C-O Bond Hydrogenolysis of Aqueous Mixtures of Sugar Polyols and Sugars over ReOx-Rh/ZrO2 Catalyst: Application to an Hemicelluloses Extracted Liquor

SSCI-VIDE+CDFA+CPI:NPR:MBEInternational audiencehydrogenolysi

Bio-adipic acid prepared by base-free aerobic oxidation of bio-based 1,6-hexanediol over Pt-Au/ZrO2 and Pd-Au/ZrO2 catalysts.

SSCI-VIDE+CDFA+MMG:NPR:CPI:MBEInternational audience1. Introduction There is an interest in the production of bio-based adipic acid derived from lignocellulosic biomass as an alternative or a supplement to the petrochemical process.1 Adipic acid is an important monomer in the manufacture of nylon 6,6 and polyurethanes, and a chemical used as food and cosmetic additives.1 It is commonly produced by nitric acid oxidation of a cyclohexanol/cyclohexanone mix.1 Recently, synthesis of 1,6-hexanediol (HDO) from renewables has been described via 5-hydroxymethylfurfural2 or tetrahydropyran-2-methanol3. Thereafter, catalytic oxidation of HDO to adipic acid can be carried out in water using oxygen and Pt/C under acidic conditions or Au/C under basic conditions.4 However, Au-Pt and Au-Pd bimetallic supported catalysts have already shown good performance in oxidation of alcohols or polyols in neutral water.5 Herein we report for the first time the oxidation of 1,6-hexanediol to adipic acid in base-free aqueous medium over Pt-Au/ZrO2 and Pd-Au/ZrO2 catalysts.2. Experimental Monometallic (Pd, Pt, Au) and Pt-Au/ZrO2 and Pd-Au/ZrO2 bimetallic catalysts with different compositions were prepared by wet impregnation of a ZrO2 support (MEL Chemicals, SBET=139 m2 g−1) with aqueous solutions of H2PtCl6, HAuCl4 and PdCl2 and NaBH4 reduction.5,6 The solids were characterized by ICP-OES, XRD, XPS, and TEM. Catalytic oxidation of HDO (0.1 mol. L-1) was carried out in water in a 300 mL batch reactor at 70°C under 40 bar of air, with a HDO/metal molar ratio of 100. Liquid samples were periodically taken during reaction and analyzed by HPLC and Total Organic Carbon (TOC). 3. Results and discussion XRD patterns of the bimetallic catalysts demonstrated the formation of Au-Pd and Au-Pt alloys whose composition, according to Vegard’s law, matched with the metal loadings. Fig.1 shows the evolution of HDO conversion and yields to the different products vs. time over 3.7%Pt/ZrO2. HDO was rapidly and totally converted within 3 h. DA was formed by sequential oxidation of HDO via 6-hydroxyhexanal (ALD), 6-hydroxyhexanoic acid (HA), and 6-oxohexanoic acid (AA) (Scheme 1). A final yield of 80% was observed after 48 h. Comparison of TOC and carbon balance from HPLC analysis were in very good agreement. Scheme 1. Reaction pathway for oxidation of HDO. Figure 1. HDO (0.1M) conversion () and yields to ALD (), HA (), AA (▲) and DA () over Pt/ZrO2 at 70°C under 40 bar of air. C balance (-), TOC (□).Table 1. HDO oxidation over ZrO2 supported Pt, Au, Pd, Pt-Au and Pd-Au. Reaction conditions: 0.1 M HDO, HDO/metal = 100, 70°C, 40 bar air, 48 h.Au/PtConv.Yield (%)Cata (Au/Pd) (%)ALDHAAADAPt-10020080AuPt0.1610000087AuPt0.4210000084AuPt0.7710000097AuPt0.910000096AuPt1.6610000096AuPt6.478532324Au-170603AuPd0.15100020162AuPd0.5895020065AuPd0.9610009081AuPd1.1210005082AuPd3.7855025013Pd-44121615HDO conversion and yields of the different products over the mono- and bimetallic catalysts containing different Au/Pt and Au/Pd ratios after 48 h are gathered in Table 1. Monometallic 3.1%Pd/ZrO2 and 3.6%Au/ZrO2 in the absence of a base were poorly active for oxidation (44% and 17% conversion after 48 h, respectively). Upon addition of Au to Pt and with increasing the Au content of the Au-Pt catalysts, the final yield of diacid increased progressively from 80% to a large maximum of 96-97% with a Au/Pt molar ratio in the range 0.8-1.7. The activity then dropped drastically and HDO conversion was even not total for Au/Pt = 6.4. The addition of Au to Pd and formation of the alloy also significantly improved the performances of the Pd catalyst. The maximum yield of DA was also observed for a Au/Pd ratio of ca. 1. However, the Au-Pd catalysts were less active than the Au-Pt catalysts; after 48 h of reaction, conversion of all intermediates was not complete. However, a higher temperature of 90°C used for Au-Pd/ZrO2 (Au/Pd ca. 1) yielded 96% DA. Comparison of the evolution of the selectivity to the different intermediates as a function of conversion shows different relative reaction rates for the different consecutive steps to DA (Scheme 1).4. Conclusions Pd-Au/ZrO2 and Pt-Au/ZrO2 prepared by a simple preparation procedure were performant catalysts for 1,6-hexanediol oxidation in non-alkaline aqueous medium. The optimization of the catalyst composition showed that adipic acid yield was the highest (96%) at Au/Pd and Au/Pt molar ratio of ca. 1 at 90°C over Pd-Au/ZrO2 and at 70°C over Pt-Au/ZrO2.References 1.S. Van de Vyver, Y. Romàn-Leshkov, Catal. Sci. Technol. 3 (2013) 1467-1479.2.J.G. de Vries, T. Buntara, P. Huat Phua, I.V. Melian Cabrera, H.J. Heeres, WO2011/149339 (2011). 3.S. P. Burt, K. J. Barnett, D. J. McClelland, P. Wolf, J. A. Dumesic, G. W. Huber, I. Hermans, Green Chem. 19 (2017) 1390.4.M. S. Ide, R. J. Davis, J. Catal. 308 (2013) 50-59.5.E. Derrien, M. Mounguengui-Diallo, N. Perret, ́ P. Marion, C. Pinel, Michele Besson, Ind. Eng. Chem. Res. (2017) DOI: 10.1021/acs.iecr.7b01576.K. Heidkamp, M. Aytemir, K.-D. Vorlop, U. Prüsse, Catal. Sci. Technol. 3 (2013) 2984-2992

