Solvent-free production of ethylene glycol monostearate through

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Solvent-free production of ethylene glycol monostearate through enzymatic esterification Gabriela N Pereira, Jefferson P. Holz, Lindomar Lerin, Mara Cristina Picoli Zenevicz, Débora de Oliveira, and José Vladimir Oliveira Ind. Eng. Chem. Res., Just Accepted Manuscript • DOI: 10.1021/acs.iecr.7b05365 • Publication Date (Web): 25 Apr 2018 Downloaded from http://pubs.acs.org on April 25, 2018

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Industrial & Engineering Chemistry Research

Solvent-free production of ethylene glycol monostearate through enzymatic esterification

Gabriela N Pereira, Jefferson P. Holz, Lindomar Lerin, Mara Cristina Picoli Zenevicz, Débora de Oliveira*, J. Vladimir de Oliveira

Federal University of Santa Catarina – USFC - Department of Chemical and Food Engineering, Florianópolis/SC, Zip Code: 88040-900, Brazil

* Corresponding author: Débora de Oliveira E-mail address: [email protected] Complete postal address: Universidade Federal de Santa Catarina (UFSC) Departamento Engenharia Química e Engenharia de Alimentos (EQA) Campus Trindade, Cx. Postal 476 88010-970 Florianópolis, SC - Brasil Phone: +1-55-48-3721-2515

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Industrial & Engineering Chemistry Research 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

Abstract This work reports new results about the solvent-free enzymatic production of ethylene glycol monostearate, an important industrially emollient ester conventionally produced by chemical route. For this purpose, reactions were carried out using two commercial immobilized lipases, evaluating the effect of temperature, agitation and enzyme concentration on the reaction conversion. It was shown that for most tested conditions, reaction conversions around 100% were achieved. The reuse of the enzyme was also evaluated with satisfactory results up to four enzyme cycles. System scale up by ninefold allowed reaching conversions of up to 99%. Chemical analyzes showed that the product obtained through enzymatic synthesis presented very good characteristics, which makes the enzymatic esterification process employed in this work an interesting and promising route for possible application at industrial scale.

Keywords: Ethylene glycol monostearate; Novozym 435; enzymatic esterification; emollient ester.


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1. Introduction The use of cosmetics has grown every year in Brazil and in the world, a proof of this was a 10% expansion in the last fifteen years in the country, making it the third place in the world ranking, estimating about USD 60 million in consumption of toiletries, perfumery and cosmetics in 20101. Concurrent with the consumption growth, there is also the generation of economic, social and environmental impacts, which are currently under discussion, resulting in an enormous need for a transition to an environmentally friendly future2. Therefore, there is an increase in awareness of the launch of green products that meet human needs without environmental damages. According to the authors3, an ecological or green product should be manufactured with the minimum amount of raw materials, being recyclable or renewable, manufactured with the maximum energy efficiency and minimum use of water, besides being biodegradable. Other definitions for the product to be considered as “green” is if it presents higher environmental performance than the traditional ones at function parity. This performance is not limited to the production phase but is extended to the product life cycle as a whole4. Based on these aspects, biotechnology arises as an improvement of existing processes or even for the creation of new products, such as the production of pharmaceuticals, cosmetics, fermentation techniques industrial, pest control, among others, and is considered nowadays a promising alternative field for the development of less pollutant processes5. Regarding cosmetics with emollient properties, one possibility is the production from fatty acids, hence replacing petroleum-based emollients. Non-toxicity, biodegradability, good fat solubility and excellent interfacial properties are the most important properties that make them useful in various formulations6.



In this context, the present work was conceived to obtain ethylene glycol monostearate, an ester with emollient properties, through enzymatic esterification reaction in a solvent- free system, operating in batch mode, determining the best processing conditions, as well as evaluating the quality of the product obtained. It is worthy noting that no studies were found in the open literature regarding the subject explored in this work and therefore, the present study is the first in the literature to report the production of ethylene glycol monostearate through enzyme-catalyzed route.

