Know-how obtained from petrochemical processes on the catalytical properties of pentasil zeolites... more Know-how obtained from petrochemical processes on the catalytical properties of pentasil zeolites is being used for selective organic syntheses in the chemistry of intermediates. The isomerization properties are demonstrated by doublebond migrations in olefins with carbonyl groups and by the aldehyde/ketone rearrangement. The dehydration properties are used in the conversion of aldehydes to 1,3-dienes, in aldol condensation reactions and for the preparation of dicarboxylic acid nitriles from acids and ammonia. Therefore this paper concentrates on hydrocarbons with carbonyl groups. 'jaddnj 'M 'e)UTeJ 'i 'g°w 'a 'M '!S0.APW '1 'J 'uJ0qLp3 'H 'L13!JePIQH 'M '1? 2117-99 'd 17261 PJ0Pi!fl9 'qJ0MAang
Two samples of MFI-type zeolites (A, SiO 2 /Al 2 O 3 = 30, 0.02 wt% Fe, and B, SiO 2 /Al 2 O 3 = ... more Two samples of MFI-type zeolites (A, SiO 2 /Al 2 O 3 = 30, 0.02 wt% Fe, and B, SiO 2 /Al 2 O 3 = 20, 0.03 wt% Fe) were dealuminated with (NH 4) 2 SiF 6 by three different methods. Method (i) consisted of aqueous treatment in a buffered solution followed by thorough washing with distilled water. Method (ii) consisted of isomorphous substitution in the solid state at moderate temperatures followed by thorough washing with deionized water. Method (iii) involved the removal of aluminum fluoro complexes by thermal decomposition after the preceding solidstate isomorphous substitution procedure. The materials were characterized by ICP-AES, physisorption of N 2 , XRD, FT-IR, PyFT-IR, and 1 H, 27 Al, 29 Si, and 19 F MAS NMR prior to and after catalytic testing for direct hydroxylation of benzene to phenol. It was shown that the materials were loaded with considerable amounts of F − in the form of Al-F and Si-F prior to the reaction, which disappeared quantitatively after the reaction. Catalytic properties, in terms of activity and the rate of deactivation, could be correlated to acid-base and textural properties. Materials prepared according to method (iii) showed the best catalytic activity. Materials prepared according to method (ii) showed moderate activity, whereas the formation of phenol was hardly detected over materials prepared according to method (i).
Oxidation of primary hydroxyl groups of potato starch to the corresponding carboxylic acids was p... more Oxidation of primary hydroxyl groups of potato starch to the corresponding carboxylic acids was performed in a fluidized bed using N 2-diluted NO 2 as oxidant. FT-IR spectrum of the oxidized starch show the presence of two absorption bands at 1743 and 1379 cm −1. The absorption at 1743 cm −1 which normally attributed to carbonyl absorption vanishes after washing the oxidized starch by water. Then two new absorption bands appeared at 1650 and 1400 cm −1 corresponding to the ionized carboxyl groups. The presence of nitrate favor the un-ionized form of carboxyl groups and then the band at 1743 cm −1 can be observed. Furthermore, the ionized carboxyl absorption (1600, 1400 cm −1) are replaced by carbonyl absorption at 1743 cm −1 by adding DCl. By means of 13 C NMR analysis, oxidized starch, show a band around 200 ppm attributed to carboxylic acid, no formic acid was detected indicating that no cleavage took place under the applied reactions conditions.
Primary hydroxyl groups were oxidized regioselectively to carboxylic acid using organic nitrosoni... more Primary hydroxyl groups were oxidized regioselectively to carboxylic acid using organic nitrosonium salts generated on supported silver catalysts, which promote disproportionation of 2,2,6,6tetramethylpiperidinyl-1-oxy (TEMPO) in aqueous solution. The oxidation reactions were performed at pH 9.5 in a batch reactor at room temperture using heterogeneous silver catalysts and peroxides as primary co-oxidants; e.g., 99 mol% selectivity to methyl-α-D-glucopyrasiduronic acid was obtained at 90% conversion of the pyranoside using a silver carbonate-celite catalyst. The efficiency of the system was increased by adding carbonates to the silver catalyst. This result is explained by the increase of the electron charge deficiency on silver in the presence of carbonate, which accelerates the nucleophilic attack of hydroxyls and/or TEMPO. In the case of the Ag-Al 2 O 3 catalyst, this result was proved by temperatureprogrammed desorption measurements using ammonia. With primary/secondary polyols, the selectivity for the primary hydroxyl groups is high. In addition, primary hydroxyl groups, as in the case of pyranosides, were oxidized more selectively than those of the furanosides. The observed regioselectivity is due to the sterical hindrance caused by the four methyl groups in TEMPO.
