MCM-41 Matrix Research Articles

Design of Nanostraws in Amine-Functionalized MCM-41 for Improved Adsorption Capacity in Carbon Capture.

Polymeric amine encapsulation in high surface area MCM-41 particles for CO2 capture is well established but has the drawback of leaching out the water-soluble polymer upon exposure to aqueous environments. Alternatively, chemical (covalent) grafting amine functional groups from an alkoxysilane such as 3-aminopropyltriethoxysilane (APTES) on MCM-41 offer better stability against this drawback. However, the diffusional restriction exhibited by the narrow uniform MCM-41 pores (2-4 nm) may impede amine functionalization of the available silanol groups within the inner mesoporous core. This leads to incomplete amine functionalization and could reduce the CO2 adsorption capacity in such materials. Our concept to improve access to the MCM-41 interior is based on the incorporation of nanostraws with larger inner diameter (15-30 nm) to create a hierarchical porosity and enhance the molecular transport of APTES. Halloysite nanotubes (HNT) are used as tubular straws that are integrated into the MCM-41 matrix using an aerosol-assisted synthesis method. Characterization results show that the intrinsic structure of MCM-41 remains unaltered after the incorporation of the nanostraws and amine functionalization. At an optimal APTES loading of 0.5 g (X = 2.0), the amine-functionalized composite of MCM-41 with straws (APTES/M40H) has a 20% higher adsorption capacity than the amine-modified MCM-41 (APTES/MCM-41) adsorbent. Furthermore, the CO2 adsorption capacity APTES/M40H doubles that of APTES/MCM-41 when normalized based on the composition of MCM-41 in the composite particle with straws. The facile integration of nanostraws in MCM-41 leading to hierarchical porosities could be effective toward the mitigation of diffusional restriction in porous materials with potential for other catalytic and adsorption technologies.

Evidence of Strong Guest-Host Interactions in Simvastatin Loaded in Mesoporous Silica MCM-41.

A rational design of drug delivery systems requires in-depth knowledge not only of the drug itself, in terms of physical state and molecular mobility, but also of how it is distributed among a carrier and its interactions with the host matrix. In this context, this work reports the behavior of simvastatin (SIM) loaded in mesoporous silica MCM-41 matrix (average pore diameter ~3.5 nm) accessed by a set of experimental techniques, evidencing that it exists in an amorphous state (X-ray diffraction, ssNMR, ATR-FTIR, and DSC). The most significant fraction of SIM molecules corresponds to a high thermal resistant population, as shown by thermogravimetry, and which interacts strongly with the MCM silanol groups, as revealed by ATR-FTIR analysis. These findings are supported by Molecular Dynamics (MD) simulations predicting that SIM molecules anchor to the inner pore wall through multiple hydrogen bonds. This anchored molecular fraction lacks a calorimetric and dielectric signature corresponding to a dynamically rigid population. Furthermore, differential scanning calorimetry showed a weak glass transition that is shifted to lower temperatures compared to bulk amorphous SIM. This accelerated molecular population is coherent with an in-pore fraction of molecules distinct from bulklike SIM, as highlighted by MD simulations. MCM-41 loading proved to be a suitable strategy for a long-term stabilization (at least three years) of simvastatin in the amorphous form, whose unanchored population releases at a much higher rate compared to the crystalline drug dissolution. Oppositely, the surface-attached molecules are kept entrapped inside pores even after long-term release assays.

The Accumulation of Electrical Energy Due to the Quantum-Dimensional Effects and Quantum Amplification of Sensor Sensitivity in a Nanoporous SiO2 Matrix Filled with Synthetic Fulvic Acid.

A heterostructured nanocomposite MCM-41<SFA> was formed using the encapsulation method, where a silicon dioxide matrix-MCM-41 was the host matrix and synthetic fulvic acid was the organic guest. Using the method of nitrogen sorption/desorption, a high degree of monoporosity in the studied matrix was established, with a maximum for the distribution of its pores with radii of 1.42 nm. According to the results of an X-ray structural analysis, both the matrix and the encapsulate were characterized by an amorphous structure, and the absence of a manifestation of the guest component could be caused by its nanodispersity. The electrical, conductive, and polarization properties of the encapsulate were studied with impedance spectroscopy. The nature of the changes in the frequency behavior of the impedance, dielectric permittivity, and tangent of the dielectric loss angle under normal conditions, in a constant magnetic field, and under illumination, was established. The obtained results indicated the manifestation of photo- and magneto-resistive and capacitive effects. In the studied encapsulate, the combination of a high value of ε and a value of the tgδ of less than 1 in the low-frequency range was achieved, which is a prerequisite for the realization of a quantum electric energy storage device. A confirmation of the possibility of accumulating an electric charge was obtained by measuring the I-V characteristic, which took on a hysteresis behavior.

