Study on the NaNp/Al2O3-SiO2 system

M-O-M[ ]-O-M [ ] is hard Pearson acid site; M = Si for silica and Al for alumina phases Al[ ]-O-Si- ⇄ -Al-O-Si[ ]- [ ] acidic sites spread on aluminum and silicon atoms create soft Pearson acid sites on aluminosilicate phase EPR study of NaNp/Al2O3-SiO2 system established presence of Pearson hard and soft acid sites on alumina-silica gels.