P oduc ion o high alue-added phenolic compounds h ough lignin
ca aly ic py olysis o e ion-exchanged hie a chical ZSM-5 and Be a zeoli es
M.I. ´
A ila
a
, M.M. Alonso-Doncel
b
, J. Cue o
b
, L. B iones
a
, G. G´
omez-Pozuelo
a
, J.M. Escola
a,c
,
D.P. Se ano
a,b
, A. Pe al
a,*
, J.A. Bo as
a,c,**
a
Chemical and En i onmen al Enginee ing G oup, ESCET, Rey Juan Ca los Uni e si y, c/ Tulip´
an s/n, 28933, M´
os oles, Mad id, Spain
b
The mochemical P ocesses Uni , IMDEA Ene gy, A da. Ram´
on de la Sag a 3, 28935, M´
os oles, Mad id, Spain
c
Ins i u o de In es igaci´
on de Tecnologías pa a la Sos enibilidad, Rey Juan Ca los Uni e si y, c/ Tulip´
an s/n, 28933, M´
os oles, Mad id, Spain
ARTICLE INFO
Keywo ds:
Lignin py olysis
Hie a chical zeoli es
ZSM-5
Be a
Ion-exchanged zeoli es
Phenolic compounds
ABSTRACT
Syn hesised H-ZSM-5 and H-Be a zeoli es wi h hie a chical po osi y (h-H-ZSM-5 and h-H-Be a) ha e been ion-
exchanged wi h alkali (Na
+
and K
+
) and alkaline-ea h (Mg
2+
) me als and ha e been e alua ed as ca alys s o
p oduce high alue-added p oduc s h ough ca aly ic py olysis o lignin. In compa ison wi h he he mal es ,
hie a chical zeoli es in acid o m a e e ec i e ca alys s o lignin py olysis, a ou ing he p oduc ion o aluable
ligh compounds al hough educing bio-oil* yield and inc easing gas and coke o ma ion. In his way, h-H-ZSM-5
zeoli e p omo es he o ma ion o oxygena ed a oma ics, being guaiacols and sy ingols he majo p oduc s.
Alkali-exchanged a ian s o his zeoli e enhance deme hyla ion eac ions imp o ing he selec i i y owa ds 2-
me hoxy-phenol and sy ingol, by modi ying acid si e p ope ies. On he o he hand, h-H-Be a zeoli e, wi h
la ge po e size and s onge acidi y, leads o highe concen a ion o oxygena ed a oma ics o bo h pa en and
ion-exchanged ca alys s. Speci ically, h-KH-Be a p omo es he p oduc ion o 2-me hoxy-phenol and sy ingol.
Besides, h-MgH-Be a s ands ou o i s g ea e selec i i y owa ds phenol and alkylphenols, such as dime hyl-
phenol. O e all, he combina ion o accessibili y, p o ided by he hie a chical po osi y, wi h he di e en na u e
and s eng h o he acid si es, induced by he ion-exchange wi h alkali and alkaline-ea h me als, allows ailo ing
he lignin ca aly ic py olysis p ocess o selec i ely p oduce high alue-added compounds.
1. In oduc ion
Lignocellulosic biomass is mainly composed o cellulose, hemicel-
lulose, and lignin [1,2]. The o me componen s ha e been widely used
in bioe hanol p oduc ion, pulp and pape enginee ing, as well as in o he
indus ies [1–3]. Howe e , he e ec i e con e sion o lignin in o
alue-added p oduc s has always been a bo leneck due o hei complex
s uc u al cha ac e is ics [4,5]. Fo pulp and pape enginee ing, up o 50
million ons o lignin was e esidue can be p oduced e e y yea [5],
which is mainly used as a low-g ade uel o powe gene a ion. Likewise,
lignin is conside ed as a was e in bio e ine ies [5], despi e con aining
abundan a oma ic g oups ha can ac as a p ecu so o he syn hesis o
uels, chemicals and ad anced ma e ials h ough a la ge a ie y o
p ocesses. The e o e, he alo isa ion o lignin esidues is o g ea sig-
ni icance o ealize ull biomass u iliza ion and he de elopmen o he
bio e ine y indus y in o ci cula economy.
Lignin is a biopolyme o med by building blocks named mono-
lignols, p-couma yl alcohol (H), coni e yl alcohol (G), and sinapyl
alcohol (S), linking h ough C-O and C-C bonds, esul ing in la ge a o-
ma ic polyme s [6,7] (Fig. 1). These monolignols p esen p-hyd ox-
yphenyl (H), guaiacyl (G), and sy ingyl (S) uni s, wi h each con aining 0,
1, and 2 o-me hoxy g oups, espec i ely [8]. The dis ibu ion o hese
uni s a ies depending on he sou ce o lignocellulose. Ha dwood lignin
p ima ily consis s o S and G uni s, wi h S uni s being mo e abundan .
So wood lignin is p edominan ly made up o G uni s, wi h only mino
amoun s o H uni s, whe eas in he lignin p esen in he baceous plan s G
uni s a e he p ima y componen s, ollowed by H and S uni s [9,10].
Se e al lignin chemical alo isa ion ou es ha e been explo ed.
Thus, ca aly ic oxida ion [11,12], hyd ogenolysis o depolyme isa ion
[13–15], and ca aly ic py olysis [16–20] ha e been e alua ed o p o-
duce bo h uels and chemicals, such as aldehydes, phenols, and a oma ic
hyd oca bons [21,22]. Among hem, ca aly ic py olysis is a e y
* Co esponding au ho .
** Co esponding au ho a : Chemical and En i onmen al Enginee ing G oup, ESCET, Rey Juan Ca los Uni e si y, c/ Tulip´
an s/n, 28933, M´
os oles, Mad id, Spain.
E-mail add esses: [email p o ec ed] (A. Pe al), [email p o ec ed] (J.A. Bo as).
Con en s lis s a ailable a ScienceDi ec
Ca alysis Today
jou nal homepage: www.else ie .com/loca e/ca od
h ps://doi.o g/10.1016/j.ca od.2025.115343
Recei ed 16 Decembe 2024; Recei ed in e ised o m 19 Ma ch 2025; Accep ed 15 Ap il 2025
Ca alysis Today 456 (2025) 115343
A ailable online 23 Ap il 2025
0920-5861/© 2025 The Au ho (s). Published by Else ie B.V. This is an open access a icle unde he CC BY-NC-ND license ( h p://c ea i ecommons.o g/licenses/by-
nc-nd/4.0/ ).
p omising ou e o ans o m lignin in o high alue-added p oduc s. In
hese p ocesses, lignin he mal py olysis apou s pass h ough he ca -
aly ic bed, p omo ing c acking eac ions such as C-C bond clea age,
hyd ogen ans e , isome iza ion, a oma ic side chain scission, deca -
bonyla ion, deca boxyla ion, and dehyd a ion. A la ge a ie y o ca a-
lys ypes ha e been es ed in he ca aly ic py olysis o lignin, such as
me al sal s, me al oxides, zeoli e ca alys s, and low-cos was e ca alys s
[23–27]. The liquid p oduc , named bio-oil, is mainly a mix u e o
phenols, which is di icul o sepa a e and pu i y. This aspec is mainly
ela ed o he complex s uc u e o lignin, being a challenge o he
scien i ic communi y o ind a ca aly ic sys em o ensu e he e icien
alo isa ion o lignin [5].
