Heterogeneous liquid-phase lactonization of 1,4-butanediol using H 3+ xPMo 12− xV xO 40 ( x=0–3) catalysts immobilized on polyaniline

Abstract

In order for successful application of heteropolyacids (HPAs) as heterogeneous catalysts to liquid-phase lactonization of 1,4-butanediol, H 3+ x PMo 12− x V x O 40 ( x=0–3) HPAs were immobilized on polyaniline (PANI) by one-step and two-step methods. Aniline was polymerized in the presence of HPA in the one-step preparation method, while HPA was immobilized on the ready-made PANI support in the two-step method. It was found that HPAs were molecularly dispersed and strongly immobilized in/on the PANI support as charge-compensating components. Most HPAs in the two-step HPAPANI catalysts were immobilized only on the surface of PANI support. The surface areas of the two-step HPAPANI catalysts were much higher than those of the one-step catalysts, which is important from the practical point of applications. Thermal stability of PANI support was much enhanced by the binding with HPA, and thermal stability of the two-step HPAPANI catalysts was superior to the one-step catalysts. In the lactonization of 1,4-butanediol, catalytic activities were in the following order: two-step HPAPANI>one-step HPAPANI>unsupported HPA; H 6PMo 9V 3O 40PANI>H 5PMo 10V 2O 40PANI>H 4PMo 11V 1O 40PANI>H 3PMo 12O 40PANI. High activity of V-containing two-step catalysts and easiness of catalyst recovery in the liquid-phase reaction make them good candidates for an energy-saving lactonization process of 1,4-butanediol.