Physico-Chemical Modifications Affecting the Activity and Stability of Cu-Based Hybrid Catalysts during the Direct Hydrogenation of Carbon Dioxide into Dimethyl-Ether

The direct hydrogenation of CO₂ into dimethyl-ether (DME) has been studied in the presence of ferrierite-based CuZnZr hybrid catalysts. The samples were synthetized with three different techniques and two oxides/zeolite mass ratios. All the samples (calcined and spent) were properly characterized with different physico-chemical techniques for determining the textural and morphological nature of the catalytic surface. The experimental campaign was carried out in a fixed bed reactor at 2.5 MPa and stoichiometric H₂/CO₂ molar ratio, by varying both the reaction temperature (200–300 °C) and the spatial velocity (6.7–20.0 NL∙g_cat⁻¹∙h⁻¹). Activity tests evidenced a superior activity of catalysts at a higher oxides/zeolite weight ratio, with a maximum DME yield as high as 4.5% (58.9 mg_DME∙g_cat⁻¹∙h⁻¹) exhibited by the sample prepared by gel-oxalate coprecipitation. At lower oxide/zeolite mass ratios, the catalysts prepared by impregnation and coprecipitation exhibited comparable DME productivity, whereas the physically mixed sample showed a high activity in CO₂ hydrogenation but a low selectivity toward methanol and DME, ascribed to a minor synergy between the metal-oxide sites and the acid sites of the zeolite. Durability tests highlighted a progressive loss in activity with time on stream, mainly associated to the detrimental modifications under the adopted experimental conditions.     

肉桂醛多相催化选择性加氢制肉桂醇的研究进展

从催化剂活性组分、助剂、载体和还原方法等多方面综述了近年来肉桂醛多相选择性加氢制备肉桂醇的方法研究,探讨了肉桂醛加氢活性和肉桂醇选择性的影响因素,并展望了肉桂醛选择性加氢的发展前景。通过催化剂设计提高非贵金属催化剂的活性、选择性和稳定性,并进一步降低反应温度和压力是今后的研究方向。     

Tryptophan reduction and histidine racemization during deprotection by catalytic transfer hydrogenation of an analog of the luteinizing hormone releasing factor

(d -Trp)⁶-LHRH:pGlu-His-Trp-Ser-Tyr-d -Trp-Leu-Arg-Pro-GlyNH₂ was prepared by solid-phase peptide synthesis using the nitro group to protect the guanidine side chain of the arginyl residue. Removal of the side-chain protecting groups was carried out by catalytic transfer hydrogenation (CTH) using palladium acetate/ammonium formate or palladium on charcoal/formic acid. We show in this paper that this deprotection method induces i) reduction of the tryptophan residue and ii) epimerization at the histidine level (with palladium acetate/ammonium formate). Despite the formation of significant amounts of reduced peptide. CTH enabled us to obtain (d -Trp)⁶-LHRH in relatively good yield.     

Plasma hydrogenated cationic detonation nanodiamonds efficiently deliver to human cells in culture functional siRNA targeting the Ewing sarcoma junction oncogene

The expression of a defective gene can lead to major cell dysfunctions among which cell proliferation and tumor formation. One promising therapeutic strategy consists in silencing the defective gene using small interfering RNA (siRNA). In previous publications we showed that diamond nanocrystals (ND) of primary size 35 nm, rendered cationic by polyethyleneimine-coating, can efficiently deliver siRNA into cell, which further block the expression of EWS/FLI-1 oncogene in a Ewing sarcoma disease model. However, a therapeutic application of such nanodiamonds requires their elimination by the organism, particularly in urine, which is impossible for 35 nm particles. Here, we report that hydrogenated cationic nanodiamonds of primary size 7 nm (ND-H) have also a high affinity for siRNA and are capable of delivering them in cells. With siRNA/ND-H complexes, we measured a high inhibition efficacy of EWS/FLI-1 gene expression in Ewing sarcoma cell line. Electron microscopy investigations showed ND-H in endocytosis compartments, and especially in macropinosomes from which they can escape before siRNA degradation occurred. In addition, the association of EWS/FLI-1 silencing by the siRNA/ND-H complex with a vincristine treatment yielded a potentiation of the toxic effect of this chemotherapeutic drug. Therefore ND-H appears as a promising delivery agent in anti-tumoral gene therapy.     

