Synthesis of Mesoporous Molecular Sieve MCM-41 in Extremely Dense System

Mesoporous molecular sieve MCM-41 has been synthesized in the extremely dense system (with H2O/Si<10) and characterized by XRD, N-2 adsorption isotherm as well as probe reactions of cracking of cumene and isomerization of o-xylene.

Synthesis of Mesoporous Silica Molecular Sieves via a NovelTemplating Scheme

Mesoporous silica molecular sieves have been synthesized under mild conditions by using in situ prepared N,N-dimethyldodecylamine oxide as template.

Immobilization of Trehalose Synthase on Mesoporous Molecular Sieve

[ Objective] This study aimed to explore the immobitizatian of trehalose synthase on mesoporous molecular sieves. [ Method] With trehalose synthase produced by genetically engineered bacteria as experimental material, rnesoporous molecular sieve MCM-41 was used as a carrier for immobilization of trehalase syn- thase. Properties of trehalose synthase before and after immobilization were compared. [ Result ] Trehalose synthase could be immohihzed on mesoporous molecular sieve MCM-41 by using physical adsorption method. Immobilization of trehalose synthase achieved the best effect at pH 3.0, with enzyme amount of 62.5 mg/g and immobilization duration of 12 h. Compared with the free u, ehalose synthase, immobilized trehalose synthase showed significantly improved pH stability and thermal stability with repeatable operation, which was conducive to the utilization and storage of enzyme. [ Conclusion] This study provided theoretical basis for the devel- opment of new immobilized trehalose synthase.

Mesoporous molecular sieve confined phase change materials with high absorption,enhanced thermal conductivity,and cooling energy charging/discharging capacity

The biggest challenge for organic phase change materials(PCMs)used in cold energy storage is to maintain high heat storage capacity while reducing the leakage risk of PCMs during the phase transition process.This is crucial for expanding their applications in the more demanding cold storage field.In this study,novel formstable low-temperature composite PCMs are prepared with mesoporous materials,namely SBA-15 and CMK-3(which are prepared using the template method),as supporting matrices and dodecane as the PCM.Owing to the combined effects of capillary forces within mesoporous materials and interactions among dodecane molecules,both dodecane/SBA-15 and dodecane/CMK-3 exhibit outstanding shape stability and thermal cycling stability even after 200 heating/cooling cycles.In comparison to those of dodecane/SBA-15,dodecane/CMK-3 exhibits superior cold storage performance and higher thermal conductivity.Specifically,the phase transition temperature of dodecane/CMK-3 is-8.81℃ with a latent heat of 122.4 J·g^(-1).Additionally,it has a thermal conductivity of 1.21 W·m^(-1)·K^(-1),which is 9.45 times that of dodecane alone.All these highlight its significant potential for applications in the area of cold energy storage.

ENCAPSULATION OF STRONG SOLID ACID NANOPARTICLES IN MESOPOROUS CHANNEL HOSTS

Mesoporous molecular sieve with Al-promoted sulfated rirconia (SZA) based strong solid acid nano-particles within its mesoporous channels was synthesized by using a one-step incipient wetness impregnation method with zirconium sulfate and aluminum sulfate as the precursors. The assemblies of SZA/MCM-41 were obtained by thermal decomposition of the precursors in air.The resultant composite was characterized with various techniques such as nitrogen physisorption, X-ray diffraction, SEM and TEM. It was shown that the well-ordered channels of MCM-41 arranged in hexagonal arrays as well as the hollow tubular morphology was retained. The strong solid acid nanoparticles were isolated born each other and highly, dispersed in the channels. Nitrogen sorption showed the expected decrease in pore volume. The catalytic activity of SZA/MCM-41 composite in the isomerization of n-butane was dramatically improved in comparison to bulk SZA or SZA/silica.

