Papers by Keyword: MCM-41

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Authors: Zhong Kui Zhao, Yi Tao Dai
Abstract: The initial activity, selectivity, and especially catalytic stability of mesoporous MCM-41 supported phosphotungstic acid (HPW) prepared by ultrasonic-assisted impregnation (UAI) method and the HY zeolite were contrastively investigated for alkenylation of p-xylene with phenylacetylene in a fixed-bed continuous flow reactor. N2 adsorption-desorption, FT-IR, X-ray diffraction (XRD) and NH3 temperature-programmed (NH3-TPD) desorption characterization techniques were employed to explore the relationship of catalyst nature and catalytic performance in alkenylation. Results illustrate that the as-prepared HPW/MCM-41 catalyst exhibits notably superior catalytic activity, selectivity and stability to microporous HY zeolite, ascribed to its well-ordered mesoporous architecture, appropriate acidic sites and high dispersity of HPW phase.
Authors: Hai Juan Zhang, Wei Qiang Wang, Jiang Hong Li, Xi Wen Zhang
Abstract: A novel synthesis route for a MCM-41 structure with Y zeolite seeds colloidal has been developed. The route is different from conversational method of highly ordered MCM-41 assembled from Y zeolite seed colloidal. The material was characterized by various techniques. The results indicate that the material has well-ordered hexagonal structure, with a thicker wall than that of the sample synthesized by a direct hydrothermal route (N-MCM-41). SEM images show a very uniform net-like morphology, which is different from the loose appearance of N-MCM-41. Furthermore, it has a stronger acid strength and a higher hydrothermal stability. The sample was used as the support of a Pd-Pt catalyst for the polyaromatics hydrogenation. It was demonstrated that the introduction of building units of Y zeolite enhances the activity of polyaromatics hydrogenation. It can be concluded that the pore structure and acidity of support is a key factor for the design of a sulfur tolerant noble metal catalyst for aromatics saturation of diesel.
Authors: Wen Rui Zheng, Min Zhang, Jing Li Xu, Tao Huang
Abstract: We present a novel method to synthesize mesoporous nickel siliceous coated on CNTs with larger hole based on the mesoporous silica coated on CNTs, the pore size of mesoporous silica coated on CNTs was enlarged to 7.8 nm from 2.72 nm. Compared to others’ work, our method is low cost, simple and high efficiency. And more importantly, this method shows great potential in applying other type of mesoporous materials such as SBA-15 etc.
Authors: Xiao Jun Sun, Xiao Chun Yan, Yu Jie Feng, Xian Bin Liu
Abstract: Four types of organo-functionalized mesoporous silicas were synthesized by post-grafting method, and characterized by powder X-ray diffraction, nitrogen adsorption/desorption and fourier transform infrared spectroscopy. In addition, adsorption behaviors of the prepared material modified with different functional groups were studied by adsorption of phenol in aqueous solution. When the concentration of phenol was 800 mg/L, the equilibrium adsorption capacity of N-aminoethyl-γ-aminopropyl-MCM-41, aminopropyl-MCM-41, mercaptopropyl-MCM-41 and propyl-MCM-41 was respectively as 2.5 times, 2.2 times, 1.9 times, and 1.7 times as that of MCM-41. It was due to the introduction of organo-functional groups, changing the polarity of the channel surface, and increasing the hydrophobic properties. N-aminoethyl-γ-aminopropyl and aminopropyl groups could generate acid-base interactions with phenol, therefore, their adsorption capacity increased much more. Besides, the pH value of the solution could significantly affect the adsorption amount of phenol on samples. The result showed that with the increase of pH, the adsorption amount of phenol increased at first, and then decreased. The maximum adsorption amount of all the prepared materials occurred at about pH value of 6.
Authors: Mei Shie Sam, Hendrik O. Lintang, Mohd Marsin Sanagi, Siew Ling Lee, Leny Yuliati
Abstract: Aniline is a toxic organic pollutant that is abundantly present in the environment. One of approaches to remove the aniline is by adsorption process. In this study, mesoporous carbon nitride (MCN) was proposed for the first time to be a potential adsorbent for aniline. The adsorption studies were carried out at room temperature on the aniline solution with various initial concentrations for both bulk carbon nitride (BCN) and MCN. Owing to its larger surface area, the MCN showed much higher adsorption capacity towards aniline compared to the BCN. This result indicated that adsorbent with large surface area is very crucial in the adsorption of aniline. Comparison study was also carried out using mesoporous silica, MCM-41, which was reported to act as a good adsorbent for aniline. The adsorption capability of MCN was found to be higher than that of MCM-41. It was suggested that the MCN with larger pore diameter might have more suitable and favourable adsorption sites for aniline compared to MCM-41. This study obviously showed that MCN would be a new potential adsorbent for removal of aniline.
