- Effect of reduction temperature on the characteristics and catalytic properties of TiO2 supported AuPd alloy particles prepared by one-step flame spray pyrolysis in the selective hydrogenation of 1-heptyne
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The bimetallic flame spray-synthesized AuPd/TiO2 catalysts (Au:Pd weight ratio 1:1) were reduced for 2 h under H2 at two different temperatures (40 °C and 500 °C) and tested in the liquid phase selective hydrogenation of 1-heptyne under mild conditions (30 °C and 4 bar H2). Based on TEM-EDX analysis of individual nanoparticles, reduction at 500 °C tends to homogenize the composition of the individual AuPd nanoparticles without significant changes of their average particle size and bulk composition. Higher reaction rate (245 μmol s-1 g cat.-1) was obtained on the AuPd/TiO2 R40 than on the AuPd/TiO2 R500 (223 μmol s-1 g cat.-1). Upon reduction at 500 °C, the bimetallic AuPd/TiO2 exhibited a similar degree of the strong-metal support interaction (SMSI) effect as the monometallic one. As revealed by XPS results, the ratios of Pd/Ti on both catalysts decreased by ca. 23%, due probably to the migration of TiOx species onto the metals. The highest yield of 1-heptene (～93%) was obtained over the bimetallic AuPd/TiO2 reduced at 40 °C in 20 min reaction time under the reaction conditions used. The high temperature reduction is unnecessary for the improvement of catalyst performances when using supported bimetallic AuPd catalysts.
- Pongthawornsakun, Boontida,Mekasuwandumrong, Okorn,Prakash, Swamy,Ehret, Eric,Santos Aires, Francisco J. Cadete,Panpranot, Joongjai
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- n-Alkene and Dihydrogen Formation from n-Alkanes by Photocatalysis using Carbonyl(chloro)phosphine-Rhodium Complexes
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n-Alkenes and dihydrogen were obtained from n-alkanes by photocatalysis using carbonyl(chloro)phosphine-rhodium complexes; the rate of alkane dehydrogenation was the same as that of propan-2-ol dehydrogenation under the same photocatalytic reaction condit
- Nomura, Kotohiro,Saito, Yasukazu
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- Characteristics and catalytic behavior of Pd catalysts supported on nanostructure titanate in liquid-phase hydrogenation
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Titanate nanowire (TNW) and nanotube (TNT) structures were synthesized by the hydrothermal reaction using spherical shape anatase TiO2 nanoparticles (TNP) as the starting material and employed as Pd catalyst supports for the liquid-phase selective hydrogenation of 1-heptyne to 1-heptene. Pd dispersion was significantly improved as the specific surface area of the supports increased in the order: Pd/TNT > Pd/TNW > Pd/TNP. While the hydrogenation rate increased with increasing number of active Pd0 surface, the selectivity to 1-heptene depended largely on the degree of interaction between Pd and the supports. The catalysts prepared by impregnation method led to a stronger metal-support interaction than those prepared by colloidal route. The selectivity of 1-heptene at complete conversion of 1-heptyne was obtained in the order: I-Pd/TNT > I-Pd/TNP > Pd/TNT ≈ Pd/TNW > Pd/TNP. Copyright
- Putdee, Somjit,Mekasuwandumrong, Okorn,Soottitantawat, Apinan,Panpranot, Joongjai
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- ALKYLATION OF PENTAERYTHRITOL BY PHASE-TRANSFER CATALYSIS 2. Crucial Effect of the Aqueous Sodium Hydroxyde Solution
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The mechanistic aspects of the alkylation of pentaerythritol (2-2'-bis(hydroxymethyl)-1,3-propanediol) (PE) by phase-transfer catalysis have been investigated.The dramatic effect of an excess and renewal of sodium hydroxide solutions on the one hand, and the solubility of the PT catalyst in the organic phase on the other, argue that the selectivity of this reaction appears to be controlled almost completely by the possible protonation of the sodium form of the alkoxide anion of PE (4).This protonation depends on the assumption that water molecules are present in the PT medium, and it based upon the observation that this PT medium is actually a three liquid-layer system.As the unusual layer (catalyst layer) may be readily hydrated, the concentrated sodium hydroxide solution can be no longer considered as an unquestionable desiccant.
- Nouguier, Robert,Mchich, Mohamed
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- Highly selective semi-hydrogenation of alkynes with a Pd nanocatalyst modified with sulfide-based solid-phase ligands
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Soluble small molecular/polymeric ligands are often used in Pd-catalyzed semi-hydrogenation of alkynes as an efficient strategy to improve the selectivity of targeted alkene products. The use of soluble ligands requires their thorough removal from the reaction products, which adds significant extra costs. In the paper, commercially available, inexpensive, metallic sulfide-based solid-phase ligands (SPL8-4 and SPL8-6) are demonstrated as simple yet high-performance insoluble ligands for a heterogeneous Pd nanocatalyst (Pd@CaCO3) toward the semi-hydrogenation of alkynes. Based on the reactions with a range of terminal and internal alkyne substrates, the use of the solid-phase ligands has been shown to markedly enhance the selectivity of the desired alkene products by efficiently suppressing over-hydrogenation and isomerization side reactions, even during the long extension of the reactions following full substrate conversion. A proper increase in the dosage or a reduction in the average size of the solid-phase ligands enhances such effects. With their insoluble nature, the solid-phase ligands have the distinct advantage in their simple, convenient recycling and reuse while without contaminating the products. A ten-cycle reusability test with the SPL8-4/Pd@CaCO3 catalyst system confirms its well-maintained activity and selectivity over repeated uses. A mechanistic study with x-ray photoelectron spectroscopy indicates that the solid-phase ligands have electronic interactions with Pd in the supported catalyst, contributing to inhibit the binding and further reaction of the alkene products. This is the first demonstration of solid-phase ligands for highly selective semi-hydrogenation of alkynes, which show strong promise for commercial applications.
- Huang, Lingqi,Hu, Kecheng,Ye, Ganggang,Ye, Zhibin
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- Directing the Rate-Enhancement for Hydronium Ion Catalyzed Dehydration via Organization of Alkanols in Nanoscopic Confinements
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Alkanol dehydration rates catalyzed by hydronium ions are enhanced by the dimensions of steric confinements of zeolite pores as well as by intraporous intermolecular interactions with other alkanols. The higher rates with zeolite MFI having pores smaller than those of zeolite BEA for dehydration of secondary alkanols, 3-heptanol and 2-methyl-3-hexanol, is caused by the lower activation enthalpy in the tighter confinements of MFI that offsets a less positive activation entropy. The higher activity in BEA than in MFI for dehydration of a tertiary alkanol, 2-methyl-2-hexanol, is primarily attributed to the reduction of the activation enthalpy by stabilizing intraporous interactions of the Cβ-H transition state with surrounding alcohol molecules. Overall, we show that the positive impact of zeolite confinements results from the stabilization of transition state provided by the confinement and intermolecular interaction of alkanols with the transition state, which is impacted by both the size of confinements and the structure of alkanols in the E1 pathway of dehydration.
- Shetty, Manish,Wang, Huamin,Chen, Feng,Jaegers, Nicholas,Liu, Yue,Camaioni, Donald M.,Gutiérrez, Oliver Y.,Lercher, Johannes A.
