Stacking Number Research Articles

Enhancement in Mechanical Properties of AA5052 Sheet for Small Ship by Cold Roll-Bonding Process

A cold roll-bonding (CRB) process was applied to enhance the mechanical properties of AA5052 sheet for small ship. Two and four AA5052 sheets of 1 mm thickness, 40 mm width and 300 mm length were stacked, then roll-bonded to a thickness of 0.5 mm and 1 mm respectively by two-pass rolling after such surface treatment as degreasing and wire brushing. The rolling was performed at ambient temperature without lubricant using a 4-high mill at rolling speed of 6.0m/sec. The as roll-bonded AA5052 sheet was then annealed for 1h at various temperatures from 200 to 500℃. The as roll-bonded AA5052 sheets showed a deformation structure in which the grains are elongated to the rolling direction, however above 300℃ they exhibited the complete recrystallization structure consisting of equiaxed grains, regardless of the stack number. The grain diameter of specimens annealed at high temperatures above 300℃ was smaller in 4-layer stack than in 2-layer stack CRB. Both tensile strength and elongation of the specimens were better in 4-layer stack than in 2-layer stack CRB. The effects of stacking number on microstructure and mechanical properties of AA5052 sheets processed by CRB and subsequent annealing were discussed in detail.

Synthesis and consequence of three-dimensionally ordered macroporous Beta zeolite supported NiW catalyst for efficient hydrocracking of 1-methylnaphthalene to BTX

The three-dimensionally ordered macroporous Beta (3DOM-Beta) zeolite was prepared and used as support of NiW sulfide catalyst for hydrocracking. The as-prepared NiW/3DOM-Beta catalyst possessed a high specific surface area and external specific surface area up to 499 m2/g and 241 m2/g, respectively, and a small average layer length (3.62 nm), a high highest average stacking number (4.64) and dispersion (fW=0.24) of metal sulfide phase, which are characteristic of high hydrogenation activity. Its high mesopore volume (0.25 cm3/g) and the highly ordered interconnected macro-meso-microporosity hierarchical structure significantly facilitated diffusive mass transfer. Compared to the NiW sulfide supported on conventional Beta (C-Beta), alkali-treated Beta (A-Beta) and nanosized Beta (Nano-Beta) zeolites, NiW/3DOM-Beta catalyst showed the highest BTX selectivity and yield of 40.7 % and 40.2 % (33.2 % and 32.6 % on NiW/C-Beta, 34.8 % and 33.9 % on NiW/A-Beta, 37.2 % and 36.6 % on NiW/Nano-Beta), and the highest hydrocracking activity (TOF=2.11 × 10-2∙s−1) as well as the smallest coking content (6.7 wt%). This work not only reveals the promotion effects of the ordered mesopore structure of supports on metal dispersion, accessibility of acid sites, diffusion of reactants and products for designing hydrocracking catalyst, but also shows the potential practical application of 3DOM zeolites with interconnected macro-meso-microporosity for the efficient catalytic conversion of macro-hydrocarbons via hydroupgrading.

Electromagnetic and thermal performance study on a canted stack of REBCO tapes

Abstract Due to the critical current limitation of a single REBCO tape, stacking methods are generally employed to increase the current carrying capacity in practical high-temperature superconducting (HTS) applications. However, the overall critical current is strongly dependent on the self-magnetic field, which is influenced by the geometrical arrangement of conductors in the stack. Due to the brittle ceramic property, REBCO tapes are conventionally bent along the thickness side of the tape. However, the difference in bending radii of the outer and inner tape surfaces in the stack may lead to fracture deformation, thereby limiting the stacking number of REBCO tapes. To balance the stacking number with the bending issue, canted stack is proposed as a variant of normal stack for REBCO tapes. As a potential HTS intermediate component, it is imperative to conduct a comprehensive study on electromagnetic and thermal performance of canted stack. The unique geometrical arrangement of canted stack introduces new factors that affect critical current and transport AC loss. This paper concludes the special influencing factors of canted stack, including canted angle, stacking number, tape width, and spatial structure. The metal interleaving method is introduced for spatial distribution changing and thermal stability. Furthermore, orthogonal analysis is performed to elucidate the comprehensive correlation among these multiple factors. This study provides insights into the overall critical current and transport AC loss for different combinations of canted stack and establishes a predicting function for critical current to support the structural design of canted stack. Based on the specific case study, the improvement effect of canted stack is confirmed by both experiments and simulations.

