Hierarchical zeolites combine the intrinsic catalytic properties of microporous zeolites and the enhanced access and transport of the additional meso- and/or macroporous system. These materials are the most desirable catalysts and sorbents for industry and become a highly evolving field of important current interests. In addition to the enhanced mass transfer leading to high activity, selectivity, and cycle time, another essential merit of the hierarchical structure in zeolite materials is that it can significantly improve the utilization effectiveness of zeolite materials resulting in the minimum energy, time, and raw materials consumption. Substantial progress has been made in the synthesis, characterization, and application of hierarchical zeolites. Herein, we provide an overview of recent achievements in the field, highlighting the significant progress in the past decade on the development of novel and remarkable strategies to create an additional pore system in zeolites. The most innovative synthesis approaches are reviewed according to the principle, versatility, effectiveness, and degree of reality while establishing a firm link between the preparation route and the resultant hierarchical pore quality in zeolites. Zeolites with different hierarchically porous structures, i.e., micro-mesoporous structure, micro-macroporous structure, and micro-meso-macroporous structure, are then analyzed in detail with concrete examples to illustrate their benefits and their fabrications. The significantly improved performances in catalytic, environmental, and biological applications resulting from enhanced mass transport properties are discussed through a series of representative cases. In the concluding part, we envision the emergence of "material-properties-by-quantitative and real rational design" based on the "generalized Murray's Law" that enables the predictable and controlled productions of bioinspired hierarchically structured zeolites. This Review is expected to attract important interests from catalysis, separation, environment, advanced materials, and chemical engineering fields as well as biomedicine for artificial organ and drug delivery systems.

Hierarchically Structured Zeolites: From Design to Application.

A non-chemically selective top-down approach towards the preparation of hierarchical TS-1 zeolites with improved oxidative desulfurization catalytic performance

Green and efficient preparation of hollow titanium silicalite-1 by using recycled mother liquid

Highly efficient oxidation of ethyl lactate (ELA) to ethyl pyruvate (EP) was realized over TS-1 in the presence of aqueous H2O2 (30 wt %) at low temperature without other solvent. A 100% ELA conversion and 97.8% EP yield were obtained at 50 °C after 9 h. The conversion rate of ELA is sensitive to the reaction temperature. High reaction temperature (70 °C) leads to an increase in conversion rate of ELA but causes the fast hydrolysis and decarboxylation of EP to form byproducts of acetic acid and CO2. On the basis of the characterization (pyridine-FTIR and UV–vis) and reaction results, active species of Ti(OOH) were proven. In addition, a nonradical mechanism for conversion of ELA to EP for this catalytic system was proposed. By kinetic analysis, the formation of Ti(OOH) is confirmed as the rate-determining step. The apparent activation energy (103.4 kJ mol–1) was also obtained. Furthermore, TS-1 was highly stable for the oxidation of ethyl lactate. There were almost no change in ELA conversion and EP yield...

Highly Efficient Oxidation of Ethyl Lactate to Ethyl Pyruvate Catalyzed by TS-1 Under Mild Conditions

Selective synthesis of propylene oxide through liquid-phase epoxidation of propylene with H2O2 over formed Ti-MWW catalyst

In this article, solid and hollow TS-1 mesocrystals (HTMs) with hierarchical porous structures were constructed through assembling TS-1 nanocrystalline blocks in a hydrothermal post-treatment method. TS-1 nanocrystalline blocks including the organic templating reagent provided solid TS-1 mesocrystals. Pre-removal of the template offered HTMs. In cyclohexanone ammoximation, the catalytic activity of HTMs depended significantly on their hollow mesocrystalline structure. Compared to solid TS-1 mesocrystals, HTMs showed excellent catalytic performances for cyclohexanone conversion with oxime selectivity up to 100%. The hollow mesocrystalline structures of TS-1 contributed to high surface areas, hierarchical porosities, robust structures, and corresponding catalytic performances.

