The Studies On Preparation Of Highly Active Geopolymer Supported CuNiAl Based Catalysts And Intrinsic Kinetics For Morpholine Synthesis

Morpholine(Mp)as a typical heterocyclic compound has great industrial importance and a wide range of applications.It is used as an intermediate and its derivatives have found applications as bactericides,pharmaceutical chemicals,and antioxidants for lubricating oils and so on.Currently,the main process used to synthesis morpholine on the reaction of diethylene glycol(DEG)and ammonia under hydrogen atmosphere in the presence of catalysts.Most of the catalysts are supported by alumina.The main problems are the poor dispersion of active component,low activity at high space velocity and poor thermal stability.Therefore,it is important to develop new catalysts with high activity and high thermal stability to improve production efficiency of morpholine and reduce production costs.This work is mainly concerned with the catalysts preparation and modification,catalysts characterization,and mechanism for synthesis morpholine and the study of kinetics.It belonged to the research field of surface science and chemical engineering.It has great important scientific research value and practical significance.In this paper,we proposed to use the geopolymer as carrier and control the acid-base properties of the geopolymer surface by the doping of Al.At the same time,the effects of the calcination temperature of the geopolymer,the loading method of Al and the doping amount of Al on the surface chemical properties,Pore structure and the activity of the catalyst active components were investigated.The characterization of physical,chemical properties and surface structure of geopolyme before and after Al doping were carried out by SEM,XRD,H2-TPR,NH3-TPD and N2-adsorption/desorption isotherms.The catalytic performance of the prepared catalysts was tested.Results showed that(1)the calcination temperature of the geopolymer has a great influence on the catalytic performance.After the calcination of the geopolymer at 600 ?,the CuO of the catalyst surface exhibits a smaller crystal size and the conversion of diethylene glycol is twice as high as that of the uncalcined ground geopolymer carrier.However,if the calcination temperature is too high,the geopolymer is formed into a silicon aluminum oxide crystal,resulting in a sharp decrease in the conversion of diethylene glycol.(2)The doping of Al into the surface of the geopolymer by co-precipitation not only improves the acid sites on the surface of the geopolymer,but also contributes to the efficient dispersion of the catalytically active component,effectively reducing the crystal size of CuO,Which significantly improved the activity of catalytic ammoniation to synthesis morpholine,and its morpholine yield was 92.1%.(3)The doping amount of Al affects the acidity of the surface of the carrier.With the increase of the doping amount of Al,the adsorption capacity of NH3 is increasing and the activity of the catalyst is volcanic.The conversion of diethylene glycol was 97.48%and the selectivity of morpholine was 97.39%when the activity of the polymer was 3%.Three catalysts with different preparation methods such as GPA-CP/IM,GPA-CP/SC,GPA-CP/AE were prepared.The crystal phase,valence state,specific surface area and dispersion of the surface active components of the catalyst were analyzed by SEM,XRD,H2-TPR,XPS,NH3-TPD and N2O titration.At the same time,the effects of space velocity and reaction temperature on the activity of the catalyst and the thermal stability of each catalyst were investigated.Results showed that(1)The reduction temperature affects the content of Cu+ on the GPA-CP/AE catalyst.The maximum Cu+/(Cu++Cu0)value is obtained by reducing the catalyst at 250 ?.The high Cu+ content promoted the adsorption of NH3,and the catalyst is supported on the catalyst.GPA-CP/AE has the highest specific surface area of copper(106.05 m2·g-1),the best dispersion of copper(15.68%),the strongest ammonia adsorption capacity and strong DEG adsorption capacity;(2)the different preparation methods has a great influence on the catalyst activity and thermal stability.The yield of morpholine on GPA-CP/AE catalyst was 96.41%at high space velocity of 1.4mL·g-1·h-1,which was twice as high as that of GPA-CP/IM and GPA-CP/SC catalyst.The yield of morpholine on GPA-CP/AE was 90.81%,while the yield of morpholine on GPA-CP/IM and GPA-CP/SC catalysts were 75.83%and 27.38%,respectively,when the reaction temperature reached 310?.Thermal stability tests shows the yield of morpholine on GPA-CP/AE catalyst was reduced by only 2.96%,while the yield of morpholine on GPA-CP/IM and GPA-CP/SC decreased by 13.01%and 28.44%,respectively,after reaction of 5 hours at 310 ?.(3)The catalyst life test was carried out at reaction temperature of 230 ? and space velocity of 0.8 mL·g-1·h-1.The performance of the catalyst prepared by the ammonia evaporation method showed that the yield of morpholine remained above 94%after 100 h reaction,showed good stability.The catalytic amination kinetics of diethylene glycol over the catalyst GPA-CP/AE was studied.The effects of reaction temperature and reactant concentration on the morpholine production rate was studied.According to the Arrhenius equation(k = k0exp(-Ea/RT)),the kinetics model was established,the equations obtained are as follows:r = 2.149 × 107e-(21.266/RT)CDEG1.84CBH31.10By comparing the experimental data and theoretical calculations,it is found that the kinetic equation obtained can well describe the process of GPA-CP/AE reaction.