Takafumi Shido

CO hydrogenation towards higher alcohols catalysed on SiO2-grafted and zeolite-entrapped Ru, Co and RuCo bimetallic clusters: Their EXAFS and FTIR characterization and catalytic performances

Some Ru and Co carbonyl clusters in zeolite pores such as Ru3(CO)12/NaY, [HRu6(CO)18]−/NaY, [Ru6(CO)18]2−/NaX, Co4(CO)12/NaY and Co6(CO)16/NaY were prepared by the ship-in-bottle technique, and characterized by FTIR and EXAFS. The RuCo bimetallic carbonyl cluster was prepared by reductive carbonylation of the oxidized RuCo/NaY, which provides the proposed assignment to [HRUCo3(CO)12]/NaY. The tailored Ru, RuCo and Co catalysts were prepared by H2 reduction from the precursors, e.g. Ru, RuCo bimetallic and Co carbonyl clusters impregnated on SiO2 and entrapped in NaY and NaX zeolites. The RuCo bimetallic carbonyl cluster-derived catalysts showed substantially higher activities and selectivities for oxygenates such as C1–C5 alcohols in CO hydrogenation (CO/H2 = 0.33-1.0, 5 bar, 519–543 K). By contrast, hydrocarbons such as methane were preferentially obtained on the catalysts prepared from Ru6, Ru3 and Co4 carbonyl clusters and provided lower CO conversion and poor selectivities for oxygenates. The RuCo bimetals are proposed to be associated with the selective formation of higher alcohols in CO hydrogenation.

Surface-grafted metal oxide clusters and metal carbonyl clusters in zeolite micropores; XAFS/FTIR/TPD characterization and catalytic behavior

SiO 2 -grafted [(μ 3 -C 4 H 7 ) 2 Rh] 2 V 4 O 12 and [(Rhcp*) 4 V 6 O 19 ] as molecular models of supported Rh catalysts characterized by EXAFS, FTIR, and TPD exhibit high catalytic activities for selective oxidation of propene towards acetone. SiO 2 -impregnated triple cubane-type complete [(RhCp*) 4 Mo 4 O 16 ] and incomplete (RhCp*) 2 Mo 3 O 9 (OMe) 4 were reduced under photoillumination (>365 nm) in CO at 300 K, forming two sets of the intense carbonyl bands at (2061 and 2021 cm -1 ) and (2092 and 2035 cm -1 ). All the carbonyls attracted to Rh and Mo sites were eliminated by the thermal evacuation at 330-440 K, leaving oxygen-deficient sites of Mo in the cubane-oxide clusters, which exhibited high catalytic activities for propene metathesis at 300-343 K. We have conducted the low-temperature homologation of methane on a series of zeolite-entrapped Ru, Rh, Co and Pt catalysts which were prepared from Ru 3 (CO) 32 /NaY, H 4 Ru 4 (CO) 12 /NaY, [HRu 6 (CO) 18 ] - /NaY, Co 4 (CO) 12 /NaY, Rh 6 (CO) 16 /NaY, [Pt 3 (CO) 3 (μ 2 -CO) 3 ] n 2- (n = 3, 4)/NaY. The carbon species [CH x ] (x = 0-3) are deposited on naked metal clusters in NaY by admission of methane at 423-623 K, which are stoichiometrically converted by hydrogen at 300-423 K towards C 1 -C 5 hydrocarbons without any formation of graphic carbons. The yields of C 2 + hydrocarbons in methane homologation were affected by the size of Ru clusters and carbon coverage θc, as follows ; Ru 3 /NaY < Ru 4 /NaY < Ru 6 /NaY < Ru (50 A) on NaY ; The reactivity of surface carbon bound to metal clusters in zeolites and mechanism for C-C bond formation are discussed in conjunction with Ru ensemble-size effects and intrazeolitic chemical circumstances.