Mn(III) Schiff base complexes containing crown ether rings immobilized onto MCM-41 matrix as heterogeneous catalysts for oxidation of alkenes

Six catalysts MnL1–MnL6, containing two crown ether rings and their analogs supported on the MCM-41 heterogeneous substrate (MnL1@MCM41-MnL5@MCM41) were synthesized and characterized. A mixture of molecular oxygen, as an oxidant, and these catalysts were used for the epoxidation of styrene. As a general result, the supported catalysts showed better performance compared with the unsupported analogs. On the other hand, the supported species, in addition to recyclability, did not require an axial base and reducing agent.

Anchoring of Cu–dimethylglyoxime complex in MCM-41 matrix: a new, recyclable, and highly efficient nanocatalyst for the green preparation of 2,3-dihydroquinazolin-4(1H)-ones

Anchoring of Cu–dimethylglyoxime complex in MCM-41 matrix: a new, recyclable, and highly efficient nanocatalyst for the green preparation of 2,3-dihydroquinazolin-4(1H)-ones

How Molecular Mobility, Physical State, and Drug Distribution Influence the Naproxen Release Profile from Different Mesoporous Silica Matrices.

Aiming to evaluate how the release profile of naproxen (nap) is influenced by its physical state, molecular mobility, and distribution in the host, this pharmaceutical drug was loaded in three different mesoporous silicas differing in their architecture and surface composition. Unmodified and partially silylated MCM-41 matrices, respectively MCM-41 and MCM-41sil, and a biphenylene-bridged periodic mesoporous organic matrix, PMOBph, were synthetized and used as drug carriers, having comparable pore sizes (∼3 nm) and loading percentages (∼30% w/w). The loaded guest was investigated by attenuated total reflectance Fourier transform infrared (ATR-FTIR) spectroscopy, powder X-ray diffraction (XRD), differential scanning calorimetry (DSC), and dielectric relaxation spectroscopy (DRS). DSC and XRD confirmed amorphization of a nap fraction incorporated inside the pores. A narrower glass transition was detected for PMOBph_nap, taken as an indication of the impact of host ordering, which also hinders the guest molecular mobility inside the pores as probed by DRS. While the PMOBph matrix is highly hydrophobic, the unmodified MCM-41 readily adsorbs water, accelerating the nap relaxation rate in the respective composite. In the dehydrated state, the faster dynamics was found for the silylated matrix since guest-host hydrogen bond interactions were inhibited to some extent by methylation. Nevertheless, in all the prepared composites, bulk-like crystalline drug deposits outside pores in a greater extent in PMOBph_nap. The DRS measurements analyzed in terms of conductivity show that, upon melting, nap easily migrates into pores in MCM-41-based composites, while it stays in the outer surface in the ordered PMOBph, determining a faster nap delivery from the latter matrix. On the other side, the mobility enhancement in the hydrated state controls the drug delivery in the unmodified MCM-41 matrix vs the silylated one. Therefore, DRS proved to be a suitable technique to disclose the influence of the ordering of the host surface and its chemical modification on the guest behavior, and, through conductivity depletion, it provides a mean to monitor the guest entrance inside the pores, easily followed even by untrained spectroscopists.

MCM-41 modified heterogeneous catalysts from rice husk for selective oxidation of styrene into benzaldehyde

