Pellet Surface Research Articles

Ignition study of hypergolic solid fuels through counterflow experiment using hydrogen peroxide spray

Hypergolic solid fuels provide rapid and reliable ignition for hybrid rockets, offering significant advantages over conventional methods. However, a practical experimental approach is necessary to study ignition and combustion behavior under realistic oxidizer flow conditions. This study introduced a novel counterflow spray experiment using 90 % rocket-grade hydrogen peroxide sprays applied to low-density-polyethylene-based fuel pellets embedded with sodium borohydride and manganese acetate tetrahydrate. The results showed that sodium borohydride caused vigorous reactions, damaging the pellets, while the addition of manganese acetate tetrahydrate moderated this effect. Hypergolic ignition and sustained combustion were achieved at oxidizer mass flow rates of 0.38–0.57 g/s, with ignition delay times of 15 to 30 ms, consistent with droplet test results. In addition, reignition was successful under the same flow conditions, although the char layer formed on pellet surface after the first ignition limited the surface additive reactivity, leading to longer ignition delay times. 3D surface analysis provided quantitative data on surface roughness across various fuel compositions and flow rates. This novel counterflow spray experiment is expected to be both effective and simple, with the ability to offer valuable insights into hypergolic ignition and combustion process.

Effect of the ash melting on heat and mass characteristics and reaction rate during corn stalk pellet gasification

In order to investigate the effect of ash melting on the gasification process of biomass pellet, a high-temperature visual gasification system was set up, meanwhile, a biomass melting gasification model for a single pellet was built. Considering that the fusion temperature range of ash is from 1418 K to 1558 K, 1396 K (below 1418 K), 1491 K (between 1418 K and 1558 K), 1591 K and 1677 K (above 1558 K) were chosen as the experimental temperatures. Results show that ash melting could absorb heat, thereby resisting the heat transfer inside pellet. When the gasification temperature is higher than 1558 K, as the larger spherical particles caused by ash melting and coalescing peels off from the pellet surface, the pellet covered by melting ash could be directly exposed to the environment, which is conducive to the heat and mass transfer.

Personalization of Intravaginal rings by droplet deposition modeling based 3D printing technology

Intravaginal rings (IVRs) are long-acting drug device systems designed for controlled drug release in the vagina. Commercially available IVRs employ a one-size-fits-all development approach, where all patients receive the same drug in similar doses and frequencies, allowing no space for dosage individualization for specific patients’ needs. To allow flexibility for dosage individualization, this study explores the impact of infill-density on critical characteristics of personalized IVRs, manufactured using droplet deposition modeling three-dimensional (3D) printing technology. The model drug was dispersed on the surface of thermoplastic polyurethane pellets using an oil coating method. IVR infill-density ranged from 60 to 100 %. The compatibility of the drug and matrix was assessed using thermal and spectroscopic analyses. The IVRs were evaluated for weight, porosity, surface morphology, mechanical properties, and in vitro drug release. The results demonstrated high dimensional accuracy and uniformity of 3D-printed IVRs, indicating the robustness of the printing process. Increasing infill-density resulted in greater weight, storage modulus, Young’s modulus, Shore hardness, and compression strength, while reducing the porosity of IVRs. All IVRs showed a controlled drug release pattern when tested under accelerated conditions of temperature for 25 days. Notably, greater infill-densities were associated with a decrease in the percentage of drug released. Overall, the study demonstrated that infill-density was an important parameter for personalizing the critical characteristics of the 3D-printed IVRs to fit individual patient needs.

Biodegradation of thermoplastic starch by a newly isolated active microbial community: Deciphering the biochemical mechanisms controlling bioprocess robustness

Defining sustainable end-of-life routes for bioplastics comprises a task of outmost importance, while biological recycling constitutes the most favorable option for several biopolymers, such as thermoplastic starch (TPS). To our knowledge, this is the first study to assess the biodegradation of TPS pellets and films in aqueous cultures employing an acclimated microbial community. Biological treatment of bioplastics displayed a two-phase pattern that included different biodegradation rates, where TPS removal in the first phase remained high and decelerated in the second phase reaching a plateau. Thus, TPS weight reduction of 14.8 % was observed using pellets following 10 d of incubation, while although films exhibited higher reduction (slightly over 30 % in 15 d), the biodegradation rate was significantly reduced thereafter. Several changes of starch related bands were detected (using FTIR) in the surface of both pellets and films during the bioprocess, indicating induction of a common biodegradation pathway. Distinct bacterial assemblages were formed during the TPS biodegradation process and statistically significant differences were detected in the abundance of several genera between the two degradation phases. Fungal communities were more stable (Fusarium and Neocosmospora were dominant at all times) and there was no effect of biofilm or degradation phase on fungal community composition. Overall, a more diverse community incorporating lower catalytic activity was gradually formed, as confirmed by the shift between k-stategist and r-stategist taxa monitored, while crystalline over amorphous regions were enhanced in the biopolymer during TPS biodegradation, responses consistent with the biodegradation rate reduction observed in the plateau stage. The study highlighted the biochemical mechanism limiting TPS biodegradation processes and the significant potential of the newly isolated community in the development of TPS waste treatment technologies.