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supporting information
p. 2304 - 2311
(2020/12/01)
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- Piperazine-promoted gold-catalyzed hydrogenation: The influence of capping ligands
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Gold nanoparticles (NPs) combined with Lewis bases, such as piperazine, were found to perform selective hydrogenation reactions via the heterolytic cleavage of H2. Since gold nanoparticles can be prepared by many different methodologies and using different capping ligands, in this study, we investigated the influence of capping ligands adsorbed on gold surfaces on the formation of the gold-ligand interface. Citrate (Citr), poly(vinyl alcohol) (PVA), polyvinylpyrrolidone (PVP), and oleylamine (Oley)-stabilized Au NPs were not activated by piperazine for the hydrogenation of alkynes, but the catalytic activity was greatly enhanced after removing the capping ligands from the gold surface by calcination at 400 °C and the subsequent adsorption of piperazine. Therefore, the capping ligand can limit the catalytic activity if not carefully removed, demonstrating the need of a cleaner surface for a ligand-metal cooperative effect in the activation of H2 for selective semihydrogenation of various alkynes under mild reaction conditions.
- Barbosa, Eduardo C. M.,Camargo, Pedro H. C.,Fiorio, Jhonatan L.,Hashmi, A. Stephen K.,Kikuchi, Danielle K.,Rossi, Liane M.,Rudolph, Matthias
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p. 1996 - 2003
(2020/04/22)
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- A Method for preparing alpha-olefins from Biomass-derived fat and oil
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The present invention relates to a method for preparing alpha-olefins from biomass-derived fats and oils. According to the preparation method, all of the various saturated or unsaturated fatty acids in the biomass-derived fats and oils can be prepared into alpha-olefins, and a conventional problem that the saturated fatty acids do not participate in a reaction or a mixture is generated due to polyunsaturated fatty acids can be solved. Thus, the present invention can be advantageously used to prepare alpha-olefins from biomass.
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Paragraph 0191-0202
(2020/09/22)
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- Kolbe Electrolysis of Biomass-Derived Fatty Acids Over Pt Nanocrystals in an Electrochemical Cell
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Electrochemical valorization of non-food biomass-derived carboxylates into fuels is promising for the conversion, storage, and distribution of renewable electricity. Herein, we demonstrate that biofuels, hydrogen, and bicarbonate can be simultaneously produced in an electrochemical cell by one-step electrolysis of free fatty acids under ambient conditions on 3D self-supported ultralow Pt loading (2 wt %) electrode. The three valuable products can naturally separate from each other during the electrolysis in the alkaline aqueous solution. The experimental suggests that Pt(100) and Pt(110) are favorable for the production of non-Kolbe and Kolbe hydrocarbons, respectively. DFT calculation further clarifies the adsorption and stabilization of the reaction intermediates on Pt(100) and Pt(110).
- Yuan, Gang,Wu, Chan,Zeng, Guorong,Niu, Xiaopo,Shen, Guoqiang,Wang, Li,Zhang, Xiangwen,Luque, Rafael,Wang, Qingfa
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p. 642 - 648
(2019/12/24)
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- Hydrogenation of hydrophobic substrates catalyzed by gold nanoparticles embedded in Tetronic/cyclodextrin-based hydrogels
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Hydrogenation of alkenes, alkynes and aldehydes was investigated under biphasic conditions using Au nanoparticles (AuNP) embedded into combinations of α-cyclodextrin (α-CD) and a poloxamine (Tetronic90R4). Thermo-responsive AuNP-containing α-CD/Tetronic90R4 hydrogels are formed under well-defined conditions of concentration. The AuNP displayed an average size of ca. 7 nm and a narrow distribution, as determined by TEM. The AuNP/α-CD/Tetronic90R4 system proved to be stable over time. Upon heating above the gel-to-sol transition temperature, the studied catalytic system allowed hydrogenation of a wide range of substrates such as alkenes, alkynes and aldehydes under biphasic conditions. Upon repeated heating/cooling cycles, the Au NP/α-CD/Tetronic90R4 catalytic system could be recycled several times without a significant decline in catalytic activity.
- Chevry,Menuel,Léger,No?l,Monflier,Hapiot
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p. 9865 - 9872
(2019/07/04)
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- An Engineered Self-Sufficient Biocatalyst Enables Scalable Production of Linear α-Olefins from Carboxylic Acids
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Fusing the decarboxylase OleTJE and the reductase domain of P450BM3 creates a self-sufficient protein, OleT-BM3R, which is able to efficiently catalyze oxidative decarboxylation of carboxylic acids into linear α-olefins (LAOs) under mild aqueous conditions using O2 as the oxidant and NADPH as the electron donor. The compatible electron transfer system installed in the fusion protein not only eliminates the need for auxiliary redox partners, but also results in boosted decarboxylation reactivity and broad substrate scope. Coupled with the phosphite dehydrogenase-based NADPH regeneration system, this enzymatic reaction proceeds with improved product titers of up to 2.51 g L-1 and volumetric productivities of up to 209.2 mg L-1 h-1 at low catalyst loadings (～0.02 mol%). With its stability and scalability, this self-sufficient biocatalyst offers a nature-friendly approach to deliver LAOs.
- Lu, Chen,Shen, Fenglin,Wang, Shuaibo,Wang, Yuyang,Liu, Juan,Bai, Wen-Ju,Wang, Xiqing
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p. 5794 - 5798
(2018/06/01)
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- Terminal alkyne insertion into a thiolate-bridged dirhodium hydride complex derived from heterolytic cleavage of H2
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Thiolate-bridged dirhodium and diiridium complexes can facilely realize heterolytic cleavage of H2 across the metal-sulfur bond to generate the corresponding hydride bridged complexes. Furthermore, terminal alkynes can insert the Rh-H-Rh fragment to afford σ:π alkenyl bridged complexes and then convert to the corresponding alkenes in the presence of a reductant and an acid.
- Zhao, Xiangyu,Yang, Dawei,Zhang, Yahui,Wang, Baomin,Qu, Jingping
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supporting information
p. 11112 - 11115
(2018/10/15)
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- A durable nanocatalyst of potassium-doped iron-carbide/alumina for significant production of linear alpha olefins via Fischer-Tropsch synthesis
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Improvement of activity, selectivity, and stability of the catalyst used in Fischer-Tropsch synthesis (FTS) to produce targeted hydrocarbon products has been a major challenge. In this work, the potassium-doped iron-carbide/alumina (K-Fe5C2/Al2O3), as a durable nanocatalyst containing small iron-carbide particles (～ 10 nm), was applied to high-temperature Fischer-Tropsch synthesis (HT-FTS) to optimize the production of linear alpha olefins. The catalyst, suitable under high space velocity reaction conditions (14–36 N L gcat?1 h?1) based on the well-dispersed potassium as an efficient base promoter on the active iron-carbide surface, shows very high CO conversion (up to ～90%) with extremely high activity (1.41 mmolCO gFe?1 s?1) and selectivity for C5–C13 linear alpha olefins.
- Park, Ji Chan,Jang, Sanha,Rhim, Geun Bae,Lee, Jin Hee,Choi, Hyunkyoung,Jeong, Heon-Do,Youn, Min Hye,Lee, Dong-Wook,Koo, Kee Young,Kang, Shin Wook,Yang, Jung-Il,Lee, Ho-Tae,Jung, Heon,Kim, Chul Sung,Chun, Dong Hyun
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p. 190 - 198
(2018/08/01)
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- Palladium-Catalyzed Electrochemical Allylic Alkylation between Alkyl and Allylic Halides in Aqueous Solution
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A new route for the direct cross-coupling of alkyl and allylic halides using electrochemical technique has been developed in aqueous media under air. Catalyzed by Pd(OAc)2, the Zn-mediated allylic alkylations proceed smoothly between a full range of alkyl halides (primary, secondary, and tertiary) and substituted allylic halides. Protection-deprotection of acidic hydrogen in the substrates is avoided.
- Lai, Yin-Long,Huang, Jing-Mei
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supporting information
p. 2022 - 2025
(2017/04/28)
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- A Simple and Versatile Approach for the Fabrication of Paper-Based Nanocatalysts: Low Cost, Easy Handling, and Catalyst Recovery
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A versatile method for the preparation of efficient and reusable nanocatalysts involving the painting of a commercial filter paper with a Pd@CNT (CNT=carbon nanotubes) ink was herein explored. The resulting paper-based material provided excellent results in the semihydrogenation of alkynes and alkynols and could be recycled at least five times without loss of activity or selectivity.
