Ratio Of Reactants Research Articles

The oscillating Fischer-Tropsch reaction.

The mechanistic steps that underlie the formation of higher hydrocarbons in catalytic carbon monoxide (CO) hydrogenation at atmospheric pressure over cobalt-based catalysts (Fischer-Tropsch synthesis) have remained poorly understood. We reveal nonisothermal rate-and-selectivity oscillations that are self-sustained over extended periods of time (>24 hours) for a cobalt/cerium oxide catalyst with an atomic ratio of cobalt to cerium of 2:1 (Co2Ce1) at 220°C and equal partial pressures of the reactants. A microkinetic mechanism was used to generate rate-and-selectivity oscillations through forced temperature oscillations. Experimental and theoretical oscillations were in good agreement over an extended range of reactant pressure ratios. Additionally, phase portraits for hydrocarbon production were constructed that support the thermokinetic origin of our rate-and-selectivity oscillations.

Preparation of Thermoplastic Cellulose Esters in [mTBNH][OAC] Ionic Liquid by Transesterification Reaction.

The transesterification of cellulose with vinyl esters in ionic liquid media is suggested as a prospective environmentally friendly alternative to conventional esterification. In this study, various long-chain cellulose esters (laurate, myristate, palmitate, and stearate) with a degree of substitution (DS) up to 1.8 have been synthesized in novel distillable ionic liquid, [mTBNH][OAC]. This IL has high dissolving power towards cellulose, which can improve homogeneous transesterification. Additionally, [mTBNH][OAC] has durability towards recycling and can be regenerated and re-used again for the next cycles of esterification. DMSO is used as a co-solvent because of its ability to speed up mass transport due to lower solvent viscosity. The optimization of the reaction parameters, such as co-solvent content, temperature (20-80 °C), reaction time (1-5 h), and a molar ratio of reactants (1-5 eq. AGU) is reported. It was found that within studied reaction conditions, DS increases with increasing reaction time, temperature, and added vinyl esters. Structure analysis using FTIR, 1H, and 13C NMR after acylation revealed the introduction of the alkyl chains into cellulose for all studied samples. The results also suggested that the substitution order of the OH group is C7-O6 > C7-O2 > C7-O3. Unique, complex thermal and rheological investigation of the cellulose esters shows the growth of an amorphous phase upon the degree of substitution. At the same time, the homogeneous substitution of cellulose with acyl chains increases the melt viscosity of a material. Internal plasticization in cellulose esters was found to be the mechanism for the melt processing of the material. Long-chain cellulose esters show the potential to replace commonly used externally plasticized cellulose derivatives.

Process variables optimization for synthesizing novel calcium-based metal-organic frameworks for feasible synthetic estrogen adsorption

Calcium-based Metal-Organic Frameworks (Ca-MOFs) hold great promise for environmental remediation due to their non-toxic nature, eco-friendliness, and cost-effectiveness. However, ensuring the structural integrity of MOFs after water exposure is crucial for industrial applications. This study investigates the physicochemical properties and structural stability of Ca-MOFs as potential adsorbents for water purification. The synthesis temperature, time, and reactant ratio significantly influence Ca-MIX's surface area and yield. The ideal conditions for synthesizing Ca-MIX, achieving a surface area of 20.45 m2/g and a yield of 18.56 kg/m³ per day, were achieved at a temperature of 120 °C, a reaction time of 16 h, and a metal-to-linker molar ratio of 1:0.33:0.33, respectively. The efficacy of a calcium-based MOF with a mixed linker, Ca-benzenedi and tricarboxylate (Ca-MIX) was explored, for removing the hazardous endocrine disrupting such EE2 from water. Ca-MIX exhibits high adsorption capacity at 97.17 μg/g and rapid 1-h adsorption. The adsorption process using the pseudo-second-order and Langmuir models were analysed, both describing it well. Notably, Ca-MIX efficiently removes EDCs like EE2, even at trace concentrations. Thus, Ca-MIX emerge as promising sorbents for adsorption-based removal of EDCs from polluted water.

