Study On Synthesis And Catalytic Performance Of Highly Stable Mesoporous Molecular Sieves

Biofuel is one of the most important renewable biomass liquid fuel.It has many advantages,such as easily obtained raw materials,simple production process,high calorific value,storage and transportation safety,renewable and environment friendly and so on,which is the ideal substitute for traditional petroleum diesel.The production of ester by esterification of fatty acid with alcohol and the hydrocarbon by high temperature pyrolysis of bio oil or waste oil are the two important ways to prepare biofuel.There are many disadvantages in traditional catalysts,such as corrosion equipment,environmental pollution,by-products,and so on.The microporous molecular sieves which are used as catalysts are restricted to relatively small molecules.The cracking oils are concentrated less than 10 carbon atom number.At the same time,the yield of liquid products is low along with coking,short life and poor regeneration performance of the catalyst.In this paper,β/Al-MCM-41 was prepared by using β as a guide.And Zr,Sn,Ti were introduced into β/Al-MCM-41 to prepare β/Zr-MCM-41,β/Sn-MCM-41,and β/Ti-MCM-41 during hydrothermal synthesis.The structure and acidity of the molecular sieves were characterized by XRD,IR,TEM,N2 adsorption desorption,NH3-TPD,py-FTIR.The results showed that the hydrothermal stability,acidity,acid amounts and activity of the catalyst were improved after the introduction of β.The ester rate could reach 74.8% while using β/Al-MCM-41 as catalyst in the esterification of oleic acid with methanol.The catalyst coud be reused,but the activity decreased after the seventh used.Ce3+(Sm3+ or La3+)~β/Al-MCM-41 molecular sieves synthesized by impregnation had improved hydrothermal stability,catalytic stability,catalytic activity and service life.The ester rate could reach 91.4%,87.8%,79.2%,respectively,while using Ce3+(Sm3+ or La3+)~β/Al-MCM-41 as catalyst in the esterification.The catalysts showed high activity after the seventh used.New high stable acidic mesoporous molecular sieves MMS-11,MMP-12,MNS-16,MNP-10,and MNC-13 were synthesized successfully using different ionic liquid as a template.MNC-13 showed high activity in the esterification of oleic acid with methanol,with ester rate of 94.1%.The three kinds of acidic mesoporous molecular sieves β/Al-MCM-41,Ce3+~β/Al-MCM-41 and MNC-13 were compared in terms of catalytic activity,hydrothermal stability and catalytic stability.The activity of molecular sieve was in communication with pore size,acidity and amounts of acid.The larger the pore size,the higher the amounts of acid,the stronger the acidity,the stronger the activity.The doping of rare earth elements and the ionic liquid environment could effectively increase the pore size of the molecular sieves,improve the acidity,increase the catalytic activity,and improve the hydrothermal stability and catalytic stability.Take the esterification of oleic acid with methanol as a model reaction,the synthesis conditions were optimized and the kinetics was studied.The average order was 1.97,1.92,1.95,respectively;and the average activation energy was 50.01kJ/mol,51.46kJ/mol,54.55kJ/mol,respectively when using β/Al-MCM-41,Ce3+~β/Al-MCM-41 and MNC-13 as catalyst.The esterification catalyzed by mesoporous molecular sieves was second order reaction.The synthesized molecular sieves were used to catalyze the esterification of oleic acid with other short chain alcohols such as ethanol,isopropanol and isobutanol.The catalysts showed high activity,indicating the synthesized molecular sieves had the versatility for the esterification of oleic acid.Various new acidic molecular sieves such as Zr-MNC-13,Ti-MNC-13,Sn-MNC-13 and basic molecular sieves such as K-MNC-13,Ca-MNC-13,Ba-MNC-13,Mg-MNC-13 were prepared by introducing metal elements.K2O/MNC-13,BaO/MNC-13,CaO/MNC-13,MgO/MNC-13 were synthesized by impregnation.The synthesized molecular sieves were used to catalyze the pyrolysis reaction of rubber seed oil and waste cooking oil.Compared with the catalytic activity,the best molecular sieves MNC-13 and K-MNC-13 were selected to optimize the reaction conditions.The catalysts exhibited excellent reusability.The optimum conditions for the pyrolysis of rubber seed oil(RSO)or waster cooking oil(WCO)using MNC-13 and K-MNC-13 as catalyst were m(catalyst): m(RSO/WCO)= 1:30,reaction temperature 410℃ and reaction time 100 min.Using MNC-13 as catalyst,the cracking conversion of RSO was 95.1% and yield of liquid product was 74.9%;the conversion of WCO was 96.7% and yield of liquid product was 73.5% under the above conditions.Using K-MNC-13 as catalyst,the cracking conversion of RSO was 96.3% and yield of liquid product was 76.5%;the conversion of WCO was 95.2% and yield of liquid product was 72.0%.The main components of liquid products were alkanes with around C15~C17 carbon atoms,similar to that of diesel fuel,which could be used as an alternative to traditional petrochemical diesel oil.