- Montiel, Laura,Delgado, Jorge A.,Novell, Marta,Andrade, Francisco J.,Claver, Carmen,Blondeau, Pascal,Godard, Cyril
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p. 3041 - 3044
(2016/10/11)
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- Carbon–Carbon Bond Formation and Hydrogen Production in the Ketonization of Aldehydes
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Aldehydes possess relatively high chemical energy, which is the driving force for disproportionation reactions such as Cannizzaro and Tishchenko reactions. Generally, this energy is wasted if aldehydes are transformed into carboxylic acids with a sacrificial oxidant. Here, we describe a cascade reaction in which the surplus energy of the transformation is liberated as molecular hydrogen for the oxidation of heptanal to heptanoic acid by water, and the carboxylic acid is transformed into potentially industrially relevant symmetrical ketones by ketonic decarboxylation. The cascade reaction is catalyzed by monoclinic zirconium oxide (m-ZrO2). The reaction mechanism has been studied through cross-coupling experiments between different aldehydes and acids, and the final symmetrical ketones are formed by a reaction pathway that involves the previously formed carboxylic acids. Isotopic studies indicate that the carboxylic acid can be formed by a hydride shift from the adsorbed aldehyde on the metal oxide surface in the absence of noble metals.
- Orozco, Lina M.,Renz, Michael,Corma, Avelino
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p. 2430 - 2442
(2016/10/24)
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- Enhancing catalytic performance of activated carbon supported Rh catalyst on heterogeneous hydroformylation of 1-hexene via introducing surface oxygen-containing groups
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Activated carbon supported rhodium (Rh/AC) catalysts with different amounts of oxygen-containing functional groups were prepared by nitric acid (HNO3) treatment at varied temperatures. Thermal analyses of Rh/AC catalysts with or without this acidic treatment were characterized by thermogravimetric analysis (TGA) and temperature programmed desorption (TPD). The change of surface oxygen-containing functional groups was characterized by Fourier transform infrared spectrometry (FTIR) and X-ray photoelectron spectroscopy (XPS). These characterization results indicated that the amount of oxygen-containing functional groups increased with the treatment temperature. The influence of these oxygen-containing functional groups on the products selectivities in heterogeneous hydroformylation reaction was investigated in detail. These abundant functional groups were benefited to improve the selectivity of n-heptanal, resulting in higher n/i (normal to iso) ratio of heptanal. The Rh/AC catalyst being treated at 80?°C had the highest n/i ratio of 2.3, due to the maximum amount of oxygen-containing functional groups, which was almost double to that of raw Rh/AC catalyst. Moreover, abundant functional groups on catalyst suppressed hydrogenation of hexene, decreasing the selectivity of hexane from 4.9% of raw Rh/AC to 0.2%. These findings disclosed that these oxygen-containing functional groups on catalysts played an extremely important role in improving the catalytic performance of heterogeneous hydroformylation reaction, providing a new viewpoint for the studies on heterogeneous hydroformylation.
- Tan, Minghui,Wang, Ding,Ai, Peipei,Liu, Guoguo,Wu, Mingbo,Zheng, Jingtang,Yang, Guohui,Yoneyama, Yoshiharu,Tsubaki, Noritatsu
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- Enzymatic Oxidative Tandem Decarboxylation of Dioic Acids to Terminal Dienes
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The biocatalytic oxidative tandem decarboxylation of C7–C18dicarboxylic acids to terminal C5–C16dienes was catalyzed by the P450 monooxygenase OleT with conversions up to 29 % for 1,11-dodecadiene (0.49 g L–1). The sequential nature of the cascade was proven by the fact that decarboxylation of intermediate C6–C11ω-alkenoic acids and heptanedioic acid exclusively gave nonconjugated 1,4-pentadiene; scale-up allowed the isolation of 1,15-hexadecadiene and 1,11-dodecadiene; the system represents a short and green route to terminal dienes from renewable dicarboxylic acids.
- Dennig, Alexander,Kurakin, Sara,Kuhn, Miriam,Dordic, Andela,Hall, Mélanie,Faber, Kurt
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supporting information
p. 3473 - 3477
(2016/07/29)
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- Synthesis, structure and thermolysis of cis-dialkylplatinum(II) complexes - Experimental and theoretical perceptions
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The formation of new C-C bonds by metal complexes always stimulates great interest because these fundamental reaction types possess numerous potential applications in organic synthesis. These reactions are well documented for a variety of transition metal complexes. Herein we report synthesis and characterization of a series of platinum-dialkyl complexes (1-10) of the type [Pt(L2)R2], (where L2 = dppp (1,3-bis(diphenylphosphino)propane or L = PPh3; R = n-butyl to n-nonyl) with a view to understand the organic product distribution patterns on thermolysis. The single crystal X-ray structures of the complexes [Pt(dppp){CH2(CH2)3CH3}2] (1) and [Pt(dppp){CH2(CH2)6CH3}2] (7) are reported. Thermal decomposition studies of these complexes show interesting behaviour; the longer chain dialkyls i.e. C7-C9 complexes undergo reductive elimination whereas the shorter chain dialkyl complexes and C3-C6 prefer only the β-hydride elimination reaction. Possible mechanistic aspects are discussed. Theoretical calculations reveal the strongest delocalizations in both complexes involve the interaction of Pt-C bond pair electron density with the trans positioned Pt-P antibonding orbital and vice-versa.
- Venkatesh, Sadhana,Sravani, Chinduluri,Janardan, Sannapaneni,Suman, Pothini,Goud, E. Veerashekhara,Pavankumar,Leninkumar, Vardi,Bhat, Haamid R.,Sivaramakrishna, Akella,Vijayakrishna, Kari,Jha, Prakash C.,Smith, Gregory S.
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- Catalytic deoxygenation of octanoic acid over silica- and carbon-supported palladium: Support effects and reaction pathways
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Octanoic acid (OA) deoxygenation was investigated over silica- and carbon-supported palladium catalysts (each containing 5 wt.% Pd) at 235-300 °C and 1 atm in a continuous flow reactor. A commercial Pd/SiO2 (A) catalyst was active for OA decarbonylation (DCN) and hydrodeoxygenation (HDO) at 260 °C under 10% H2; subsequent hydrogenation (HY) and DCN of the primary products, 1-heptene and octanal, respectively, produced n-heptane. Under equivalent conditions, a Pd/SiO2 (B) catalyst prepared using Pd(NO3)2 and Aerosil 300 produced n-heptane with very high selectivity (>99%) via DCN/HY. In contrast, a commercial Pd/C (A) catalyst was highly active and selective to n-heptane (>98%) and CO2 (65%) under these conditions. Moreover, CO2 selectivity and n-heptane yield increased with reaction temperature consistent with direct decarboxylation (DCX). Increasing H2 partial pressure resulted in markedly lower activity and CO2 selectivity; however, Pd/C (A) had negligible activity under He. Pd/C (A) exhibited greater water-gas shift (WGS) activity than Pd/SiO2 (A); however, differences in WGS activity alone cannot explain the observed support effect. A more highly dispersed Pd/C (B) catalyst was more active at 260 °C under H2 than Pd/C (A); however, under 10% H2, it had lower activity, CO2 selectivity (55%), and stability. Pd/C (A) and Pd/C (B) have very similar textural properties, but Pd/C (A) has a much higher Na content. By comparison, Pd supported on high-purity acetylene carbon black exhibited only DCN activity. These results indicate that carbon surface properties (e.g., polar functional groups, alkali metal content) influence the fatty acid deoxygenation performance of Pd/C catalysts.
