Zirconia Support Research Articles

Surface engineered sustainable nanocatalyst with improved coke resistance for dry methane reforming to produce hydrogen

The ever-growing carbon-based economy has led to alarming increases in greenhouse gas (GHG) emissions, particularly methane (CH4) and carbon dioxide (CO2). These emissions accelerate global warming, pollution and environmental challenges. Methane Dry Reforming (DRM) offers a promising technology to address this issue by converting CH4 and CO2 into a valuable syngas (CO + H2) mixture, which is a valuable fuel and a building block for many important chemical reactions (Fischer-Tropsch process). However, finding affordable and environmentally friendly catalysts for large-scale applications remains a critical hurdle. This study delves into the development of stable nickel-zirconia catalysts prepared via impregnation method. The weight percentage of nickel and zirconia was varied to optimize the catalyst's activity by controlling deactivation phenomenon that is a major challenge at higher temperatures during DRM. Various characterization techniques (XRD, FT-IR, SEM-EDX, TGA, TEM and BET) were employed to evaluate synthesized catalysts physio-chemical properties. Additionally, catalytic performance was assessed at temperatures ranging from 550 to 750 °C and a gas hourly space velocity (GHSV) of 72,000 mL/h.gcat. Among tested catalysts, 15% Ni/ZrO2 displayed remarkable conversion values for both CH4 (62.9%) and CO2 (64.9%). Importantly, it exhibited significantly lower weight loss (ca. 15.42%) compared to other variants, indicating better resilience against coke deposition. This enhanced stability can be attributed to synergistic interplay between nickel and zirconia support, effectively suppressing carbon formation. These findings demonstrate potential of 15% Ni/ZrO2 as a promising catalyst for experimental DRM application. With the obvious high activity and stability, 15% Ni/ZrO2 candidate serves as an eco-friendly candidate for greenhouse gas conversion into green fuel energy, contributing to a sustainable economy and clean environment.

3D printing of porous zirconia support for solid oxide fuel cells with high cell performance

This work reports the preparation and characterization of a 3D-printed porous 3 mol% yttria-stabilized zirconia (3YSZ) inert-supported micro-tubular solid oxide fuel cell (MT-SOFC) with high cell performance. For the first time, the impacts of pore-former particle size and mass fraction on the microstructure of 3D-printed porous 3YSZ, along with the influences of debinding atmosphere and pre-sintering temperature on the flexural strength and the shrinkage rate, were comprehensively explored. Optimal results were achieved using a particle size of 3 μm and a mass fraction of 30 wt%, facilitating the preparation of a printable 3YSZ photocurable slurry with a relatively low apparent viscosity of 4.2 Pa s at a shear rate of 30 s−1. Notably, 3D-printed porous 3YSZ debound in nitrogen and sintered in air at 1400 °C exhibited the highest flexural strength of ∼80.2 MPa compared to debinding in air or vacuum. Based on flexural strength and shrinkage rate considerations, the 3D-printed porous 3YSZ debound in nitrogen and pre-sintered at 1150 °C was deemed suitable as an inert support for SOFC. Cells prepared using this optimized approach demonstrated exceptional performance, achieving a maximum power density of 876.8 mW cm−2 at 850 °C, surpassing inert-supported MT-SOFCs fabricated using traditional methods. The outstanding cell performance underscores the successful application of 3D printing technology in preparing porous 3YSZ inert supports for SOFCs, offering an attractive approach for cell preparation and porous ceramics.

Boosting Methane Combustion over Pd/Y2O3-ZrO2 Catalyst by Inert Silicate Patches Tuning Both Palladium Chemistry and Support Hydrophobicity.

