Applied Ca alysis B: En i onmen al 291 (2021) 120076
A ailable online 1 Ma ch 2021
0926-3373/© 2021 The Au ho s. Published by Else ie B.V. This is an open access a icle unde he CC BY-NC-ND license
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Coke deac i a ion and egene a ion o HZSM-5 zeoli e ca alys s in he
oligome iza ion o 1-bu ene
Ma a Díaz , E a Epelde*, Jos´
e Valecillos*, Sepideh Izaddous , And ´
es T. Aguayo, Ja ie Bilbao
Depa men o Chemical Enginee ing, Uni e si y o he Basque Coun y (UPV/EHU), P. O. Box 644, 48080, Bilbao, Spain
ARTICLE INFO
Keywo ds:
Oligome iza ion
1-bu ene
HZSM-5 zeoli e
Coke deac i a ion
Regene a ion
ABSTRACT
The deac i a ion phenomenon o HZSM-5 ca alys s (SiO
2
/Al
2
O
3
a io =30–280) in he 1-bu ene oligome iza ion
has been s udied. Expe imen s we e pe o med in a ixed-bed eac o a 175−325 ◦C; 1.5−40 ba ; and, 2−6 g h
mol
C
−1
. Used ca alys s we e analyzed by: empe a u e-p og ammed sweeping wi h N
2
(TPS-N
2
), soluble coke
analysis by gas ch oma og aphy/mass spec ome y (GC/MS); Fou ie - ans o m in a ed spec oscopy (FTIR);
empe a u e-p og ammed oxida ion (TPO), and; combined TPO/FTIR. The main deac i a ion cause is he olig-
ome (so coke) con inemen in he ca alys ma ix, which depends on he eac ion condi ions ( empe a u e and
p essu e). So coke is emo ed by TPS-N
2
a 400 ◦C, whe eas he emaining ha d coke, by combus ion. Two
ypes o ha d coke a e dis inguished, which a e loca ed in he ca alys ma ix and in he zeoli e mic opo es, being
he second ac ion mo e e ac o y o combus ion. The low de eloped na u e o so coke acili a es ca alys
egene a ion, which is ully achie ed by he combus ion o ha d coke a 500 ◦C.
1. In oduc ion
The oligome iza ion o C
2
-C
5
ole ins is an a ac i e and e sa ile
ou e o selec i ely p oduce en i onmen ally iendly syn he ic ans-
po a ion uels [1,2], especially i ole ins a e p oduced om sou ces
al e na i e o con en ional oil-based s eam c acking and FCC uni s [3].
Among hese ou es o ligh ole in sus ainable p oduc ion, he con e -
sion o oxygena es de i ed om biomass (me hanol, dime hyl e he
(DME), bioe hanol o bio-oil) [4–7], was es o consume socie y (mainly
polyole ins) [8–10], and CO
2
[11] a e he mos p omising ones. Like-
wise, he di ec syn hesis o ole ins om CH
4
[12] is ecei ing a g ea
a en ion.
The p oduc s o ole in oligome iza ion a e mainly composed o a
mix u e o alkenes, ee o he e oa oms and sulphu , wi h low concen-
a ion o naph henes and a oma ics, which a e a hyd ogena ion s ep
can be used as gasoline, je uel and diesel uel blending componen s
[13–15]. In addi ion o oligome iza ion and co-oligome iza ion e-
ac ions, he eac ion mechanism includes skele al and double bond
isome iza ion, hyd ogen ans e , c acking and cycliza ion eac ions
[13,16,17]. Fu he mo e, he p oduc dis ibu ion g ea ly depends on
he ope a ing condi ions (p essu e, empe a u e and space ime)
[18–22] and he ca alys p ope ies (acidi y and shape selec i i y) [1,2,
23–27]. A key a ge in he ole in oligome iza ion p ocesses is he use o
ac i e, selec i e and s able ca alys s [1,2,15]. The HZSM-5 zeoli e based
ca alys s mee hese ea u es, hough he shape selec i i y o he HZSM-5
zeoli e (MFI s uc u e) limi s he o ma ion o hyd oca bons in he
ac ion o middle dis illa es. The deac i a ion o he HZSM-5 zeoli e is
ela ed o bo h acid si e and po e blocking, whe e he con inemen o
oligome p oduc s plays a subs an ial ole, due o hei in e nal di usion
limi a ions [18,23,28].
The e a e di e en s a egies o imp o e ac i i y-selec i i y-s abili y
o he ca alys s based on HZSM-5 zeoli e [14,23,25,26,29]. Co ma e al.
[23] s udied he e ec o se e al modi ica ions o HZSM-5 zeoli es
(SiO
2
/Al
2
O
3
=20–80) o he oligome iza ion o p opylene and pen ene
a 200 ◦C and 40 ba . They epo ed ha high B ¨
ons ed acid si e densi y
and small c ys alli es imp o ed bo h p opylene con e sion and ca alys
s abili y. In he oligome iza ion o pen ene, addi ional mesopo osi y
o med by se e al desilica ion ea men s was c ucial in o de o g ea ly
imp o e ca alys s abili y. Sil a e al. [27] es ed se e al MFI-based
mic o/mesopo ous zeo ypes p epa ed ia bo om-up app oaches in he
oligome iza ion o 1-bu ene a 250 ◦C and 40 ba . O e all, he zeo ypes
p o ided wi h a egula mo phology, nanoc ys alli es and wi h a high
le el o mesopo osi y pe o med be e han he comme cial zeoli es o
he p oduc ion o middle dis illa es. We ecen ly explo ed he capaci y
o HZSM-5 zeoli e based ca alys s o he oligome iza ion o 1-bu ene a
low p essu e (1.5 ba ) [21] and high p essu e condi ions [22], o
maximizing naph ha (C
5-
C
11
) and diesel (C
12-
C
20
) yields. The ca alys s
* Co esponding au ho s.
E-mail add esses: [email p o ec ed] (E. Epelde), [email p o ec ed] (J. Valecillos).
Con en s lis s a ailable a ScienceDi ec
Applied Ca alysis B: En i onmen al
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h ps://doi.o g/10.1016/j.apca b.2021.120076
Recei ed 21 Janua y 2021; Recei ed in e ised o m 23 Feb ua y 2021; Accep ed 25 Feb ua y 2021
Applied Ca alysis B: En i onmen al 291 (2021) 120076
2
we e p epa ed wi h a hie a chical s uc u e o he pa icle, by agglom-
e a ing he zeoli e in a mesopo ous ma ix (which also p o ides me-
chanical s eng h). Unde he wide ange o ope a ing condi ions s udied
( empe a u e, p essu e, space ime and pa ial p essu e o bu ene in he
eed), he ca alys s eached a pseudo-s eady s a e a e 10−20 h on
s eam, by keeping a ema kable emaining cons an ac i i y a e a
ansien s a e o apid deac i a ion.
