BUSCADOR RECOLECTA

Synthesis of hydrocalumite–TiO2 hybrid systems and their use in photodegradation of ibuprofen is reported for the first time. Hydrocalumite was prepared with Al3+ recovered from an aluminum slag (circular economy), TiO2 was deposited on hydrocalumite by hydrolysis of titanium(IV) isopropoxide, and the solids thus obtained were calcined at 400 and 750 ºC. The solid calcined at 400 ºC was essentially amorphous, showing the presence of calcite due to the fixation of atmospheric CO2, while the solid calcined at 750 ºC was composed of mayenite, perovskite and rutile. The calcined solids were used for catalytic degradation of ibuprofen (50 ppm in aqueous solutions) under UV irradiation, obtaining better results than when using commercial TiO2–P25 from Degussa. Under the specific conditions used, the degradation took place in the initial steps of the process, mainly giving rise to species with higher molecular mass than initial ibuprofen., This research was funded by Universidad de Salamanca (Plan I–B2). AJ thanks Universidad de Salamanca and Banco Santander for a predoctoral contract. AG is grateful for financial support from the Spanish Ministry of Science and Innovation (AEI/MINECO) through project PID2020–112656RB–C21.

In this work, a hibonite-type Ni/La-hexaaluminate (Ni/LHA) synthesized from an industrial
waste is used and compared as catalyst in the dry reforming of methane (DRM) at 973 K.
The structure, catalytic behavior, and stability during a run time of at least 50 h of three Nicatalysts obtained from two commercial supports and two preparation methods were used
for comparison. An aluminum solution (9.40 g/L) obtained from an aluminum saline slag
waste by acid extraction was used to synthesize the hexaaluminate by mixing with a
stoichiometric amount of lanthanum nitrate and methanol/Peg400/PegMn400 under hydrothermal conditions at 493 K for 16 h. The Ni/LHA catalyst (10 wt% NiO) was obtained by
impregnation of the synthesized support, calcined previously at 1473 K for 2 h. The
resulting solids were characterized by several techniques as: X-ray diffraction (XRD), N2
adsorption at 77 K, temperature-programmed reduction (TPR), scanning electron microscopy (SEM) and transmission electron microscopy (HR-TEM). In order to compare the
catalytic behavior and properties of the Ni/LHA catalyst, three Ni catalysts obtained from
two commercial supports (g-Al2O3 and SiO2) and two preparation methods (wet impregnation (I) and precipitation-deposition (PD)) were synthesized. Analysis of the TPR patterns
for the catalysts allowed the type of metal support interaction and NiO species to be
determined, with a weak interaction with the support being observed in Ni/LHA and NieI/
SiO2. The NiO species observed, with crystallite sizes between 9.7 and 40.4 nm, confirm the
X-ray structural analyses. The Ni/LHA catalyst was found to be active and very stable in the
DRM reaction after 50 h. The catalytic behavior was evaluated from the CO2 and CH4 conversions, as well as the H2/CO selectivity, with values of 99% over almost all the time
range evaluated. The behavior of this catalyst is comparable to that of NieI/Al2O3 and NiPD/SiO2. The results found indicating that the strong interaction of nickel with the support
favors the stability of the catalysts in the DRM reaction., The authors are grateful for financial support from the Spanish
Ministry of Science and Innovation (MCIN/AdslEI/10.13039/501100011033) through project PID2020-112656RBC21.
JJTH thanks Universidad Pública de Navarra for a postdoctoral
grant. AG also thanks Santander Bank for funding via
the Research Intensification Program.

This study describes the procedures followed to synthesize ceramic-MOF filters using aluminum saline slag
wastes. Briefly, the raw aluminum saline slags were washed at 80 ◦C to significantly reduce the saline content
and eliminate gases. The pretreated material was mixed with glucose (G/S ratios between 0.2 and 1.6) and
acetone by stirring for 4 h. After this time, the resulting solid was dried at 60 ◦C and then at 190 ◦C. During the
glucose caramelization step, PegMn400 was also added and the temperature increased to 1200 ◦C. The obtained
solid was impregnated with precursor solutions to achieve a supported ZIF-8 MOF. The ceramic-MOF filters were
characterized by X-ray diffraction (XRD), N2 adsorption at 77 K, X-ray fluorescence (XRF), scanning electron
microscopy (SEM) and transmission electron microscopy (HR-TEM), thereby confirming the presence of a
structure that allows dispersion of the synthesized and supported ZIF-8. Finally, the performance of these
ceramic-MOF filters as CO2 adsorbents was evaluated in the temperature range 50–300 ◦C, with isosteric heats of
19 kJ/mol being obtained using the Clausius-Clapeyron equation., The authors are grateful for financial support from the Spanish
Ministry of Science and Innovation (AEI/MINECO) and Government of
Navarra through projects PID2020-112656RB-C21 and 0011-3673-
2021-000004. JJTH thanks Universidad Pública de Navarra for a postdoctoral
grant.

