•Organosilane functioned fumed silica were used to synthesized MOR nano-rods bundles.•MOR nano-rods of 30–80 nm resulted in mesopores in the bundles.•MOR nano-rods bundles have high adsorption of mesitylene.•MOR nano-rods bundles have remarkable catalytic performance for large molecules.Hierarchical mordenite zeolite nano-rods bundles were successfully synthesized by a novel approach of using organosilane functioned fumed silica as silicon source. The organic moiety linked on the surface of fumed silica inhibits the growth of zeolite crystal into large size, leading to the nano-rods assembled bundles. The mordenite nanorods bundles exhibited significantly improved mesitylene adsorption capacity compared with the conventional mordenite. As a catalyst, the hierarchical mordenite nanorods bundles showed remarkable catalytic performance in the benzylation of mesitylene by benzyl chloride, due to the efficient diffusion rate and improved accessibility of the active sites in the hierarchical mordenite nanorods bundles.Hierarchical mordenite zeolite nano-rods bundles were successfully synthesized by a novel approach of using organolilane functioned fumed silica as silicon source. The nano-rods bundles showed remarkable accessibility of mesopores to bulky molecules, which lead to high catalytic performance in large molecules involved reactions.Download high-res image (129KB)Download full-size image

•A spherical nanocrystal aggregates of ZSM-5 with mesopores and advanced catalysis.•High external surface area and mesoporous volume from inter-nanocrystals only.•67% of Bronsted acid sites in the catalyst for big molecules are accessibly valid.•The reaction rate of big molecule on the catalyst increases by more than 50 times.The spherical self-assemblies of ZSM-5 nanocrystals were hydrothermally synthesized by using organo-functionalized mesoporous silica (MS) as silica source. The prepared materials were well characterized by XRD, FTIR of framework vibration, SEM, TEM, N2 adsorption/desorption and TG analyses, to reveal their hierarchical architectures. The ZSM-5 nano-aggregates are composed of size-tunable nanocrystals, and the size and different morphologies of nanocrystals changed significantly from silanized MS rather than unsilanized MS. Spontaneously stacking of nanocrystals in the zeolitic crystallization based on degrees of silanization on MS surface results in the ZSM-5 samples have high external surface area and mesopore volume from intercrystalline among the nanoparticles. The evaluations of NH3-TPD, pyridine- and 2,6-ditertbutylpyridine-adsorbed FTIR as well as catalytic performances in benzylation reaction of 1,3,5-trimethylbenzene for the ZSM-5 zeolitic samples display the accessibility of acid sites and the catalytic activities for the synthesized hierarchical ZSM-5 zeolites are remarkably enhanced. It is clear that the results can be ascribed to the advantages of hierarchical ZSM-5 zeolites for the catalytic conversion of larger molecule, because of the reduction of the steric limitations and faster diffusion of the reaction species.Download high-res image (143KB)Download full-size image

Probing the mesopore architecture in mesoporous zeolites is of importance for large scale applications of the materials. In this work, the adsorption and diffusion of mesitylene with larger molecule size in mesoporous ZSM-5 zeolites were carried out, in order to acquaint the availability and interconnectivity of mesopores in zeolite crystals. The comparisons of the shape of adsorption isotherms and the mesopore volume calculated from mesitylene and N2 adsorption in mesoporous ZSM-5 zeolites with different mesoporosities can be used to discriminate two cases of mesopores: accessible mesopores connected to external surface of the zeolite crystals and non-accessible meso-voids that are occluded in the microporous matrix. Furthermore, the effective diffusivity and activation energy of mesitylene in mesoporous ZSM-5 extracted from ZLC desorption curves as a function of mesopore volume calculated from mesitylene adsorption reveal the enhancement of mesopore interconnectivity to molecule diffusion in zeolite crystals.