Hydrophobic Modification of Spherical Y2O3:Eu3+ Powder Using Nonfluorinated Alkyl Silanes

AbstractEuropium‐doped yttrium oxide (Y2O3:Eu3+) is one of the main red‐emitting luminescent materials currently used in light‐emitting devices owing to its high luminous efficiency, high color purity, and other excellent optical characteristics. However, Y2O3:Eu3+ is hydrophilic, which is a major obstacle to its long‐term application in high‐humidity outdoor environments. Hydrophobic modification is a viable solution to this problem, and can give Y2O3:Eu3+ many excellent properties and functions, such as self‐cleaning ability, anti‐static performance, oil/water separation functions, and corrosion resistance. This study reports the preparation of hydrophobic Y2O3:Eu3+ particles modified with nonfluorinated alkyl silanes. Several influencing factors, including the length of the carbon chain in the silane coupling agent, the pH value of the reaction system, the reaction temperature, and the ratio of reactants, on the hydrophobicity of the prepared samples are studied in detail, and the optimal conditions are determined. A superhydrophobic Y2O3:Eu3+ material with a water contact angle of 151.6° is finally obtained. Moreover, FTIR, TG, SEM, XPS, XRD, and PL are used to explore the mechanism of the hydrophobic modification and the structural and fluorescence performance changes imparted by this modification.

Elucidating the role of synthesis conditions on Zr-MOF properties and yield

Metal-organic frameworks (MOFs) are a new type of ultra-high surface area porous materials with applications in catalysis, energy storage, and gas adsorption. Compared to other MOFs, Zirconium-based MOFs (Zr-MOFs) demonstrate improved stability due to strong bonds between tetravalent zirconium and carboxylate ligands, making them applicable in real world conditions. This study aims to investigate optimal synthesis conditions for the solvothermal fabrication of Zr-MOFs by looking at two promising tetratopic ligand-based MOFs, Zr-TCPP and Zr-TPTC. By systematically investigating the impact of synthesis parameters on yield, crystallinity, and morphological characteristics, both general and specific trends were determined. The present work demonstrated that the ideal reactant ratio was twice the actual Zr:ligand ratio in the final structure. Stronger acid modulators were found to produce more crystalline samples for MOFs with flexible ligands (Zr-TPTC), where formic acid use resulted in more crystalline samples compared to acetic acid; however, this lowered the yield. The effect of temperature on yield was non-linearly dependent on the reactant ratio used for synthesising flexible Zr-TPTC. For MOFs with rigid ligands (Zr-TCPP), increasing synthesis temperature did not affect yield but decreased crystallite size and improved phase selectivity. Stability tests in water and acid were performed on both MOFs to assess the effect on crystallinity and morphology and the results showed expected trends for Zr-MOFs. The optimized synthesis parameters for Zr-TCPP resulted in a superior method of producing PCN-222 with higher yield and crystallinity. On the other hand, a new Zr-TPTC MOF with high yield and crystallinity was synthesised using the optimized parameters. This study thus elucidates the role of synthesis parameters on Zr-MOF properties and yield and furthers the understanding of MOF synthesis mechanisms, expanding the potential for their applicability in industry.

An α, β-unsaturated ketone alkylation and efficient reduction protocol for the synthesis of 3α-hydroxy-3β-methyl-4,4-dimethyl-5α-21-bromo-19-nor-pregnan-20-one

Alkyl-substituted testosterone derivatives are promising platforms for new drug discovery in medicinal chemistry. This approach provides a simple and efficient method for introducing an alkyl substituent to steroids at the C-4 position. In this study, the novel compound 3α-hydroxy-3β-methyl-4,4-dimethyl-5α-21-bromo-19-nor-pregnan-20-one is synthesized from 19-nor-testosterone. The protocol involves methylation of the dienolate, reduction of the alkene, the Grignard reaction of the carbonyl group, a Wittig reaction, hydroboration with BH3, the oxidation and bromination with a 49% overall yield. For the methylation and reduction steps, the effects of the base, solvent, and reactant ratio on the conversion and yield are investigated. The structures of the synthesized compounds are determined by nuclear magnetic resonance (NMR) and high-resolution mass spectrometry (HRMS) (electrospray ionization (ESI)).