Authors: Cíntia de Castro Costa, Dulce Maria de Araújo Melo, Antonio Eduardo Martinelli, Maria do Socorro Braga Fontes, Marcus Antônio de Freitas Melo, Joana Maria de Farias Barros
Abstract: The CO2 adsorption technology using solid adsorbent shas been considered as a promising approach to reduce CO2 emissions. Therefore, research has been developed to obtain efficient and economically viable adsorbents. The mesoporous materials of the MCM-41 type are among the candidates for effective adsorbents as a result of easy synthesis and structure which favors the flow of gas. The aim of this study was to improve the synthesis of MCM-41 using mixtures of cationic surfactants and apply in CO2 capture. The cationic surfactants used weretetradecyltrimetylammonium bromide (TTMABr - C17H38NBr) and cetyltrimethylammonium bromide (C19H42NBr) and their mixture in a ratio of 1:1. The CO2 adsorption was investigated using the gravimetric method at 298K and pressure varying up to 40 bar. The resulting materials, C17, C19 and C17C19, were characterized by XRD, FTIR, TG and SEM. The results revealed significant differences in the structure of the materials and amount of of CO2 adsorbed.
Authors: M. Gómez-Ruiz, José Aarón Melo-Banda, C.E. Ramos Galván, S.E. López, R.R. Silva, R.I. Alamilla, J.M. Domínguez
Abstract: The present work, the HPA Keggin structure was supported on four different MCM phase types (hexagonal, spherical, elliptical, and cubic); their catalytic properties were tested in the alkylation of benzene with propylene in order to produce cumene. In the reaction, parameters like propylene flow, reaction temperature, phase type, as well as WHSV-1, HPA, and Cs content in the best MCM phase support were studied. The results showed that the MCM-48 with (30 wt. % HPA) catalyst had the best behavior in catalytic activity, showing the higher conversion and selectivity toward cumene as the main product.
Authors: Hua Feng Zhou, Yong Jin Yang, Jin Son Zhang
Abstract: In this paper, mesoporous MCM-41 and Al-MCM-41(Si/Al =100, 70, 40, 10, 5) molecular sieves were synthesized by direct hydrothermal process and characterized by various analytical techniques. Their catalytic performance in the synthesis of dioctyl phthalate (DOP) was also studied. The results show that while keeping the mesostructure of Al-MCM-41(Si/Al=100, 70, 40), increasing Al content can increase the acidity and so forth effectively improve the catalytic activity. But too much aluminum incorporation can destroy the structure of Al-MCM-41(Si/Al=10). The Al-MCM-41 molecular sieves with proper Si/Al ratios have good catalytic activity and stability in DOP synthesis. When Al-MCM-41(40) was used as the catalyst, A high PA conversion of 98.45% can be reached in 4 h. After being reused for five times, Al-MCM-41(40) still remains good catalytic activity.
Authors: Zhi Dong Han, Feng Xu, Li Jiang, Zheng Quan Jiang, Peng Wang
Abstract: MCM-41 mesoporous silica was prepared by hydrothermal method. 2-carboxyethyl phenyl phosphinic acid (CEPPA) was loaded on MCM-41 by solution method. The structure of MCM-41 and its supported CEPPA was studied by X-ray diffraction (XRD), transmission electron microscope (TEM) and scanning electron microscopy (SEM) coupled with energy dispersive spectrometer (EDS). The results revealed that CEPPA was successfully loaded on MCM-41 with Si/P molar ratio of about 20:1. The XRD spectrum of MCM-41 supported CEPPA was different from MCM-41, indicating the structure of MCM-41 was changed after loading of CEPPA. CEPPA molecule moved into the mesoporous structure and filled in the mesopores, leading to the disappearance of characteristic diffraction peaks of MCM-41. The interaction between hydroxyl group of CEPPA and silanol of MCM-41 made it stable for CEPPA to be in the mesopores and on the surface of MCM-41. MCM-41 supported CEPPA also showed the similar mesoporous structure with long-range order to MCM-41 when observed by TEM. SEM provided further evidences of the similar particle size and different morphology.
Authors: Hsin Liang Huang, H. Paul Wang, Y.L. Wei, Tung Li Hsiung
Abstract: X-ray absorption near edge structural (XANES) and X-ray absorption fine structural (EXAFS) spectroscopies have been used to study chemical structure of nanosize copper extracted in the channels of MCM-41. The component-fitted XANES spectra show that about 95% of copper are adsorbed on the surfaces of MCM-41 at 298 K. A small amount of nanosize CuO in MCM-41 is also found. The adsorbed copper (Cu(II)(ads)) in the channels of MCM-41 may be oxidized and form nanosize CuO as calcined at 573 and 923 K. By EXAFS, it is observed that the nanosize CuO in MCM-41 possesses a Cu-O bond distance of 1.97 Å with a coordination number (CN) of 2.6, indicating the existence of linear type Cu3O4 cluster. Interestingly, calcinations of the nanosize CuO in MCM-41 at 923 K has led to a formation nanowire-type CuO (in the channels of MCM-41) with a length of 50-100 nm and width of about 5-9 nm.
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