Mechanical‐Stress‐Induced Lithiation and Structural Evolution Driven by Excess Lithium Predisposing Short Circuits at the Surface of Garnet Solid Electrolytes

AbstractCubic‐garnet solid electrolyte has garnered significant attention in all‐solid‐state batteries (ASSBs) due to its ionic conductivity and chemical robustness against Li metal. However, the short‐circuit formation at low current density poses a significant obstacle with the main cause remaining ambiguous. Here, the lithium‐penetration mode originating from phase transformation is unveiled at the sintered pellet surface via mechanically induced lithiation. Mechanical stress applied during polishing under excess lithium content induces lithiation into the cubic‐garnet structure, leading to partial structural evolution into the tetragonal phase. This surface alteration induces current constriction, hindered by sluggish interfacial Li‐ion transport from the tetragonal phase, which exhibits low ionic conductivity, causing short circuits. By reducing mechanical stress, mitigating surface strain, and restoring the cubic phase, stable operation is ensured without short‐circuit formation in both Li symmetric and hybrid‐full cells. This insights illuminate the origin of lithium penetration related to phase transition at the surface of cubic‐garnet and pave the way for enhancements in ASSB development.

Microstructural Instability and Its Effects on Thermoelectric Properties of SnSe and Na-Doped SnSe.

Effects of thermal cycling on the microstructure and thermoelectric properties are studied for the undoped and Na-doped SnSe samples using X-ray computed tomography and property measurements. It is observed that thermal cycling causes significant cracks to develop, which decrease both the electrical and lattice thermal conductivities but do not affect the thermopower. The zT values are drastically reduced after the repeated heat treatment. It is important to account for density changes during cycling to obtain accurate values of the thermal conductivity. Even before thermal cycling, the spark-plasma sintered (SPS) samples have a significant number of microcracks. The orientation of cracks within the SPS pellets and their effect on the microstructure are influenced by the presence of a Na-rich impurity. The SnSe and Sn0.995Na0.005Se samples without the impurity develop cracks and exhibit grain growth parallel to the pellet surface, which is also the plane of the 2D SnSe layers. The Sn0.97Na0.03Se sample containing the impurity develops cracks that are orthogonal to the pellet surface. Such an orientation of cracks in Sn0.97Na0.03Se inhibits grain growth. All samples appear mechanically unstable after thermal cycling.

Effects of biomass feedstock and applied pressure on the binding mechanism and pellet qualities

To expand the sources of feedstocks for pelleting and enhance the applicability of the pelleting device, 7 types of feedstocks with representative chemical component contents from different resources were densified. The pressure-time (P-T) curves and energy consumption were used to analyze the densification process and binding mechanism. Specific energy density and densification effects were evaluated pellet qualities and classified feedstock types. Results showed that the densification process was first affected by the feedstock types and then applied pressure. Biomass chemical component contents significantly influence the densification process, the required time, and the final pellet length. Energy consumption in the compression stage is much more than in the extrusion stage. The exponential stage consumes more than 90 % of the total energy. Energy conversion efficiency varies from 62.19 % to 95.06 % with the feedstock types and applied pressures. Single pellet density, densification effects, and specific energy densities increased with the rising applied pressure. BB, SD, PN, CS, and SB can be used as primary feedstocks. SR and ROC act as secondary feedstocks or lubricants. Cellulose, hemicellulose, and lignin of plant cell walls are solid bridges. Extractives, fat, and protein in the plant cells are binders and lubricants to make the pellet surface smooth. This paper could provide further insight into various biomass feedstock densification and general design for pelleting devices.

Insights into the Dual Anticancer and Antibacterial Activities of Composites Based on Silver Camphorimine Complexes.

