Controlled-surfactant-directed solvothermal synthesis of γ-Al2O3 nanorods through a boehmite precursor route

Ceramic one-dimensional particles are fascinating nanomaterials for sustainable future industries. Nanorods of γ-Al₂O₃ with single crystallinity and 10 nm diameter regime were newly developed through solvothermal procedure between AlCl₃·6H₂O, NaOH, and sodium dodecylbenzene sulfonate at 200 °C for 24 h. Controlling the pH values, reaction time, temperature, and effect of surfactant during the solvothermal reaction was studied to control the morphology and structure of nanorods. The solvothermal procedure for preparing γ-AlOOH nanorods followed lamellar growth, assembly, and ripening routes. The γ-AlOOH nanorods were converted to γ-Al₂O₃ through calcination reaction at 500 °C for 3 h. The produced γ-Al₂O₃ nanorods were 10 nm average width, 100–200 nm average length, and exposed with [101] orientation and a linear structure. FTIR, HRTEM, FESEM, XRD, and X-ray photoelectron spectroscopy methods were used for characterizing the prepared nanomaterials. New features and applied fields are predictable for the designed γ-AlOOH and γ-Al₂O₃ nanorods.     

Low-temperature synthesis of BiVO4 crystallites in molten salt medium and their UV–vis absorption

BiVO₄ crystallites were successfully synthesized by a low-temperature molten salt method. XRD analysis and SEM observation showed that the incorporation of salt medium in the preparing process would greatly lower the formation temperature of BiVO₄ phase, and promote their crystallization. UV–vis spectra evidenced their better optical absorption and visible light response than that of TiO₂-P25.     

Improvement of lactulose synthesis through optimization of reaction conditions with immobilized β-galactosidase

Kluyveromyces lactis β-galactosidase was immobilized on silica gels using a covalent bonding method. To improve lactulose synthesis using immobilized β-galactosidase, the optimal reaction conditions, such as lactose and fructose concentrations, pH and ionic strength of the buffer, loading amount of the enzyme and temperature, were determined. Lactulose synthesis using the immobilized β-galactosidase was markedly improved after optimization of the reaction conditions. When the lactulose synthesis was carried out at 47 °C using 40% (w/v) lactose, 20% (w/v) fructose and immobilized β-galactosidase of 12 U/ml in 50 mM sodium phosphate buffer at pH 7.5, the lactulose concentration and specific productivity were 15.80 g/l and 1.32 mg/U·h, respectively. In addition, when the immobilized β-galactosidase was reused for lactulose synthesis, its catalytic activity retained 60.5% after 10 reuses.     

Facile solvothermal synthesis of mesoporous Cu₂SnS₃ spheres and their application in lithium-ion batteries

Three dimensional (3D) mesoporous Cu(2)SnS(3) spheres composed of nanoparticles were synthesized by a simple solvothermal route. As anode materials for lithium-ion batteries, they delivered remarkably enhanced cycling performances. This could be attributed to the 3D mesoporous structure which may be propitious to the accommodation of volume expansion. Besides, a possible electrochemical reaction mechanism was proposed based on cyclic voltammetry (CV) testing results and confirmed by subsequent ex situ XRD studies. In addition, the influence of testing temperature on cycling performance has also been investigated.     

Coal liquefaction technologies—Development in China and challenges in chemical reaction engineering

With fast increasing demand in liquid transportation fuels, limited and unevenly distributed petroleum resources, and volatile petroleum prices, coal liquefaction technologies have again received the world's attention since the beginning of this century. China has actively pursued R&D of coal liquefaction technologies in the past decade and is deploying the first and the largest direct coal liquefaction plant since WWII and the largest indirect coal liquefaction plants after Sasol, South Africa. This paper analyzes the historical developments of coal liquefaction technologies from science point of view, presents recent developments of the technologies in China, and identifies challenges of the technologies towards successful industrial application.     

