Carbon dioxide plasma decomposition

Figure 14 Schematic diagram of the capillary plasma reactor developed for the decomposition of carbon dioxide (Mori et al., 2006 reproduced with permission).

The capillary plasma reactor consists of a Pyrex glass body and mounted electrodes which are not in direct contact with the gas flow in order to eliminate the influence of the cathode and anode region on CO2 decomposition. Analysis of downscaling effects on the plasma chemistry and discharge characteristics showed that the carbon dioxide conversion rate is mainly determined by electron impact dissociation and gas-phase reverse reactions in the capillary microreactor. The extremely high CO2 conversion rate was attributed to an increased current density rather than to surface reactions or an increased electric field. 

Single pulse, shock tube decomposition of acetic acid in argon inv olves the same pair of homogeneous, molecular first-order reactions as thermolysis (19). Platinum on grapliite catalyzes the decomposition at 500—800 K at low pressures (20). Ketene, methane, carbon oxides, and a variety of minor products are obtained. Photochemical decomposition yields methane and carbon dioxide and a number of free radicals, wliich have complicated pathways (21). Electron impact and gamma rays appear to generate these same products (22). Electron cyclotron resonance plasma made from acetic acid deposits a diamond [7782-40-3] film on suitable surfaces (23). The film, having a polycrystalline stmcture, is a useful electrical insulator (24) and widespread industrial exploitation of diamond films appears to be on the horizon (25). 

The endothermic plasma-chemical process of carbon dioxide decomposition, illustrated in Fig. 5-1, can be presented by the summarizing formula... 

This process can be considered the first plasma-chemical stage of a two-step process for ly drogen production from water. The second stage in this case is formic acid decomposition with formation of hydrogen and carbon dioxide ... 

Non-Thermal Plasma Synthesis of Formic Acid in CO2-H2O Mixture. Determine the minimum energy efficiency of the plasma-chemical HCOOH synthesis in the CO2-H2O mixture (9-60) required for effective hydrogen production in the double-step cycle (9-60) and (9-61). Assume that thermodynamically about 70% of the total energy required for hydrogen production from water should be consumed in this case for decomposition of formic acid (9-61) to form hydrogen and to recycle carbon dioxide back to the plasma process. 

Rico, V. J., Hueso, J. L., Cotrino, J., Gonzalez-Elipe, A. R. (2010). Evaluation of different dielectric barrier discharge plasma configurations as an alternative technology for green Cl chemistry in the carbon dioxide reforming of methane and the direct decomposition of methanol. Journal of Physical Chemistry A, 114 ), 4009—4016. 

Ma, B., Balachandran, U., Chao, C. C., Park, J. H., Segre, C. U. (1997). Oxygen permeation in Sr—Fe—Co—O dense cetamic membranes. British Ceramic Transactions, 73, 169—177. Mahesh, S., Akira, K. (2010). Carbon dioxide decomposition by plasma methods and apphcation of high energy and high density plasmas in material processing and nano-stmctures. Transactions of JWRI39, 11—25. 

Next, low-temperature (<150°C), low-pressure torr) oxygen plasmas oxidized organic components of the sample to CO2. Decomposition of inorganic carbon present (dolomitic limestone rock and calcite/calcium oxalate accretions) was prevented by running the plasmas at low-temperature. Carbon dioxide from the sample was flame-sealed into a glass tube cooled to liquid nitrogen temperature (-194°C), after water had been frozen out with a dry-ice/ethanol slurry (-58°C), and finally sent for radiocarbon analysis at the Center for Accelerator Mass Spectrometry at the Lawrence Livermore National Laboratory (LLNL-CAMS). It was necessary to utilize an AMS measurement due to the small sample size. 

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