2. Material and Methods 2.1. Materials The following substrates were used for the esterification reactions: vegetable stearic acid (purity above 99 %, melting point between 56 and 62 oC, ALMAD, Fats and Derivatives - Brazil) and ethylene glycol PA (Vetec). Three commercial lipases, kindly donated by Novozymes (Brazil/Araucária - PR), were tested: 1) Novozym 435, a commercial lipase produced from Candida antarctica immobilized on macroporous acrylic ion exchange resin. According to the manufacturer, such enzyme can be employed at temperatures in the range of 40-70 °C. 2) NS 88011, a commercial lipase from Candida antarctica immobilized on a hydrophobic polymer resin, and 3) Free Candida antarctica type B lipase.

2.2. Enzymatic synthesis of ethylene glycol monostearate The assays for the enzymatic production of ethylene glycol monostearate were carried out in 150 mL jacketed reactor with mechanical stirring (IKA RW 20) with a propeller-shaped four-blade stirrer rod (R 1342) and the temperature was controlled by a thermostatic bath (MQBMP - 01) (Figure 1). In this step, a concentration of 2 wt% of


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two different immobilized lipases (Novozym 435 and NS 88011) was adopted to evaluate the direct influence of the agitation, 600 and 1000 rpm. First, stearic acid was added and complete solubilisation was expected, then ethylene glycol was added to the reaction system. Afterwards, about 1 g of the sample was withdrawn for the determination of acid number (time zero) and then the biocatalyst was added. After 6 hours of reaction another aliquot was removed to determine the reaction conversion and consequently the most appropriate agitation level and enzyme content for the system under investigation.

2.3. Kinetic evaluation Effect of temperature After the preliminary tests and the choice of the best biocatalyst for the system, the following reaction conditions were tested: 1:1 substrates molar ratio, 600 rpm and 48 h of reaction, at 65, 70, 75 and 80 °C.

Effect of enzyme concentration Having determined the best temperature at 75 °C with fixed stirring at 600 rpm and substrates molar ratio of 1:1, tests were performed varying the enzyme concentration: 0.1, 0.3, 0.5, 0.7 and 1 wt% of enzyme loading.

2.4. Study of lipase reuse for the synthesis of ethylene glycol monostearate To recover the enzyme at the end of the reaction, the biocatalyst was separated from the reaction medium by decantation and filtration. After washing with n-hexane in a becker at 50 °C, solvent excess was removed, and the biocatalyst left in the oven for



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about 1 h at 40 °C7,8. After this procedure, the biocatalyst was successively employed in other reactions until a significant conversion decay was observed. 2.5. Scale up At this process step, the amount of substrates was increased by about nine times in order to check the influence of scale up, of extreme importance to purpose the process in an industrial level. For this procedure, a reactor volume of 150 mL was changed to a 500 mL one. The exchange for a larger rod was also made to aid the agitation effectiveness.

2.6. Measurement of acidity index The determination of the acidity index (or acid number) gives an important information in the evaluation of the amount of acid consumed in the esterification reaction, that is, the greater the amount of acid reacted with the alcohol, the lower the acidity index, which is defined as the amount of potassium hydroxide needed to neutralize one gram of sample. This index was determined following the AOCS methodology Cd 3d-639. First, approximately 1 g of the sample was diluted, and 3-4 drops of phenolphthalein was added to approximately 40 mL of a 1:1 ether / ethanol solution. This mixture was then titrated with 0.1 M potassium hydroxide (KOH) under vigorous stirring until the color change to pink. The acidity index was determined according to Equation 1:

=

.

(1)

where AI is the acidity index (AI, wt%), VKOH is KOH solution volume (mL) employed in the titration, CKOH is the concentration of KOH solution (mol/L), 56.1 is the molecular mass of potassium hydroxide (gmol−1), and m is the sample mass (g).


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2.6.1. Determination of reaction conversion The conversion determination was done through the relation between the indexes of final and initial acidity, according to Equation 2:

% =

100

(2)

where AIf is the final acidity index (mg KOH / g) and AIi is the initial acidity index (mg KOH / g). The experimental errors were calculated based on the replicates of the experiments.