Deactivation mechanism of NiWS/SAPO-11 catalyst in hydroisomerization of n-hexadecane: Insights into coke deposition behavior and active phase migration

The application of non-noble metal supported catalysts in the hydroisomerization of long-chain n-alkanes is a novel field, and there is currently not any research available on the deactivation process of these catalysts. We investigated into the deactivation mechanism of NiWS/SAPO-11 catalyst in the hydroisomerization of n-hexadecane in this work for the first time. Specifically, coke deposition behavior and active phase migration were investigated. The reduction of catalytic efficiency of the catalyst was partially aided by the decrease in specific surface area, pore volume, and acid density. From the perspective of the active phase, the clusters of NiWS active phase migrated as the reaction time increased, mostly resulting in an increase in both the stacking number and the length of active phase slabs. The migration of active phase increased the distance between active phase clusters and metal sites, and decreased the utilization ratio of active metal atoms. From the perspective of coke deposition, the coke formed on the catalyst includes soft coke and hard coke. The formation and evolution of coke on the catalyst were investigated. The soft coke (aliphatic compounds) progressively transformed into hard coke (polycyclic aromatic hydrocarbons and graphite-like), and the coke gradually migrated from the external surface of the catalyst to the pore channels as the reaction time increased. It is expected to provide theoretical basis and reference value for the deactivation research and design of non-noble metal supported hydroisomerization catalyst.

Electro-mechano transduction of stacked triboelectric nanogenerator considering wave force: Modeling, validation and applications

Aiming at the low-frequency characteristics of ocean wave energy, triboelectric nanogenerators (TENGs) provide an efficient collection method. We propose a multi-layer contact-separation mode triboelectric nanogenerator (MS-TENG) based on a frequency-up mechanism to collect water wave energy. First, we study the effects of frequency rising and TENG unit stacking on the output of the MS-TENG. Experiments show that the short-circuit current of the MS-TENG with 12 layers stacked is 152.16 μA when the rotating speed is 60 rpm. Compared with a single TENG unit, the short-circuit current of the MS-TENG is increased by 6.35 times. Second, the hydrodynamic simulation method is used to study the force and energy capture efficiency of floating bodies with different shapes in water waves. The results show that the energy capture efficiency of the cylindrical floating body is 70.14 % higher than that of the spherical floating body under the same volume. Third, we use a cylindrical floating body to package the MS-TENG. In water tank experiments, when the load resistance is 4 MΩ, the peak power density of the packaged MS-TENG is 14.56 W/m3. In addition, with the help of the MS-TENG, we set up a wireless temperature and humidity monitoring system to realize the preliminary marine environmental monitoring.

Predicting anion diffusion in bentonite using hybrid machine learning model and correlation of physical quantities

Radionuclide diffusion will be influenced by numerous factors. Establishing a model that can elucidate the internal correlation between mesoscopic diffusion and the microscopic structure of bentonite can enhance the comprehension of radionuclide diffusion mechanisms. In this study, a light gradient boosting machine (LightGBM) was employed to predict the effective diffusion coefficients of HCrO4−, I−, and CoEDTA2− in bentonite. The model's hyperparameters were optimized using the particle swarm optimization (PSO) algorithm. Several correlated physical quantities, such as mesoscopic parameters (total porosity, rock capacity factor, and ion molar conductivity) and microscopic parameters (ionic radius and montmorillonite stacking number) were incorporated to develop a machine learning model that incorporated micro- and meso-scale features. The predictive performance of PSO-LightGBM was verified using diffusion experiments, which investigated the diffusion of HCrO4−, I−, and CoEDTA2− at compacted dry densities of 1200–1800 kg/m3 using a through-diffusion method. Spearman correlation and Shapley additive explanation analyses revealed that the compacted dry density, ionic diffusion coefficient in water, ionic radius, and total porosity were the top-four influencing factors among the 16 input features. Partial dependence plot analysis elucidated the relationship between the effective diffusion coefficient and each input feature. The analysis results were consistent with the experimental findings, demonstrating the reliability of machine learning. Due to the incorporation of multi-scale features, the PSO-LightGBM model demonstrated enhanced predictive accuracy, linking the microstructure of bentonite to radionuclide diffusion, and providing a comprehensive interpretation of the diffusion mechanism.

