Catalytic Conversion Research Articles

Migration roles of different oxygen species over Cu/CeO2 for propane and soot combustion

Determining the migration rules of oxygen species in catalytic combustion, especially for catalysts composed of transition metal oxides, is essential yet challenging. This study hydrothermally synthesized nanosphere-structured cerium dioxide (CeO2) and its copper-loaded catalysts (Cu/CeO2) to identify the distinct functions of superficial oxygen species (O) and lattice oxygen (O2–). The presence of Cu-Ce solid solution at the Cu/CeO2 interface lowered the apparent activation energy for the catalytic combustion of propane and soot. The catalytic combustion of propane followed the Mars-van Krevelen mechanism, with O2– serving as the dominant reactive phase while O played a subordinate role. The solid–solid reaction between soot and superficial oxygen of the catalyst was responsible for catalyzed soot combustion. The O species produced by surface defective sites exhibited higher activity than O2–, which drained easily at the beginning of the reactions. The isotopic oxygen exchange tests revealed the mechanism of metal oxide (CuO/CeO2) interactions for active oxygen species migration, with the results demonstrating the solid solution at the phase interface as portholes for oxygen migration, thus increasing oxygen mobility between the gaseous phase and the surface by lowering the migration activation energy. In situ, infrared results showed that the reaction path of soot catalytic combustion was single, without any intermediate production formation, compared to multiple paths in the propane oxidation process. This study provided an easily implemented and widely applicable method, which deepens our understanding of the characterization of the function and migration of predominant oxygen species in diverse combustion reactions involving oxide-based catalysts. Additionally, this study clarified differences and similarities between the reaction mechanisms of solid–solid and solid–gas catalysis.

Silica-assisted Pt1/CeO2 single-atom catalyst for enhancing the catalytic combustion performance of VOCs by inducing H2O activation

Due to the competitive adsorption of water and reactants at the active sites, especially the water toxicity of platinum-based single-atom catalysts, it is of great importance to improve the low-temperature activity and the water resistance of catalysts for the catalytic combustion of benzene. In this work, it was found that constructing a SiO2 shell layer on the catalyst not only "immobilized" the Pt single atoms, but also effectively weakened the adsorption of H2O on the Pt active sites, which resulted in excellent water resistance of the Pt single-atom catalysts. The comprehensive characterization results demonstrated that the participation of water molecules in the catalytic oxidation reaction of benzene could be effectively promoted by enhancing the strong metal-support interactions (SMSI) at the core-shell interface, which would change the electronic structure of the catalyst surface. As a result, the Pt1/CeO2@SiO2-4 catalyst with a Pt-O-Si active interface exhibits good activity (T = 190 °C) as well as excellent water resistance under the wet condition (10 vol%). This project provides a promising strategy for the design of Pt-based core-shell catalysts with excellent water resistance.

Heteropolyacid promoted lignin-MOF derived spherical catalyst for catalytic hydrogen transfer of 5-hydroxymethylfurfural

Catalytic conversion of biomass-derived value-added chemicals was of great significance for the utilization of renewable biomass resources to instead of fossil chemicals. Biomass-derived lignin was regarded as an important support and 5-hydroxymethylfurfural (HMF) was a vital platform chemical derived from cellulose. Herein, a series of lignin-MOF hybrid catalysts were prepared and modified with different heteropolyacids (HPAs), which were then successfully introduced into the selective conversion of HMF to 5-hydroxymethylfurfuryl alcohol (MFA). The effect of different HPA, calcination temperature, etc. were all studied, and all catalysts were well characterized. It was confirmed that silicotungstic acid modified catalyst (Ni3Co-MOF-LS@HSiW) exhibited the best catalytic performance, while the highest conversion of HMF was up to 100%, with the best MFA yield of 86.5%. The finding in this study could provide novel insights for the utilization of lignin and preparation of value-added biomass-derived chemicals.

