Make your own free website on Tripod.com

Extraction of Caffeine/Coffee Oil Using Liquid-Liquid Extraction

Introduction

Caffeine is known medically as trimethylxanthine and possesses the chemical formula C8H10N402.  It occurs naturally in over 60 plants, including coffee beans, tea leaves and cocoa nuts.  In its pure state, it exists as a bitter white powder.  Caffeine is used in the medical field as well as food processes.  Medically, caffeine is used as a cardiac stimulant and a mild diuretic.  In the food industry, caffeine is marketed as a means to boost energy.  It can be found in most type of colas, coffee, tea and chocolate products.  Caffeine is also prevalent in over-the-counter stimulants, such as Vivarin and NoDoz.  The primary source of pure caffeine is the process of decaffeinating coffee and tea.

Proposed Design Problem & Solution

There are 2 methods of decaffeinating coffee, the indirect and direct means.  The indirect means uses water as the decaffeinating agent.  It is passed through the coffee beans and released into a separate chamber.  There, it is decaffeinated.  The water is then returned to the coffee to restore its natural flavor.  The direct method mixes an organic decaffeinating agent, such as dichloromethane, ethyl acetate or supercritical carbon dioxide, directly with the coffee.  The caffeine binds to this substance and then is removed from the coffee, usually through boiling.  The direct means of decaffeinating is the process we choose to replicate.

Detailed Flow Chart from SuperPro

The various steps in the decaffeinating process can be found in the SuperPro flowchart in Appendix A.

Literature Review

Fourier transform infrared determination of caffeine in roasted coffee samples

Fresenius Journal of Analytical Chemistry (2000) 366: 319-322

            Coffee contains several alkaloids, caffeine being the most important one.  For consumer information, it is required to accurately determine the caffeine concentration in commercially roasted coffee.  A new procedure has been developed for the Fourier transform infrared (FT-IR)

determination  of caffeine in roasted coffee samples.  It uses the same type of decaffeinating agents we used in our experimental procedures.  The CHCl3 extracted the caffeine from the wetted coffee samples.  The FT-IR procedure then measured absorbance to determine the concentration of caffeine in the coffee.  The extraction of caffeine by organic solutions was successful in this study, which furthered our hypothesis that caffeine could be obtained using this type of process in our experimental process.

Effects of caffeine, caffeine-associated stimuli, and caffeine-related information on physiological and psychological arousal

Psychopharmacology DOI 10.1007/s002132100841

            Caffeine is a known stimulant.  The study conducted in this journal article tested the physiological and psychological effects caffeine had on various individuals.  The caffeine-associated stimuli increased alertness, contentedness and skin conductance levels.  The information that the drink contained caffeine alone decreased calmness in the subjects.  Decaffeinated drinks (including coffee) were placebos given to subjects.  After consumption, increased contentedness was reported.  The authors concluded that the caffeine-associated stimuli increased arousal and information about the content of the drink modulated arousal in the direction indicated by the information.  The caffeine evidently effected the subjects and the time and research put into this study show the demand for caffeine on the market as well as decaffeinated products.

Mauldin, R.F., Burns, D.J., Keller, I.K, Koehn, K.K., Johnson, M.J, Gray, S.L. Theory of

Supercritical Fluid Extraction via the Discovery Approach Chem. Educator. 1999, 183-185.

            Supercritical CO2 is a new technology that is being explored for the use in extraction.  It involves high pressure CO2 which can be used to extract organic compounds, like caffeine or nicotine.  This can be used to obtain a product, or be used to take the product out, like for the decaffeination of coffee.  This is a very good alternative to other extraction methods because it is non-toxic and easy to separate from the product of interest. 

Sarmento, M., Pires, M., Cabral, J., and Aires-Barros, M.  1997.  Liquid-liquid extraction of a recombinant protein, cytochrome b5, from an impure extract using aqueous two-phase systems.  Bioprocess Engineering.  16: 295-297.

Liquid-liquid extraction is used extensively in chemical and pharmaceutical industry, though it was not until recently that this technique has been used to recover bipolymers (proteins) because of their low solubility in organic solvents and the denaturing effect the solvents have on the structure of the protein

A two-phase system of polyethylene glycol and potassium phosphate salts were used to perform a liquid-liquid extraction of cytochrome b5 from sheared Escherichia coli cells.  This extraction process was a single step process that allowed the complete removal of cell debris and a nearly 67% recovery of the target protein from the aqueous layer.  . 