Oxidation of diols in aqueous solution over supported- Pt, Pt-Au and Pd-Au catalysts: influence of chain length of diol and of catalyst composition

SSCI-VIDE+CDFA+MMG:NPR:CPI:MBEInternational audienceSelective oxidation with air of -diols to hydroxyl-carboxylic acids and diacids over heterogeneous catalysts is a green attractive route for the production of polymers [1]. Noble metals are commonly used for this reaction [2] and the composition of the catalyst may affect the reaction rate, the reaction pathway and thus the final yields. Moreover, the carbon number of diol could also have an influence. The objectives of this study were to compare monometallic Pt/ZrO2 and bimetallic Pt-Au/ZrO2 and Pd-Au/ZrO2 catalysts for oxidation of C4-C6 aliphatic diols.The series of catalysts were prepared by wet-impregnation of ZrO2 (109 m2 g-1) with aqueous solution of metallic salts and NaBH4 reduction [3]. XRD patterns (Fig. 1) show Pt particles sizes of ca ~ 7 nm over monoclinic ZrO2; AuPt and AuPd alloys were formed over Pt-Au/ZrO2 and Pd-Au/ZrO2 materials with particles of ca ~ 5 nm, as confirmed by TEM analysis. The composition of the alloys by XRD were close to the nominal Au/Pt and Au/Pd ratios of 1 of the solids.Oxidation reactions of diols (1,4-butanediol BDO, 1,5-pentanediol PDO and 1,6-hexanediol HDO) were performed in a 300 mL batch reactor (0.1 M diol in water) under 40 bar air at 70°C or 90°C. Liquid samples of the reaction medium were regularly collected and analysed by HPLC and for Total Organic Carbon TOC.Conversion of the diol was very rapid and the reaction was sequential via the corresponding hydroxy-aldehyde (ALD), hydroxy-acid (HA), aldehyde-acid (AA) and diacid (DA) (Scheme 1). During oxidation of BDO, cyclization reactions took place and formed -butyrolactone (GBL), which was poorly reactive.Regardless of the nature of the catalyst, the rate of oxidation of the diol decreased withdecreasing chain length; the order of rate was Pt > Pt-Au > Pd-Au. Moreover, the productsdistribution at similar conversion (50-60%) was different according to the catalyst (Table 1).Theinitial selectivity to ALD was high over Pt and the oxidation of the aldehyde group took placesmoothly; in contrast, over Pd-Au ALD was very rapidly converted to HA, which wasconsequently formed with high initial selectivity.Under the same reaction conditions after 48 h of reaction, the yield of DA increased with thechain length. The Au-Pt catalyst yielded 66% succinic acid, 81% glutaric acid, and 96% adipicacid (Table 1). Reactions performed at 90°C improved the yield of DA over Pd-Au catalyst to97% after 48 h and greatly accelerated oxidation of BDO over Pt-Au.In conclusion, Pt/ZrO2 catalyst is active for oxidation of diols to the diacids. The use of bimetalliccatalysts allowed to improve the final yield of DA. By adjusting the operating conditions, onecan obtain very selectively the desired acid

