High-pressure Reactor Research Articles

Evaluation of the synergistic effect of platinum-supported graphene materials on methylcyclohexane decomposition via flow reactor experiments and reactive force-field molecular dynamics simulations

Hydrogen technology is a viable alternative to carbon-based energy sources. However, the widespread use of hydrogen energy is limited by its low volumetric energy density, complex supply chain, and difficulties related to hydrogen storage. This study investigates the influence of Pt-supported graphene additives on hydrogen formation and decomposition of methylcyclohexane (MCH), which is a potential hydrogen carrier, by conducting high-pressure liquid flow reactor experiments and reactive force-field molecular dynamics simulations. This investigation represents a notable improvement in the MCH decomposition and hydrogen generation efficiencies through enhanced catalytic dehydrogenation facilitated by Pt-decorated functionalized graphene sheets (Pt@FGSs). Experimental results indicate that under fixed reaction conditions, the bicomposite structure of the Pt@FGSs at a loading concentration of 50 ppmw reduces the dehydrogenation energy and increases the conversion rate by up to 45%. The yields of products such as hydrogen and low-carbon species are also significantly improved. Notably, hydrogen formation is enhanced by a factor of approximately 2, demonstrating the effectiveness of Pt@FGSs in facilitating fuel decomposition and promoting hydrogen production. In addition, reactive force-field molecular dynamics simulations elucidate possible enhancement mechanisms, in which Pt nanoparticles attach to FGSs and catalyze the dehydrogenation of MCH and its derivatives. The production of a higher amount of the produced hydrogen is evidenced by the desorption of H atoms attached to the Pt surface. This study provides valuable insights that can accelerate the transition towards sustainable and effective decarbonization strategies using MCH as a hydrogen carrier.

Foamed ceramic based γ-Al₂O₃ coated catalysts with different preparation methods for ethyl nicotinate hydrogenation reaction

This study investigated the catalytic hydrogenation of ethyl nicotinate using Pd/Al2O3-SiO2 foam ceramic catalysts prepared via sol-gel impregnation (SI), sol-gel precipitation (SP), precipitation-impregnation (PI), and co-precipitation (CP). We aimed to evaluate the performance and stability of these catalysts as coatings on foam ceramic surfaces in a high-pressure hydrogen reactor at 403 K and 5 MPa. Various physicochemical characterization methods were employed to correlate catalytic performance with physicochemical properties. Results indicated that sol-gel prepared supports had higher specific surface areas, more acidic sites, and better metal-carrier interactions compared to the precipitation method. SEM analyses revealed flatter and smoother coatings from the sol-gel method, while TEM showed uniform Pd distribution with impregnation. Ultimately, the SI method provided the best catalytic performance with a conversion of 86.77%. The conversion of the substrate remained above 80% after five cycles.

Deciphering the CO2 hydrates formation dynamics in brine-saturated oceanic sediments using experimental and machine learning modelling approach

One of the potential strategies for limiting global warming is capturing excess amounts of industry CO2 emissions and sequestrating it inside the oceanic sediments as CO2 hydrates. The seabed consists of sediments with different porosity and sizes, which can significantly impede the kinetics of CO2 hydrates. To address these challenges, in this novel work the CO2 hydrate kinetics and morphologies have been investigated in brine-rich [3.5 wt% NaCl] coarse sediments [porosity = 0.28, Ø =0.5-1.5 mm], granule sediments [porosity = 0.43, Ø =1.5-3 mm] and dual sediments [coarse + granules] inside a high-pressure reactor [3.5 MPa, 1-2 oC] with artificial seabed. According to the key experimental results, the water-to-hydrate conversion [%] was estimated to be 67.24 (± 3.02) % for coarse sediments, 49.58 (± 4.97) % for dual sediments (coarse + granules), and 27.68 (± 5.21) % for granules. In-situ Raman spectroscopy was used to evaluate the real-time solubility of CO2 [0.023 mol/mol], and image processing thresholding was used to identify CO2 hydrate distribution patterns. A mathematical model was proposed as a major contribution to predict CO2 hydrates kinetics in sediments, using 94,203 data points. The model was trained via a supervised machine-learning [ML] algorithm and can predict CO2 hydrate kinetics with an AARD of 7.54-8.47%.