Hydroxyapatite (HAp) is a widely used biocompatible material in orthopedic composite preparations. However, HAp composites that exhibit both anticancer and antibacterial activities through bioactive coordination complexes are relatively rare. To explore orthopedic applications, we blended several silver camphorimine compounds with HAp to create [Ag(I)] composites. All compounds [Ag(NO3)(L)n] (n = 1,2) based on camphorimine (LA), camphor sulfonimine (LB) or imine bi-camphor (LC) ligands demonstrated significant cytotoxic activity (IC50 = 0.30-2.6 μgAg/mL) against osteosarcoma cancer cells (HOS). Based on their structural and electronic characteristics, four complexes (1-4) were selected for antibacterial evaluation against Escherichia coli, Burkholderia contaminans, Pseudomonas aeruginosa, and Staphylococcus aureus. All complexes (1-4) revealed combined anticancer and antibacterial activities; therefore, they were used to prepare [Ag(I)]:HAp composites of 50:50% and 20:80% weight compositions and the activities of the composites were assessed. Results showed that they retain the dual anticancer and antibacterial characteristics of their precursor complexes. To replicate the clinical context of bone-filling applications, hand-pressed surfaces (pellets) were prepared. It is worth highlighting that no agglutination agent was necessary for the pellet's consistency. The biological properties of the so-prepared pellets were assessed, and the HOS cells and bacteria spreading on the pellet's surface were analyzed by SEM. Notably, composite 4B, derived from the bicamphor (LC) complex [Ag(NO3)(OC10H14N(C6H4)2NC10H14O)], exhibited significant anticancer activity against HOS cells and antibacterial activity against P. aeruginosa, fostering potential clinical applications on post-surgical OS treatment.

A comparison of additive manufactured to injection molded Martian regolith based polymer matrix composites

The completed study investigated the creation of Martian regolith simulant composite parts using injection molding and additive manufacturing. Traditional manufacturing techniques such as injection molding are not feasible on the Martian surface therefore in-situ processes must be developed using additive manufacturing processes to prepare habitats prior to having a human presence on the surface. The goal of this study was to investigate the impacts of additive manufacturing on the material property values between parts made using traditional injection molding and additive manufacturing. Martian regolith simulant composite pellets were created by combining a Martian regolith simulant at 40 wt% loading with polypropylene via twin screw extrusion. This material was then used to create test specimens using injection molding and additive manufacturing. Samples underwent tensile, flexural, Izod impact, and immersion density tests according to ASTM International and standardized test instructions. Additive manufactured parts saw a nearly 40% reduction in tensile and flexural strength with more than double the tensile modulus when compared to injection molded parts. The flexural modulus for additive manufacturing was around 36% that of the injection molded part with a minor decrease in density of around 13%. The collected test results suggested that while there were differences in the material property values between the manufacturing processes, a more interesting foaming behavior of the extrudite was observed during the additive manufacturing process resulting in an extremely rough and pitted surface. This rough surface finish was a stark comparison to the smooth injection molded parts. This observed foaming behavior in the polymeric composite material during thermal processing prompted the theory that thermal releases from the Martian regolith simulant was the most likely cause of the observed differences. Pellet surface moisture tests, Martian regolith simulant thermogravimetric analyses, and literature reviews of thermal decomposition of the Martian regolith simulant constituents revealed that most likely olivine releases oxygen and hydrated silica releases water during the thermal processing of the Martian regolith simulant composite. During a closed mold process such as injection molding, these volatile gases are forced out of the part by the pressures of the molding process, but in an open to atmosphere process such as additive manufacturing these gases foam to the surface during cooling leaving the part with an inferior surface finish.

Trichoderma aureoviride hyphal pellets embedded in corncob-sodium alginate matrix for efficient uranium(VI) biosorption from aqueous solutions

The discharge of effluents containing uranium (U) ions into aquatic ecosystems poses significant risks to both human health and marine organisms. This study investigated the biosorption of U(VI) ions from aqueous solutions using corncob-sodium alginate (SA)-immobilized Trichoderma aureoviride hyphal pellets. Experimental parameters, including initial solution pH, initial concentration, temperature, and contact time, were systematically examined to understand their influence on the bioadsorption process. Results showed that the corncob-SA-immobilized T. aureoviride hyphal pellets exhibited maximum uranium biosorption capacity at an initial pH of 6.23 and a contact time of 12 h. The equilibrium data aligned with the Langmuir isotherm model, with a maximum biosorption capacity of 105.60 mg/g at 301 K. Moreover, biosorption kinetics followed the pseudo-second-order kinetic model. In terms of thermodynamic parameters, the changes in Gibbs-free energy (ΔG°) were determined to be −4.29 kJ/mol at 301 K, the changes in enthalpy (ΔH°) were 46.88 kJ/mol, and the changes in entropy (ΔS°) was 164.98 J/(mol·K). Notably, the adsorbed U(VI) could be efficiently desorbed using Na2CO3, with a maximum readsorption efficiency of 53.6%. Scanning electron microscopic (SEM) analysis revealed U(VI) ion binding onto the hyphal pellet surface. This study underscores the efficacy of corncob-SA-immobilized T. aureoviride hyphal pellets as a cost-effective and environmentally favorable biosorbent material for removing U(VI) from aquatic ecosystems.

