Jou nal o Analy ical and Applied Py olysis 170 (2023) 105928
A ailable online 18 Feb ua y 2023
0165-2370/© 2023 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/).
S udy on he ole o he eac ion ime in he upcycling o HDPE by
co-hyd oc acking i wi h VGO
F ancisco J. Vela
a
, Robe o Palos
a
,
b
, Suní Rod íguez
a
, M. Josune Azkoi i
b
, Ja ie Bilbao
a
,
Alazne Gu i´
e ez
a
,
*
a
Depa men o Chemical Enginee ing, Uni e si y o he Basque Coun y UPV/EHU, PO Box 644, 48080 Bilbao, Spain
b
Depa men o Chemical and En i onmen al Enginee ing, Uni e si y o he Basque Coun y UPV/EHU, Plaza Ingenie o To es Que edo 1, 48013 Bilbao, Spain
ARTICLE INFO
Keywo ds:
Hyd oc acking
Plas ic
Vacuum gasoil
Was e e ine y
Fuel
ABSTRACT
Pu suing he aim o imp o ing he cu en was e plas ics managemen s a egy, we ha e in es iga ed he co-
hyd oc acking o high-densi y polye hylene (HDPE) wi h acuum gasoil (VGO) o e a P Pd/HY ca alys o
con e ing his blend in o high-quali y uels. In pa icula , he wo k was ocused on assessing he e ec s o he
eac ion ime on he p oduc yields and on he composi ion o he gas, naph ha and ligh cycle oil (LCO) ac-
ions, which was de e mined by ch oma og aphic means. The expe imen al uns we e ca ied ou in a 100 mL
semi con inuous s i ed ank eac o a ying he eac ion ime be ween 15 and 120 min and main aining cons an
he es o he a iables a 420 ◦C ( empe a u e eached using an elec ical hea ing jacke and ollowing a 5 ◦C
min
−1
hea ing amp), 80 ba and a ca alys o oil mass a io o 0.075 g
ca
g
oil
−1
. The esul s shown ha a 120 min a
naph ha ac ion ich in 1- ing a oma ics and wi h a RON alue o 92.5 was ob ained, while he LCO ac ion was
mainly iso-pa a inic wi h a ce ane index o 43.8. Hence, hese ac ions could be used in he co esponding
blending s ages o comme cial gasoline and diesel. Fu he mo e, he coke deposi ed on he ca alys was analyzed
by means o TPO, ob aining ha i was mainly o med a sho con ac imes (<15 min) and ha i s na u e
e ol ed wi h con ac ime being less condensed a long con ac imes.
1. In oduc ion
Global plas ic gene a ion has inc eased es lessly in he las decades,
eaching a alue o 353 M ons in 2020 [1]. Howe e , he was e man-
agemen and ecycling s a egies con inue o all sho . Indeed, he poo
de elopmen o he ecycling indus ies has caused ha mo e han 90%
o he was e plas ics e e gene a ed ha e ended land illed, incine a ed
o dispe sed in a na u al en i onmen once hei li e cycle has eached
i s end [2]. As a consequence o his mismanagemen , he massi e
accumula ion o plas ic deb is in e es ial and aqua ic en i onmen s
has occu ed, leading o i s deg ada ion and agmen a ion in o mic o-
plas ics. In his way, he pollu ion caused by mic oplas ics is o pa ic-
ula conce n gi en he long-las ing na u e and he widesp ead p esence
o hese pa icles [3]. Fu he mo e, he eme gence o COVID-19 disease
has b ough a huge consump ion o single-use plas ic-made heal hca e
and pe sonal p o ec ion equipmen , he alo iza ion o which equi es
he es ablishmen o app op ia e s a egies [4]. The pandemic has also
delayed he poli ics o he de eloped coun ies di ec ed o cap global
plas ic p oduc ion [5] and o eplace he con en ional plas ic made om
ossil uels (99% o he cu en p oduc ion) wi h o he biodeg adable
ma e ials [6]. Hence, he ecycling o was e plas ics is a huge challenge
o mode n humankind conside ing he se e e en i onmen al and heal h
issues de i ed om hei mismanagemen .
I should be highligh ed ha he plas ic ecycling echnologies, in
pa icula he mochemical p ocesses (py olysis, gasi ica ion, ca aly ic
c acking and hyd oc acking), ha e acqui ed an impo an ma u i y le el
gi en hei e sa ili y and scaling-up capaci y [7–9]. The aim has been
mainly ocused on he p oduc ion o uels o aw chemicals by means o
selec i e p ocesses ha equi e he use o ca alys s [10]. Palos e al. [11]
analyzed he di icul ies o he ins alla ion o new indus ies o he
p oduc ion o high-quali y uels (gasoline and diesel) and hei subse-
quen comme cializa ion. Consequen ly, hey p oposed ha he bes
s a egy o sol ing in he sho - e m he se e e p oblem o was e plas ic
s ock is in ol ing oil- e ine ies in he plas ics ecycling chain (Was e
Re ine y) wi hin he Ci cula Economy amewo k. The al e na i e
s a egies ha a Was e Re ine y can o e a e: (i) he di ec co- eeding o
* Co esponding au ho .
E-mail add ess: [email p o ec ed] (A. Gu i´
e ez).
Con en s lis s a ailable a ScienceDi ec
Jou nal o Analy ical and Applied Py olysis
jou nal homepage: www.else ie .com/loca e/jaap
h ps://doi.o g/10.1016/j.jaap.2023.105928
Recei ed 7 No embe 2022; Recei ed in e ised o m 14 Feb ua y 2023; Accep ed 17 Feb ua y 2023
Jou nal o Analy ical and Applied Py olysis 170 (2023) 105928
2
he was e plas ics o al eady exis ing uni s; (ii) he co- eeding o plas ic
py olysis oil (PPO) wi h benchma k eeds ock; and (iii) he ins alla ion
o new ad hoc designed alo iza ion uni s. Mo eo e , he uels and
seconda y p oduc s ob ained in a Was e Re ine y could be en i ely
alo ized and hei composi ion would be adap ed using he sepa a ion
and e o ming uni s a ailable in e ine ies (usually al eady dep ecia ed
uni s), easing hei subsequen comme cializa ion. Among he uni s
a ailable in e ine ies o alo izing was e plas ics, he mos a ac i e
ones o he co- eeding a e he luid ca aly ic c acking (FCC) [12,13] and
he hyd oc acking uni s [14].
Hyd oc acking is a key p ocess so ha oil e ine ies can co e he
inc easing demand o uels and pe ochemicals om e e mo e hea y
c ude, wi h a la ge numbe o con aminan s (S, N, me als, asphal enes)
and p oducing a highe yield o dis illa ion esidue [15]. Based on hei
high e sa ili y, hyd oc acking uni s a e conside ed app op ia e o he
p oduc ion o uels om al e na i e eeds, such as bio-oil (liquid p oduc
ob ained in he as py olysis o biomass) and esidua om he con-
sume s socie y [16]. The alo iza ion o was e plas ics would allow o
in ensi y he alo iza ion o oil, aking in o accoun ha cu en ly mo e
han 9 w % o oil is used in he p oduc ion o plas ics [17]. In addi ion o
he en i onmen al ad an ages o ecycling was e plas ics, wi h he use o
hyd oc acking uni s, he uels p oduced would comply wi h he legal
equi emen s o a limi ed en i onmen al impac in hei combus ion. In
his sense, he eco e y in a e ine y, which al eady has he app op ia e
and dep ecia ed equipmen , also acili a es he minimiza ion o g een-
house gas emissions gene a ed in he p oduc ion o uels.
Muni e al. [18] e iewed he ecen ad ances in he s udy o hy-
d oc acking ca alys s, ocusing on he e ec s o he ope a ing condi ions
( empe a u e, hyd ogen p essu e, eac ion ime) on he con e sion,
yield and composi ion o he uels ob ained in he hyd oc acking o
di e en plas ics. The expe imen a ion has been commonly pe o med
in s i ed ba ch eac o s, wi h alues o empe a u e and hyd ogen
p essu e wi hin he anges o 300–450 ◦C and 2–15 MPa, espec i ely.
Fu he mo e, hyd oc acking shows impo an ad an ages o he p o-
duc ion o uels wi h espec o o he polyole ins alo iza ion al e na-
i es. Among hem, i should be highligh ed ha : (i) he o e c acking,
which is a usual phenomenon in ise FCC uni s, is inhibi ed. In his way,
an excessi e p oduc ion o C
1
-C
4
gaseous p oduc s is es ic ed [19]; and
(ii) he bi unc ional ca alys s used in hyd oc acking boos bo h he
c acking and he isome iza ion eac ions, p oducing high yields o
iso-pa a inic gasoline [20,21]. The mechanism occu s h ough ca be-
nium ions o highly acidic ca alys s, bu o weak acid si es, he ee
adical mechanism is he mos p edominan one. Vance e al. [22]
explained he o ma ion o iso-pa a ins in he hyd oc acking o LDPE
o e a P -WZ ca alys by he p e e en ial adso p ion o polyme chains
and hei pa ial isome iza ion p io o c acking. In his mechanism, he
me al- o-acid si e mola a io o he ca alys has a ele an ole in he
dis ibu ion and isome iza ion deg ee o he p oduc s. Ko s e al. [23]
compa ed he condi ions and selec i i y o he p oduc s ob ained in he
hyd oc acking and in he hyd olysis o polyole ins, highligh ing he
lowe ene gy demand o he hyd oc acking p ocess.