Synthesis of imidazo[2,1-b]thiazoles through the reaction of thiohydantoins and α-bromoketones

Imidazo-fused heterocycles are used as anticancer agents. In this study, some novel imidazo[2,1-b]thiazoles were synthesized from thiohydantoins and α-bromoketones in good yields. This method has the advantages of simple operation, high yields, and mild reaction conditions and uses less toxic and low-cost chemical reagents.     

Bromonitrothiolene-1,1-dioxides in a ‘halogen dance’ reaction

The chemical behavior of 4-bromo-3-methyl-4-nitro-2- and 2-bromo- 3-methyl-4-nitro-3-thiolene-1,1-dioxides in different solvents has been studied. These dioxides can undergo halo- and prototropic rearrangements, simultaneously in polar solvents, under very mild conditions. These transformations lead to another isomer, 2-bromo-3-methyl-4-nitro-2-thiolene-1, 1-dioxide and products of disproportionation, such as 2,4-dibromo-3-methyl-4-nitro-2-thiolene-1,1-dioxide and Δ²- and Δ³-nitrothiolene dioxides.     

Stability of cenospheres in lightweight cement composites in terms of alkali–silica reaction

This paper presents an experimental study on characteristics and stability of cenospheres used in lightweight cement composites. ASTM C227 and C1260 tests were used to evaluate if cenospheres are potentially deleterious due to alkali–silica reaction (ASR). Natural sand was used as control. Examination by scanning electron microscope with energy-dispersive X-ray spectroscopy and analyses by X-ray diffractometer and thermogravimetry were conducted on samples with cenospheres after 9-month C227 and C1260 tests to better understand the behavior of cenospheres exposed to high alkaline environments and higher temperatures in these tests. Results indicate that cenospheres are not potentially deleterious due to ASR. Expansion of the mortar specimens tested to ASTM C227 and C1260 seems to be affected by the pozzolanic reactivity of cenospheres. Fine cenospheres showed limited pozzolanic reactivity at 28–30 °C and 38 °C, but exhibited significant pozzolanic reactivity at 80 °C with aluminum tobermorite [Ca₅Si₅Al(OH)O₁₇? 5H₂O] identified as the main reaction product.     

Dynamic covalent cross-linked polymer gels through the reaction between side-chain β-keto ester and primary amine groups

A dynamic covalent gel network was constructed via the coupling reaction between the pendant primary amine groups of poly(l-leucine methacryloyloxyethyl ester) (P(H₂N-Leu-EMA)) and the side-chain β-keto ester functionalities of poly(2-(acetoacetoxy)ethyl methacrylate) (PAEMA) by varying the molar ratios of P(H₂N-Leu-EMA)/PAEMA and the concentration of polymers in different solvents at room temperature. Fourier transform infrared (FT-IR) spectroscopy and solid-state ¹³C nuclear magnetic resonance (NMR) study confirmed the newly formed enamine bonds in the polymeric gel. Rheological studies showed that the mechanical strength of gels increased with increasing weight percentage (wt.%) of polymers in solution. Furthermore, polymer gels can be transferred to the mixture of starting polymer solutions by regulating the pH of the system, which can be further transformed into the gel state by adding an external base.     

Formulating Portland cement–reactive alumina blend through thermodynamic modeling to prevent the alkali–silica reaction

This study aims to formulate solid and aqueous compositions of hydrated Portland cement incorporated with reactive alumina (RA) via thermodynamic modeling, with the goal to prevent alkali–silica reaction (ASR). Based on SEM/EDS point analysis, the uptake of Al into C–S–H was corrected in the thermodynamic modeling to improve the accuracy. The predicted solid and aqueous compositions were validated by means of XRD, TGA, and ICP. An accelerated mortar bar test was also carried out to confirm the ASR mitigating efficiency, and a preliminary relationship among the ASR expansion, solid assemblage, and aqueous species was established. The critical content for RA is around 5.75% in the studied systems, above which katoite precipitates, resulting in increased Al concentration in the pore solution (∼0.8 mmol/L); hence, ASR can be effectively inhibited.     