Terrestrial environmental and biological systems are being threatened by the tremendous amount of human carbon dioxide emissions. Therefore, it is crucial to develop a sustainable energy system based on CO2 as chemical feedstock. In this review, an introduction to the CO2 activation and transformation has been made, together with a more comprehensive study of the catalytical reduction of CO2 to methane, methanol, and formic acid, which are currently contemplated as chemical feedstocks and/or promising energy carriers and alternative fuels., The authors are grateful for financial support from the Spanish Ministry of Science and Innovation (AEI/MINECO) through project PID2020-112656RB-C21. AG and ISS also thank Santander Bank for funding via the Research Intensification Program.

Aluminum saline slags is a waste of the metallurgical industry that presents serious environmental problems
since it needs very extensive areas for its disposal, the toxicity it causes in the atmosphere and groundwater, in
addition to high transportation costs. The valorization of this residue by the synthesis of alumina, a compound
widely used in the chemical industry, generates a high impact and great interest. In this work, the strategies for
synthesizing alumina from aluminum saline slags are reviewed in a context of growing demand for this metal and
environmental crisis. The first sections present the aluminum production processes, both from natural bauxite
(primary process) and from the recycling of materials with a high aluminum content (secondary process); paying
attention to the waste generated and what environmental problems they produce. The main investigations that
have allowed to address the recovery of the waste generated are described below, focusing on the processes of
recovery/extraction of the aluminum present in its composition. The aluminum in these residues can be found as
a metal or forming other compounds such as simple or mixed oxides. Chemical processes are the most relevant,
especially those that deal with the acid and alkaline extraction of the metal. The most important section of the
work reports on the methods of synthesis of Al2O3, highlighting the methods of precipitation, sol-gel, hydrothermal synthesis, and combustion, among others. The work ends with a summary and conclusions section., Spanish Ministry of Science and Innovation (MCIN/AEI/10.13039/501100011033) through project PID2020-112656RB-C21. Open access funding provided by Universidad Pública de Navarra.

This work describes the synthesis of platinum-nickel/lanthanum hexaaluminates (PtNi/LHA) and their performance in terms of stability and catalytic activity in the dry reforming of methane (DRM) at 973 K. An Al solution (9.40 g/L) obtained from an Al saline slag waste by acid extraction was used to synthesize the hexaaluminate by mixing with a stoichiometric amount of lanthanum nitrate and methanol/Peg400/PegMn400 under hydrothermal conditions at 493 K for 16 h. After calcination at 1473 K for 2 h, the presence of LHA was confirmed. Wet impregnation of the synthesized support was used to obtain an initial Ni/LHA catalyst (10 wt% NiO) and the modified PtNi/LHA catalysts (0.2–1 wt% Pt). The support and catalysts were characterized by X-ray diffraction (XRD), N2 adsorption at 77 K, temperature- programmed reduction (TPR), scanning electron microscopy (SEM) and transmission electron microscopy (HR- TEM). The analysis of the TPR patterns for the catalysts allowed the type of metal support interaction and NiO species to be determined, with a weak interaction with the support being observed in all cases. The presence of Pt promoted NiO reducibility. The PtNi/LHA catalysts synthesized were found to be active and very stable in the DRM reaction after reaction for 50 h. The catalytic behavior was evaluated from the CO2 and CH4 conversions, as well as the H2/CO selectivity, with values of between 89% and 92% in almost all the time range evaluated. The presence of Pt improved the stability and catalytic performance of Ni/LHA thus improving resistance to coke formation., The authors are grateful for financial support from the Spanish Ministry of Science and Innovation (MCIN/AEI/10.13039/ 501100011033) through project PID2020-112656RB-C21. JJTH thanks Universidad Pública de Navarra for a pre-doctoral grant. AG also thanks Santander Bank for funding via the Research Intensification Program.

