Piero Frediani

Catalytic upgrading of pyrolytic oils to fuel over different zeolites

The upgrading of wood pyrolysis oils produced in the ENEL fast-pyrolysis plant located in Bastardo, Italy, and in the Union Fenosa fast-pyrolysis plant located in La Coruna, Spain, was studied by using HZSM-5 and H-Y zeolites in a fixed-bed laboratory scale reactor, at different temperatures and residence times. The products of the catalytic upgrading were a liquid fraction, char, coke, tar and gas. While the upgraded liquid obtained by using the HZSM-5 consisted of easily separable organic and aqueous layers, the liquid obtained by using the HY zeolite consisted of a single phase in which the organic components were either dispersed or dissolved in the water. The effect of temperature, catalyst type and residence time in the reactor on the yields of the fractions obtained (oil, char, tar, coke, gas and aqueous fraction) and on the characteristics of the upgraded oils was examined.

Homogeneous catalytic hydrogenation of free carboxylic acids in the presence of cluster ruthenium carbonyl hydrides

Abstract Saturated monocarboxylic acids up to C 6 , several bicarboxylic acids and some of the corresponding anhydrides are hydrogenated in the homogeneous phase with H 4 Ru 4 (CO) 8 (PBu 3 ) 4 as catalyst to give the corresponding alcohols (present among the reaction products as esters) or lactones at 100–200°C under a pressure of 100–200 atm of hydrogen. Anhydrides react at temperatures lower than those needed for acids. Esters are not reduced. Only δ-valerolactone is hydrogenated to 1,5-pentanediol. Ruthenium carbonyl carboxylates have been recovered at the end of the reaction and appear to be catalytically active intermediates.

Phosphine-substituted ruthenium carbonyl carboxylates

Abstract The behaviour of the [Ru2(CO)4(CH3COO)2]n/tributylphosphine/acetic acid system has been investigated as a function of reaction conditions and molar ratios of reactants. Tricyclohexylphosphine and triethylphosphite were also used as ligands and investigation was extended to the related oxalic, malonic, succinic, glutaric and adipic acid derivatives. These derivatives were isolated and characterized in view of their possible role as catalysts in the homogeneous hydrogenation of carboxylic acids in the presence of phosphine- or phosphite-substituted ruthenium carbonyl derivatives.

Asymmetric synthesis by chiral ruthenium complexes : II. Enantioselective hydrogenation of α,β-unsaturated carboxylic acids catalyzed by ruthenium complexes containing the ligand ()-diop

Abstract Cluster rutheniumcarbonyl hydrides complexes containing ()-DIOP as asymmetric ligand are efficient catalysts for asymmetric reduction of α,β-unsaturated acids at 90–120°C under hydrogen pressure. Optical yields up to 68% have been achieved. The course of the reaction has been investigated by IR spectroscopy using a high pressure cell.

Asymmetric synthesis by chiral ruthenium complexes: XI. Asymmetric hydrogenation of tiglic acid in the presence of phosphine substituted ruthenium carbonyl carboxylates☆

Abstract The enantioface-discriminating hydrogenation of tiglic acid in the presence of (−)-DIOP substituted carbonyl carboxylato complexes of ruthenium has been investigated in order to identify the factors affecting the stereoselectivity of this reaction. The carboxylato ligand present in the catalytic intermediate does not seem to make a significant contribution to the stereoselectivity of this process. The stereoselectivity seems to be associated with the presence of the optically active phosphine. The catalytic system develops during the reaction through intermediates having a higher enantioface-discriminating activity than the initial and the final ruthenium complexes.

Asymmetric synthesis by chiral ruthenium complexes : III. Regioselectivity and asymmetric induction in catalytic hydrogenation of α,β-unsaturated dicarboxylic acids

Abstract The homogeneous catalytic hydrogenation of citraconic and mesaconic acids in the presence of H4Ru4(CO)8[(—)-DIOP]2 gives, in addition to (—)(S)-methylsuccinic acid, a mixture of λ-lactones in ratios which depend on the substrate and the reaction temperature. An exceptionally high regioselectivity is obtained in the hydrogenation at 120°C of the more hindered carboxyl group of mesaconic acid.