Enhancing the conversion of waste motor oil into diesel-like fuels using mineral-impregnated biochar catalysts

This study shows how the presence of metal-impregnated biochar influences the kinetics of the catalytic conversion of waste motor oil (WMO) into a diesel-like fuel (DLF). First, the initial metal concentration in the wet impregnation process was optimized, showing that high metal concentrations tend to clog the biochar pores, reducing the reaction’s conversion and speed. Zinc and calcium showed higher kinetic constants at the optimized conditions than nickel, while the yield- and selectivity-to-liquid products were unaffected. Then, a reduction method was developed for impregnating metal particles of calcium oxide to enhance the metal dispersion at the biochar surface. This material showed the best performance in the reaction due to the presence of small particles instead of metal agglomerates. An increase of about 280% in the kinetic constant at 420 °C and a much lower activation energy (246 kJ mol−1) compared to the thermal cracking (308 kJ mol−1) was obtained. Finally, the DLF from the best catalytic system was analyzed. Interestingly, the fuel showed similar rheological properties to commercial diesel with a similar hydrocarbon distribution but with the presence of smaller hydrocarbon chains.

Porous hollow nanospheres nickel phosphide and its high catalytic hydrogenation performance on naomaohu coal soluble portion and model compounds

The catalytic conversion of oxygen-containing aromatic ring in lignite under mild conditions is crucial to obtain clean liquid fuel. Here, hollow nanosphere Ni3P-500–24 catalysts were prepared at a calcination temperature of 500 °C and acid-etching time of 24 h. The porous hollow nanospheres structure could expose more catalytic sites, and the electron-rich nickel exhibited a good catalytic activity. The conversion rate of benzyl phenyl ether (BPE) was 100 % (140 ℃, 1 MPa H2, 2 h), and the main products were methylcyclohexane and cyclohexanol, indicating that the catalyst had good catalytic hydrocracking performance. In addition, the catalyst exhibited certain deoxygenation activity and high product selectivity for other oxygen-containing model compounds. For the catalytic hydrogenation of Naomaohu coal (NMHC) soluble portion, the content of alkanes increased from 19 % to 47 %, while the content of oxygen-containing compounds decreased from 56 % to 21 %, which further demonstrate that the catalyst have good catalytic hydrogenation and deoxygenation performance. Density Functional Theory (DFT) calculations showed that the properties of the Ni3P-500–24 catalyst was similar to noble metal, which could activate H2 to produce two kind of active hydrogen: H radical and diatomic hydrogen. The synergistic pathways for the transfer of active hydrogen during the catalytic hydroconversion (CHC) process were analyzed. Above results could provide theoretical guidance for the conversion of lignite into high-quality clean liquid fuels.

Catalytic converter theft: An examination of the elasticity of crime

Catalytic converter theft: An examination of the elasticity of crime

Structural basis of chorismate isomerization by Arabidopsis ISOCHORISMATE SYNTHASE1.

Salicylic acid (SA) plays a crucial role in plant defense against biotrophic and semi-biotrophic pathogens. In Arabidopsis (Arabidopsis thaliana), isochorismate synthase 1 (AtICS1) is a key enzyme for the pathogen-induced biosynthesis of SA via catalytic conversion of chorismate into isochorismate, an essential precursor for SA synthesis. Despite the extensive knowledge of ICS1-related menaquinone, siderophore, tryptophan (MST) enzymes in bacteria, the structural mechanisms for substrate binding and catalysis in plant isochorismate synthase (ICS) enzymes are unknown. This study reveals that plant ICS enzymes catalyze the isomerization of chorismate through a magnesium-dependent mechanism, with AtICS1 exhibiting the most substantial catalytic activity. Additionally, we present high-resolution crystal structures of apo AtICS1 and its complex with chorismate, offering detailed insights into the mechanisms of substrate recognition and catalysis. Importantly, our investigation indicates the existence of a potential substrate entrance channel and a gating mechanism regulating substrate into the catalytic site. Structural comparisons of AtICS1 with MST enzymes suggest a shared structural framework with conserved gating and catalytic mechanisms. This work provides valuable insights into the structural and regulatory mechanisms governing substrate delivery and catalysis in AtICS1, as well as other plant ICS enzymes.

