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Article

Kinetic and reactive distillation for acrylic

acid synthesis via transesterificationCuncun Zuo, Tingting Ge, Chunshan Li, Shasha Cao, and Suojiang Zhang

Ind. Eng. Chem. Res., Just Accepted Manuscript DOI: 10.1021/acs.iecr.6b01128 Publication Date (Web): 15 Jun 2016

Downloaded from http://pubs.acs.org on June 17, 2016

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1. Introduction

Acrylic acid, an important organic raw material and synthetic resin monomer, is widely used in

adhesives, paints, chemical fibers, leathers, textiles and photosensitive resin plates industries. The

global market for acrylic acid has recently showed strong growth with the increasing demand of

superabsorbent polymers, adhesives, and sealants.1,2

Emerging economies demand superabsorbent

polymers, which has become the main driving force of the acrylic industry. In addition, the booming

construction is another main thrust for the rapid growth in acrylic. Obtaining methyl acrylate using

acrylic acid as the reacted material is a promising method.3-5 The primary drawbacks of methyl

acrylate hydrolysis in synthesizing acrylic acid are the high activation energy and long time to reach

equilibrium.6Using acetic acid instead of water to synthesize acrylic acid can effectively alleviate

the problems in these two areas.

Transesterification, which is an important chemical reaction in industries, includes three

reaction types-alcoholysis, acidolysis, and ester exchange reaction. These reactions can be performed

using base catalysts7,8

such as metal hydroxides, metal alkoxides, alkaline-earth oxides, and

hydrotalcites. Moreover, acid catalysts9-14

such as sulfuric, sulfonic, phosphoric, and hydrochloric

acids can also be used to catalyze the transesterification reaction. Ion-exchange resin has recently

received much attention because of its significant superiorities over the routine method of conducting

the sequential reaction and separation15-17

. The adsorption and kinetic parameters for the

transesterification of methyl acetic with hexanol was determined under different experimental

conditions using the ion-exchange resinAmberlyst-131 as the catalyst18

. Y. Liu et al.19

investigated

the kinetic of the transesterification of methyl acetic with n-octanol in a batch stirred reactor

catalyzed by the cation exchange resin Amberlyst 15. Van de Steene et al.16successfully obtained

methyl acetic by the transesterification of ethyl acetic with methanol over the ion-exchange resin

Lewatit K1221. J. He et al.15

established a non-equilibrium stage model to describe the reactive

distillation and used the Newton-Homotopy method to simulate the transesterification of methyl

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acetic with n-butanol. Alonso et al.20

studied the polarity effect of the esters on the transesterification

reaction rate with sulfuric acid (homogeneous) and Dowex DR2030 sulfonic resin (heterogeneous) as

catalysts; the positive effect of the heterogeneous acid catalysis of H-bond in stabilizing the active

intermediate involved in the rate determining step was identified. Sertet al.18

developed a

heterogeneous LangmuirHinshelwoodHougenWatson (LHHW) type reaction rate model for the

hexyl acetic synthesis , and the UNIQUAC model was used to account for the non-ideal

thermodynamic behavior of reactants and products in the transesterification of methyl acetic

with1-hexanol catalyzed by the cation exchange resin Amberlyst-131.

A strongly acidic cation-exchange resin (NKC-9) was developed in this study for catalyzing

transesterification to synthesize acrylic acid when azeotrope does not exist in the system and the

equilibrium time is shorter compared with the hydrolysis reaction of methyl acrylate. The same

experiment was repeated under different reaction conditions to obtain the optimised operating

parameters, adsorption parameters, and kinetic parameters. Given the non-ideality of the liquid phase

from the ideal solution in the reaction system, the NRTL model was selected to correct the molar

fractions and the activity coefficients were calculated using the UNIFAC method; and the adsorption

equilibrium constants for the four components with NKC-9 were determined by performing

adsorption experiments between two non-reacting species. The kinetic data were correlated with the

PH and LH models. Finally, the simulation and calculation of the catalytic transesterification for

acrylic acid synthesis in the reactive distillation column were performed.

2. Experimental

2.1. Materials

2.1.1 Chemicals

Acetic acid, acrylic acid, and methyl acetic, purchased from Sinopharm Chemical Reagent Co.,

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Ltd., are of analytical grade. Hydrochloric acid and sodium chloride were also purchased from the

same chemical reagent factory. Methyl acrylate with a purity of more than 99.57 wt. %, was bought

by Baishun Chemical Reagent (Beijing) Co., Ltd. Distilled water was homemade in our laboratory

and used to wash the apparatus and catalysts.

2.1.2 Catalyst

NKC-9, a highly cross-linked polystyrene-divinylbenzene resin functionalized with sulfonic

groups, was used as the catalyst in our study. The relevant characteristics of the NKC-9 resin are

summarized in Table 1. Before NKC-9 was used for the catalysts for the transesterification reaction,

the purchased resins were soaked in 10 wt. % NaCl solution for more than 20 h. Then, the salt

solution was removed and the resin was washed with clear water and dried at 353.15 K under

vacuum for 14 h.

Table 1. Physicochemical characteristics of the resin (NKC-9).

2.1.3 Analytics

All samples were analyzed using gas chromatography (GC-2010, Shimadzu, Japan) with a BID

detector and a chromatographic capillary column Rtx-Wax (30m0.25mm0.25m). The column

temperature increased to 433.15 K with a programmed temperature method. The vaporizing chamber

and detector temperatures were set to 433.15 and 453.15 K, respectively. High purity helium gas

(>99.9999%) was used as carrier. An external standard method was used to quantitatively analyze all

samples.

2.2. Apparatus and procedure

2.2.1 Kinetic

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The kinetic experiments of the transesterification of methyl acrylate with acetic acid were

performed in a 250 mL three-neck flask equipped with a reflux condensing tube, thermometer, and

sampling device. A mechanical stirrer was used to mix the reactants. The reaction temperature was

controlled to within 0.1 K by Super thermostat water bath. First, methyl acrylate and the catalyst

were heated to the desired reaction temperature in the reactor. Acetic acid was preheated to the

desired reaction temperature and then quickly poured into the reactor. The transesterification reaction

then started. The kinetic of the transesterification reaction was investigated by analyzing the

composition of small samples which were withdrawn from the liquid mixture at regular intervals.

After a steady state was achieved, the product was collected in a sampling flask.

