Fabrication of SAPO-34 Crystals with Different Morphologies by Microwave Heating

Abstract

The crystal size and shape of the silicoaluminophosphate molecular sieve SAPO-34 have been effectively controlled in the reaction system of Al 2 O 3 -P 2 O 5 -SiO 2 -TEAOH-H 2 O under microwave radiations. Nano sheet-like SAPO-34 crystals are obtained when using colloidal silica as the silica source. When TEOS is used as the source of silica, homogeneous SAPO-34 crystals with a particle size of about 100 nm are formed, and the morphology of the crystals changes from uniform nano particles (*100 nm) to microspheres (*1.5 lm) by varying the H 2 O/Al 2 O 3 molar ratio. To further investigate the morphology control of SAPO-34, the synthetic factors, such as the silica source, water content, crystallization time and aging time have been studied in detail.

Methanol to olefins: activity and stability of nanosized SAPO-34 molecular sieves and control of selectivity by silicon distribution

“…SAPO-34 was synthesized by microwave heating as reported by Lin et al 20 . The composition of the synthesis gel was 1 Al(OPri)3 : 2 H3PO4 : 0. hours.…”

“…An increase in rate of diffusion can be achieved by preparing CHA type materials with smaller crystalline size. For doing that, a dry gel synthesis method 15 , the use of a combination of different SDA [16][17][18][19] , as well as the use of microwaves 20,21 has been applied to the synthesis of SAPO-34 with the objective of enhancing lifetime of the catalyst for the reaction of methanol to olefins. It has been found that a combination of TEAOH and morpholine in the synthesis results in a decrease of the size of the crystals with the corresponding increase in lifetime 17 .…”

“…In this work we have synthesized nanosized samples of SAPO-34 following the microwave method reported by Lin et al 20 and have studied the activity, lifetime and selectivity in the reaction of methanol to olefins. The catalytic performance and stability of nanoSAPO-34 has been compared with other samples of SAPO-34 synthesized by conventional hydrothermal methods using a mixture of morpholine and TEAOH as structure directing agents, which has been reported to also give small crystal size 17 .…”

Nanosize-Enhanced Lifetime of SAPO-34 Catalysts in Methanol-to-Olefin Reactions

“…The nanosized SAPO-34 catalysts were prepared under microwave radiations following previously reported method by using colloidal silica or TEOS as the silicon source. 24 The SAPO-34 catalysts with medium and ordinary size were obtained with Na 2 SiO 3 solution as the silicon source under hydrothermal or microwave-assisted conditions. Typically, the finely ground Al(OPr i ) 3 was first mixed with TEAOH solution and deionized water at room temperature until dissolved completely.…”

Control of Morphology and Acidity of SAPO-5 for the Methanol-To- Olefins (MTO) Reaction

“…In fact, the catalyst life of SAPO-34 can be improved by decreasing the crystallite size without varying the acid amount due to the improvement in the mass transfer inside the pores of the catalyst [7,13]. The synthesis of smaller-sized SAPO-34 compared with SAPO-34 synthesized by the conventional method has been attained by using various approaches, such as dry-gel method and microwave-assisted heating [14][15][16][17][18][19][20][21][22]. These smaller-sized SAPO-34 catalysts exhibited a longer catalyst life compared with the conventional SAPO-34 catalyst in the MTO reaction.…”