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。     

Challenges of Utilizing Healthy Fats in Foods

Over the past few decades, the Dietary Guidelines for Americans has consistently recommended that consumers decrease consumption of saturated fatty acids due to the correlation of saturated fatty acid intake with coronary artery disease. This recommendation has not been easy to achieve because saturated fatty acids play an important role in the quality, shelf life, and acceptability of foods. This is because solid fats are critical to producing desirable textures (e.g., creaminess, lubrication, and melt-away properties) and are important in the structure of foods such as frozen desserts, baked goods, and confectionary products. In addition, replacement of saturated fats with unsaturated fats is limited by their susceptibility to oxidative rancidity, which decreases product shelf life, causes destruction of vitamins, and forms potentially toxic compounds. This article will discuss the fundamental chemical and physical properties in fats and how these properties affect food texture, structure, flavor, and susceptibility to degradation. The current sources of solid fats will be reviewed and potential replacements for solid fats will be discussed.     

Investigations into the C‐deuteriation of silyl enol ethers derived from aryl alkyl ketones

Results are reported on the regioselective C‐deuteriation of a series of silyl enol ethers derived from aryl alkyl ketones using deuterium (D₂) gas as the deuterium source and palladium‐on‐barium sulfate as the mediator. These results highlight the numerous reaction pathways and different product types available from simple deuteriation of substituted enol precursors. Copyright © 2006 John Wiley & Sons, Ltd.     

Applications of ammonium formate-catalytic transfer hydrogenation.

Dehalogenation of chlorine bound to aromatic nuclei has been achieved using ammonium formate-catalytic transfer hydrogenation (AF-CTH) techniques. The use of deuterated ammonium formate as the transfer agent in the CTH process when performed in a deuterated solvent medium results in the predominant formation of the labeled product. Thus, ND₄+ DCOO^- - CTH of [D-Ala², p-ClPhe⁴]-Leu-enkephalin in 80% CD₃COOD/D₂O yielded [D-Ala², Phe (4D)⁴]-Leu-enkephalin. Levels of D-incorporation were measured by fast atom bombardment-mass spectrometry (FAB-MS) and/or by ¹³C n.m.r. spectroscopy. Using D-labeled and unlabeled ammonium formate in stoichiometrically similar reactions, it was concluded that the hydrogenation exhibited a primary kinetic isotope effect. Reactant and product concentrations were determined by amino acid analysis and reversed phase HPLC.     

载体对草酸二甲酯加氢铜基催化剂的影响

以草酸二甲酯加氢反应为基础,研究了二氧化硅载体对铜基催化剂加氢反应性能的影响。催化剂分别以气相硅溶胶、硅胶、二氧化硅为载体,采用沉淀沉积法制备了Cu/SiO2催化剂(wCu=0.20),分别记为CS1、CS2、CS3,催化剂的活性从CS3、CS2到CS1依次增加。XRD测试物相结构表明:氧化态CS2和CS3中存在CuO晶相,而氧化态CS1中活性组分呈无定形分布。还原态催化剂的XRD测试表明催化剂中有Cu2O和Cu0存在,且Cu2O/Cu0的比例按CS3、CS2、CS1顺序增加,XPS分析证实了3个催化剂表面Cu2O/Cu0的比例有相应的变化趋势。这说明Cu2O和Cu0与草酸二甲酯加氢反应活性相关,提高Cu2O的含量,可以提高催化剂的活性。     

A new solution synthesis of locust adipokinetic hormone

An alternative synthesis of locust adipokinetic hormone (AKH-I) is described using the pentafluorophenyl ester method. During purification a by-product (ca. 20%) was isolated and characterized as [Thr(Bzl)]⁵-AKH-I. Hydrogenolytic cleavage of this benzyl ether bond could not be pursued to completion because partial saturation of the indole ring of Trp started. Thus, this protecting group combination should preferably be avoided. AKH-I had no effect on the central nervous system of vertebrates.     