The use of Diatomaceous Earth (DE) as a promising support of a synthetic metalloporphyrin is reported, trying to
heterogenize metalloporphyrin catalysts to mimicking enzyme site isolation and improving reaction selectivity.
New multifunctional hybrid materials consisting of DE amino–functionalized with aminopropyltriethoxysilane
(DE–APTES), followed by grafting with [meso–tetrakis(pentafluorophenyl)porphinato]iron(III)
(DE–APTES–FeTFPP), were prepared and fully characterized. FeTFPP was grafted into DE–APTES via the amine
groups (band at 1570 cm–1
). The brown color of the materials indicated that FeTFPP was immobilized in the
matrix; a Soret band characteristic of ironporphyrin located in a confined space, was found at 416 nm. Leaching
studies confirmed that the ironporphyrin was entrapped and not just adsorbed on the silica surface. DE was
composed of typical quartz and cristobalite crystalline phases and amorphous silica. The intensity of its characteristic reflection at 22◦ (2θ) decreased in the presence of FeTFPP, evidencing that the ironporphyrin influenced the organization of the material. Catalytic tests using DE–APTES–FeTFPP in cyclooctene epoxidation to
cyclooctene oxide (56 % yield, with complete selectivity for the epoxide) and cyclohexane oxidation (4 % yield of
oxidized products, with ketone/alcohol selectivity ~ 3:1), evidenced the versatility of the catalyst and the
multifunctionality of the resulting hybrid materials and the ability of DE as a promising natural support for
ironporphyrin catalysts. Finally, the capacity of the materials as CO2 adsorbents was evaluated in the temperature range 100–200 ◦C. DE–APTES showed a maximum adsorption capacity of 1.26 mmol/g at 100 ◦C, 18 times
higher than the value found under the same conditions for the non–functionalized support., The Brazilian research group acknowledges the support from research funding agencies Fundação de Amparo à Pesquisa do Estado de São Paulo, FAPESP (2020/06712-6), and Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES) finance code 001 and Conselho Nacional de Desenvolvimento Científico e Tecnológico, CNPq (311767/2015-0, 303135/2018-2, 310151/2021-0, 305180/2019-3 and 405217/2018-8). The equipment of Brazilian research group has been financed by FAPESP (1998/11022-3, 2005/00720-7, 2011/03335-8, 2012/11673-3 and 2016/01501-1). Authors from Universidad Pública de Navarra are grateful for financial support from the Spanish Ministry of Science and Innovation (AEI/MINECO) through project PID2020-112656RB-C21. LS thanks the Universidad Pública de Navarra for a post-doctoral Margarita Salas grant, financed by the European Union-Next Generation EU.

Aluminum was extracted from saline slags via an alkaline method and employed in the synthesis of Layered Double Hydroxides (LDH) with various M2+ cations (Co, Mg, Ni and Zn), while Al and Fe were the M3+ cations, using the co-precipitation method and a M2+/M3+ 2:1 ratio. The structural characterization of the samples was performed with powder X-ray diffraction (PXRD), scanning electron microscopy (SEM), nitrogen physisorption at 77 K, thermogravimetric analysis (TGA), temperature-programmed reduction (TPR) and X-ray photoelectron spectroscopy (XPS). Their catalytic performance was tested for the oxidation of olefins (cyclooctene) and their biomimetic potential was analyzed. Results show a great selectivity towards epoxides with no other products obtained. Reaction yields followed the descending order Co4AlFe, Zn4AlFe, Ni4AlFe, and Mg4AlFe, the sample
with cobalt as M2+ converting up to 85% of cyclooctene., This work was funded by the Spanish Ministry of Science and Innovation (MCIN/AEI/10.13039/501100011033) through project
PID2020-112656RB-C21. The Brazilian authors thank Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq) and the Brazilian research funding agency Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP) (2020/06712-6). Open access funding provided by Universidad Pública de Navarra. LS thanks the Universidad Pública de Navarra for a post-doctoral grant. AG also thanks Banco Santander for funding through the Research Intensification Program.