High-turnover aminopyridine-based Pd-catalysts for Suzuki–Miyaura reaction in aqueous media

A high-turnover catalytic system based on commercially available aminopyridines (L) and PdCl₂ has been developed for Suzuki–Miyaura reaction in aqueous media. Reactions of arylboronic acids with a wide range of aryl iodides, bromides and chlorides proceeded in the presence of these catalysts for a short time in aqueous media to afford the cross-coupling products in high yields. Furthermore, this protocol allows tolerating a wide range of functional groups.     

Effect of pressure on elemental diffusion in sulfur–iron reaction

The reaction between sulfur and iron under high pressure and high temperature (HPHT) was studied. Sulfur–iron reaction models under different pressure levels were constructed. The morphology and formation mechanism of the reactants were comprehensively analyzed by scanning electron microscopy, energy-dispersive spectroscopy–line scanning, metallographic microscopy, and Raman spectroscopy. The results indicated that the pressure of the reaction could significantly affect the diffusion behavior of sulfur and iron during the reaction. With an increase in pressure, the diffusion of iron in the system was inhibited, whereas that of sulfur was enhanced. The pressure distribution gradient at the reaction interface was simulated by finite element calculation. The effect of pressure gradient as the driving force of the reaction on the diffusion behavior of elements was evaluated by thermodynamics combined with experimental results. Based on the experimental results, finite element simulation, and formula derivation, a new standpoint was proposed: the diffusion of substances in the HPHT system was affected by the pressure gradient at the interface.     

Palladium-catalyzed efficient Suzuki–Miyaura reaction of potassium aryltrifluoroborates in water

An efficient and environment-friendly protocol has been developed for the palladium-catalyzed Suzuki–Miyaura reaction of potassium aryltrifluoroborates with (hetero)aryl halides in water without any additive. This method allows the preparation of a variety of biaryls and heterobiaryls in excellent yields. In addition, the cross-coupling product can be isolated in good yields and high purity by simple filtration and recrystallization as the reaction was performed on gram scale.     

α-Benzoyloxylation of dimethyl trisulfide and a novel reaction of the resultant trisulfide benzoate

Reaction between sulfinate anions and α -benzoate of dimethyl disulfide produces a novel α -thiolbenzoate disulfide. Thiolbenzoate appears to arise from the reaction of a contaminant, α -benzoate of dimethyl trisulfide, present in benzoate disulfide. Benzoate trisulfide is formed by the reaction of benzoic anhydride with dimethyl trisulfide, a contaminant in commercial dimethyl disulfide.     

Anomalous enantioselectivity in the sharpless asymmetric dihydroxylation reaction of 24-nor-5β-cholest-23-ene-3α,7α,12α-triol: Synthesis of substrates for studies of cholesterol side-chain oxidation

Recently we described a block in bile acid synthesis in cerebrotendinous xanthomatosis (CTX), a lipid storage disease related to an inborn error of bile acid metabolism. In this disease a defect in hepatic microsomal (24S) hydroxylation blocks the transformation of 5β-cholestane-3α,7α,12α,25-tetrol into (24S) 5β-cholestane-3α,7α,12α,24,25-pentol and cholic acid. Mitochondrial cholesterol 27-hydroxylation has also been reported to be abnormal in CTX subjects, but the relative importance of the enzymatic defect in this alternative microsomal pathway (namely, the 24S hydroxylation of 5β-cholestane-3α,7α,12α,25-tetrol relative to the abnormality in mitochondrial 27-hydroxylase) has not been established in CTX. To delineate the sequence of side-chain hydroxylations and the enzymatic block in bile acid synthesis, we synthesized the (23 R and 23 S) 24-nor-5β-cholestane-3α,7α,12α,23,25-pentols utilizing a modified Sharpless asymmetric dihydroxylation reaction on 24-nor-5β-cholest-23-ene-3α,7α,12α-triol, a C₂₆ analog of the naturally occurring C₂₇ bile alcohol, 5β-cholest-24-ene-3α,7α,12α-triol. Stereospecific conversion of the unsaturated 24-nor triol to the corresponding chiral compounds (23R and 23S), 24-nor-5β-cholestane-3α,7α,12α,23,25-pentols, was quantitative. However, conversion of the unsaturated 24-nor triol to the chiral nor-pentols had absolute stereochemistry opposite to the products predicted by the Sharpless steric model. The absolute configurations and enantiomeric excess of the C₂₆ nor-pentols and the C₂₇ pentols (synthesized from 5β-cholest-24-ene-3α,7α,12α-triol for comparison) were confirmed by nuclear magnetic resonance and lanthanide-induced circular dichroism Cotton effect measurements. These results may contribute to a better understanding of the role of the 24S-hydroxylation vs. 27-hydroxylation step in cholic acid biosynthesis. Presented in part at the 216th American Chemical Society National Meeting (Medicinal Chemistry Division, Abs. 368), Boston, MA, August 21–26, 1998.     

