油脂中不同位置脂肪酸氢化速率的研究

通过大豆油和玉米油在相同的氢化反应条件下 ,用不同的催化剂选择性氢化 .运用反应比、lnIv t图及速率常数计算等不同方法 ,论证脂肪酸在甘三酯不同位置上的氢化速率是否相同 .结果表明 :大豆油氢化时 ,亚麻酸、亚油酸、油酸在Sn - 1 ,3位较Sn - 2位氢化反应得更快 ;玉米油氢化时 ,亚油酸在Sn - 1 ,3位氢化速率大于Sn - 2 ,而油酸在甘三酯不同位置上的氢化速率差异因催化剂不同而有所区别 ,对大多数催化剂来说 ,Sn - 1 ,3位氢化速率大于Sn - 2位 ,用催化剂SP7催化氢化时 。

补充脂肪对奶牛瘤胃脂肪酸生物氢化和流通速率的影响

美国密歇根大学Kevin等学者使用泌乳奶牛补充脂肪改变饱和度来确定脂肪酸生物氢化和流通速率。该试验通过脂肪酸十二指肠流量除以它们各自的瘤胃库容量来确定流通速率。生物氢化速率的确定需要一个模型来说明脂肪酸在库之间的转移。选择8头安装瘤胃和十二指肠瘘管的经产荷斯坦奶牛，采用4×4拉丁方设计共进行了21d试验。试验分为对照组和补充25g／kg脂肪酸替代品改变饱和度的处理组，

食用高芥酸菜油氢化技术的研究

在研究了低芥酸菜油氢化技术的基础上,以类似的方法用L_(27)(3^(13))正交表对高芥酸菜油氢化技术进行研究,结果表明:高芥酸菜油氢化速度比低芥酸菜油慢得多,操作参数要求较高。操作参数对氢化速度影响的大小次序为:温度、催化剂浓度、氢气压强和搅拌强度,该次序与低芥酸菜油同,但温度与催化剂浓度、温度与压强的交互作用对反应速度的影响较明显,这与低芥酸菜油有区别。另外,产品碘值与熔点的对应关系受温度与催化剂浓度交互作用的影响很大,随温度增加,催化剂浓度亦要增加,才能有较好的选择性。实验得出高芥酸菜油氢化油的最佳生产条件为:温度190℃,催化剂浓度0.22％Ni,氢气压强0.38MPa和210℃,0.44％Ni,0.18MPa。在该两条件下,反应的选择性最好,且具有适宜的反应速度。

超声波对氢化向日葵油的影响

本文考察了超声波对向日葵油氢化速率的影响。用两种不同的镍催化剂,在保持较高的氢化选择性条件下,超声波可使向日葵油的氢化速率提高30—70%,超声波对形成脂肪酸的反式异构体没有影响。

影响棕榈油软酯氢化的因素探讨

本文研究了反应温度、反应压力、搅拌速率和催化剂用量对氢化速率以及棕榈油软脂的熔点、反式脂肪酸含量和SFC的影响,得出各因素对氢化反应影响均较为显著,其中反应温度150℃、反应压力0.3MPa、搅拌转速800r/min和催化剂用量0.15%的条件下氢化反应速率较快,棕榈油软脂的反式脂肪酸含量最低,熔点最高,SFC曲线最为平滑。

Effect of ferrite content on dissolution kinetics of gibbsitic bauxite under atmospheric pressure in NaOH solution

The dissolution property of high-ferrite gibbsitic bauxite and the effect of ferrite content on the dissolution kinetics of gibbsitic bauxites in sodium hydroxide solution under atmospheric pressure from 50 to 90 °C were systematically investigated.The dissolution property of high-ferrite gibbsitic bauxite is increased by increasing the dissolution temperature and the Na OH concentration or decreasing the particle size of bauxite,which is easy to dissolve under atmospheric pressure.The kinetic equations of gibbsitic bauxites with different ferrite contents during the dissolution process at different temperatures for different times were established,and the corresponding activation energies were calculated.The ferrite in the gibbsitic bauxite reduces the dissolution speed and increases the activation energy of dissolution,the diffusion process of which is the rate-controlling step.

