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Kinetics and modelling study on etherification of glycerol using isobutylene by in-situ production from tertiary-butanol Jasvinder Singh, JITENDRA KUMAR, Mahendra S Negi, Dinesh P Bangwal, Savita Kaul, and Madhukar Omkarnath Garg Ind. Eng. Chem. Res., Just Accepted Manuscript • DOI: 10.1021/acs.iecr.5b00079 • Publication Date (Web): 24 Apr 2015 Downloaded from http://pubs.acs.org on May 3, 2015

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Industrial & Engineering Chemistry Research

Kinetics and modelling study on etherification of glycerol using isobutylene by in-situ production from tertiary-butanol Jasvinder Singh*, Jitendra Kumar, M.S. Negi, Dinesh Bangwal, Savita Kaul, M.O. Garg Biofuels Division, Indian Institute of Petroleum, Dehradun – 248005 (INDIA)

ABSTRACT Experimental results on etherification of glycerol by isobutylene using Indion-130 catalyst are presented. Experiments were carried out at five different temperatures between 45 - 85oC in an autoclave with mechanical stirring. The isobutylene was produced in-situ from tertiary butanol in another autoclave connected in series. Experiments were conducted for duration of 24 hours with sample collection (for analysis) every two hours. Samples were analyzed by gas chromatography for monitoring Mono-, Di- and Tri- tertiary butyl glycerol ethers (MTBG, DTBG, and TTBG). The studies reveal that the optimal temperature for maximum production of DTBG is 55oC. A multi-lump kinetic model has been developed and global rate constants have been evaluated.

INTRODUCTION Oxygenated fuels have a history of reducing exhaust emissions from motor vehicles. Additions of methyl tert-butyl ether (MTBE) and ethanol have been successful in reducing CO and non-evaporative hydrocarbon emissions from gasoline engines1. The success of oxygenated gasoline has sparked interest in the use of oxygenated compounds as particulate matter (PM) emissions reducing additives in diesel fuel 2. Besides the current commercial oxygenates additives (MTBE, ETBE and TAME) applied in gasoline3, the utilization of oxygenates in diesel fuel became priority as a result of stringent legislative regulations reducing air pollution 4. Oxygenated diesel *

Corresponding Author Email: [email protected]; Phone: +91 135 2525 784

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fuels are of importance to both environmental compliance and efficiency of diesel engine 5. It is well known that the blending of oxygenated additives with diesel fuels could be a promising way of improving the combustion efficiency of internal combustion engine with a significant reduction of pollutant emissions. Among several proposed oxygenated additives to blend with diesel, the ethers of glycerol could hold a prominent role 6.

Glycerol is a by-product obtained during the production of biodiesel. As the biodiesel production is increased exponentially, the crude glycerol generated from the transestrification of vegetable oils has also been generated in a large quantity 7. With the increasing production of biodiesel, a glut of glycerol has been created causing market prices to plummet. This situation warrants finding alternative uses for glycerol. Glycerol is directly produced with high purity levels (at least 98%) by biodiesel plants

8-11

. It is

well known that glycerol cannot be directly added to fuel because of its polymerization in high temperatures and partial oxidation to toxic acrolein and it is insoluble in hydrocarbon mixture 12. Research efforts to find new application for glycerol as a low feedstock for functional derivatives have led to the introduction of a number of selective processes for converting glycerol into valued product 12, 13. A recent interest has been focused on its use as renewable starting material for the synthesis of oxygenated fuel additives (biooxygenates)14. Glycerol is converted to tert-butyl glycerol by the reaction with isobutylene and/or t-butyl alcohol in the presence a solid acid catalyst.15-21. This reaction produces a mixture of mono-t-butyl ethers (MTBE), di-t-butyl ethers (DTBG) and tri-t-butyl ether (TTBG). Good solubility of higher ethers, DTBG and TTBG, in diesel and gasoline turns them into excellent additives with a large potential for diesel and biodiesel formulation. Owing to the fact that unpleasant water-soluble methyl tert-butylether

