Key Takeaways & Executive Findings
- •• • Pd/Al2O3-M achieved 95.2% isoprene conversion and 98.3% selectivity to semi-hydrogenated isoamylenes at 60 °C and 1 MPa H2, outperforming conventional Pd/Al2O3 and demonstrating superior selectivity control critical for C5 stream purification. • • In anthraquinone hydrogenation, Pd/Al2O3-M delivered a hydrogenation efficiency of 15.8 g/L, a 27.4% increase over the reference catalyst (12.4 g/L), indicating enhanced productivity for H2O2 synthesis. • • The flower-like alumina microspheres, assembled from nanosheets, increased Pd dispersion and metal-support interaction, resulting in a higher surface Pd content and more abundant active sites, as confirmed by characterization. • • The catalyst maintained stable performance over 24 h in isoprene hydrogenation, evidencing good durability under industrially relevant conditions.
Abstract
Alumina microspheres with a lamellar-assembled flower-like morphology were synthesized via a urea-assisted hydrothermal method and used as supports to prepare Pd/Al2O3-M catalysts by incipient wetness impregnation. The catalytic performance was evaluated in the selective hydrogenation of isoprene and the hydrogenation of 2-ethylanthraquinone for hydrogen peroxide production, and compared with a commercial alumina-supported Pd catalyst (Pd/Al2O3). Characterization revealed that the flower-like structure, composed of stacked nanosheets, promoted high Pd dispersion and enhanced metal-support interaction, leading to a higher surface Pd content and more abundant active sites. Under 60 °C and 1 MPa H2, Pd/Al2O3-M achieved 95.2% conversion of isoprene with 98.3% total selectivity to isoamylenes, and exhibited good stability over 24 h. In anthraquinone hydrogenation, it reached a hydrogenation efficiency of 15.8 g/L, a 27.4% improvement over Pd/Al2O3 (12.4 g/L). The study demonstrates that modulating carrier morphology is an effective strategy to simultaneously enhance activity, selectivity, and stability of Pd catalysts, offering a promising approach for designing efficient hydrogenation catalysts.
1. Introduction
The selective hydrogenation of dienes and alkynes is a pivotal process in the petrochemical industry, particularly for upgrading C5 fractions from naphtha cracking. These streams contain reactive diolefins like isoprene that cause polymerization and fouling in downstream units. Palladium-based catalysts are widely used due to their high activity, but they often suffer from over-hydrogenation, reducing selectivity to valuable mono-olefins. Similarly, the anthraquinone route for hydrogen peroxide production relies on efficient Pd catalysts to achieve high hydrogenation efficiency while suppressing side reactions. Conventional alumina-supported Pd catalysts face limitations in dispersion and metal-support interaction, leading to suboptimal performance. This study addresses these bottlenecks by engineering the carrier morphology—specifically, synthesizing flower-like alumina microspheres with a lamellar structure to enhance Pd dispersion and interaction, thereby improving catalytic performance in both reactions.
The experimental protocol employs a urea-assisted hydrothermal method to produce alumina microspheres with a well-defined flower-like morphology composed of stacked nanosheets. This unique structure provides a high surface area and abundant anchoring sites for Pd nanoparticles, leading to stronger metal-support interactions and higher Pd dispersion compared to commercial alumina. The resulting Pd/Al2O3-M catalyst demonstrates significantly improved activity and selectivity in isoprene hydrogenation and anthraquinone hydrogenation, as evidenced by quantitative metrics. This approach offers a practical strategy for designing high-performance hydrogenation catalysts by modulating support morphology, addressing the industrial need for more efficient and selective catalysts.
Loading authentic research manuscript (Pages 1–5)...
SHANG Bin, SUN Limin, HU Xiaoli, LAI Weikun, FANG Weiping, YI Xiaodong (2026). Selective Hydrogenation Performance of Pd Catalysts Supported on Alumina Microspheres. Journal of Fuel Chemistry and Technology. https://doi.org/10.3724/2097-213X.2025.JFCT.0037
Research & Educational Purpose Only: The translations, structured abstracts, analytical annotations, and data reports provided by SinoGreenTechare intended exclusively for academic research, internal corporate R&D, and educational benchmarking. They do not constitute formal engineering, chemical safety, legal, or professional advice.
Copyright & Intellectual Property Notice: Original copyright of the underlying source articles and experimental data remains with the respective authors, institutions, and original publishing journals. SinoGreenTech claims intellectual property only over its proprietary translations, analytical syntheses, and AEO structured enhancements in accordance with international fair use and academic citation principles.
Frequently Asked Questions
What is the specific improvement in Pd dispersion and metal-support interaction achieved with the flower-like alumina microspheres compared to commercial alumina?
