Solid Gas Research Articles

Electric-Field-Induced Solid-Gas Interfacial Chemical Reaction in Carbon Nanotube Ensembles: Route toward Ultra-sensitive Gas Detectors.

The electric field at the sharp pointed tips of single wall carbon nanotube ensembles has been utilized to kinetically accelerate hitherto unobserved chemical reactions at the heterogeneous solid-gas interfaces. The principle of ″action-of-points″ drives specific chemical reactions between the defect sites of single wall carbon nanotubes (CNTs) and ppb levels of gaseous hydrogen sulfide. This is manifested as changes in the electrical conductivity of the conductive CNT-ensemble (cCNT) and visually tracked as enthalpic modulations at the site of the reaction through infrared thermometry. Importantly, the principle has been observed for a variety of analytes such as NH3, H2O, and H2S, leading to distinctly correlatable changes in reactivity and conductivity changes. Theoretical calculations based on the density functional theory in the presence and absence of applied electric field reveal that the applied electric field activates the H2S gas molecules by charge polarization, yielding favorable energetics. These results imply the possibility of carrying out site-specific chemical modifications for nanomaterials and also provide transformative opportunities for the development of miniaturized e-nose-based gas analyzers.

Development of a solid phase microextraction gas chromatography tandem mass spectrometry methodology for the analysis of sixty personal care products in hydroalcoholic gels ˗ hand sanitizers ˗ in the context of COVID-19 pandemic

Because of the coronavirus pandemic, hydroalcoholic gels have become essential products to prevent the spread of COVID-19. This research aims to develop a simple, fast and sustainable microextraction methodology followed by gas chromatography tandem mass spectrometry (GC-MS/MS) to analyze simultaneously 60 personal care products (PCPs) including fragrances allergens, synthetic musks, preservatives and plasticizers in hand sanitizers. Micro-matrix-solid-phase dispersion (μMSPD) and solid-phase microextraction (SPME) were compared with the aim of obtaining high sensitivity and sample throughput. SPME demonstrated higher efficiency being selected as sample treatment. Different dilutions of the sample in ultrapure water were assessed to achieve high sensitivity but, at the same time, to avoid or minimize matrix effect. The most critical parameters affecting SPME (fibre coating, extraction mode and temperature) were optimized by design of experiments (DOE). The method was successfully validated in terms of linearity, precision and accuracy, obtaining recovery values between 80 and 112% for most compounds with relative standard deviation (RSD) values lower than 10%. External calibration using standards prepared in ultrapure water demonstrated suitability due to the absence of matrix effect. Finally, the simple, fast and high throughput method was applied to the analysis of real hydroalcoholic gel samples. Among the 60 target compounds, 39 of them were found, highlighting the high number of fragrance allergens, at concentrations ranging between 0.01 and 217 μg g−1. Most of the samples were not correctly labelled attending cosmetic Regulation (EU) No 1223/2009, and none of them followed the World Health Organization (WHO) recommendation for hand sanitizers formulation.

Catalytic fast pyrolysis of soybean hulls: Focus on the products

Catalytic upgrading (with HZSM-5 zeolite) of the fast pyrolysis volatiles obtained from soybean hulls, a low cost and highly available biomass waste, has been investigated. The composition and yield of solid, liquid and non-condensable gas fractions obtained in the 400–600 ºC range during fast pyrolysis (FP) and catalytic fast pyrolysis (CFP) have been compared. The solid, liquid and non-condensable gas fraction obtained during FP and CFP have been characterized and compared. FP of soybean hull delivers liquid yields from 38% to 45% as temperature increases, while CFP slightly decreases the liquid yield to 37–42%. The characterization of the bio-oil has revealed that CFP increases more than 21% the amount of high-value species such as phenols, along with improvements of 30% in the heating value and reduction of the total acidity number by 15%. The biogas yield increase in CFP due to the deoxygenation and cracking reactions catalyzed by zeolite HZSM-5. The composition in FP shifts from being mostly CO2 and CO at 400 ºC towards a higher presence of hydrogen, methane and C2-C3 hydrocarbons at 500–600 ºC. CFP at 500 °C and 600 °C enhances the formation of hydrogen, methane and paraffinic C2-C3 hydrocarbons, which boosts the heating value of the gas to more than 15 kJmol−1. CFP does not cause any substantial changes in char composition, which is enriched in carbon while losing volatile matter as pyrolysis temperature increases and with char heating values between 25 and 27 MJ Kg−1. The presence of narrow microporosity has been confirmed by CO2 physisorption, while SEM images of the char reveal the presence of macropores. These results highlight the benefits of CFP for enhancing the production of bioenergy and bioproducts from soybean hulls.