2.7. Product analyses Iodine value: The iodine value of an oil or fat is the measure of its insaturation and is expressed in terms of the number of centigrams of iodine absorbed per gram of the sample (% iodine absorbed). First, the sample was melted and filtered to remove possible solid impurities and traces of moisture. Then, approximately 0.25 g was weighed in a 250 mL Erlenmeyer flask with a cap and 10 mL cyclohexane was added. After that, 25 mL Wijs solution was transferred to the Erlenmeyer flask containing the sample. After capping the Erlenmeyer flask and stirring gently with rotation, it was allowed to stand in the dark at room temperature for 30 min. Then, 10 mL of the 15% potassium iodide solution and 100 mL of freshly boiled and cold water was added. Titration was done with 0.1 M sodium thiosulphate solution until a poor yellow color appeared, adding 1 to 2 mL of 1% starch indicator solution and continuing the titration until the blue color completely disappeared. In parallel with the sample, the same procedure was performed in blank. Iodine value was determined by: Iodine =

(Vb − Va ).M .12.68 P

(3)



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where M is the molarity of Na2S2O3 (mol/L), solution, Vb the volume (mL) spent in blank titration, Va the volume (mL) spent in sample titration, P sample mass (g) and 12.68 is the molecular weight of potassium iodide (g/mol);

Density at 20 °C: density was determined through a pycnometer, using water as reference liquid. First, a sample of ethylene glycol monostearate product was melted. Meanwhile, the pycnometer that was in an oven at 100 °C, was weighed and water was added taking note of water mass. Afterwards, the same procedure was employed with the product sample and density determined by: D=

A B

(4)

where A and B denote, respectively, the mass of the sample (g) and mass of water (g).

Saponification index: for this determination, approximately 4 g of the sample was melted and then 50 mL of KOH alcohol solution was added together with the sample, allowing to boil (using a condenser) gently until complete saponification of the sample (approximately 1 h). Afterwards, 1 mL of phenophthalein indicator solution was added and resulting solution was titrated with 0.5 M hydrochloric acid solution until disappearance of the pink heart, according to methodology A.O.C.S., Cd 3-2510. The saponification index was then determined according to, Saponification index =

56.1.M KOH .( B − A) P

(5)

where MKOH is the molarity of KOH solution (mol/L), A is the volume spent on sample measurement (mL), B the volume spent on titration of blank (mL), and P is the sample mass (g).


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Hydroxyl index: for the determination of the hydroxyl number, the AOCS Method Cd 13-6011 was used. Briefly, 10 g of ethylene glycol monostearate sample was weighed in a 250 mL round bottom flask. Then, 5 mL of the pyridine-acetic anhydride reagent (3 v:1 v) was added and the flask was placed in a water bath for 1 h under reflux. After heating, 10 mL of water was added to the flask and heated in a water bath with additional reflux time of 10 min. Using a total of 25 mL of butyl alcohol, the condenser and the sides of the flask were internally washed. Finally, 1 mL of phenolphthalein indicator solution was added and titrated with 0.5 M alcoholic potassium to a pink heart. The same was carried out without the presence of ethylene glycol monostearate to give the blank. In parallel with the previous experiment, 9 g of the ester was weighed into an Erlenmeyer flask to determine the acidity. In addition, 10 mL of pyridine and 1 mL of phenolphthalein indicator solution was added, and it was titrated with 0.5 M alcoholic potassium until a heart turned pink. The hydroxyl number was then determined by, ! "#$ =

%&'(.)*. +. .

.(

(6)

where A represents the volume (mL) of the KOH solution, B denotes the volume (mL) of KOH solution for the blank holder, in mL, C is the sample mass (g) used in the titration, S the volume (mL) of the KOH solution, W the sample mass (g) used for acetylation, N the normality or molarity of alcoholic potassium (mol/L), and 56.01 is the KOH molar mass (g/mol).

Color analysis: color was measured by a colorimeter (Chorma Meter CR-400, Konica Minolta) operating in the CIELAB system (L *, a *, b *, C, h). The L * index measures brightness and varies from black to white; (+ a *) for green (-a *), while a



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coordinate b * varies from yellow (+ b *) to blue (-b *)12. The calculations for the color difference ∆E * were done through: ∆- ∗ = /∆01 + ∆3 ∗1 + ∆4 ∗²

(7)