Among all he ca aly ic sys ems e alua ed o lignin alo isa ion
h ough py olysis, he use o zeoli es s ands ou , as bo h hei acidi y and
po osi y can be uned du ing hei syn hesis. These wo ac o s play a
c ucial ole in he eac ion pe o mance, in luencing bo h he ex en o
lignin depolyme isa ion and he dis ibu ion o esul ing p oduc s.
Howe e , mos comme cial zeoli es ha e po e sizes below han 1 nm,
which is an impo an d awback o he decomposi ion o hea y lignin
oligome s in o ligh e compounds o indus ial in e es . This limi a ion
has mo i a ed he use o hie a chical zeoli es wi h enhanced accessi-
bili y o his applica ion [18]. Hie a chically o de ed zeoli es a e
ino ganic ma e ials ha ing mul iple le els o po osi y, in ol ing mic o-,
meso- and/o mac opo es in he same c ys alline s uc u e [28–30].
Focusing on he ca aly ic py olysis o lignin o e zeoli ic ca alys s, acid
si es acili a e he b eakdown o lignin by ca alysing C-C and C-O bond
clea ages, while he po e s uc u e a ec s he selec i e di usion o e-
ac an s and p oduc s. Fo ins ance, mic opo ous ZSM-5 a ou s mono-
cyclic a oma ic hyd oca bons, while mesopo ous ZSM-5 p oduces mo e
alkylphenols [27,31,32]. Howe e , he small mic opo e size o ZSM-5
zeoli e limi s access o la ge phenols, po en ially causing ca alys
deac i a ion [27]. Some s udies indica e ha he op imal po e size o
zeoli es in lignin py olysis alls wi hin he ange o 6.5–8.4 Å, sugges ing
ha hie a chical Be a zeoli e, wi h la ge 12-membe ed ing po es
(7.6 ×6.4 Å) and an imp o ed accessibili y, may be one o he mos
sui able zeoli ic ma e ials in his applica ion [18,33].
In p e ious wo ks o ou g oup, we epo ed an enhanced selec i i y
owa ds oxygena ed a oma ics (phenols and alkylphenols) employing as
ca alys s nanoc ys alline K-ZSM-5 and K-USY zeoli es in he ca aly ic
py olysis o whea s aw due o i s igh combina ion o acid p ope ies
and good accessibili y [19,20]. O he ecen wo k has been ocused on
ca aly ic py olysis o lignin employing nanoc ys alline zeoli es
ion-exchanged wi h me als, con i ming he di e ences in p oduc s dis-
ibu ion depending on he Lewis and B øns ed acid si es concen a ion
[17]. Since he ca ion exchange p edominan ly occu s o e he B øns ed
acid si es o bo h H-ZSM-5 and H-Be a pa en zeoli es, he esul ing
ca alys s p esen an enhanced concen a ion o Lewis acid si es. Thus,
guaiacols p oduc ion was imp o ed using NaH-ZSM-5 and KH-ZSM-5 as
ca alys s, whe eas alkylphenols o ma ion was inc eased o e MgH-Be a
and KH-Be a zeoli es. Guaiacols a e aluable compounds in a a ie y o
indus ies and in e es ing chemicals in he syn hesis o ag ances, cos-
me ics, pes icides and pha maceu icals. Fla ou ing agen s like anillin
and oas ed co ee a e p oduced employing guaiacol as a p ecu so , and
i is also used as an analgesic, an isep ic and seda i e d ug. On he o he
hand, alkylphenols a e used as aluable in e media es (an ioxidan s,
pha maceu icals and polyme s) in di e en indus ial p ocesses [34].
The e o e, i has been con i med ha high alue-added compounds can
be ob ained om he ca aly ic py olysis o esidual lignin, con ibu ing
o he alo isa ion o his ype o was e.
In his con ex , he p esen s udy ocuses on he p oduc ion o high
alue-added phenolic compounds h ough lignin ca aly ic py olysis
using ion-exchanged hie a chical H-ZSM-5 and H-Be a zeoli es. This
app oach aims o p o e ha hie a chical po osi y imp o es he acces-
sibili y o lignin py olysis p oduc s o he ac i e cen es o ca alys s. In
addi ion, he ion exchange o hese hie a chical zeoli es wi h alkali and
alkaline-ea h me als (Na
+
, K
+
and Mg
2+
) allows he ine- uning o hei
acid p ope ies since he ca ion exchange occu s o e B øns ed acid si es,
esul ing in an inc ease o he Lewis acidi y concen a ion. This s udy
also assesses he occu ence o a syne gic e ec , owing o he combi-
na ion o good accessibili y and balanced acidi y, o ind an op imal
ca aly ic sys em o p oduce oxygena ed a oma ic compounds om
lignin py olysis.
Fig. 1. Schema ic illus a ion showing ep esen a i e s uc u e o lignin wi h s uc u es o he monome s couma yl alcohol (H), coni e yl alcohol (G) and sinapyl
alcohol (S).
M.I. ´
A ila e al.
Ca alysis Today 456 (2025) 115343
2
2. Expe imen al p ocedu es
2.1. Ca alys s
2.1.1. Syn hesis o hie a chical zeoli es
The H-ZSM-5 zeoli e wi h hie a chical po osi y (h-H-ZSM-5) was
syn hesised using he silanised nuclei c ys alliza ion me hod ou lined in
p io s udies [28]. The ma e ials used included aluminium isop opoxide
(IPA, Ald ich, 98 w .%) as he aluminium sou ce, e ae hyl o hosilica e
(TEOS, Ald ich, 98 w .%) as he silica sou ce, e ap opylammonium
hyd oxide (TPAOH, Al a Aesa , 40 w .%) as he s uc u e-di ec ing agen ,
and Milli-Q wa e . The mola composi ion o he ini ial syn hesis gel was 1
Al
2
O
3
: 90 SiO
2
: 16.5 TPAOH: 2250 H
2
O. Silanisa ion s ep was pe o med
a 90 ◦C unde e lux and a mosphe ic p essu e o 6 h, wi h
N-(2-N-benzylaminoe hyl)-3-aminop opyl ime hoxysilane (Ph-2A, Gel-
es , 92 w .%) used as he silanising agen (8 mol.% in espec o he silicon
con en in he ini ial gel). The esul ing gel was placed in o PTFE-lined
s eel au ocla es and subjec ed o c ys alliza ion unde au ogenous p es-
su e a 170 ◦C o 7 days. A e c ys alliza ion, he solid was eco e ed by
cen i uga ion and d ied a 110 ◦C. To emo e bo h he
s uc u e-di ec ing and silanising agen s and ac i a e he ca alys , he
ma e ial was calcined in s a ic ai a 550 ◦C o 5 h wi h a hea ing a e o
1.8 ◦C/min.
