POLYIMIDE-ZEOLITE MIXED MATRIX MEMBRANE (MMM) FOR BIOGAS PURIFICATION

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1 POLYIMIDE-ZEOLITE MIXED MATRIX MEMBRANE (MMM) FOR BIOGAS PURIFICATION Budiyono*,c, T.D. Kusworo, A.F. Ismil b, I.N. Widis, S. Johri c, nd Sunrso c Deprtment of Chemicl Engineering, University of Diponegoro, Jl. Prof. Sudhrto SH No. 1, Semrng, Indonesi b Advnced Membrne Reserch Technology Center, Fculty of Chemicl nd Nturl Resources Engineering, Universiti Teknologi Mlysi, UTM, Skudi, Johor Bhru, Mlysi c Deprtment of Animl Agriculture, University of Diponegoro, Jl. Prof. Sudhrto SH No. 1, Semrng, Indonesi *Corresponding Author emil: budhi.66@gmil.com Abstrct Biogs hs being become significnt potentil s n lterntive energy source due to the limittion of energy from fossil. In this study, new type of mixed mtrix membrne (MMM) consisting of polyimide-zeolite ws synthesized nd chrcterized for biogs purifiction. The MMM consists of medium concentrtion of polymer (20 %wt polyimide), 80 % N-Methyl-2- pyrrolidone (NMP) nd 25 % zeolite 4A in totl solid were prepred by dry/wet phse inversion technique. The fbricted MMM ws chrcterized using SEM nd gs permetion. Post tretment coting procedure ws lso conducted. The reserch showed tht surfce coting by 3 % silicone rubber towrd MMM PI 20 % gve the significnt effect to improve membrne selectivity. The idel selectivity for CO 2 /CH 4 seprtion incresed from 0.99 for before coting to 7.9 fter coting for PI-Zeolite MMM, respectively. The results suggest tht PI-Zeolite MMM with good post tretment procedure will increse the membrne selectivity nd permebility with more sver polymer requirement s well s energy sving due to low energy for mixing. Keyword: mixed mtrix membrne, polyimide, zeolite, biogs purifiction Introduction Biogs hs being become significnt potentil s n lterntive energy due to the limittion of energy source from fossil. This is due to its chrcteristics i.e. renewble source, environment friendly, clen, chep nd verstile fuel. However, the use of biogs still hs limittion due to low-qulity of biogs contining substntil mounts of CO 2 (20-45 vol%) nd H 2 S (0-1 vol%) in ddition to min component CH 4 (55-80 vol%). In ddition, biogses re lso frequently sturted by wter vpour. The presence of CO 2 s n incombustible gs reduce its clorific vlue nd mke it uneconomicl to compress nd trnsport to longer distnces [1]. The H 2 S content poses serious problems of odor, toxicity for humn nd niml helth, nd corrosion [2]. If biogs is clened up sufficiently, biogs hs the sme chrcteristics s nturl gs (NG) [3]. There is lot of potentil if biogs could be mde vible s trnsport vehicle fuel like Compressed Nturl Gs (CNG). Besides the use of biogs s vehiculr fuel, smll scle or bulk biogs storge for domestic consumption lso represent potentilly lrge mrket. Therefore biogs purifiction before compression t high pressure for storge in cylinders is essentil.