Experimental Plan:

            The unit operations we choose to run in the laboratory included mixing, settling and pumping a variety of materials different places.  A large vessel was required for the mixing of the coffee with the saturated NaCl solution and the ethyl acetate.  It was placed on a stir plate with a stir bar for 10 minutes.  Once the solution was completely mixed, it was pumped into a smaller settling vessel.  Here, two distinct layers formed due to the differences in densities.  The oily organic layer, which contained the caffeine, was found on top.  This layer was pumped into another vessel.  The remaining layer was the decaffeinated coffee.  This coffee, in industry, would be purified to remove any remaining decaffeinating agent.  The oily organic layer was then boiled to remove the decaffeinating agent, ethyl acetate.  Pure caffeine was not obtained at this time due to the fact that the caffeine was still suspended in the oil.  The oil would need to be evaporated, and then the caffeine would need to be re-crystallized in order to obtain pure caffeine.

Updated Gantt Chart See Appendix B

Results and Discussion:

            Our experiment demonstrated a successful set-up and was triumphant in removing caffeine from the coffee, however we did not obtain pure caffeine.  The caffeine was trapped inside the oil instead of binding only with the ethyl acetate.  Further unit operations would have been required to achieve pure white powder caffeine.  This process proved to be an effective way to remove caffeine from coffee.  On the other hand, a more effective means may eliminate the oily layer and have the caffeine only in solution with the ethyl acetate.  The oils extracted by the ethyl acetate were an unexpected problem, but it did not affect the decaffeinating process greatly.

Economic Analysis:

The equipment used for our unit operations included a mixer and three pumps.  All materials were scaled up using the appropriate formulas and a cost analysis was performed.  The basic formulas and results are found in the chart below while all the details of the calculations can be found in Appendix C.

 

 

Scale Up Factors

 

 

Cost Analysis

 

Agitator

   

 

 

Pump 1

 

 

 

Pump 2

 

 

 

Pump 3

 

 

 

Total Cost

 

 

$221,440

  Appendix


Appendix A:

Appendix B

 

Appendix C                                                                     Scale-up of Agitator

 

Density of ethyl acetate = 894.5 kg/m

Dynamic Viscosity of ethyl acetate = 0.426 x 10-3 Pas.

Density of water = 1000 kg/m

Dynamic Viscosity of water = 0.86 x 10-3 Pas

Density of saturated salt solution (NaCl) = 1100 kg/m

Dynamic Viscosity of saturated salt solution = 0.89 x 10-3 Pas.

 

Density of mixture (water/saturated salt solution) = 1050 kg/m

Dynamic Viscosity of mixture (water/saturated salt solution) = 0.9 x 10-3 Pas.

Volume of mixture (water/saturated salt solution) in lab scale = 350 mL.

Volume of ethyl acetate in lab scale = 100 mL.

Total volume in mixing chamber in lab scale = 450 mL.

Approximate density of fluid in mixing chamber = (1050 kg/m) (0.777) + (894.5 kg/m) (0.222) = 1015 kg/m. 

Approximate dynamic viscosity of fluid in mixing chamber = (0.9 x 10-3 Pas) (0.777) + (0.426 x 10-3 Pas) (0.222) = 0.795 x 10-3 Pas.

 

Volume of lab scale reactor = 500 mL. 

Diameter of reactor = 8 cm = 0.08 m. 

Diameter of impeller = 2 in = 0.0508 m.

Speed of lab mixer = 30 rpm = 3.14 rad/s. 

 

  Re = 20701 = 2.1 x 104 turbulent assume Np = 5.

 

P = 0.05 W = scale power.

 

tm = 1.9 s.

Since keeping the time on scale-up is not feasible, we scaled up our mixing time to 20 s.  Using a new mixing time, we had to calculate a new impeller speed.

Using a scaled-up vessel (3-m radius by 5-m height), a scaled-up impeller diameter of 2.5 m, and the scaled-up time of 20 s, we were able to calculate our new Ni.

Ni = 0.67 rad/s = 6.4 rpm.

Re = 5.36 x 106.  Use Np = 5.

