Cromatografia

Journal of Chromatographic Science, Vol. 49, May/June 2011

A Review of Chromatographic Characterization Techniques for Biodiesel and Biodiesel Blends
R.E. Pauls
Chemical Sciences and Engineering Division, Argonne National Laboratory, Argonne, IL 60439, USA

Abstract
This review surveys chromatographic technology that has been applied to the characterization of biodiesel and its blends.Typically, biodiesel consists of fatty acid methyl esters produced by transesterification of plant or animal derived triacylglycerols. Primary attention is given to the determination of trace impurities in biodiesel, such as methanol, glycerol, mono-, di-, and triacylglycerols, and sterol glucosides. The determination of the fatty acid methyl esters, trace impurities in biodiesel, and thedetermination of the biodiesel content of commercial blends of biodiesel in conventional diesel are also addressed.

tent contamination of other products such as jet fuel with biodiesel is also of increasing interest. In this review we focus on the application of chromatographic methods for the characterization of biodiesel and its blends. Primary attention is given to methods related to final productanalysis rather than those employed in monitoring transesterification reactions, although these are cited where appropriate. Many approaches employed to characterize B100 are similar to those employed in the food industry. In this review, a number of recent references from this area relevant to biodiesel are cited, especially those employing multidimensional separations. Many of thesemultidimensional approaches should see increased application to biodiesel in the future.
Table I. ASTM D 6751-08 Specification*
Property Test Method Limit Units ppm (μg/g) °C

Introduction
Biodiesel is produced by transesterification of vegetable or animal derived triacylglycerols with methanol. Currently, soy-, palm-, and rapeseed-derived oils are most frequently employed in biodiesel production. Theresulting fatty acid methyl esters (FAME) are referred to as B100. Ethanol and other higher alcohols are also employed in the transesterification reaction in place of methanol. The pure FAME or B100 is blended with conventional diesel to produce commercial fuels. These fuels are referred to as Bx where x is the percent biodiesel or FAME blended; a 10 percent blend of B100 in conventional diesel isreferred to as B10. Both ASTM (1) and European Union (2) have published standard specifications for B100 FAME used in diesel blending. These specifications reference specific analytical methods including GC (methanol, free glycerol, mono-, di-, and triacylglycerols), elemental analysis, as well as physical property tests. Table I is adapted from the ASTM D 6751-08 specification for B100. In additionto the standard tests cited in Table I, the chromatographic determination of a number of other biodiesel properties is of interest. These include determination of the amount of biodiesel in blends, identification and measurement of trace impurities in biodiesel that can negatively (or positively) impact biodiesel performance, and analyses performed to determine the type and origin of the FAME. Thedetermination of the inadver*Author to whom correspondence should be addressed: email repauls@sbcglobal.net

Total Ca and Mg EN 14538 5 max Flash Point (closed cup) D 93 93 min Alcohol Control Either: Methanol EN 14110 0.2 max Flash Point D 93 130 min Water and sediment D 2709 0.050 max Kinematic viscosity, 40 ˚C D 445 1.9-6.0 Sulfated ash D 874 0.020 max Sulfur D 5453 0.0015 max Copper stripcorrosion D 130 No. 3 max Cetane number D 613 47 min Cloud point D 2500 Report Carbon residue D 4530 0.050 max Acid number D 664 0.50 max Cold soak filterability Annex A1 of D 6751 360 max Free glycerol D 6584 0.020 max Total glycerol D 6584 0.240 max Phosphorus D 4951 0.001 max Distillation temperature, 90% recovered D 1160 360 max Total Na and K EN 14538 5 max Oxidation stability EN 14112 3 min...