Use Of Fine-grained Catalytically Active
Use of Fine-grained Catalytically Active
Particles for Chlororganic Waste Neutralization
R. Perestoronina
State Design and Research Institute of Chemical Engineering “Khimtekhnologiya”, Vilesov st. 1, 93400 Severodonetsk,
Lugansk region, Ukraine, Fax: (06452) 25367, e-mail: nio12@ixt.lg.ua
Production and usage of a number of valuable chlororganic products without due account for ecological consequences has lead to appreciable pollution of environment. A burial, biochemical treatment and combustion do not always solve chlororganic wastes neutralization problems. Therefore there is an actual problem of development of more effective methods and technologies for these waste neutralization.
At present complete catalytic oxidation is considered as promising direction from standpoint of economics and ecology. An important issue is creation of catalysts having optimal structure. This catalysts structure must guarantee stable activity and selectivity. Catalysts heat resistance and strength to attrition are important catalysts characteristics too. The porous structure of catalysts is limitation for a number of reactions at stage of reactants diffusion to a catalytic surface. Besides, use of catalysts on carriers for complete oxidation of waste containing tarry components inevitably results in pores blockage by coke, resins, salts.
The mentioned aspects limit classic catalysts use for neutralization of waste, which as a rule represents a composition of a broad spectrum of compounds of different classes. Besides, presence of heteroatoms (sulphur, nitrogen, chlorine etc.) in waste components during complete oxidation reduces a service life of catalyst due to its poisoning.
The institute “KHIMTEKHNOLOGIYA” offers a new kind of catalysis – “aerosol catalysis”. It is based on applying catalytically active compounds in a fine-grained state without any carrier. Researches have shown that size of catalysts particles in reaction zone is at the level of micro- and nanometers (on the average 100 nm). Catalytically active particles continuously pass through fluidized bed of
inert material. Glass or quartz beads, silica gel, sand can be used as inert material. Combination of fluidized bed of inert particles and moving particles of catalyst dust in the reaction zone has the following positive properties – absence of temperature and concentration gradients, providing mass- and heat transfer processes and high effectiveness and chemical process rate.
The experimental researches of complete oxidation process for example of chlorine containing wastes in an aerosol of catalyst have shown that this technology provides complete conversion of components to carbon dioxide, water and hydrogen chloride. Oxides of transition metals and mixtures thereof were used as catalysts. From a number of investigated catalysts it is possible to recommend the catalyst on the basis of iron oxide as available, low-toxic and possessing reasonable activity for operation.
For elimination of hydrogen chloride from off-gases an alkaline agent (calcined soda, chalk, lime etc.) is entered directly in the catalysis zone. Thus neutral salts - chlorides are generated.
Thus aerosol catalysis technology allows for effective neutralizing multicomponent wastes including water, resins, salts, and organic compounds of various classes with simultaneous fixation of acid gases.
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