1 PROGRESSES IN CATALYTIC MEMBRANE REACTORS Enrico Drioli, Enrica Fontananova Institute on Membrane Technology (ITM-CNR), c/o University of Calabria, Via P. Bucci, 17/C, 87030, Rende (CS), Italy Department of Chemical Engineering and Materials, University of Calabria, Via P. Bucci, Rende (CS), Italy. Tel.: ; Fax: ; Web site:
2 Catalysis: one of chemistry s most important and powerful technologies Sustainable Chemistry Strategic Research Agenda 2005 (www.suschem.org) The concept of sustainable growth calls for additional and substantial developments in catalysis
3 Main characteristics of an ideal catalyst : - low costs, - high selectivity, - high stability under reaction conditions, - non-toxicity, - green properties first of all recoverability (possibility to reuse more times the same catalyst). Most of these requirements can be heterogenization of the catalyst using materials. addressed by the appropriate support Among the different heterogenization strategies, the entrapping of catalysts in membranes, membranes or in general the use of a catalyst confined in a catalytic membrane reactor (CMR), offers new possibility for the design of new catalytic processes.
4 Catalytic membranes reactors (CMRs) are integrated systems that combine chemical conversions with a physical separation process guided by a membrane General advantages of an integrated membrane processes: synergic effects simplicity possibility of automatization advanced levels E. Drioli, M. Romano, Industrial Engineering Chemical Research, 40 (2001) E. Drioli, E. Fontananova, Chemical Engineering Research & Design 82 (A12) (2004) of
5 Membrane technologies and process intensification strategy: a road to sustainability Production Costs Remote control Design and Scale-Up Process Flexibility Energy consumption Process Intensification Waste generation Equipment size
6 a b Scanning electron microscopy (SEM) images of the cross section of a flat sheet (a) and of a hollow fiber (b) membrane prepared from a modified polyetheretherketone known as PEEK-WC
7 Common membrane processes combined with reactions Process Driving Force Mode of transport Species Passed Species Retained Microfiltration (MF) Pressure difference kpa Size esclusion convection Solvent (water) and dissolved solutes Suspended solids, fine particulars, some colloids Ultrafiltration (UF) Pressure difference kpa Size esclusion convection Solvent (water) and low molecular weight solutes (<1000 Da) Macrosolutes and colloids Size esclusion Solution diffusion Donnan exclusion Solvent (water), low molecular weight solutes, monovalent ions Molecular weight compounds >200 Da multivalent ions Diffusion partition Compounds soluble in the extraction solvent Compounds non soluble in the extraction solvent Solution diffusion Gas molecules having low molecular weight or high solubilitydiffusivity Gas molecules having high molecular weight or low solubility-diffusivity High permeable solute or solvents Less permeable solute or solvents Nanofiltration (NF) Pressure difference MPa Membrane Based Solvent Extration (MBSX) Chemical potential or concentration difference Gas Separation (GS) Pressure difference MPa Chemical potential or concentration Solution diffusion II WORKSHOP NAZIONALE AICIng -difference Messina, Settembre 2007 Pervaporation (PV)
8 Filtration spectrum of some pressure driven membrane operations
9 Membrane contactors Among separation techniques involving membranes, membrane contactors (MC) are expected to play a decisive role for the design of alternative production systems appropriate for sustainable growth. The basic idea is to use a solid, microporous, hydrophobic polymeric matrix in order to create an interface for mass transfer and/or reaction between two phases: large exchange area and independent fluiddynamic allow a perfectly and easily controlled operation. CONCENTRATE STRIPPING Accurel PP membrane
10 MEMBRANE CONTACTORS
11 Membrane contactors
12 The combination of advanced molecular separation and chemical conversion, realized in a CMR, is expected to offer viable solutions to the main drawback of the homogeneous catalysis: the catalyst recycling. In addition, the membrane can actively take part in the reactive processes by controlling the concentration profiles thanks to the possibility to have membrane with well defined properties (materials & structure) The selective transport properties of the membranes can be used to shift the equilibrium conversion, to selectively remove products and by-products from the reaction mixture, to selectively supply the reagents.
13 Sketch of some different CMRs S. Miachon,J.-A. Dalmon, Topics in Catalysis,29 (2004) Extractor: The membrane is used to Distributor: The membrane controls Contactor: remove a reaction product from the the introduction of one of the Membrane is used reaction zone. reactants in the reaction zone. to facilitate the contact between Advantages: Advantages: reactants and Increase reaction yields in equilibrium Reactants concentration is kept at a catalyst. limited reactions; low level in the entire reaction zone improving the selectivity towards a increasing selectivity of reactions Advantages: primary product in consecutive (e.g. selective oxidations) and/or Improvements in reactions via its selective extraction reducing the possible dangerous activity and through the membrane. interations (e.g. ﬂammable mixtures) selectivity
14 Role of the membrane: Inert Catalytically active Nature of the membrane: Organic Inorganic Metallic Nature of the catalyst: Organic Inorganic Biological
15 CMR set-up to evaluate the performance of the CMR: flat sheet membrane reactor; batch experiments for a fast but incomplete screening (no evaluation of the membrane selective transport) tubular membrane reactor; I.F.J. Vankelecom, Chem. Rev. 102 (2002)
16 Membrane functions in a CMR retaining and recycling of the catalyst (retention in the reactor of fine particles, enzymes and homogeneous catalysts or heterogenization of catalyst in the membrane) The heterogenization of catalysts in membrane is particularly suitable for catalyst design at the atomic and molecular level!
