011; Received in revised form 20 September 2011; Accepted 23 September 2011

last years (Kolah et al., 1996; Masamoto and Matsuzaki, 1994;Zhang et al., 2011).

The key to a successful design of such methylal processesis the detailed knowledge of the reaction kinetics. In orderto keep thermodynamic consistency to phase equilibriummodel, also reaction kinetics must be described by an activity-based model (Hasse, 2003). Moreover, it must be consideredthat the educt of methylal synthesis, the methanolic, aqueousformaldehyde solution, is itself a complex reacting solutionin which oligomerization reactions occur (Hahnenstein et al.,1994). They have to be taken into account explicitly in devel-oping predictive reaction kinetic models of reactions in whichformaldehyde solutions are used as educts (Maiwald et al.,2006).

Masamoto and Matsuzaki (1994) carried out reac-tion kinetics experiments of methylal synthesis in abatch and tubular-xed-bed-reactor at very low ini-tial formaldehyde-concentrations (up to 0.051 g/g, initialmethanol-concentrations between 0.2 and 0.6 g/g). The modelthese authors use to describe their experimental data is basedon overall concentrations rather than on true speciation, i.e.

see front matter 2011 The Institution of Chemical Engineers. Published by Elsevier B.V. All rights reserved.j.cherd.2011.09.014imental study and model of reerogeneously catalyzed methy

er Drunsela, Mario Rennerb, Hans Hassea,

of Engineering Thermodynamics, University of Kaiserslautern, Erw

form GmbH, Hauptstrasse 30, 55120 Mainz, Germany

b s t r a c t

eaction kinetics of the heterogeneously catalyzed formation of m

olutions are studied in a plug ow reactor at 323, 333 and 343 K

5 (Rohm and Haas) as catalyst. Parameters of an activity-based p

tted to the experimental results. The model is based on the true

cludes the oligomerization reactions of formaldehyde in aqueous

escribes the experimental data well and is suited for process sim

hase equilibria have to be described simultaneously.tion kineticsl synthesis

hrdinger-Strae 44, 67663 Kaiserslautern,

lal from aqueous methanolic formaldehyde

g the acidic ion exchange resin Amberlyst

o-homogeneous reaction kinetic model are

ation in the reacting solution and explicitly

anolic solutions. The reaction kinetic model

ions in which both chemical reactions and

chemical engineering research and design 9 0 ( 2 0 1 2 ) 696703 697

does not explicitly account for the chemistry in aqueous andmethanolic formaldehyde solutions, and is furthermore notactivity based. Moreover, no comparison between the modeland the experiments was carried out so that the quality ofthe model remains unclear.

Kolah et al. (1996) accomplished experimental and model-based investigations on methylal production by batch andcontinuous reactive distillation. The authors developed anactivity-based model based on the true speciation, but onlyconsidered the formation of the rst hemiacetal in methano-lic and the rst glycol in aqueous formaldehyde solutions.Dedicated reaction kinetic experiments were carried out andresults are graphically shown, but not used in the descriptionof the reactive distillation simulations as chemical equi-librium was assumed for the methylal formation reaction.Unfortunately, no comparison between the reactive distil-lation expeneither posdata.

In the methylal-foreactor. Thchemical eresin AmbeTernary miused as a feed is varmethanol cature rangeto process tures side pmethyl formmay becomtures reactactivity-basresults of i.e. accounthyde in aquof the expthe presenmation reaoligomerizahyde solutiare alwaysstants of tthe activityour group FAC group

Table 1 UNIFAC group assignment (Kuhnert, 2004).

Component Group

Formaldehyde 1CH2OWater 1H2OMethanol 1CH3OMethylal 1C3H8O2Methylene glycol 1HO(CH2O)HHemiformal 1CH3O, 1CH2OHPoly(oxymethylene)glycol (n 1)CH2O, 2OH, 1CH2Poly(oxymethylene)hemiformal (n 1)CH2O, 1CH3O, 1CH2OH

Table 2 UNIFAC size (ri) and surface (qi) parameters ofpure components/groups (Kuhnert, 2004).