Catalytic conversion of mannose to 5-hydroxymethylfurfural promoted by hydrophobic halloysite-based catalyst in biphasic system

A novel halloysite (Hal) based acidic catalyst was synthesized by anchoring functional alkyl group and Cr site and catalyzed the selective conversion of mannose to 5-hydroxymethylfurfural (HMF) in NaCl-H2O/dimethyl sulfoxide/methyl isobutyl ketone (MIBK) biphasic system. Herein, adjusting the hydrophilicity/hydrophobicity of catalyst by modifying the octyl group can facilitate the HMF yield. The density functional theory (DFT) calculation and in-situ FT-IR results revealed that increasing the hydrophobicity of catalyst surface weakened the interaction between HMF, water molecule and acid sites and inhibited the rehydration of HMF. Moreover, the synergistic effect between Cr and sulfonic group active sites remarkedly promoted the isomerization of mannose to fructose and the dehydration of fructose to HMF, and the 48.1% yield of HMF was obtained. This study provides references for the high value conversion of hemicellulose with the high efficiency reaction system.

Integrated and Automated: Liquid Metal‐based System for Full Cycle CO2‐to‐Carbon Conversion

AbstractThe urgency for carbon neutrality is driving the need for cost‐effective Carbon Capture and Conversion (iCCC) technology, but the lack of a unified platform for capture, release, and the subsequent in situ catalytic conversion has hindered its widespread adoption. To address this gap, it have showcased the feasibility of achieving an energetically balanced design intertwining CO2 capture and in situ conversion through a continuous gas‐to‐solid reaction process on the customized liquid metal‐based reaction system. The system exhibits a remarkable carbon production capability, achieving a peak yield of 550.57 µmolC mmol CO2‐−1 accompanied by 100% carbon conversion rate. The vertically bottom‐up spiral reactor design introduces significant mass transfer enhancements, resulting in a higher conversion yield rate of 8658.3 µmol h−1 (323.24 µmolC mmolCO2‐−1) while requiring an energy input of only 30.79 GJ t−1 CO2 in a 1.508×10−3 m3 unit. The solid carbon produced in the continuous setup also holds the potential for high‐end application value, such as being a high‐performance material for wave adsorption or acting as an efficient photocatalyst. This research insights are poised to chart new pathway into refining the design strategy for CO2 solidification processes, particularly the seamless melding of carbon capture and in situ conversion.

Abstract PO2-18-08: Identification of novel genetic/therapeutic vulnerabilities in breast cancer

Abstract Background: Breast cancer is the most commonly diagnosed cancer and the leading cause of cancer death among women worldwide. Triple negative breast cancer (TNBC) is an aggressive subtype that is defined by the lack of expression of estrogen and progesterone receptors in the absence of HER2 amplification or overexpression. TNBC represents 15-20% of all breast cancers and occurs more frequently in young premenopausal women. TNBC often ends with a poor clinical outcome due to high histological grade, rapid recurrence in many patients combined with few treatment options. These realities highlight the urgent need to identify novel therapeutics vulnerabilities that can be leveraged to improve TNBC patient outcomes. Methods: We utilized the publicly available DepMap and Kaplan Meier datasets to identify essential genes that were unique to TNBC cells and whose expression levels were associated with worse patient outcomes. siRNA based approaches were used to confirm the relevance of top hits in mediating cancer cell phenotypes including viability, cell-cycle profiles and induction of apoptosis among others. A novel drug currently being developed was identified for the top hit in these studies and was subsequently employed in multiple in vitro approaches to characterize the mechanisms of action in TNBC as well as initial efficacy studies using clinically relevant ex vivo patient derived models. Results: Using the DepMap database, we interrogated genome-wide sgRNA knockout screens conducted in over 40 breast cancer cell lines to identify specific genes whose expression was required for cell viability in TNBC cells, but not other breast cancer cell lines. This endeavor identified 6 genes (CTPS1, HUS1, PRKRA, RAD1, RAD9A and RHOA) that were preferentially essential in TNBC cells. Further profiling of these genes revealed that CTPS1 expression is higher in cancer relative to normal tissue and that its expression is further upregulated in chemotherapy- and PARPi-resistant models. Knockdown of CTPS1 in TNBC cells was shown to decrease cell proliferation and viability with no effects observed in estrogen receptor+ cell lines. Using a first-in-class, highly selective and orally bioavailable CTPS1 inhibitor (STP938) developed by Step-Pharma, we identified IC50s in the low nM range for many TNBC cell lines, including cell models that are resistant to existing standard-of-care therapies. Inhibition of CTPS1 was shown to arrest cells in S phase. Conclusions: Our studies have identified CTPS1 as an essential gene in TNBC. CTPS1 encodes an enzyme responsible for the catalytic conversion of UTP (uridine triphosphate) to CTP (cytidine triphosphate), an essential step in the biosynthesis of nucleic acids. These findings are timely in light of the recent and ongoing development of the first-in-class CTPS1 inhibitor, STP938, for which first-in-human studies are underway for refractory B- and T-cell lymphomas. Based on our initial studies using this drug, we provide pre-clinical evidence of its efficacy in multiple models of primary and advanced TNBC. Efforts are currently underway to move this work toward a clinical trial for TNBC patients. Citation Format: Xiyin Wang, Michael Emch, Lauren Voll, Rebecca Russell, Esther Rodman, Philip Beer, John Hawse. Identification of novel genetic/therapeutic vulnerabilities in breast cancer [abstract]. In: Proceedings of the 2023 San Antonio Breast Cancer Symposium; 2023 Dec 5-9; San Antonio, TX. Philadelphia (PA): AACR; Cancer Res 2024;84(9 Suppl):Abstract nr PO2-18-08.

