Abstract: Aluminium and zirconium containing mesoporous MMS-H materials were synthesized and characterized using XRD and N2 adsorption/desorption analysis. The mesoporous materials were applied for the esterification of glycerol (GL) with lauric acid (LA) in supercritical CO2 (SCC) medium. The catalyst shows high conversion up to 93% with the formation of equal amount of lauric acid monoglyceride (Monolaurin; ML) and diglyceride (Dilaurin; DL). The catalytic activity in SCC medium was higher than those in mesitylene and without solvent under N2 atmosphere. The coke formation was less in SCC medium compared to those in the other reaction medium.
Abstract: Nano-sized β-zeolite was synthesized in presence of two templates viz., tetraethyl ammonium hydroxide and cetyltrimethylammonium bromide by steaming dry-gel precursors.
Abstract: Iron containing mesoporous materials (FeMMSH) with zeolite building units were first time synthesized. The iron(III) in FeMMSH materials are present in tetrahedral, and distorted tetrahedral framework which were evident from EPR and DRUV-VIS spectra.
Abstract: Cyclopentadienyl ruthenium phosphane and carbene complexes are grafted on the surface of mesoporous SBA-15 molecular sieves through an aminosilane linker. The nature of the support after the grafting is examined by powder XRD, TEM and N(2) adsorption/desorption analysis. Elemental analysis, FT-IR, DRIFTS, TG-MS and MAS-NMR studies confirm the successful grafting of the complexes on the surface. The grafted materials are applied for catalytic aldehyde olefination and cyclopropanation.
Abstract: The structural and acidic properties of two new highly stable meso-/microporous composite materials (MMS-H and RMM-1) developed recently were characterized by various analytical and spectroscopic techniques. Comparing to their structural analogue, Al-MCM-48, these novel aluminosilicates materials comprising zeolite secondary building units were found to have superior catalytic activities, as illustrated by ethylbenzene alkylation reaction.
Abstract: The acid properties of various sulfated and metal-promoted zirconium oxide (ZrO2) catalysts have been studied by solid-state 31P MAS NMR, FT-IR and TPD using the adsorbed trimethylphosphine oxide (TMPO), pyridine and ammonia as the probe molecule, respectively. Sulfated zirconia (SZ) catalysts having varied sulfur contents and metal promoter (M = Al, Ga and Fe) were prepared by solâgel method. Effects of sulfation and promoter on the detailed qualitative and quantitative information of acid sites, viz. types (Brønsted versus Lewis), strengths and distributions, on various synthesized SZ and M/SZ were examined by 31P MAS NMR of adsorbed TMPO in conjunction with elemental analyses by ICP-MS. By comparison, pyridine-IR and NH3-TPD methods are capable of providing only qualitative information of the overall acidity. It was found that while the parent ZrO2 possesses only weak Lewis acidities, elaborated sulfation treatment leads to formation and coexistence of strong Brønsted (B) and Lewis (L) acid sites whose variations can readily be followed. On the other hand, incorporation of different metal promoters onto SZ, led to simultaneous formation/elimination and variations of B- and L-sites with varied strengths and distributions. As a result, Ga/SZ was found to possess more B- than L-sites, whereas an opposite trend was observed for Al/SZ. As for Fe/SZ, a pronounced increase in both concentration and strength of acid sites were found. With an exception of Ga/SZ, the âvery strongâ acid sites observed for various SZ and M/SZ catalysts were found to be associated more to L- than B-sites.
Abstract: A tetrahydro-salen copper(II) complex (1) is grafted on the iodosilane modified surfaces of MCM-41 and MCM-48. The presence of complex 1 on the surfaces is evidenced by 1H MASâNMR, elemental analysis and TG-MS. The strucutre of the supports after modification remains intact, which is evident from powder XRD, N2 adsorption/desorption (BET), and TEM analysis. The grafted materials are applicable as catalysts for cyclooctene epoxidation and they are found to maintain activity for several runs.