This study examined the preparation of MCM-41, Ni-MCM-41 and Co-MCM-41 from silica extracted from rice husk ash (RHA) via sol–gel technique. The materials were characterized by X-ray Diffraction (XRD), Transmission Electron Microscopy (TEM), Fourier Transform Infrared Spectroscopy (FT-IR), Diffuse reflectance UV–Vis (DR/UV–Vis),Energy Dispersive X-ray Spectrometry (EDX), N 2 adsorption–desorption and NH 3 TPD. XRD and TEM analyses showed reduction in the long range order upon the introduction of heteroatoms into MCM-41 framework. Successful substitution of Si 4 + with metal cations was verified by the shifting in the siloxane (Si-O-Si) bond. Presence of nickel phyllosilicates was evidenced from the FT-IR and DR/UV–Vis investigations. Mesoporous behavior with capillary condensation was unchanged even after the incorporation of Ni and Co species into the MCM-41 matrix. MCM-41 and modified MCM-41 catalysts were evaluated in the liquid-phase oxidation of styrene for 4 h under the influence of reaction parameters such as reaction temperature, catalyst loading, types of solvent and molar ratio of styrene : H 2 O 2 . Under the optimum condition of 343 K, 0.20 g catalyst, 1:4 molar ratios and DMF as the reaction medium, the activity was found to increase following the trend: Ni-MCM-41 (79.9%) >Co-MCM-41(56.6%) > MCM-41 (40.7%). Benzaldehyde was the sole product over Ni-MCM-41 and Co-MCM-41 while MCM-41 gave benzaldehyde (96.0%) and styrene oxide (4.0%). Surface characteristics and TPD acidity strength was found to govern the catalysis. Negligible leaching (0.448 ppm) and exceptional activity during successive reruns demonstrates that Ni-MCM-41 was beyond doubt, heterogeneous in nature. This research signifies a successful conversion of waste biomass into value added products. • Cobalt and nickel supported MCM-41 catalysts were synthesized from rice husk. • The catalyst was active in the oxidation of styrene at mild condition. • Benzaldehyde was the sole product over the modified MCM-41 catalysts. • The catalysis of Ni-MCM-41 was heterogeneous in nature with minor leaching. • Successful conversion of waste biomass into benign product.

Effects of synthesis methods on performance of CuZn/MCM-41 catalysts in methanol steam reforming

CuZn-based catalysts are active in production of hydrogen by methanol steam reforming. However, there is a need to have further insight on their physico-chemical properties to improve selectivity to hydrogen. Therefore, a series of CuZn/MCM-41 catalysts was synthesized by four different routes; one pot hydrothermal synthesis (OPMCM), co-impregnation (COMCM), serial impregnation (SRMCM) and copper impregnated on Zn-MCM-41 (ZNMCM). Samples of catalysts were characterized by X-ray diffraction (XRD), transmission electron microscopy (TEM), scanning electron microscopy (SEM) coupled with energy dispersive X-ray spectroscopy (EDS), inductively coupled plasma (ICP) emission spectrometry, Fourier transform infrared (FTIR) spectroscopy, thermogravimetric analysis (TGA) and X-ray photoelectron spectroscopy (XPS). XRD revealed disruption in the ordered pore network typical in MCM-41 for all catalysts synthesized and also showed that the one pot synthesis catalyst had wide spread dispersion of Cu and Zn. SEM micrographs captured irregularly shaped particles of different sizes. While XPS showed that different Cu and Zn species were formed within the catalyst matrix. XPS also confirmed that there was wide spread dispersion and interaction of Cu and Zn with MCM-41 matrix in the OPMCM catalyst. COMCM and OPMCM demonstrated the highest activity with 88 and 65% methanol conversion with corresponding H2 selectivity of 91 and 86% respectively. They are better than SRMCM and ZNMCM which had average H2 selectivity of 19% and 31% respectively. CO selectivity was less than 1.8% for the COMCM and OPMCM catalysts. While SRMCM and ZNMCM had CO selectivity's as high as 8.9% and 7.2% respectively. The data generated shows that catalytic activity is largely affected by the nature of Cu species within the catalyst matrix.

Regulation of the size of metal iron nanoparticles in channels of mesoporous silica matrices (MCM-41, SBA-15) and structure and magnetic properties of the received nanocomposites МСМ-41/Fe0 and SBA-15/Fe0

In modern methods of synthesis of nanostructured materials based on mesoporous silica matrices (MCM-41, SBA-15), it is not possible to simultaneously fine adjust both the pore diameter and the thickness of the separating walls. This article presents the results of work on the creation of composites based on mesoporous silica matrices MCM-41 and SBA-15, reinforced with metallic Fe nanoparticles (Fe NPs). The article considers a new way of ultrafine regulation of the pore radius and separating wall thickness mesoporous silica SBA-15. In this work, we studied the changes in their structural and magnetic characteristics by directionally adjusting the geometric parameters of the porous structure of the initial matrices. The following methods are applied to adjust the silica pore parameters: hydrothermal treatment and templating using a micellar expander. The technique is based on building up aluminum-oxygen nanolayers on the pore walls using gas-phase atomic layer deposition technique (ALD). Studying room-temperature magnetization of Fe NPs obtained during the synthesis in a matrix of mesoporous silica MCM-41 (pore size of 3–5 nm) allowed us to establish superparamagnetic properties of such magnetic materials, which allows to use them in medicine for targeted drug delivery. Fe NPs in the mesoporous silica SBA-15 matrix with a pore size of 3–6 nm also exhibit superparamagnetic properties, and these composites showed a coercive force increase with an increase in the original matrix pore size.