In his wo k, he hyd oc acking o a blend o high densi y poly-
e hylene (HDPE) and acuum gas oil (VGO) o e a P Pd/HY ca alys has
been in es iga ed. Paying special a en ion o he e ec s o he eac ion
ime on he con e sion o bo h eeds and on he dis ibu ion and
composi ion o he p oduc s. The aim o he wo k is o p og ess owa ds
he knowledge o he ideal ope a ing condi ions o he co- eeding o
was e plas ics wi h a e ine y s eam, which is a e e ence eeds ock o
hyd oc acking uni s due o i s high a oma ici y. The hyd oc acking o
VGO has been ex ensi ely s udied in he li e a u e, using di e en
bi unc ional ca alys s [24], bu no he join hyd oc acking o poly-
ole ins and VGO. In a p e ious wo k [25] we assessed he e ec s o
co- eeding HDPE (20 w %) wi h VGO ob aining ha he co- eeding
inc eased he con e sion o VGO and boos ed he o ma ion o
naph ha. Fu he mo e, i was es ablished ha 420 ◦C was he app o-
p ia e empe a u e o maximizing he HDPE con e sion wi hou
ob aining an excessi e o e c acking o he naph ha ac ion. In a sub-
sequen wo k [26], we de e mined he impo ance o H
2
p essu e on he
dis ibu ion and composi ion o he p oduc s. I was ob ained ha
ope a ing a 80 ba he composi ion o he ac ions ob ained was simila
o ha o e ine y gasoline and diesel. This wo k is a con inua ion o he
p e ious ones. This ime, he e olu ion o he dis ibu ion and compo-
si ion o he p oduc s wi h he con ac ime o he ca alys has been
es ablished. In addi ion, he coke deposi ed on he ca alys has been
s udied, complemen ing he knowledge o his p ocess and o e ing in-
o ma ion o in e es o de elop a s a egy o co- eeding was e plas ics
in o e ine y hyd oc acking uni s.
2. Expe imen al
2.1. Ma e ials
The acuum gasoil (VGO) was p o ided by Pe ono S.A. e ine y
(Muskiz, Spain). I consis ed o a mix u e o he hea y gasoils p oduced
in he acuum dis illa ion, isb eake and coke uni s a ailable in he
e ine y. Besides, as he VGO is commonly used in he e ine y as he
benchma k eeds ock o he luid ca aly ic c acking (FCC) uni , i was
hyd o ea ed wi hin he e ine y acili ies o educe i s con en s o sul u
and ni ogen. The main physicochemical p ope ies o he VGO ha e
been displayed in Table 1. An in-de ail explana ion o he echniques and
p ocedu es ollowed o i s cha ac e iza ion can be ound elsewhe e
[26]. In sho , i was a hea y s eam (boiling ange o 314–519 ◦C) wi h
low con en s o he e oa oms (510 and 305 ppm o sul u and ni ogen,
espec i ely), which minimized he poisoning o he suppo ed noble
me als o he ca alys . Fu he mo e, i should be highligh ed i s high
con en o a oma ic compounds (48.4 w %), in which he con ibu ion o
poly-a oma ics was qui e ema kable (15.8 w %).
The high-densi y polye hylene (HDPE) was pu chased om Dow
Chemical (Ta agona, Spain). I s main p ope ies, which ha e been
p o ided by he supplie , ha e been also ela ed in Table 1. Be o e being
used, he pelle s o HDPE we e g inded a c yogenic condi ions o educe
hei size (<100 µm).
A P Pd/HY ca alys (pa icle size 125–350 µm) was used o he
HDPE/VGO blend hyd oc acking. The ca alys was syn hesized in ou
acili ies ollowing he p ocedu e shown in Fig. S1. In essence, he HY
zeoli e (CBV712, supplied by Zeolys In e na ional) was calcined a
Table 1
Physical and chemical p ope ies o he eeds.
VGO HDPE
Physical p ope ies
densi y a 25 ◦C (g mL
−1
) 0.8912 0.9403
iscosi y a 37.8 ◦C (cS ) 34.2 –
a e age molecula weigh (g mol
−1
) 377 46,200
highe hea ing alue (MJ kg
−1
) 45 43
Simula ed dis illa ion (◦C)
IBP−FBP 314–519 –
T
50
−T
95
415–491 –
Dis illa ion ac ions (w %)
naph ha (<216 ◦C) 0.17 –
LCO (216–350 ◦C) 4.48 –
HCO (>350 ◦C) 95.4 –
Elemen al analysis (w %)
C 87.3 85.7
H 12.5 14.3
N 305
a
–
O −–
S (ppm) 510
b
–
Composi ion (w %)
pa a ins 14.0 –
naph henes 35.3 –
ole ins −–
1− ing a oma ics 20.3 –
2− ing a oma ics 12.4 –
3
+
− ing a oma ics 15.8 –
F.J. Vela e al.
Jou nal o Analy ical and Applied Py olysis 170 (2023) 105928
3
550 ◦C (hea ing a e o 5 ◦C min
−1
) o ob ain i s acidic o m. Nex , he
HY zeoli e was suspended in dis illed wa e a 80 ◦C and pH =7 o
enhance he elec os a ic a ac ion. Then, noble me als we e inco po-
a ed om aqueous solu ions o P (NH
3
)
4
(NO
3
)
2
and Pd(NH
3
)
4
(NO
3
)
2
,
bo h pu chased om Sigma-Ald ich. Once adso p ion equilib ium was
eached (~24 h), he excess o wa e was emo ed in a o a y acuum
e apo a o a 80 ◦C. A e ha , he ca alys was d ied o e nigh a
110 ◦C and, inally, i was calcined a 450 ◦C o 2 h (hea ing a e o 5 ◦C
min
−1
). Subsequen ly, he ca alys was cha ac e ized h ough se e al
echniques and ob ained esul s we e ela ed in Table S1 in Supple-
men a y Ma e ial. A desc ip ion o he p ocedu es was al eady p o ided
[25]. B ie ly, i has a me al con en o 1.19 w % o P and 0.53 w % o Pd
measu ed by ICP-AES. The TEM image (Fig. S2) shows ha P Pd me allic
si es a e well dispe sed on he su ace o he HY zeoli e. F om he N
2
adso p ion-deso p ion iso he ms i was ob ained ha he speci ic su ace
o he ca alys is o 620 m
2
g
−1
, wi h a ema kable con ibu ion o he
mic opo es (543 m
2
g
−1
). Rega ding i s acidic p ope ies, he o al
acidi y and a e age s eng h o he ca alys (1.69 mmol g
−1
and 135 kJ
mol
−1
, espec i ely) we e ob ained by means o a e -bu yl amine
empe a u e p og ammed deso p ion, whe eas he B øns ed o Lewis
acidic si es a io (1.53) was de e mined by py idine FTIR analysis. The
HY zeoli e was chosen as he suppo because i s good p ope ies in
e ms o acidi y and speci ic su ace a ea ensu e a good pe o mance in
he hyd oc acking o he s eam used in his wo k.
2.2. Expe imen al uni and p oduc analysis
The blend used o he hyd oc acking es s was composed o 20 w %
o HDPE and 80 w % o VGO. The ope a ion ook place in a 100 mL
s ainless s eel s i ed ank semi-ba ch eac o sys em om PID Engi-
nee ing & Tech. (schema ic diag am a ailable in Fig. S3). The eac o
sys em was also equipped wi h o he auxilia y i ems, such as wo gas
cylinde s (N
2
and H
2
) connec ed o a gas mass low con ol sys em, a
empe a u e con olle ha ac ed o e an elec ical hea ing jacke and a
con ol p essu e al e, among o he s [25]. The eac o essel was
loaded wi h bo h esh ca alys (3 g) and eed (40 g o he HDPE/VGO
blend) and, a e pe o ming a leak es o ensu e ha he eac o was
ai igh closed, i was hea ed up o 420 ◦C ollowing a hea ing amp o
5 ◦C min
−1
and p essu ized a 80 ba wi h pu e H
2
. The p essu e was
kep cons an a 80 ba by es ablishing a con inuous hyd ogen low (200
mL min
−1
). The s i ing was ac i a ed once he desi ed ope a ing con-
di ions we e eached, es ablishing ha e y momen as ze o ime.