Lotus leaf inspired hierarchical micro-nano structure on NdYbZr2O7 ceramic pellet with enhanced volcanic ash repellence

Volcanic ash dispersed in the air adheres to thermal barrier coatings (TBCs) on the hot section components of gas turbines, posing a severe threat to aviation safety. Here, we report a novel strategy inspired by lotus leaf for mitigating the molten volcanic ash adhesion and corrosion. A hierarchical micro-nano structure composed of arrayed micro-conoids and numerous nanoparticles were constructed on the surface of NdYbZr2O7 ceramic pellet by ultrafast laser direct writing technology, whose morphology could be changed by optimizing the processing parameters. The laser-ablated pellet exhibits larger contact angle of molten volcanic ash than the original one, revealing an enhanced resistance repelling volcanic ash. This phenomenon is primarily attributed to the air trapped in the micro-grooves, together with these nanoparticles. Note that the evolution of viscous force and capillary force with time accelerates the transition of molten volcanic ash from the Cassie state to the Wenzel state and reduces its contact angle. Also, this structure effectively inhibits the infiltration of molten volcanic ash by rapidly developing a reaction layer. These findings are an important step toward the design and development of next-generation silicate ash-repellent TBCs.

Fabrication and characterization of biocomposite pellets from cassava starch and oil palm empty fruit bunch fibers

Oil palm empty fruit bunches (OPEFB) are lignocellulosic biomass that can be used to produce a biocomposite as an alternative to substitute non-renewable materials, such as plastic. Generally, the production of biocomposites uses OPEFB, which has been processed into cellulose, microcrystalline cellulose, or nanocellulose and is mixed with starch. However, the OPEFB pretreatment into various types of cellulose requires a long process and many chemicals. The OPEFB pretreatment with less process, such as cutting to shorter fibers and without chemicals, was expected to shorten the process. This study aims to produce and evaluate the characteristics of biocomposite pellets from a combination of cassava starch and OPEFB fibers. Short OPEFB fibers (3-5 mm) with varying concentrations of 0, 5, 10, 15, and 20% were added to the cassava starch before mixing with other materials. The twin screw extruder used to produce biocomposite pellets was set at six temperature zones ranging from 85-140 °C and the screw speed in the range of 160-190 rpm. The results show that higher concentrations of OPEFB fibers produced darker pellets, which tended to be greyish. The biocomposite pellets had densities of 1.322-1.417 g cm-3. SEM results show some agglomerations on the surface of starch-OPEFB fibers biocomposite pellets. The water solubility of biocomposite pellets ranged from 32.97 – 36.44%. In conclusion, biocomposite pellets could be produced from a mixture of cassava starch and OPEFB fibers up to 20%. In its application for rigid packaging production, the biocomposite pellets’ performance could be improved by mixing them with recycled polypropylene.

Assessment of silver-based calcium silicate hydrate as a novel SERS sensor

This study aims at synthesizing a novel Surface-Enhanced Raman Spectroscopy (SERS) sensor based on a nanostructured substrate, calcium silicate hydrate (C-S-H), the main hydration product of Portland cement. The procedure involves first the incorporation of silver within the nanostructure of the gel (C-S-Ag-H) and second the modification of the surface of pellets of the newly synthesized material by laser irradiation at 532 nm or 355 nm. The assessment of the SERS activity revealed no amplification of the organic molecule rhodamine B (RdB) signal, used as a probe, on the C-S-Ag-H before laser irradiation. However, after laser irradiation, the SERS effect was comparable to that of reference colloidal Ag nanoparticles (NPs). This SERS response is attributed to an increase in the concentration of metallic silver on the surface of the C-S-Ag-H pellets upon laser irradiation and material ablation as revealed by X-ray Photoelectron Spectroscopy (XPS). Further enhancement of the SERS signals was induced by depositing colloidal Ag NPs on the irradiated pellets, giving rise to interparticle hot spots where the electromagnetic field is further intensified.

