High-pressure densities and P–T–x–y diagrams for carbon dioxide+linalool and carbon dioxide+limonene

Liquid and vapor densities for carbon dioxide+linalool, and carbon dioxide+limonene were measured by using a system consisting of two vibrating tube densimeters. The P–T–x–y diagrams and saturated liquid and vapor densities for these two binary mixtures were determined at 313, 323 and 333 K, respectively, as well as at pressures up to 11 MPa. The density of the saturated CO₂ phase increased with increasing pressure. At higher pressure, the density of the liquid phase decreased with increasing pressure, corresponding to an increasing amount of carbon dioxide.     

Dispersion of single-walled carbon nanotubes in dimethylacetamide and a dimethylacetamide–cholic acid mixture

A way of dispersing single-walled carbon nanotubes in preparing stable suspensions with high concentrations of individual nanotubes in amide solvents is described. The obtained suspensions are studied via Raman spectroscopy. The dependence of the degree of single-walled carbon nanotube (SWNT) dispersion in individual and mixed amide solvents on the type of solvent, the mass of nanotubes, and the concentration of cholic acid is established. A technique for processing spectral data to estimate the diameters and chiralities of individual nanotubes in suspension is described in detail.     

Kinetics and mechanistic study of pyridinium hydrobromide perbromide-induced carbon–carbon bond scission

The title investigation shows that pyridinium hydrobromide perbromide (PHPB) induced electron transfer reaction in pentaamminecobalt(III) complexes of α-hydroxy acids

Palladium on carbon–bromobenzene mediated esterification and transesterification

A series of carboxylic acids were converted into their corresponding esters using the Pd/C catalyzed hydrogenation conditions in the presence of catalytic bromobenzene in alcohols and the method could also be applicable for the transesterification of esters. Good to excellent yields were obtained for different aliphatic or aromatic starting materials. The success of this esterification relies on the in situ generation of hydrobromic acid (HBr) from bromobenzene which provides a mild and acidic reaction environment. The palladium catalyst exhibits a remarkable activity and is reusable for up-to three consecutive cycles.     

Synthesis of a novel gelatin–carbon nanotubes hybrid hydrogel

This letter focuses on the first result the preparation and its swelling behavior of a novel hybrid gelatin hydrogel with carbon nanotubes. A novel hybrid gelatin hydrogel with carbon nanotubes was synthesized by physical mixing method. The structure of the novel hydorgel obtained was characterized by SEM. Besides, the swelling behavior of the hydrogel synthesized was measured at different temperature. The results indicated that carbon nanotubes added could maintain the stability of the hybrid hydrogel at 37 °C. This suggests that the hybrid gelatin hydrogel with carbon nanotubes could be used in biomedical field. Besides, its application in protein concentrating has been discussed.     

High-pressure phase equilibria for the carbon dioxide–2-methyl-1-butanol,carbon dioxide–2-methyl-2-butanol,carbon dioxide–2-methyl-1-butanol–water,and carbon dioxide–2-methyl-2-butanol–water systems

High-pressure vapor–liquid equilibria for the binary carbon dioxide–2-methyl-1-butanol and carbon dioxide–2-methyl-2-butanol systems were measured at 313.2 K. The phase equilibrium apparatus used in this work is of the circulation type in which the coexisting phases are recirculated, on-line sampled, and analyzed. The critical pressure and corresponding mole fraction of carbon dioxide for the binary carbon dioxide–2-methyl-1-butanol system at 313.2 K were found to be 8.36 MPa and 0.980, respectively. The critical point of the binary carbon dioxide–2-methyl-2-butanol was also found 8.15 MPa and 0.970 mole fraction of carbon dioxide. In addition, the phase equilibria of the ternary carbon dioxide–2-methyl-1-butanol–water and carbon dioxide–2-methyl-2-butanol–water systems were measured at 313.2 K and several pressures. These ternary systems showed the liquid–liquid–vapor phase behavior over the range of pressure up to their critical point. The binary equilibrium data were all reasonably well correlated with the Redlich–Kwong (RK), Soave–Redlich–Kwong (SRK), Peng–Robinson (PR), and Patel–Teja (PT) equations of state with eight different mixing rules the van der Waals, Panagiotopoulos–Reid (P&R), and six Huron–Vidal type mixing rules with UNIQUAC parameters.     

