Dry Gel Conversion Synthesis Research Articles

Recent advances in the synthesis of TS-1 zeolite.

Heteroatomic zeolites as an important class of zeolites, have been widely applied in industrially catalytic processes due to their unique properties. As one of the most representative heteroatomic zeolites, titanosilicate zeolites have been extensively used in the selective oxidations of organic substrates with H2O2 such as cyclohexanone ammoximation, epoxidation of alkenes, and phenol hydroxylation. In this review, recent advances in the synthesis of TS-1 zeolite are briefly summarized, including use of low-cost raw materials (organic templates, silicon, and titanium sources), development of new synthesis routes (post-treatment synthesis, dry-gel conversion synthesis, solvent-free synthesis, and microwave-assisted synthesis), and new strategy for enhanced mass transfer in TS-1 crystals (synthesis of hierarchical and nanosized TS-1 zeolite). This review might help researchers to have a deep understanding on the synthesis of TS-1 zeolite and provide a new opportunity for the design and preparation of highly efficient TS-1 catalysts in the future.

On the Anti-Corrosion Property of Dry-Gel-Conversion-Grown MFI Zeolite Coating on Aluminum Alloy.

MFI zeolite film coated on AA6061 alloy was prepared from fumed silica modified with/without n-octyldecyltrimethoxysilane (ODS) by means of dry gel conversion (DGC) method. The DGC-grown MFI zeolite film could form a strong barrier to protect AA6061 surface against the corrosion from NaCl solution. By using fumed silica as a starting material, the hydrophilicity and anti-corrosion capability of the MFI zeolite film declined with increasing humidity in the DGC synthesis. By silanization with ODS, the surface hydrophobicity of the MFI zeolite film increased, leading to substantial enhancement in anti-corrosion capability. On the other hand, MFI film grown from ODS-modified fumed silica exhibited low hydrophilicity and a much improved anti-corrosion protection property by four orders of magnitude, even stronger than the ODS post-treated MFI film. The strong anti-corrosion capability is attributed to the “thick layer” surface hydrophobicity of zeolite crystal.

Dry gel conversion synthesis and performance of glass-fiber MIL-100(Fe) composite desiccant material for dehumidification

Abstract Metal organic frameworks (MOFs) MIL-100(Fe) is considered to be a promising porous adsorbent for dehumidification due to its good hydrophilicity and hydrothermal stability. However, the powdery MIL-100(Fe) prepared by the conventional hydrothermal method is not suitable for industrial rotary desiccant dehumidifier. In order to produce a high-performance rotor core component, a new dry gel conversion in situ synthesis strategy for glass-fiber MIL-100(Fe) monolithic adsorbent was proposed in this paper. The effects of the reaction sol concentration on the crystalline phase, morphology, pore structure, adsorption/desorption performance and the cycling stability of the monolith were discussed in detail. The results showed that MIL-100(Fe) crystals which evenly dispersed in the surface and voids of glass fiber, could be conveniently synthesized in the reaction sols with molar ratios of 1Fe (III)/0.67BTC/xH2O (x = 93–185). Among them, the MIL-100(Fe) monolith obtained at x = 93 exhibited a high loading (85.7%), large BET specific surface area (1441 m2/g), S-shaped water vapor adsorption isotherm and high saturated adsorption ratio (0.496 g/g) at 298 K and 60% RH, low desorption activation energy (48.28 kJ/mol) as well as a reliable cycling stability. Favorable adsorption/desorption performance of MIL-100(Fe) monolith and convenient dry gel preparation process provide a guidance for the manufacture of high-performance dehumidification rotary wheel.

Dry gel conversion synthesis of Cu/SSZ-13 as a catalyst with high performance for NH3-SCR

Abstract Selective catalytic reduction (SCR) of NOx with zeolite catalysts has been reported as the most promising technique for the removal of NOx from diesel engine exhaust. In this research, SSZ-13 zeolite doped with Cu species was synthesized by dry gel conversion (DGC) method and applied as a catalyst for NH3-SCR. The obtained Cu/SSZ-13 was characterized using X-ray diffraction (XRD), energy-dispersive X-ray (EDX), Scanning Electron Microscopy (SEM), NMR spectroscopy, ESR spectroscopy, nitrogen adsorption. Cu/SSZ-13 synthesized by DGC method has higher crystallinity and porosity than that synthesized by conventional hydrothermal synthesis (HTS) method. Due to its higher crystallinity and porosity, higher amount of Cu ions was introduced into SSZ-13 synthesized by DGC method, leading to a higher catalytic performance for the SCR of NOx compared with Cu/SSZ-13 prepared by HTS. In addition, Cu/SSZ-13 synthesized by DGC method showed higher hydrothermal stability.

