Carbon templating

Keywords Microwave synthesis Mesoporous zeolite Carbon template Sn-MFI Baeyer-Villiger Oxidation... 

The synthesis of carbon templated mesoporous tin MFI catalysts with different Si/Sn was carried out using microwave and in typical synthesis methodology TEOS, TPAOH, [Sn(C5H70)2]2]Cl2, ethanol and water were employed where the molar composition of the reaction mixture was 0.06 TPAOH 0.67 H20 0.028 TEOS 1.3 g EtOH X mg of tin precursor (X = 85, 63, 42, 21 mg). This synthesis mixture was stirred for 90 min at room temperature and then Black pearl 2000 carbon (10% wt. of TEOS) was added and again stirred for 4 h vigorously. The crystallization of C-meso-Sn-Silicalite was performed in a Teflon cup placed in a microwave oven (MARS-5, CEM, maximum power of 1200 W). 

The carbon templated tin incorporated mesoporous silicalite catalysts with MFI structure were successfully synthesized using microwave and well characterized using all the physico-chemical techniques. The catalytic activity of these catalysts was studied for liquid phase Baeyer-Villiger oxidation of various cyclic ketones using hydrogen peroxide. All the catalyst showed high conversion ( 100%) for bicyclic ketones with 100% selectivity to the corresponding lactone. 

Ahmad M, Grancher N, Heil M et al 2002 Action spectrum for cryptochrome-dependent hypocotyl growth inhibition in A-rabidopsis. Plant Physiol 129 774—785 Baldwin JM, Schertler GF, Unger VM 1997 An alpha-carbon template for the transmembrane helices in the rhodopsin family of G-protein-coupled receptors. J Mol Biol 272 144—164 Batni S, Scalzetti L, Moody S A, Knox BE 1996 Characterization of the Xenopus rhodopsin gene. J Biol Chem 271 3179-3186... 

Thiophenes have served as important four-carbon templates for molecular elaboration. Both functionalized cyclic and acyclic chains can be generated by carrying out conventional reactions on the thiophene nucleus and then performing a Raney nickel desulfurization at or near the very end of the scheme. Thus, the major constituent (279) of the Panamanian ant, Atta columbica, was made by Friedel-Crafts acylation of the thiophene derivative (277), followed by Grignard addition to the carbonyl group of (278), dehydration, and reductive desulfurization (Scheme 57) (60JOC1754). 

Baldwin JM, Schertler GF, Unger VM. An alpha-carbon template for the transmembrane helices in the rhodopsin family of G protein-coupled receptors. J Mol Biol 1997 272 144-164. 

Scheme 6.15 Synthesis of precatenane 56 by carbonate-templated oxidative dimerization [64]. Reagents and conditions (a) KOH, EtOH, THF (b) CuCl, CuCl2, py, rt. 

With zeolites application of electron tomography has provided unique information on the nature of mcsoporcs that have been obtained by secondary treatments or the use of carbon templates. 

The porous skeleton of activated carbon can be used as a template on which to construct other porous materials, for example, Si02, Ti02 and AI2O3. The oxide is first dissolved in supercritical CO2 (see Section 8.13) and then the activated carbon template is coated in the supercritical fluid. The carbon template is removed by treatment with oxygen plasma or by calcination in air at 870 K, leaving a nano-porous ( nano refers to the scale of the pore size) metal oxide with a macroporous structure that mimics that of the activated carbon template. 

The nitrogen adsorption isotherm recorded on ZSM-5 zeolite prepared without carbon displays almost rectangular shape being typical for purely microporous materials (Fig. 3). The isotherms on all samples prepared using carbon template (Fig. 3) posses both micro- and mesoporous features. The almost vertical rise of the adsorbed amount of nitrogen up to ptp = 0.05 corresponds to the volume filling of micropores. The isotherms exhibit hysteresis loops at plpo > 0.4, which are indicative for the capillary condensation in mesopores. The distribution of these... 

H.Wang, J.S. Yu, X.D. Li, and D.P. Kim, Inorganic polymer-derived hollow SiC and filled SiCN sphere assemblies from a 3DOM carbon template, Chem. Commun., 2352-2353(2004). 

The other method for preparing ordered mesoporous materials is the so-called hard template method using hard mesoporous silica or replicated carbon templates. The metal precursors are filled into hard templates. In this method, heat treatment can be performed at a higher temperature without structural collapse and highly crystallised materials can be obtainedl ° ] (Figure 3.6). 

Ordered mesoporous crystalline CuO was produced by using a hard carbon template (CMK-3) prepared by using an SBA-15 template. This two-step templating method produced well-ordered hexagonal (similar... 

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