Association Between Serum Aldehydes and Hypertension in Adults: A Cross-Sectional Analysis of the National Health and Nutrition Examination Survey.

BackgroundExposure to ambient pollutants and chemicals were found to be associated with increased risk of hypertension. However, the relationship between the increased aldehyde exposure and hypertension are still unclear. This study aimed to investigate the potential associations of serum aldehydes levels with prevalent hypertension.MethodsA total of 1,733 U.S. adults with data on hypertension outcome and serum aldehydes measurement from the National Health and Nutrition Examination Survey 2013–2014 were included. The serum levels of aldehydes were measured via an automated analytical method using solid phase microextraction gas chromatography and high-resolution mass spectrometry. Multivariate logistic regression models were adopted to assess the associations between six selected aldehydes exposure (benzaldehyde, butyraldehyde, heptanaldehyde, hexanaldehyde, isopentanaldehyde, and propanaldehyde) and prevalence of hypertension.ResultsThe mean age was 48.0 ± 16.7 years and an approximately equivalent of sex distribution was observed (female 49.9%). There seems to be a numerically higher level of hexanaldehyde in participants with hypertension when compared to participants without hypertension (2.6 ± 3.9 ng/mL vs. 2.3 ± 1.1 ng/mL). After adjusting for potential confounders, the odds ratio (OR) for hypertension was 2.15 [95% confidence interval (CI): 1.33–3.51] in participants from the highest quartile of serum hexanaldehyde concentration in comparison to those from the lowest quartile. Subgroup analyses and sensitivity analyses showed generally similar results.ConclusionIn summary, current evidence suggested that increased serum hexanaldehyde level was positively associated with prevalent hypertension in U.S. adults.

Visible-light-driven solvent-free photocatalytic CO2 reduction to CO by Co-MOF/Cu2O heterojunction with superior selectivity

It is highly desirable to discover MOFs matrix composites with controlled reduction selectivity in the general understanding of the CO2 reduction reaction (CO2RR) in electro- and photocatalytic process. Herein, we demonstrate a facile strategy to prepare metal organic framework hybrid composites (xCMC) using the Co-based MOF [Co2(TMTA)(HCOO)(bidb)(H2O)]∙DMF (H3TMTA = 1,3,5-trimethyl-2,4,6- tricarboxyl- phenylbenzene, bidb = 1,4-bis(1-imidazoly)benzene) and nanocrystalline cuprous oxide. The resulting hybrid catalyst with p-n heterojunction exhibited enhanced photocatalytic CO2 reduction activity with remarkable CO production rate of 3.83 μmol g−1h−1, ca. 9.6 times higher than that of pure Cu2O. Compared with other reaction routes, the present photocatalytic reduction of CO2 with superior selectivity to CO occurs in the interface of solid–gas reaction without the use of photosensitizers or sacrificing reagents. In addition, the mechanism for photocatalytic CO2 reduction was also well discussed. The present work provides unique insight into constructing MOF-based photocatalysts with heterojunction for visible-light-driven CO2 reduction under solid–gas reaction conditions.

Numerical Study on the Effect of Wall Thickness on the Combustion Characteristics of Non-premixed Hydrogen Micro-jet Flame

The effect of wall thickness on the combustion characteristics of nonpremixed hydrogen micro-jet flames was studied by two-dimensional numerical computation with a detailed reaction kinetics for the development of hydrogen micro-burner. The hydrogen jet diffusion flames achieved by micro-tubes with the same inner diameter and length but different wall thicknesses were investigated. The heat exchange between solid tube and gases were included in the numerical computation. The distributions of flame temperature, OH radicals, details of thermal interaction, and combustion efficiency were analyzed for comparison. It was found that the temperature distribution, flame shape, and heat recirculation are changed with the fuel flow velocity, and they are affected by wall thickness. The mechanism of wall thickness on the combustion characteristics of hydrogen jet diffusion flame was clarified. Finally, an interesting numerical experiment was conducted to give a further explanation of the effect of heat recirculation and to provide guidance of the thermal management of the micro-burner.