Dry Gel Conversion Synthesis of Hierarchical Porous MIL-100(Fe) and Its Water Vapor Adsorption/Desorption Performance

With an S-shaped water sorption isotherm and high vapor uptake, as one of the famous metal organic frameworks (MOFs), MIL-100(Fe) (MIL stands for Materials of Institute Lavoisier) has been consider...

State-of-the-Art Advances and Challenges of Iron-Based Metal Organic Frameworks from Attractive Features, Synthesis to Multifunctional Applications.

Metal organic frameworks (MOFs), as an original kind of organic-inorganic porous material, are constructed with metal centers and organic linkers via a coordination complexation reaction. Among uncountable MOF materials, iron-containing metal organic frameworks (Fe-MOFs) have excellent potential in practical applications owing to their many fascinating properties, such as diverse structure types, low toxicity, preferable stability, and tailored functionality. Here, recent research progresses of Fe-MOFs in attractive features, synthesis, and multifunctional applications are described. Fe-MOFs with porosity and tailored functionality are discussed according to the design of building blocks. Four types of synthetic methods including solvothermal, hydrothermal, microwave, and dry gel conversion synthesis are illustrated. Finally, the applications of Fe-MOFs in Li-ion batteries, sensors, gas storage, separation in gas and liquid phases, and catalysis are elucidated, focusing on the mechanism. The aim is to provide prospects for extending Fe-MOFs in more practical applications.

Green and efficient dry gel conversion synthesis of SAPO-34 catalyst with plate-like morphology

SAPO-34 catalyst with plate-like morphology was designed and synthesized for the first time, by the dry gel conversion method using cheap triethylamine as a structure-directing agent assisted with seed suspension containing nanosheet-like SAPO-34 seed. The latter played an important role in formation of SAPO-34 (CHA-type) with plate-like morphology. In addition, the yield of the product in the synthesis system containing seed suspension reached 97%, 15% higher than that obtained in the corresponding synthesis system without the seed suspension. Meanwhile, the plate-like SAPO-34 catalysts synthesized by this method exhibited higher selectivity to light olefins and longer lifetime in methanol-to-olefins (MTO) reaction than the traditional cubic SAPO-34 catalyst. This work provides a new technical route for green and efficient synthesis of SAPO-34 catalysts with improved MTO performance.

Dry-gel conversion synthesis of Cr-MIL-101 aided by grinding: high surface area and high yield synthesis with minimum purification

A dry gel conversion synthesis aided by fine-grinding of the synthesis precursors produces a MIL-101 product with a high surface area greater than 4100 m(2) g(-1) and a product yield approaching 90% in a very reproducible manner after only simple water washing.

Dry gel conversion synthesis of shape controlled MFI type zeolite materials

Acid treated silica fibers, coming either from asbestos cord waste or calcium aluminosilicate glass, were engaged as reactants to product MFI type zeolite fibers applying a dry gel conversion (DGC) type synthesis. The impact of amorphous silica fiber shape and synthesis conditions on morphology of the final product was investigated. Enhanced zeolite nucleation and restricted crystal growth are necessary to maintain the initial fiber morphology. Whereas a DGC type crystallization in hydroxide media results in the formation of zeolite fibers, the use of fluoride ions leads to the formation of large individual zeolite particles. Synthesis conditions have to be adapted to form zeolite particles with an average size smaller than the silica fiber diameter to allow a good conservation of the fiber morphology. Final zeolite fibers have textural properties comparable to a standard zeolite product and are promising for adsorption applications.

Dry gel conversion synthesis of SAPO- and CoAPO-based molecular sieves by using structurally related preformed AlPO precursors as the starting materials

Several Si and Co substituted AlPO 4-based molecular sieves with AFI, AEL and CHA structures including SAPO- n and CoAPO- n (where n = 5, 11 and 34) have been synthesized under dry gel conversion (DGC) conditions by using the pre-prepared AlPO-based precursors which have been demonstrated previously to be structurally related to the target molecular sieves. We show that highly crystalline SAPO- n and CoAPO- n can be prepared by this approach. Unlike conventional DGC method where the Si source is mixed with P and Al sources at the very beginning to form an initial amorphous dry gel, in this work the Si is slowly introduced to the surface of the dry powder of the semi-crystalline or crystalline AlPO-based precursor via vapor phase, and subsequently incorporated into the framework gradually. The Si environments in the SAPOs prepared by this approach appear to be more diversified compared to those in the corresponding sieves made by the normal hydrothermal synthesis (HTS) method. One feature of this synthesis is that the Si substitution in the lattice may only occur at some specific positions. This is due to the fact that since certain P sites in the precursors are directly carried into the framework of the final sieves, they are not available for Si incorporation. This finding may have implication to the locations of the catalytic sites in the SAPO-based catalysts. Similarly, for CoAPO- n, the Co source was mixed with the preformed AlPO-based precursor before DGC treatment. CoAPO-5 has a higher degree of the Co incorporation than that of the CoAPO-5 made under normal HTS conditions.