Self-Bonded Zeolite Beta/MCM-41 Composite Spheres

Self-bonded zeolite Beta/MCM-41 composite spheres were prepared using a two-step synthesis procedure. In the first step, mesoporous zeolite Beta spheres were obtained using anion exchange resin as macrotemplate. In the second step, the MCM-41 or Al-MCM-41 was grown both on sphere surfaces and in the pore structure of the pre-formed zeolite Beta spheres. Finally, the templating agents used in the synthesis of mesophase were removed by calcination leaving behind self-bonded Beta/MCM-41 composite spheres. Beta/MCM-41 composites were characterized by XRD, SEM and nitrogen adsorption measurements. Materials with controlled macroshape, composition and complex porosity were prepared by the approach.     

Preparation and characterization of Beta/MCM-41composite zeolite with a stepwise-distributed pore structure

A Beta/MCM-41 composite zeolite with a stepwise-distributed pore structure was prepared with a silica-alumina source originated from alkaline treatment of zeolite Beta. The material was characterized by various techniques. The results indicated that this composite possesses a mesopore system of MCM-41 and the microporous structure of Beta zeolite. Hydrothermal stability and acidity was improved over MCM-41 due to the introduction of Beta building units into the mesopore walls. The composite was used as the support of a Pd-Pt catalyst for the hydrogenation of naphthalene in the presence and absence of 4, 6-dimethyldibenzothiophene. It was demonstrated that the catalyst has an enhanced activity and sulfur tolerance during naphthalene hydrogenation.     

Synthesis of Ru-modified MCM-41 Mesoporous Material, Y and Beta Zeolite Catalysts for Ring Opening of Decalin

Ru modified MCM-41 mesoporous material, Y and Beta zeolites were synthesized, characterized and investigated in ring opening of decalin. Ru-MCM-41 catalysts were prepared using ion-exchange, impregnation and in situ synthesis methods. Ru-MCM-41, Ru-Y and Ru-Beta zeolite catalysts were characterized using XRD, SEM, EDXA, FTIR, XRF and nitrogen adsorption. Ru modification of MCM-41, Y and Beta zeolites did not influence the parent phase purity of materials. Microporous H-Beta and H-Y catalysts showed larger number of Brønsted acid sites than H-MCM-41 mesoporous material. Method of Ru introduction in MCM-41 was observed to influence conversion of ring opening of decalin and selectivity to ring opening products. Ru-MCM-41-IE catalyst prepared by ion-exchange method exhibited higher conversion of decalin than Ru-MCM-41-IMP and Ru-MCM-41-IS catalysts prepared by impregnation and in situ synthesis methods. Ru-MCM-41-IS catalyst prepared by in situ method showed higher selectivity to ring opening products than Ru-MCM-41-IE and Ru-MCM-41-IMP catalysts.     

Synthesis and catalytic performance of novel hierachically porous material beta-MCM-48 for diesel hydrodesulfurization

Novel hierachically porous material Beta-MCM-48 was successfully synthesized from Beta zeolite seeds by two-step hydrothermal crystallization method using Cetyltrimethylammonium Bromide as the mesostructure directing agent. Beta-MCM-48 composite synthesized at the optimization conditions possessed Beta microporous structure and cubic Ia $ \overline{ 3} $ 3 ¯ d mesoporous structure simultaneously. Meanwhile, the acidity of Beta-MCM-48 was similar to Beta zeolite and higher than MCM-48 mesoporous material. A series of Al₂O₃-Beta-MCM-48 supported NiMo catalysts with different Beta-MCM-48 contents were prepared by the incipient-wetness impregnation method. The catalytic performances were evaluated using DaQing Fluid Catalytic Cracking diesel as feedstock in a high pressure microreactor. Hydrodesulfurization results indicated that NiMo/Al₂O₃-Beta-MCM-48 catalyst exhibited better activities than that of NiMo/Al₂O₃ traditional catalyst. NiMo/Al₂O₃-Beta-MCM-48 catalyst obtained the highest activity as the Beta-MCM-48 content in the support was 20 wt %, and the corresponding sulfur content of the hydrotreated product reached to 23.02 μg g^?1.     

