| Ethyl orthosilicate is a widely used as a sort of industrial materials. Currently, thedomestic ethyl orthosilicate production is produced in gap method, with large pollution,high consumption. With the development of request in the field of environmentprotection, it is imperative to develop a new technology of cleaner production forpreparing ethyl orthosilicate by silicon tetrachloride with large output, good quality, highyield, low pollution.This paper firstly discusses the semi-continuous process for preparing ethylorthosilicate by silicon tetrachloride,with HCl carried out of the system by boilingsolvent. The influences of solvent, feed methods, flow rate of nitrogen, ratio of rawmaterials, feed rate and reaction time on the yield of ethyl orthosilicate are experimented.The optimum reaction conditions synthesis of ethyl silicate intermittent were given:n-hexane as solvent, ethanol droped into silicon tetrachloride, flow rate of N270mL/min，feed ratio (silicon tetrachloride/ethanol, mole ratio)1:4.6,reaction temperature50℃and feed rate of ethanol70ml/h. The yield of ethyl orthosilicate was75%underoptimum reaction conditions.The synthesis of ethyl orthosilicate by semi-continuous reaction distillation methodwas investigated on the basis of the semi-continuous method. The experimental resultsshow that the this process is evidently better than semi-continuous method. Thereaction was obviously improved by distillation, reducing nitrogen disturbance in thesystem. The by-product HCl gas is removed from the reaction zone in time, so thechemical equilibrium is broken. The conversion of raw materials is increased and the sideeffects less occur.Based on the results of semi-continuous reaction distillation method, synthesis ofethyl orthosilicate was researched by home-made equipment in the lab. The influences offactors on the yield of product were investigated and the factors were optimized. Singlefactor design study the effect of feed location，feed temperature, feed ratio，feed rate andreflux ratio on the yield of product. The orthogonal was designed to focuse on influences of factors of feed ratio (A), reflux ratio (B) and feed rate (C) on the yield of product. It isconcluded that the influence degree of the three factors on the reaction is A> C> B. Theoptimal combination of the reaction distillation conditions is as follows: ethanol andsilicon tetrachloride at the room temperature, n-hexane at bubble-point temperature, feedratio4.20:1by molar, the ethanol feed rate about90ml/h and the reaction reflux ratio1.7.Under the condition of the optimal conditions, ethyl orthosilicate yield was93.86%.The process simulation software of Aspen plus has been used to simulate thecontinuous reaction-rectification process. The NRTL thermodynamic model was appliedto simulate the tower kettle temperature and the vapor and liquid phase. The theory platenumber for the esterification reaction process and theory of reflux ratio was gotten. Thesimulation results are as follows: the operation conditions is atmospheric pressure, theoptimum reflux ratio1.5, theoretical plate count20,feed mole ratio was4.15:1(ethanol:silicon tetrachloride), the suitable feed location for ethanol at the eighth, silicontetrachloride at thirteen, n-hexane at fourteen. Aspen Plus simulation results show it isfeasible to synthetize ethyl silicate by continuous reaction rectification, and thesimulation research can provide a theoretical basis for reaction rectification processoptimization in the actual production process. It can be applied to subsequent pilot scaledesign of the tower. |
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