Design, synthesis and preliminary biological evaluation of brain targeting L-ascorbic acid prodrugs of ibuprofen

L-Ascorbic acid（AA,vitamin C） exhibits a high concentration in the brain.The transportation of AA in brain is mainly mediated by the glucose transporter 1（GLUT₁） and the Na⁺-dependent vitamin C transporter SVCT₂.While L-ascorbic acid C6-O conjugation has been investigated as a tool to enhance brain drug delivery,C5-O conjugation and C5-O & C6-O conjugation as brain targeting tools have not been reported.In this letter,ibuprofen was linked directly to C5-O,C6-O and C5-O & C6-O positions of L-ascorbic acid with eater bonds,providing prodrug 1,2 and 3,respectively,to improve their targeting abilities in the brain.Prodrug 1,2 and 3 were synthesized in facile ways with good yields.And the preliminary evaluation in vivo illustrated that prodrug 2 had a better targeting ability than prodrug 1. Moreover,prodrug 3,whose C5-O & C6-O positions were both modified,had good targeting ability for brain which will provide an important evidence for our further study on C5-0- & C6-0- di-derivatives of L-ascorbic acid.     

Catalytic degradation of polystyrene using HUSY catalysts

Summary The addition of carbon dioxide to phenyl glycidyl ether (PGE) was investigated in a semi-batch reactor using immobilized quaternary ammonium chloride catalysts. Five different catalysts were prepared with the following supports : (1) soluble poly(ST-<Emphasis Type=Italic>co</Emphasis>-VBC) [C1], (2) insoluble poly(ST-DVB-VBC) [C2], (3) macroporous poly(ST-DVB-VBC) [C3], (4) poly(ST-<Emphasis Type=Italic>co</Emphasis>-VBC)-MMT [C4] (5) modified MCM-41 [C5]. The addition of carbon dioxide to PGE can be considered as a pseudo-first order process with respect to the concentration of PGE. The pseudo-first order rate constant for the catalysts decreased in the series C1&gt;C3&gt;C2&gt;C4&gt;C5. The activation energy for C1 to C5 catalysts was 8.6, 20.9, 19.9, 23.9, and 26.8 kJ/mol, respectively. The immobilized catalysts can be reused in least 4 successive runs without any considerable loss of their initial reactivities.     

Selective hydrogenation of furfuryl alcohol to tetrahydrofurfuryl alcohol over Ni/γ-Al2O3 catalysts

Research on Chemical Intermediates - A series of nickel-based catalysts (with &lt;5&nbsp;nm Ni particle size) with γ-alumina as a support (x wt% Ni/γ-Al2O3, x represents the Ni...     

Enhancement of epoxidation efficiencies for Ta-SBA15 catalysts. The influence of modification with -EMe3 (E = Si, Ge, Sn) groups

Site-isolated Ta(V) centers were introduced onto the surface of a mesoporous SBA-15 support via the thermolytic molecular precursor method. After thermal treatment under oxygen, the resulting Si-OH and Ta-OH sites of TaSBA15-O(2)were modified with a series of trimethyl group 14 species, Me(3)E-, by treatment with Me(3)E-NMe(2) (E = Si, Ge, Sn) reagents. The resulting surface-modified catalysts (Me(3)E)(cap)TaSBA15 exhibit a significantly increased rate of cyclohexene epoxidation with H(2)O(2) as an oxidant, and provided a decreased amount of allylic oxidation products with respect to the unmodified material, TaSBA15-O(2). The rate of nonproductive H(2)O(2) decomposition, as monitored via (1)H NMR spectroscopy, significantly decreased after the surface modification. The structure of the TaSBA15 catalysts and potential Ta(V) epoxidation intermediates (formed upon treatment of Ta(V) materials with H(2)O(2)) were probed using UV-visible absorbance and diffuse-reflectance UV-visible spectroscopy. A Ta(V)(η(2)-O(2)) intermediate species is proposed for the TaSBA15-O(2), (Me(3)Si)(cap)TaSBA15, and (Me(3)Ge)(cap)TaSBA15 catalysts, while intermediate species for the (Me(3)Sn)(cap)TaSBA15 catalysts could not be characterized.     

