Influence of Crystallinity of HZSM-5 Zeolite on Its Dealumination Rate

Sano, Tsuneji; Ikeya, Hisanori; Kasuno, Takekazu; Wang, Z.B.; Kawakami, Yusuke; Soga, Kazuo

doi:10.1016/s0144-2449(97)00052-3

Cited by 83 publications

(71 citation statements)

References 26 publications

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“…Our previous study found that the dealumination rate of MFI type zeolite with a large number of silanol groups (structure defects) is larger than that of zeolite with small defects 53) , and results in structural collapse. To clarify the effect of structure defects on the acid stability, the chemical states of the silicon in the CHA type zeolites synthesized by interzeolite conversion and in SSZ-13 were investigated by 29 Si MAS NMR with and without 1 H _29 Si cross polarization (CP).…”

Section: Acid Stabilitymentioning

confidence: 97%

High Potential of Interzeolite Conversion Method for Zeolite Synthesis

Sano

Itakura

Sadakane

2013

J. Jpn. Petrol. Inst.

104

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Many types of zeolites such as beta (hereinafter, BEA), CHA, LEV, RUT, and MFI were successfully synthesized by interzeolite conversion of FAU, BEA, and LEV type zeolites as starting materials under various hydrothermal synthesis conditions. The crystallization rates of zeolites using such starting zeolites were notably elevated compared to rates observed in conventional hydrothermal syntheses using amorphous aluminosilicate gels. This characteristic enhancement in the crystallization rate results from the generation of locally ordered aluminosilicate species (nanoparts) through the decomposition/dissolution of the starting zeolite, resulting in assembly and evolution into another type of zeolite. The structural similarity between the starting zeolite and the final crystallized zeolite is a crucial factor for interzeolite conversion. These findings strongly indicate that the interzeolite conversion route is an attractive strategy for zeolite synthesis and zeolite design will be possible after methods to selectively assemble the nanoparts are established.

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Section: Acid Stabilitymentioning

confidence: 97%

High Potential of Interzeolite Conversion Method for Zeolite Synthesis

Sano

Itakura

Sadakane

2013

J. Jpn. Petrol. Inst.

104

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“…[21][22][23][24][25]. When used as catalysts or supports, zeolites with smaller crystal size and higher surface area show better catalytic activity and selectivity [26,27].…”

Section: Introductionmentioning

confidence: 99%

Synthesis and characterization of H-ZSM-5 zeolites and their catalytic performance in CH3Br conversion to aromatics

Tao

Yin

et al. 2011

Reac Kinet Mech Cat

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Described in this paper are the synthesis, characterization and catalytic application of H-ZSM-5 zeolites for the conversion of CH 3 Br into aromatics. The H-ZSM-5 zeolites were fabricated by hydrothermal crystallization using n-butylamine (BTA) as a template and characterized by XRD, SEM and NH 3 -TPD techniques. The effects of batch SiO 2 /Al 2 O 3 ratio, alkalinity, NaCl/Al 2 O 3 ratio, seed crystals, and crystallization time on the yield, structure/texture and catalytic performance were systematically studied. Adopting the optimum sol (SiO 2 /Al 2 O 3 = 70, BTA/SiO 2 = 0.2847, Na 2 O/SiO 2 = 0.1237, H 2 O/SiO 2 = 37.4, NaCl/Al 2 O 3 = 60, and seed/SiO 2 = 5 wt%) and under the most preferable crystallization conditions of 100°C/24 h-170°C/24 h, H-ZSM-5 zeolites of high crystallinity and small size (300-700 nm) were obtained. Good catalytic performance was observed over the H-ZSM-5 zeolites (aromatic yield up to 44.2%). However, unlike the modification of large commercial HZSM-5, the use of MoO 3 or PbO as modifying agents for the small-size H-ZSM-5 zeolites results in a decline of catalytic performance. The relationship between the structure and the catalytic efficiency of as-synthesized H-ZSM-5 samples were investigated. It was found that with crystallinity enhancement and/or decline in crystal size, there is improvement of catalytic performance.

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“…However, phosphorus-impregnated H-ZSM-5 (P/ H-ZSM-5) exhibits lower activity for catalytic cracking than H-ZSM-5, because the Brønsted acidity of P/ H-ZSM-5 is lower than that of H-ZSM-5. Sano et al reported that protons catalyze the dealumination of H-ZSM-5 29) . Therefore, a catalyst with lower Brønsted acidity may exhibit higher steaming stability, but lower activity for catalytic cracking.…”

Section: Steaming Stability Of H-zsm-5 Ag-zsm-5 and Cu-zsm-5mentioning

confidence: 99%

Selective Formation of Light Olefins by Catalytic Cracking of Naphtha Components over ZSM-5 Zeolite Catalysts

Kubo

Iida

Namba

et al. 2018

J. Jpn. Petrol. Inst.

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Catalytic cracking of C6-8 hydrocarbons as model naphtha components was evaluated over H-ZSM-5 catalysts with various Si/Al ratios at 723-923 K to selectively form light olefins. The highest ethylene propylene yield was 59.7 C-% with a propylene/ethylene ratio of ca. 0.72 at 99.6 % conversion in the cracking of n-heptane over H-ZSM-5 (Si/Al 31) at 923 K. The selectivities and activation energies indicated that monomolecular cracking was predominant at temperatures higher than 923 K. Next, cracking of various C6-8 hydrocarbons on H-ZSM-5 at high temperatures in the presence of another hydrocarbon was also investigated. Coexistent 1-hexene did not affect the cracking rate of n-heptane, cyclohexane, or methylcyclohexane, also indicating that monomolecular cracking was predominant at temperatures as high as 923 K. In contrast, coexistent cyclohexane and methylcyclohexane considerably affected the cracking rate of n-heptane because of their slow diffusion in the pores of H-ZSM-5. Moreover, catalysts with activity equal or higher than that of H-ZSM-5 and steaming stability higher than that of H-ZSM-5 were examined. The 194 %Cu-ZSM-5 and 95 %Ag-ZSM-5 zeolites exhibited high steaming stabilities and higher cracking activities than H-ZSM-5 and P/H-ZSM-5. In particular, 194 %Cu-ZSM-5 exhibited an ultra-high steaming stability under conditions such as 1023 K and 10 h presumably because Cu 2 and Cu cations in the 194 %Cu-ZSM-5 are not reduced to Cu 0 at a high temperature of 1023 K in the presence of O2.

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Influence of Crystallinity of HZSM-5 Zeolite on Its Dealumination Rate

Cited by 83 publications

References 26 publications

High Potential of Interzeolite Conversion Method for Zeolite Synthesis

High Potential of Interzeolite Conversion Method for Zeolite Synthesis

Synthesis and characterization of H-ZSM-5 zeolites and their catalytic performance in CH3Br conversion to aromatics

Selective Formation of Light Olefins by Catalytic Cracking of Naphtha Components over ZSM-5 Zeolite Catalysts

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