The chemoselective alkylation and olefination of alkylnitriles with alcohols have been developed by simply controlling the reaction atmosphere. A binuclear rhodium complex catalyzes the alkylation ...reaction under argon through a hydrogen‐borrowing pathway and the olefination reaction under oxygen through aerobic dehydrogenation. Broad substrate scope is demonstrated, permitting the synthesis of some important organic building blocks. Mechanistic studies suggest that the alkylation product may be formed through conjugate reduction of an alkene intermediate by a rhodium hydride, whereas the formation of olefin product may be due to the oxidation of the rhodium hydride complex with molecular oxygen.
There's something in the air: A binuclear rhodium complex catalyzes the chemoselective alkylation and olefination of alkylnitriles with alcohols, with the selectivity controlled solely by the reaction atmosphere. The reactions have broad substrate scope and could be applied to the synthesis of unique amino acids.
More hip than nano: Bielawski and co‐workers recently demonstrated the remarkable ability of graphene oxide to catalyze the oxidation of a variety of alcohols to the corresponding ketones/aldehydes, ...alkenes to the corresponding diones, and alkynes to the corresponding hydrates—a process they termed “carbocatalysis”. These efficient metal‐free reactions mark a promising convergence of heterogeneous catalysis with graphene science.
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•Simplified kinetic models were developed for benzyl alcohol oxidation.•Model discrimination was applied to find the most appropriate kinetic model.•At low temperature, toluene ...formation is dominated by disproportionation.•At high temperature, toluene formation is dominated by hydrogenolysis.
Bimetallic Au-Pd nanoparticles supported on TiO2 show excellent catalytic activity and selectivity to benzaldehyde in the solvent-free transformation of benzyl alcohol to benzaldehyde, where toluene is the main observed by-product, together with smaller amounts of benzoic acid, benzyl benzoate and dibenzyl ether. However, despite the industrial relevance of this reaction and importance of tuning the selectivity to the desired benzaldehyde, only a few attempts have been made in the literature on modeling the reaction kinetics for a quantitative description of this reaction system. A kinetic model for the oxidation of benzyl alcohol over Au-Pd is proposed in this paper. The model assumes that hydrogenolysis, disproportionation and dehydrogenation reactions may occur in parallel, and it has been found satisfactory after a model discrimination procedure was applied to a number of simplified candidate models developed from microkinetic studies. Despite its relative simplicity, the proposed model is capable of representing the reactant conversion and distribution of products observed in experiments carried out at different temperature, pressure and catalyst mass in a stirred batch reactor. Major findings include the quantitative evaluation of the impact of hydrogenolysis and disproportionation pathways on benzaldehyde production. At low temperature the disproportionation reaction is the dominant route to toluene formation, while hydrogenolysis dominates at high temperature.
The present study analyzes the emission pattern of Decanol combined Jatropha biodiesel (JBD100) fueled diesel engine and compared with conventional diesel fuel (D100). Experiments were conducted in a ...single-cylinder, 4-stroke naturally aspirated diesel engine with an eddy current dynamometer at a constant speed of 1800 rpm. Modified fuel was prepared using a mechanical agitator, in which the Decanol concentration was varied from 10 to 20% to JBD100. The physicochemical properties of Decanol combined biodiesel are within ASTM limits. JBD100 promotes a lower level of carbon monoxide (CO) hydrocarbon (HC), and smoke emissions with notable increases in NO
x
and carbon dioxide (CO
2
) emissions. An inclusion of 20% Decanol in JBD100 reduces the NO
x
, Smoke, CO, and HC emission by 7.4%, 4.4%, 5.7%, and 5.9%, respectively, under full brake power.
Nanoporous Carbohydrate Metal–Organic Frameworks Forgan, Ross S; Smaldone, Ronald A; Gassensmith, Jeremiah J ...
