Supported Au25 clusters were prepared through the calcination of Au25(SC12H25)18 on hierarchically porous carbon nanosheets under vacuum at temperatures in the range of 400–500 °C for 2–4 h. TEM and EXAFS analyses revealed that the thiolate coverage on Au25 gradually decreased with increasing calcination temperature and period and became negligibly small when the calcination temperature exceeded 500 °C. The catalysis of these Au25 clusters was studied for the aerobic oxidation of benzyl alcohol. Interestingly, the selectivity for benzaldehyde formation was remarkably improved with the increase in the amount of residual thiolates on Au25, while the activity was reduced. This observation is attributed to the dual roles of the thiolates: the reduction of the oxidation ability of Au25 by electron withdrawal and the inhibition of the esterification reaction on the cluster surface by site isolation.

Highly selective production of ethylene from bioethanol dehydration over hierarchical ZSM-5 nanosheets.

The superior catalytic performance of amine-grafted hierarchical basic FAU-type zeolite nanosheets for the aldol condensation of 5-hydroxymethylfurfural (5-HMF) and acetone (Ac) has been achieved due to the synergistic effect of hierarchical structures, featuring basic active sites together with surface modification. This results in an unprecedented yield of 4-[5-(hydroxymethyl)furan-2-yl]but-3-en-2-one (HMB) close to 100%. The catalytic activity can be easily tuned by changing the degree of basicity corresponding to the nature of basic sites and surface modification.

No abstract

Propane dehydrogenation (PDH) is the extensive pathway to produce propylene, which is as a very important chemical building block for the chemical industry. Various catalysts have been developed to increase the propylene yield over recent decades; however, an active site of monometallic Pt nanoparticles prevents them from achieving this, due to the interferences of side-reactions. In this context, we describe the use of promoter-free hierarchical Pt/silicalite-1 nanosheets in the PDH application. The Pt dispersion on weakly acidic supports can be improved due to an increase in the metal-support interaction of ultra-small metal nanoparticles and silanol defect sites of hierarchical structures. This behavior leads to highly selective propylene production, with more than 95% of propylene selectivity, due to the complete suppression of the side catalytic cracking. Moreover, the oligomerization as a side reaction is prevented in the presence of hierarchical structures due to the shortening of the diffusion path length.

As the catalytic performances typically depend on various factors, especially the distribution of Al species in the zeolite framework, in this contribution, hierarchical nanospherical ZSM-5 zeolites have been successfully synthesized using uniform aluminosilicate (AS) nanobeads containing silica and alumina species as a starting material to improve the Al dispersion in the framework. The synthesized zeolites were characterized by means of XRD, TEM, SEM, EDS, N 2 physisorption, 27 Al MAS NMR, and NH 3 -TPD. This example demonstrates that the use of AS nanobeads can effectively control the uniform Al distribution. Subsequently, the synthesized materials were tested for their catalytic activity in the alkylation of benzene with ethanol to ethylbenzene. Interestingly, the designed ZSM-5 nanospheres prepared by using AS nanobeads clearly exhibit an improvement of the catalytic performance in terms of benzene conversion and ethylbenzene selectivity compared with the conventional ZSM-5 and the ZSM-5 nanospheres prepared by using a typical synthesis method. The reason for the improved benzene conversion (60%) and ethylbenzene selectivity (62%) on Hie-SZSM-5-AS relates to the generated mesoporous structure as well as a homogeneous distribution of Al frameworks directed by AS nanobeads. The synthesis approach reported herein illustrates an efficient way to control Al species as well as Al distribution in the zeolite framework, eventually enhancing the catalytic performance in acid catalyzed reaction, such as in the case of benzene alkylation with ethanol.

The chemical state and acidity of ceria incorporated in hierarchical zeolites have been successfully tuned due to the presence of hierarchical structures of zeolite nanosheets and interaction between ceria and...

Over the past decades, the catalytic cracking catalysts for hydrocarbon oil upgrading have been extensively developed to increase the yield of light olefins. In this context, we report the fabrication of the core‐shell ZSM‐5@aqueous miscible organic‐layered double hydroxides prepared by the growth of layered double hydroxides (LDH) precursors on zeolite surfaces. The deposited LDH results in a decrease of the number of strong Brønsted acid sites on zeolite surfaces and its transformation at high temperature leads to produce the highly dispersed metal oxides deposited on external surfaces of zeolites. Therefore, the acid‐base properties of designed surfaces are modified, eventually resulting in the suppression of competing hydride transfers and further side reactions. As a result, there is a significant enhancement in light olefins production compared with the pristine zeolite. In addition, the designed catalysts exhibit high recycling stability and reusability. This first example opens up the new perspectives for the development of modified acid‐base zeolites using zeolite@aqueous miscible organic‐layered double hydroxides for the catalytic upgrading of hydrocarbons.