The H-Be a zeoli e wi h hie a chical po osi y (h-H-Be a) was also
syn hesised using he silanised nuclei c ys alliza ion me hod acco ding
o p io s udies [29,30]. A solu ion comp ising aluminium lakes
(Ald ich, 99.9 w .%), umed silica (Ald ich), e ae hylammonium hy-
d oxide (TEAOH, Al a Aesa , 35 w .% aqueous solu ion), and Milli-Q
wa e was aged a oom empe a u e o 20 h. A e wa ds, i unde -
wen p ec ys allisa ion in s eel au ocla e eac o s lined wi h PTFE a
135 ◦C o 3 days o encou age he de elopmen o Be a p o ozeoli ic
nanouni s. The mola composi ion o he ini ial syn hesis gel was 1.5
Al
2
O
3
: 60 SiO
2
: 15.5 TPAOH: 2400 H
2
O. The esul ing gel was subjec ed
o he c ys alliza ion p ocess (135 ◦C o 7 days) using he same sila-
nising agen (Ph-2A) p e iously desc ibed o he h-H-ZSM-5 sample.
Likewise, he solid p oduc ob ained om he c ys alliza ion ea men
was eco e ed and p ocessed ollowing he same p ocedu e desc ibed
be o e o h-H-ZSM-5 zeoli e.
2.1.2. P epa a ion o ion-exchanged zeoli es
The wo p e iously syn hesised hie a chical zeoli es we e subjec ed
o ion exchange wi h alkaline ea h (Mg
2+
) and alkali (Na
+
and K
+
)
ca ions acco ding o he p ocedu e ea lie desc ibed [17]. Typically, 5 g
o zeoli e powde we e imme sed in 50 mL o a 0.4 M aqueous solu ion
o he co esponding chlo ide sal o 24 h a 25 ◦C. The sal s employed
o he ion exchange included NaCl (Sigma Ald ich, 99.0 w .%), KCl
(Scha lab, 99.0 w .%) and MgCl
2
(Fishe Scien i ic, 99.0 w .%). A e
he ion exchange, he zeoli es we e sepa a ed by cen i uga ion, insed
wi h Milli-Q wa e , d ied a 110 ◦C o e nigh , and subsequen ly calcined
in s a ic ai a 550 ◦C o 5 h wi h a hea ing a e o 1.8 ◦C/min.
P io o hei u ilisa ion as ca alys s, bo h he hie a chical and ion-
exchanged zeoli es we e pelle ised by comp ession unde 8 ons o
p essu e o ce o 30 s, hen c ushed and sie ed h ough ASTM s anda d
sie es o ob ain pa icles in he 180–250
μ
m size ange.
2.1.3. Ca alys s cha ac e isa ion
The con en s o aluminium and Na, K and Mg me als in he ca alys s
we e analysed using induc i ely coupled plasma - op ical emission
spec oscopy (ICP-OES) wi h a Va ian Vis a AX spec ome e . P e i-
ously, he samples we e dissol ed in a H
2
SO
4
/HF acid solu ion. X- ay
di ac ion (XRD) da a we e collec ed using a Philips X
′
pe di ac-
ome e wi h CuK
α
adia ion. A gon adso p ion-deso p ion iso he ms
we e measu ed wi h a Mic ome i ics 3Flex Adso p ion Analyze , he
samples being p io ou gassed a 300 ◦C unde acuum o 5 h. The
speci ic su ace a ea was calcula ed using he B unaue -Emme -Telle
(BET) me hod, and he Non-Local Densi y Func ional Theo y (NL-DFT)
me hod was employed o di e en ia e he con ibu ions o mic opo es,
mesopo es and ex e nal su ace a ea o he o al su ace a ea [35]. To al
po e olume was es ima ed om he adso bed amoun a a ela i e
p essu e o 0.95. T ansmission elec on mic oscopy (TEM) images and
ene gy-dispe si e X- ay (EDX) analysis we e pe o med using a JEOL
JEM1400-Flash mic oscope ope a ing a 120 kV.
The acidi y and s eng h o he acid si es in he zeoli es we e
examined h ough py idine adso p ion and deso p ion ollowed by
Fou ie ans o m in a ed spec oscopy (FTIR/PYR). Sel -suppo ing
wa e samples (8–15 mg/cm²) we e placed in o a high- empe a u e
cell wi h a CaF₂ window. Ac i a ion was ca ied ou unde acuum a
525 ◦C o 1 h. Py idine was hen adso bed a 150 ◦C unde 4 mba
p essu e, and FTIR spec a we e eco ded be ween 4000 and
400 cm⁻¹ (4 cm⁻¹ esolu ion wi h 128 scans). A Jasco FT/IR-4600
spec ome e wi h a iglycine sulpha e (TGS) de ec o was used o
his analysis. To assess he s eng h o he acid si es, FTIR spec a we e
also eco ded a e deso p ion o py idine a high acuum and di e en
empe a u es (150, 250, 350, and 450 ◦C), using an equilib a ion ime o
25 min o each empe a u e. Quan i ica ion o he acid si es was pe -
o med by analysing speci ic py idine ib a ion modes and co e-
sponding abso p ion coe icien s a ailable in he li e a u e [36]. These
included he py idinium PyH⁺ band a 1545 cm⁻¹ (
ε
h-H-ZSM-5
=
1.09 cm⋅µmol
−1
;
ε
h-H-Be a
=1.12 cm⋅µmol
−1
) and he py idine PyL band
a ~1455 cm⁻¹ (
ε
h-H-ZSM-5
and
ε
h-H-Be a
=1.71 cm⋅µmol
−1
;
ε
Meh-H-ZSM-5
and
ε
Meh-H-Be a
=1.72 cm⋅µmol
−1
).
2.2. Lignin used as eeds ock
The lignin selec ed as aw ma e ial o be p ocessed in he py olysis
es s was a Tano is P o obind 1000 sample, which is ob ained h ough
Soda p ocess ex ac ion om non-woody biomass and p o ided in
powde o m by PLT Inno a ions [37]. The lignin was cha ac e ised
acco ding o Eu opean S anda ds o de e mine he p oxima e (mois u e,
ash, and ola ile ma e con en s) and ul ima e analyses, which a e
summa ised in Table 1. The ull cha ac e iza ion de ails o his ma e ial
can be ound in a p e ious publica ion by ou esea ch g oup [17].
Be o e conduc ing he py olysis es s, he lignin was comp essed in o
uni o m able s using a hyd aulic p ess wi h an 8 ons p essu e o ce
applied o 30 s. The able s we e hen c ushed and passed h ough
ASTM s anda d sie es o achie e he equi ed pa icle size o eeding
in o he py olysis eac o (0.5 – 1 mm).
2.3. Lignin py olysis es s
A de ailed desc ip ion o he expe imen al se up used o he ca a-
ly ic py olysis es s is p o ided in a p e ious wo k [38]. I consis s o a
labo a o y-scale down- low ixed-bed s ainless s eel eac o (16 mm
inne diame e , 400 mm leng h) wi h an ex-si u con igu a ion, ea u ing
sepa a e he mal and ca aly ic zones, each hea ed by independen
elec ic u naces. The empe a u es a e moni o ed by K- ype he mo-
couples posi ioned in bo h zones. In each expe imen , lignin (4 g, p e-
iously d ied o elimina e mois u e) was used as eeds ock. Fo he
ca aly ic es s, ca alys - o-lignin mass a ios (C/L) o 0.2 and 0.4 we e
e alua ed. The lignin was ed wi h a pa icle size in he 0.5–1 mm in-
e al, while he ca alys pa icles anged om 180 o 250
μ
m. The ex-
pe imen s we e ca ied ou a a mosphe ic p essu e, wi h empe a u es
Table 1
P oxima e and ul ima e analyses o lignin.