Cluster ruthenium hydrogenation catalysts

Abstract Tetraruthenium dodecacarbonyl tetrahydride and some of its phosphine-substituted derivatives have been tested as homogeneous hydrogenation catalysts. The hydrogenation of cyclohexanone in the presence of H 4 Ru 4 (CO) 12 is first order with respect to the catalyst concentration, the substrate concentration and the partial pressure of hydrogen. The ruthenium cluster is recovered unchanged at the end of the reaction.

Regio- and stereoselective dimerization of 1-alkynes catalyzed by an Os(II) complex

Abstract The complex [(PP 3 )OsH(N 2 )]BPh 4 is a catalyst precursor for the regio- and stereoselective dimerization of HCCR (RPh, SiMe 3 ) to ( Z )-1,4-disubstituted-but-3-en-l-ynes (PP 3 P(CH 2 CH 2 PPh 2 ) 3 ). In the presence of H 2 O or C 2 H 5 OH, the catalytic reaction with HCCSiMe 3 selectively gives but-3-en-l-ynyl-trimethyisilane. A detailed study under different experimental conditions, the detection of some intermediates, and the use of isolated complexes in independent reactions, taken altogether, permit mechanistic conclusions which account for the observed products. A key-role is played by (vinylidene)σ-alkynyl complexes which transform into η 3 -butenynyl derivatives via intramolecular CC bond formation. The Os(II) η 3 -butenynyl complexes are likely reagents in the rate determining step of the catalytic cycle, and produce free ( Z )-1,4-disubstituted-but-3-en-l-ynes upon σ-bond metathesis reaction with HCCR. The 16-electron fragments [(PP 3 )OsX] + (X  H, Cl, CCR) are capable of promoting the 1-alkyne to vinylidene tautomerism. In particular, the (vinylidene)hydride [(PP 3 )OsH{CC(H)-SiMe 3 }]BPh 4 has been isolated and properly characterized. Since the stoichiometric reaction of the latter compound with HCCSiMe 3 gives vinyltrimethylsilane, the formation of (vinylidene)hydride species is suggested to be an effective step, alternative to 1-alkyne insertion, in the reduction of 1-alkynes to alkenes assisted by hydrido metal complexes.

Alkene isomerization by non-hydridic phosphine substituted ruthenium carbonyl carboxylates

Abstract The behaviour of phosphine substituted ruthenium carbonyl carboxylates in the presence of hex-1-ene has been followed by IR and NMR spectroscopies. The complex Ru4(CO)8(MeCO2)4(PBu3)2 reacts at room temperature with a large excess of hex-1-ene giving the Ru2(CO)4(MeCO2)2(PBu3)(hex-1-ene) compound. The same complex is formed from Ru2(CO)4(MeCO2)2(PBu3)2 and hex-1-ene at 80°C. Mononuclear Ru(CO)2(MeCO2)2(PBu3)2 is not transformed under the same conditions. Catalytic tests performed at 80°C in the presence of Ru4(CO)8(MeCO2)4(PBu3)2 or Ru2(CO)4(MeCO2)2(PBu3)2 indicate that these complexes display almost the same catalytic activity in hex-1-ene isomerization in agreement with the formation of the same intermediate. Working in the presence of Ru4(CO)8(MeCO2)4(PBu3)2 at 80°C, an 85% conversion was obtained after 70 h. The isomeric olefins had a trans/cis ratio of 4.5. A reaction scheme has been suggested to rationalise the behaviour of these complexes.

Ruthenium carbonyl carboxylate complexes with nitrogen-containing ligands III. Catalytic activity in hydrogenation☆

Abstract Several mononuclear and dinuclear ruthenium carbonyl acetate complexes containing bipyridine or phenanthroline have been tested as catalysts in the hydrogenation of alkenes, alkynes and ketones. They are active in polar solvents and in water and the nitrogen-containing ligands are unaltered at the end of the hydrogenation.