LaNiO3 Perovskite Catalysts Research Articles

Cu-doped LaNiO3 perovskite catalyst for DRM: revisiting it as a molecular-level nanocomposite.

Dry reforming of methane (DRM) was extensively studied on Cu-doped LaNiO3 catalysts. The main findings of this work are as follows: (i) thermal switching of the catalyst phase between the parent perovskite and molecular-level nanocomposite of individual components formed in situ during DRM, (ii) reusability of the catalyst with enhanced activity, and (iii) regeneration of the catalyst phase at a lower temperature than that required for the formation of the parent perovskite. The present investigation provides an extensive analysis and understanding of the DRM reaction using Cu-doped LaNiO3 compared to the result reported by Moradi et al., (Chin. J. Catal., 2012, 33, 797-801) and hence provides new insights into its catalytic activity. Phase-pure LaNi1-xCuxO3 catalysts, specifically LaNi0.8Cu0.2O3, exhibited high catalytic activity towards the DRM reaction (97% CH4 and 99% CO2 conversion with an H2/CO ratio of ∼1.4-0.9). Remarkably, although the initial perovskite phase primarily decomposed into its component phases after DRM, its catalytic activity was barely affected and maintained even after 100 h. The regeneration of the initial perovskite from the disintegrated binary phases via annealing at temperatures even lower than the synthesis temperature together with the amazing retention of activity was very intriguing. The parallel activity of the pristine perovskite and its degraded binary mixtures makes it difficult to identify the actual components responsible for the DRM activity. Accordingly, we have explained the sustained activity of the degraded perovskite catalyst in the context of nanocomposite formation at the molecular level in the reforming atmosphere with the availability of Ni0 and NiO, as revealed by the thoroughly characterized samples in the as-prepared, aged, and regenerated forms.

Uncovering the critical function of lanthanum in CH4 production from CO2 using exsolved LaNiO3 perovskite catalysts

The exsolved LaNiO3 perovskite catalyst exhibits superior performance compared to supported Ni/La2O3 attributed to the critical La–Ni arrangement differences, including Ni encapsulation and lanthana's affinity for hydroxide/carbonate formation.

Hydrogen-rich syngas production from acetic acid as bio-oil model compound: Effect of intermediate phases (La2NiO4, La2O3 and Ni) of LaNiO3 catalyst

In biomass gasification, bio-oil is the main component of the condensable by-products. It is considered an attractive source for H2 production via steam reforming. This study conducted acetic acid as a bio-oil model compound with LaNiO3 perovskite catalyst due to its high oxygen vacancies and active sites. However, the perovskite structure of LaNiO3 catalysis can be destroyed by produced H2 gas, forming additional phases, including La2NiO4, La2O3 and Ni. The LaNiO3 and different phases were synthesized via a sol-gel method to probe its contribution and interaction with the H2 gas produced from steam reforming of acetic acid. Through 300 min of reaction in steam to carbon (S/C) ratio of 3, the results showed that reduced-LaNiO3 has stable H2 gas production, while the other phases decrease with time. In particular, CH4 is the main composition with the La2O3 phase. A series of characterization techniques, such as XRD, BET, XPS, SEM, TG, H2-TPR and (CO2 and O2)-TPD, were utilized to investigate fresh and used samples. The results showed that the LaNiO3-reduced phase has high oxygen storage capacity, oxygen mobility, oxygen vacancies and surface area, preventing coke deposition. In contrast, the LaNiO3 and La2NiO4 phases have poor coke deposition resistance.

Effect of Ca on Perovskite La1−xCaxNiO3 Catalyst for CO2 Hydrogenation‐to‐Light Hydrocarbons in a Dielectric Barrier Discharge Plasma Reactor

Herein, the effects of the incorporation amount of Ca on the formation of C2–C4 in the hydrogenation of CO2‐to‐light hydrocarbons are studied in a hybrid dielectric barrier discharge–perovskite catalysis system. A series of La1−xCaxNiO3 (x = 0.1, 0.2, 0.3, 0.4) catalysts are prepared by a modified nitrate citric acid method. The catalysts are characterized by Brunauer−Emmett−Teller, X‐ray diffraction, transmission electron microscopy, H2‐temperature‐programmed reduction, CO2‐temperature‐programmed desorption, and X‐ray photoelectron spectroscopy. The results shows that NiO is dissolved on the catalyst surface after calcination, while NiO size increases with the rise of Ca amount. Meanwhile, different degrees of crystal defects are formed in La1−xCaxNiO3, leading to change of specific surface area, adsorbed oxygen amount, weak basic sites, and reductibility of NiO. The results show that the hydrogenation performance of LaNiO3 perovskite catalysts is enhanced by doping Ca cation in the A site, while the La0.7–Ca0.3–Ni catalyst exhibits the optimum performance and achieves CO2 conversion as high as 83.1% with selectivity of C2–C4 as 11.8%. The characterization results show that the perovskite La0.7–Ca0.3–Ni catalyst has lattice defects in the structure, high proportion of adsorbed oxygen, and more weak basic sites, thus promoting the adsorption and activation of CO2 and then resulting in a higher CO2 conversion.

