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조득희,이영길,박상언 한국화학공학회 1990 Korean Chemical Engineering Research(HWAHAK KONGHA Vol.28 No.3
냉동증류법을 이용하여 C_8-방향족화합물의 여러 혼합물로부터 고순도의 p-크실렌을 분리하였다. 냉동증류의 과정 중 액상혼합물이 결정화되는 성분의 어는 점 이하로 과냉각되는 현상이 관찰되었으며 원료중의 p-크실렌 함량이 적을수록 수율이 감소하는 경향들 보였다. 그러나, 원료 중의 p-크실렌의 함량에 따른 제한이 있었으며 그 이하의 함량에서도 고순도 분리가 이루어지기 위하여서는 완전한 단열조건이 필요함을 알았다. Super-pure p-xylene was obtained from the various combinations of C_8 aromatics by the distillative freezing method. The super-cooling effect was observed during distillative freezing operation. As the concentration of impurities in feed increased, the yield of product decreased. However, it was found that the concentration of p-xylene at feed composition was limited to get super-pure p-xylene. And adiabatic conditions during experiment should be considered as a great importance through distillative freezing operation.
A New Synthesis method of Hydrotalcites
조득희,장태선,이동구,( Jianfeng Yu ) 한국공업화학회 2002 한국공업화학회 연구논문 초록집 Vol.2002 No.0
Hydrotalcite is an anionic clay consist of positively charged brucite-like layers separated by charge-balancing hydrated gallery anions which can represented by the general formula [M<sub>ll1</sub>-xM<sub>lll</sub>x(OH)<sub>2</sub>]x+An-x/nㆍmH<sub>2</sub>O, where M<sub>ll</sub>=Mg, Zn, Co, Ni, Mn, Cu;M<sub>lll</sub>=Al, Cr and A= gallery anion. Titration coprecipitation at low supersaturation, at constant pH, is the method most frequently used in the preparation of Hydrotalcite, the conditions most commonly utilized are the following:pH ranging from 7 to 10, temperature 60~80°C, low concentration of reagents and low flow of the two streams. The pH value in the method is controlled with the relative titration speed of the two streams. In high supersaturation, another titration coprecipitation method, the solution containing M(ll) and M(lll) cations is added to a basic solution in three minutes at 80~90°C. In this paper the special decomposability of a compound at the temperature higher than 90° C was used to control the pH value in the synthesis of hydrotalcites. This compound and M(ll), M(lll) nitrates can form a homogeneous solution, so the pH value is uniform everywhere in the solution whileit decomposes. The hydrotalcites of Mg-Al, Zn-Al, and Ni-Al with higher crystallinity could be synthesized by a method that uses this compound. It is believable thatthese resultsare related to the pH values of precipitation of different metal cations in the solutions. XRD, IR and SEM analysis is to be discussed.