Observation of broad triangular Frank-type stacking faults and characterization of stacking faults with emission wavelengths below 430 nm in 4H–SiC epitaxial layers

Frank-type stacking faults in 4H–SiC epitaxial layers were investigated using room-temperature photoluminescence mapping and high-angle annular dark-field high-resolution scanning transmission electron microscopy. Remarkably, the intrinsic Frank-type stacking fault (5,2) and intrinsic multilayer Frank-type stacking fault (4,2), which have been reported to have elongated triangular shapes to date, were found to have broader triangular shape, which was typical shape of Shockley-type stacking faults. The shaping of stacking faults could be explained based on the directions of the partial dislocations bounding the stacking faults. Formation models for the intrinsic (5,2) and (4,2) stacking faults were proposed. In addition, we observed Frank-type stacking faults (3,2,2,3) and (3,3) and Shockley-type stacking faults (3,3,3,2,3,2) and (3,2,3,3,3,2), which were not reported before. All of these stacking faults were composed with the stacking numbers 2 and 3 in the Zhdanov notation and showed very close characteristic photoluminescence emission wavelengths of 427–428 nm. Formation models for the stacking faults of (3,2,2,3), (3,3), (3,3,3,2,3,2), and (3,2,3,3,3,2) were proposed, also. Based on the proposed formation models of (4,2) and (3,3) stacking faults, formation models for the Frank-type stacking faults (4,1) and (3,2) were discussed. Finally, we pointed out that the (4,1) Frank-type stacking fault should be the intrinsic not the extrinsic fault, and the (3,2) Frank-type stacking fault is the extrinsic fault.

Wafer-level substrate-free YIG single crystal film for a broadband tunable terahertz isolator

Yttrium iron garnet (YIG) is a promising material for various terahertz applications due to its special optical properties. At present, a high-quality YIG wafer is the desire of terahertz communities and it is still challenging to prepare substrate-free YIG single crystal films. In this work, we prepared wafer-level substrate-free La:YIG single crystal films, for the first time, to our knowledge. Terahertz optical and magneto-optical properties of La:YIG films were characterized by terahertz time domain spectroscopy (THz-TDS). Results show that the as-prepared La:YIG film has an insertion loss of less than 3 dB and a low absorption coefficient of less than 10 cm−1 below 1.6 THz. Benefitting from the thickness of the substrate-free YIG films and low insertion loss, their terahertz properties could be further manipulated by simply using a wafer-stacking technique. When four La:YIG films were stacked, there was an insertion loss of less than 10 dB in the range of 0.1−1.2 THz. The Faraday rotation angle of the four-layer-stacked La:YIG films reached 19°, and the isolation could reach 17 dB. By further increasing the stacking number to eight pieces, a remarkable Faraday rotation angle of 45° was achieved with an isolation of 23 dB, which is important for practical application in the THz band. This material may provide a milestone opportunity to make various non-reciprocal devices, such as isolators and phase shifters.

