Study On Catalytic Dechlorination Of 1,2 - Dichloropropane

In the thesis, the FeCl₃-AlCl₃-TiCl₄/AC catalyst was prepared, which was applied to the reaction of 1,2-dichloropropane to propylene in catalytic dechlorination. The effects of different reaction conditions on catalyst activity were investigated in fixed bed reactor. The catalyst was characterized by XRD, BET, SEM and some other methods. It was also investigated that 1,2-dichloropropane occurred elimination reaction with NaOH solution or NaOH alcohol solution to prepare 1-allyl chloride, and the effects of different reaction conditions on eliminate reaction in autoclave reactors were investigated.1.1,2-dichloropropane catalytic dechlorinationThe FeCl₃-AlCl₃-TiCl₄/AC catalyst was prepared by impregnation supporting method with FeCl₃, AICl₃ and TiCl₄ as the active component and activated carbon as the carrier. The catalyst was characterized by XRD, SEM, BET and other means. The XRD and SEM results showed that after the metal chlorides were loaded to the surface of activated carbon, graphite characteristic diffraction peaks were still evident. It indicated that the metal chlorides were loaded to the surface of activated carbon equably and they did not damage to the graphite structures of activated carbon. The BET results showed that the specific surface area was 1081.4 m2/g, pore volume was 0.23 cm3/g, and there existed mesopores and the major part of micropores. It can be seen from the NH3-TPD spectra that there are many weak acid sites and a small amount of acid sites in the catalyst.The effect of FeCl₃-AlCl₃-TiCl₄/AC catalyst on 1,2-dichloropropane dechlorination was investigated. The results showed that when the temperature was 250℃to 300℃, FeCl₃-AlCl₃-TiCl₄/AC catalyst mainly catalyzed 1,2-dichloropropane dehydrochlorination generate 1-allyl chloride. When the temperature was higher than 350 ℃, catalyst mainly catalyzed 1,2-dichloropropane off chlorine to propylene. The change trend of the both is in contrast. And the total selectivity is about 91%. At low space velocity, FeCl₃-AlCl₃-TiCl₄/AC catalyst was mainly applied to 1,2-dichloropropane off chlorine to propylene. As airspeed increasing, the selectivity of propylene decreased. When the reaction temperature was 460℃and the quality of the space velocity was 0.6h"’, the catalytic activity of FeCl₃-AlCl₃-TiCl₄/AC catalyst for 1,2-dichloropropane was the highest, the conversion of 1,2-dichloropropane was more than 99% and the selectivity of propylene was 87.9%.2.1,2-dichloropropane elimination reaction of chlorinated hydrocarbonsThe influences of different solvents, reaction temperature, mole ratio and other factors on the elimination reaction with alkaline eliminating 1,2-dichloropropane to 1-allyl chloride as a probe were investigated, using an autoclave reactor.a.1,2-dichloropropane, as a raw material, occurred elimination reaction with aqueous NaOH under the surfactant. The optimal reaction conditions for the reaction were that the temperature was 150℃, the molar ratio of NaOH and 1,2-dichloropropane was 1.1:1, the molar concentration of NaOH was 12mol/L, using cetyl trimethyl ammonium bromide as the surfactant in an amount of 0.5wt%1,2-dichloropropane and the reaction time was 2h. The conversion of 1,2-dichloro-propane reached 94.7%, and the selectivity of 1-allylchloride was 69%.b.1,2-dichloropropane, as a raw material, occurred elimination reaction with alcoholic solution of NaOH. The optimal reaction conditions for the reaction were that the temperature was 80 ℃, the molar ratio of NaOH and 1,2-dichloro-propane was 1.1:1, the mass ratio of ethanol and 1,2-dichloropropane was 1.85:1 and the reaction time was 1h. The conversion of 1,2-dichloropropane reached 97.5%, and the selectivity of 1-allyl chloride was 57.7%.c.1,2-dichloropropane, as a raw material, occurred elimination reaction with NaOH methanol solution. The optimal reaction conditions for the reaction were that the temperature was 90 ℃, the molar ratio of NaOH and 1,2-dichloro-propane was 1.4:1, the mass ratio of anhydrous methanol and 1,2-dichloropropane was 1.34:1 and the reaction time was 0.5h. The conversion of 1,2-dichloro-propane reached 96.2%, and the selectivity of 1-allyl chloride was 63.2%.The results showed that the elimination reaction favored the stronger alkaline and/or the the greater concentration of the offensive reagents, the higher the reaction temperature and the smaller polar solvents. Compared with using alcohol as the solvent, using water as the solvent needed low cost. In which case, the selectivity of 1-allyl chloride was relatively the highest. The disadvantages of using water as the solvent were that it needed high reaction energy and the surfactant. Also, a large amount of chlorinated organic wastewater was produced which would cause environmental pollution. Compared with using water as a solvent, the products can be reused after separated when using alcohol as a solvent. Compared with using alcohol as the solvent, the selectivity of 1-allyl chloride was higher when using methanol as the solvent. And the price of methanol was lower than ethanol’s. In summary,1,2-dichloropropane reacted with NaOH methanol solution had the best results.