Solid Surface Area Research Articles

International comparisons in the field of measuring specific adsorption of gases and specific surface area of solids: optimizing the number of comparisons to ensure calibration and measurement capabilities

International comparisons in the field of measuring specific adsorption of gases and specific surface area of solids: optimizing the number of comparisons to ensure calibration and measurement capabilities

Influence of design parameters on natural convection heat transfer in additively manufactured body centered cubic lattice structures

The natural convection heat transfer mechanism of the body centered cubic (BCC) lattice structure needs to be clarified for its application in passive cooling thermal management. The BCC lattice heat sinks with various design parameters, such as strut diameter and unit cell length, were fabricated using the laser powder bed fusion process. Subsequently, the thermal performance was experimentally determined for variations in design parameters. The thermal performance tended to be maximized when the relative density of the lattice heat sink constituted approximately 10 %. The numerical analysis was performed to figure out the heat transfer mechanism and investigate the effects of inclination angles. According to numerical results, a lattice heat sink with a smaller strut diameter at the given unit cell length entrains more air than one with a larger strut diameter. However, decreasing strut diameter led to a negative impact on conduction and radiation heat transfer due to the reduction in solid region and surface area. Depending on the inclination angle, thermal performance of a lattice heat sink proportionally decreases. The main cause of performance degradation was the hindrance of plume motion by the base of the heat sink.

Prediction of Protein-DNA Interface Hot Spots Based on Empirical Mode Decomposition and Machine Learning.

Protein-DNA complex interactivity plays a crucial role in biological activities such as gene expression, modification, replication and transcription. Understanding the physiological significance of protein-DNA binding interfacial hot spots, as well as the development of computational biology, depends on the precise identification of these regions. In this paper, a hot spot prediction method called EC-PDH is proposed. First, we extracted features of these hot spots' solid solvent-accessible surface area (ASA) and secondary structure, and then the mean, variance, energy and autocorrelation function values of the first three intrinsic modal components (IMFs) of these conventional features were extracted as new features via the empirical modal decomposition algorithm (EMD). A total of 218 dimensional features were obtained. For feature selection, we used the maximum correlation minimum redundancy sequence forward selection method (mRMR-SFS) to obtain an optimal 11-dimensional-feature subset. To address the issue of data imbalance, we used the SMOTE-Tomek algorithm to balance positive and negative samples and finally used cat gradient boosting (CatBoost) to construct our hot spot prediction model for protein-DNA binding interfaces. Our method performs well on the test set, with AUC, MCC and F1 score values of 0.847, 0.543 and 0.772, respectively. After a comparative evaluation, EC-PDH outperforms the existing state-of-the-art methods in identifying hot spots.

International comparisons in the field of measurement of specific adsorption of gases and specific surface area of solids: the optimal amount to ensure calibration and measurement capabilities

Indicators of the accuracy of measurements of the most important characteristics of the structure of porous and dispersed materials - specific adsorption of gases, specific surface area, specific pore volume and pore size – are considered. The performance of sorbents, catalysts and membranes in the chemical and petroleum industries, including the purification of substances and materials, depends on the values of these characteristics. It has been established that for mutual recognition of national standards and certificates of calibrations and measurements of porosity characteristics of solid substances performed by national metrological institutes, it is required to organize and successfully participate in three international key comparisons under the auspices of the Consultative Committee for Amount of Substance: Metrology in Chemistry and Biology of the International Bureau of Weights and Measures. The results of the participation of national metrology institutes and designated organizations of Germany, China, Japan, Brazil, Turkey and Russia in three international key comparisons in the field of measurements of specific adsorption of gases (nitrogen, argon, krypton) and specific surface area of solids (zeolite, silicon oxides and aluminum) are presented. Carrying out the optimal number of comparisons makes it possible to register in the Key Comparison Database of the International Bureau of Weights and Measures the measuring and calibration capabilities of the national metrological institutes of the participating countries for various matrices in a wide range of measurements of specific adsorption of gases 0.001–25 mol/kg and specific surface area of solids 0.1–1500 m2/g. Based on the results of these three international key comparisons, 18 of broad calibration and measurement capabilities of the Russian participant, the D. I. Mendeleev Institute for Metrology, were entered into the Key Comparison Database; two of these items are currently undergoing examination, including reference materials produced by this institute. A comparative analysis of the results of measurements of the specific surface area of solids using nitrogen and krypton as adsorbates was performed. It has been established that the uncertainty of the measurement results of the specific surface area is significantly less in the case of using krypton as an adsorbate with a specific surface area of less than 1 m2/g, which is due to the higher values of the relative pressure of krypton compared to nitrogen. The use of calibration and testing laboratories in Russia of certified reference materials of sorption properties presented in the Key Comparison Database of the International Bureau of Weights and Measures will ensure metrological traceability in the field of measurements of porosity characteristics.