Hydrothermal carbonization of primary sewage sludge in a prototype reactor: Sensitivity analysis of key parameters for hydrochar and liquid phase upscaling and reuse

Hydrothermal carbonization (HTC) of untreated sewage sludge with high water content was evaluated as an alternative to usual wastewater treatment. This bold approach allowed bioproducts useful as biofuel and nutrient sources to be obtained directly from raw sludge. HTC experiments were performed in a scalable arrangement (technology readiness level >4) composed of a 10-liter high-pressure reactor. The influence of the experimental conditions, including temperature (180-220°C), reaction time (60-120min), and pH (6.5-12.0), was evaluated on nutrients and heavy metal distribution through the liquid phase by a 23 central composite design with a triple central point. The bioproducts were characterized by a set of six analytical techniques, and the results were refined by statistical procedures (Principal Component Analysis and Response Surface Methodology). pH is a variable that impacts bioproducts’ characteristics, making it a guiding factor for application. Basic pH promotes transfer of components from solid to liquid phase, while natural pH favors the heating value of hydrochars. Liquid phase is a carbon- and nitrogen-rich source that can be useful for plant nutrition, mainly due to the increase of ammonia nitrogen from 20.6 to 51.7wt.% under pH 6.5, and an expressive decrease of chemical oxygen demand from 32 to 6-16 mgO2L-1. The hydrochar can be considered a renewable solid fuel, reaching up to 12.43 MJ kg-1 under pH 6.5; the basic pH favored an increase in the O/C ratio and lower HHV values. HTC of primary sewage sludge can replace steps of a conventional treatment station and promotes treated wastewater reuse.

Kinetics of CO2 hydrate formation in clayey sand sediments: Implications for CO2 sequestration

Hydrate-based CO2 sequestration beneath oceanic sediments is an emerging technique that involves the injection of CO2 into the hydrate stability zone (HSZ) beneath the seabed, forming hydrate cap that structurally traps the injected CO2 and reduces the risk of leaking CO2 from the storage sediment. Gas hydrates are adequately stable in sand sediments saturated with fresh water; however, the salinity of oceanic water impairs hydrate formation kinetics, stability, and CO2 storage capacity. In addition to sandstones, marine sediments are composed of many clay minerals that could affect hydrate formation. Therefore, this study experimentally simulates CO2 injection into sand and clayey sand sediments to assess the potential of CO2 hydrate formation. CO2 hydrates are formed inside a high-pressure reactor, which contains unconsolidated sediment bed/pack (silica sand; mixed sand with bentonite clay: 5 wt% and 10 wt%), saturated with de-ionized water or brine (3.3 wt% NaCl). Hydrate formation experiments were performed at 4 MPa pressure and 274.15 K temperature. Results show that CO2 hydrate formed within the sand sediment, with induction times of 6 and 8.5 h, for the de-ionized and brine systems, respectively. CO2 gas mole uptake in the de-ionized system was 71.54 mmol/mol however, in the brine system the gas uptake was 56.95 mmol/mol. Hence this 20.4% reduction in the gas uptake indicated the inhibition effect of salinity. In contrast, in the brine-saturated 5 wt% clay-sand sediment, the induction time was 6.5 h, indicating the promoting effect of the nano-sized clay particles. However, the gas uptake in this brine-saturated clay-sand sediment was reduced by 45.51% compared to the brine-saturated sand sediment. Increasing the clay content to 10 wt% prevented CO2 hydrate formation due to porosity reduction. Moreover, de-ionized water in clayey sand sediments prevented hydrate formation due to clay swelling. Finally, CO2 hydrate formation at the end of each experiment was visually confirmed.