- Sun, Keyi,Schulz, Taylor C.,Thompson, Simon T.,Lamb, H. Henry
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- Unexpected cleavage of ether bonds of 1,3-dimethoxypropane in Grignard-Wurtz synthesis of a MgCl2-donor adduct
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Diethers are an important group of electron donors in Ziegler-Natta catalysts. A simple diether, 1,3-dimethoxypropane was studied as an electron donor in Grignard-Wurtz synthesis of a MgCl2-donor adduct. 1,3-Dimethoxypropane was unexpectedly found to undergo a cleavage reaction during the synthesis producing methoxy groups (OCH3). Each mole of 1,3-dimethoxypropane produced approximately 2 moles of methoxy groups, which are probably bound to magnesium chloride as methoxymagnesium chloride. A Grignard reagent, BuMgCl formed in the Grignard-Wurtz reaction most likely causes the cleavage of the ether bonds in 1,3-dimethoxypropane and there seem to be at least two parallel reaction paths taking place and producing at least two different by-products. The first step in the cleavage of 1,3-dimethoxypropane is a Grignard reagent (BuMgCl) induced elimination of OCH3, which gives 3-methoxy-1-propene. This intermediate product reacts further in a substitution reaction caused by the Grignard reagent producing 1-heptene as the by-product. The cleavage of the ether bond in 3-methoxy-1-propene and formation of OCH3 can also occur through another reaction path, which produces propene as the by-product.
- Nissinen, Ville,Pirinen, Sami,Pakkanen, Tuula T.
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- A process for preparing 1-heptene method
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The invention relates to a preparation method for 1-heptene. The method comprises a step of contacting ethylene and internal olefin for a cross metathesis reaction in the presence of a catalyst so as to obtain 1-heptene. The catalyst is composed of a compound as shown in a formula (I) and/or a compound as shown in a formula (II). The method has high selectivity and a high conversion rate; with the method, the catalyst shows high activity at a low temperature in a short period of time. The method has the advantages of simpleness, easy operation, controllable reaction conditions and low energy consumption.
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Paragraph 0029-0030; 0031-0032
(2017/02/09)
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- The effect of TiO2 particle size on the characteristics of Au-Pd/TiO2 catalysts
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The nanocrystalline TiO2 materials with average crystallite sizes of 9 and 15 nm were synthesized by the solvothermal method and employed as the supports for preparation of bimetallic Au/Pd/TiO2 catalysts. The average size of Au-Pd alloy particles increased slightly from sub-nano (2 crystallite size from 9 to 15 nm. The catalyst performances were evaluated in the liquid-phase selective hydrogenation of 1-heptyne under mild reaction conditions (H2 1 bar, 30 °C). The exertion of electronic modification of Pd by Au-Pd alloy formation depended on the TiO2 crystallite size in which it was more pronounced for Au/Pd on the larger TiO2 (15 nm) than on the smaller one (9 nm), resulting in higher hydrogenation activity and lower selectivity to 1-heptene on the former catalyst.
- Kittisakmontree, Prathan,Yoshida, Hiroshi,Fujita, Shin-Ichiro,Arai, Masahiko,Panpranot, Joongjai
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- Selective hydrogenation by novel composite supported Pd egg-shell catalysts
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Two organic-inorganic mixed phase supports were prepared, comprising an alumina filler and polymers of different chemical nature. Four low loaded Pd catalysts were prepared. Good activities and selectivities were obtained during the hydrogenations of styrene, 1-heptyne and 2,3-butanedione. The catalysts were found to have excellent mechanical properties and could be used in applications needing high attrition resistance and crushing strength. In this sense, processes for fine chemicals using slurry reactors or processes for commodities using long packed beds could advantageously use them.
- Carrara,Badano,Betti,Lederhos,Rintoul,Coloma-Pascual,Vera,Quiroga
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- Hydroconversion of carboxylic acids using mesoporous SBA-15 supported NiMo sulfide catalysts under microwaves
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Hydrogenation of octanoic acid was performed in a continuous manner, using microwaves (MW), and a supported metal sulfide catalyst. SBA-15, AlSBA-15 and ZrSBA-15 supported NiMo hydrotreating catalysts were prepared by an incipient wetness impregnation method in order to investigate the role of support acidity. Extrudates of the supported NiMo powders were prepared and sulfided. Octanoic acid in dodecane (10%) was introduced in the continuous flow reactor by means of an HPLC pump and co-fed with hydrogen at a working pressure of 0.5 MPa, while varying the reaction parameters such as temperature and feed flow rate (0.1, 0.25, and 0.5 mL min-1). The power applied to the monomodal cavity varied in the range of 15-150 W and corresponding temperature from 200-350 °C. Catalysts and supports were characterized by small- and wide-angle XRD, N2-physisorption (BET, BJH), HRTEM, ICP-MS, and NH3-TPD. The thermal response under MW showed that the extrudates containing SBA-15 (with or without Al or Zr) exhibited a strong MW response. The comparison of the catalytic activities showed that all SBA-15 supported NiMo catalysts exhibited the same activity range but the selectivity as compared to NiMo/Al2O3 catalysts was different.
- Meechai, Titiya,Leclerc, Emmanuel,Laurenti, Dorothée,Somsook, Ekasith,Geantet, Christophe
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p. 101707 - 101712
(2015/12/08)
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- New cofactor supports α,β-unsaturated acid decarboxylation via 1,3-dipolar cycloaddition
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The bacterial ubiD and ubiX or the homologous fungal fdc1 and pad1 genes have been implicated in the non-oxidative reversible decarboxylation of aromatic substrates, and play a pivotal role in bacterial ubiquinone (also known as coenzyme Q) biosynthesis or microbial biodegradation of aromatic compounds, respectively. Despite biochemical studies on individual gene products, the composition and cofactor requirement of the enzyme responsible for in vivo decarboxylase activity remained unclear. Here we show that Fdc1 is solely responsible for the reversible decarboxylase activity, and that it requires a new type of cofactor: a prenylated flavin synthesized by the associated UbiX/Pad1. Atomic resolution crystal structures reveal that two distinct isomers of the oxidized cofactor can be observed, an isoalloxazine N5-iminium adduct and a N5 secondary ketimine species with markedly altered ring structure, both having azomethine ylide character. Substrate binding positions the dipolarophile enoic acid group directly above the azomethine ylide group. The structure of a covalent inhibitor-cofactor adduct suggests that 1,3-dipolar cycloaddition chemistry supports reversible decarboxylation in these enzymes. Although 1,3-dipolar cycloaddition is commonly used in organic chemistry, we propose that this presents the first example, to our knowledge, of an enzymatic 1,3-dipolar cycloaddition reaction. Our model for Fdc1/UbiD catalysis offers new routes in alkene hydrocarbon production or aryl (de)carboxylation.
- Payne, Karl A. P.,White, Mark D.,Fisher, Karl,Khara, Basile,Bailey, Samuel S.,Parker, David,Rattray, Nicholas J.W.,Trivedi, Drupad K.,Goodacre, Royston,Beveridge, Rebecca,Barran, Perdita,Rigby, Stephen E. J.,Scrutton, Nigel S.,Hay, Sam,Leys, David
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supporting information
p. 497 - 501
(2015/07/02)
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- Gold nanocluster-catalyzed semihydrogenation: A unique activation pathway for terminal alkynes
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We report high catalytic activity of ultrasmall spherical Au 25(SC2H4Ph)18 and rod-shaped Au 25(PPh3)10(C≡CPh)5X 2 (X = Br, Cl) nanoclusters supported on oxides for the semihydrogenation of terminal alkynes into alkenes with >99% conversion of alkynes and ～100% selectivity for alkenes. In contrast, internal alkynes cannot be catalyzed by such "ligand-on" Au25 catalysts; however, with "ligand-off" Au25 catalysts the internal alkynes can undergo semihydrogenation to yield Z-alkenes, similar to conventional gold nanoparticle catalysts. On the basis of the results, a unique activation pathway of terminal alkynes by "ligand-on" gold nanoclusters is identified, which should follow a deprotonation activation pathway via a R′-C≡C-[AunLm] (where L represents the protecting ligands on the cluster), in contrast with the activation mechanism on conventional gold nanocatalysts. This new activation mode is supported by observing the incorporation of deprotonated -C≡CPh as ligands on rod-shaped Au25(PPh3)10(C≡ CPh)5X2 nanoclusters under conditions similar to the catalytic reaction and by detecting the R′-C≡C-[Au n(SC2H4Ph)m] via FT-IR spectroscopy.
