Download Calometric Measurement of Saponification Reaction

Note Number 11
Saponification with Atlas
application notes
Calometric Measurement of Saponification
Reaction of Sunflower Seed Oil
Dr. Neil Campbell†, Daniel Harvey*, Robert Clowes†, Prof. Adam J Kowalski*
Centre for Materials Discovery (CMD)† and the Ultra Mixing and Processing Facility (UMPF)*, University of Liverpool, Crown Street,
Liverpool, Merseyside, L69 7ZD, United Kingdom
Introduction
The term saponification is commonly used to describe the chemical process that results in the
formation of soap. Saponification in this context involves the hydrolysis of an ester, under basic
conditions, to form an alcohol and a carboxylate salt. When aqueous sodium hydroxide, caustic
soda, is added to pure oil (e.g. coconut oil) at temperatures in excess of 80°C the reagents react to
form soap and glycerol. Saponifiable substances are those that can be converted into soap (mainly
fats and oils) and is a chemical reaction that has been used since the byzantine era1. Within
industry this process is carried out on multi-tonne scale2 to produce soap bases for a numerous
applications. It is therefore of commercial interest to gain further understanding of these processes;
namely with the aim of further optimization, cost saving and product performance enhancement.
Figure 1. General reaction mechanism for saponification reaction.
Atlas Application Note Atlas 11 ‐ Saponification with Atlas Page 1 © 2009 Syrris Ltd All Rights reserved Figure 2. Reaction scheme for saponification reaction of sunflower oil.3
Experimental
Green chemistry research is a highly topical area of interest to both industry and academia. The
aim of this study was to determine the required kinetics involved to produce soap from a cheap,
renewable and easily replenishable source of oil. The saponification of sunflower seed oil was
therefore selected for the measurement of the reactions calorimetery using the Atlas Potassium
reactor. A set concentration and volume of sodium hydroxide was placed within the reactor vessel
whilst being both heated and stirred until reaction temperature was reached. Once reaction
temperature was reached sunflower oil was added to the reaction vessel at a controlled rate via the
Atlas syringe pump whilst the reaction temperature was held using the apparatus set up as shown
in figure 3 on the next page.
Atlas Application Note Atlas 11 ‐ Saponification with Atlas Page 2 © 2009 Syrris Ltd All Rights reserved Figure 3. Atlas Potassium Calorimetery Reactor equipment setup. A) Power controller for power
compensation reactor heater, B) Jacket-In temperature probe (Tj), C) Vacuum triple jacketed
500ml reactor containing 400ml (0.4Mols) of NaOH(aq) with pH, temperature (Tr) and turbidity
probes, D) Controlled overhead mechanical stirrer, E), Reagent feed delivered by controlled Atlas
syringe pump, F) Feed reservoir of 100ml (0.15Mols) sunflower oil.
As the reaction progresses both soap and glycerol are formed. Due to the constant mixing glycerol
is slowly dissolved in the NaOH(aq) solution whilst the soap is dispersed throughout the entire
reactor vessel. This can be visually observed as it forms a cloudy solution and can be monitored in
real-time using the turbidity probe. This also provides a suitable method of monitoring the reaction
progression.
Atlas Application Note Atlas 11 ‐ Saponification with Atlas Page 3 © 2009 Syrris Ltd All Rights reserved Figure 4. Clear NaOH(aq) solution before reaction (left), turbid emulsion is formed during reaction,
which can be and monitored using turbidity probe.
Figure 5. The graph shows the Atlas Syringe Pump cumulative volume (µl) of the sunflower oil
feed over the course of the reaction (Green). Online monitoring of the reaction turbidity (%) was
shown to follow the progress of the reaction, and therefore could be used as good reaction
monitoring technique (Red).
Once the reaction has reached completion the stirring is stopped and the products are allowed to
separate out. The oil forms the organic phase whilst the glycerol byproduct remains dissolved in
the aqueous phase, allowing easy recovery of the product through the collection tap at the bottom
of the reactor (Figure 6 on next page).
Atlas Application Note Atlas 11 ‐ Saponification with Atlas Page 4 © 2009 Syrris Ltd All Rights reserved Figure 6. The product is easily recovered after reaction completion (3hrs) as the liquid soap makes
up the organic layer (top) whilst glycerol and any un-reacted sodium hydroxide remain dissolved
within the aqueous layer (bottom).
Results
The enthalpy of formation of the soap product is calculated using Power Compensation
Calorimetery (PCC). This is achieved through the control and online monitoring of the power
applied through the compensation heating rod (which is inserted directly into the reaction-content)
and control of the temperature of the heating fluid entering the insulated vacuum triple jacketed
reactor (Tj) in order to maintain the required constant temperature of the reaction mixture (Tr)4-7.
The calculation of the enthalpy of reaction was conducted using the Atlas Calorimetery Software.
The calculation also includes the compensation for the mass addition of the feed reagent through
the accurate measurement of the temperature of the feed and the ability to setup fluid profiles for
the temperature dependence of the specific heat capacity and the density of the feed solution (see
figure 7).
Atlas Application Note Atlas 11 ‐ Saponification with Atlas Page 5 © 2009 Syrris Ltd All Rights reserved Figure 7. Online process monitoring showing reaction calometic calculation through Atlas
Calorimetery Software.
Conclusion
Using the Atlas Potassium Reactor and power-compensation calorimetery the measurement of the
traditional isothermal saponification process for sunflower oil was conducted. The process was
shown to be an exothermic reaction calculated at a value of 8.78 KJ/Mol which is comparable to
results reported for similar saponification reactions in the literature8. The unusual curve in the
reaction enthalpy is caused by the system following a heterogeneous liquid-liquid reaction. The
quantification of mass transfer between phases can solved using double-film model7. In addition it
was shown that the measurement of turbidity can be utilized to follow the progression of the
reaction to completion.
Establishing these baseline measurements is essential to allow further research in examining the
effects of different process conditions and techniques on this reaction and the physical properties
of the final product. By improving the efficiency of this reaction through mimicking scale-up
conditions large energy and cost savings could be made to this important industrial process.
Atlas Application Note Atlas 11 ‐ Saponification with Atlas Page 6 © 2009 Syrris Ltd All Rights reserved References
1. Willcox, Michael (2000). "Soap". in Hilda Butler. Poucher's Perfumes, Cosmetics and Soaps
(10th edition ed.). Dordrecht: Kluwer Academic Publishers. pp. 453. "The earliest recorded
evidence of the production of soap-like materials dates back to around 2800 BCE in
Ancient Babylon."
2. M. Mattikow, Journal of the American Oil Chemists’ Society, 1940, 14, 184.
3. J. Van Gerpen, B. Shanks, R. Pruszko, D. Clements, G. Knothe, Biodiesel Production
Technology, August 2002 – January 2004.
4. H.M. Andersen, J. Polym. Sci. Part A-1, 1966, 4, 783.
5. H.M. Andersen, J. Polym. Sci. Part A-1, 1969, 7, 2889.
6. W. Köhler, O. Riedel, H. Scherer, Chem. Ing. Tech, 1972, 44, 1216.
7. A. Zogg, F. Stoessel, U. Fischer, K. Hungerbühler., Thermochimica Acta, 2004, 419, 17.
8. N. Mouhab, L. Balland, I. Ben Talouba and J. M. Cosmao., Chemical Engineering and
Processing, 2008, 47, 363.
Atlas Application Note Atlas 11 ‐ Saponification with Atlas Page 7 © 2009 Syrris Ltd All Rights reserved