Image-based finite element modeling of air flow and thermal transport in Al-fiber-sintered porous materials

In this study, the pressure drop and heat transfer in a heat-transfer tube filled with a sintered porous medium comprising Al fibers were investigated using computational fluid dynamics (CFD) simulations. We reconstructed the sintered fibrous porous structure and generated a computational mesh using X-ray computed tomography data, and the simulated pressure drop and heat transfer agreed well with those reported by Enoki et al. [2021]. The differences in both the form coefficient and the permeability between two different samples can be explained from the differences in both the specific solid surface area and the porosity. Further, the CFD simulations indicated that thermal conduction of the Al solid phase enhanced the heat exchange between the air and Al fibers. To examine the effect of solid-phase thermal conduction, we generated a model of a heat-transfer tube having an ideal wire mesh structure, in which we introduced the interfacial thermal conductivity between Al fibers and the inner tube wall as additional factors. We also performed CFD simulations with four different shell-region thicknesses and found that even a very narrow gap of 5 to 10 μm heavily affected the heat-exchange performance because of the low thermal conductivity of the shell region.

Effect of Intermittent Low-Pressure Radiofrequency Helium Cold Plasma Treatments on Rice Gelatinization, Fatty Acid, and Hygroscopicity.

To establish the safe and reproducible effects of cold plasma (CP) technology on food products, this study evaluated the gelatinization parameters, fatty acid profile, and hygroscopic properties of rice grains repeatedly treated with low-pressure radiofrequency (RF) helium CP (13.56 MHz, 140 Pa, 120 W-20s, 0-4 times, and 300 g sample). Compared with the untreated (zero times) sample, with an increase in CP treatment times from one to four on rice, the water contact angle and cooking time decreased, while the water absorption rate and freshness index increased, and the pH value remained unchanged. CP repeating treatments essentially had no effect on the gelatinization enthalpy, but significantly increased the peak temperature of gelatinization. From the pasting profile of rice that has been repeatedly CP treated, the peak, breakdown, and setback viscosities in flour paste decreased. CP repeating treatments on rice did not change the short-range molecular order of starch. Compared with the untreated sample, the first helium CP treatment maintained the content of C18:1n9c, C18:2n6c, and C18:3n3, but the second to fourth CP treatment significantly decreased contents of these fatty acids (FAs) as the C18:0 content increased. The first three CP treatments can increase the water and sucrose solvent retention capacity in rice flours. CP repeatedly treated rice first exhibits the similar monolayer water content and solid surface area of water sorption. Principal component analysis shows that contact angle, pasting parameters, and fatty acid profile in milled rice are quite sensitive to CP treatment. Results support that the effect of low-pressure RF 120W helium CP treatment 20 s on rice grains is perdurable, and the improvement of CP intermittent treatments on rice cooking and pasting properties is an added benefit, and the hygroscopic properties of rice was kept.

Influence of pin-perforation shape on thermohydraulic performance of circular pin-fin heat sinks under turbulent flow