3. Results and Discussion 3.1. Preliminary tests It is known that the agitation may be a relevant parameter in esterification reactions, since it helps the miscibility between the substrates, promotes mixture homogeneity and can also prevent the enzyme decantation in the reactor13. Thus, as a first step for the production of ethylene glycol monostearate the agitation was evaluated at 600 and 1000 rpm, keeping fixed the concentration of 2 wt% of the two commercial immobilized lipases (Novozym 435 and NS 88011). Figure 2 shows the conversions obtained in this step, where it can be noted that very close values were observed for the two agitation levels tested. So, it was decided to adopt the agitation at 600 rpm for the next experiments as it was a lower energy expenditure, and vary the enzyme concentration from 0.5 to 2 wt% at 6 h reaction time and temperature of 75 °C. Such temperature value was defined based on the melting point of stearic acid (56-62 °C - solid at room temperature), as lower temperatures would hinder reaction to proceed satisfactorily. At this step, free CALB lipase was also tested, but it did not perform efficiently, possibly due to the relatively high temperature employed which might have caused denaturation of the protein molecule14. The next tests were then conducted using only the immobilized commercial lipases that are in fact more stable, temperature-resistant.


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Figure 3 presents the conversion results for Novozym 435 and NS 88011 lipases at different concentrations (0.5, 1 and 2 wt%), at the following conditions: 75 °C, 600 rpm and substrates molar ratio of 1:1 for 6 h reaction time. It can be observed that after 6 h the best conversions were achieved when 2 wt% of enzyme was used. However, it should be noted that that very satisfactory result was also reached using 1 wt% Novozym 435. Accordingly, taking into account the high price of this immobilized enzyme and better results found compared with NS 88011, the next tests were conducted using 1 wt% of Novozym 435, varying now the reaction temperature and enzyme concentration.

3.2. Influence of temperature System temperature can play a key role in enzymatic catalysis, since each enzyme has an optimal range of use, so that the temperature was varied to verify its influence on the production of ethylene glycol monostearate. However, according to Figure 4, very similar results were obtained for all temperatures tested (65 to 80 °C). Based on these results, it was decided to adopt 75 °C for subsequent experiments, as it is a safer temperature to work with stearic acid, which is solid at room temperature and has a melting point between 56 and 62 °C.

3.3. Influence of enzyme concentration Tests for the production of ethylene glycol monostearate were conducted varying the enzyme concentration, keeping constant temperature at 75 °C, stirring at 600 rpm and 1:1 substrates molar ratio. Figure 5 shows that the enzymatic esterification process seems to be viable and should be tested at industrial level, as low enzyme concentrations afforded satisfactory results, even for 0.1 wt% enzyme for which



approximately 90% conversion was reached. In study for the production of propylene glycol monoester using the enzyme Lipozyme IM-77 in solvent system, it was observed that the highest conversion was obtained using excess of the acyl donor and large amount of enzyme,15 already for this study the stoichiometric reaction and extremely low amounts of enzyme led to high conversions (99%).

3.4. Reuse of the biocatalyst In this stage, the reuse of the biocatalyst was evaluated aiming at the possible application in the industrial level. Figure 6 shows the results of reaction with reuse of enzymes over 5 cycles, where it can that a very satisfactory performance was observed up to 4 cycles of reuse, with approximately 70% of conversion, which was not observed for the fifth cycle, as it may have occurred the loss of enzymatic activity related to the contact of the enzyme with the reagents/substrates, in addition to washing with solvent n-hexane.

3.5. Scale-up The increase of scale in bioprocesses is of extreme importance. The challenge is to produce large quantities with high productivity and product quality16. In bioprocesses the three scales are: laboratory, pilot plant and industrial production17. The scale enlargement is of paramount importance in directing how the reaction will be conducted on larger amounts of substrate. Typically, the problems associated with scaling up come from the fact that the times required for the mechanisms to occur increase with increasing scale. Figure 7 shows the results for scale-up evaluation in glass jacketed reactor and mechanical agitation, where enhancement was from a 150 mL reactor to a


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500 mL reactor. In terms of amount of reagents, the scale was expanded ninefold. As shown in Figure 7, one can verify that even increasing the amount of substrate by about 9 times, the system remained unchanged and with conversions close to 100% in 48 hours of reaction, thus being very promising to use on an industrial level.

