Mid-infrared analysis of biodiesel

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Courtesy of Spectro Scientific

The biodiesel industry is growing rapidly. and so is the need for analysis 10 ensure quality product and keep biodiesel in good standing. Biodiesellhat has residual glycerin, glycer· ides, or inorganic salts from the production process can cause problems such as Iilter plugging and injector coking in a diesel engine. The biodiesel blend ralio also can affect cold weather performance, lax incentives and warranty Issues. Product quality begins at the production facility and extends 10 the final burn in the engine. Mid·infrared analyzers oller a quick quality control check lor production monitoring and for measuring the blend ralio.

The production facility

There are several sleps in the production process where mldinfrared analysis is useful, such as lesting incoming leed slock for Free Fatty Acids (FFA) and water, monitoring total glycerides during the btodiesel reaction process and measuring the water in reclaimed methanollo be reused fOf blodiesel production.

Incoming feedstocks

A map problem for blodie~ producers has been obtaining affordable and reliable feedstocks. Almost every week another headline touts another potential blodiese! feedstock, anything from algae, dirty diapers Of Patagonian rainforest fungi. Biodiesel is typically made from animal fats or vegetable oils, which are chemically reacted With an alcohol (methanol or ethanol) and a calalysl (sodium or potassium hydroxide) to produce an alkyl methyl ester or biodiesel; a process called transesterihcation. Feedstocks with dIfferent FFA and water levels require the alcohol and catalyst to be adjusted 10 ensure a complete reaction. Higher FFA levels often require a pretreatment step to remove FFA's. When moisture levels in feedstocks are over 0.5 percent, the water deactivates the catalyst and inhibits the reaction.

The approved method lor FFA analysis is a non-aqueous potentiometric acid-base titration, to determine the acid number. and Karl Fischer Titration. to measure moisture in feedstocks. Both tests are time consuming and require skilled techniCians. Because FFA and water measurements 10 feedstock are process control measurements and do not need 10 be approved methods. Infrared analYSIS can be substituted as a Quick test for producers.

Water can be extracted from the feedstock with acetonitrile and measured in extract at 6.6 microns (165Ocm). Measuring FFA invotves adding a weak base to form a salt with a carbonyl absorption band that is shifted away from that of the blodlesel ester. Even with sample preparation. either measurement by Infrared spectroscopy takes less than five minules and does not require a skIlled techntclan.

During the reaction process

Imperial Weslern Products (IWP), a BQ-9000 accredited manufacturer of biodiesel in Southern California. utilizes multiple sel while in-process. IWP found that the use of Ihe InfraSpec VFA-IR Spectrometer for making pass/fait determinations decreased the wait time for a lab result by about 40 minutes. They estimated that with the reduced analysis time from an infrared analyzer, they were able to increase reactor throughput by 15-20 percent.

Checking methanol for water

Methanol recovered Irom the finished biodiesel is reused for the next reaction. The InfraSpec VFA-IR Spectrometer gives a direct measurement of water in methanol with an accuracy of +/- 0.20 percent. As mentioned earlier, water can inhibit the reaction process, making it importanllo verify that the residual water in the methanol is at an acceptable level.

Biodiesel in diesel blend ratio

In a published paper on biodiesel blend quality submitted by the National Renewable Energy Laboratory the chief problem found with biodiesel blends was inaccurate blend ratios. Having a correct biodiesel blend ram is important for cold weather performance, tax incentives, as well as engine warranties.

Any state that has adopted the modified ASTM method 0975 can now include up to five percent biodiesel in the diesel fuel without reporting the biodiesel content. Blenders who are limited to a 20 percent biodiesel blend (B2O) need to know prior to mixing if the fuel already contains biodiesel. as well as the percentage of biodiesel. in order to correctly blend B20.

Portland, Ore., is the nation's first city to create a renewable fuels standard requiring than all diesel fuel sold within city limits contain a minimum 5 percent biodiesel. Minnesota was one of the first states 10 mandate 2 percent soy based biodiesel blends in 2002. Making sure the biodiesel percentage is correctly labeled at the fuel station pump is the state Weights and Measures Agency's responsibility. Oregon and Minnesota's.

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