6

has been

prohibited in many places and is not environmentally friendly, mixtures of DTBG and TTBG are not soluble in water. Thus, they can be incorporated into fuels in order to reduce significantly emissions of particles, CO and aldehydes12,

22-24

. The addition of these

ethers into biodiesel also decreases the cloud point to a value similar to conventional diesel 25. Few works have been reported on the development of kinetic models that properly describe the etherification of glycerol performed with either isobutylene or tert-butyl alcohol 26. Frusteri et al.17 suggested a simplified potential kinetic model to describe the main reaction between glycerol and tert-butyl alcohol, based on empirical reaction orders of the reactants estimated by data fitting.


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Reaction orders with respect to glycerol and tert-butyl alcohol were determined considering initial glycerol conversion values under the excess method as reaction conditions. Product distribution was not included in this model. Kiatkittipong et al.27 proposed two lumped kinetic models for glycerol etherification with tert-butyl alcohol: a power law based on activities and mole fractions and a Langmuir−Hinshelwood (LH-A) model in which only the strongest adsorption components were taken into account. The LH-A model gave the best fit of the experimental results. Kinetic parameters were calculated with an Arrhenius equation, and Equilibrium constants were obtained with Gani’s group contribution method. The aim of present work was to study the kinetic modeling of glycerol etherification with isobutylene at different reaction temperature (45-80°C) using an ion exchange commercial resin Indion130 as the catalyst. The isobutylene used for the reaction is being generated in-situ in another autoclave from t-butanol. The results are discussed here. MATERIALS & METHODS The reactants used were tert-butyl alcohol (TBA, 2methyl-2propanol), glycerol from M/s Merck and reference sample of mono ether and N,O-bis (trimethylsilyl) trifluoroacetamide (BSTFA) from Sigma Aldrich Chemicals. Commercial strong acid ion exchange resin Indion-130 supplied by M/S INDION is used as catalyst. The concentration of the active sites, i.e. sulfonic acid, in the catalyst was 4.9 equiv/kg. Before the experiment the catalyst was washed with methanol and dried to remove water and impurities from the catalyst pores. Etherification reaction were carried out in two bench-top-high-pressure reactors (450 mL and 250 mL) with detachable heads (construction of type 316 stainless steel from Parr Instrument Company, Moline, IL) were used for etherification of glycerol with tertbutyl alcohol in presence of Indion 130 ion exchange resin as a heterogeneous catalyst. The two reactors were connected in series such that one is dehydration reactor of tert. butanol to produce isobutylene and another is etherification reactor to react the glycerol with isobutylene to produce tert-butyl ethers of glycerol. The 238.65 g (3.221mol) of tert-butanol (TB) and 23.86 g (10%) of heterogeneous catalyst Indion-130 were taken in the 450 ml pressure reactor (dehydration reactor) at 600 RPM to form isobutylene at 90oC. 75.2 g (0.814mol) of glycerol (G) containing 15 g (20%) of same catalyst charged in etherification reactor. Once, the desired temperature of first reactor is attained, the valve to the second reactor is opened to pass isobutylene continuously in the second



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reactor through a common port connected to both reactors to form Glycerol tert-butyl ethers. Tert-butyl alcohol/glycerol molar ratio 4:1 was used in all experiments and temperature range studies was from 45°C to 85°C each experiment run for 24 hr and samples were collected after every 2 hr and analyzed by GC to monitor the reaction. The system pressure was recorded to be between 6 – 7 kg/cm2 Gas chromatographic Analysis Samples were analyzed with Agilent technologies7890A - gas chromatograph equipped with a HP-1 capillary column (15m x 0.53 mm x 1.0 µm) and a flame ionization detector. The detector temperature was programmed at 350oC with a flow rate of 2.0 m L / min. The injector temperature was set at 300oC and Nitrogen was used as the carrier gas. The oven temperature was programmed with an initial temperature of 60oC (held for 2 min) , 15oC/min. to 180oC (hold -0), 7oC/min to 230oC (hold-0) and finally 30OC/min to 350oC with hold time of 10min. Quantitative analysis was based on response factors of standard reference samples analyzed under the same conditions. The standard samples used were Glycerol reference sample and (±) – 3 – tert – Butroxy – 1,2 – propanediol (Mono ether), supplied by Aldrich KINETIC MODELLING Experimental data has been listed in Table 1. Since the reaction system does not allow analyzing the instantaneous concentration of iso-butene, Langmuir-Hinshelwood type kinetics cannot be modeled. Therefore a lumped parameter model was attempted assuming homogeneous first order kinetic. Further, in the present reactor system, the isobutylene is being generated by in-situ conversion; as