Supported palladium (Pd) catalysts are widely utilized to reduce the emission of exhaust CH4 from lean-burn engines by catalytic combustion. A large amount of water vapor in the exhaust makes hydroxyls accumulate on the catalyst surface at temperatures below 450 °C, leading to severe catalyst deactivation. Tuning palladium chemistry and inhibiting water adsorption are critical to developing active catalysts. Modifying the support surface with inert silicates would both change the palladium-support interaction and decrease water adsorption sites. This study reports an improved Pd/Y2O3-ZrO2 catalyst by constructing silicate patches on yttria-stabilized zirconia (Y2O3-ZrO2) support. The silicates hindered electron transfer from Y2O3-ZrO2 oxygen vacancies to palladium, which optimized palladium chemistry, especially the reducibility of active PdO species, and thereby boosted CH4 conversion under dry conditions. The temperature of 90% methane conversion (T90) over the catalyst decreased from 386 to 309 °C. Moreover, the inert silicates decreased surface oxygen vacancies of Y2O3-ZrO2 to improve support hydrophobicity, thereby inhibiting hydroxyl accumulation. The poisoning effect of water on the active sites located on the palladium-silicate interface was alleviated. When reaction gases contained 10 vol % water, the silicate-modified catalyst still showed higher activity with T90 of 404 °C, which is lower than T90 of 452 °C for unmodified catalyst. This work represents a step forward in preparing high-performance palladium catalysts for low-temperature wet methane combustion.

Impact of doping ZrO2 with Sn on CO2 hydrogenation over dispersed Ru

Thermocatalytic CO2 hydrogenation is a scalable route to renewable fuels and chemicals that can also mitigate climate change. Here, we demonstrate how subtle changes in a mixed phase zirconia support induce large changes in catalyst activity and selectivity. Ru/SnxZr1-xO2 catalysts were prepared using co-precipitated Sn-doped ZrO2. Ru/ZrO2 and Ru/Sn0.01Zr0.99O2 both comprised tetragonal (t-) and monoclinic (m-) ZrO2 nanoparticles decorated by RuO2·H2O clusters. Ru/Sn0.2Zr0.8O2 exhibited similar textural properties and metal speciation, however, X-ray diffraction evidenced new crystalline phases wherein Sn atoms substituted for Zr. Operando XRD evidenced minimal perturbation of ZrO2 and Sn-doped ZrO2 phases, despite which 20 atom% Sn switched product selectivity from 99% CH4 for Ru/ZrO2 to 67% CO for Ru/Sn0.2Zr0.8O2, due to increased support CO2 adsorption capacity/strength. Operando infrared spectroscopy identify linear surface CO* as a catalytic spectator with (bi)carbonate a precursor to reactive HCOO*/carboxylate intermediates to methane. Sn0.2Zr0.8O2 promotes CO2/(bi)carbonate/formate decomposition, favouring a reverse water gas shift pathway.

Dry Reforming of Methane with Mesoporous Ni/ZrO2 Catalyst

Dry reforming of methane has exhibited significant environmental benefits as it utilizes two major greenhouse gases (CO2 and CH4) to produce synthesis gas, a major building block for hydrocarbons. This process has gained industrial attention as catalyst deactivation due to coke deposition being a major hindrance. The present study focuses on the dry reforming of methane over Ni-supported mesoporous zirconia support. Ni metal was loaded over in-house synthesized mesoporous zirconia within the 0–15 wt% range using the wet impregnation method. The physicochemical properties of the synthesized catalysts were studied using various characterization techniques, namely, XRD, SEM, FTIR, TGA, and N2 adsorption-desorption techniques. The activity of all the catalysts was evaluated at 750°C and gas hourly space velocity (GHSV) of 72000 ml/h/gcat for 9 hours (540 min). The deactivation factor indicating a loss in conversion with time is reported for each catalyst. 10 wt% Ni/ZrO2 showed the highest feed conversion of about 68.8% for methane and 70.2% for carbon dioxide and the highest stability (15.1% deactivation factor and 21% weight loss) for dry reforming of methane to synthesis gas.

Mechanism of Catalytic CO2 Hydrogenation to Methane and Methanol Using a Bimetallic Cu3Pd Cluster at a Zirconia Support.

For very small nanocluster-based catalysts, the exploration of the influence of the particle size, composition, and support offers precisely variable parameters in a wide material search space to control catalysts' performance. We present the mechanism of the CO2 methanation reaction on the oxidized bimetallic Cu3Pd tetramer (Cu3PdO2) supported on a zirconia model support represented by Zr12O24 based on the energy profile obtained from density functional theory calculations on the reaction of CO2 and H2. In order to determine the role of the Pd atom, the performance of Cu3PdO2 with monometallic Cu4O2 at the same support has been compared. Parallel to methane formation, the alternative path of methanol formation at this catalyst has also been investigated. The results show that the exchange of a single atom in Cu4 with a single Pd atom improves catalyst/s performance via lowering the barriers associated with hydrogen dissociation steps that occur on the Pd atom. The above-mentioned results suggest that the doping strategy at the level of single atoms can offer a precise control knob for designing new catalysts with desired performance.

