Examinando por Autor "Escola, J. M."

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Catalytic conversion of low-density polyethylene using a continuous screw kiln reactor
(ELSEVIER, 2002) Aguado, José; Serrano, D. P.; Escola, J. M.; Garagorri, E.
Both thermal and catalytic cracking of low-density polyethylene (LDPE) have been investigated using a screw kiln reactor. Thermal degradation gives rise to a broad product distribution whereas catalytic cracking over Al-MCM-41 leads mainly to hydrocarbons within the gasoline range (C5 ¿ C12) with selectivities up to 80%. The increase of the screw speed between 3 and 15 rpm in the catalytic experiments allows the plastic feed rate to be varied in the range 20 ¿ 41 g/h. The changes observed in the TOF values when varying the screw speed point out a decrease of the activity per site with increasing residence times, which may be due to the catalyst deactivation or to a contribution of the degradative extrusion at higher screw speeds. Likewise, a certain increase in the selectivity towards the gasoline fraction is observed at short residence times. On the other hand, PIONA analyses indicate that, regardless of the screw speed, the main components of the gasoline are olefins (50%) and isoparaffins (20%) whereas the aromatic content is always below 6%, with a proportion of benzene lower than 0.1%.
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.
Critical issues for the deployment of plastic waste pyrolysis
(Royal Society of Chemistry, 2023-08-14) Giglio, E; Marino, A; Pizarro, P; Escola, J. M.; Migliori, M; Giordano, G; Serrano, D. P.
Despite the urgent need to valorize plastic waste, subtracting them from uncontrolled release into the environment, and the availability of consolidated thermal and catalytic technologies, the large-scale deployment of pyrolysis as a reference technology for the efficient processing of plastic waste still faces significant challenges. Accordingly, this review is focused on a number of issues that are essential for the industrial development of plastic waste pyrolysis technologies: i) the use of heterogenous catalysts for a better control of the product properties and the softening of the operation conditions, analyzing the important limitations derived from catalyst deactivation, ii) the different types of treatments investigated for the safe removal of halogens, which are often present in the pyrolysis oils in the form of Cl- and Br-containing organic compounds, thus avoiding health and environmental problems and the corrosion of equipment, iii) the co-processing of plastic waste with other feedstocks (biomass, petroleum fractions, used tires, etc.), which may result in significant synergistic effects, and iv) the multi-scale modelling of plastics pyrolysis processes as an essential tool for the design of large scale plants.
Direct synthesis of mesoporous M-SBA-15 (M = Al, Fe, B, Cr) and application to 1-hexene oligomerization
(ELSEVIER, 2009) van Grieken, R.; Escola, J. M.; Moreno, J.; Rodríguez, R.
M-SBA-15 materials (M = Al, B, Cr, Fe) were prepared by different direct synthesis methods, characterized and tested catalytically in the 1-hexene oligomerization reaction at 125ºC. Al-SBA-15 were synthesized within the range Si/Al=12-86 using aluminium isopropoxide as aluminium source. 27Al MAS NMR spectra point out that the three Al-SBA-15 samples contain more tetrahedral aluminium than octahedral and the ratio tetrahedral / octahedral diminished with increasing aluminium contents. B-SBA-15 was prepared with a Si/B=51-106 using two direct synthesis methods (sol-gel and hydrothermal) and three different boron sources (solid boric acid, aqueous boric acid and boron isopropoxide). The best results in terms of boron incorporation (Si/B = 51) were achieved with solid boric acid and the sol-gel method, although a lower degree of mesoscopic ordering was obtained compared to the hydrothermal procedure. 11B MAS NMR showed that trigonal boron is the principal coordination state obtained after calcination. Cr-SBA-15 was also achieved by direct synthesis method at different pH (1.5, 3, 5) but the incorporation degree was low, at best Si/Cr = 240 at pH = 5. UV-vis spectroscopy indicated that all Cr species were Cr6+ formed during the calcination step. Oligomerization of 1-hexene at 125ºC showed that the highest conversion (~ 30%) was attained over Al-SBA-15 (Si/Al=30) although Cr-SBA-15 material exhibited close conversion (21%) despite its low heteroatom content (Si/Cr = 240). Dimers were the major products over Al-SBA-15, Cr-SBA-15 and Fe-SBA-15 catalysts (selectivity ¿ 40%) while strikingly, sol gel B-SBA-15 lead mostly to heavy oligomers (> 60%), with less than 10 % of dimers.
Feedstock recycling of agriculture plastic film wastes by catalytic cracking
(ELSEVIER, 2004) Serrano, D.P.; Aguado, José; Escola, J. M.; Garagorri, E.; Rodríguez, J. M.; Morselli, L.; Palazzi, G.; Orsi, R.