Group

CH2O

2

2O)H

H H

ll as 13.

Ch

ldehy use

soles ns, yme

+ CH2O HO(CH2O)CH3 HF1

(I)

2O)n1CH3 + CH2O HO(CH2O)nCH3 HFn

(n 2) (II)

CH2O HO(CH2O)H MG1

(III)

Table 3

Group i up j

6 7 8 9

1 83.36 0.0 238.4 238.42 300.0 219.3 a2,8(T) 289.63 83.4 0.0 0.0 410.04 300.0 142.4 289.6 289.65 156.4 112.8 137.1 137.16 447.8 697.2 697.27 273.0 238.4 238.48 16.5 128.6 0.09 16.5 128.6 0.0

a2,3(T)/K = 4, 100/(T/K), a8,2(T)/K = 1018.57 + 329, 900/(T/K) .riments and the model is shown, so that it issible to validate the authors assumptions nor their

present work, reaction kinetic experiments ofrmation were carried out in a tubular xed-bede conditions are chosen so that also data on thequilibrium are obtained. The acidic ion exchangerlyst 15 of Rohm and Haas is used as a catalyst.xtures of formaldehyde, water and methanol arefeed. The concentration of formaldehyde in theied in the range between 0.05 and 0.15 g/g, theoncentration is about 0.8 g/g. The studied temper-

is 323343 K. These choices are made accordingdevelopment considerations. At higher tempera-roducts such as dimethyl ether, formic acid andate, which were not observed in the present study,e important (Kuhnert, 2004), at lower tempera-

ion rates are unnecessarily low. Parameters of aned pseudo homogeneous model are tted to the

the experiments based on their true speciation,ing for the oligomerization reactions of formalde-eous methanolic solutions. Under the conditions

eriments carried out in the present work, i.e. ince of the strong acidic catalyst, the methylal for-ction is the kinetically limiting step whereas thetion reactions in aqueous methanolic formalde-ons are so fast that it can be assumed that they

in chemical equilibrium. The equilibrium con-hese reactions as well as the UNIFAC model for

coefcients were taken from previous work from(Kuhnert, 2004; Kuhnert et al., 2006). The UNI-assignment, the volume- and surface parameters

H2O C3H8OHO(CHOHCH2CH3OCH2OCH3O

as weTables

2.

FormamonlyThese mixtursolutiopoly(ox

CH3OH

HO(CH

H2O +

UNIFAC interaction parameters ai,j/K (Kuhnert, 2004).

Gro

1 2 3 4 5

867.8 0.0 189.2 237.7 254.5 a2,3(T) 189.5 229.1

0.0 a3,2(T) a3,2(T) 237.7 59.2 191.8 a2,3(T) 229.1 28.06 353.5 28.06 353.5

251.5 1318.0 251.5 1318.0 986.5 0.0 423.8 0.0 774.8 1164.8

128.6 a8,2(T) 0.0 181.0 249.1 128.6 181.0 71.2 181.0 249.1

225.5 + 0.7205(T/K), a3,2(T)/K = 1031.0 1.749(T/K), a2,8(T)/K = 451.64 11Group number ri qi

1 0.9183 0.7802 0.9200 1.4003 2.9644 2.716

4 2.6744 2.9405 1.0000 1.2006 0.6744 0.5407 1.1459 1.0888 1.2044 1.1249 1.4311 1.432

the group interaction parameters are given in

emical system

de is a gas at ambient conditions and com-d in liquid aqueous or methanolic solutions.utions are highly reactive multicomponent(Walker, 1963). In methanolic and aqueous

poly(oxymethylene)hemiformals HFns andthylene)glycols MGns are formed:

698 chemical engineering research and design 9 0 ( 2 0 1 2 ) 696703

HO(CH2O)n H + CH O HO(CH O) H (n 2) (IV)

As formtions have al. (1994), Mtherein. Ththat underequilibriumwhich is mlal. It can tinstantanemainly depand the mthe presenEven thougin the reacTypical numlated by thKuhnert (20Whereas Rformaldehythe formatin the prescatalysts, tacetals:

HO(CH2O)n

The rst acthe reactioby Kolah eacetals withat the conddetected inthe model.