Significance of pH and iron-sulfur chemistry for molybdenum sequestration under sulfidic conditions

Molybdenum (Mo), a redox-sensitive trace metal, plays an important role in recording ancient oxygenation and deoxygenation events as a paleoredox proxy. The mobility and reactivity of Mo in aqueous conditions are closely tied to the chemistry of reduced sulfur and iron species. However, our current knowledge on the formation, structure, stability, and condensation pathways of FeMoS clusters in aqueous settings remains limited, which has driven the current study. In this study, we conducted systematic experiments investigating the interactions between dissolved Mo (initially introduced as molybdate, MoO42−, or tetrathiomolybdate, MoS42−), ferrous iron (Fe2+), and sulfide (ΣH2Saq) in variously defined abiotic sulfidic systems to determine the external conditions (i.e., pH, and reactant concentrations and ratios) necessary for the formation of solid-phase Fe-Mo sulfides. Solution samples of each system were monitored using ultraviolet-visible spectroscopy (UV–vis) to track the degree of thiolation of dissolved Mo species. Precipitates were analyzed using X-ray photoelectron spectroscopy (XPS) and transmission electron microscopy (TEM) to determine their elemental compositions and valences, and structure (i.e., crystalline or amorphous), respectively. All FeMoS precipitates were amorphous and contained 76–90% Mo(IV) and 10–24% Mo(V) with a trend toward lower Mo(IV):Mo(V) ratios with increasing pH. The degree of Mo thiolation, which was strongly dependent on solution pH and Fe2+ concentrations, greatly affected the amount of Mo sequestered (i.e., an increased degree of Mo thiolation in solution led to an increased amount of Mo in the final FeMoS precipitate). These findings suggest that changes in pH and Fe2+ concentrations may be responsible for the sulfide-independent variations in Mo behavior observed in euxinic basins.

Study on the Fluorination Process of Sc2O3 by NH4HF2.

Research on rare-earth fluorides is of urgent and critical importance for the preparation and emerging applications of high-purity alloys. The fluorination of Sc2O3 by NH4HF2 to fabricate ScF3 is investigated. The effects of the fluorination temperature, time and mass ratio of reactant on the fluorination rate and fluoride are discussed in this work. The fluorination reaction was first confirmed using thermodynamic calculation. The thermal and mass stability of the fluorination process were analyzed by thermogravimetric and differential scanning calorimetric (TG-DSC). The as-obtained products at different fluorination temperatures were characterized by Powder X-ray diffraction (PXRD), scanning electron microscopy (SEM) and high-resolution transmission electron microscopy (HRTEM). The results indicated that the fluorination began at room temperature (RT) with the formation of (NH4)3ScF6. With the increase of temperature, the reaction proceeded sequentially through the formation of NH4ScF4, (NH4)2Sc3F11, and finally ScF3. The fluorination rate increased with the increase of fluorination temperature and holding time. ScF3 with a purity of 99.997 wt.% could be obtained by fluorination at 400 °C for 2 h.

Two new Keggin-based copper-organic complexes constructed from pyrazole derivatives: Syntheses, structures and catalytic properties

By regulating the initial reactant molar ratio, two new Keggin-based copper-organic complexes formulated as [Cu2(H2O)(L)2(HL)2](HPMo12O40)·2H2O (1) and [Cu4L4(H2O)2](H3PMo12O40) (2) (HL = 1-(4-carboxylbenzyl)-3-(pyrazine-2-yl)]pyrazole) have been synthesized triumphantly under hydrothermal conditions. Single crystal X-ray diffraction analyses show that compound 1 is a 3D supramolecular structure constructed by 1D metal–organic chains [Cu2(H2O)(L)2(HL)2]n2n+ and PMo12 anions via hydrogen bonds. Compound 2 is a 2D [Cu2L2(H2O)]n coordination polymeric network containing left and right helical chains. By hydrogen bonding interactions between adjacent [Cu2L2(H2O)]n networks and PMo12 anions, the 2D network extends to a 3D supramolecular structure. The two compounds can not only photocatalytic degrade methylene blue and Rhodamine B, but also have electrocatalytic reduction of H2O2, BrO3- and NO2– and oxidation of ascorbic acid. Moreover, their electrochemical sensing properties have also been studied. These results suggest compounds 1 and 2 can be used as multifunctional materials.

