Tungsten Heteropoly Acid Makes the Biodiesel Greener

The focus of attention is that US President Trump announced his withdrawal from the Iran Nuclear Dear and restarted economic sanctions against Iran. Due to this, the international oil price had risen again and hit a new high in the past three years.

The reason why we care the oil price so much is that oil is so important for a country even the individual life. It is related to our quality of life and the cost of living. Oil is called "the blood of industry" and is a strategic resource to maintain the working of modern society. The direct manifestation is that, most of our cars use gasoline and diesel as fuel, which are originally refined from Oil. To get rid of dependence on oil, people have never stopped exploring new energy sources. It is happy that we had some breakthroughs.

According to the Xinhua News Agency, biodiesel has entered some of the gas stations in Shanghai, labeled as B5, which refers to 2-5% biodiesel is blended in to petrochemical diesel. The price of this diesel can be 0.3 RMB cheaper per liter than conventional diesel.

As we all know, biodiesel is mainly refined from the “gutter oil”, which refers to illegal recycled waste cooking oil. But it is not just limited to the “gutter oil”. Other animal and vegetable oils can also be used as raw materials. The synthesis process is usually done by simple transesterification reaction. In some developed countries, the standard for raw oil diesel has reached B10, even B20, which means that it is feasible to blend less than 20% biodiesel into petrochemical diesel.

Biodiesel is a new measure to recycle waste oil from the kitchen. The B5 biodiesel is cheap and environmentally friendly. It has better lubricity than ordinary diesel. In the process of transformation of waste oil into biodiesel, catalysis is an indispensable process. And catalysts are the top priority of the catalytic process.

In the synthesis of biodiesel, traditional inorganic acids and alkali catalysts (such as sulfuric acid, tetrabutyl titanate, solid acid catalysts, etc.) have the problems of strong corrosive, non-renewable, and easy to causing saponification reactions. These problems fail the intention of biodiesel. So it is necessary to find a catalyst that will not produce these negative effects. Well, tungsten products can come in handy. Among the esterification reactions, the most effective substitute for the conventional acid catalyst is the tungsten heteropolyacid salt. The most widely used tungsten heteropolyacid catalysts are phosphotungstic acid and silicotungstic acid.

It is understood that in the petrochemical field, the tungsten heteropoly acid can replace the traditional catalyst, its catalytic activity is 100-1000 times that of the inorganic acid, the catalytic reaction can be carried out under very mild conditions, and the side reaction is not easy to occur. The reaction of tungsten heteropoly acid as an acid catalyst can be catalyzed by esterification and vinegar exchange reaction, nitration reaction, hydrocarbon hydration reaction, dealkylation reaction, etherification reaction of epoxide, etc., and most of the petrochemical industry needs to use The catalyst chemical products can replace the traditional inorganic acid with tungsten heteropoly acid salt. The most important thing is that the tungsten catalyst is non-toxic and harmless, clean and environmentally friendly.

However, tungsten heteropoly acid salt also has some shortcomings in the ester reaction. Taking phosphotungstic acid as an example, in the process of biodiesel production, the heteropoly acid itself is easily soluble in water, and the process of catalyzing the esterification reaction is mostly multiphase. Catalytic reaction, the esterification rate is limited. In order to improve the efficiency of their reactions, recently, chemists have successfully reformed the phosphotungstate by means of doping and synthesis, and successfully developed a biodiesel tungsten catalyst with catalytic efficiency and cost advantage. To some extent, the production cost of biodiesel is reduced.

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