17 Example 1: 1 coupling of photocatalysis and membrane processes in water purification 4-nitrophenol mineralization 2 C6H5NO O2 12 CO2 + 2 HNO3 + 4 H2O Scheme of a membrane photoreactor with TiO2 immobilized in a PSF membrane (catalytically active membrane) R. Molinari et al. Journal of Membrane Science 206 (2002) Scheme of a membrane photoreactor system with TiO2 particles suspended confined by means of a UF or NF membrane (inert membrane)
18 Membrane functions in a CMR selective removal of products from the reaction mixture to prevent consecutive reactions or to circumvent the limitation by the equilibrium (dehydrogenations, esterifications, etc.); selective supply of reactants to reduce the number of process steps required (e.g. integrated oxygen separation for partial oxidation) or to influence the selectivity of the reaction (provide reactants in selective form, influence on the concentration profile). The separation function often results in enhanced selectivity and/or yield!
19 Example 2: improved selectivity in consecutive reactions by extration of a primary product (i-octene - C8) in a zeolite membrane reactor (ZMR) respect to a a conventional fixed bed reactor (FBR) Liquid-phase oligomerization of i-butene 2 C4H8 C8H16 E. Piera et al. Catalysis Today 67 (2001)
20 Example 3: increase of the reaction yield respect to a conventional reactor by selective removal of the product (H2) Isobutane (ic4) dehydrogenation in an extractor-type CMR C4H10 C4H8 + H2 A: MFI zeolite membrane A: Pd membrane L. van Dyk et al. Catal. Today 82 (2003) 167 A: MFI-zeolite membrane growth on a tubular alumina host material; B: Pd membrane electroless deposited on the same tubular support. (1) experimental data; (2) modelling; (3) thermodynamic equilibrium in a conventional reactor.
21 Example 4: dense mixed-oxide membranes used for partial oxidations of methane CH4 + ½ O2 CO + 2 H2 V.V. Kharton et al. Catalysis Letters 99 (2005) SrFe0.7Al0.3O3-d (SFA) perovskite like oxide- exhibits substantial catalytic activity towards partial oxidation of methane It has been proposed that the oxygen species diﬀusing through the membrane generate at its surface very active and selective oxygen entities that give higher yields that molecular oxygen.
22 Perovskite Perovskite-structured oxides can be used as solid electrolytes for oxygen separation. Both oxygen ions and electronic defects are transported in an internal circuit in the membrane material. Perovskite membranes are interesting systems not only for their possible applications (e.g., fuel cells, oxygen generators, oxidation catalysts) but also for the fundamental fascination of fast oxygen transport in solid state ionic. The migration ion within the perovskite lattice takes place along the edge of the BO6 octahedron into neighbouring vacancy. M. Saiful Islam, Solid State Ionics (2002) 75 85
23 SEM photographs of an asymmetric membrane of perovskite-type oxide (La0.6Sr0.4Co0.2Fe0.8O3-δ) and temperature-dependence oxygen permeation flux of the asymmetric membrane and a sintered membrane disc W. Jin et al. Journal of Membrane Science 185 (2001)
24 Use of a mixed oxygen ion electronic conductor for oxygen separation with direct reforming of methane, followed by the use of a mixed protonic electronic conductor for hydrogen extraction The products are thus pure hydrogen and synthesis gas with reduced hydrogen content, the latter suitable for example, Fisher Tropsch synthesis of methanol. T.Norby/SolidStateIonics125(1999)1 11
25 Membrane functions in a CMR In some cases, the membrane defines the reaction volume e.g. by providing a contacting zone for two immiscible phases (phase transfer catalysis) Exclusion of polluting solvents and reducing the environmental impact of the process
26 Example 5: Cyclohexane oxidation by tertiary-butyl hydroperoxide at room temperature using FePcY-Zeozymes occluded in a PDMS O OH O2 + Separating the two immiscible reactant phases the membrane: eliminates the need for a solvent Incorporation of iron phthalocyanine (FePc) actively controls the concentration complex in the supercages of zeolitey and of the reactants near the active sites subsequent incorporation of these zeolite crystals in I.F.J. Vankelecom et al.j. of Catalysis the PDMS-membrane. 163 (1996)
27 Further advantages of the CMRs: An integrated process involves lower investment costs Membrane separations often have the advantage of operating at much lower temperatures, especially when compared with thermal processes such as reactive distillation. They might thus provide a solution for the limited thermal stability of either catalyst or products. Furthermore, the membrane separation processes is not restricted to volatile components. Under specific conditions, the heat dissipated in an exothermic reaction can be used in an endothermic reaction, taking place at the opposite side of the membrane, like, e.g., in hydrogenation/dehydrogenation. The downstream processing of the products can be substantially facilitated when they are removed from the reaction mixture by means of a membrane. III.F.J. WORKSHOP Vankelecom, NAZIONALE AICIng Chem. - Messina, Rev Settembre (2002)
28 CMRs have been investigated for a broad variety of reactions, however there is still a large discrepancy between the many investigations on CMRs in academic and a few industrial applications. An industrial example is the consortium of BP/Amoco, Praxair, Statoil, SASOL, and Phillips Petroleum working on solid oxide membrane reactor based synthesis gas production. The main problem is the development of reliable and ﬁnancially competitive membranes.
29 Typical limitations in CMRs: Manufacturing cost of the membranes and modules Limited membrane life time Considerable technical complexity of the process which renders modeling and prediction more difficult
30 The understanding of properties, behavior and synthesis of materials is fundamental in order to exploit the potential use of novel highly complex composite systems, molecules and new multifunctional materials derived from them. Computational strategies, theoretical, simulation and modelling are key tools to be considered in CMRs
31 ORGANIC OR INORGANIC MEMBRANES?
32 I norganic m em branes Advantages Disadvantages Resistance to aggressive environments High capital costs High thermal stability Generally low permeability of the highly selective (dense) membranes at medium temperatures Resistance to high pressure Brittleness Difficult membrane-to-module sealing at high temperatures
33 CMRs for high temperature applications Due to the generally severe conditions of heterogeneous catalysis, most CMR applications use inorganic membranes which can be dense or porous, inert or catalytically active.
