Abstract
Acidic oil, which is easily obtained and with lower cost, is a potential raw material for biodiesel production. Apart from containing large quantity of FFAs (free fatty acids), acidic oil usually contains some amount of inorganic acid, glycerides and some other complex components, leading to complicated effect on lipase’s catalytic performance. Exploring the efficient process of converting acidic oil for biodiesel production is of great significance to promote the use of acidic oil. A two-step conversion process for acidic soybean oil was proposed in this paper, where sulfuric acid-mediated hydrolysis was adopted first, then the hydrolyzed free fatty acid, collected from the upper oil layer was further subject to the second-step esterification catalyzed by immobilized lipase Novozym435. Through this novel process, the negative effect caused by harmful impurities and by-product glycerol on lipase was eliminated. A fatty acid methyl ester (FAME) yield of 95% could be obtained with the acid value decreased to 4 mgKOH/g from 188 mgKOH/g. There was no obvious loss in lipase’s activity and a FAME yield of 90% could be maintained with the lipase being repeatedly used for 10 batches. This process was found to have a good applicability to different acidic oils, indicating it has great prospect for converting low quality oil sources for biodiesel preparation.
Highlights
Biodiesel, as a novel and renewable biofuel, generally consists of fatty acid esters, which are prepared by transesterification or esterification of triglycerides or FFAs with short-chain alcohols [1]
To reduce the above-mentioned proposed a two-step process involving sulfuric acid-mediated hydrolysis and the esterification negative effects during the lipase-mediated process for biodiesel production, we proposed a two-step catalyzed by lipase at mild reaction conditions
The results showed that the acidic soybean oil contained large quantity of free fatty acids soybean oil (Table 1)
Summary
As a novel and renewable biofuel, generally consists of fatty acid esters (mainly fatty acid methyl ester or fatty acid ethyl ester), which are prepared by transesterification or esterification of triglycerides or FFAs (free fatty acids) with short-chain alcohols [1]. Biodiesel has many well-recognized advantages of fair combustion performance, renewability, degradability and environmental friendliness [2]. As a substitute for fossil fuels, biodiesel is gaining more and more attention in recent years. Despite of the well-recognized advantages, the high cost of biodiesel has been the large limitation for its sustainable application. The raw materials account for more than 70% of the total cost of biodiesel product [3]. Seeking materials with rich sources and low price will significantly reduce the cost of biodiesel and promote its extensive use worldwide
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