Mineralization reaction between CO2 and coal ash produced from underground coal gasification: Implication for in situ carbon sequestration

Underground coal gasification (UCG) represents a promising clean and low-carbon energy technology, which could create a suitable cavity for in situ carbon sequestration by mineralization reaction between CO2 and coal ash produced from UCG. This may assist in achieving a net-zero carbon emission goal for UCG projects. To determine the carbonation efficiency and mineralization potential of CO2 mineral sequestration in abandoned UCG cavity, coal ash produced from the gasification of three different low-rank coal samples was used in this study. A comparative experiment was conducted using a group of high-calcium fly ash from a coal-fired power plant. All mineralization reaction experiments were performed in a high-temperature and high-pressure reactor, with CO2 pressures ranging from 2 to 8 MPa and temperatures ranging from 40 to 80°C. These conditions were selected to simulate the sequestration conditions in the UCG cavity. Real-time monitoring of CO2 pressure in the reactor was used to assess the impact of solid-to-water ratio, temperature, and pressure on the CO2 mineralization. X-ray diffraction and scanning electron microscopy were employed to identify the presence of newly formed carbonate minerals associated with mineralization reaction. The results indicated that the coal ash produced by gasification pretreatment at 900°C contains a substantial quantity of alkaline-earth oxides, such as calcium oxide (CaO), with a relative mass fraction reaching 25.9%. It provided an adequate supply of alkali metal ions for the mineralization reaction, which exhibited comparable efficacy in mineralizing CO2 to that observed in high-calcium fly ash. Without stirring, at lower solid-to-water ratio, the maximum amount of CO2 consumed through mineralization was increased by up to 74.12%. Carbonation efficiency decreased with rising temperatures below 70°C due to the limited dissolution of CO2 in water, it increased with elevated pressure but decreased in the supercritical state, potentially attributable to the dissolution of carbonate minerals in a supercritical CO2 environment. The process of mineralization reaction between CO2 and coal ash aligned well with the Surface Coverage Model (R2 values ranging from 0.92 to 0.99). A preliminary estimation based on Chinese coal reserves revealed that the potential of CO2 sequestration capacity in UCG cavities by mineralization ranging from 29 to 102 Gt, an additional 517 Gt CO2 may be stored when filled with fly ash. This paper provides theoretical bases for predicting the maximum carbonation efficiency under high-pressure and high-temperature conditions in UCG cavities, and research directions for achieving a net-zero carbon emission goal for UCG projects.

Effects of indigenous microorganisms on the CO2 adsorption capacity of coal

The adsorption capacity of coal is a crucial criterion for CO2 sequestration in deep unminable coal seams. Previous studies have documented how indigenous microorganisms interact with supercritical carbon dioxide (ScCO2) in coal. But how these interactions affect the adsorption capacity were rarely investigated. In this study, we treated bituminous coal samples with ScCO2-H2O and ScCO2-H2O-microorganism interactions in high-pressure reactors for 120 days at 35 °C and 10 MPa, respectively. After the treatments, we characterized both coal pore types and structures. The comparisons between two different post-treatments indicate that no significant change in coal pore types but notable alterations in pore structures are observed. Specifically, the treated coal with microorganisms exhibits a significant increase in micropore specific surface area (SSA) and surface roughness than the one without them. However, changes in meso/macropore structures and overall pore complexity of the coal sample treated with microorganisms were less pronounced than in coal sample treated with ScCO2-H2O alone. FTIR spectra analysis indicated that the absorption peak intensity of oxygen-containing groups and aliphatic functional groups in the sample treated with microorganisms decreased much more significantly than the sample treated without microorganisms. The CO2 adsorption capacity slightly increased in all treated samples at equilibrium pressures below 2.5 MPa. Above this pressure, the coal sample treated with microorganisms maintained a higher CO2 adsorption capacity, while the sample treated without microorganisms exhibited lower CO2 adsorption capacity compared to untreated coal sample. The increased SSA and the reduced oxygen-containing functional groups of coal after the treatment exerted antagonistic effects on CO2 adsorption. These findings suggest that indigenous microorganisms in coal seams affect CO2 adsorption through antagonistic effects, necessitating site-specific microbial assessments.

ZnH2P4N8: Case Study on Topochemical Imidonitridophosphate High-Pressure Synthesis.