Since he aim o he wo k was o assess he e ec s o he eac ion
ime, his pa ame e was a ied wi hin he ange o 15–120 min,
whe eas he es o he pa ame e s we e main ained cons an a he
ollowing alues: 420 ◦C (measu ed wi h a K ype he mocouple), 80 ba
( egula ed wi h a PID con olle ), ca alys o oil mass a io o 0.075 g
ca
g
oil
−1
and s i ing a e o 1300 pm. These alues we e es ablished based
on he esul s ob ained in ou p e ious wo ks, since hey ensu ed good
yields o naph ha and LCO ac ions wi h composi ions simila o hose
o he indus ial ac ions [25–27].
P io o he hyd oc acking eac ions, he P Pd/HY ca alys was
educed ex-si u in a ixed bed eac o a 400 ◦C o 4 h using a 80 mL
min
−1
s eam o H
2
dilu ed in N
2
(0.375 ol a io) o ensu e he o al
ac i a ion o he me allic si es.
The gases lea ing he eac o we e cooled in a double pipe condense
and he ligh es ac ion (C
1
-C
4
) was collec ed in a gas sampling bag o
be analyzed. The gas ac ion was analyzed by ch oma og aphic means
in an Agilen 6890 GC equipped wi h an FID de ec o and a HP-PONA
column (50 m ×0.2 mm ×0.5 µm).
The liquid p oduc s we e sepa a ed om he uncon e ed HDPE
(which has been deno ed as wax om his poin on) and he spen
ca alys by ollowing a wo-s age sol en ac iona ion me hod [25]. The
me hodology has been summa ized in Fig. S4. In sho , he i s s age
was pe o med a oom empe a u e and using e ahyd o u an as
ex ac ing agen o emo e he hyd oca bons om he p oduc s. While
in he second s ep, he wax was sepa a ed om he spen ca alys
ope a ing a 130 ◦C and using xylene as sol en . Finally, spen ca alys
was d ied in an o en a 150 ◦C o 24 h o ensu e ha xylene was o ally
emo ed. A e wa ds, o ully cha ac e ize he composi ion o he liquid
p oduc s, hey we e submi ed o a ious analyses. Fi s ly, he boiling
ange dis ibu ion o he liquid p oduc s was analyzed ollowing he
p ocedu e desc ibed in he ASTM D2887 S anda d. I was used an Agi-
len 6890 GC ch oma og aph p o ided wi h an FID de ec o and a
DB-2887 semi-capilla y column (10 m ×0.53 mm ×3.00 µm). This
analysis allowed o lump he liquid p oduc s in he ollowing ac ions:
naph ha (C
5
-C
12
), ligh cycle oil (LCO, C
13
-C
20
) and hea y cycle oil
(HCO, C
21+
). Secondly, he PIONA composi ion o he naph ha and LCO
ac ions was ob ained by comp ehensi e ch oma og aphy in combi-
na ion wi h mass spec ome y (GC×GC/MS). The equipmen and i s
con igu a ion ha e been explained in p e ious wo ks [14,25]. Thi dly,
he esea ch oc ane numbe (RON) o he naph ha ac ion was calcu-
la ed om gas ch oma og aphic da a as desc ibed by Ande son e al.
[28]. Fou hly, he ce ane index o he LCO ac ion was compu ed ac-
co ding o he ASTM D4737 S anda d.
The coke deposi ed on he ca alys was analyzed by means o em-
pe a u e p og ammed oxida ion (TPO) analysis in a TA Ins umen s
TGA-Q 5000 he mobalance. The p ocedu e ollowed o he analysis
co esponds has been widely epo ed in he li e a u e o cha ac e izing
he coke p oduced in he upg ading o hyd oca bon s eams [29].
2.3. Reac ion indices
Fo e alua ing he ex en o he hyd oc acking eac ions, di e en
eac ion indices we e de ined. Since he eed used was a blend o HDPE
and VGO, a con e sion index was de ined o desc ibing he con e sion
o each one. The con e sion o VGO, was e alua ed in e ms o he
disappea ance o i s hea ies ac ion, he HCO ac ion, which ep e-
sen s 95.4 w % o i s composi ion (Table 1):
VGO con e sion :XHCO =(mHCO)ini ial − (mHCO) inal
(mHCO)ini ial
⋅100 (1)
whe e (m
HCO
)
ini ial
is he mass o HCO ed in o he sys em and (m
HCO
)
inal
is he mass o HCO ob ained a e he eac ion ime.
The plas ic con e sion was de ined as ollows:
HDPE con e sion :XHDPE =(mHDPE)ini ial − (mHDPE) inal
(mHDPE)ini ial
⋅100 (2)
whe e (m
HDPE
)
ini ial
is he mass o HDPE ed in o he sys em and
(m
HDPE
)
inal
is he mass o HDPE (wax) ob ained a e he eac ion ime.
In addi ion, he yield o each p oduc ac ion was de ined as he
mass o ac ion i o med o he o al amoun o eed:
Yi=mi
(mVGO +mHDPE)ini ial
⋅100 (3)
3. Resul s and discussion
3.1. Hyd oc acking yield and con e sion
Fig. 1 depic s he e olu ion wi h he eac ion ime o he dis ibu ion
o p oduc yields, oge he wi h he HCO and HDPE con e sions (X
HCO
and X
HDPE
, espec i ely). A ending o he e olu ion o bo h ypes o
con e sion, i can be seen how di e en he eac ion a es o he HCO
and he HDPE we e. In his way, he HDPE eac ed e y slowly, while he
hyd oc acking a e o he VGO was e y as . Focusing on he la e ,
wi hin 15 min o eac ion he yield o he HCO ac ion dec eased om
76.2 o 33.6 w % (X
HCO
=55.9%) and con inued dec easing g adually
o 90 min (20.4 w %). F om his poin on, a pseudo-s able s a e was
eached and he same HCO con e sion alue was ob ained a 90 and
120 min (73.2%) alue. I has o be men ioned ha he c acking o he
F.J. Vela e al.
Jou nal o Analy ical and Applied Py olysis 170 (2023) 105928
4
HDPE chains p oduced C
13+
molecules ha we e quan i ied wi hin he
LCO and HCO ac ions, con ibu ing o he global esul o an almos
cons an HCO con e sion abo e 90 min [30]. In con as , he yield o
naph ha inc eased con inuously, going om 20.9 w % a 15 min o
36.9 w % a 120 min. Simila ly, he p oduc ion o gases inc eased wi h
he eac ion ime, eaching a inal yield o 25 w % a 120 min. The yield
o coke also inc eased om 1.1 o 1.6 w % a 15 and 120 min, espec-
i ely, which exposed ha he deposi ion o coke was such a as
phenomenon.
As a o emen ioned, he ini ial hyd oc acking a e o he HDPE was
negligible compa ed o ha o he VGO. In his way, he HDPE con-
e sion was almos null a 15 min and i emained in mode a e alues
(9.2%) a 30 min. F om his poin on, X
HDPE
inc eased up o 28.2 % a
60 min and eached a inal alue o 63.9% a 120 min. This e olu ion o
he HDPE con e sion wi h eac ion ime was in conco dance wi h ha
p e iously ob ained by Pan e al. [30] in he hyd oc acking o HDPE a
400 ◦C, 1 MPa o H
2
and using a NiMo/Al
2
O
3
ca alys . Equally, Ali e al.
[31] epo ed an inc ease in he con e sion om 30.6 % o 86.9% in he
30–60 min ange in he hyd oc acking o a blend composed o LDPE and
pe oleum esid ope a ing a 430 ◦C, 1220 psig o H
2
and using a
NiMo/γ-Al
2
O
3
ca alys . P e iously, Joo e al. [32] also ob ained a
quali a i ely simila e olu ion o he plas ic con e sion in he hyd o-
c acking o a e na y blend composed o LDPE, coal and pe oleum esid
wo king a 430 ◦C, 8.3 MPa o H
2
and using a NiMo/Al
2
O
3
ca alys .
The di e en hyd oc acking a e o he HDPE and he VGO can be
mainly a ibu ed o he limi a ions ha he HDPE molecules aced in he
ca aly ic c acking, since hey mus unde go h ough he mal c acking o
educe he HDPE chains o smalle compounds capable o di using o
he inne po ous s uc u e o he ca alys . To e alua e he ole o he
ca alys , Fig. S5 compa es, unde he same ope a ing condi ions, he
esul s o hyd oc acking VGO and HDPE/VGO blend wi hou ca alys
wi h hose ob ained in he hyd oc acking o HDPE/VGO blend wi h
ca alys . As i can be seen, he use o he ca alys is equi ed o p omo e
he con e sion o HDPE and VGO in o liquid uels (naph ha and LCO)
and gases.
3.2. Gas p oduc s
The e olu ion wi h he eac ion ime o he composi ion o he gas
p oduc s ob ained in he hyd oc acking o he HDPE/VGO blend has
been displayed in Fig. 2. A clea p edominance o he C
3
and he C
4
compounds was ob ained o all he eac ion imes, which exposed ha
he p edominan hyd oc acking mechanism is ha o ca benium ion
eac ion [33]. No e ha ligh ole ins we e no de ec ed a any eac ion
ime gi en he high hyd ogena ion ac i i y o he me als in he ca alys .