2.2.2 Adsorption experiments

The adsorption equilibrium constant of liquid on the surface of the catalyst was needed for the

adsorption-based kinetic model. Four binary non-reactive mixtures considered the different reactants

in the NKC-9 surface using the Popken et al. assumption26

. The binary liquid mixture was

formulated with a total weight of 20 g and a composition of 25 wt. % of the stronger adsorbing

species at the beginning of the adsorption experiments. The liquid mixture and catalyst were heated

at a constant temperature (298.15 K) for 24 h. The liquid samples were prepared and analyzed by GC

after reaching adsorption equilibrium.

2.2.3 Swelling experiments

Swelling experiments were conducted at 298.15 K in a sealed and graduated cylinder with a

volume of 100.1 cm3 to investigate the swelling capacity of resin catalyst on single substrate.Approximately 5 cm

3 of the vacuum-dried catalyst was placed in the cylinder, and then a single

substrate was gradually added until the liquid level was about 1cm3higher than the catalyst level. A

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sealed and graduated cylinder was placed in an ultrasonic bath, and the catalyst volume was

measured after 24 h. The experiment was repeated at least thrice in order to increase experimental

accuracy of the results.

2.2.4 Fixed-bed Experiments

To obtain the optimised space-time, we investigated the transesterification in a fixed-bed reactor

packed with the pretreated NKC-9 catalyst. The catalyst load (W) was 0.684 g catalyst/mL reactor

volume for the basic case. The experiment was repeated to study the effect of space-time on the

conversion rate of methyl acrylate with different space-time values.

3. Results and discussion

3.1. Calculation of activities and thermodynamic properties

Considering that the reaction system of acrylic acid synthesis greatly deviated from ideal

solution, the NRTL and UNIQUAC models were chosen to correct the non-ideality of the liquid

phase. The multicomponent expressions for the activity coefficient for the NRTL and UNIQUAC

equations are available in Supporting Information. Moreover, the experimental and calculated VLLE

data for the acrylic acid/methyl acetate and acetic acid/methyl acrylate binary systems are also

clearly listed in Supporting Information. The VLLE data for acetic acid/acrylic acid, acetic

acid/methyl acetate, and methyl acrylate /acrylic acid binary systems are stored in the database of

Aspen. With respect to the VLLE data of methyl acetic/methyl acrylate binary system, Tu et al.have

conducted experiments and obtained detailed data.21

Furthermore, we investigated the deviations

between the calculated and experimental values through the NRTL and UNIQUAC models for

acrylic acid / methyl acetate and acetic acid / methyl acrylate, which were clearly shown in Table 2.

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According to the deviation above, the NRTL model demonstrated better results compared with the

UNIQUAC model. Thus, we only calculate the binary interaction parameters of the NRTL model for

acetic acid, methyl acrylate, acrylic acid, and methyl acetate (Table 3).

Table 2. Deviations between the calculated and experimental values onx1,y1, and Tthrough the

NRTL and UNIQUAC models for acrylic acid / methyl acetate and acetic acid / methyl acrylate.

Table 3. Binary interaction parameters of the NRTL model for acetic acid, methyl acrylate, acrylic

acid, and methyl acetate.

3.2. Kinetic experiments and optimization of transestrification conditions

3.2.1. Elimination of Mass Transfer Resistance.

To study the reaction kinetic, the effects of internal and external diffusion on transestrification

must be excluded. To investigate the internal diffusion involved in the reaction system, NKC-9 resin

catalyst was screened into several different particle sizes, including 28, 32, and 35 mesh. The same

experiment was repeated with different particle sizes at the same stirring speed, reaction temperature,

catalyst load, and reactants molar ratio. The conversion rate of methyl acrylate is defined as the ratio

of the amount of methyl acrylate reacted and the initial amount of methyl acrylate. Figure 1 shows

that when the catalyst particle size is 32 mesh, the conversion rate of methyl acrylate was almost

unaffected by the particle size. However, when the catalyst particle size is 28 mesh, the conversion

rate of methyl acrylates lightly decreased. External diffusion effects could be eliminated by

increasing the stirring speed, and the experiment was repeated with the stirring speed range from 300

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to 500 rpm. As can be seen from Figure 2, when the stirring speed was increased to 300 rpm, the

conversion rate of methyl acrylate was almost constant, which indicated the external mass transfer is

not the rate limiting step at that time.22

Sanz et al.23

investigated the external diffusion and found that

it does not usually control the overall reaction rate unless when the stirring speed was low or when

the reactants were viscous. Thus, all further experiments were performed under stirring speed of 300

rpm. The catalyst particle size of 32 mesh and stirring speed 300 rpm were required to ensure the

experimental accuracy.

Figure 1. Effect of the catalyst particle size on the conversion rate of methyl acrylate using NKC-9 as

the catalyst (300 rpm; 80 C; = 1:1; the catalyst load was 0.10 g catalyst / g liquid mixture).

Figure 2. Effect of the stirring speed on the conversion rate of methyl acrylate using NKC-9 as the

catalyst (28 mesh; 80 C;

= 1:1; the catalyst load was 0.10 g catalyst / g liquid mixture).

3.2.2 Effect of Catalyst Load.

The same experiment was repeated at 353.15 K with initial molar ratio of acetic acid and methyl

acrylate being 1 (= 1: 1), catalyst particle size of 28 mesh, and stirring speed of 300 rpm. Theeffect of catalyst load on the conversion rate of methyl acrylate can be determined by changing the

amount of catalyst load. To detection the autocatalytic effect of the acetic acid, a blank assay

experiment was performed in the absence of catalyst. Figure 3 indicated without catalyst the

autocatalytic behavior of acetic acid can be negligible because the conversion rate of methyl acrylate

below to 4% after 30 h. In addition, the reaction equilibrium time of transesterification was

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decreased with the increase in catalyst load. As shown in Figure 4, it is obvious that the reaction rate

constant increases linearly with the addition of catalyst load. The reaction rate constant, k0and the

concentration of catalyst load, Ccat can be expressed as: k+ / k+ (0.08 g catalyst / g liquid

mixture)=114.7Ccat.(g/ g liquid mixture)-8.26. Such behavior is attributed to the increased amount of

acidic sites for reaction with the addition of catalyst load.23

Figure 3. Effect of catalyst load (NKC-9) on the conversion rate of methyl acrylate (353.15 K,

= 1: 1, 28 mesh, and 300 rpm).

