Examinando por Autor "Serrano, D. P."

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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%.
Conversion of Stearic Acid into Bio-Gasoline over Pd/ZSM-5 Catalysts with Enhanced Accessibility
(MDPI, 2019-06-11) Arroyo, Marta; Briones, Laura; Escola, José María; Serrano, D. P.
Palladium supported on nanocrystalline ZSM-5 (n-ZSM-5, Si/Al = 32) and hierarchical ZSM-5(h-ZSM-5) with different acidity (Si/Al = 33, 51, 122) were tested in the liquid-phase conversion of stearic acid undernitrogenatmosphere(6bar). TheincorporationofPdintoZSM-5zeoliteincreased significantly the share of gasoline in the reaction products due to the promotion by this metal of both decarboxylation and hydrogen transfer reactions. Likewise, the Pd nanoparticles dispersed over the zeolitic support favored the conversion of light olefins formed by end-chain cracking reactions into gasoline-range hydrocarbons according to an oligomerization/cyclization/aromatization pathway. Additionally, Pd/h-ZSM-5 gave rise to higher conversion and selectivity towards gasoline than Pd/n-ZSM-5, due mainly to the enhanced accessibility and improved Pd dispersion achieved when using the hierarchical zeolite. The decrease in the Si/Al atomic ratio in Pd/h-ZSM-5 samples resulted in a rise in the stearic acid conversion, although it was lower than expected. This finding denotes that, for supports with high acid sites concentration, the Pd availability became the limiting factor as the metal was loaded in similar amounts in all catalysts. Finally, the increase of the reaction temperature with the Pd/h-ZSM-5 (122) catalyst augmented both stearic acid conversion and gasoline selectivity, since it enhanced the conversion of the light olefins, formed as primary cracking products, into liquid hydrocarbons. Therefore, it can be concluded that Pd supported on hierarchical ZSM-5 zeolite is a convenient catalyst for obtaining bio-gasoline from oleaginous feedstock.
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.
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.
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.
Tailoring the properties of hierarchical TS-1 zeolite synthesized from silanized protozeolitic units
(2012) Serrano, D. P.; Sanz, R.; Pizarro, P.; Moreno, I.; ELSEVIER
Hierarchical TS-1 zeolites, characterized by having a secondary porosity within the supermicro/mesopore region (1.5-6 nm), have been synthesized following a procedure based on the silanization of protozeolitic units, which are previously generated by means of a precrystallization step. The silanization agent, phenylaminopropyltrimethoxysilane (PHAPTMS) acts as crystal growth inhibitor, hindering partially the protozeolitic units growth and aggregation during the crystallization treatment. Both the duration of the precrystallization step and the proportion of the organosilane compound added to the synthesis gel have a significant influence on the physicochemical and textural properties of the resultant materials. Thus, the best precrystallization time, leading to the most enhanced textural properties, is comprised between 22-24 hours. Using this time an appropriate balance between the number of protozeolitic units formed and their size is reached. On the other hand, by controlling the organosilane compound proportion added to synthesis gel, the contribution of the secondary porosity can be tailored. Likewise, amounts of organosilane larger than 5 mol% provide to a secondary porous system more uniform in size. The catalytic activity of these materials was evaluated in 1-octene and cyclohexene epoxidation reactions, using tert-butylhydroperoxide (TBHP) as oxidant. The olefin conversion and TOF values reached by hierarchical TS-1 zeolites are remarkably superior to that obtained with the conventional microporous TS-1 zeolite, being higher when the modification degree of the textural properties is more pronounced. These results can be ascribed to the higher accessibility of both TBHP and olefin to the titanium active sites located in the secondary porous system. Likewise, these zeolites exhibit a high oxidant efficiency and total selectivity to epoxide, parameters which are not affected by the presence of the secondary porosity.
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 %).
Unravelling the effectiveness of the small partial substitution of Fe by Ni in La0.9Sr0.1Fe1-xNixO3 perovskites to improve their performance in dry reforming of methane
(Elsevier, 2024-09-15) Romay, María; Serrano, D. P.; Escola, J. M.; Pizarro, P.
Despite the potential of dry reforming of methane (DRM) to valorize CH4 and CO2 into syngas, it must face the rapid catalyst deactivation and competition between reactions that reduce the H2/CO ratio below 1. Perovskitebased catalysts are promising due to their high thermal stability and high oxygen mobility that reduce deactivation by carbon deposition. This work demonstrates the beneficial effect of partially substituting Fe (from 1 to 10 % mol) by Ni in La0.9Sr0.1FeO3 perovskite. For that purpose, an extensive study combining multiple activity tests, characterization of the perovskites and determination of reaction extents by linear programming (LP) optimization was performed. Cofeeding CH4 and CO2 was very effective to keep the perovskite stable while it was severely damaged when feeding only CH4. The perovskite with 5 % Fe substitution (La0.9Sr0.1Fe0.95Ni0.05O3) exhibited the best performance, with CH4 and CO2 conversions of 90 and 95 %, respectively, and H2/CO of 1.1. XPS analysis revealed larger amount of oxygen vacancies than in the Ni-free perovskite. SEM analysis after reaction showed Ni nanoparticles ex-soluted on the perovskite surface. Therefore, the enhanced activity was attributed to a higher oxygen mobility and the role of Ni as DRM catalyst. Analysis of the reaction extents by LP optimization at different reaction conditions revealed changes in the reaction pathways that favored higher H2 yield. XRD, XPS and TG/DTG/DSC of the 5 % Ni-perovskite throughout reaction time showed the progressive appearance of new phases, the generation of more Fe3+ species and oxygen vacancies, and higher coke deposition. Finally, a great stability of the La0.9Sr0.1Fe0.95Ni0.05O3 perovskite was attained when applied in chemical looping dry reforming mode as demonstrated running 50 cycles of alternative DRM and CO2-regeneration steps.