Carbonaceous residues from biomass gasification as catalysts for biodiesel production

Tars and alkali ashes from biomass gasification processes currently constitute one of the major problems in biomass valorisation,generating clogging of filters and issues related with the purity of syngas production.To date,these waste residues find no useful applications and they are generally disposed upon generation in the gasification process.A detailed analysis of these residues pointed out the presence of high quantities of Ca(>30 wt%).TG experiments indicated that a treatment under air at moderate temperatures(400-800 C) decomposed the majority of carbon species,while XRD indicated the presence of a crystalline CaO phase.CaO enriched valorized materials turned out to be good heterogeneous catalysts for biodiesel production from vegetable oils,providing moderate to good activities(50%-70% after 12 h) to fatty acid methyl esters in the transesterification of sunflower oil with methanol.     

Efficient Synthesis of the Nucleus of Atorvastatin Calcium

An efficient synthetic route for the parent nucleus of atorvastatin calcium was successfully established through the modification of the related reactions. Under the optimized conditions, compound 1 was obtained in 61.2% yield (lit. 51.4%) from methyl isopropyl ketone via five steps. Two impurities generated by the aldol condensation of methyl isopropyl ketone were identified by gas chromatography–mass spectrometry and their generation can be inhibited by reducing the mixing time of methyl isopropyl ketone and NaH. One oxybromination protocol with hydrogen peroxide was employed to make the best of bromine. A debromination by-product was isolated and confirmed by ¹H NMR, ¹³C NMR, and high-resolution mass spectrometry and its generation mechanism was discussed. The impurity can be inhibited by protecting the reaction from light and easily removed by recrystallization.     

Quantitative analysis of calcium and fluorine by high-sensitivity low-energy ion scattering: Calcium fluoride

Low-energy ion scattering (LEIS) probes the atomic composition of the outer surface. Well-defined reference samples are used for the quantitation. For elements like fluorine and calcium, it is not easy to find suitable, clean, and homogeneous references, since fluorine is a gas and calcium is a very reactive metal. In contrast to surface analytic techniques such as XPS, the extreme surface sensitivity of LEIS makes it difficult to use stable compounds like CaF₂ as reference, since these compounds are not homogeneous at the atomic scale. With LEIS, CaF₂ is not expected to show an atomic ratio F/Ca = 2.0. Thus, before CaF₂ can be used as reference, its atomic surface concentrations have to be determined. Here, 3-keV He⁺ scattering by a LiF(001) single crystal, an evaporated layer of Ca, and a Cu foil are used as basic references. High-purity CaF₂ is available in two forms: a single crystal and a powder. For a practical reference, powders are preferred, since if bulk impurities segregate to the surface, they will be dispersed over a large surface area. It is found that both CaF₂ (111) and powder have similar F/Ca atomic ratios. This confirms the F termination for both samples. For the powder, the F and Ca signals are reduced by 0.77 ± 0.03 in comparison with those for the single crystal. The atomic sensitivity factors and relative sensitivity factors have been determined for F, Ca, and Cu.     

钠氟石温致结构变化的拉曼光谱研究

本文测定了钠氟石(NaF·2CaO·SiO2)的常温拉曼光谱, 并运用Dmol3密度泛函(DFT) 理论对其晶体中主要结构单元的简正振动模式进行了计算。通过实验值与计算值的比较, 确定了其特征峰的归属。同时, 采用高温拉曼光谱仪原位实测了钠氟石在不同的升温速率下的变温拉曼光谱。研究表明, 钠氟石在缓慢升温过程中会分解成NaF和Ca2SiO4; 快升至熔点附近, 熔化成液态, 快冷至室温, 仍分解成β- Ca2SiO4。     

Aluminum,calcium and zinc complexes supported by potentially tridentate iminophenolate ligands: synthesis and use in the ring‐opening polymerization of lactide

The coordination chemistry of the potentially tridentate phenoxyethyl‐ and benzylaminoethyl‐iminophenol pro‐ligands {ONO}H and {ONN}H on to calcium, zinc and aluminum centers has been studied. {ONO}Ca(N(SiMe₃)₂)(THF) (1) was prepared by a one‐pot salt metathesis procedure but the analogous reaction with {ONN}H led to intractable mixtures. Reaction of {ONO}H and {ONN}H with ZnEt₂ (0.5 or 1 equiv.) systematically led to isolation of the corresponding homoleptic complexes {ONO}₂Zn (2) and {ONN}₂Zn (3). The dimethylaluminum complexes {ONO}AlMe₂ (4) and {ONN}AlMe₂ (5) were readily prepared by treatment of AlMe₃ with 1 equiv. of the corresponding pro‐ligands. Compounds 2 and 4 both feature monomeric structures in the solid state, with chelating iminophenolate ligands and free‐hanging phenoxyethyl arms. The amido complex 1 was shown to be a moderately active initiator for the controlled ring‐opening polymerization (ROP) of racemic lactide at room temperature, yielding polylactides with high initiation efficiencies, relatively narrow polydispersities and a slight heterotactic bias. Immortal polymerizations were achieved by combining excess isopropanol to 1, offering up to 50 macromolecules per metal center, with well‐controlled molecular features. The dimethylaluminum compounds 4 and 5 initiated the controlled ROP of lactide in the presence of 1 equiv. of benzyl alcohol as a co‐initiator but required higher temperatures. Copyright © 2012 John Wiley & Sons, Ltd.     