mentioned in previous subsection, glycerol / t-butanol is taken in the molar ratio is 1:4. The glycerol concentration was constantly monitored in the system by taking periodic samples. Therefore absence of isobutylene or tert-butanol concentration will not significantly affect the predictions of instantaneous yields. Although the two reactors are separate and iso-butylene is being produced in-situ in first reactor and being fed to second batch reactor in continuous mode, yet the whole system of two reactors fulfils the conditions of “a batch”. Therefore, the assumption of batch kinetics can define the reactor system with reasonable accuracy. Though the model so developed may not be completely generic but it can predict the yields for a given catalyst. With incorporation of certain catalyst dependent parameters it may also be made generic for various catalysts.


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A multi-lump kinetic model was envisaged according to the reaction scheme suggested by Klepáčová et al.1. They have presented the reaction for etherification of glycerol with iso-butene as well as those with tert-butanol. In present case we have converted tertiary butanol to iso-butene using in-situ conversion in a separate autoclave, the reactions considered for modelling were those with iso-butene. Three primary reactions were considered as follows. G + IB

k1 k2

MTBG

--(1)

MTBG + IB

k3 k4

DTBG

--(2)

DTBG + IB

k5 k6

TTBG

--(3)

In addition, two secondary reactions are considered as follows. 2 DTBG 2 MTBG

k7 k8 k9 k10

TTBG + MTBG

--(4)

DTBG + G

--(5)

Assumed lumps are Glycerol (G), Mono-tertiary butyl ether of glycerol (MTBG), Di-tertiary butyl ether of glycerol (DTBG), and Tri-tertiary butyl ether of glycerol (TTBG). All the reactions were assumed to be reversible. Thus ten rate constatnts are required to define the complete reaction system. Dimerization or iso-butene is not anticipated because it is being produced in-situ in another reactor, and thus unlikely to be present in excess in reaction system to undergo dimerization. Parameter Estimation Rate equations for the assumed reaction system can be represented with following four equations for assumed lumps. ௗሾீሿ ௗ௧

= −݇ଵ ሾ‫ܩ‬ሿ + ሺ݇ଶ + ݇ଽ ሻሾ‫ܯ‬ሿ + ݇ଵ଴ ሾ‫ܩ‬ሿሾ‫ܦ‬ሿ

-- (6)



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ௗሾெሿ ௗ௧

= −݇ଵ ሾ‫ܩ‬ሿ + ሺ݇ଶ + ݇ଷ + ݇ଽ ሻሾ‫ܯ‬ሿ + ሺ݇ସ + ݇଻ ሻሾ‫ܦ‬ሿ − ଼݇ ሾ‫ܯ‬ሿሾܶሿ + ݇ଵ଴ ሾ‫ܩ‬ሿሾ‫ܦ‬ሿ

ሺ݇ସ + ݇଻ ሻሾ‫ܦ‬ሿ + ଼݇ ሾ‫ܯ‬ሿሾܶሿ − ݇ଵ଴ ሾ‫ܩ‬ሿሾ‫ܦ‬ሿ

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-- (7)

-- (8) -- (9)

It is mentioned that the square brackets in the equations refer to the weight percent of the various fractions at time t. The above equations can be solved simultaneously using any of the Runge-Kutta class of methods. In present case Runge–Kutta– Fehlberg sixth order method was employed to solve these equations for instantaneous yield of various lumps. Kinetic parameters k1 through k10 were estimated using differential evolution method (DEM) reported by Storn and Price

28

.

