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

Abstract

Royal Society of ChemistryLi, Z.; Martínez Triguero, LJ.; Concepción Heydorn, P.; Yu, J.; Corma Canós, A. (2013 AbstractNanoSAPO-34 molecular sieve synthesized in microwave environment with 20nm of crystal size showed higher lifetime than SAPO-34 prepared by conventional hydrothermal method in the reaction of methanol to olefins. It has been found that silicon distribution strongly affects lifetime and selectivity. Thus, silicon at the border of the silicon islands gives higher lifetime and lower C2/C3 ratio. This change in activity and selectivity is better explained in terms of different silicon distribution than on preferential diffusion of ethene through the 8MR pores and agrees with transition-state selectivity. The effects of equilibrium of olefins and deactivation by coke were isolated,showing that after full formation of hydrocarbon pool, selectivity is independent of deactivation by coke.

Facile synthesis of SAPO-34 with small crystal size for conversion of methanol to olefins

“…Moreover, the peak at 1651 cm −1 corresponds to the vibration of hydroxyl groups from adsorbed water on samples. In addition, the broad peak centered at 3445 cm −1 corresponds to Si\OH and P\OH groups interacting through H-bonds [15]. In comparison of SAPO-34-H-M and SAPO-34-V-M samples, the intensity of all the vibration bands for SAPO-34-L-M-T and SAPO-34-L-M is stronger.…”

“…Hydrothermal method, as the conventional strategy, has been applied in the preparation of SAPO-34 by numerous researchers [4][5][6][7][8][9][10][11][12][13][14][15]. However, separation between solvents and solid products is required by filtration or centrifugation, and partial organic SDAs are inevitably preserved in the liquid phase, resulting in the wastewater pollutants and downstream purification system installation [16].…”

Synthesis of nano-SSZ-13 and its application in the reaction of methanol to olefins

“…4,[13][14][15][16] In the case of SAPO-34, its performance has been improved by developing mesopores [17][18][19][20][21][22] and by synthesizing crystals of smaller size. [23][24][25][26][27][28][29][30][31] The use of dual templates, which implies small organic struture directing agent for the formation of micropores and large organic molecular surfactants for developing mesopores as a strategy to prepare meso-MFI, has been proposed 32,33 . The large molecular surfactant hexadecyl trimethyl ammonium bromide (CTAB) firstly used to prepare MCM-41 has been employed to the synthesis of hierarchical zeolites in the dual template method.…”

Complex relationship between SAPO framework topology, content and distribution of Si and catalytic behaviour in the MTO reaction

“…Some authors have reported on the effect of the silicon content in the catalytic performance of SAPO catalysts. [31][32][33][34] The framework of microporous aluminophosphates is built up of AlO4 and PO4 tetrahedra connected through the oxygen atoms in an alternating arrangement. SAPO materials are formed by the isomorphous substitution of trivalent Al and pentavalent P atoms by tetravalent Si atoms.…”