Cobalt based catalysts on alkali-activated zeolite foams for N2O decomposition

ca alys s A icle Cobal Based Ca alys s on Alkali-Ac i a ed Zeoli e Foams o N2O Decomposi ion Zdenˇek Tišle 1, Anna Klego á2, Eliška S obodo á1,* , Jan Ša ᡠ1, Ka eˇ ina S ejco á1, Jan Kohou 1, S anisla Šlang 3, Ka eˇ ina Pacul o á2, Daily Rod íguez-Pad ón4and Roman Bulánek 5 1Unipe ol Cen e o Resea ch and Educa ion, a.s, A eál Chempa k 2838, Záluží1, 436 70 Li íno , Czech Republic; [email p o ec ed] (Z.T.); [email p o ec ed] (J.Š.); ka e ina.s ejco a@unic e.cz (K.S.); [email p o ec ed] (J.K.) 2Ins i u e o En i onmen al Technology, VSB-Technical Uni e si y o Os a a, 17. lis opadu 15/2172, 708 00 Os a a, Czech Republic; [email p o ec ed] (A.K.); [email p o ec ed] (K.P.) 3Cen e o Ma e ials and Nano echnologies, Facul y o Chemical Technology, Uni e si y o Pa dubice Nam. Cs. Legii, 530 02 Pa dubice, Czech Republic; s anisla [email p o ec ed] 4Depa amen o de Química O gánica, Campus de Rabanales, Uni e sidad de Có doba, Edi icio Ma ie Cu ie (C-3), C a Nnal IV-A, Km 396, E14014 Co doba, Spain; [email p o ec ed] 5Depa men o Physical Chemis y, Facul y o Chemical Technology, Uni e si y Pa dubice, S uden ská573, 532 10 Pa dubice, Czech Republic; [email p o ec ed] *Co espondence: eliska.s obodo a@unic e.cz Recei ed: 16 Oc obe 2020; Accep ed: 27 No embe 2020; Published: 30 No embe 2020   Abs ac : In his wo k, we s udied he e ec o alkali-ac i a ed zeoli e oams modi ica ions on p ope ies and ca aly ic ac i i y o cobal phases in he p ocess o ca aly ic decomposi ion o N 2 O. The zeoli e oam suppo s we e p epa ed by alkali ac i a ion o na u al zeoli e ollowed by acid leaching and ion exchange. The cobal ca alys s we e syn hesised by a di e en deposi ion echnique (di ec ion exchange (DIE) and incipien we ness imp egna ion (IWI) me hod o cobal on zeoli e oams. Fo compa ison, ca alys s on selec ed suppo s we e p epa ed and he p ope ies o all we e compa ed in ca aly ic es s in he pelle o m and as c ushed ca alys s o de e mine he e ec o in e nal di usion. The ca alys s and suppo s we e in de ail cha ac e ized by a a ie y o echniques. The ca alys ac i i y s ongly depended on he s uc u e o suppo and syn hesis p ocedu e o a cobal ca alys . Ion exchange me hod p o ided ac i e phase wi h highe su ace a eas and si es wi h be e educibili y, bo h o hese ac o s con ibu ed o highe N 2 O con e sions o mo e han 80% a 450 ◦ C. A la ge in luence can also be a ibu ed o he p esence o alkali me als, in pa icula , po assium, which esul ed in a modi ica ion o elec onic and acid base p ope ies o he cobal oxide phase on he ca alys su ace. The p omo ional e ec o po assium is be e educibili y o cobal species. Keywo ds: na u alzeoli e;clinop iloli e;zeoli e oam;alkaliac i a ion;cobal ca alys ;N 2 Odecomposi ion 1. In oduc ion The alkali-ac i a ed ma e ials ha e p ope ies e y simila o zeoli es bu do no o m c ys alline s uc u es. These ma e ials can be p epa ed by ac i a ing a a ie y o aluminosilica e componen s. Raw ma e ials o he p epa a ion o hese ma e ials, e.g., na u al zeoli es, mos o en occu as compac ine-g ained ocks o med by sedimen a y o olcanic ac i i y, whose main componen is zeoli e clinop iloli e, belonging o he g oup o heulandi e, accompanied by mine als om he g oup o eldspa s, clays and mica. Due o hei p ope ies, na u al zeoli es a e widely used as so ben s o wa e pu i ica ion (Cs + , Rb + and NH 4+ ) o gases (NH 3 ) [ 1 , 2 ]. They do no ha e sui able p ope ies o use in ca alysis, which equi es hei modi ica ion by p ocesses such as dealumina ion [ 3 , 4 ], desilica ion o Ca alys s 2020,10, 1398; doi:10.3390/ca al10121398 www.mdpi.com/jou nal/ca alys s Ca alys s 2020,10, 1398 2 o 21 ion exchange [ 5 ]. These modi ica ions imp o e he p ope ies in he desi ed di ec ion, e.g., inc ease he speci ic su ace a ea o educe he con en o accompanying elemen s (Fe, K, Na, Ca and Mg). The same modi ica ion p ocedu es can be used o modi y he p ope ies o zeoli e oams which, in addi ion o almos any desi ed shape (pelle s, blocks, c umb) and mac opo osi y no p esen in he o iginal zeoli e ma e ial, impa he desi ed p ope ies o he zeoli e ma e ial. Mac opo osi y is ad an ageous no only o di usion easons bu also o s uc u al easons, as his ma e ial educes weigh o ca alys /so p ion bed and hus he complexi y o he equipmen and i s obus ness equi emen s [6]. Alkali-ac i a ion o na u al zeoli e p oduces a oam ma e ial consis ing o he o iginal zeoli e (clinop iloli e) s uc u e and he N/K-A-S-H binde ma ix (Na 2 O/K 2 O-Al 2 O 3 -SiO 2 -H 2 O) ha binds he indi idual g ains o aluminosilica e componen . This binde ma ix is o med by he eac ion o he alkaline ac i a o wi h an aluminosilica e (na u al zeoli e). These ma e ials wi h he addi ional mac opo ous s uc u e a e p epa ed by alkaline ac i a ion o na u al zeoli e wi h a mixed ac i a o based on po assium hyd oxide and sodium silica e. The mac opo ous s uc u e is ob ained by oaming an ac i a ed mix u e o me al powde s (Al, Mg, Zn) [ 6 – 8 ], solu ions con aining hyd ogen pe oxide [ 8 , 9 ], silica ume o silicon powde [ 10 , 11 ]. Subsequen eac ion o hese componen s wi h he alkaline ac i a o esul s in he e olu ion o a gas which oams he ac i a ed mix u e. The oaming o he alkali-ac i a ed mix u e and ollowing pos -syn hesis modi ica ion o p epa ed ma e ials e.g., by acid leaching c ea e a well pe meable oam s uc u e o low densi y in which mic o-, meso-andmac opo esa ep esen . Acidleachingiso enused o pos -syn hesismodi ica iono zeoli es o emo e amewo k aluminium and, in he case o alkali-ac i a ed ma e ials, o he accompanying elemen s (K, Na, Ca, Fe, Mg), p esen ed in he basic zeoli e g ains o binde ma ix. This leaching o he ma e ial c ea es addi ional po osi y, which is impo an o he easie pe meabili y o oams [ 8 ]. The second op ion o pos -syn hesis modi ica ion o oams is he ion exchange (IE). This me hod is widely used o zeoli es and due o he simila i y o alkali-ac i a ed ma e ials, his echnique can also be used o he emo ing o