The impact of pin-perforation shape on the thermohydraulic performance of circular pin–fin heat sinks (CPFHS) under turbulent flow conditions is numerically assessed using a computational fluid dynamics software. The convective heat transfer efficiency, hydraulic resistance, and thermohydraulic performance of four pin-perforation shapes: square diamond, triangle, hexagon, and circle, are evaluated under various turbulent flow conditions (Reynolds number between 24,484 to 55,088). The sizes of all pin-perforation shapes are under a constraint that the ratio of the air–solid interfacial surface area to the total volume of pin-perforated CPFHS must be the same. The results show that all pin-perforated CPFHS demonstrate a higher Nusselt number compared to unperforated CPFHS. Those with circular perforations exhibit the highest Nusselt number with up to 39% improvement compared to unperforated CPFHS, followed by those with hexagonal, triangular, and diamond perforations, respectively. The Nusselt numbers correlate with the ease of fluid flow within perforations which is expressed using the average air velocities through perforations. In terms of hydraulic resistance, all pin-perforated CPFHS exhibit a reduction in friction factor compared to unperforated CPFHS. Among these, the largest decrease in friction factor, up to 15.8%, is observed in CPFHS featuring circular perforations, followed by those with hexagonal, diamond, and triangular perforations, respectively. The friction factors are influenced by the ratio of perforation perimeter to cross-sectional area. All pin-perforated CPFHS have a thermal performance factor greater than 1, indicating an improvement in thermohydraulic performance compared to unperforated CPFHS. CPFHS with circular perforations yield the highest thermal performance factor, reaching up to 1.44, followed by hexagonal, triangular, and diamond pin configurations, in descending order. With increasing Reynolds numbers, thermal performance factors of pin-perforated CPFHS initially rise, then gradually decline, suggesting that thermohydraulic advantages due to pin–fin perforations are diminishing as the flow become more turbulent.

Direct and non-contact measurement of liquid fraction in unconstrained encapsulated PCM melting

Almost all of the experiments on PCM melting rely on temperature measurement. However, based on the experimental evidence, the presence of a thermometer in the solid PCM affects the results. Because the solid phase covers the probe and in fact, the solid phase temperature is measured instead of the liquid phase. On the other hand, since the PCM sticks to the probe, the regime of melting can change from unconstrained to constrained melting. In this study, a new method is proposed to measure directly the liquid mass fraction of PCM during melting. This method can be categorized as a non-contact measurement method and is based on the image processing technique.In this method, images of the melting process are prepared under controlled conditions at successive times. By performing image processing techniques, the solid core boundary is determined and the enclosed area is calculated and divided by the solid phase initial surface area. The method was applied to PCM melting inside a cylinder. Meanwhile, the problem was also simulated numerically by the multi-phase method (VOF). The multi-phase method allows considering the change in the total volume of PCM (summation of volumes of both solid and liquid phases) due to the difference between solid and liquid densities. Good agreement was observed between numerical and experimental results. The RMSE was 1.8 %. Moreover, it was observed that the shapes and sizes of the solid core in experimental images and numerical results at different times match well. But for lower solid volume fractions, the solid core sinks deeper in experimental images in comparison with numerical results.

Kinetics and spectroscopic characterization of silica nanoparticles formed while etching quartz in hydrofluoric acid

The kinetic regularities of the silica nanoparticles formed during the quartz etching in hydrofluoric acid were explored for the first time. The main drivers for nanoparticle formation, as well as for the etching reaction of quartz, are the concentration of hydrofluoric acid and the ratio of the solid surface area to the liquid volume. Kinetic factors combined with nanoparticle interaction and agglomeration lead to kinetic changes of their concentrations. The proportion of nanoparticles in the weight balance with the dissolved solids decreases significantly and remains in the 0.03% range during quartz etching. XPS analysis of nanoparticles identified elements of Si, O, and F in chemical states such as Si–O, Si-Ox, SiO2, and F–Si. FT-IR reflection also identified the stretching and bending vibration peaks of the Si–O–Si and O–H. The wide fluorescence peak with a maximum at ∼633–650 nm matches the spectrums of known non-bridging oxygen centers ≡Si–O∙. The UV absorption band with maximum in the range of 195–197 nm, detected for nanoparticle samples in liquid, belongs to the silica E’ defect centers ≡Si. In some spots of the deposited nanoparticles Raman peaks are recorded, which is typical for crystal forms of silica. Using AFM, 3D images of nanoparticles deposited on silicon or glass wafers reveal the grain size range of the particles and the feedback between the morphology of the deposited layers and the surface hydrophilicity. The high stability of the quartz etching nanoparticles in hydrofluoric acid explained their structural specificity because they have a surface fluorinated layer consisting of Si–F bonds around the silica grains. The lack of known molybdate-reactive silica inspection methods for the analysis of etching nanoparticles is disclosed. On the basis of the experimental data, new approaches are proposed for the cleaning of quartz parts from particles and for operative inspection of cleanliness.Silica, nanoparticles, etching, quartz, fluorescence, FT-IR, XPS, NP-ICP-MS.

