Preparation and characterization of ordered mesoporous Mg–Al–Co hydrotalcite based catalyst for decarboxylation of jatropha oil

This paper reported preparation of novel order mesoporous Mg–Al–Co hydrotalcite based catalysts through sol–gel procedure using precursors such Mg(NO₃)₂, Al(NO₃)₃ and Co(NO₃)₂ and Na₂CO₃. The catalyst also contained both acidity and basicity being very convenient for decarboxylation process of vegetable oil to green hydrocarbons. The alkaline media was maintained at pH 10 during the processes. Molar ratio of metal cations and temperature of the sol–gel processes were investigated for their effect in the mesoporous structure formation. The results showed that the procedure should be established at 70 °C with the molar Mg/Al/Co ratio of 1/5/0.2. Acidity and basicity of the mesoporous hydrotalcite based catalyst were demonstrated for their co-existence. The as-synthesized material at the suitable conditions was used as catalyst for decarboxylation of jatropha oil to obtain green hydrocarbons mainly belonging to diesel fraction. The decarboxylation was carried out at 400 °C for 3 h in closed auto-pressurized reactor exhibiting a yield of diesel involving hydrocarbons of over 70% after distillation and analysis. The result also confirmed that the acidity and basicity greatly accelerated the activity of the catalyst. Some techniques were used to characterizing the catalyst including XRD, SEM, TEM, TGA, NH₃-TPD, CO₂-TPD and BET, and GC–MS was also used to analyze the main product composition.     

X-ray absorption spectroscopies of Mg-Al-Ni hydrotalcite like compound for explaining the generation of surface acid sites

Hydrotalcite-like compound containing metal cations such as Mg²⁺, Al³⁺ and Ni²⁺ was characterized using Ni K-edge EXAFS and in situ Ni K-edge XANES techniques for clarifying its bonding environment around Ni²⁺ sites and structure changes during calcination from room temperature to 550 °C, respectively. At the fixed molar ratio of Mg/Ni/Al of 2/1/1, the results obtained from EXAFS analysis showed a slight blue shift before and after the calcination at 550 °C and a reduction in white line peak; the best fits of the two samples revealed tiny change in coordination number about 7 for Ni-O path but considerable difference for Ni-Mg(Al) path from about 4.5 to 9.5, confirming a modification from brucite like to mixed oxide structure. On the other hand, bond distances of the Ni-O and Ni-Mg paths nearly fixed at about 2.06 Å to 3.0 Å reflected stability of the cationic bond order on each plane, but partial collapse and decomposition of the interlayer formed by water molecules and anion CO ₃ ^2? after the calcination. Linear combination fit extracted from the in situ Ni K-edge XANES also confirmed the changes along with the calcination such as slow and fast decreases of brucite fraction at 150 °C and 330 °C, respectively, in corresponding to the mixed oxide fraction increases. The achieved bonding structures were also applied to explain acid-base occurrence of the hydrotalcite-like material, especially the acid sites generated by different static charges along with the bonds. The explanation was illustrated by NH₃-TPD method.     

Insight into adsorption mechanism of cationic dye onto agricultural residues-derived hydrochars: Negligible role of <Emphasis Type="Italic">π-π</Emphasis> interaction

Hydrochars derived from golden shower pod (GSH), coconut shell (CCH), and orange peel (OPH) were synthesized and applied to remove methylene green (MG5). The results indicated that the hydrochars possessed low specific surface areas (6.65-14.7m²/g), but abundant oxygen functionalities (1.69-2.12mmol/g). The hydrochars exhibited cellular and spherical morphologies. Adsorption was strongly dependent on the solution pH (2-10) and ionic strength (0-0.5M NaCl). Equilibrium can be quickly established in the kinetic study (60-120 min). The maximum Langmuir adsorption capacities at 30 °C followed the order GSH (59.6mg/g)>CCH (32.7mg/g)>OPH (15.6mg/g)> commercial glucose-prepared hydrochar (12.6mg/g). The dye adsorption efficiency was determined by the concentrations of oxygen-containing functionalities on the hydrochar surface. The adsorption process occurred spontaneously (? ΔG^o) and exothermically (?ΔH^o). Desorption studies confirmed the reversible adsorption process. Oxygenation of the hydrochar surface through a hydrothermal process with acrylic acid contributed to increasing MG5 adsorption and identifying the negligible role of π-π interaction to the adsorption process. The analysis of Fourier transform infrared spectrometry demonstrated that the aromatic C=C peak did not significantly decrease in intensity or shift toward higher/lower wavenumbers after adsorption, which further confirms the insignificant contribution of π-π interaction. Electrostatic attraction played a major role in adsorption mechanisms, while minor contributions were accounted for hydrogen bonding and n-π interactions. The primary adsorption mechanisms of MG5 onto hydrochar were similar to biosorbent, but dissimilar to biochar and activated carbon (i.e., π-π interaction and pore filling).     

Synthesis and characterization of the carbon nanotube-based composite materials with poly(3,4-ethylenedioxythiophene)

We report a procedure to prepare a conducting nano-composites composed of multi-walled carbon nanotubes (MWNTs) and PEDOT by using a poly(sodium 4-styrenesulfonate) (PSSNa) as a inter-linking molecule between MWNT and PEDOT. When PSSNa chains are introduced on the MWNTs via physicochemical interaction, the surface of MWNT becomes negatively charged, and PSS-modified MWNTs promote the effective association of the positively charged PEDOT chains. The resulting MWNT-PSS/PEDOT composites are characterized by a better interconnection between MWNT and PEDOT components.     