- Li, Gao,Jin, Rongchao
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p. 11347 - 11354
(2014/11/08)
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- Improved metathesis lifetime: Chelating pyridinyl-alcoholato ligands in the second generation grubbs precatalyst
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Hemilabile ligands can release a free coordination site "on demand" of an incoming nucleophilic substrate while occupying it otherwise. This is believed to increase the thermal stability and activity of catalytic systems and therefore prevent decomposition via free coordination sites. In this investigation chelating pyridinyl-alcoholato ligands were identified as possible hemilabile ligands for incorporation into the second generation Grubbs precatalyst. The O,N-alcoholato ligands with different steric bulk could be successfully incorporated into the precatalysts. The incorporation of the sterically hindered, hemilabile O,N-ligands improved the thermal stability, activity, selectivity and lifetime of these complexes towards the metathesis of 1-octene. A decrease in the activity of the second generation Grubbs precatalyst was additionally observed after incorporating a hemilabile O,N-ligand with two phenyl groups into the system, while increasing their lifetime.
- Du Toit, Jean I.,Jordaan, Margaritha,Huijsmans, Carlijn A. A.,Jordaan, Johannes H. L.,Van Sittert, Cornelia G. C. E.,Vosloo, Hermanus C. M.
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p. 5522 - 5537
(2014/06/10)
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- Room temperature dehydrogenation of ethane, propane, linear alkanes C4-C8, and some cyclic alkanes by titanium-carbon multiple bonds
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The transient titanium neopentylidyne, [(PNP)Ti≈CtBu] (A; PNP-≈N[2-PiPr2-4-methylphenyl] 2-), dehydrogenates ethane to ethylene at room temperature over 24 h, by sequential 1,2-CH bond addition and β-hydrogen abstraction to afford [(PNP)Ti(η2-H2C-CH2)(CH 2tBu)] (1). Intermediate A can also dehydrogenate propane to propene, albeit not cleanly, as well as linear and volatile alkanes C 4-C6 to form isolable α-olefin complexes of the type, [(PNP)Ti(η2-H2C-CHR)(CH2 tBu)] (R = CH3 (2), CH2CH3 (3), nPr (4), and nBu (5)). Complexes 1-5 can be independently prepared from [(PNP)Ti-CHtBu(OTf)] and the corresponding alkylating reagents, LiCH2CHR (R = H, CH3(unstable), CH 2CH3, nPr, and nBu). Olefin complexes 1 and 3-5 have all been characterized by a diverse array of multinuclear NMR spectroscopic experiments including 1H- 31P HOESY, and in the case of the α-olefin adducts 2-5, formation of mixtures of two diastereomers (each with their corresponding pair of enantiomers) has been unequivocally established. The latter has been spectroscopically elucidated by NMR via C-H coupled and decoupled 1H-13C multiplicity edited gHSQC, 1H- 31P HMBC, and dqfCOSY experiments. Heavier linear alkanes (C 7 and C8) are also dehydrogenated by A to form [(PNP)Ti(η2-H2C-CHnPentyl)(CH 2tBu)] (6) and [(PNP)Ti(η2-H 2C-CHnHexyl)(CH2tBu)] (7), respectively, but these species are unstable but can exchange with ethylene (1 atm) to form 1 and the free α-olefin. Complex 1 exchanges with D 2C-CD2 with concomitant release of H2C-CH 2. In addition, deuterium incorporation is observed in the neopentyl ligand as a result of this process. Cyclohexane and methylcyclohexane can be also dehydrogenated by transient A, and in the case of cyclohexane, ethylene (1 atm) can trap the [(PNP)Ti(CH2tBu)] fragment to form 1. Dehydrogenation of the alkane is not rate-determining since pentane and pentane-d12 can be dehydrogenated to 4 and 4-d12 with comparable rates (KIE = 1.1(0) at ～29 C). Computational studies have been applied to understand the formation and bonding pattern of the olefin complexes. Steric repulsion was shown to play an important role in determining the relative stability of several olefin adducts and their conformers. The olefin in 1 can be liberated by use of N2O, organic azides (N3R; R = 1-adamantyl or SiMe3), ketones (O-CPh2; 2 equiv) and the diazoalkane, N2CHtolyl2. For complexes 3-7, oxidation with N2O also liberates the α-olefin.
- Crestani, Marco G.,Hickey, Anne K.,Gao, Xinfeng,Pinter, Balazs,Cavaliere, Vincent N.,Ito, Jun-Ichi,Chen, Chun-Hsing,Mindiola, Daniel J.
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supporting information
p. 14754 - 14767
(2013/10/22)
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- Reactivities of mixed organozinc and mixed organocopper reagents: 9. Solvent dependence of group transfer selectivity in sp3C coupling and acylation of mixed diorganocuprates and diorganozincs
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The selectivity and/or reactivity of organyl group transfer of mixed diorganocuprates in their alkyl coupling in THF depends on N- or O-donor solvents as cosolvents. Selective n-Bu group transfer is observed in room temperature alkylation of Grignard reagent derived stoichiometric n-BuPhCuMgBr reagent in THF:cosolvent and solvation effects do not change the group transfer ability. However, in the alkylation of catalytic mixed cuprates derived from CuI catalyzed n-BuPh2ZnMgBr and n-Bu2PhZnMgBr, group transfer ability depends on the solvation effect and it can be controlled by using N- or O-donor solvents. In alkylation of CuI catalyzed mixed zincate n-BuPh 2ZnMgBr and also n-Bu2PhZnMgBr in THF at reflux temperature Ph group transfer takes place (n-Bu/Ph transfer ratio is 1:9 and 4:6, respectively) whereas n-Bu transfer increases in THF:NMP (1:1) resulting n-Bu/Ph transfer ratio of 4:6 and 8:2, respectively. Group transfer ability in allylation of n-BuPhZn seems not to be solvent dependent. The solvent effect on the group transfer ability has been found to be dependent also on the R 1 and R2 partnership in room temperature benzoylation of catalytic mixed cuprates, R1R2CuZnI, derived from CuI catalyzed R1R2Zn. These results are briefly discussed in terms of solvation of mixed diorganocuprate and diorganozinc reagents and provide useful information in their atom-economic alkyl, allyl and acyl coupling reactions.
- Erdik, Ender,Ero?lu, Fatma,Kalkan, Melike,Pekel, ?zgen ?mür,?zkan, Duygu,Serdar, Ebru Z.
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p. 235 - 241
(2013/10/01)
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- A highly selective route to linear alpha olefins from biomass-derived lactones and unsaturated acids
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This work demonstrates the use of Lewis-acid catalysts, such as gamma-alumina and tungstated alumina, for selective production of linear alpha olefins by decarboxylation of lactones and unsaturated carboxylic acids.
- Wang, Dong,Hakim, Sikander H.,Martin Alonso, David,Dumesic, James A.