Tailored synthesis of plate-like SAPO-11 molecular sieve and its application in non-noble metal-supported catalyst for efficient hydroisomerization of long-chain n-alkanes

The tailored synthesis of plate-like SAPO-11 molecular sieve was achieved by introducing seed-surfactant directing agent into the synthesis system for the first time. The effects of morphological change of SAPO-11 molecular sieve on the physicochemical properties of SAPO-11 and the active phase properties of the catalyst were analyzed via a series of characterization techniques. The hydroisomerization of n-hexadecane was used as the model reaction to evaluate the catalytic performance of NiWS supported catalysts based on SAPO-11 molecular sieve with different morphologies. The plate-like SAPO-11 possessed better textural properties and acidity than pseudo-spherical SAPO-11. Meanwhile, the stacking number, dispersion and metal sulfidation degree of the active phase of sulfided NiW/SAPO-11-P were improved, and its high proportion of type II active phase optimized the metal–acid synergistic catalytic mechanism. Through tracking and analyzing the crystallization process of plate-like SAPO-11, the formation mechanism of plate-like SAPO-11 was investigated and revealed. The adsorption kinetics, diffusion behavior and catalytic kinetics of n-hexadecane on the catalysts were emphatically investigated. The optimized support structure and active phase properties improved the intrinsic catalytic activity and hydroisomerization reaction path priority of NiW/SAPO-11-P. It was found that the hydroisomerization reaction on NiW/SAPO-11-P was carried out under the reaction-limiting conditions, while the hydroisomerization reaction on NiW/SAPO-11-C was carried out under the reaction-controlling conditions. The effects of plate-like SAPO-11 on the activity stability of the catalyst was investigated, and the essential reasons for the differences in activity stability of the catalysts were revealed through comprehensively analyzing the coke formation difference and diffusion behavior difference. It is expected to provide reference for the tailored design of SAPO-11 molecular sieve with special morphology and the preparation of efficient hydroisomerization catalyst.

In situ synthesis of mesoporous NiS2-MoS2 sphere-flower hybrid for hydrodesulfurization of thiophene and 4,6-dimethyl-dibenzothiophene

A series of new NiS2-MoS2-x (x = 0–0.5) sphere-flower hybrids with different Ni/Mo molar ratios, synthesized via a one-pot hydrothermal method, were used as catalysts for hydrodesulfurization (HDS) of thiophene (TP) and 4,6-dimethyl-dibenzothiophene (4,6-DMDBT). The characterizations show that the microstructure of MoS2, including the size of MoS2 nano-flowers, the length of MoS2 slabs, and the number of defects, was regulated by changing Ni/Mo ratios. Increasing the Ni/Mo ratio in the NiS2-MoS2-x catalysts significantly boosts their HDS activity, with the optimum ratio being 0.2. In addition, the NiS2-MoS2-0.2 catalyst exhibits the best direct desulfurization performance, which is associated with the minimum ratio of average slab length (Lav) to average stacking number (Nav) as well as the highest concentration of Ni-promoted Mo sites and sulfur vacancies. Moreover, Ni-containing NiS2-MoS2-x catalysts, characterized by a highly stable sphere-flower configuration, exhibit superior structural stability and catalytic durability than the Ni-free NiS2-MoS2-0 catalyst.

Mechanistic insight into the coke formation tendency during upgradation of crude oil in slurry phase batch reactor using MoS2 and its various oil soluble catalysts

This work intends to provide a deep insight on how can the MoS2 and its oil soluble analogues synthesized using various organic acid ligands (oleate, palmitic acid, lauric acid, stearic acid) efficiently fits well into the landscape of refinery and petrochemical integrations. The slurry phase hydroprocessing of crude oil has been efficiently carried out at 420 °C temperature and 120 bar H2 pressure. The hydroprocessing of crude oil presents the prominent results by increasing the lighter and more valuable fractions in the crude oil, as obtained from SARA analysis result, boiling point distribution, viscosity, sulfur and MCR data. The oil soluble MoS2 catalyst (MLT) synthesized from sodium oleate presented better hydroprocessing activity (65 % VR conversion) than other catalysts due to the small crystallite size, greater hydrophobic interaction, low stacking number and slab length. In this study, the comprehensive analysis of the solid coke obtained from both thermal and catalytic reactions are conducted using the XRD to get various structural parameters (average layer distance between two aromatic sheets (dm), average inter-chain layer distance (dλ), average perpendicular height of stack of aromatic sheets (Lc), average diameter of aromatic sheet (La), and average number of stacked aromatic sheets (M)) to elucidate the coke formation mechanism. These findings highlight the crucial role of catalysts in activating supplied hydrogen gas and promoting the hydrocracking reactions.