Stereoselective hydrogenation on the exocyclic and conjugated double bond of sesquiterpene lactones by Aspergillus versicolor D-1

Aspergillus versicolor D-1 was employed to convert dehydrocostuslactone (1) and 3-hydroxy-1(10),3,11(13)-guaiatriene-12,6-olide-2-one (5) stereoselectively. The reactions occurring were specific hydrogenation on the exocyclic α,β-double bond of sesquiterpene lactones with excellent conversion. Products were identified by the analysis of their spectra such as UV, IR, MS, ¹H, ¹³C NMR, and NOESY, and the structure of one new compound was elucidated. The characteristic of the stereoselective hydrogenation was also discussed and suggested.     

Effect of Oxide Coating on Performance of Copper-Zinc Oxide-Based Catalyst for Methanol Synthesis via Hydrogenation of Carbon Dioxide

The effect of oxide coating on the activity of a copper-zinc oxide–based catalyst for methanol synthesis via the hydrogenation of carbon dioxide was investigated. A commercial catalyst was coated with various oxides by a sol-gel method. The influence of the types of promoters used in the sol-gel reaction was investigated. Temperature-programmed reduction-thermogravimetric analysis revealed that the reduction peak assigned to the copper species in the oxide-coated catalysts prepared using ammonia shifts to lower temperatures than that of the pristine catalyst; in contrast, the reduction peak shifts to higher temperatures for the catalysts prepared using L(+)-arginine. These observations indicated that the copper species were weakly bonded with the oxide and were easily reduced by using ammonia. The catalysts prepared using ammonia show higher CO₂ conversion than the catalysts prepared using L(+)-arginine. Among the catalysts prepared using ammonia, the silica-coated catalyst displayed a high activity at high temperatures, while the zirconia-coated catalyst and titania-coated catalyst had high activity at low temperatures. At high temperature the conversion over the silica-coated catalyst does not significantly change with reaction temperature, while the conversion over the zirconia-coated catalyst and titania-coated catalyst decreases with reaction time. From the results of FTIR, the durability depends on hydrophilicity of the oxides.     

Contribution of foods to trans unsaturated fatty acid intake in a group of Irish adults

OBJECTIVE: To assess fat intake with particular focus on trans unsaturated fatty acid (TUFA) intake and the major sources of TUFA among Irish individuals using a Fat Intake Questionnaire (FIQ), designed specifically for an Irish context. SUBJECTS AND METHODS: A total of 105 healthy volunteers (43 females, 62 males; aged 23-63 years) were recruited from Dublin Airport Medical centre, Republic of Ireland. Dietary intake was assessed using an 88 food item/food group semi-quantitative FIQ, which was developed and validated for the Irish population. RESULTS: Mean energy intake was 10.6 MJ day(-1), and 34% was provided by fat. Saturated, monounsaturated, polyunsaturated, trans unsaturated fatty acids and linoleic acid contributed 13%, 10%, 6%, 2% and 5% of energy respectively. Mean TUFA intake was 5.4 g day(-1) (range 0.3-26). Margarine spreads provided the majority of TUFAs (1.93 g day(-1)), but the contribution was significantly greater for men compared with women (2.35 g day(-1) versus 1.33 g day(-1); P = 0.024). Milk and meat also contributed more to TUFA intake for men compared with women, but confectionery was a significantly greater contributor for women (8.6% versus 3.1% respectively, P = 0.01). CONCLUSIONS: Although the mean TUFA intake of the total group was 5.4 g day(-1) and was within current dietary recommendations (2% energy intake), some individuals had intakes as high as 26 g day(-1). Public health efforts are therefore required to reduce TUFA intake in those individuals with high intakes.     

Analysis of Multiphase Flow and Heat and Mass Transfer for Ammonium Chloride Crystallization of the High-Pressure Heat Exchanger in Hydrogenation Unit

The corrosion failure of the high-pressure heat exchanger in a petrochemical enterprise was simulated. A multiphase flow and heat and mass transfer simulation shows that the vortex core with a higher gas phase content and lower temperature is the region of easy crystallization, located on both sides of the center of the tube. The crystallization process occurs in the gas phase. As the reaction progresses, the crystallization range spreads from the tube wall to the center of the tube bundle, and the inner diameter of the tube bundle decreases continuously. In Fluent, a user-defined function, based on the ammonium chloride crystallization reaction, is loaded. The results show that crystallization first occurs in the tube bundles on both sides of the center of the tube and that the corrosion is aggravated by the erosion wall surface of crystal particles at the elbow, which is consistent with the actual corrosion failure location.