The presence of emerging pollutants (EPs) in water is a major environmental concern. This study evaluates for the first time the removal of three EPs, namely triclosan (TCS), 2,6-dichlorophenol (2,6-DCP), and bisphenol A (BPA), 90 μmol/dm3, from water through both Fenton- and photo-Fenton-like reactions using montmorillonite (Mt) and aluminum interlayered pillared clays (Al-PILC) as catalytic supports. The catalysts (Fe2O3/TiO2/Mt and Fe2O3/TiO2/Al-PILC) were evaluated in single-component solutions and in an equimolar mixture. Two Al-PILC were synthesized from a hazardous waste, namely aluminum saline slag, using either the acid (Al-PILCAE) or the alkaline (Al-PILCBE) aluminum extract as precursors. The third Al-PILC was obtained by the conventional method using a commercial aluminum salt (Al-PILCCM). Catalytic supports were impregnated at 10 and 20 wt% titanium. Iron loadings from 1 to 20 wt% were tested for Mt, while only 20 wt% iron was tested for Al-PILC. All catalysts were characterized using several techniques and the results confirmed the formation of TiO2 and Fe2O3. Almost 100 % of TCS and 2,6-DCP were removed by both Fenton-like (240 and 420 min, respectively) and photo-Fenton-like reactions (30 and 90–120 min, respectively) using the Al-PILC based catalyst. The maximum removal for BPA was 80.14 ± 1.93 % after 120 min under photo-Fenton-like conditions using Al-PILCBE. The catalysts synthesized using the four catalytic supports showed good results for the removal of TCS by both processes, while for 2,6-DCP and BPA the best results were obtained using Al-PILCAE and Al-PILCBE as catalytic supports. Finally, a degradation pathway was suggested for every pollutant based on the by-products identified during the reactions by HPLC-MS. The results revealed that the materials used in this work are suitable catalysts for removing emerging pollutants from water by both Fenton- and photo-Fenton-like reactions., The authors are grateful for financial support from the Spanish Ministry of Science and Innovation (MCIN/AEI/10.13039/501100011033) through project PID2020-112656RB-C21 Open access funding provided by Universidad Pública de Navarra. YC thanks the Universidad Pública de Navarra for a pre-doctoral grant (IberusTalent, European Union's H2020 research and innovation program under Marie Sklodowska-Curie grant agreement N° 801586). AG also thanks Banco Santander for funding via the Research Intensification Program.

Fixed-bed column studies are generally conducted to consider possible applications in water-purification processes. In this work, three synthetic alumina pillared interlayered clays (Al-PILC) were analyzed in fixed-bed
column studies for use as sorbents for solid-phase extraction (SPE) for the first time. Adsorption processes
were studied for triclosan (TCS), which is an emerging pollutant (EP) that has been shown to have several health
effects. Breakthrough curves were investigated by varying process parameters such as bed height (0.25–0.75 cm),
inlet TCS concentration (20–60 mg/cm3
), and flow rate (0.5–3 cm3
/min). Bohart-Adams, Bed Depth Service Time
(BDST), and Thomas models were satisfactory applied to the results obtained for fixed-bed columns. The
adsorption of TCS was successfully optimized for use in SPE for the three adsorbents studied using response
surface methodology with a Box–Behnken design (RSM-BBD). The models developed were adequate for the
experimental data (95% significance level), with high regression parameters (98.9–99.1). The optimum values
for TCS adsorption on the fixed-bed column were 378.04, 367.78, and 378.93 mg (amount of adsorbent packed
into the column), 0.5 cm3
/min (flow rate), 4.24, 3.96, and 3.85 (pH), and 2.56, 1.93, and 1.13 mg/dm3 (inlet
TCS concentration) for Al-PILCAE, Al-PILCBE, and Al-PILCCM, respectively. From these results synthetic Al-PILC
are effective and promising sorbents that can be used for analytical purposes in SPE, and that RSM-BDD is an
effective and reliable tool for evaluating and optimizing the adsorption conditions for emerging contaminants in
a fixed-bed column system., The authors are grateful for financial support from the Spanish Ministry of Science and Innovation (MCIN/AEI/10.13039/501100011033) through project PID2020-112656RB-C21. YC thanks the Universidad Pública de Navarra for a pre-doctoral grant (IberusTalent, European Union's H2020 research and innovation program under Marie Sklodowska-Curie grant agreement N° 801586). AG also thanks Banco Santander for funding via the Research Intensification Program.