Hollow TS-1 mesocrystals: hydrothermal construction and high catalytic performances in cyclohexanone ammoximation

The epoxidation of propylene to propylene oxide with H2O2 using a micron-sized TS-1 catalyst with hollow structure in a low-pressure continuous slurry reactor was investigated. Under the optimized reaction conditions, the process was successfully run for 247 h with superior selectivity (98.7%) and yield (96.4%) of propylene oxide. The reaction pressure was only 0.23 MPa which was much lower than that in the fixed-bed, and the catalyst stability was excellent. Though the deactivation of catalyst occurred after 247 h, the selectivity to propylene oxide was still kept above 97.5%, which was significantly better than the experimental results in the fixed-bed reactor. Washing deactivated catalyst with H2O2 can easily remove bulky byproducts deposited inside micropores and recover catalytic activity. This research verified the safety and high catalyst efficiency of epoxidation of propylene in a slurry reactor.

Highly Selective Epoxidation of Propylene in a Low-Pressure Continuous Slurry Reactor and the Regeneration of Catalyst

The spray-forming process of the nano-titanium silicalite (TS-1) zeolite was investigated and optimized in the lab in order to obtain materials with microsphere morphology and superior catalytic activity in cyclohexanone ammoximation on the industrial scale. The effects of spray-forming parameters, such as the state of the TS-1 raw material, load ratio, solid content, binder content, and calcination temperature, on the physicochemical and catalytic properties of TS-1 microspheres were investigated in detail. It was interesting to find that the shape of the spray-forming sample formed by wet powders was more intact than the sample formed by dried powders. Furthermore, the spray-forming process was successfully scaled up to a large spray device (LGZ-1000) according to the similarity principle of load ratio, and the shape of the TS-1 microspheres was as perfect as the spray-forming samples in the lab. The similarity principle of the load ratio for the spray-forming of titanium silicate was established and verified for the first time. The spray-forming TS-1 microspheres produced in the industry were used in cyclohexanone ammoximation, and ketone conversion and oxime selectivity were as high as 99.9 and 99.4%, respectively.

https://pubs.acs.org/doi/pdf/10.1021/acsomega.8b02561

Fabrication of Microspheres by Nano-TS-1 Crystals via a Spray-Forming Process: From Screening to Scale-up.

The invention provides a safe low-energy-consumption forming method for a titanium-silicon molecular sieve spray The method comprises the steps that an additive is added into hydro-thermal synthesized titanium-silicon molecular sieve crystallization liquid at first to enable the titanium-silicon molecular sieve crystallization liquid to be preclustered to a millimeter-sized cluster; organic matter such as most water and temple agent is separated out; the preclustered cluster is dispersed into an acid aqueous solution, spraying is carried out at the low inlet temperature and the high feeding speed to enable the cluster to achieve secondary dehydration so as to be clustered into micron-sized particles, roasting is carried out, and a spherical TS-1 catalyst is obtained The problems that mixing is uneven and a spray head is blocked when raw powder spray is adopted are solved, and the potential safety hazard of organic matter carbonization or burning explosion caused when inlet and outlet temperature is too high during crystallization liquid concentration spraying is avoided

Safe low-energy-consumption forming method for titanium-silicon molecular sieve spray

The invention belongs to the technical field of catalysts and in particular relates to a modified TS-1 molecular sieve as well as a preparation method and application of the modified TS-1 molecular sieve. The preparation method of the modified TS-1 molecular sieve comprises the following steps: modifying TS-1 by using organic alkali in the presence or absence of a template agent, then carrying out hydro-thermal treatment to obtain the modified TS-1 molecular sieve; the template agent is quaternary ammonium salt. A modified TS-1 molecular sieve catalyst is simple in production and preparation method and low in production cost. The catalyst is mild in condition and high in catalytic activity when the catalyst is applicable to cyclohexanone ammonia oximation reaction and propylene epoxidation reaction.

Ye Xiaoxue

Papers

Hollow TS-1 mesocrystals: hydrothermal construction and high catalytic performances in cyclohexanone ammoximation

Highly Selective Epoxidation of Propylene in a Low-Pressure Continuous Slurry Reactor and the Regeneration of Catalyst

Fabrication of Microspheres by Nano-TS-1 Crystals via a Spray-Forming Process: From Screening to Scale-up.

Safe low-energy-consumption forming method for titanium-silicon molecular sieve spray

Modified TS-1 molecular sieve as well as preparation method and application thereof