Alkene hydrogenation over palladium supported on a carbon–silica material

Palladium catalysts supported on a carbon–silica material were synthesized. Hydrogenation by molecular hydrogen was studied in the presence of straight-chain and cyclic olefins. As distinct from what is observed for olefins having a phenyl substituent, for aliphatic alkenes the reaction rate decreases with an increasing conversion due to the accumulation of hydrogenation products. The synthesized palladium catalysts show a higher hydrogenation activity than Pd/C.     

Investigation of a hybrid thermochemical Cu–Cl cycle,carbon capturing,and ammonia production process

In this paper, a new integrated system is proposed consisting of four subsystems, including a Cu–Cl cycle, a carbon capture cycle (sodium-based sorbent), an ammonia production unit, and a methanation unit. Carbon capturing cycle with sodium-based sorbent could adsorb 1.5 times more than other sorbents such as amine-based sorbent. Moreover, Cu–Cl cycle is one of the promising cycles in terms of economic and low temperature. Therefore, integrating these two cycles with ammonia and methane production unit is the novelty for this paper. Also, Aspen plus software was used to simulate the developed system to evaluate the process of the system. Moreover, sensitivity analysis and mass/energy balance are performed for the developed systems through the simulation. The energy required to capture carbon dioxide was found to be 6.313 MW per kg of CO₂, and the overall efficiency of the system is equal to 19.6%.

     

Investigation of lipase-catalyzed Michael-type carbon–carbon bond formations

Conjugate additions of carbon nucleophiles to appropriate acceptor molecules were investigated with respect to the synthetic potential and stereochemistry of the products. Reactions of short-chain α,β-unsaturated ketones and mono-substituted nitroalkenes with CH-acidic carboxylic ester derivatives were catalyzed by various immobilized lipases. Using methyl nitroacetate complete conversion with methyl vinyl ketone and trans-β-nitrostyrene was obtained. The reactions proceeded without enantioselectivity. Evidence for enzyme catalysis is provided by the observation that after denaturation of Candida antarctica lipase B or inhibition no reaction took place. Docking studies with the chiral addition product methyl 2-methyl-2-nitro-5-oxohexanoate did not reveal any specific binding mode for this reaction product, which would have been the requirement for stereoselective additions. These results support the experimental findings that the conjugate addition takes place without enantiopreference.     

The preparation and characterization graphene-cross-linked phenol–formaldehyde hybrid carbon xerogels

A new synthesis route based on polycondensation of phenol and formaldehyde cross-linked by graphene oxide (GO) was developed. Wet gel after gelation was converted into an organic xerogel by ambient pressure drying to obtain GO-cross-linked phenol–formaldehyde (PF) organic xerogels (GOCPFOX). Graphene-cross-linked PF carbon xerogels (GCPFCX) were produced by carbonization. The morphology and chemical structure of GOCPFOX and GCPFCX were analyzed. The electrochemical behavior of GCPFCX as an electrode material in electric double-layer capacitors (EDLCs) was investigated. Results show that the high mechanical strength of GO increased the gel skeleton strength; thus, organic xerogels exhibit very low drying shrinkage. Scanning electron micrographs indicated that addition of GO altered the gel structure. Thus, when GO was added into the PF solution, the PF molecular chains were anchored on the surface of GO by chemical and physical interaction. The GCPFCX-10 sample achieved the highest specific surface area, mesoporous volume, and specific capacity with 378 m²/g, 0.56 cm³/g, and 116 F/g, respectively. Hence, GCPFCX is a potential material for EDLCs owing to its low production cost and ability to avoid supercritical drying.     