DEM is an optimization technique from the family of genetic algorithms, reported to be successfully tested for the design situations that required tuning of up to 60 parameters. The advantages of DEM include its robustness along with simple structure of algorithm, ease of use, fast speed and capability to find global optima. While gradient methods sometimes lead to local optimal solutions, genetic algorithm based methods are known to converge to global minima due to independence on initial guess and random search methodology. However, upper and lower bounds of values assumed by variables are to be specified judiciously. These were the reasons for our choice of this optimization method. For parameter estimation, sum of fractional error Ef, as given below, was minimized.

-- (10)

value of the product yield, and

Where

is the experimental

is theoretically calculated yield with the derived model equations (6) through (9).


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Minimization of the sum of squares of error as well as percent error was also tried, but the minimization of Ef yielded the best results. Optimal governing parameters for DEM were selected on the basis of recommendations by Gämperle et al.29 RESULTS AND DISCUSSIONS As mentioned in previous subsection, experimental measurements for in-situ conversion of tert-butyl alcohol to isobutylene were not taken; the heterogeneous reaction kinetics could not be established. Hence a global kinetics approach was applied. Instantaneous yield of Glycerol, Mono, di and tri-tertiary butyl glycerol ethers (MTBG, DTBG and TTBG) were measured using GC analysis. Experimental data analysis The experimental yield data for Glycerol, MTBG, DTBG and TTBG has been listed in Table 1. These data also have been plotted in Figures 1 – 4 respectively for Glycerol, MTBG, DTBG and TTBG yields at different temperatures. Depletion of Glycerol (figure 1) indicates exponential decay trend, which indicates first order rate kinetics. The experimental data on MTBG conversion (figure 2) indicates an increase during initial phase of reaction and then decreases to a minimum level. As the temperature rises from 45 to 85 oC, the peak value of conversion reaches earlier. Also both the peak value as well as stable value increase with increase in temperature. These results are well in agreement with the earlier experimental studies earlier reported

4, 30, 31

by Klepáčová and co

workers. This behavior is also imperative from the reaction scheme assumed for analysis. Initially the glycerol fraction undergoes conversion to MTBG, which subsequently converts to DTBG via forward reaction (2). As evident from the estimated rate constants, k1, k3 and k5, the rate of forward reaction is faster for reaction 1 and 2 but relatively slow for conversion to TTBG via reaction 3. Therefore initially the instantaneous concentration of MTBG increases. As the concentration of MTBG becomes in excess, the secondary reactions represented by eq. 5 starts contributing the conversion of DTBG in addition to that by equation 3. These reactions become successively dominant, contributing to decrease the concentration of MTBG in the reaction system. The instantaneous conversion of DTBG is plotted in Figure 3. As evident from these curves, the concentration of DTBG increases constantly for initial period of 15 - 18 hours. But after this time it tends to attain a constant value. This peak value of DTBG concentration decreases with increase in reaction temperature. This can be attributed to higher conversion of DTBG to TTBG and



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MTBG at higher temperatures by secondary reaction represented by eq. 4. The stable value of DTBG in later part of reaction can be explained due to secondary reaction after excess concentration of DTBG accumulates after some time. The concentration of TTBG in reactor has been plotted in Figure 4. The percent concentration profiles of TTBG are also similar to those of DTBG. Here the peak value of percent concentration of TTBG increases with increase in reaction temperature; becomes maximum at 65 – 75 oC and then further decreases at 85 oC. It is obvious because TTBG is not converted to further products. However decreases in maximum yields at very high temperatures (beyond 75 oC), may be attributed to possible backward reaction represented by equations 3 and 4. This may result in accumulation of DTBG instead of TTBG at higher temperature. Analysis of developed model Glycerol etherification has been reported to be an acid catalyzed reaction and various studies are available on etherification reaction using various catalysts