The flower-like alumina microspheres, composed of stacked nanosheets, provided a higher surface area and more anchoring sites, leading to increased Pd dispersion and stronger metal-support interaction. This was confirmed by characterization, which showed a higher surface Pd content and more abundant active sites on Pd/Al2O3-M compared to Pd/Al2O3.
How does the Pd/Al2O3-M catalyst perform under industrially relevant conditions in terms of stability and selectivity?
Under 60 °C and 1 MPa H2, Pd/Al2O3-M achieved 95.2% conversion of isoprene with 98.3% selectivity to semi-hydrogenated isoamylenes, and maintained stable performance over 24 h, indicating good durability. In anthraquinone hydrogenation, it reached a hydrogenation efficiency of 15.8 g/L, a 27.4% improvement over the reference catalyst.
What are the potential scalability challenges for the urea-assisted hydrothermal synthesis of alumina microspheres?
The synthesis method is scalable in principle, but challenges include controlling the uniformity of the flower-like morphology at larger scales and ensuring reproducibility. The use of urea as a precipitating agent and hydrothermal conditions may require optimization of temperature, pressure, and reaction time to achieve consistent quality. Cost considerations include the need for high-purity precursors and energy-intensive hydrothermal processing.
How does the catalytic performance of Pd/Al2O3-M compare to other advanced Pd catalysts reported in literature?
The performance metrics (95.2% conversion, 98.3% selectivity) are competitive with or superior to many reported Pd-based catalysts for isoprene hydrogenation. The 27.4% improvement in anthraquinone hydrogenation efficiency over a commercial catalyst highlights the advantage of the tailored support morphology. However, direct comparison requires standardized testing conditions.
What is the industrial significance of achieving 98.3% selectivity to isoamylenes in isoprene hydrogenation?
High selectivity to semi-hydrogenated products is crucial to preserve the value of mono-olefins in C5 streams. A selectivity of 98.3% minimizes over-hydrogenation to alkanes, reducing feedstock loss and simplifying downstream separation. This directly impacts process economics by improving yield and reducing waste.
Related Chinese Research & Cross-Citations
Recent Advances in Carbon-Based Materials for CO2 Capture and Utilization
CO2 capture and utilization (CCU) technologies are critical for mitigating global warming and promoting resource circularity. Carbon-based materials, with tunable pore structures, abundant active sites, high specific surface area, and excellent chemical stability, show significant potential for CO2 capture and conversion. This review systematically analyzes the adsorption behaviors and performance variations of activated carbon, porous carbon, graphene, and carbon nanotubes in CO2 capture. For utilization, recent advances in catalytic applications for methanation, reverse water-gas shift (RWGS), dry reforming of methane (DRM), and alcohol synthesis are emphasized. The benefits and drawbacks of carbon materials regarding adsorption capacity, catalytic activity, and stability are evaluated, and their potential in integrated CCU technologies is discussed. Key strategies for enhancing performance through structural modulation and surface modification are elucidated. This review provides theoretical guidance for future development and large-scale implementation of carbon-based materials in CCU.
Fabrication and Microwave Absorption Performance of FexOy/TiO2/C Composites Derived from Red Mud
Red mud, an industrial solid waste from alumina production, poses severe environmental challenges. This study presents a resource-efficient strategy to convert red mud into high-performance microwave absorbing materials. FexOy/TiO2/C composites were synthesized via a sol-gel method using starch as carbon source, followed by carbothermal reduction. The phase composition and microstructure were optimized by adjusting calcination temperature and raw material ratio. The optimal sample, RmCT-5.4-700, exhibited a minimum reflection loss (RLmin) of -30.2 dB at 14.0 GHz with an effective absorption bandwidth (EAB) of 5.3 GHz at a coating thickness of 2.0 mm. The superior absorption performance is attributed to the synergistic effects of dielectric components (TiO2, graphitized carbon) and magnetic components (Fe3O4/Fe). Carbothermal reduction introduces defects that induce dipole polarization, while the conductive network formed by graphitized carbon and Fe3O4/Fe particles enhances conductive loss. Heterogeneous interfaces between Fe3O4, Fe, TiO2, and the red mud matrix promote interfacial polarization. The magnetic loss of Fe3O4/Fe improves impedance matching, facilitating electromagnetic wave penetration and absorption. This work not only provides a novel route for red mud valorization but also contributes to the high-value utilization of solid wastes.