Selective production of guaiacol from lignin via catalytic transfer hydrogenolysis using Ru-Cu/Zirconia

In this study, the effect of calcination temperature of zirconia support (400, 600, and 800 °C) and the role of bimetallic Ru-Cu over monometallic (Cu, Ru) catalysts are evaluated for catalytic transfer hydrogenolysis of alkali lignin. The prepared catalysts were characterized extensively for crystallinity, pore size distribution, acidity, thermal stability and chemical oxidation state. The transformation of zirconia from non-crystalline to crystalline phase was observed with increasing calcination temperature. The pores transformed from wide ink bottle shape into cylindrical shape with increased calcination temperature. The XPS analysis revealed the existence of Cu0 (60%) in presence of Ru with a concomitant reduction in Ru4+ on the surface of the catalyst, which is attributed to increased crystallinity of zirconia in the presence of copper. High yields of total monomers (32.4 wt.%) and guaiacol (12.7 wt.%) were obtained under the optimized condition (270 °C, 3 h) with Ru-Cu/ZrO2 when ZrO2 was calcined at 800 °C. The mesoporous nature of zirconia and the strong metal-support interaction exhibited by Ru-Cu are shown to influence the formation of monomers. Increase in temperature from 225 to 270 °C enhanced the yield of guaiacol, 4-methyl guaiacol and 4-ethyl guaiacol with a concomitant reduction in the yield of trans-isoeugenol, demonstrating the cleavage of C–C bonds. The recyclability tests of the catalyst showed that the yield of guaiacol remained stable even after two cycles of catalyst reuse without calcination.

Performance Study of Methane Dry Reforming on Ni/ZrO2 Catalyst

Dry reforming of methane (DRM) has important and positive environmental and industrial impacts, as it consumes two of the top greenhouse gases in order to produce syngas (H2 and CO) and thus hydrogen (H2). The performance of DRM of conversions of CH4 and CO2 was investigated over Ni/ZrO2 catalysts. The catalytic performance of all prepared catalysts for DRM was assessed in a micro-tubular fixed bed reactor under similar reaction conditions (i.e., activation and reaction temperatures at 700 °C, a feed flow rate of 70 mL/min, reaction temperature, and a 440 min reaction time). Various characterization techniques, such as BET, CO2-TPD, TGA, XRD, EDX, and TEM, were employed. The zirconia support was modified with MgO or Y2O3. The yttria-stabilized zirconia catalyst (5Ni15YZr) provided the optimum activity performance of CH4 and CO2 conversions of 56.1 and 64.3%, respectively, at 700 °C and a 70 mL/min flow rate; this catalyst also had the highest basicity. The Ni-based catalyst was promoted with Cs, Ga, and Sr. The Sr-promoted catalyst produced the highest enhancement of activity. The influence of the reaction temperature and the feed flow rate on 5Ni15YZr and 5NiSr15YZr indicated that the activity increased with the increase in the reaction temperature and lower feed flow rate. For 5Ni3Sr15YZr, at a reaction temperature of 800 °C, the CH4 and CO2 conversions were 76.3 and 79.9%, respectively, whereas at 700 °C, the conversions of CH4 and CO2 were 66.6 and 79.6% respectively.

Dry Reforming of Methane with Ni Supported on Mechanically Mixed Yttria-Zirconia Support

This study focuses on CH4 reforming with CO2 over Ni supported on yttria mixed with zirconia support. Different loading of yttria was used to enhance the performance of Ni towards achieving the optimum activity. The physicochemical properties of both fresh calcined and used catalysts were studied using a range of characterization techniques. The specific surface area measurement by the BET method showed a progressive increase in the area with an increase in yttria loading. The monoclinic (m- ZrO2) and tetragonal (t- ZrO2) phases were identified on all the samples by the XRD analysis. A reduction in the intensity of m- ZrO2 was observed on adding Ni to the catalysts while the diffraction pattern of crystalline yttria was not identified. The reducibility analysis showed the influence of yttria. It induces the formation of NiYO3 species with stronger active metal-support interaction. From the catalytic test, 5Ni/10Y-Z-3215 had the highest feed conversion of about 68 and 88% for CH4 and CO2 respectively. The TEM analysis showed a uniform dispersion of NiO particles over the mixed yttria-zirconia support with no agglomeration of the active metal particles after the reaction. The measurement of the quantity of carbon deposits by the TGA revealed that the increase in yttria loading enhanced the gasification of carbon deposits with 5Ni/20Y-Z-3215 recording the lowest weight loss of about 28%.Graphical

