Synthesis of Hierarchical Silicoaluminophosphate (SAPO) Molecular Sieves by Post‐Synthetic Modification and Their Catalytic Application

Abstract

Silicoaluminophosphates SAPO-34 (CHA topology) and SAPO-5 (AFI topology) molecular sieves are selectively prepared by hydrothermal method using templates tetraethylammonium hydroxide and triethylamine, respectively and suitably modified. Hierarchical SAPO-34 & SAPO-5 catalysts were post-synthetically prepared by facile acid (HNO 3 and HCl) and base (NaOH) etching. X-ray diffraction (XRD), Thermogravimetric analysis (TG), FT-IR and Scanning Electron Microscope (SEM) were employed to investigate structural changes of the molecular sieves. Hierarchical SAPO-34 & SAPO-5 were used for the ring opening reaction of propylene oxide with morpholine producing the corresponding β-amino alcohols, and catalytic activity of the acid-treated SAPO-34 & SAPO-5 was compared with that of alkali treated counterparts. The catalytic performance of the acid treated materials was found better than the base treated one. 91 % conversion was achieved using acid treated SAPO-34, whereas 74 % conversion was achieved using alkali treated SAPO-34.

Alkylation of Toluene to Mono‐benzylated Toluene over Micro‐mesoporous Zeolite: Effect of Post‐synthetic Treatment and Catalytic Application

“…Additionally, low angle XRD was performed on all the base and acid treated zeolite, in the 2θ range of 0.7 to 10°. As shown in Figure 1 the base treated Beta zeolite show a peak at 3.04° 2θ, which typically represents the mesoporous phase [33] . Similarly, ZSM‐5‐BT, Y‐BT and all acid treated samples also exhibit a peak at 3.04° 2θ.…”

“…As shown in Figure 1 the base treated Beta zeolite show a peak at 3.04°2θ, which typically represents the mesoporous phase. [33] Similarly, ZSM-5-BT, Y-BT and all acid treated samples also exhibit a peak at 3.04°2θ. These results indicate that the hierarchy was successfully generated in H-Beta, H-Y, and H-ZSM-5.…”

“…Typically, in the first method, in a round bottom flask, 80 ml of (0.5 M) HNO 3 solution was added and heated to 90 °C for 4 hours with 4 g of parent material. [33] After the acid treatment, the samples were collected, spun down to remove debris, rinsed in deionized water, and dried at 80 °C for the night. Samples dealuminated with 0.5 N HNO 3 are indicated by the -AT suffix.…”

“…[28,29] After dealumination, many aluminophosphates (AlPOs) and silicoaluminophosphates (SAPOs), including SAPO-11, SAPO-34, SAPO-5, SBA-15, MCM-41, Beta, and ZSM-5, have been employed in various reactions. [30][31][32][33][34][35][36] To date, there has been no extensive research into the catalytic utilisation of modified zeolites in the toluene alkylation reaction. [14,37] These studies, however, used metal impregnation [14,38] or dealumination [37] to prepare the hierarchical zeolites for the toluene alkylation reaction.…”

“…Acid leaching is accomplished through the hydrolysis of Al−O bonds in microporous molecular sieves using definite concentration of acid solution ultimately resulting in the dealumination [28,29] . After dealumination, many aluminophosphates (AlPOs) and silicoalumino‐phosphates (SAPOs), including SAPO‐11, SAPO‐34, SAPO‐5, SBA‐15, MCM‐41, Beta, and ZSM‐5, have been employed in various reactions [30–36] . To date, there has been no extensive research into the catalytic utilisation of modified zeolites in the toluene alkylation reaction [14,37] .…”