Four-channel Catalytic Micro-reactor Based on Alumina Hollow Fiber Membrane for Efficient Catalytic Oxidation of CO

The traditional automotive catalytic converter using commercial ceramic honeycomb carriers has many problems such as high back pressure, low engine efficiency, and high usage of precious metals. This study proposes a four-channel catalytic micro-reactor based on alumina hollow fiber membrane, which uses phase inversion method for structural molding and regulation. Due to the advantages of its carrier, it can achieve lower ignition temperature under low noble metal loading. With Pd/CeO2 at a loading rate of 2.3% (mass), the result showed that the reaction ignition temperature is even less than 160 °C, which is more than 90 °C lower than the data of commercial ceramic substrates under similar catalyst loading and airspeed conditions. The technology in turn significantly reduces the energy consumption of the reaction. And stability tests were conducted under constant conditions for 1000 hours, which proved that this catalytic converter has high catalytic efficiency and stability, providing prospects for the design of innovative catalytic converters in the future.

Halogenated extinguishing agent interference on CO catalytic oxidation over CuCeOx catalyst at low temperature: Mechanism and resistance strategy

The effects of bromotrifluoromethane (CF3Br) as a representative of halogenated extinguishing agents on CO removal through catalytic combustion over Cu-Ce bimetallic oxides (CuCeOx) were investigated at low temperatures. Gaseous CF3Br can decrease CO conversion to threaten the stability of CuCeOx, especially under the higher CF3Br concentration and weight hourly space velocity. The potential interactions between CF3Br and CuCeOx and the subsequent formation of a few halides on the catalyst surface are responsible for the variations in the CO oxidation performance of CuCeOx. Moreover, the mechanism of CF3Br interference on CO catalytic oxidation over CuCeOx catalyst was proposed. The presence of CF3Br might slow the reaction of adsorbed CO (carbonyls) on Cu sites with surface active oxygen and compete with gaseous O2 for adsorption on oxygen vacancies of the ceria support to cover Ce sites by resulting deposition of inactive species. Significantly, the complete deactivation of CuCeOx catalyst by CF3Br is difficult because of the stronger and more effective interaction between CuCeOx catalyst and CO rather than CF3Br at low temperatures.

