Zeolite-encapsulated manganese(III)salen complexes

Manganese(III) complexes of [N,N'-ethylenebis(salicylidene-aminato)] (salen), [N,N'-ethylenebis(5-chloro-salicylidene-aminato)] (Cl<SUB>2</SUB>Salen), [N,N'-ethylenebis(5-bromo-salicylidene-aminato)] (Br<SUB>2</SUB>Salen) and [N,N'-ethylenebis(5-nitro-salicylidene-aminato)] [(NO<SUB>2</SUB>)<SUB>2</SUB>Salen] have been encapsulated in the supercages of zeolite X by the zeolite synthesis method. The catalysts have been characterized by FTIR, UV-Vis and EPR spectroscopic techniques, XRD, SEM, thermal and elemental analysis, as well as nitrogen adsorption and cyclic voltammetric studies. The extent of encapsulation of the Mn(III)Salen complexes in zeolite X varies with the nature of the substituent group on the aromatic ring. While bromo groups enhance encapsulation, substitution with -NO<SUB>2</SUB> groups decreases the amounts of Mn(III) complexes encapsulated in the cavities of the zeolites. Cyclic voltammetric data indicate that the zeolite matrix facilitates the reduction of Mn(III) to Mn(II), suggesting that it behaves like an electron-withdrawing substituent. The aerobic oxidation of styrene to benzaldehyde, styrene oxide and phenylacetaldehyde over these catalysts is also reported

Direct oxidation of propane to isopropanol

Propane has been oxidised to a mixture of isopropanol and acetone at ambient conditions with high activity and selectivity using phthalocyanine complexes of Fe, Co and Cu encapsulated in zeolites as catalysts and O2/tertiary butyl hydroperoxide as oxidants

Oxidation of para-xylene over zeolite-encapsulated copper and manganese complexes

Salen, saltin and salcyhexen complexes of copper and manganese, encapsulated in the cavities of zeolite NaX have been investigated as catalysts for the aerobic oxidation of para-xylene in the absence of added halogen promoters and using tertiary-butyl hydroperoxide as the initiator at low temperatures. Significant conversion levels (upto 50-60%) are attained. The major products include toluic acid, toluyl aldehyde and toluyl alcohol. The zeolite-encapsulated complexes did not undergo any colour change during the reaction and could be easily separated and reused many times. In contrast, the neat complexes, while they were active in the first cycle, were completely destroyed during the run and changed colour. They, however, gave lower conversions compared to the encapsulated catalysts. Conversion increases when electron-withdrawing substituents (like Cl, Br and NO) are substituted in the aromatic ring

Selective oxidation over copper and manganese salens encapsulated in zeolites

Copper and Mn(III)(X<SUB>2</SUB>-salen) complexes, where salen<SUP>2-</SUP>=N,N'-ethylenebis(salicylideneaminato) and X=H, Cl, Br or (NO<SUB>2</SUB>), encapsulated in the cavities of zeolites NaX and NaY, have been synthesized and characterized by various physicochemical measurements. Samples obtained by synthesizing the complexes 'in situ' in the cavities of the zeolite by the 'flexible ligand' method contain a higher concentration of the complex than those obtained by synthesizing the zeolites around the preformed copper complex. Substitution of the aromatic hydrogen atoms of the salen ligand by electron-withdrawing groups like -Cl, -Br and NO<SUB>2</SUB> has two major effects: (1) retention and concentration of the copper complex in the zeolite cavities is enhanced (due to the larger size of the substituents); and (2) the spectral properties of the encapsulated complex are modified. Cyclic voltammetric data indicate that the zeolite matrix facilitates the reduction of Mn(III) to Mn(II), suggesting that it behaves like an electron-withdrawing substituent. The rates of decomposition of H<SUB>2</SUB>O<SUB>2</SUB> and tert-butyl hydroperoxide as well as the selective, low-temperature oxidation of phenol, styrene and para-xylene are all enhanced by electron-withdrawing substituents on the salen ligand

Zeolite-encapsulated Cu(II)-salen complex as a catalyst for oxidation of cyclohexanol

1-3Cu (salen) complex encapsulated in zeolite Y is characterized by elemental analysis, IR, UV-vis and ESR spectroscopy and is shown to be a catalyst for the selective oxidation of cyclohexanol to cyclohexanone in the presence of H2O2 under much milder conditions (80°C) than those in current practice

Zeolite-encapsulated copper (X<SUB>2</SUB>-salen) complexes

Copper (X2–salen) complexes, where salen2-=N,N'-ethylenebis(salicylideneaminato) and X=H, Cl, Br or (NO2), encapsulated in the cavities of zeolites NaX and NaY, have been synthesized and characterized by various physicochemical measurements. Samples obtained by synthesizing the complexes in situ in the cavities of the zeolite by the ‘flexible ligand' method contain a higher concentration of the complex than those obtained by synthesizing the zeolites around the pre-formed copper complex. Substitution of the aromatic hydrogen atoms of the salen ligand by electron withdrawing groups like –Cl, –Br and –NO2 has two major effects: (1) retention and concentration of the copper complex in the zeolite cavities is enhanced (due to the larger size of the substituents) and (2) the electronic and spectral properties of the encapsulated complex are modified. The rates of decomposition of H2O2 over these encapsulated, substituted copper salens approach those of natural catalase enzymes and correlate with the rates of oxidation of phenol

Advanced Hydrogen Transport Membranes for Vision 21 Fossil Fuel Plants

During this quarter work was continued on characterizing the stability of layered composite membranes under a variety of conditions. Membrane permeation was tested up to 100 hours at constant pressure, temperature, and flow rates. In addition, design parameters were completed for a scale-up hydrogen separation demonstration unit. Evaluation of microstructure and effect of hydrogen exposure on BCY/Ni cermet mechanical properties was initiated. The fabrication of new cermets containing high permeability metals is reported and progress in the preparation of sulfur resistant catalysts is discussed. Finally, a report entitled ''Criteria for Incorporating Eltron's Hydrogen Separation Membranes into Vision 21 IGCC Systems and FutureGen Plants'' was completed

Advanced Hydrogen Transport Membranes for Vision 21 Fossil Fuel Plants

During this quarter composite layered membrane size was scaled-up and tested for permeation performance. Sintering conditions were optimized for a new cermet containing a high permeability metal and seals were developed to allow permeability testing. Theoretical calculations were performed to determine potential sulfur tolerant hydrogen dissociation catalysts. Finally, work was finalized on mechanical and process & control documentation for a hydrogen separation unit

Advanced Hydrogen Transport Membranes for Vision 21 Fossil Fuel Plants

During this quarter, work was focused on testing layered composite membranes under varying feed stream flow rates at high pressure. By optimizing conditions, H{sub 2} permeation rates as high as 423 mL {center_dot} min{sup -1} {center_dot} cm{sup -2} at 440 C were measured. Membrane stability was investigated by comparison to composite alloy membranes. Permeation of alloyed membranes showed a strong dependence on the alloying element. Impedance analysis was used to investigate bulk and grain boundary conductivity in cermets. Thin film cermet deposition procedures were developed, hydrogen dissociation catalysts were evaluated, and hydrogen separation unit scale-up issues were addressed