| Epichlorohydrin (ECH) is a very important fine chemical production with a high value and mostly used as synthetic intermediates. Its products have been widely applied to many fields such as automobile manufacturing, aerospace, electronics and construction. The industrialization of its production processes originates early. At present, epichlorohydrin is mainly produced by three methods including chloropropylene process, propenyl acetate process and glycerol hydrochlorination process. However, the first two of them are high cost of investment, environmental unfriendly, high energy consuming and heavily dependent on petroleum resource. The development of glycerol hydrochlorination process based on biodiesel industry is widely favored. With petroleum resource being increasingly scarce and global environmental issues becoming more prominent, the production technology of epichlorohydrin need to be improved. So, many research scholars and experts have done a lot of researches and have made some progress. These researches are probably divided into two directions. One is looking for other renewable energy to replace petroleum resource and another is to optimize the traditional process to reduce environmental pollution.According to the background above, the process of saponification to generate epichlorohydrin was studied. Traditional saponification process of dichloropropanol is determined using the liquid-liquid homogeneous catalysis in general, thus producing great amount of waste and alkaline waste water those are difficult to handle. The application of solid base catalysts solves that problem as it promotes dehydrochlorination of dichloropropanol to generate epichlorohydrin in the gas phase. This way using the solid-liquid heterogeneous catalysis has many advantages such as easy separation of the product, mild operating conditions, no corrosion of the reactor and no waste water pollusion. It is an environment-friendly production route.Thermodynamic studies have been done to search the optimal condition and reaction temperature theoretically about the l,3-dichloro-2-propanol dehydrochlorination by means of the group contribution method and quantum chemistry. Besides, the solid base supported on NaZSM-5 zeolite, Al2O3 and ZrO2 is prepared by impregnation with suitable oxides. Among the most appropriate substances which create or improve basicity upon introducing into the solid base are alkali earth metal compounds. The physicochemical properties of a solid base catalyst are examined by X-ray diffraction (XRD). Then a fixed-bed continuous reactor is used to carry out the catalytic experiments so as to determine the optimal reaction conditions. After the effect of flow rates of carrier gas on reaction is discussed, the optimal flow rate of carrier gas is determined to be 164.39 mL/min. The following experiments are carried out under the optimal flow rate. By contrast, a solid base catalyst with the best catalytic effect is selected. The main conclusions were as follows.(1) Thermodynamic study by means of the group contribution shows that the reaction of dehydrochlorination of 1,3-dichloro-2-propanol is endothermic. When the temperature is higher than 970 K, the reaction can proceed spontaneously. In addition, the equilibrium conversion is 71% at 970 K.(2) The thermodynamic calculation based on density functional theory (DFT) in quantum chemistry shows:when the temperature is higher than 575 K, the reaction can proceed spontaneously. So, it is consistent with the experimental temperature. The higher the temperature is, the better the equilibrium conversion is.(3) XRD of solid base catalysts shows that catalysts prepared by modified do not destroy the original crystal structure of the precursor. The main part of the alkaline earth metal oxide in the solid base catalyst exists in the form of highly dispersed crystal phase. With the amount of alkaline earth metal oxides increasing, the intensities of the peak characteristic for the zeolite precursor weaken gradually. When the amount reaches a critical content, there will be a free state in the form affecting the stability of the solid base catalyst.(4) The catalytic properties are discussed when the solid base is supported on NaZSM-5 zeolite. If the Si/Al ratio of zeolite is identical, the solid base catalyst carrying CaO exhibits better on conversion than that carrying MgO. In terms of selectivity, it is contrary. Compared the effect of different Si/Al ratio on catalytic properties, the solid base prepared from zeolite (Si/Al=50) exhibits better than others. However, its optimum load decreasing and the low temperature of reaction are preferred. Considered from conversion and selectivity only, when the load of MgO on zeolite (Si/Al=80) is 10% and the reaction temperature is 360℃, it exhibits an excellent catalytic activity with the conversion and selectivity are 100% and 96.0%, respectively.(5) The catalytic properties are discussed when the solid base is supported on Al2O3 and ZrO2. If the load is identical, the solid base catalyst supported on Al2O3 exhibits better on conversion than that supported on ZrO2. In terms of selectivity, it is contrary. Particularly, when the load of MgO on ZrO2 is 5% and the reaction temperature is 330℃, it exhibits an excellent catalytic activity with the conversion and selectivity are 98.6% and 97.8%, respectively. Further more, the low temperature of reaction is preferred, because it can save energy and prevent carbon from concentrating. |
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