New hydrophilic carbon molecular sieve membranes for bioethanol dehydration via pervaporation

Tubular supported carbon molecular sieve membranes (CMSMs) with high hydrophilicity and perm-selectivities for water suitable for ethanol dehydration were developed from a Novolac oligomer phenolic resin as precursor. Alpha alumina supported CMSMs resulted in 1.69 times higher surface roughness than zirconia supports. The higher surface roughness resulted in 48% higher selective layer thickness. According to pervaporation results, water permeance decreased by the increase in selective layer thickness and mole based selectivity of water- ethanol was enhanced. The oligomer with 3982 g/mol molecular weight enabled membrane to reach high selectivity with one-layer coating. Performance of the membranes are compared with literature data in terms of mole-based selectivity vs. water permeance. CMSMs could be a potential substitution for traditional ethanol dehydration methods with offering higher performance and as a result reducing the final price of bioethanol to be used as a sustainable energy source.

Heterogeneous Fenton-like oxidation of ibuprofen over zirconia-supported iron and copper catalysts: effect of process variables

In this study, a series of iron and copper-based catalysts with varying metal loadings are prepared by wet impregnation over zirconia support and tested as catalyst for the treatment of ibuprofen with a Fenton-like process. The textural and morphological properties of catalysts are investigated by standard techniques. Both iron and copper-based catalysts when loaded with 7.5 wt% of metal affords maximum mineralization activities of 80 and 70% respectively, under optimal conditions. In addition, they only lose 1.7% (0.3 mg) of iron and 6.2% (0.9 mg) of copper during oxidation process. Catalysts exhibit better activities at pH 3 and 5 respectively for Fe and Cu. Iron-based catalysts lose their activities when recycled and the activity of 7.5%Fe/ZrO2 catalyst decreased °ʇfrom 80 to 38% after 3 cycles. On the contrary Cu-based catalysts maintain their high activity when recycled. Overall, copper-based catalysts are very promising materials with enhanced catalytic activity and high stability for the degradation of ibuprofen in heterogeneous Fenton-like process.

Catalytic reforming of glycerol in hot compressed water: Role of metal and support

The objective of this study is to maximize the hydrogen yield from hydrothermal reforming of glycerol by screening different catalysts. Catalysts with different active metals (Platinum, Ruthenium, Palladium, Nickel and Rhodium) on alumina support and palladium with different supports (Alumina, Titania, Zirconia, Activated Carbon, Ceria modified Zirconia) were synthesized, characterized, and tested at hydrothermal conditions (450 °C and 250 bar) for glycerol reforming up to 6 h duration. With different metals, maximum carbon gasification efficiency of 70% and hydrogen yield of 2.023 mol/mol was achieved with platinum metal while the lowest carbon gasification efficiency of ~ 7.5 was obtained with nickel-based catalyst with a very low hydrogen yields of 0.021 mol/mol. Since, the amount of active metal loading (~ 1.5 wt%) was very low, in the case of nickel it led to inactive and stable phase of NiAl2O4 having poor catalytic performance. With different supports, maximum carbon gasification efficiency of ~ 65% and hydrogen yield of 2.475 mol/mol was obtained with ceria modified zirconia support. Lowest conversion and hydrogen yield of 17.3% and 0.155 respectively were achieved with titania support. The order of gasification efficiency with respect to different supports was in the order of CeZrO2 ~ ZrO2 > Al2O3 > AC > TiO2. Analysis of the spent catalysts showed significant phase change of alumina support from γ-Al2O3 to α-Al2O3 with maximum coke deposition evident from the thermogravimetric analysis without any catalyst deactivation. These findings provide new opportunities for rational design of catalyst for the hydrothermal conversion of glycerol to hydrogen rich product gas.