Performance Analysis of Ammonia Converter in Ammonia Unit Factory

<p>An ammonia converter is a catalyzed reactor that facilitates the synthesis of NH<sub>3</sub> (ammonia) from hydrogen (H<sub>2</sub>) and nitrogen (N<sub>2</sub>). Several studies have shown that the performance of this reactor significantly influences the operational efficiency and productivity of ammonia plants. Therefore, this study aims to evaluate the performance of an ammonia converter by assessing the effect of operating conditions on the reactant conversion and reaction products using design and actual data. The operating conditions examined included temperature, pressure, ratio of reactants, and inert mole utilized during the NH<sub>3</sub> synthesis process. The results showed that the highest NH<sub>3</sub> yield of 20.28% was achieved in actual data with 351.5<sup>o</sup>C temperature, 154.32 kg/cm<sup>2 </sup>pressure, 3.58 raw material ratio, and 3.57% inert mole (sixth dataset). The performance efficiency of an ammonia converter can be assessed using temperature, reactant ratio, and inert moles, while the pressure factor was insignificant due to dataset fluctuations. Based on the evaluation results, the converter experienced a decrease in performance due to a discrepancy in the existing operating conditions between the design and actual data.<strong></strong></p>

Large-Scale Synthesis of Tunable Fluorescent Carbon Dots Powder for Light-Emitting Diodes and Fingerprint Identification.

The emergence and fast development of carbon dots (CDs) provide an unprecedented opportunity for applications in the field of photoelectricity, but their practicability still suffers from complicated synthesis procedures and the substrate dependence of solid-state fluorescence. In this study, we design a unique microwave-assisted solid-phase synthesis route for preparing tunable fluorescent CD powders with yellow, orange, and red fluorescence (Y-CDs, O-CDs, R-CDs) by simply adjusting the mass ratio of reactants, a method which is suitable for the large-scale synthesis of CDs. The Y-/O-/R-CDs were systematically characterized using physics and spectroscopy techniques. Based on the perfect solid-state fluorescence performance of the proposed fluorescent CD powders, the Y-/O-/R-CDs were successfully applied for the construction of multi-color and white light-emitting diode devices at low cost. Furthermore, the Y-CDs displayed much higher yield and luminous efficiency than the O-CDs and R-CDs and were further used for fingerprint identification on the surfaces of glass sheets and tinfoil. In addition, the R-CD aqueous solution fluorescence is sensitive to pH, suggesting its use as a pH indicator for monitoring intracellular pH fluctuations. The proposed series of fluorescent powders composed of CDs may herald a new era in the application of optical components and criminal investigation fields.

Preparation of Mesoporous γ-Alumina from Red Mud Waste

In this paper, a novel green and cost-effective synthesis method in this field is presented. Mesoporous γ-alumina was obtained by inorganic in situ crystallization, and sodium aluminate as an aluminum origin was abstracted from red mud. The influence mechanism of the reactant ratio of NaHCO3 to NaAlO2, the reaction temperature and the concentration of the template was systematically investigated. As indicated by the results, the obtained mesoporous γ-alumina possesses extensive specific surface areas, narrow pore size distribution, nearly spherical particle morphology and wormlike structure pores. This green and economical synthesis method can be used for the preparation of alternative mesoporous or various porous materials as well.

Morphological evolution of plate-like B-site complex perovskite Pb(ZrxTi1-x)O3 microcrystals

Crystallographic texturing of polycrystalline ferroelectric ceramics is an effective approach to achieve single crystal-like properties via templated grain growth method (TGG). The TGG process strongly depends on the use of anisotropic single crystal templates. In this work, novel B-site complex Pb(ZrxTi1-x)O3(PZT) platelets are successfully fabricated via topochemical molten salt synthesis (TMSS). The Aurivillius phase of PbBi4Ti4O15(PBT) is obtained as precursor by molten salt method. Morphological evolution of Pb(ZrxTi1-x)O3 is investigated by varying the relative molar ratio of reactants and calcination temperature. However, the results of Raman spectroscopy show that the incorporation of Zr4+ content increases the instability of the perovskite structure. At 1100°C, it is possible to synthesize Pb(Zr0.2Ti0.8)O3 plate-like microcrystal templates with high aspect ratios and preferential orientations. These well-shaped microcrystals are suggested as a potential template material for the TGG fabrication of lead-based piezoelectric textured ceramics.