Abstract: η5-Cp(COOMe)MoCl(CO)3 is grafted on the surface of mesoporous MCM-41 and MCM-48 materials through available silanol groups. The structural intactness of the supporting materials is confirmed by powder XRD and N2 adsorption analysis. The presence of the Mo complex on the surface is confirmed by FT-IR and elemental analysis. The catalysts are successfully applied for cyclooctene epoxidation.
Abstract: The complex [(â)-menthylCp]Mo(CO)3Cl (1) was synthesized by the reaction of Mo(CO)3(EtCN)3 with [(â)-menthylCpH] to produce the hydride [(â)-menthylCp]Mo(CO)3H. The latter compound was then reacted with CCl4 to form [(â)-menthylCp]Mo(CO)3Cl (1). Compound 1 was tested as catalyst for the epoxidation of cis-cyclooctene, styrene and trans-β-methylstyrene in the presence of tert-butyl hydroperoxide (TBHP) at 55 °C using chloroform as solvent. Results under homogeneous conditions prompted the authors to immobilize complex 1 on mesoporous MCM-41 and MCM-48 surfaces leading to the grafted materials AM-41CpMoChi and AM-48CpMoChi. The presence of the organometallic complexes in the materials was confirmed by powder X-ray diffraction, N2 adsorption/desorption isotherms, TEM, EA, FT-IR, 1H MAS NMR and TG-MS. AM-41CpMoChi and AM-48CpMoChi were also tested as epoxidation catalysts. The catalytic examinations also included leaching experiments, and the reusing of the grafted materials for several runs.
Abstract: (η[5]-C[5]Me[5])Ru(PPh[3])[2]Cl (1) is heterogenized on the surface of mesoporous molecular sieves by direct grafting on mesoporous aluminosilicates or by reaction of an aminosilane-linker-modified silicate surface with the chloride ligand. Elemental analyses reveal that the grafted samples contain 0.2-1.8 wt% Ru. The retaining of long-range ordering of mesoporous MCM-41 and MCM-48 after grafting is evidenced from XRD, N[2] adsorption-desorption and TEM analysis. FT-IR, TG-MS, [29]Si and 'H CP MAS-NMR spectra confirm the successful grafting of complex 1 on the surface of these mesoporous materials. Mesoporous materials grafted with complex 1 are found to be promising catalysts for the cyclopropanation of styrene with ethvl diazoacetate.
Abstract: A novel route to heterogenize an organorhenium(VII) oxide, derived from the well examined methyltrioxorhenium(VII) (MTO), on the surface of an iodosilane-modified MCM-41 is applied. The successful grafting of the -CH(2)-ReO3 moiety on the surface was evidenced by 1H CP MAS NMR, IR spectroscopy, TG-MS, and elemental analysis. XRD and TEM analyses confirm the retaining of long-range ordering throughout the grafting process. The rhenium loading of the mesoporous material after heterogenization of MTO is found to be 1.25 wt%. Despite containing formally a derivative of the very sensitive benzyltrioxorhenium(VII) the material is stable at room temperature and applicable as a heterogeneous catalyst for aldehyde olefination reactions.
Abstract: Cu(NCCH3)6][B(C6F5)4]2 and [Cu(NCCH3)6][B{C6H3(CF3)2}4]2 are immobilized on poly(4-vinylpyridine). Both resulting materials (Cu(II) complexes immobilized on polymer) are applicable as catalysts for the cyclopropanation of olefins at room temperature. The immobilized Cu(II) compounds are quite stable and recyclable for several catalytic runs, however with some decrease in the catalytic activity.
Abstract: A copper complex with weakly coordinating anions is grafted on the surface of mesoporous SBA-15 molecular sieves through an aminosilane linker. The nature of the support after the grafting is examined by powder XRD, TEM and N2 adsorption/desorption analysis. Elemental analysis, FT-IR, TGâMS and MAS-NMR studies confirm the successful grafting of the complexes on the surface. The grafted material is applied as catalysts for aldehyde olefination.