Indeed, p essu es abo e 20 ba a e enough o comple ely hyd ogena e
he ligh ole ins [26]. A 15 min, gases we e mainly o med by p opane
(73.6 w %), small amoun s o C
4
pa a ins (13.7 w %) and e hane (9 w
%) and me hane in such a low concen a ion (3.7 w %). A ending o he
end ollowed by he di e en compounds, i can be seen ha me hane,
e hane and iso-bu ane ollowed ema kably inc easing ends, while
p opane dec eased wi h eac ion ime. The e o e, a 120 min he con-
cen a ion o me hane and e hane in he gases inc eased up o 12.4 and
16.5 w %, espec i ely. Bo h he concen a ion o n- and iso-bu ane also
inc eased (14.2 and 24.4 w %, espec i ely), being he g ow h o he
la e by a mo e ema kable. Howe e , p opane emained as he mos
abundan compound (32.6 w %), in spi e o he inc easing ends o he
es o compounds.
I should be ema ked ha o 60 min onwa ds he concen a ion o
he iso-bu ane unde wen a no ably inc ease, which coincided wi h he
boos ing expe ienced by he HDPE con e sion (Fig. 1). Thus, i can be
concluded ha he dissol ed HDPE mac omolecules ha e su e ed no
only β–scission eac ions, bu also isome iza ion eac ions in he acidic
si es o he ca alys . In addi ion, ca alys deac i a ion will ha e a ma ked
impac on hese esul s, since he loss o ac i i y will p omo e he o -
ma ion o gas p oduc s by means o he mal c acking.
3.3. Naph ha ac ion
The naph ha ac ion ob ained a each eac ion ime was cha ac e -
ized acco ding o PIONA (pa a ins, iso-pa a ins, ole ins, naph henes
and a oma ics) analysis (Fig. 3). No e ha ole inic compounds we e
de ec ed in he naph ha ac ion, since hey we e p ima y p oduc s ob-
ained in he c acking o he HDPE chains, he hyd ogena ion o which is
ha de han ha o C
2
-C
4
ole ins. None heless, he concen a ion o
ole ins de ec ed was below 1.5 w % o all he eac ion imes, exposing
once again he high hyd ogena ion ac i i y o he ca alys .
Fo a eac ion ime o 15 min, an alipha ic naph ha ac ion was
ob ained, in which he concen a ion o n-pa a ins, iso-pa a ins and
naph henes accoun ed o 7.2, 33.9 and 20.9 w %, espec i ely. Thus,
he concen a ion o a oma ics was o 36.7 w %, being he mono-
a oma ics he p edominan ones (33.6 w %). A longe eac ion imes,
i can be seen ha he concen a ion o alipha ics was educed, whe eas
ha o o al a oma ics inc eased (no e ha he educ ion o he con-
cen a ion o A
2
a oma ics has been abso bed by he inc ease in he A
1
a oma ics). In his way, o a eac ion ime o 120 min he naph ha
ac ion was mainly a oma ic (48.1 w %), being clea ly domina ed by
mono-a oma ics (46.3 w %) and wi h a small concen a ion o di-
Fig. 1. E olu ion wi h he eac ion ime o he p oduc yields and con e sions.
Fig. 2. E olu ion wi h he eac ion ime o he gas composi ion.
F.J. Vela e al.
Jou nal o Analy ical and Applied Py olysis 170 (2023) 105928
5
a oma ics (1.8 w %). Fu he mo e, he concen a ion o pa a ins (n-
and iso-pa a ins), naph henes and ole ins a 120 min was o 37.3, 13.9
and 0.6 w %, espec i ely. None heless, in spi e o he dec easing end
ollowed by he concen a ion o o al pa a ins, he concen a ion o
linea pa a ins inc eased om 7.2 o 9.7 w % when inc easing he e-
ac ion ime om 15–120 min. Consequen ly, he concen a ion o
ami ied pa a ins was educed om 33.7 o 27.6 w %, espec i ely.
Simila ends we e p e iously obse ed by Pan e al. [30] in he
composi ion o he liquid p oduc ob ained in he hyd oc acking o nea
HDPE a 400 ◦C, 1 MPa and using a Ni/Al
2
O
3
ca alys .
The a o emen ioned inc ease o he concen a ion o A
1
a oma ics
can be a ibu ed o he hyd odea oma iza ion (HDA) ac i i y o he
ca alys . In his way, he 2- ing a oma ics wi hin he naph ha ac ion
we e pa ially hyd ogena ed, leading o he o ma ion o 1- ing a o-
ma ics. Likewise, he polya oma ic compounds wi hin he LCO ac ion
we e also con e ed in o A
1
compounds h ough HDA eac ions, since
benzene, oluene and xylenes a e he main p oduc s ob ained in HDA
eac ions [34]. Fu he mo e, he B øns ed acid si es o he ca alys
(Table S1) played a key ole in he mechanism o he HDA eac ions,
since he pola i y o hese acid- ype si es p omo ed he adso p ion o
highly pola A
2
and A
3+
compounds [35].
The e olu ion wi h he eac ion ime ollowed by he RON has been
also displayed in Fig. 3. The esul s show ha qui e high RON alues
we e ob ained o he whole ange o eac ion ime s udied. In his way,
a 15 min he RON was o 89.9 and i inc eased up o 92.5 a e 120 min.
The inc easing end ollowed by he RON layed on he inc easing
concen a ion o a oma ics and o iso-pa a ins, since hese ypes o
compounds ha e a posi i e impac o e RON. Mo eo e , as eac ion
ime wen by, he leng h o he HDPE chains dec eased a he same ime
ha he b anching numbe inc eased, boos ing bo h high RON alues
[36]. Vasile e al. [37] in es iga ed he hyd oc acking o he oil ob ained
in he py olysis o elec ic appliances ob aining a RON o 90.9 ope a ing
a 350 ◦C, 6.5 MPa and using a DHC-8 comme cial ca alys . The lowe
RON alues ob ained by hem can be a ibu ed o he low concen a ion
o iso-pa a ins hey had in hei naph ha ac ion, which undoub edly
played o he de imen o he RON.
To sum up, ega ding he composi ion and he RON alues o he
naph ha ac ion ob ained, i can be concluded ha his ac ion is
app op ia e o being used in he blending o comme cial gasoline in
e ine ies. Thus, by p ope ly blending his naph ha wi h o he naph has
p oduced in con en ional e ine y uni s, a comme cial gasoline ha will
comply wi h he Eu opean en i onmen al policies can be p oduced.
3.4. LCO composi ion and ce ane index
The e olu ion wi h eac ion ime o he PIONA composi ion o he
LCO ac ion has been collec ed in Fig. 4. No e ha : (i) he concen a ion
o naph henes was below 0.1 w % in all he cases; and (ii) no ole ins
we e de ec ed, so hese amilies o compounds we e no included in his
igu e. I should be highligh ed ha he e olu ion wi h he eac ion ime
ollowed by he concen a ion o he amilies o compounds wi hin he
LCO ac ion ollowed opposi e ends o hose wi hin he naph ha
ac ion (Fig. 3). A sho eac ion imes (15 and 30 min) he composi-
ion ob ained was qui e simila , being he a oma ic compounds he
p edominan ones. The a e age concen a ion o 1-, 2- and 3
+
- ing a -
oma ics was o 8.0, 43.2 and 7.1 w %, espec i ely. Wi hin he alipha ic
compounds, iso-pa a ins p edomina ed o e n-pa a ins (33.8 s. 7.9 w
%, espec i ely).
Acco ding o he a o emen ioned e ec o eac ion ime on p oduc
yields (Fig. 1), he HDPE con e sion was signi ican ly boos ed a 60 min.
Thus, his boos in he con e sion o he HDPE chains was e lec ed in
he composi ion o he LCO ac ion (Fig. 4). In his way, a 60 min he
LCO ac ion became mo e pa a inic (46.7 w %) and less a oma ic
(53.3 w %) han be o e, e en hough i s na u e was s ill a oma ic. This
change in he composi ion was by a mo e e iden a 120 min, whe e
he pa a ins accoun ed o 56.6 w % and he a oma ics o 43.4 w %.
Two main ac o s con ibu ed o ob ain hese esul s. Fi s ly, he con-
e sion o he HDPE chains o ligh e compounds, which we e mos ly
long linea pa a ins wi hin he boiling ange o he LCO ac ion [38].
Indeed, i occu s in wo consecu i e s eps as desc ibed by Pan e al. [39].
Ini ially, he polye hylene chains a e depolyme ized by andom scis-
sions, p oducing long alkenes as p oduc s. These sho e chains can
di use in o he mic opo es o he zeoli e and access he acid and me allic
ac i e si es a ailable on i s su ace. A e wa d, hese alkenes a e con-
e ed o pa a ins h ough a ca boca ionic mechanism gi en he high
H
2
p essu e a ailable in he sys em [16]. In addi ion, he long and linea
pa a inic chains p oduced in he hyd oc acking o he HDPE we e hen
isome ized h ough skele al ea angemen and subsequen ly hyd o-
c acked in he B øns ed acid si es o he ca alys [33].