34 Palladium membranes for selectivity improvement in dehydrogenation and hydrogenation reactions: only hydrogen could permeate through the Pd membrane with a 100% selectivity The mechanism involves a series of steps: 1) adsorption 2) dissociation 3) ionization 4) diffusion 5) reassociation 6) desorption Pd-Rh alloy layer Support V.M. Gryaznov, Petroleum Chemistry 35 (1995) To reduce the Pd consumption is possible to produced dense palladium alloy layers (Pd-Ag, Pd-Rh, etc.) on thermostable porous support
35 Combination of the dehydrogenation on one surface of the Pdbased catalytic membrane and hydrogenation by the diffused hydrogen on the other surface V. Gryaznov, Catalysis Today 51 (1999) 391±395
36 Other examples of inorganic membrane reactors E. Drioli et al. Clean Products and Processes 2 (2000)
37 Typical examples of inorganic membrane reactors Drioli12-14 et al. Clean Products II WORKSHOP NAZIONALE AICIngE. - Messina, Settembre 2007 and Processes 2 (2000)
38 Polymeric membranes are usually used when the reaction temperatures are lower, i.e. in the field of fine chemicals or when biocatalysts are present
39 Advantages of polymeric membranes A much wider choice of polymeric membranes is available as compared with metallic or ceramic membranes, and the costs are generally lower. The technology to manufacture polymeric membranes is much better developed than the one for inorganic and metallic membranes. The relatively low operating temperature of polymeric catalytic membranes are also associated with less stringent demands for the materials needed in the module construction.
40 Although polymeric membranes are generally less resistant to high temperature and aggressive chemicals than inorganic or metallic membranes, many polymeric materials as amorphous perfluoro polymers (Hyflon) resistant under rather harsh conditions, are available. Moreover, many reactions of relevant interest in fine chemical synthesis or in the water treatment take place under mild conditions.
41 Basic principles of the heterogenization of catalysts in polymeric membranes Major issues in the polymer selection: good affinity for the catalyst in order to avoid catalyst leaching and to have a good adhesion between polymer and catalyst with dispersion of the same mechanical, thermal, and chemical stability under reaction conditions good transport properties for the reagents and products
42 For a porous membrane, the choice of polymer is of less importance for transport properties in comparison with dense membranes, as permeation does not take place through the polymer matrix but through the membrane pores. However the membrane material is relevant for the stability and surface properties, such as wettability and fouling. Depending on the pore and molecule size, molecules are transported through porous membranes via viscous flow, Knudsen flow, molecular diffusion, surface diffusion, capillary condensation, or molecular sieving. Transport through dense membranes follows the solution-diffusion model, according to which a molecule first sorbs in the polymer before it diffuses through it and finally desorbs again.
43 Transport mechanism through porous membranes Viscous flow Knudsen flow Surface diffusion Capillar condensation
44 Transport mechanism through porous membranes In viscous flow 1 J η ε r P HagenJ= Poiseuille 8η τ x equation r pores radius η viscosity τ tortuosity ε surface porosity ε = n π r / A 2 2 p n p A m number of the pores membrane area m
45 Transport mechanism through porous membranes In Knudsen flow J π nr D p J= RTτ l 2 1 M k D Knudsen diffusion coefficient k 8 RT D = 0.66r πm T temperature M molecular weight n number of the pores k w w W
46 Transport mechanism through dense membranes Solution-diffusion Permeability ( P ) = So lub ility ( S ) x Diffusivity ( D)
47 Also interface phenomena have to be considered!
48 The performance of liquid phase pressure driven membrane operation is particularly influenced by concentration polarisation phenomena dc Jc + D = Jc dx Eric M. Vrijenhoek, Seungkwan Hong, Menachem Elimelech; Journal of Membrane Science 188 (2001) J. Mueller, R. H. Davis, Journal of Membrane Science 116 (1996) p
49 Fouling is another phenomenon that can considerably change the system performance during a membrane process, Membrane fouling is the deposition of retained particles, colloids, emulsions, suspensions, macromolecules, salts, etc. on or in the membrane.
50 Main techniques used in concentration polarization subsequent fouling: order to control phenomena and turbulence promoters corrugated membrane surfaces pulsatile flow vortex generation two-phase flow (solid/liquid and gas/liquid two phase flow)
51 Membranes and biotechnological tools can be used for improving traditional production systems. Typical examples of application include: new and improved foodstuffs, in which the desired nutrients are not lost during thermal treatment; novel pharmaceutical products enantiomeric compositions; with well-defined wastewater treatment wherein pollution by traditional processes is a problem.
52 Biocatalytic membranes reactors Recirculated (external) MBR Biocatalyst Biocatalyst continuously flushed segregated within along membrane membrane module Integrated MBR Biocatalyst entrapped within membrane pores Biocatalyst gelified on membrane Biocatalyst bound to membrane Support binding Cross-linking Ionic Covalent Physical Adsorption binding Binding Biocatalyst immobilized using different methods Giorno, L., Drioli, E., Trends in Biotechnology, 2000, 18, The immobilization of enzymes and microbial cell in artificial membranes it is a well accepted technique that reproduces in many aspects the natural operating conditions in living systems.