Green methodology based on active air sampling followed by solid phase microextraction and gas chromatography-tandem mass spectrometry analysis to determine hazardous substances in different environments related to tire rubber

A fast, efficient, and simple air sampling methodology was developed to study a high number of volatile and semivolatile organic compounds in air above tire rubber materials and surfaces made of recycled tire rubber. The proposed method, based on active sampling (solid-phase extraction, SPE) using a small quantity of sorbent material (25 mg) followed by solid-phase microextraction (SPME) and gas chromatography-tandem mass spectrometry analysis, was developed with the aim of determining 40 organics substances including polycyclic aromatic hydrocarbons (PAHs), plasticizers, antioxidants, and vulcanization agents. An experimental design was carried out to study the influence of main factors such as type of SPME fibre, solvent addition, headspace volume, stirring, as well as the factor interactions. Method performance showed good linearity in a broad concentration range (0.05 to 200 ng m−3, for most compounds), with coefficients of determination (R2) higher than 0.9900. Whole method precision (≤ 16 %) and accuracy were also satisfactory, obtaining quantitative recoveries (mean values between 80 and 110 % in most cases). Limits of detection and quantification have also been calculated, yielding values of sub ng m−3 for most compounds. The validated method was applied to outdoor and indoor air environments including playgrounds, football pitches and warehouses showing the presence of most target compounds in the samples achieving high levels for some PAHs (concentrations up to 51 ng m−3), benzothiazole (BTZ), diisobutyl- dibutyl- and di-(2-ethylhexyl)- phthalate, among others, reaching concentrations up to hundreds of ng m−3 (BTZ). This is the first time that the combination of techniques SPE and SPME is applied for these families of chemicals, and it is also the first time that this approach is proposed for the simultaneous multiclass compound extraction of substances of different chemical families. The whole sampling and extraction procedure is performed in a short period of time (61 min) allowing high throughput. The elimination of the use of organic solvents and waste generation by using only 25 mg of sorbent and a SPME fibre than are both reused makes the method sustainable and in consonance with the principles of the green chemistry. The method can be implemented in any routine lab and easily automated using a SPME autosampler.

Oxygen Isotopic Composition of U3O8 Synthesized From U Metal, Uranyl Nitrate Hydrate, and UO3 as a Signature for Nuclear Forensics.

Triuranium octoxide (U3O8) is one of the main compounds in the nuclear fuel cycle. As such, identifying its processing parameters that control the oxygen isotopic composition could be developed as a new signature for nuclear forensic investigation. This study investigated the effect of different synthesis conditions such as calcination time, temperature, and cooling rates on the final δ18O values of U3O8, produced from uranium metal, uranyl nitrate hydrate, and uranium trioxide as starting materials. The results showed that δ18O of U3O8 is independent of the above-listed starting materials. δ18O values of 10 synthetic U3O8 were similar (9.35 ± 0.46‰) and did not change as a function of calcination time or calcination temperature. We showed that the cooling rate of U3O8 at the end of the synthesis process determines the final oxygen isotope composition, yielding a significant isotope effect on the order of 30‰. Experiments with two isotopically spiked 10 M HNO3, with a difference of δ18O ∼75‰, show that no memory of the starting solution oxygen isotope signature is expressed in the final U3O8 product. We suggest that the interaction with atmospheric oxygen is the main process parameter that controls the δ18O value in U3O8. The uranium mass effect, the tendency of uranium ions to preferentially incorporate 16O, is expressed during the solid–gas oxygen exchange, which occurs throughout cooling of the system.