The use of biofuels offers advantages over existing fuels because they come from renewable sources, they are biodegradable, their storage and transport are safer, and their emissions into the atmosphere are lower. Biomass is one of the most promising sustainable energy sources with a wide variety of organic materials as raw material. Chemical, biochemical, and thermochemical methods have been proposed to obtain biofuels from raw materials from biomass. In recent years, a thermochemical method that has generated great interest is hydrothermal liquefaction. In this paper, a brief review of the main sources for liquid biofuels and the synthesis processes is presented, with special emphasis on the production of biofuels using hydrothermal liquefaction by using waste generated by human activity as raw material., The authors are grateful for financial support from the Spanish Ministry of Science and Innovation (AEI/MINECO) and the Government of Navarra through projects PID2020-112656RB-C21 and PC034-035 BIOGASOLANA. AG also thanks Santander Bank for funding via the Research Intensification Program.

Hydrogen temperature-programmed reduction (H2-TPR) has become a very useful and common technique for the chemical characterization of solids as it is sensitive to the study of reducible species in catalysis and is considered to be a fingerprint for the reducibility of metal oxide catalysts. However, although modeling of H2-TPR patterns has been extensively studied, little attention has been paid to the effect of particle-size distribution (PSD). The complexity of modeling H2-TPR patterns arises from the fact that the chemistry of metal oxide reduction depends on several factors, including particle size, nature of the support material and confinement within the porous structure, amongst others. In order to identify the kinetic reaction model governing the reduction of certain metal oxides and to explore the effect of PSD, pure metal oxides that only exhibited the particle size difference effect were used to model the H2-TPR patterns. Kinetic and thermodynamic data, which are very useful for characterizing heterogeneous catalysts, were obtained from this study. This work presents a simple procedure for modeling H2-TPR patterns of various metal oxides (i.e., CuO, Ag2O, and NiO) used as active phases in several reactions of environmental and energetic interest using several solid-state reaction kinetic models and considering their PSDs. The results obtained show that modeling the H2-TPR profiles provides information regarding the PSD of metal oxide catalysts that undergo a single-step reduction and only present the particle size difference effect., The authors are grateful for the financial support received from the
Spanish Ministry of Science and Innovation (MCIN/AEI/10.13039/
501100011033) through project PID2020-112656RB-C21. Open access
funding provided by Universidad Pública de Navarra. JVR thanks the
Universidad Pública de Navarra for a post-doctoral María Zambrano
grant, financed by the European Union-Next Generation EU.

The use of saline slag, a hazardous waste generated during the recycling of aluminum, as aluminum source for
the synthesis CuAl layered double hydroxides (LDH) is for the first time reported in this study. Due to the JahnTeller effect, divalent copper–aluminum LDH come usually with impurities and a pure CuAl LDH is not easy to
obtain. The effect of synthesis pH has been examined by comparing LDH synthesized at various pH, ranging from
6 to 12 via a co-precipitation method using aluminum obtained from an alkaline extraction of the slag. For
comparison purposes, a sample was synthesized at pH = 9 using commercial aluminum Al(NO3)3⋅9H2O instead of
extracted aluminum. The effects of the aging time and calcination temperature are also discussed. The LDH and
their calcined metal mixed oxide (layered double oxide, LDO) have been analyzed with several characterization
techniques: powder X-ray diffraction (PXRD), N2 adsorption at − 196 ◦C, thermogravimetric analysis (TGA),
temperature programmed reduction (TPR), scanning electron microscopy (SEM), transmission electron microscopy and energy-dispersive X-ray spectroscopy (TEM and EDS). Synthesis pH has been proved not only to have a
significant effect on the nature of secondary phases but also on the structure and morphology of the samples., The authors are grateful for financial support from the Spanish
Ministry of Science and Innovation (MCIN/AEI/10.13039/
501100011033) through project PID2020-112656RB-C21. Open access
funding provided by Universidad Pública de Navarra for a post-doctoral
Margarita Salas grant, financed by the European Union-Next Generation
EU.