30, 31

. Table 2 lists the estimated kinetic parameters at different temperatures from 45 to 85 oC. The

Arrhenius constants have also been evaluated for assumed reactions and are tabulated in Table 3. The rate constants k1, k3, k6 and k7 appear to have the largest values, whereas k5 and k10 assumes the least. This shows the dominance of forward reactions represented by equations 1, 2 and backward reaction represented by 3, among primary reactions. Predicted values from the kinetic model for all the three fractions, as well as that of Glycerol depletion are in good agreement with experimental data. In case of MTBG the experimental trend shown for instantaneous yield is followed by developed kinetic model, but predicted values show more error in the beginning of reaction. This excess amount of error may be explained as follows. The developed model includes a certain amount of empiricism due to non availability of instantaneous isobutylene concentration in the etherification reactor. Initially the concentration of isobutylene may be less and it may behave as the limiting reactant. Nevertheless, the kinetic model must be assuming a constant concentration throughout the reaction regime. Due to this the initially the predicted values of MTBG may be higher as compared to experimental values. In later part of reaction, the predicted values show less error due to the presence of isobutylene fraction in adequate concentration. The predictions of DTBG fractions are in good agreement with experimental values. It may be observed that the error in predicted values decreases with increase in reaction temperature. This may be attributed to the higher values of rate constant k9 which governs the conversion of MTBG to DTBG. At lower temperatures, this secondary reaction would not be dominant initially.


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Therefore, the predicted yield of DTBG may appear higher than the experimental one. After initial time of 6 – 7 hours, the secondary reaction may become appreciable, so the predicted values become accurate due to agreement of the assumed model with experimental fact. Unlike the prediction of MTBG and DTBG, it is observed that prediction of yields becomes more accurate as the temperature of reaction increases. The larger error in prediction of yields may be due to higher value of rate constant k7 which decides the yield of TTBG due to secondary reactions. Since the secondary reaction represented by eq. 4 may not be dominant at lower temperature and concentration, the prediction error will be large at less severity, either in terms of temperature or residence time. Figures 5 shows the parity plots of predicted values of MTBG, DTBG and TTBG yield at various temperatures. It may be observed that prediction of most of these experimental values (almost 90 %) is within the error range of 20%. Conclusions A novel method for etherification of glycerol has been discussed using isobutylene obtained by in-situ conversion from tertbutanol in another autoclave. Periodic samples were collected and analyzed by Gas chromatography. The obtained data has been analyzed vis-à-vis other similar studies available in literature. The results were found to be in good agreement with those of other researchers. A simplified multi-lump kinetic model was also conceptualized and kinetic parameters were estimated using differential evolution method with the help of in-house developed computer code in C++. Estimated kinetic parameters were found to predict the yield within acceptable range. A critical evaluation of these kinetic parameters has also been presented. This simplified model does not include details of catalyst parameters and isobutylene concentrations. But it may be quite useful for prediction of yields of glycerol etherification within acceptable range, using similar catalyst.