An Analytical Method to Estimate Supersaturation in Gas–Liquid Systems as a Function of Pressure-Reduction Step and Waiting Time

When the concentration of a gas exceeds the equilibrium concentration in a liquid, the gas–liquid system is referred as a supersaturated system. The supersaturation can be achieved by either changing the pressure and/or temperature of the system. The gas from a supersaturated liquid escapes either through bubble nucleation that usually occurs on solid surface and/or gas diffusion through the gas–liquid interface. The bubble nucleation requires a minimum threshold supersaturation. A waiting time is required to observe whether the applied supersaturation is sufficient to initiate bubble nucleation. When the supersaturation is not sufficient to cause bubble nucleation, some or all of the supersaturated gas may diffuse out from the liquid through the gas–liquid interface before further reducing the pressure in order to increase the supersaturation. In this article, using Fick’s second law of diffusion and Henry’s law, an analytical method is proposed to estimate the level of supersaturations generated in three gas–liquid systems at different step-down pressures. Characteristic times of the gas–liquid systems were estimated to validate whether the waiting times used in this study are in accordance with the semi-infinite diffusion model used to estimate the supersaturations generated.

Secretory Products in Petals of Centaurea cyanus L. Flowers: A Histochemistry, Ultrastructure, and Phytochemical Study of Volatile Compounds.

(1) Background: Centaurea cyanus L. is a medicinal plant whose flowers are widely used in herbal medicine. The aim of the study was to localise flower tissues that are responsible for the production of secretory products in petals and to analyse the volatile compounds. The volatile compounds of the flowers of this species have not been investigated to date. (2) Methods: Light, fluorescence, scanning and transmission electron microscopy techniques were used in the study. Lipophilic compounds were localised in the tissues using histochemical assays. Volatile compounds were determined with the use of solid phase microextraction (SPME) and gas chromatography-mass spectrometry (GC-MS). (3) Results: The study showed production of secretion in the petal parenchyma, whose ultrastructure has features of a secretory tissue. The lipophilic secretion was localised in the cells and intercellular spaces of the parenchyma and in the walls and surface of epidermal cells, where it accumulated after release through cuticle microchannels. Sesquiterpenes were found to constitute the main group of volatile compounds, with the highest content of β-caryophyllene (26.17%) and α-humulene (9.77%). (4) Conclusions: Given the presence of some volatile components that are often found in resins (caryophyllene, delta-cadinene) and the abundant secretion residues on the epidermal surface, we suppose that the C. cyanus secretion released by the flowers is a resinaceous mixture (oleoresin), which is frequently found in plants, as shown by literature data. This secretion may play an important role in the therapeutic effects of C. cyanus flowers.

A cell design for correlative hard X-ray nanoprobe and electron microscopy studies of catalysts under in situ conditions.

To improve the understanding of catalysts, and ultimately the ability to design better materials, it is crucial to study them during their catalytic active states. Using in situ or operando conditions allows insights into structure-property relationships, which might not be observable by ex situ characterization. Spatially resolved X-ray fluorescence, X-ray diffraction and X-ray absorption near-edge spectroscopy are powerful tools to determine structural and electronic properties, and the spatial resolutions now achievable at hard X-ray nanoprobe beamlines make them an ideal complement to high-resolution transmission electron microscopy studies in a multi-length-scale analysis approach. The development of a system to enable the use of a commercially available gas-cell chip assembly within an X-ray nanoprobe beamline is reported here. The novel in situ capability is demonstrated by an investigation of the redox behaviour of supported Pt nanoparticles on ceria under typical lean and rich diesel-exhaust conditions; however, the system has broader application to a wide range of solid-gas reactions. In addition the setup allows complimentary insitu transmission electron microscopy and X-ray nanoprobe studies under identical conditions, with the major advantage compared with other systems that the exact same cell can be used and easily transferred between instruments. This offers the exciting possibility of studying the same particles under identical conditions (gas flow, pressure, temperature) using multiple techniques.

Deeper Insight into the Volatile Profile of Rosa willmottiae with Headspace Solid-Phase Microextraction and GC-MS Analysis.

