12-P-05 - Study of relationship between mordenite acidity and structure with calcination temperature

Zhu, Zhirong; Chen, Q.; Chen, W.

doi:10.1016/s0167-2991(01)81436-1

Cited by 3 publications

(2 citation statements)

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“…The amount of loading after surface functionalization was determined by elemental analysis. According to the elemental contents (C/H/N/S) of the silylated products, the loadings of the grafted groups (Γ) for all the silylated materials were calculated in the unit of millimole per gram of pure silica (mmol/g SiO 2 ) 8a Δ W SiO 2 represents the inorganic SiO 2 contents in weight percent.…”

Section: Experiments Sectionmentioning

confidence: 99%

“…However, high-temperature calcination is usually preceded before functionalization in standard methods. This would lead to more surface silanol condensation and reduce the Si−OH density for the subsequent surface modification . While one can recover the surface silanols by adding a trace amount of water, the procedure becomes complicated and difficult to control.…”

Section: Introductionmentioning

confidence: 99%

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Direct Method for Surface Silyl Functionalization of Mesoporous Silica

2004

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A direct method of surface silyl modification and simultaneous surfactant removal of mesoporous silica is investigated in its physicochemical details. Twelve different silanes of various functionalities are studied. The method employs an alcohol solution of silanes to allow the simultaneous surfactant/silyl exchange process, which results in a more uniform monolayer coverage of the surface and a higher amount of surface attachments of silane. We vary the solution concentration of silanes to study the effect on loadings. It is found that the variation of the surface loading of the silyl group follows a Langmuir adsorption model closely. The method gives one a well-controlled monolayer coverage of the surface. The loadings are determined by the exchange equilibrium. Fittings of the loading data to Langmuir adsorption isotherms give one the adsorption equilibrium constants and maximum surface loadings. We categorize the silanes into three different groups according to the values of the equilibrium constants and discuss them with respect to molecular structures. We also report on the extensive characterizations of the surfacefunctionalized mesoporous materials, such as nitrogen adsorptions, X-ray diffraction, 29 Si magic-angle spinning NMR, 13 C magic-angle spinning NMR, and IR spectroscopy. The method provides one with a convenient and highly controllable approach to the surface functionalization of mesoporous silica.

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Section: Experiments Sectionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Direct Method for Surface Silyl Functionalization of Mesoporous Silica

2004

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Influence of Metallic Modification on Ethylbenzene Dealkylation over ZSM‐5 Zeolites

Jia

et al. 2015

Chin. J. Chem.

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A series of metal-modified HZSM-5 catalysts were prepared by impregnation and were used for ethylbenzene dealkylation of the mixed C8 aromatics (ethylbenzene, m-xylene and o-xylene). The effects of different supported metals (Pt, Pd, Ni, Mo) on catalytic performance, including reaction conditions, were investigated. The physicochemical properties of catalysts were characterized by means of XRD, BET, TEM and NH 3 -TPD. Experimental results showed that metallic modification obviously increased the ethylbenzene conversion and reduced the coke deposition, greatly improving the catalyst stability. The distinction of ethylbenzene conversion depended on the interaction between hydrogenation reactivity and acidic cracking of bifunctional metal-modified zeolites. Compared with Pt and Ni, Pd and Mo were easier to disperse into HZSM-5 micropores during loading metals. The acidic density of different metal-modified HZSM-5 declined in the following order: HZSM-5＞ Pt/HZSM-5＞Pd/HZSM-5＞Ni/HZSM-5＞Mo/HZSM-5. The activity of ethylene hydrogenation decreased with Pt/HZSM-5＞Pd/HZSM-5＞Ni/HZSM-5＞Mo/HZSM-5. In comparison, Pd/HZSM-5 showed the best catalytic performance with both high activity and high selectivity, with less cracking loss of m-xylene and o-xylene. Moreover, the following reaction conditions were found to be preferable for ethylbenzene dealkylation over Pd/HZSM-5: 340 ℃, 1.5 MPa H 2 , WHSV 4 h −1 , H 2 /C8 4 mol/mol.

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