Methane combustion over palladium catalysts with manipulated aggregation on zirconia support

Methane combustion over palladium catalysts with manipulated aggregation on zirconia support

Influence of the Reduction Temperature and the Nature of the Support on the Performance of Zirconia and Alumina-Supported Pt Catalysts for n-Dodecane Hydroisomerization

Catalysts based on zirconia- and alumina-supported tungsten oxides (15 wt % W) with a small loading of platinum (0.3 wt % Pt) were selected to study the influence of the reduction temperature and the nature of the support on the hydroisomerization of n-dodecane. The reduction temperature has a major influence on metal dispersion, which impacts the catalytic activity. In addition, alumina and zirconia supports show different catalytic properties (mainly acid site strength and surface area), which play an important role in the conversion. The NH3-TPD profiles indicate that the acidity in alumina-based catalysts is clearly higher than that in their zirconia counterparts; this acidity can be attributed to a stronger interaction of the WOx species with alumina. The PtW/Al catalyst was found to exhibit the best catalytic performance for the hydroisomerization of n-dodecane based on its higher acidity, which was ascribed to its larger surface area relative to that of its zirconia counterparts. The selectivity for different hydrocarbons (C7–10, C11 and i-C12) was very similar for all the catalysts studied, with branched C12 hydrocarbons being the main products obtained (~80%). The temperature of 350 °C was clearly the best reduction temperature for all the catalysts studied in a trickled-bed-mode reactor.

Effect of Mesostructured Zirconia Support on the Activity and Selectivity of 4,6-Dimethydibenzothiophene Hydrodesulfurization

In contrast with the conventional CoMoS/alumina catalyst, the use of amorphous mesostructured ZrO2 as support for the dispersion of the CoMoS active phase in deep hydrodesulfurization (HDS) of 4,6-dimethyldibenzothiophene led to a higher promotion rate and a better sulfidation of the cobalt species. The CoMoS, dispersed over mesostructured amorphous ZrO2 as catalyst, also induced a modification of the main desulfurization way; in this case, a shift towards direct desulfurization selectivity was observed. This result was unexpected regarding the literature. Indeed, the hydrogenated route was observed for commercial zirconia. The designed catalysts are therefore more eco-friendly, since they consume less hydrogen. This implies a better use of the fossil resources.

Enhancement of Oxidation of Formic Acid through Application of Zirconia Matrix for Immobilization of Noble Metal Catalytic Nanoparticles

Electrocatalytic activity of common noble metal (platinum, bimetallic platinum-ruthenium and palladium) nanoparticles (both unsupported and supported on Vulcan carriers) toward electrooxidation of formic acid in acid medium (0.5 mol dm–3 H2SO4) can be significantly enhanced by dispersing them over thin film of zirconia (ZrO2). The enhancement effects concern increases of the electrocatalytic current densities (normalized against the mass of noble metal catalysts) recorded under both cyclic voltammetric and chronoamperometric conditions. The observations can be rationalized in terms of the ability of zirconia nanostructures to provide active hydroxyl groups capable of inducing the removal of the inhibiting COOH or CO type adsorbates from their surfaces. The role of Vulcan carriers is in improving electronic conductivity, in addition to facilitating distribution of catalytic metal sites at the electrocatalytic interface. Regarding dissimilar mechanisms for HCOOH oxidations at Pt, PtRu and Pd nanoparticles, the activating capabilities of zirconia differ depending on the potential applied thus reflecting distinct nature of electronic or chemical interactions. Specific interactions between the zirconia support and noble metal nanoparticles are also possible, particularly in the case of Pd-based catalysts where the enhancement effects are the most pronounced. Finally, it should be emphasized that, historically, representatives of Russian school of electrochemistry, including V.S. Bagotsky, were one of the first world-wide who investigated the formic acid oxidation and emphasized the importance of metal—support interactions during electrooxidation of small organic molecules at noble metal nanoparticles.

Alloying Effect of Silver on Zirconia Support Manipulated Palladium Catalyst for Methane Combustion

PdAg/ZrO2 alloy catalysts calcined at different temperatures were employed to elucidate the effect of support-metal interaction (SMI) on methane combustion. Combustion activity was depressed when the sample was calcined at an elevated temperature from 500 °C to 700 °C. However, calcination at 850 °C enhanced the beneficial SMI, which facilitated a more active phase for the oxidation reaction. The high-resolution transmission electron microscopy experiments show that a special micro-domain structure at the interface is formed during the reduction pretreatment. H2-TPR and O2-TPD measurements illustrate that the active phase would undergo reconstruction upon redox cycles. The active phase manipulated by the support is more suitable for combustion reaction in the course of temperature altering.