‘Ship-in-bottle’ synthesis of platinum carbonyl clusters in titania- or zirconia-modified mesoporous channels of FSM-16. Structural characterization and catalysis in CO hydrogenation

Abstract Mesoporous channels (2.7 and 4.7 nm pore size) of FSM-16 were modified with titania or zirconia by the impregnation and hydrolysis of Ti or Zr alkoxides with subsequent calcination. Platinum carbonyl clusters [Pt3(CO)6]n 2− (n=4–6) were synthesized in the modified FSM-16 by the reaction of H2PtCl6 with CO and H2O at 323 K, and the clusters were characterized by IR and UV–Vis spectroscopies. Evacuation of the Pt carbonyl clusters at 573 K gave nanoparticles in FSM-16, and the resulting Pt/TiO2 (or ZrO2)/FSM-16 catalysts showed higher CO conversions and selectivities to C2–C3 alkanes in CO hydrogenation than the unmodified Pt/FSM-16.

Molecular modelling of supported metal catalysts: SiO2-grafted [{(η3-C4H7)2Rh}2V4O12] and [{Rh(C2Me5)}4V6O19] are catalytically active in the selective oxidation of propene to acetone

SiO2-grafted [{η3-C4H7)2Rh}2 V4O12] and [{Rh(C2Me5)}4V6O19], as molecular models of supported Rh catalysts characterized by EXAFS, FTIR and TPD studies, exhibit high catalytic activities for the selective oxidation of propene to Acctone.

Structural characterization of photoreduced complete and incomplete cubane-type molybdenum oxide clusters in CO and their catalytic behavior in propene metathesis reaction

SiO2-impregnated complete and incomplete cubane-type molybdenum oxide clusters such as [(RhCp*)4Mo4O16] (I) and [(RhCp*)2Mo3O9(OMe)4] (II) were photoreduced with a UHP-Hg lamp (> 365 nm) in CO, resulting in the formation of catalytically active species for propene metathesis at 300 K. The CO-photoreduced Mo oxide clusters were characterized by EXAFS, IR, XPS and TPD technique. The results suggest that the Mo-O4c (four-centered bridging oxygens) in I were specifically reduced with CO under the illumination to produce two sets of subcarbonyl species, e.g., those characteristic of the IR bands at 2061 and 2021 cm−1, which were thermally inactive for the13CO exchange reaction but very active under illumination at 300 K, possibly assignable to Mo(CO)x (x = 2, 3), whereas those at 2092 and 2035 cm−1 due to Rh(CO)2, which were readily exchangeable with13CO at 300 K in dark. Removal of both carbonyls attached on Rh and Mo in photoreduced I and II by evacuation at 375–440 K led to the formation of oxygen-deficient Mo4+/Mo5+ sites, which exhibited high catalytic activities in propene metathesis at 300 K to produce an equimolar mixture of ethene and 2-butenes. The CO-photoreduced incomplete cubane Mo oxide cluster (II) exhibited higher activities and higher trans/cis ratios of 2-butenes in the reaction, compared with those on the photoreduced I.

EXAFS/FT-IR characterization of tetra-iridium carbonyl clusters bound to tris-(hydroxymethyl)phosphine grafted silica surface catalytically active for propene oxidation to acetone

Abstract Structure and catalytic activity of Ir4(CO)12 bound to tris-(hydroxymethyl)phosphine (THP) grafted silica ( THP SiO 2 ) was investigated by means of EXAFS, FT-IR and kinetic studies. It was found that Ir4(CO)12 was uniformly attached on THP SiO 2 by substitution of CO by THP (Ir4/THP/SiO2). The tetra-iridium carbonyl cluster framework was remained during the substitution of THP ligands and two THP ligands coordinated to the iridium carbonyl clusters to form Ir 4 (CO) 10 (THP SiO 2 ) 2 . species. When Ir4/THP/SiO2 was evacuated at 373 K, bridge CO was desorbed and Debye-Waller factor of IrIr contribution derived from EXAFS analysis was increased which suggested that the cluster framework was distorted by the evacuation at 373 K. The resulting sample evacuated at 373 K was an active catalyst for hydroformylation of ethene and partial oxidation of propene, while the Ir4/THP/SiO2 without evacuation exhibited poor catalytic activities. The propene oxidation reaction proceed on the Ir4/THP/SiO2 evacuated at 323–353 K under subatmospheric pressures to give acetone as a product in high selectivity. The ethene hydroformylation proceed on the evacuated Ir4/THP/SiO2 at lower temperatures compared with other conventional iridium catalysts. EXAFS characterization and kinetic studies suggested that the catalytic activities were associated with the structural distortion of the iridium cluster framework due to surface attachment by the bidentate phosphine substitution.

