Application of Large Pore MCM-41 Molecular Sieves To Improve Pore Size Analysis Using Nitrogen Adsorption Measurements

The Y/MCM-41 composite molecular sieves were synthesized in the method of hydrothermal crystallization with cetyltrimethylammonium bromide (CTMABr) as the template agent. The as-prepared composite molecular sieves were characterized by the means of X-ray powder diffraction (XRD), Fourier transform infrared spectroscopy (FT-IR), the thermogravimetric and differential thermal analysis (TG-DTA) and the nitrogen adsorption test. The experimental results were shown as follows: the Y/MCM-41 composite molecular sieves kept properties of Y-zeolites and MCM-41 molecular sieves. In the XRD and FT-IR spectra, it can be found both characteristic peaks of Y-zeolites and MCM-41 molecular sieves. The pore size distribution plot indicated that the Y/MCM-41composite molecular sieves had micro-mesoporous structure, and the average pore size were about 1.5 nm and 15 nm. The decomposition temperature of the template agent was at 320 °C, and the calcined temperature of Y-zeolites was at about 560 °C. There showed an endothermic process constantly in the DTA curve, and there was little mass loss in the TG curve, indicating the obtained Y/MCM-41 composite molecular sieves had higher thermal stability.

Download Full-text

Benzene Adsorption Isotherms on MCM-41 and their Use for Pore Size Analysis

Adsorption ◽

10.1023/b:adso.0000046355.96657.6d ◽

2004 ◽

Vol 10 (3) ◽

pp. 195-203 ◽

Cited By ~ 12

Author(s):

Jerzy Choma ◽

Marcin Kloske ◽

Mietek Jaroniec ◽

Jerzy Klinik

Keyword(s):

Pore Size ◽

Adsorption Isotherms ◽

Size Analysis ◽

Benzene Adsorption ◽

Pore Size Analysis ◽

Mcm 41

Download Full-text

Improved Pore-Size Analysis of Carbonaceous Adsorbents

Adsorption Science & Technology ◽

10.1260/026361702760254487 ◽

2002 ◽

Vol 20 (3) ◽

pp. 307-315 ◽

Cited By ~ 25

Author(s):

J. Choma ◽

M. Jaroniec ◽

M. Kloske

Keyword(s):

Film Thickness ◽

Pore Size ◽

Nitrogen Adsorption ◽

Distribution Functions ◽

Computational Method ◽

Carbon Surface ◽

Size Analysis ◽

Macroporous Silica ◽

Pore Size Analysis ◽

Wide Range

An improvement was proposed for the pore-size analysis of active carbons based on low-temperature (77 K) nitrogen adsorption isotherms measured over a wide range of relative pressures (5 × 10−7–0.995). It was shown that the applicability of the Barrett, Joyner and Halenda (BJH) computational method based on the Kelvin equation could be extended significantly towards small mesopores and large micropores when a proper t-curve was used to represent the film thickness of nitrogen adsorbed on the carbon surface. It was proposed that the aforementioned t-curve be obtained from the nitrogen adsorption isotherm at 77 K on a macroporous carbon black by fitting its multilayer part to the calibrated t-curve for nitrogen adsorbed at 77 K on a macroporous silica. To date, the Harkins–Jura or Halsey t-curves have been used to describe the pressure-dependence of the film thickness. This appears to be inaccurate, especially in the range of low relative pressures. It was shown that this inaccuracy makes the pore-size analysis questionable. However, the t-curve proposed in this work gave the pore-size distribution functions for the carbons studied thereby reproducing the total pore volume and showing realistic behaviour in the range at the borderline between micropores and mesopores.

Download Full-text