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supporting information
p. 7040 - 7042
(2013/09/02)
-
- Synthesis and catalytic investigation of organophilic Pd/graphite oxide nanocomposites
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Low-loaded, organophilic Pd/graphite oxide (Pd/GO) nanocomposites were synthesized from different Pd complex precursors by applying graphite oxide as a host material and tetradecyltrimethylammonium bromide (C14TAB) as a stabilizer. Structural investigation of the Pd/GO samples was performed by ICP-AES, XRD, N2 sorption and TEM measurements. It was found that monodispersed Pd nanoparticles were formed, ranging in size between 1 and 6 nm, both on the external surface and in the interlamellar space of GO. The samples proved to be highly active and selective catalysts for liquid-phase alkyne hydrogenations. The variation in the catalytic performances was attributed to the difference in the amount of interlamellar Pd particles, which participated in the reactions as active sites.
- Mastalir,Szabó,Király,Dékány
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experimental part
p. 104 - 107
(2012/03/26)
-
- Impact of fluorine substituents on the rates of nucleophilic aliphatic substitution and β-elimination
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A measure of the quantitative effect of proximate fluorine substituents on the rates of SN2 and E2 reactions has been obtained through a study mainly of reactions of fluorinated n-alkyl bromides with weak base, strong nucleophile azide ion and strong base/nucleophile methoxide ion in the protic solvent methanol and the aprotic solvent, DMSO. The order of reactivity for SN2 reactions of azide in methanol at 50 °C was found to be: n-alkyl-Br > n-alkyl-CHFBr > n-perfluoroalkyl-CH2CH 2Br n-perfluoroalkyl-CH2Br > n-alkyl-CF2Br. Approximate relative rates of reaction were: 1, 0.20, 0.12, 1 × 10 -4, -5. The order of reactivity for E2 reactions was found to be: n-perfluoroalkyl-CH2CH2Br n-alkyl-CF2Br > n-alkyl-CHFBr > n-alkyl-Br. The approximate relative rates for reaction of methoxide in methanol at 50 °C were: 1100, 4.4, 1.9, 1.
- Martinez, Henry,Rebeyrol, Adele,Nelms, Taylor B.,Dolbier Jr., William R.
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experimental part
p. 167 - 175
(2012/03/27)
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- Cross coupling reactions of multiple CCl bonds of polychlorinated solvents with Grignard reagent using a pincer nickel complex
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The nickel(II) complex of a bulky pincer-type ligand, N,N′-bis(2,6- diisopropylphenyl)-2,6-pyridinedicarboxamido, was examined for sp 3-sp3 coupling of Grignard reagents with polychlorinated solvents. The nickel(II) complex catalyzed CC coupling of polychlorinated alkyl halides, such as dichloromethane (CH2Cl2), chloroform (CHCl3), and carbon tetrachloride (CCl4), with various Grignard reagents. The effective activation of multiple CCl bonds proceeded under ambient reaction conditions and within a short time (20 min). This catalyst displays the highest activity yet reported for this reaction type, with catalyst loading as low as 0.4 mol% and turnover frequency (TOF) as high as 724 h-1. The catalyst is capable of replacing all chlorine atoms with CC bond formations for all of the polychlorinated solvents under investigation. The catalytic process could prove to be an efficient method of remediation of toxic polychlorinated solvents while generating synthetically and commercially important chemicals.
- Gartia, Yashraj,Nasini, Udaya Bhasker,Ghosh, Anindya,Biswas, Abhijit,Stadler, Matthew
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p. 322 - 327,6
(2020/07/30)
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- A novel iron complex for cross-coupling reactions of multiple C-Cl bonds in polychlorinated solvents with grignard reagents
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A novel iron(III) complex (2) of a pincer ligand [1, N2,N6-bis(2,6- diisopropylphenyl)pyridine-2,6-dicarboxamide] was developed and used for remediation of polychlorinated solvents via sp3-sp3 coupling of Grignard reagents with C-Cl bonds. The use of an iron catalyst for such coupling reactions is highly desirable due to its greener and more economical nature. Complex 2 was characterized using various spectroscopic techniques: electrospray ionization mass spectrometer (ESI-MS, m/z 575.1), cyclic voltammetry (E 1/2, 0.03 V and ΔE, 0.97 V), and ultraviolet visible (UV/Vis) spectroscopic techniques. The iron(III) complex showed efficient activation of multiple C-Cl bonds and catalyzing C-C coupling of polychlorinated alkyl halides, such as dichloromethane (CH2Cl2), chloroform (CHCl3), and carbon tetrachloride (CCl4), with various Grignard reagents under ambient reaction conditions. Complex 2 showed exceptional activity with reactions approaching near completion in about 5 min. With the required catalyst loading as low as 0.2 mol%, considerably high turnover numbers (TON = 483) and turnover frequency (TOF = 5,800 h-1) were obtained. None of the products detected during the reaction contained any chlorine, indicating an efficient dechlorination method while synthesizing products of synthetic and commercial interest. Interestingly, the catalyst was capable of replacing all chlorine atoms in each polychlorinated solvent under the investigations with high conversion. Springer Science+Business Media, LLC 2012.
- Gartia, Yashraj,Pulla, Sharon,Ramidi, Punnamchandar,Farris, Carolina Costa,Nima, Zeid,Jones, Darin E.,Biris, Alexandru S.,Ghosh, Anindya
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p. 1397 - 1404
(2013/01/15)
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- Total synthesis of tulearin C
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With the help of the smaller brother: Although alkyne metathesis will always be the little brother of alkene metathesis, it allows problems to be solved that are currently beyond reach of the more famous sibling. This notion is exemplified by the tulearin macrolides, which could only be selectively forged by ring-closing alkyne metathesis (RCAM)/transreduction using the latest generation of alkyne metathesis catalysts.
- Lehr, Konrad,Mariz, Ronaldo,Leseurre, Lucie,Gabor, Barbara,Fuerstner, Alois
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supporting information; experimental part
p. 11373 - 11377
(2012/01/11)
-
- PRODUCING ALPHA-OLEFINS
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Methods for producing alpha-olefins. The methods include selectively isomerizing an alpha-olefin to a mixture of beta-olefins and ethenolyzing at least a portion of the mixture of beta-olefins to an alpha-olefin.
- -
-
Page/Page column 6-7
(2011/07/30)
-
- Thermolysis studies on platinacycloalkane complexes
-
Thermal decomposition studies on platinacycloalkanes of the type Pt(CH 2)mL2 (where m = 6,7,8,10 and L2 = dppp {1,3-bis(diphenylphosphino)propane}, dppe {1,2-bis(diphenylphosphino) ethane} or L = PPh3, tBu3P) are described. The results reveal that the organic product distribution depends on various factors such as the nature of ligand, the metal system, the mode of decomposition, the ring size and the temperature. Possible mechanistic pathways for the formation of various products are discussed. These platinacycloalkanes can be used as models for metallacycloalkane intermediates in catalytic reactions.
- Zheng, Feng,Sivaramakrishna, Akella,Moss, John R.
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scheme or table
p. 2457 - 2465
(2011/06/26)
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- Regiochemical aspects of the platinum oxide catalyzed hydrosilylation of alkynes
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The platinum-catalyzed hydrosilylation of unsymmetrical substituted arylalkynes with various hydrosilanes was investigated and the reaction selectivity of various para-substituted substrates was compared with that of their corresponding orthosubstituted derivatives. We showed that heterogeneous platinum oxide is a very efficient catalyst for such hydrosilylations and that H-Si bond addition proceeds in a stereoselective cis-fashion. The regioselectivity was found to be under the control of the ortho-substituent rather than due to the nature of the platinum catalyst. Arylalkynes with an ortho-substituent provided predominantly to exclusively α-selectivity, regardless of the electronic nature of the substituent. The precise contributions of steric, electronic, and coordinative factors controlling the regioselectivity of the H-Si bond addition are discussed. Georg Thieme Verlag Stuttgart.