Determining air-water interfacial areas for the retention and transport of PFAS and other interfacially active solutes in unsaturated porous media

The objective of this work was to determine the methods that produce the most representative measurements and estimations of air-water interfacial area specifically for the retention and transport of PFAS and other interfacially active solutes in unsaturated porous media. Published data sets of air-water interfacial areas obtained with multiple measurement and prediction methods were compared for paired sets of porous media comprising similar median grain diameters, but one with solid-surface roughness (sand) and one without roughness (glass beads). All interfacial areas produced with the multiple diverse methods were coincident for the glass beads, providing validation of the aqueous interfacial tracer-test methods. The results of this and other benchmarking analyses demonstrated that the differences in interfacial areas measured for sands and soil by different methods are not due to errors or artifacts in the methods but rather the result of method-dependent differential contributions of solid-surface roughness. The contributions of roughness to interfacial areas measured by interfacial tracer-test methods were quantified and shown to be consistent with prior theoretical and experiment-based investigations of air-water interface configurations on rough solid surfaces. Three new methods for estimating air-water interfacial areas were developed, one based on the scaling of thermodynamic-determined values and the other two comprising empirical correlations incorporating grain diameter or NBET solid surface area. All three were developed based on measured aqueous interfacial tracer-test data. The three new and three existing estimation methods was tested using independent data sets of PFAS retention and transport. The results showed that the method based on treating air-water interfaces as smooth surfaces as well as the standard thermodynamic method produced inaccurate air-water interfacial areas that failed to reproduce the multiple measured PFAS retention and transport data sets. In contrast, the new estimation methods produced interfacial areas that accurately represented air-water interfacial adsorption of PFAS and associated retention and transport. The measurement and estimation of air-water interfacial areas for field-scale applications is discussed in light of these results.

Catalytic methane halogenation by bromine over microporous SAPO-34 zeolite material towards methyl bromide, dibromomethane and hydrogen bromide

Background:Bromination-based methane conversion is one of the promising separate ways of CH4 valorisation. Both methyl bromide/dibromomethane that are formed can be subsequently transformed into more useful compounds. SAPO-34 could also improve the selectivity (S) towards bromomethane during bromination.Methods:To evaluate the performance of SAPO-34 in this reaction process, the influence of time, temperature (T) and weight hourly space velocity (WHSV) rate was investigated in a packed-bed reactor. T was in the range of 310–420 ∘C, while WHSV was 0.22–1.20 h−1. The molar CH4 to bromine ratio was 5.4:1. GC–MS was used for analysis of products. Material was characterized by XRD, SEM, NH3-TPD, N2 physisorption.Significant findings:In the material used for the reaction crystallinity was decreased, solid surface area was reduced, and the density of Brønsted acid sites was also reduced compared to the fresh material. Changes can be attributed to Al2O3 loss or also the breakage of Al–O–P bonds, caused by hydrogen bromide ions that are produced. A presence of coke was observed on the zeolite at T higher than 360 ∘C. CH2Br2 decomposes, while CH3Br is released in intermediate gas phase. Catalytic yield increase compared to homogeneous one was not notable, which indicates on the prevalence of elementary radical mechanism. The highest S for CH3Br was around 90% at 310 ∘C with the WHSV of 1.20 h−1.

Superhydrophobicity Can Enhance Convective Heat Transfer in Pressure-Driven Pipe Flow

Summary Theoretical evidence is given that it is possible for superhydrophobicity to enhance steady laminar convective heat transfer in pressure-driven flow along a circular pipe or tube with constant heat flux. Superhydrophobicity here refers to the presence of adiabatic no-shear zones in an otherwise solid no-slip boundary. Adding such adiabatic no-shear zones reduces not only hydrodynamic friction, leading to greater fluid volume fluxes for a given pressure gradient, but also reduces the solid surface area through which heat enters the fluid. This leads to a delicate trade-off between competing mechanisms so that the net effect on convective heat transfer along the pipe, as typically measured by a Nusselt number, is not obvious. Existing evidence in the literature suggests that superhydrophobicity always decreases the Nusselt number, and therefore compromises the net heat transfer. In this theoretical study, we confirm this to be generally true but, significantly, we identify a situation where the opposite occurs and the Nusselt number increases thereby enhancing convective heat transfer along the pipe.

