Supercritical Fluids: A Powerful Decaffeination Tool

GOABAONE KGOPA

17001016

APPLICATION OF SUPERCRITICAL FLUIDS (WATER,CARBON DIOXIDE)

APPLICATION OF SUPERCRITICAL FLUID (CARBON DIOXIDE)

DECAFFEINATION OF COFFEE

High-pressure vessels (operating at roughly 250 to 300 times atmospheric pressure) are employed to spread the carbon dioxide through a bed of premoistened, green coffee beans. At such pressures, carbon dioxide takes on unique, ‘supercritical’ properties that enhance its usefulness as a solvent. Supercritical carbon dioxide has a density like that of a liquid, but its thickness and diffusivity are comparable to those of a gas.

These aspects significantly lower its pumping costs. Carbon dioxide is considered a popular solvent because it has a relatively low pressure critical point, and it is naturally thick. The icaffeine-rich icarbon idioxide iexiting ithe iextraction ivessel iis ieither ichannelled ithrough ia ibed iof iactivated icharcoal ior ithrough ia iwater i’bath’ itower ito iabsorb ithe icaffeine. iThe icarbon idioxide iis ithen irecirculated iback ito ithe iextraction ivessel. iSupercritical icarbon idioxide idecaffeination irequires igreater iexpenditure iin ithe iform iof icapital ithan iof ilabor i, ibut iit iresults iin ivery igood iproduction.

iIt itypically ican iextract i96 ito i98 ipercent iof ithe icaffeine ioriginally ipresent iin ithe ibeans. i iThe iextracted icaffeine iis, ion ithe iother iside, isold ito ithe ipharmaceutical iand ifood iindustries.

ADVANTAGES iCheap, ieasily iavailable iat ihigh ipurities iCarbon idioxide iis iconsidered ia ipopular isolvent ibecause iit iis inaturally iabundant iand ihas ia irelatively ilow ipressure icritical ipointIt ihas ia iconvenient icritical itemperature i(31.04?C). iThis ienables iextractions ito ibe icarried iout iat iprovisional ilow itemperature i(often ias ilow ias i40 ior i50?C), idecreasing ithe idanger iof ithermalabile icompounds.

DISADVANTAGES

Cleanup istep iis ineededcapital-cost iintensiveCOSMETIC iINDUSTRYAntioxidant isuch ias ipolyphenols, icarotenoids iand itocopherols i(vitamin iE), iwhich iare ifound iin ia iwide ivariety iof ifruits iand ivegetables i(beta icarotene iin icarrots, ilycopene iin itomato…) ican ibe iselectively iextracted iusing isupercritical iCO2. iCO2 iextracted ioils iadd ivalue ito icosmetics ienhancing itheir ifunctional iaction iand i/ ior ipleasant iattributes i.The iphenolic icompounds ihave ibeen itraditionally iextracted iusing ia iSoxhlet iextraction imethod, iwhich iis ia icontinuous isolid/liquid iextraction. iIn ithis imethod, ia isolid iwhich icontains ithe imaterial ito ibe iextracted iis iplaced iin ia ithimble iwhich iis imade iout iof ia imaterial iwhich iwill icontain ithe isolid ibut iallow iliquids ito ipass ithrough, ilike ia ifilter ipaper. iThe ithimble icontaining ithe imaterial iis iplaced iin ithe isoxlet iextractor. iAn iorganic isolvent iis ithen iheated iat ireflux. iAs iit iboils iits ivapour irises iup iand iare icondensed iby ia icondenser. iThe icondensed isolvent ithen ifills iup ithe ithimble iwith ienough isolvent iuntil iit iautomatically isiphons iback idown iinto ithe icontainer iof iorganic isolvent i.this iprocess itakes iover iand iover iagain iuntil iall ithe imaterial ito ibe iextracted ifrom ithe isolid iin ithe ithimble iis inow iextracted iinto ithe iorganic isolvent. iADVANTAGES

Fast, iselective iand ithe iproducts iare ifree iof iresidual isolvents.

provide imaximum iyields, ipreserving ihighest iquality iwith iantioxidant iactivity, imaking ithe ifinal iproduct isuitable ifor iuse iin icosmetic iindustry.

