| 1,3-propanediol(1,3-PDO) is an important monomer in the synthetic new polyester material (1,3-propanediol terephthalate (PTT)). PTT shows a well application prospect in many aspects, such as synthetic fibre, thermoplastic material and thin film, which has high economic value. The combined process of hydration of acrolein (ACR) to3-hydroxypropionaldehyde (3-HPA) and hydrogenation of3-HPA to1,3-propanediol was studied in this paper, which effectively solved the technical route problem from acrolein to1,3-propanediol. The catalyst composition and process parameters of hydration and hydrogenation process were studied. The research results have significance on guiding the design of industrial equipment and amplification, which improve the competition of1,3-propanediol in China.The research of acrolein hydration to3-HPA was carried out in this paper. Through quantitative calculation of hydration reaction network, the advantages of moderate PH resin catalyst were analyzed by thermodynamics and transition state theory. D-751catalyst was selected as the optimal catalyst of hydration reaction by filtrate experiments. The advantage of D-751catalyst was proved from the perspective of acid strength and catalyst space structure. The reaction behavior under different process conditions was studied of D-751catalyst, the optimized process conditions was:feed concentration of acrolein12±3%, reaction temperature50±2℃, space velocity1.0-1.5h-1, atmospheric pressure. Under the optimize condition, the stability experiment was carried out. Three kinds of method such as adding inhibitor, lower acrolein mass fraction in the raw material and lower reaction temperature were put forward to improve the stability of the catalyst. Under the modified process conditions, the average conversion of hydration for acrolein was higher than53.5%, the selectivity of3-HPA was above90%, and the stability was above2000h, which reached foreign technology level, shown a good prospect of industrial application.The intrinsic dynamics research of hydration reaction was completed, the simulation results were agreed well with experimental results, which is more believable.Then, the process of hydration product3-HPA hydrogenation to prepare1,3-propanediol was studied. Ni-Mo/HM catalyst was taken as optimization catalysts for hydrogenation reaction by early stage of the research group. By researching on its deactivation behavior, the loss of the active component Ni on catalyst surface and catalyst channel blocked by 3-HPA autopolymer were two main reasons of hydrogenation catalyst deactivation. To avoid the deactivation, the distribution of the Ni on catalyst and the behavior of3-HPA autopolymerization were investigated. The two-stage fixed-bed hydrogenation process of3-HPA was studied from the angle of reaction engineering to ensure the high conversion of3-HPA and weaken the autopolymerization behavior of3-HPA. The condition of two-stage fixed-bed hydrogenation process was optimized, the results showed:the optimized condition of the first stage was reaction temperature50-70℃, mole ratio of hydrogen/3-HPA7,hydrogen pressure5Mpa, space velocity1.8h-1, and the conversion rate of3-HPA and the selectivity of1,3-propanediol could be over70%and99%; the optimized condition of the second stage was reaction temperature110℃, hydrogen pressure5Mpa, mole ratio of hydrogen/3-HPA7, space velocity1.8h-1, and the conversion of3-HPA reached100%, the selectivity of1,3-propanediol could be over99%. The two-stage process had better effect than domestic industry on processing handling capacity, stability, activity and selectivity.Based on the research of hydration and hydrogenation process, the seperation method was established of hydration and hydrogenation product, which realized the effective combination of hydration and hydrogenation process. Simulation and optimization were conducted on aldehyde removal tower of3-HPA, vacuum distillation tower was selected to remove aldehyde from ACR hydration product. The optimized aldehyde tower process was: theoretical plate number was6, reflux ratio was1.2to1.5, the tower kettle temperature<65℃, vacuum degree is0.019-0.0185Mpa (pabs). Under optimized condition, the acrolein content is0.09%-0.15%in tower kettle, acrolein recovery can reach96.09%-96.85%. According to the calculation, the process conditions of hydrogenation product separation were determined, the order of hydrogenation product separation was dealcohol tower, dehydration tower, light-component separation tower and weight-component separation tower. Finally, the whole bench-scale technological process was established.Based on the test of bench-scale experiment, the amplification scheme of hydration and hydrogenation reactor was determined on pilot tests. The results of pilot tests show, the single-way conversion of ACR hydration was50%-60%, the selectivity of3-HPA was above90%; the conversion of3-HPA hydrogenation was100%, the selectivity of3-HPA was above99%.The pilot plant run1200h stably, the purity of1,3-propanediol product was above99.5%, the chroma was less than10#, the aldehyde content is less than30ppm. The product had better effect than Shell company, which satisfied the imported product requirement. Finally, according to the results of pilot amplification, preliminary design of the hundred-ton industrial unit was carried out. Adiabatic bed reactor was selected as the industrial hydration reactor, the isothermal bed reactor was selected as the industrial hydrogenation reactor.. The main equipment selection scheme was proposed, and the economic benefit was estimated. This research provided technical support for industrial amplification... |
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