Effect of Water-Ethanol Extraction as Pre-Treatment on the Adsorption Properties of Aloe vera Waste.

The adsorption properties of Aloe vera (Aloe barbadensis Miller) for the uptake of Methylene Blue (MB) from water were investigated after pre-treating the material with water–ethanol solutions at different ethanol concentrations: 0% v/v (AV0), 25% v/v (AV25), and 50% v/v (AV50). The pre-treated materials were characterized as follows: the pHZC was evaluated to be 6, 5.7, and 7.2 for AV0, AV25, and AV50, respectively; from BET-BJH analysis the mesoporous nature of the material and an increase from 108.2 (AV0) to 331.7 (AV50) m2/kg of its solid surface area was observed; TG analysis revealed a significat increase in volatile compounds from the untreated (5.4%) to the treated materials (8.9%, 10.3%, and 11.3% for AV0, AV25, and AV50, respectively). Adsorption batch tests were then performed to investigate the equilibrium, the kinetics, and the thermodynamics of the process. Results suggested that the Langmuir model was in agreement with the experimental results, and values for qmax of 199 mg/g, 311 mg/g, and 346 mg/g were calculated for AV0, AV25, and AV50, respectively. The kinetic results were used to develop a mathematical model to estimate the effective diffusion coefficient for each type of Aloe adopted. Effective diffusion coefficients of 5.43·10−7 cm2/min, 3.89·10−7 cm2/min, and 5.78·10−7 cm2/min were calculated for AV0, AV25, and AV50, respectively. It was found that pre-treatment, on the one hand, enhances the adsorption capacity of the material and on the other, reduces its affinity toward MB uptake.

Soil Cycles of Elements simulator for Predicting TERrestrial regulation of greenhouse gases: SCEPTER v0.9

Abstract. The regulation of anthropogenic carbon dioxide (CO2) is an urgent issue – continuously increasing atmospheric CO2 from burning fossil fuels is leading to significant warming and acidification of the surface ocean. Timely and effective measures to curb CO2 increases are thus needed in order to mitigate the potential degradation of natural ecosystems, food security, and livelihood caused by anthropogenic release of CO2. Enhanced rock weathering (ERW) on croplands and hinterlands may be one of the most economically and ecologically effective ways to sequester CO2 from the atmosphere, given that these soil environments generally favor mineral dissolution and because amending soils with crushed rock can result in a number of co-benefits to plant growth and crop yield. However, robust quantitative evaluation of CO2 capture by ERW in terrestrial soil systems that can lead to coherent policy implementation will require an ensemble of traceable mechanistic models that are optimized for simulating ERW in managed systems. Here, we present a new 1D reactive transport model – SCEPTER. The model is designed to (1) mechanistically simulate natural weathering, including dissolution/precipitation of minerals along with uplift/erosion of solid phases, advection plus diffusion of aqueous phases and diffusion of gas phases, (2) allow targeted addition of solid phases at the soil–atmosphere interface, including multiple forms of organic matter (OM) and crushed mineral/rock feedstocks, (3) implement a range of soil mixing regimes as catalyzed by soil surface fauna (e.g., bioturbation) or humans (e.g., various forms of tilling), and (4) enable calculation of solid mineral surface area based on controlled initial particle size distributions coupled to a shrinking core framework. Here we describe the model structure and intrinsic thermodynamic/kinetic data, provide a series of idealized simulations to demonstrate the basic behavior of the code, and evaluate the computational and mechanistic performance of the model against observational data. We also provide selected example applications to highlight model features particularly useful for future prediction of CO2 sequestration by ERW in soil systems.