DISADVANTAGES

Some iphenolic icompounds iare ithermosensitive, itherefore ihigher iextraction itemperatures ishould ibe icarefully iused ito iensure iproper iextraction iand iminimize ilight iinduced idegradation, idevoid iof ichemical imodification iand iprotect iit ifrom ioxidation.

An iincrease ion ipressure ican iresult iin ian iincrease iin ithe ifluid idensity, iwhich ialters isolute isolubility iPOLYMER iAND iPLASTICS iINDUSTRIESSupercritical iCO2 iis ia igood iplasticizing iagent iin iparticular ibecause iit ireduces ithe iglass itransition itemperature. iThe ifluid iis icompressed ito ielevated ipressures iabove iits icritical ipressure, ito imake iit isupercritical. iThe ipolymer iis ithen iexposed ito ithe isupercritical ifluid iand iswells. iAs ithe ifree ivolume iin ithe ipolymer iis iincreased, ithe iSCF ican ipenetrate ideeply iinto ithe imatrix iand ithe iimpurities iare idissolved iby ithe isupercritical ifluid. iAs iany ivolatile imaterials iwithin ithe ifeed imatrix iwill ithen ipartition ithemselves iwithin ithe isupercritical iphase, ithese iare iremoved iwith ithe iSCF iduring ithe iextraction ifrom ithe ifeed isystem. iIn ithe ide-pressurisation iphase ithe ipressure iis iquickly ireduced iand ithe isupercritical ifluid iand iimpurities idiffuse iout iof ithe ipolymer. iThe iSCF ican ithen ibe iremoved iby ichanges ito itemperature iand/or ipressure, ileaving inegligible iSCF iin ithe iextracted imaterial iand ithe iSCF ican ibe irecycled iby irecompression. iThe iresulting ipolymer iproperties iare ithen iimproved iwith ireference ito iresistance, ithermal istability, ipurity.

ADVANTAGES

The idissolving ipower iof ithe isupercritical ifluid iis ieasily icontrolled iand imanipulated iby ipressure iand/or itemperatureNo iharmful iresidue iis ileft ias isolvents iare inontoxic.

Supercritical ifluids ihave iability ito isometimes iachieve iseparations ithat iare inot ipossible iby itraditional iprocessesDISADVANTAGES

Whilst irecycling iand icost isavings ican ibe iachieved iby ia irecompression iof ithe isolvent, iequipment iinstallation ican ibe icostly iand icomplex.

An ielevated iworking ipressure iis irequired iwith iassociated icosts iand ihazardsmaterials, iincluding iceramics iand iceramic icomposites, imay ibe ichosen ifor ithese icomponents. iWHAT IS STANDARD PRESSURE

A pressure at which standardized measurements may be made, 

NORMAL PRESSURE IS EQUAL TO

1,013.25 mbar (101,325 Pa; 1,013.25 hPa), equivalent to 760 mm Hg, 29.9212 inches Hg, or 14.696 psi.

REFERENCES

Padrela, L.; Rodrigues, M.A.; Velaga, S.P.; Matos, H.A.; Azevedo, E.G. (2009). “Formation of indomethacin-saccharin cocrystals using supercritical fluid technology”. European Journal of Pharmaceutical Sciences. 38 (1): 9-17

Sang-Do Yeo & Erdogan Kiran (2005). “Formation of polymer particles with supercritical fluids: A review”. The Journal of Supercritical Fluids. 34 (3): 287-308. doi:10.1016/j.supflu.2004.10.006.

Brunner, G. (2010). “Applications of Supercritical Fluids”. Annual Review of Chemical and Biomolecular Engineering. 1: 321-342. doi:10.1146/annurev-chembioeng-073009-101311. PMID 22432584.