3. Ex

3.1. Ch

The feedstpared by diParaformal(purity 99.9was bidistidard methmethanol, matographAgilent J&P30 m, lm method wahyde in thformaldehytrations of measured. imum relat4% for formconsiderederror for mboiling sub

4 erlys

chanonic t conte beast in

ling p

c vo./g bu

woruct d

Ca

presohmn ovapac

5440nt pumenand m, see

Exp

perir setn kiyll, ed mum he cuilibuire

reacctor

herme reastedactor

a pr ord

ure ir is immersed in a thermostatted bath. Prior to enteringctor the feed passes a pre-heating section (coiled tube)

thermostatting bath in which it is heated up to reac-mperature. The reactor consists of 9 tubes made of thebased steel 2.4605 with an inner diameter of 10.3 mm.ngth of the tubes is 128 mm for tubes 14, 257 mm forbes 5 and 6, and 385 mm for the tubes 79. The tubeslled with catalyst swollen in methylal (smallest vol-f. Table 4). In order to avoid destruction of the catalystlling during the experiments, an expansion space of a

of about 5 mm was left in each tube. At the inlet of thebe and at the outlets of all other tubes, sample portsated (X1X10 in Fig. 1) which allow collecting sampleslysis and, hence, determining the concentration prole

the reactor. The sample ports are equipped with a cool-tem to avoid partial evaporation while taking samples1 2 2 n MGn

aldehyde is an important chemical, these reac-intensively been studied, see e.g. Hahnenstein etaiwald et al. (2003), Ott et al. (2005) and referencese reaction rates are very high at low pH-values so

the conditions of the present study the chemical of the Reactions (I)(IV) is attained on a time scaleuch faster than that of the formation of methy-herefore be assumed that equilibrium is attainedously. The equilibrium distribution of the oligomersends on the overall formaldehyde concentrationethanol/water ratio. At the conditions studied int work, HF1 and MG1 are the predominant species.h monomeric formaldehyde plays the central roletion network, its concentration is always very low.

bers are of the order of 5 105 mol/mol (calcu-e use of the model and parameters published by04)) for the conditions studied in the present work.eactions (I)(IV) occur in all methanolic, aqueousde solutions and, hence, no catalyst is needed,ion of acetals which is discussed now only occursence of acidic catalysts. In the presence of suchhe hemiacetals HFn react with methanol forming

CH3 + CH3OHH+H3CO(CH2O)nCH3 + H2O (V)

etal (n = 1) is methylal. A more detailed scheme ofn mechanism of methylal formation is discussedt al. (1996). The formation of the longer-chained

more than one CH2O group (n > 1) is not importantitions studied in the present work. They were not

the experiments and are therefore not included in

perimental

emicals and analysis

ock that was used for the experiments was pre-ssolving paraformaldehyde in methanol and water.dehyde was purchased from Merck, methanol%) was purchased from Sigma Aldrich and waterlled. Gas chromatography with the internal stan-od was applied to determine the fractions ofwater and methylal. An Agilent 6980N gas chro-

equipped with a heat conductivity detector and an HPINNOWax column (diameter 0.32 mm, lengththickness 0.32 m) was used. The sodium sultes applied to determine the fraction of formalde-

e mixtures (Walker, 1963). Upon the analysis, thede oligomers are split up, hence, overall concen-methanol, water, methylal and formaldehyde areEach sample was analyzed several times, the max-ive deviations were 3% for methanol, 6% for water,aldehyde and 5% for methylal. These numbers are

also as estimated error of the analysis. The highethylal is due to the difcult handling of that low-stance.

TableAmb

Ion exHarmFinesCoarsCataly

Swel

Specicat

a Thisb Prod

3.2.

