Al2O3 Catalyst Research Articles

Production of Branched Alkanes by Upcycling of Waste Polyethylene over Controlled Acid Sites of SO4/ZrO2‐Al2O3 Catalyst

Branched alkanes, which enhance the octane number of gasoline, can be produced from waste polyethylene. However, achieving highly selective production of branched alkanes presents a significant challenge in the upcycling of waste polyethylene, and the maximum selectivity for branched alkanes reported up to date is about 70%. Here, we report a one‐pot process to convert polyethylene into gasoline‐range hydrocarbons (C4‐C13) with yield of 73.3% over SO42‐ZrO2‐Al2O3 catalyst at 280 °C. The proportion of branched alkanes reaches 90.1% within the C4‐C13 fraction. Incorporation of sulfate group endows the catalyst with strong Lewis acid sites and weak and moderate Brønsted acid sites. In situ X‐ray absorption, in situ infrared spectroscopy, in situ small angle neutron scattering, and DFT calculations reveal that polyethylene activation occurs through the synergy between sulfate groups and strong Lewis acid sites (Zr sites). The weak and moderate Brønsted acid sites preferentially catalyze the isomerization and type A β‐scission processes, which favors the formation of branched alkanes, while suppressing competing reactions that produce straight‐chain alkanes.

Production of Branched Alkanes by Upcycling of Waste Polyethylene over Controlled Acid Sites of SO4/ZrO2‐Al2O3 Catalyst

Branched alkanes, which enhance the octane number of gasoline, can be produced from waste polyethylene. However, achieving highly selective production of branched alkanes presents a significant challenge in the upcycling of waste polyethylene, and the maximum selectivity for branched alkanes reported up to date is about 70%. Here, we report a one‐pot process to convert polyethylene into gasoline‐range hydrocarbons (C4‐C13) with yield of 73.3% over SO42‐ZrO2‐Al2O3 catalyst at 280 °C. The proportion of branched alkanes reaches 90.1% within the C4‐C13 fraction. Incorporation of sulfate group endows the catalyst with strong Lewis acid sites and weak and moderate Brønsted acid sites. In situ X‐ray absorption, in situ infrared spectroscopy, in situ small angle neutron scattering, and DFT calculations reveal that polyethylene activation occurs through the synergy between sulfate groups and strong Lewis acid sites (Zr sites). The weak and moderate Brønsted acid sites preferentially catalyze the isomerization and type A β‐scission processes, which favors the formation of branched alkanes, while suppressing competing reactions that produce straight‐chain alkanes.

Co‐precipitation of Sn and Al Precursors to Create Additional Acid Sites of Pt/Sn‐Al2O3 catalysts for propane dehydrogenation

Alumina‐supported PtSn catalysts have been industrialized as the major catalysts for propane dehydrogenation, where Sn serves as an essential promoter. Herein, we synthesized a variety of Sn‐doped alumina supports by regulating the precipitation order of Sn and Al precursors as follows: Sn precursor precipitated before Al, co‐precipitated with Al, precipitated immediately after Al, or precipitates after two hours of Al. The effect of Sn promoter on the surface acidic properties of alumina and, ultimately, on propane dehydrogenation was further investigated. The Sn species introduced by co‐precipitation in alumina created additional surface strong acid sites, attributed to more Sn4+ species on the surface which are able to remain stable during the subsequent treatment. Consequently, the co‐precipitated Sn species in the corresponding catalyst donate more electrons to Pt and reduce the metal particle size. As a result, the catalyst with Pt supported on the co‐precipitated support (Sn+Al) exhibits superior initial propane conversion (43.2%) and stability (kd = 0.035 h‐1). This study provides new insight into the interaction between the two key components, tin promoter and alumina support, of Pt/Sn‐Al2O3 catalysts.