Synthesis, Characterization and Mechanical Properties of Nanocomposites Based on Novel Carbon Nanowires and Polystyrene

Carbon into polymer nanocomposite is so far a common additive for the enhancement of the polymer properties. The properties of the polymer, such as thermal, and especially its mechanical properties, are improved by the homogeneously dispersed carbon nanoparticles on the polymer matrix. In this study, carbon wires in nano dimensions are, for the very first time, synthesized via the hard templating method from the silicate matrix MCM-41, and used as nano additives of polystyrene. The carbon nanowires were chemically oxidized, and further modified by attaching octadecylamine molecules, for the development of organic functionalities onto carbon nanowires surface. The nanocomposite materials of polystyrene with the modified carbon nanowires were prepared by a solution-precipitation method at three nano additive to polymer loadings (1, 3 and 5 wt%). The as-derived nanocomposites were studied with a combination of characterization and analytical techniques. The results showed that the thermal and mechanical properties of the polystyrene nanocomposites gradually improved while increasing nano-additive loading until 3 wt%. More specifically, the 3 wt% loading sample showed the best mechanical properties, while the 5 wt% sample was difficult to achieve satisfactory dispersion of carbon nanowires and consequently has a wide range of values.

The Nano-Confinement Effect on the SCO Behavior of [Fe(NH2trz)3](NO3)2 1D Chains in MCM-41

A polymeric chain spin-crossover (SCO) compound [Fe(NH2trz)3](NO3)2 was embedded in the pores of mesoporous silica MCM-41, which yielded an M@S composite. The obtained material was characterized by infrared spectrometry, powder X-ray diffractometry, gas sorption studies, electron microscopy, and atomic absorption. The temperature-induced SCO behavior of the composite was monitored by temperature-variable magnetic measurement. The results indicate that the spin transition curve of the composite was evidently shifted to a higher temperature in comparison to bulk [Fe(NH2trz)3](NO3)2. The shift in the transition temperature for M@S [versus bulk [Fe(NH2trz)3](NO3)2] amounted to Tc↑ = 362 K [347 K] and Tc↓ = 327 K [314 K] (magnetic data). The significant difference in the SCO behavior of [Fe(NH2trz)3](NO3)2 when embedded in the MCM-41 matrix may be attributed to the strengthened cooperativity of compound S and the nano-confinement pressure of SiO2 walls.

Effects of synergetic effect between Co and γ-Fe2O3 in confined silica matrix of MCM-41 on the formation of free radicals for the advanced oxidation technology

For the advanced oxidation processes (AOPs), the kind of active radicals is closely linked with the catalytic performance, and thus the formation of free radicals is a key step during the reaction process. In this study, the bi-component catalyst of γ-Fe2O3@Co-MCM-41 were successfully prepared by a facile one-pot hydrothermal method, and the synergetic effect between γ-Fe2O3 and Co is terrified to be the important factor for the stimulation of different radicals. The results demonstrate that cobalt (II) species are incorporated in the framework, while the magnetic γ-Fe2O3 are encapsulated in the silica matrix of MCM-41. Notably, the obvious synergetic effect is built between cobalt and γ-Fe2O3 at the adjacent locations inside the silica matrix, and the iron oxides are more reducible. In the peroxymonosulfate(PMS)/Catalyst system, this synergetic effect in γ-Fe2O3@2Co-MCM-41 stimulates more reactive radicals of SO4− and OH, while 2Co/γ-Fe2O3@MCM-41 mainly produces SO4−. Both SO4− and OH radicals are confirmed to be of great advantage to AOPs, thus the γ-Fe2O3@2Co-MCM-41 catalyst displays the highest degradation efficiency (0.0778 min−1) in Orange II degradation, which is over three times higher than that of 2Co/γ-Fe2O3@MCM-41, and the reasonable reaction mechanism is proposed.

Improving oxygen sensing performance via inner-molecular π-π stacking in a series of phosphorescent Cu(I) complexes.