Secondly, he HDA ac i i y o he ca alys sa u a ed he a oma ics
wi hin he LCO ac ion and p omo ed hei subsequen c acking and
ing opening o ligh e molecules wi hin he naph ha ac ion [40]. The
HDA mechanism implied a complex eac ion sys em ha depends on he
p ope ies o he ca alys , composi ion o he eac ion medium, and e-
ac ion condi ions. Ka akhano e al. [34] simpli ied he mechanism in o
he ollowing eac ions: (i) hyd ogena ion eac ions ( e e sible), also
Fig. 3. E olu ion wi h he eac ion ime o he naph ha composi ion and o he
RON index. Key: n-P, n-pa a ins; i-P, iso-pa a ins; N, naph henes; O, ole ins;
A
1
, 1- ing a oma ics; A
2
, 2- ing a oma ics.
Fig. 4. E olu ion wi h he eac ion ime o he LCO composi ion and o he
ce ane index. Key: n-P, n-pa a ins; i-P, iso-pa a ins; A
1
, 1- ing a oma ics; A
2
, 2-
ing a oma ics; A
3+
, 3
+
- ing a oma ics.
F.J. Vela e al.
Jou nal o Analy ical and Applied Py olysis 170 (2023) 105928
6
called sa u a ion eac ions; (ii) isome iza ion eac ions ( e e sible), also
called skele al ea angemen s; (iii) hyd oc acking eac ions, which a e
he C–C bond b eak eac ions o he o ma ion o new C–H bonds ( ing
opening eac ions o he naph henic ings a e also conside ed); and (i )
dealkyla ion eac ions, which a e he C–C bond b eak eac ions be ween
benzene ings and subs i uen alkyl chains ha esul in he emo al o
he alkyl subs i uen s. Thus, he a oma ics wi hin he LCO ac ion, such
as me hylnaph halene, acenaph hylene and py enes, we e i s con-
e ed in o simple a oma ics by pa ially sa u a ing hem. I should be
conside ed ha some o he a oma ics ob ained as p oduc in his i s
s ep o he HDA mechanism could be small enough o be pa o he
naph ha ac ion. Then, hese a oma ics can unde go ei he isome iza-
ion, hyd oc acking o dealkyla ion eac ions, p oducing simple
alipha ic compounds (especially pa a ins and naph henes) [41].
Fu he mo e, he monoa oma ics and non-a oma ic compounds can also
in e ac wi h polya oma ics o p oduce well-s uc u ed coke [42].
The e o e, a ending o he HDA mechanism o he VGO and
conside ing ha he HDPE chains wen in o depolyme iza ion and hy-
d ogena ion eac ions, long eac ion imes will p omo e he p oduc ion
o pa a inic LCO ac ions. In addi ion, when he ex en o HDPE hy-
d oc acking in he HDPE/VGO blend p og essed, he incidence in he
p oduc dis ibu ion was mo e impo an due o he compe i ion o he
alkenes coming om he HDPE agains he VGO componen s o be
adso bed in he ac i e si es o he ca alys .
The e olu ion o he ce ane index o he LCO ac ion wi h he e-
ac ion ime has been also collec ed in Fig. 4. The ce ane index is ela ed
o he composi ion o he LCO ac ion so ha i is a o ed by he
con en o pa a ins and in e sely p opo ional o a oma ics concen-
a ion [43]. By inc easing eac ion ime, wo simul aneous e ec s ha
end o p oduce pa a inic compounds we e p omo ed. On one hand, he
HDA o he VGO compounds and, on he o he hand, he depolyme -
iza ion and c acking o he HDPE molecules. Thus, he ce ane index
showed a clea inc easing end ha goes om 33.3 o 43.8 when
inc easing he eac ion ime om 15 m o 120 min. Mo eo e , a 60 min
he ce ane index inc eased ab up ly (38.0) as a consequence o he
a o emen ioned ema kable inc ease o he HDPE con e sion (Fig. 1).
The ce ane index ob ained was no ably highe han ha epo ed by
Dagonikou e al. [44] in he hyd oc acking o LCO, since hey achie ed a
alue o 32.0 ope a ing a 380 ◦C, 1200 psig o H
2
and using a NiMo/-
γ-Al
2
O
3
ca alys .
Acco ding o he cu en Eu opean legisla ion (EN 590 S anda d),
comme cial diesel mus ha e a minimum ce ane index o 46.0, which is a
alue sligh ly highe han hose ob ained o eac ion imes o 90 and
120 min (42.5 and 43.8, espec i ely). The e o e, he LCO ac ion ob-
ained in he hyd oc acking o he HDPE/VGO blend canno be di ec ly
used o eeding in e nal combus ion engines, bu i can be used in he
blending s age o he comme cial diesel pool in e ine ies.
Apa om he yield and composi ion o he naph ha and LCO ac-
ions, he amoun o he gas ac ion o med a each eac ion ime mus
be also conside ed. Indeed, i could be a c i ical pa ame e since he gas
ac ion is o ally composed o pa a ins ha lack o comme cial in e es ,
as hey canno be used as aw ma e ials in he manu ac u e o chemical
and polyme p oduc s. The e o e, his ac mus be aken in o accoun
when selec ing he op imal weigh hou ly space eloci y o ope a e in a
con inuous hyd oc acking eac o , which will be se acco ding o he
comme cial in e es o e e y single oil e ine y.
3.5. Coke deposi ion
Fig. 5 shows he TPO p o iles o he ca alys s used in he hyd o-
c acking o he HDPE/VGO blend o eac ion imes o 15, 60 and
120 min. In iew o hei shape, he TPO p o iles we e decon olu ed in o
wo Gaussian peaks, allowing us o dis inguish wo ypes o coke: coke
ype I and coke ype II. The o me bu n a low empe a u e
(375–400 ◦C), whe eas he la e equi ed highe empe a u es
(440–475 ◦C). The ela ion o combus ion empe a u e wi h coke
loca ion and na u e was es ablished acco ding o p e ious wo ks abou
he ca aly ic c acking o a blend o HDPE and VGO unde FCC condi ions
[29], he hyd oc acking o py enes on a NiW/Al ca alys [42] and he
c acking o was e polyole ins [45].
The esul s ob ained om he decon olu ion o he TPO p o iles ha e
been summa ized in Table 2, whe e he o al con en o coke, he
maximum bu ning empe a u e (T
Max
) and he con en o each ype o
coke ha e been displayed. The e olu ion wi h eac ion ime o he o al
con en o coke exposed ha almos all he coke was o med in he i s
30 min o eac ion, since he g owing a e o he coke o longe eac ion
imes was by a smalle .
Analyzing he esul s ob ained a 15 min (Fig. 5), coke ype I had i s
maximum o combus ion a 415 ◦C while coke ype II a 453 ◦C. In
addi ion, he a ea unde he cu e o coke ype I was lowe han ha o
coke ype II, meaning ha he con en o he la e was highe (Table 2).
Coke ype I was p esumably composed o depolyme ized chains o HDPE
(deg aded mac omolecules ob ained in he ini ial c acking o he HDPE)
and hea y molecules wi hin he VGO ha we e e ained on he su ace
o he ca alys . Conside ing ha he con e sion o HDPE in o p oduc
ac ions was negligible a 15 min (Fig. 1), i can be assumed ha he
con ibu ion o long HDPE chains ha canno access he po ous s uc-
u e o he ca alys was qui e ele an . Howe e , i should be also aken
in o accoun ha he me allic si es o he ca alys (P Pd) could ca alyze
he combus ion o he coke and hus would con ibu e o lowe he
Fig. 5. TPO p o iles o coke deposi ed in he ca alys o di e en eac-
ion imes.
Table 2
Decon olu ion esul s o Gaussian peaks om he TPO p o iles o he coke
deposi ed in he used ca alys o di e en eac ion imes.
Reac ion ime (min) 15 60 120
Coke con en (w %) 14.9 18.8 21.2
Coke I
T
Max
(◦C) 415 435 423
Con en (w %) 33.9 47.3 31.8
Coke II
T
Max
(◦C) 453 470 460
Con en (w %) 66.1 52.7 68.2
F.J. Vela e al.
Jou nal o Analy ical and Applied Py olysis 170 (2023) 105928
7
combus ion empe a u e [46]. The highe combus ion empe a u e o
coke ype II was associa ed wi h he combus ion o a coke wi h a lowe
H/C a io and ha was, p esumably, placed inside o he po ous s uc-
u e o he ca alys [47]. In spi e o being i s combus ion empe a u e
highe han ha o coke ype I, i was indeed qui e mode a e (T
Max
<
480 ◦C). This esul exposed ha , based on he classi ica ion es ablished
by Baue and Ka ge [48], i was an amo phous and poo ly s uc u ed
coke. This ac can be a ibu ed o he ac i i y o he ca alys o he
hyd oc acking o he coke p ecu so s ha limi ed he condensa ion o
hese in e media e molecules and, especially, hei de elopmen o-
wa ds g aphi ic s uc u es [49].