Synthesis of hollow ceria-zirconia solid solution particles by spray pyrolysis with organic ligands and its oxygen storage capacity

CeO2-based materials have been explored as oxidative catalysts owing to the reversible oxygen absorption and release behavior. The catalytic property is stabilized by addition of ZrO2 to form the solid solution. Hollow CeO2-ZrO2 solid solution particles were prepared by a spray pyrolysis method with organic additives, characterized by SEM, XRD and TEM, and evaluated for oxygen storage capacity (OSC). Spherical hollow particles with a size of about 500 nm formed, which were composed of about 10 nm nanoparticles. CeO2-rich particles had cubic crystal structure, while tetragonal phase was included in ZrO2-rich particles. The addition of organic ligands was effective to form uniform solid solution and increase specific surface area. The spray-pyrolysis temperature should be low to keep the specific surface area. At 50 mol% ZrO2, although the specific surface area was not so high as 20 m2/g, the maximum OSC of 650 μmol-O2/g was achieved. It was found that the OSC depends on ZrO2 content and the oxygen release rate increases with specific surface area.

Assessing the Interrelationship of Microstructure, Properties, Drug Release Performance, and Preparation Process for Amorphous Solid Dispersions Via Noninvasive Imaging Analytics and Material Characterization.

The purpose of this work is to evaluate the interrelationship of microstructure, properties, and dissolution performance for amorphous solid dispersions (ASDs) prepared using different methods. ASD of GDC-0810 (50% w/w) with HPMC-AS was prepared using methods of spray drying and co-precipitation via resonant acoustic mixing. Microstructure, particulate and bulk powder properties, and dissolution performance were characterized for GDC-0810 ASDs. In addition to application of typical physical characterization tools, we have applied X-Ray Microscopy (XRM) to assess the contribution of microstructure to the characteristics of ASDs and obtain additional quantification and understanding of the drug product intermediates and tablets. Both methods of spray drying and co-precipitation produced single-phase ASDs. Distinct differences in microstructure, particle size distribution, specific surface area, bulk and tapped density, were observed between GDC-0810 spray dried dispersion (SDD) and co-precipitated amorphous dispersion (cPAD) materials. The cPAD powders prepared by the resonant acoustic mixing process demonstrated superior compactibility compared to the SDD, while the compressibility of the ASDs were comparable. Both SDD powder and tablets showed higher in vitro dissolution than those of cPAD powders. XRM calculated total solid external surface area (SA) normalized by calculated total solid volume (SV) shows a strong correlation with micro dissolution data. Strong interrelationship of microstructure, physical properties, and dissolution performance was observed for GDC-0810 ASDs. XRM image-based analysis is a powerful tool to assess the contribution of microstructure to the characteristics of ASDs and provide mechanistic understanding of the interrelationship.

Boiling on nano-porous structures: Theoretical analysis and molecular dynamics simulations

The nano-porous structures have been employed to enhance the boiling heat transfer. To optimize the nano-porous structures so as to improve the boiling heat transfer, it is necessary to disclose the impacts of the nano-porous structures on the characteristics of boiling. Experimentally, it is difficult to observe the phenomena of boiling inside the nano-porous structure. An alternative way is to resort the theoretical and modeling analysis. In the present study, we fist perform a theoretical analysis on boiling on the nano-porous structures from the macroscopic perspective. We find that the boiling inception time is proportional to the ratio of the void volume to the solid surface area; and that the critical heat flux is a power law function of the pore size, with the exponent of 1.5. To demonstrate these theoretical analysis, we then perform the molecular dynamics simulations on boiling of argon on the copper based nano-porous structures. The molecular dynamics simulations demonstrate the theoretical analysis. It is revealed that the boiling inception time is a power law function with respect to the ratio of the void volume to the solid surface area. The exponent for the power law relation between the critical heat flux and the pore size is 1.232. The critical heat flux occurs at the moment when the surface of the nano-porous structures is completely covered by the vapor film.

Catalytic hydrocracking reactions of tetralin biomass tar model compound to benzene, toluene and xylenes (BTX) over metal-modified ZSM-5 in ambient pressure reactor

