Examinando por Autor "Briones, L."

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Catalytic upgrading of a model polyethylene pyrolysis oil by hydroconversion over Ni-containing hierarchical Beta zeolites with tailored acidity
(Elsevier, 2023) Briones, L.; Cordero, A.; Alonso-Doncel, M.; Serrano, D.P.; Escola, J.M.
Valorization of waste polyolefins by a sequential combination of thermal pyrolysis and catalytic hydroconversion over a bifunctional metal/acid catalyst (e.g. zeolite) is an efficient route to produce transportation fuels. However, the zeolite strong acidity typically causes extensive cracking and loss of liquid fuels. In this work, mild dealumination with oxalic acid of a hierarchical Beta zeolite was used to achieve Ni 7%/h-Beta catalysts with Si/ Al ratios within the 25 – 130 range. These catalysts were tested in the hydroconversion of a model mixture of LDPE thermal pyrolysis product (1-dodecene/n-dodecane, 50/50 w/w). The highest share of liquid fuels (~ 90%) was achieved over 7% Ni/h-Beta (SiAl = 130). Besides, due to its high accessibility and tailored acidity, the product contained a meaningful amount of isoparaffins (12%) and a negligible content of olefins (< 3.5%). Thus, this catalyst holds promise for plastic waste hydroconversion towards transportation fuels.
Catalytic upgrading of lignin-derived bio-oils over ion-exchanges H-ZSM-5 and H-Beta zeolites
(Elsevier, 2023-10-20) Avila, M.I.; Alonso-Doncel, M.M.; Briones, L.; Gómez-Pozuelo, G.; Escola, J. M.; Serrano, D.P.; Peral, A.; Botas, J. A.
H-ZSM-5 and H-Beta zeolites ion-exchanged with alkali (Na+ and K+) and alkaline-earth (Mg2+) metals have been explored for the catalytic fast pyrolysis of lignin. Incorporating these metals led to a significant change in the acidic properties of the parent zeolites turning into mostly Lewis-type acidity. Catalytic fast pyrolysis experiments of lignin were performed in a fixed bed reactor with ex-situ configuration operating at 550 ◦C (thermal zone) and 450 ◦C (catalytic zone), atmospheric pressure and under a nitrogen flow. Moreover, two catalysts to lignin mass ratios (C/L = 0.2 and 0.4) were studied. Compared with non-catalytic tests, the use of parent zeolites caused a decrease in the bio-oil* (water-free basis) yield due to enhanced production of gases, water, and the coke deposition on the catalyst. In addition, the quality of bio-oil* was improved since it presents a lower oxygen content regarding the thermal test. H-Beta zeolite showed a higher deoxygenation degree than H-ZSM-5, but the latter exhibited a higher share of light components in the bio-oil* that can be detected by GC-MS analyses. Both catalysts promoted the production of light oxygenates, aromatics, and oxygenated aromatics. Regarding the effect of the incorporation of metals, oxygenated aromatic compounds were the predominant family in the biooil* obtained with all ion-exchanged zeolites. Likewise, significant differences were observed among the catalysts regarding the main components of this family (alkylphenols, guaiacols, syringols, catechols, and methoxybenzenes), achieving guaiacols concentrations in bio-oil* near to 24 wt.% for NaH-ZSM-5 and KH-ZSM-5 catalysts, and alkylphenols concentrations close to 16 wt.% for MgH-Beta and KH-Beta zeolites.
Production of high value-added phenolic compounds through lignin catalytic pyrolysis over ion-exchanged hierarchical ZSM-5 and Beta zeolites
(Elsevier, 2025-08-01) Ávila, M.I.; Alonso-Doncel, M.M.; Cueto, J.; Briones, L.; Gómez-Pozuelo, G.; Escola, J.M.; Serrano, D.P.; Peral, A.; Botas, J.A.