The unde s anding o he deac i a ion phenomenon in ole in oligo-
me iza ion eac ions is challenging because he con en ional mecha-
nisms o coke o ma ion (ca alyzed by acid si es) [5,8,30–32] a e
condi ioned by he con inemen o oligome s, which block he mic o-
po es and es ic hei accessibili y. The coke deposi ion is ela ed o he
limi ed di usion o o med liquid p oduc s, which a e apidly e ained
in he mic opo es [23,33]. The p esence o mesopo es a o s he di u-
sion o p oduc s, gi ing way o a be e ca aly ic pe o mance and less
coke con en [23,26,34].
Fu he mo e, he p esence o con ined species masks he esul s
ob ained in he analysis o spen ca alys s by using con en ional ech-
niques. Addi ionally, i hinde s he in e p e a ion o he esul s based on
he e ec o he eac ion condi ions ( empe a u e and p essu e), as he
agg ega ion s a e o he oligome p oduc s (as liquid o gas) changes,
and his a ec s hei con inemen capaci y. Likewise, he p o ocols o
emo ing he apped oligome s and deposi ed coke on he acid si es
should be de ined o he ca alys egene a ion.
This wo k ocuses on s udying he deac i a ion and egene a ion o
HZSM-5 zeoli e based ca alys s in he oligome iza ion o 1-bu ene a low
and high p essu e condi ions (1.5−40 ba ) [21,22], wi h he aim o
easonably unde s anding hese phenomena, by dis inguishing be ween
so coke (con ined oligome s) and ha d coke (mo e de eloped ca bo-
naceous species). The exis ence o hese wo coke ac ions was al eady
es ablished by Co ma e al. [23]. Likewise, we ha e es ablished he
sui able condi ions o he emo al o so coke (by sweeping) and ha d
coke (by combus ion) in o de o eco e he ca alys p ope ies. Fo his
pu pose, we ha e s udied he e ec o he SiO
2
/Al
2
O
3
a io o he
HZSM-5 zeoli e and o he mos ele an eac ion condi ions (especially
empe a u e and p essu e) on he amoun and composi ion o coke
deposi ed on he ca alys . In o de o obse e he di e ences be ween
so and ha d coke, we ha e sequen ially used di e en analysis ech-
niques: empe a u e-p og ammed sweeping wi h N
2
(TPS-N
2
) o so
coke; gas ch oma og aphy/mass spec ome y (GC/MS) o soluble coke
in CH
2
Cl
2
; Fou ie ans o m in a ed (FTIR) spec oscopy alone o
combined wi h empe a u e-p og ammed oxida ion (TPO) o o al coke
and ha d coke ( emained a e sweeping so coke); and, TPO analysis o
ha d coke, whose emo al equi es combus ion. The de e io a ion o he
physical and acid p ope ies o he used ca alys s has been s udied by
using N
2
and NH
3
adso p ion-deso p ion, espec i ely. Addi ionally,
eac ion- egene a ion cycles ha e been ca ied ou o es ablish he
sui able condi ions o coke sweeping o combus ion in o de o assu e a
o al egene a ion o he ca alys s.
2. Expe imen al
2.1. Ca alys s
HZSM-5 zeoli e based ca alys s wi h h ee di e en SiO
2
/Al
2
O
3
mola a io (30, 80 and 280) p o ided wi h a hie a chical po ous
s uc u e ha e been used in his s udy. The p ocedu e o ca alys
p epa a ion and cha ac e iza ion, as well as hei main physical and acid
p ope ies a e de ailed in Sec ion S1 and Table S1 o he Suppo ing
In o ma ion.
2.2. Equipmen and condi ions o eac ion and egene a ion
Expe imen al uns we e pe o med in an au oma ed eac ion sys em
(PID Technol., Mad id, Spain) equipped wi h a s ainless-s eel ixed-bed
eac o (in e nal diame e , 9 mm) and a pis on pump (Gilson 307) o
eeding 1-bu ene in liquid phase. A de ailed desc ip ion o he expe i-
men al se up used can be ound elsewhe e [21] and i s low diag am is
shown in Fig. S1 (Sec ion S2). Ca alys pa icles we e mixed wi h ine
SiC (pa icle diame e , 90
μ
m) so as o ensu e a cons an heigh (1.5−2
cm) and iso he mal condi ions in he ca aly ic bed [5]. P io o e-
ac ions, ca alys s we e in si u p e ea ed a 450 ◦C o 3 h unde a mo-
sphe ic p essu e in N
2
(50 cm
3
min
−1
), in o de o emo e mois u e om
he ca alys . The ollowing ope a ing condi ions we e es ed: 175−325
◦C; 1.5−40 ba ; space ime, up o 6 g
ca alys
h mol
C
−1
(as p essu e is aised
a lowe space ime is needed o each he same con e sion le el);
ca alys mass, 0.1−0.55 g; 1-bu ene (99 %, Ai Liquide) dilu ed wi h
ine gas N
2
(30 ol%.); and, ime on s eam (TOS) up o 20 h. In Sec ion
S3 o he Supplemen a y In o ma ion, he e ec o he eac ion p essu e
(1.5−40 ba ) on he agg ega ion s a e ( apo o liquid) o he 1-bu ene
eed (dilu ed in 30 ol% o N
2
) and ha o he mos ep esen a i e
lumped p oduc s (non-con e ed bu ene, p opylene, bu ane, C
5
-C
7
ole-
ins, C
8
-C
11
ole ins and C
12+
ole ins) has been analyzed a 225 ◦C
(Table S2) and 275 ◦C (Table S3). The simula ions ha e been ca ied ou
using PRO-II .10 p ocess simula ion so wa e using he Peng Robinson
he modynamic model o calcula e he apo and liquid mola ac ion
o each condi ion. The esul s shown in Table S2-S3 e eal ha he
1-bu ene eed is in apo phase unde all he eac ion condi ions es ed
in ou wo k. We can also p edic ha unde high p essu e condi ions
(abo e 10−20 ba ) he oligome p oduc s a e pa ially p esen in liquid
phase [24,35]. I should be no ed ha when he composi ion o he e-
ac ion medium comp ises hese oligome s, pa o 1-bu ene will also be
in liquid phase. The liquid s a e o a signi ican ac ion o he eac ion
medium will condi ion he kine ic esul s (including p oduc dis ibu-
ion and ca alys deac i a ion), as he oligome iza ion eac ion s eps will
be limi ed by he di usion o he di e en compounds o he eac ion
medium. Fu he mo e, he liquid s a e o he oligome s (especially o he
hea ies ones) will acili a e hei con inemen , as pa o so coke. This
si ua ion also akes place in he a oma ic alkyla ion eac ions [36].
The p ocedu e o p oduc analysis and he eac ion indices (con-
e sion, yield and selec i i y o each lumped p oduc s) a e summa ized
in Sec ion S4 o he Suppo ing In o ma ion.
Wi h he aim o s udying he ca alys egene a ion, eac ion-
egene a ion cycles we e ca ied ou ollowing wo s eps o he in si u
egene a ion o he ca alys s (a e sweeping wi h N
2
a he eac ion
empe a u e): (1) sweeping wi h N
2
a 400 ◦C (1 h); and, (2) coke
combus ion wi h a con inuous low o ai (40 cm
3
min
−1
), ollowing a
hea ing amp o 10 ◦C min
−1
up o 500 ◦C, which was kep o 0.5 h.