Design of active phase structure with high activity and stability in residue hydrotreating reactions

The catalyst with well-dispersed (Ni)MoS2 active phase characteristic of short slab length and low stacking numbers was designed by strengthening metal-support interaction (MSI) and metal dispersion, which displayed high activity and long-term stability in real-life residue hydrodesulfurization (HDS) reactions. Furthermore, the impacts of pseudo-boehmite and catalyst calcination temperature on surface properties were thoroughly investigated. Mo equilibrium adsorption method, Al27 NMR, XRD, Raman, UV–Vis DRS, and H2-TPR characterization showed that the hydroxyl groups concentration and tetrahedral cation vacancies increased upon reducing the pseudo-boehmite extrudates calcination temperature. Increasing calcination temperature of the catalysts further strengthened MSI, resulted in well-dispersed Mo species with enhanced MSI. Therefore, well-dispersed (Ni)MoS2 active phase was acquired on novel designed catalyst. XPS coupled with HRTEM indicated that the more potential active sites, less propensity for active phase evolution and gradual increase in sulfidation degree with processing time contributed to the high HDS performance of the designed active phase. This work can deepen our understanding toward evolution pattern of active phase during residue HDS catalysts, and give guidance for developing high performance catalyst by strengthening MSI and enhancing metal dispersion.

Engineering Symmetry Breaking Enables Efficient Bulk Spin‐Orbit Torque‐Driven Perpendicular Magnetization Switching

AbstractTo overcome the interfacial nature of spin‐orbit torque (SOT) in bilayers, novel bulk SOT (BSOT) is widely investigated to implement high‐density and low‐power spintronic devices. However, the underlying mechanism of efficient BSOT switching remains unclear, especially the anomalously enhanced effective spin Hall angle (θSH) with increasing ferromagnet thickness (tFM), due to lacking simple and high‐tunable material systems. Here, a series of Pt/Co multilayers with invariable thickness gradient and varying stacking numbers is designed to systematically explore BSOT origin and enable efficient switching via engineering symmetry breaking. As tFM increases, the critical current density decreases while the switching efficiency and θSH build up. Comparative experiments directly demonstrate that gradient‐induced local spin current is more efficient than that in the bilayer. Moreover, x‐ray absorption spectroscopy (XAS) results reveal that the increasing stacking number can effectively engineer the symmetry breaking at Pt/Co interface to induce strong interfacial spin‐orbit coupling. On this basis, it is concluded that the BSOT effect, as well as the anomalously enhanced switching efficiency, and θSH arises from gradient‐induced bulk and interface symmetry breaking. These findings clarify the underlying mechanism of BSOT, and broaden the scope of material engineering to improve switching efficiency and inspire more memory and computing applications.

Eco-friendly polycaprolactone-bound diatomite filter for the removal of metal ions and micro/nanoplastics from water

Over the last few decades, pollution levels in aquatic environments due to heavy metal ions and micro/nanoplastics have increased owing to industrial development, causing adverse effects on microorganisms. Adsorbent-based filtration is a well-developed technique for removing contaminants from aquatic environments. However, this technique should be improved from the perspectives of eco-friendliness and cost-effectiveness, as commercial adsorbents require energy-intensive synthesis and post-processing with chelating agents. In this study, an eco-friendly filtration system was developed. This system employs biodegradable, natural materials, such as diatomite to remove metal ions and micro/nanoplastics and polycaprolactone (PCL) to make the free-form shapes. The filter removes metal ions via adsorption and micro/nanoplastics via physical size filtration and adsorption. This PCL-bound diatomite filter was fabricated from a mixture of acetone, PCL, and diatomite, varying its size, thickness, shape, and stacking number for a particular objective and usage. The adsorption capacity, kinetics, and permeation flux of the membrane were measured, and the stacking number of the membranes were optimized to maximize the removal efficiency of the target contaminants. This filter is completely biodegradable, as indicated by the degradation of the PCL binder within 60 days in water, without any treatment. The degradable, eco-friendly PCL-bound diatomite filter is a low-cost and sustainable component that can be utilized in various applications, especially potable drinking water production from river in developing country and filtering the micro/nanoplastics from the commercially bottled drinking water in daily life.