As the distribution center of Rosa in the world, China has abundant wild germplasm resources, which can contribute to the breeding of modern roses. To explore the potential value of wild roses distributed in the Sichuan–Tibet region, solid phase microextraction (SPME) and gas chromatography–mass spectrometry (GC–MS) were used to determine the volatile organic compounds (VOCs) in Rosa willmottiae flowers at three flowering stages (bud stage, initial flowering stage, full flowering stage). Meanwhile, we compared the VOCs of R. willmottiae with different phenotypes (double flowers and single flowers). A total of 74 volatile compounds were identified. The results show that the essential substances belong to alcohols and terpenoids. The main volatile organic compounds are 2-phenyl ethanol (20.49%), benzyl alcohol (10.69%), β-maaliene (8.66%), geranyl acetate (8.47%), and (+)-α-long pinene (6.127%). Different flowering stages had great influence on the volatile profile, from the bud stage to full flowering stage; the content of terpenoids released decreased by 6.17%, whereas alcohols and esters increased by 8.58% and 11.56%, respectively. The chemical diversity and the content of the main components with a different phenotype were not significantly different. Our result will provide a theoretical basis for the development and utilization of Rosa willmottiae in Sichuan and Tibet.

System Pr –Pd–O: Phase Diagram and Thermodynamic Properties of Ternary Oxides Using Solid-State Cells with Special Features

Abstract An isothermal section of the phase diagram for the system Pr– Pd–O at 1223 K has been established by equilibration of samples representing 13 different compositions, and phase identification after quenching by optical and scanning electron microscopy (SEM), X-ray diffraction (XRD), and energy dispersive analysis of X-rays (EDX). The binary oxide PdO was not stable at 1223 K. Three oxide phases were stable along the binary Pr– O; Pr2O3, Pr7O12 and a phase of variable composition between these two oxides designated as σ. Two ternary oxides Pr4PdO7 and Pr2Pd2O5 were identified and their crystal structures were determined. Liquid alloy, the intermetallic compounds PrPd, Pr3Pd4, PrPd3, PrPd5, and Pd-rich solid solution (Pds.s.) were found to be in equilibrium with Pr2O3. Based on the phase relations, two solid-state cells were designed to measure the Gibbs energies of formation of the two ternary oxides. An advanced version of the solid-state cell incorporating a buffer electrode was used for high temperature thermodynamic measurements. The function of the buffer electrode, placed between reference and working electrodes, was to absorb the electrochemical flux of the mobile species through the solid electrolyte caused by trace electronic conductivity. The buffer electrode prevented polarization of the measuring electrode and ensured accurate data. Yttria-stabilized zirconia was used as the solid electrolyte and pure oxygen gas at a pressure of 0.1 MPa as the reference electrode. Electromotive force measurements, conducted in the temperature range 925 – 1400 K, indicated the presence of a third ternary oxide Pr2PdO4, stable below 1150 ± 9 K. Additional solid state cells were designed to study this compound. The standard Gibbs energy of formation of the interoxide compounds from their component binary oxides Pr2O3 and PdO can be represented by the following equations: Pr 4 PdO 7 : Δ f ( ox ) G o /J ⋅ mol − 1 = − 43 540 + 0.74 T ( ± 150 ) Pr 2 PdO 4 : Δ f ( ox ) G o /J ⋅ mol − 1 = − 38 805 + 1.91 T ( ± 120 ) Pr 2 Pd 2 O 5 : Δ f ( ox ) G o /J ⋅ mol − 1 = − 68 640 + 1.28 T ( ± 270 ) $$\eqalign{ & {\rm{P}}{{\rm{r}}_4}{\rm{Pd}}{{\rm{O}}_7}:{{\rm{\Delta }}_{{\rm{f}}\left( {{\rm{ox}}} \right)}}{G^{\rm{o}}}{\rm{/J}} \cdot {\rm{mo}}{{\rm{l}}^{ - 1}} = - 43\,540 + 0.74\,T\left( { \pm 150} \right) \cr & {\rm{P}}{{\rm{r}}_2}{\rm{Pd}}{{\rm{O}}_4}:{{\rm{\Delta }}_{{\rm{f}}\left( {{\rm{ox}}} \right)}}{G^{\rm{o}}}{\rm{/J}} \cdot {\rm{mo}}{{\rm{l}}^{ - 1}} = - 38\,805 + 1.91\,T\left( { \pm 120} \right) \cr & {\rm{P}}{{\rm{r}}_2}{\rm{P}}{{\rm{d}}_2}{{\rm{O}}_5}:{{\rm{\Delta }}_{{\rm{f}}\left( {{\rm{ox}}} \right)}}{G^{\rm{o}}}{\rm{/J}} \cdot {\rm{mo}}{{\rm{l}}^{ - 1}} = - 68\,640 + 1.28T\left( { \pm 270} \right) \cr} $$ Crystallographic data for all three ternary oxides have been determined based on the thermodynamic information, isobaric phase diagrams and isothermal chemical potential diagrams for the system Pr–Pd –O are developed.