2.3. Used ca alys cha ac e iza ion
P io o cha ac e iza ion, all he used ca alys samples we e i s ly
swep in he eac o wi h 30 cm
3
min
−1
o N
2
a he eac ion empe a u e
Nomencla u e
C
c,
C
ci
To al coke con en and i coke ac ion con en in he
ca alys , espec i ely (w %)
E
i
Ac i a ion ene gy o he combus ion o each i coke
ac ion (kJ mol
−1
)
i
Mass ac ion o each i coke ac ion (w %)
k
1,
k
2
Kine ic cons an s o he combus ion o coke ype I and
II, espec i ely (a m
−1
h
−1
)
S
BET
, S
mic o
BET speci ic su ace a ea and mic opo e su ace a ea,
espec i ely (m
2
g
−1
)
TOS Time on s eam (h)
W Ca alys mass (g)
W/F
0
Space ime (g h mol
C
−1
)
X Con e sion (%)
M. Díaz e al.
Applied Ca alysis B: En i onmen al 291 (2021) 120076
3
o 20 min in o de o ensu e he ep oducibili y o analyses [37,38]. The
de e io a ion o physical and acid p ope ies o he coked ca alys
samples we e measu ed using he same me hods applied o esh
ca alys cha ac e iza ion (Sec ion S1). Tempe a u e-p og ammed
sweeping wi h N
2
(TPS-N
2
) o con ined oligome s (so coke) and
empe a u e-p og ammed oxida ion (TPO) wi h ai o emaining coke
(ha d coke) we e ca ied ou in a TGA Q5000TA he mobalance
(The mo Scien i ic) as p e iously epo ed [22]. Fo he TPS-N
2
analysis,
~15 mg o sample we e apidly ea ed wi h N
2
a 200 ◦C o 15 min in
o de o emo e adso bed wa e , and subsequen ly hea ed up o 400 ◦C
(10 ◦C min
−1
) in 40 cm
3
min
−1
o N
2
and kep o 20 min. TPO analysis
o emaining ha d coke was ca ied ou by in oducing 40 cm
3
min
−1
o
ai , wi h a hea ing amp o 3 ◦C min
−1
up o 575 ◦C, which was kep o 1
h ( o ensu e comple e combus ion o coke). The p ocedu e o quan i-
ying he amoun o each ac ion o ha d coke and hei combus ion
kine ics is summa ized in Sec ion S5 o he Supplemen a y In o ma ion.
In o de o iden i y he o al e ained species ( o al coke) on he used
ca alys s, a soluble coke ex ac ion wi h CH
2
Cl
2
was ca ied ou [39–42].
Fi s ly, ~100 mg o used ca alys sample we e dissol ed in HF (Me ck,
40 %), wi h a sample/HF a io o 10 g cm
−3
in a Te lon con aine o 1 h.
A e wa d, he acid solu ion was neu alized wi h a NaOH solu ion.
Secondly, he o ganic phase was ex ac ed by adding ~ 3 cm
3
o CH
2
Cl
2
(Sigma-Ald ich, 99.8 %). Finally, he liquid sample (ex ac ) was
analyzed in a GC–MS (Shimadzu QP2010) and GC-2010 gas
ch oma og aph.
FTIR and combined FTIR-TPS-N
2
and FTIR-TPO spec oscopic mea-
su emen s we e ca ied ou o he analysis o o al and ha d coke (a e
he sweeping ea men ) in a Nicole 6700 spec opho ome e (The mo-
Fishe Scien i ic) using a ansmission cell (60 scans, and esolu ion o 4
cm
−1
). The used ca alys samples (30 mg) we e suppo ed on a KB (300
mg) disc and placed in he chambe , whe e hey we e ou gassed a 200
◦C unde acuum o emo e wa e and adso bed con aminan s, and FTIR
spec a we e aken. Fo he TPS-N
2
, he sample was hea ed up o 400 ◦C
a 10 ◦C min
−1
wi h N
2
(30 cm
3
min
−1
) and kep iso he mally o 20 min.
Subsequen ly, o he TPO, he sample was cooled down o 100 ◦C, he
low was swi ched o ai (60 cm
3
min
−1
) a 100 ◦C, and he empe a u e
was aised up o 550 ◦C a 5 ◦C min
−1
and kep iso he mally o 1 h o
he comple e combus ion o ha d coke. Fo bo h TPS-N
2
and TPO mea-
su emen s, FTIR spec a we e eco ded e e y 5 min; and, simul a-
neously, e luen gas was analyzed using a mass spec ome e (OmniS a
The moS a ) eco ding a ious mass pe cha ge (m/z) signals ela ed o
hyd oca bons and CO
2
.
3. Resul s
The mos signi ican esul s o his wo k ocus on he cha ac e iza-
ion o coke, as he main esponsible o ca alys deac i a ion; and, on
he ca alys egene a ion. The ini ial hypo hesis, which is checked in his
wo k, is ha coke comp ises wo ypes o compounds, as p e iously
es ablished [23]: (1) so coke, cons i u ed by he oligome s con ined in
he ca alys po ous s uc u e (pa icula ly in he ma ix); and, (2) ha d
coke. This la e ac ion o coke is mo e s uc u ed and will be o med
by condensa ion and hyd ogen ans e eac ions, which a e ca alyzed
by he acid si es o he HZSM-5 zeoli e and will lead o he o ma ion o
polycyclic a oma ic s uc u es (mainly bicyclic and icyclic a oma ics)
[33,43,44].
3.1. E ec o he eac ion condi ions on he ca alys deac i a ion
The e ec o he eac ion condi ions on he bu ene con e sion and
p oduc yield and selec i i y has been ex ensi ely s udied in p e ious
wo ks a low p essu e [21] and high p essu e [22] condi ions. He ein,
we b ie ly epo in Sec ion S6 o he Suppo ing In o ma ion he e ec
o he eac ion condi ions on he ca alys s abili y (deac i a ion) o
con ibu e o a be e unde s anding o he main causes o deac i a ion.
As an example o he ex ensi e kine ic s udy, Fig. S2 shows he
e olu ion wi h ime on s eam o he con e sion o 1-bu ene o he
ca alys s p epa ed wi h di e en SiO
2
/Al
2
O
3
a ios (g aphs a and b, o
low and high p essu e, espec i ely) and es ed unde di e en em-
pe a u es (g aph c) and p essu es (g aph d). The e olu ion wi h ime on
s eam o he main oligome yields (C
8-
C
11
=
, C
5-
C
7
=
and C
12+
=
) unde hese
condi ions a e shown in Figs. S3-S7. The in e p e a ion o hese esul s
equi es o i s ly conside he e ec o he a iables s udied on he e-
ac ion ex en (which will a ec he concen a ion o he compounds in
he eac ion medium) and on he agg ega ion s a e o he oligome
p oduc s as gas o liquid.