Gels dried under supercritical and ambient conditions: a comparative study and their subsequent conversion to silica–carbon composite aerogels

In present work, we have prepared gels with various compositions of methyltrimethoxysilane—3-(2,3-epoxypropoxy) propyltrimethoxysilane (MTMS-GPTMS) using a two-step acid base sol–gel process. To make a comparative study between the two common drying routes, we prepared gels under supercritical and also under ambient conditions. The density of the supercritically dried hybrid aerogels lies between 0.18 and 0.31 gcm^?3, while the density of the ambient dried ones ranges between 0.35 and 0.42 gcm^?3. The surface area of MTMS-0.25 GPTMS aerogel dried under supercritical conditions, has been found to be 464 m² g^?1 with a pore volume and average pore diameter of 1.24 cm³ g^?1 and 11 nm respectively. The same composition dried under ambient conditions is found to have similar properties i.e. a BET surface area of 439 m² g^?1, pore volume of 1.22 cm³ g^?1 and average pore diameter of 11 nm. The aerogels were later pyrolyzed yielding silica/carbon composite aerogels. The pyrolized aerogels possessed a surface area as high as 207 m² g^?1 with a total pore volume of 0.98 cm³ g^?1. The pyrolysed aerogels were also calcined to yield carbon free materials.     

Computational identification of a global carbon–sulfur triply bonded isomer SCBO

Searching for stable sulfur–carbon triply bonded molecules has been of great interest from both the fundamental and applied viewpoints. The known polyatomic sulfur–carbon triply bonded molecules are usually not the global minima. Here, we report a potential energy surface investigation of a tetra-atomic molecule [S,C,B,O] in both doublet and quartet states. The B3LYP and M06-2X methodologies with 6-311+G(3df,2p) and aug-cc-pVTZ basis sets were applied for geometrical optimization and CCSD(T)/aug-cc-pVTZ for single-point energy calculations. The thermodynamically most stable isomer is the linear SCBO 01 (0.0 kcal/mol). Kinetically, SCBO 01 is separated from the other isomers and fragments by the rather high barriers of at least 44.7 kcal/mol. In particular, isomer SCBO 01 contains a typical carbon–sulfur triple bond based on the systematic analysis from the structure, vibrational frequency, molecular orbital, Wiberg bond index, and adiabatic bond dissociation energy. In addition, there exists a second low-lying isomer, i.e., linear SBCO 02 (7.3 kcal/mol) with S≡B triple bonding, whose kinetic stability is governed by its fragmentation to ²SB+¹CO (30.4 kcal/mol). The remaining isomers are either kinetically unstable with low conversion barriers or energetically very high lying. We propose that the simple two-body association between SC and BO, SB and CO pairs can preferentially lead to the formation and stabilization of SCBO 01 and SBCO 02, respectively. The isomer SCBO 01, which is the global structure and extraordinarily stable against both isomerization and fragmentation, strongly deserves future laboratory studies.     

Enhanced physical and chemical adsorption of carbon dioxide using bimetallic copper–magnesium oxide/carbon nanocomposite

Mixed Cu and Mg oxides on nitrogen-rich activated carbon (AC) from Nypha fruticans biomass were characterized and their CO₂ adsorption performance was measured. Highly dispersed CuO and MgO nanoparticles on AC was obtained using an ultrasonic-assisted impregnation method. The optimum adsorbent is 5%CuO–25%MgO/AC having good surface properties of high surface area, pores volume and low particles agglomeration. The higher content of MgO of 5%CuO–25%MgO/AC adsorbent contributes to less metal carbide formation which increases their porosity, surface area and surface basicity. XPS analysis showed some amount of nitrogen content on the surface of the adsorbent which increased their surface basicity towards selective CO₂ adsorption. The presence of moisture accelerated the CO₂ chemisorption to form a hydroxyl layer on the surfaces. The 5%CuO–25%MgO/AC adsorbent successfully adsorbed CO₂ via physisorption and chemisorption of 14.8 and 36.2 wt%, respectively. It was significantly higher than fresh AC with better selectivity to CO₂.     