Contrasting platinum trajectories in three major French rivers using dated sediment cores (1910–2021): From geochemical baseline to emerging source signals

Platinum (Pt) is a Technology Critical Element (TCE) which, since the 1990s, has been mainly used in the industry in catalytic converters for automobile emission control. Previous studies have shown Pt contamination of road-side sediments and surface sediments in urban rivers and lakes but few of them have addressed temporal variations. The present work presents historical Pt concentration trends in 137Cs-dated sediment cores from floodplains or secondary channels at the outlets of three major French watersheds (Loire, Rhone, and Seine Rivers) covering the past ∼110 years, i.e., from the 1910s to 2021. Platinum baseline levels in the sediment were estimated for the Loire River (0.76 ± 0.22 μg kg−1 for the period ∼1910-∼1955) and the Rhone River (1.64 ± 0.41 μg kg−1), and historical Pt variations seem to reflect variations in hydrodynamics and grain size composition. Since the early 2000s, Pt concentrations in the Loire and the Rhone River sediments tend to increase (>2.5 μg kg−1) and were attributed to the use of car catalytic converters, an emerging technology since the 1990s using >50 % of European Pt demand. High and variable historical Pt concentrations (up to 14.6 μg kg−1) in the Seine River sediments may reflect legacy Pt sources due to former anthropogenic activities in this watershed, such as the use of Pt-based catalysts for petroleum refinery since the end of the 1940s, coal handling and precious metals refining, probably concealing the likely presence of an emerging traffic-related Pt signal. This first comparison of historical Pt concentration trends in sediments from contrasting watersheds allows to distinguish signals originating from different natural and anthropogenic sources (background level, historical sources, road traffic).

Tungsten phosphide on nitrogen and phosphorus-doped carbon as a functional membrane coating enabling robust lithium-sulfur batteries

Lithium-sulfur batteries (LSBs) hold great potential as future energy storage technology, but their widespread application is hampered by the slow polysulfide conversion kinetics and the sulfur loss during cycling. In this study, we detail a one-step approach to growing tungsten phosphide (WP) nanoparticles on the surface of nitrogen and phosphorus co-doped carbon nanosheets (WP@NPC). We further demonstrate that this material provides outstanding performance as a multifunctional separator in LSBs, enabling higher sulfur utilization and exceptional rate performance. These excellent properties are associated with the abundance of lithium polysulfide (LiPS) adsorption and catalytic conversion sites and rapid ion transport capabilities. Experimental data and density functional theory calculations demonstrate tungsten to have a sulfophilic character while nitrogen and phosphorus provide lithiophilic sites that prevent the loss of LiPSs. Furthermore, WP regulates the LiPS catalytic conversion, accelerating the Li-S redox kinetics. As a result, LSBs containing a polypropylene separator coated with a WP@NPC layer show capacities close to 1500 mAh/g at 0.1C and coulombic efficiencies above 99.5 % at 3C. Batteries with high sulfur loading, 4.9 mg cm−2, are further produced to validate their superior cycling stability. Overall, this work demonstrates the use of multifunctional separators as an effective strategy to promote LSB performance.

Operando investigation of catalytic trichloroethylene combustion via metal-doped CeO2 nanorods

The remediation of chlorinated volatile organic compounds is an intractable issue for it typically requires high temperatures and generates undesirable byproducts. This work utilized a series of representative transition metals (i.e., Cr, Cu, V) to modify the morphology, surface oxygen, and acidity of the CeO2 nanorods for trichloroethylene (TCE) treatment. A spectroscopic operando DRIFTS-online GCMS reactor was introduced to examine the catalytic performance and elucidate the reaction pathway. Among them, Cr-CeO2 exhibited 50 % (T50) and 90 % (T90) TCE conversions with no byproduct at 171 °C and 241 °C, respectively. The performances of Cu-CeO2 (T90 = 391 °C), V-CeO2 (T90 = 423 °C) and CeO2 (T90 = 494 °C) were inferior to Cr-CeO2 (T90 = 241 °C), with obvious C2Cl4 generated in the TCE oxidation. It reveals that TCE adsorbed on Cr-CeO2 is dechlorinated on acidic sites and oxidized to carbonate/formate intermediates by the surface oxygen then facilely to carbon oxides, while TCE is adsorbed as chlorinated species (CH2ClCH2O−) on the other three catalysts which occupy the surface and require higher temperature to be oxidized. The abundant medium-strong acidic sites and surface oxygen species of Cr-CeO2 nanorods are responsible for the low-temperature activation via C-Cl cleavage on acidic sites and fast oxidation of hydrocarbon intermediates in the TCE oxidation, respectively.