Plasma treatment of Ni and Pt catalysts for partial oxidation of methane

Summary In this work DBD (dielectric barrier discharge) plasma treatments of 10%Ni/Al₂O₃and 1%Pt/Al₂O₃catalysts have been conducted to study the principles of plasma treatment of supported catalysts. It was found that 10%Ni/Al₂O₃and 1%Pt/Al₂O₃catalysts treated by plasma exhibit a higher catalytic activity and a better stability than the catalysts prepared without plasma treatment. Methane conversion over the plasma treated catalyst is 3-5% higher than on untreated catalysts. The metal species dispersion also increased after plasma treatment, which leads to improvement of the interaction between active species and supports, the catalytic activities and the resistance to carbon deposition.</o:p>     

Synthesis of Na2WO4-MnxOy supported on SiO2 or La2O3 as fiber catalysts by electrospinning for oxidative coupling of methane

The oxidative coupling of methane (OCM) is an attractive route to convert natural gas directly into value-added chemical products (C₂₊). This work comparatively investigated SiO₂- or La₂O₃-supported Na₂WO₄-Mn_xO_y (denoted as NWM) catalysts in powder and fiber forms. The powder catalysts were prepared using a co-impregnation method and the fiber catalysts were prepared successfully using an electrospinning technique. The NWM/La₂O₃ fiber catalysts were activated at low temperature (500 °C) and had a 4.7% C₂₊ yield, with the maximum C₂₊ yield of 9.6% at 650 °C, while the NWM/SiO₂ fiber catalyst was activated at 650 °C and had a maximum C₂₊ yield of 20.4% at 700 °C. The XPS results in the O 1s region indicated that NWM/La₂O₃ had a lower binding energy than NWM/SiO₂, suggesting that the lattice oxygen species is easily released from the catalyst surface and creates vacancy sites that enhance performance. The stability test of the catalysts indicated that the La₂O₃-containing catalysts had excellent activity and high thermal stability, while the SiO₂-containing catalysts had a higher C₂₊ yield when the prepared catalysts were compared at 700 °C. Considering the same component catalysts, the fiber catalysts achieved higher performance because their heat and mass transfer properties were enhanced.     

Remarkable Enhancement in the Dispersion and Low-Temperature Activity of Catalysts Prepared via Novel Plasma Reduction-Calcination Method

A novel plasma reduction and calcination (PR&C) method has been recently developed. Upon the experimental investigations on methane conversions, including partial oxidation, methane combustion, NO reduction by methane and CO₂ reforming, the catalysts prepared by this PR&C method exhibit a remarkable enhancement in the dispersion, low-temperature activity and stability. A plasma-enhanced acidity has also been addressed, which would play an important role in the improved dispersion. The PR&C method is leading to a better preparation of supported catalysts, esp., those for methane conversion.     

The nature of the surface species formed on Au/TiO2 during the reaction of H2 and O2: an inelastic neutron scattering study

Inelastic neutron spectroscopy (INS) has been employed to identify surface species formed during the H2-O2 reaction on Au/TiO2 catalysts. Determination of the surface intermediates formed in this reaction is crucial to develop a mechanistic understanding for the direct vapor-phase propylene epoxidation reaction and synthesis of H2O2. Although the presence of intermediate hydroperoxo species (during these reactions) has been suggested in literature, it has never been demonstrated. Our studies provide direct evidence for the formation of surface hydroperoxo species during the H2-O2 reaction.     

New binary systems Mg-M-O (M=Y, La, Ce): Synthesis and physico-chemical characterization

New binary oxide Mg-M-O (M=Y, La, Ce) systems are obtained by co-precipitation and characterized by adsorption methods, X-ray diffraction method (XRD), X-ray photoelectron spectroscopy (XPS) and Fourier transform infrared (FTIR) spectroscopy of adsorbed probe molecules (CO and CDCl₃). It is shown that Mg-Y-O systems after calcination at 450-750 °C represent the physical mixtures of MgO and Y₂O₃, while the components of Mg-La(Ce)-O systems interact to form La₂MgO_x and (Ce,Mg)O₂ solid solutions, respectively. From XPS data, the surface of the binary systems is enriched with lanthanide ions. Addition of ≈5 mol% M₂O₃ to MgO results in an increase in concentrations of strong and weak Lewis acidic sites, the content of the latter being much higher and changing in the series: MgO<Mg-Ce-O<Mg-La-O<Mg-Y-O. At the same time basic sites become stronger in the binary systems but their total content decreases in comparison to that in individual MgO. Mg-M-O samples containing ≈5 mol% M₂O₃ are highly-dispersed and characterized by bimodal porous texture.     