P oxima e analysis
a
(w .%) Ul ima e analysis
b
(w .%)
Vola ile ma e Ash Fixed ca bon C H N S O
c
61.7 1.3 37.0 60.0 5.2 0.7 0.4 33.7
a
D y basis;
b
D y ash- ee basis;
c
De e mined by di e ence.
M.I. ´
A ila e al.
Ca alysis Today 456 (2025) 115343
3
se o 550 ◦C in he he mal zone and 450 ◦C in he ca aly ic one.
P io o each es , he lignin chambe and eac ion sys em we e
pu ged wi h 100 mL/min o ni ogen. Once he a ge empe a u es in
bo h zones we e eached, he lignin was loaded in o he eac o , and
py olysis was pe o med o 10 min unde a cons an ni ogen low o
100 mL/min. Du ing py olysis, he lignin decomposes in o cha (accu-
mula ing in he he mal zone), non-condensable gases and py oly ic
apou s, which pass h ough he ca aly ic zone. The apou s a e
condensed using a sys em o wo s ainless s eel essels cooled by an ice-
wa e ba h, while he non-condensable gases a e collec ed in a o alise ,
which also measu es gas olume ia wa e displacemen . A e each
expe imen , he composi ion o gases, cha , coke ( o med on he ca a-
lys ), and bio-oil a e de e mined using a ious analy ical echniques, as
nex desc ibed.
2.3.1. Analysis o he lignin py olysis p oduc s
The condensed bio-oil om he ca aly ic py olysis es s was sepa-
a ed in o wo phases by decan a ion, which a e named as aqueous- ich
liquid phase and o ganic- ich liquid phase. The aqueous- ich liquid
phase con ains mos o he pola compounds, including wa e , in com-
pa ison o he o ganic- ich liquid phase which con ains he compounds
wi h highe molecula weigh . The wa e con en in each phase was
measu ed using Ka l Fische i a ion, ollowing he ASTM E202–08
p ocedu e a e dilu ion o 50 % wi h e hanol. The ca bon (C), hyd ogen
(H), ni ogen (N), and sulphu (S) con en o bo h phases was de e -
mined wi h a The moFishe Flash Sma mic o-elemen al analyse , and
he oxygen (O) con en was calcula ed by di e ence. The o ganic com-
pounds p esen in he wo liquid phases ( e e ed o as bio-oil*, on a
wa e - ee basis) we e iden i ied using gas ch oma og aphy-mass spec-
ome y (GC-MS) wi h a B uke ® SCION 436-GC sys em (elec on en-
e gy: 70 eV, emission: 300 V, helium low a e: 1 mL/min). The column
used was a WCOT used silica HP5-MS UI (30 m ×0.25 mm ×0.25 mm).
Compounds we e iden i ied by compa ing hei spec a wi h he NIST EI-
MS lib a y ( .2.0), wi h a minimum ma ch sco e o 700. Once iden i ied,
compounds we e classi ied in o di e en amilies based on hei unc-
ional g oups: ca boxylic acids (CA), ligh oxygena es (LO, including
aldehydes, alcohols, ke ones, and e he s), u ans (FUR), oxygena ed
a oma ics (O-AR), and a oma ic hyd oca bons (AR). Quan i a i e anal-
ysis was achie ed h ough ex e nal calib a ion, using 19 s anda d
compounds commonly ound in he mal and ca aly ic bio-oils: ace ic
acid, p opanoic acid, bu anone, die hoxyp opane, cyclopen enone,
u u al, phenol, guaiacol, c esol, dime hylphenol, c eosol, sy ingol,
ime hoxybenzene, oluene, xylene, s y ene, ime hylbenzene, naph-
halene, and n-hep ane. Fo o he de ec ed compounds, esponse ac o s
we e a e aged acco ding o hei g oup. The di e ence be ween he
o al bio-oil yield and GC-MS de ec ed compounds was used o es ima e
he amoun o hea y o oligome ic species no de ec ed by GC-MS.
Non-condensable gases we e analysed using a Va ian CP-4900
mic o-gas-ch oma og aph equipped wi h Molsie e 5 Å and PPQ col-
umns, and a he mal conduc i i y de ec o (TCD), wi h a gon and he-
lium as ca ie gases, espec i ely. Quan i ica ion was pe o med using
calib a ion s anda ds o N
2
, O
2
, H
2
, CO, CO
2
, CH
4
, C
2
H
4
, C
2
H
6
, C
3
H
6
,
C
3
H
8
, C
4
H
8
, and C
4
H
10
.
The C, H, N, S, and O con en in he cha and coke was measu ed
using he The moFishe Flash Sma mic o-elemen al analyse . The
amoun o coke deposi ed on he ca alys was de e mined by
empe a u e-p og ammed oxida ion (TPO) unde an ai a mosphe e,
using a TA Ins umen s SDT 650 he mobalance (up o 900 ◦C a a
hea ing a e o 10 ◦C/min). Finally, he o e all mass balance was closed
wi h a eco e y o o e 95 w .% om he combined weigh o he gas,
bio-oil, cha , and coke ac ions.
3. Resul s and discussion
3.1. Ca alys s cha ac e isa ion
Two di e en hie a chical zeoli es we e syn hesised and named as h-
H-ZSM-5 and h-H-Be a. Acco ding o he da abase o zeoli e s uc u es
published by he IZA S uc u e Commission, bo h zeoli es showed
di ac ion pa e ns cha ac e is ic o MFI and BEA s uc u es, espec-
i ely (Fig. S1). h-H-ZSM-5 (Fig. S1a) possesses wide di ac ion peaks,
wi h low in ensi y, ypical o hie a chical zeoli es consis ing o small
c ys alline domains, as con i med by TEM (Fig. S2a and b). Small c ys-
alline uni s wi h sizes lowe han 20 nm a e de ec ed, while hese en-
i ies a e pa ially g ouped in globula agg ega es o la ge dimensions
(150–300 nm), which is ypical o hie a chical zeoli es wi h in e pa -
icle mesopo osi y [28]. Wide peaks o low in ensi y a e also de ec ed in
he h-H-Be a di ac ion pa e n (Fig. S1b), sugges ing he p esence o
small c ys als o a high p opo ion o s uc u al de ec s in his ma e ial
[39]. Thus, TEM mic og aphs (Fig. S3a and b) show ha his ma e ial is
o med by ellip ical pa icles (300–600 nm in size) possessing a poly-
c ys alline dis o ed s uc u e. A e magni ica ion (Fig. S3b), i can be
obse ed ha hese pa icles a e o med by small and di e en nano-
c ys alline domains (<20 nm) and di ac ion inges a e clea ly isible,
deno ing he c ys allini y o hese zeoli es [28,40]. The physicochemical
p ope ies o bo h syn hesised zeoli es a e summa ised in Table 2. Si/Al
mola a ios o h-H-ZSM-5 and h-H-Be a (de e mined by ICP-OES) we e
61 and 20, espec i ely.