As shown in Figs. S2a (1.5 ba ) and S2b (40 ba ), he highes dec ease
in bu ene con e sion is obse ed o he lowes SiO
2
/Al
2
O
3
a io. This
ac is a ibu ed o he highes acid si e densi y and acid s eng h o HZ-
30 ca alys , which a o s he o ma ion o oligome s [21–23,45], which
a e pa ially con ined in he ca alys . I should be no ed ha a low
p essu e condi ions (Figu e S2a), he deac i a ion le el is lowe a 325
◦C han a 275 ◦C (Fig. S2c), which is ela ed o a highe e apo a ion o
oligome s; and, hus, o a lowe con inemen o hese species in he
ca alys . Fu he mo e, abo e 275 ◦C, seconda y eac ions (mainly
c acking and hyd ogen ans e ) a e a o ed, gi ing way o he o ma-
ion o ligh e oligome s and pa a ins, as we p e iously epo ed [21].
The eac ion p essu e (Fig. S2d) also plays a signi ican ole on he
ca alys s abili y, being he dec ease o he bu ene con e sion highe as
he p essu e is aised, due o he highe concen a ion o hea ie olig-
ome s (as i will be seen la e ). In e es ingly, he esul s o all he ca -
alys s and es ed condi ions show a as ini ial deac i a ion pe iod,
ollowed by a pseudo-s eady s a e a e 4−5 h on s eam, in which an
almos cons an emaining ac i i y is kep (excep o 40 ba (Fig. S2d)).
This beha io has also been epo ed in he li e a u e [18,20,28], and i
is associa ed wi h a deac i a ion mechanism in which a
pseudo-equilib ium s a e is eached in he deposi ion o he species
esponsible o deac i a ion. The e ec o p essu e and empe a u e
could be ela ed o he agg ega ion s a e o componen s in he eac ion
medium. A 225 and 275 ◦C and abo e 10−20 ba , mos o oligome s
o med a he beginning o he eac ion emain adso bed in he ca alys
in liquid phase, as p e iously checked by simula ions in PRO II so wa e
(Table S2-S3). Such liquid oligome s will cause he blockage o he
zeoli e mic opo es and lead o a apid deac i a ion a he beginning o
he eac ion.
3.2. So coke
The amoun o so coke in he spen ca alys s has been de e mined
by TPS-N
2
a 200−400 ◦C wi h a amp o 10 ◦C min
−1
. Unde hese
condi ions, he emo ed species a e oligome s (so coke) con ined in he
mesopo ous ma ix o he ca alys , whe eas he mos de eloped ca bo-
naceous species (ha d coke), mainly con ined in he mic opo es o he
zeoli e, would equi e highe empe a u es o sweeping o e en a
combus ion s ep o hei emo al. Fig. 1 shows he TPS-N
2
p o iles a
di e en eac ion p essu es (Fig. 1a) and eac ion empe a u es
(Fig. 1b). As seen, by inc easing he eac ion p essu e he amoun o so
coke no ably inc eases om 5.7 w % a 1.5 ba o 19.4 w % a 40 ba ,
which could be ela ed o he highe o ma ion o hea y oligome s
(Fig. S6) and o hei lowe ola ili y, which a o he con inemen in he
ca alys pa icle.
Likewise, an inc ease in he eac ion empe a u e (Fig. 1b) gi es way
o an inc ease o he so coke con en , om 9.5 w % a 150 ◦C o 19.5 w
% a 275 ◦C. This e ec is mo e signi ican abo e 200 ◦C, which is
cohe en wi h he highe amoun o hea ie oligome s o med a highe
empe a u e (Fig. S7). In e es ingly, he maximum empe a u e o he
deso p ion peak shi s owa d highe empe a u e ( om 277.8 ◦C o
150 ◦C o 317.7 ◦C o 275 ◦C) as he eac ion empe a u e is aised. This
could be ela ed o he highe molecula weigh o hea y oligome s ha
need highe empe a u es o hei sweeping [24].
In o de o explo e he na u e o he emo ed species, we ca ied ou
he TPS-N
2
o so coke in a used HZ-30 ca alys sample (deac i a ed a
M. Díaz e al.
Applied Ca alysis B: En i onmen al 291 (2021) 120076
4
275 ◦C and 10 ba ) using in si u FTIR spec oscopy o he used ca alys
wi h simul aneous analysis o he gaseous e luen using MS. This
sweeping ea men a he eac ion empe a u e aims o simula e he
sweeping o so coke h oughou he eac ion. The e olu ion wi h
inc easing empe a u es o he di e en ial FTIR spec a ( he spec um o
he deac i a ed ca alys is sub ac ed) is shown in Fig. S8. The main FTIR
bands ha show an e olu ion wi h inc easing empe a u es a e hose
ela ed o oligome s (1378, 1461, 1608, 2856, 2871, 2923, 2930, 2960
cm
−1
) and some bands also ela ed o monocyclic a oma ics (1504 and
1608 cm
−1
) [43]. The mos p ominen MS signals (Fig. 2a) co espond o
cha ac e is ic agmen s o oligome s (m/z =28, 41, 43, 55, 57), while
he e is a sligh p esence o MS signals ela ed o alkyla ed a oma ics
(m/z =78, 91). The e olu ion wi h ime (and inc easing empe a u es)
o he de i a i e o he maximum in ensi y (dI/d ) o selec ed FTIR
bands (1462, 1608, 2871 and 2960 cm
−1
) (Fig. 2b) indica es he
emo al o hese species and ma ches he e olu ion o he MS signals
e y sa is ac o ily.
The esul s in Figs. 1 and 2 make e iden ha he majo i y o he
ca bonaceous ma e ials on he ca alys s a e con ined oligome s (so
coke), whose p esence p o ides he coke wi h a high deg ee o he e o-
genei y and he mal ins abili y, making di icul he analysis o coke and
used ca alys s. Thus, when we compa e he physical p ope ies o he
used ca alys s (Table 1) wi h hose o esh ca alys s (Table S1) we
obse e an appa en se e e de e io a ion o he ca alys p ope ies ha
does no co espond o he deac i a ion beha io shown in Fig. S2. An
appa en ull blockage o he mic opo es is obse ed o he HZ-30 and
HZ-80 ca alys s, and an almos ull blockage o he HZ-280 ca alys
a e 10−20 h on s eam. Mesopo e olume is also educed, bu o a
lesse ex en , sugges ing ha he po e blockage by coke o ma ion is
mo e p onounced in he mic opo es a he han in he mesopo es, which
is common in he zeoli e based ca alys s [26,33,35]. Thus, a subs an ial
dec ease in BET su ace is obse ed o he used ca alys s. I mus be
highligh ed ha he deg ee o po e blocking on HZSM-5 zeoli e obse ed
is no common o his zeoli e in he con e sion o hyd oca bons [46,
47], oxygena es [5] and polyole ins [31,44], unless o ull deac i a ion
condi ions. Howe e , ou ca alys s ha e shown a s able emaining ca -
aly ic ac i i y (Fig. S2). The e o e, his appa en po e blockage could be
ela ed o he p esence o so coke [33,35] ha , unde he condi ions o
he N
2
adso p ion-deso p ion analyses (-194 ◦C), ha e blocked he ac-
cess o N
2
. Howe e , unde he eac ion condi ions, he emaining ca -
aly ic ac i i y can be ela ed wi h a ce ain deg ee o so coke mobili y,
which could acili a e he access o bu ene o he acid si es. The di icul y
on he analysis o spen ca alys s in he p esence o so coke has also
been epo ed by Hen y e al. [48].
