Nitrogen Loss and Structural Change of Nitrogen-incorporated SBA-15 Mesoporous Materials Under Different Treatment Condi
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an Liua) State Key Laboratory of High Performance Ceramics and Superfine Microstructure, Shanghai Institute of Ceramics, Shanghai, 200050 People’s Republic of China (Received 20 January 2005; accepted 25 February 2005)
Work on nitrogen loss and structural change of nitrogen-containing SBA-15 mesoporous materials after heat treatment in air or water treatment is described herein. The nitrogen-containing SBA-15 lost nitrogen after being treated in air at high temperature or in water, the mesoporous structure of which was very well maintained and did not collapse. HRTEM, N2 sorption, powder XRD, and SEM were used to study the structural ordering and morphology of the mesoporous silicon oxynitride materials before and after treatment. FTIR and C/N/H elemental analysis confirmed that nitrogen loss occurred after the mesoporous silicon oxynitride material was treated. Nitrogen was lost via hydrolysis of ammonium groups when mesoporous silicon oxynitride material was treated in water and by being substituted by oxygen from air when it was heated in air at high temperature. I. INTRODUCTION
The replacement of liquid acids and bases by solids as catalysts in organic reactions is a requisite for environmentally benign preservation. Compared to many known solid acid catalysts in modern fine chemicals, solid base catalysts available are still far fewer.1–3 Therefore, new solid base catalysts are imminently desirable to meet the need of the fine-chemical industry.4 In the 1990s, it was found that nitrogen incorporation was an effective way to synthesize new solid basic materials.5–7 The basicity of these nitrogen-containing materials is attributed to adsorbed ammonium ions, terminal NH2, and bridging NH and N3− onto the surface of the materials.8,9 The discovery of ordered mesoporous molecular sieves gives us a new choice to make nitrogen-containing silica mesoporous sieves.10 These sieves exhibit large surface area, regular porosity, adjustable pore size, and high pore volume, so this kind of mesoporous material is very suitable for catalyst or catalyst supports. Mesoporous silica sieves have been proved to be very stable in inert atmosphere.11 Thus, by treating the ordered mesoporous silica in ammonia or nitrogen gas, ordered mesoporous silicon oxynitride was made. Up to now, some a)
Address all correspondence to this author. e-mail: [email protected] DOI: 10.1557/JMR.2005.0285 2296
http://journals.cambridge.org
J. Mater. Res., Vol. 20, No. 9, Sep 2005 Downloaded: 16 Mar 2015
researchers12–14 have synthesized ordered silicon oxynitride mesoporous sieves using silica mesoporous sieves as matrices via different methods, but they did not appraise the stability of nitrogen incorporated into mesoporous silica sieves in air atmosphere and water. And stability is an important parameter of evaluating a kind of catalytic material. For instance, Haskouri et al.12 prepared mesoporous silicon oxynitride, ICMUV-6, but they did not evaluate the stability of nitrogen incorporated into the mesoporous silica sieves. Kapoor et al.13
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