Ultrasonic assisted enhanced catalytic effect of perovskite to promote depolymerization of lignin

The search for renewable energy sources to replace fossil fuel has made lignin a promising carbon-containing resource. In this paper, LaNiO3 perovskite catalyst supported by mesoporous carrier with specific pore structure was prepared by the pore filling of MCM-41 with citrate complex precursors of nickel and lanthanum. Then the catalysts applied to maize straw lignin depolymerization. The results of low-angle XRD, N2 adsorption-desorption, IR spectroscopy and SEM confirmed that the catalyst has been successfully manufactured. Based on the yield of phenolic monomer, low molecular weight lignin derived bio-oil and high molecular weight lignin derived bio-oil as standard, the catalyst showed best catalytic effect when the reaction temperature was 250 °C, the reaction time was 6 h, the ratio of lignin to catalyst mass was 5: 1 and with ultrasonic assist. The yield of phenolic monomer was 11.46 wt% and that of bio-oil was 68.0 wt%. In general, this method is an excellent embodiment of the principle of Lignin-first as well as an excellent strategy for the production of value-added phenolics and high-quality bio-oils from lignin. It plays an important role in promoting the high value utilization of lignin in the future.

Effect of preparation method and B-side metal type on the physicochemical properties of LaBO3 perovskite catalyst and its catalytic behaviour in the biomass pyrolysis

Although perovskites are extensively investigated in many areas, studies using perovskites as catalysts for biomass pyrolysis are still quite limited. While various transition metals can be inserted into perovskites to form different perovskites, it is critical to investigate the effects of various transition metallic substituents on the characterization of catalysts. This work involves the evaluation of nine perovskite-type catalysts in terms of their effectiveness and suitability for pyrolysis of date stone biomass. LaCoO3, LaMnO3 and LaNiO3 perovskite catalysts were prepared by sol-gel, hydrothermal and microwave methods and characterized by X-ray powder diffraction, scanning electron microscopy and surface area measurement. Pyrolysis of date stones has been performed in tubular reactor at 520 °C with 100 °C/min and a nitrogen gas flow rate of 100 cm3/min. The influences of catalyst preparation method on catalytic cracking of pyrolysis vapours in terms of bio-oil yields were examined. Additionally, the effect of B metal in ABO3 perovskite structure on catalyst character and pyrolysis yields were examined in detail. According to results, highest bio-oil yield was achieved as 23.4% with LaMnO3 catalyst synthesized with sol-gel method. All perovskite-type catalysts have reduced the bio-oil yield and improved the water and gaseous yield as expected. This study paves the way for developing more challenging perovskite catalysts for the renewable energy sources.

LaNiO3 as a precursor of Ni/La2O3 for reverse water-gas shift in DBD plasma: Effect of calcination temperature

Reverse water–gas shift (RWGS) is considered as a promising reaction to convert CO2 into CO, which together with H2, can be used for the synthesis of Fisher-Tropsch chemicals. In this study, a hybrid dielectric barrier discharge (DBD) plasma-catalysis system was developed for RWGS at room temperature. LaNiO3 perovskite catalysts calcined at 600, 700, 800 and 900 °C (denoted as LNO-600, LNO-700, LNO-800 and LNO-900) were synthesized and tested for RWGS in DBD plasma reactor. Different methods including XRD, N2 adsorption-desorption, H2-TPR, TEM, CO2-TPD, O2-TPD, XPS, XANES, EXAFS and TG-DTA were employed for the characterization of fresh, reduced and spent catalysts. The results showed that a fully crystallized LaNiO3 perovskite structure could be formed only at temperatures of >800 °C, and lower calcination temperatures resulted in the presence of NiO and amorphous La2O3. Ni was extracted from the LaNiO3 perovskite structure to form Ni supported on La2O3 support (Ni/La2O3) after reduction for all catalysts. The CO2 conversion did not show obvious difference over different catalysts. However, the maximum CO selectivity and the minimum CH4 selectivity were achieved over LNO-600. The higher catalytic activity of LNO-600 should be attributed to its higher Ni dispersion, smaller Ni particle size and stronger metal-support interaction. It should be noted LNO-800 showed the highest coke resistance ability, due to the highest ratio of surface adsorption oxygen and largest oxygen storage capacity evidenced by the XPS and O2-TPD results. In addition, the effect of H2/CO2 ratio on the performance of RWGS was studied and a H2/CO2 ratio of 2:1 was confirmed to be the optimum for the simultaneous achievement of higher CO2 conversion and CO selectivity.