Figure 4. Effect of catalyst load on the forward reaction rate constant at 353.15 K with initial molar

ratio of acetic acid and methyl acrylate being 1.

3.2.3. Effect of molar ratio of acetic acid and methyl acrylate.

The experiments were conducted at the initial molar ratio of acetic acid and methyl acrylate

varying from 1:1 to 3:1 at 353.15 K with catalyst load being 0.1 g/g, catalyst particle size of 28 mesh,

and stirring speed of 300 rpm. According to the theories of reversible equilibrium reaction, increased

the amount of one reactant can enhance the equilibrium conversion rate of the other reactants. Figure

5 shows the effect of molar ratio of reactants on the conversion rate of methyl acrylate. It was

obvious that the conversion rate of methyl acrylate was gradually increased with the increase in the

initial molar ratio of reactants. When the initial molar ratio increased from 1:1 to 2:1, the increment

of equilibrium conversion rate of methyl acrylate was about 8%, and the increment was almost the

same when the initial molar ratio increased from 2:1 to 3:1. However, the residual amounts of acetic

acid were about 51%, 71.5%, and 78.4%, respectively. The separation between acetic acid and

acrylic acid liquid mixture was hard, which can be attributed to the H-bonds interactions of acid

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molecules. Hence, in despite of high conversion rate of methyl acrylate, the high molar ratio of

reactants will increase the difficulty in the separation of acrylic acid at the same time. Combining

two considerations, the initial ratio of reactants of 1:1 was the best choice.

Figure 5. Effect of molar ratio of reactants on the conversion rate of methyl acrylate using NKC-9 as

catalyst (353.15 K, 28 mesh, 300 rpm, and the catalyst load was 0.10 g catalyst/g liquid mixture).

3.2.4. Effect of reaction temperature.

The experiments were conducted at the reaction temperature varying from 343.15 to 363.15 K

with catalyst load being 0.1 g/g, initial molar ratio of 1:1, catalyst particle size of 28 mesh, and

stirring speed of 300 rpm. As shown in Figure 6, the conversion rate of methyl acrylate remarkably

increase with the elevated temperature, but the increment of equilibrium conversion rate for methyl

acrylate from 343.15 to 353.15 K was higher compared with the change in the conversion rate of

methyl acrylate when the reaction temperature increase from 353.15 to 363.15K. According to the

Arrhenius law, high temperature make molecules move faster, collide more vigorously, and therefore

greatly increased the likelihood of bond cleavages and rearrangements, but the excessive high

reaction temperature was inadvisable due to the presence of double bond in methyl acrylate and

acrylic acid. Thus, the optimized reaction temperature for the transeatrification was 353.15 K

through synthetically consideration.8, 24

Figure 6. Effect of reaction temperature on the conversion rate of methyl acrylate using NKC-9 as

the catalyst (= 1: 1, 28 mesh, 300rpm, and the catalyst load was 0.1 g catalyst/g liquid mixture).

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3.3. Kinetic Model and Equilibrium Constant

The rate expression rA is determined by the hypothesis ofthe reaction mechanism. A

pseudo-homegeneous (PH) and an adsorption Langmuir-Hinshelwood (LH)16, 18, 25, 26

models were

adopted to investigate the kinetic of the catalytic transesterification of methyl acrylate with acetic

acid over NKC-9 catalyst. The reaction rate r expression in a constant volume reactor can be listed as

follows:

= 11

(1)

where, is the quality of the catalyst; is the stoichiometric coefficients of substance inreaction; is the molarity of substance; tis the recation time.

What is the main difference between the PH (ideal) and PH modelsis that the latter one takes

molecular properties into consideration such as the size, inter-atomic forces, spatial structures.

Moreover, the PH model was modified by using the activity instead of concentration. In the PH

(ideal) model, rPHwas listed as below:

= (2)

where , , and were the molar fraction of acetic acid, methyl acrylate, acrylic acidand methyl acetate, respectively. and were the forward reaction rate constant and theequilibrium constant.

In order to simplify the reaction kinetic equation, pseudo homogeneous dynamic model was

applied to the catalysis reaction. With the reference to other ester hydrolysis reaction26

, the reaction

was assumed to be the second order reaction. The reaction rate r of reversible reaction can be

expressed as follows:

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= = ( ) (3)

After organized and integral, equation was shown as follows:

= 1g. 2C ( g.)+ 12C ( + g.)+ 1 = (4)Where , represent the concentration of acrylic acid and methyl acetate. was selectedas the variable, and other variables were calculated on basis of stoichiometric numbers and the

following several formulas: g = 4, = , = (C+ ), = 1 1/, where CMA0and CHAc0 represent the initial concentration of methyl acrylate and acetic acid.

, , and the equilibrium constant Keqas well as the concentration value of every pointin Figure 6 were brought into the Eq 4, and the relationship of Z and t was plotted in Figure 7. The

straight line was obtained from fitting the data using the least squares method, and the slope

represents the forward reaction rate constant, as shown in Table 4. The correlation coefficient R2are

all above 0.98, indicating a better linear fitting and reliable experimental data.

Figure 7. The curve of Z and t

Table 4. The reaction rate constants at different temperatures

The experimental results demonstrate the temperature had a great effect on the reaction rate, and

the relationship between them can be described using Arrhenius equation (5):

= ( ) (5)The above formula was taken the logarithm, getting the equation (6):

= (6)

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1ln k and 1 / T were plotted in one figure, the forward and adverse reaction rate constant were

illustrated in Figure8, respectively. The slope of the straight line fitted was -E / R.

Figure 8.Relationship between the forward reaction or the adverse reaction rate constant and the

temperature.

The linear equation of the forward reaction rate constant and the temperature was described

with Y=7.722-7.175X,E+and k+.0were calculated:= 59.65 and.= 2.26 10.Overall, the relationship formula 9 of forward reaction rate constant and temperature in methyl

acrylate hydrolysis reaction was obtained

= 2.257 10 exp(7174.8 ) (7)The linear equation of the adverse reaction rate constant and the temperature was described with

Y=-11.368-0.362X, E-and k-.0were calculated: = 3.010 and .= 1.156 10.

Overall, the relationshipformula10 of adverse reaction rate constant and temperature in methyl

acrylate hydrolysis reaction was obtained

= 1.156 10 exp(361.8 ) (8)Experimental conversion curve of methyl acrylate and the dynamics simulation curve were

compared under the condition that temperature of 353.15 K, catalyst load of 0.75 g/g, and0B

of 1.