High activity in catalytic cracking of large molecules over a novel micro-micro/mesoporous silicoaluminophosphate

Abstract  

A novel micro-micro/mesoporous silicoaluminophosphate ZSM-5-SAPO-5/MCM-41 (define as MZS-5) composite material with regular spherical morphology was synthesized through a novel process of the self-assembly of CTAB surfactant micelles with silica-alumina source which originated from the alkaline treatment of ZSM-5 zeolite. The physical properties of the MZS-5 composite material were characterized by XRD, FT-IR, Nitrogen adsorption–desorption, SEM and Py-FTIR techniques. Catalytic tests showed that the MZS-5 composite catalyst exhibited higher catalytic activity compared with the conventional microporous ZSM-5, SAPO-5 zeolite and mesoporous Al-MCM-41 molecular sieve for catalytic cracking of 1,3,5-triisopropylbenzene (TIPB). The remarkable catalytic reactivity of TIPB molecules was mainly attributed to the presence of the hierarchical zeolite structure. In the MZS-5 structure, the mesopores provided pathways for transportation of larger molecules and the microporous ZSM-5 and SAPO-5 zeolite provided acidic sites for catalytic activity.     

Pilot synthesis and commercial application in FCC catalyst of MCM-41 zeolite

MCM-41 zeolite in the grade of 600 kg was successfully synthesized and the MCM-41 added FCC catalyst was firstly prepared. The results indicate that the pilot samples of mesoporous Al-MCM-41 bear the typically uniform mesopore structure and considerable acidity and hydrothermal stability. The MCM-41 added FCC catalyst is positively capable to crack heavy oil feedstock, in which the yields of the diesel and lighter oil increased 1.85 and 3.47%, respectively and coke yield decreased 0.29%. Commercial application in FCCU indicate that optimization of nanopores of MCM-41 added faujasite zeolite might result in an industrial process to design novel FCC catalysts.     

Dimerization of 1-butene in liquid phase reaction: Influence of structure, pore size and acidity of Beta zeolite and MCM-41 mesoporous material

Dimerization of 1-butene in liquid phase was studied over H-Beta zeolite catalyst and MCM-41 mesoporous material in an autoclave at temperature of 473 K and at pressure of 20 bar using n-heptane as a solvent. Liquid phase product analysis was carried out using GC-MS and a pattern recognition technique, Soft Independent Modeling of Class Analogy (SIMCA). Acidity of the catalysts was determined by FTIR, phase purity using X-ray powder diffraction, surface area by nitrogen adsorption and morphology of zeolite and mesoporous material crystals using scanning electron microscope. Influence of acidity, pore size and structure of H-Beta zeolite and H-MCM-41 mesoporous material on the conversion of n-butene and selectivity to C₈ hydrocarbon such as 2,2,4-trimethylpentene, dimethylpentene and 2-methylpentene was investigated. H-MCM-41 mesoporous material exhibited higher selectivities to C₈ hydrocarbons than H-Beta zeolite catalyst. However, conversion of n-butene was higher over H-Beta zeolite catalyst than H-MCM-41 mesoporous material.     

Efficient catalysis of mesoporous Al-MCM-41 for Mukaiyama aldol reactions

Mesoporous aluminosilicates, Al-MCM-41 (Si/Al = 20 and 50), efficiently catalyzed Mukaiyama aldol reaction of benzaldehyde with 1-(trimethylsiloxy)cyclohexene in CH₂Cl₂ at 0 °C to afford the corresponding β-trimethylsiloxy ketone in quantitative yield. On the other hand, mesoporous silica (MCM-41), amorphous SiO₂–Al₂O₃, and H–Y and H-ZSM-5 zeolites barely catalyzed the reaction. Additionally, the less ordered Al-MCM-41 prepared by mechanical compression exhibited much lower catalytic activity compared with Al-MCM-41, indicating that the presence of the ordered mesoporous structure in aluminosilicates is crucial for the catalysis. The Al-MCM-41 catalyzed Mukaiyama aldol reaction was applicable to a wide range of aldehydes and silyl enol ethers. Furthermore, the Al-MCM-41 catalyst could be recycled at least three times without any loss in the yield. Thus, mesoporous aluminosilicates are promising heterogeneous catalysts for fine chemicals synthesis.     

The preparation of Fe<Superscript>3+</Superscript> ion-exchanged mesopore containing ZSM-5 molecular sieves and its high catalytic activity in the hydroxylation of phenol