Compa ing he esul s ob ained a 60 min wi h hose a 15 min, he
TPO p o iles we e displaced owa ds highe empe a u es (coke ypes I
and II bun a 435 and 470 ◦C, espec i ely). This esul could be ela ed
o mo e condensed s uc u es (lowe H/C a io) ha we e loca ed mo e
in e nally in he s uc u e o he ca alys [50]. A his eac ion ime, coke
ype II con inue o be he main one (52.7 w % in Table 2). Fu he mo e,
simila ly o he coke o med a 15 min, he bu ning empe a u es o he
coke deposi ed a 60 min exposed ha i was a low-de eloped coke [48].
A 120 min, he amoun o coke deposi ed was bigge han ha
deposi ed in he p e ious eac ion imes. Howe e , compa ing he TPO
p o ile wi h ha ob ained a 60 min, he maximum combus ion em-
pe a u es we e displaced o lowe alues o bo h ypes o coke (423 and
460 ◦C o coke ypes I and II, espec i ely). Thus, om 60 min onwa d,
he coke did no con inued condensing, bu i was pa ially hyd oge-
na ed. This ac could be due o he hyd ogen dono cha ac e o he
HDPE molecules [51], which could con ibu e o educe he a oma ici y
and o inc ease he H/C a io o he coke. Fu he mo e, sha pe p o iles
we e ob ained, which mean ha he coke ob ained a 120 min was less
he e ogeneous. Hence, i was a ime long enough o he coke p ecu so s
and o he ca bonaceous s uc u es o e ol e. In addi ion, he coke
could be co ela ed wi h low-s uc u ed compounds based on he com-
bus ion empe a u es o bo h ypes o coke [48].
To explain he commen ed e ec o he eac ion ime on he con en
and cha ac e is ics o he coke, he change in he composi ion o he
eac ion medium mus be also aken in o accoun . Acco ding o he
e olu ion wi h eac ion ime ollowed by he p oduc yield and con-
e sions (Fig. 1), he coke o med du ing he i s 15 min o eac ion
would come om he hyd oc acking o he VGO, since he HDPE con-
e sion was e y low (X
HDPE
<2 %). Besides, conside ing he a oma ic
na u e o he VGO (Table 1) i s hyd oc acking would p oduce mo e
de eloped s uc u es [42], esul ing in a displacemen o i s combus ion
empe a u e owa ds highe alues a 60 min. Fo longe eac ion imes
(120 min), he con e sion o he HDPE was no ably p omo ed and he
composi ion o he coke will be modi ied and i will be bu n a lowe
empe a u es (Table 2). This phenomenon lied in he modi ica ion o he
composi ion o he eac ion medium ha would p oduce a coke ac ion
wi h a g ea e H/C a io [49], also in luenced by he hyd ogen dono
cha ac e o he deg aded HDPE molecules [51]. Fu he mo e, o low
alues o HDPE con e sion ( eac ion imes below 60 min), he ac ion
o coke ype I inc eased wi h eac ion ime, whe eas ha o coke ype II
dec eased. Indeed, he amoun o bo h ypes o coke we e almos equal
a 60 min (47.3 and 52.7 w % o coke ype I and ype II, espec i ely).
None heless, ex ending he eac ion ime up o 120 min en ailed an in-
c ease o he coke ype II (up o 68.2 w %), p esumably because he
alkenes o med in he decomposi ion o he HDPE we e submi ed o
oligome iza ion and condensa ion eac ions leading o he o ma ion o
polya oma ic s uc u es. Those eac ions we e su ely ca alyzed by he
acid si es o he zeoli e and ook place in pa allel wi h he p oduc ion o
uel-like molecules.
Fu he mo e, he s abili y o he ca alys was s udied, using i in
h ee successi e eac ion- egene a ion cycles. The egene a ion p o ocol
consis ed on wo successi e s ages: i) sweeping wi h N
2
o 2 h a 400 ◦C;
and, ii) coke combus ion wi h ai dilu ed in ni ogen o 19 h a 400 ◦C.
The ca alys ully eco e ed i s p ope ies a e egene a ion and he
esul s we e ep oduced in he successi e eac ions.
4. Conclusions
In he hyd oc acking o he HDPE/VGO blend unde he s udied
condi ions (420 ◦C, 80 ba and using a P Pd/HY ca alys ), he eac i i y
o he VGO and he HDPE is e y di e en . Indeed, he eac i i y o he
HCO is qui e as since he e y beginning, whe eas ha o he HDPE is
no ele an un il 60 min. Fu he mo e, he kine ics o bo h eeds is also
di e en since he con e sion o he VGO ends o a cons an alue
(73.2 w %) o imes o e 90 min, while ha o HDPE inc eases expo-
nen ially wi h eac ion ime (65 w % a 120 min). I should be high-
ligh ed he inc ease o he yield o naph ha wi h he eac ion ime
(36.9 w % a 120 min) bu also an undesi ed inc ease o gas (25 w %).
The e ec o he eac ion ime o e he composi ion o he gas,
naph ha and LCO ac ions is o e all ele an . In he gas ac ion, he
concen a ion o p opane dec eases wi h eac ion ime and ha o
me hane, e hane, n- and iso-bu ane inc eases. Fu he mo e, an inc ease
in he eac ion ime p omo es he o ma ion o 1- ing a oma ics in he
naph ha ac ion (46.3 w % a 120 min), a he same ime ha he
concen a ion o iso-pa a ins and naph henes dec eases (13.9 and
27.6 w %, espec i ely). Consequen ly, he RON alue inc eases un il
eaching i s maximum alue o 92.5.
The LCO ac ion is mainly composed o 2- ing a oma ics and iso-
pa a ins, he concen a ion o which ollows opposi e ends. Thus,
he concen a ion o he di-a oma ics dec eases wi h eac ion ime, bu
ha o ami ied pa a ins inc eases, eaching inal alues o 43.4 and
33.8 w %, espec i ely. As a consequence o he changes in composi ion,
he ce ane index inc eases, eaching i s maximum alue (43.7) a
120 min
The ca alys used shows an impo an con en o coke (abou 20 w
%), which is mainly deposi ed in he i s 15 min o eac ion. The TPO
analysis exposes he exis ence o wo ac ions o coke (coke ypes I and
II), which a e deposi ed espec i ely on he ex e nal su ace o he
ca alys pa icles and inside o he mic opo es o he zeoli e used as he
suppo . Coke ype I, which bu ns a a lowe empe a u e, has been
ela ed o hea y componen s wi hin he VGO and HDPE mac omolecules
e ained in he ca alys . Coke ype II is he main one and i s con en
inc eases in pa allel wi h he con e sion o HDPE. This ac exposes he
ole o he hyd oca bons de i ed om he hyd oc acking o HDPE in he
o ma ion o ca aly ic coke, which is ca alyzed by he acid si es o he
zeoli e.
The esul s will se e o es ablish a solid basis o con inue p o-
g essing o he co- eeding o was e plas ics oge he wi h he benchma k
eeds o he hyd oc acking uni s. I will con ibu e o each he goals o
alo izing seconda y e ine y s eams a he same ime ha he chal-
lenge o managing was e plas ics a ionally and a a la ge scale is sol ed.
CRediT au ho ship con ibu ion s a emen
F ancisco J. Vela: In es iga ion, Fo mal analysis, W i ing – o iginal
d a . Robe o Palos: Fo mal analysis, W i ing – o iginal d a , W i ing
– e iew & edi ing, Visualiza ion, Concep ualiza ion. Suní Rod íguez:
In es iga ion, Fo mal analysis. M. Josune Azkoi i: Me hodology,
P ojec adminis a ion, Visualiza ion. Ja ie Bilbao: W i ing – e iew &
edi ing, Supe ision, P ojec adminis a ion, Funding acquisi ion.
Alazne Gu i´
e ez: Supe ision, Me hodology, Visualiza ion,
Concep ualiza ion.
Decla a ion o Compe ing In e es
The au ho s decla e he ollowing inancial in e es s/pe sonal e-
la ionships which may be conside ed as po en ial compe ing in e es s:
Alazne Gu i´
e ez epo s inancial suppo was p o ided by Spain Min-
is y o Science and Inno a ion. Alazne Gu i´
e ez epo s inancial sup-
po was p o ided by Eu opean Regional De elopmen Fund. Ja ie
Bilbao epo s inancial suppo was p o ided by Basque Go e nmen .
F.J. Vela e al.
Jou nal o Analy ical and Applied Py olysis 170 (2023) 105928
8
Da a A ailabili y
Da a shown in he pape a e p ope y o he au ho s.