Na and K ions o exchanging ano he ca ion [8]. Ni ous oxide (N 2 O) is conside ed as an impo an pollu an con ibu ing o he g eenhouse e ec e en hough i is no he majo con ibu o . Howe e , unlike he main con ibu o s (CO 2 and CH 4 ), i is much mo e e icien g eenhouse gas [ 12 ]. The la ges indus ial sou ces o N 2 O emissions a e was e gases om ni ic acid p oduc ion plan s in a global amoun o mo e han 400 k o N 2 O pe yea [ 12 ]. Ca aly ic decomposi ion o N 2 O can be pe o med di ec ly in he NH 3 bu ne ( empe a u e a ound 900 ◦ C, ca alys s based on oxides, spinels and pe o ski e ma e ials) o behind he bu ne , when he gas empe a u e is only 250–500 ◦ C. In addi ion o he possibili y o he mal decomposi ion o N 2 O (by inc easing he gas empe a u e o 750–1000 ◦ C), non-selec i e o selec i e ca aly ic educ ion o N2O ( equi ing he addi ion o educing agen s such as hyd ogen, na u al gas, LPG, NH3, e c.) is he mos economically ad an ageous di ec ca aly ic decomposi ion o N 2 O. The low- empe a u e ca aly ic decomposi ion o N 2 O (up o 450 ◦ C) o ni ogen and oxygen o e s an a ac i e way o dec ease N 2 O emissions in ail gas om ni ic acid p oduc ion plan s. Resul s om a numbe o ca aly ic sys ems ha e been published. Fo example, ca alys s based on ansi ion me als (Cu, Co, Ni, Fe) o ca alys s based on p ecious me als (Rh, Ru, Pd) using a ious ca alys suppo s (ZnO, CeO 2 , Al 2 O 3 , TiO 2 , Z O 2 , zeoli es, hyd o alci es and pe o ski es). This s udy is ocused on cobal -based ca alys s ha show excellen ca aly ic ac i i ies a low empe a u e (≤450 ◦C) in he decomposi ion o N2O [12–30]. Ca alys s based on syn he ic zeoli es a e success ully used and s udied in a numbe o ca aly ic applica ions including ca aly ic decomposi ion o ni ous oxide. Syn he ic cobal modi ied zeoli es (Be a, Y, ZSM-5, e c.) [ 31 ], e en ually modi ied by o he me als like i on o coppe [ 32 ], we e o en s udied. These ca alys s show e y good esul s in he ca aly ic decomposi ion o N 2 O, con e sions each up o 100% a 425 ◦C and gi en expe imen al condi ions [33]. The disad an age in compa ison wi h na u al zeoli es and ma e ials o med he e om, o example, alkali-ac i a ed oams, is in pa icula ha hei syn hesis is ela i ely ime-consuming and economically demanding. On he o he hand, he use o leached modi ied na u al zeoli e wi h subsequen ion exchange (IE) encoun e s some limi a ions, such as unsa is ac o y ex u al p ope ies o limi ed IE capaci y [34]. Ca alys s 2020,10, 1398 3 o 21 In addi ion o zeoli e ca alys s, o he ypes o ca alys s p epa ed, o example, by imp egna ion o o he suppo s, p ecipi a ed ca alys s o ca alys s p epa ed by o he echniques based on he p esence o spinel phases o cobal o mixed Co-Mn-Al phases a e s udied o ca aly ic N 2 O decomposi ion [11,24,27,35] . Modi ica ion o he cobal spinels wi h a small amoun o alkali me als signi ican ly inc eases he ac i i y o he ca alys , alkali me al p omo e lowe s he wo k unc ion o he cobal spinel acili a ing edox p ocesses ha occu be ween he ca alys su ace and he eac ion oxygen in e media esp oduced du ing he N 2 Odecomposi ionleading o hesigni ican inc easein heca aly ic ac i i y[ 14 , 17 , 23 , 27 , 35 – 38 ]. Syn hesiscondi ionso heCospineloxidecouldsigni ican lya ec ca aly ic p ope ies. Di e en me hods we e desc ibed o he p epa a ion o cobal oxide-based ca alys s: (co)-p ecipi a ion om cobal ni a e solu ion using di e en p ecipi a ion agen s like Na 2 CO 3 [ 20 , 39 ], K 2 CO 3 [ 40 , 41 ], (NH 4 ) 2 CO 3 [ 16 ], KOH [ 42 ] and NH 3· H 2 O, NaOH [ 39 ], by he mal ea men o cobal ni a e [ 24 , 43 , 44 ], cobal ca bona e [ 14 , 24 ] o cobal benzoa e-dihyd azina e complex [ 45 ] and by solu ion combus ion syn hesis om cobal ni a e and u ea [ 43 ]. Equally, he deposi ion o ac i e phase on sui able suppo has a signi ican impac . The e o e, he selec ion o sui able suppo could lead o mo e e icien u iliza ion o ac i e phase. I is achie ed by applying a hin ac i e laye o he suppo ma e ial. Suppo ed cobal oxide N 2 O ca alys s we e s udied mainly on di e en monoli hs [ 46 – 49 ], sie es [32,50], able s, pelle s o ex uda es [29,51] and ce amic oams [52]. The wo k aims o p epa e cobal ca alys s based on alkali-ac i a ed zeoli e oams and de e mine he in luence o ca alys suppo modi ica ions and cobal oxide loading me hod on physic-chemical p ope ies and ca aly ic ac i i y in N 2 O decomposi ion. Acid leaching and ion exchange o alkali ac i a ed zeoli e oam (AZF) we e used o p epa e ca alys suppo s, which we e subsequen ly imp egna ed wi h cobal ni a e, and a e annealing, cobal oxide ca alys s we e ob ained. The same me hod was used o p epa e compa a i e ca alys s using alumina as a suppo . The e ec o di e en p epa a ion on he p ope ies o he ac i e phase was s udied on ca alys s p epa ed by di ec ion exchange (DIE) o basic alkali ac i a ed zeoli e oam, as well as he p omo ional e ec o manganese in Co ca alys in ca aly ic decomposi ion o N 2 O. The e ec o Mn, was moni o ed in ou s udy because CoMnAl HTC 4:1:1 ca alys s a e o en epo ed o ha e e y good esul s.S udied ca aly ic ma e ials showed signi ican di e ences in he ex u al p ope ies and chemical composi ion o he ac i e phase esul ing in signi ican di e ences in ac i i y depending on he chosen modi ica ion me hod. All ca alys s we e cha ac e ized by a ious ins umen al echniques and es ed in he N 2 O ca aly ic decomposi ion in ine gas. The ob ained esul s showed he u he possible use o ca alys s based on alkali-ac i a ed zeoli e oams in ca aly ic applica ions. In he ield o indus ial ca alysis, in addi ion o he ca aly ic esul s, he ease o syn hesis, a o dabili y and he p ice o he ca alys s used a e also impo an , and he e o e, hese ma e ials ha e a lo o o e . 