Catalytic styrene combustion over Pt/ZSM-5 Catalysts: Elucidating the deactivation mechanism induced by surface acid sites

Catalytic oxidation plays a pivotal role in styrene elimination, yet the development of highly active and robust catalysts remains a challenge. This work aims to elucidate the mechanisms underlying styrene oxidation and catalyst deactivation over the Pt@ZSM-5 catalyst. The Pt@ZSM-5 catalyst with low Si/Al ratio and high surface acidity leads to generation of small Pt particle, the initial activity of the catalyst varies in a volcanic curve with the size of Pt particles. Notably, the Pt@ZSM-5–40 catalyst with Pt particle size of 3.3 nm exhibits the highest reaction rate of 1.6 µmol gPt−1 s−1 at 100 °C. However, the Pt@ZSM-5 catalysts undergo significant deactivation at their T80 (the temperature styrene conversion of 80 %). Through comprehensive characterizations and detailed mechanistic studies, it has been observed that intermediates from styrene oxidation accumulate heavily on the catalyst, especially for the Pt@ZSM-5 catalyst with high acidity. Improving the reaction temperature could inhibit the deactivation which is dependent on the surface acidity of Pt@ZSM-5 catalyst. For instance, the Pt@ZSM-5–800 and Pt@ZSM-5–1200 catalysts remains high activity when reaction is operated at T99+30, whereas a substantially higher reaction temperature (T99+80) is required for both Pt@ZSM-5–18 and Pt@ZSM-5–40 catalysts to counteract deactivation. Our primary results provide insights to develop effective and robust catalyst for styrene oxidation.

Plasma driven exsolution of Ca as the adjacent dechlorinated site in La0.8Ca0.2MnO3 perovskite: a highly mineralization chlorobenzene oxidation catalyst

The degradation of chlorine-containing volatile organic compounds (CVOCs) utilizing catalytic combustion technology is subject to the catalyst chlorine poisoning, which is resulted from the chlorination of active phases, even though the structural stable perovskite. The reaction between Ca species and dissociated chlorine species is demonstrated as an efficient way to inhibited chlorine poisoning of the active phase. Herein, a Ca substituted partial La prepared La0.8Ca0.2MnO3 (named as L8C2MO) perovskite was treated by 5% H2/Ar plasma driven route (the treated sample was denoted as L8C2MO-P), which was applied for the chlorobenzene oxidation removal. The integrated characterization results of XRD, XPS, HRTEM, etc. confirmed that Ca (mainly exhibited as CaCO3) was successfully exsolved from La0.8Ca0.2MnO3 and simultaneously leaved oxygen vacancies on the surficial layers. The continuous catalytic oxidation experiments illustrated that the conversion efficiency of L8C2MO was unexpectedly decreased compared with that of LaMnO3 (LMO in short) sample, while that of L8C2MO-P was nearly maintained the oxidation capacity, with approximately 12°C of 90% chlorobenzene conversion temperature (T90) higher than that of LMO. Importantly, the CO2 and inorganic chlorine species yields were significantly enhanced for L8C2MO and L8C2MO-P. The characteristic of used samples showed a possible chlorinated Ca species formation while the status of Mn phases was hardly changed, suggesting the exsolved Ca could inhibited the poison of Mn sites by binding with dissociative chlorine species. Additionally, oxygen vacancies that generated along with Ca exsolution process was definitely contributed to the deep oxidation of chlorobenzene. The possible reaction route was also studied by in situ DRITS and GCMS. The work provides a potential route as in situ growth of adjacent sites to protect active phases from chlorine poison in CVOCs catalytic oxidation process.