A mesoporous beta zeolite was hydrothermally prepared directly by silanizing silica without any mesoporous template via the bond-blocking principle. Si–C bond-blocking arose during the crystalline growth. The crystallization took more than 10 days, but the material had a fairly stable structure and could even be processed up to 32 days later in the hydrothermal system. XRD, N2-adsorption/desorption and TEM/SEM characterization of the materials indicated that the beta zeolite is truly a sponge-like mesoporous zeolite with a BEA topological structure, which consists of self-sustaining macroscopic sized zeolitic aggregates assembled from nanosized crystalline domains of beta zeolite with intracrystalline mesopores. The mesoporous beta zeolite possessed an extremely large external surface area and adjustable mesoporosity. Compared to conventional beta zeolite, FTIR results of pyridine (Py) and 2,6-di-tert-butylpyridine (DTBPy) demonstrated an increase of the Lewis-site contribution and a large improvement for the accessibility of bulky molecules in the mesoporous beta zeolite. Finally the mesoporous beta zeolite exhibited significant activity in the transesterification reaction of triolein to afford methyl oleate (biodiesel) due to the accessibility increase and diffusion-limitation reduction of large lipids to acid sites in the H-beta zeolite framework.

ZSM-5 zeolites with different mesoporosities were prepared by alkaline treatment and characterized by powder XRD and nitrogen adsorption. Two C7 hydrocarbons of n-heptane and toluene were employed as probe molecules to investigate the effects of the introduction of mesopore on the adsorption and diffusion properties of ZSM-5 zeolites by comparing the experimental results of the samples treated and untreated by using NaOH. Adsorption isotherms were measured gravimetrically in the pressure range 0–32 mbar and from 293 to 338 K. The isotherms of microporous and mesoporous ZSM-5 were successfully fitted by using the Langmuir–Freundlich model and the dual-site Langmuir–Freundlich model, respectively. Henry’s constants and the initial heats of adsorption calculated from the adsorption isotherms as well as the fitting parameters displayed that the interactions between adsorbent and adsorbate were weakened after the introduction of mesopore, and the interactions between the adsorbates with microporous surface are much stronger than that between them with the mesoporous surface. Diffusion measurements were undertaken using the zero length column (ZLC) technique at partial pressure of p/p0 < 0.000 15 from 333 to 393 K. The results showed that the effective diffusion constants (Deff/R2) of the two C7 hydrocarbons increased greatly in the presence of mesopores, while the corresponding activation energy decreased due to the reduced diffusion resistance and the shortened diffusion path in the mesoporous zeolites. Also, higher and much more dramatic enhancement of the efficient diffusivities as a function of mesoporous volume for toluene relative to that for n-heptane were found, indicating that the diffusion of n-heptane is controlled by the micropore diffusion and that the diffusion of toluene is exclusively determined by mass transfer through the mesopores.

The thermal responsive SiO2-PNIPAAm composites were designed and successfully synthesized. The structure, morphology, surface composition and temperature sensitive property in aqueous solution were investigated by Fourier transform infrared spectroscopy (FTIR) and transmission electron microscopy (TEM), X-ray photoelectron spectroscopy (XPS), contact angle measurement instrument and dynamic light scatter (DLS). FTIR measurement and N1s and C1s core-level spectrum of XPS illustrate that PNIPAAm is grafted availably. TEM analysis revealed the difference between bare SiO2 and PNIPAAm-functionalized SiO2. The measurements of water contact angle and DLS show that the hydration transition temperature of the thermal responsive SiO2-PNIPAAm composites is 304 K. The different grafted PNIPAM content has the obvious effect on the water contact angle measure and DLS for SiO2.Highlights► A simple method of thermal responsive silica nanoparticle /PNIPAM hybrids. ► Low impact on the environment using absolute alcohol as solvent. ► Contact angle measurement is used to examine the temperature switching behavior.

We have synthesized a series of zeolite ZSM-5 samples with hierarchical porous structure and tunable accessibility using organosilane as silanizing agent. Their structural and textural properties were characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM), transmission electron microscopy (TEM) and nitrogen adsorption. We derived the acidity property and accessibility of acidic sites in the hierarchical zeolites from the Fourier transform infrared spectroscopy (FTIR) of samples with the adsorption of pyridine and 2,6-dimethylpyridine (DMPy), and found that the accessibility index was linearly correlated with the external surface area of hierarchical zeolite whose hierarchical factor is a constant. Furthermore, the hierarchical ZSM-5 has exhibited a high catalytic activity and long life in both benzylation reaction of benzene by benzyl alcohol and methanol-to-gasoline reaction. The results show that the present synthesis route is highly effective to enhance the accessibility of Brønsted acid sites in zeolite ZSM-5.Graphical abstractHighlights► A new silanizing agent is used in the synthesis of hierarchical ZSM-5 with intercrystal mesopores. ► ACI is a key factor to the hierarchical zeolites whose HF is a constant. ► The ACI is linearly correlated with the external surface area. ► Adsorption of dimethylpyridine by IR is suitable for the hierarchical zeolites. ► The hierarchical ZSM-5 zeolite with high ACI is favor to bulky molecular reaction.