Alors que les ressources fossiles decroissent, le concept de bio-raffinerie est une approche tres... more Alors que les ressources fossiles decroissent, le concept de bio-raffinerie est une approche tres attrayante pour la production de produits chimiques a partir de ressources renouvelables. Dans ce contexte, les derives d’acides gras insatures, obtenus par hydrolyse de triglycerides issus de vegetaux, sont une categorie importante de substrats. Leur conversion en composes a haute valeur ajoutee est un objectif majeur qui peut etre atteint grâce a la catalyse, et plus particulierement grâce a la metathese des alcenes. De plus, dans un esprit de meilleure separation entre produits et catalyseurs, et pour des questions de recyclage, l’emploi de catalyseurs heterogenes est de grand interet. L’heterogeneisation de catalyseurs commerciaux a base de ruthenium a ete entreprise. Les materiaux hybrides ont ete prepares en deux etapes: apres une cationisation a l’aide de sels d’argent, les especes organometalliques ont ete immobilisees par echange ionique dans les aluminosilicates mesoporeuses de type MCM-41. Ces nouveaux catalyseurs ont ete caracterises par RMN du solide, IR, DRX, BET, analyse elementaire et ATG. Ils ont ete employes avec succes dans differentes reactions de metathese impliquant le substrat-type, l’oleate de methyle. Les reactions etudiees sont l’homometathese, l’ethenolyse et la metathese croisee avec des olefines fonctionnalisees issues des acides acrylique et crotonique. Bien que le recyclage n’ait pas ete couronne de succes, les catalyseurs supportes permettent de realiser toutes ces reactions, ce qui represente dans certains cas le premier exemple de telles transformations par catalyse heterogene avec des activites et selectivites elevees.
Zeolites X, Y, and DAY have been modified by a post-synthetical dealumination procedure to genera... more Zeolites X, Y, and DAY have been modified by a post-synthetical dealumination procedure to generate mesopores that are completely surrounded by micropores. In these novel host materials several bulky transition metal salen complexes have been occluded via the "ship-in-a-bottle" synthesis approach. Both the host materials and the "ship-in-a-bottle" catalysts have been characterized by FTIR spectroscopy and nitrogen adsorption. Additionally, the "ship-in-a-bottle" catalysts have been characterized by thermogravimetric analysis and ICP-AES spectroscopy. The catalysts have been tested in the stereoselective epoxidation of R-(+)-limonene and (−)-␣-pinene with molecular oxygen as oxidant. The best results so far-100% conversion, 96% selectivity and 91% de-were achieved with the immobilized (R,R)-(N,N)-bis(3,5-di-tert-butylsalicylidene)-1,2-diphenylethylene-1,2-diaminocobalt complex in the epoxidation of (−)-␣-pinene.
Know-how obtained from petrochemical processes on the catalytical properties of pentasil zeolites... more Know-how obtained from petrochemical processes on the catalytical properties of pentasil zeolites is being used for selective organic syntheses in the chemistry of intermediates. The isomerization properties are demonstrated by doublebond migrations in olefins with carbonyl groups and by the aldehyde/ketone rearrangement. The dehydration properties are used in the conversion of aldehydes to 1,3-dienes, in aldol condensation reactions and for the preparation of dicarboxylic acid nitriles from acids and ammonia. Therefore this paper concentrates on hydrocarbons with carbonyl groups. 'jaddnj 'M 'e)UTeJ 'i 'g°w 'a 'M '!S0.APW '1 'J 'uJ0qLp3 'H 'L13!JePIQH 'M '1? 2117-99 'd 17261 PJ0Pi!fl9 'qJ0MAang
Two samples of MFI-type zeolites (A, SiO 2 /Al 2 O 3 = 30, 0.02 wt% Fe, and B, SiO 2 /Al 2 O 3 = ... more Two samples of MFI-type zeolites (A, SiO 2 /Al 2 O 3 = 30, 0.02 wt% Fe, and B, SiO 2 /Al 2 O 3 = 20, 0.03 wt% Fe) were dealuminated with (NH 4) 2 SiF 6 by three different methods. Method (i) consisted of aqueous treatment in a buffered solution followed by thorough washing with distilled water. Method (ii) consisted of isomorphous substitution in the solid state at moderate temperatures followed by thorough washing with deionized water. Method (iii) involved the removal of aluminum fluoro complexes by thermal decomposition after the preceding solidstate isomorphous substitution procedure. The materials were characterized by ICP-AES, physisorption of N 2 , XRD, FT-IR, PyFT-IR, and 1 H, 27 Al, 29 Si, and 19 F MAS NMR prior to and after catalytic testing for direct hydroxylation of benzene to phenol. It was shown that the materials were loaded with considerable amounts of F − in the form of Al-F and Si-F prior to the reaction, which disappeared quantitatively after the reaction. Catalytic properties, in terms of activity and the rate of deactivation, could be correlated to acid-base and textural properties. Materials prepared according to method (iii) showed the best catalytic activity. Materials prepared according to method (ii) showed moderate activity, whereas the formation of phenol was hardly detected over materials prepared according to method (i).