Likewise, he de e mina ion o he emaining acid p ope ies in he
used ca alys s by using TPD-NH
3
(Fig. 3) e idences ha he p esence o
so coke a ec s he measu emen s. The ca alys s exhibi a sha p
dec ease in hei o al acidi y espec o he one o esh ca alys , whe e
Fig. 1. E ec o p essu e (a) and empe a u e (b) on he TPS-N
2
p o iles o he
used HZ-30 ca alys . Reac ion condi ions: space ime, 2 g
ca alys
h mol
C
−1
; (a) 275
◦C; (b) 30 ba .
Fig. 2. E olu ion wi h ime (and inc easing empe a u es) du ing he TPS-N
2
o
so coke o he: (a) MS signals ela ed o oligome s (m/z =28, 41, 43, 55, 57)
and alkyla ed a oma ics (m/z =78, 91). (b) De i a i e o he maximum in-
ensi y (dI/d ) o selec ed FTIR bands (1462, 1608, 2871 and 2960 cm
−1
).
Reac ion condi ions: HZ-30 ca alys ; 275 ◦C; 10 ba ; space ime, 2 g
ca alys
h mol
C
−1
.
Table 1
Physical p ope ies o he ca alys s used unde di e en condi ions. Reac ion
empe a u e, 275 ◦C. Sweeping condi ions in he eac o be o e analysis: 275 ◦C
( eac ion empe a u e), 20 min.
SiO
2
/
Al
2
O
3
mola
a io
Reac ion condi ions S
BET
(m
2
g
−1
)
S
mic o
(m
2
g
−1
)
V
meso
(cm
3
g
−1
)
V
mic o
(cm
3
g
−1
)
P
(ba )
W/
F
0a
TOS
(h)
30 1.5 6 20 73 0 0.22 0
40 2 10 37 0 0.15 0
80 1.5 6 20 91 0 0.27 0
40 2 10 50 0 0.16 0
280 1.5 6 20 100 6 0.27 0.003
40 2 10 66 0 0.22 0
a
in g
ca alys
h mol
C
−1
.
M. Díaz e al.
Applied Ca alysis B: En i onmen al 291 (2021) 120076
5
he s ong acid si es (peak a high empe a u e), ela ed o he B ¨
ons ed
acid si es and p e e en ially loca ed in he in e io o he zeoli e mi-
c opo es [26], a e p ac ically blocked. A subs an ial dec ease in he acid
si es o mode a e and weak acidi y (b oad peak a lowe empe a u e),
which a e p esen in he ma ix, is also obse ed, bu o a lesse ex en in
compa ison o he s ong acid si es. Fo he HZ-280 ca alys , wi h a low
amoun o acid si es, he emaining o al acidi y is e y low.
I should be no ed ha he appa en blockage o he acid si es is
lowe han he one obse ed o he mic opo e olume (Table 1). This
di e ence could be explained because he di usion o NH
3
a he
adso p ion empe a u e (150 ◦C) will be p esumably highe han ha o
N
2
a -196 ◦C.
3.3. Analysis o o al coke
3.3.1. GC/MS o soluble coke
The ch oma og ams o he compounds ex ac ed wi h CH
2
Cl
2
om
he o al coke o used HZ-30 ca alys a 1.5 and 40 ba a e depic ed in
Fig. S9. Unde bo h eac ion p essu es, he iden i ied compounds a e
mainly ole ins and some me hyla ed monocylic a oma ics. These esul s
a e in good ag eemen wi h hose species iden i ied by TPS-N
2
/MS
(Fig. 2). Pa icula ly, a 40 ba , a high amoun o e ained hyd oca bons
is obse ed, which consis o long chain alkenes up o C
20
, whose o -
ma ion is a o ed a high p essu e. In addi ion, he coke deposi ed a 1.5
ba shows a highe amoun o a oma ic compounds, which can be
o med by seconda y eac ions (c acking, hyd ogen ans e ) om
sho e hyd oca bon chains han hose o med a high p essu e.
3.3.2. FTIR spec oscopy
Fig. 4 shows he wo mos impo an egions o bond ib a ion in he
FTIR spec a o o al coke deposi ed on he HZ-30 ca alys s a 1.5 and 40
ba . The ib a ions in he egion o 3200−2700 cm
−1
mos ly co espond
o ole ins (asymme ic and symme ic s e ching) and monocyclic a o-
ma ics, while he ib a ions in he egion o 1650−1350 cm
−1
co e-
spond o a oma ics and some bending modes o alipha ics (ole ins). A
de ail assignmen o he obse ed bands based on he li e a u e [31,32,
43,49,50], is summa ized in Table S4.
An inc ease in eac ion p essu e gi es way o a s ong g ow h o CH
2
and CH
3
abso p ion bands a 2960, 2927, 2870 cm
−1
, 1462 and 1450
cm
−1
, co esponding especially o ole ins [44,48,49,51]. Unde bo h
condi ions, an in ense band a 1608 cm
−1
is obse ed, which is cha -
ac e is ic o ole ins oo [44]. In he case o coke deposi ed a 1.5 ba , he
bands a 1508 and 1572 cm
−1
a e mo e p onounced, which is indica i e
o a oma ic species p esen in he soluble ac ion o ha d coke, due o
he seconda y c acking and hyd ogen ans e eac ions. Howe e ,
unde bo h p essu e condi ions, he s e ching bands o C
–
H o a o-
ma ics (3000–3200 cm
−1
) a e no signi ican , which means ha he
a oma ic s uc u es should be highly alkyla ed [48].
Fig. 5 shows he FTIR spec a o coke deposi ed on he HZ-30 ca a-
lys s a 10 ba , be o e and a e sweeping wi h N
2
a 550 ◦C. As we
p e iously epo ed using TPS-N
2
o he used ca alys s (Sec ion 3.2), a
g ea amoun o e ained oligome s (so coke) a e emo ed a e his
sweeping ea men , which is e idenced by he dec ease in he in-
ensi ies o he CH
2
and CH
3
abso p ion bands assigned o hese species
(2960, 2927, 2870 cm
−1
, 1462 and 1450 cm
−1
). In e es ingly, a b oad
band a ~1570−1590 cm
−1
is obse ed a e sweeping, cha ac e is ic o
mo e e ol ed polycyclic a oma ic compounds emained as ha d coke [8,
47,50,52]. Al hough sweeping a high empe a u e (550 ◦C) is su icien
o emo ing so coke, his p ocedu e also modi ies he s uc u e o he
emaining species, as a consequence o he phenomenon o coke aging in
Fig. 3. De e io a ion o he acidi y (TPD-NH
3
p o iles) o he ca alys s used
unde di e en condi ions. (a) Di e en SiO
2
/Al
2
O
3
o he zeoli e, 275 ◦C, 1.5
ba , 6 g
ca alys
h mol
C
−1
. b) Di e en p essu e, 275 ◦C, 2 g
ca alys
h mol
C
−1
. c)
Di e en empe a u e, 1.5 ba , 6 g
ca alys
h mol
C
−1
. Sweeping condi ions be o e
analysis: 275 ◦C ( eac ion empe a u e), 20 min.