This study evaluates the photocatalytic degradation of 2,6-dichlorophenol (2,6-DCP), triclosan (TCS) and bisphenol A (BPA) by ultraviolet (UV) and visible (VIS) light in the presence of TiO2/catalysts synthesized by wet impregnation followed by calcination. The catalyst supports used were three alumina pillared clays (Al-PILC) synthesized using various aluminum sources and montmorillonite (Mt) as raw material. One of the Al-PILC was prepared following the conventional method (Al-PILCCM), using a commercial aluminum salt, and the other two were synthesized using a saline slag, with the aluminum used being extracted with the alkaline (Al-PILCBE) or the acid (Al-PILCAE) method. Mt was impregnated with various amounts of titanium (1, 5, 10, and 20 wt% Ti) and evaluated for the photodegradation of the aforementioned pollutants, comparing the results with those obtained using commercial anatase. Due to the higher conversion rates, 10 and 20 wt% Ti were chosen to impregnate the Al-PILC and to evaluate the photocatalytic performance. All materials were characterized by several techniques, which confirmed the successful formation of TiO2 in the anatase phase. In all cases, photodegradation was higher when using UV light and the most photodegraded pollutant was TCS (85.15 ± 0.49%), followed by 2,6-DCP (65.43 ± 0.79%) and, to a lesser degree, BPA (36.15 ± 0.65%). Al-PILC showed higher photodegradation percentages, with Al-PILCAE exhibiting the highest values for both types of light. An analysis of the photoproducts by HPLC-MS suggested that the preferred pathway for TCS and 2,6-DCP photodegradation depends on the type of light used., The authors are grateful for financial support from the Spanish Ministry of Science and Innovation (MCIN/AEI/10.13039/501100011033) through project PID2020-112656RB-C21. YC thanks the Universidad Pública de Navarra for a pre-doctoral grant (IberusTalent, European Union's H2020 research and innovation program under Marie Sklodowska-Curie grant agreement N° 801586). AG also thanks Banco Santander for funding via the Research Intensification Program.

Layered double hydroxides (LDH) have been proposed as the materials that offer the best performance in the moderate-temperature range, between 200 and 450 °C, for CO2 adsorption, so the effect of some synthesis parameters and surface modification on their adsorption capacities is herein investigated. This work reports the use of M2+ (Co, Mg, Ni and Zn)/Al layered double hydroxides synthesized with a 3:1 molar ratio by the co-precipitation method and using aluminum extracted from saline slags as source of this metal as CO2 adsorbents. The synthesis and use of Zn/TiAl is also reported considering several proportions of Al-Ti. Structural characterization and comparison of the series has been achieved using powder X-ray diffraction (PXRD), scanning electron microscopy (SEM), nitrogen physisorption at single bond196 °C and thermogravimetry measurements (TGA). The performance of calcined LDH as CO2 adsorbents was evaluated in the 50 – 400 °C temperature range and 80 kPa and results show that Ni6Al2 and Mg6Al2 samples present a significant adsorption capacity at low temperature (0.382 and 0.292 mmolCO2/g, respectively). At 400 °C only Mg6Al2 maintains its high adsorption capacity (0.275 mmolCO2/g) compared to the other calcined LDH. Its adsorption capacity at moderate-temperature range was proven to be better than that of a commercial Mg6Al2 sample. In all materials the CO2 adsorption capacity at 200–450 °C increased by incorporating potassium (K2CO3 and KOH as sources) up to 0.58 mmolCO2/g for Mg6Al2 +K2CO3. The addition of the amine TEPA in the low-temperature range worked for Co6Al2 and Mg6Al2 (increment > 40 %). In the case of Zn6Al2, the partial substitution of Al by Ti also increased the CO2 adsorption capacity from 0.177 to 0.244 mmolCO2/g, finding isosteric heats between 17.07 and 23.30 kJ/mol using the Clausius-Clapeyron equation., The authors are grateful for financial support from the Spanish
Ministry of Science and Innovation (MCIN/AEI/10.13039/
501100011033) through project PID2020-112656RB-C21. LS thanks the
Universidad Pública de Navarra for a post-doctoral Margarita Salas
grant, financed by the European Union-Next Generation EU.