Modification of Talc and Mechanical Properties of Polypropylene-Modified Talc Composite Drawn Fibers

A large amount of the polypropylene (PP) produced worldwide is used in the form of fibers. In this work, a new modification route for talc and PP is investigated, which is based on the in situ polymerization of a silane–siloxane monomer mixture on the surface of talc particles or PP pellets, respectively. The obtained modified talc and PP samples were used for the development of PP-talc composite drawn fibers. Tensile tests, thermogravimetry (TGA), and X-ray diffraction (XRD) were used for the characterization of the materials. It was observed that such a modification procedure resulted in the exfoliation of some talc particles. Enhanced tensile strength was observed for composite drawn fibers of a low talc content (1% with respect to PP) and a low modifier content (2% with respect to talc), while co-aggregation of talc and silicone may occur at high silicone and talc contents, resulting in the inferior mechanical performance of the corresponding composites. It was concluded that the produced silicone polymer simultaneously acts as a modifier, antioxidant, and compatibilizer. The proposed modification route is promising and should be further optimized.

Wurster Technology-Assisted Step-by-Step Engineering of Multi-layered Pellets (Sprinkles): Microscopy, Micro-CT, and e-Tongue-Based Analysis.

The advancement in the formulation and characterization techniques have paved the path for development of new as well as modification of existing dosage forms. The present work explores the role of micro-computed tomography (micro-CT) as advanced characterization technique for multi-layered-coated pellets to ascertain the quality of coated pellets. The work further explored in-house e-tongue technique for understanding palatability of formulation in early stages of development thus by reducing clinical taste evaluation time. The developed multi-layered-coated pellets were characterized using microscopy (optical and electron microscopy). The obtained results demonstrated formation of spherical-shaped pellets with uniform coating. The uniform coating was further confirmed by results obtained from scanning electron microscopy (SEM) and cross-sectional SEM analysis, which showed visible difference in pellet surface before and after multi-layered coating. The micro-CT results confirmed the visible demarcation of layers (drug and polymer, i.e., hydroxypropyl methylcellulose (HPMC) and eudragit (EPO)) along with uniform thickness of various layering. The dissolution study of developed pellets suggested the role of layering EPO on drug release from pellets. The e-tongue analysis proved to be an excellent tool for early prediction of taste masking of drug via multi-layered pellets and can serve as potential platform for taste masking with high specificity. The overall results suggest the suitability of developed multi-layered platform as efficient dosage form (sprinkle) in pediatric/geriatric product development.

Mechanism of iron grains aggregation and growth in metalized pellet under the alternating magnetic fields

The direct reduction-magnetic separation method is highly efficient for producing metallic iron powder from low-grade complex ore resources. However, the limitation lies in the small average size of iron grains, which impedes the subsequent separation between metallic iron and gangue minerals. To address this, a novel method utilizing induction heating was introduced to stimulate the aggregation and growth of iron grains. Our study systematically investigated the growth kinetics behavior of iron grains under alternating magnetic fields. Additionally, we compared the impact of induction heating versus conventional heating on iron grain growth and delved into the mechanism through which the magnetic effect enhances the aggregation and migration of iron grains. The results indicate that iron grains can effectively aggregate and migrate to the edges of cracks or pellet surface under alternating magnetic fields, realizing the increase of average iron grain size and the pre-separation of metallic iron from gangue minerals. Specifically, the average iron grain size increased from 12.95 μm to 36.58 μm when induction heating temperature at 1300 °C for 100 min. Additionally, the total iron grade of concentrate reached 94.60% with ball milling 30 min and magnetic field intensity of 750 Gs. Finally, the growth model of iron grains under alternating magnetic fields was established and the mechanism of magnetic effect on promoting iron grains growth was revealed.

Laser-Induced Plasmas of Plutonium Dioxide in a Double-Walled Cell.

Plutonium research has been stifled by the significant number of administrative controls and safety procedures, space and instrumentation limitations in radiological gloveboxes, and the potential for personnel and equipment contamination. To address the limited number of spectroscopic studies in Pu-bearing compounds in the current scientific literature, this work presents the use of double-walled cells (DWCs) in "clean" buildings/laboratories as an alternative to research in radiological gloveboxes. This study reports the first laser-induced breakdown spectroscopy (LIBS) experiments of a PuO2 pellet contained within a DWC, where the formation of elemental (atomic and ionic) species as well as the evolution from elemental to molecular products (PuxOy) was measured. Raman spectroscopy was also used to characterize the surface of the ablated pellet and the particulates deposited on the window of the inner cell. The full width half-maximum of the T2g band enabled us to obtain an estimate of the temperature at the pellet surface after the ablation pulse and the particulates based on the crystal lattice disorder. Particulates deposited on the window of the DWC during laser ablation were characterized using scanning electron microscopy, where molten irregular particulates and spheroids were observed. This exciting research conducted in a DWC describes our initial attempts to incorporate LIBS in the arsenal of spectroscopic tools for nuclear forensics applications.

