Propylene epoxidation in a microreactor with electric heating

Gas phase propylene epoxidation on gold catalysts has attracted wide attention from industry and academia due to its high selectivity. However, it suffers from low propylene conversion and rapid catalyst deactivation. Experiments showed that propylene conversion could be increased by raising H₂, O₂, or C₃H₆ concentration in the feed, but the feed compositions were within the explosion limit. It was also shown that the activity of the used catalyst could be fully recovered, but the regeneration temperature was 280 °C, much higher than that for reaction. Therefore a microchannel reactor was devised to suppress explosion and was constructed with Fecralloy, to raise the temperature rapidly for catalyst regeneration by electric heating. In two minutes the temperature of the reactor could be raised from 50 to 300 °C. Catalysts were coated on the alloy belt by dip coating, and the performance of the reactor was evaluated under different operating conditions. Results showed that in the microreactor the overall reaction rate was controlled mainly by the intrinsic reaction rate, and also influenced by film diffusion to a certain extent. The deactivated catalyst was regenerated in the microchannel reactor and the activity was fully recovered.     

Relationship of threshold diameter and Darcean permeability in unconsolidated porous structures

Experiment was conducted on the threshold pressure for atmospheric air through unconsolidated narrow size distributed mini sphere and sand particles at low flow rates. The threshold diameter calculated from measured threshold pressure showed that it does not follow the traditional similarity theory. This is consistent with our experiment on accurate permeability measurement, and can be explained as a result of gas slip flow within such micro pore structure. Our current work tend to find the method to predict the permeability-threshold pressure relationship for unconsolidated porous structures.     

西门子S7系列PLC在自控系统中的应用

阐述了S7—400H应用特点使用中存在的问题、解决方案。     

Reaction kinetics study of asymmetric polymer-polymer interface

In this study, the reaction kinetics of asymmetric polymer-polymer interface was experimentally and theoretically studied. A new rheological method correlating the change of rheological property of reactive system with the conversion of the in situ formed copolymers was applied to study the reaction kinetics of PBT/epoxy reactive system. Then, the new method was proved to be useful by comparing its results with that obtained from the conventional endgroup determination method. Moreover, the conversion of PBT/epoxy reactive system from rheological method could be well fitted by the numerical analysis, from which the kinetic constant and the diffusion constant of epoxy in PBT could be determined simultaneously.     

EVAPORATION FROM POROUS MEDIA: A CAPILLARY MODEL OF A PENETRATING FRONT

A capillary tube model was solved to investigate the influence of mass transfer coefficient, temperature, and front depth on the evaporation rate during the penetrating-front period of water-filled porous media dried in hot air. The results show that increasing the flow rate of the drying air is not so efficient as increasing the sample temperature. Due to attenuating diffusion rate, the rate of liquid front migration decreases with time. The calculations explain the falling rate period behavior of sandstone heated at 121°C. Trends depicted by the model may be useful for the design of heating conditions for drying processes.     

纳米SiO_2粒子在环氧树脂中的分散工艺研究

研究了纳米SiO2在环氧树脂中的均匀分散工艺,探讨了超声波振荡和超声波分散时间对纳米SiO2/EP复合材料力学性能的影响,确定了最佳分散工艺。SEM表明,采用高剪切与超声波复合分散工艺比高剪切工艺的分散效果好;测试了复合材料的力学性能,进一步证明纳米SiO2具有增韧增强作用。     

气体控制参数对气体辅助成型产品翘曲的影响

从气体辅助注射成型工艺的角度探讨了气体的延迟时间和第一段压力这两个关键的参数对槽的影响进而对产品翘曲变形的影响，结果表明：虽然通过使用气体辅助注射成型技术能改善产品变形，但并不能完全消除变形；造成产品变形的原因和机理十分复杂，只有进行从设计到工艺的全方位考察才能有效的控制变形，气体手指效应也是造成产品变形的一个重要因素，工艺上可以通过调整延迟时间和气体压力来减小产品的变形量。     

Effects of soaking soybeans in dilute acids on biologically active components

Soaking soybeans in dilute acids affected activities of lipoxygenase, trypsin inhibitor and urease. Effects of soaking time, acid concentration and soaking temperature were investigated. Lipoxygenase activity was completely eliminated by soaking in 0.3 M HC1 at either 23°C or 40°C for 8 hr. Less than 50% trypsin inhibitor remained and urease was inactivated to an acceptable level (0.04 ΔpH).     

二氧化硫在钒催化剂上氧化动力学的研究——Ⅲ.几种工业钒催化剂的动力学方程式的比较

<正>作者等过去的工作已经证实,由于扩散过程的影响、温度范围的不同、或化学组成的差异,二氧化硫在钒催化剂上的氧化动力学方程式可能具有不同的形式。反应物及生成物与催化剂之间的相互作用,可能使催化剂具有不同的颜色与活性,因而即使温度相同,由于催化剂在层内所处的部位不同,其催化活性可能并不一致。这些复杂性给工业设计带来了很大的困难。因此,合理的简化是完全必要的。 作者等选取了几种不同的工业钒催化剂,用实验方法求得了适用于它们的动力学方程式,进行比较和讨论,提出了一个简便的、合理的、可以用作设计基础的动力学方程式。