2 A vriety of processes re being used for removing CO 2 nd H 2 S from NG in petrochemicl industries. Severl bsic mechnisms re involved to chieve selective seprtion of gs constituents. These my include physicl or chemicl bsorption, dsorption on solid surfce, membrne seprtion, cryogenic seprtion nd chemicl conversion. However, membrne seprtion processes hve emerged during the lst two decdes. This is due to the fct tht membrne seprtion processes my offer more cpitl nd energy efficiency when compred to the conventionl seprtion processes [4]. In ddition, dvntge of membrne technology is its simplicity, i.e. no bsorbent, which hs to be regenerted; it cn be esily retrofitted, modulrized nd scled-up for severl pplictions [5]. Commercil membrne systems for gs seprtion were vilble since the mid-1970s, but the most importnt innovtion for lrge-scle commerciliztion of polymeric membrnes for gs seprtion ws chieved by Perme (now Air Products) in 1980 [6]. Currently, the min chllenge in ppliction of the membrne technology for gs seprtion is how to get the mterils with higher permebility nd selectivity s well s good therml stbility [7]. Generlly, better selectivity is obtined with glssy polymers. The glssy stte offers more structured sieving mtrix thn the rubbery stte s well s higher lod bering properties llowing for high pressure drop cross the membrne. Typicl glssy polymers used in membrnes for commercil gs seprtion re polysulphone, cellulose cette nd polyimide [8-9]. Among oh these polymers, romtic polyimide were well known hs the excellent properties, e.g. high therml stbility, chemicl resistnce, mechnicl strength, nd low dielectric constnt [4]. However, due to the generl limittions in polymeric membrne performnce such s low permebility [10] mny reserch efforts hve been focused on developing membrnes with selective inorgnic fillers. One such system is hybrid membrne. Hybrid membrnes composed orgnic-inorgnic hs ttrcted ttention s the future membrne mteril. Hybrid membrnes or mixed mtrix membrne concept combines the dvntges of high seprtion cpbilities of the moleculr sieves nd the desirble mechnicl properties nd economicl processing cpbilities of polymers. The intent of this type of membrne is to tke dvntge of the low cost nd good processbility of polymers with the excellent seprtion performnce of zeolites. An effort to decrese polymer cost of polyimide nd increse processbility, Kusworo et l. [11] hs mixed PI nd polyether sulphone (PES) with rtio 20:80 by 25 wt% of totl polymer in N-Methyl-2-pyrrolidone (NMP). These membrne composites offer reltively low cost of polymer besides esy to cst the polymer solution so it will reduce the mixing power. Therefore, the objective of the present study is to synthesize nd chrcterize the high selectivity of CO 2 /CH 4 of polyimide-zeolite mixed mtrix membrne t medium polymer concentrtion for biogs purifiction. In the present study ws lso exmined the effect of coted nd uncoted mixed mtrix membrne on the seprtion performnce of fbricted membrne. Experimentl Mteril selection The selection considertion of polymers nd fillers in this reserch is to obtin the MMM formed hve high permebility nd selectivity of CO 2 /CH 4. The polyimide polymer is selected due to it s chrcteristics tht polyimide polymer formed by romtic rings nd functionl groups of big volume, which ct like moleculr sieves, s mteril for membrnes used for gs seprtion is resonble. Due to high glss trnsition temperture nd low solubility of polymer, it is possible to pply polyimide in wide rnge of tempertures nd pressures. Moreover, the polymer is chrcterized by high selectivity nd permebility to the

3 gses in comprison to the others. According to Ho et l. [12], polyimide mde from 6FDA- HAB hs CO 2 /CH 4 selectivity up to 60. Polyimide polymers used in this reserch ws mtrimide resin. Mtrimide ws obtined from Alf Aesr Johnson Mtthey Compny USA. The mtrimide polymers were dried overnight in vcuum oven t 120 C before dope preprtion. N-methyl-pyrrolidinone (NMP) from Merck ws selected s the solvent due to its low toxicity. The chemicl structure of the polyimide is shown in Fig. 1. Figure 1: Chemicl structure of polyimide Zeolite moleculr sieve ws selected due to their high selectivity nd comptibility towrds polr compounds, such s H 2 S [12]. Therefore, the inorgnic filler moleculr sieve involved ws zeolite 4A purchsed from Aldrich nd the prticle size ws 2 mm. In order to remove the dsorbed wter vpour or other orgnic vpors, ll zeolite prticles were dehydrted t 300 o C for 3 h before use. Fbriction of symmetric flt sheet MMM In this study, the polymer solution consists of 20 wt% PI polymer 80% NMP nd 25 wt % zeolite in the totl of solid. The homogeneous polyimide were prepred ccording to the following procedure; the inorgnic moleculr sieve prticles were dispersed into the solvent nd stirred for 24 h followed by the ddition of desired mount of polyimide. The solution ws gitted with stirrer t lest 24 h to ensure complete dissolution of the polymer. Before csting, the homogeneously prepred solution ws degssed under vcuums for 3 h. Flt sheet membrne ws prepred ccording to the dry/wet phse inversion technique. The solution ws poured onto cler, flt nd smooth glss plte tht ws plced on the trolley. Stinless steel support csting knife ws used to spred the solution to uniform thickness by pneumtic force. Membrnes were cst t different sher rtes by vrying the speed of the trolley (csting speed). The glss plte with the membrne film ws then immersed into the cogulnt bth or wter bth. During this process, solvent exchnge occurred nd solidified the membrne film to complete membrne structure. To ensure ll of the solvent in the membrne structure is removed, membrnes were immersed in n queous bth for 1 dy, followed by immersion in methnol for 4 h nd irdried for 24 h t room temperture. The mixed mtrix membrnes were finlly dried in oven t 120 C for 4 h to remove ll the residul solvents. Post-tretment procedure The membrne sheets were coted with highly permeble elstomeric silicone polymer (Sylgrd 184 Dow Corning). The membrne coting ws done fter the uncoted membrnes were tested. The intention of coting is to fill ny surfce pinholes or defects on membrne surfce. Membrnes were submerged in the 3% w/w solution of silicone in n- hexne for 24 hours nd subsequently plced in oven for 3 dys t 120 o C to llow curing before permetion testing.

