Structured-Catalysts-and-Reactors：结构化催化剂与反应器课件

,*,Click to edit Master title style,Click to edit Master text styles,Second level,Third level,Fourth level,Fifth level,Click to edit Master title style,Click to edit Master text styles,Second level,Third level,Fourth level,Fifth level,*,Structured Catalysts and Reactors,K.Rajalakshmi,CH09M003,Structured Catalysts and React,1,An inherent feature of conventional packed-bed reactors is their,random and structural maldistributions.,Random maldistributions result in:,(1)Non uniform access of reactants to,the catalytic surface,worsening,the overall process performance,(2)Unexpected hot spots and thermal,runaways of exothermic reactions.,(3)Fouling and attrition,Structured-Catalysts-and-Reactors：结构化催化剂与反应器课件,2,Effect of liquid channeling on column efficiency for a system with a relative volatility of 1.07.Total number of theoretical plates,N,of 10,20,40,and 100 at top liquid composition,X,of 90 and 60 mole percent.,Manning and Cannon,Ind.Eng.Chem.,49,347(1957),Effect of liquid channeling on,3,Structured catalysts(reactors)are promising as far as the elimination of,these drawbacks of fixed beds is concerned.,Structured Catalysts and Reactors(2nd edition)2019 Andrzej Cybulski and Jacob A.Moulijn,Structured catalysts(reactors,4,Monoliths,Monoliths are structures that contain various types of interconnected or,separated channels in a single block of material,.,Monolithic reactors are those filled with monoliths that are either made,of porous catalytic material or the catalytic material is deposited,(washcoated)in the channels of an inert monolithic support.,In both arrangements,the channel walls function as catalyst and the,channels provide space for flow of gas and/or liquid.,Ceramics:Cordierite,alumina,titania,silica,Metal,MonolithsMonoliths are structu,5,Advantages,No filtering of catalyst necessary,No attrition of catalyst,Low pressure drop,High geometric surface area,Efficient mass-transfer,In the case of internal diffusion limitations:,more efficient use of catalyst due,to thin catalytic layer,Easy scale up,Disadvantages,Relatively high manufacturing cost,Little practical experience in multi-phase applications,Advantages,6,History,Automotive Catalytic Converters,pellet filled catalytic converter,monolith catalytic converter,Monolith Key Features:,no attrition,high surface area,low pressure drop,rapid light-off,HistoryAutomotive Catalytic Co,7,Hydrodynamics and mass transfer,For co-current gasliquid flow,several flow,regimes can occur.The preferred one usually,is the so-called Taylor or slug flow.This type,consists of gas bubbles and liquid slugs flowing,consecutively through the small monolith,channels.The gas bubble fills up the whole,space of the channel and only a thin liquid,film separates the gas from the catalyst.,Hydrodynamics and mass transfe,8,The rate of mass transfer in taylor flow is large due to the following,reasons.,First the liquid layer between bubble and catalyst coating is thin,increasing mass transfer.,Secondly,the liquid slugs show an internal recirculation during their,travel through a channel.Because of this,radial transfer of,mass is increased.,The gas bubbles push the liquid slugs forward as a piston and a type of,plug flow is created.,Taylor flow can be induced in single-phase liquid phase reactions over,monoliths by adding an inert gas component,.,The rate of mass transfer in,9,Gas-liquid-solid system,Gas-liquid-solid system,10,Selectivity ImprovementBenzaldehyde hydrogenation,Batch,slurry,monoliths or extrudates,slurry 50 m,monolith 4 cm,extrudates 1.7x 5 mm,Pilot,monoliths 1 cm -variation cell density,trickle bed 4.7 cm,extrudates 1.7x 5 mm,Selectivity ImprovementBenzal,11,T.A.Nijhuis et al.Chemical Engineering Science 56(2019)823-829,T.A.Nijhuis et al.Chemical,12,Benzaldehyde hydrogenation-selectivities,at 50%conversion,T.A.Nijhuis et al.Chemical Engineering Science 56(2019)823-829,Benzaldehyde hydrogenation-,13,Catalytic hydrogenation of anthraquinone,SiO,2,-used as the monolith support material,Palladium-active catalyst component.,Structured-Catalysts-and-Reactors：结构化催化剂与反应器课件,14,Comparison of monolithic,slurry and packed-bed reactors,R.Edvinsson Albers et al.Catalysis Today 69(2019)247252,Comparison of monolithic,slur,15,Membrane reactors,Catalyst-membrane systems are promising structured catalysts.,The combination of reaction and membrane separation can result in,increase in the reaction yield beyond what the reaction equilibrium,allows and/or modifying the process selectivity.,Membrane reactorsCatalyst-memb,16,Classification of membrane reactor configurations according to membrane function and location,Structured Catalysts and Reactors”(2nd edition)2019 Andrzej Cybulski and Jacob A.Moulijn,Classification of membrane rea,17,Based on material consideration,Membrane Reactors,Inorganic membrane reactors,Organic membrane reactors,Dense(metal),membrane,Porous,membrane,Based on material consideratio,18,Potential applications of Inorganic membrane reactors,Conversion enhancement of equ