Zouhair Boukha

Universidad del País Vasco / Euskal Herriko Unibertsitatea | UPV/EHU · Chemical Engineering

Hydroxyapatite (HA) is an emergent catalytic material able to contribute effectively to the improvement of a number of strategic applications, including energy transformation and the generation of high added‐value products processes. As a catalyst support, it is widely used because of its interesting structural and chemical properties. In this mini...

The performance of nickel supported on lanthana-modified hydroxyapatite (HAP) catalysts is investigated in the CO2 methanation. The addition of La (1-6.6 wt.%) leads to a surface enrichment following a sequential multilayer deposition model. Moreover, La addition systematically improves the dispersion of Ni particles and their reducibility, which i...

The viability of gold supported on lanthanum-modified HAP catalysts is investigated for CO preferential oxidation (PROX) in H2-rich stream. All samples comprise small nanoparticles (NPs) of Au (< 4 nm). Addition of La enhances the chemisorption of CO, whereas it lowers that of H2 and H2O. Moreover, lanthanum improves the reducibility of the catalys...

Proton-exchange-membrane fuel cells (PEMFCs) appear to be the most promising solution for future automotive applications. Facing the lack of efficient hydrogen storage and transportation solutions, current research is focused on the development of on-board catalytic reformers. In this strategy, the purity of hydrogen stream is still an unresolved i...

The combustion of lean methane was studied over palladium, rhodium, platinum, and ruthenium catalysts supported on hydroxyapatite (HAP). The samples were prepared by wetness impregnation and thoroughly characterized by BET, XRD, UV-Vis-NIR spectroscopy, H2-TPR, OSC, CO chemisorption, and TEM techniques. It was found that the Pd/HAP and Rh/HAP catal...

Biogenic hydroxyapatite (NHAp) was prepared by calcination of waste pork bones and investigated as catalytic support for Ni and Cu metals in the water–gas shift (WGS) reaction. Part of the doped Cu was ion exchanged with Ca ions in the NHAp structure. Also, XPS data showed that after Cu doping, nickel d-hole density increased due to adjacent Cu ato...

In the present study, a series of four hydroxyapatite (HAP) supported palladium samples, with a Pd loading close to 0.5%, obtained through their calcination at 773, 873, 973, or 1073 K has been investigated. These samples have been characterized using a wide battery of complementary techniques. From these studies, it was found that the rise of the...

The performance of a series of Pt/La(x)/HAP catalysts was investigated in the WGS reaction. It was found that the addition of La into the Pt/HAP catalyst enhances its OSC, hinders the incorporation of Pt species into the HAP framework, promotes its reducibility, decreases the Pt particle size and markedly improves its WGS activity. Moreover, the sh...

A series of Ni/hydroxyapatite samples presenting different Ca/P molar ratios were synthesised to study the influence of the hydroxyapatite support composition on their catalytic properties in the dry reforming of methane. Our results reveal that a preparation starting from a sub-stoichiometric composition (Ca/P < 1.67)followed by the impregnation o...

A series of Cu/HAP catalysts was prepared by impregnation and characterised by TEM, BET, DRS, XPS, H2-TPR, XRD, TEM and FTIR techniques. H2-TPR and DRS data revealed that at low concentration (< 1%) large fraction of Cu incorporated the HAP framework. The increase of the Cu loading significantly increased the density of the CuO particles spread ove...

CuO-ZnO/HAP catalysts were prepared by co-impregnation and tested in the water-gas shift reaction. The prepared samples were thoroughly characterised by a wide number of analytical techniques including N2 physisorption, XRD, DRS, XPS, H2-TPR, N2O chemisorption, CO-TPD, H2-TPD, CO2-TPD, OSCC and OSC techniques. The properties of the synthesised mate...

Rh/hydroxyapatite samples were prepared by impregnation and investigated for the partial oxidation (POM) and steam reforming (SRM) of methane. The catalysts were analysed by BET, XRD, DRS, XPS, H2-TPR, TEM, H2 chemisorption, CO2-TPD and NH3-TPD techniques. The characterisation results showed that, after calcination, Rh existed in three different fo...

Hydroxyapatite (HAP) support has been synthesised and impregnated with different amounts of Pd. The prepared Pd/HAP catalysts have been thoroughly characterised by BET, XRD, TEM, UV-visible-NIR, FTIR, XPS, CO2-TPD and NH3-TPD techniques and tested in the DCE oxidation reaction. The characterisation of the catalysts has revealed a clear evolution o...