Feedstock recycling by catalytic cracking of a real plastic film waste from Almeria greenhouses (Spain) towards valuable hydrocarbon mixtures has been studied over several acid catalysts. The plastic film waste was mostly made up of ambient degraded low-density polyethylene (LDPE) and ethylene-vinyl acetate copolymer (EVA), the vinyl acetate content being around 4 wt %. Nanocrystalline HZSM-5 zeolite (crystal size ¿ 60 nm) was the only catalyst capable of degrading completely the refuse at 420ºC despite using a very small amount of catalyst (plastic / catalyst mass ratio of 50). However, mesoporous catalysts (Al-SBA-15 and Al-MCM-41), unlike it occurred with virgin LDPE, showed fairly close conversions to that of thermal cracking. Nanocrystalline HZSM-5 zeolite led to 60 wt % selectivity towards C1 - C5 hydrocarbons, mostly valuable C3 - C5 olefins, what would improve the profitability of a future industrial recycling process. The remarkable performance of nanocrystalline HZSM-5 zeolite was ascribed to its high content of strong external acid sites due to its nanometer dimension, which are very active for the cracking of bulky macromolecules. Hence, nanocrystalline HZSM-5 can be regarded as a promising catalyst for a feasible feedstock recycling process by catalytic cracking.
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.
Modified wacker TBHP oxidation of 1- DODECENE
(ELSEVIER, 2008) Escola, J. M.; Botas, Juan Ángel; Aguado, José; Serrano, D. P.; Vargas, C.; Bravo, M.
A higher 1-olefin (1-dodecene) was oxidized to 2-dodecanone and other ketones in a modified Wacker system featured by omitting the use of copper chloride and employing tert-butylhydroperoxide (TBHP) as oxidant. Acetonitrile was the solvent of choice due to its higher selectivity towards 2-dodecanone, the reaction occurring mostly in the interface. A maximum in conversion and selectivity was measured for a ratio [CH3CN] / [1-dodecene] = 10. The temperature abatement enhances the 2-dodecanone selectivity (61% at 40ºC) because of the lower extent of the competing isomerization reactions. An optimum in 2-dodecanone selectivity was found for a [TBHP] / [1-dodecene] ratio = 7. The use of H2O2 as oxidant led towards slower oxidation rates than TBHP. Other palladium salts (PdSO4 and Pd(CH3COO)2) and several R-CN solvents (propionitrile, benzonitrile, isobutyronitrile) yielded lower performances than palladium chloride and acetonitrile, respectively. On the contrary, ß-ciclodextrin, a phase transfer catalyst, improved the selectivity towards 2-dodecanone.
Nitrogen and Sulphur Poisoning in Alkene Oligomerization over Mesostructured Aluminosilicates (Al-MTS, Al-MCM-41) and Nanocrystalline n-HZM-5
(ELSEVIER, 2008) Van Grieken, R.; Escola, J. M.; Moreno, J.; Rodriguez, R.
Oligomerization of 1-hexene in the presence of model poisons such as thiophene (700 - 7000 ppm of sulphur) and n-butylamine (25 - 250 ppm of nitrogen), either alone or in combination, were tested at 200ºC, 50 bar and using n-octane as solvent, over three catalysts: two uniformly mesostructured silica-alumina (Al-MTS, Al-MCM-41) and a nanocrystalline HZSM-5 zeolite. A content of 700 ppm of sulphur (adding thiophene) or/and 25 ppm of nitrogen (adding n-butylamine) after a TOS = 240 min. led towards roughly 10 -20% decrease in conversion over nanocrystalline HZSM-5, without significant changes in selectivity. On the contrary, a feeding of 1-hexene with 7000 ppm of sulphur and 250 ppm of nitrogen showed a drastic drop of conversion (from 90 to 27%) over n-ZSM-5 zeolite with a significant increase in the selectivity towards lighter oligomers (dimers, C7 - C8 isomers). This fact suggests that the strong acid sites of the zeolite are deactivated by poison adsorption and heavy oligomers/coke deposition both inside the micropores and over the external surface. In contrast, neither Al-MTS nor Al-MCM-41 catalysts were meaningfully affected by the poisons (especially Al-MTS), even for high concentration conditions, due to its high surface area and medium acid strength distribution. TG analyses of the mesoporous catalysts indicate weight losses of ~ 20-25%, with a contribution of 6 to 8% at 400 - 500ºC, assigned to the removal of deposited coke. Oligomerization of a FCC effluent under the same conditions over Al-MTS catalyst leads to a remarkable 58% conversion with a oligomer selectivity over 90% (32% of them C13 - C18).
Oxidation of heavy 1- olefins (C12= - C20=) with TBHP using a modified Wacker system
(ELSEVIER, 2010) Escola, J. M.; Botas, Juan Ángel; Vargas, C.; Bravo, M.