53 Thermophylic microbial cells (Caldariella acidophila or Sulfolobus solfataricus) have been successful immobilized, without loss of activity, in cellulose acetate artificial membranes, since in the early eighties M. De Rosa, A. Gambacorta, E. Esposito, E. Drioli, S. Gaeta, Thermophylic microbial cells immobilized in cellulose acetate membranes, Biochimie 62 (1980)
54 The possibility of using phase inversion technique for preparing artificial polymeric membranes entrapping free enzyme or whole cells containing the desired enzyme has been limited by the requirement to avoid non-aqueous solvents in the casting solution and thermal treatment which typically denature the enzyme. On the contrary, thermophilic microorganism showing high resistance to acid, organic solvents, classical denaturating agents (e.g. urea, guanidine, etc) and temperature up to 100 C, offer interesting opportunity for the immobilization of biological catalysts in polymeric artificial membranes.
55 Submerged membrane bioreactors (SMBRs) are today considered as a BAT (Best Available Technology) Permeate In the submerged MBR the driving force is achieved by pressurizing the bioreactor or creating negative pressure on the permeate side. A diffuser is usually placed directly beneath the membrane module to facilitate scouring of the filtration surface. Aeration and mixing are also achieved by the same unit. Cleaning of the membrane is usually achieved principally by bubbling, but also by permeate backpulsing and occasional by chemical backwashing. SMBRs have been successfully applied in wastewater treatment providing an effective alternative to conventional processes such as activated sludge The reduction in energy consumption associated with the recirculation cost and the low transmembrane pressures required make SMBRs well suited to relatively large-scale applications. Reactor Membrane unit Feed Gas Diffuser
56 Classic Sewage Treatment process Primary treatment Effluent Primary sedimentation Secondary treament (Activated Sludge Process) Anoxic/ Aerobic Secondary clarifier (sedimentation) Replaced by a Submerged Membrane Bioreactor Micro- Ultra-filtration operation combined with biomass treatment Tertiary treament Disinfection
57 Effluent Primary sedimentation Anoxic/ Aerobic Secondary clarifier (sedimentation) Disinfection The membrane bioreactor (MBR) combines biological treatment with membrane separation. The treated water is separated from the purifying bacteria (active sludge) by a process of membrane filtration rather than in a settling tank as in conventional systems. Only the treated effluent passes through the membrane. It is then pumped out. The sludge is recovered and dewatered. Improved performance: The biomass contained in an MBR is far more concentrated, varied and lasting than in a conventional system. These properties enhance treatment efficiency.
58 Wastewater treatment by Submerged membrane bioreactor Final effluent quality suitable for reuse Small footprint < 50% of a conventional plant Easy to control, can be monitored remotely Less sludge production, generally 40% less
59 Schematic representation of external MBR Schematic representation of SMBR In the early 1990s, MBR installations were mostly constructed in external configuration, in which case the membrane modules are outside the bioreactor and biomass is recirculated through a filtration loop. This limited wider application in treatment of municipal wastewater. After the mid 1990s, with the development of submerged MBR system, MBR applications in municipal wastewater extended widely. The concept of immersed membranes was conceived in the late 1980s/early 1990s by independent teams in Japan and Canada. In Japan, University of Tokyo professors Aya and Yamamoto, conducted laboratory experiments with fine hollow fibers immersed in an activated sludge reactor. They published their results in the late 1980s in a Japanese journal.
60 External modules Immersed modules
61 Example of effluents requirements and achievable value by SMBR Paramenter Regulation limit (mg/l) SMBR design value (mg/l) COD BOD TSS 35 5 TN - 10 TP - 10 Data from a Zenon plant in Brescia (Italy) for treatment of sewage water
62 Representative costs for life cycle for the Zenon MBR System 15% 8% 40% 37% Chemicals Membrane Energy Equipment
63 MBR for wastewater treatment in Porto Marghera: the largest membrane bioreator unit in the world! Eni and Ondeo Industrial Solutions have designed and built the MBR wastewater treatment unit in order to extract remaining pollutants in tertiary water prior to disposal into the Venetian Lagoon. UF section of the MBR plant in Porto Marghera (VE)
64 The ultrafiltration unit, containing submerged PVDF hollow fibers membranes (ZeeWeed by Zenon), is designed to treat 1600 m3/h of wastewater with a COD/h of 445 kg. There are two interconnected UF lines. Each line contains 4 unit composed by 9 ZeeWeed modules. Total membrane area: m2 Suspended matter of the treated water <1mg/L: respect of the regulations dealing with wastewater disposal in the Venetian Lagoon. Scheme of the UF unit containing 9 ZeeWeed modules
65 Heterogenization of polyoxometalates in polymeric membranes for oxidation reactions
66 Catalytic oxidation reactions are nowadays widely in different fields: Hydrocarbons transformation (petrolchemical industry) Selective oxidation of organic substrates (fine chemical synthesis) Degradation of organic pollutants (wastewater treatment) Membrane technology could offer interesting possibilities in catalytic oxidations: The use of non-covalent supports that bring together catalysts and substrates in a suitable nano-environment may be particularly advantageous