3.6. Analysis of product quality As expected, in the case of ethylene glycol monostearate produced in this work by enzymatic esterification (1 wt% Novozym 435, temperature of 75 oC, 600 rpm and 1:1 substrates molar ratio, 48 h reaction) the iodine value obtained was zero. Regarding density at 20 °C, 0.89 g/cm³ was determined for the ethylene glycol monostearate produced, while a value of 201.03 mg KOH/g for the saponification index was measured. The hydroxyl number obtained was 15.92 mg KOH/g, noting that there is not a standard recommended value, but it depends solely on the customer requirement involved. For color analysis, operating in the CIELAB system the values obtained are shown Table 1, where ∆E* figures were calculated according to Equation 7, resulting in values close to 100, which shows the tendency of white color prevalence for the ethylene glycol monostearate produced, a desired result for practical product applications.

4. Conclusions Results reported in this work showed that Novozym 435 enzyme is effective for the production of ethylene glycol monostearate, thus opening a promising area to the development of green processes. It was also demonstrated the possibility of biocalyst



reuse, which helps making the reaction process economically feasible. Besides, the scale up tested proves the possibility of adopting the enzymatic route at industrial scale. It was also shown through characterization analyzes that the product obtained via enzymatic synthesis presents positive characteristics that may meet the required specifications for practical applications.

Acknowledgements The authors thank CNPq and CAPES for the scholarships and financial support of this work. Supporting Information Attached, following the table in the figure. 5. References (1) Euromonitor, 2016 - The economy of beauty: the personal hygiene sector, perfumery and cosmetics. Available at: https://economiadeservicos.com/2016/04/19/a-economiada-beleza-o-setor-de-higiene-per-me-perfumaria-e-cosmeticos/ Accessed on December 23, 2017. (2) Rasmussen, J. E. Transitioning to Green: implementing a comprehensive environmental sustainability initiative on a university campus. Doctoral Dissertation, California State University, Long Beach, CA, USA, 2011. (3) Ottman, J. A. Green Marketing: Challenges and Opportunities for the New Age of Marketing. 1st ed. São Paulo: Makron Books Ltda, 1994, 44. (4) Fraccascia, L.; Giannoccaro, I.; Albino, V. Green product development: What does the country product space imply?. Journal Of Cleaner Production, 2018, 170,1076. (5) Ferreira, M. E.; Faleiro F.G. Biotechnology: advances and applications in plant genetic improvement. In: Faleiro G.F; Neto, A. LF (ed. Savanas: challenges and strategies for the balance between society, agribusiness and natural resources, Symposium, Chapter 23, p.765-792, Planaltina, DF: EMBRAPA Cerrados, 2008. (6) Khan, N. R.; Rathod, V. K. Enzyme catalyzed synthesis of cosmetic esters and its intensification: A review. Process Biochemistry, 2015, 50, 1793.


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(7) Lerin, L.; Ceni G.; Richetti A.; Kubiak G.; Vladimir Oliveira J.; Toniazzo G.; Treichel H.; Oestreicher E. G.; Oliveira D. Successive cycles of utilization of Novozym 435 in three different reaction systems. Brazilian Journal of Chem Engineering. Rio de Janeiro, 2011, 181. (8) Castro, H. F.; Anderson, W.A. Fine chemicals by biotransformation using lipase. Química Nova, 1995, 18, 544. (9) AOCS (1973). Official methods and recommended practices of the American Oil Chemists’ Society. Method Cd 3d-63. (10) AOCS (2003). Official methods and recommended practices of the American Oil Chemists’ Society. Method Cd 3-25. (11) AOCS (1997). Official methods and recommended practices of the American Oil Chemists’ Society. Method Cd 13-60.

