(46f) Ion Exchange Resins for Biodiesel Purification

Specialty ion exchange resins can be utilized to bind and remove trace impurities from a biodiesel process stream. After the bulk separation of the glycerin, the biodiesel stream is simply passed though a column of the dried ion exchange resin to bind and remove both ionic salts (such as Na+ and Ca++0, trace catalysts, soaps, and glycerin. The dried resin also acts as a desiccant retaining and removing trace water from the biodiesel feed.

The efficiency and life of a resin to reduce and remove impurities from the biodiesel will depend upon how well bulk separation of the biodiesel and glycerin are made. A resin operation step should be viewed as a polishing process to remove trace materials in the 275-750ppm range, not as a replacement for optimizing the bulk separation.

Generally a lead-lag two column continuous feed system is recommended for most operations. In many cases, a third column should be considered in order to ensure continuous operations and reduce down times. Specialty ion exchange resins, like the DOWEX(TM) DR-G8 resin can be applied to improve and enable a producer to meet ASTM or EN specifications at the point of production to reduce rework and lessen blending concerns.