聚偏二氯乙烯用途及生产技术

介绍聚偏二氯乙烯共聚物性能、品种及主要用途和国内外生产应用概况,分析了国内开发及市场现状提出对开发此类产品的建议。     

Development of a microchannel catalytic reactor system

The purpose of this article is to demonstrate the applicability of microreactors for use in catalytic reactions at elevated temperatures. Microchannels were fabricated on both sides of a silicon wafer by wet chemical etching after pattern transfer using a negative photoresist. The walls of the reactor channel were coated with a platinum layer, for use as a sample catalyst, by sputtering. A heating element was installed in the channel on the opposite surface of the reactor channel. The reactor channel was sealed gas-tight with a glass plate by using an anodic bonding technique. A small-scale palladium membrane was also prepared on the surface of a 50-Μm thick copper film. In the membrane preparation, a negative photoresist was spin-coated and solidified to serve as a protective film. A palladium layer was then electrodeposited on the other uncovered surface. After the protective film was removed, the resist was again spin-coated on the copper surface, and a pattern of microslits was transferred by photolithography. After development, the microslits were electrolitically etched away, resulting in the formation of a palladium membrane as an assemblage of thin layers formed in the microslits. The integration of the microreactor and the membrane is currently under way.     

Tribo-electrostatic beneficiation of fly ash for ash utilization

The study was conducted to obtain the scale-up factor and the optimum design criteria for the development of a commercial scale electrostatic separator using a continuous, bench-scale electroseparator composed of two vertical electrode plates and an ejector-tribocharger. Tests of the charge density and separation efficiency to study the removal possibility of unburned carbon from coal fly ash were evaluated under various operating conditions. It was found that the experimental conditions for obtaining the maximum charge density were an air flow rate of 1.75 m³/min and a feed rate of less than 50 kg/hr when operated at lower than 30% relative humidity using a SUS304 ejector tribocharger. Also, the optimum instrument conditions for recovering the clean ash with less than LOI3% at yield over 65% when operated at above experimental conditions were found to be a diffuser slit gap of 4 mm, and a distance between diffuser slit and splitter of 15 cm. Overall, the feed rate per unit electrode surface area was about 0.074 kg/cm2 hr, which can be used as a scale-up factor of the electroseparator. Presented at the Int’/Sym. on Chem. Eng. (Cheju, Feb. 8–10, 2001), dedicated to Prof. H. S. Chun on the occasion of his retirement from Korea University.     

Characterization of pyrolytic lignins with different activities obtained from bio-oil

Pyrolytic lignin, the water-insoluble fraction in bio-oil, often shows a high content and has strong intermolecular interactions with other compounds in bio-oil. In order to obtain pure pyrolytic lignin and facilitate the utilization of aqueous phase obtained from water extraction of bio-oil, methanol–water extraction method was employed to further separate the bio-oil water-insoluble phase in this paper. Different technologies, including Fourier transform infrared spectroscopy, gel permeation chromatography, and nuclear magnetic resonance, were adopted to characterize the structures of pyrolytic lignins with different activities obtained through this method. Both the heating value and the polymerization degree of high-molecular-weight pyrolytic lignin were higher than those of low-molecular-weight pyrolytic lignin. The molecular weight distribution of high-molecular-weight pyrolytic lignin was relatively wider, among which the contents of dimers to pentamers all accounted for 12% –18%,while the low-molecular-weight pyrolytic lignin mainly consisted of trimers(75.38%). The pyrolytic lignins had similar basic structures, both of which contained syringyl and guaiacyl units, whereas the low-molecular-weight pyrolytic lignin had more abundant syringyl units, reactive carbonyl groups and hydroxyl groups. Meanwhile,thermogravimetric study revealed that the final char residue yield of low-molecular-weight pyrolytic lignin was lower than that of high-molecular-weight pyrolytic lignin.     