Fig. 4. E ec o p essu e on he FTIR spec a o he used HZ-30 ca alys . Re-
ac ion condi ions: 275
◦C; space ime, 6 g
ca alys
h mol
C
−1
. Sweeping o he
ca alys be o e analysis: 275 ◦C ( eac ion empe a u e), 20 min.
M. Díaz e al.
Applied Ca alysis B: En i onmen al 291 (2021) 120076
6
which dehyd ogena ion and polyme iza ion eac ions ake place [38,
52]. These esul s highligh he impo ance o coke aging in he s ep o
sweeping o so coke, which should be aken in o conside a ion o he
ca alys egene a ion. The no able eco e y o he speci ic su ace o he
ca alys (238 m
2
g
−1
a e he sweeping ea men and 266 m
2
g
−1
o
he esh ca alys ) and i s acidi y (0.34 mmol
NH3
g
−1
and 0.38 mmol
NH3
g
−1
, espec i ely) gi es e idence o he impac o so coke on he
ca alys ac i i y loss. The main cause o no achie ing a comple e e-
co e y o he physical and acid p ope ies is he p esence o ha d coke on
he acid si es. In addi ion, we ha e also checked ha he H/C a io o
coke be o e his high empe a u e sweeping ea men shows alues o
~1.9, which is cohe en wi h he high con en o oligome s (so coke).
A e he sweeping ea men , he H/C a io alues dec eases down o
~0.75.
3.4. Analysis o ha d coke
The amoun o ha d coke was de e mined by he TPO o he
emaining species a e he TPS-N
2
(Sec ion 3.2), and, he e o e, a e
he emo al o so coke. Fig. 6 shows he e ec o he eac ion em-
pe a u e on he TPO p o iles o he HZ-30 ca alys used a 1.5 ba
(Fig. 6a) and 40 ba (Fig. 6b). Two ac ions o ha d coke a e dis in-
guished acco ding o he combus ion empe a u e: coke I, bu ning a low
empe a u e (420−440 ◦C), and coke II, bu ning a highe empe a u e
(520−550 ◦C). The p esence o hese coke ac ions is common in
di e en eac ions ca alyzed by HZSM-5 zeoli es. Coke I is deposi ed in
he ca alys ma ix (mesopo ous s uc u e), which acili a es i s com-
bus ion a lowe empe a u es, whe eas coke II is deposi ed in he mi-
c opo es, and, he e o e, i s combus ion akes place a highe
empe a u es because o he cons ains imposed by shape selec i i y [5,
31,32].
I is impo an o highligh he high con en o ha d coke a 1.5 ba
(Fig. 6a) coinciding wi h he low con en o so coke a his low p essu e
(Fig. 1a), which indica es ha low p essu es a o he o ma ion o ha d
coke, due o seconda y eac ions o c acking and hyd ogen ans e . A
low p essu e condi ions (1.5 ba , Fig. 6a) i is no ewo hy o men ion he
inc ease in o al coke con en and, pa icula ly, in he amoun o coke II
as he empe a u e is aised, which is consis en wi h he highe eloci y
o oligome iza ion eac ions and seconda y eac ions o o m ha d coke.
The la e e ec is especially ele an , in iew o he inc ease in he peak
o coke II obse ed while inc easing empe a u e. This e ec is also
obse ed a 40 ba (Fig. 6b), bu he lowe coke con en ob ained unde
hese condi ions makes his compa ison di icul .
The amoun o wo coke ac ions has been quan i ied by TPO
analysis (Sec ion S5). The esul s summa ized in Table 2 gi e e idence o
he highe eac i i y o coke I (highe kine ic cons an and lowe
appa en ac i a ion ene gy) in compa ison o coke II. The inc ease in he
ac i a ion ene gy o he combus ion o coke I deposi ed a 1.5 ba as he
eac ion empe a u e is aised could be explained by he highe ex en o
he condensa ion eac ions. This e ec is no obse ed o coke II. The
maximum appa en ac i a ion ene gy a 250 ◦C may indica e ha abo e
his empe a u e, and o he o ma ion o his coke ac ion, he p es-
ence o ligh oligome s accessing he mic opo ous s uc u e a he han
hei highe condensa ion a e is mo e impo an . The e ec o em-
pe a u e on he ola ili y o coke p ecu so s is a enua ed a 40 ba , and,
hus, a high p essu e condi ions, he kine ic pa ame e s o coke com-
bus ion, and p esumably coke composi ion, sligh ly a y in he
225−275 ◦C empe a u e ange.
Fig. 7 shows he TPO p o iles co esponding o he combus ion o
Fig. 5. E ec o sweeping ea men wi h N
2
(550 ◦C) on he FTIR spec a o he
used HZ-30 ca alys s. Ope a ing condi ions: 275 ◦C, 10 ba , 2 g
ca alys
h mol
C
−1
.
Sweeping condi ions be o e analysis: 275 ◦C ( eac ion empe a u e), 20 min.
Fig. 6. E ec o eac ion empe a u e on he TPO p o iles o he combus ion o
he ha d coke deposi ed on HZ-30 ca alys . Reac ion condi ions: (a) 1.5 ba , 6
g
ca alys
h mol
C
−1
, TOS =10 h. (b) 40 ba , 2 g
ca alys
h mol
C
−1
, TOS =20 h.
Sweeping condi ions be o e analysis: 400 ◦C, 20 min.
Table 2
E ec o he eac ion empe a u e on he ha d coke con en (C
c
), coke I ac ion
(
c1
) and on he kine ic pa ame e s o he combus ion o each ha d coke ac ion
deposi ed on he HZ-30 ca alys a 1.5 ba and 40 ba and di e en eac ion
empe a u es. The esul s co espond o he TPO p o iles plo ed in Fig. 6.
T
(◦C)
C
c
(w
%)
C1
(%)
Coke I Coke II
k
1
(a m
−1
h
−1
)
E
1
(kJ
mol
−1
)
k
2
(a m
−1
h
−1
)
E
2
(kJ
mol
−1
)
1.5 ba
a
225 1.39 88.8 21 ±3 45 ±1 7 ±1 162 ±18
275 2.13 78.2 22 ±2 55 ±1 9 ±1 217 ±12
325 6.21 52.2 48 ±3 62 ±1 9 ±0 119 ±4
40 ba
b
225 1.05 87.5 25 ±3 68 ±5 3 ±1 244 ±33
250 1.13 71.9 22 ±5 58 ±4 4 ±1 230 ±13
275 1.52 73.4 21 ±4 68 ±9 4 ±1 221 ±13
a
space ime, 6 g
ca alys
h mol
C
−1
.
b
space ime, 2 g
ca alys
h mol
C
−1
.