Abstract: Acylperrhenate is grafted on the surface of mesoporous silicates and aluminiosilicate molecular sieves through available surface silanol and acidic hydroxy groups. The intactness of the mesoporous supports and the nature of the catalytic species is demonstrated by XRD, TEM, FT-IR, N2 adsorption-desorption and elemental analysis. The grafted materials are applied for alkene epoxidation. The catalysts are found to be stable against decomposition on the surfaces and to exhibit good catalytic activity. However, during the course of repeated catalytic runs, some leaching associated with subsequent decomposition of the catalyst is observed, reducing the activity of the materials.
Abstract: [Cu(NCCH3)4][BF4]2 can be heterogenized by an ion exchange method on mesoporous NaAlMCM-41 and NaAlMCM-48 materials. The heterogenized complex and the homogeneous Cu compound are applicable for the cyclopropanation of olefins at 303 K. Comparable yields are observed for non-bulky olefins, olefins with bulkier substituents lead to lower yields. [Cu(NCCH3)4][BF4]2 grafted on mesoporous surfaces (as heterogeneous catalyst) are relatively stable and recyclable for several catalytic runs with only slight decrease in catalytic activity.
Abstract: Na+[η5-CpMo(CO)3]â is grafted on aromatic silane (iodo-benzyl trimethoxy silane) modified surfaces of MCM-41 and MCM-48 molecular sieves. The XRD, N2 adsorptionâdesorption, and TEM analysis provide strong evidence that the mesoporous structure of the supporting materials retains its long range ordering after the grafting process, despite significant reductions of the surface area, pore-volume and pore size. The appearance of strong IR bands around 2016 and 1956 cmâ1 as well as 3010 cmâ1 on the grafted samples showing the presence of carbonyl as well as aromatic functional groups, evidences the successful grafting of the η5-CpMo(CO)3 complexes. Elemental analysis reveals 6.4 and 8.3 wt% Mo on the SM-41ASG and SM-48ASG samples, respectively. The appearance of new 29Si CP MAS-NMR peaks around â61.4, and â69.6 ppm (T2 and T3) indicates the esterification of silanol groups by the methoxy group of the silane ligand. The samples prepared by this in situ method show high loading of Mo and also good catalytic activity and selectivity for olefin-epoxidation.
Abstract: A series of compounds of the type CpMoR(CO)3 and RCpMo(CO)3CH3 (R = (CH2)3Si(OMe)3 or CH2Si(OEt)3), containing a (CH2)nSi(OR)3 functionality as a side chain, either fixed to the metal itself or to the cyclopentadienyl ligand are prepared and spectroscopically characterized. These molecules are applicable as precursors for both homogeneous and heterogeneous phase catalysts. Their homogeneous catalytic activity in the olefin epoxidation is in the same order of magnitude as that of their methyl and chloro analogues of the types CpMo(CO)3R and CpMo(CO)3Cl.
Abstract: 5-CpMo(CO)3R complexes containing siloxane functional groups [(CH2)3Si(OMe)3 or (CH2)Si(OEt)3] attached to either the cyclopentadiene ligand or directly to Mo were grafted on the mesoporous materials MCM-41 and MCM-48 by reaction of the OR (R=Me, Et) moieties in the silane ligand and surface silanol groups (Si-OH). For the sake of comparison mesoporous materials modified with silane groups were reacted with Na+[CpMo(CO)3]-. The XRD, N2 adsorption-desorption, and TEM analyses provide strong evidence that the mesoporous structure of the supporting material retains its long-range ordering throughout the grafting process, despite significant reductions in surface area, pore volume and pore size. The appearance of strong IR bands around 2016 and 1956 cm-1 on the grafted samples also shows that the 5-CpMo(CO)3R complexes have been successfully grafted. Elemental analysis reveals that the grafted samples contain 0.3-3.5 wt % Mo. 29Si CP MAS-NMR spectra give clear evidence for a reduction in the numbers of the Q3 and Q2 sites. The formation of new peaks around -49.8, -57.9, and -66.2 ppm (T1, T2, and T3) indicates esterification of silanol groups by the alkoxy groups of the silane ligand. Both the in situ and ex situ prepared samples show good catalytic activity for the epoxidation of cyclooctene.