Chiral Calcium–BINOL Phosphate Catalyzed Diastereo‐ and Enantioselective Synthesis of syn‐1,2‐Disubstituted 1,2‐Diamines: Scope and Mechanistic Studies

A highly enantioselective, chiral, Lewis acid calcium–bis(phosphate) complex, Ca[ 3 a ]_n, which catalyzes the electrophilic amination of enamides with azodicarboxylate derivatives 2 to provide versatile chiral 1,2‐hydrazinoimines 4 is disclosed. The reaction gives an easy entry to optically active syn‐1,2‐disubstituted 1,2‐diamines 6 in high yields with excellent enantioselectivities, after a one‐pot reduction of the intermediate 1,2‐hydrazinoimines 4 . The geometry and nature of the N‐substituent of the enamide affect dramatically both the reactivity and the enantioselectivity. Although the calcium–bis(phosphate) complex was a uniquely effective catalyst, the exact nature of the active catalytic species remains unclear. NMR spectroscopy and MS analysis of the various calcium complexes Ca[ 3 ]_n reveals that the catalysts exist in various oligomer forms. The present mechanistic study, which includes nonlinear effects and kinetic measurements, constitutes a first step in understanding these calcium–bis(phosphate) complex catalysts. DFT calculations were carried out to explore the mechanism and the origin of the enantioselectivity with the Ca[ 3 ]_n catalysts.     

环己烯制备实验中氯化钙脱除环己醇的研究

环己烯的制备是一个经典的有机化学实验项目，实验中用无水氯化钙脱除有机相中微量的环己醇。然而没有文献证实氯化钙具有良好的脱除环己醇的能力，需要通过实验进行验证。另外，还比较了氯化钙吸附异戊醇和乙醇的性能，以分析其对醇类物质的脱除能力。测试结果表明氯化钙脱除乙醇的效率较好，而吸附环己醇和异戊醇的能力弱，吸附时间长。可以作为教学实验的补充材料，供实验者参考。     

Calcium Hydride Cation [CaH]+ Stabilized by an NNNN‐type Macrocyclic Ligand: A Selective Catalyst for Olefin Hydrogenation

Reaction of dibenzyl calcium complex [Ca(Me₄TACD)(CH₂Ph)₂], containing the neutral NNNN‐type macrocyclic ligand Me₄TACD (Me₄TACD=1,4,7,10‐tetramethyl‐1,4,7,10‐tetraazacyclododecane), with triphenylsilane gave the cationic dinuclear calcium hydride [Ca₂H₂(Me₄TACD)₂](PhCHSiPh₃)₂ which was characterized by NMR spectroscopy and single‐crystal X‐ray diffraction. The cation can be regarded as the ligand‐stabilized dimeric form of hypothetical [CaH]⁺. Hydrogenolysis of benzyl calcium cation [Ca(Me₄TACD)(CH₂Ph)(thf)]⁺ gave dicationic calcium hydrides [Ca₂H₂(Me₄TACD)₂][BAr₄]₂ (Ar=C₆H₄‐4‐^tBu; C₆H₃‐3,5‐Me₂) containing weakly coordinating anions. In THF, they catalyzed the isotope exchange of H₂ and D₂ to give HD and the hydrogenation of unactivated 1‐alkenes.     

Use of some Inorganic and Organic Compounds as Decontaminants for Cobalt-60 and Caesium-134 by Clover Plant Grown on Inshas Sandy Soil

Outdoor lysimeter experiments were carried out to elucidate the effect of 4 inorganic and 3 organic salts on ⁶⁰Co and ¹³⁴Cs uptake and dry matter yield of three cuts of clover in the soils of Inshas. A new concept was proposed for assessing the difference in capacity of soil to supply radionuclides to plants as affected by applied inorganic or organic compounds. A relation of plant tissue radionuclide content with time can be expressed in an exponential equation with corresponding regression coefficients. When the same plant species is grown on the same soil differing only in the applied compounds (e.g. Fe-EDDHA, Fe-DTPA, Fe-OAC, Fe(COO)₂, Al(OH)₃, Ca(H₂PO₄)₂, Fe₂O₃) the derived equation will change. Differences of either Co or Cs accumulation with time between control and any other treatment were evaluated. The data also show that Fe-DTPA is preferred for ⁶⁰Co as enhancing compound for plant uptake (for decontamination use), compared with other applied salts, on the other hand, any tested salts did not significantly effect ¹³⁴Cs taken by clover. It was also found that more than 70% of the total cobalt uptake was accumulated in the roots which indicate that Co is less mobile in plants than Cs.