Journal of the American Chemical Society,
01/2012, Letnik:
134, Številka:
1
Journal Article
Recenzirano
The binding of alkali and alkaline earth metal cations by macrocyclic and diazamacrobicyclic polyethers, composed of ordered arrays of hard oxygen (and nitrogen) donor atoms, underpinned the ...development of host–guest supramolecular chemistry in the 1970s and 1980s. The arrangement of −OCCO– and −OCCN– chelating units in these preorganized receptors, including, but not limited to, crown ethers and cryptands, is responsible for the very high binding constants observed for their complexes with Group IA and IIA cations. The cyclodextrins (CDs), cyclic oligosaccharides derived microbiologically from starch, also display this −OCCO– bidentate motif on both their primary and secondary faces. The self-assembly, in aqueous alcohol, of infinite networks of extended structures, which have been termed CD-MOFs, wherein γ-cyclodextrin (γ-CD) is linked by coordination to Group IA and IIA metal cations to form metal–organic frameworks (MOFs), is reported. CD-MOF-1 and CD-MOF-2, prepared on the gram-scale from KOH and RbOH, respectively, form body-centered cubic arrangements of (γ-CD)6 cubes linked by eight-coordinate alkali metal cations. These cubic CD-MOFs are (i) stable to the removal of solvents, (ii) permanently porous, with surface areas of ∼1200 m2 g–1, and (iii) capable of storing gases and small molecules within their pores. The fact that the −OCCO– moieties of γ-CD are not prearranged in a manner conducive to encapsulating single metal cations has led to our isolating other infinite frameworks, with different topologies, from salts of Na+, Cs+, and Sr2+. This lack of preorganization is expressed emphatically in the case of Cs+, where two polymorphs assemble under identical conditions. CD-MOF-3 has the cubic topology observed for CD-MOFs 1 and 2, while CD-MOF-4 displays a channel structure wherein γ-CD tori are perfectly stacked in one dimension in a manner reminiscent of the structures of some γ-CD solvates, but with added crystal stability imparted by metal–ion coordination. These new MOFs demonstrate that the CDs can indeed function as ligands for alkali and alkaline earth metal cations in a manner similar to that found with crown ethers. These inexpensive, green, nanoporous materials exhibit absorption properties which make them realistic candidates for commercial development, not least of all because edible derivatives, fit for human consumption, can be prepared entirely from food-grade ingredients.
•Utilization of n-butanol for powering a diesel engine.•N-butanol vapours are premixed along with air.•Higher brake thermal efficiency was noticed with n-B20.•Lower levels of nitric oxide and toxic ...emissions were noticed with n-B20.
Many investigations have been carried on the utilization of ethanol and methanol fuels in diesel engine to study the performance and regulated emission characteristics. However, very few investigations are made with discussion on the unregulated emissions. So the present work is focussed on the investigation of performance and emissions (both regulated and unregulated) from premixed n-butanol vapours in a single cylinder, four stroke, direct injection diesel engine and the results are presented in this paper. In this work n-butanol was used as a fuel owing to its longer-chain structure compared to methanol or ethanol, resulting in a lower specific heat of vaporization and greater enthalpy of combustion, while lowering water susceptibility and greater possibility than ethanol or methanol fuel. Subsequently, n-butanol has properties considerably closer to diesel fuel than ethanol, rendering it best to mix or fumigated with normal diesel fuel. In this work, n-butanol is fumigated along with the air in three different volume percentages such as 10, 20 and 30. About 14.76% higher brake thermal efficiency was noticed when 20% n-butanol was fumigated compared with the neat diesel operation. The oxides of nitrogen, acetaldehyde and acrolene emissions are reduced by 11.4%, 20.08% and 40.81% respectively. However, the HC, CO, formaldehyde and acetone emissions are increased with increased percentages of n-butanol.
Hidrogel merupakan polimer yang mengalami ikat silang dan digunakan pada berbagai aplikasi termasuk untuk media tanam. Kemampuan utamanya yaitu dapat menyerap dan mengikat air dalam jumlah yang ...besar. Salah satu jenis hidrogel yang telah banyak dikembangkan sebagai media tanam adalah hidrogel dari poliakrilat. Namun, hidrogel dengan bahan utama poli (asam akrilat) masih memiliki beberapa kekurangan yaitu sifat mekanik dan penyerapan terhadap air yang masih rendah. Penggunaan Polivinil Alkohol (PVA) dilakukan untuk meningkatkan berbagai parameter karakteristik dari hidrogel yang dihasilkan. Pada penelitian ini berhasil dilakukan sintesis hidrogel dari poli (asam akrilat) dan PVA dengan menggunakan asam sitrat sebagai agen pengikat silang serta ammonium persulfate sebagai inisiator. Penelitian ini dilakukan untuk mengetahui pengaruh PVA terhadap karakteristik hidrogel poli(asam akrilat)-PVA. Variasi konsentrasi PVA yang digunakan adalah 5%, 10%, 15%, 20% dan 25% (b/v). Karakteristik yang dianalisis meliputi fraksi gel, rasio swelling, sifat mekanik (tensile strength dan elongation). Struktur kimia dianalisis menggunakan Fourier Transform Infrared Spectroscopy (FTIR). Hasil penelitian menunjukkan bahwa dengan adanya penambahan PVA dari 5% sampai 25% menyebabkan nilai fraksi gel nsik dari 73% sampai 80.9%. Nilai rasio swelling dengan komposisi PVA 5% sampai 25%% berkisar dari berkisar 6212% sampai 4141%. Nilai tersebut telah memenuhi persyaratan untuk aplikasi media tanam (300-600%). Sifat mekanik hidrogel ditinjau dari nilai tensile strength. Nilai tensile strength yang diperoleh dari penelitian ini yaitu pada 15% sebesar 1.05 MPa. Nilai tersebut telah memenuhi standar kuat mekanik sebagai media tanam yaitu antara 0,55-22,34 MPa. Sedangkan hasi analisis FTIR telah menunjukkan bahwa terdapat gugus PVA dalam hidrogel.
