Light Olefins Synthesis from Methanol and Dimethylether over SAPO-34 Nanocrystals

Abstract

The catalytic properties of SAPO-34 nanocrystals (crystal size: 75 nm) on methanol-to-olefins (MTO) and dimethylether-to-olefins (DTO) reactions were compared with those of SAPO-34 (crystal size: 800 nm). The SAPO-34 nanocrystals showed a longer catalyst lifetime in both the reactions than 800 nm-sized SAPO-34. The rate of catalyst deactivation of SAPO-34 was similar for both the MTO and DTO reactions indicating that the reaction of MeOH to DME and the diffusion of MeOH and DME into the SAPO-34 nanocrystals are fast and are not a rate limiting process. A possible reason for the long catalyst lifetime of the SAPO-34 nanocrystals is a short residence time in a crystal for the produced hydrocarbons because of a shorter diffusion length.

Synthesis of LPG via DME from syngas in two-stage reaction system

“…It is well known that light olefins could be produced from methanol or dimethyl ether (DME) over SAPO-34 due to its small pore size of 3.8 Å × 3.8 Å [16,17]. ZSM-5 with relatively larger pore size of 5.5 Å × 5.6 Å showed high selectivity for gasoline [18,19].…”

Effect of Crystal Size on Acetone Conversion over SAPO-34 Crystals

“…The product stream after 15 min was analyzed with a Shimadzu GC-14B gas chromatograph equipped with a flame ionization detector using GS-Al 2 O 3 PLOT column (J&W scientific) and a Shimadzu GC-8A gas chromatograph equipped with thermal conductivity detector using Porapak Q column (Shinwa Chemical Industries, Ltd.). catalysts lifetime than 0.8 lm-sized crystals at the same W SAPO-34 /F Acetone , as is the case in the methanol-to-olefins (MTO) and DTO reactions [16]. This result indicates that coke deposition is slower on smaller SAPO-34 crystals.…”

“…75 nm and 0.8 lm-sized SAPO-34 crystals were synthesized by a dry gel conversion (DGC) and a hydrothermal synthesis (HTS) methods, respectively, as described elsewhere [16]. Boehmite (AlOOH), 85 wt% phosphoric acid (both from Wako Pure Chemical Industries Co.) and colloidal silica (LUDOX HS-40, Aldrich) containing 40 wt% of SiO 2 were used as sources of aluminum, phosphorous, and silicon, respectively.…”

“…To investigate the reaction site of acetone conversion over SAPO-34, selective coke deposition within the pores of SAPO-34 nanocrystals via the DTO reaction was applied for examination of the reaction site over the SAPO-34 catalysts. The SAPO-34 cage like pores can be blocked by the coke depositions through the MTO and DTO reactions [16]. From the TG analysis, the amount of carbon deposited on the SAPO-34 nanocrystals was a 23 wt% of the mass of SAPO-34 crystals.…”

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

“…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].…”