Investigations on the durability of several Congo basin wood species

International audienceThe sawdust of ten wood species was studied to assess their natural resistance to decay. The extractives and lignin contents were primarily determined (between 2.7-16.0% and 26.8-35.9% respectively) to give an overview of the chemical distribution. Then, a phytochemical screening (colorimetric methods) characterized the different chemical functional groups in all extracts studied. Antioxidant activity indicated values comprised between 18 and 175 µmol AAE/µg of extract correlated to total phenolic content which were comprised between 51 and 935 mg eq. of gallic acid/g of extract. The resistance to decay of extracted and unextracted sawdust against the two white-rot fungi was evaluated and showed that extractives amounts and compositions partially influenced wood durability

Oxydation catalytique de diols et triols biosourcés en diacides surcatalyseurs mono et bimétalliques Pt/ZrO2, Pt-Au/ZrO2 et Pd-Au/ZrO2

SSCI-VIDE+CDFA+MMG:NPR:CPI:MBENational audienceLa substitution partielle des dérivés de la pétrochimie par ceux issus de la biomasse lignocellulosique abondante est un des grands enjeux actuels. Dans cette démarche de développement durable, la production de synthons polyols partiellement hydroxylés, en particulier les -diols, pour la synthèse de polymères biosourcés devient réaliste [1]. Dans ce travail, nous avons étudié l’oxydation catalytique par l’air en phase aqueuse des diols C4-C6 (butane-1,4-diol « BDO», pentane-1,5-diol «PDO» et hexane-1,6-diol «HDO») et d’un triol (l’hexane-1,2,6-triol «HTO») en diacides (DA) correspondants sur des catalyseurs Pt, Pt-Au et Pd-Au supportés sur zircone. Ces catalyseurs aux métaux nobles supportés sont particulièrement intéressants pour cette réaction et l’utilisation de systèmes bimétalliques permet de s’affranchir de l’utilisation de base soluble [2].La caractérisation des catalyseurs préparés par imprégnation voie humide et réduction par NaBH4 (DRX, MET, EDX, XPS) a mis en évidence la formation d’alliage AuPt et AuPd [3]. La réaction est réalisée dans un réacteur batch avec 0.1 M de substrat dans l’eau sous 40 bar d’air à 70°C ou 90°C. Les prélèvements liquides au cours de la réaction sont analysés par HPLC.La conversion du diol est très rapide et la réaction jusqu’au diacide a lieu de façon séquentielle ; l’une des fonctions alcool est oxydée en acide (HA), via l’aldéhyde (ALD), puis la deuxième fonction alcool est oxydée via l’aldéhyde acide (AA) (Figure 1). Dans le cas du BDO, la -butyrolactone (GBL) est également observée comme intermédiaire. Dans les mêmes conditions, après 48 h à 70°C, le rendement en DA augmente avec la longueur de chaine du diol (Figure 2). Le catalyseur Pt-Au/ZrO2 (Au/Pt at. ~1) est le plus efficace (rendements en acides adipique, glutarique, et succinique de 96%, 81%, et 66% après 48 h). Une température de 90°C, d’une part accélère la conversion des intermédiaires sur Au-Pd (rendement de 97% après 48 h), et d’autre part accélère la vitesse d’oxydation de la GBL peu réactive jusqu’à un rendement en acide succinique de 80%. La présence d’une fonction hydroxyle dans HTO réduit fortement l’activité des catalyseurs dans cette réaction. En conclusion, les catalyseurs Pt-Au et Pd-Au supportés convertissent les diols dérivés de la biomasse en diacides pour la synthèse de biopolymères avec de très bons rendements

Oxydation catalytique de diols et triols biosourcés en diacides surcatalyseurs mono et bimétalliques Pt/ZrO2, Pt-Au/ZrO2 et Pd-Au/ZrO2