Damage Mechanism of High Chromia Refractory in the Slag Tapping Hole of Commercial Entrained-Flow Gasifiers
The service life of refractory bricks in the slag tapping hole of entrained-flow gasifiers is a critical bottleneck for long-term stable operation. This study investigated the damage mechanism of high chromia refractories in four commercial coal-water slurry gasifiers by analyzing gasification coal samples and corroded refractory bricks. Slag characteristics, including crystallization and viscosity-temperature behavior, were evaluated. Results revealed that low-viscosity slag induces more severe refractory damage. To mitigate slag crystallization risk, a safe slag tapping temperature range is recommended as tICT−t2.5 when tICT exceeds t25. Interior morphology of corroded bricks exhibited cracks, primarily attributed to molten slag penetration and subsequent reactions with refractory material. SEM-EDS analysis of slag-aggregate and slag-matrix interfaces identified reduction in Cr2O3 content as the earliest damage characteristic. XRD detected no zirconium-containing spinel in cracks, indicating that thermal expansion mismatch between newly formed phases and the refractory matrix drives crack propagation. A damage mechanism is proposed: initial Cr2O3 depletion compromises both matrix and aggregate, facilitating slag ingress and new phase formation, ultimately leading to structural failure. Early detection or prevention of Cr2O3 reduction is essential to prolong refractory service life.
Research advances in the pyrolysis recycling of waste wind turbine blades
The global energy landscape is undergoing a profound transformation, with wind energy gaining increasing prominence due to its clean and renewable nature. However, as installed wind power capacity expands, disposal of waste wind turbine blades (WWTB) has emerged as a significant challenge. These blades are predominantly composed of epoxy resin (EP) polymers, carbon fibers (CFs), and glass fibers (GFs). Improper disposal exacerbates environmental concerns and leads to loss of valuable resources, particularly carbon-based materials. Pyrolysis technology, a versatile and environmentally sustainable method for resource recovery, has garnered considerable attention for WWTB disposal. This work presents a comprehensive review of pyrolytic recycling of WWTB, focusing on principles and classifications of pyrolysis technology, key factors influencing the pyrolysis process, as well as pyrolysis methods, equipment, products, and their applications. Through in-depth analysis of current research, this review identifies critical unresolved issues and provides a forward-looking perspective on emerging research trends. The review highlights that pyrolysis can effectively recover glass fibers and carbon fibers with mechanical property retention depending on process conditions, and that catalytic pyrolysis can enhance the quality of recovered products. Economic analysis indicates that collaborative disposal methods can improve cost-effectiveness. Future research should focus on optimizing process parameters for large-scale industrial application and developing more efficient catalysts to improve product selectivity and fiber quality.
Citric Acid-Modified HUSY Zeolite Catalyzes Alkylation of Phenol with Cyclohexanol for High-Density Aviation Fuel Precursors
Lignin-derived oxygenated aromatics, particularly phenols and aromatic ethers, are promising feedstocks for synthesizing high-density, high-heat-sink aviation fuels via alkylation-hydrogenation processes. This study systematically evaluates the catalytic performance of various zeolites (Hβ, HZSM-5, MCM-41, and HUSY) in the alkylation of phenol with cyclohexanol. Characterization demonstrates that HUSY zeolite exhibits superior catalytic activity due to its favorable pore architecture and well-balanced acid site distribution, which synergistically facilitate molecular diffusion and catalytic transformations. To further enhance catalytic properties, HUSY was modified with citric acid at various concentrations and compared with NaOH and oxalic acid treatments. Results reveal that citric acid treatment preserves crystallinity while modulating acidity and pore structure. All modified zeolites enhance phenol alkylation activity. Notably, HUSY-0.5M, exhibiting the highest medium-strong acid to total acid ratio, achieves superior performance: 80.4% phenol conversion and 99.6% selectivity for alkylation products. The catalyst also shows high activity for various lignin-derived compounds (p-cresol, anisole, guaiacol), demonstrating broad applicability. This work provides a new strategy for valorizing lignin-derived phenols into high-value fuel precursors through alkylation.
Hydrogen Production and Structure Evolution Mechanism during Thermochemical Conversion of Microalgae Pellet in Molten Hydroxide Salts
This study investigates the thermochemical conversion behavior of microalgae pellets in a molten hydroxide salt (80% NaOH-20% Na2CO3) system and its influence on hydrogen production. By comparing temperature evolution, gas release characteristics, and structural evolution of pellets with and without molten salt, and integrating char alkalization experiments, the regulatory mechanism of molten salt on reaction pathways and hydrogen production was systematically analyzed. Results indicate that molten salt significantly enhances internal heat transfer efficiency, achieving a central heating rate of 177 °C/s, effectively alleviating thermal hysteresis. Concurrently, molten salt promotes pore development through penetration, erosion, and catalytic effects, resulting in a porosity increase of 53.2%–104.3% after 10 s of reaction. Conversion efficiency is markedly improved, with the dominant reaction pathway shifting to char alkalization after only 70 s. Furthermore, when heating rate is increased above 600 °C, hydrogen yield from char alkalization improves more significantly, primarily attributed to the synergistic promotion of molten salt catalysis and rapid heating on volatiles reforming. This study provides a theoretical foundation for understanding efficient hydrogen production from biomass in molten hydroxide salts.