Experimental Study On Ion Content In Biodiesel

Biodiesel has the advantages of biological decomposition,low toxicity,high flash point,good combustibility,good lubricity and mutual solubility.However,some ions in biodiesel affect its performance indexes.This paper focuses on the sodium,ammonium,potassium,triethanolamine,calcium,magnesium,fluoride,chloride,bromide,sulfur,phosphorus,nitrogen,formic acid,acetic acid and propionic acid in the biodiesel samples,the effects of the kinds of biodiesel,the methods of biodiesel preparation and adding antioxidants?2,6-Di-tert-butyl-p-cresol?on these ions contents were studied.The results showed that the concentrations of Na⁺ and K⁺ as well as Ca²⁺ and Mg²⁺ in soybean oil biodiesel,palm oil biodiesel,camellia seed oil biodiesel and peanut oil biodiesel were less than 5 mg·kg^-1,which met the requirement of GB/T 20828-2015 of biodiesel blend stock?BD100?for diesel engine fuels;the concentrations of Na⁺ and K⁺as well as Ca²⁺ and Mg²⁺ in cottonseed oil biodiesel,biodiesel,flax seed oil,sesame oil biodiesel and waste cooking oil biodiesel were slightly greater than 5 mg·kg^-1;the ammonium contents in 15 kinds of biodiesel were all least,while the triethanolamine content were higher in corn oil biodiesel and sunflower seed oil biodiesel.When the effects of biodiesel preparation methods on these cation contents,the concentrations of Na⁺ and K⁺ as well as Ca²⁺ and Mg²⁺ in the waste cooking oil biodiesel prepared by the heat collection type constant temperature heating magnetic stirrer alkali catalysis method and Jatropha biodiesel prepared by the two-step method at middle and low temperatures were less than 5 mg·kg^-1 the concentrations of Na⁺ and K⁺ in the rubber seed oil based biodiesel reached 23.134 mg·kg^-1,therefore,it is recommended that other preparation technologies should be applied to synthesize rubber seed oil based biodiesel.After the waste cooking oil biodiesel samples produced by the two-step method at middle and low temperatures were added 0.0537 g the antioxidant,the combined concentration of Na⁺and K⁺ was greatly reduced,while the concentration of Ca²⁺ and Mg²⁺ was increased by 51%and 136%separately.Some anions containing F-,NO₃^-,SO₄^2-,HCOO^-and CH₃COO^-in the waste cooking oil biodiesel and the rubber seed oil based biodiesel prepared by the two-step method at middle and low temperatures as well as and the Jatropha biodiesel prepared by the heat collection type constant temperature heating magnetic stirrer alkali catalysis method were detected.Large amounts of PO43-were detected in the Jatropha biodiesel.CH₃CH₂COO^-was detected in the waste cooking oil biodiesel.The contents of HCOO^-,CH₃COO^-,CH₃CH₂COO^-in the rubber seed oil based biodiesel were most.Cl-,Br-,NO₃^-,SO₄^2-,PO43-,HCOO^-,CH₃COO^-,CH₃CH₂COO^-were detected in the Jatropha biodiesel prepared by the tubular reactor ultrasonic assisted alkali catalysis method,which was different from that prepared by the heat collection type constant temperature heating magnetic stirrer alkali catalysis method,and the contents of Br-,NO₃^-,SO₄^2-were most.The concentrations of these anions were greatly reduced after the waste cooking oil biodiesel samples produced by the two-step method at middle and low temperatures were added 0.0537 g the antioxidant.