Mesoporous pure-silica templates

The use of mesoporous pure-silica templates without the presence of any catalyst other than the surface silanol groups is desirable. With the pure-silica SBA-15 template, Mokaya and coworkers demonstrated the preparation of nitrogen-doped OMC materials [137,160,161]. They concluded that the CVD temperature is an... 

Preparation of SBA-15 The pure silica SBA-15 mesoporous material was made according to the literature using tri-block poly(ethylene oxide)-poly(propylene oxide)-poly(ethylene oxide), (EO)2o(PO)to(EO)2o, as a template in acidic conditions. For example, 4 g of [(EO)2o(PO)7o(EO)2o] was dissolved into the solution of 30 mL of deionized water and 120 ml of HCI (2 mol L ), followed by the addition of 9.15 ml of tetraethyl orthosilicate (TEOS, >98%) slowly. Then the... 

As an alternative to the two-step approach, mesoporous silica with organic moieties covalently linked to their internal surface could be obtained in a single-step cocondensation of siloxane and organosiloxane precursors using similar supramolecular templating techniques as those for the synthesis of pure silica. Successful one-step syntheses of MCM-41 silicas modified with alkyl, phenyl, vinyl. cyanoethyL amine, thiol, and propylsulfonic acid moieties were reported in the literature.Similar preparations were extended to MCM-48 silica and to meso-... 

Ordered mesoporous carbons, prepared by nanocasting, have also been used successfully as templates for the synthesis of hierarchical zeolites [159, 160). This is the case of CMK-3, an ordered mesoporous carbon attained by nanoreplication of pure silica SBA-15. The hierarchical zeolites obtained by employing CMK-3 as a template mainly present supermicropores or small mesopores with a size around 2 nm. The textural properties of the hierarchical zeohtes can be tuned by changing the type of CMK-3 carbon used. A modification of this method consists of directly impregnating the composite SBA-15-carbon or MCM-41-carbon with TPAOH and leaving the mixture crystallizing hydrothermally under steam. After calcination, a mesoporous ZSM-5 is formed with mesopore sizes around 3.5 and... 

We also employed pure-silica SBA-15 as a template to prepare OMCs [135]. Figure 2.21 shows the nitrogen adsorption-desorption isotherms and BJH-PSD curves (inset) of SBA-15 silica, and a templated OMC sample. The presence of hysteresis loops indicates that both samples are mesoporous. The pore sizes derived from the adsorption branches were 7.2 nm for the template and 3.4 nm for the carbon. The surface area (676 m /g) and pore volume (0.72 cmVg) of the... 

P-28 - Synthesis of pure and iron-containing mesoporous silica. Effect of washing and removal of template on the porous structure... 

---