Membrne chrcteriztion A Supr 35 VP Field Emission Scnning Electron Microscopy (FESEM) ws used to ensure the symmetric structure nd to determine the dimension of the fibers.

4 Membrne chrcteriztion A Supr 35 VP Field Emission Scnning Electron Microscopy (FESEM) ws used to ensure the symmetric structure nd to determine the dimension of the fibers. Membrne smples were frctured in liquid nitrogen. The membrnes were mounted on n luminum disk with double surfce tpe nd then the smple holder ws plced nd evcuted in sputter-coter with gold. Module fbriction nd gs permetion experiment Membrnes formed were exposed to two different gses CH 4 nd CO 2 nd were mesured its permebilities. The permetion test involved the use of gs permetion cell in which the membrne ws plced on sintered metl plte nd pressurized t the feed side. Gs permetion rtes were mesured by constnt pressure system using sop bubble flow meter. Fig. 2 illustrtes the gs permetion cell set up. The cross-membrne pressure difference ws mintined 1 br. Pressure normlized gs permetion flux or permence for gs i, (P/l) i, in (GPU), cn be clculted s follows: æ Pö Qi ç = (1) è l øi ADp where Q i is the volumetric flow rte of gs i, Dp is pressure difference cross membrne (cmhg), A is membrne ffective surfce re (cm 2 ) nd l is membrne skin thickness (cm). The idel seprtion fctor cn be clculted by using eqution below: i / j i / j = ( P / l) ( P / l) i j (2) Figure 2: Gs permetion test cell Results nd discussion Morphology of symmetric PI-Zeolite mixed mtrix membrnes An understnding of how preprtion conditions led to different morphologies is vitl for generting mixed mtrix membrnes with desirble trnsport properties. The FESEM nlysis ws performed in order to investigte the effect of preprtion process such s the

7th Interntionl Conference on Membrne Science nd Technology (MST2009) effect of medium polymer concentrtion on the morphology of mixed mtrix membrnes nd the reltion with the seprtion performnce of

Koros nd co-workers [13] observed tht mixed mtrix membrne with zeolite nd glssy polymer possessed poor polymer-sieve contct.

Moreover, the interfce between polymer mtrix nd inorgnic filler plys n importnt role to determine the performnce of fbricted mixed mtrix membrnes.

5 7th Interntionl Conference on Membrne Science nd Technology (MST2009) effect of medium polymer concentrtion on the morphology of mixed mtrix membrnes nd the reltion with the seprtion performnce of these membrnes. As suggested by previous study [13-14] tht the min problems fced during fbriction of mixed mtrix membrne were surfce effects, ggregtion nd poor polymer-sieve contct. Koros nd co-workers [13] observed tht mixed mtrix membrne with zeolite nd glssy polymer possessed poor polymer-sieve contct. It ws found tht the mixed mtrix membrne contined the unselective voids of bout mm round the sieves. Moreover, the interfce between polymer mtrix nd inorgnic filler plys n importnt role to determine the performnce of fbricted mixed mtrix membrnes. Therefore, in this study, the fesibility of fbriction mixed mtrix membrne t medium polymer concentrtion ws investigted. Hence, the chrcteriztion nd comprison of polyimide-zeolite for uncoted nd coted would be further discussed. FESEM chrcteriztion ws crried out on the fbricted membrne in order to determine the qulittive nlysis of polyimide-zeolite mixed mtrix membrne. The FESEM microgrphs of the polyethersulfone zeolite mixed mtrix hollow fiber membrne re shown in Figures 3-5. c b d Figure 3: SEM picture of symmetric uncoted net polyimide membrne t the: () cross section nd (b) outer surfce imge lyer (c) coted membrne t cross section nd (d) t outer surfce imge lyer Figures 3-d illustrtes the prtil cross-sectionl re of representtive net polyimide membrne with uncoted nd coted. As cn be seen from the SEM microgrphs, of ll membrnes exhibited the porous structure. The skin lyer of net PI membrne becme incresingly denser when membrne ws subjected silicone coting s shown in Figures 3c-d. Figure 3 ws lso presented tht the net PI membrne clerly revels the presence of some

