Examinando por Autor "Pizarro, P."

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Catalytic hydrodeoxygenation of m-cresol over Ni2P/hierarchical ZSM-5
(Elsevier B.V., 2018) Berenguer, A.; Bennett, J.A.; Hunns, J.; Moreno, I.; Coronado, J.M.; Lee, A.F.; Pizarro, P.; Wilson, K.; Serrano, D.P.
Bifunctional catalysts comprising Ni2P supported over a hierarchical ZSM-5 zeolite (h-ZSM-5) were synthesized and applied to the hydrodeoxygenation (HDO) of m-cresol, a model pyrolysis bio-oil compound. Surface and bulk characterization of Ni2P/h-ZSM-5 catalysts by XRD, TEM, DRIFTS, TPR, porosimetry and propylamine temperature-programmed desorption reveal that Ni2P incorporation modifies the zeolite textural properties through pore blockage of the mesopores by phosphide nanoparticles, but has negligible impact of the micropore network. Ni2P nanoparticles introduce new, strong Lewis acid sites, whose density is proportional to the Ni2P loading, accompanied by new Brönsted acid sites attributed to the presence of P–OH moieties. Ni2P/h-ZSM-5 is ultraselective (97%) for m-cresol HDO to methylcyclohexane, significantly outperforming a reference Ni2P/SiO2 catalyst and highlighting the synergy between metal phosphide and solid acid support. m-Cresol conversion was proportional to Ni2P loading reaching 80 and 91% for 5 and 10 wt% Ni respectively. Turnover frequencies for m-cresol HDO are a strong function of Ni2P dispersion, evidencing structure sensitivity, with optimum activity observed for 4 nm particles.
CO2 adsorption on amine-functionalized clays
(Elsevier B.V., 2019) Gómez-Pozuelo, G.; Sanz-Pérez, E.S.; Arencibia, A.; Pizarro, P.; Sanz, R.; Serrano, D.P.
Carbon capture using amine-modified porous sorbents is one of the main proposed technologies to reduce the CO2 atmospheric concentration. In this work, a wide series of inexpensive clays have been selected to assess their role as supports of amine-containing sorbents for CO2 capture. Montmorillonite, bentonite, saponite, sepiolite and palygorskite have been hydrated and functionalized by three routes: (a) grafting with aminopropyl (AP) and diethylenetriamine (DT) organosilanes; (b) impregnation with polyethyleneimine (PEI); and (c) double functionalization by impregnating previously grafted samples. XRD, FTIR and N2 adsorption-desorption analyses along with nitrogen content and CO2 adsorption properties (thermogravimetry and fixed bed) have been evaluated for bare and functionalized clays. Under dry conditions (45 °C, 1 bar), grafted and impregnated samples yielded CO2 uptakes as high as 61.3 and 67.1 mg CO2/g ads (for Sepi-DT and Paly-PEI, respectively), with the latter being the best-performing sample in terms of CO2 uptake. On the contrary, double-functionalized samples displayed poor CO2 adsorption properties, probably due to pore-blocking problems related to their high organic loading. The presence of 5% H2O in the feed gas resulted in CO2 uptake increments from 17 to 27%. The adsorption performance of AP, DT and PEI-containing samples was maintained after three adsorption-desorption cycles
Engineering the acidity and accessibility of the zeolite ZSM-5 for efficient bio-oil upgrading in catalytic pyrolysis of lignocellulose
(Royal Society of Chemistry, 2018) Hernando, H.; Hernández-Gimenez, A.M.; Ochoa-Hernández, C.; Bruijnincx, P.C.A.; Houben, K.; Baldus, M.; Pizarro, P.; Coronado, J.M.; Fermoso, J.; Cejka, J.; Weckhuysen, B.M.; Serrano, D.P.
The properties of the zeolite ZSM-5 have been optimised for the production and deoxygenation of the bio-oil∗ (bio-oil on water-free basis) fraction by lignocellulose catalytic pyrolysis. Two ZSM-5 supports possessing high mesopore/external surface area, and therefore enhanced accessibility, have been employed to promote the conversion of the bulky compounds formed in the primary cracking of lignocellulose. These supports are a nanocrystalline material (n-ZSM-5) and a hierarchical sample (h-ZSM-5) of different Si/Al ratios and acid site concentrations. Acidic features of both zeolites have been modified and adjusted by incorporation of ZrO2, which has a significant effect on the concentration and distribution of both Brønsted and Lewis acid sites. These materials have been tested in the catalytic pyrolysis of acid-washed wheat straw (WS-ac) using a two-step (thermal/catalytic) reaction system at different catalyst/biomass ratios. The results obtained have been assessed in terms of oxygen content, energy yield and composition of the produced bio-oil∗, taking also into account the selectivity towards the different deoxygenation pathways. The ZrO2/n-ZSM-5 sample showed remarkable performance in the biomass catalytic pyrolysis, as a result of the appropriate combination of accessibility and acidic properties. In particular, modification of the zeolitic support acidity by incorporation of highly dispersed ZrO2 effectively decreased the extent of secondary reactions, such as severe cracking and coke formation, as well as promoted the conversion of the oligomers formed initially by lignocellulose pyrolysis, thus sharply decreasing the proportion of the components not detected by GC-MS in the upgraded bio-oil∗
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.
ZSM-5 zeolites performance assessment in catalytic pyrolysis of PVC-containing real WEEE plastic wastes
(Elsevier, 2022-05-01) Marino, A.; Aloise, A.; Hernando, H.; Fermoso, J.; Cozza, D.; Giglio, E.; Migliori, M.; Pizarro, P.; Giordano, G.; Serrano, D.P.
Catalytic pyrolysis of plastic wastes is a promising way for their conversion into valuable products. By modulating the catalyst properties and operating conditions, it is possible to direct the product distribution to obtain oils that may be suitable both as fuels and as chemicals. However, the efficient and safe removal of the halogens, often contained in plastic wastes, remains as a great challenge. In this work, the catalytic behaviour of ZSM-5 zeolites in the pyrolysis of a real chlorinated plastic waste of the electric and electronic equipment sector (WEEE), consisting of PE with about 3.4% of PVC, was investigated. To that end, three zeolite samples with different acidity and accessibility were synthesized and assayed. A thermal pre-treatment was applied to the plastic waste at 350 ºC, which allowed a chlorine removal of 87% from the WEEE feedstock. The pyrolysis tests were carried out in a downdraft fixed-bed stainless steel reactor, with a catalyst/feedstock ratio of 0.2, at temperatures of 600 ºC and 450 ºC in the thermal and catalytic zones, respectively, of the reaction system. In comparison with thermal pyrolysis, that mainly produced waxes, the product distribution changed considerably by contacting the pyrolysis vapours with ZSM-5 zeolites, leading to a strong enhancement in the yield of oil and gases. The largest yield of oil (about 60 wt%), having a concentration of monoaromatics (mainly BTX) above 50 wt%, was attained over the desilicated ZSM-5 sample. Regarding chlorine distribution, about 90% was accumulated in the char fraction, probably captured by the inorganic components present in the raw WEEE waste. Coke was the second fraction in terms of Cl concentration, followed by wax and oil, whereas this halogen was almost not detected in the gases. The lowest concentration of Cl in the oil was attained with the desilicated zeolite, with a value below 90 ppm, which could facilitate the subsequent processing of this stream in refinery units.