M. Díaz e al.
Applied Ca alysis B: En i onmen al 291 (2021) 120076
7
ha d coke deposi ed on he HZ-30 ca alys unde di e en p essu e
condi ions. A aise in p essu e gi es way o a dec ease in ha d coke
deposi ion, as summa ized in Table 3, om 2.91 w % (1.5 ba ) o 1.52
w % (40 ba ). This could be linked o he lowe concen a ion o bu ene
and ola ile ligh oligome s in he eac ion medium, which a e p e-
sumably mo e ac i e in he o ma ion o ha d coke. Fu he mo e, he
highe con en o so coke would pa ially supp ess he eac ions o ha d
coke o ma ion, as he di usion o bu ene and ola ile ligh oligome s
and hei con ac on acid si es will be hinde ed by he componen s in
liquid phase.
I mus be no ed ha he ha d coke con en in Tables 2 and 3 is lowe
han ha epo ed by Coelho e al. [18] o he oligome iza ion o
1-bu ene on a HZSM-5 zeoli e o SiO
2
/Al
2
O
3
=30 o TOS o 21 min and
a bu ene pa ial p essu e o 0.5 ba . This could be ela ed o he
agglome a ion o he zeoli e (50 w %) on a ma ix, while hey used a
pu e zeoli e as ca alys . Mo eo e , he se e e condi ions o he sweeping
s ep (TPS-N
2
) p io o he TPO measu emen s in his wo k condi ion he
composi ion o emaining ha d coke and i s combus ion.
The TPO o ha d coke in he HZ-30 ca alys (deac i a ed a 275 ◦C
and 10 ba and swep by TPS-N
2
) was also s udied by using in si u FTIR
spec oscopy and wi h simul aneous analysis o he gaseous e luen
using MS. Du ing his expe imen , we obse ed he e olu ion o he FTIR
bands ela ed o a oma ics (1462 and 1572 cm
−1
) and some alipha ics
co esponding o oligome s o subs i uen s o a oma ics (1378, 2871,
2930, 2960 cm
−1
). Fig. 8 shows he e olu ion wi h ime (and inc easing
empe a u e) o he MS signal co esponding o CO
2
(m/z =44) (Fig. 8a)
and o he de i a i e o he maximum in ensi y (dI/d ) o selec ed FTIR
bands (1378, 1462, 1572 and 2871 cm
−1
) (Fig. 8b). Rega ding he
e olu ion o hese bands, i s , he ligh e componen s o ha d coke
(2871 cm
−1
) a e emo ed by combus ion a lowe empe a u es gi ing
ise o he CO
2
signal. These componen s ha e an alipha ic na u e and
may be a ibu ed o emaining oligome s o subs i uen s o a oma ics
ha a e easily emo ed a he TPO condi ions. Second, he bands
cha ac e is ics o a oma ics (1378, 1462 and 1572 cm
−1
) show a nega-
i e e olu ion a lowe empe a u es (a he ime ha he ligh e species
a e emo ed) and a posi i e e olu ion a highe empe a u es. The
nega i e e olu ion indica es ha hese species pa ially e ol e in he
ca alys wi hou being emo ed ye , indica ing he occu ence o an
aging p ocess ha leads o he o ma ion o mo e de eloped/condensed
polycyclic a oma ics [38,52]. Upon u he inc eases o he empe a u e
(hea ing amp), hese species show a posi i e e olu ion indica ing ha
hey a e e en ually emo ed by combus ion.
3.5. Ca alys egene a ion
A key ac o in he easibili y o he bu ene oligome iza ion is he
ca alys egene a ion o he use in successi e eac ion- egene a ion
cycles wi h a ep oducible beha io . Al hough a comple e combus ion
o deposi ed coke has been obse ed a 575 ◦C in he TPO analysis
(Sec ion 3.3), he o al eco e y o he ca aly ic ac i i y (ca alys
egene a ion) mus be checked. Hence, eac ion- egene a ion cycles
ha e been pe o med, ollowing he p ocedu es desc ibed in Sec ion 2.2
Acco ding o he TPS-N
2
esul s o he used ca alys s (Sec ion 3.2),
so coke can be easily emo ed a e sweeping. Hence, a egene a ion
s a egy based on sweeping wi h N
2
(40 cm
3
min
−1
) a 400 ◦C o 1 h has
been analyzed. We ha e checked ha his is he minimum empe a u e
o o ally emo ing so coke, in ag eemen wi h he TPS-N
2
p o iles
shown in Fig.3. This sweeping is a p io s ep o coke combus ion, aiming
o emo e mos o he compounds con ined wi hin he ca alys po ous
s uc u e, whose uncon olled combus ion may gene a e ho spo s and
i e e sible de e io a ion o ca alys acidi y. The esul s co esponding
o he eac ion-sweeping cycles o a HZ-30 ca alys unde se e e
deac i a ion condi ions a e plo ed in Fig. 9. As obse ed, by emo ing
con ined oligome s he ini ial ac i i y is almos eco e ed as well as he
ini ial p oduc yield. This obse a ion e eals ha he main cause o he
ca alys deac i a ion obse ed in he ea ly s ages o he eac ion is he
Fig. 7. E ec o p essu e eac ion on he TPO p o iles o he coke deposi ed on
HZ-30 ca alys . Reac ion condi ions: 275
◦C, 2 g
ca alys
h mol
C
−1
; TOS =20 h.
Sweeping condi ions be o e analysis: 400 ◦C, 20 min.
Table 3
E ec o eac ion p essu e on he ha d coke con en (C
c
), coke I ac ion (
c1
) and
on he kine ic pa ame e s o he combus ion o each coke ac ion deposi ed on
he HZ-30 ca alys . The esul s co espond o he TPO p o iles plo ed in Fig. 7.
P essu e
(ba )
C
c
(w
%)
C1
(w
%)
Coke I Coke II
k
1
(a m
−1
h
−1
)
E
1
(kJ
mol
−1
)
k
2
(a m
−1
h
−1
)
E
2
(kJ
mol
−1
)
1.5 2.91 78.2 22 ±2 55 ±1 9 ±1 217 ±12
20 1.83 85.8 34 ±5 48 ±2 7 ±1 230 ±11
40 1.52 73.4 21 ±4 68 ±9 4 ±1 221 ±13
Fig. 8. E olu ion wi h ime (and inc easing empe a u es) o he: (a) CO
2
MS
signal. (b) De i a i e o he maximum in ensi y (dI/d ) o selec ed FTIR bands,
du ing he TPO analysis o he ha d coke deposi ed on HZ-30 ca alys . Reac ion
condi ions: 275 ◦C, 10 ba , 2 g
ca alys
h mol
C
−1
, TOS =20 h. Sweeping condi ions
be o e analysis: 400 ◦C, 20 min.
M. Díaz e al.
Applied Ca alysis B: En i onmen al 291 (2021) 120076
8
con inemen o oligome s (so coke). A ound 90 % o he ca bonaceous
species e ained on he spen ca alys s can be a ibu ed o his so coke.
The incomple e eco e y o he ini ial ac i i y may be caused by he
p esence o ha d coke o med du ing he eac ion and by he aging o
so coke o o m ha d coke unde sweeping a high empe a u e [38,
52]. Thus, ha d coke ha emains a e sweeping (Sec ion 3.3) will
equi e a subsequen combus ion s ep o i s comple e emo al.