67 Heterogenization of polyoxometalates (active in photo-oxidation reactions and operating in water with O2) in polymeric membranes Catalyst entrapped in the membrane Phase inversion F Catalyst on the surface of plasma modified membranes Ar/NH3 plasma F C F C F i + W10 PVDF-W10 PVDFPVDF PVDF PVDF-NH2 PVDF-NH2-W12 W12 = H3PW12O40 W10 = TBA4 W10O32 Van der Waals W12 aq. interactions catalyst-polymer! M. Bonchio, M. Carraro, G. Scorrano, E. Fontananova and E. Drioli, Advanced Ionic interactions polymer! Synthesis & Catalysis, 2003, 345, E. Fontananova et al. Heterogenization of polyoxometalates on the surface of plasma modified polymeric membranes (In preparation). catalyst-
68 Catalyst entrapped in the membrane Characteristic bands of TBA4W10O PVDF (blank) (cm-1) %T PVDF-W10 (25.0 wt%) W10 (in KBr) Group Vibration 595 W-Oc-W streching 803 W-Ob-W streching 958 W=O streching 2870 CH2 (TBA group) sym. streching Wave number cm- 1 The catalyst structure is preserved within the polymeric membrane
69 Catalyst entrapped in the membrane Phenol photodegradation by porous PVDF-W10 catalytic membranes in a CMR OH TMP=0 bar CO2 + H2O Ct / C0 1 TMP=0.5 bar 0.9 TMP=1 bar 0.8 TMP=1.5 bar PVDF-W10 (14.3 wt%); 0.88 micromoles PVDF-W10 (25.0 wt%); 1.73 micromoles PVDF-W10 (33.3 wt%); 2.83 micromoles 1 Ct/C Time (min) Ct is the phenol concentration at the time t C0 is the initial concentration Time (min) Effect of the catalyst loading (CL)and TMP on phenol degradation: maximum efficiency was reached with CL= 25.0 wt% and TMP=1 bar E. Fontananova, L. Donato, E. Drioli, M. Bonchio, M. Carraro, G. Scorrano, Heterogeneous Photo-Oxidation Performed By Polymeric Catalytic Membranes, 7th International Conference on Catalysis in Membrane Reactors (ICCMR7) Sept. 2005, Cetraro (CS) Italy E. Fontananova, E. Drioli, L. Donato, M. Bonchio, M. Carraro, G. Scorrano, Heterogeneous photooxidation of phenol by catalytic membranes, 7th World Congress IIon WORKSHOP NAZIONALE AICIng - Messina, SettembreSeptember 2007 Recovery, Recycling and Re-integration (R 05), Beijing China, 25-29, 2005
70 Catalyst entrapped in the membrane PHENOL DEGRADATION (%) TIME (min) W10 (homogeneous) PVDF-W10 (25.0 wt%) Phenol mineralization (TOC loss %) TIME (min) W10 (homogeneous) PVDF-W10 (25.0 wt%) The % of phenol degradation is similar in both homogeneous and heterogeneous reactions An higher % of phenol mineralization is observed with the catalytic membrane Catalytic membranes can be recycled without loss of activity in successive catalytic runs
71 Catalyst on the surface of plasma modified membranes XPS analyses of native and modified PVDF membrane by plasma technique Substrate C% O% W4f% P2p% F% N% O/C N/C W/C F/C PVDF 54,2 1, ,8 / 0, ,80 PVDF-NH2 57,6 4, ,1 9,4 0,08 0,16-0,48 PVDF-NH2-W12 53,1 18,3 3,5 0,4 19,3 5,1 0,34-0,07 0,36 N% value is a measure of the efficiency of the grafting of N-groups. This value diminishes from 9,4 for PVDF-NH2 to 5,1 for PVDF-NH2-W12, due to the linking with the catalyst that partially quench the nitrogen groups. W-based catalysts binding can be monitored by the XPS W%. The W4f peak in the XPS spectra of the catalytic membrane shows two major components and this behaviour is typical of tungsten oxides
72 Catalyst on the surface of plasma modified membranes Phenol photodegradation by PVDF-NH2-W12 0 Process k (min-1) R2 W PVDF-NH2-W12 (TMP=0) PVDF-NH2-W12 (TMP=1 bar) ln (n/n0) PVDF-NH2-W12 (TMP=1 bar) -0.7 PVDF-NH2-W12 (TMP=0 bar) -0.8 W Time (min) First order plot for the photocatalytic degradation of phenol in homogeneous W12 and heterogeneous PVDF-NH2-W12 reactions (n0 are the initial moles of phenol and nt the moles at the time t) Catalytic activity is dependent on the transmembrane pressure (concentration and contact time catalyst-substrate) Heterogeneous photodegradation is faster than homogeneous due to high affinity polymer-substrate and optimal dispersion of the catalyst on membrane surface The catalytic membranes are stable and recyclable E. Fontananova, L. Donato, E. Drioli, L. Lopez, P. Favia, R. d Agostino, Chemistry of Materials 18 (2006) L. C. Lopez, M. G. Buonomenna, E. Fontananova, G. Iacoviello, E. Drioli, R. d Agostino, P. Favia, Advanced Functional Materials 16 (2006), IIL.C. WORKSHOP NAZIONALE AICIng - Messina, Settembre 2007 Lopez, M.G. Buonomenna, E. Fontananova, E. Drioli, P. Favia, R. d Agostino, PLASMA PROCESSES & POLYMERS, 4 (2007)
73 New hydrophobic polymer for catalyst heterogenization: Hyflon Copolymers of tetrafluoroethylene (TFE) and 2,2,4trifluoro, 5trifluorometoxy 1,3 dioxide (TTD) Perfluoro polymer F F O Tg (AD60x) =110 C Tg (AD80X)=135 C F F O WCA=108 ±1 O F F F CF3 TTD n m TFE V. Arcella, P. Colaianna, P. Maccone, A. Sanguineti, A. Gordano, G. Clarizia, E. Drioli, Journal of Membrane Science 163 (1999) V. Arcella, A. Gordano, P. Maccone, E. Drioli, Patent US Patent deposited 24/05/2000, N. 09/576,992 Thermal decomposition temperature >400 C Highly transparent to light from deep UV to near infrared High O2 solubility 0.33 cm3/(cm3bar) n = 0.85 for Hyflon AD80X and 0.6 for Hyflon AD60X, respectively and m=1-n
74 (nbu4n)4w10o32 (TBAW10) heterogenised in Hyflon Cross section Surface Catalyst aggregates Poor dispersion of the catalyst!!! Low affinity polymer-catalyst!!!