New nonplatinum electrocatalysts based on Ru for the direct oxidation of ethanol in an alkaline fuel cell

Anodic catalysts of the RuM type (RuNi, RuNiPd, RuCr, and RuV) for the oxidation of ethanol in an alkaline electrolyte were synthesized and studied. The activity of the catalysts increased in the series RuNi < RuCr < RuV and as the specific surface area of the carbon carrier grew. The RuV catalyst was found to be most active and stable because of its structural features, namely, the formation of the RuV solid solution decorated with oxides.     

The electrochemical activity of two binary alloy catalysts toward oxygen reduction reaction in 0.1 M KOH

The platinum group metals (Pt, Ir and Ru) and the carbide-derived carbon support with the very high specific surface area were used to synthesise the low noble metal loading Pt-C, IrPt-C and RuPt-C alloy catalysts. The alloying of the platinum group metals in the studied catalysts was proved by the several independent physical characterization methods like: the X-ray diffraction, time of flight secondary ion mass-spectrometry, X-ray photoelectron spectroscopy, scanning and transmission electron microscopy. The electrocatalytic activity toward oxygen reduction reaction of the synthesised catalysts in an alkaline solution was studied and compared with the commercially available Pt-Vulcan. The combined and detail approach using the transmission electron microscopy and inductively coupled plasma mass spectrometry for estimation of the surface area of metal particles is provided. The noticeably higher calculated mass corrected and specific kinetic current density values for Pt-C catalyst were established. For IrPt-C and RuPt-C alloy catalysts, mass corrected current density values are comparable with the commercial Pt-Vulcan. The specific kinetic current density values increase in the following sequence: RuPt-C < IrPt-C < Pt-Vulcan < Pt-C.     

硫中毒对Cu/γ-Al_2O_3催化含硫低浓度甲烷燃烧特性的影响

采用浸渍法制备了质量分数11.32%Cu/γ-Al2O3催化剂,采用固定床反应器,考察了SO2浓度(0~0.02%)对低浓度甲烷(体积分数,3%)催化燃烧特性的影响,通过反应前后催化剂的微观结构及化学成分检测,结合理论分析,探讨了催化反应的硫中毒原因。研究表明,SO2的通入导致了Cu/γ-Al2O3催化剂活性及稳定性的降低,在同一反应温度下,甲烷转化率随着SO2浓度的增加而下降。SEM、EDS、FT-IR、XRD表征结果表明,SO2会导致Cu/γ-Al2O3催化剂表面出现结块现象,催化剂表面有硫元素的累积,且以硫酸盐的形式存在,其主要成分为硫酸铜(CuSO4)。在富氧条件下,SO2分子及氧离子在Cu2+上吸附所形成的硫酸铜,附着在催化剂表面,形成一层坚硬的外壳,是产生硫中毒现象的根本原因。     

不同制备方法对Ba/MgO催化剂催化甲烷氧化偶联反应性能的影响(英文)

采用ＢＥＴ、ＸＲＤ、ＳＥＭ和ＸＰＳ等方法对Ｂａ／ＭｇＯ催化剂进行了分析,并且对该催化剂对甲烷氧化偶联反应的性能进行了测试。结果表明,制备方法对Ｂａ／ＭｇＯ催化剂的催化性能有很大影响。采用淤浆法制备的Ｂａ／ＭｇＯ催化剂具有合适的比表面积和表面氧物种分布,因此对甲烷转化显示出良好的催化活性。而采用机械混合或浸渍等方法制备的催化剂由于表面不均匀以及表面烧结等原因其活性较差。     

Deep Oxidation of Methane over Nano-Sized Ferrites with Spinel Structures

Ferrites with spinel structures as catalysts for the deep oxidation of methane have been studied by X-ray phase analysis and temperature programmed reduction. The most active catalysts are the nano-sized ferrites of cobalt and nickel, prepared by the decomposition of polynuclear complexes, with Al₂O₃ as carrier and with addition of a surface active agent to increase the thermal stability of the catalysts. At low temperatures (up to 450 °C), the effect of the size factor appears with the increase in specific catalytic activity of cobalt and nickel ferrites with decreasing of their particles. A correlation of the catalytic activity with the quantity and mobility (reactivity) of oxygen in the ferrites has been established.     