2. Resul s and Discussion 2.1. Cha ac e isa ion o he Ca alys s and Suppo s Zeoli e oam used as ca alys suppo was p epa ed by oaming o alkali-ac i a ed na u al zeoli e mix u e. Ob ained po ous solid oam ma e ial was pos -syn hesis modi ied (i) by acid leaching wi h 3M HCl o (ii) by ion-exchange ea men using 1M NH4NO3. As-p epa ed zeoli e oam (AA-S, Table 1) had a highe alkali me als con en han na u al zeoli es due o he use o mixed alkaline ac i a o KOH +Na 2 SiO 3 . Chemical composi ion o Al 2 O 3 can be seen in Appendix ATable A1. A pa o he alkaline ac i a o occu ed in a o m o mixed Na/K silica e, which can be seen in images om SEM equipped wi h EDS analyse as a lea -like pa icles (Figu e 1). Ion-exchange ea men o AA-S sample using NH 4 NO 3 solu ion (AA-N) educed p edominan ly con en o K and Na ca ions. A pa o K + and Na + ions was in “unchangeable posi ions” apped inside o he zeoli e and/o o he aluminosilica es amewo k [ 4 , 8 ]. Resul s o chemical composi ion analysis (Table 1) showed a no iceable e ec o HCl leaching (AA-D). HCl mos ly educed he alkali Ca alys s 2020,10, 1398 4 o 21 con en (K, Na) in addi ion o o he elemen s (Fe, Ca, Mg and especially Al), which esul ed in o highe Si/Al a io (up o 11.8 om he o iginal 5.8). Table 1. Chemical composi ion and speci ic su ace a ea o ca alys s and zeoli e oam suppo s. Sample Chemical Composi ion (w .%) Si/Al Ra io (mol/mol) Co/AM * Ra io SSA ** (m2/g) Si Al K Na Ca Fe Co Mn AA-S 33.4 5.5 7.2 2.9 2.3 0.9 - - 5.8 - 15.0 AA-N 37.8 6.3 1.6 0.3 1.7 1.1 - - 5.8 - 23.4 AA-D 42.0 3.4 1.1 0.2 0.5 0.7 - - 11.8 - 111.7 AA-S-Co 30.5 5.1 6.6 2.6 2.1 0.9 6.4 - 5.7 0.4 13.5 AA-N-Co 35.0 6.0 1.4 0.2 1.6 1.0 5.7 - 5.6 2.1 27.7 AA-D-Co 38.7 3.5 1.1 0.2 0.4 0.7 5.4 - 10.6 2.5 49.9 AA-IE-Co 32.0 5.2 4.1 0.5 1.7 0.9 6.3 - 5.9 0.9 115.8 AA-IE-CoMn 31.9 5.2 4.2 0.5 1.7 0.9 5.4 0.8 5.9 0.7 118.6 * AM =alkali me als (Na +K), ** SSA =speci ic su ace a ea (BET). Ca alys s 2020, 10, x FOR PEER REVIEW 4 o 22 Na) in addi ion o o he elemen s (Fe, Ca, Mg and especially Al), which esul ed in o highe Si/Al a io (up o 11.8 om he o iginal 5.8). Figu e 1. Mac opo ous s uc u e o zeoli e oam AA-S (a), c ys alline Na/K silica e (whi e a ow) in AA- S (b) and lea es o Na/K silica es in AA-S-Co ca alys (c). Table 1. Chemical composi ion and speci ic su ace a ea o ca alys s and zeoli e oam suppo s. Sample Chemical Composi ion (w .%) Si/Al Ra io (mol/mol) Co/AM * Ra io SSA ** (m2/g) Si Al K Na Ca Fe Co Mn AA-S 33.4 5.5 7.2 2.9 2.3 0.9 - - 5.8 - 15.0 AA-N 37.8 6.3 1.6 0.3 1.7 1.1 - - 5.8 - 23.4 AA-D 42.0 3.4 1.1 0.2 0.5 0.7 - - 11.8 - 111.7 AA-S-Co 30.5 5.1 6.6 2.6 2.1 0.9 6.4 - 5.7 0.4 13.5 AA-N-Co 35.0 6.0 1.4 0.2 1.6 1.0 5.7 - 5.6 2.1 27.7 AA-D-Co 38.7 3.5 1.1 0.2 0.4 0.7 5.4 - 10.6 2.5 49.9 AA-IE-Co 32.0 5.2 4.1 0.5 1.7 0.9 6.3 - 5.9 0.9 115.8 AA-IE-CoMn 31.9 5.2 4.2 0.5 1.7 0.9 5.4 0.8 5.9 0.7 118.6 * AM = alkali me als (Na + K), ** SSA = speci ic su ace a ea (BET). These h ee ypes o suppo based on zeoli e oams (AA-S, AA-N, AA-D) and one comme cial suppo s (γ- Al2O3) we e used o p epa e cobal ca alys s wi h 5 w .% Co con en . The ac ual cobal con en anged om 4.8 o 6.4 w .%, as de e mined by XRF he sligh ly highe cobal con en was due o he non-s oichiome ic wa e con en o he cobal ni a e hyd a e. The las wo ca alys s es ed (AA- IE-Co and AA-IE-CoMn) we e p epa ed by a di ec ion-exchange me hod using a solu ion o cobal ni a e, and mix u e o cobal ni a e wi h manganese ni a e, espec i ely. The cobal con en o AA-IE-Co ca alys s was 6.3 w .% and he cobal con en o he AA-IE-CoMn ca alys was 5.4 w .% and manganese 0.8 w .%, espec i ely. The cobal con en was a e age o he whole pelle , so he cobal con en in he ac i e laye o AA-IE-Co ca alys is highe han 6.3 w .% ( heo e ically up o abou 13 w .% o abou up 11 w .% o AA-IE-CoMn ca alys ). The mola a io o Co/Mn is 6.5:1, he di e ence compa ed o he a ge a io (Co/Mn 4:1) is due o he di e en cou se o p ecipi a ion o Co and Mn ions du ing he o ma ion o he laye in he pelle . Ca alys s p epa ed using his me hod had a signi ican ly highe con en o po assium and sligh ly highe con en o sodium in compa ison wi h a ca alys imp egna ed on AA-N suppo . This showed ha cobal p ecipi a ion p ecluded comple e ion-exchange o Na+ and K+ ions by Co2+ ion. Highe Na and K con en s we e obse ed only o he AA-S-Co ca alys , bu he alkalis we e p esen he e in he o m o Na/K silica es. As Table 1 shows, he p esence o hese componen s had a e y nega i e e ec on he speci ic su ace a ea (SSA) because he silica es closed he po es. Addi ionally, due o po e opening and cleaning, he e was also an inc ease in speci ic su ace a ea (SSA) wo imes o (AA-N) and mo e han se en imes o AA-D. SSA o ca alys s did no change signi ican ly compa e o o iginal suppo s. The dec ease o SSA was obse ed only o alumina and AA-D suppo ed ca alys , which could ha e been caused by pa ially blocking he po es wi h cobal , mo e p ecisely, i s oxide. This dec ease in AA-D was ela ed o blockade o clinop iloli e mic opo es which ha e been eleased by acid leaching [4,8]. The ca alys s AA-IE-Co and AA-IE-CoMn p epa ed in his way exhibi ela i ely high speci ic su ace (SSA) a eas compa ed o ca alys s employing di e en ly modi ied zeoli e oam suppo s (Table 1). This was p obably pa ially caused by c ) Figu e 1. Mac opo ous s uc u e o zeoli e oam AA-S ( a ), c ys alline Na/K silica e (whi e a ow) in AA-S (b) and lea es o Na/K silica es in AA-S-Co ca alys (c). These h ee ypes o suppo based on zeoli e oams (AA-S, AA-N, AA-D) and one comme cial suppo s ( γ - Al 2 O 3 ) we e used o p epa e cobal ca alys s wi h 5 w .% Co con en . The ac ual cobal con en anged om 4.8 o 6.4 w .%, as de e mined by XRF he sligh ly highe cobal con en was due o he non-s oichiome ic wa e con en o he cobal ni a e hyd a e. The las wo ca alys s es ed (AA-IE-Co and AA-IE-CoMn) we e p epa ed by a di ec ion-exchange me hod using a solu ion o cobal ni a e, and mix u e o cobal ni a e wi h manganese ni a e, espec i ely. The cobal con en o AA-IE-Co ca alys s was 6.3 w .% and he cobal con en o he AA-IE-CoMn ca alys was 5.4 w .% and manganese 0.8 w .%, espec i ely. The cobal con en was a e age o he whole pelle , so he cobal con en in he ac i e laye o AA-IE-Co ca alys is highe han 6.3 w .% ( heo e ically up o abou 13 w .% o abou up 11 w .