Fu he mo e, bo h hie a chical pa en zeoli es we e ion-exchanged
using alkali and alkaline-ea h me al sal s acco ding o he p ocedu e
explained in he expe imen al sec ion. Consequen ly, Na
+
, K
+
and Mg
2+
ca ions a e in oduced by pa ially subs i u ing H
+
ca ions and modi-
ying he chemical composi ion o he samples. All he ion-exchanged
ma e ials exhibi Si/Al mola a ios simila o hose o hei co e-
sponding pa en zeoli es, wi h alues close o 60 and 20 o he ZSM-5
and Be a- ype zeoli es, espec i ely. Mo eo e , no signi ican s uc-
u al changes a e app ecia ed o e ion-exchanged zeoli es (Fig. S1, S2
and S3) [17]. Bo h, XRD di ac og ams and TEM mic og aphs indica e
ha ion-exchanged zeoli es exhibi simila c ys allini y and s uc u al
ea u es han hei pa en ones.
Compa ing he esul s a ained o e bo h ypes o zeoli es, a mo e
success ul ion exchange p ocess is achie ed o e he h-H-ZSM-5 zeoli e.
In his case, he ca ion o aluminium mola a io (Me/Al) is close o he
maximum heo e ical alue a ainable i he nega i e cha ges ela ed o
Al a oms we e comple ely coun e balanced by ca ions (Me/Al =1 o
Na
+
and K
+
, and 0.5 o Mg
2+
). Mo eo e , homogeneous Me dispe sion
is app ecia ed o e he zeoli e su ace and no impu i y phases ela ed o
me al oxides a e de ec ed (Fig. S1). Fu he mo e, no me al oxide pa i-
cles we e de ec ed by TEM (Fig. S2 and S3), and TEM-EDX elemen al
mapping demons a es he uni o m dis ibu ion o Na, K and Mg o e
bo h h-H-ZSM-5 and h-H-Be a zeoli es (Fig. S4 and S5). On he o he
hand, a e ion exchange, despi e he highe mass o ca ion inco po a ed
(Table 2, m
Me
, w .%), h-MeH-Be a zeoli es each only Me/Al mola a io
alues close o 50 % o he maximum heo e ical alue achie able. In
his case, he highes deg ee o ion exchange is ob ained o e he h-NaH-
Be a (Na/Al =0.61). This di e ence in he deg ee o ion exchange o e
bo h ypes o zeoli es is he same as ha obse ed and discussed in a
p e ious wo k o ou g oup whe e H-ZSM-5 (MFI; Si/Al =52) and H-
Be a (BEA; Si/Al =20) nanoc ys alline comme cial zeoli es we e ion-
exchanged ollowing a simila p ocedu e [17]. Signi ican di e ences
in ex u al p ope ies, he highly dis o ed BEA amewo k s uc u e,
and he e y di e en Si/Al mola a ios and acid p ope ies o bo h
zeoli es a e some o he easons ha explain he exis ence o a highe
p opo ion o e ec i e ion exchange si es o e h-H-ZSM-5 in compa ison
o h-H-Be a zeoli e.
M.I. ´
A ila e al.
Ca alysis Today 456 (2025) 115343
4
A e ion exchange a small modi ica ion in he ex u al p ope ies o
syn hesised zeoli es is obse ed (Fig. S6 and S7). Bo h pa en zeoli es, h-
H-ZSM-5 (Fig. S6a) and h-H-Be a (Fig. S7a) display adso p ion a e y
low ela i e p essu es due o mic opo e illing, ollowed by an impo an
A adso p ion a in e media e ela i e p essu es (0.1 <P/P
0
<0.8)
ela ed o he con inuous adso p ion in he mesopo es o he hie a chical
zeoli es. Ion-exchanged zeoli es show simila shape o hei co e-
sponding H- o m zeoli es bu deno e a sligh ly lowe so p ion capaci y.
This ac is co obo a ed in Table 2, whe e he ex u al p ope ies o he
di e en ma e ials de i ed om he A so p ion analyses a e lis ed.
Ca ion-exchanged ma e ials mani es an app eciable educ ion in hei
o al su ace a ea (BET). Mo eo e , me al ca ion exchange gene a es a
clea mic opo e blockage in h-H-Be a zeoli e, while his e ec is lowe ,
bu no negligible, o e h-H-ZSM-5 (V
MIC
and S
MIC
). This ac is consis-
en wi h he exchange o p o ons by me al ca ions o la ge ionic adius.
The di e ence obse ed in bo h amilies o ma e ials can be ela ed o
he highe ca ion mass amoun inco po a ed in he h-H-Be a zeoli e
(m
Me
, w .%, Table 2) due o i s highe Al con en .
FTIR analyses o adso bed py idine a di e en empe a u es we e
pe o med o iden i y and quan i y he acid cen es ( ype, na u e and
s eng h) p esen in he di e en ma e ials. Table 3 lis s he B øns ed
and Lewis acid si es concen a ion de ec ed by his echnique a 150 ◦C.
h-H-ZSM-5 con ains a highe p opo ion o B øns ed acid si es, esul ing
in a mola a io o Lewis o B øns ed acid cen es (L/B) o 0.6. A e ion
exchange his a io is modi ied, inc easing he p opo ion o Lewis acid
si es and gi ing ise o highe L/B a ios, om alues close o 1 o h-
MgH-ZSM-5, o 8 o h-KH-ZSM-5. h-H-Be a zeoli e p esen s a mo e
balanced L/B a io han h-H-ZSM-5, wi h a alue o 0.9. A e ion-
exchange, he L/B a io almos doubles o h-MgH-Be a, inc easing
his a io in highe ex en o h-KH-Be a (L/B =3.2) and h-NaH-Be a (L/
B =6.6).
The e o e, a la ge dec ease in B øns ed acidi y is obse ed o
alkaline (Na
+
and K
+
) ion-exchanged zeoli es, due o he subs i u ion o
H
+
associa ed wi h his ype o acid si es by alkaline ca ions. B idged
hyd oxyl g oups esponsible o BAS a e p e e en ial ion-exchange si es
o alkaline ca ions esul ing in he la ge educ ion o BAS. Conse-
quen ly, he ion-exchange o H
+
by ex a amewo k alkali ca ions gen-
e a es LAS, inc easing he popula ion o his ype o acid si es, as poin ed
ou abo e. Addi ionally, de ec si es such as SiO
-
and silanols (Si-OH) o
ex a amewo k Al, can also con ibu e as ion-exchange si es and o he
o ma ion o LAS o di e en na u e. The amoun o his ype o ion-
exchange si es is expec ed o be signi ican in hese ypes o hie a chi-
cal zeoli es exhibi ing a high p opo ion o ex e nal su ace a ea. On he
o he hand, i would be easonable o expec simila esul s when
magnesium is used as ca ion in he ion-exchange p ocess. Howe e , in
his case, despi e he p ope e iciency o he ion-exchange p ocess, he
educ ion in he amoun o BAS is less impo an . While o alkaline
ca ions a e he ion-exchange p ocess, a BAS educ ion be ween 75 %
and 90 % o ZSM-5 ype zeoli es and 70–85 % o Be a ype ones is
ob ained, when Mg
2+
is ion-exchanged his dec ease is lowe han 20 %
o 25 % o ZSM-5 and Be a ype zeoli es, espec i ely. Di e en ly o
alkaline (uni alen ) ca ions, he dis ance be ween ion-exchange si es is
an impo an ac o when Mg
2+
is in ol ed, because his ca ion in e ac s
wi h wo b idged hyd oxyl ion-exchange si es only i hey a e loca ed
wi hin a ce ain dis ance. The p obabili y o his p oximi y be ween wo
b idged hyd oxyls is no ele a ed in bo h h-H-ZSM-5 and h-H-Be a ze-
oli es, because hei high Si/Al mola a ios (61 and 20, espec i ely),
and he e o e he amoun o BAS dec eases o a lesse ex en han when
mono alen alkali ca ions a e ion-exchanged. These esul s a e in
ag eemen wi h p e ious indings, indica ing ha exchangeable p o ons
a e less e icien ly eplaced by Mg
2+
ia ion-exchange, han ia o he
me hods such as imp egna ion [41]. Thus, o h-MgH-ZSM-5 and
h-MgH-Be a, only a limi ed numbe o b idged hyd oxyls a e ans-
o med in o Mg(OH)
+
si es (LAS) due o hei in e ac ion wi h sol a ed
Mg
2+
[42,43]. Addi ionally, and simila ly o alkaline ca ions, LAS o
di e en na u e could also be gene a ed due o he in e ac ion o Mg
2+
wi h dis inc de ec si es exis ing in he hie a chical zeoli ic s uc u es,
con ibu ing o he no able inc ease in he LAS popula ion obse ed o
magnesium ion-exchanged hie a chical zeoli es [17,19,44].