The results were shown in Figure 9.

Figure 9. Comparison between the experimental data and simulation data.

As shown in Figure 9, the experimental values and dynamics simulation results had a good

inosculation, indicating the validity of the kinetic equation.

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Related parameter identification based on the above model, kinetic equation of

transesterification were shown the general expression, as follows:

r = ( /)

(1 + + + + ) (9)

where refer to the activity of substances, refer to the adsorption equilibrium constant ofsubstances; when n=2 or 0, equation will be turned into LH model (assuming the reaction on the

catalyst was the rate determining step) and PH model, respectively. Among of the equations , the rate

constant of reaction, kcan be calculated by Arrhenius equation, as shown equation (10).

= exp, (10)Where ke

0andEA,erefer to pre-exponential Arrhenius factor and activation energy.

To sum up, the kinetic models for transesterification were obtained, as shown in Table 5.

Table 5. Different kinetic models and their identification parameters.

3.3.1. Determination of reaction equilibrium constant.

By definition,Chemical reaction equilibrium constantKeqcan be solving by Eq 11, where , refer to the mole fraction and activity coefficient of component respectively. The chemical

equilibrium constant for the reaction was shown in Table 6,based on the experimental data.

= ( )=

= (11)

Table 6. Reaction equilibrium constants at different temperatures.

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According to the equation of Vant Hoff, there was a certain relationship between the chemical

equilibrium constant and temperature. From the equation, the enthalpies of reactions in non-ideal and

ideal liquid were about 57.45 and 56.64 kJ/mol, respectively.

To the activity meter:ln= 6.910 10/ + 19.12 (12)To the concentration meter:ln= 6.813 10/ + 19.09 (13)

3.3.2. Determination of adsorption equilibrium constant.

The results of our measurements of the swelling ratio which is the volume of

solvent-equilibrated resin divided by the dry volume of the resin in a sealed graduated cylinder are

reported in Table 7. The values given are mean values of at least three experiments conducted at

298.15 K. Assuming that the resin beds volume changes in the same way as the volumes of the

individual resin microspheres, adsorbed volumes can be calculated from the swelling ratio. Also

assuming ideal mixing, that is, no excess volume, the adsorbed mass and amount per gram of catalyst

can be calculated.

Table 7. Specific volumetric dilatation of NKC-9 resin catalyst for single substrate.

According to Popken et al.,26

the relationship between the liquid and resin polymer can be

described by Eq. 14:

( ) =

(14)

where refers to the initial total solvent weight (g); refers to the catalyst mass (g);

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refers to the overall weight fraction of component i; and refer to the equilibriumliquid-phase weight fraction of solvent i andj, respectively; and refer to the adsorbed massof solvent iandj.

Assuming Langmuir-type adsorption based on mass, the following relationship for the mass

coverage mis/m

s can be obtained, with m

s being the total adsorbed mass and j the liquid phase

activities.Krefers to the adsorption equilibrium constant for the solvents.

= 1 + (15)

Combining Eqs.14 and 15 for the binary case, the following relation is obtained :

( ) =

1 + + (16)Four nonreactive binary pairs including acetic acid/acrylic acid (1), methyl acrylate/acrylic acid

(2), acrylic acid/methyl acetate (3), and methyl acrylate/methyl acetate (4) were investigated to

maximize the adsorption strength differences in order to ensure the experimental accuracy. The

results of a fit of all four adsorption equilibrium constants fited to all the data are illustrated in

Figures 10 and 11 and reported in Table 8.

Figure 10. Relative adsorption of acrylic acid from acrylic acid (AA)/acetic acid (HAc) and acrylic

acid (AA)-methyl acrylate (MA) mixtures over NKC-9 catalyst and calculated dependence assuming

constant adsorbed mass.

Figure 11. Relative adsorption of methyl acrylate from a mixture of methyl acrylate (MA)/methyl

acetic (MeAc) and relative adsorption of acetic acid from a mixture of acetic acid (HAc)/methyl

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acetic (MeAc) over NKC-9 catalyst and calculated dependence assuming constant adsorbed mass.

Table 8. Results of the regression for the nonreactive binary adsorption data at 298.15 K.

3.3.3. Determination ofreaction rate constant, activation energy and pre-exponential.

According to the dynamic model, the relevant parameter was identified by using nonlinear least

square method on the basis of the experimental data. Taking SRS in the Eq 17 as the objective

function of recognition, the identification parameters were obtained when the objective function

acquire the minimum.

SRS = ( )

(17)

where , refer to the value of calculated and experimental reaction rate, respectively.As shown in Figure 12 and Table 9, different model identification have different refers to the

former factor, this is because of a description of the different model in a different way.27-29

However,

the value of activation energy was almost the same, and equal to 99.75 kJ/mol.

Table 9. Identification of activation energy , and pre-exponential for for different models.

Figure 12. ln~ 1000/ relationship.

3.3.4. Verification the results of different models.

Based on the kinetic modelsobtained from the experiments, the experimental values (the initial

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conditions) involved in reaction process were recalculted to get a series of caluculated values. By

comparing the experimental and calculation values using mean relative deviation (MRD) as the

standard, the accuracy of the LH and PH models turned out to be higher than that of the LH model

(ideal). Taking the non-ideal of liquid mixture into consideration, the reaction process can be better

described, as shown in Table 10.

MRD/% = 1(

) 100 (18)

Table 10. Comparison between experimental and calculated values using different models.

3.4. Determination of Space-Time of the Fixed-Bed Reactor.

To investigate the effect of space-time () on the conversion rate of methyl acrylate under the

optimised reaction conditions achieved by the batch reactor, a series of experiments were performed

with different space-time in a fixed-bed reactor packed with NKC-9 resin catalyst. The space-time

for the fixed-bed reactor was defined as the function of the effective volume of reactor () andvolumetric flow rates of reactants (F), and the equation was described as= /. As shown inFigure 13, it is obvious that the conversion rate of methyl acrylate gradually increase before the

space-time achieves to 4h, but the conversion rate value keeps almost as a constant after 4 h. These

results demonstrate that 4h was the optimised space-time for the fixed-bed reactor.

Figure 13. Effect of space-time on the conversion rate of methyl acrylate in the fixed-bed reactor

(353.15 K= 1: 1the catalyst load (W) was 0.684 g catalyst/mL reactor volume).

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3.5. Reaction Distillation.