Nitridophosphates are subject of current research, as they have a broad spectrum of properties and potential applications, such as ion conductors or luminescent materials. Yet, the subclass of imidonitridophosphates has been studied less extensively. The primary reason is that the controlled N-H functionalization of nitridophosphates is not straight forward, making targeted synthesis more challenging. Inspired by the high-pressure (HP) post-synthetic modification of nitridophosphates, we present the topochemical HP deprotonation of phosphorus nitride imides using the high-pressure polymorph β-PN(NH) as an example. Additional incorporation of Zn2+ results in the first quaternary transition metal imidonitridophosphate ZnH2P4N8. The crystal structure was elucidated by single-crystal X-ray diffraction (SCXRD), energy-dispersive X-ray spectroscopy (EDX), powder X-ray diffraction (PXRD) and solid-state magic angle spinning nuclear magnetic resonance spectroscopy (MAS NMR). In addition, the presence of H as part of an imide group was confirmed by IR spectroscopy. The potential of this defunctionalization approach for controlling the N-H content is demonstrated by the preparation of partially deprotonated intermediates ZnxH4-2xP4N8 (x≈0.5, 0.85). This topochemical high-pressure reaction represents a promising way to prepare, control and manipulate new imide-based materials without altering their overall anionic framework.

Comparative Study Between Design and Parameter Adjustment for Profit Maximization of Low-Density Polyethylene (LDPE) Production in High-Pressure Tubular Reactor

Low density polyethylene (LDPE) market becomes increasingly competitive and profit margins are tightening, manufacturers must create solutions to optimize profit in LDPE high pressure tubular reactors. Thus, in this study, the optimization of LDPE was proposed and conducted by improving the design and parameter adjustment of the LDPE tubular reactor. A mathematical model was developed and validated with industrial data by using MATLAB R2021. Input parameter study was carried out to investigate the effect of initiator concentration (CI), monomer concentration (CM), and solvent concentration (CS) to the ethylene conversion rate, reaction temperature rate, and final product grade, respectively. The CM was identified as the most significant parameter to influence LDPE polymerization process. CM increment results in the highest reaction temperature peak, which was originating from 249.58 to 299.21oC. The highest MFI value was also obtained when the CM was increased from 0.01954 to 0.01979 mol/cm3. Then, a comparative study between design and parameter adjustment for profit maximization in LDPE High Pressure Tubular Reactor was conducted. With the profit of RM166.83 million/year, compared to RM106.83 million/year, double reaction zones demonstrates that it has much better ethylene conversion rate compared to single reaction zone with optimization.

CO2 hydrogenation over Fe-Mn-Zn spinel oxide nanohybrids precatalysts

Catalytic CO2 hydrogenation using green hydrogen is a promising approach for mitigating CO2 emissions and utilizing CO2 as a feedstock. While Fe-based catalysts produce long-chain hydrocarbons under high-pressure CO2 hydrogenation reactions, the C2+ hydrocarbon yield tends to be insufficient at low-pressure conditions over the catalyst. This study reports the enhancement of light olefin selectivity of CO2 hydrogenation over Fe-based catalysts at low pressure via nanoscale hybridization with manganese (Mn) and zinc (Zn) oxides. The resulting hybridized catalyst exhibited distinctive performance in terms of CO2 hydrogenation to light olefins at relatively low pressure (0.7 MPa) in terms of CO2 conversion rate and C2–C4 yield with high olefin rates. Mn and Zn incorporation in Fe oxide decreased the reduction temperature, forming more Fe carbide phase. CO2 adsorption capability at relevant temperatures seems to be improved when Mn and Zn are present. This mixed oxide precatalyst approach can be extended to other elements.

Kinetic study on the effect of ice nucleation and generation on methane hydrate dissociation below the quadruple point