Scalable Atomic‐Layer Tailoring of Abundant Oxide Supports Unlocks Superior Interfaces for Low‐Metal‐Loading Dehydrogenation

Liquid organic hydrogen carriers (LOHCs) offer a promising solution for global hydrogen infrastructure, but their practical application faces two key challenges: sluggish dehydrogenation processes and the reliance on catalysts with high noble metal loadings. This study presents a scalable approach to reduce noble metal usage while maintaining high catalytic activity. We synthesized an ultralow Pt content (0.1 wt%) catalyst using γ‐Al2O3‐based pellet support with atomic layer deposition (ALD) of TiO2. Advanced characterization techniques reveal that the thin ALD‐TiO2 shell provides a heterogeneous interface, confining electronically rich Pt‐nanoparticle ensembles. The catalyst outperforms both equivalent Pt‐content catalysts and a commercial 0.5 wt% Pt/γ‐Al2O3 catalyst in homocyclic LOHC dehydrogenation. This study provides insights into the beneficial role of ALD‐engineered interfaces for catalytic supports and offers an efficient approach for scalable production of low‐noble‐metal‐content catalysts, with implications for various catalytic processes.

Production of synthetic high-octane gasoline from associated petroleum gas

The article proposes a method for producing high-octane gasoline from associated petroleum gas (APG), which consists of a combination of the processes of direct aromatization of APG and Fischer-Tropsch synthesis (FT). The APG aromatization process was experimentally studied in a flow-through installation at a pressure of 0,1 MPa and a temperature of 450-600 °C on a ZnO/ZSM-5/Al2O3 catalyst. It has been shown that at a temperature of 600 °C the degree of conversion of C3+ hydrocarbons is 27,8%, and the yield of aromatic hydrocarbons is 10,9 %. The synthesis of FT was studied on a hybrid Co-Al2O3/SiO2/ZSM-5/Al2O3 catalyst at a temperature of 250 °C, pressure 1,0 MPa, GHSV 1000 h-1. A pilot batch of synthetic gasoline fraction with a volume of 1 liter was produced at a pilot plant, and its main physicochemical and operational properties were analyzed. It has been shown that compounding the gasoline fraction of the FT synthesis and direct aromatization products of APG makes it possible to increase the octane number from 78,5 to 92,8 units, while the density increases from 710 to 778 kg/m3. The proposed technological solutions can be used for processing APG into high-octane synthetic gasoline using GTL modular units.

Influence of Partial Incineration and Optimized Acid Leaching on the Remanufacturing of Ni–Mo/γ–Al2O3 Catalysts

Influence of Partial Incineration and Optimized Acid Leaching on the Remanufacturing of Ni–Mo/γ–Al2O3 Catalysts

Favorable formation of needle-shaped NiAl2O4 phase over macroporous Ni/CexZr1-xO2–Al2O3 catalysts in one-pot preparation and coke-resistant catalytic performance in dry reforming of methane

In this study, we report the formation of needle-shaped NiAl2O4 via favorable interactions between Ni and Al species over macroporous Ni/CexZr1-xO2–Al2O3 catalysts for dry reforming of methane (DRM) and its remarkable improvement in the catalytic performance. The macroporous catalysts prepared by a one-pot (OP) method promote a favorable interaction between Ni and Al species that results in the formation of unique needle-shaped NiAl2O4 due to easy access to each other compared with that by incipient wetness impregnation. The NiAl2O4 phase in the calcined catalysts transforms into highly dispersed Ni and defective Al2O3 via the Ni exsolution in the reduction step. The presence of oxygen vacancies near Ni0 species facilitates the CO2 activation and enhances the catalyst stability over DRM. The optimized distribution of active sites with abundant defects over macroporous Ni/CexZr1-xO2-Al2O3 catalysts (OP) result in high conversions of CH4 and CO2 and a low coking rate in DRM.

A Highly Efficient Catalytic Co-Combustion of Aromatic and Oxygenated Volatile Organic Compounds (VOCs) via H2-Driven Onsite Heating

Catalytic combustion, a highly efficient technique for reducing volatile organic compounds (VOCs), is the focus of this study. We investigate the improved catalytic efficiency of the physical mixing of nanosized Pt and atomically dispersed Co, supported on Al2O3 catalysts (Pt-Co)/Al2O3 (PM) for the catalytic combustion of VOCs. The catalyst efficiency is evaluated for the hydrogen-assisted catalytic oxidation of various VOCs, including aromatic and oxygenated VOCs such as benzene, toluene, methanol, and formic acid. Our study aims to understand the impact of hydrogen incorporation on the combustion process of various VOCs. The findings of this work underscore the potential of hydrogen-assisted catalytic ignition, which can achieve ignition at ambient temperature, a significant departure from conventional electric heating that typically requires additional energy to raise the temperature. Various characterization techniques, such as BET, STEM, and XRD, are employed to assess the structure–activity relationship of the catalyst. The optimal hydrogen concentration for complete VOC conversion is 3%. Notably, even at a lower hydrogen concentration of 2%, benzene and methanol reach an ideal ignition temperature of over 500 °C when introduced into the physically mixed catalyst. This study highlights the significant potential of hydrogen-assisted catalytic combustion, inspiring further research and offering a promising method to reduce VOCs effectively.