Curving the CO2 atmospheric levels is one of the challenges of this century, given its direct impact on climate
change. Of the several strategies of CO2 capture and storage, sorption-enhanced water–gas shift (SEWGS) process, a combination of CO2 adsorption and the water–gas shift reaction, has been appointed as one of the most
promising techniques due to is low energy consumption and high efficiency. SEWGS operating settings at both
moderate temperature (200–450 ◦C) and high pressure (more than 10 bar) bring the need to find an adsorbent
capable of working at these conditions. Calcined layered double hydroxides (LDH) have been proven to give the
best results in this range of pressure/temperatures even though its performance can be greatly improved. Herein,
a state-of-art of the research accomplished up until now is presented. Several strategies can be followed to
improve the adsorbents performance: the synthesis method, LDH composition, modifications employed to promote their adsorption capacity or how the adsorption conditions can affect their efficiency, The authors are grateful for financial support from the Spanish
Ministry of Science and Innovation (MCIN/AEI/10.13039/
501100011033) through project PID2020-112656RB-C21. LS thanks
Open access funding provided by Universidad Pública de Navarra for a
post-doctoral Margarita Salas grant, financed by the European Union-
Next Generation EU. AG also thanks Banco Santander for funding
through the Research Intensification Program.

The adsorption phenomenon has been used extensively to achieve and explain solid-state reactions, control contamination, and purify liquids and gases. This process implies the use of a porous medium or a material with specific adsorption centers where the interactions with the reagents occur. Determination of the properties of adsorbent or catalyst materials that do not contain specific adsorption sites by physical gas adsorption is a well-established procedure in most research and quality-control laboratories. However, characterizing the specific centers by selective adsorption—chemisorption—remains an open question for discussion and study. The specific centers involved are often acidic/basic and metallic; in most cases, reagents are adsorbed and desorbed in these centers, whose determination allows controlling the processes and comparing the materials. The techniques and procedures presented herein facilitate the evaluation and the qualitative and quantitative determination of the surface properties of the materials using chemisorption processes for metallic and acidic/basic sites. The aim of this work is to review these techniques and procedures, including the updates published by several researchers, who mostly strive to explain the results of bifunctional metallic and acid–base catalytic behavior., The author is grateful for financial support from the Spanish Ministry of Science and Innovation (AEI/MINECO) and Government of Navarra through projects PID2020-112656RB-C21 and 0011-3673-2021-000004. Open access funding provided by Universidad Pública de Navarra . AG also thanks Santander Bank for funding via the Research Intensification Program.

A management process for saline slags, one of the wastes from Secondary Aluminum Production, is proposed. The process begins with a grinding step, followed by washing with water, which removed the fluxing salts but provoking the hydrolysis of AlN, yielding Al(OH)3 and ammonia. Sieving of the solid generated an intermediate and a fine fraction. The first one was rich in metallic aluminum, and can also be returned to the Secondary Aluminum Production. The fine fraction was submitted to a extraction process in acid (HCl or HNO3) or alkaline (NaOH, KOH or CsOH) conditions, under reflux at 90 ºC, obtaining an Al(III) solution that can be used in the synthesis of aluminum-based solids. HCl (1-8 mol/L) and NaOH (1-4 mol/L) were used as reference solutions, HNO3, NaOH and KOH were used under specific conditions; the slag fraction:extraction solution solid:liquid ratio was also varied. The optimum extraction conditions were: extraction time 2 h, solid:liquid ratio 3:10, concentration 3 mol/L for the NaOH medium and 4 mol/L for the HCl medium. More than 30% of the aluminum present in the fraction smaller than 0.4 mm was recovered (the remaining aluminum was present as insoluble phases, corundum and spinel). Acid or basic media can be selected depending on the final use of Al(III) solutions, the basic medium leading to an Al(III) solution with a lower amount of impurities. The hazardousness of the solid obtained after the extraction process was greatly decreased, making possible the use of this solid residue in sectors such as construction., This work was supported by 'Memoria de D. Samuel Solórzano Barruso' Foundation (FS/11-2020). AJ thanks Universidad de Salamanca and Banco Santander for a predoctoral contract. AG is grateful for financial support from the Spanish Ministry of Science and Innovation (MCIN/AEI/10.13039/501100011033) through project PID2020-112656RB-C21. AG also thanks Santander Bank for funding via the Research Intensification Program.