In the 15 of Rgives atotal cto DINdiffereexperiwater values

3.3.

The exreactoreactio2009; RThe fethe drwith tpre-eqnot reqin thethe reaMultiting this adjuthe reensuretion. Into ensreactothe reain thetion tenickel-The lethe tuwere ume, cby swelengthrst tuare locfor anaalong ing sysProperties of the acidic ion exchange resint 15.

ge capacity (mmol H+/g dry cat.) 4.88a

mean size water swollen (mm) 0.600.85b

ent (1.180 mm) Max. 5%b

ternal porosity (mL pore volume/g cat. dry) 0.4b

roperties Water MeOH Mal

lume (mL bulk swollenlk dry cat.)

2.8a 2.9a 2.5a

k.ata sheet.

talyst

ent work, the acidic ion exchange resin Amberlyst and Haas was used to catalyze the reaction. Table 4erview of its properties. The determination of theity was carried out in the present work according3. Additionally, the swelling of the catalyst in there solvents used in the present work was studied

tally at room temperature. The swelling is similar inethanol and lower in pure methylal. For numerical

Table 4.

erimental procedure

ments were carried out in a plug ow reactor. The-up has been successfully used in many previousnetic studies (Schmitt and Hasse, 2006; Parada,2009). A scheme of the reactor is shown in Fig. 1.ixture is prepared gravimetrically and stored in

D1. As methylal is only produced upon contactatalyst, a one feed arrangement is sufcient. Aration regarding the formation of the oligomers isd as that equilibrium is established extremely fasttor as explained above. A constant ow through

is provided by a piston pump (type Bischoff HPD 200). The mass ow was determined by weigh-ctor efuent. The desired pressure in the reactor

by a back-pressure valve located at the outlet of. It was set to about 5 bar in the present work tooper operation of the pump and avoid evaporiza-er to adjust the desired reaction temperature andsothermal conditions during the experiments, the


TITITI TITITI TITITI

PIPIPI

X6X6X6X8X8X8

X10X10X10

Fig. 1 Sch

from the hotance thermto monitortemperaturthe temperthe reactor ing sampleproceedingstate modeto be sufcment of thfrom the re

3.4. Exp

The studieTable 5. Thfeed ow e333.15 and

Table 5

Feed

F1 F2 F3 TITITI TITITITITITI

X5X5X5X7X7X7X9X9X9D1D1D1

eme of the plug ow reactor (X sample port, T temperature mea

t pressurized reactor. Seven calibrated Pt100 resis-ometers (accuracy 0.1 K) are located in the tubes

the temperature during the experiment. The sete was maintained constant within the accuracy ofature measurement. After all settings were done,was left undisturbed for at least 120 min before tak-s from all sample ports against the ow direction

from X10 to X1 in order not to disturb the steady of the reactor. Even though 120 min were knownient from preliminary experiments, the establish-e steady state was monitored by taking samplesactor outlet.

erimental program

d three feed compositions (F1F3) are given ine default feed mass ow was 10 g/min. With thatxperiments were carried out for all feeds at 323.15,

343.15 K. In a mass ow study carried out for F2

Overall feed compositions.

MeOH Water (g/g) Fa

0.8 0.05 0.150.8 0.1 0.10.86 0.07 0.07

at 343.15 K check for a

3.5. Exp

Fig. 2 showsmeasured ofunction ofdifferent liqthe ratio ofthe samplevarying liqshould be the same ptransfer beles are intransfer limies, a constconsumptio

Fig. 3 illreaction kition rate iequilibriumThus, the compositiothree expethe same TITITI

D2D2D2

X1X1X1

X2X2X2

X4X4X4

X3X3X3surement, P pressure measurement, D drum).

the feed was increased up to 30 g/min in order ton inuence of external mass transfer.

