微孔-介孔分子筛课件

微孔介孔分子筛Microporous crystalline zeolitesZeolites are porous crystalline solids whose pores are of molecular dimensions thereby providing size and shape selectivity for guest molecules.they are widely used catalysts,ion-exchangers and adsorbentsAdvantages:high internal surface uniform pore size crystalline frameworks high stability and activityDisadvantages:small size of thechannels cavitiesSEMStructure and Synthesis Microporous,crystalline molecular sieves are formed by TO4 tetrahedra(T:Si,Al,Ge,Ga,Zn,etc.)that are organized in a manner such that micropores(sizes below 2 nm)of uniform dimensions are produced.Hydrothermal synthesis is usually adopted as the most effective method a typical crystallizationprocedure:water,a source of the T atoms,a mineralizing agent(OH-and/or F-),a structure-directing agent(SDA).aging in the temperature range of 363523 K vapor phase transport(VPT)exposure of dry amorphous aluminosilicate gelsin a vapor phase of ethylenediamine(EDA),triethylamine(Et3N)and water at elevated temperatures and pressures.Mesoporous materials Since the discovery of ordered mesoporous silicate materials,they have attracted considerable attention for their potentially wide applications in catalysis,adsorption,and ion exchange,etc.advantages :well-ordered channel high surface area larger pore size and volume disadvantages:amorphous framework weak activity poor hydrothermal stabilityGeneral structuresSynthesis routes Obviously,combine the advantages both of zeolites and mesoporous molecular sieves displa-ys extensive applications in many fields.And Much effort has therefore been undertaken to synthesize new type of materials.Designed synthesis of crystalline zeolites with mesopores is still a major challenge in the field of advanced materials.Micropores+mesoporesMesopores+macroporesMicropores+mesopores+macroporesPrepare mesoporous zeoliteszeolites:smaller zeolite particles，inserting larger pores into particles.mesoporous materials:assembly of pre-formed seed，transform amorphous to crystallized framework or wall Synthesis routes:Two stepsABCA:solid-state transformation Desilication treatment B:assembly of zeolite seeds Deposition or impregnation of zeolite precursorsTemplated with mesoporous carbon or organic aerogelTemplated with carbon particles or nanofibersSynthesis with mixed precursors Zeolites particles+TEOS,TEOS/0.5TEA/0.1TEAOH/11H2O synthesis follow in TUD procedure and hydrothermal treatment 4 h at 170 oC C:solid rearrangement processTransport:TPAOH was impregnated to mesoporous materialsAfter evaporation the water,then VPT at 170 OC for 24hJ.AM.CHEM.SOC.2006,128,10636-10637One step:direct synthesis with mixed templatesShangbin Liu,direct synthesis of highly stable MMS-H containing zeolite building unitesWith the mixture of CTAB and Brij30.Feng-Shou Xiao:synthesis with cationic polymer polydiallyldimethylammoniumchlorideYongde Xia and Robert Mokaya,the key point:The molecularly ordered aluminosilica-surfactant mesophases,hydrothermal crystallization of cetyltri-methylammonium hydroxide/Al,Si/H2O systems at 135 C for 12 days.Template Removal via H2O2-Mediated OxidationSynthesis mesoporous zeolites using the amphiphilic organosilanes as a mesopore-directing agent.Nature materials ADVANCE ONLINE PUBLICATIONEmbed certain polymers into zeolites crystals during synthesisAngew.Chem.Int.Ed.2006,45,1 4Future ScopeEnhance the crystallinity and mesoporous ordering,simplify the synthesis process.Template with aerogel displays great potential Direct synthesis will provoke extensive interest.