Oxidation of primary hydroxyl groups of potato starch to the corresponding carboxylic acids was p... more Oxidation of primary hydroxyl groups of potato starch to the corresponding carboxylic acids was performed in a fluidized bed using N 2-diluted NO 2 as oxidant. FT-IR spectrum of the oxidized starch show the presence of two absorption bands at 1743 and 1379 cm −1. The absorption at 1743 cm −1 which normally attributed to carbonyl absorption vanishes after washing the oxidized starch by water. Then two new absorption bands appeared at 1650 and 1400 cm −1 corresponding to the ionized carboxyl groups. The presence of nitrate favor the un-ionized form of carboxyl groups and then the band at 1743 cm −1 can be observed. Furthermore, the ionized carboxyl absorption (1600, 1400 cm −1) are replaced by carbonyl absorption at 1743 cm −1 by adding DCl. By means of 13 C NMR analysis, oxidized starch, show a band around 200 ppm attributed to carboxylic acid, no formic acid was detected indicating that no cleavage took place under the applied reactions conditions.
Primary hydroxyl groups were oxidized regioselectively to carboxylic acid using organic nitrosoni... more Primary hydroxyl groups were oxidized regioselectively to carboxylic acid using organic nitrosonium salts generated on supported silver catalysts, which promote disproportionation of 2,2,6,6tetramethylpiperidinyl-1-oxy (TEMPO) in aqueous solution. The oxidation reactions were performed at pH 9.5 in a batch reactor at room temperture using heterogeneous silver catalysts and peroxides as primary co-oxidants; e.g., 99 mol% selectivity to methyl-α-D-glucopyrasiduronic acid was obtained at 90% conversion of the pyranoside using a silver carbonate-celite catalyst. The efficiency of the system was increased by adding carbonates to the silver catalyst. This result is explained by the increase of the electron charge deficiency on silver in the presence of carbonate, which accelerates the nucleophilic attack of hydroxyls and/or TEMPO. In the case of the Ag-Al 2 O 3 catalyst, this result was proved by temperatureprogrammed desorption measurements using ammonia. With primary/secondary polyols, the selectivity for the primary hydroxyl groups is high. In addition, primary hydroxyl groups, as in the case of pyranosides, were oxidized more selectively than those of the furanosides. The observed regioselectivity is due to the sterical hindrance caused by the four methyl groups in TEMPO.
Alors que les ressources fossiles decroissent, le concept de bio-raffinerie est une approche tres... more Alors que les ressources fossiles decroissent, le concept de bio-raffinerie est une approche tres attrayante pour la production de produits chimiques a partir de ressources renouvelables. Dans ce contexte, les derives d’acides gras insatures, obtenus par hydrolyse de triglycerides issus de vegetaux, sont une categorie importante de substrats. Leur conversion en composes a haute valeur ajoutee est un objectif majeur qui peut etre atteint grâce a la catalyse, et plus particulierement grâce a la metathese des alcenes. De plus, dans un esprit de meilleure separation entre produits et catalyseurs, et pour des questions de recyclage, l’emploi de catalyseurs heterogenes est de grand interet. L’heterogeneisation de catalyseurs commerciaux a base de ruthenium a ete entreprise. Les materiaux hybrides ont ete prepares en deux etapes: apres une cationisation a l’aide de sels d’argent, les especes organometalliques ont ete immobilisees par echange ionique dans les aluminosilicates mesoporeuses de type MCM-41. Ces nouveaux catalyseurs ont ete caracterises par RMN du solide, IR, DRX, BET, analyse elementaire et ATG. Ils ont ete employes avec succes dans differentes reactions de metathese impliquant le substrat-type, l’oleate de methyle. Les reactions etudiees sont l’homometathese, l’ethenolyse et la metathese croisee avec des olefines fonctionnalisees issues des acides acrylique et crotonique. Bien que le recyclage n’ait pas ete couronne de succes, les catalyseurs supportes permettent de realiser toutes ces reactions, ce qui represente dans certains cas le premier exemple de telles transformations par catalyse heterogene avec des activites et selectivites elevees.
Zeolites X, Y, and DAY have been modified by a post-synthetical dealumination procedure to genera... more Zeolites X, Y, and DAY have been modified by a post-synthetical dealumination procedure to generate mesopores that are completely surrounded by micropores. In these novel host materials several bulky transition metal salen complexes have been occluded via the "ship-in-a-bottle" synthesis approach. Both the host materials and the "ship-in-a-bottle" catalysts have been characterized by FTIR spectroscopy and nitrogen adsorption. Additionally, the "ship-in-a-bottle" catalysts have been characterized by thermogravimetric analysis and ICP-AES spectroscopy. The catalysts have been tested in the stereoselective epoxidation of R-(+)-limonene and (−)-␣-pinene with molecular oxygen as oxidant. The best results so far-100% conversion, 96% selectivity and 91% de-were achieved with the immobilized (R,R)-(N,N)-bis(3,5-di-tert-butylsalicylidene)-1,2-diphenylethylene-1,2-diaminocobalt complex in the epoxidation of (−)-␣-pinene.
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Papers by Wolfgang Hölderich