In this paper, six phosphorescent Cu(I) complexes with three diamine ligands and two phosphorous ligands were prepared. Detailed discussion was performed on these complexes, including single crystals, quantum mechanics theoretical calculation, absorption spectra, emission spectra, emission quantum yields and excited state decay dynamics. Large conjugation planes and π-π stacking were found in these complexes. Their emission was originated from MLCT excited state. Long-lived emissive center was observed due to this MLCT-based decay and the help from π-π stacking. Such long-lived emissive state and the large conjugation planes in these complexes offered enough collision probability with O2 molecules, making themselves potential oxygen sensing probes. These six complexes were then doped into silica supporting matrix MCM-41 spheres. The resulting composite samples and their emission sensing response towards O2 were discussed in detail. The optimal sample showed sensitivity as high as 7.80 with response time of 14s. A careful discussion between Cu(I) complex molecular structure and sensing performance was performed. It was concluded that both a long lifetime and a large conjugation plane lead to improved sensing sensitivity since they increased the collision probability with O2 molecules. On the other hand, it was found that both sensing response and recovery times were mainly controlled by O2 diffusion in supporting matrix.

Preparation and Application of CuO@RHA/MCM-41 Nanocomposite for the Synthesis of Fused pyrano[4,3-b]chromenones

An efficient procedure for the synthesis of fused pyrano[4,3-b]chromene derivatives via three-component condensation reaction of aromatic aldehydes, 2-naphthol and 4-hydroxycoumarin, using CuO@RHA/MCM-41 nanocomposite at room temperature, is described. This nanocomposite consists of CuO nanoparticles and MCM-41 matrix obtained from Rice Husk Ash (RHA). This method provides several advantages, such as simple work-up, eco-friendly procedure and short reaction time along with high yields. All of synthesized compounds were characterized by IR, NMR and Elemental analyses.

Dynamics of Confined Short-Chain alkanol in MCM-41 by Dielectric Spectroscopy: Effects of matrix and system Treatments and Filling Factor.

The dynamics of n-propanol confined in regular MCM-41 matrix with the pore size Dpore = 40 Å, under various matrix conditioning and sample confining conditions, using broadband dielectric spectroscopy (BDS), is reported. First, various drying procedures with the capacitor filling under air or N2 influence the BDS spectra of the empty MCM-41 and the confined n-PrOH/MCM-41 systems, but have a little effect on the maximum relaxation time of the main process. Finally, various filling factors of n-PrOH medium in the optimally treated MCM-41 system lead to unimodal or bimodal spectra interpreted in terms of the two distinct dynamic phases in the confined states.

Fischer-Tropsch studies in a 3D-printed stainless steel microchannel microreactor coated with cobalt-based bimetallic-MCM-41 catalysts

Fischer-Tropsch (FT) synthesis was carried out using 3D-printed stainless steel (SS) microreactors, containing channels of dimensions 500 μm × 500 μm ×2.7 cm, to study the effect of Fe, Ru, and Ni on Co-MCM-41 catalyst. The mono and bimetallic cobalt-based catalysts: 15 % Co-MCM-41, 10 %Co5% Ru MCM-41, 10 %Co 5%Ni MCM-41, and 10 %Co 5%Fe MCM-41 were synthesized using one-pot hydrothermal method and characterized by SEM-EDX, TEM, TPR, FTIR, XPS, and low and wide angle XRD techniques. All the catalysts exhibited high surface area without the loss of ordered mesoporous structure as confirmed by large BET surface areas (400- 1000 m2/g) and low angle XRD data. The metal nanoparticles were in the range of 35−50 nm and well dispersed in a hexagonal matrix of MCM-41. TPR data indicate that all other metal oxides except that of cobalt can be reduced with H2 below 600 °C. Cobalt is present most likely as cobalt silicates that can only be reduced with H2 at a temperature over 650 °C. The microchannels of SS reactor were uniformly coated by dip coating a slurry of the catalyst with polyvinyl alcohol (PVA). The catalytic performance for FT synthesis was carried out in the SS microreactor at atmospheric pressure in the temperature range of 180–300 °C with H2/CO molar ratio of 3. Incorporation of the second metal in the Co-MCM-41 framework and the operating temperature had a significant effect on CO conversion and selectivity towards C1-C4 alkanes in FT synthesis. While the highest CO conversion of 74 % was obtained for CoFe-MCM-41 at 240 °C, the highest selectivity towards butane (11 %) and propane (39 %) was observed for CoRu-MCM-41 at 240 °C and CoFe-MCM-41 at 210 °C, respectively. The rate of deactivation of the catalysts -followed the order: CoRu-MCM-41> CoNi-MCM-41> Co-MCM-41> CoFe-MCM-41, indicating that CoFe-MCM-41 is the most suitable catalyst for F–T synthesis in terms of long term stability.