Structrue and Characteristics of Mesoporous Silica Synthesized in Acid Medium and Its Reaction Mechanism

Structrue and pore characteristics of the mesoporous silica synthesized in acid medium were studied by means of XRD, HRTEM, BET, FT-IR, DSC-TGA, and the reaction mechanism was also investigated deeply. The results show that mesopores in the sample possess hexagonal arrays obviously, whereas the structure of silica matrix is amorphous. The results also show that the acting mode of silica and CTMA+ inside the mesopores was chemical bonding force. The structure of mesoporous silica was mainly dependent on the aggregational condition of micelle of CTMA+ as well as their liquid-crystallized status. In addition, condensation and dehydration of silicate radicals were accompanied in the process of calcination, which resulted in the mesoporous structure ordered in local range and the pore sizes largening.

Large Pore Mesoporous MCM-41 Templated from Cetyltriethylammonium Bromide

Following hydrothermal synthesis process, MCM-41 was synthesized by using cetyltriethylammonium bromide as templating agent. The experimental results showed that MCM-41 with pore diameter in the range of 4-7 nm can be obtained by adjusting nsurf/nsi. It was proved that cetyltriethylammonium bromide is an effective templating agent for increasing pore diameter of molecular sieve MCM-41.

Mesoporous molecular sieve-based materials for catalytic oxidation of VOC: A review

As the main contributor of the formation of particulate matter as well as ozone, volatile organic compounds(VOCs) greatly affect human health and the environmental quality. Catalytic combustion/oxidation has been viewed as an efficient, economically feasible and environmentally friendly way for the elimination of VOCs. Supported metal catalyst is the preferred type of catalysts applied for VOCs catalytic combustion because of the synergy between active components and support as well as its flexibility in the composition. The presence of support not only plays the role of keeping the catalyst with good stability and mechanical strength, but also provides a large specific surface for the good dispersion of active components, which could effectively improve the performance of catalyst as well as decrease the usage of active components, especially the noble metal amount. Mesoporous molecular sieves, owing to their large surface area, unique porous structures, large pore size as well as uniform pore-size distribution, were viewed as superior support for dispersing active components. This review focuses on the recent development of mesoporous molecular sieve supported metal catalysts and their application in catalytic oxidation of VOCs. The effect of active component types, support structure, preparation method, precursors, etc. on the valence state, dispersion as well as the loading of active species were also discussed and summarized. Moreover, the corresponding conversion route of VOCs was also addressed.This review aims to provide some enlightment for designing the supported metal catalysts with superior activity and stability for VOCs removal.

CO2 capture over molecular basket sorbents:Effects of SiO2 supports and PEG additive

The objective of this work is to study the influences of silica supports and PEG additive on the sorption performance of molecular basket sorbent（MBS） for COcapture consisting of polyethylenimine and one of the following supports: SBA-15（2-D structure）, TUD-1（3-D sponge-like structure） and fumed silica HS-5（3-D disordered structure）. Effects of the supports regarding pore structures and pore properties, the PEI loading amount as well as the sorption temperature were examined. Furthermore, polyethylene glycol（PEG） was introduced as an additive into the sorbents and its effect was investigated at different PEI loadings and sorption temperatures. The results suggest that the pore properties of MBS（after PEI loading） play a more important role in the COsorption capacity, rather than those of the supports alone.MBS with 3D pore structure exhibits higher COsorption capacity and amine efficiency than those with 2D-structured support. Among the sorbents studied, fumed silica（HS-5） based MBS showed the highest COsorption capacity in the temperature range of 30-95 °C, probably due to its unique interstitial pores formed by the aggregation of polymer-loaded SiOparticles. It was found that the temperature dependence is directly related to the PEI surface coverage layers. The more PEI surface coverage layers, the higher diffusion barrier for COand the stronger temperature dependence of COcapacity. 3D MBS exceeds 2D MBS at the same PEI coverage layers due to lower diffusion barrier. Adding PEG can significantly enhance the COsorption capacity and improve amine efficiency of all MBS, most likely by alleviating the diffusion barrier within PEI bulk layers through the inter-molecular interaction between PEI and PEG.