Correlation of Magnetomechanical Coupling and Damping in Fe80Si9B11 Metallic Glass Ribbons.

Understanding the correlation between magnetomechanical coupling factors (k) and damping factors (Q-1) is a key pathway toward enhancing the magnetomechanical power conversion efficiency in laminated magnetoelectric (ME) composites by manipulating the magnetic and mechanical properties of Fe-based amorphous metals through engineering. The k and Q-1 factors of FeSiB amorphous ribbons annealed in air at different temperatures are investigated. It is found that k and Q-1 factors are affected by both magnetic and elastic properties. The magnetic and elastic properties are characterized in terms of the magnetomechanical power efficiency for low-temperature annealing. The k and Q-1 of FeSiB-based epoxied laminates with different stacking numbers show that a -3 dB bandwidth and Young's modulus are expressed in terms of the magnetomechanical power efficiency for high lamination stacking.

Highly Efficient Quasi 2D Blue Perovskite Electroluminescence Leveraging a Dual Ligand Composition

AbstractPerovskite light‐emitting diodes (PeLEDs) are advancing because of their superior external quantum efficiencies (EQEs) and color purity. Still, additional work is needed for blue PeLEDs to achieve the same benchmarks as the other visible colors. This study demonstrates an extremely efficient blue PeLED with a 488 nm peak emission, a maximum luminance of 8600 cd m−2, and a maximum EQE of 12.2% by incorporating the double‐sided ethane‐1,2‐diammonium bromide (EDBr2) ligand salt along with the long‐chain ligand methylphenylammonium chloride (MeCl). The EDBr2 successfully improves the interaction between 2D perovskite layers by reducing the weak van der Waals interaction and creating a Dion–Jacobson (DJ) structure. Whereas the pristine sample (without EDBr2) is inhibited by small stacking number (n) 2D phases with nonradiative recombination regions that diminish the PeLED performance, adding EDBr2 successfully enables better energy transfer from small n phases to larger n phases. As evidenced by photoluminescence (PL), scanning electron microscopy (SEM), and atomic force microscopy (AFM) characterization, EDBr2 improves the morphology by reduction of pinholes and passivation of defects, subsequently improving the efficiencies and operational lifetimes of quasi‐2D blue PeLEDs.

Effect of organic phosphorus addition on the state of active metal species and catalytic performance of NiW/Al2O3 hydrodesulfurization catalyst

This article proposes a novel organic additive 1-hydroxyethylidene-1,1-diphosphonic acid (HEDP) for the preparation of NiW/Al2O3 efficient hydrodesulfurization (HDS) catalysts. The effects of HEDP on the nature of the tungsten and nickel species supported on the support surface after drying and calcination steps were revealed by employing ultraviolet–visible spectroscopy (UV–Vis), Raman spectroscopy, N2 adsorption–desorption and H2 temperature programmed reduction (H2-TPR). While the slab morphology and the proportion of NiWS phases were determined by X-ray photoelectron spectroscopy (XPS) and high-resolution transmission electron microscopy (HRTEM). Finally, dibenzothiophene (DBT) was used as a probe to evaluate the effects of HEDP modification on the catalytic performance of the prepared catalyst. The results indicate that the addition of HEDP can facilitate the formation of more polymerized tungsten oxide species and improve the availability of surface nickel atoms. The weakened interaction between active metals and support generate higher stacking numbers and shorter slab lengths among WS2 crystals on the corresponding catalyst, promote the sulfidation of both Ni and W species and enhance the proportion of NiWS phase. The catalytic evaluation results show that the HEDP-modified catalyst exhibits efficient HDS activity and higher DDS selectivity compared to the phosphoric acid-modified reference catalyst, which is attributed to a large number of accessible NiWS active sites. The present work relates the addition of organic additives with the formation of NiW species and the catalytic activity. The results highlight that the addition of HEDP is an effective strategy to improve the performance of HDS catalysts.

