Phosphotungstate anions supported on spherical beads of carbon as highly efficient catalysts for the dehydration of propan-2-ol to propene

摘要

There is a continuing need to develop new catalysts for the dehydration of propan-2-ol as opposed todi-iso-propyl ether. The reaction has been extensively studied using zeolites [1] or clays [2] with typical selectivities for propene in the region of 20-40%. The eaction has been used in order to monitor the catalytic behaviour of solids and activity correlates in many cases with the acidity of the solid [3-5]. Phosphotung states supportd on carbons,zirconias or silicas having been prepared by Matijevic and Perez-maqueda [7],but in all cases,the product is present as a powder. In many cases,the above materials are extremely brittle and deteriorate rapidly when used as catalysts. As a contribution to the preparation of acidic/basic or redox catalysts in a bead form a versatile method has been developed for the support of porous oxide sinpyrolysed ion-exhange beads. In previous cases,attampts ahve been made to remove the carbon matrix but this does not appear to be necessary. A conventional anion-exchange was used in htis study,the strongly basic Amberlite IRA-93 (Cl) loaded with tungsten from an queous solutionof sodium tungstate. After washing withwater,converting to either tungstate or phosphotung state and again washing with water hte product,after pyrolysis of the metal-loaded ion-exchange resin,consists of discrete (typically again washing with water the product,afte rpyrolysis of the metal-loaded ion-exchange resin,consists of discrete (typically 0.2-0.5 mm diameter) sphericalparticles of catlayst-loaded carbon,the spherical integrity of the unpyrolysed anion loaded resin being maintained. The tungstate was found to convert up to to 80% propan-2-ol to propene and better than 95% converstion if phosphotungstate was used.