The promoting effect of Co addition on the behaviour of the Pd/HAP system in WGS reaction has been investigated. Hydroxyapatite-supported bimetallic PdCo samples have been prepared by two consecutive impregnation steps with solutions of Co and Pd precursors, respectively. The resulting catalysts have been thoroughly characterised by BET, XRD, H2-TP...

Calcined bone which is mainly composed by hydroxyapatite (HAp) was used as catalytic support of transition metals (Ni, Cu, Co, Fe) for WGS reaction. The catalysts were characterised by TGA, ICP, XRD, FTIR, H2-TPR, H2 chemisorption, OSC, CO2-TPD and N2 adsorption. The activity and selectivity was investigated and correlated with the chemical, struct...

The catalytic performance of synthesised calcium-deficient hydroxyapatite supported Pd catalysts are examined for various CO elimination processes, namely CO total oxidation, CO preferential oxidation and water gas shift reactions. The prepared samples loaded with different amounts of palladium (0.5–2%) are thoroughly characterised by a wide number...

Calcium-deficient hydroxyapatite (HAP) loaded with different amounts of cobalt are synthesised and characterised by several techniques including N2 physisorption, XRD, TEM, H2-TPR, UV–vis-NIR DRS, XPS spectroscopy and volumetric adsorption of CO2 and NH3 molecules techniques. The Co(x)/HAP catalysts are tested in the oxidation of 1,2-dichloroethane...

The selective catalytic reduction of NOx with NH3 was investigated over microstructured reactors based on Cu/Al2O3 films deposited onto stainless steel microgrids. The catalytic activity results showed that these Cu/Al2O3 films were more active and selective to produce N2 compared to the conventional catalysts in powder shape with the same copper l...

Magnesia modified nickel aluminate spinel catalysts were synthesised and characterised by BET, TEM, XRD, H2-TPR, XPS, CO2-TPD and TGA-MS techniques. The addition of this promoter induced significant changes in the textural, structural and chemical properties of the resulting spinel derived catalysts. Thus, it enhanced the resistance of the deposite...

The catalytic activity of VOx species supported on TiO2 was investigated in the simultaneous destruction of NO and 1,2-dichlorobenzene (o-DCB), as typical pollutants molecules in the off-gases from municipal waste incinerator (MWI) plants. Catalysts with different vanadium loading were prepared in order to obtain different VOx species and character...

The selective CO oxidation reaction in H2-rich gas mixture (COPROX) was investigated over microstructured reactors based on Cu/Al2O3 films deposited onto stainless steel microgrids. The catalytic activity results showed that these Cu/Al2O3 films were more active and selective to produce CO2 compared to the conventional catalysts in powder shape wit...

The suitability of NiAl2O4-based catalysts for steam reforming of isooctane, which is used here as a surrogate for gasoline, was examined at moderate temperatures (600-700 °C) during a relatively prolonged time on stream (about 30 h). A series of catalysts with a varying nickel loading in the 10-33 wt.% range were prepared by co-precipitation. This...

Abstract Homogeneous and well-adhered alumina washcoat was deposited onto stainless steel microgrids. Alumina-washcoated stainless steel microgrids loaded with different amounts of copper were synthesised and characterised by several techniques including SEM-EDS, N2 adsorption at −196 °C, XRD, temperature programmed reduction (H2-TPR), UV–visible–N...

The suitability of the nickel aluminate phase as an effective precursor for producing highly active and stable Ni/alumina catalysts was investigated in the steam reforming of methane with a H2O/CH4 ratio of 3 in the 450–650 °C temperature range. Particularly, the effect of the preparation route, including dissolution followed by crystallization, co...

The catalytic performance of bulk nickel aluminate catalysts synthesised by co-precipitation (NiAl2O4-CP) and co-dissolution (NiAl2O4-D) was examined for various methane reforming reactions, namely partial oxidation, steam reforming and oxidative steam reforming. The calcined and reduced spinels were thoroughly characterised by a wide number of ana...

In this study, AA5083 samples were butt welded under a conduction regime with high-power diode laser (HPDL). Various mixtures composed of Ar and CO2 were used as a shielding gas. The influence of the shielding gas composition on the microstructure and on the properties of laser welds was analyzed. The weld beads were deeply characterized by metallo...

This paper is devoted to the characterisation of Ni/alumina reforming catalysts. A special attention was paid to the control of the catalytic properties by the synthesis route of bulk and supported catalysts. In this sense it was shown that the massive formation of NiAl2O4 phase, associated with low NiO/NiAl2O4 molar ratios on the catalyst surface,...