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14. N.M. Ribeiro, A.C. Pinto, C.M. Qintella, G.O. da Rocha, L.S.G. Teixeira, Lilian L.N. Guariero, Maria do Carmo Rangel, Marcia C.C. Veloso, Michelle J.C. Rezende, Rosenira Serpa da Cruz, Ana Maria de Oliveira, Ednildo A. Torres, Jailson B. de Andrade. The role of additives for diesel and diesel blended (Ethanol or Biodiesel) fuels: A review., Energy and fuels, 2007, 21, pp, 24332445 15. Ozbay, N.; Oktar, N.; Dogu, G.; Dogu, T. , Conversion of biodiesel by-product glycerol to fuel ethers over different solid acid catalysts, Int. J.Chem. React. Eng. 2010, 8. 16. Rahmat, N.; Abdullah, A. Z.; Mohamed, A. R. Recent progress on Innovative and potential technologies for glycerol transformation into fuel additives: A critical review. Renewable Sustainable Energy Rev. 2010, 14, 987–1000. 17. Frusteri, F.; Arena, F.; Bonura, G.; Cannilla, C.; Spadaro, L.; Di Blasi, O. Catalytic Etherification of Glycerol by tert-Butyl Alcohol to Produce Oxygenated Additives for Diesel Fuels. Appl. Catal. A, 2009, 367, 77−83. 18. Klepacova, K.; Mravec, D.; Hajekova, E.; Bajus, M. Etherification of glycerol. Pet. Coal, 2003, 45, 54–57. 19. Barsa, E. A.; Steinmetz, B. M. Preparation of glycerol tert-butyl ethers. Private communication, 2010. 20. Behr, A.; Eilting, J.; Irawadi, K.; Leschinski, J.; Lindner, F. Improved utilization of renewable resources: New important derivatives of glycerol. Green Chem. 2008, 10, 13–30. 21. Di Serio, M.; Casale, L.; Tesser, R.; Santacesaria, E. New process for the production of glycerol tert-butyl ethers, Energy Fuels 2010, 24, 4668–4672. 22. Kesling HS, Karas LJ and Liotta FJ. Diesel fuel, US Patent 5308365 (1994) 23. Melero, J.A., Vivente, G.; Morales, G.; Paniagua, S.; Moreno, J.M.; Roldán, R.; Ezquerro, C. & Pérez, C., Acid-catalyzed etherification of bio-glycerol and isobutylene over sulfonic mesostructured silicas. Applied Catalysis A: General, 2008, Vol.346, pp. 44-51 24. María Pilar Pico, Juana María Rosas, Sergio Rodríguez, Aurora Santos, Arturo Romero Glycerol etherification over acid ion exchange resins: effect of catalyst concentration and reusability. Journal of Chemical Technology & Biotechnology November 2013, 2027-2038



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25. Rahmat, N.; Abdullah, A. Z., Mohammed A. R. Recent progress on innovative and potential technologies for glycerol transformation into fuel additives: a critical review. Renewable and Suitable Energy Reviews, 2010, Vol.14, 987-1000 26. M. Pilar Pico, Arturo Romero, Sergio Rodríguez, Aurora Santos, Etherification of Glycerol by tert-Butyl Alcohol: Kinetic Model, Ind. Eng. Chem. Res., 2012, 51, pp 9500–9509 27. Kiatkittipong, W.; Intaracharoen, P.; Laosiripojana, N.; Chaisuk, C.; Praserthdam, P.; Assabumrungrat, S. Glycerol ethers synthesis from glycerol etherification with tert-butyl alcohol in reactive distillation. Comput. Chem. Eng. 2011, 35, 2034−2043. 28. Kenneth Price and Rainer Storn, Differential Evolution, Dr. Dobb’s Journal, 1997, 18-24 29. Gämperle,

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Table 1 Experimental data for kinetics study of Glycerol etherification

S.N.

Sample code

Feed

Reaction Temp., oC

Components

1.

GTBE-9

Glycerol = 75g Catalyst=15.0 g

45

2.

GTBE-4


55

3.

GTBE-5


65

4.

GTBE-14


75

5.

GTBE-13


85

Tri – Ether Di – Ether Mono Ether Glycerol Unidentified Tri – Ether Di – Ether Mono Ether Glycerol Unidentified Tri – Ether Di – Ether Mono Ether Glycerol Unidentified Tri – Ether Di – Ether Mono Ether Glycerol Unidentified Tri – Ether Di – Ether Mono Ether Glycerol Unidentified

Time, h 2 0.0 6.7 31.6 52.4 9.1 4.58 2.22 9.73 77.1 6.25 0.31 8.66 25.6 52.9 12.5 0.41 1.77 8.75 83.6 5.20 0.51 2.37 12.39 78.92 4.85

4 4.4 4.8 41.2 27.1 22.4 4.73 72.0 17.4 4.50 1.01 0.0 31.5 35.2 11.1 22.1 0.53 5.43 18.4 73.1 2.45 0.53 5.30 13.58 72.92 7.32

