Polish Journal of Chemical Technology (v.9, #1)
The influence of iron compounds in the sulfuric acid catalyst on the SO2 oxidation process
by Marcin Grobela; Piotr Grzesiak; (pp. 2-6).
The catalytic oxidation process of SO2 to SO3 is the main stage of sulfuric (VI) acid production. The process run could be disordered by reason of the increased inactivation of sulfuric acid catalyst during SO2 oxidation process. This paper includes the influence study of the iron quantity and forms, which is introduced into the catalyst active phase, on the reaction rate of the SO2 oxidation process.
Keywords: catalyst active phase; reaction rate; inactivation
The influence of the catalyst on the kinetics of ethyl metacrylate synthesis
by Mirosław Grzesik; Teresa Witczak; (pp. 7-9).
The synthesis of ethyl metacrylate in the liquid phase was studied. Tungstophosphoric and molybdophosphoric acids, which belong to heteropolyacids group, were used as a catalyst. The chemical compounds from this group are often utilized in the catalysis with regard to their activity and selectivity. The rate equations, reaction rate constants and equilibrium constants have been determined. The reaction order and the kinetic parameters of the kinetic relations were determined by the integral method. All rate equations are formulated with activities taking the non ideal effects of the compounds into consideration. It was found that the kinetics of the esterification of the presented reactions was non-elementary
Keywords: esterification; heteropoliacids; kinetics
Structured catalytic reactor for VOC combustion
by Andrzej Kołodziej; Joanna Łojewska; Tadeusz Kleszcz; (pp. 10-14).
VOC emission has recently become a challenge for environmental protection. Catalytic combustion seems a promising method of VOC removal, however, there are still more specific demands concerning the process. The reactor design has to assure enhanced transfer properties accompanied by low flow resistance to reduce the pumping costs. Neither the packed beds nor the classic ceramic monoliths are able to fulfil the requirements.
To solve the problem we propose a wire gauze structure composed of several gauze sheets staked. A number of mass transfer and flow resistance experiments were performed for two gauze types and correlations were derived for the Sherwood number and the friction factor. The results were found to be in a reasonable agreement with the literature available.
The studied gauze structures were compared with a classic monolith for the assumed case study. The calculated length of the gauze structured reactor was significantly shorter, up to ten times, when compared with a classic ceramic monolith, but the pressure drop was higher.
Keywords: structured catalyst; gauze; mass transfer; diffusional limitation; performance efficiency
Promoted cobalt oxide catalyst on the metallic structured reactor filling for VOC combustion as an alternative to noble metal catalysts
by Joanna Łojewska; Andrzej Kołodziej; Jerzy Żak; (pp. 15-19).
VOC combustion is a demanding process for both the reactor and the catalyst design. As we have proved in recent papers the diffusional limitation of reaction rate that occurs during combustion may be overcome by designing the metallic microstructures used as reactor internals. Their application on an industrial scale depends on the development of an efficient method of catalyst layering on metallic supports and the optimisation of a fine catalyst structure which would not change the elaborated microstructure geometry. In this study we propose the Langmuir-Blodgett (LB) film method to deposit various metals (Al, Co) in the form of catalyst organic precursors. The film forming abilities of the precursors were checked by surface pressure measurements upon film compression, Brewster Angle Microscopy and by the monolayers stability measurements. The amount of the deposited materials was controlled by the LB parameters and verified by the TG measurements. The catalyst obtained in this way were characterized at various stages of the preparation by SEM/XFS, XPS, AFM and RM methods and tested in n-hexane combustion. Oxidation of the Al washcoat precursor led to the formation of γ-Al2O3 improving the properties of the Al2O3 layer (α phase) developed on the pre-calcined CrAl carrier. Oxidation of cobalt stearate deposited on the CrAl produced dispersed Co3O4 spinel. The cobalt catalysts were active in combustion showing resistance to sintering. Compared to standard Pt supported catalyst it demonstrated twice as low activation energy (50 kJ/mol).
Keywords: Langmuir-Blodgett technique; structured carrier; wash-coat layer; Raman microscopy; XPS quantitative analysis
Oxidation of hexafluoropropylene with molecular oxygen
by Egbert Meissner; Agnieszka Wróblewska; (pp. 20-22).
The results of the oxidation of hexafluoropropylene (HFP) to hexafluoropropylene oxide (HFPO) have been presented. The oxidation was carried out in an autoclave within the range of temperatures of 120 - 170°C and in the presence of an organic solvent (carbon tetrachloride). Molecular oxygen was used here as an oxidizing agent. The influence of: the molar ratio of HFP/O from 13.4 to 4.09:1, the process temperature, the addition of inert gas (nitrogen) from 4 to 18 atm and the periodical dosing of oxygen were investigated. The functions describing the process were: the conversion of HFP and the yield of HFPO in relation to HFP consumed. The presented process is very interesting owing to a wide application of HFPO.
Keywords: hexafluoropropylene; hexafluoropropylene oxide; epoxidation; oligomerization
The effect of supports on coke deposition on supported platinum and platinum-tin catalysts investigated by FT-IR spectroscopy
by Zenon Sarbak; (pp. 23-26).