A series of Fe³⁺ containing catalysts were synthesized using ion-exchange technique over hierarchically porous ZSM-5 (M-ZSM-5) and micro-mesoporous composite ZSM-5/MCM-41 (ZSM-5/MCM-41), respectively. The prepared catalysts were characterized by X-ray diffraction, scanning electron microscope, transmission electron microscope, N₂ adsorption–desorption, UV–Vis spectroscopy, temperature programmed reduction and inductively coupled plasma-optical emission spectroscopy. The characterization results exhibit that the hierarchically porous ZSM-5 was synthesized with intracrystalline mesopores, while the micro-mesoporous composite ZSM-5/MCM-41 was prepared with the well-ordered mesopores. Furthermore, the results also prove that the existence of iron in the catalysts was mainly presented in the form of Fe³⁺ ions. Catalytic performances of the samples for phenol hydroxylation were compared by using H₂O₂ as oxidant. Under the optimized conditions, Fe³⁺ ion-exchanged M-ZSM-5 (Fe-M-ZSM-5) shows that a phenol conversion of 42.3% obtained with 92.5% selectivity to dihydroxybenzenes, whereas Fe³⁺ ion-exchanged ZSM-5/MCM-41 (Fe-ZSM-5/MCM-41) give 46.2% phenol conversion and 90.1% dihydroxybenzenes selectivity, which are all better than most reported results. The recyclability tests show that Fe-ZSM-5/MCM-41 with ordered mesoporous structure and bigger surface area has better anti-deactivation performance than Fe-M-ZSM-5. The excellent catalytic performances were due to the improved diffusion performance with newly created mesopores and the highly active Fe³⁺ species obtained by ion-exchange technique.     

Efficient catalysis of mesoporous Al-MCM-41 for Mukaiyama aldol reactions

Mesoporous aluminosilicates, Al-MCM-41 (Si/Al = 20 and 50), efficiently catalyzed Mukaiyama aldol reaction of benzaldehyde with 1-(trimethylsiloxy)cyclohexene in CH₂Cl₂ at 0 °C to afford the corresponding β-trimethylsiloxy ketone in quantitative yield. On the other hand, mesoporous silica (MCM-41), amorphous SiO₂–Al₂O₃, and H–Y and H-ZSM-5 zeolites barely catalyzed the reaction. Additionally, the less ordered Al-MCM-41 prepared by mechanical compression exhibited much lower catalytic activity compared with Al-MCM-41, indicating that the presence of the ordered mesoporous structure in aluminosilicates is crucial for the catalysis. The Al-MCM-41 catalyzed Mukaiyama aldol reaction was applicable to a wide range of aldehydes and silyl enol ethers. Furthermore, the Al-MCM-41 catalyst could be recycled at least three times without any loss in the yield. Thus, mesoporous aluminosilicates are promising heterogeneous catalysts for fine chemicals synthesis.     

Synthesis and catalytic performance of a bi-phase core-shell zeolite composite

A zeolite composite Y/Beta with core-shell structure was synthesized by adding tetraethylammonium bromide (TEABr) exchanged NaY zeolite into the pre-reacted mixture used to prepare Beta zeolite. The composite was characterized by XRD, N₂ adsorption, SEM, and FTIR spectra of pyridine. The results show that the composite is composed of a core zeolite Y and a shell of intergrown zeolite Beta crystals, representing dual microporous structures of both Y and Beta zeolites and a new mesoporous structure. The composite has a high activity in n-octane catalytic cracking because of the formation of intergrowths and the change of acidity due to the distorted interface and surface defects.     

Catalytic performance of metal ion doped MCM-41 for methanol dehydration to dimethyl ether

Metal ion doped MCM-41 mesoporous molecular sieves (M-MCM-41, M = Al, Ga, Sn, Zr and Fe) were prepared using a hydrothermal synthesis method, with metal chlorides serving as the dopant sources. The M-MCM-41 structures were characterized by Fourier transform infrared spectroscopic (FTIR) analysis, X-ray diffraction, energy dispersive spectroscopy and N₂ adsorption–desorption measurement. The surface of M-MCM-41 acidities were determined by NH₃ temperature-programmed desorption and pyridine-adsorption FTIR analysis, and their catalytic performance for methanol dehydration to dimethyl ether (DME) was evaluated. The results showed that the prepared M-MCM-41, which exhibited a structure similar to that of MCM-41 with long-range ordered mesoporous structure, contained weak acidic sites. The number of weak acid sites in Al-MCM-41 increased as the Al content increased. The Al content in Al-MCM-41 had an important effect on its catalytic performance, where the highest catalytic activity was 80 and 100 % DME selectivity was achieved at a Si/Al molar ratio of 10. For MCM-41 doped with various types of metal ions, M-MCM-41 (M = Al, Ga, Sn and Zr) also presented a similar wide distribution of acidity, and their catalytic activities were ranked in the following order: Al-MCM-41 > Ga-MCM-41 > Zr-MCM-41 > Fe-MCM-41 > Sn-MCM-41, which were related to the coordination of the metal ions.     