erimental results

the result of the mass ow study in a plot in whichverall methylal concentrations are depicted as a

the pseudo retention time of the mixture at twouid loads. The pseudo retention time is dened as

the mass of catalyst between the reactor inlet and point and the mass ow of the reacting liquid. Foruid mass ows but otherwise same conditions, itexpected that the reaction extent is the same forseudo retention time if there is no effect of masstween the liquid and the solid catalyst. The pro-dependent of the liquid load, thus external massitations can be neglected. For the subsequent stud-ant mass ow of 10 g/min was chosen to keep then of reactants low.ustrates the inuence of the temperature on thenetics for the same feed. As expected, the reac-ncreases with rising temperature. The chemical, however, is nearly independent of temperature.heat of reaction is small. The inuence of feedn on the reaction is shown in Fig. 4. Results fromriments are depicted which were carried out attemperature but with different molar ratios of


0

0

0

0

0

Fig. 2 Resto study thmethylal fofunction ofrates 9.5 m(cf. Table 5for the eye

0

0

0

0

Fig. 3 Resmethylal mcatalyst for343.15 K (for the eye

methanol/frium concethat ratio. Tnot signic

The comlater in Dru

4. Re

4.1. Ov

The experima pseudo hterm for a c

dnidt

= icH+

cat

0

0

Reslal m0 2 4 6 80

.02

.04

.06

.08

0.1

.12

ults of reaction kinetic experiments carried oute inuence of the liquid ow rate on the

Fig. 4 methyrmation: overall methylal mass fraction as a the pseudo retention time (cf. text) for the ow3/(m2 h) () and 28.5 m3/(m2 h) (). The feed is F2), the temperature is 343.15 K. The line is a guide.

0 10 20 30 40 50 60 70 800

.02

.04

.06

.08

0.1

ults of reaction kinetic experiments: overallass fraction as a function of the mass of dry

the temperatures 323.15 K (), 333.15 K (), and). The feed is F3 (cf. Table 5). The lines are guides.

ormaldehyde in the feed. As expected, the equilib-ntration of methylal decreases upon an increase ofhe time that is needed to reach the equilibrium isantly affected.plete data set for all experiments will be publishednsel (2011).

action kinetic model

erview

ental reaction kinetic results were correlated withomogeneous activity based model. The reactionontrol volume is given by

,drymcatr, (1)

catalyst formethanol/fF3 (), cf. Tguides for

where cH+

cat,dthe controlence betwedescribed h

r = kf(T)aHF

The applicreactor yiel

dx(n)i

dmcat= 1

n

where dx(ni

tion of comcontains a git is assumsolution doeven strictling point fothe reactioapproach

kf,b(T) = kf,

where T0 dtrarily chosforward antemperaturbased therby

K(T) = kf(Tkb(T

Only the reV) were exwas assum0 10 20 30 40 50 60 70 800

.05

0.1

.15

0.2

ults of reaction kinetic experiments: overallass fraction as a function of the mass of dry

different values of the number of the molar ratioormaldehyde. Feed F1 (), Feed F2 (), and Feedable 5. The temperature is 343.15 K. The lines arethe eye.

rymcat is the number of active catalyst sites within volume. The overall reaction rate r is the differ-en forward and backward reaction rate which isere using a second order activity based approach:

1aMeOH kb(T)aMalaH2O. (2)

ation of Eqs. (1) and (2) to a stationary plug owds

icH+cat,dry(kf(T)aHF1aMeOH kb(T)aMalaH2O), (3)

)/dmcat is the differential change of the mole frac-ponent i in a differential section of the reactor thativen differential mass of catalyst. In the derivation,

ed that the overall molar density of the reactinges not change. Note that this assumption is noty needed, as also Eq. (3) can be postulated as a start-r the correlation. The temperature dependency ofn rate constants is described using the Arrhenius

b(T0)exp

[Ef,b

R

(1T

1T0

)], (4)

enotes a reference temperature which can be arbi-en and kf,b(T0) the reaction rate constants for thed backward reaction, respectively, at the referencee. The reaction rate constants and the activitymodynamic equilibrium constant K(T) are related

)). (5)

action kinetics of the methylal formation (Reactionplicitly considered. For the reasons given above, ited that for all other reactions the (activity based)


Table 6 Parameters for calculating the activity based chemical equilibrium constants of Reactions (I)(IV) using thecorrelation given in Eq. (6).