Synthesis,structure and thermal properties of propylene oxide–carbon dioxide–L-lactide terpolymers

1. Download : Download full-size image

     

Metal free amide synthesis via carbon–carbon bond cleavage

A metal-free oxidative coupling of methyl ketones and primary amines to amides has been developed. The reaction tolerates a variety of functional groups, and is operationally simple. The reaction is proposed to go through a radical pathway to form the triiodomethyl ketone intermediate and the amide is formed by the nucleophilic attack of amine on triiodomethyl ketone carbonyl.     

Highly active ferrocenylamine-derived palladacycles for carbon–carbon cross-coupling reactions

{[(N-Methyl-N-p-R-benzyl)amino]benzyl}ferrocenes 4a–c (R = H(a), OCH₃(b), CH₃(c)) were synthesized by N-methylation of the corresponding sec-amines 3a–cwith the reagent CH₃I-t-BuOK. Treatment of 4a–c with Na₂PdCl₄ in the presence of NaOAc produced a pair of palladacycles σ-Pd[(η⁵-C₅H₅)Fe(η⁵- C₅H₃CH(C₆H₅)N(CH₃)CH₂-C₆H₄-R)]Cl(PPh₃) 5a–c (R = same as before) consisting of R_NR_P and S_NS_P configurations. The structure of 5a was determined by single crystal X-ray analysis. High catalytic activities of 5a–c for the Suzuki coupling of aryl chlorides with phenylboronic acid and the Heck reaction of bromobenzene with styrene were observed.     

Electrochemical detection of DNA methylation using a glassy carbon electrode modified with a composite made from carbon nanotubes and β-cyclodextrin

We describe a method for detecting DNA methylation. It is based on direct oxidation of DNA bases at a glassy carbon electrode (GCE) modified with film of a multiwalled carbon nanotube-β-cyclodextrin composite. This nano-structured film causes a strong enhancement on the oxidation current of DNA bases due to its large effective surface area and extraordinary electronic properties. Well-defined peaks were obtained as a result of electro-oxidation of guanine (at 0.67 V), adenine (at 0.92 V), thymine (at 1.11 V), cytosine (at 1.26 V), and 5-methylcytosine (at 1.13 V; all data vs. saturated calomel electrode (SCE)). The potential difference between 5-methylcytosine and cytosine (130 mV) is large enough to enable reliable simultaneous determination and analysis. The interference by thymine can be eliminated by following the principle of complementary pairing between purine and pyrimidine bases in DNA. The modified electrode was successfully applied to the evaluation of 5-methylcytosine in a fish sperm DNA, the methylation level of cytosine was found to be 7.47 %, and the analysis process took less than 1 h.     

Structural and electrochemical characterization of LiFePO4/C prepared by a sol–gel route with long- and short-chain carbon sources

A fast and convenient sol–gel route was developed to synthesize LiFePO₄/C composite cathode material, and the sol–gel process can be finished in less than an hour. Polyethyleneglycol (PEG), d-fructose, 1-hexadecanol, and cinnamic acid were firstly introduced to non-aqueous sol–gel system as structure modifiers and carbon sources. The samples were characterized by X-ray powder diffraction, field emission scanning electron microscopy, and elemental analysis measurements. Electrochemical performances of LiFePO₄/C composite cathode materials were characterized by galvanostatic charge/discharge and AC impedance measurements. The material obtained using compound additives of PEG and d-fructose presented good electrochemical performance with a specific capacity of 157.7 mAh g⁻¹ at discharge rate 0.2 C, and the discharge capacity remained about 153.6 mAh g⁻¹ after 50 cycles. The results indicated that the improved electrochemical performance originated mainly from the microporous network structure, well crystalline particles, and the increased electronic conductivity by proper carbon coating (3.11%).