SSCI-VIDE+CDFA+MMG:NPR:CPI:MBEInternational audienceLa substitution partielle des dérivés de la pétrochimie par ceux issus de la biomasselignocellulosique abondante est un des grands enjeux actuels. Dans cette démarche dedéveloppement durable, la production de synthons polyols partiellement hydroxylés, en particulierles -diols, pour la synthèse de polymères biosourcés devient réaliste [1]. Dans ce travail, nousavons étudié l’oxydation catalytique par l’air en phase aqueuse des diols C4-C6 (butane-1,4-diol« BDO», pentane-1,5-diol «PDO» et hexane-1,6-diol «HDO») et d’un triol (l’hexane-1,2,6-triol«HTO») en diacides (DA) correspondants sur des catalyseurs Pt, Pt-Au et Pd-Au supportés surzircone. Ces catalyseurs aux métaux nobles supportés sont particulièrement intéressants pourcette réaction et l’utilisation de systèmes bimétalliques permet de s’affranchir de l’utilisation debase soluble [2].La caractérisation des catalyseurs préparés par imprégnation voie humide et réduction par NaBH4(DRX, MET, EDX, XPS) a mis en évidence la formation d’alliage AuPt et AuPd [3]. La réaction estréalisée dans un réacteur batch avec 0.1 M de substrat dans l’eau sous 40 bar d’air à 70°C ou90°C. Les prélèvements liquides au cours de la réaction sont analysés par HPLC.La conversion du diol est très rapide et laréaction jusqu’au diacide a lieu de façonséquentielle ; l’une des fonctions alcool estoxydée en acide (HA), via l’aldéhyde (ALD), puisla deuxième fonction alcool est oxydée vial’aldéhyde acide (AA) (Figure 1). Dans le cas duBDO, la -butyrolactone (GBL) est égalementobservée comme intermédiaire.Dans les mêmes conditions, après 48 h à 70°C,le rendement en DA augmente avec la longueurde chaine du diol (Figure 2). Le catalyseur Pt-Au/ZrO2 (Au/Pt at. ~1) est le plus efficace(rendements en acides adipique, glutarique, etsuccinique de 96%, 81%, et 66% après 48 h).Une température de 90°C, d’une part accélère laconversion des intermédiaires sur Au-Pd(rendement de 97% après 48 h), et d’autre partaccélère la vitesse d’oxydation de la GBL peuréactive jusqu’à un rendement en acidesuccinique de 80%.La présence d’une fonction hydroxyle dans HTOréduit fortement l’activité des catalyseurs danscette réaction.En conclusion, les catalyseurs Pt-Au et Pd-Ausupportés convertissent les diols dérivés de labiomasse en diacides pour la synthèse debiopolymères avec de très bons rendements

Oxidation of diols in aqueous solution over supported- Pt, Pt-Au and Pd-Au catalysts: influence of chain length of diol and of catalyst composition

SSCI-VIDE+CDFA+MMG:NPR:CPI:MBEInternational audienceSelective oxidation with air of -diols to hydroxyl-carboxylic acids and diacids over heterogeneous catalysts is a green attractive route for the production of polymers [1]. Noble metals are commonly used for this reaction [2] and the composition of the catalyst may affect the reaction rate, the reaction pathway and thus the final yields. Moreover, the carbon number of diol could also have an influence. The objectives of this study were to compare monometallic Pt/ZrO2 and bimetallic Pt-Au/ZrO2 and Pd-Au/ZrO2 catalysts for oxidation of C4-C6 aliphatic diols.The series of catalysts were prepared by wet-impregnation of ZrO2 (109 m2 g-1) with aqueous solution of metallic salts and NaBH4 reduction [3]. XRD patterns (Fig. 1) show Pt particles sizes of ca ~ 7 nm over monoclinic ZrO2; AuPt and AuPd alloys were formed over Pt-Au/ZrO2 and Pd-Au/ZrO2 materials with particles of ca ~ 5 nm, as confirmed by TEM analysis. The composition of the alloys by XRD were close to the nominal Au/Pt and Au/Pd ratios of 1 of the solids.Oxidation reactions of diols (1,4-butanediol BDO, 1,5-pentanediol PDO and 1,6-hexanediol HDO) were performed in a 300 mL batch reactor (0.1 M diol in water) under 40 bar air at 70°C or 90°C. Liquid samples of the reaction medium were regularly collected and analysed by HPLC and for Total Organic Carbon TOC.Conversion of the diol was very rapid and the reaction was sequential via the corresponding hydroxy-aldehyde (ALD), hydroxy-acid (HA), aldehyde-acid (AA) and diacid (DA) (Scheme 1). During oxidation of BDO, cyclization reactions took place and formed -butyrolactone (GBL), which was poorly reactive.Regardless of the nature of the catalyst, the rate of oxidation of the diol decreased withdecreasing chain length; the order of rate was Pt > Pt-Au > Pd-Au. Moreover, the productsdistribution at similar conversion (50-60%) was different according to the catalyst (Table 1).Theinitial selectivity to ALD was high over Pt and the oxidation of the aldehyde group took placesmoothly; in contrast, over Pd-Au ALD was very rapidly converted to HA, which wasconsequently formed with high initial selectivity.Under the same reaction conditions after 48 h of reaction, the yield of DA increased with thechain length. The Au-Pt catalyst yielded 66% succinic acid, 81% glutaric acid, and 96% adipicacid (Table 1). Reactions performed at 90°C improved the yield of DA over Pd-Au catalyst to97% after 48 h and greatly accelerated oxidation of BDO over Pt-Au.In conclusion, Pt/ZrO2 catalyst is active for oxidation of diols to the diacids. The use of bimetalliccatalysts allowed to improve the final yield of DA. By adjusting the operating conditions, onecan obtain very selectively the desired acid