Natural gas hydrates (NGHs) have captured worldwide attention because of its huge resources and high energy density. Deep depressurization by dropping the pressure below the quadruple point is recognized as a promising exploitation method. However, the impact of ice formation on NGHs dissociation within depressurization is still controversial. Thus, we examine the dissociative behavior of NGHs at low temperature below the quadruple point using a high-pressure reactor. It primarily focuses on how ice formation affects heat and mass transfer, as well as the kinetics of hydrate dissociation. The results indicate that during the hydrate dissociation process, liquid water initially transforms into metastable supercooled water, which then transitions to solid ice under external disturbance. Ice nucleation predominantly occurs in two locations: within the free water phase and on the surface of hydrate particles. A double-edged effect of ice on NGHs dissociation is observed: the latent heat released by ice nucleation and generation could accelerate the hydrate breakdown (positive effect), while the decrease in permeability along with the self-preservation effect from ice formation tends to inhibit the NGHs dissolution (negative effect). In addition, a higher pressure drawdown rate can accelerate both ice nucleation and formation, which in turn shortens the freezing induction time. The increase of water saturation (SA) and the decrease of hydrate saturation (SH) can significantly reduce the mining time and strengthen both the hydrate dissociation rate (QH) and gas production rate (QP). Therefore, hydrate sediments with higher SA or lower SH are more conductive to gas recovery of low-temperature NGHs deposits in permafrost regions.

NiMo-MMO catalyst derived from LDHs precursors toward the deep hydrogenation of pyrene

A series of Ni-based catalysts were prepared via structural topological transformation from the Ni@Al2O3 layered double hydroxides (LDHs) precursors, and applied for the deep catalytic hydrogenation saturation of pyrene in a high-pressure reactor. The pore structures, active species dispersion, surface morphology, amount and type of acid of the prepared catalysts were characterized by BET, XRD, SEM, TEM, XPS, SEM, NH3-TPD and Py-IR. We studied the influence of physicochemical properties of Ni-based catalysts on the regularity and mechanism of deep hydrogenation of pyrene. Meanwhile, the synergy between Ni and Mo, and the interaction between active metals and support were discussed to further reveal the constitutive relationship during the hydrogenation reaction of pyrene. The results of the evaluation of the catalytic hydrogenation of pyrene show that the as-prepared NiMo mixed metal oxide (MMO) catalyst showed excellent catalytic activity: ∼95% pyrene conversion, 90.12% for the selectivity of deep hydrogenation products (hexahydropyrene, decahydropyrene and hexadecahydropyrene). It was expected that the successfully preparation and utilization of NiMo-MMO catalyst could provide a theoretical basis for the design of this kind of catalysts for deep catalytic hydrogenation of polycyclic aromatic hydrocarbons (PAHs).

A multi-modal high pressure and high temperature reaction cell for combined x-ray spectroscopy, scattering, and imaging.

A free-standing and compact reaction cell for combined in situ/operando x-ray spectroscopy, scattering, and imaging measurements at high pressures and high temperatures is described. The cell permits measurements under realistic operating conditions (up to 50bar and 1000°C), under static and flow conditions (up to 100 ml/min), over a wide range of hard x-ray energies, variable detection modes (transmission, fluorescence, and scattering), and at all angles of rotation. An operando XAS, x-ray fluorescence, x-ray computed tomography, and x-ray diffraction computed tomography case study on the reduction of a heterogeneous catalyst is presented to illustrate the performance of the reaction cell.

Continuous processing of JP-10 production: Hydroisomerization of endo-tetrahydrodicyclopentadiene to exo-tetrahydrodicyclopentadiene using a novel bimetal catalyst of Ba/Se supported on TiO2/SO4

High-energy-density liquid fuels can be utilized as an energetic supplement to conventional fuels and are essential for volume-limited aerospace vehicles to boost payload and flying range. JP-10 has attracted much attention because of its high density, flash point, high volumetric heat, and low freezing point. Here we report the hydroisomerization of endo-tetrahydrodicyclopentadiene to exo-tetrahydrodicyclopentadiene (the main component of JP-10) was investigated over the TiO2/SO4 supported Ba(10 %)/Se(5–20 %) catalysts. This work aims to examine changes in continuous processing settings to maximize exo-THDCPD production, selectivity, and conversion. It was discovered that the synthesized TiO2/SO4/Ba(10 %)/Se(5–20 %) heterogeneous catalysts were novel, more effective, affordable, environmentally friendly, and simple to produce. The catalyst’s physicochemical characteristics were examined using FT-IR, BET, XRD, HR-SEM, HR-TEM, TGA and NH3-TPD. The produced TiO2/SO4/Ba(10 %)/Se(5–20 %) nano-catalysts have good catalytic activity and a wide range of active Lewis and Brønsted acid sites. Evaluation of the isomerization of endo-THDCPD to exo-THDCPD was conducted in a high-pressure fixed-bed continuous reactor operating at 200 °C, 20 bar of pressure, and 4.0mol/h of H2 flow rate. According to the investigations, the synthesized catalyst with a 15 % Se load performs exceptionally well, exhibiting 100 % conversion, 98.5 % selectivity, and 98.5 % yield at an H2 flow rate of 10 ml/min. The isomerized product is used in Jet Propellant-10, a high-density fuel. Under ideal circumstances, exo-THDCPD with a high degree of purity (>98 wt%) was produced without the need for any sort of separation technique.