- Hamze, Abdallah,Provot, Olivier,Brion, Jean-Daniel,Alami, Mouad
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p. 2025 - 2036
(2008/02/10)
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- Decane oxidation in a shock tube
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The ignition delay of n-decane and oxygen diluted in argon was investigated for a series of mixtures ranging from 0.49 to 1.5% decane and 4.16 to 23.25% O2 diluted in argon. The temperature range was 1239-1616 K and the pressure range was 1.82-10.0 atm. All experiments were performed in a heated shock-tube. An overall ignition delay equation was deduced for 144 experiments: τ = 10-12 exp(+34240/RT)|C10H22| 0.60[O2]-1.305[Ar]0.08 s. Product distribution from preignition periods were measured. Detailed simulation schemes available in the literature were checked and a corrected model is proposed that fits well our experiments.
- Olchansk, Erna,Burcat, Alexander
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p. 703 - 713
(2008/02/12)
-
- OLEFINIC METATHESIS IN THE PRESENCE OF PHENOLIC COMPOUNDS
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According to the present invention there is provided a metathesis reaction between at least two olefinic compounds which are the same or different, each olefinic compound comprising a non-cyclic olefin or a compound which includes a non-cyclic olefinic moiety. The metathesis reaction is carried out in the presence of a Grubbs first generation catalyst and is characterised therein that it is carried out in the presence of a phenolic compound in the form of a phenol or a substituted phenol, which substituted phenol includes at least one hydroxyl and at least one further moiety other than H and OH attached to an arene ring.
- -
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-
- Formation of aldehydes and ketones via reduction of alkyl monohalides by electrogenerated nickel(I) salen in dimethylformamide in the presence of water, oxygen, and light
-
Addition of a stoichiometric amount of a primary alkyl monohalide (1-bromooctane) to a solution of electrogenerated nickel(I) salen in dimethylformamide containing water, followed by irradiation with a xenon arc lamp and brief exposure to air, results in the formation of an aldehyde (1-octanal). Analogous experiments with a secondary alkyl monohalide (2-bromohexane) afford a ketone. Other products are alkanes, alkenes, and dimers that arise from classic radical coupling and disproportionation of alkyl radicals.
- Vanalabhpatana, Parichatr,Peters, Dennis G.
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p. 3245 - 3247
(2007/10/03)
-
- The gas-phase oxidation of n-hexadecane
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Since n-hexadecane or cetane is a reference fuel for the estimation of cetane numbers in diesel engines, a detailed chemical model of its gas-phase oxidation and combustion will help to enhance diesel performance and reduce the emission of pollutants at t
- Fournet,Battin-Leclerc,Glaude,Judenherc,Warth,Come,Scacchi,Ristori,Pengloan,Dagaut,Cathonnet
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p. 574 - 586
(2007/10/03)
-
- Semi-volatile and particulate emissions from the combustion of alternative diesel fuels
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Motor vehicle emissions are a major anthropogenic source of air pollution and contribute to the deterioration of urban air quality. In this paper, we report results of a laboratory investigation of particle formation from four different alternative diesel fuels, namely, compressed natural gas (CNG), dimethyl ether (DME), biodiesel, and diesel, under fuelrich conditions in the temperature range of 800-1200°C at pressures of approximately 24 atm. A single pulse shock tube was used to simulate compression ignition (CI) combustion conditions. Gaseous fuels (CNG and DME) were exposed premixed in air while liquid fuels (diesel and biodiesel) were injected using a high-pressure liquid injector. The results of surface analysis using a scanning electron microscope showed that the particles formed from combustion of all four of the above-mentioned fuels had a mean diameter less than 0.1 μm. From results of gravimetric analysis and fuel injection size it was found that under the test conditions described above the relative particulate yields from CNG, DME, biodiesel, and diesel were 0.30%, 0.026%, 0.52%, and 0.51%, respectively. Chemical analysis of particles showed that DME combustion particles had the highest soluble organic fraction (SOF) at 71%, followed by biodiesel (66%), CNG (38%) and diesel (20%). This illustrates that in case of both gaseous and liquid fuels, oxygenated fuels have a higher SOF than non-oxygenated fuels. Motor vehicle emissions are a major anthropogenic source of air pollution and contribute to the deterioration of urban air quality. In this paper, we report results of a laboratory investigation of particle formation from four different alternative diesel fuels, namely, compressed natural gas (CNG), dimethyl ether (DME), biodiesel, and diesel, under fuelrich conditions in the temperature range of 800-1200°C at pressures of approximately 24 atm. A single pulse shock tube was used to simulate compression ignition (CI) combustion conditions. Gaseous fuels (CNG and DME) were exposed premixed in air while liquid fuels (diesel and biodiesel) were injected using a high-pressure liquid injector. The results of surface analysis using a scanning electron microscope showed that the particles formed from combustion of all four of the above-mentioned fuels had a mean diameter less than 0.1 μm. From results of gravimetric analysis and fuel injection size it was found that under the test conditions described above the relative particulate yields from CNG, DME, biodiesel, and diesel were 0.30%, 0.026%, 0.52%, and 0.51%, respectively. Chemical analysis of particles showed that DME combustion particles had the highest soluble organic fraction (SOF) at 71%, followed by biodiesel (66%), CNG (38%) and diesel (20%). This illustrates that in case of both gaseous and liquid fuels, oxygenated fuels have a higher SOF than non-oxygenated fuels.
- Sidhu, Sukh,Graham, John,Striebich, Richard
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p. 681 - 690
(2007/10/03)
-
- 1,1,2,2-Tetrafluoroethyl-N,N-dimethylamine: A new selective fluorinating agent
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The title compound has been prepared in 96-98% yield by the reaction of tetrafluoroethylene and dimethylamine. 1,1,2,2-Tetrafluoroethyl-N,N-dimethylamine (1) is found to be an effective reagent for the conversion of alcohols into alkyl fluorides. Reaction of 1 and primary alcohols proceeds with high yield formation of the corresponding alkyl fluorides at elevated temperature. However, the reaction of secondary and tertiary alcohols rapidly takes place at 0-10°C, producing corresponding alkyl fluorides as major product along with some olefins.
- Petrov,Swearingen,Hong,Chris Petersen
-
-
- Fine particle and gaseous emission rates from residential wood combustion
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Residential wood combustion emissions were analyzed to determine emission rates and to develop chemical emissions profiles that represent the appliances and woods typically used in wood-burning-communities. Over 350 elements, inorganic compounds, and organic compounds were quantified. A range of 4-9 g/kg dry fuel of particulate matter(a dilution stack sampler equipped with a 2.5-μm particle selective cyclone. Emissions were diluted 20-70 times, cooled to ambient temperature, and allowed 80 s for condensation prior to collection. Wood type, wood moisture, burn rate, and fuel load were varied for different experiments. Fine particle and se mivolatile organic compounds were collected on filter/PUF/XAD/PUF cartridges. Inorganic samples and mass were collected on Teflon and quartz filters. Volatile organic carbon compounds were trapped with Tenax (C8- C20), canister (C2-C12), and 2,4-dinitrophenylhydrazine impregnated cartridges (carbonyl compounds). Analysis of particle and semivolatile organic species was conducted by gas chromatography/mass spectrometry. Teflon filters were analyzed for mass by gravimetry, trace elements were analyzed by X-ray fluorescence and ammonium was analyzed by automated colorimetry. Quartz filters were analyzed for organic and elemental carbon by thermal/optical reflectance, and forts were analyzed by ion chromatography. Select quartz filters were analyzed by accelerator mass spectrometry for carbon-12 and carbon-14 abundance. Canister and Tenax samples were analyzed by gas chromatography with a flame ionization detector, and carbonyl compounds were analyzed by high-performance liquid chromatography. Residential wood combustion emissions were analyzed to determine emission rates and to develop chemical emissions profiles that represent the appliances and woods typically used in wood-burning communities. Over 350 elements, inorganic compounds, and organic compounds were quantified. A range of 4-9 g/kg dry fuel of particulate matter (a dilution stack sampler equipped with a 2.5-μm particle selective cyclone. Emissions were diluted 20-70 times, cooled to ambient temperature, and allowed 80 s for condensation prior to collection. Wood type, wood moisture, burn rate, and fuel load were varied for different experiments. Fine particle and semivolatile organic compounds were collected on filter/PUF/XAD/PUF cartridges. Inorganic samples and mass were collected on Teflon and quartz filters. Volatile organic carbon compounds were trapped with Tenax (C8-C20), canister (C2-C12), and 2,4-dinitrophenylhydrazine impregnated cartridges (carbonyl compounds). Analysis of particle and semivolatile organic species was conducted by gas chromatography/mass spectrometry. Teflon filters were analyzed for mass by gravimetry, trace elements were analyzed by X-ray fluorescence, and ammonium was analyzed by automated colorimetry. Quartz filters were analyzed for organic and elemental carbon by thermal/optical reflectance, and ions were analyzed by ion chromatography. Select quartz filters were analyzed by accelerator mass spectrometry for carbon-12 and carbon-14 abundance. Canister and Tenax samples were analyzed by gas chromatography with a flame ionization detector, and carbonyl compounds were analyzed by high-performance liquid chromatography.
