Synthesis and Characterization of SAPO-34-H(Hierarchical)[J].
Synthesis and Characterization of Intergrowth Structured SAPO-18/SAPO-34[J].
Synthesis of SAPO-34/ZSM-5 Composite and Its …
Based on the proposed hydrocarbon pool mechanism, the polymethylbenzenium ions are formed during the reaction, which act as the important reaction intermediates for olefin production. However, these polymethylbenzenium ions can further turn into bulk organic species as coke deposition accommodated in the large cavities connected by narrow channels, thus covering the active sites of catalysts leading to the rapid deactivation during methanol conversion. This is indeed the main problem associated with the SAPO-34 catalysts. To overcome the inherent diffusion limitations and retard coke deposition, various synthetic strategies have been developed in recent years, and considerable efforts are focused on the reduction of crystal sizes of the catalysts or the introduction of secondary larger pores into the zeolite crystals to form hierarchical structures. The nanosized and hierarchical SAPO-34 catalysts demonstrate significant advantages in the enhancement of mass transfer and decrease of coke formation rate as compared with their traditional microporous counterparts with larger crystal sizes.
In a new review published in the Beijing-based National Science Review, scientists at the State Key Laboratory of Inorganic Synthesis and Preparative Chemistry, Jilin University in Changchun, China, and at SINOPEC Corporation, Science & Technology Development Department in Beijing, China, summarize recently advanced synthesis strategies for SAPO-34 zeolite catalysts in MTO Conversion. Co-authors Qiming Sun, Zaiku Xie and Jihong Yu mainly focus on representing the state-of-the-art synthetic strategies for preparing nanosized and hierarchical SAPO-34 catalysts with excellent MTO performance and the industrialization of SAPO-34 catalysts for the MTO reaction. The authors also discuss some current limitations as well as future prospects for the synthesis of SAPO-34 catalysts.
Synthesis and application of ZSM-5/SAPO-34 and SAPO-34…
Qiming Sun, Zaiku Xie, and Jihong Yu
The State-of-the-Art Synthetic Strategies for SAPO-34 Zeolite Catalysts in Methanol-to-Olefin Conversion
Natl Sci Rev, 2017, doi: 10.1093/nsr/nwx0103
(2000) In-situ synthesis of SAPO-34 molecular sieves on monolithic cordierite substrates. CHEM J CHINESE U, 21 (12) 1801 - 1804.
Improving SAPO-34 membrane synthesis - ScienceDirect
SAPO-34 molecular sieves are synthesized using various structure directing agents (SDAs). Cu-SAPO-34 catalysts are prepared via aqueous solution ion exchange (IE). Catalysts are characterized with surface area/pore volume measurements, temperature programmed reduction (TPR), electron paramagnetic resonance (EPR), and nuclear magnetic resonance (NMR) spectroscopies. Catalytic properties are examined using standard ammonia selective catalytic reduction (NH3–SCR) and ammonia oxidation reactions. During solution IE, different SAPO-34 samples undergo different extent of structural damage via irreversible hydrolysis. Si content within the samples (i.e., Al–O–Si bond density) and framework stress are key factors that affect irreversible hydrolysis. Even using very dilute Cu acetate solutions, it is not possible to generate Cu-SAPO-34 samples with only isolated Cu2+ ions. Small amounts of CuO species always coexist with isolated Cu2+ ions. Highly active and selective Cu-SAPO-34 catalysts for NH3-SCR are readily generated using this synthesis protocol, even for SAPO-34 samples that degrade substantially during solution IE. High-temperature aging is found to improve the catalytic performance. This is likely due to reduction of intracrystalline mass-transfer limitations via formation of additional porosity in the highly defective SAPO-34 particles formed after IE.
SAPO-34 molecular sieve can be synthesized rapidly with microwave irradiation from a gel containing tetraethylammonium hydroxide (TEAOH) as a template.
Synthesis and Characterization of SAPO-34 …
Research advances in SAPO-34 synthesis - CNKI
An appropriate amount of ZSM-5 seeds (in protonic form) was added to the synthesis precursor of SAPO-34.
Synthesis of SAPO-34 molecular sieve with …
Mesoporous SAPO-34 was synthesized by using TPOAC in the synthesis gel.
Abstract: Synthesis of High Performance SAPO-34 …
Synthesis of SAPO-18/34 intergrowth zeolites and their enhanced stability for dimethyl ether to olefins
In-situ synthesis of SAPO-34 molecular ..
Nanosized SAPO-34 (100–500 nm) is synthesized from colloidal solutions in the presence of tetraethylammonium hydroxide as a template at different hydrothermal conditions using conventional and microwave heating. The SAPO-34 is structurally related to the naturally occurring mineral Chabazite and used for the catalytic production of olefins.
Synthesis of SAPO-34 Molecular Sieve Membranes by …
Abstract: Solvent-free method was used to prepare copper contained SAPO-34 small pore zeolite by mixing, grinding and heating the raw materials with Cu-TEPA added. Compared to the conventional hydrothermal synthesis, the absence of solvent has effectively reduced the waste production, increased the yield, accelerated the crystallization period and eliminated the unsafe high pressure. Otherwise, the use of low-cost Cu-TEPA in direct synthesis will greatly expand the use of those catalysts. The so-prepared zeolite show good crystallization of typical SAPO-34 cube-like crystal structure, excellent BET surface area and pore volume, good NO adsorption properties and diverse acid sites brought by copper. It possessed excellent activity and high N2 selectivity for NH3-SCR DeNOx at wide temperature range, and good hydrothermal stability which was beneficial to the diesel engine NH3-SCR application.
In-situ synthesis of SAPO-34 molecular sieves on ..
A new seeding method, the steam-assisted conversion seeding, was used to prepare the high-quality SAPO-34 molecular sieve membranes by secondary growth method on the low cost macroporous α-Al2O3 supports. The seeds with different sizes of 2 μm, 1 μm, 500 nm, and 100 nm were mixed in the synthesis solution to prepare the seeds-containing pastes which was coated on the surface of the support. The effects of the particle size on the paste layers, seed layers and membranes were investigated. A perfect seed layer was formed displayed, effectively modified the defects of the macroporous α-Al2O3 support and then, induced a continuous, compact and no obvious pinholes SAPO-34 membrane. The SAPO-34 membrane displayed high performance in the pervaporation dehydration of 90wt% IPA/water mixtures at 348 K, showing water ?ux up to 1.396 kg/(m2·h) and separation factor at 973.
Solvent-Free synthesis of Cu-SAPO-34 zeolite for NH3 …
SAPO-34 synthesized by microwave irradiation is homogeneous and small in size and shows acidity and a stable performance in the dehydration of methanol and 2-butanol to olefins, suggesting potential applications in acid catalysis.
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