Molecular probe dynamics and free volume heterogeneities in n-propanol confined in a regular MCM-41 matrix by ESR and PALS.

A combined investigation of the spin probe TEMPO mobility and the free volume holes in n-propanol (n-PrOH) confined in a regular virgin MCM-41 matrix by means of ESR or PALS techniques, respectively, is reported. Dynamics of spin probe TEMPO alters at several characteristic ESR temperatures which are close to the characteristic PALS ones reflecting the changes in o-Ps annihilation and the related free volume. Correlations between these characteristic ESR and PALS temperatures indicate the common physical origins of the respective changes in the free volume expansion and the TEMPO mobility in the confined liquid n-PrOH. The significant difference in dynamic heterogeneity of TEMPO after confinement and free volume dispersion reflect the strongly altered structural-dynamic relationships in the confined n-PrOH medium with respect to the bulk situation.

MCM-41-supported Fe(Mn)/Cu bimetallic heterogeneous catalysis for enhanced and recyclable photo-Fenton degradation of methylene blue

Highly efficient bimetallic heterogeneous photo-Fenton catalysts (Fe2O3/CuO@MCM-41, FCM and MnOx/CuO@MCM-41, MCM) have been successfully prepared via wet impregnation over a mesoporous MCM-41 silica support. FESEM images demonstrate that the metal oxides are highly dispersed on the surface of the MCM-41 matrix consisting of the ordered 2D hexagonal mesostructure. XPS results indicate that the bimetallic oxides species in FCM and MCM are Fe2O3, CuO and MnOx, CuO, respectively. The as-prepared dual-heterojunctions have a significant enhancement of catalytic activities under visible light, compared with the material containing monometal, and prevents the leaching of metal ions species. The degradation efficiencies of MB can be up to 99.65% and 98.22% within 45 min irradiation for FCM1:2 and MCM1:0.5, respectively. And the degradation efficiencies still can reach up to 92% after 10 cycles. Moreover, the synthesized bimetallic dual-heterojunctions catalysts can be employed in very mild condition, and little difference in catalytic effect was observed under different pH value (3.0–9.0). The improved photocatalytic activity can be ascribed to the sufficient interfacial contact between different components for photo energy transfer and e−/h+ pairs separation, which greatly enhance cycle reaction of Fe3+/Fe2+ or Mn4+/Mn3+/Mn2+ after introducing CuO. This research provides a new approach for the development of an effective heterogeneous photo-induced Fenton (Fenton like) catalyst with vast potential for organic pollutant removal.

MCM-41-supported vanadium catalysts structurally modified with Al or Zr for thiophene hydrodesulfurization

Vanadium catalysts supported on Al(Zr)-MCM-41-type materials were prepared by impregnation. Textural and structural properties, elemental composition and electronic structure were determined by N2 physisorption, small-angle XRD, SEM–EDX and UV–vis DRS, respectively. Al-containing materials showed mostly of Al framework and a small fraction of Al extra-framework species. Zr-containing materials presented almost exclusively small clusters of ZrxOy covering the MCM-41 matrix. Vanadium catalysts, showed the presence of isolated V5+ species and to a lesser extent polymeric chains likely as small crystallites of V2O5. The catalytic results revealed that VAlM30 catalyst, characterized by a Si/Al atomic ratio of 30, was the most active in thiophene hydrodesulfurization, which could be associated to better textural properties and high dispersion of the vanadium species.

Effect of phosphorus and mesopore modification on the HZSM-5 zeolites for n-decane cracking

The objective of this work is to investigate the catalytic effect of a series of modified HZSM-5 zeolites on n-decane cracking at 500 °C and atmospheric pressure. The zeolite catalysts were prepared with phosphorus and/or mesopore modification by excessive impregnation and/or hydrothermal treatment, and were characterized with various methods including SEM, TEM, XRD, FTIR, N2 adsorption-desorption measurement and NH3-TPD. Results show that the addition of phosphorus adjusted the distribution and strength of acid sites in the zeolite crystals. The introduced mesoporous structure improved the diffusion of reactants and products in zeolite pores during n-decane cracking. With appropriate acid amounts and distribution, as well as short channels and high specific surface area, the modified HZSM-5 nanoparticles exhibited higher catalytic activity, better light olefins selectivity and longer lifetime, compared with the original HZSM-5 zeolite. The phosphorus modified HZSM-5 zeolites coupling with MCM-41 matrix was proved to be a promising catalyst for the thermal cracking of n-decane.