In the present work, a highpower diode laser has been employed to weld six aluminum alloys (1050, 2017, 2024, 5083, 6082, and 7075) under conduction regime. Controlling the experimental variables, butt joints with higher penetration than those previously reported in the literature for this regime could be obtained, demonstrating the weldability of...

The application of laser beam welding to aluminium alloys has some complications, mainly due to their high reflectivity, high thermal conductivity and low viscosity. In order to increase the laser absorption of aluminium alloys, some surface treatments has been applied in the literature, such as the application of dark coatings or sandblasting. How...

The application of laser beam welding to aluminum alloys has some complications, mainly due to their high reflectivity, high thermal conductivity and low viscosity. In order to increase the laser absorption of aluminum alloys, some surface treatments has been applied in the literature, such as the application of dark coatings or sandblasting. Howev...

Laser beam welding (LBW) show clear advantages compared with other techniques, as the low heat input, the high localization ability, the high welding speed, the high flexibility, the high weld quality and the high production rate. However, its applicability to aluminum alloys is limited, as they generally have high reflectivity, high thermal conduc...

Titanium alloys present excellent mechanical and corrosion properties, being widely employed in different industries such as medical, aerospace, automotive, petrochemical, nuclear and power generation, etc. Ti6Al4V is the α-β alloy most employed in industry. The modification of its properties can be achieved with convectional heat treatments and/o...

The high strength, low density and superior corrosion resistance allow titanium alloys to be widely employed in different industrial applications. The properties of these alloys can be modulated by different heat treatments, including laser processing. In the present paper, laser remelting treatments, performed with a high power diode laser, were a...

Laser beam welding (LBW) show clear advantages compared with other techniques, as the low heat input, the high localization ability, the high welding speed, the high flexibility, the high weld quality and the high production rate. However, its applicability to aluminium alloys is limited, as they generally have high reflectivity, high thermal condu...

Ti6Al4V is the α-β alloy most employed in industry. The modification of its properties can be achieved with conventional heat treatments and/or with laser processing. Laser remelting (LR) has been applied to Ti6Al4V by other authors with excimer and Nd-YAG laser, employing pure argon as shielding gas to prevent risk of oxidation. In the present con...

In the present work, laser texturization treatments have been performed for the first time on aluminum alloys to increase their absorption and weld penetration. Adjusting the experimental conditions, laser texturization increases the roughness and decreases the diffuse and specular reflectance of surfaces. The textured samples were subsequently sub...

In this paper, a three-dimensional numerical model was developed to study laser welding in an aluminium alloy (AA5083). The CFD model was used to solve the governing equations of conservation of mass, momentum and energy, so as to obtain the morphology, velocity field and temperature field of the melted zone in steady state. The predicted dimension...

We investigate a series of three La2O3/Al2O3 samples, with a lanthana loading close to the theoretical monolayer, obtained by calcination at 773K, 973K, or 1173K from a common precursor. The samples were characterized by N2 adsorption at 77K, X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), a variety of nano-analytical and nano-stru...

The authors are grateful for the opportunity to reply to the comments on our previous contribution (González-Rovira et al 2008 Nanotechnology 18 495305). We would like to clarify some aspects regarding the aim of our studies along with the morphological, chemical and structural features of the nanomaterials synthesized.

An electrodeposition process is used to synthesize nanotubes of a lanthanum-containing phase, employing porous alumina membranes as templates. This method should lead to the formation of La(OH)(3) nanowires, according to the previous results presented by Bocchetta et al (2007 Electrochem. Commun. 9 683-8), which can be decomposed to La(2)O(3), as t...

Palladium loaded calcium-hydroxyapatite, Pd(z)/CaHAp, and calcium-fluoroapatite, Pd(z)/CaFAp, were synthesised and characterised by TEM, XRD, IR and UV–vis–NIR spectroscopies. Introduction of palladium does not change the structure of CaHAp and CaFAp. The average size of PdO particles was found to be around 4–5 nm on Pd(1)/CaHAp but larger (6–7 nm)...

Calcium-hydroxyapatite and calcium-fluoroapatite loaded with different amounts of nickel were synthesized and characterized by several techniques including scanning electron microscopy, temperature programmed reduction (TPR), UV–visible–NIR and XPS spectroscopy. Three types of nickel species were detected in the two series of catalysts (i) Ni2+ ion...