The tetralin hydrocracking process into benzene, toluene, and xylenes (BTX) was investigated over metal-modified (Ga, Nb, Ni, NiMo, Sn, W, Zr or H3[P(W3O10)4])/ZSM-5 zeolite catalysts without sulfidation procedures, mechanism was analyzed, and compared with a pristine microporous material in a packed bed reactor under applied atmospheric pressure (p). This experimental study presents an investigation of the metal-promoted ZSM-5 for the BTX production under the ambient p for the first continuously-operated time. It is demonstrated that metal-wise there are no significant improvements in the formation of BTX. The yield of 43.1 mol% towards BTX over the parent HZSM-5 (SiO2/Al2O3 = 30) at 420 °C after 4 h on time on stream (TOS) was achieved, while methane, ethylene, ethane, propylene and propane were main gas products. The outstanding functional performance of HZSM-5 was mainly ascribed to structure, its high dealkylation and a measured large amount of the solid surface area in tandem with the porosity, protonating total Brønsted (BAS)/Lewis (LAS) acidity and BAS/LAS ratio. However, BTX dropped drastically with increasing TOS due to coke. It was found that HZSM-5 was the most affected within studied reaction conditions, but could be easily regenerated with preserving realistic catalytic chemistry. The pathway of cracking was proposed. Simultaneously, the 5wt%Zr/ZSM-5 catalyst possessed the highest selectivity (SBTX = 24.2 mol%; TOS = 25 h; 370 °C) due to the low diffusion thermomigration of the Zr species into framework compared to parent zeolite under the same reaction conditions after a long TOS. Influence of metal loading on the activity of ZSM-5 zeolite was systematically studied and the complex relationship between physicochemical properties and catalytic activity of bifunctional catalysts was observed. All these findings shed light, on how the incorporation of different metals affects BTX selectivity.

Sorption equilibrium moisture and isosteric heat of Chinese wheat bran products added to rice to increase its dietary fibre content

More and more people concern about supplementing dietary food with wheat bran to increase fibre content, but there has been little study of the sorption isotherms and isosteric heats of wheat bran fibre products, which are important to the quality and storage durability of such commodities. This study collected equilibrium moisture content (EMC) and equilibrium relative humidity (ERH) data on six Chinese wheat bran products via the static gravimetric method and analysed their sorption isosteric heats. Results showed that all six wheat bran products had sigmoidal isotherms. The data were best fitted by polynomial, modified GAB, modified Oswin, and modified Halsey models. The relative safe moisture contents of the six wheat bran products were 12.20%–13.86% wet basis (w.b.). The heat of vaporization of wheat bran products approached the latent heat of pure water at around a moisture content (MC) of 22.5% and approximately 2450 kJ/kg. A process of extrusion and ultrafine grinding reduced the solid surface area and sorption isosteric heats of the monolayer, multilayer and condensed water regions in the wheat bran products. In the temperature range of 10–37 °C, the EMC of sorption in monolayer, multilayer and condensed water regions decreased with increasing temperature. The milled rice to which 1%–3% 200-mesh wheat bran product was added maintained its texture when made into cooked rice and its thermomechanical properties when made into rice dough. After processing by extrusion and ultrafine grinding, wheat bran products have a lower solid surface area and lower monolayer water content ( M m ) and sorption isosteric heat values. Some 3% 200-mesh wheat bran product can be added to cooked rice for increasing its fibre content and making it more nutritious.

Surface evolution of aluminosilicate glass fibers during dissolution: Influence of pH, solid-to-solution ratio and organic treatment

Materials made of synthetic vitreous mineral fibers, such as stone wool, are widely used in construction, in functional composites and as thermal and acoustic insulation. Chemical stability is an important parameter in assessing long term durability of the products. Stability is determined by fiber resistivity to dissolution, where the controlling parameters are solid surface area to solution volume ratio (S/V), pH and composition of the fibers and organic compounds used as binders. We investigated stone wool dissolution under flow through conditions, far from equilibrium, at pH range of 2 to 13, as well as under batch conditions, close to equilibrium, for up to 28 days, where S/V ranged from 100 to 10000 m−1. The dissolution rate of stone wool shows minimum at pH 8.5 and increases significantly at pH < 4.5 and pH > 12. In close to equilibrium conditions, S/V defines the steady state concentration for the leached components. Decreased dissolution rate could result from evolution of a surface leached layer or the formation of secondary surface phases or both. We suggested three dissolution rate controlling mechanisms, which depend on pH. That is, dissolution is controlled by: a SiO2 rich surface layer at pH < 4.5; by adsorption of an Al and Al-Si mixed surface layer at 5 < pH < 11 and by divalent cation adsorption and formation of secondary phases (silicates, hydroxides) at pH ∼ 13. The organic compounds, used to treat the stone wool fibers during manufacture, had no influence on their dissolution properties.