•Comprehensive comparison of combustion, performance and emission characteristics of ternary fuel blends.•Higher CPmax, HRRmax and Rmax values of alcohol blends.•Very close BTE values to each other ...for all fuels used in the experiments.•Significant reduction in smoke emissions with the addition of alcohols.
Interest in alternative and clean energy has increased in order to meet increasing energy need and control over air pollution. In this context, studies on renewable alternative fuels such as biodiesel and alcohols for diesel engines continue intensively. However, pure biodiesel cannot be used alone in diesel engines due to its high density and viscosity. Therefore, in order to improve the density and viscosity of the biodiesel blend, alcohols are used as a fuel additive. The objective of this study is to evaluate the effect of the biodiesel and various alcohols additions to petroleum-based diesel fuel (DF) on combustion, performance and emissions of a single-cylinder diesel engine at different engine loads. In preparing the fuel blends used in the experiments, 20% cottonseed biodiesel was first mixed with DF and coded as B20. The mixture ratio was set at 20% biodiesel: 10% butanol, 10% ethanol, or 10% methanol and coded as B20Bu10, B20E10, and B20M10, respectively.
Our results showed that ignition delay (ID) of the biodiesel and alcohol blends was longer than that of DF because of their low cetane numbers. The values of maximum cylinder pressure (CPmax), maximum pressure rise (Rmax), and maximum heat release rate (HRRmax) of B20 and their locations were very close to the DF at all the loads. However, due to the low cetane number of the alcohols and the rapid combustion of the fuel accumulated in the combustion chamber during the long ignition delay, the CPmax, HRRmax and Rmax values of the alcohol blends were higher than those of B20 and DF for all the engine loads. This difference was more apparent at the high engine loads. Since the heating values of the biodiesel and alcohols were lower than those of DF, the B20 and alcohol blends had higher brake specific fuel consumption (BSFC) values. The brake thermal efficiency (BTE) values of all the fuels used in the experiments were very close to each other, followed a similar trend and reached their maximum at 0.27 MPa. The B20 and alcohol blends led to a slight increase in nitrogen oxide (NOx) and hydrocarbons (HC) emissions while reducing smoke and carbon monoxide (CO) emissions. With the addition of the alcohols, a significant reduction in smoke emissions was observed at all the engine loads due to the high oxygen content and low C/H of the alcohols.
Catalytic Organometallic Reactions of Ammonia Klinkenberg, Jessica L.; Hartwig, John F.
Angewandte Chemie (International ed.),
January 3, 2011, Letnik:
50, Številka:
1
Journal Article
Recenzirano
Odprti dostop
Until recently, ammonia had rarely succumbed to catalytic transformations with homogeneous catalysts, and the development of such reactions that are selective for the formation of single products ...under mild conditions has encountered numerous challenges. However, recently developed catalysts have allowed several classes of reactions to create products with nitrogen‐containing functional groups from ammonia. These reactions include hydroaminomethylation, reductive amination, alkylation, allylic substitution, hydroamination, and cross‐coupling. This Minireview describes examples of these processes and the factors that control catalyst activity and selectivity.
Get a move on ammonia: Reactions of ammonia catalyzed by transition‐metal complexes allow direct access to primary amines and other nitrogen‐containing functional groups. This Minireview presents recent advances in catalyst development that have led to the reaction of a variety of substrates with ammonia.
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