Immobilization of acetylcholinesterase on functionalized SBA-15 mesoporous molecular sieve for detection of organophosphorus and carbamate pesticide

The immobilization of acetylcholinesterase （ACHE） on amino functionalized SBA-15 mesoporous sieves （NH2-SBA-15） was explored for detection of organophosphorus and carhamate pesticides. Several methods have been studied and the ＂adsorption-crosslinking＂ is found to be the best one. Firstly, AChE and bovine serum albumin （BSA） were adsorbed in turn on the surface of NH2-SBA-15 by electrostatic adsorption, and then glutaraldehyde was added for cross-linking the amino group of AChE. The NH2-SBA- 15 showed around 95% immobilization efficiency and the specific activity of immobilized AChE （ACHE- NH2-SBA-15） reached 130% relative to free AChE under optimal immobilization conditions. It was found AChE-NH2-SBA-15 retained 94.0% and 82.8% of its initial activity after 60days at 4℃ and 25℃, respectively. It remained 55.0% of its initial activity after 6 times recycling. During the detection of pesticide, the AChE-NH2-SBA-15 showed wider linear range and much lower limit of detection compared with free ACHE. The current method showed good recovery （93.8%-109.3%） and low RSD （〈5%） for both standard solution and real vegetable samples of Carbaryl and Trichlorfon. It was believed that AChE-NH2- SBA- 15 could be exploited as a fast, sensitive and low-cost biocatalyst towards the detection of pesticides residues which could be stored at room temperature for a long time.

Ti incorporation in MCM-41 mesoporous molecular sieves using hydrothermal synthesis

Abstract Titanium-containing mesoporous materials （Ti-MCM-41） were obtained by hydrothennal synthesis. Such materials are active catalysts for the transesterifica- tion of dimethyl oxalate and phenol to produce diphenyl oxalate. To understand the role of the Ti in the catalytic process, Ti-MCM-41 samples with different Si/Ti ratios （from 5 to 100） were prepared and the samples were analyzed by Fourier transform infrared spectroscopy, UV- visible spectroscopy, and ammonia temperature pro- grammed desorption. It was concluded that the Ti is incorporated into the framework of the MCM-41 and formed weak Lewis acid sites. In addition, the number of Ti（IV） sites increased as the amount of titanium increased. X-ray powder diffraction, N2 adsorpfion-desorption and transmission electron microscopy results showed that the Ti-MCM-41 samples have a hexagonal arrangement of mono-dimensional pores. A large number of Ti（IV） sites coupled with the mesoporous structure and large pore diameters are favorable for the transesterification catalytic properties of Ti-MCM-41.

Direct Immobilization of Phosphine-Rhodium Complex on MCM-41 for Propene Hydroformylation

MCM 41 molecular sieve supported Rh PPh 3 catalysts were prepared by the in situ assembling of the metal complex from smaller moieties of Rh(acac)(CO) 2 and ligand of PPh 3. The resulted guest/host materials(Rh PPh 3/MCM 41) were characterized by X ray powder diffraction, FTIR and 31 P( 1H) NMR, and served as catalysts for propene hydroformylation. The results showed negligible change in MCM 41 framework after propene hydroformylation at 393 K. Higher hydroformylation activities were obtained on Rh PPh 3/MCM 41 catalysts compared to that on Rh PPh 3/SiO 2.

Effect of synthesis conditions on particle size of HMS

HMS mesoporous molecular sieve was synthesized hydrothermally by using dodecylamine （DDA） as template and tetethylorthosilicalite （TEOS） as silicon source. The influence of the hydrothermal synthesis conditions on HMS particle size was studied systematically. The results showed that the smaller particle was obtained under the condition of DDA/SiO2=0.27, H2O/SiO2=66.7, EtOH/SiO2=6.5 mol and synthesis time of 18 h. The presences of additives （TW20, TW60, SP60 and Neopelex） also helped to the reduction of particle size. The HMS mesoporous molecular sieve with particle size around 60-100 nm was obtained by using TW20 or TW60 as an additive. In addition, TEM image showed that HMS mesoporous molecular sieve with pariticle size about 20-100 nm was synthesized in microemulsion.