Gasification of sago dreg waste in a top-lit updraft fixed bed gasifier: Syngas composition and its effect with additional Al2O3 as catalyst

Sago-based foods have become a staple food in eastern Indonesia. Sago waste, as a by-product, has the potential to be used as a renewable energy fuel. This research aims to use sago dregs waste as an energy source by converting it into renewable energy using Top Lit Updraft (TULD) fixed bed gasification. Al2O3, a potential solid waste derived from coal fly ash, is also being investigated for use in sago dreg pellets.The two various Al2O3 contents in sago dreg pellets that will be examined with 5 % Al2O3 and 10 % Al2O3. Operational parameters employed in the gasification process involving the TULD reactor, such as gasification temperature, air flow rate, air-to-fuel ratio (AFR), and syngas assessment. According to the results, adding Al2O3 as a catalyst to sago dreg pellets can improve syngas production (H2, CO, and CH4). The most significant alteration is that the average hydrogen gas (H2) content has increased, with the greatest being in 5 % Al2O3 with 31.65 %, and 10 % Al2O3 with 29.94 %. Meanwhile, the CO and CH4 gas content was found to be highest at 10 % Al2O3, with each experiencing an increase in average (CO 4.33 % and CH4 26.45 %) as compared to sago dregs pellets without Al2O3. Finally, sago dregs pellets with an Al2O3 catalyst have a high potential as an alternative energy fuel for internal combustion engines with H2/CO of 1.65 and 1.51 respectively, for 5 % Al2O3 and 10 % Al2O3, with low tar content.

Effect of Ga-Promoted on Ni/Zr + Al2O3 Catalysts for Enhanced CO2 Reforming and Process Optimization

AbstractIn this study, zirconia-modified alumina support (S) was used to investigate Ga-promoted Ni catalysts for dry reforming of methane (DRM). The catalysts (Ni + (0–3) wt% Ga/S) were prepared using the wet impregnation method and calcined at 700 °C for 3 h. The inclusion of Ga enhanced the surface area, basicity, and metal-support interaction of the Ni-Ga/S catalysts. Smaller Ni particles containing Ga were seen in the TEM. The most active and stable catalyst was Ni + 2.0 Ga/S, having a conversion of 35% CO2 and 28% CH4 at 600 °C and displaying less (17%) carbon deposition. Furthermore, the DRM process was optimized by a mathematical model. The model determined the optimal conditions as follows: temperature (800 °C), gas flow rate (GHSV—30,000 ml h−1gcat−1), and methane to carbon dioxide ratio (1:1). The model predicts CH4 and CO2 conversions of 76.76% and 82.0%, respectively, and an H2/CO ratio of 1.02, compared to experimental results showing CH4 conversion at 74.56%, CO2 conversion at 83.25%, and an H2/CO ratio of 1.01. The model demonstrates excellent agreement with the experimental observations, exhibiting less than 3% error. Graphical Abstract

Catalytic pyrolysis of cashew de-oiled shell and spent lemongrass

Residual/ spent biomasses are rising each day due to the increased processing of crops to extract essential oils. An efficient method is required for its management and value-addition. Therefore, this study aims to explore the catalytic pyrolysis of two residual biomasses, i.e., cashew de-oiled shell and spent lemongrass biomass. Different metal oxide(s) catalysts prepared using Al2O3 support, i.e., Fe2O3/Al2O3, Co3O4/Al2O3, Mn2O3/Al2O3, and NiO/Al2O3, are considered for this study. From the product distribution, it was analysed that the incorporation of catalyst led to a decrease in the bio-oil yield as compared to non-catalytic pyrolysis, which showed that Al2O3-supported catalysts promote the cracking reactions of pyrolysis vapours and produce lighter molecules. It was found that the incorporation of catalysts significantly affected the content of the functionalities present in the pyrolysis bio-oil. Fe2O3/Al2O3 was observed to greatly increase the area % of phenolics up to 52.35 and 75.57 area % in spent lemongrass and cashew de-oiled shell bio-oil, respectively. Metal oxide catalysts were also observed to reduce the oxygenates and produce high-quality bio-oil. Overall, this study demonstrates the effective utilization of cashew de-oiled shell and lemongrass biomass for cleaner energy/chemicals production through catalytic pyrolysis, highlighting the potential of metal oxide supported on Al2O3 catalysts in biomass valorization.