A series of nanosized ZSM-5 zeolite samples with intracrystalline mesopores has been synthesized using organosilane functioned fumed silica as silica source and tetrapropylammonium hydroxide as microporous structure directing agent. The organic moiety linked on the surface of fumed silica blocks the growth of zeolite crystal, forming the nanosized zeolite crystal and intracrystalline defects inside the nano-crystal. The formation of the mesopores is by bond-blocking function in crystallization. The XRD results indicate that the samples are high crystalline ZSM-5 and the TEM images show that the samples are nanosized with the size ca. 20 nm and the intracrystalline mesopores about 3 nm exist inside the nanosized crystal.Highlights► Nanosized ZSM-5 zeolite with intracrystalline mesopores was first prepared. ► The formation of the mesopores is by bond-blocking function in crystallization. ► The intracrystalline mesopores result in a spread hierarchical zeolite. ► The organic functioned silica source is essential for such material.

•Mg2 + and Ca2 + competitive exchange properties in the meso-zeolite LTA•There are two kinds of ion-exchange sites in the meso-zeolites.•The lower activation energy and higher rate of ion-exchange in mesopore structures•The Dual-site Langmuir isotherms for the equilibrium of Ca2 + and Mg2 + exchangeThe Mg2 + and Ca2 + exchange properties in the meso-zeolite LTA were investigated. These meso-zeolite materials with intracrystalline mesopores ca. 3 nm were prepared using organic functioned fumed silica as silica source. The Dual-site Langmuir (D-L) expression appropriately describes the equilibrium data for the Ca2 + and Mg2 + exchange. The fitting results with D-L model suggest that two kinds of ion-exchange sites in the meso-zeolites exist, one in the part of intrinsic micropore structure (internal surface area) and the other one in the part of established mesopore structure (external surface area). The latter site has lower enthalpy values of Ca2 + or Mg2 + exchanges than the former one. Ca2 + or Mg2 + exchange kinetics is conducted at 273 K, 288 K and 308 K. The results show the emergence of mesopores lowering the activation energy of ion exchange and accelerating Mg2 + exchange extremely in the materials. The diffusion rate of hydrated Mg2 + in the meso-zeolite LTA increases by 17.5 times, higher than that of conventional LTA at 273 K. And the meso-zeolite LTA possesses large Mg2 + competitive ability in a solution containing Ca2 + and Mg2 +. These properties make the meso-zeolite LTA a suitable material which could be used effectively in hard water softening and detergent building for Mg2 + removing.Download full-size image

A mesoporous beta zeolite was hydrothermally prepared directly by silanizing silica without any mesoporous template via the bond-blocking principle. Si–C bond-blocking arose during the crystalline growth. The crystallization took more than 10 days, but the material had a fairly stable structure and could even be processed up to 32 days later in the hydrothermal system. XRD, N2-adsorption/desorption and TEM/SEM characterization of the materials indicated that the beta zeolite is truly a sponge-like mesoporous zeolite with a BEA topological structure, which consists of self-sustaining macroscopic sized zeolitic aggregates assembled from nanosized crystalline domains of beta zeolite with intracrystalline mesopores. The mesoporous beta zeolite possessed an extremely large external surface area and adjustable mesoporosity. Compared to conventional beta zeolite, FTIR results of pyridine (Py) and 2,6-di-tert-butylpyridine (DTBPy) demonstrated an increase of the Lewis-site contribution and a large improvement for the accessibility of bulky molecules in the mesoporous beta zeolite. Finally the mesoporous beta zeolite exhibited significant activity in the transesterification reaction of triolein to afford methyl oleate (biodiesel) due to the accessibility increase and diffusion-limitation reduction of large lipids to acid sites in the H-beta zeolite framework.