The oxidation of heavy olefins (CB12 B¿ CB20B) was carried out using a modified Wacker system with TBHP as oxidant and acetonitrile as solvent at 80ºC. This system allowed the oxidation of 1-octadecene giving rise to 90% conversion with 60% selectivity towards 2-octadecanone after 2 h while the addition of ß-cyclodextrins did not increase the production of 2-octadecanone. The oxidation of a equimolar mixture of n-dodecane + 1-dodecene enhanced markedly the selectivity towards 2-dodecanone yielding 63% instead of 34% in n-paraffin absence after 2 h, likely due to a dilution effect of the n-dodecane which reduces the extent of the isomerisation reactions. The oxidation of a equimolar mixture CB12PB=P + CB16PB=P + CB20PB=P in presence of equimolar amounts of their corresponding n-paraffins gave rise to practically complete conversion and selectivities towards 2-methylketones within 70 ¿ 90%, enhancing with decreasing chain length due to their higher solubility in the biphasic system. The activity of the catalyst dropped after two reaction cycles, indicating its deactivation by formation of palladium clusters. However, it was possible to obtain similar results in terms of activity and selectivity by decreasing the [1-dodecene]/[PdClB2B] ratio to 100, which is expected to increase the catalyst lifetime by decreasing the extent of palladium aggregation. In this regard, the reported system is rather promising for the oxidation of heavy 1-olefins towards methyl ketones.
Performance of a continuous screw kiln reactor for the thermal and catalytic conversion of polyethylene - lubricating oil base mixtures
(ELSEVIER, 2003) Serrano, D. P.; Aguado, José; Escola, J. M.; Garagorri, E.
Both thermal and catalytic cracking of mixtures consisting of low-density polyethylene (LDPE) and a lubricating oil base have been investigated in a continuous screw kiln reactor, provided with two reaction zones operating at different temperatures (T1/T2). The incorporation of the lubricating oil into the plastic leads to a significant decrease in its viscosity which favours the mixture flow through the reactor. Thermal cracking at 450/500ºC of LDPE-lubricating oil base mixtures with compositions ranging from 40/60 to 70/30 w/w % led in all cases to their almost complete conversion (~ 90 %) towards a broad spectrum of C1-C40 hydrocarbons. Catalytic cracking of a 70/30 (w/w %) LDPE - lubricating oil base mixture over mesoporous Al-MCM-41 catalysts at 400/450ºC proceeded with lower activity with regards to the pure LDPE catalytic cracking. This result is related to both the lower reactivity of the oil compared to the pure polyolefin and to the poisoning of the catalyst acid sites by sulphur/nitrogen - containing compounds present in the lubricant oil base. However, at higher temperatures (450/500ºC), complete conversion of the mixture was attained over both Al-MCM-41 and nanocrystalline HZSM-5 (n-HZSM-5) catalysts. Al-MCM-41 materials leads mainly to C5 - C12 products (65 % selectivity) whereas lighter hydrocarbons were formed preferentially over n-HZSM-5 (63 % selectivity towards C3 - C5 compounds). These results demonstrate that the screw kiln reactor is an efficient system for the continuous processing of plastic - lubricant oil mixtures by thermal and catalytic treatments.
Thermal and catalytic cracking of a LDPE-EVA copolymer mixture
(ELSEVIER, 2003) Serrano, D. P.; Aguado, José; Escola, J. M.; Rodríguez, J. M.; Morselli, L.; Orsi, R.
Catalytic cracking of a plastic mixture consisting of LDPE and EVA copolymer (86/14 w/w) over mesoporous Al-SBA-15 and Al-MCM-41 materials as well as nanocrystalline HZSM-5 zeolite (crystal size ¿ 35 nm) has been carried out in a batch reactor at 400 - 420ºC. The release of acetic acid formed from the EVA decomposition was observed within the temperature range 350 - 400ºC. The most active catalyst was nanometer size HZSM-5 that led to complete conversion of the plastic mixture at 420ºC whereas both Al-MCM-41 and Al-SBA-15 were meaningfully less active. In addition, the polymer mixture was more difficult to be cracked both thermally and catalytically than pure LDPE. This result has been ascribed to the occurrence of crosslinking reactions leading to a fast deactivation by coke fouling especially over mesoporous catalysts (Al-MCM-41 and Al-SBA-15) because of their open structure. A high selectivity towards C1 - C5 hydrocarbons (¿ 75 %) was attained over nanometer size HZSM-5, most of them being valuable C3 - C4 olefins. PIONA analyses of the C6 - C12 hydrocarbon fraction obtained at 420ºC indicates that olefins were the main components whereas a significant amount of aromatics was also obtained both thermally and catalytically (> 15 %).