EXAFS characterization and selective olefin hydroformylation on Rh4, Rh2Co2 and RhCo3 carbonyl clusters attached to tris-hydroxymethylphosphine-grafted silica

Rh4-xCox(CO)12 (x = 0, 2, 3) are attached by carbonyl substitution to THP (tris-hydroxymethylphospine)-grafted silica keeping their cluster frameworks. They have been characterized by Rh K-edge EXAFS (extended X-ray absorption fine structure) and Fourier transform IR spectroscopy. They exhibited high catalytic activity with > 98% selectivity in gas phase hydroformylation of ethene and propene to give aldehydes under mild conditions (40 kPa and 300–373 K).

Ship-in-Bottle synthesis of Pt and Ru carbonyl clusters in NaY zeolite micropore and ordered mesoporous channels of FSM-16; XAFS/FTIR/TPD characterization and their catalytic behaviors

Abstract Ru3(CO)12, H4Ru4(CO)12, [Pt9(CO)18]2− were synthesized in NaY cages by “ship-in-bottle” technique. Thermostable robust platinum clusters [Pt15(CO)30]2− combined with R4N+ (R=Me,Et,Bu and Hex) and MV2+ were encapsulated in the ordered hexagonal mesoporous channels of FSM-16(27.5 diameter) which were characterized by FTIR, EXAFS and HRTEM methods. They remain their flexibility of cluster frameworks and exhibited remarkedly higher catalytic activites for the water-gas-shift reaction, compared with Pt9-Pt12 clusters restricted in NaY micropores(12). Highly disperesed Pt aggregates (ca 15 size) in FSM-16 channels were uniformally prepared from the Pt15 carbonyl clusters by the evacuation, at 323–473K to controlled removal of CO. The coordinatively unsaturated Pt aggregates in FSM-16 exhibited catalytic activities in the hydrogenation of ethene and butadiene selectively towards butenes.

EXAFS and FTIR characterization of tetrarhodium carbonyl clusters attached on tris-(hydroxymethyl)phosphine grafted silica catalytically active for olefin hydroformylation

The structure of the cluster framework in Rh4(CO)12 attached on tris-(hydroxy-methyl)phosphine (P(CH2OH)3,THP) modified SiO2 was studied by EXAFS and IR spectroscopies in conjunction with their catalytic activities and selectivities for the olefin hydroformylation reaction. Rh4(CO)12 was attached on THP/SiO2 by phosphine substitution with remaining Rh4 framework (Rh4/THP/SiO2), which gives the IR bands at 2068, 2044 cm−1 and 1870, 1840 cm−1 due to the linear and bridge CO of the Rh4 clusters. EXAFS study suggested that Rh4 clusters on THP/SiO2 were coordinated by two adjacent phosphine ligands of THP/SiO2 and that the Rh4 framework was fairly distorted. The Rh-Rh distance of Rh4/THP/SiO2 was 0.05 Å longer than that of Rh4(CO)12 crystal. Rh4/THP/SiO2 exhibited the selective formation of propanal in the gas phase hydroformylation of ethene under mild conditions (>98% of propanal formation in 300–373 K, 40 kPa). In contrast, the attached Rh6(CO)16, [Rh(CO)2Cl]2 on THP/SiO2 and Rh4(CO)10(THP)2 on SiO2 were not active for the hydroformylation, which implies that the distorted Rh4 clusters attached on THP/SiO2 are catalytically active and selective towards aldehydes in the olefin hydroformylation.

Low-temperature catalytic decomposition of NO over excess-loading gold(I) in NaY zeolite

The intrazeolite Aul in NaY zeolite exhibits remarkable catalytic activities in the decomposition of NO to N2(N2O) and O2 at low temperatures; the NO decomposition reaction proceeds through the sequential formation of N2O3 and N2O intermediates on Aul/NaY at 300–673 K.