Fig. 10 shows he e olu ion wi h ime on s eam o bu ene con e -
sion and o he yields co esponding o he main ole in ac ions (C
5-
C
7
=
,
C
8-
C
11
=
and C
12
+
) wi h he esh ca alys (Fig. 10a) and a e a egene a ion
ea men (Fig. 10b) based on he combus ion o coke wi h a con inuous
low o ai (40 cm
3
min
−1
), ollowing a hea ing amp o 10 ◦C min
−1
om 275 ◦C up o 500 ◦C (a which he CO
2
o ma ion is negligible). As
seen, he ca alys eco e s i s ac i i y and he e olu ion o con e sion
and ole in yields wi h ime on s eam wi h he egene a ed ca alys a e
simila o hose ob ained wi h he esh ca alys . These esul s gi e also
e idence o he high hyd o he mal s abili y o his ca alys . I mus be
poin ed ou ha he deg ada ion o he acidic si es in he egene a ion
(by dehyd oxyla ion o B ¨
ons ed si es o Lewis) is a oided, as he ca a-
lys calcina ion empe a u e o i s equilib a ion (575 ◦C) is no excee-
ded du ing egene a ion (a 500 ◦C) [53,54]. Fu he mo e, he
agglome a ion o he zeoli e wi h a ma ix a o s he dissipa ion o he
hea gene a ed du ing he coke combus ion.
4. Conclusions
The use o di e en echniques o he analysis o he spen ca alys s
in a wide ange o eac ion condi ions has allowed us o ob ain a gene al
iew o he complex phenomenon o ca alys deac i a ion in he oligo-
me iza ion o ole ins. The esul s p esen ed in his wo k co espond o
he oligome iza ion o 1-bu ene on HZSM-5 zeoli es embedded in a
mesopo ous ma ix o γ-Al
2
O
3
and
α
-Al
2
O
3
, bu he conclusions a e o
gene al in e es o making p og ess on he imp o emen o he ca alys
s abili y o he oligome iza ion o o he ole ins.
The main cause o ca alys deac i a ion is he blockage o he po es o
he ma ix and he zeoli e by so coke ha is composed o oligome s ha
a e he p ima y eac ion p oduc s. The eac ion p essu e and empe a-
u e in luence he o ma ion a e, composi ion and agg ega ion s a es
(liquid o gas) o hese oligome s, which a ec s hei capaci y o being
con ined in he po ous s uc u e. Fu he mo e, i also con ibu es o he
ca alys deac i a ion he p esence in he ma ix and in he zeoli e mi-
c opo es o ha d coke. This coke is cons i u ed by ole inic and a oma ic
species ha a e o med by seconda y eac ions ca alyzed by he acid
si es (in which he hyd ogen ans e eac ion plays a key ole). The
sweeping o so coke wi h an ine gas (N
2
) a high empe a u e also
con ibu es o he o ma ion o his ha d coke by an aging phenomenon.
The combus ion o he ha d coke ac ion in he ca alys ma ix is
a o ed by he accessibili y o ai in o he mesopo ous s uc u e and
p obably by he mo e hyd ogena ed and less s uc u ed na u e o his
coke. The amoun o ha d coke deposi ed in he zeoli e mic opo es is
lowe (which is cha ac e is ic o HZSM-5 zeoli es), and as a highe
combus ion empe a u e, a lowe kine ic cons an and a highe appa en
ac i a ion ene gy o i s combus ion in compa ison o he combus ion o
ha d coke deposi ed in he ma ix.
A ca alys egene a ion p ocedu e based on sweeping wi h an ine
gas a high empe a u e almos o ally eco e s he ca alys ac i i y.
Howe e , a comple e ca alys egene a ion equi es he combus ion o
coke wi h ai a a ela i e low empe a u e (500 ◦C). Hence, a ep o-
ducible beha io o he ca aly ic pe o mance in successi e eac ion-
egene a ion cycles has been achie ed in he oligome iza ion o 1-
Fig. 9. E olu ion o bu ene con e sion and C
5-
C
7
=
, C
8-
C
11
=
and C
12
+
ac ion yield
wi h ime on s eam in a eac ion-sweeping cycle on HZ-30 ca alys . (a) Fi s
eac ion ( esh ca alys ); (b) Second eac ion ( egene a ed ca alys ). Reac ion
condi ions: 250 ◦C, 40 ba , 1 g
ca alys
h mol
C
−1
. Regene a ion condi ions:
Sweeping wi h a con inuous low o N
2
a 400 ◦C (40 cm
3
min
−1
).
Fig. 10. E olu ion o bu ene con e sion and C
5-
C
7
=
, C
8-
C
11
=
and C
12
+
ac ion
yield wi h ime on s eam in a eac ion- egene a ion cycle on HZ-30 ca alys .
(a) Fi s eac ion ( esh ca alys ); (b) Second eac ion ( egene a ed ca alys ).
Reac ion condi ions: 275 ◦C, 40 ba , 2 g
ca alys
h mol
C
−1
. Regene a ion condi-
ions: Coke combus ion wi h a con inuous low o ai (40 cm
3
min
−1
), ollowing
a hea ing amp o 10 ◦C min
−1
om 275 ◦C up o 500 ◦C.
M. Díaz e al.
Applied Ca alysis B: En i onmen al 291 (2021) 120076
9
bu ene.
CRediT au ho ship con ibu ion s a emen
Ma a Díaz: Concep ualiza ion, Me hodology, In es iga ion, Da a
cu a ion. E a Epelde: Fo mal analysis, Valida ion, Da a cu a ion,
W i ing - o iginal d a . Jos´
e Valecillos: Me hodology, Visualiza ion,
In es iga ion, W i ing - o iginal d a . Sepideh Izaddous : In es iga-
ion, Fo mal analysis, W i ing - e iew & edi ing. And ´
es T. Aguayo:
So wa e, Resou ces, Supe ision, P ojec adminis a ion, Funding
acquisi ion. Ja ie Bilbao: Concep ualiza ion, Supe ision, W i ing -
o iginal d a , P ojec adminis a ion, Funding acquisi ion.
Decla a ion o Compe ing In e es
The au ho s decla e no compe ing inancial in e es .
Acknowledgmen s
This wo k has been ca ied ou wi h he inancial suppo o he
Minis y o Economy and Compe i i eness o he Spanish Go e nmen
(P ojec s PID2019/108448RB-100 and CTQ2016-79646-P), he ERDF
unds and he Basque Go e nmen (P ojec IT1218-19). M. Díaz is
g a e ul o he PhD g an om he Depa men o Educa ion, Uni e si y
and Resea ch o he Basque Go e nmen (PRE_2014_1_344). J. Valecillos
and S. Izaddous a e hank ul o he Minis y o Economy, Indus y and
Compe i i eness o he Spanish Go e nmen o hei g an s BES-2014-
069980 and BES-2017-080077, espec i ely. The au ho s also hank o
echnical and human suppo p o ided by IZO- SGIke o UPV/EHU and
Eu opean unding (ERDF and ESF).
Appendix A. Supplemen a y da a
Supplemen a y ma e ial ela ed o his a icle can be ound, in he
online e sion, a doi:h ps://doi.o g/10.1016/j.apca b.2021.120076.
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