A simulation model of a reactive distillation process is indispensable to design columns and

optimise processes incorporating the reactive distillation technology. The EQEQ approach, the

simplest modeling approach, was used in our study. Assuming phase and chemical equilibrium in

each stage, a reactive distillation column was modeled. The column was axially discretized into

equilibrium stages and the height of each stage was equivalent to the height of a theoretical plate

(HETP) of the used packing. The kinetic model obtained from the stationary solution in a batch

reactor (Section 3.3) was used to describe the chemical equilibrium of the reactive distillation

column. It was assumed that the chemical equilibrium was reached in each stage in the column. The

RADFRAC block of Aspen Plus30-35

and the Newton homotopy arc length differential method with a

good convergence were used to determine the optimised reactive distillation column set-up, and

maximising yield was the optimisation target.

The reactive distillation column is separated into four sections by two feed inlets, and the four

sections are rectifying section, the extractive distillation section, reaction section, and stripping

section (Figure 14). The main function of the rectifying section is to separate the low-boiling product

and acetic acid, and the important function of the extractive distillation section is to separate some

minimum-boiling point azeotrope by acetic acid to ensure the purity of low-boiling product, although

there is no azeotropic phenomenon in this reaction system. The reaction section is the main place

where the transesterification takes place, and the function of the stripping section is to separate the

high-boiling product (acrylic acid) from the reaction mixtures. Acetic acid is fed at the top inlet, and

methyl acrylate is fed at the bottom inlet. In the paper, the kinetic results obtained from the

experiments in a batch reactor were used for the simulation of the reactive distillation (RD) process,

and the amount of catalyst that is immobilised in the reactive section was set to 0.10 g catalyst / g

liquid mixture. Figure 15 shows the temperature/pressure vs. column height in the reactive

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distillation column. The temperature within the reactive distillation column was in the vicinity of

353.15 K used to study the reaction kinetic. And he operating pressure of the column was 0.065 MPa.

The optimisation of theoretical plates number, reflux ratio, HAc feeding position, and MA feeding

position were clearly shown in the Supporting Information, and the optimization results were given

in Table 11. Figure 16 illustrates the vapor-liquid composition distribution in the reactive distillation

column.

Figure 14. Schematic diagram of reactive distillation column.

Table 11. Parameters and results of simulation and optimization.

Figure 15. Distribution of temperature and pressure in reactive distillation column.

Figure 16. VaporLiquid composition distribution in reactive distillation column.

3.6. Long-life evaluation.

The mixture solution of acetic acid and methyl acrylate with a molar ratio of 1:1 is formulated.

The reaction temperature and space-time were set to 353.15K and 4h to investigate the life of the

catalyst- NKC-9.

Figure 17. Lifetime evaluation of NKC-9.

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As can be seen from Figure 17, the conversion rate and selectivity of methyl acrylate did not

change visibly after a long period of running such as 1200 h in a fixed-bed reactor, which

convincingly verified the long life of the catalyst. Compared with the catalyst after a short time

running, there was a slight decrease in the conversion rate of methyl acrylate, which may be

attributed to the adsorption of macromolecular polymerization inhibitor on NKC-9 resin catalyst.

The macromolecular polymerization inhibitor can occupy the acid site of the catalyst and block its

pore structure, resulting in the weakening of the catalytic activity to some extent. Figure 18 shows

the PM photomicrographs of the fresh and used NKC-9 catalyst in the fixed-bed reactor, the changes

in the catalyst morphology are clearly shown. No. 1 is the photomicrograph of fresh catalyst, which

is an inerratic ball with the smooth and uniform surface. No. 2, 3, and 4 present the morphology

structure of the used catalyst, and there are different damages containing pits, cracks, and

fragmentation caused by collision and squeeze in the fix-bed reactor after over 1000 h long time

running. However, the catalyst breakage was found less than 5 wt. % after sieving the catalyst.

Figure 18. PM photomicrographs (of the fresh and used NKC-9catalyst (1. Fresh catalyst; 2, 3, and 4.

Used catalyst; magnification: eyepiece 20objective lens 30).

4. Conclusions

The NKC-9 resin catalyst has shown a good catalytic activity for the transesterification of

methyl acrylate with acrylic acid. By batch reaction experiments, the optimised operating parameters

were obtained including a catalyst load of 0.1 g catalyst/g liquid mixture, reaction temperature of

353.15 K, molar ratio of reactants of 1:1, stirring speed of 300rpm, and catalyst particle size of >32

mesh. According to the swelling and adsorption equilibrium experiments, the adsorption of methyl

acetic and acetic acid was found to stronger than that of acrylic acid and methyl acrylate. Using

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several models to fit the kinetic experimental data, the LH model turned out to be the most suitable

for the transesterification involved, having taken the activity and adsorption equilibrium constants

into consideration. In addition, 4.0 h was the most appropriate space-time in the fixed-bed reactor for

the acrylic acid synthesis. At last, a reaction distillation process was proposed and simulated, and the

methyl acrylate conversion rate of 94.5 % and the acrylic acid concentration of 98.0% in the tower

bottom were achieved under the optimised parameters.

Acknowledgments

The authors gratefully acknowledge the National Program on Key Basic Research Project (No.

2015CB251401), National Science Fund for Excellent Young Scholars (No. 21422607), Key

Program of National Natural Science Foundation of China (NO. 91434203), and Research Supported

by the CAS/SAFEA International Partnership Program for Creative Research Teams.

Nomenclature of the signs, marks, and simplified characters used.

Signs/marks /simplified characters Physical meaning/meaning

P-H

L-H

LHHW

r

ccat

t

x

k

Keq

c

Pseudo-Homogeneous

Langmuir-Hinshelwood

LangmuirHinshelwoodHougenWatson

initial molar ratio of acetic acid to methyl acrylate

reaction rate

catalyst load (g catalyst / g liquid)

quality of the catalyst

molarity of substance

stoichiometric coefficient

the recation time

molar fraction

reaction rate constant (Lmol

-1s

-1)

thermodynamic equilibrium constant

molar concentration

activity

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EA/E

ko

W

MRD

eqi,j

cal

exp

activity coefficient

apparent activation energy (kJ mol1

)

pre-exponential Arrhenius factor (mol s1

g1

)

weight fraction

mean relative deviation

equilibriumcomponents

calculated value

experimental value

space-time

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References

(1) Zuo, C., Pan, L., Cao, S., Li, C., Zhang, S. Catalysts, kinetics, and reactive distillation for methyl

acetate synthesis.Ind. Eng. Chem. Res.2014, 53, 10540-10548.