Synthesised H-ZSM-5 and H-Beta zeolites with hierarchical porosity (h-H-ZSM-5 and h-H-Beta) have been ion-exchanged with alkali (Na+ and K+) and alkaline-earth (Mg2+) metals and have been evaluated as catalysts to produce high value-added products through catalytic pyrolysis of lignin. In comparison with the thermal test, hierarchical zeolites in acid form are effective catalysts for lignin pyrolysis, favouring the production of valuable light compounds although reducing bio-oil* yield and increasing gas and coke formation. In this way, h-H-ZSM-5 zeolite promotes the formation of oxygenated aromatics, being guaiacols and syringols the major products. Alkali-exchanged variants of this zeolite enhance demethylation reactions improving the selectivity towards 2-methoxy-phenol and syringol, by modifying acid site properties. On the other hand, h-H-Beta zeolite, with larger pore size and stronger acidity, leads to higher concentration of oxygenated aromatics for both parent and ion-exchanged catalysts. Specifically, h-KH-Beta promotes the production of 2-methoxy-phenol and syringol. Besides, h-MgH-Beta stands out for its greater selectivity towards phenol and alkylphenols, such as dimethylphenol. Overall, the combination of accessibility, provided by the hierarchical porosity, with the different nature and strength of the acid sites, induced by the ion-exchange with alkali and alkaline-earth metals, allows tailoring the lignin catalytic pyrolysis process to selectively produce high value-added compounds.
Tailoring the preparation of USY zeolite with uniform mesoporosity for improved catalytic activity in phenol/isopropanol alkylation
(Elsevier, 2025-06-15) Molina, C.; Abdrassilova, A.; Ávila, M.I.; Alonso-Doncel, M.M.; Cueto, J.; Gómez-Pozuelo, G.; Briones, L.; Botas, J.A.; Serrano, D.P.; Peral, A.; Escola, J.M.
The preparation of hierarchical USY zeolite, exhibiting uniform mesoporosity and high Si/Al atomic ratio (48–52), has been investigated by means of a surfactant/ammonia post-treatment applied to a commercial USY sample. The procedure involved the use of temperatures within 40–135 °C, a low ammonia concentration solution (0.05 N) and hydrothermal synthesis times of 20 h. When working at 40–80 °C, the obtained USY samples exhibit enhanced intraparticular mesoporosity (324–418 m2 g−1), showing increasingly uniform mesopores around 4.0 nm, while holding a remarkable zeolitic microporosity (413–363 m2 g−1). In contrast, higher temperatures resulted in a steady abatement of crystalline zeolitic domains, with a total collapse of the zeolite structure at 135 °C. These hierarchical USY materials were tested in the alkylation of phenol with isopropanol, wherein one of the obtained products, e.g. 2,6-diisopropylphenol (Propofol), is the most important intravenous anaesthetic in the market. Interestingly, the generation of the uniform mesoporosity in USY samples led to an enhancement of both the phenol conversion and the selectivity towards C-alkylation products. Thus, the sample treated at 60 °C (USY-60) gave rise to the highest selectivity towards C-alkylation products (84 %) and poly-alkylphenols formation (72 %), with an encouraging selectivity towards 2,6-diisopropylphenol (43 %).
The notable features of mesoporous aluminosilicates as catalytic supports for hydrodearomatization and hydrodesulfurization of fuels
(Elsevier, 2024-12-13) Abdrassilova, Albina; Vassilina, G.; Abdildina, K.; Briones, L.; Peral, Angel; Escola, J. M.
Despite being discovered more than 25 years ago, mesoporous aluminosilicates are still very relevant materials, considering the huge number of publications appearing every year harnessing them. Their notable features such as high BET surface area, accessible mesopore size, mild acidity and tunable pore wall thickness have resulted in different successful catalytic applications. Additionally, different kinds of mesoporous aluminosilicates may be found in literature (MCM-41, MCM-48, HMS, SBA-15, SBA-16, etc.) that allow to tailor to certain extent some physicochemical properties such as the spatial group, mesopore size and dimension, the pore wall thickness and consequently the hydrothermal stability, for the wanted catalytic application. This review is focused on discussing the main characteristics of the most common mesoporous aluminosilicates and exploring their reported performance in literature as supports of bifunctional catalysts for the hydrodearomatization (HDA) and desulfurization (HDS) of fuels. Although their hydrothermal stability has always been questioned by their lack of crystallinity, several successful applications of both MCM-41 and SBA-15 as supports of bifunctional catalysts for HDA/HDS of model compounds such as dibenzothiophene (DBT) can be found in literature, which in some cases interestingly also point out the prolonged stability of the catalyst, leading towards high yields of fuels by its mild acidity. Additionally, supported metal catalysts over mesoporous aluminosilicates might be the basis for the preparation of advanced bulk metal hydroprocessing catalysts, by application of different etching strategies. Therefore, this review will show these promising catalytic outcomes that opens up the application of mesoporous aluminosilicates as supports of bifunctional catalysts devoted to HDA/HDS of not only model sulfur/aromatic compounds but true fuels as well such as those proceeding from Kazakhstan oil.