Dodecylamine Phosphotungstate Catalyst

Esterification is an important unit reaction in organic synthesis. In traditional methods, liquid acids such as sulfuric acid, phosphoric acid and p-toluene sulfonic acid are often used as catalysts. There are some problems such as difficult separation of catalysts from products, high energy consumption, corrosion equipment and environmental pollution.

At present, heteropoly acids have been widely used in esterification. Tungsten heteropoly acids, represented by phosphotungstic acid and silicotungstic acid, are green, non-toxic, acidic and selective. They are widely used as catalysts for esterification. However, heteropoly acids are also soluble in polar reaction media, low specific surface area and poor thermal stability. Therefore, researchers believe that the catalytic performance of heteropoly acids may be improved if the dispersion of active component heteropoly acid on the surface of the carrier is improved and supported heteropoly acid catalysts with high activity and excellent stability are obtained.

A method of synthesizing long chain carboxylic esters catalyzed by dodecylamine phosphotungstate has been developed by some scholars. The preparation process of dodecylamine phosphotungstate catalyst includes:

Under the condition of continuous stirring at room temperature, ethanol solution containing 0.0005 mol of dodecylamine was slowly dripped into water solution containing 0.001 mol of phosphotungstic acid, and then 5 g MCM-41 was added. The solvent ethanol and water were removed by evaporation at 80 ~℃ and roasted at 200 ~℃ for 4 h. The solid obtained was MCM-41 Supported Phosphotungstic Acid dodecylamine salt.

The esterification process of dodecylamine phosphotungstate catalyst:

Add 0.05mol of adipic acid, 0.15mol of isooctyl alcohol, 5mL of water-containing cyclohexane and 0.2g of prepared MCM-41-loaded phosphotungstic acid dodecylamine catalyst into 100mL three-necked flask, assemble thermometer and condense The tube and the water separator were heated to 165 °C, reacted for 1.5 h, cooled, centrifuged, and the liquid phase product was calculated by acid value method. The acid value was analyzed according to GB/T 1668-2008, and the esterification rate was 99.0%. .

The phosphotungstic acid dodecylamine catalyst has the characteristics of soluble and insoluble heteropolyacid salt, and is insoluble in organic solvents such as methanol, ethanol, butanol and isooctanol, so that it can be stably present on the surface of the carrier, and is not in the catalytic reaction process. Dissolution will occur. In addition, the phosphotungstic acid dodecylamine salt has a good oleophilic dodecyl group and has a good affinity for long-chain fatty alcohols. Therefore, the dispersibility of the active component in the catalyst is good, the effective utilization rate is high and it is not easy to be lost, the product yield is high, the catalyst and the product are easily separated, and the catalyst has excellent reusability.

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