% o AA-IE-CoMn ca alys ). The mola a io o Co/Mn is 6.5:1, he di e ence compa ed o he a ge a io (Co/Mn 4:1) is due o he di e en cou se o p ecipi a ion o Co and Mn ions du ing he o ma ion o he laye in he pelle . Ca alys s p epa ed using his me hod had a signi ican ly highe con en o po assium and sligh ly highe con en o sodium in compa ison wi h a ca alys imp egna ed on AA-N suppo . This showed ha cobal p ecipi a ion p ecluded comple e ion-exchange o Na + and K + ions by Co 2+ ion. Highe Na and K con en s we e obse ed only o he AA-S-Co ca alys , bu he alkalis we e p esen he e in he o m o Na/K silica es. As Table 1 shows, he p esence o hese componen s had a e y nega i e e ec on he speci ic su ace a ea (SSA) because he silica es closed he po es. Addi ionally, due o po e opening and cleaning, he e was also an inc ease in speci ic su ace a ea (SSA) wo imes o (AA-N) and mo e han se en imes o AA-D. SSA o ca alys s did no change signi ican ly compa e o o iginal suppo s. The dec ease o SSA was obse ed only o alumina and AA-D suppo ed ca alys , which could ha e been caused by pa ially blocking he po es wi h cobal , mo e p ecisely, i s oxide. This dec ease in AA-D was ela ed o blockade o clinop iloli e mic opo es which ha e been eleased by acid leaching [ 4 , 8 ]. The ca alys s Ca alys s 2020,10, 1398 5 o 21 AA-IE-Co and AA-IE-CoMn p epa ed in his way exhibi ela i ely high speci ic su ace (SSA) a eas compa ed o ca alys s employing di e en ly modi ied zeoli e oam suppo s (Table 1). This was p obably pa ially caused by he o ma ion o po ous cobal and cobal -manganese oxides o igina ing om p ecipi a ed hyd oxides on he zeoli e oam su ace, o by pa ial cleaning o he zeoli e oam su ace (an inc ease o c ys allini y o in ensi y espec i ely was obse ed, Figu e 2) and accessibili y o po es. The inc ease in he su ace a ea has no ye been sa is ac o ily explained bu has been e i ied by epea ed measu emen s. Ru kowska [ 53 ] s a es ha he inc ease in su ace a ea o he samples (Cu, Fe and Co be a zeoli es) could be ela ed o he seconda y ec ys alliza ion o zeoli es du ing he p epa a ion o ca alys s. In his case, i could also be caused by changes in he binde N/K-A-S-H phase o by he gene a ion o addi ional po osi y be ween he cobal and manganese hyd oxides deposi ed on he sample su ace. Ca alys s 2020, 10, x FOR PEER REVIEW 5 o 22 he o ma ion o po ous cobal and cobal -manganese oxides o igina ing om p ecipi a ed hyd oxides on he zeoli e oam su ace, o by pa ial cleaning o he zeoli e oam su ace (an inc ease o c ys allini y o in ensi y espec i ely was obse ed, Figu e 2) and accessibili y o po es. The inc ease in he su ace a ea has no ye been sa is ac o ily explained bu has been e i ied by epea ed measu emen s. Ru kowska [53] s a es ha he inc ease in su ace a ea o he samples (Cu, Fe and Co be a zeoli es) could be ela ed o he seconda y ec ys alliza ion o zeoli es du ing he p epa a ion o ca alys s. In his case, i could also be caused by changes in he binde N/K-A-S-H phase o by he gene a ion o addi ional po osi y be ween he cobal and manganese hyd oxides deposi ed on he sample su ace. Since he samples a e p edominan ly mac opo ous ma e ials, ex u es o ca aly ic suppo s and p epa ed ca alys s we e de e mined ia Hg po osime y. The ob ained esul s (Figu e 2) showed ha o he suppo s con ain p edominan ly bigge po es. Zeoli e oams ha e b oad po e spec um om mesopo es o mac opo es o supe mac opo es wi h a diame e o en hs o hund eds o mic ome es wi h co esponding po e mean size housands nm. To al in usion olume o zeoli e oams a ies om 0.65 (AA-S) o 0.75 mL/g (AA-D). In usion olume o hei “mesopo es” is om 0.06 mL/g (AA-S), 0.07 mL/g (AA-N) o 0.09 mL/g (AA-D). Inc ease in o al in usion olume and sha e o AA-D suppo mesopo es was caused by cleansing he su ace om he excess alkali ac i a o and mine al sedimen s inside he po es o na u al zeoli e. In he case o cobal ca alys s as well o used ca alys s (a e ca aly ic eac ion o N2O decomposi ion), he e we e no big changes (dec eases) obse ed in in usion olume. Changes we e only due o blocking he po es wi h cobal oxide. In con as , an inc ease o he mesopo e olume was obse ed in AA-IE-Co and AA-IE-CoMn ca alys s (bo h 0.09 mL/g), which can be a ibu ed o cobal oxides o med du ing he ca alys syn hesis. Alumina as compa a i e suppo is pu ely mesopo ous ma e ial wi h he o e all in usion olume o 0.5 mL/g and mean po e diame e 5.6 nm, Co-Al2O3 ca alys shows a pa ial educ ion in in usion olume due o cobal oxides deposi ed on he su ace (Appendix A Figu e A1). Figu e 2. Po e dis ibu ion o suppo s, esh and used cobal ca alys s. SEM-EDS mapping o ca alys pelle c oss-sec ion (Figu e 3) showed iden ical mac opo ous s uc u e o he ca alys s (e e y i s igu e in he ow) and homogeneous dis ibu ion o cobal on he Figu e 2. Po e dis ibu ion o suppo s, esh and used cobal ca alys s. Since he samples a e p edominan ly mac opo ous ma e ials, ex u es o ca aly ic suppo s and p epa ed ca alys s we e de e mined ia Hg po osime y. The ob ained esul s (Figu e 2) showed ha o he suppo s con ain p edominan ly bigge po es. Zeoli e oams ha e b oad po e spec um om mesopo es o mac opo es o supe mac opo es wi h a diame e o en hs o hund eds o mic ome es wi h co esponding po e mean size housands nm. To al in usion olume o zeoli e oams a ies om 0.65 (AA-S) o 0.75 mL/g (AA-D). In usion olume o hei “mesopo es” is om 0.06 mL/g (AA-S), 0.07 mL/g (AA-N) o 0.09 mL/g (AA-D). Inc ease in o al in usion olume and sha e o AA-D suppo mesopo es was caused by cleansing he su ace om he excess alkali ac i a o and mine al sedimen s inside he po es o na u al zeoli e. In he case o cobal ca alys s as well o used ca alys s (a e ca aly ic eac ion o N 2 O decomposi ion), he e we e no big changes (dec eases) obse ed in in usion olume. Changes we e only due o blocking he po es wi h cobal oxide. In con as , an inc ease o he mesopo e olume was obse ed in AA-IE-Co and AA-IE-CoMn ca alys s (bo h 0.09 mL/g), which can be a ibu ed o cobal oxides o med du ing he ca alys syn hesis. Alumina