Influence of alkali metal doping on surface properties and catalytic activity/selectivity of CaO catalysts in oxidative coupling of methane

Surface properties （viz. surface area, basicity/base strength distribution, and crystal phases） of alkali metal doped CaO （alkali metal/Ca= 0.1 and 0.4） catalysts and their catalytic activity/selectivity in oxidative coupling of methane （OCM） to higher hydrocarbons at different reaction conditions （viz. temperature, 700 and 750 ℃; CH4/O2 ratio, 4.0 and 8.0 and space velocity, 5140-20550 cm^3 ·g^-1·h^-1） have been investigated. The influence of catalyst calcination temperature on the activity/selectivity has also been investigated. The surface properties （viz. surface area, basicity/base strength distribution） and catalytic activity/selectivity of the alkali metal doped CaO catalysts are strongly influenced by the alkali metal promoter and its concentration in the alkali metal doped CaO catalysts. An addition of alkali metal promoter to CaO results in a large decrease in the surface area but a large increase in the surface basicity （strong basic sites） and the C2＋ selectivity and yield of the catalysts in the OCM process. The activity and selectivity are strongly influenced by the catalyst calcination temperature. No direct relationship between surface basicity and catalytic activity/selectivity has been observed. Among the alkali metal doped CaO catalysts, Na-CaO （Na/Ca = 0.1, before calcination） catalyst （calcined at 750 ℃）, showed best performance （C2＋ selectivity of 68.8% with 24.7% methane conversion）, whereas the poorest performance was shown by the Rb-CaO catalyst in the OCM process.     

New multinuclear half-titanocene catalysts in the syndiospecific polymerization of styrene

The syndiospecific polymerization of styrene with a new class of multinuclear transition metal catalysts in the presence of methylalumoxane and triisobutylaluminum has been investigated. The new multinuclear catalysts [(η⁵-C₅Me₅)Ti]₄(μ-O)₆ and [(η⁵-C₁₃H₁₇)Ti]₄(μ-O)₆ were received by reaction of the corresponding mononuclear compounds with water and characterized by X-ray crystal structure analysis. The molecular structure of both complexes is tetrameric with six bridging oxygen atoms between the four titanium atoms, forming an adamantane-like cage structure with a substituted cyclopentadienyl ligand remaining η⁵-bonded to each titanium atom.The bulky [(η⁵-C₁₃H₁₇)Ti]₄(μ-O)₆ shows higher polymerization conversions than [(η⁵-C₅Me₅)Ti]₄(μ-O)₆. The polymerization activity is significantly increased by an enhancement of the MAO concentration after a short retardation period and levels off at MAO/[(η⁵-C₁₃H₁₇)Ti]₄(μ-O)₆ molar ratios above about 600. Triisobutylaluminum increases the polymerization yield to a maximum at a TIBA/[(η⁵-C₁₃H₁₇)Ti]₄(μ-O)₆ molar ratio of about 30-100, but considerably decreases it at higher molar ratios below the polymerization conversion reached without any additional aluminum alkyl. Both compounds affect molecular weight and molecular weight distribution without any influence on the stereospecificity of the different catalytic sites active in polymerization reactions.The new multinuclear transition metal catalysts reach about 30-50% of the polymerization activity of the mononuclear catalysts on a molar basis and show a remarkably high catalytic activity in complex-coordinative polymerizations even after storage in non-inert-atmosphere conditions. The active polymerization sites of the multinuclear catalysts are not as uniform as the active sites of the mononuclear catalysts are and provide polystyrenes of a slightly lower syndiospecificity, but do not significantly influence the weight average molecular weights.     

Optimization of Mn-Mg-Al Mixed Oxides Composition on their Activity towards the Total Oxidation of Aromatic and Oxygenated VOCs

A series of mixed oxides (Mn-Mg-Al) is prepared by coprecipitation via a hydrotalcite route with different manganese ratios. Structural, textural, and redox properties are studied by XRD, N₂-sorption, H₂-TPR, and XPS techniques. Mn_xMg_6-xAl₂-O mixed oxides (with 0≤x≤6) are tested in the total oxidation of ethanol and toluene, two probe molecules representing respectively oxygenated and aromatic VOCs. Catalysts with higher manganese contents have shown the best catalytic performance for the oxidation of both ethanol and toluene. The surface activity of the materials is mainly related to the presence of manganese species in three different oxidation states (+II, +III, and +IV) in the bulk and on the material's surface. Since high Mn-content catalysts showed similar physicochemical properties and catalytic activity, Mn₄Mg₂-O is selected as the optimal composition of these materials. Furthermore, its aging test is compared to that of noble metal-based commercial catalysts (Pd/γ-Al₂O₃).