THE INFLUENCE OF DEPOSITION CONDITIONS ON THE ACTIVITY OF THE IRON-CHROME CATALYST

The article is devoted to optimization of technological parameters of the process of manufacturing a precipitated medium-temperature catalyst for steam conversion of carbon (II) oxide.A feature of the manufacture of an iron-chromium catalyst within the framework of this article is the use of a solution of iron and chromium salts obtained by leaching the spent catalyst with a solution of nitric acid.By draining the solution of nitrates and ammonia water, a precipitate is obtained -a mixture of iron and chromium hydroxides.To characterize the properties of the precipitate, the value of the specific resistance during filtration (SRF) was used, on which the filtration speed and the choice of filtration equipment depend.The aim of the work was determined: to study the dependence of the SRF of the precipitate, the specific surface area and the activity of the catalyst obtained from the precipitate on the precipitation parameters: the concentration of the salt solution, which is determined by the concentration of nitric acid Z 1 (from 20 to 40 %) during leaching of the spent catalyst, the concentration of ammonia water Z 2 (from 5 to 20 %) and the aging time of the precipitate Z 3 (from 3 to 90 minutes).Using the Excel LINEST function, a second-order equation was obtained, for example, to estimate the catalyst activity (rate constant):Using the Excel Solver add-in, the optimal (maximum rate constant) conditions for precipitation were found: Z 1 = 26.4%, Z 2 = 5 %, Z 3 = 3 min.A similar processing of experimental data was carried out for the specific surface area of the catalyst and the SRF of the precipitate.The calculation determined the conditions for the maximum specific surface area: Z 1 = 21.9 %, Z 2 = 5 %, Z 3 = = 3 min.and the minimum specific resistance of the precipitate: Z 1 = 20 %, Z 2 = 5 %, Z 3 = 27 min.The obtained data indicate the need to use 20-26 % nitric acid when leaching the spent catalyst, 5 % ammonia water and the minimum aging time of the precipitate after precipitation.The closeness of the values of the optimal parameters Zi for the three objective functions is confirmed by the close relationship between them: the pair correlation coefficients are in the range of 0.83-0.98.Taking into account the fact that the best dissolution of the spent catalyst occurs in 40 % acid, the resulting nitrate solution must be diluted twice before precipitation.