Acknowledgemen s
This wo k has been ca ied ou wi h he ollowing inancial suppo :
(i) g an PID2021–125255OB-I00 unded by MCIN/AEI/10.13039/
501100011033 and by “ERDF A way o making Eu ope”; (ii) he Eu o-
pean Union’s Ho izon 2020 Resea ch and Inno a ion P og am unde he
Ma ie Skłodowska-Cu ie Ac ions (g an No 823745); and, (iii) he Bas-
que Go e nmen (g an IT1645-22).
The au ho s acknowledge Pe ono S.A. e ine y o p o iding he
eed used in he wo k.
Appendix A. Suppo ing in o ma ion
Supplemen a y da a associa ed wi h his a icle can be ound in he
online e sion a doi:10.1016/j.jaap.2023.105928.
Re e ences
[1] OECD, Global Plas ics Ou look, OECD, Pa is, 2022, h ps://doi.o g/10.1787/
de747ae -en.
[2] I. An onopoulos, G. Fa aca, D. Tonini, Recycling o pos -consume plas ic
packaging was e in he EU: eco e y a es, ma e ial lows, and ba ie s, Was e
Manag. 126 (2021) 694–705, h ps://doi.o g/10.1016/j.wasman.2021.04.002.
[3] K. Hu, Y. Yang, J. Zuo, W. Tian, Y. Wang, X. Duan, S. Wang, Eme ging
mic oplas ics in he en i onmen : p ope ies, dis ibu ions, and impac s,
Chemosphe e 297 (2022), 134118, h ps://doi.o g/10.1016/j.
chemosphe e.2022.134118.
[4] A.L. Pa ício Sil a, J.C. P a a, T.R. Walke , A.C. Dua e, W. Ouyang, D. Ba cel`
o,
T. Rocha-San os, Inc eased plas ic pollu ion due o COVID-19 pandemic:
challenges and ecommenda ions, Chem. Eng. J. 405 (2021), 126683, h ps://doi.
o g/10.1016/j.cej.2020.126683.
[5] M. Be gmann, B.C. Alm o h, S.M. B ande , T. Dey, D.S. G een, S. Gundogdu,
A. K iege , M. Wagne , T.R. Walke , A global plas ic ea y mus cap p oduc ion,
Science 376 (2022) (1979) 469–470, h ps://doi.o g/10.1126/science.abq0082.
[6] V. Beghe o, R. Sole, C. Bu anello, M. Al-Abkal, M. Facchin, Recen ad ancemen s
in plas ic packaging ecycling: a mini- e iew, Ma e ials 14 (2021) 4782, h ps://
doi.o g/10.3390/ma14174782.
[7] G. Lopez, M. A e xe, M. Amu io, J. Al a ez, J. Bilbao, M. Olaza , Recen ad ances
in he gasi ica ion o was e plas ics. A c i ical o e iew, Renew. Sus ain. Ene gy
Re . 82 (2018) 576–596, h ps://doi.o g/10.1016/j. se .2017.09.032.
[8] M. Solis, S. Sil ei a, Technologies o chemical ecycling o household plas ics – A
echnical e iew and TRL assessmen , Was e Manag. 105 (2020) 128–138, h ps://
doi.o g/10.1016/j.wasman.2020.01.038.
[9] M.I. Jahi ul, M.G. Rasul, D. Schalle , M.M.K. Khan, M.M. Hasan, M.A. Haz a ,
T anspo uel om was e plas ics py olysis – a e iew on echnologies, challenges
and oppo uni ies, Ene gy Con e s. Manag. 258 (2022), 115451, h ps://doi.o g/
10.1016/j.enconman.2022.115451.
[10] A. Eschenbache , T. My s ad, N. Bech, J.Ø. Duus, C. Li, P.A. Jensen, U.
B. Hen iksen, J. Ah en eld , U.V. Men zel, A.D. Jensen, Co-p ocessing o wood and
whea s aw de i ed py olysis oils wi h FCC eed—P oduc dis ibu ion and e ec
o deoxygena ion, Fuel 260 (2020), 116312, h ps://doi.o g/10.1016/j.
uel.2019.116312.
[11] R. Palos, A. Gu i´
e ez, F.J. Vela, M. Olaza , J.M. A andes, J. Bilbao, Was e e ine y:
he alo iza ion o was e plas ics and end-o -li e i es in e ine y uni s. a e iew,
Ene gy Fuels 35 (2021) 3529–3557, h ps://doi.o g/10.1021/acs.
ene gy uels.0c03918.
[12] E. Rod íguez, A. Gu i´
e ez, R. Palos, F.J. Vela, M.J. Azkoi i, J.M. A andes, J. Bilbao,
Co-c acking o high-densi y polye hylene (HDPE) and acuum gasoil (VGO) unde
e ine y condi ions, Chem. Eng. J. 382 (2020), 122602, h ps://doi.o g/10.1016/j.
cej.2019.122602.
[13] R. Palos, E. Rod íguez, A. Gu i´
e ez, J. Bilbao, J.M. A andes, C acking o plas ic
py olysis oil o e FCC equilib ium ca alys s o p oduce uels: kine ic modeling,
Fuel 316 (2022), 123341, h ps://doi.o g/10.1016/j. uel.2022.123341.
[14] D. T ueba, R. Palos, J. Bilbao, J.M. A andes, A. Gu i´
e ez, P oduc composi ion and
coke deposi ion in he hyd oc acking o polys y ene blended wi h acuum gasoil,
Fuel P ocess. Technol. 224 (2021), 107010, h ps://doi.o g/10.1016/j.
up oc.2021.107010.
[15] A. Ma a i, H. Albazzaz, M.S. Rana, Hyd op ocessing o hea y esidual oil:
oppo uni ies and challenges, Ca al. Today 329 (2019) 125–134, h ps://doi.o g/
10.1016/j.ca od.2018.10.067.
[16] J.W. Thybau , G.B. Ma in. Mul iscale Aspec s in Hyd oc acking: F om Reac ion
Mechanism O e Ca alys s o Kine ics and Indus ial Applica ion, 1s ed., Else ie
Inc, 2016 h ps://doi.o g/10.1016/bs.aca .2016.10.001.
[17] D. Whi ehouse, Plas ic ecycling h ea ens oil demand g ow h, 2019.
[18] D. Muni , M.F. I an, M.R. Usman, Hyd oc acking o i gin and was e plas ics: a
de ailed e iew, Renew. Sus ain. Ene gy Re . 90 (2018) 490–515, h ps://doi.o g/
10.1016/j. se .2018.03.034.
[19] F.J. Vela, R. Palos, D. T ueba, J. Bilbao, J.M. A andes, A. Gu i´
e ez, Di e en
app oaches o con e was e polyole ins in o au omo i e uels ia hyd oc acking
wi h a NiW/HY ca alys , Fuel P ocess. Technol. 220 (2021), 106891, h ps://doi.
o g/10.1016/j. up oc.2021.106891.
[20] A. Bin Jumah, V. Anbumu hu, A.A. Teds one, A.A. Ga o h, Ca alyzing he
hyd oc acking o low densi y polye hylene, Ind. Eng. Chem. Res 58 (2019)
20601–20609, h ps://doi.o g/10.1021/acs.iec .9b04263.
[21] A. bin Jumah, A.A. Teds one, A.A. Ga o h, Hyd oc acking o i gin and pos -
consume polyme s, Mic opo ous Mesopo ous Ma e . 315 (2021), 110912, h ps://
doi.o g/10.1016/j.mic omeso.2021.110912.
[22] B.C. Vance, P.A. Ko s, C. Wang, Z.R. Hin on, C.M. Quinn, T.H. Epps, L.T.J. Ko ley,
D.G. Vlachos, Single po ca alys s a egy o b anched p oduc s ia adhesi e
isome iza ion and hyd oc acking o polye hylene o e pla inum ungs a ed
zi conia, Appl. Ca al. B 299 (2021), 120483, h ps://doi.o g/10.1016/j.
apca b.2021.120483.
[23] P.A. Ko s, B.C. Vance, D.G. Vlachos, Polyole in plas ic was e hyd ocon e sion o
uels, lub ican s, and waxes: a compa a i e s udy, Reac . Chem. Eng. 7 (2022)
41–54, h ps://doi.o g/10.1039/d1 e00447 .
[24] B. B owning, P. Al a ez, T. Jansen, M. Lac oix, C. Gean e , M. Tayakou -Fayolle,
A e iew o he mal c acking, hyd oc acking, and slu y phase hyd ocon e sion
kine ic pa ame e s in lumped models o upg ading hea y oils, Ene gy Fuels 35
(2021) 15360–15380, h ps://doi.o g/10.1021/acs.ene gy uels.1c02214.
[25] F.J. Vela, R. Palos, J. Bilbao, J.M. A andes, A. Gu i´
e ez, E ec o co- eeding HDPE
on he p oduc dis ibu ion in he hyd oc acking o VGO, Ca al. Today 353 (2020)
197–203, h ps://doi.o g/10.1016/j.ca od.2019.07.010.
