Development Of Catalyst For Isopropanolamine Synthesis And Fluidization Process

The synthesis of isopropanolamine from propylene oxide and liquid ammonia can be divided into ammonia method and liquid ammonia method.The ammonia method has high energy consumption and poor selectivity of monoisopropanolamine.The liquid ammonia method is catalyzed by solid acid in heterogeneous phase without water,which can save energy consumption,reduce reaction pressure and equipment investment.In the liquid ammonia synthesis process,the performance of catalyst is the key factor affecting the development of liquid ammonia process.In this paper,the preparation of isopropanolamine synthesis catalyst,the modification of catalyst,the factors affecting catalyst performance,the reasons for catalyst deactivation and the conditions for catalyst deactivation and regeneration were studied.The catalysts were characterized by XRD,IR,TG/DTA,BET and NH₃-TPD,and their activities were evaluated under the conditions of reaction temperature160℃,reaction pressure 0.4 Mpa and WHSV 0.1 kg/kg h^-1.1.Based on the application of solid acid catalysts in the ring-opening reaction of epoxides,the catalytic properties ofγ-Al₂O₃,（NH₄）₂SO₄/Al₂O₃,strong acidic cation exchange resin,TS-1 and HZSM-5 catalysts for the synthesis of isopropanolamine from propylene oxide and ammonia were investigated.Firstly,the parallel experiments were carried out in a high-pressure reactor at 60℃,and then the activity evaluation was carried out in a fixed-bed reactor at the same condition.The catalysts were characterized by XRF,NH₃-TPD and thermogravimetry to determine the causes of catalyst deactivation,regeneration conditions and factors affecting the catalytic performance.The results showed thatγ-Al₂O₃,strongly acidic ion exchange resin and TS-1 were not suitable for the reaction,（NH₄）₂SO₄/Al₂O₃ had good catalytic performance at the beginning,and the loss of NH₄⁺in the process of deactivation and regeneration was the reason for the decline of catalytic performance;The HZSM-5 catalyst with Si/Al ratio of 38 was suitable for this reaction,and the PO conversion was as high as 88.07%,and the selectivity of monoisopropanolamine was42.29%.The results showed that the acid site distribution of the catalyst might be the main factor affecting the catalytic performance,and washing with water before calcination was an environmentally friendly,economical and effective method for catalyst regeneration.2.Using HZSM-5 with Si/Al ratio of 38 as the precursor and diammonium phosphate as the modifier,different amounts of PZSM-5 catalysts were prepared by incipient wetness impregnation and used for synthesis of isopropanolamine from propylene oxide.The effect of impregnation amount on the structure and performance of the catalyst and the reason for the decrease of the regeneration performance of the catalyst after deactivation were systematically investigated.The results showed that phosphorus modification did not change the crystal structure of the catalyst.The specific surface area and the number of strong acid sites decreased with the increase of P content.When the P content reached 15%,the strong acid sites disappeared completely,but there were still moderate acid sites;Under the same conditions,the conversion of PO was 79.19%,the selectivity of monoisopropanolamine was66.7%,and the concentration of aminopropanol decreased by 2.31%compared with that before modification,and the selectivity of monoisopropanolamine decreased to 59.61%after deactivation and regeneration.The results showed that the increase of MIPA selectivity was mainly due to the decrease of the amount of strong acid on the surface of the catalyst,and the decrease of the performance after deactivation and regeneration was mainly due to the loss of phosphate during water washing and the re-exposure of some strong acid on the surface;3.HZSM-5 with Si/Al ratio of 38 was modified by ion exchange with KCl,KNO₃ and K₂SO₄ as potassium sources,and the strong acid and the amount of strong acid on the surface of the catalyst were adjusted.The effects of ionic modification on the crystal structure,pore volume,pore size and acid site distribution of the catalysts,and the effects of preparation methods and reaction temperature on the performance of the catalysts were systematically studied.The results showed that the ion modification had little effect on the crystal structure,pore volume and pore size of the catalyst,but the specific surface area decreased,and the amount of medium-strong acid and strong acid decreased significantly.Under the conditions of 80℃,0.5 mol/L salt solution and 8 h of exchange,the medium and strong acid in the catalyst can be completely eliminated,and it is of little significance to continue to increase the salt concentration.Under the same conditions,the conversion of PO was 90.3%,the selectivity of monoisopropanolamine was 71.98%,and the conversion of monoisopropanolamine was still above 88%after 120 h continuous operation.The results show that the presence of weak acid in KZSM-5 is the main reason for its better performance than that of PZSM-5,and K⁺will not be lost in the regeneration process,so that the performance of KZSM-5 after deactivation and regeneration does not change much.4.In order to obtain higher selectivity of monoisopropanolamine,higher conversion of propylene oxide and solve the problems of catalyst deactivation and replacement,the process of fluidized catalytic synthesis of isopropanolamine was explored.KZSM-5microspheres were used as catalyst for fluidization process development,which had smaller particle size,faster carrier gas flow rate and mass transfer rate.Through the combination of theoretical calculation and cold model test,the filling amount of catalyst was determined to be 400 g,the carrier gas flow rate was 0.064 m/s,and the catalyst supplement amount was16.35 g/h.Under the optimal reaction conditions of 160℃and WHSV of 0.01 kg/kg h^-1,the conversion of PO and the selectivity of MIPA were 98.23%and 81.93%,respectively,which were improved compared with the fixed-bed process.A kinetic model was established based on the experimental data,and the pre-exponential factors and activation energies of different reactions were calculated.The error between the experimental values and the fitted values of each component concentration was within±15%,which indicated that the model could be used to describe the fluidized catalytic synthesis of isopropanolamine.