7th Interntionl Conference on Membrne Science nd Technology (MST2009) mcrovoids under the skin lyer.

occurred in the substructure. Additionl silicone coting only sels defects of the outermost skin, thus the overll fiber selectivity is not improved.

Figures 4-5 presents the prtil cross-sectionl re of representtive PI-zeolite mixed mtrix membrne with nd without silicone coting.

6 7th Interntionl Conference on Membrne Science nd Technology (MST2009) mcrovoids under the skin lyer. Moreover, both net membrnes coted nd uncoted hve substructure reltively thick nd hve pore sizes suitble for Knudsen diffusion, the determining step of the overll selectivity is the Knudsen diffusion occurred in the substructure. Additionl silicone coting only sels defects of the outermost skin, thus the overll fiber selectivity is not improved. The FESEM microgrphs of the polyimide zeolite mixed mtrix membrne t medium polymer concentrtion re shown in Figures 4-5. Figures 4-5 presents the prtil cross-sectionl re of representtive PI-zeolite mixed mtrix membrne with nd without silicone coting. voids voids voids voids b c Figure 4: SEM picture of symmetric uncoted polyimide-zeolite mixed mtrix membrne t the: () cross section nd (b) outer surfce imge lyer Figures 4-c clerly revels the presence of some gglomertion of zeolite nd voids in the interfce of zeolite nd polymer mtrix. As suggested by previous study tht during fbriction of polyimide-zeolite membrne, one fctor plys gret importnce is prticle gglomertion due to sedimenttion or migrtion to the surfce [13-15]. Due to the totlly different physicl properties nd difference in density between zeolite nd polymers, precipittion of zeolite my occur during the MMM preprtion, resulting in formtion of inhomogeneous zeolite nd polymer phses in the filled membrne. The gglomertion of zeolites will cuse the pinholes tht cnnot be reched by polymer segments, forming s nonselective defects in the MMM. On the medium concentrtion of polymer ws generlly the zeolite prticle do not hve enough time to precipitte; while the solvent ws rpidly evported to form membrne. Moreover, the zeolite prticle will tend to form gglomertion.

Furthermore becuse of the silicone coting effect the pcked chins in the polymer mtrix denser nd the pcked structure in the outer skin lyer provide high degree of size nd shpe discrimintion between

7 The effect of silicone coting on the morphology of PI-zeolite mixed mtrix membrne ws depicted in the Figure 5. The FESEM microgrphs revel tht the mixed mtrix membrne with silicone coting hs denser on the outer skin lyer compred to uncoting membrne. Furthermore becuse of the silicone coting effect the pcked chins in the polymer mtrix denser nd the pcked structure in the outer skin lyer provide high degree of size nd shpe discrimintion between the gs molecules. Figure 5-b depicted tht the interfcil gps between polymer host nd zeolite cn reduce with post tretment membrne with silicone rubber coting. Moreover, the smooth surfce of PI-zeolite membrne in the Figure 5b indictes tht the zeolite prticle dheres well to the polymer mtrix. Foremost, by referring to Figures 4-5, the differences in dhesion between PI-zeolite with post tretment using silicone rubber coting cn be successfully distinguished. The post tretment using silicone rubber cn sel the voids between zeolite nd polymer host. No voids (). (b). Figure 5: SEM picture of symmetric coted polyimide-zeolite mixed mtrix membrne t the: () cross section nd (b) outer surfce imge lyer Gs seprtion performnce of PI-zeolite mixed mtrix membrne In the gs seprtion performnce, the criteri which is importnt in determining whether the membrne re clssified s good or not ws determined by the bility of the membrne to give the high enhncement in gs seprtion performnce thn others membrne. Thus, this testing ws crried out in order to study the membrne effectiveness due to the effect of chemicl modifiction on crbon nnotubes surfce. The membrne effectiveness in the gs seprtion performnce ws determined by the membrne permebility nd selectivity for tested biogs purifiction. In this study, we were used gs smple of CO 2 nd CH 4 to represent the biogs product. The gs permetion properties for ech flt sheet crbon nnotubes mixed mtrix membrne were mesured by using vrible pressure constnt volume method. The permebility nd selectivity for tested gses CO 2 /CH 4 obtined were presented in Tble 1. The Tble 1 summrizes the permebility nd selectivity dt of uncoted PI, coted PI, uncoted PI-zeolite nd coted PI-zeolite. Generlly, the ide to put inorgnic filler into orgnic polymer ws enhnced gs permebility of polymer nnocomposites membrnes ws due to the disturbed polymer chin pcking by the nnofillers [16]. Therefore, the well dispersed nd good dherence of crbon nnotubes will