(2) Ma, J.; Zhang, M.; Lu, L.; Yin, X.; Chen, J.; Jiang, Z. Intensifying esterification reaction between

lactic acid and ethanol by pervaporation dehydration using chitosan-TEOS hybrid membranes. Chem.

Eng. J.2009, 155, 800-809.

(3) Yang, X. G., Zhang, J. Q., Liu, Z. T. The nickel-catalyzed hydroesterification of acetylene with

methyl formate to methyl acrylate.Appl. Catal. A. Gen.1998, 173, 11-17.

(4) Tang, C. M., Li, X. L., Wang, G. Y. A highly efficient catalyst for direct synthesis of methyl

acrylate via methoxycarbonylation of acetylene.Korean. J. Chem. Eng.2012, 29, 1700-1707.

(5) Jiao, T., Li, C., Zhuang, X., Cao, S., Chen, H., Zhang, S. The new liquidliquid extraction method

for separation of phenolic compounds from coal tar. Chem. Eng. J.2015, 266, 148-155.

(6) Li, Y. P., Huo, Q., Zuo, C. C., Cao, S. S., Wang, E. Q. Resin Material Used in Methyl Acrylate

Hydrolysis Reaction.Adv. Mater. Res.2014, 1035, 307-312.

(7) Zhang, B., Ding, G., Zheng, H., Zhu, Y. Transesterification of dimethyl carbonate with

tetrahydrofurfuryl alcohol on the K2CO3/ZrO2catalystFunction of the surface carboxylate species.

Appl. Catal. B: Environ.2014, 152, 226-232.

(8) Thimmaraju, N., Shamshuddin, S. Z. M., Pratap, S. R., Venkatesh.Transesterification of diethyl

malonate with benzyl alcohol catalyzed by modified zirconia: Kinetic study. J. Mol. Catal. A-Chem.

2014, 391, 55-65.

(9) Wang, J. Q., Sun, J., Cheng, W. G., Shi, C. Y., Dong, K., Zhang, X. P., et al. Synthesis of dimethyl

carbonate catalyzed by carboxylic functionalized imidazolium salt via transesterification reaction.

Page 24




26/60

Catal. Sci. Technol.2012, 2, 600-605.

(10) Kuschnerow, J. C., Titze-Frech, K., Schulz, P. S., Wasserscheid, P., Scholl, S. Continuous

Transesterification with Acidic Ionic Liquids as Homogeneous Catalysts. Chem. Eng. Technol.2013,

36, 1643-1650.

(11) Schenzel, A. Catalytic transesterification of cellulose in ionic liquids: sustainable access to

cellulose esters. Green. Chem.2014, 16, 3266-3271.

(12) Peng, Y., Cui, X., Zhang, Y., Feng, T., Tian, Z., Xue, L. Kinetics of Transesterification of Methyl

Acetate and Ethanol Catalyzed by Ionic Liquid.Int. J. Chem. Kinet.2014, 46, 116-125.

(13) Haken, J. K., Ho, D. K. M. Studies in transesterification VI. Ion-exchange catalysis. J. Appl.

Chem.2007, 20, 101-104.

(14) Kotadia D A, Soni S S. Sulfonic acid functionalized solid acid: an alternative eco-friendly

approach for transesterification of non-edible oils with high free fatty acids. Monatshefte Fuer

Chemie/chemical Monthly.2013, 144, 1735-1741.

(15) He, J., Xu, B., Zhang, W., Zhou, C., Chen, X. Experimental study and process simulation of

n-butyl acetate produced by transesterification in a catalytic distillation column. Chem. Eng. Process.

2010, 49, 132-137.

(16) Steene, E. V. D., Clercq, J. D., Thybaut, J. W.Adsorption and reaction in the transesterification

of ethyl acetate with methanol on Lewatit K1221.J. Mol. Catal. A-Chem.2012, 359, 57-68.

(17) Shen, L., Wang, L., Wan, H., Guan, G. Transesterification of Methyl Acetate with n-Propanol:

Reaction Kinetics and Simulation in Reactive Distillation Process. Ind. Eng. Chem. Res.2014, 53,

3827-3833.

(18) Sert E, Atalay F S. Determination of Adsorption and Kinetic Parameters for Transesterification

ge 25 of 59




27/60

of Methyl Acetate with Hexanol Catalyzed by Ion Exchange Resin. Ind. Eng. Chem. Res.2012,51,

6350-6355.

(19) Liu, Y., Wei, M., Gao, L., Li, X., Mao, L. Kinetics of transesterification of methyl acetate and

n-octanol catalyzed by cation exchange resins.Korean. J. Chem. Eng.2013, 30, 1039-1042.

(20) Alonso, D. M., Granados, M. L., Mariscal, R., Douhal, A. Polarity of the acid chain of esters

and transesterification activity of acid catalysts.J. Catal.2009, 262, 18-26.

(21) Tu, C. H., Wu, Y. S., Liu, T. L. Isobaric vapor-liquid equilibria of the methanol, methyl acetate

and methyl acrylate system at atmospheric pressure.Fluid. Phase. Equilibr.1997, 135, 97-108.

(22) Tesser, R., Casale, L., Verde, D. Kinetics and modeling of fatty acids esterification on acid

exchange resins. Chem. Eng. J.2010, 157, 539-550.

(23) Sanz, M. T., Murga, R., S. Beltrn, A., Cabezas, J. L., Coca, J. Autocatalyzed and

Ion-Exchange-Resin-Catalyzed Esterification Kinetics of Lactic Acid with Methanol.Ind. En. Chem.

Res.2002, 41, 512-517.

(24) Ali, S. H., Merchant, S. Q. Kinetics of the esterification of acetic acid with 2-propanol: Impact

of different acidic cation exchange resins on reaction mechanism. Inter. J. Chem.Kinet. 2006, 38,

593-612.

(25) Ewa BoekWinkler, Jurgen Gmehling. Transesterification of Methyl Acetate and n-Butanol

Catalyzed by Amberlyst 15.Ind. En. Chem. Res.2006, 45, 6648-6654.

(26) Popken, T., Gotze, L., Gmehling, J. Reaction Kinetics and Chemical Equilibrium of

Homogeneously and Heterogeneously Catalyzed Acetic Acid Esterification with Methanol and

Methyl Acetate Hydrolysis.Ind. En. Chem. Res.2000, 39, 2601-2611.