Fig. 2 displays he concen a ion o B øns ed and Lewis acid cen es
measu ed a e e acua ion a di e en empe a u es ( om 150 ◦C o
450 ◦C). This allows he quan i ica ion o he concen a ion and s eng h
o he di e en acid si es o be de e mined. h-H-ZSM-5 consis s mainly o
B øns ed acid si es (BAS) o medium-high acid s eng h. A e he
e acua ion a 350 ◦C i main ains mos o he 60 % o BAS, and a 450 ◦C
his alue is s ill highe han 37 % (Fig. 2a). Magnesium exchange e-
duces he concen a ion o BAS, inc easing ha o Lewis acid si es (LAS),
main aining an ele a ed numbe o acid cen es (acidi y), cha ac e ised
by medium o high-s eng h BAS and medium-s eng h LAS. A e he
Table 2
Physicochemical and ex u al p ope ies o hie a chical and ion-exchanged h-H-ZSM-5 and h-H-Be a zeoli es.
Sample m
Mea
(w .%)
Me/Al
b
Si/Al
b
S
BETc
(m
2
/g)
S
MICd
(m
2
/g)
S
EXT-MESOe
(m
2
/g)
V
MICd
(cm
3
/g)
V
TOT
(cm
3
/g)
h-H-ZSM¡5 - - 61 540 337 203 0.194 0.415
h-MgH-ZSM−5 0.38 0.60 62 448 295 153 0.170 0.356
h-KH-ZSM−5 1.00 0.96 61 443 298 145 0.172 0.377
h-NaH-ZSM−5 0.52 0.86 62 474 305 169 0.176 0.368
h-H-Be a - - 20 630 420 210 0.248 0.429
h-MgH-Be a 0.46 0.26 22 534 363 171 0.214 0.382
h-KH-Be a 1.25 0.43 21 527 348 179 0.205 0.399
h-NaH-Be a 1.13 0.61 20 508 339 169 0.200 0.391
a
Me al weigh pe cen age (ICP-OES);
b
Mola a io (ICP-OES);
c
BET su ace a ea;
d
Mic opo e su ace a ea and mic opo e olume (NL-DFT me hod);
e
Ex e nal-Mesopo e su ace a ea;
To al po e olume (P/P
0
≈0.95).
Table 3
Acid p ope ies o h-H-ZSM-5 and h-H-Be a-based ca alys s.
Sample FTIR-PYR (150 ◦C)
BAS (mmol/g)
a
LAS (mmol/g)
b
L/B
c
h-H-ZSM¡5 0.165 0.093 0.6
h-MgH-ZSM−5 0.136 0.147 1.1
h-KH-ZSM−5 0.017 0.136 8.0
h-NaH-ZSM−5 0.039 0.156 4.0
h-H-Be a 0.256 0.229 0.9
h-MgH-Be a 0.197 0.332 1.7
h-KH-Be a 0.072 0.232 3.2
h-NaH-Be a 0.040 0.264 6.6
a
Concen a ion o B øns ed acid si es;
b
Concen a ion o Lewis acid si es;
c
LAS/BAS mola a io.
M.I. ´
A ila e al.
Ca alysis Today 456 (2025) 115343
5
e acua ion a 350 ◦C, mo e han 30 % and 50 % o BAS and LAS,
espec i ely, a e e ained (Fig. 2a and b). On he o he hand, bo h, h-KH-
ZSM-5 and h-NaH-ZSM-5 a e composed mainly o weak LAS, possessing
he la e a sligh ly highe p opo ion o BAS o low acid s eng h. As i
was expec ed, conside ing i s highe Al con en and i s cha ac e is ic
dis o ed s uc u e, h-H-Be a possesses an ele a ed acidi y (Fig. 2c and
d) and bo h BAS and LAS can be ca ego ised as acid cen es o medium o
s ong acid s eng h. A e ion-exchange, and simila ly o h-H-ZSM-5-
based zeoli es, he p opo ion o LAS inc eases, exhibi ing h-MgH-Be a
bo h BAS and LAS o medium-high acid s eng h, while medium acid
s eng h BAS and weak LAS a e de ec ed o e bo h h-KH-Be a and h-
NaH-Be a ca alys s.
These esul s a e in ag eemen wi h p e ious wo ks om ou g oup
and o he au ho s [17,45] con i ming ha he ion exchange wi h alkali
and alkaline-ea h ca ions p oduces mainly weak LAS. Fu he mo e, as
he deg ee o ion exchange inc eases, he acid na u e o he ca alys s
u ns in o Lewis- ype, esul ing in a educ ion in hei acid s eng h.
3.2. The mal py olysis o lignin
Fig. 3a shows he p oduc s yield dis ibu ion ob ained om he
he mal py olysis o lignin. I can be obse ed ha he main p oduc is
he solid by-p oduc cha , ollowed by bio-oil* (wa e - ee basis), non-
condensable gases and wa e .
Pe manen gases (Fig. 3b) p ima ily include CH
4
, CO
2
, CO, and ligh
hyd oca bons (e hane, e hylene, p opene, p opylene, bu ane and
bu ene), which esul om he b eakdown o lignin’s me hoxy,
ca bonyl, and e he linkages. CO
2
and CO a e p oduced h ough
deca boxyla ion and deca bonyla ion eac ions, espec i ely, while
me hane and o he hyd oca bons a e o med om he clea age o
me hoxy g oups and he c acking o C-C bonds wi hin he lignin
polyme .
On he o he hand, he componen s p esen in he bio-oil* ac ion
ha e been de e mined employing GC-MS analyses, using calib a ion
me hods o ob ain quan i a i e da a on bo h mass yield ela ed o he
s a ing aw lignin and hei concen a ion in he bio-oil* ac ion.
