Characterization and performance of rare-earth modified molecular sieve

With acidic neodymium(Nd)salt and lanthanum(La)salt as modifying agents,the rare-earth ion-doped molecular sieves were prepared by impregnation,filtration,desiccation and calcination of 13X molecular sieve.The modified adsorbents were characterized using Fourier transform infrared spectroscopy(FTIR),X-ray diffraction(XRD)and X-ray photoelectron spectroscopy(XPS).The desorption performance of the rare-earth molecular sieves was evaluated by temperature programmed desorption(TPD)and thermogravimetry(TG),and their adsorptive performance was tested by static state adsorption.FTIR spectra and XRD spectra indicate that the rare-earth doping has no effect on the composition of molecular sieve,while the crystallinity of modified molecular sieve has a little decline.XPS analysis shows that part of sodium in the molecular sieve is replaced by La atoms or Nd atoms.Differential thermogravimetry(DTG)and Temperature Programe Desorption(TPD) curves indicate that the desorption activated energy of rare-earth doped molecular sieve is lower than that of molecular sieve,which is proved by the reduction of the peak temperatures in DTG curve at the maximum thermogravimetric rate and in TPD curve at the maximum vapor desorption rate.