6 0.0 21.1 51.9 18.6 8.0 7.76 50.6 31.1 8.00 2.38 4.65 39.2 25.2 25.9 4.92 1.20 14.7 36.13 45.08 2.72 4.07 43.65 32.13 17.46 1.62

8 1.1 22.0 55.1 13.8 7.7 3.25 38.9 38.9 16.6 2.17 2.42 63.5 27.3 5.61 1.10 3.06 26.7 47.56 18.92 3.80 0.70 10.78 15.94 72.4 0.11


10 3.3 76.2 16.0 1.8 2.36 13.5 62.2 18.9 3.73 1.65 8.61 55.0 26.7 4.04 5.09 2.95 33.8 29.4 29.7 3.90 5.25 47.7 37.8 7.40 1.67

12 3.95 89.1 6.18 0.0 0.6 23.1 60.4 11.6 1.45 3.12 2.81 65.9 23.7 3.92 3.55 6.04 46.1 35.8 6.99 3.07 1.07 7.60 11.17 75.9 2.85

14 0.23 92.2 5.14 0.23 2.03 13.1 85.5 0.1 0.1 1.1 9.46 47.8 19.5 3.50 19.5 6.84 47.39 34.7 5.05 5.47 4.73 27.81 24.02 42.9 0.47

16 0.11 89.5 4.69 0.58 4.81 4.82 84.6 8.71 0.58 1.17 13.1 55.8 19.7 3.12 7.97 6.88 50.5 31.0 8.73 2.67 8.42 49.9 33.96 5.53 2.51

18 0.33 91.1 4.87 0.33 2.87 4.79 80.8 10.1 1.16 3.11 4.60 69.2 21.1 2.57 2.30 7.16 49.3 35.5 5.47 2.63 8.99 50.58 32.85 5.21 5.21

20 0.10 94.3 4.07 0.0 1.32 0.66 84.0 5.33 3.33 6.0 17.8 62.2 14.4 2.55 2.55 7.76 49.9 32.8 7.66 1.78 9.25 52.37 31.12 3.62 3.62

22 0.0 94.5 3.96 0.10 1.04 8.16 83.0 7.03 0.12 1.50 4.08 79.8 13.9 0.96 1.20 6.67 47.7 34.6 7.49 3.27 5.34 9.94 0.52 83.3 0.52

24 0.20 94.2 3.77 0.10 1.67 4.32 85.6 8.29 0.84 0.72 0.10 75.0 19.3 1.06 4.46 6.92 44.1 34.0 7.46 7.56 0.10 3.51 8.37 86.45 1.44


1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60

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Table 2 Estimated rate constants at different temperatures Temperature

Rate constant, h-1

45

55

65

75

85

k1 k2 k3 k4 k5 k6 k7 k8 k9 k10

0.475686 0.161723 0.241899 0.010589 0.073272 0.326849 0.406865 0.152356 0.39071 0.007989

0.803433 0.184892 0.032726 0.016986 0.182128 0.391279 1.42775 0.171022 0.58756 0.024733

0.702791 0.213563 0.121999 0.000792 0.298148 0.547506 0.220348 0.228552 0.699127 0.030023

0.134436 0.02155 0.249276 0.131922 0.306188 0.977655 2.323516 0.235924 1.312936 0.050942

0.155168 0.269188 0.330309 0.297257 0.047559 0.035516 0.052152 0.016084 0.471775 0.002813

Table 3 Estimated Arrhenius constants S.N. 1 2 3 4 5 6 7 8 9 10

Rate constant k1 k2 k3 k4 k5 k6 k7 k8 k9 k10

E, kJ/mol 23.6043 12.12225 5.73021 82.3514 44.4649 33.0909 49.7112 14.7745 34.911745 50.2350


A, hr-1 3827.626 15.84731 2.2034 2.92E11 1.79E6 8.00E4 7.78E7 40.4473 2.05E5 5.34E6

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Kinetics and Modeling Study on Etherification of ... - ACS Publications

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