as compa a i e suppo is pu ely mesopo ous ma e ial wi h he o e all in usion olume o 0.5 mL/g and mean po e diame e Ca alys s 2020,10, 1398 6 o 21 5.6 nm, Co-Al 2 O 3 ca alys shows a pa ial educ ion in in usion olume due o cobal oxides deposi ed on he su ace (Appendix AFigu e A1). SEM-EDS mapping o ca alys pelle c oss-sec ion (Figu e 3) showed iden ical mac opo ous s uc u e o he ca alys s (e e y i s igu e in he ow) and homogeneous dis ibu ion o cobal on he su ace o he modi ied zeoli e oam ca alys suppo in he case o AA-N-Co and AA-D-Co ca alys s (Figu e 3b,c). In case o imp egna ion o he AA-S suppo (Figu e 3a), an a ea non-co e ed by cobal was obse able in he middle o he pelle , which could be caused by p ecipi a ion o cobal hyd oxide du ing imp egna ion p ocess by alkali agen s in he zeoli e oam. This as-c ea ed laye was blocking u he imp egna ion inside he pelle . Ce ainly, his will also be a ec ed by he inhomogenei y o he pelle s caused by he syn hesis me hod used. A simila e ec was obse ed du ing p epa a ions ia he di ec ion-exchange me hod. As can be seen in Figu e 3d,e cobal was obse ed only on he ou e su ace o he pelle in he o m o a ing. The dep h o cobal pene a ion eached app oxima ely 0.7 mm. The di e ence in dep h compa ed o AA-S-Co was due o di e en ca alys p epa a ion condi ions (solu ion concen a ion, empe a u e, e c.). Manganese dis ibu ion showed a decline in con en om he su ace o he co e, bu in compa ison wi h cobal , he e was no a s ong bo de line. The e was a signi ican decline in con en o sodium and po assium (obse able om g ey and yellow colou in ensi y on Figu e 3) in he ollowing o de : AA-S-Co, AA-IE-Co/AA-IE-CoMn, AA-N-Co and AA-D-Co and dis ibu ion in he whole c oss-sec ion is in ag eemen wi h esul s o chemical analysis (XRF). Ca alys s 2020, 10, x FOR PEER REVIEW 6 o 22 su ace o he modi ied zeoli e oam ca alys suppo in he case o AA-N-Co and AA-D-Co ca alys s (Figu e 3b,c). In case o imp egna ion o he AA-S suppo (Figu e 3a), an a ea non-co e ed by cobal was obse able in he middle o he pelle , which could be caused by p ecipi a ion o cobal hyd oxide du ing imp egna ion p ocess by alkali agen s in he zeoli e oam. This as-c ea ed laye was blocking u he imp egna ion inside he pelle . Ce ainly, his will also be a ec ed by he inhomogenei y o he pelle s caused by he syn hesis me hod used. A simila e ec was obse ed du ing p epa a ions ia he di ec ion-exchange me hod. As can be seen in Figu e 3d,e cobal was obse ed only on he ou e su ace o he pelle in he o m o a ing. The dep h o cobal pene a ion eached app oxima ely 0.7 mm. The di e ence in dep h compa ed o AA-S-Co was due o di e en ca alys p epa a ion condi ions (solu ion concen a ion, empe a u e, e c.). Manganese dis ibu ion showed a decline in con en om he su ace o he co e, bu in compa ison wi h cobal , he e was no a s ong bo de line. The e was a signi ican decline in con en o sodium and po assium (obse able om g ey and yellow colou in ensi y on Figu e 3) in he ollowing o de : AA-S-Co, AA-IE-Co/AA-IE-CoMn, AA-N-Co and AA-D-Co and dis ibu ion in he whole c oss-sec ion is in ag eemen wi h esul s o chemical analysis (XRF). Figu e 3. SEM-EDS elemen al mapping o sodium (g ay), po assium (yellow), cobal (g een) and manganese (b own) on c oss sec ion a ea o AA-S-Co (a), AA-N-Co (b), AA-D-Co (c), AA-IE-Co (d) and AA-IE-CoMn (e) ca alys s. The c ys alline s uc u e o ma e ials was de e mined using X- ay powde di ac ion (XRD). In case o zeoli e oam suppo ed ca alys s, he analysis showed clinop iloli e o be a main c ys alline phase Figu e 3. SEM-EDS elemen al mapping o sodium (g ay), po assium (yellow), cobal (g een) and manganese (b own) on c oss sec ion a ea o AA-S-Co ( a ), AA-N-Co ( b ), AA-D-Co ( c ), AA-IE-Co ( d ) and AA-IE-CoMn (e) ca alys s. Ca alys s 2020,10, 1398 7 o 21 The c ys alline s uc u e o ma e ials was de e mined using X- ay powde di ac ion (XRD). In case o zeoli e oam suppo ed ca alys s, he analysis showed clinop iloli e o be a main c ys alline phase wi h ypical e lec ions a 2 he a 9.9 ◦ , 11.2 ◦ , 17.5 ◦ and 22.4 ◦ (PDF 83-1261) along wi h o he mino phases in he na u al zeoli e, belonging o he mine alogic g oup o clays and eldspa s (Figu e 4a). Thedi ac og amsshowed hedi e ence in c ys allini y o in ensi ies o main e lec ionso clinop iloli e espec i ely depending on he modi ica ion me hod used. The c ys allini y o alkali-ac i a ed ma e ial was lowe in compa ison wi h he o iginal na u al zeoli e [ 8 ]. This may be caused by a pa ial s uc u e dis up ion du ing he alkaline ac i a ion. The e was a signi ican inc ease in c ys allini y a e IE using NH 4 NO 3 caused by su ace cleansing. In con as , a e leaching wi h 3M HCl, he e was a dec ease in c ys allini y connec ed wi h dis up ion o he zeoli e s uc u e due o emo ing Al om he clinop iloli e c ys alline ma ix. Du ing he modi ica ion p ocess, he e was a change in in ensi ies a 2 he a 11.2 ◦ /9.9 ◦ ha co esponded o planes (020) and (200), caused by he di e ence in elec on densi y in ha plane. F om he o iginal a io 0.5 in he na u al zeoli e, he alue inc eases a e alkali-ac i a ion o 0.8 and a e leaching wi h HCl o IE ea men , i dec eases o 0.4 [ 8 ]. Compa a i e ca alys s showed ypical b oad e lec ions o γ-Al2O3(2 he a 46.5◦and 67.3◦, PDF 74-2206) (Appendix AFigu e A2). Ca alys s 2020, 10, x FOR PEER REVIEW 7 o 22 wi h ypical e lec ions a 2 he a 9.9°, 11.2°, 17.5° and 22.4° (PDF 83-1261) along wi h o he mino phases in he na u al zeoli e, belonging o he mine alogic g oup o clays and eldspa s (Figu e 4a). The di ac og ams showed he di e ence in c ys allini y o in ensi ies o main e lec ions o clinop iloli e espec i ely depending on he modi ica ion me hod used. The c ys allini y o alkali-ac i a ed ma e ial was lowe in compa ison wi h he o iginal na u al zeoli e [8]. This may be caused by a pa ial s uc u e dis up ion du ing he alkaline ac i a ion. The e was a signi ican inc ease in c ys allini y a e IE using NH4NO3 caused by su ace cleansing. In con as , a e leaching wi h 3M