Physical Layer Authentication Based on Channel Polarization Response in Dual-Polarized Antenna Communication Systems

This study presents a novel approach for physical layer authentication based on channel polarization response (CPR). CPR is sensitive to variation in the physical properties of scatterers, and the CPR difference between various channels is higher than the channel frequency response (CFR) under rich scattering scenarios. Additionally, the estimation of CPR is continuous, the authentication interval can be adjusted according to the channel coherence time, then the proposed scheme can be applied to any rich scattering scenarios, including highly dynamic scenarios. Since the received polarization state is fixed during the channel coherence time, we can coherently stack the received polarization state to improve the signal to noise ratio (SNR) and the estimation accuracy of CPR, thereby achieving high authentication accuracy under ultra-low SNR. Moreover, since the transmitted polarization state of various transmitters is different, because of their unique hardware deficiencies, and since the CPR is dependent on the transmitted polarization state, the CPR of other transmitters is different, allowing the resolution of co-located attacks. We theoretically drive the false alarm probability, detection probability, optimal discriminant threshold, computational complexity, optimal stacking numbers, and optimal CPR points for authentication. Furthermore, extensive simulations and experiments are performed to verify the validity and effectiveness of the proposed scheme.

In‐situ Synthesis of Gallium‐Containing SAPO‐11 Molecular Sieves and Superior Catalytic Performance of Their NiWS Supported Catalysts for Hydroisomerization of n‐Hexadecane

AbstractIn order to prepare a high‐performance SAPO‐11 (silicoaluminophosphate‐11) based non‐noble metal supported catalyst for the hydroisomerization of long‐chain n‐alkanes, gallium‐modified SAPO‐11 molecular sieve was successfully synthesized by the in‐situ synthesis method, and the NiWS supported catalyst was prepared for the hydroisomerization of n‐hexadecane. The effects of Ga‐modification on the physicochemical properties of SAPO‐11 molecular sieve, the active phase properties, and the catalytic performance of the catalyst were studied. Through a series of physicochemical characterizations, it was found that the introduction of Ga increased the mesoporous volume of SAPO‐11 molecular sieve, reduced their acid density and strength, but improved the amount of medium‐strong Brønsted acid. The Ga‐modification weakened the interaction between the active metals and the support, increased the sulfidation degree of active metals, and increased the stacking number and dispersion of active phase. The results of catalytic performance evaluation showed that the catalytic activity and isomerization selectivity of the Ga‐modified SAPO‐11 molecular sieve based catalysts were improved, and the yield of i‐hexadecane of NiW/2Ga‐SAPO‐11 was the highest, which was 40.30 % higher than that of NiW/SAPO‐11. By analyzing the distribution of isomeric products, it was found that the Ga‐modified SAPO‐11 molecular sieve was helpful in improving the hydroisomerization depth of n‐hexadecane over the catalyst.

Porosity investigation of compacted bentonite using through-diffusion method and multi-porosity model

The diffusion behavior of ReO4− and HSeO3− in low-grade bentonites was firstly investigated under different compacted dry densities. The effective diffusion coefficient, the accessible porosity, and the rock capacity factor were measured by a through-diffusion method. The effective diffusion coefficient was approximately three times in Zhisin bentonite with 36.8 wt% of montmorillonite than that in GMZ bentonite with 74.5 wt% of montmorillonite. The porosity distribution of the compacted bentonite was analyzed by a multi-porosity model. The effects of the compacted dry density, the ionic strength, and the stacking number on porosities were discussed. The compacted dry density had obvious influence on the accessible porosity, the diffuse double layer porosity, and the interlayer porosity. The effects of ionic strength and stacking number were mainly on the diffuse double layer porosity, leading to the alteration of the accessible porosity and the effective diffusion coefficient. Moreover, the multi-porosity model could successfully predict the trend of effective diffusion coefficient in compacted bentonite combined with Archie law, which provides a useful tool to understand the relationship between the microstructure of montmorillonite and the diffusion of radionuclide anions.