[26] F.J. Vela, R. Palos, J. Bilbao, J.M. A andes, A. Gu i´
e ez, Hyd ogen p essu e as a
key pa ame e o con ol he quali y o he naph ha p oduced in he hyd oc acking
o an HDPE/VGO blend, Ca alys s 12 (2022) 543, h ps://doi.o g/10.3390/
ca al12050543.
[27] F.J. Vela, R. Palos, D. T ueba, T. Co de o-Lanzac, J. Bilbao, J.M. A andes,
A. Gu i´
e ez, A six-lump kine ic model o HDPE/VGO blend hyd oc acking, Fuel
333 (2023), 126211, h ps://doi.o g/10.1016/j. uel.2022.126211.
[28] P.C. Ande son, J.M. Sha key, R.P. Walsh, Calcula ion o he esea ch oc ane
numbe o mo o gasolines om gas ch oma og aphic da a and a new app oach o
mo o gasoline quali y con ol, J. Ins . Pe . 58 (1972) 83–94.
[29] E. Rod íguez, G. Elo di, J. Valecillos, S. Izaddous , J. Bilbao, J.M. A andes,
P. Cas a˜
no, Coke deposi ion and p oduc dis ibu ion in he co-c acking o was e
polyole in de i ed s eams and acuum gas oil unde FCC uni condi ions, Fuel
P ocess. Technol. 192 (2019) 130–139, h ps://doi.o g/10.1016/j.
up oc.2019.04.012.
[30] Z. Pan, X. Xue, C. Zhang, D. Wang, Y. Xie, R. Zhang, E alua ion o p ocess
pa ame e s on high-densi y polye hylene hyd o-lique ac ion p oduc s, J. Anal.
Appl. Py olysis 136 (2018) 146–152, h ps://doi.o g/10.1016/j.jaap.2018.10.011.
[31] M.F. Ali, M.N. Siddiqui, S.S.H.H. Redhwi, M. Nahid, S.S.H.H. Redhwi, M.F. Ali,
S udy on he con e sion o was e plas ics/pe oleum esid mix u es o
anspo a ion uels, J. Ma e . Cycles Was e Manag 6 (2004) 27–34, h ps://doi.
o g/10.1007/s10163-003-0102-x.
[32] H.K. Joo, C.W. Cu is, E ec o eac ion ime on he cop ocessing o low-densi y
polye hylene wi h coal and pe oleum esid, Ene gy Fuels 11 (1997) 801–810,
h ps://doi.o g/10.1021/e 960158y.
[33] J. Wei kamp, Ca aly ic hyd oc acking-mechanisms and e sa ili y o he p ocess,
ChemCa Chem 4 (2012) 292–306, h ps://doi.o g/10.1002/cc c.201100315.
[34] E. Ka akhano , A. Maximo , Y. Ka dashe a, M. Vinniko a, L. Kuliko ,
Hyd o ea ing o ligh cycle oil o e suppo ed on po ous a oma ic amewo k
ca alys s, Ca alys s 8 (2018) 397, h ps://doi.o g/10.3390/ca al8090397.
[35] C.M. Halmenschlage , M. B a , I.T. Apan, A. de Kle k, Hyd oc acking acuum gas
oil wi h wax, Ca al. Today 353 (2020) 187–196, h ps://doi.o g/10.1016/j.
ca od.2019.07.011.
[36] E. S au e , J.A. Dolan, Re a Newman, Flammable and Combus ible Liquids, in:
Handbook o Sa e y and Heal h o he Se ice Indus y - 4 ol Se , CRC P ess,
London, 2020, pp. 199–233, h ps://doi.o g/10.1201/b16087-54.
[37] C. Vasile, M.A. B ebu, T. Ka ayildi im, J. Yanik, H. Da ie, Feeds ock ecycling om
plas ics and he mose s ac ions o used compu e s. II. Py olysis oil upg ading,
Fuel 86 (2007) 477–485, h ps://doi.o g/10.1016/j. uel.2006.08.010.
[38] X. Zhang, H. Lei, G. Yada alli, L. Zhu, Y. Wei, Y. Liu, Gasoline- ange hyd oca bons
p oduced om mic owa e-induced py olysis o low-densi y polye hylene o e
ZSM-5, Fuel 144 (2015) 33–42, h ps://doi.o g/10.1016/j. uel.2014.12.013.
[39] M. Pan, J. Zheng, Y. Liu, W. Ning, H. Tian, R. Li, Cons uc ion and p ac ical
applica ion o a no el zeoli e ca alys o hie a chically c acking o hea y oil,
J. Ca al. 369 (2019) 72–85, h ps://doi.o g/10.1016/j.jca .2018.10.032.
[40] D.E. Rome o, M. Rigu o, E.J.M. Hensen, In luence o he size, o de and opology
o mesopo es in bi unc ional Pd-con aining acidic SBA-15 and M41S ca alys s o n-
hexadecane hyd oc acking, Fuel P ocess. Technol. 232 (2022), 107259, h ps://
doi.o g/10.1016/j. up oc.2022.107259.
[41] R. Palos, T. Kek¨
al¨
ainen, F. Duodu, A. Gu i´
e ez, J.M. A andes, J. J¨
anis, P. Cas a˜
no,
De ailed na u e o i e py olysis oil blended wi h ligh cycle oil and i s
hyd op ocessed p oduc s using a NiW/HY ca alys , Was e Manag. 128 (2021)
36–44, h ps://doi.o g/10.1016/j.wasman.2021.04.041.
[42] W. Wang, X. Cai, H. Hou, M. Dong, Z. Li, F. Liu, Z. Liu, S. Tian, J. Long, Di e en
mechanisms o coke p ecu so o ma ion in he mal con e sion and deep
hyd op ocessing o acuum esidue, Ene gy Fuels 30 (2016) 8171–8176, h ps://
doi.o g/10.1021/acs.ene gy uels.6b01488.
F.J. Vela e al.
Jou nal o Analy ical and Applied Py olysis 170 (2023) 105928
9
[43] A. Gu i´
e ez, J.M. A andes, P. Cas a˜
no, M. Olaza , J. Bilbao, P elimina y s udies on
uel p oduc ion h ough LCO hyd oc acking on noble-me al suppo ed ca alys s,
Fuel 94 (2012) 504–515, h ps://doi.o g/10.1016/j. uel.2011.10.010.
[44] V. Dagonikou, S. Beze gianni, D. Ka onis, LCO upg ading ia dis illa ion and
hyd op ocessing echnology, Ene gy Fuels 33 (2019) 1023–1028, h ps://doi.o g/
10.1021/acs.ene gy uels.8b04024.
[45] P. Cas a˜
no, G. Elo di, M. Iba˜
nez, M. Olaza , J. Bilbao, Pa hways o coke o ma ion
on an MFI ca alys du ing he c acking o was e polyole ins, Ca al. Sci. Technol. 2
(2012) 504–508, h ps://doi.o g/10.1039/c2cy00434h.
[46] A. Ochoa, B. A ambu u, B. Valle, D.E. Resasco, J. Bilbao, A.G. Gayubo, P. Cas a˜
no,
Role o oxygena es and e ec o ope a ing condi ions in he deac i a ion o a Ni
suppo ed ca alys du ing he s eam e o ming o bio-oil, G een Chem. 19 (2017)
4315–4333, h ps://doi.o g/10.1039/c7gc01432e.
[47] P. Cas a˜
no, A. Gu i´
e ez, I. Hi a, J.M. A andes, A.T. Aguayo, J. Bilbao, Deac i a ing
species deposi ed on P -Pd ca alys s in he hyd oc acking o ligh -cycle oil, Ene gy
Fuels 26 (2012) 1509–1519, h ps://doi.o g/10.1021/e 2019676.
[48] F. Baue , H.G. Ka ge, Cha ac e iza ion o coke on zeoli es, in: Molecula Sie e,
Science and Technology, Cha ac e iza ion II., Sp inge , Be lin, 2007, pp. 249–364,
h ps://doi.o g/10.5040/9781474217408.ch-005.
[49] M. Guisne , P. Magnoux, O ganic chemis y o coke o ma ion, Appl. Ca al. A Gen.
212 (2001) 83–96, h ps://doi.o g/10.1016/S0926-860X(00)00845-0.
[50] B. Valle, P. Cas a˜
no, M. Olaza , J. Bilbao, A.G. Gayubo, Deac i a ing species in he
ans o ma ion o c ude bio-oil wi h me hanol in o hyd oca bons on a HZSM-5
ca alys , J. Ca al. 285 (2012) 304–314, h ps://doi.o g/10.1016/j.
jca .2011.10.004.
[51] K. Kohli, R. P ajapa i, S.K. Mai y, B.K. Sha ma, Hyd oc acking o hea y c ude/
esidues wi h was e plas ic, J. Anal. Appl. Py olysis 140 (2019) 179–187, h ps://
doi.o g/10.1016/j.jaap.2019.03.013.
F.J. Vela e al.