A B C D

MG1 30.946 4.819 103 3.741 4.534 103MG2 3 3.741 4.534 103MGn, n3 3.741 4.534 103HF1HF2HFn, n3

Fig. 5 Reaforward anand Feed F

chemical ecorrelation

ln(Ki(T)) = A

The equilibthe activity(with somefrom Kuhnwater, metinert compthat Kuhnefrom the onhad to be cparameterswere ttedthe equilibEq. (5). It isas a conseD are zero.describing in Matlab.

0

0

0

0

0

0

0

0

Com (line43.1

Table 7 formation

kf(T0) (mo

0.322 30.941 5.653 1030.933 5.361 103

1.130 103 2.510 1041.129 103 2.551 1041.129 103 2.563 104

2.9 2.95 3 3.05 3.16

5

4

3

2

1

0

backward

forward

ction rate constants from individual ts ofd backward reaction (Feed F1 (), Feed F2 ()

Fig. 6 modelat T = 33 (), cf. Table 5) and trend line ts ().

quilibrium conditions are fullled. The following for the equilibrium constants was used:

+ B(T/K)

+ Cln(T/K) + D(T/K). (6)

rium constants of the Reactions (I)(IV) as well as coefcient model, which is of the UNIFAC type

individually adjusted parameters) were adoptedert (2004), who studied mixtures of formaldehyde,hanol, and methylal, but treated methylal as anonent as no catalyst was used in their study. Notert (2004) assumed a reaction scheme that differse presented here so that the equilibrium constantsonverted. The result is presented in Table 6. The

describing the methylal formation (Reaction V) to the data from the present work. From these,rium constant of Reaction (V) can be found using

consistent with the form presented in Eq. (6), butquence of Eqs. (4) and (5) the parameters C and

The differential-algebraic-equation (DAE) systemthe reaction system was implemented and solved

formaldehy

4.2. Fit

The reactiohas four adtted to thconcentrattrue concenmodel fromlibrium forreactions wSubsequenexperimensum of theexperimenfunction. Owere takenequilibriumoverweightpared to tholigomers mum chainThe amounkinetic conto obtain aof all accom

Parameters of the reaction kinetic model (cf. Eq. (5)) and equilibr. The reference temperature is T0 = 333.15 K.

l/(molH+ s)) kb(T0) (mol/(molH+ s)) Ef (kJ/mol)

0.0125 54.65 1.984 102 0.3161.984 102 0.3161.984 102 0.316

0 10 20 30 40 500

.1

.2

.3

.4

.5

.6

.7

.8

parison of overall concentration betweens) and experimental data (symbols) for feed F25 K: methanol (), water (), methylal () andde ().ting procedure and results

n kinetic model described in the previous sectionjustable parameters kf,b(T0) and Ef,b which weree present experimental data. Since only overallions were obtained as results of the experiments,trations had to be calculated rst. Therefore, the

Kuhnert (2004) was applied and chemical equi- the methylene glycol and hemiformal formationas assumed to determine the species distribution.tly, reaction rate constants kf,b were tted for eacht individually using a least square method with the

deviations of concentrations between model andt for methylal, methanol and water as objectivenly the rst eight data points of each experiment

into account, as the remaining ones were always data and including them would have led to an

of the equilibrium part of the experiment com-e kinetic part. HF1 and MG1 are the predominantat the conditions studied here. Thus, the maxi-

length of oligomers that was considered is n = 5.ts of longer oligomers are negligible. Fig. 5 showsstants obtained from the individual ts. In order

single set of parameters that describes the entityplished experiments, the reaction rate constants

ium constants (cf. Eq. (6)) of the methylal

Eb (kJ/mol) A () B ()