Hydroxycarbonate apatite formation, cytotoxicity, and antibacterial properties of rubidium-doped mesoporous bioactive glass nanoparticles

Rubidium (Rb) has been shown to impact biological activity. This work synthesized Rb-doped mesoporous bioactive glass nanoparticles (MBGNs) based on the composition 70SiO2–30CaO mol% with a sol-gel method. Rb2O was substituted for CaO in concentrations of 5 and 10 mol%. The influence of Rb incorporation on the hydroxycarbonate apatite (HCA) formation, cytotoxicity, and antibacterial capacity of particles was evaluated. XRD analysis confirmed the amorphous structure of the particles. In vitro, biomineralization studies showed HCA on the surface of MBGN and Rb-doped MBGN pellets after 7 days of soaking in simulated body fluid (SBF). An inhibition zone of Escherichia coli (E.coli) and Staphylococcus aureus (S. aureus) around Rb-doped MBGN pellets was detected, while MBGN pellets did not show any inhibition zone. Additionally, MC3T3-E1 pre-osteoblastic cells demonstrated cytocompatibility when exposed to Rb-MBG suspensions at different concentrations of up to 250 µg/ml. Based on their overall properties, Rb-containing MBGNs are proposed for biomedical applications, such as filler nanoparticles in composite bone scaffolds.

Pyrocatalysis-driven dye degradation by Zn Doped NBT-BT: A comparative analysis between powder and bulk

The present work investigates pyrocatalytic degradation of methylene blue (MB) dye in water using 0.94Na1/2Bi1/2TiO3-0.06BaTiO3 (NBT-6BT). The poled NBT-6BT degraded MB dye 7 % more (81 %) than the unpoled NBT-6BT (74 %). The degradation is enhanced by doping ZnO in NBT-6BT-xZnO (where x = 0.005, 0.01 and 0.02) from 81.5 % to 87 % with increasing Zn doping from 0.5 mol % to 2 mol %, respectively. The dye concentration and powder amount is varied to understand the effect on dye degradation. Scavengers test and fluorescence experiment ensured the presence of ·OH radical in the pyrocatalysis process. The repeatability test is performed to analyze the feasibility of 0.94Na1/2Bi1/2TiO3-0.06BaTiO3-0.02ZnO (NBT-6BT-0.02ZnO) for practical application. The limitation of powder for pyrocatalysis is overcome by studying the poled bulk pellets of NBT-6BT and NBT-6BT-0.02ZnO. The quantity of MB dyes (2.5–15 mL) and pellet surface area (30–240 mm2) with a fixed dye concentration of 5 mg L−1 are varied to understand the effect on pyrocatalytic degradation. It was found that with increasing pellet surface area, degradation increases.

Investigating the coupling between transport and reaction within a catalyst pellet using operando magnetic resonance spectroscopic imaging

In heterogeneous catalysis, the distribution of reactant and product species within a catalyst pellet are of central importance to the catalyst performance, and ultimately to the overall conversion and selectivity achieved in commercial-scale reactors. Despite this importance, fundamental understanding of pellet scale behaviour at operando conditions is limited due to the coupled, multi-scale nature of the underlying transport processes, and the limited techniques capable of mapping the intra-pellet composition at industrially relevant length scales. Here, we demonstrate the coupling between transport and reaction at the pellet scale by using operando magnetic resonance spectroscopic imaging (MRSI) to map the liquid composition within Pd/γ-Al2O3 catalyst pellets at an isotropic in-plane spatial resolution of 86 µm during a styrene hydrogenation reaction. The results reveal that asymmetric liquid wetting at the pellet surface, typical of that occurring in trickle-bed reactors, causes significant composition heterogeneity across a catalyst pellet. Due to the wetting inhomogeneity, commonly used 1D reaction-diffusion models are inadequate for describing the observed composition heterogeneity across the pellet. The results reported here provide unique experimental insight into the coupling between transport and reaction at the pellet scale within an operating reactor.