8 be effectively incresed the gs permebility due to more effectively insert between polymer chins of the mtrix. Tble 1: Biogs purifiction performnce of PI-Zeolite mixed mtrix membrne Single gs permence (GPU) Selectivity Membrne CO 2 CH 4 CO 2 /CH 4 Uncoted net PI Coted net PI Uncoted PI-zeolite Coted PI-zeolite As shown in Tble 1, the permebility of uncoted PI nd uncoted PI-zeolite membrne for ll gses were very high. These results indicted tht these membrnes hve big porosity or mny voids were formed on the uncoted PI-zeolite mixed mtrix membrne s shown in the Figure 4. However, the selectivity vlues for uncoted net PI nd uncoted PI-zeolite t 20 wt% polymer concentrtion for ll gses were very low. These might be n indiction of the Knudsen diffusion behviour resulted in the membrne due to the presence of severe voids between zeolite prticles nd gglomertion s shown in Figure 3-b nd Figure 4. Generlly, Knudsen-diffusion controls the permetion of gs through porous membrne nd the selectivity for binry gs in Knudsen-diffusion is given by eqution s follow 1/ 2 ém Aù o = ê ú (3) ëm Bû where M A nd M B re the moleculr weights of component A nd B, respectively. Eqution 3 indicted tht Knudsen-diffusion does not offer ttrctive seprtion fctors, especilly for gses of comprble moleculr weight. The previous study of Vu et l. [13] suggested tht sedimenttion of moleculr sieve prticles usully ws cused by low viscosity of mixed mtrix slurries. As supported by the FESEM in Figure 4, the gs trnsport could occur through the submicron gps between the polymer mtrix wll nd the zeolite prticles. As the gs trnsport through those unselective voids, it hd been ssumed to be the Knudsen diffusion behviour, the permebility of CH 4 nd CO 2 becme lrger due to gs flowing through the interfce between zeolite prticles nd polymer mtrix. Moreover, the unselective voids would be functioned s pinholes tht llow ll gses molecules pss rpidly without ny selectivity. Thus, the permebility of ll gses is incresed thus reducing the gs selectivity. Hence, the selectivity of the resulted membrne ws lower thn tht of the net polymer. In this study, we investigted the effect of simple post tretment to sel the unselective void on the PI-zeolite membrne using silicone rubber. Tble 1 shows the comprison of permebility nd selectivity for tested biogs purifiction between coted nd uncoted PIzeolite membrne. From the tbulted dt obtined, it cn be observed tht the PI-zeolite mixed mtrix membrne fbricted with medium polymer concentrtion coted with silicon rubber yield low permebility nd increse the selectivity in the seprtion of CO 2 /CH 4 compred to the uncoted membrnes. The increse of selectivity from 0.99 to 7.99 might be cused by suppression Knudsen diffusion mechnism using the silicone rubber coting. This is probbly due to the defects t the outermost skin lyer hve been seled by the silicone coting. The surfce structure of the membrne ws improved by reducing the defects on the membrne surfce, hence resulting in increse selectivity nd low permebility. Therefore, the