Mn-Na2WO4/SiO2-tridymite with improved stability and selectivity for high-pressure oxidative coupling of methane

Elevated pressures are essential for industrial chemical processes. Oxidative coupling of methane (OCM) is also preferred to be operated at high pressures. This study investigates high-pressure OCM with operando temperature visualization over the Mn-Na2WO4/SiO2 and Mn-K2WO4/SiO2 catalysts (initially with cristobalite SiO2), which have potential applicability in the selective conversion of CH4 to olefins and paraffins frequently measured at ambient pressure. At high pressure condition of 0.9 MPa, we observed the decrease in C2-4 selectivity and stability with time. During the deactivation, the hotspot generated in the catalyst bed was found to shift towards the end of the bed and sintered the catalyst in the process. High-pressure OCM condition was necessary to cause a phase transformation from SiO2-cristobalite to SiO2-tridymite, resulting from high temperatures in the presence of high H2O pressure (>100 kPa) and was found to play a major part in loss of surface area of active site (Na and K). The hotspot’s influence was reduced by increasing the CH4/O2 ratio, and treatment to form SiO2-tridymite prior to the start of the reaction was found to significantly increase the high-pressure stability. After optimizing the reaction conditions and catalyst, the C2-4 selectivity decreased only from 77.0 % to 76.5 % with a CH4 conversion of 12.7 % over 100 h at a total pressure of 901 kPa and a furnace temperature of 775 °C with Mn(2 wt%)-Na2WO4(5 wt%)/SiO2-tridymite catalyst. In addition, a practical method is proposed to design SiO2-tridymite supported alkali metal catalyst. The insights obtained could be used to design new catalysts and minimize stability issues during high-pressure OCM reactions and in other catalyst systems.

Preparation of zwitterionic polymer and its application for dual-functional inhibition in deepwater drilling

During deep-water drilling operations, due to the conditions with low temperature and high pressure in the wellbore, methane hydrate can be easily formed in the presence of methane and plug the wellbore. In addition, the deep-water sediments are dominated by clay-silty with weak cementation, so well instability may be occurred due to clay hydration. In order to inhibit hydrate formation and clay hydration in deepwater drilling, a zwitterionic polymer AADV was synthesized through quaternary copolymerization of AM/AMPS/DMDAAV/VAC. The hydrate inhibition performance of AADV was evaluated in a high-pressure reactor chamber, and the results showed that AADV can delay the hydrate formation time from 330 min in pure water to 2204 min, indicating an excellent inhibition effect of hydrate formation. Meanwhile, 1 % AADV can significantly reduce the linear swelling rate of the calcium-based bentonite to 3.69 % for 10 h and increase the rolling recovery rate to 94.7 %, suggesting an excellent inhibition effect on clay hydration. The mechanism of dual-functional inhibition of AADV was further analyzed. The zwitterionic group in AADV and the hydrophilic amide group can strongly adsorb the water molecules through a strong hydration effect and the hydrogen bonding effect, respectively, which contributes to destroy the water molecules cage structure, and thus to suppress the hydrate formation. Besides, AADV can effectively obstruct mass transfer of methane molecules by increasing the viscosity of the aqueous phase and absorbing on the hydrate surface, leading to hydrate formation inhibition. For the inhibition of clay hydration, the SEM and XRD results proved that AADC inhibits the clay hydration through the film-forming effect. In addition, the contact angle of Na-Bent/AADC composite reached to 55.68° when the polymer concentration increased to 2 %, suggesting that the hydrophobicity of Na-Bent surface can be enhanced after AADC treatment. AADV can wrap around clay particles and form hydrophobic film through adsorption and intercalation, preventing the intrusion of external fluids and inhibiting clay hydration.