Electrical and Optical Properties of Conducting Polymer/Porous Silicon Structures

Electrical and optical properties of diode structures based on porous silicon (PS) and thin films of phenylene vinylene oligomer (PVO) have been studied. Steady-state photoluminescence spectroscopy show that the structure of the luminescence band depends on the PS morphology. We assign the observed effect to the morphology-dependent penetration of PVO material into the pores. Current-voltage characteristics of the PVO/PS diodes are studied and interpreted assuming Schottky emission and hopping transport of carriers aspossible mechanisms of d.c. electrical conduction.     

Kinetics and mechanism of the formation of doped skeletal copper catalysts: the effect of zincate compared to undoped and chromate-doped systems

Addition of zincate to the leach liquor for the preparation of skeletal copper increases the copper surface area; however it does not stabilize the structure against rearrangement. The leaching kinetics have been studied using a rotating disc electrode (RDE) at 269–293 K in 2–8 M NaOH and 0.0005–0.1 M Na₂ZnO₂. Zincate ions precipitate as zinc oxide, due to the local consumption of hydroxide ions near the leach front as the aluminium dissolves. This oxide hinders the aluminium dissolution, slowing the leaching rate. It also hinders copper dissolution/redeposition and prevents copper diffusion, thus reducing the structural rearrangement significantly, and causing the formation of a much finer copper structure with increased surface area. The zinc oxide redissolves as the leach front passes, releasing the copper to rearrange once more, thereby allowing the surface area to decrease with time. The activation energy for leaching was found to be 84 ± 6 kJ mol^–1.     

Ammonium nitrogen removal characteristics of zeolite media in a Biological Aerated Filter (BAF) for the treatment of textile wastewater

The main objective of this study is to evaluate ammonium nitrogen removal characteristics of zeolite media in Biological Aerated Filter (BAF) process for treatment of textile wastewater. Several biofilters were conducted to compare the performance of natural zeolite with sand and granular activated carbon (GAC) as packing media. The removal of NH₄⁺-N on the BAF reactor packed with natural zeolite media was more efficient than that with sand and GAC. After biofilm was well developed on the surface of zeolite media, the removal of NH₄⁺-N by ion exchange, nitrification, and biological synthesis was estimated as 35.1%, 40.2%, and 22.3%, respectively. The natural zeolite pretreated with heat and HCl solution showed higher ammonium removal efficiency than that with NaOH solution. No significant difference on ammonium adsorption capacity was observed when nature zeolite was neither pretreated by heat nor hydrochloric acid solution. This study shows that natural zeolites has the feasibility to be chosen as a useful media in BAF process for the treatment of textile wastewater.     

Grafting of polystyrene “from” and “through” surface modified titania nanoparticles

We report the surface modification of titania (TiO₂) nanoparticles with azo-based radical initiator and vinyl (acrylate) polymerizable groups. This is achieved through the reaction of the surface hydroxyl groups of the titania with acid halides. Polymer (specifically, polystyrene) was grafted “from” the surface using the azo-modified titania, and “through” the surface of the vinyl-modified surface. Both conventional radical and reversible addition-fragmentation chain transfer (RAFT) polymerizations were performed. The surface-modified titania and the polystyrene-titania nanocomposites were characterized using IR spectroscopy, thermogravimetric analysis and gel permeation chromatography.     

Effects of Light‐Induced Regularity on the Physical Properties of Multiphase Polymers

A method that combines UV irradiation and pausing was developed to manipulate the regularity and the length scales of the morphology generated by phase separation in full‐interpenetrating polymer networks of polystyrene and poly(methyl methacrylate). Upon increasing the pause time of photopolymerization and photo‐crosslink processes, the morphology gradually changes from hexagonal‐like packing to random structures. The width of the loss tan δ obtained for these phase‐separated materials changes with the morphological regularity, suggesting a potential technique for fabrication of mechanical bandgap materials.

     

Direct evidence of oxygen evolution from Li1+ x (Ni1/3Mn1/3Co1/3)1? x O2 at high potentials

Li_1+x (Ni_1/3Mn_1/3Co_1/3)_1−x O₂ (NMC) oxides are among the most promising positive electrode materials for future lithium–ion batteries. A voltage “plateau” was observed on the first galvanostatic charging curve of NMC in the extended voltage region positive to 4.5 V vs. Li/Li⁺ for compounds with x > 0 (overlithiated compounds). Differences were observed in the cycling stability of the overlithiated and stoichiometric (x = 0) NMC oxides in this potential region. A differential plot of the charge vs. potential profile in the first cycle revealed that, for the overlithiated compounds, a large irreversible oxidative peak arises positive to 4.5 V vs. Li/Li⁺, while in the same potential region only a small peak due to the electrolyte oxidation is detected for the stoichiometric material. Differential Electrochemical Mass Spectrometry (DEMS) was used to investigate the high voltage region for both compounds and experimental evidence for oxygen evolution was provided for the overlithiated compounds at potentials positive to 4.5 V vs. Li/Li⁺. No oxygen evolution was detected for the stoichiometric compound.