Influence of monovalent cations and CuO nanoparticles on X-nanozeolite in uranium anionic species separation from contaminated drinking water

The main purpose of this work was the modification of NaX nanozeolite using copper oxide nanoparticles and various monovalent cations such as K~+, Cs~+, and Ag~+in order to make the negatively charged zeolite surface accessible for anionic forms of uranium which are the most dominant species of uranium in the contaminated radioactive waters at natural p H. Various methods such as the X-ray fluorescence(XRF), X-ray powder diffraction(XRD), field emission scanning electron microscopy(FE-SEM), transmission electron microscopy(TEM), Fourier transform infrared spectroscopy(FT-IR), and atomic absorption spectroscopy(AAS) were used to characterize the final synthesized absorbents. Batch technique was used to study the adsorption behavior of uranium ions from polluted drinking water by Na X nanozeolite and its modified forms. In order to better understand the performance of them, the results were compared with those that were obtained for synthesizing bulk NaX zeolite and Na-form of clinoptilolite natural zeolite. Preliminary results indicated that uranium sorption increased as the loading level of CuO nanoparticles on NaX nanozeolite increased from 2.1 wt% to 11.2 wt%. In addition,from the obtained data, an increase in uranium removal efficiency resulted as charge/ionic radius ratio of exchanged cation decreased. Also, the effect of contact time, solid–liquid ratio, initial concentration and temperature on the adsorption process was studied. It is worth mentioning that, in this study, the sorption of uranium was performed under natural conditions of pH and the presence of competing cations and anions which are available in drinking waters.     

Construction of molecule-selective mixed matrix membranes with confined mass transfer structure

Extraordinary mass transfer phenomenon is usually found when the small molecules pass through a confined structure, whose effective size is commensurate with the mean free path of the molecules. Small changes in the confined mass transfer structure (including size, morphology and properties) will lead to significant fluctuations of the mass transfer coefficient. The mass transfer of the penetrant molecules in the dense membranes for pervaporation, gas separation and so on, is located in the scope of confined mass transfer. Incorporating nanofillers into polymer matrix to construct mixed matrix membranes (MMMs) is an effective approach to tune the confined mass transfer structure and enhance the performance of the widely used polymeric membranes. This reviewfocuses on the construction andmanipulation of the confined structure in the polymeric membranes via incorporating one-dimensional (1D), two-dimensional (2D) and three-dimensional (3D) fillers.The comparison of the MMMs for pervaporation is summarized, and the research prospective of the MMMs is provided.     

A TBP/BTBP-Based GANEX Separation Process – Part 3: Fission Product Handling

A Group ActiNide EXtraction (GANEX) separation system for transmutation has been developed, combining CyMe₄-BTBP with TBP and cyclohexanone. This new GANEX solvent has proven efficient in actinide extraction but also been found to extract some undesired fission products and corrosion products. Three major fission products were primarily selected for the study: Mo, Zr, and Pd. There are three main strategies for handling the extraction problem, all of which have been investigated and discussed; these are Pre-extraction, Suppression, and Scrubbing. The only strategy that was found to control the behavior of all three main fission products was suppression by the combination of two water-soluble complexing agents bimet and mannitol.     

Solvent Extraction of Lanthanides(III) with N‐Cinnamoyl‐N‐phenylhydroxylamine and Its Trifluoromethyl Derivative

Abstract

N‐m‐Trifluoromethylcinnamoyl‐N‐phenylhydroxylamine (CF₃‐CPHA) was synthesized. The acid‐dissociation constant and distribution constant between chloroform and water of CF₃‐CPHA and N‐cinnamoyl‐N‐phenylhydroxylamine (CPHA), which was the mother compound of CF₃‐CPHA, were determined spectrophotometrically. The extraction behavior of tervalent lanthanides (Ln), Pr, Eu, and Yb into chloroform solution containing CPHA or CF₃‐CPHA was studied. They are extracted as self‐adduct chelates, LnL₃(HL)₃, where L and HL denote the ligand anion and neutral ligand, respectively. The extraction constants and separation factors for the lanthanides with CPHA and CF₃‐CPHA were evaluated. The extraction constant with CPHA are smaller than that obtained with CF₃‐CPHA. However, it is observed that CPHA possesses higher selectivity than CF₃‐CPHA.     

Mechanism of Particle Separation in Small Hydrocyclone

The mechanism of particle separation in a small hydrocyclone is analyzed in this study. The separation efficiency of particles is affected by two major effects, the centrifugal and underflow effects. The fundamentals of these effects on the selectivity curve are derived from the theories of hydrodynamics. Three JIS particulate samples are separated in a 10-mm hydrocyclone. The proposed mechanism can be demonstrated by the available data. An increase in split ratio leads to an increase in the separation efficiency only for fine particles; consequently, a decrease in the separation sharpness results in a remarkable fishhook phenomenon. When the feed rate is increased by increasing the pressure drop through the hydrocyclone, the entire partial separation efficiency will be improved, but the separation sharpness and fishhook depth have no substantial varieties. The proposed mechanism can be used for explaining these phenomena, for the selection of optimum operating conditions, and for the hydrocyclone design.