Construction of La/Al2O3 nanorod-like catalyst with rich basic sites: Enabling efficient conversion of COS-superior selectivity and theoretical insights

The introduction of surface basic sites to COS hydrolysis catalysts can improve H2O activation and COS adsorption, leading to enhanced catalytic performance. However, maximizing the concentration of basic sites remains a challenge due to the limited exposed surface area of these catalysts. Herein, a La/Al2O3 catalyst with abundant alkaline sites to catalyze the hydrolysis of COS was prepared by a simple ammonia-assisted hydrothermal method. This synthesized La/Al2O3 catalyst exhibits a thin rod-like structure formed by the random accumulation of nanoparticles. Lanthanum, one of the most abundant rare earth metals, is an ideal doping aid to further promote the COS-catalyzed hydrolysis performance of Al2O3. Characterization studies show that the proper lanthanum loading effectively enhances the formation of basic sites, leading to improved lattice oxygen reactivity and –OH adsorption capacity. As a result, the prepared La-loaded Al2O3 nanorod sample with abundant basic sites exhibits nearly 100 % COS conversion and total H2S yield at 160 °C. In addition, the reaction pathways and deactivation mechanisms for selective catalytic hydrolysis of COS on the La-doped Al2O3 catalyst were revealed by using in situ DRIFTS to evaluate COS adsorption and hydrolysis. Density functional theory calculations showed that La loading enhances the electron transfer between the La and Al atoms, improves the formation of basic sites, and enhances the adsorption of –OH. This study provides new insights into the design of efficient alumina-based catalysts for the catalytic hydrolysis of COS.

Selective reduction of CO2 to CO over alumina-supported catalysts of group 5 transition metal carbides

We show the applicability of a preparation method, previously reported for obtaining tailored bulk VCx catalysts, for alumina-supported G5TMCs. The characteristics of the G5TMCs/Al2O3 catalysts and their behaviour in the selective reduction of CO2 to CO through the RWGS reaction is reported. VCx/Al2O3 catalysts were active, stable and highly selective; meanwhile NbC/Al2O3 and TaC/Al2O3 were not active. VCx/Al2O3 catalysts exhibited selectivity to CO over 99.5 % at temperature above 773 K. The characteristics of alumina-supported vanadium carbide particles depended on the vanadium precursor and on the atmosphere used during the catalyst preparation. XPS characterization of VCx/Al2O3 catalysts revealed the presence of carbide species on surface before and after RWGS reaction. The catalytic behaviour of VCx/Al2O3 is analysed in the light of their characteristics and compared with bulk VCx counterparts. The most performant catalyst, VC(Pr)/Al2O3, was stable over 4 days at 723 K, with ∼100 % selectivity to CO and CO2 conversion of ∼11 %.

Highly Stable Ni-B/Honeycomb-Structural Al2O3 Catalysts for Dry Reforming of Methane.

Two-component catalysts have garnered significant attention in the field of catalysis due to their ability to inhibit Ni sintering. In the present work, honeycomb-structuralstructured Al2O3-supported Ni and B were prepared to enhance coke tolerance during dry reforming of methane (DRM). Transmission electron microscopy (TEM) results revealed that the average particle sizes on Ni/Al2O3 and Ni-0.16B/Al2O3 were 7.6 nm and 4.2 nm, respectively, indicating that B can effectively inhibit Ni sintering. After a 100-hour reaction, the conversion of CH4 and CO2 on Ni/Al2O3 decreased by approximately 5 %, whereas on Ni-0.16B/Al2O3, there was no significant decrease in CH4 and CO2 conversion, with values of approximately 81.6 % and 87.2 %, respectively. In situ DRIFT spectra demonstrated that Ni-0.16B/Al2O3 enhanced the activation of CO2, thus improving the catalyst's stability. A Langmuir-Hinshelwood-Hougen-Watson (LHHW) model was developed for intrinsic kinetics, and the resulting kinetic expressions were well-fitted fit to the experimental data, with R2 values exceeding 0.9. ActivationThe activation energies were also calculated. The outstanding stability of Ni-0.16B/Al2O3 can be attributed to its stable honeycomb structure and B's ability to significantly inhibit Ni sintering, reduce catalyst particle size, and enhance coke tolerance.