HCl, he e was a dec ease in c ys allini y connec ed wi h dis up ion o he zeoli e s uc u e due o emo ing Al om he clinop iloli e c ys alline ma ix. Du ing he modi ica ion p ocess, he e was a change in in ensi ies a 2 he a 11.2°/9.9° ha co esponded o planes (020) and (200), caused by he di e ence in elec on densi y in ha plane. F om he o iginal a io 0.5 in he na u al zeoli e, he alue inc eases a e alkali-ac i a ion o 0.8 and a e leaching wi h HCl o IE ea men , i dec eases o 0.4 [8]. Compa a i e ca alys s showed ypical b oad e lec ions o γ-Al2O3 (2 he a 46.5° and 67.3°, PDF 74-2206) (Appendix A Figu e A2). Figu e 4. Powde di ac ion pa e ns o suppo s (a) and esh ca alys s (b). Cobal ca alys s p epa ed using hese suppo s showed signi ican c ys alline s uc u es co esponding o Co3O4 (2 he a 31.5°, 36.9°, 45.0°, 55.7°, 59.6° and 65.6°, PDF 65-3103). These we e he mos appa en in case o using alumina as suppo (Appendix A Figu e A2). In case o o he suppo s (Figu e 4b), he e was only one e lec ion isible (36.9° 2 he a), while AA-D suppo ed ca alys s showed he e lec ions co esponding o clinop iloli e (2 he a 9.9° and 11.2°) and o he mino phases (clays and eldspa s) wi h no signi ican in ensi ies co esponding o cobal oxide. This indica ed homogeneous dis ibu ion o cobal on he su ace wi hou he o ma ion o a c ys alline Co3O4 phase. C ys alli e size o Co3O4 calcula ed using he Sche e equa ion om he e lec ion 36.9° 2 he a is 12 nm o ca alys s wi h alumina suppo . I was no possible o e alua e he c ys alli e size in o he ca alys s due o o e lap o cobal oxide di ac ion wi h line assigned o he clinop iloli e, qua z o ano hi e. Analysis o he used ca alys s (Appendix A Figu e A3), samples labelled wi h addi ional –U, ca alys s a e hei usage o N2O decomposi ion es ) did no show any signi ican changes in he c ys alline s uc u e compa ed wi h esh ca alys s. Powde di ac ion pa e ns o Al2O3 can be seen in Appendix A Figu e A2. A e using he ca alys s in he eac ion es only sligh dec eases in in ensi y a e no iceable. Only in he case o he AA-D-Co-U ca alys , he e was a signi ican dec ease in in ensi ies 2 he a 27.8°, 28.0° and o he s co esponding o ano hi e (PDF 71-0748). Tempe a u e-p og ammed ammonia deso p ion (NH3-TPD) showed signi ican di e ences in he amoun and s eng h o acid si es (Figu e 5a) o each ca alys (Table 2). While he ca alys suppo ed on indus ial suppo (Al2O3-Co) showed low acidi y (Appendix A Table A2, Figu e A4a), he zeoli e oam suppo ed ca alys s showed changes in acidi y depending on he suppo modi ica ion me hod du ing ca alys p epa a ion. In gene al, peaks a low empe a u es, below 200 °C a e a ibu ed o weakly acidic si es o physiso bed ammonia, and peaks a highe empe a u es in he ange o 200–400 °C a e associa ed wi h he in e ac ion o NH3 wi h acidic B øns ed si es a ibu ed o s ongly acidic si es. Peaks Figu e 4. Powde di ac ion pa e ns o suppo s (a) and esh ca alys s (b). Cobal ca alys s p epa ed using hese suppo s showed signi ican c ys alline s uc u es co esponding o Co 3 O 4 (2 he a 31.5 ◦ , 36.9 ◦ , 45.0 ◦ , 55.7 ◦ , 59.6 ◦ and 65.6 ◦ , PDF 65-3103). These we e he mos appa en in case o using alumina as suppo (Appendix AFigu e A2). In case o o he suppo s (Figu e 4b), he e was only one e lec ion isible (36.9 ◦ 2 he a), while AA-D suppo ed ca alys s showed he e lec ions co esponding o clinop iloli e (2 he a 9.9 ◦ and 11.2 ◦ ) and o he mino phases (clays and eldspa s) wi h no signi ican in ensi ies co esponding o cobal oxide. This indica ed homogeneous dis ibu ion o cobal on he su ace wi hou he o ma ion o a c ys alline Co 3 O 4 phase. C ys alli e size o Co 3 O 4 calcula ed using he Sche e equa ion om he e lec ion 36.9 ◦ 2 he a is 12 nm o ca alys s wi h alumina suppo . I was no possible o e alua e he c ys alli e size in o he ca alys s due o o e lap o cobal oxide di ac ion wi h line assigned o he clinop iloli e, qua z o ano hi e. Analysis o he used ca alys s (Appendix AFigu e A3), samples labelled wi h addi ional –U, ca alys s a e hei usage o N 2 O decomposi ion es ) did no show any signi ican changes in he c ys alline s uc u e compa ed wi h esh ca alys s. Powde di ac ion pa e ns o Al 2 O 3 can be seen in Appendix AFigu e A2. A e using he ca alys s in he eac ion es only sligh dec eases in in ensi y a e no iceable. Only in he case o he AA-D-Co-U ca alys , he e was a signi ican dec ease in in ensi ies 2 he a 27.8◦, 28.0◦and o he s co esponding o ano hi e (PDF 71-0748). Tempe a u e-p og ammed ammonia deso p ion (NH 3 -TPD) showed signi ican di e ences in he amoun and s eng h o acid si es (Figu e 5a) o each ca alys (Table 2). While he ca alys suppo ed on indus ial suppo (Al 2 O 3 -Co) showed low acidi y (Appendix ATable A2, Figu e A4a), he zeoli e oam suppo ed ca alys s showed changes in acidi y depending on he suppo modi ica ion me hod du ing ca alys p epa a ion. In gene al, peaks a low empe a u es, below 200 ◦ C a e a ibu ed o weakly Ca alys s 2020,10, 1398 8 o 21 acidic si es o physiso bed ammonia, and peaks a highe empe a u es in he ange o 200–400 ◦ C a e associa ed wi h he in e ac ion o NH 3 wi h acidic B øns ed si es a ibu ed o s ongly acidic si es. Peaks a empe a u es abo e 400 ◦ C co espond o he in e ac ion o NH 3 wi h Lewis acids and a e a ibu ed o Co-O species ha o m e y s ongly acidic si es [54–56] Ca alys s 2020, 10, x FOR PEER REVIEW 8 o 22 a empe a u es abo e 400 °C co espond o he in e ac ion o NH3 wi h Lewis acids and a e a ibu ed o Co-O species ha o m e y s ongly acidic si es [54–56] The highes o al acidi y exhibi ed ca alys p epa ed ia imp egna ion o ion-exchange modi ied suppo (AA-N-Co), which con ained a high popula ion o s ong acid si es, i.e., si es wi h high NH3 deso p ion empe a u e. The acidi y o AA-S-Co and AA-D-Co ca alys s is abou one- hi d in compa ison and e y simila o each o he , which is p obably due o poo a ailabili y o acid si es in he base zeoli e–clinop iloli e o AA-S-Co and in case o AA-D-Co due o acid cen e emo al du ing acid leaching. Samples p epa ed using di ec