CFD simulation of mesoscale structures in mono and bidispersed fluidized bed pyrolysis reactors

Pyrolysis of biomass and organic matter in fluidized bed reactors have become popular in recent years due to the efficient conversion of biomass to bio-fuels. Among others, the presence of mesoscale structures produced by the transient nature of gas solid flow governs the performance of fluidized bed reactors. In the present study, monodispersed system with the particle size of 155 µm and bidispersed system with particle sizes of 128 and 1500 µm are simulated by the multi-fluid model with the kinetic theory of granular flow closure laws. The objective is to investigate the effect of size distribution and solid volume fraction on the hydrodynamics of gas-solid flows. The ANSYS Fluent® software is used for the simulations and the slip velocity, heterogeneity index as well as mixing index are investigated. A two dimensional fully periodic domain is used to investigate the slip velocity at five different solid concentrations in dilute range. The slip velocity, which represents the interaction between solid particles and gas, calculated by simulation is higher than that calculated through Richardson-Zaki’s correlation. The mixing index is found to be minimum for a solid volume concentration of 5%. The heterogeneity index is significantly less than 1 for both cases with bidisperesed system having lower value as compared to monodispersed system. The image analysis of solid fraction contours exhibits that mesoscale structures are dense and non-uniform for solid fractions of 0.05 and are small and uniform of solid fractions of 0.025 and 0.075.

Effects of the interaction between neighboring droplets on the stability of nanoscale liquid bridges

The mechanism of mechanical and hydraulic properties of unsaturated clays at the nanoscale hasn’t been fully understood, especially for three-phase systems. Through molecular dynamics (MD) and a series of microscopic test methods, the stability of kaolinite-water-CO2 under Dh, Sr, M∗, ds∗ and ε∗ was evaluated. The results of density field, adsorption, contact angle and capillary force of water and CO2 molecules indicated that Dh and M∗ controlled the coalescence and jumping of adjacent droplets, while the wettability of minerals depended on Sr and ε∗. When the two droplets ranged from coalescence to separation, not only the contact angle enlarged, but the capillary force declined. Although the rise of ε∗ will enhance the wettability of kaolinite, it will cause the liquid bridge to break and be adsorbed on the surface of particle in the form of a liquid film if it’s too high. In this case, contact angle of liquid bridges suddenly dropped to zero. The capillary force will also present a trend of first increasing and then decreasing. In the three-phase environment, the enlargement of Sr induced CO2 molecules to be adsorbed on the surface of solid and liquid phase due to hydrogen bonds, thereby reducing the wettability of minerals. Subsequently, capillary force became smaller. In addition, CO2 and H2O molecules at the interface were arranged in order, and the thickness of adsorption layer was from small to large: solid–gas, solid–liquid, gas–liquid. By fitting the critical conditions of liquid bridges in instability and fracture, it may be beneficial to explain macroscopic unsaturated theory and long-term experimental observations.

Solids lateral mixing and compartmentalization in dynamically structured gas–solid fluidized beds

An adequate use of gas pulsation can create an ordered, dynamically structured bubble flow in a bed of Geldart B particles. A structured bed is more homogeneous, responds to external control and is scalable. While earlier studies have focused on describing the self-organization of the gas bubbles, the solid mixing and gas–solid contact patterns have remained unclear. In this work, the solids circulation and mixing behavior in structured and unstructured beds at various pulsation frequencies are compared with a traditional fluidized bed operation. The degree of lateral mixing is hereby quantified through an effective lateral dispersion coefficient extracted from CFD-DEM (discrete element modelling) simulations in a thin fluidized bed system. Mixing shows major quantitative and qualitative differences amongst the investigated cases. The coordinated motion of the gas bubbles wraps the solid flow into a series of compartments with minimal interaction, whereby effective lateral dispersion coefficients are an order of magnitude lower than in an unstructured operation. More importantly, unlike a traditional bed, dispersion in a structured bed is driven by advection and is no longer a diffusive process. Compartmentalization decouples the time scales of micro- and macromixing. Every pulse, the compartments rearrange dynamically, causing a level of local axial mixing that is scale-independent. While further work is necessary to fully understand the compartmentalization at a larger scale, the circulation described here indicates that a dynamically structured bed can provide a tight control of mixing at low gas velocities and a narrower distribution of stresses in the solid phase compared to traditional devices.