P = 149200 W = 200 hp.

Cost Analysis of Agitator

Our scaled-up agitator will be a single blade Rushton turbine.

Base cost of 200 hp agitator (dual turbine read from chart) $90,000.

Fmod = 2.0

Fm for single blade turbine = 0.82

CIpresent = 392.7, CIbase = 324

$178,897.

Scale-up of Pump 1 (from mixer to settler)

The volumetric flow from mixer to settler was selected as 0.1 m/s.  The pipe diameter was selected as 10 cm = 0.1 m.

= (0.1 m/s) (1015 kg/m) 101.5 kg/s

  0.0078 m.

Q = v A v = 12.73 m/s

Leq = 3 35 0.1 + 0.5 + 5 = 16.0 m

  Re = 1.6 x 106   turbulent

  f = 0.0275

  142.6 m/s

   ws = 223.6 m/s

 = 22.79 m

For the following brake horsepower calculation, we chose our pump efficiency to be 0.5.  This was done to give an overestimate of cost, rather than an underestimate.

Brake hp = 45384.7 W 60.9 hp

 

Cost Analysis of Pump 1

Our scaled-up pump will be a turbine with a brake horsepower of 60 hp.

Base cost of turbine = $7000. 

Fmod = 1.80

Fm = none

$15,272

 

Scale-up of Pump 2 (from settler (ethyl acetate))

The volumetric from mixer to settler was calculated to be 22% of the original flow or 0.022 m/s.  The pipe diameter was selected as 5 cm = 0.05 m.

= (0.022 m/s) (894.5 kg/m) 19.7 kg/s

  0.002 m.

Q = v A v = 11.2 m/s

Leq = 5 35 0.05 + 1 + 4.75 + 1 +5 = 20.5 m

Re = 1.2 x 106 turbulent

f = 0.003

301 m/s

ws = 366 m/s

 = 37.31 m

For the following brake horsepower calculation, we chose our pump efficiency to be 0.5.  This was done to give an overestimate of cost, rather than an underestimate.

Brake hp = 14420.8 W 19.3 hp

 

Cost Analysis of Pump 2

Our scaled-up pump will be a turbine with a brake horsepower of 19 hp.

Base cost of turbine = $4000. 

Fmod = 1.80

Fm = none

$8727

 

Scale-up of Pump 3 (from settler (wastage))

The volumetric from mixer to settler was calculated to be 78% of the original flow or 0.078 m/s.  The pipe diameter was selected as 7.5 cm = 0.075 m.

= (0.078 m/s) (1050 kg/m) 81.9 kg/s

  0.0044 m.

Q = v A v = 17.6 m/s

Leq = 3 35 0.075 + 1 + 5 = 13.875 m

Re = 1.54 x 106 turbulent

f = 0.0278

318 m/s

ws = 473.3 m/s

 = 48.25 m

For the following brake horsepower calculation, we chose our pump efficiency to be 0.5.  This was done to give an overestimate of cost, rather than an underestimate.

Brake hp = 77531.9 W 103.9 hp

 

Cost Analysis of Pump 3

Our scaled-up pump will be a turbine with a brake horsepower of 100 hp.

Base cost of turbine = $8500. 

Fmod = 1.80

Fm = none

$18,544

Total Cost = $221,440

 

 

 

   

 

 

 

 

 

 

 

 

                                                                                            

Our Settling Tank

 


 

 

Our Mixing Tank

 

   

 

Chemicals of Interest

References

Doran, Pauline M. Bioprocess Engineering Principles. Academic Press, San Diego: 1995.

http://www.sciam.com/0697issue/0697working.html

http://antoine.frostburg.edu/chem/senese/101/matter/faq/decaffeinating-coffee.shtml

http://www.cariboucoffee.com/aco.cfm?ct=a

Walker, Terry.  BE 3340: Process Design in Biological Engineering.  2002.

Garrigues, Jose M., Zouhair Bouhsain, Salvador Garrigues and Miguel de la Guardia. Fourier transform infrared determination of caffeine in roasted coffee samples, Fresenius Journal of Analytical Chemistry. 

Mikalsen, Anita, Bard Bertelsen and Magna Arve Flaten. Effects of caffeine, caffeine-associated stimuli, and caffeine-related information on physiological and psychological arousal, Psychopharmacology.