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Decolorization, Taste and Odor Removal in Corn Sweetener Refining

Starch hydrolyzate plants around the world are utilizing high surface area synthetic adsorbents to replace granular and powdered activated carbon for removal of color, taste, odor, HMF (hydroxymethylfurfural) and other impurities from sweetener solutions. The Macronet™ line of chemically regenerated styrenic adsorbents offers economic, aesthetic, purity and ease of process advantages for replacing carbon in the production of bottler’s quality syrup.

Purolite adsorbents for corn sweetener refining and improving corn sweetener quality include:

Organic impurities are attracted and held to adsorbents by surface energies such as Van der Waals forces. Since adsorption is a surface phenomenon, the Macronet adsorbents are manufactured with large surface area in the range of 800-1100 square meters/gram. But molecules are three dimensional and not flat, so it is important for the surface area to conform to the molecular size of the impurities being adsorbed for the collective surface energy to be large enough to retain them. Thus, the surface area must be employed in micropores which are small enough to form an “adsorption cavity.”

Most of the surface area of Macronet adsorbents are contained in adsorption cavities of less than 20 Angstroms diameter. Macronet also contains a significant population of large transport pores which facilitate rapid diffusion from the bulk fluid into the microporous region where adsorption occurs.

The hydrophobic styrene/divinylbenzene matrix of the Macronet will readily adsorb nonpolar hydrophobic impurities. Since many of the impurities are polar or even ionizable molecules, the presence of hydrophilic ion exchange functional groups on the matrix improves the range of impurities which can be removed by attracting more hydrophilic compounds. The hydrophilic functional groups also improve the ease of regeneration of the adsorbent.

Macronet Operating Options

A. Color Adsorber for Non-demineralized Syrups
Macronet MN152 replaces conventional carbon powdered treatment of glucose syrups. Expensive and dirty powdered carbon and carbon filters are replaced with a simple chemically regenerated unit operation which produces no solid discharge to handle.

B. Taste and Odor Polishing
The primary and secondary ion exchange pairs remove the vast majority of impurities, leaving the MN500 available to remove the difficult taste and odor impurities and polish the color even further.

C. Color, Taste and Odor Polishing
A layered bed of MN152 over MN502 offers improved color and heat color removal in addition to taste and odor polishing.

D. Color, Taste and Odor Polishing with Enhanced pH and Conductivity Stability
The layered bed of MN152 over MN502 is air mixed prior to service to offer mixed bed quality pH and conductivity.

E. Color, Taste and Odor Polishing with Enhanced pH Stability
A layered bed of MN152 over a weak acid cation resin is air mixed prior to service to offer better pH stability.

Service and Regeneration Sequence for Macronet™ MN102, MN152 or MN502
Step Solution Temp (°C) Flow (BV/hr) Volume (BV) Time (min) Comments
Service Syrup 40-60 2-5 30-200 Variable Downflow
Sweeten Off Demineralized water or condensate 40-60 2-5 2 Variable Downflow
Backwash1 Demineralized water or condensate 30-60 2.5-3.7 gpm/ftof vessel area 1.5-2.0 30 Upflow 50% expansion
NaOH In2 1N NaOH 40-60 1 1.5 90 Downflow
Slow Rinse Demineralized water or condensate 40-60 2 2 60 Downflow
HCl In3,4 0.1N HCl 40-60 2 3 90 Upflow
Slow Rinse Demineralized water or condensate 40-60 2 2 60 Upflow
Fast Rinse5 Demineralized water or condensate 40-60 4 4 60 Downflow
Sweeten On Syrup 40-60 2-5 1 Variable Downflow

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