CO2 Reforming of Methane over LaNiO3 Perovskite Supported Catalysts: Influence of Silica Support

The study presents the dry reforming of methane using natural Kaolin silica as catalyst support. The silica-supported LaNiO3 perovskite catalysts (20LaNiO3/SiO2 and 40LaNiO3/SiO2) and bulk LaNiO3 catalyst were synthesized by auto-combustion method. The resulting catalysts were characterized by X-ray diffraction (XRD), N2 adsorption - desorption isotherm measurement, scanning electron microscopy (SEM) and temperature-programmed reduction (TPR). After reduction at 700 °C, they were used as catalysts for the reaction of dry reforming of methane into synthesis gas at atmospheric pressure at 800 °C. The reduced 40LaNiO3/SiO2 exhibited high catalytic activity. This result was attributed to the small Ni metallic particles obtained from the reduced perovskite highly dispersed on the support and the good reducibility. The increase of reduction temperature at 800 °C resulted in a further enhancement of the catalytic performance of 40LaNiO3/SiO2 catalyst. Copyright © 2019 BCREC Group. All rights reserved

Catalytic wet air oxidation of Reactive Black 5 in the presence of LaNiO3 perovskite catalyst as a green process for azo dye removal

The removal of textile azo dye, Reactive Black from the aqueous solutions by catalytic wet air oxidation in the presence of LaNiO3 perovskite catalyst has been investigated. The most suitable reaction conditions were determined by testing various the catalyst loadings, reaction temperature and pressure values, and the initial pH of the Reactive Black 5 solutions. The most suitable reaction conditions with 0.61 L/min of air flow rate were found to be 1 g/L of LaNiO3 loading, 50 °C of reaction temperature, 1 atm of reaction pressure, and, pH = 3 for the oxidation of 100 mg/L Reactive Black solutions. Under these conditions the degradation and the decolorization efficiencies were evaluated as 65.4% and 89.6%, respectively. The phytotoxicity analyzes were carried out by using Lepidium sativum. According to the toxicity tests a remarkable decrease in the growth inhibition was achieved by the catalytic wet air oxidation in the presence of LaNiO3 catalyst. The growth inhibition in the untreated and treated dye solutions were calculated as 49.3% and 23.7%, respectively.

Combined steam and CO2 reforming of methane over La1-xSrxNiO3 perovskite oxides

The effect of Sr addition to LaNiO3 perovskite catalysts was studied for the steam-CO2 reforming of methane. X-ray diffraction (XRD) patterns indicate that different ionic radii caused distortion of the perovskite lattice and produced alien phases such as La2-xSrxNiO3±δ and Sr0.5La1.5NiO4. Moreover, these different phases affected reduction behavior. The influence of Sr mainly appeared in the steam-CO2 reforming of methane reaction. SrO species adsorbed CO2 during the reaction and produced SrCO3, which has a better ability of eliminating carbon sources by producing La2O2CO3, and by this means, carbon formation was significantly suppressed. However, the addition of Sr species covered the support sites leading to large-sized nickel particles by reducing the interaction between the support and active metals, thus the catalytic activity was decreased by an increase in Sr concentration on the catalysts. Therefore, we recommend using a small amount of Sr in the perovskite-based catalysts to obtain superior resistance to carbon deposition with moderate catalytic activity.

The effects of partial substitution of Ni by Zn in LaNiO3 perovskite catalyst for methane dry reforming

A series of LaNi1−xZnxO3 (x=0.2, 0.4, 0.6, 0.8 and 1.0) perovskite-type oxides were synthesized via sol–gel related method by using propionic acid as solvent. The reaction was performed under continuous flow of feed stream which included CO2, CH4 and helium as diluting agent, under atmospheric pressure. The prepared catalysts were characterized by X-ray diffraction (XRD) and temperature-programmed reduction (TPR). The results showed that the conversion rates of CO2 and CH4 increased as Ni was partially substituted by Zn. Considering the mentioned rates, among these catalysts, LaNi0.8Zn0.2O3 was the most effective catalyst. TPR results showed that partial substitution of Ni by Zn increased the temperatures of reduction peaks, leading to the more stable perovskite structure compared to LaNiO3 structure. It indicates that Zn stabilizes the perovskite structure. Also, TGA results showed that LaNi0.8Zn0.2O3 was more resistant to coke formation in comparison with LaNiO3 during 75h time on stream stability test.