Periodic Packing Mode for Trickle-Bed Reactors: Experiments and Modeling

A periodic packing mode of trickle-bed reactor (TBR) for the gas limited reaction was proposed. Hy-drogenation of 2-ethylanthraquinone over Pd/Al2O3 in a laboratory-scale TBR was taken as a test reaction for determining whether the periodic packing mode is advantageous. The effects of operating conditions and packing type on TBR performance were experimentally examined to demonstrate the cause-effect relationships. A mathe-matic model of TBR considering axial dispersion and fractional wetting was developed to quantitatively illuminate the reason of performance enhancement.

Effect of Boundary Layers on Polycrystalline Silicon Chemical Vapor Deposition in a Trichlorosilane and Hydrogen System

This paper presents the numerical investigation of the effects of momentum, thermal and species boundary layers on the characteristics of polycrystalline silicon deposition by comparing the deposition rates in three chemical vapor deposition （CVD） reactors. A two-dimensional model for the gas flow, heat transfer, and mass transfer was coupled to the gas-phase reaction and surface reaction mechanism for the deposition of polycrystalline silicon from trichlorosilane （TCS）-hydrogen system. The model was verified by comparing the simulated growth rate with the experimental and numerical data in the open literature. Computed results in the reactors indicate that the deposition characteristics are closely related to the momentum, thermal and mass boundary layer thickness. To yield higher deposition rate, there should be higher concentration of TCS gas on the substrate, and there should also be thinner boundary layer of HCl gas so that HCl gas could be pushed away from the surface of the substrate immediately.

Chemical vapor deposition of SiC at different molar ratios of hydrogen to methyltrichlorosilane

Chemical vapor deposition(CVD) of SiC from methyltrichlorosilane(MTS) was studied at two different molar ratios of H2 to MTS(n(H2) /n(MTS) ) . The total pressure was kept as 100 kPa and the temperature was varied from 850 to 1 100 ℃ at a total residence time of 1 s. Steady-state deposition rates as functions of reactor length and of temperature,investigated at different n(H2) /n(MTS) values,show that hydrogen exhibits strongly influences on the deposition rate. Especially,the deposition of Si co-deposit can be obtained in broader substrate length and at higher temperatures with increasing hydrogen partial pressure. Influence of hydrogen on the deposition process was also studied using gas phase composition and deposit composition analysis at various n(H2) /n(MTS) . SEM micrographs directly show the variation of surface morphologies at various n(H2) /n(MTS) . It can be found that the crystal grain of the deposit at 1 100 ℃ is better developed and the crystallization is also improved with increasing n(H2) /n(MTS) .

Direct Z-scheme CdS-CdS Nanorod Arrays Photoanode: Synthesis,Characterization and Photoelectrochemical Performance

Direct Z-scheme CdO-CdS 1-dimensional nanorod arrays were constructed through a facile and simple hydrothermal process. The structure, morphology, photoelectrochemical properties and H2 evolution activity of this catalyst were investigated systematically. The morphology of the obtained nanorod is a regular hexagonal prism with 100-200 nm in diameter. The calcination temperature and time were optimized carefully to achieve the highest photoelectrochemical performance. The as-fabricated hybrid system achieved a photocurrent density up to 6.5 mA/cm2 and H2 evolution rate of 240 μmol·cm-2·h-1 at 0 V vs. Ag/AgCl, which is about 2-fold higher than that of the bare CdS nanorod arrays. The PEC performance exceeds those previously reported similar systems. A direct Z-scheme photocatalytic mechanism was proposed based on the structure and photoelectrochemical performance characterization results, which can well explain the high separation efficiency of photoinduced carriers and the excellent redox ability.