Application of micro X-ray diffraction to investigate the reaction products formed by the alkali–silica reaction in concrete structures

Alkali–silica reaction (ASR) is one of the most important deterioration mechanisms in concrete leading to substantial damages of structures worldwide. Synchrotron-based micro-X-ray diffraction (micro-XRD) was employed to characterize the mineral phases formed in micro-cracks of concrete aggregates as a consequence of ASR. This high spatial resolution technique enables to directly gain structural information on ASR products formed in a 40-year old motorway bridge damaged due to ASR.Micro-X-ray-fluorescence was applied on thin sections to locate the reaction products formed in veins within concrete aggregates. Micro-XRD pattern were collected at selected points of interest along a vein by rotating the sample. Rietveld refinement determined the structure of the ASR product consisting of a new layered framework similar to mountainite and rhodesite.It is conceivable that understanding the structure of the ASR product may help developing new technical treatments inhibiting ASR.     

The wetting behaviour and reaction kinetics in diamond–silicon carbide systems

The wetting behaviour of silicon on diamond and the interaction of diamond with molten silicon were investigated. It was found that diamond is well wetted by molten silicon reaching a contact angle of about 20° after melting. The wetting is caused by the rapid formation of a SiC interlayer by nucleation of silicon carbide grains on the surface of the diamond. Investigations of the interaction of silicon with CVD diamond, using SEM, showed that the initial rate of SiC formation is very fast and is significantly reduced after the formation of a 4–6 μm thick dense SiC interlayer. At that stage further growth is likely to be controlled by the diffusion of Si and C through the grain boundaries of the silicon carbide interlayer. The results were compared with the interaction of silicon with glassy carbon.     

A graphical design method for reaction–extraction processes in quaternary systems

This paper proposes a graphical design method for quaternary systems in simultaneous chemical and physical liquid–liquid equilibrium (reaction–separation process). The reactive phase equilibrium data and the stage by stage calculation are represented into two projections diagrams with rectangular coordinates. The graphical method has been applied to reversible reactive systems where all of the components of the reaction have the same stoichiometric coefficient. This graphical method allows estimating the number of reactive theoretical stages, the limits of the solvent to feed ratio (D/F), the extent of reaction and the conversion. Results obtained for seven design problems (involving four different reactive systems) are in good agreement with state of the art simulation software and with literature.     

Efficient structured catalysts for ethylene production through the ODE reaction: Ni and Ni–Ce on ceramic foams

Ni and Ni–Ce oxides alumina-supported formulations onto alpha-alumina foams were prepared, characterized and evaluated in the oxidative dehydrogenation of ethane (ODE) reaction. The catalysts were appropriately deposited on ceramic foams with a uniform, mechanically stable coverage. Besides, the structured systems were active and selective in the ODE reaction, demonstrating that the incorporation method was successful to obtain adequate active sites. Cerium markedly improved the ethane conversion due to a synergistic effect with nickel oxide, thus leading to a significant increment in ethylene productivity compared to that of the cerium-free system. An optimal Ce/Ni ratio was found which maximized the catalytic performance.