Investigation on H2/CH4 blended combustion in a micro-tube with dual-inlet at varied operating conditions

Combustion characteristics of premixed H2/CH4/Air in a combustor with dual-inlet are investigated under various operating conditions. Effects of reactants ratio in the two inlets, dual-inlet setting and flow rates on the combustion characteristics and heat transmission are compared and analyzed. Results demonstrate that the setting of dual-inlet strongly affects burning such as OH generation and consumption, and the weak flame is formed in the second-inlet, modifying the species distribution and gas temperature. For the seven conditions with 28 cases under a kept H2/CH4 blended ratio mCH4 = 5%, the case of 20% H2/CH4/Air imported via the second-inlet achieves a better thermal performance, where reactions around the second-inlet contribute to the sufficient burning, heat release, heat transfer of gas-wall and gases. It also reduces the heat loss through exhaust gases, resulting in a higher burner radiation temperature, and the mean radiation temperature of case 19 is 55 K higher than that of case 21. Moreover, the radiation power of the combustor can be further improved by optimizing the second-inlet setting. The combustor with the distance of the two inlets L = 14 mm obtains a higher thermal performance, where the Tm reaches 1254 K and is 16 K higher than the stepped tube and the radiation power reaches 44.1 W under condition of mf = 3.339 × 10-5kg/s andmCH4 = 5%.

Two-step hydrothermal synthesis of active carbon-dots with high temperature and salt resistance for injection pressure reduction and enhanced oil recovery

Ultrasmall carbon nanomaterials show enormous potential in the development of unconventional oil resources for reducing injection pressure and improving oil recovery. However, the high temperature and salinity reservoir conditions and the poor activity of carbon nanoparticles hinder their practical applications. In this study, carbon nanoparticles (CDs) are readily synthesized by citric acid (CA) and ethylenediamine (EDA) through a hydrothermal reaction. The results show that a change in the type and density of oxygen hydrophilic groups by adjusting the molar ratio of reactants can improve CDs dispersibility and stability at a temperature of 90 °C and salinity of 16 × 104 mg/L. The active carbon nanoparticle (sm-CDs) is obtained by surface modification of CDs with erucate amidopropyl betaine (EAB), which enhances surface activity while retaining the original temperature and salt resistance. Core flooding tests show 0.03 wt% sm-CDs nanofluid provides a pressure-reduced rate of 63.5% and an enhancement in oil recovery of 23.0%. The results of atomic force microscopy (AFM) with hydrophobic probe reveal sm-CDs can effectively reduce the adhesion between alkanes and lipophilic surfaces, which alter microscopic surface wetting from oil-wet to uniformly water-wet. This study provides a feasible strategy for the efficient development of carbon-based active nanofluids, especially in unconventional reservoirs.

Analysis of PEMFC undershoot behavior and performance stabilization under transient loading

A global full state model considering both steady and dynamic performance of proton exchange membrane fuel cell (PEMFC) is developed to analyze the voltage undershoot behavior and performance stabilization under transient loading. The research investigates the underlying causation of operating conditions, reactant starvation level and control strategy of undershoot behavior. Experiments are conducted to obtain data for calibrating the model. The voltage undershoot principles and the alleviation method are investigated. The results show that the model deviations are limited within 2% relative errors. The voltage undershoots and voltage delay-time recovery under transient loading could be accurately characterized by exploring the internal substance transport and heat transfer. The voltage undershoot amplitudes are mainly influenced by the reactant concentration ratio of consumption part to initial part before loading in membrane electrode assembly. Moreover, the performance stabilization methods can be developed for loading boundary definition and operating parameter adjustment. The study is significant to provide a guidance for the enhancement of PEMFC performance stability.

Chemically vs Enzymatically Synthesized Polyglycerol-Based Esters: A Comparison between Their Surfactancy.

Polyglycerol fatty acid esters (PGFAEs) are gaining interest in several industrial sectors due to their excellent surfactant properties and their wide range of hydrophilic-lipophilic balance (HLB) values. Moreover, they can be prepared from renewable resources, i.e., fatty acids and glycerol. In this study, polyglycerol-2 stearic acid esters (PG2SAEs) were synthesized by the enzymatic esterification of polyglycerol-2 (PG2) and stearic acid (SA) using the immobilized lipase Novozym 435 as a biocatalyst in a solvent-free system. Reaction conditions, i.e., temperature (80 °C), reactant ratio (1:1.8), and enzyme loading (2.7% w/w), were finely optimized; furthermore, biocatalyst recycling was studied by assessing the residual activity of the lipase after each reaction cycle, up to 20 times. The composition of the enzymatically synthesized products (E) was roughly evaluated by chromatographic methods and mass spectrometry and compared with that of the esters obtained by acid-catalyzed esterification (C). Then, the surfactant properties of the prepared polyglycerol-based surfactants were investigated by interfacial tension studies. Specifically, the emulsifying capacity and stability and the rheological behavior of O/W emulsions prepared in the presence of E were deeply investigated in comparison with those of the chemically synthesized and commercially available product C.