(27) Zuo, C., Li, Y., Li, C., Cao, S., Yao, H., Zhang, S. Thermodynamics and Separation Process for

Page 26




28/60

Quaternary Acrylic Systems.Aiche. J.2015, 62, 228-240.

(28) Li, C., Zhang, X., He, X., Zhang, S. Design of separation process of azeotropic mixtures based

on the green chemical principles.J. Clean. Prod.2007, 15, 690-698.

(29) Ray, N. M., Ray, A. K. Determination of adsorption and kinetic parameters for methyl oleate

(biodiesel) esterification reaction catalyzed by amberlyst 15 resin. Can. J. Chem. Eng.2016.

(30) Li, C., Zhang, X., Zhang, S., Suzuki, K. Environmentally conscious design of chemical

processes and products: Multi-optimization method. Chem. Eng. Res. Des.2009, 87, 233-243.

(31) Gangadwala, J., Surendra Mankar, A., Mahajani, S., And, A. K., Stein, E. Esterification of

Acetic Acid with Butanol in the Presence of Ion-Exchange Resins as Catalysts. Ind. Eng. Chem.

Res.2003, 42, 2146-2155.

(32) Ewa BoekWinkler, Jrgen Gmehling. Transesterification of Methyl Acetate and n-Butanol

Catalyzed by Amberlyst 15.Ind. En. Chem. Res.2006, 45, 6648-6654.

(33) Lee, M. J., Hsientsung Wu, A., Lin, H. Kinetics of Catalytic Esterification of Acetic Acid and

Amyl Alcohol over Dowex.Ind. En. Chem. Res.2000, 39, 4094-4099.

(34) Li, C., Wozny, G., Suzuki, K. Design and synthesis of separation process based on a hybrid

method.Asia-Pac. J. Chem. Eng.2009, 4, 905-915.

(35) Li, C., Zhang, X., Zhang, S. Environmental Benign Design of DMC Production Process. Chem.

Eng. Res. Des.2006, 84, 1-8.

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Figure and Table Captions

Figure 1. Effect of the catalyst particle size on the conversion rate of methyl acrylate using NKC-9 as

the catalyst (300 rpm; 80 C; = 1:1; the catalyst load was 0.10 g catalyst / g liquid mixture).Figure 2. Effect of the stirring speed on the conversion rate of methyl acrylate using NKC-9 as the

catalyst (28 mesh; 80 C; = 1:1; the catalyst load was 0.10 g catalyst / g liquid mixture).Figure 3. Effect of catalyst load (NKC-9) on the conversion rate of methyl acrylate (353.15K, =1: 1, 28 mesh, and 300 rpm).Figure 4. Effect of catalyst load on the forward reaction rate constant at 353.15 K with initial molar

ratio of acetic acid to methyl acrylate being 1.

Figure 5. Effect of molar ratio of reactants on the conversion rate of methyl acrylate using NKC-9 as

catalyst (353.15K, 28 mesh, 300rpm, and the catalyst load was 0.10 g catalyst/g liquid mixture).

Figure 6. Effect of reaction temperature on the conversion rate of methyl acrylate using NKC-9 as

the catalyst (= 1: 1, 28 mesh, 300rpm, and the catalyst load was 0.10 g catalyst/g liquid mixture).Figure 7. The curve of Z and t

Figure 8. Relationship between the forward reaction or the adverse reaction rate constant and the

temperature.

Figure 9. Comparison between the experimental data and simulation data.

Figure 10. Relative adsorption of acrylic acid from acrylic acid (AA)/acetic acid (HAc) and acrylic

acid(AA)-methyl acrylate(MA) mixtures over NKC-9 catalyst and calculated dependence assuming

constant adsorbed mass.

Figure 11. Relative adsorption of methyl acrylate from a mixture of methyl acrylate(MA)/methyl

acetic(MeAc) and relative adsorption of aceticacid from a mixture of acetic acid(HAc)/methyl

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acetic(MeAc)over NKC-9catalyst and calculated dependence assuming constant adsorbed mass.

Figure 12. ln~ 1000/ relationship.Figure 13. Effect of space-time on the conversion rate of methyl acrylate in the fixed-bed reactor

(353.15K= 1: 1the catalyst load (W) was 0.684g catalyst/mL reactor volume).

Figure 14. Schematic diagram of reactive distillation column.

Figure 15. Distribution of temperature and pressure in reactive distillation column.

Figure 16. VaporLiquid composition distribution in reactive distillation column.

Figure 17. Lifetime evaluation of NKC-9.

Figure 18. PM photomicrographs of the fresh and used NKC-9catalyst (1. Fresh catalyst; 2.3.4. Used

catalyst; magnification: eyepiece 20objective lens 30).

Table 1. Physicochemical characteristics of the resin (NKC-9).

Table 2. Deviations between the calculated and experimental values on x1, y1, and T through the

NRTL and UNIQUAC models for acrylic acid / methyl acetate and acetic acid / methyl acrylate.

Table 3. Binary interaction parameters of the NRTL model for acetic acid, methyl acrylate, acrylic

acid, and methyl acetate.

Table 4. The reaction rate constants at different temperatures.

Table 5. Different kinetic models and their identification parameters.

Table 6. Reaction equilibrium constants at different temperatures.

Table 7. Specific volumetric dilatation of NKC-9 resin catalyst for single substrate.

Table 8. Results of the regression for the nonreactive binary adsorption data at 298.15 K.

Table 9. Identification of activation energy , and pre-exponential for for different models.Table 10. Comparison between experimental and calculated values using different models.

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Table 11. Parameters and results of simulation and optimization.

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Figure 1.

0 3 6 9 12 15 18 21

0

10

20

30

40

50

35 mesh

32 mesh

28 meshConversionrateofmethylacrylate/%

Reaction time / h

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Figure 2.

0 5 10 15 20 25

0

5

10

15

20

25

30

35

40

45

50

55

500rpm

400rpm

300rpm

0 rpm

Conversionrateofmethylacrylate/%

Reaction time / h

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Figure 3.

0 5 10 15 20 25 30

0

10

20

30

40

50

0.12g Catalyst/g Liquid mixture



None


Reaction time / h

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Figure 4.