XNi/Ni0.05Ce0.20Zr0.75O2 Solid Solution over a CO2 Methanation Reaction

A Ni-modified ceria–zirconia support with Ni impregnation at different Ni-loading catalysts for a CO2 methanation reaction was systematically studied. The corresponding structures of each catalyst were characterized by Brunauer–Emmett–Teller surface area analysis, X-ray powder diffraction, X-ray fluorescence, H2 temperature-programmed reduction, CO2 temperature-programmed desorption, Fourier transform infrared, scanning electron microscopy, transmission electron microscopy, X-ray photoelectron spectroscopy, and thermogravimetric/differential thermal analysis. The results showed that Ni-modified Ce–Zr oxide improved the basic properties as well as the oxygen vacancies. A gradual increase in Ni loading from 15 to 45 wt % was found to increase medium-strong basic sites, and surface Ce3+and Ni0 species along with oxygen vacancies favor high activity. The CO2 methanation activity was related to the amount of Ni loadings where the 45Ni/Ni005CZO catalyst was reported to be the most active catalyst. This is due to the high amount of Ni surface suitable for H2 activation and high medium basic sites to accommodate CO2 activation, leading to high catalytic activity.

Efficient hydrogen production through the chemical looping redox cycle of YSZ supported iron oxides

The chemical looping process, where an oxygen carrier is reduced and oxidized in a cyclic manner, offers a promising option for hydrogen production through splitting water because of the much higher water splitting efficiency than solar electrocatalytic and photocatalytic process. A typical oxygen carrier has to comprise a significant amount of inert support, to maintain stability in multiple redox cycles, thereby resulting in a trade-off between the reaction reactivity and stability. Herein, we proposed the use of ion-conductive yttria-stabilized zirconia (YSZ) support Fe2O3 to prepare oxygen carriers materials. The obtained Fe2O3/YSZ composites showed high reactivity and stability. Particularly, Fe2O3/YSZ-20 (oxygen storage capacity, 24.13%) exhibited high hydrogen yield of ∼10.30 mmol g−1 and hydrogen production rate of ∼0.66 mmol g−1 min−1 which was twice as high as that of Fe2O3/Al2O3. Further, the transient pulse test indicated that active oxygen diffusion was the rate-limiting step during the redox process. The electrochemical impedance spectroscopy (EIS) measurement revealed that the YSZ support addition facilitated oxygen diffusion of materials, which contributed to the improved hydrogen production performance. The support effect obtained in this work provides a potentially efficient route for the modification of oxygen carrier materials.

Preferential oxidation of carbon monoxide in a hydrogen-rich gas stream over supported gold catalysts: the effect of a mixed ceria–zirconia support composition

The effect of the ceria–zirconia (CeO2–ZrO2) support composition of a gold (Au) catalyst (Au/Ce1−xZrxO2, where x is the molar ratio), prepared by deposition–precipitation, on its catalytic activity was investigated in the preferential carbon monoxide (CO) oxidation. A maximum CO conversion level of 94% was obtained with 1% by weight Au/Ce0.75Zr0.25O2 at 50 °C, while the presence of water and carbon dioxide in the feed stream had only a slight effect on the catalytic activity. Catalyst characterizations were performed to investigate the effect of the Ce:Zr molar ratios on the redox properties and physicochemical properties of the obtained Au/CeO2–ZrO2 catalysts. It was found that a certain amount of Ce in the Au/CeO2–ZrO2 catalyst promoted solid solution formation and facilitated the activity of Au3+ and Au0 nanoparticles with a small crystallite size. The enhanced catalytic activity of Au/Ce0.75Zr0.25O2 was attributed to the presence of more oxygen vacancies, easier reducibility, and appropriate amount of Au3+ species, as confirmed by Fourier transform Raman spectroscopy and hydrogen-temperature-programme reduction analyses, respectively. The catalytic activity showed a high stability for a long period of time (28 h).