Synthesis of Al-MCM-41 and FCC diesel hydrorefining study

Mesostructured aluminosilicates (MCM-41) with ordered 2-dimensional hexagonal structure were successfully synthesized via the alkali-treatment step and nanocrystal aluminosilicates assembly in the basic and hydrothermal synthesis conditions by sol?Cgel approach. Highly hydrothermally stable MCM-41 coupled with large surface area and pore volume is desirable. To find out the optimum conditions, An orthogonal experiment L₁₆(4³) with three factors and four levels was adopted and the effects were also discussed. Various techniques including X-ray diffraction (XRD), N₂ adsorption-desorption, temperature program desorption and fourier transform infrared spectroscopy were used to monitor the physical?Cchemical properties of MCM-41. When the synthesis was operated under 80?°C lasting 1?h with C_NaOH 0.5?mol/L and molar ratio of CTAB to ZSM-5 0.15, the synthesized MCM-41 possessed high specific surface area 1,150?m²/g, large pore volume 1.23?cm³/g with appropriate acid distribution as well as highly hydrothermal stability. In addition, the results reveal that the as-synthesized samples have a uniform phase without MFI structure. Samples have a 5-membered ring in the framework and have a better hydrothermal stability than the conventional Al-MCM-41. Performance evaluation was carried out on a 20?mL fixed-bed hydrorefining unit with the Daqing FCC diesel as feedstock. The sulfur and nitrogen removal is 99.3% and 99.6%, respectively, while the cetane number was increased by 5.4.     

C-radioisotope labeled methanol conversion over H- and Cs- modified ZSM-5, Beta zeolites and MCM-41 mesoporous molecular sieve

The Na–MCM-41 mesoporous molecular sieve, Na–ZSM-5 and Na–Beta zeolites have been modified by Cs- and H- using ion-exchange method and characterized by XRD, SEM and nitrogen adsorption. The conversion of methanol was studied over H- and Cs- modified ZSM-5, Beta zeolites and MCM-41 mesoporous molecular sieve. Methanol was in ¹¹C-radioisotope labeled form in-order to follow its conversion during the catalytic process, since the radioactivity method provides a very sensitive detection possibility to investigate the conversion of small amounts of methanol and some intermediates at different reaction times and temperatures. The understanding of reaction mechanism is important for side-chain methylation over Cs–zeolite catalysts by methanol, as they are more selective than other alkali exchanged zeolites (Li, Na and K). The reaction pathway of the transformation of methanol to hydrocarbons and aldehydes has been elaborated.     

Characterization and catalytic performance of mesoporous molecular sieves Al-MCM-41 materials

Mesoporous Al-MCM-41 materials of different Si/Al ratios have been synthesized and characterized by X-ray powder diffraction, ²⁷Al and ²⁹Si MAS NMR, differential thermogravimetric analysis, N₂ adsorption measurements, FT-IR and catalytic cracking of alkanes. The experimental results show that the incorporation of aluminium into the framework of MCM-41 has a great effect on the degree of long-distance order, the surface acidities and the mesoporous structures of the materials. With increase of the aluminium content, the amounts of tetrahedral framework aluminium and the acid sites on the samples increase, but the acid strength decreases. Al-MCM-41 materials exhibit high activity for n-C₁₆ ⁰ cracking and good selectivity for producing low carbon alkylenes, particularly for i-C₄ ⁼.     

Vapor-Phase Isopropylation of Phenol over Fe-Containing Al-MCM-41 Molecular Sieves

Al-MCM-41 and Fe-containing MCM-41 molecular sieves are hydrothermally synthesized. The low-angle XRD analysis shows that iron incorporation in Al-MCM-41 retains the hexagonal structure of MCM-41. The higher d-spacing values of Fe-Al-MCM-41 catalysts than those of Al-MCM-41 indicate the incorporation of iron into the framework. The mesoporous nature of the materials was confirmed by nitrogen adsorption isotherms. Electron paramagnetic resonance (EPR) and diffuse reflectance spectra (DRS) techniques confirm the tetrahedral coordination of iron into the Al-MCM-41 framework. Acidity of the synthesized catalysts was analyzed by both TPD of ammonia and pyridine-adsorbed FT-IR spectroscopy. The acidity measurements indicate that iron incorporation increases both Lewis and Brønsted acidity of the catalysts. Vapor-phase isopropylation of phenol with the new'alkylating agent isopropyl acetate was carried over the H-forms of the above catalysts. The phenol to isopropyl acetate ratio of 1?:?2 and the phenol space velocity of 1.1 h^-1 were found to be the optimum conditions for better phenol conversion and para isomer (4-isopropyl phenol) selectivity. On comparison, the Fe-incorporated Al-MCM-41 catalysts show significantly higher phenol conversion and selectivity toward the important product 4-isopropyl phenol (4-IPP) may be due to stronger Brønsted acid sites generated by the strengthening effect of nearby Lewis acid sites. Further, the undesired and dialkylated products selectivity are found to be lower over Fe-incorporated Al-MCM-41 than pure Al-MCM-41 catalysts.     