9 gs trnsport mechnism tht dominted this coted membrnes re combintion of moleculr sieving nd solution diffusion. This phenomenon indicted tht the voids generted by the unfvourble interction between polymer nd zeolite cn be reduced using silicone rubber coting. Conclusion In this study, the polyimide-zeolite ws fbricted for mixed mtrix membrne for biogs purifiction. Bsed on the experimentl results nd nlysis, the following conclusions cn be mde. v The FESEM for the cross-sectionl nd surfce re imges of mixed mtrix membrne films indicted tht the simple post tretment such s silicone rubber coting cn be used to reduce the interfce voids between inorgnic prticles with polymer host in the fbriction of mixed mtrix membrne. v The coted PI-zeolite mixed mtrix membrnes hd incresed the CO 2 /CH 4 selectivity nd reduce permebility of methne gs. v The PI-zeolite mixed mtrix membrnes hve been potentilly pplied on the biogs purifiction References [1] Kpdi, S.S., V.K. Vijy, S.K. Rjesh, R. Prsd., Biogs scrubbing, compression nd storge: perspective nd prospectus in Indin context, Renew. Energy 30 (2005) [2] Truong, L.V.A., N. Abtzoglou., A H 2 S rective dsorption process for the purifiction of biogs prior to its use s bioenergy vector, Biomss nd Bioenergy, 29 (2005) [3] Esteves, I.A.A.C., M.S.S. Lopes, P.M.C. Nunes, J.P.B. Mot. Adsorption of nturl gs nd biogs components on ctivted crbon, Seprtion nd Purifiction Technology 62 (2008) [4] Lin, W.H., nd T.S.Chung.. Gs permebility, diffusivity, solubility, nd ging chrcteristics of 6FDA-durene polyimide membrnes, Journl of Membrne Science, 186 (2001), [5] Bker, R.W., Membrne Technology nd Applictions, McGrw-Hill, New York, (2000) pp [6] Bker, R.W., Future directions of membrne gs seprtion technology, Ind. Eng. Chem. Res. (2002), [7] Lin, H. nd B.D. Freemn Gs solubility, diffusivity nd permebility in poly(ethylene oxide), J. Membr. Sci. 239: [8] Stern, S.A., Polymers for gs seprtion: The next decde, J. Membr. Sci. 94 (1994): 1 6. [9] Robeson, L.M., Polymer membrnes for gs seprtion, Curr. Opin. Solid Stte Mter. Sci., 4(1999) [10] Robeson, L.M., Correltion of seprtion fctor versus permebility for polymeric membrnes, J. Membr. Sci. 61 (1991) [11] T.D. Kusworo, A.F. Ismil, A. Mustf, T. Mtsuur, Dependence of membrne morphology nd performnce on preprtion conditions: The sher rte effect in membrne csting, Sep. Purif. Technol. 61 (2007) [12] H.Y., Young, K. Yng,W.H. Young, nd K. Seff., Crystl structure of hydrogen sulfide sorption complex of zeolite LTA, Zeolites, 17(1996):

10 [13] Vu, D.Q., Koros, W.J. nd Miller, S.J. Mixed Mtrix Membrnes Using Crbon Moleculr Sieves I. Preprtion nd Experimentl Results, Journl of Membrne Science, 211(2003): [14] Jing, L.Y., T.S. Chung, C. Co, Z. Hung, S. Kulprthipnj, Fundmentl understnding of nno-sized zeolite distribution in the formtion of the mixed mtrix single- nd dul-lyer symmetric hollow fiber membrnes, J. Membr. Sci. 252 (2005): [15] Li, Y. Gun, H. M. Chung, T. S. Kulprthipnj, S., Effects of Novel Silne Modifiction of Zeolite Surfce on Polymer Chin Rigidifiction nd Prtil Pore Blockge in Polyethersulfone (PES) Zeolite Mixed Mtrix Membrnes. Journl of Membrne Science, 275 (2006) [16] T. Rmnthn, F.T. Fisher, R.S. Ruoff, L.C. Brinson, Amino-functionlized crbon nnotubes for binding to polymers nd biologicl system, Chem. Mter., 17 (2005) [17] Vu, D.Q., Koros, W.J. nd Miller, S.J. Mixed Mtrix Membrnes Using Crbon Moleculr Sieves I. Preprtion nd Experimentl Results, Journl of Membrne Science, 211 (2003):

Synthesis and Characterization of Polyimide-Zeolite Mixed Matrix Membrane for Biogas Purification

Synthesis and Characterization of Polyimide-Zeolite Mixed Matrix Membrane for Biogas Purification Interntionl Journl of Bsic & Applied Sciences IJBAS-IJENS Vol:10 No:01 1 Synthesis nd Chrcteriztion of Polyimide-Zeolite Mixed Mtrix Membrne for Biogs Purifiction Budiyono #,,1, T.D. Kusworo #,2, A.F.