Abstract: η5-CpMo(CO)3Cl is grafted on H-zeolite-à (H-Ã) and H-zeolite-Y (H-Y) by the reaction of acidic protons with chloro-ligand. The XRD pattern of the zeolites after grafting remains intact and there is no additional peak obtained, indicating the absence of Mo oxide cluster formation during the grafting process. The successful grafting of intact CpMo(CO)3 moieties is evidenced by IR spectroscopy and elemental analysis. Elemental analysis further reveals that H-Y zeolite shows higher Mo complex loading. The obtained heterogeneous materials are found to be efficient and recyclable catalysts for olefin epoxidation.
Abstract: Optically active molybdenum(VI) dioxo complexes bearing hydrosalen derivatives as ligands were synthesized, grafted on the surface of MCM-41 and MCM-48 and examined as catalysts for asymmetric epoxidation. In case of cis-β-methylstyrene and trans-β-methylstyrene moderate enantiomeric excesses of up to 31% can be reached when the reaction is carried out at room temperature. The catalysts can also be applied for non-chiral oxidation reactions.
Abstract: A novel, one-step synthesis of a highly stable mesoporous molecular sieve (MMS-H), which has a structure analogous to MCM-48 but which contains zeolite building units, is reported. A variety of experimental techniques - X-ray diffraction (XRD), N2 adsorption/desorption, transmission electron microscopy (TEM), Fourier-transform infrared (FTIR) spectroscopy, hyperpolarized 129Xe NMR, and solid-state 27Al and 31P magic-angle spinning (MAS) NMR spectroscopies - have been used to characterize the framework structure, porosity, and acidity of this novel mesoporous/microporous composite material, which is also found to possess superior thermal, hydrothermal, steam, and mechanical stabilities.
Abstract: The η5-CpMo(CO)3 moiety is grafted directly or with an aromatic-iodosilane linker on SBA-15 (SBA-15DG and SBA-15ASG) surfaces. The appearance of strong IR bands around 2016 and 1956 cmâ1 on the grafted samples demonstrate the presence of carbonyl groups and evidence the successful grafting of the η5-CpMo(CO)3 moiety. Elemental analyses reveal 1.5 and 4.9 wt.% Mo on the SBA-15DG and SBA-15ASG samples, respectively. The XRD analyses, N2 adsorptionâdesorption curves, and TEM analyses provide strong evidence that the mesoporous structures of the supporting materials retain their long range ordering throughout the grafting process, despite significant reductions of the surface areas, pore volumes and pore sizes. The modified materials are found to be active for the catalytic epoxidation of cyclooctene. The catalytic activity of the SBA-15ASG sample remains largely unchanged throughout several recycling experiments.
Abstract: An acetonitrile complex of composition [Mn(NCCH3)6][B(C6F5)4]2(1) is grafted on Na-AlMCM-41/48 and H-AlMCM-41/48 by ion exchange. A metal loading of 0.25â0.6 wt% is achieved; the grafting of complex 1 is found to yield higher loading on Na-AlMCM-41/48 compared to H-AlMCM-41/48. Powder X-ray diffraction, N2 adsorptionâdesorption and TEM analysis of the grafted materials confirm the retention of long range ordering of the materials throughout the grafting process. FT-IR, EPR, TG-MS and elemental analyses confirm the successful grafting of the Mn(II) complex in the channels of the mesoporous materials, retaining the octahedral nitrile environment around the Mn2+ cation. The obtained materials are applied as heterogeneous initiators for the polymerization of isobutene.
Abstract: Cu(NCCH3)6][B(C6F5)4]2 can be heterogenized by ion exchange on NaAlMCM-41 and NaAlMCM-48. In the latter case, the observed loading is twice as high as in the first case. [Cu(NCCH3)6][B(C6F5)4]2 is applicable both in homogeneous and heterogeneous media for the aziridination of olefins at 30 °C. Good yields are observed for non bulky olefins, olefins with bulkier substituents lead to lower yields. [Cu(NCCH3)6][B(C6F5)4]2 grafted on mesoporous surfaces (as heterogeneous catalyst) is stable and recyclable for several catalytic runs with only slight decrease in catalytic activity.