Ni-based catalysts are highly efficient in methane-reforming processes. In the particular case of methane reforming in the presence of carbon dioxide, or dry reforming of methane (DRM), it is necessary to modify and control the initial properties of the catalyst to confer on it resistance to carbon deposition in particular, and to sintering of the Ni metal particles. In this regard, catalytic supports and promoters of different natures have been proposed. Likewise, the addition of small amounts of noble metals to avoid oxidation of the Ni active phase during the reforming reaction has been proposed. Catalyst preparation methods have also been identified as being of particular interest, since they can affect the structure of the Ni metal particles. In this review, the thermodynamic and kinetic aspects of the dry reforming of methane reaction are presented first. The most recent developments in synthetic methods (impregnation, sol-gel, co-precipitation, equilibrium deposition filtration, atomic layer deposition, non-thermal glow discharge plasma, multi-bubble sonoluminescence, 'core-shell' structure) aimed at maximizing the dispersion and thermal resistance of Ni particles are then discussed and compared. The catalytic supports used to promote dispersion of the active metallic phase, the oxygen-storage capacity, and the metal/support interaction are also described. The review then addresses the fact that both the nature of the support and the addition of promoters and other metallic phases that modify the surface properties can control the interaction between the metal and the support, the electronic density of the active phase, and the degree of Ni reduction. Finally, new lines of research focused on the DRM process to make the reaction conditions milder and favor the process at low temperatures are also summarized. © 2021 Taylor & Francis., The authors are grateful for financial support from the Spanish Ministry of Science and Innovation (MCIN/AEI/10.13039/501100011033) through project PID2020-112656RB-C21. JJTH thanks Universidad Pública de Navarra for a pre-doctoral grant. AG also thanks Santander Bank for funding via the Research Intensification Program.

Alumina-supported nickel catalysts are used to facilitate many reactions at various scales. However, the deactivation
of these catalysts is an important problem that has prompted the search for solutions such as the addition
of other metals that act as promoters. In this research, the interactions that form between the support and the
metals have been studied, a fundamental property that directly affects the performance of the catalyst. With this
idea, several Ni-Pd and Ni-Mo bimetallic and various Ni-Mo-Pd trimetallic samples have been prepared, and the
reduction capacity of the oxide phases by temperatura-programmed reduction has been analyzed and studied. It
has been found that in bimetallic catalysts, Pd favors the appearance of NiO species that are more easily reducible
than Mo. In the same way, the data obtained from the trimetallic simples suggest that the impregnation order of
Mo and Pd is not a determining factor in these catalysts. In addition, it has been found that the co-impregnation
of Ni with Pd gives better results than the sequential impregnation of these metals. The results obtained have also
shown that the order of nickel impregnation is decisive. In the case of Ni-Mo catalysts, by impregnating the
molybdenum first, catalysts with better reducing properties can be obtained., The authors are grateful for financial support from the Spanish
Ministry of Science and Innovation (AEI/MINECO) and the Government
of Navarra through projects PID2020-112656RB-C21 and PC034-035
BIOGASOLANA. Open access funding provided by Universidad Pública
de Navarra. JJTH thanks Universidad Pública de Navarra for a postdoctoral
grant. AG also thanks Santander Bank for funding via the
Research Intensification Program.

Lanthanum aluminate-based perovskite (LaAlO3) has excellent stability at high temperatures, low toxicity, and high chemical resistance and also offers wide versatility to the substitution of La3+ and Al3+, thus, allowing it to be applied as a catalyst, nano- dsorbent, sensor, and microwave dielectric resonator, amongst other equally important uses. As such, LaAlO3 perovskites have gained importance in recent years. This review considers the extensive literature of the past 10 years on the synthesis and catalytic applications of perovskites based on lanthanum and aluminum (LaAlO3). The aim is, first, to provide an overview of the structure, properties, and classification of perovskites. Secondly, the most recent advances in synthetic methods, such as solid-state methods, solutionmediated methods (co-precipitation, sol–gel, and Pechini synthesis), thermal treatments (combustion, microwave, and freeze drying), and hydrothermal and solvothermal methods, are also discussed. The most recent energetic catalytic applications (the dry and steam reforming of methane; steam reforming of toluene, glycerol, and ethanol; and oxidative coupling of methane, amongst others) using these functional materials are also addressed. Finally, the synthetic challenges, advantages, and limitations associated with the preparation methods and catalytic applications are discussed., The authors are grateful for financial support from the Spanish Ministry of Science and Innovation (MCIN/AEI/10.13039/501100011033) through project PID2020-112656RBC21. HJM thanks the Universidad Pública de Navarra for a doctoral grant. AG also thanks Banco Santander for funding via the Research Intensification Program.