0.08 0.09 0.10 0.11 0.12

1

2

3

4

5

6

k+

/k+

(0.08gcatalyst/gliquidmixture)

Catalyst Concentration (g/g)

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Figure 5.

0 5 10 15 20 25 30

0

10

20

30

40

50

60

70

B0=3:1

B0=2:1

B0=1:1


Reaction time/h

Pred. B0=3:1

Pred. B0=2:1

Pred. B0=1:1

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Figure 6.

0 5 10 15 20 25 30

0

10

20

30

40

50

60

363.15K

353.15K

343.15K

Conversionrateofmethylacrylate

/%

Reaction time / h

Pred.363.15K

Pred.353.15K

Pred.343.15K

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Figure 7.

0 2 4 6 8 10 12 14 16

0.0

0.1

0.2

0.3

0.4

343.15K

353.15K

363.15K

Z

Reaction time / h

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Figure 8.

2.70 2.75 2.80 2.85 2.90

-13.2

-12.9

-12.6

-12.3

-12.0

-11.7

lnk

1000/T(K-1)

The forward reactionThe adverse reaction

Y=7.722-7.175X

Y=-11.368-0.362X

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Figure 9.

0 5 10 15 20 25

0

5

10

15

20

25

30

35

40

45

50

55

ConversionratioofMA/%

Reaction time / h

Experimental data

Model simulation data

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Figure 10.

0.0 0.2 0.4 0.6 0.8 1.0

-0.5

-0.4

-0.3

-0.2

-0.1

0.0

0.1

0.2

AA+MA

AA+HAc

wL AA

m0(w1

0-w1

L)/mcat

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Figure 11.

0.0 0.2 0.4 0.6 0.8 1.0

-0.2

-0.1

0.0

0.1

0.2

0.3

0.4

MeAc+MA

MeAc+HAc

wL

MeAc

m0(w1

0-w1L

)/mcat

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Figure 12.

2.76 2.80 2.84 2.88 2.92

-6

-5

-4

lnk

e

103

T-1

/K-1

PH(ideal)

PH

LH

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Figure 13.

0 1 2 3 4 5 6 7 8 9 10

0

10

20

30

40

50

60


Space-time / h

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Figure 14.

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Figure 15.

420 400 380 360 340 320

0

10

20

30

40

50

0.07 0.08 0.09 0.10

MA feeding position

Numberoftheoreticalplates

Temperature in vapor phase / K

HAc feeding position

Pressure in the column

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Figure 16.

0 5 10 15 20 25 30 35 40 45 50

0.0

0.1

0.2

0.3

0.4

0.5

0.6

0.7

0.8

0.9

1.0

Vapor phase composition

MassFraction

Stage Number

HAc

MeAcMA

AA

Liquid phase composition

HAc

MeAc

MA

AA

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Figure 17.

0 100 200 300 400 500 600 700 800 900 1000 1100 1200

0

20

40

60

80

100

Ratio/%

Run time / h

Selectivity

Yield

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Figure 18.

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Table 1.

Properties Parameters

Skeleton Styrene-divinybenzene

Type Strong acidStructure Macroreticular

Functional group Sulfonic(SO3H)

Ionic form H+

Moisture (by weight) Less than 10%

Surface area (m2/g) 50

Particle size 28-35(mesh)

Internal porosity(ml pore/ml bead) 0.36

Concentration of acid sites (meq./g dry) 4.7

Bulk density(Kg/m3) 608

Average pore diameter (nm) 48.2

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Table 2.

Model AAD(x1)b AAD(T)

b AAD(y1)

b

VLE for Acrylic acid (1)+ Methyl acetic (2)

NRTL 0.0012 0.0314 0.0003

UNIQUAC 0.0029 0.0336 0.0005VLE for Acetic acid (1)+ MA (2)

NRTL 0.0025 0.045 0.0002

UNIQUAC 0.0028 0.054 0.0002

AAD(y)b=(1/N) ;AAD(T)b=(1/N) ;AAD(x)b=(1/N)

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Table 3.

(i)/(j) (K) (K) Acetic acid(1)/Methyl acrylate (2) 13.4560 -28.4105 -5151.3602 11039.0889 0.3

Acetic acid (1)/Acrylic acid (3) 0 0 283.0157 42.5680 0.3

Acetic acid (1) / Methyl acetic (4) 0 0 -239.2462 415.2702 0.3

Methyl acrylate (2)/Acrylic acid (3) 0 0 620.1444 -295.8599 0.3

Methyl acetic (4)/ Methyl acrylate (2) 0.5018 -0.6913 463.8299 -361.4648 0.3

Acrylic acid (3)/ Methyl acetic (4) 4.9081 23.5597 -2250.4919 -6440.8516 0.3

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Table 4.

Reaction temperature

K

Forward reaction rate

constants

k+106(Lmol-1s-1)

Adverse reaction rate

constants

k-106(Lmol-1s-1)

343.15 1.8106 4.1953

353.15 3.2869 6.2853

363.15 6.5658 11.061

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Table 5.

ModelChemical Equilibrium

constant

Pre-exponential

factorActivation energy Adsorption equilibrium constant

PH(ideal)

, - - - -

PH , - - - -LH ,

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Table 6.

Temperature/KChemical equilibrium constant

(Activity)

Chemical equilibrium constant

(concentration)

343.15 0.3452 0.4321

353.15 0.6906 0.9224

363.15 1.3727 1.6984

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Table 7.

Substrate Swelling ratio of volume

Methyl acrylate 1.267

Acetic acid 1.283

Acrylic acid 1.251

Methyl acetic 1.242

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Table 8.

Equilibrium Adsorbed Mass

mS/mcat= 0.95

Adsorption Equilibrium Constants

KHAc=3.15

KMA=3.07

KAA=2.89

KMeAc=4.15

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Table 9.

Model mol g s ,(kJ )PH(ideal) 9.42 10 107.84

PH

1.30 10 99.75

LH 2.17 10 99.75

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Table 10.

Model SRS MRD/%

PH(ideal) 1.96210-8

4.727

PH 0.195110-8

1.717

LH 0.153410-8 1.302

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Table 11.

parameters results

Operating pressure 0.065MPa

Theoretical plates number 50

HAc feeding position 11

MA feeding position 45

Reflux ratio 2.5:1

Feed 1.0Methyl acrylate conversion rate 94.5%

Acrylic acid concentrations in the tower bottom 98.0%

ge 59 of 59 Industrial & Engineering Chemistry Research

acrylic axide

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