- Mcdonald, Jacob D.,Zielinska, Barbara,Fujita, Eric M.,Sagebiel, John C.,Chow, Judith C.,Watson, John G.
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p. 2080 - 2091
(2007/10/03)
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- Polyoxometalates as reduction catalysts: Deoxygenation and hydrogenation of carbonyl compounds
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Excellent deoxygenation of ketones and aldehydes is achieved with Keggin-type polyoxometalates in the presence of hydrogen (see Equation (1) for an example). The mixed addenda phosphovanadomolybdate [PV2Mo10O4]5- was found to be the best catalyst. X-ray diffraction and IR studies suggest that the polyoxometalates are structurally stable under the strongly reducing conditions.
- Kogan, Vladimir,Aizenshtat, Zeev,Neumann, Ronny
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p. 3331 - 3334
(2007/10/03)
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- Free and polymer-bound tricyclic azaphosphatranes HP(RNCH2CH2)3N+: Procatalysts in dehydrohalogenations and debrominations with NaH
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The commercially available nonionic base P(CH3NCH2CH2)3N (1a) was shown earlier to be superior to DBU as a stoichiometric reagent for the conversion of primary and secondary alkyl halides to alkenes (Arumugam, S.; Verkade, J.G.J. Org. Chem. 1997, 62, 4827). The precursor cation HP(CH3NCH2CH2)3N+ (2) to 1a, which is more stable and less expensive, is reported herein to be an efficient procatalyst for these reactions and also for the debromination of vicinal dibromides using Nail as a relatively inexpensive stoichiometric hydride source in CH3CN at room temperature. In dehydrohalogenations requiring more than ca. 10 h, the CH2CN- ion also acts as a base. By itself, Nail does not function well or at all under the same conditions. A catalytic cycle is proposed in which hydride deprotonates cation 2 liberating catalytic la. The cations HP(HNCH2CH2)3N+, (3) and HP[N(polymer)CH2CH2]N(CH2CH2NH)2+ (4) are also shown to function as procatalysts for the efficient dehydrohalogenation of RX and for the debrommation of vicinal dibromides. The preparation of the heterogeneous procatalyst 4(OTf) is also described.
- Liu, Xiaodong,Verkade, John G.
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p. 4840 - 4843
(2007/10/03)
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- Selective catalytic dechlorination of chloro alkanes over iron-based catalysts
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A selective vapour phase dehydrochlorination (DHC) of chloro alkanes was achieved over a simple iron oxide catalyst system. The chloro alkanes were selectively dehydrochlorinated to their corresponding alkenes. This catalyst was also found to be effective for the removal of chlorine from fuel oil derived from the degradation of PVC containing waste plastics.
- Lingaiah,Uddin, Md. Azhar,Shiraga, Yoshitaka,Tanikawa, Hiroyuki,Muto, Akinori,Sakata, Yusaku,Imai, Tomoyuki
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p. 1321 - 1322
(2007/10/03)
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- Absolute rate expressions for hydrogen atom abstraction from molybdenum hydrides by carbon-centered radicals
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A new family of basis rate expressions for hydrogen atom abstraction by primary, secondary, and tertiary alkyl radicals in dodecane and benzyl radical in benzene from the molybdenum hydride Cp*Mo(CO)3H and for reactions of a primary alkyl radical with CpMo(CO)3H in dodecane are reported (Cp* = η5-pentamethylcyclopentadienyl, Cp = η5-cyclopentadienyl). Rate expressions for reaction of primary, secondary, and tertiary radical clocks with Cp*Mo(CO)3H were as follow: for hex-5-enyl, log(kl/M-1 s-1) = (9.27 ± 0.13) - (1.36 ± 0.22)/θ, θ = 2.303RT kcal/mol; for hept-6-en-2-yl, log(k/M-1 s-1) = (9.12 ± 0.42) - (1.91 ± 0.74)/θ; and for 2-methylhept-6-en-2-yl, log(k/M-1 s-1) = (9.36 ± 0.18) - (3.19 ± 0.30)/θ (errors are 2σ). Hydrogen atom abstraction from CpMo(CO)3H by hex-5-enyl is described by log(k/M-1 s-1) = (9.53 ± 0.34) - (1.24 ± 0.62)/θ. Relative rate constants for 1°:2°:3° alkyl radicals were found to be 26:7:1 at 298 K. Benzyl radical was found to react 1.4 times faster than tertiary alkyl radical. The much higher selectivities for Cp*Mo(CO)3H than those observed for main group hydrides (Bu3SnH, PhSeH, PhSH) with alkyl radicals, together with the very fast benzyl hydrogen-transfer rate, suggest the relative unimportance of simple enthalpic effects and the dominance of steric effects for the early transition-state hydrogen transfers. Hydrogen abstraction from Cp*Mo(CO)3H by benzyl radicals is described by log(k/M-1 s-1) = (8.89 ± 0.22) - (2.31 ± 0.33)/θ.
- Franz, James A.,Linehan, John C.,Birnbaum, Jerome C.,Hicks, Kenneth W.,Alnajjar
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p. 9824 - 9830
(2007/10/03)
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- Pyrolysis of hexadecane
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The kinetics of thermal decomposition of hexadecane was studied in a flow tubular reactor from stainless steel. The experiments were performed in the temperature range of 700 to 780°C for the mass ratio of steam to hydrocarbon 3 : 1. The hexadecane pyrolysis took place according to the first-order reaction with a frequency factor of 3.5 . 109 s-1 and an activation energy of 162 kJ mol-1. In the pyrolysis products there were above all 1-alkenes. From alkanes, methane and ethane and less propane were formed in a higher degree. The prevailing compounds are ethene and propene whose amount increases with increasing temperature and residence time. The content of 1-alkenes higher than 1-pentene decreases with increasing conversion which gives evidence of their decomposition owing to their lower stability in comparison with the lighter 1-alkenes. The formation of dienes (1,3-butadiene and propadiene) and benzene also confirmed the course of secondary reactions. The observed higher formation of hydrogen results from the reaction of steam with coke deposited on the walls of the reactor or with hydrocarbon radicals. The evidence of the coke formation is given also by the presence of carbon oxides whose amount grew with the pyrolysis severity. The high content of 1-hexene in comparison with the other higher 1-alkenes is probably caused by the isomerization of alkyl radicals by 1,5-hydrogen transfer.
- Bartekova, Elena,Bajus, Martin
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p. 1057 - 1069
(2007/10/03)
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