75 Possible solution: exchange of the counterion of W10 with a fluorinated one (PFA) H C 3 H3C CF2 F2C CH3 CF2 F2C CF2 F2C CF2 F2C CF2 F2C CH3 CF2 CF2 F2C F2C CF2 CF2 F2F2C CF 2 C CF2 C F2 N+ CF2 F2C CF2 H3C CF2 F2C CF2 F2C CF2 F2C CF2 F2C CF2 F2C CF 2 F2 F 2 F C 2 F2 H3C C C C C N+ F2 F C C 2 CH3 F2 F2 C + 4- H3C H3C CH3 N F2 F F2 C2 C C C C C F2 F2C H3C F2 F2 F2C CF2 F2C F2C CF2 CF2 F2C F2C CF2 CF2 H3C F C 2 CF2 F2C CH3 PFA-W10 M. Carraro, M. Gardan, G. Scorrano, E. Drioli, E. II WORKSHOP NAZIONALE AICIng - Messina, Settembre 2007 N+ F2C CF2 F2 F C C C2 F2 C F2 C CH3 F2C F2 CF2 F2C CF2 F2C CF2 F2C CF2 F2C CF2 F2C F2C CH 3 CF2 F2C CH3 Fontananova and M. Bonchio, Chem Comm. 43 (2006)
76 Membrane preparation by phase inversion induced by solvent evaporation Sol 1: PFA-W10 in Esafluoropropanol (6.8 wt%) Mixing Sol 2: Sol 1 = (g/g): homogeneous solution Sol 2: Hyflon in Galden (2.4 wt%) Solvent evaporation Hy-PFAW10 dense membranes Membrane Loading PFA-W10 (wt % ) Thickness (µm) ± ± ± ± ± ±3
77 PFAW10 heterogenised in Hyflon (#2) Cross section Surface Good dispersion of the catalyst!!!
78 DR-UV spectra of the Hy-PFAW10 membrane W10 in water (10-4 M) W10 in membrane CT band characteristic of the W10 The catalyst hetrogenized in membrane presents the CT band at 324 nm
79 Hyflon-PFA-W10 membranes were tested for the oxidation of ethylbenzene OOH W10O32 OH O 4- + λ > 345 nm, po2=1 atm T= 20 C O2 Membrane Solution under magnetic stirrer hν Batch experiments for a fast but incomplete screening of the catlytic membranes
80 TON Ethylbenzene photooxidation by different catalytic membranes Hy-PFAW10 Hy-TBAW10 PDVF-TBAW time (h) Reaction conditions: ethylbenzene, 1.1 ml; po2 1 atm; λ>345 nm; T=25 Hy-PFAW10 50 µm, 0.18 µmol. Hy-TBAW10 76 µm, 0.2 mmol. PVDF-TBAW mm, 0.32 Higher efficiency with the fluorinated W10 in Hyflon membranes M. Carraro, M. Gardan, Scorrano, E.Settembre Drioli, E.2007 Fontananova II WORKSHOP NAZIONALE AICIngG. - Messina, and M. Bonchio, Chem Comm. 43 (2006)
81 Oxidation of ethylbenzene Catalyst Solvent Cat. µmol Products, mm (% 1:2:3) TBAW10 CH3CN (36: 32:32) 351 PFAW10 HFP (56: 23:21) 581 PVDF-TBAW10 neat (45: 23:32) 78 Hy-TBAW10 neat (14: 66:20) 443 Hy-PFAW10 neat (25: 41:34) 1198 a a TON 1: peroxide, 2: alcohol, 3: keton. Reaction conditions: ethylbenzene, 1.1 ml; po2,1 atm; l>345 nm; T=25 C; 4 h irradiation time. Turnover number calculated as products (mol)/catalyst (mol). a pseudoneat conditions by addition of 20 µl of solvent Higher selectivity for the alchool with Hyflon membranes, in particular with Hyflon-PFA-W10 M. Carraro, M. Gardan, Scorrano, E.Settembre Drioli, E.2007 Fontananova II WORKSHOP NAZIONALE AICIngG. - Messina, and M. Bonchio, Chem Comm. Chem Comm. 43 (2006)
82 SW % = W w Wd 100 Wd W w and W d are the weight of swollen and dry membrane at 30±1 C LogP is the logarithm of the partition coefficient between n-octanol and water The more hydrophobic polymeric material, i.e. Hyflon, has a higher affinity towards the more hydrophobic (higher LogP value) liquid: ethylbenzene. On the contrary it has a low affinity for the more hydrophilic liquid: 2-phenylethanol. These data can contribute to explain the high reactivity of the catalyst heterogenized in Hyflon membranes (high affinity for the reagent) and the high selectivity (low affinity for the product of interest, i.e. the alcohol, which limits the possibility of over-oxidation of the same). The better performance of the catalytic Hyflon membranes can depend also from electronic effect of the perfluorinated polymer (electron attractor) on the catalyst Moreover it is also well known that fluorinated environment can promote oxidation reactions
83 Morphological analyses of Hyflon membrane containing the TBA-W10 clearly revealed the presence of catalyst aggregates On the other hand, the use of a fluorinated cations linked to the decatungstate anion (PFA-W10) improves the affinity between catalyst and polymer and the catalyst can be thoroughly dispersed in the membrane. Batch experiments of ethylbenzene (neat) oxidation were carried out with Hyflon-PFA-W10 membranes. These systems showed super catalytic performance (higher turnover number and better selectivity) compared to homogeneous catalyst Future work will be aimed in order to improve the membrane preparation method and testing these new and promising catalytic membranes in a real CMR operating with flow through both for neat oxidations of organic compounds
84 Enzyme Membrane Reactors (EMR) for Enantiomeric Production
85 Production of optically pure (S)-naproxen Naproxen ((S)-2-(6-Methoxy-2-naphthyl) propionic acid) is an important member of the family of 2-aryl propionic acid derivatives, which is widely used as nonsteroidal anti-inflammatory drug. (S)-naproxen is 28 times more active than the (R)-naproxen Lipase from Candida rugosa preferentially hydrolyses (S)-naproxen ester Reaction scheme lipase COOH COOCH3 CH3O H2O CH3O (R,S)-naproxen methyl ester + COOCH3 CH3O (S)-naproxen (R)-naproxen methyl ester
86 Emulsion&Enzyme Loaded Membrane Reactor L ip a s e in o r g a n ic / w a t e r p h a s e Lipase H2 O Membrane
87 2.00E E-01 S-Naproxen 1.20E-01 mmol R-Naproxen 8.00E E E Time (h) Behavior of S- and R-isomer as a function of time in emulsion and enzyme immobilised in a two separate phase enzyme-emulsion membrane reactor
88 E E E-02 ee (-) Production µ(mol) 4.E E Time (h) ( S) naproxen ( R) naproxen ee Behaviour of stability and selectivity as a function of time for experiments in semi-continuous mode (20% organic dispersed phase, enzyme mainly present within the membrane pores).