MCM-41 Prepared with Ionic Liquid and Cethytrimethylammonium Bromide as Co-templates

The mesoporous molecular sieves MCM-41 were prepared using room tempera-ture ionic liquid （RTIL） synthesized in laboratory and cethytrimethylammonium bromide （CTAB） as compound templates for the first time. They were prepared under low aging temperature and short aging time. Via characterizing by XRD and nitrogen adsorption instrument, MCM-41 synthesized by this new method exhibited good crystal structure and narrow pore distribution. The following pre-paratory conditions was optimal： the molar ratio of RTIL to CTAB was 1.0∶1.0, aging at 80 ℃, for 40 h and calcined at 540 ℃. It is found that the acidified MCM-41 improves its activity as catalyst over the unmodified ones.

Effect of Templates on the Structure and Stability of Ti-TMS

Pure Mesoporous TiO2 molecular sieves (Ti-TMS) were synthesized with different templates for the first time and the templates can be successfully removed by refluxing the samples in the EtOH/H2O/KOH solution. The XRD pattern and TEM confirm that the uniformity and stability of Ti-TMS2 synthesized with dodecylamine as template is obviously inferior to that of Ti-TMS1 prepared with dodecylphosphate and hexadecylphosphate as templates. Furthermore, after the templates were removed, the mesostructure of Ti-TMS1 was preserved to a great degree than that of Ti-TMS2.

Thermal decomposition of poly(ethylene terephthalate)/mesoporous molecular sieve composites

The nonisothermal and isothermal degradation processes of poly(ethylene terephthalate)/mesoporous molecular sieve(PET/MMS)composites synthesized by in-situ polymerization were studied by using thermogravimetric analysis in nitrogen.The nonisothermal degradation of the composite is found to be the first-order reaction.An iso-conversional procedure developed by Ozawa is used to calcu-late the apparent activation energy(E),which is an average value of about 260 kJ/mol with the weight conversion from 0%to 30%,and is higher than that of neat PET.Isothermal degradation results are confirmed with the nonisothermal process,in which PET/MMS showed higher thermal stability than neat PET.The polymer in mesoporous channels has more stability due to the protection of the inorganic pore-wall.These results indicate that mesoporous MMS in PET/MMS composites improve the stability of the polymer.

Synthesis of nano SnO2-coupled mesoporous molecular sieve titanium phosphate as a recyclable photocatalyst for efficient decomposition of 2,4-dichlorophenol

It is essential to develop a cheap, recyclable, and efficient photocatalyst to help degrade pollutants contaminating the environment. Herein, mesoporous molecular sieve titanium phosphate （MMS-TiP） was used as an efficient nano-photocatalyst to degrade 2,4-dichlorophenol （2,4-DCP） and to oxidize CO. The catalyst was successfully synthesized by a simple and convenient hydrothermal method in the presence of a tri-block copolymer surfactant. Exceptional photoactivity of the optimized MMS-TiP mainly depends on its porous structure, with a large surface area by means of O2 temperature-programmed desorption curves and fluorescence spectra related to the amounts of produced hydroxyl radical. Interestingly, the photocatalytic activity of the prepared MMS-TiP could be greatly improved by coupling with nanocrystalline SnO2. This is likely due to the increase in the lifetime and separation of photogenerated charges by transferring electrons to SnO2 and was observed by steady-state surface photovoltage spectra and time-resolved surface photovoltage responses. The SnOa-coupled MMS-TiP exhibits better photocatalytic performance for 2,4-DCP degradation and better self-settlement than those of the commercial catalyst P25 TiO2. Moreover, it was confirmed by radical-trapping experiments that ·O2^- is the main activated species for the photocatalytic degradation of 2,4-DCP, and is photogenerated by electron transfer from MMS-TiP to SnO2. Furthermore, the main intermediates in the degradation of 2,4-DCP, like parachlorophenol superoxide and 1,2-benzenediol superoxide radicals, were detected, and a possible decomposition pathway related to ·O2^- attack is proposed. These experimental results provide new strategies for developing a recyclable molecular sieve- based nano-photocatalyst with high photocatalytic activity for environmental remediation.