Examinando por Autor "Peral, A."

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Catalytic cracking of polyethylene over zeolite mordenite with enhanced textural properties
(ELSEVIER, 2008) Aguado, José; Serrano, D.P.; Escola, J. M.; Peral, A.
Catalytic cracking of low density polyethylene (LDPE) has been investigated using different samples of mordenite zeolite as catalysts. In order to obtain materials with different textural properties, a new synthesis method based on the functionalization of the zeolite seeds with an organosilane was employed. Mordenite samples with BET and external surface areas in the range 385-485 m2/g and 9-57 m2/g respectively, were prepared. LDPE catalytic cracking reactions were performed at 420 ºC for 2h in a batch reactor provided with a screw stirrer under a continuous nitrogen flow. Thermal cracking of LDPE leads to plastic conversion lower than 30%, while values of 40% are reached when traditional mordenite is used as catalyst. In contrast, when mordenite samples with enhanced textural properties were employed, a plastic conversion of 60% is attained, both gas (C1-C5) and gasoline (C6-C12) fractions being obtained as main products. On the contrary, gasoline fraction is not observed and a heavier hydrocarbon fraction in the range C13-C35 is detected when thermal cracking or even catalytic cracking over traditional mordenite samples are carried out. The formation of lighter hydrocarbon products (C6-C12) over mordenite samples with enhanced textural properties is assigned to the higher activity and accessibility of their acid sites, which promotes both end-chain and random scission cracking reactions of the polymer molecules.
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.
Hierarchical ZSM-5 zeolites synthesized by silanization of protozeolitic units: mediating the mesoporosity contribution by changing the organosilane type
(Elsevier, 2014) Serrano, D. P.; Pinnavaia, T. J.; Aguado, J.; Escola, J. M.; Peral, A.; Villalba, L.
Hierarchical ZSM-5 zeolites were prepared by crystallization of silanized protozeolitic units employing silylated polypropylene oxide diamine polymers as organosilanes. The influence of the (Sipol/ Sigel) molar ratio was investigated within 0 - 0.15 range. High synthesis yields (~90%) of well-crystallized hierarchical zeolites exhibiting a high proportion of secondary porosity (additional to the zeolitic micropores) was reached for (Sipol/Sigel) molar ratios lower than 0.08. The usage of the silylated polymer resulted in hierarchical ZSM-5 with larger mesopores (4-20 nm) in higher share than the hierarchical ZSM-5 prepared with a smaller organosilane (phenyl-aminopropyl-trimethoxysilane, PHAPTMS). However, it also contained meaningfully lower amount of acid sites and with less acid strength. The best catalytic performance in the cracking of low density polyethylene (LDPE) was showed by the material prepared from a (Sipol/Sigel) ratio of 0.03. Noteworthy, in addition to the gasoline range fraction (C6-C12), light C1-C5 olefins are the main reaction products, which are interesting feedstock for the petrochemical industry. Its catalytic performance is similar to the hierarchical ZSM-5 prepared using the smaller organosilane (PHAPTMS), which is indicative that the enhanced accessibility to the acid sites due to the presence of larger mesopores (4-20 nm) makes up for the lower amount and strength of its acid sites. Thereby, it is possible to enhance the mesoporosity by using bulkier organosilane (silylated polymers) but at the expense of losing acid properties.