Renewable Diesel Production over Mo-Ni Catalysts Supported on Silica

Nickel catalysts promoted with Mo and supported on silica were studied for renewable diesel production from triglyceride biomass, through the selective deoxygenation process. The catalysts were prepared by wet co-impregnation of the SiO2 with different Ni/(Ni + Mo) atomic ratios (0/0.84/0.91/0.95/0.98/1) and a total metal content equal to 50%. They were characterized by XRD, XPS, N2 physisorption, H2-TPR, and NH3-TPD. Evaluation of the catalysts for the transformation of sunflower oil to renewable (green) diesel took place in a high-pressure semi-batch reactor, under solvent-free conditions. A very small addition of Mo, namely the synergistic Ni/(Ni + Mo) atomic ratio equal to 0.95, proved to be the optimum one for a significant enhancement of the catalytic performance of the metallic Ni/SiO2 catalyst, achieving 98 wt.% renewable diesel production. This promoting action of Mo has been attributed to the significant increase of the metallic Ni active phase surface area, the suitable regulation of surface acidity, the acceleration of the hydro-deoxygenation pathway (HDO), the creation of surface oxygen vacancies, and the diminution of coke formation provoked by Mo addition.

High-Pressure Reactions Can Turn Nonporous Rocks into Sponges

Mathematical models describe how water moves through rocks in deep Earth.

Experimental study on the effect of hydrate saturation in reservoir on microwave heating hydrate decomposition gas production

Microwave heating technology is an effective method to promote the decomposition of hydrates, with hydrate saturation being an important parameter influencing this process. This study has synthesized natural gas hydrates with different saturations within a high-pressure reaction vessel to conduct experiments on the decomposition of natural gas hydrates by microwave heating. The reservoir temperature, gas production dynamics, and energy utilization rate are investigated for hydrate saturations of 30.26 %, 35.63 %, and 39.61 %, respectively. The results indicate that increasing hydrate saturation enhances the microwave penetration depth, which in turn elevates the reservoir temperature and accelerates hydrate decomposition. When the hydrate saturation increases from 30.26 % to 39.61 %, the gas production time decreases. Simultaneously, both the volume and rate of gas production increase, accompanied by enhanced energy utilization rate. When the hydrate saturation is 39.61 %, the experiment achieves an average gas production rate of 1.17 L/min, a total volume of 19.73 L, and an energy utilization rate of 2.716. The research results can promote the application of microwave heating technology in the development of hydrates.

P1-xTa8+xN13 (x=0.1-0.15): A Phosphorus Tantalum Nitride Featuring Mixed-Valent Tantalum and P/Ta Disorder Visualized by Scanning Transmission Electron Microscopy.

We report on the synthesis, crystal, and electronic structure, as well as the magnetic, and electric properties of the phosphorus-containing tantalum nitride P1-xTa8+xN13 (x=0.1-0.15). A high-pressure high-temperature reaction (8 GPa, 1400 °C) of Ta3N5 and P3N5 with NH4F as a mineralizing agent yields the compound in the form of black, rod-shaped crystals. Single-crystal X-ray structure elucidation (space group C2/m (no. 12), a=16.202(3), b=2.9155(4), c=11.089(2) Å, β=126.698(7)°, Z=2) shows a network of face- and edge-sharing Ta-centered polyhedra that contains small vacant channels and PN6 octahedra strands. Atomic resolution transmission electron microscopy reveals an unusual P/Ta disorder. Mixed-valent tantalum atoms exhibit interatomic distances similar to those in metallic tantalum, however, the electrical resistivity is quite high in the order of 101 Ω cm. The density of states and the electron localization function indicate localized electrons in both covalent and ionic bonds between P/Ta and N atoms, combined with less localized electrons that do not contribute to interatomic bonds.