54.74 3.22 11.0


determined in the individual ts were correlated by a trendline t fromrate constamarized inconstant ofEq. (5). Theincluded innegligible enumber foied here. Frfrom the exbased (therKx can be fshows an eof the expeand the oveThe agreemtions betwe1.79% for whyde. The from the lo

5. Co

Knowledgeessential focolumns. Ierogeneousmethanolicow reactoinuence oics and cheinterestinggeneous acresults. Thereactions inand is, henthe overallreactions, tstep. Only were tted taken fromimental rescan also bein which chdescribed s

AbbreviatioFa foHF heMal mMeOH mMG m

List of symbc toa acai,j UE aci, j Uk reK rem mn m

n number of formaldehyde segments in formaldehydeolstUreUteremov

bacafoco

ence

, J., Si(oxy

ored ceptsl, J.-Otillatalde

sersla, M., fahrenstei-NMRtionhano

H., 2dma

Futunheild, Mhyla5965.A.K.,aldetive

7372rt, C.,rkomsis. Urt, C.,rer, tainiuid hanomaldh preka, J.8. Selonceient

ld, Miter, Cctroschemperald, MR speual realde

917.oto, thesi which both activation energies Ef,b and reactionnts kf,b(T0) were determined. The results are sum-

Table 7. From this also the chemical equilibrium the methylal formation can be determined using

resulting parameters A and B of Eq. (6) are also Table 7. The B parameter corresponds to an almostnthalpy of reaction of 0.09 kJ/mol. The resultingr K is about 25.9 in the temperature range stud-om this, for concentrations typically encounteredperiments in the present work, the mole fractionmodynamically inconsistent) equilibrium constantound. The resulting numbers are about 5.1. Fig. 6xample of the comparison between the correlationrimental reaction data taken in the present workrall correlation in terms of overall concentrations.ent is excellent. The average overall relative devia-en model and experiments are 0.57% for methanol,ater, 5.77% for methylal and 8.77% for formalde-high relative deviations for formaldehyde resultw concentrations.

nclusion

of reaction kinetics and chemical equilibrium isr the design of reactors and reactive distillation

n the present work, experimental studies on het- catalyzed formation of methylal from aqueous,

formaldehyde solutions were carried out in a plugr. As a catalyst, Amberlyst 15 was used. Both thef temperature and initial concentrations on kinet-mical equilibrium were studied in a range that is

for process design. Parameters of a pseudo homo-tivity based model were tted to the experimental

model explicitly accounts for the oligomerization the system formaldehyde, water, and methanol,

ce, based on the true concentrations rather than on ones. In the resulting complex system of coupledhe formation of methylal is the rate determiningthe parameters describing the methylal formationto the experimental data, all other parameters were

the literature. The new model described the exper-ults well. It is thermodynamically consistent and

used in models of reactive distillation processesemical reaction and phase equilibrium have to beimultaneously.

nsrmaldehydemiformalethylalethanolethylene glycol

olstal catalyst capacitytivityNIFAC group interaction parametertivation energyNIFAC groupsaction rate constantaction equilibrium constantassole number

qir riT T0

x(n)

x(n)

Indicesb cat fi

Refer

BurgerPolytailcon

DrunsedesformKai

GringVer

Hahne13Csolumet

Hasse,SunandWei

Kaufhomet438

Kolah, formreac370

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egert, M., Strfer, E., Hasse, H., 2010.methylene) dimethyl ethers as components ofdiesel fuel: properties, synthesis and purication. Fuel 89 (11), 33153319.., 2011. Entwicklung von reaktions-

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Experimental study and model of reaction kinetics of heterogeneously catalyzed methylal synthesis1 Introduction2 Chemical system3 Experimental3.1 Chemicals and analysis3.2 Catalyst3.3 Experimental procedure3.4 Experimental program3.5 Experimental results

4 Reaction kinetic model4.1 Overview4.2 Fitting procedure and results

5 ConclusionReferences

methyl al

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