The cobalt-based ZIF-67 has been evaluated for the adsorptive propylene/propane separation in a fixed bed. Characterization techniques and dynamic measurements have been performed over ZIF-67 to evaluate its potential in this defiant process. Cobalt promotes a more rigid framework than zinc in the isostructural ZIF-8. Although the adsorption affinity of ZIF-67 for both hydrocarbons is similar, the lower flexibility of the framework makes ZIF-67 behave with a clear preference towards propane. This inverse selectivity promotes the enrichment in propylene content upon breakthrough, and may simplify the separation scheme. Therefore, ZIF-67 adsorptive separation is presented as an alternative to energy-demanding distillation.

Deactivation of Ni/La₂O₃-αAl₂O₃ catalyst in ethanol steam reforming (ESR) was studied in order to establish the optimal conditions for maximizing H₂ production and achieving steady behavior. The ESR reactions were conducted in a fluidized bed reactor under the following operating conditions: 500-650 °C; space-time up to 0.35 g_catalyst h/g_EtOH; and steam/ethanol (S/E) molar ratio in the feed, 3-9. The features of the deactivated catalysts and the nature and morphology of the coke deposited were analyzed by temperature-programmed oxidation, X-ray diffraction, scanning electron microscopy, and Raman spectroscopy. Catalyst deactivation was solely caused by coke deposition, especially by encapsulating coke, with acetaldehyde, ethylene, and ethanol being the main precursors, whose concentration was high for lower values of space-time. Conversely, the filamentous coke formed from CH₄ and CO (with their highest concentration for intermediate values of space-time) had a much lower impact on deactivation. Owing to the effect of space-time on the extent of reactions leading to the formation of coke precursors, the Ni/La₂O₃-αAl₂O₃ catalyst stability was enhanced by increasing space-time. The increase in temperature and S/E ratio was also beneficial since both variables promoted coke gasification. Consequently, a steady H₂ yield throughout 200 h reaction was attained at 600 °C, a space-time of 0.35 g_catalyst h/g_EtOH, and S/E > 3.

The Ti-containing metal organic framework (MOF) MIL-125 has been used as sacrificial precursor to obtain TiO₂ materials through the MOF-mediated synthesis route. In this study, Fe³⁺ was deposited on the surface of MIL-125 after its hydrothermal synthesis. Targeted Fe-doped titania photocatalysts were prepared through the direct calcination in air of Fe/MIL-125 crystals and/or by using a two-step method, including carbonization in inert atmosphere followed by calcination in air. The relationship between the synthesis conditions and the properties of the Fe-doped titania nanopowders, such as Fe content, porosity, phase composition and particle size was investigated. From elemental mapping, X-ray photoelectron spectroscopy, X-ray absorption spectroscopy, UV–Vis absorption spectroscopy and photoluminescence emission spectra, the presence of highly dispersed Fe³⁺ ions incorporated into the TiO₂ crystal lattice was confirmed, which led to a significant red shift of photoresponse towards visible light and reduced the recombination rate of electron-hole pairs at low iron content. By varying the pre-carbonization temperature, both crystal size and phase composition in the final materials were modulated. The performance of Fe-doped titania materials in photocatalytic water-splitting was tested for hydrogen evolution. Optimal photocatalytic performance was found at 0.15 and 0.5 wt% iron concentration and exceeded those of non-doped titania and commercial anatase both under visible and UV light irradiation, respectively, and among the highest reported in literature for these systems.

Separation of propylene/propane is one of the most challenging and energy consuming processes in the chemical industry. Propylene demand is increasing and a 99.5% purity is required for industrial purposes. Adsorption based solutions are the most promising alternatives to improve the economical/energetic efficiency of the process. Zeolitic Imidazolate Frameworks (ZIFs) combine the desired characteristics from both MOFs and zeolites: tunability and flexibility from metal organic frameworks, and exceptional thermal and chemical stability from zeolites. In order to enlighten the role of the cation in the sodalite ZIF-8 framework for propane/propylene separation, dynamic breakthrough measurements have been performed over ZIF-8(Zn), ZIF-67 (i.e. ZIF-8(Co)) and MUV-3 (i.e. ZIF-8(Fe)), all isostructural materials based on the same linker (2-methylimidazole). Cation substitution has a remarkable influence in the framework flexibility, and, consequently, in SOD-ZIF selectivity for light hydrocarbons. The differences between the crystallographic pore sizes of the material and the molecular dimensions of propane and propylene are so small, that the slightest change in the framework causes notable advantages/disadvantages in the final application. While cobalt is known to promote a more rigid framework resulting in an adsorption selectivity towards propane, iron presents the inverse effect yielding selectivity to propylene. Zinc has an intermediate effect. A threshold pressure in the isotherm is observed for propylene uptake by ZIF-67 at 273 and 298 K, and only at the lower temperature for ZIF-8. Inlet mixture composition does not highly influence the adsorptive selectivity, although it clearly affects the pure hydrocarbon recovery. Over ZIF-67 breakthrough experiments at 298 K yield a temporary pure propylene flow representing 10–15% of the amount fed. ZIF-67 is a promising candidate for propylene/propane adsorptive separation.