Coke deposit is produced from ethylene on the surface of the platinum and platinum-tin catalysts supported on two various Al2 O3, SiO2 and SiO2 -Al2O3. The coke amount and the structure depend on the type and the amount of the components introduced onto the catalyst support and on the type of the support. It has been found that the surface area of the support has no significant effect on the type of species in the coke deposit. The analysis of the FT-IR spectra has shown the presence of different species on the surface of the catalysts, including carboxyl groups, pseudo-graphite (polyaromatic) structures, polyphenylene groups, acetyl groups, carbonyl groups of acetone and formate type, enol species.
Keywords: FT-IR; coke deposit; Pt-Sn catalysts; Al2O3SiO2SiO2-Al2O3.
Structural and textural characterisation of NiMo catalysts supported on various zeolites
by Zenon Sarbak; Grażyna Fabiś; Sławomir Binkowski; (pp. 27-32).
Structural and textural properties of nickel-molybdenum catalysts supported on four various type of zeolites of different chemical composition and porous structure have been studied by the methods of IR, XRD and the low-temperature sorption of nitrogen. The catalysts have been obtained by the two-stage impregnation of the supports with the solutions of nickel and molybdenum salts by the method of incipient wetness. The catalysts have been shown to preserve the structure characteristic of the appropriate zeolite supports.
Keywords: Zeolites; NiMo catalysts; structural properties; surface area; porosity
A quick method to determine the content of sulfates in silicic and aluminosilicate fillers
by Barbara Sołtysik; (pp. 33-35).
The paper presents the possibility of using barium-selective electrode to a potentiometric determination of sulfates in silicic and aluminosilicate fillers. The results of sulfates potentiometric titration in silicic and aluminosilicate fillers are described. A statistical interpretation of the results was carried out. The recommended method is based on the end-point detection of sulfates potentiometric titration in hydro-alcoholic medium by means of barium chlorate(VII) titrant. The potentiometric titration, which uses an ion-selective electrode as the indicator for the end-point was applied as the analytical technique. The parameter ranges for accurate sulfates determination in model solutions and the method of samples' preparation for analysis were investigated.
Keywords: sulfates; potentiometric titration; silicic fillers; aluminosilicate fillers
Cold plasma in the nanotechnology of catalysts
by Jacek Tyczkowski; Ryszard Kapica; (pp. 36-42).
In the paper the preparation of catalysts with the use of cold plasmas is discussed. A special attention is focused on nanocatalysts. In general, there are three main trends in this field: (1) plasma enhanced preparation of "classical" catalysts, (2) plasma sputtering of catalytically active compounds, especially metal and metal oxide nanoparticles, and (3) plasma-enhanced metal-organic chemical vapor deposition (PEMOCVD) of very thin metal and metal oxide films with specific nanostructure. It is shown that the cold plasma techniques are very effective methods for designing the nanocatalysts with distinct and tunable chemical activity, specificity and selectivity. Finally, our preliminary investigations concerning CoOX catalytic films fabricated by the PEMOCVD method are presented.
Keywords: catalysis; nanostructures; cold plasma; metal-organic chemical vapor deposition; cobalt oxides thin films
The influence of organic diluents and solvents on the stability of PVC plastisol water dispersions
by Edwin Makarewicz; Krzysztof Jan´czak; (pp. 43-50).
The work presents the research, the aim of which is to specify the influence of organic diluents and solvents such as xylene, toluene, n-butyl acetate and butanol as well as cyclohexanone on the stability of water dispersions of the PVC plastisol containing various surface-active agents (SAA). The applied surfactants were characterised by a specific ethoxylation number, molecular mass, the Hildebrand parameter, hydrophilic-hydrophobic balance, surface activity, the limiting viscosity number, the Haller interaction constant, the limiting equivalent conductivity and the Kohlrausch-Onsager equation "b" constant. Basing on the molar refraction and the Hildebrand parameter, the interactions between the plastisol constituents and the constituents of water dispersions of the PVC plastisol were established. The sedimentation tests on the PVC plastisol water dispersions stabilized by various surface-active agents with an organic diluent or solvent added indicated that the addition resulted in the dispergation yield, a reduction in the PVC plastisol molecular size in water dispersion and the increased Huggins interaction constant, showing both surface lyophilisation and higher adsorption of surface-active agents.
Keywords: water dispersions of polymers; surface-active agents (SAA); PVC plastisol
Preparation of the TiO2 photocatalyst using pressurized ammonia
by Beata Wawrzyniak; Magdalena Janus; Barbara Grzmil; Antoni W. Morawski; (pp. 51-56).
The industrial hydrated amorphous titanium dioxide (TiO2ċ xH2O) was modified by treatment inside a chemical reactor under elevated pressure at low temperatures for 4 hours in an ammonia atmosphere. On the basis of the FTIR/DRS analysis the presence of nitrogen was confirmed. The XRD patterns of all of the catalysts exhibit mainly the diffraction lines of anatase phases. The photocatalytic activity of the modified photocatalysts was determined and compared to TiO2-P25 (Degussa, Germany). The high rate of phenol and dye degradation was obtained for the catalysts modified at 180°/15atm. TiO2-P25 showed similar activity in phenol decomposition like TiO2-15bar, whereas it was more active in dye decomposition.
Keywords: photocatalysis; TiO2-nitrogen; dye decolorization; TiO2 preparation under pressure