A comprehensive review of the production methods and effect of parameters for glycerol-free biodiesel production

This review appraises the latest scientific progress and the accomplishments of interesterification technology as an alternative to conventional transesterification reaction. The merits and limitations of various types of catalytic techniques as well as non-catalytic supercritical glycerol-free processes have been elucidated with a comprehensive comparison. Contrary to the cheap price of glycerol, the higher-revenue by-products, triacetin and glycerol carbonate, will boost the gross profit margin of biodiesel production. The influences of reaction parameters such as reactant ratio, catalyst loading, reaction time, temperature, and co-solvent addition are also addressed. According to the latest research, the alkali-catalyzed and non-catalytic supercritical interesterifications are preferable due to higher yield. Methyl acetate, ethyl acetate and dimethyl carbonate do not inhibit lipase activity, unlike typical alcohols. Acidic catalysis may be the way forward to resolve the extreme operating conditions of non-catalytic supercritical interesterification, high cost of enzymes and manage waste feedstocks with high free fatty acid and water contents under moderate conditions. Currently, the majority of interesterification reactions were undertaken on laboratory size, whereas just a handful was evaluated on a pilot scale. A continuous research in interesterification technology is necessary by conducting a thorough investigation of the feasibility of state-of-the-art technology to engage a wide array of feedstocks. Future study should also concentrate on microbes and agricultural waste as a sustainable route for energy recovery from renewable feedstocks.

Preparation of Ca(OH)2 nanoparticles by impinging stream reaction precipitation method

AbstractIn this paper, Ca(OH)2 nanoparticles are prepared by impinging stream co‐precipitation method. The process of preparing nanoparticles by impinging stream is optimized. The influence of process variable, such as dispersant type, dispersant dosage, circulating flow rate, reactant concentration ratio of OH− and Ca2+, reaction temperature and circulation time, on the particle size of Ca(OH)2 nanoparticle are investigated. The results show that the concentration ratio of reactants has a significant effect on the size of Ca(OH)2 nanoparticles. The optimal process conditions are obtained by single factor experiment, PEG6000, 3.3% dispersant dosage, Q = 1000 L · h−1, C = 1.88, T = 46.68°C and t = 60 min. The average particle size of Ca(OH)2 nanoparticles prepared under these conditions is 107.67 nm. According to the microstructure analysis, the prepared Ca(OH)2 nanoparticles samples have high purity and a good crystal structure. The powder dispersed with a marked hexagonal crystal shape and good thermal decomposition.

Diselenide Dianion’s Dual Powers: PdSe2Polymorph Control and Pd3Se10Superatomic Crystal Creation

There is a diverse family of palladium selenide compounds, including semiconducting orthorhombic PdSe2 (O-PdSe2) and monoclinic PdSe2 (M-PdSe2), which are unusual among transition-metal dichalcogenides as they are composed of diselenide dianions Se22–. Thus far, the solution syntheses of materials with Se–Se bonds typically require the in situ reduction of Se precursors. Here, we explore the use of electrochemically precise reactions between Na2Se2 and a Pd2+ source, Na2PdCl4, as a solution-phase route to selectively form different PdSe2 polymorphs in the absence of surfactants. By altering the reactant molar ratios and time, we map out a synthetic phase space diagram that shows how to create a wide variety of palladium selenide phases. With increasing Se22–/Pd2+ molar ratios, regions are identified where Pd17Se15, M-PdSe2, and O-PdSe2 exist as the dominant or exclusive thermodynamic product. Additionally, we discover Pd3Se10, a superatomic crystal composed of Pd6Se20 cube-shaped clusters held together by van der Waals forces, which forms as a kinetic product under short reaction times. In total, the use of the diselenide dianion precursor allows for the selective solution-phase synthesis of M-PdSe2 or O-PdSe2, as well as the discovery of a previously unreported palladium selenide phase.