(12) Konica M. Precise Color Communication: Color control from perception to instrumentation. Konica Minolta Sensing, Inc. 3- 91, Daisennishimachi, Sakai. Osaka 590-8551, Japan, 1998. (13) Remonatto, D.; Trentin Santin M.C.; Valério A.; LERIN L.; Batistella L.; Ninow L.J.; Vladimir Oliveira J.; Oliveira D. Lipase-catalyzed glycerolysis of soybean and canola oils in a free organic solvent system assisted by ultrasound. Applied Biochemistry Biotechnology. 2015, 176, 850. (14) Gomes, F. M.; Paula A. V.; Silva S. G.; Castro H. F. Determination of catalytic properties in aqueous and organic medicine of Candida rugosa lipase immobilized in cellulignin chemically modified by carbonylidimidazole. Chemistry. 2006, 29, 710. (15) Shaw, J; Wu, H.; Shieh, C. Optimized enzymatic synthesis of propylene glycol monolaurate by direct esterification. Food Chemistry. 2003, 81, 91. (16) Xing, Z.; Kenty B.M.; Li Z.J.; Lee S.S. Scale-up analysis for a CHO cell culture process in large-scale bioreactors. Biotechnology Bioengineering. 2009, 103, 733. (17) Junker, B. H.. Scale-up methodologies for Escherichia coli and yeast fermentation processes. Journal of Bioscience and Bioengineering. 2004, 97, 347.



Figure Caption

Table 1: L *, a *, b * and ∆E * values for the sample of the ethylene glycol monostearate, in outer and inner layer (external and internal value, respectively) of the product, obtained at: substrates molar ratio: 1:1; temperature: 75 ºC; 48 hours of reaction; 600 rpm; 1 wt% Novozym 435. Figure 1 - Schematic representation of the apparatus used for performing the experiments (1 - jacketed reactor, 2 - mechanical stirrer, 3 - thermostatic bath). Figure 2 - Conversion in ethylene glycol monoestearate using Novozym 435 and NS 88011 commercial lipases as catalysts in two different agitation levels (600 and 1000 rpm), keeping fixed: temperature: 75 ºC; substrates molar ratio: 1:1; 2 wt% of enzyme; 6 hours of reaction. Figure 3 - Conversion in ethylene glycol monostearate after 6 hours of reaction, using different concentrations of both Novozym 435 and NS 88011, under the following conditions: 75 °C, 600 rpm; substrates molar ratio 1:1; 6 hours of reaction. Figure 4 - Conversion in ethylene glycol monoestearate as a function of time at different temperatures, keeping fixed: substrates molar ratio: 1:1; 1 wt% Novozym 435; 600 rpm; 48 hours of reaction. Figure 5 - Conversion in ethylene glycol monostearate versus time for different concentrations of Novozym 435, at fixed: substrates molar ratio: 1:1; temperature: 75 ºC; shaking: 600 rpm, reaction time: 48 hours. Figure 6 - Reuse Cycle. Conversion in ethylene glycol monostearate as a function of time during enzymatic reuse for Novozym 435, keeping fixed: substrates molar ratio: 1:1; temperature: 75 ºC; Shaking: 600 rpm; 1 wt% Novozym 435; 48 hours of reaction.


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Figure 7 - Conversion in ethylene glycol monostearate in the magnification scale step, at: substrates molar ratio: 1:1; temperature: 75 ºC; Shaking: 600 rpm; 1 wt% Novozym 435; 48 hours of reaction.



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Table 1 Index

External Value

Internal Value

L*

82.58

83.59

a*

-0.94

-0.75

b*

2.40

1.99

∆E*

82.62

83.61


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Fig.1 -



Fig. 2 -

100 Conversion (%)

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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90 80 NOVO 435

70

NS 88011

60 50 600

1000 Agitation (rpm)


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Fig. 3 -

100 Conversion (%)

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


80 60 Novo 435

40

NS 88011

20 0 0.5%

1% Enzyme (w/w)

2%



Fig. 4 -

100 95 Conversion (%)

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

90 85 65 ºC 70 º C

80

80 ºC 75 ºC

75 70 2

6

10 14 18 22 26 30 34 38 42 46 50 Time (h)


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Fig. 5 -

Conversion (%)

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


95 85 75 65 55 45 35 25 15 5

1% 0.7% 0.5% 0.3% 0.1%

0

4

8

12 16 20 24 28 32 36 40 44 48 Time (h)



Fig. 6 -

100 90 80 Conversion (%)

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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70 60

Cycle 1

50

Cycle 2

40

Cycle 3

30

Cycle 4 Cycle 5

20 10 0 0

10

20 30 Time (h)

40


50

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Fig. 7 -

100 Conversion (%)

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


90 80 70 60 50 40 0

4

8

12 16 20 24 28 32 36 40 44 48 Time (h)




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Solvent-free production of ethylene glycol monostearate through

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