89 The production and selectivity of the enzyme-loaded membrane reactor were affected by: the membrane cut-off, which affects the membrane loading capacity; the amount of enzyme immobilized; the immobilization site, which affected O/W interface. Very small microemulsion were prepared membrane Emulsifier using UF membrane. by O/W interface problem was overcome in E-EMR, where native enantioselectivity was observed as reaction occurred at the organic/water interface
90 Membrane technology in petrochemical industry
91 Catalytic membrane reactors (CMRs): new opportunities in the petrochemical field Air Coke A OEA Byi Membrane r Operation to flares Feedstock MF for Water Treatment (coke removal) CRACKING FURNACES Diution Steam Pure H 2 Water MR FOR CO CLEAN-UP GAS COMPRESSION HOT SECTION MCs for Acid Gas Removal H2 Acid gas Condensed stream MRs FOR ETHYLENE PRODUCTION C4+ Membrane GS H2 RECOVERY MCs for Water Purification DISTILLATION CH4 C3+ C2+ Membrane GS ETHYLENE/ ETHANE Membrane GS PROPYLENE/ PROPANE C2H4 Ethane/Propane recycle Reference plant: 800,000 t/a ethylene; ethylene yield = 31%; propylene yield = 18%; H2 yield = 1% (weight basis) energy consumption = 30 GJ/t ethylene P. Bernardo, A. Criscuoli, G. Clarizia, G. Barbieri, E. Drioli G. Fleres and M. Picciotti, Clean Technologies and Environmental Policy, (2003), 6 (2004) C3H6
92 Ethylene by catalytic processes Cracking processes: energy and capital intensive. Highly endothermic reactions, complex furnaces, coking. Catalytic processes: reduced energy consumption Ethane oxidative dehydrogenation (EOD) Promising new way to produce ethylene C2H6 + 1 / 2 Ο 2 C2H 4 + Η 2 Ο Exothermic and not equilibrium limited Coking limited by O2; no need for steam Long-term stable operation Significantly less investment expected!
93 Ethane oxidative dehydrogenation (EOD) with O2 controlled addition in a CMR C2 H / 2 Ο 2 Air side ½ O2 + 2 e O - O2- e- 2- Catalytic membrane C2H6 + O2- C2H4 + H2O + 2 e- Reaction side * C2H 4 + Η 2 Ο O2 separation from air Oxygen conducting membranes*: oxygen selective transport at high T (>700 C) Activated oxygen provided to the ethane side Akin and Lin, J Membr Sci 209 (2002) 457. Improved safety (O2 and C2H6 separated) Better heat management Air can be fed to the MR process (large amounts of inert N excluded) Intensified II WORKSHOP NAZIONALE AICIng - Messina, Settembre 2007
94 Ethylene by EOD: Exergetic analysis Conversion Selectivity TR1 80 TR2 63 MR1 MR2 [TR1 Monolith reactor (Pt-Cu on MgO)] DOW: Bharadwaj et al., US Patent No. 6,566,573 (2003). [TR2 (Perovskite catalyst)] Donsì et al., J Catal 209 (2002) 51. [MR1 (catalytic membrane)] Akin and Lin, J Membr Sci 209 (2002) 457. [MR2 (Perovskite catalytic membrane)] Rebeilleau et al., Catal Today 104 (2005) 131 C efficiency, % Exergy losses, kj/mol ethylene TR 1 TR1 TR1+GS TR2 MR1 56 MR2 TR 2 C Efficiency = P. Bernardo, G. Barbieri, E. Drioli,, An exergetic analysis of membrane unit operations integrated in the Ethylene Production cycle, IICHERD WORKSHOP AICIng - Messina, Settembre 2007 (2006), NAZIONALE accepted. MR1 MR2 mol C C 2 H mol C C 2 H 6
95 Reaction Metrics: Ethylene production by Ethane oxydehydrogenation kg INTOT CH +O CH +HO Mass Intensity = kg Ethylene Mass Intensity, 2 kg IN/kg ethylene 8,6 8,2 Molar Intensi ty, m ol IN/m ol ethylene 5,8 11,5 2,9 7,9 5,5 4,3 TR 1 TR 2 MR1 MR2 TR 1 TR 2 MR1 MR2
96 Reaction Metrics: Ethylene production by Ethane oxydehydrogenation Considering the air required to produce the O2 for the reactor Mass Intensity, kg IN/kg ethylene 8,2 8,6 8,2 5,5 TR 1 TR 2 MR1 MR2
97 Reaction Metrics: Ethylene production by Ethane oxydehydrogenation C2H6 + O2 C2H4 + H2O C Efficiency = mol CC 2 H mol CC 2 H 6 Formed 2 FC2H4 = 100 Feed 2 FC2H6 C efficiency, % = YC 2 H 6 Reaction Yield TR 1 TR 2 56 MR1 MR2
98 Membrane technology in H2 production
99 Integrated Membrane Plant for H2 production by Water Gas Shift Reaction CO + H2O = CO2 + H2 H0298 = - 41 kj/mol Steam Feed HDS Retentate Reforming ra mb Me ca Sili WGS-MR ne Pd -A lloy Me mb ra n H2 e Fuel Support Retentate Catalyst Sweep Membrane Feed SS-Shell Permeate
100 MR CO Conversion, - WGSR in Silica MR SiO2 selective layer 1 µm; dpore <1 nm Allumina intermediate layer 5 µm; 50 Selectivity, - Before reaction bar 3 bar Temperature, C H2/CO bar 6 bar After reaction H2/CO 0 TREC Before reaction After reaction The catalytic membrane reactor overcomes the traditional reactor equilibrium conversion (TREC) Temperature, C Brunetti A., Barbieri G., Drioli E., Lee K.-H., Sea B., Lee D.-W., WGS Reaction in Membrane Reactor Using a Porous Stainless Steel Supported Silica Membrane. Chemical Engineering and Processing 46 (2007)