ion-exchange ea men showed sligh ly lowe acidi y han AA-N-Co, bu no s ong acid si es. Table 2. Acidi y o cobal ca alys s de e mined by ammonia TPD. Sample cSUM (μmol/g) Tmax1 (°C) cmax1 (μmol/g) Pmax1 * (%) Tmax2 (°C) cmax2 (μmol/g) Pmax2 * (%) Tmax3 (°C) cmax3 (μmol/g) Pmax3 * (%) AA-S-Co 501 175 501 100 - - - - - - AA-N-Co 1542 173 1313 85 390 229 15 - - - AA-D-Co 593 158 446 75 255 70 12 382 77 13 AA-IE-Co 1446 178 1379 95 247 27 2 362 40 3 AA-IE-MnCo 1211 187 1211 100 - - - - - - * P = popula ion o he ele an si es, index 1– i s decon olu ion peak, 2–second decon olu ion peak and 3– hi d decon olu ion peak. Figu e 5. Acidi y (a) and basici y (b) o cobal ca alys s de e mined by NH3-TPD and CO2-TPD, espec i ely. The basici y o he ca alys s was de e mined by empe a u e p og ammed deso p ion o CO2 (CO2- TPD). The da a ob ained (Table 3, Figu e 5b) showed signi ican low empe a u e peaks a ound 110 °C o ion-exchange ea ed (AA-N-Co) ca alys , di ec ion-exchange ea ed (AA-IE-Co and AA-IE-CoMn) ca alys s and a simila maximum is also obse ed o he Al2O3-Co ca alys (Appendix A Table A3, Figu e A4b). The basici y is ela ed o he alkali con en , i.e., alkali me als (Na + K) in he sample (Table 3). The AA-S-Co ca alys had he highes alkali con en , bu a la ge pa o he alkali me als was inaccessible o he in e ac ion ( hey we e enclosed in he binde N(A)-A-S-H phase), while in he case o AA-IE-Co and AA-IE-CoMn ca alys s which had also highe SSA, alkali me als we e mo e a ailable and he samples showed high o e all basici y, especially also he con en o weakly basic si es. On he o he hand, he basici y o he samples may also be ela ed o he adso p ion o CO2 on he pola adso p ion cen es, i.e., on all coo dina ion unsa u a ed ca ions p esen in he sample. Figu e 5. Acidi y ( a ) and basici y ( b ) o cobal ca alys s de e mined by NH 3 -TPD and CO2-TPD, espec i ely. Table 2. Acidi y o cobal ca alys s de e mined by ammonia TPD. Sample cSUM (µmol/g) Tmax1 (◦C) cmax1 (µmol/g) Pmax1 * (%) Tmax2 (◦C) cmax2 (µmol/g) Pmax2 * (%) Tmax3 (◦C) cmax3 (µmol/g) Pmax3 * (%) AA-S-Co 501 175 501 100 - - - - - - AA-N-Co 1542 173 1313 85 390 229 15 - - - AA-D-Co 593 158 446 75 255 70 12 382 77 13 AA-IE-Co 1446 178 1379 95 247 27 2 362 40 3 AA-IE-MnCo 1211 187 1211 100 - - - - - - * P =popula ion o he ele an si es, index 1– i s decon olu ion peak, 2–second decon olu ion peak and 3– hi d decon olu ion peak. The highes o al acidi y exhibi ed ca alys p epa ed ia imp egna ion o ion-exchange modi ied suppo (AA-N-Co), which con ained a high popula ion o s ong acid si es, i.e., si es wi h high NH 3 deso p ion empe a u e. The acidi y o AA-S-Co and AA-D-Co ca alys s is abou one- hi d in compa ison and e y simila o each o he , which is p obably due o poo a ailabili y o acid si es in he base zeoli e–clinop iloli e o AA-S-Co and in case o AA-D-Co due o acid cen e emo al du ing acid leaching. Samples p epa ed using di ec ion-exchange ea men showed sligh ly lowe acidi y han AA-N-Co, bu no s ong acid si es. The basici y o he ca alys s was de e mined by empe a u e p og ammed deso p ion o CO 2 (CO 2 -TPD). The da a ob ained (Table 3, Figu e 5b) showed signi ican low empe a u e peaks a ound 110 ◦ C o ion-exchange ea ed (AA-N-Co) ca alys , di ec ion-exchange ea ed (AA-IE-Co and AA-IE-CoMn) ca alys s and a simila maximum is also obse ed o he Al 2 O 3 -Co ca alys (Appendix A Table A3, Figu e A4b). The basici y is ela ed o he alkali con en , i.e., alkali me als (Na +K) in he sample (Table 3). The AA-S-Co ca alys had he highes alkali con en , bu a la ge pa o he alkali me als was inaccessible o he in e ac ion ( hey we e enclosed in he binde N(A)-A-S-H phase), while in he case o AA-IE-Co and AA-IE-CoMn ca alys s which had also highe SSA, alkali me als we e mo e a ailable and he samples showed high o e all basici y, especially also he con en o weakly basic si es. On he o he hand, he basici y o he samples may also be ela ed o he adso p ion o CO 2 on he pola adso p ion cen es, i.e., on all coo dina ion unsa u a ed ca ions p esen in he sample. Ca alys s 2020,10, 1398 9 o 21 Table 3. Basici y o cobal ca alys s de e mined by CO2-TPD. Sample cSUM (µmol/g) Tmax1 (◦C) cmax1 (µmol/g) Pmax1 * (%) Tmax2 (◦C) cmax2 (µmol/g) Pmax2 * (%) Tmax3 (◦C) cmax3 (µmol/g) Pmax3 * (%) AA-S-Co 213 105 42 20 186 161 76 321 10 14 AA-N-Co 125 110 82 66 363 14 11 437 30 23 AA-D-Co 156 112 36 23 204 44 28 289 76 49 AA-IE-Co 306 111 215 70 338 91 30 - - - AA-IE-MnCo 408 113 227 56 273 181 44 - - - * P =popula ion o he ele an si es, index 1– i s decon olu ion peak, 2–second decon olu ion peak and 3– hi d decon olu ion peak. The esul s o he H 2 -TPR analysis pe o med on he ca alys pelle s show signi ican di e ences in H 2 consump ion (Table 4), which co esponds o he con en o a ious o ms o Co oxides p esen on he su ace o he ca alys suppo . Co 3 O 4 educ ion akes place in wo s eps, mos o en pa ame e s o educ ion o Co 3+ o Co 2+ a e he empe a u e ange o 250–300 ◦ C and highe han 400 ◦ C o educ ion o Co 2+ o Co 0 [ 9 , 10 ]. F om he ob ained TPR p o iles (Figu e 6) i can be seen ha he educ ion ook place in he wo s eps, bu signi ican di e ences a e obse ed o he indi idual ca alys s. The esul s o he H2-TPR analysis pe o med on he Al2O3 can be seen in Appendix ATable A4 and Figu e A5. Table 4. Reducibili y o cobal ca alys s de e mined by TPR. Sample cSUM (µmol/g) Tmax1 (◦C) cmax1 (µmol/g) Pmax1 * (%) Tmax2 (◦C) cmax2 (µmol/g) Pmax2 * (%) Tmax3 (◦C) cmax3 (µmol/g) Pmax3 * (%) AA-S-Co 360 289 77 21 330 218 61 478 65 19 AA-N-Co 875 304 704 80 483 171 20 - - - AA-D-Co 260 284 76 29 306 184 71 - - AA-IE-Co 176 222 60 34 418 116 66 - - - AA-IE-MnCo 500 239 337 67 303 163 33 - - - * P =popula ion o he ele an si es, index 1– i s decon olu ion peak, 2–second decon olu ion peak and 3– hi d decon olu ion peak. Ca alys s 2020, 10, x FOR PEER REVIEW 9 o 22 Table 3. Basici y o cobal ca alys s de e mined by CO2-TPD. Sample cSUM (μmol/g) Tmax1 (°C) cmax1 (μmol/g) Pmax1 * (%) Tmax2 (°C) cmax2 (μmol/g) Pmax2 * (%) Tmax3 (°C) cmax3 (μmol/g) Pmax3 * (%) AA-S-Co 213 105 42 20 186 161 76 321 10 14 AA-N-Co 125 110 82 66 363 14 11 437 30 23 AA-D-Co 156 112 36 23 204 44 28 289 76 49 AA-IE-Co 306 111 215 70 338 91 30 - - - AA-IE-MnCo 408 113 227 56 273 181 44 - - - * P = popula ion o he ele an si es, index 1– i s decon olu ion peak, 2–second decon olu ion peak and 3– hi d decon olu ion peak. The esul s o he H2-TPR analysis pe o med on he ca alys pelle s show signi ican di e ences in H2 consump ion (Table 4), which co esponds o he con en o a ious o ms o Co oxides p esen on he su ace o he ca alys suppo . Co3O4 educ ion akes place in wo s eps, mos o en pa ame e s o educ ion o Co3+ o Co2+ a e he empe a u e ange o 250–300 °C and highe han 400 °C o educ ion o Co2+ o Co0 [9,10]. F om he ob ained TPR p o iles (Figu e 6) i can be seen ha he educ ion ook place in he wo s eps, bu signi ican di e ences a e obse ed o he indi idual ca alys s. The esul s o he H2-TPR analysis pe o med on he Al2O3 can be seen in Appendix A Table A4 and Figu e A5. Table 4. Reducibili y o cobal ca alys s de e mined by TPR. Sample cSUM (μmol/g) Tmax1 (°C) cmax1 (μmol/g) Pmax1 * (%) Tmax2 (°C) cmax2 (μmol/g) Pmax2 * (%) Tmax3 (°C) cmax3 (μmol/g) Pmax3 * (%) AA-S-Co 360 289 77 21 330 218 61 478 65 19 AA-N-Co 875 304 704 80 483 171 20 - - - AA-D-Co 260 284 76 29 306 184 71 - - AA-IE-Co 176 222 60 34 418 116 66 - - - AA-IE-MnCo 500 239 337 67 303 163 33 - - - * P = popula ion o he ele an si es, index 1– i s decon olu ion peak, 2–second decon olu ion peak and 3– hi d decon olu ion peak. Figu e 6. H2-TPR p o iles o cobal ca alys s. The shi o he educ ion peaks may occu due o (i) he p esence o alkali [35] which gene ally lowe s empe a u es o educ ion o cobal species, o (ii) due o he in e ac ion be ween he Co3O4 spin Figu e 6. H2-TPR p o iles o cobal ca alys s. The shi o he educ ion peaks may occu due o (i) he p esence o alkali [ 35 ] which gene ally lowe s empe a u es o educ ion o cobal species, o (ii) due o he in e ac ion be ween he Co 3 O 4 spin phase and he suppo used [ 51 ]. In case o he alumina suppo ed ca alys , only one wide educ ion peak was e iden wi h wo maxima a 435 ◦ C and 479 ◦ C, indica ing cobal species in e ac ion wi h Al 2 O 3 o o m Co alumina es wi h s onge oxygen bonds ha dec ease educibili y (Appendix A Table A4, Figu e A5) [ 11 ]. The ca alys using he AA-S basic suppo exhibi ed a wide educ ion peak Ca alys s 2020,10, 1398 16 o 21 Table A2. Acidi y o cobal ca alys de e mined by ammonia TPD. Sample cSUM (µmol/g) Tmax1 (◦C) cmax1 (µmol/g) Pmax1 * (%) Tmax2 (◦C) cmax2 (µmol/g) Pmax2 * (%) Tmax3 (◦C) cmax3 (µmol/g) Pmax3 * (%) Al2O3-Co 296 173 178 60 283 118 40 - - - * P =popula ion o he ele an si es, index 1– i s decon olu ion peak, 2–second decon olu ion peak and 3– hi d decon olu ion peak. Table A3. Basici y o cobal ca alys de e mined by CO2TPD. Sample cSUM (µmol/g) Tmax1 (◦C) cmax1 (µmol/g) Pmax1 * (%) Tmax2 (◦C) cmax2 (µmol/g) Pmax2 * (%) Tmax3 (◦C) cmax3 (µmol/g) Pmax3 * (%) Al2O3-Co 145 109 31 21 144 89 61 263 25 18 * P =popula ion o he ele an si es, index 1– i s decon olu ion peak, 2–second decon olu ion peak and 3– hi d decon olu ion peak. Table A4. Reducibili y o cobal ca alys de e mined by TPR. Sample cSUM (µmol/g) Tmax1 (◦C) cmax1 (µmol/g) Pmax1 * (%) Tmax2 (◦C) cmax2 (µmol/g) Pmax2 * (%) Tmax3 (◦C) cmax3 (µmol/g) Pmax3 * (%) Al2O3-Co 109 - - - 435 85 80 479 24 20 * P =popula ion o he ele an si es, index 1– i s decon olu ion peak, 2–second decon olu ion peak and 3– hi d decon olu ion peak. Ca alys s 2020, 10, x FOR PEER REVIEW 16 o 22 Table A2. Acidi y o cobal ca alys de e mined by ammonia TPD. Sample cSUM (μmol/g) Tmax1 (°C) cmax1 (μmol/g) Pmax1 * (%) Tmax2 (°C) cmax2 (μmol/g) Pmax2 * (%) Tmax3 (°C) cmax3 (μmol/g) Pmax3 * (%) Al2O3-Co 296 173 178 60 283 118 40 - - - * P = popula ion o he ele an si es, index 1– i s decon olu ion peak, 2–second decon olu ion peak and 3– hi d decon olu ion peak. Table A3. Basici y o cobal ca alys de e mined by CO2 TPD. Sample cSUM (μmol/g) Tmax1 (°C) cmax1 (μmol/g) Pmax1 * (%) Tmax2 (°C) cmax2 (μmol/g) Pmax2 * (%) Tmax3 (°C) cmax3 (μmol/g) Pmax3 * (%) Al2O3-Co 145 109 31 21 144 89 61 263 25 18 * P = popula ion o he ele an si es, index 1– i s decon olu ion peak, 2–second decon olu ion peak and 3– hi d decon olu ion peak. Table A4. Reducibili y o cobal ca alys de e mined by TPR. Sample cSUM (μmol/g) Tmax1 (°C) cmax1 (μmol/g) Pmax1 * (%) Tmax2 (°C) cmax2 (μmol/g) Pmax2 * (%) Tmax3 (°C) cmax3 (μmol/g) Pmax3 * (%) Al2O3-Co 109 - - - 435 85 80 479 24 20 * P = popula ion o he ele an si es, index 1– i s decon olu ion peak, 2–second decon olu ion peak and 3– hi d decon olu ion peak. Figu e A1. Po e dis ibu ion o Al2O3 suppo , esh and used cobal ca alys . Figu e A1. Po e dis ibu ion o Al2O3suppo , esh and used cobal ca alys . Ca alys s 2020,10, 1398 17 o 21 Ca alys s 2020, 10, x FOR PEER REVIEW 17 o 22 Figu e A2. Powde di ac ion pa e ns o Al2O3 suppo , esh and used cobal ca alys . Figu e A3. Powde di ac ion pa e ns o used cobal ca alys s. Figu e A2. Powde di ac ion pa e ns o Al2O3suppo , esh and used cobal ca alys . Ca alys s 2020, 10, x FOR PEER REVIEW 17 o 22 Figu e A2. Powde di ac ion pa e ns o Al2O3 suppo , esh and used cobal ca alys . Figu e A3. Powde di ac ion pa e ns o used cobal ca alys s. Figu e A3. Powde di ac ion pa e ns o used cobal ca alys s. Ca alys s 2020, 10, x FOR PEER REVIEW 18 o 22 Figu e A4. Acidi y (a) and basici y (b) o Al2O3 cobal ca alys de e mined by NH3-TPD and CO2-TPD, espec i ely. Figu e A5. H2-TPR p o iles o Al2O3 cobal ca alys . Figu e A4. Acidi y ( a ) and basici y ( b ) o Al 2 O 3 cobal ca alys de e mined by NH 3 -TPD and CO2-TPD, espec i ely. Ca alys s 2020,10, 1398 18 o 21 Ca alys s 2020, 10, x FOR PEER REVIEW 18 o 22 Figu e A4. Acidi y (a) and basici y (b) o Al2O3 cobal ca alys de e mined by NH3-TPD and CO2-TPD, espec i ely. Figu e A5. H2-TPR p o iles o Al2O3 cobal ca alys . Figu e A5. H2-TPR p o iles o Al2O3cobal ca alys . 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