Abstract: A novel class of mesoporous aluminosilicate molecular sieves has been prepared by replication from carbon mesoporous molecular sieves (CMKs) using zeolite precursors and characterized by a variety of analytical and spectroscopic techniques, such as XRD, N2 adsorption/desorption, SEM/TEM, IR, hyperpolarized (HP) 129Xe, and 31P MAS NMR. These replicated mesoporous materials (RMMs), namely RMM-1 and RMM-3 prepared from CMK-1 and CMK-3, were found to exhibit mesoporous structures respectively analogous to Al-MCM-48 and Al-SBA-15 but possess unique microporous characteristics due to the presence of zeolite secondary building units in the framework. Consequently, these RMMs are also found to have superior thermal, hydrothermal, and mechanical stabilities and with improved acidic properties compared to their respective parent counterparts. The RMM-3 so prepared represents the first synthesis of protonated aluminosilicate with an SBA-15 structure prepared by a nonacidic route.
Abstract: CpMo(CO)(3)Cl reacts with the hydroxyl (Si-OH or Si-OH-Al) functionalities of mesoporous molecular sieves such as MCM-41, MCM-48 and its aluminium analogues during grafting. XRD, N(2) adsorption-desorption, BET surface area analysis and TEM show the resulting samples as being well ordered and maintaining a uniform pore size. FT-IR spectra, elemental analysis, (13)C and (29)Si CP MAS NMR spectra confirm the successful grafting. In the presence of excess TBHP the materials show high activity in cyclooctene epoxidation and good stability.
Abstract: Liquid-phase catalytic oxidation of certain alkylaromatics over mesoporous (Cr)MCM-41 molecular sieves in the presence of chlorobenzene and tertiary butylhydroperoxide showed high substrate conversion and excellent product selectivity. The high catalytic activity of the materials is attributed to the complete oxidation of chromium ions to hexavalent chromium and the absence of pentavalent chromium in the mesoporous matrix.
Abstract: Isomorphously substituted GaMCM-41 molecular sieves with different Si:Ga ratio were synthesized and characterized systematically by various analytical and spectroscopic techniques. Temperature-programmed desorption of ammonia was used to identify the nature of acidic sites. For the first time, the vapor-phase tertiary butylation of phenol reaction was carried out over protonated GaMCM-41. The catalysts showed higher (phenol) conversion and good (para-tertiary butyl phenol) selectivity over the Al- and Fe-analogs of MCM-41. Further, the gallosilicates showed good stability both before and after the reaction compared to the aluminosilicates or ferrisilicates.
Abstract: Vapour phase butylation of phenol was carried out over a sulfated zirconia solid superacid catalyst in the temperature range 448â473 K using t-butyl alcohol as the alkylating agent. A good substrate (phenol) conversion and excellent product (para-tertiary BP) selectivity was obtained. The catalytic activity remains nearly the same on repeated use of the catalyst. Further, the catalyst was not deactivated when the reaction was carried out for a longer duration, i.e., even after several hours of reaction.
Abstract: Chromium-containing mesoporous MCM-41 and MCM-48 silicate molecular sieves were synthesized and characterized. Unlike the chromium-containing microporous materials, the mesoporous analogues show significant activity for the chosen (ethylbenzene oxidation) reaction even after several recycling or washing treatments.
Abstract: Trivalent-iron-substituted mesoporous molecular sieve catalysts (FeMCM-41) were synthesized hydrothermally and characterized systematically by various analytical and spectroscopic techniques. Temperature-programmed desorption studies of ammonia of the protonated catalyst (HâFeMCM-41) indicate a broad distribution of the acid sites. Vapour-phase alkylation of phenol with t-butyl alcohol (2-methyl-2-propanol) was carried out over this solid acid catalyst and p-t-butyl phenol was obtained as the major product with high selectivity.