The oxidative steam reforming (OSR) of raw bio-oil (obtained by fast pyrolysis of pine sawdust) has been studied on a Rh/CeO₂-ZrO₂ catalyst under a wide range of operating conditions (600-750 °C; steam-to-carbon molar ratio, 3-9; oxygen-to-carbon molar ratio, 0.34; space time, 0.15-0.6 g_catalyst h/g_bio-oil) in order to delimit the suitable conditions for high and stable H₂ production. The runs were conducted in a two-step system provided with a thermal step (at 500 °C) for bio-oil vaporization and pyrolytic lignin retention, followed by an online catalytic reforming step in a fluidized bed reactor. The spent catalyst was characterized by temperature-programmed oxidation, temperature-programmed reduction, and transmission electron microscopy in order to ascertain the causes of deactivation and the effect of the reaction conditions on these causes. The evolution with time on stream of both bio-oil oxygenates conversion and yields of reaction products shows different periods and catalyst states, with two sharp changes associated with different catalyst deactivation causes: (i) change in the states of Rh species and aging of the support (with fast dynamics) and (ii) coke deposition (at low temperature) or Rh sintering (at high temperature, with slow dynamics).

The regenerability of Ni catalysts in reforming reactions is a key factor for process viability. Accordingly, this study addresses the regeneration of two spinel NiAl₂O₄ type catalysts by reaction-regeneration cycles in the oxidative steam reforming (OSR) of raw bio-oil. The spinel type catalysts were prepared by different methods including a supported Ni/La₂O₃-αAl₂O₃ catalyst and a bulk NiAl₂O₄ catalyst. The experimental set-up consists of two units connected in series for i) the thermal treatment of bio-oil at 500 °C, in order to control the deposition of pyrolytic lignin, followed by; ii) the oxidative steam reforming (OSR) of the remaining oxygenates in a fluidized bed catalytic reactor. The conditions in the OSR reaction step were: 700 °C; oxygen/steam/carbon ratio (O/S/C), 0.34/6/1; space time, 0.75 g_catalysth/g_bio-oil (for supported catalyst) and 0.15 g_catalysth/g_bio-oil (for bulk catalyst). Three different strategies have been studied in the regeneration step by coke combustion, including the in situ regeneration inside the reactor at 650 °C and 850 °C, and the ex situ regeneration in an external oven at 850 °C, for 4 h in all the cases. The behavior of the fresh and regenerated catalysts has been explained according to their metallic properties, determined by different characterization techniques (temperature programmed reduction (TPR), X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), and transmission electronic microscopy (TEM)). According to these results, the combustion ex situ of the catalyst at 850 °C is able to completely regenerate the bulk catalyst, since these regeneration conditions lead to the total recovery of the NiAl₂O₄ spinel phase together with negligible loss of Ni on the surface in the catalyst. These novel results are crucial for future industrial implementation of the process.

A reaction scheme has been proposed for the oxidative steam reforming (OSR) of raw bio-oil on a Rh/CeO₂-ZrO₂ catalyst, based on the study of the effect reaction conditions (temperature, space time, oxygen/carbon ratio and steam/carbon ratio) have on product yields (H₂, CO, CO₂, CH₄, hydrocarbons). The runs were performed in a two-step system, with separation of pyrolytic lignin (first step) followed by catalytic reforming in a fluidized bed reactor (second step), under a wide range of reaction conditions (600–750 °C; space time, 0.15–0.6 g_catalysth/g_bio-oil; oxygen to carbon molar ratio (O/C), 0–0.67; steam to carbon molar ratio (S/C), 3–9). The catalyst is very active for bio-oil reforming, and produces high H₂ yield (between 0.57 and 0.92), with low CO yield (0.035–0.175) and CH₄ yield (below 0.045) and insignificant light hydrocarbons formation. The proposed reaction scheme considers the catalyzed reactions (reforming, water gas shift (WGS) and combustion) and the thermal routes (decomposition/cracking and combustion). The deactivation of the catalyst affects progressively the reactions in the following order: CH₄ reforming, hydrocarbons reforming, oxygenates reforming, combustion and WGS.