Al hough esul s a e p esen ed on a wa e - ee basis, he aqueous- ich
and o ganic- ich liquid phases o he bio-oil we e analysed sepa a ely
o assess he dis ibu ion o di e en compound amilies. The concen-
a ions o each amily in he bio-oil* ha e been summa ised in Fig. 3c
and d. Mino i y amilies (CA, LO, FUR and AR) wi h p opo ions lowe
han 1.5 w .% in he bio-oil* a e depic ed in Fig. 3c, while he concen-
a ion o he main bio-oil* amily, i.e. oxygena ed a oma ics, is close o
32 w .% (Fig. 3d). The de ail o O-AR amily acco ding o i s majo
componen s, g ouped in alkylphenols (ALK), guaiacols (GUA), sy ingols
(SYR) and ca echols (CAT), is also shown in Fig. 3d. The bio-oil* de i ed
om he mal py olysis is ich in oxygena ed a oma ics, speci ically
alkylphenols (4.1 w .%), sy ingols (9.3 w .%), and guaiacols (18 w .%).
The p esence o hese compounds ag ees well wi h he lignin composi-
ion, which includes in hei s uc u e p-hyd oxyphenyl, sy ingyl, and
Fig. 2. Concen a ion o a,c) B øns ed (C
B
), and b,d) Lewis (C
L
) acid si es o he zeoli e samples, p obed by FTIR/py idine, as a unc ion o he deso p ion
empe a u e.
M.I. ´
A ila e al.
Ca alysis Today 456 (2025) 115343
6
guaiacyl uni s [46]. Howe e , in he absence o ca alys s (pu e he mal
p ocess), he bio-oil* p esen s a high oxygen con en (23.7 w .%), which
may nega i ely a ec i s s abili y and quali y as a uel. Mo eo e , a
ela i ely low concen a ion o ligh componen s, de ec ed by he GC-MS
analyses, was iden i ied in he bio-oil* (38.3 w .%), indica ing a limi ed
con e sion o lignin in o high alue-added compounds [17]. As i has
been ep esen ed in he scheme o Fig. 4, du ing he mal decomposi ion,
lignin unde goes nume ous eac ions, he C–C and C–O–C side chains
b eak apa , p oducing phenols o hyd oxybenzenes, which con ain
unc ional g oups such as ca boxyl, me hoxy, o ca bonyl [47]. These
g oups can u he decompose, gene a ing ligh gases. Depolyme isa ion
eac ion akes place, leading o an inc ease in hea y me hoxyphenols in
he bio-oil. Addi ionally, epolyme iza ion eac ions con ibu e o he
o ma ion o cha [48]. In pa allel, hyd ogena ion, dehyd ogena ion,
deme hyla ion, and deme hoxyla ion eac ions ake place, esul ing in
he o ma ion o majo compounds such as guaiacols, ca echols, and
alkyl phenols [49]. Addi ionally, he p esence o a small amoun o u an
de i a i es in he bio-oil composi ion ob ained h ough lignin py olysis
Fig. 3. The mal py olysis o lignin a) F ac ions yields, b) Gaseous componen s yield (GO: gaseous ole ins, GP: gaseous pa a ins), c) O e all concen a ion o
compound amilies in he bio-oil* (excluding O-AR), and d) Concen a ion o o al oxygena ed a oma ic compounds (O-AR) and hei sub- amilies.
Fig. 4. Main ype o p oduc s esul ing om he non-ca aly ic py olysis o lignin.
M.I. ´
A ila e al.
Ca alysis Today 456 (2025) 115343
7
a ises om he deg ada ion o esidual holocellulose emaining a e he
P o obind 1000 lignin ex ac ion p ocess, accoun ing o less han 4 w .
% [50].
3.3. Ca aly ic py olysis o lignin employing h-MeH-ZSM-5 and h-MeH-
Be a zeoli es
This sec ion shows he esul s ob ained in he ca aly ic py olysis o
lignin employing hie a chical H-ZSM-5 and H-Be a zeoli es, including
bo h pa en and ca ion-exchanged ma e ials. Based on s udies pe -
o med by ou esea ch eam on lignocellulosic biomass and lignin py-
olysis [17,19,20], he selec ed empe a u es we e 550 ◦C and 450 ◦C
o he he mal and ca aly ic zones, espec i ely, and wo di e en
ca alys - o-lignin (C/L) a ios we e es ed (0.2 and 0.4) o e alua e he
ca alys impac on he p oduc s dis ibu ion. The mass yields o lignin
py olysis p oduc s e e ed o he ed lignin a e summa ised in Figs. 5
and 6, o pa en and ca ion-exchanged ZSM-5 and Be a- ype zeoli es,
espec i ely. Fo compa a i e pu poses, he non-ca aly ic es esul s
ha e also been included.
I is impo an o no e ha , gi en ha he he mal py olysis s age is
he same o all he es s, he amoun o cha p oduced was ela i ely
cons an (~ 40 w .%). In e ms o py olysis ac ion dis ibu ion, he use
o h-H-ZSM-5 and h-H-Be a zeoli es, combined wi h an inc eased C/L
a io, esul s in lowe bio-oil* yields. This is ela ed o he highe o -
ma ion o wa e , gases, and coke, which likely occu s as he apou s
om he he mal zone a e con e ed o e he ca alys bed. I can be
obse ed (Fig. 6) ha he bio-oil yields o h-H-Be a zeoli e a e lowe
compa ed o hose p oduced wi h h-H-ZSM-5 (Fig. 5). Rega ding wa e
p oduc ion, he inc ease compa ed o he non-ca aly ic p ocess is e y
simila o bo h zeoli es, wi h sligh ly highe alues obse ed o h-H-
ZSM-5. This e ec becomes mo e p onounced wi h an inc ease in he C/
L a io.
The acidic p ope ies o zeoli es, which a e p ima ily de e mined by
he Si/Al a io, a e c ucial in in luencing he mechanisms and e iciency
in con e sion o lignin decomposi ion apou s. Zeoli es wi h highe Si/
Al a ios, such as h-H-ZSM-5 (Si/Al =61), ha e lowe acidi y compa ed
o hose wi h lowe Si/Al a ios, like h-H-Be a (Si/Al =20) [51]. This
di e ence in acidi y can lead o dis inc lignin apou s con e sion
pa hways, including a ia ions in deoxygena ion eac ions [52].
h-H-Be a, wi h i s lowe Si/Al a io and highe acidi y, p omo es deox-
ygena ion p ocesses inc easing gas p oduc ion and highe coke yield,
which is o med by he ca bon deposi s gene a ed om successi e
oligome iza ion and polyme iza ion eac ions [53]. In con as ,
h-H-ZSM-5, wi h highe Si/Al a io and lowe acidi y, exhibi s lowe gas
and coke p oduc ion [54]. La ge po e olumes a ou c acking e-
ac ions, which inc eases gas p oduc ion, as well as a oma iza ion and
polyme iza ion eac ions, leading o a highe yield o coke [55,56]. This
beha iou aligns wi h he la ge mic opo e size and olume o H-Be a
zeoli e, which con ibu es o i s highe coke p oduc ion compa ed o
h-H-ZSM-5. Speci ically, p oduced coke yields o 3.4 w .% a a C/L a io
o 0.2 and 8.2 w .% a 0.4, a e de ec ed o h-H-ZSM-5 zeoli e. In
con as , h-H-Be a zeoli e showed highe coke yields o 6.0 w .% a
C/L =0.2 and 11.0 w .% a C/L =0.4. Addi ionally, h-H-Be a exhibi ed
inc eased gas p oduc ion conce ning he he mal es , wi h alues o
0.4 w .% a C/L =0.2 and 1.6 w .% a C/L =0.4, whe eas h-H-ZSM-5
induces a lowe gas p oduc ion, wi h a educ ion o up o 0.2 w .% a
C/L =0.4. Fo h-H-Be a, he highe BAS concen a ion enhances
c acking eac ions, esul ing in g ea e ole in o ma ion and o e all gas
yield. Con e sely, h-H-ZSM-5, exhibi ing a mode a ely educed BAS
con en , in ensi ies deoxygena ion eac ions, pa icula ly h ough wa e
o ma ion, u he ampli ying his e ec [19].