Heterogeneous numerical modelling for the auto thermal reforming of crude glycerol in a fixed bed reactor

A mathematical model for the catalytic autothermal reforming (ATR) reaction of synthetic crude glycerol to hydrogen in a fixed bed tubular reactor (FBTR) and over an in-house developed metal oxide catalyst is presented in this work. The heterogeneous model equations account for a two-phase system of solid catalyst and bulk feed gas. Also, the ATR of crude glycerol reaction scheme and intrinsic kinetic rate model over an active, selective, and stable nickel-based catalyst were integrated in the developed model. Also, the model was validated using experimental data generated in our labs for the ATR of synthetic crude glycerol. The modelling results adequately described the detailed gas product composition and distribution, temperature profiles, and conversion propagation in the axial direction of the fixed bed reactor over a wide range of reaction temperature (773–923 K) and mass-time (12.71–158.23 g cat·min·(mol C) −1 ). The crude glycerol conversion predicted with the model showing a close resemblance to those obtained experimentally with an average absolute deviation (AAD) of less than 8%. The maximum crude glycerol conversion and hydrogen yield were found to be 92% and 3 mol hydrogen/mol crude glycerol, respectively. Also, the gas product concentration profile in the reactor was adequately described (90%) accuracy with a hydrogen concentration of 39 vol%.

Structures and Spectra of Halide Hydrate Clusters in the Solid State: A Link between the Gas Phase and Solution State.

This Review describes and assesses known solid-state examples of halide hydrates that are discrete in nature. Most of these are chloride hydrates, and most discrete clusters are dihalides, with very few mono- or multi-halide species found in the solid state. Polymeric chloride hydrates, on the other hand, are mostly 2D layered structures. We also observe that there is a gap in the chloride:water ratio between 8-20 waters per chloride. Isolated clusters can be found with 1-3 waters per chloride, 2D layers with 2-8 waters, and 3D semiclathrates with 20-38 waters. However, 1D chains comprise only 1-2 waters per chloride. [Cl(H2 O)]- is the only species found in both the solid state and gas phase and is also the only halide hydrate with a free OH group. Infrared spectra in the ν(OH) region are distinctive and useful for identification. Agreement between computed (gas phase) and experimentally-observed solid state structures and their vibrational spectra gives us confidence that discrete halide hydrate species observed in the solid state provide a useful link between gas phase species and structural motifs of halide hydrates in solution, especially microsolvated ion-pairs.

A double-walled sapphire single-crystal gas-pressure cell (type III) for in situ neutron diffraction.

In situ neutron diffraction is an important characterization technique for the investigation of many functional materials, e.g. for hydrogen uptake and release in hydrogen storage materials. A new sapphire single-crystal gas-pressure cell for elastic neutron scattering has been developed and evaluated; it allows conditions of 298 K and 9.5 MPa hydrogen pressure and 1110 K at ambient pressure. The pressure vessel consists of a sapphire single-crystal tube of 35 mm radius and a sapphire single-crystal crucible as sample holder. Heating is realized by two 100 W diode lasers. It is optimized for the D20 diffractometer, ILL, Grenoble, France, and requires the use of a radial oscillating collimator. Its advantages over earlier sapphire single-crystal gas-pressure cells are higher maximum temperatures and lower background at low and high diffraction angles. The deuterium uptake in palladium was followed in situ for validation, proving the potential of the type-III gas-pressure cell for in situ neutron diffraction on solid-gas reactions.

Efficient Visible-Light Photoreduction of CO2 to CH4 over an Fe-Based Metal–Organic Framework (PCN-250-Fe3) in a Solid–Gas Mode

Efficient Visible-Light Photoreduction of CO₂ to CH₄ over an Fe-Based Metal–Organic Framework (PCN-250-Fe₃) in a Solid–Gas Mode