Catalytic performance of steam reforming of ethanol at low temperature over LaNiO3 perovskite

A LaNiO3 perovskite catalyst was prepared using the coprecipitation–oxidation hydrothermal method, followed by calcination at 600 °C for 2 h. The as-prepared sample was composed of La(OH)3 in nanorod structures and was covered with poorly crystalline Ni(OH)2. The mixed metal hydroxides were converted into cubic LaNiO3 perovskite after calcination at 600 °C. A catalytic steam reforming of ethanol (SRE) reaction for hydrogen production was performed in a fixed-bed reactor. The catalyst was reduced in situ in hydrogen at 400 °C prior to the reaction. The ethanol conversion reached 100% at 300 °C with 70% hydrogen selectivity. The highly catalytic activity of the reduced catalyst was due to the well-dispersion of Ni particles on the surface of active catalyst was formed in the in situ reduced catalyst. After a 80 h time-on-stream test at 350 °C, the used catalyst presented a La2O2CO3 component that was formed owing to the reaction of the CO2 product with La2O3. La2O2CO3 acted as a carbon reservoir to eliminate the deposited carbon and further stabilized the Ni particles on the La2O3 surface, which resulted in the highly catalytic activity during the entire reaction period. The deposited carbon after the SRE reaction was further examined by TGA, TPR, elemental analysis, and TEM.

A comparison study on methane dry reforming with carbon dioxide over LaNiO3 perovskite catalysts supported on mesoporous SBA-15, MCM-41 and silica carrier

The supported LaNiO3 perovskite catalysts on mesoporous carrier (LaNiO3/SBA-15, LaNiO3/MCM-41 and LaNiO3/SiO2) with different pore structures have been synthesized via filling the pores of mesoporous silica with citrate complex precursors of nickel and lanthanum, with further treatments. The catalysts were characterized by means of N2 physisorption, XRD, HRTEM+EDX, TPR, temperature-programmed hydrogenation (TPH) and TGA techniques, and their catalytic performances were measured in methane dry reforming with carbon dioxide to hydrogen and synthesis gas (syngas). The results of low-angle XRD, N2 physisorption and TEM analysis showed that LaNiO3 perovskite was formed inside the channels of mesoporous supports, and the introduction of LaNiO3 perovskite did not destroy the mesoporous structure of support. The pore structure had a substantial influence on the catalytic performance. LaNiO3/MCM-41 exhibited the higher initial catalytic activity, owing to the higher Ni dispersion, while LaNiO3/SBA-15 was superior to LaNiO3/MCM-41 in the long-term stability, which could be due to the stable silica matrix restricted the agglomeration of nickel species. The hexagonal mesopores of LaNiO3/SBA-15 were still kept intact after reaction, while the mesoporous structure in LaNiO3/MCM-41 was collapsed during the reaction, which resulted in metal particles aggregation to certain extent. For comparison, the carbon deposition was responsible for the remarkable decrease of catalytic activity over LaNiO3/SiO2 sample, evidenced by TGA and TPH results.

The influence of partial substitution of alkaline earth with La in the LaNiO3 perovskite catalyst

Abstract For enhancing the operation and increasing the activity of LaNiO3 catalyst in the reaction of dry reforming of methane, La was partially substituted by alkaline earth elements. The most effect was related to Ba with concentration of 0.1 (La0.9Ba0.1NiO3). XRD results showed that by adding alkaline earth the size of nickel particles is decreasing. Also, this test shows that adding Ba to the LaNiO3catalyst leading to the formation of La2NiO4 phase. There is a possibility that this phase plays a fundamental role in increasing the activity of the catalyst.

Effects of Partial Substitution of Ni by Cu in LaNiO3 Perovskite Catalyst for Dry Methane Reforming

A series of ternary perovskite type oxides LaNi 1- x Cu x O 3 ( x = 0.2, 0.4, 0.6, 0.8, and 1.0) were synthesized via the sol-gel method in propionic acid. Partial substitution of Ni by Cu showed higher activities and selectivities towards syngas products. LaNi 0.8 Cu 0.2 O 3 was the most active toward the CH 4 and CO 2 conversions, and was selective for syngas products. Temperature-programmed reduction results showed that the addition of Cu facilitates the reduction of Ni 3+ to Ni 0 , which is the main reason for the higher performance of this catalyst. The effect of Cu addition to LaNiO 3 as LaNi 1- x Cu x O 3 ( x = 0.2, 0.4, 0.6, 0.8, and 1.0) perovskite type oxides on the dry reforming of methane has been investigated. LaNi 0.8 Cu 0.2 O 3 showed the best performance with superior reduction of the nickel.