化工工艺设计过程中几种决策方法的应用

催化裂化汽油通过加氢处理可有效降低硫含量,是清洁汽油或清洁汽油调和油生产的重要过程。随着环保标准的日益严格,汽油加氢技术的研发和使用正日益受到重视,在技术开发、工艺设计、项目投资的过程中要面临诸多决策问题,从管理学角度对不同级别决策问题适用的决策方法和模型进行了介绍,并对定量决策方法、定性决策方法以及定量与定性相结合的决策方法使用场合提出了一些建议。     

Effect of Modification of Amorphous Silica with Ammonium Agents on the Physicochemical Properties and Hydrogenation Activity of Ir/SiO2 Catalysts

The modification of commercial silica with solutions of NH₄F or NH₄Cl salts, followed by thermal treatment, enabled generation of the acidic sites in SiO₂ and changed its textural properties. The use of ammonium salts solution also caused the generation of additional porosity. Using NH₄F solution caused significant decrease in the specific surface area and the increase in the average pore diameter. The number and strength of resulting acid sites depend on the nature of anion in the applied ammonium salt and the concentration of salt solution. It has been found that the sample treated with NH₄F presented higher total acidity (TPD–NH₃) and the amount as well as the strength of acid sites increased with the concentration of the used modifier. As modified amorphous SiO₂ materials used as a support for iridium (1 wt %, Ir(acac)₃) nanoparticles permitted to obtain highly active catalysts for toluene hydrogenation under atmospheric pressure. The highest activity (expressed as the apparent rate and TOF) was obtained for iridium catalysts supported on silica modified by NH₄F with the highest acidity. The modification of silica with NH₄F favors the generation of centers able to adsorb toluene, which results in higher activity of this catalyst.     

Side reactions in peptide synthesis

During the hydrogenolytic removal of the benzyl ester from the pentapeptide Boc-Asp(OBzl)-Ala-Phe-Ile-Gly-OEt, either with hydrogen gas or ammonium formate in the presence of palladium-on-charcoal as catalyst, variable amounts (5–30%) of an unexpected by-product were always obtained. The compound was eventually identified as Boc-Asc-Ala-Phe-Ile-Gly-OEt (Asc = aminosuccinyl). The application of field desorption mass spectrometry as a diagnostic tool is reported. The study of this side reaction, carried out on the pentapeptide and two other dipeptide models, showed that: 1) palladium-on-charcoal may induce Asc formation; 2) the contemporary presence of the catalyst and a base (even in trace amounts) greatly increases the by-product formation; 3) the side reaction is sequence and solvent dependent; 4) the Asc formation is completely prevented by adding a few equivalents of acetic or formic acid. Some mechanistic considerations are also reported.     

柴油加氢装置中氢气管道的材质选择

综合分析了某柴油加氢装置中氢气管道在反应部分（包括压缩机）、循环氢脱硫、低分气脱硫和膜分离部分,根据其不同的设计条件,综合考虑其设计温度,设计压力及其介质特性等因素确定工艺管道的材质。     

Electrocatalytic hydrogenation of alkenes on LaNi5 electrodes

In this paper a new electrocatalytic hydrogenation process is reported based on the use of LaNi₅ electrodes. The charge/discharge of hydrogen within the intermetallic compound through cyclic voltammetry experiments was observed using a powder microelectrode in classical aqueous KOH medium, as well as in other buffered aqueous or hydro-organic media. Most voltammograms are modified in the presence of unsaturated compounds, which indicates that a hydrogenation reaction occurs. Electrocatalytic hydrogenation on a preparative scale was carried out with three unsaturated compounds taken as models (methyl vinyl ketone, 1-decene, 5-hexen-2-one) and it was found that only the CC bond is hydrogenated with Faradaic efficiencies up to 100%.     

Isolation,identification, and characterization of a palladium complex in the catalytic deprotection of a protected peptide

The final catalytic deprotection in the large scale synthesis of thymopentin (Arg-Lys-Asp-Val-Tyr) produced an impurity which had not previously been observed. Isolation by preparative HPLC and spectroscopic characterization led to a postulated structure of the impurity as the 1: 1 thymopentin-palladium complex. A complex corresponding to the proposed structure was independently synthesized and shown to have identical chromatographic and spectroscopic properties with the isolated material. Proton and carbon (13) NMR were used to determine the coordination sites of the peptide with palladium. The susceptibility of the complex to hydrogenation indicated a possible source for its formation.