Boosting catalytic combustion of diesel soot particles over potassium-promoted CoMn-Co3O4 dual spinel structure catalyst

Catalytic oxidation is an effective method to remove soot particles from diesel exhaust, and the key aspect of this technology is to develop highly effective catalysts. In this work, a potassium-promoted dual spinel structure was prepared for soot elimination with the self-sacrificing template strategy. The highest activity was presented by the CoMn-0.2 H-10%K catalyst under a loose contact mode, with the temperature of soot conversion reaching 90% and turnover frequency value of 365 °C and 3.76×10−3 s−1, respectively. The catalyst was found to have a high content of oxygen vacancy and a superior ability for lattice oxygen migration, which led to elevated performance for soot combustion. The formation of K-OMS-2 at the interface between the CoMn spinel and the Co3O4 spinel was one of the reasons for the elevated lattice oxygen migration at low temperatures. This work provides an effective way to prepare transition metal catalysts for soot combustion.

Surface oxygen vacancy vs oxygen storage capacity in cubic ceria based nanocatalysts for low temperature catalytic combustion of fuels

A series of praseodymium (Pr) doped cubic ceria nanoparticles (CeO2 NPs) with different ratio of cerium (Ce) and ‘Pr’ was synthesized by hydrothermal method. Manganese (‘Mn’) doped cubic CeO2 NPs with 10:90 ratio of Mn:Ce and undoped cubic CeO2 NPs have also been synthesized. The crystalline structure of the synthesized nanomaterials has been studied by powder X-Ray diffraction (XRD) and Rietveld analysis. In the Raman spectrum, the intensity of F2g signal at 450–460 cm−1 decreased while the intensity of extrinsic vacancy at 570–580cm−1 increased by doping with ‘Pr’ or ‘Mn’ in cubic CeO2 nanocrystals. X-ray photoelectron spectroscopy (XPS) results showed that surface oxygen vacancy of cubic CeO2 NPs increased by doping with 25 % of ‘Pr’. The ‘Pr’ doped CeO2 NPs (Pr:Ce = 25:75) exhibited higher surface adsorption dynamic oxygen storage capacity (OSCDyn), while the ‘Mn’ doped cubic CeO2 NPs (Mn:Ce = 10:90) showed increased bulk lattice OSCDyn. The ‘Pr’ doped cubic CeO2 NPs (Pr:Ce = 25:75) exhibited better low temperature catalytic combustion activity, and their nanodispersion in mineral turpentine oil (MTO) added liquefied petroleum gas (LPG) exhibited better fuel efficiency with a flame temperature of 912 °C.

Towards understanding the role of acidity on levulinic acid conversion using alumina-niobia mixed oxide-supported catalysts

The catalytic transformation of levulinic acid (LA) represents a pivotal advancement towards establishing a sustainable biorefinery industry. Hence, this study investigated the intricate role of the catalyst acidity, which remains relatively unexplored, in the catalytic transformation of LA. A range of alumina-niobia supported nickel-copper catalysts, with varying alumina (Al) to niobia (Nb) ratios, was synthesized and characterized. The results of characterization techniques revealed that the strength, quantity, and nature of the acidic sites of the catalysts were modified by the variations in the Al to Nb ratios. Further, a correlation between the acidic properties of the catalysts and the result of the reaction runs and poisoning experiments was established. Specifically, Lewis acid sites were responsible for the conversion of LA into angelica lactone (AL), which can be subsequently hydrogenated to gamma-valerolactone (GVL). Conversely, Brønsted acid sites are required for the ring-opening reactions of GVL which led to the formation of 2-methyltetrahydrofuran (MTHF) and valeric acid (VA). Notably, selectivities as high as 85.0% for MTHF and 67.0 % for VA were achieved with Ni-Cu/Al-Nb (6) and Ni-Cu/Nb2O5, respectively. To the best of our knowledge, this represents the highest MTHF selectivity in solvent-free catalytic conversion of LA. Additionally, based on our findings, we propose a comprehensive reaction pathway employing alumina-niobia-supported nickel-copper catalysts, shedding light on the intricate interplay of acidity in the LA conversion process. This study not only deepens our understanding of LA transformation but also holds great promise for optimizing catalytic processes in pursuit of sustainable and eco-friendly biorefinery technologies.