On he o he hand, signi ican di e ences in he p oduc s dis ibu-
ion a e obse ed in he py olysis expe imen s employing ion exchanged
h-H-ZSM-5 and h-H-Be a zeoli es wi h Na
+
, K
+
, and Mg
2+
. The exchange
o H
+
ions in he zeoli e amewo k wi h Na
+
, K
+
, and Mg
2+
ca ions lead
o impo an changes in he acidi y and signi ican a ia ions in he
ex u al p ope ies [57], p o oking a educ ion in he coke o ma ion
o e he ZSM-5 ion-exchanged zeoli es, pa icula ly a a C/L a io o 0.4.
In he case o h-MgH-ZSM-5 zeoli e, he concen a ion o LAS/BAS si es
is mo e balanced, gi ing ise o a highe con e sion o py olysis apou s
o e his ca alys and an inc ease in wa e and gas yields.
In Figs. 7 and 8 he concen a ion o GC-MS de ec ed compounds in
he bio-oil* (d y-basis) a e ep esen ed. The non-de ec ed ma e (di -
e ence un il 100 %) is ela ed wi h he p esence o hea y compounds
ha canno be analysed by GC-MS. I can be obse ed ha he use o
ca alys s inc eases he concen a ion o GC-MS de ec ed compounds in
he bio-oil* . This can be a ibu ed o he ac ha he ca alys s gene a e
ligh e compounds by con e sion o oligome ic species and hea y
alkoxy phenols ypically ound in pu e lignin. In compa ison o non-
ca aly ic expe imen s, when using h-H-ZSM-5 and h-H-Be a zeoli es,
al hough bio-oil* mass yields diminish, he p opo ion o de ec ed spe-
cies inc ease up o 36 w .% o h-H-ZSM-5 and 51 w .% o h-H-Be a,
espec i ely. These indings demons a e ha aw zeoli es e ec i ely
con e oligome s in o smalle molecules.
On he o he hand, employing h-MeH-ZSM-5 and h-MeH-Be a zeo-
li es as ca alys s esul s in signi ican ly highe concen a ions o GC-MS
Fig. 5. P oduc mass yields om ca aly ic py olysis o lignin o e hie a chical
and ion-exchanged h-H-ZSM-5 zeoli es.
Fig. 6. P oduc mass yields om ca aly ic py olysis o lignin o e hie a chical
and ion-exchanged h-H-Be a zeoli es.
M.I. ´
A ila e al.
Ca alysis Today 456 (2025) 115343
8
de ec ed componen s compa ed o hose ob ained using he pa en ze-
oli es, which indica es ha he ion-exchanged zeoli es a e mo e e icien
in ans o ming oligome s in o bio-oil* de ec able compounds compa ed
o pu e acidic zeoli e. Howe e , he excep ion is he h-NaH-Be a zeoli e,
pa icula ly a a C/L a io o 0.4, being he de ec ed ac ion in his case
simila o ha ob ained using he pa en zeoli e. This phenomenon may
be a ibu ed o he ma kedly ele a ed amoun o me al ion-exchanged
eached. I is possible ha his loading is p omo ing condensa ion and
polyme isa ion eac ions, which simul aneously inhibi s c acking e-
ac ions ha would inc ease ligh e species. This inding is consis en
wi h p e ious esul s ob ained by ou g oup wo king simila ly wi h a
Na
+
ion-exchanged comme cial nanoc ys alline H-Be a zeoli e [17]. I is
impo an o no e ha , in compa ison o ou p e ious wo k [17], whe e
nanoc ys alline zeoli es we e es ed in he same eac ion, he concen-
a ion o bio-oil* GC-MS de ec ed componen s inc eases when hie a -
chical ca alys s a e employed (5 – 15 w .%). Thus, he highe
accessibili y o hie a chical ZSM-5 and Be a zeoli es a ou s he p o-
duc ion o a bio-oil* wi h a highe concen a ion o de ec ed com-
pounds, no only in compa ison o he non-ca aly ic es , bu also in
compa ison o analogous zeoli es wi h lowe p opo ion o ex e nal
su ace a ea.
Figs. 9 and 10 summa ise he bio-oil* composi ion ob ained in he
ca aly ic py olysis o lignin employing hie a chical and ion-exchanged
H-ZSM-5 and H-Be a zeoli es, espec i ely, as ca alys s, including he
he mal esul s o compa ison pu poses. I can be obse ed ha all he
GC-MS de ec ed compounds a e also p oduced om he he mal
decomposi ion o lignin, bu hei quan i ies inc ease wi h he use o
ca alys s. This ac can be a ibu ed o he hea y/oligome ic species
decomposi ion/con e sion eac ions ha a e p omo ed when he py o-
ly ic apou s pass h ough he ca aly ic bed. The use o app op ia e
ca aly ic sys ems o lignin py olysis se es o enhance c acking e-
ac ions, deoxygena ion, dehyd a ion, and deme hyla ion. Fig. 11 dis-
plays a p oposed p ocesses scheme o he he mal and ca aly ic lignin
decomposi ion, which will be desc ibed in de ail in he subsequen
sec ions.
Signi ican inc emen s, ega ding he non-ca aly ic es , a e de ec ed
Fig. 7. O e all concen a ion o GC-MS de ec ed and non-de ec ed componen s
in he bio-oil* ob ained in he lignin ca aly ic py olysis o e hie a chical and
ion-exchanged h-H-ZSM-5 zeoli es.
Fig. 8. O e all concen a ion o GC-MS de ec ed and non-de ec ed componen s
in he bio-oil* ob ained in he lignin ca aly ic py olysis o e hie a chical and
ion-exchanged h-H-Be a zeoli es.
Fig. 9. Bio-oil* GC-MS molecula analysis ob ained in he lignin py olysis o e
hie a chical and ion-exchanged h-H-ZSM-5 zeoli es (CA: ca boxylic acids, LO:
ligh oxygena es, FUR: u ans, AR: a oma ic hyd oca bons and O-AR: oxygen-
a ed a oma ics).
Fig. 10. Bio-oil* GC-MS molecula analysis ob ained in he lignin py olysis
o e hie a chical and ion-exchanged h-H-Be a zeoli es (CA: ca boxylic acids,
LO: ligh oxygena es, FUR: u ans, AR: a oma ic hyd oca bons and O-AR:
oxygena ed a oma ics).
M.I. ´
A ila e al.
Ca alysis Today 456 (2025) 115343
9