Klebsiella Pneumoniae Communiy-Acquired Pneumonia in a Trisomic at Omar Bongo Ondimba's Army Instruction Hospital (HIA OBO)

Kp community-acquired pneumonia is rarely encountered. Its prevalence is higher in Asia, where a higher strain virulence was demonstrated [1,2]. It’s a pyo-pneumothorax, which usually occurs on debilitated or&nbsp; immuno-compromised patients. It is a severe disease&nbsp;associated with high mortality. Here, we report the observation of a Kp community-acquired pneumonia occurring in a genetic disorder context.</p

Oxydation catalytique de diols et triols biosourcés en diacides surcatalyseurs mono et bimétalliques Pt/ZrO2, Pt-Au/ZrO2 et Pd-Au/ZrO2

SSCI-VIDE+CDFA+MMG:NPR:CPI:MBEInternational audienceLa substitution partielle des dérivés de la pétrochimie par ceux issus de la biomasselignocellulosique abondante est un des grands enjeux actuels. Dans cette démarche dedéveloppement durable, la production de synthons polyols partiellement hydroxylés, en particulierles -diols, pour la synthèse de polymères biosourcés devient réaliste [1]. Dans ce travail, nousavons étudié l’oxydation catalytique par l’air en phase aqueuse des diols C4-C6 (butane-1,4-diol« BDO», pentane-1,5-diol «PDO» et hexane-1,6-diol «HDO») et d’un triol (l’hexane-1,2,6-triol«HTO») en diacides (DA) correspondants sur des catalyseurs Pt, Pt-Au et Pd-Au supportés surzircone. Ces catalyseurs aux métaux nobles supportés sont particulièrement intéressants pourcette réaction et l’utilisation de systèmes bimétalliques permet de s’affranchir de l’utilisation debase soluble [2].La caractérisation des catalyseurs préparés par imprégnation voie humide et réduction par NaBH4(DRX, MET, EDX, XPS) a mis en évidence la formation d’alliage AuPt et AuPd [3]. La réaction estréalisée dans un réacteur batch avec 0.1 M de substrat dans l’eau sous 40 bar d’air à 70°C ou90°C. Les prélèvements liquides au cours de la réaction sont analysés par HPLC.La conversion du diol est très rapide et laréaction jusqu’au diacide a lieu de façonséquentielle ; l’une des fonctions alcool estoxydée en acide (HA), via l’aldéhyde (ALD), puisla deuxième fonction alcool est oxydée vial’aldéhyde acide (AA) (Figure 1). Dans le cas duBDO, la -butyrolactone (GBL) est égalementobservée comme intermédiaire.Dans les mêmes conditions, après 48 h à 70°C,le rendement en DA augmente avec la longueurde chaine du diol (Figure 2). Le catalyseur Pt-Au/ZrO2 (Au/Pt at. ~1) est le plus efficace(rendements en acides adipique, glutarique, etsuccinique de 96%, 81%, et 66% après 48 h).Une température de 90°C, d’une part accélère laconversion des intermédiaires sur Au-Pd(rendement de 97% après 48 h), et d’autre partaccélère la vitesse d’oxydation de la GBL peuréactive jusqu’à un rendement en acidesuccinique de 80%.La présence d’une fonction hydroxyle dans HTOréduit fortement l’activité des catalyseurs danscette réaction.En conclusion, les catalyseurs Pt-Au et Pd-Ausupportés convertissent les diols dérivés de labiomasse en diacides pour la synthèse debiopolymères avec de très bons rendements