101 Integrated Membrane systems in energy production H2 CO2 CO H2O HYDROCARBON REFORMER WATER GAS SHIFTER H2 CO2 CO (low) H2O CO -SELECTIVE 2 MEMBRANE SEPARATOR From U.S. Patent 6,579,331, ExxonMobil property H2 CO2 (low) CO (low) H2O METHANATOR H2 CH4(low) FUEL CELL CO2 Membranes have a central role both in hydrogen production (CMRs) and purification (GS) and in the fuel cells as proton exchange membrane (PEM)!
102 Process intensiﬁcation by miniaturization Micro-reactors have demonstrated their clear advantages in catalysis and micro-reaction engineering is rapidly developing Advantages: reduction of length scale decreasing of heat and mass transfer distances decrease realization of specific interfaces for multiphase flow smaller reagent volumes and correspondingly lower costs Properties Micro-reactor Conventional reactor internal volume 1-10 µl >> 1 ml speciﬁc surface m2/m3 100 m2/m m2/m3 100 m2/m3 laminar character turbulent phase boundary surfaces for liquid/ liquid mixtures ﬂows
103 Micro-membranes fabricated using standard MEMS microfabrication processes enable new applications because of their small size, fast thermal response times and high efficiency
104 Pd-based micro-membranes for the Water Gas Shift Reaction in a miniature fuel processor for micro fuel cells Schematic of the integrated microreactor Karnik et al.journal of microelectromechanical systems, 12 (2003)
105 An innovative potential application of membrane technology in catalysis and in catalytic membrane reactors, might be the possibility to produce catalytic crystals with a well defined size, size distribution and shape, by membrane crystallization Lysozyme Trypsin Di Profio, G. Curcio, E. Drioli E. Membrane crystallization of lysozyme: kinetic aspects. Journal of Crystal Growth 2003; 257: Di Profio, G. Curcio, E. Drioli E. Trypsin crystallization by membrane-based techniques. Journal of Structural Biology 2005; 150:
106 Driving force: vapour pressure difference p ( c, T ) = p ( T ) a ( c, T ) 0 temperature difference thermal membrane crystallization concentration difference osmotic membrane crystallization supersaturated solution nucleation and crystal growth
107 The presence of the polymeric membrane increases the probability of nucleation with respect to other locations in the system (heterogeneous nucleation) Lysozyme crystals grown on PP microporous hydrophobic membrane G. Di Profio, E. Curcio, E. Drioli, Journal of Crystal Growth, 257 (2003)
108 The value of the activation barrier is a crucial parameter to be controlled! Polymeric materials can be used to promote and modulate the nucleation process that often represents the limiting step in macromolecular crystallization (Curcio, E. Fontananova, G. Di Profio, E. Drioli, Journal of Physical Chemistry B.; 110(25) (2006) ) 1 PP G h et G / G hom (-) 0.8 het = G hom Hyflon cos α + 4 cos α PDMS PVDF(KF2800) 0.6 PVDF(KF2800)-LiCl-2,5% PVDF(KF2800)-PVP-2,5% 0.4 PVDF(Kynar460) PVDF(Kynar460)-PVP-2, contact a ngle ( ) Reduction in the free energy of the nucleation barrier due to heterogeneous nucleation as a function of the lysozime solution (40 mg/ml; 2% wt NaCl) contact angle with some polymeric surface
109 Glycine polymorphs selection in membrane crystallization γ - Polymorph γ - Polymorph α - Polymorph ph 6.1 Glycine dissolved in pure water: ph Static system Dynamic system J/(mL/h) Polymorph v/µm sec-1 Polymorph 6,9 x 10-3 γ 349,6 γ 13,8 x 10-3 γ 539,9 γ 18,4 x 10-3 α 709,1 α 20,7 x 10-3 α 899,9 α 23,0 x 10-3 α 989,9 α 27,9 x 10-3 α 1349,8 α 34,5 x 10-3 α 1845,5 α G. Di Profio, S. Tucci, E. Curcio, E. Drioli, Cystal Growth & Design, in press
110 Selective polymorphs crystallization by controlling the rate of achievement of supersaturation Low flow rate γ-polymorph Solvent Vapor Solvent Vapor High flow rate α-polymorph Stripping Solution Glycine Solution Solvent Vapor Solvent Vapor The control of the rate for the achievement of supersaturation allows to switching from a kinetically to a thermodynamically controlled nucleation stage thus triggering the production of either a stable or metastable form. G. Di Profio, S. Tucci, E. Curcio, E. Drioli, Cystal Growth & Design, in press
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