Hydro-co-processing Jatropha oil and crude oil blend with Ni-Mo-supported Al2O3 catalyst to produce hybrid fuels: the effect of catalyst particle size

Hydro-co-processing Jatropha oil and crude oil blend with Ni-Mo-supported Al2O3 catalyst to produce hybrid fuels: the effect of catalyst particle size

Modulating the Reaction Pathway of Ni2P/Al2O3 by Introducing Different Noble Metals for Hydrodesulfurization of Diesel.

Regulating the reaction pathway of a hydrodesulfurization (HDS) catalyst to achieve ultradeep desulfurization of diesel is a low-energy-consumption yet effective strategy but remains a tricky challenge. Herein, we present a Ni2P/Al2O3 catalyst with mesoporous properties synthesized by a facile hydrothermal-temperature-programmed reduction and normal impregnation (TPRI) method, and then different precious metals with similar loadings were introduced to prepare M-Ni2P/Al2O3 (M = Pt, Pd) catalysts through incipient wetness impregnation. Their structures were analyzed by a series of characterization methods, and their catalytic performances were examined for 4,6-dimethyldibenzothiophene (4,6-DMDBT) HDS. The correlation characterization results revealed that the kind of precious metals significantly affected the surface acidity and then the metal-support interaction (MSI) between Ni2P and Al2O3. Among them, the Pt-Ni2P/Al2O3 catalyst exhibits superior HDS activity with 88.5% 4,6-DMDBT conversion to Pd-Ni2P/Al2O3 (76.3%) and pristine Ni2P/Al2O3 (58.6%) catalysts under reaction conditions of 3.4 MPa, 340 °C, and LHSV = 4.8 h-1. This should be due to the introduction of Pt, which significantly facilitates the dissociation rate of H2 and the subsequent generation of more active hydrogen species than Pd, thereby promoting the formation of Brønsted acid sites, remarkably facilitating the isomerization (ISO) pathway, and markedly enhancing the 4,6-DMDBT HDS conversion of Pt-Ni2P/Al2O3. This work provides an efficient protocol to tame the reaction pathway and thereafter the catalytic performance of the HDS catalyst in the future.

Hydrolysis of carbonyl sulfide using non-ionic surfactant-modified mesoporous γ-Al2O3 catalysts with high efficiency

Carbonyl sulfur (COS) was difficult to be removed by conventional desulfurization technologies because of its stable chemical properties. Mesoporous γ-Al2O3 (MA) showed excellent potential for hydrolysis of COS, but the catalyst life was greatly shortened with the progress of the reaction. Therefore, improving the catalyst life is the key to MA which can apply to hydrolysis of COS. In this study, P123 modified mesoporous γ-Al2O3 (P-MA) catalyst was prepared by sol–gel method, and it was regulated by template agent and acidity regulator. These preparation conditions of P-MA were optimized to improve the hydrolysis efficiency of COS. The effects of temperature, space velocity, relative humidity and oxygen concentration for the hydrolysis efficiency of COS were studied. The results show that the optimized P-MA catalyst is suitable for COS low-temperature hydrolysis reaction, and it can maintain 99 % for 10 h under the tough reaction conditions. The only crystal of P-MA was γ-Al2O3 with large specific surface area and uniform distribution pore, which are beneficial to the COS hydrolysis. In addition, the hydrolysis efficiency of COS can also remain 97 % for 10 h in the O2 and CO2 atmosphere, indicating that the P-MA catalyst has a specific anti-poisoning ability. The kinetics and reaction mechanism of COS catalytic hydrolysis were studied, which showed that the adsorption of H2S was the key to hindering the continuous reaction. The P-MA can effectively inhibit the adsorption of H2S, which greatly improved COS hydrolysis life of P-MA. This study provided a theoretical basis for the application of Al2O3 catalyst in the COS hydrolysis.

