Tubular reactor, plasma

Chen X, Marquez M, Rozak J, Marun C, Luo J, Suib SL, Hayashi Y, Matsumoto H (1998) H2O splitting in tubular plasma reactors. J Catal 178 372-377... 

Depositions were done in a hot-wall tubular plasma reactor at a frequency of 410 kHz. Deposition temperatures ranged from 300° to 400°C, and pressures from 830 mTorr to 1.5 Torr. Gases used were SiH4, N20, 02, PH3 and B2H6, with the latter two diluted by argon. The boron and phosphorus concentrations were adjusted by changing the reactant gas mixture. 

THE PRODUCTION OF HYDROGEN FROM METHANE USING TUBULAR PLASMA REACTORS... 

X 1.00" rectanglar samples were cut from LDPE roll film (Penn Fibre). A sample was then placed 15" from the inlet inside a 2 x 1" OD quartz tubular plasma reactor. Two external copper electrodes separated by 3.5" were located across the rectangular sample. The base pressure of the system was then pumped down to below 1 mtorr. Plasma modification by sulfur dioxide was accomplished by flowing SO2 at a rate of 10 cm jyp min-i into the plasma reactor using the mass flow controller. After the system pressure was stabilized with a continuous flow of the reactive gas, it was regulated... 

Plasma surface modification of PET powder was carried out by using vinyl chloride (VC) plasma, operating at 13.56 MHz for 15 minutes, at 10 Watts, in the tubular plasma reactor system, (Figure 1). 

A twin torch plasma furnace, where DC anode and cathode arcs were coupled together above an aluminum melt, was developed for synthesis of AIN UFPs in order to control the aluminum evaporation rate and the concentration of nitrogen atoms in the plasma column independently (19). A two-stage transferred-arc plasma reactor was built for AIN synthesis, where aluminum is evaporated in a transferred-arc plasma chamber and then reacted in a separate tubular reactor, allowing a better control of the reaction conditions (20). Arc plasma technique has been modified and... 

The tubular-type plasma reactor system used in the study consists of a reactor chamber, power supply, monomer feed, and pumping-out units, as depicted in Figure 19.1. One side of the glass tube is connected to a monomer inlet and the other side to a vacuum pump with O-ring joints. A radio frequency power generator of 13.56 MHz is coupled to two capacitive copper electrodes, which are 1 cm wide and 6 cm apart. The radio frequency power was controlled by an L-C matching network and monitored by power meter. 

Wang et al. [51] studied the separation of a water/acidic mixture by pervapora-tion using a plasma-treated asymmetric poly(4-methyl-l-pentene) (TPX) membrane, which was further dip-coated with polyacryUc acid (PAA). The asymmetric TPX membrane was prepared by the wet phase inversion technique. Membranes were treated with residual air plasma in a tubular-type reactor. The modification of the... 

The plasma system consisted of a standard vacuum pump and a tubular Pyrex reactor with a 13.56 MHz RF generator coupled to it using external copper electrodes [26]. During the experiments, surfaces of PVC powder and PE granules were modified in carbon tetrachloride and vinyl chloride plasma for the first polymer, and in acetylene plasma for the latter. The plasma treatment conditions are presented in Table 7. Plasma is known to yield mainly surface modifications with a minimum (if any) of plasma polymerization. The oligomer VCO was also used without application of plasma to prepare reference blends. 

The hydrodynamic factors that influence the plasma polymerization process pose a complicated problem and are of importance in the application of plasma for thin film coatings. When two reaction chambers with different shapes or sizes are used and when plasma polymerization of the same monomer is operated under the same operational conditions of RF power, monomer flow rate, pressure in the reaction chamber etc., the two plasma polymers formed in the two reaction chambers are never identical because of the differences in the hydrodynamic factors. In this sense, plasma polymerization is a reactor-dependent process. Yasuda and Hirotsu [22] systematically investigated the effects of hydrodynamic factors on the plasma polymerization process. They studied the effect of the monomer flow pattern on the polymer deposition rate in a tubular reactor. The polymer deposition rate is a function of the location in the chamber. The distribution of the polymer deposition rate is mainly determined by the distance from the plasma zone and the... 

Fig. 6 Schematic representation of the vertical tubular reactor for plasma polymerization onto powders [41]...

Figure 7.7 depicts type of plasma polymer of TFE depending on the location in a small tube reactor [7]. In the tubular reactor shown, the formation of F would occur at the upstream side of the reactor, where the monomer flow makes contact with the luminous gas phase of TFE. Then, the — CF3 could be used as a labeled species or an indicator of the change in the chemical nature of the polymer due to the kinetic pathlength of a growing species. The XPS data obtained with polymers... 

Ihara and Yasuda investigated the deposition behavior of methane in the medium-sized tubular reactor with 13.56 MHz radio frequency discharge [2]. They observed that the critical WjFM value, WjFM), for methane was 8GJ/kg, and nearly 100% of monomers were converted to the plasma polymer beyond this critical WjFM value. As shown in Figure 19.5, the critical WjFM value of perfluoropropene in the small reactor is around 6GJ/kg and the DjFM is 15%, and the corresponding value in the medium is around 4GJ/kg, and the maximal conversion is around 30%. In the large reactor, (WIFM) is about 1 GJ/kg and the maximal DjFM is 20%. The lower value of the critical WjFM for C3F6 than that for CH4 is explained in Chapter 7. 

The effects of the discharge power on the distribution of polymer deposition in a tubular reactor (Fig. 20.1) are shown in Figures 20.19-20.22. Figure 20.19 depicts the change in polymer deposition pattern due to the discharge power observed in the plasma polymerization of styrene at a fixed flow rate of 5.6 seem. 

An important implication of the data obtained with both a tubular reactor and a bell jar reactor is that the polymer deposition onto a stationary substrate cannot be uniform due to the diffusional transport of polymer-forming species and the path-dependent growth mechanism. The variation of polymer deposition rates at various locations becomes smaller as the system pressure decreases because the diffusional displacement distance of gaseous species increases at lower pressure. It is important to recognize that a certain degree of thickness variation always exists when the plasma polymer is deposited onto a stationary substrate regardless of the type of reactor and the location of the substrate in the reactor. 

Smolinsky, G. Flamm, D.L. The plasma oxidation of CF4 in a tubular-alumina fast-flow reactor. J. Appl. Phys. 1979, 50, 4982-4987. 

In addition, the use of electrodless glow discharge will produce different results than those with internal electrodes. In the former case, rare gases such as He, Ar was introduced from one end of the tubular reactor and the plasma was sustained by a rf coil outside the reactor. Gaseous monomer was fed into the afterglow of a rare gas and polymer film deposited on the substrate placed downstream. Yasuda, et. al. (18) observed that the deposition rate in electrodeless discharge was independent of the power input and increased in proportional to the square of the monomer pressure. 

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