A designed Mn2O3/MCM-41 nanoporous composite for methylene blue and rhodamine B removal with high efficiency

The authors report a facile chemical precipitation method for the fabrication of a highly ordered mesoporous Mn₂O₃/MCM-41 composite. Examination of the acquired samples using X-ray diffraction (XRD), scanning electron microscopy (SEM), transmission electron microscopy (TEM), X-ray photoelectron spectroscopy (XPS), and nitrogen adsorption–desorption measurement has provided fundamental insight into the structure and properties of the Mn₂O₃/MCM-41 composite. It is found that the as-prepared Mn₂O₃/MCM-41 composite has a highly ordered mesoporous structure with a specific surface area of 793 m² g⁻¹. The performance of Mn₂O₃/MCM-41 composite as a remover was further demonstrated in the removal of azo dyes of methyl orange (MO), Congo red (CR), methylene blue (MB), and rhodamine B (RB) with/without visible light irradiation at room temperature. The results show that the Mn₂O₃/MCM-41 composite has an excellent removal performance for MB and RB, making it a promising candidate for wastewater treatment.     

Effect of Al content on the assembly of Al-MSU-S mesostructures: zeolite seed structure change from zeolite LZY to LTA with increasing Al content

Al-MSU-S mesoporous molecular sieve catalysts with Al contents ranging from 2.5 to 50 mol% have been prepared from “zeolite seed” solutions and C₁₆ TMABr templates. Hexagonal mesoporous structures are formed that exhibit significantly higher amounts of tetrahedrally coordinated Al than analogous Al-MCM-41 catalysts. The Al-MSU-S catalysts also possess smaller pores than corresponding Al-MCM-41 materials. Catalytic cumene cracking activity is very high over the low Al content materials (2.5 mol%), approaching that of zeolite ZSM-5, but the catalytic activity decreases with increasing Al. As the Al content is increased, the Al atoms remain tetrahedrally coordinated but become less accessible to the cumene reagent. This and knowledge of zeolite synthesis suggest the formation of zeolite seeds other than the large pore LZY, such as the small pore LTA structure.     

Phase transition of mesoporous SiO<Subscript>2</Subscript> impregnated with an organic templating agent by post-synthetic microwave heating

Mesoporous silica SBA-15 samples were subjected to microwave heating for 10–40 min at 393 and 443 K after dry-impregnation with TPAOH (tetrapropylammonium hydroxide) to prepare a mesoporous material with zeolytically ordered pore walls. Physicochemical properties of the materials prepared were characterized by XRD, N₂ adsorption at 77 K, SEM, TEM, UV–vis and FT-IR spectroscopies. These investigations revealed that selective transformation of amorphous pore walls of SBA-15 to crystalline zeolytic phase is difficult to be achieved and a mixed phase of mesoporous silica/zeolite composite material was obtained, instead. Microwave heating time, temperature, TPAOH concentration, and hydrothermal stability of the mesoporous host materials tested (MCM-41, HMS, and SBA-15) were important factors to maintain the mesopore structure of the host materials during the post-synthetic microwave heating treatment.     

Carbon spheres prepared from zeolite Beta beads

Porous carbon beads were prepared from macroporous anion-exchange resin beads preliminary converted into resin-zeolite Beta composite or pure zeolite Beta spheres. Two synthesis procedures were used depending on the initial template employed. In a series of experiments, the resin from the resin-zeolite Beta composite was directly carbonized into carbon. In another series of experiments, the resin was removed by oxidation at 600 °C leaving behind self-bonded zeolite Beta beads, which were filled with carbon by chemical vapor deposition (CVD) of propylene. As a final step for both procedures, the zeolite was dissolved in hydrofluoric acid. All the carbons prepared inherited the macroscopic spherical shape of the template spheres as well as the morphology of the primary particles building up the beads. The synthesis procedure and the carbonization temperature or the temperature for CVD of carbon employed influenced the ordering and the pore structure of the produced carbons. The carbons prepared by direct carbonization showed relatively low surface areas, less than 1000 m² g⁻¹, and no zeolite structural regularity. The samples obtained via CVD maintained the zeolite ordering with a periodicity of 11.7 Å and had surface areas of over 2000 m² g⁻¹.