Selective production of phenol from the end-of-life wind turbine blade through catalytic pyrolysis

This study employed catalytic pyrolysis to enhance the selectivity and yield of phenol in the pyrolysis oil derived from the end-of-life wind turbine blade (WTB). It was confirmed that the NiO(10)/Al2O3 catalyst exhibited the best activity, reaching a phenol selectivity of 28.57 % at 500 °C with a heating rate of 10 °C/min. Furthermore, a competitive phenomenon between the catalytic formation of phenol and that of gaseous products was observed. Characterization results indicated that at lower loading content of NiO on the Al2O3 carrier, NiAl2O4 crystals tended to form preferentially, which reduced catalyst activity by covering surface strong acid sites. With increasing the loading content of NiO, saturation of NiAl2O4 formation occurred, and free NiO crystals became dominant. This resulted in the creation of abundant Lewis acid sites, enhancing the catalytic formation of phenol. Whilst, excessive accumulation of free NiO crystals increased strong acid sites and significantly generated lattice oxygen, promoting the cracking of pyrolysis oil to gaseous products, which was detrimental to phenol enrichment but facilitated the production of H2-rich syngas. The conclusions offered valuable insights for upgrading pyrolysis products derived from epoxy resin polymers during the recovery of end-of-life WTB.

Surface Carbon Formation and its Impact on Methane Dry Reforming Kinetics on Rhodium‐Based Catalysts by Operando Raman Spectroscopy

AbstractA mechanism for carbon deposition and its impact on the reaction kinetics of Methane Dry Reforming (MDR) using Rhodium‐based catalysts is presented. By integrating Raman spectroscopy with kinetic analysis in an operando‐annular chemical reactor under strict chemical conditions, we discovered that carbon deposition on a Rh/α‐Al2O3 catalyst follows a nucleation‐growth mechanism. The dynamics of carbon aggregates at the surface is found to be ruled by the CO2/CH4 ratio and the inlet CH4 concentration. The findings elucidate the spatiotemporal development of carbon aggregates on the catalyst surface and their effects on catalytic performance. Furthermore, the proposed mechanism for carbon formation shows that the influence of CO2 on MDR kinetics is an indirect result of carbon accumulation over time frames exceeding the turnover frequency, thus reconciling conflicting reports in the literature regarding CO2′s kinetic role in MDR.

Fe2O3/γ-Al2O3 and NiO/γ-Al2O3 catalysts for the selective catalytic oxidation of ammonia

Ammonia, a significant atmospheric pollutant, requires effective emission control due to its inherent toxicity and the generation of secondary pollutants like particulate matter. This control can be achieved through various methods, including catalytic processes. Therefore, our study focuses on evaluating the potential of catalysts based on iron oxide and nickel oxide supported on γ–Al2O3 for the selective catalytic oxidation of NH3 to N2 (NH3-SCO). The γ–Al2O3 was obtained by thermal decomposition of aluminum hydroxide, and 5 or 10 wt% of Fe or Ni was added through wetness incipient impregnation. XRD diffractograms confirmed the formation of the γ–Al2O3 phase. XRD, H2-TPR, and UV–vis DRS data showed the presence of Fe2O3, NiO, and NiAl2O4 in the catalysts. Introducing metal oxides onto the support led to a drop in the specific area, pore size, pore volume, and NH3 desorption, which was higher for the catalysts containing Fe. The catalysts were active in NH3-SCO, and the insertion of Fe or Ni was essential because it promoted a significant increase in the NH3 conversion (∼75 % Fe and ∼55 % Ni), compared to pure support (∼8 %), mainly from 400 °C. However, doubling the metal content has not resulted in a considerable increase in NH3 conversion. The N2 selectivity was higher for the catalysts containing Ni (∼85 %) from 400 °C compared to catalysts containing Fe (∼76 %). Such behavior was due to the larger surface area of the Ni-containing catalysts. Despite that, the 5Fe/γ–Al2O3 catalyst emerged as the most effective option for NH3-SCO applications, combining higher NH3 conversion and good N2 selectivity.