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Spent hydrodesulfurization catalyst (HDS) is considered as the important secondary resource for Mo and Ni. The separation of Mo from HDS was usually conducted by soda roasting and water leaching, while Ni remained in the leached residue. This study proposed a method to recover Ni from leached residue by H2SO4 leaching and solvent extraction, and Ni was recycled in the form of NiO. The results showed that the optimum Ni leaching process were conducted using 30% H2SO4 with liquid–solid ratio of 10 at 70 ℃ for 120 min. The optimal extraction was accomplished using 30% di-(2-ethylhexyl) phosphate (P204) saponification at pH value 6.0 with organic/aqueous (O/A ratio) of 1 for 1 min. Additionally, 20% H2SO4 could be used to strip Ni from organic phase with O/A ratio of 10. Finally, NiSO4 was calcined at 850 ℃ for 1.0 h to obtain NiO. The Ni leaching kinetic analysis showed that the activation energy of Ni leaching process was 16.10 kJ/mol, which was accorded with the shrinkage unreacted kernel model controlled by internal diffusion. This study provided an alternative method to recycle Ni and given a deeper insight to the leaching mechanism during H2SO4 leaching Ni from spent catalyst. [ABSTRACT FROM AUTHOR]

Abstract Assuming the leakage of hazardous liquid chemicals in factories and chemical plants caused by natural disasters or human error, it is important to precisely estimate exposure risk and design appropriate evacuation plans and risk‐reduction measures. The exposure risk of indoor residents to leaked chemicals may be estimated using direct measurements or theoretical/numerical estimations of gas‐phase concentrations. Although mathematical models of gas‐phase concentration in the workplace are essential for predicting exposure concentrations at the design stage, practical models have not yet been fully established. We previously proposed practical numerical models to assess indoor gas‐phase concentration distributions after the accidental leakage of liquid chemicals using liquid toluene as a representative hazardous chemical. In this study, the leakage of liquid ethyl acetate, a commonly used organic solvent, into mortar flooring was reproduced in a small test chamber, and numerical analysis was performed. The results showed that the time history of the chamber exhaust concentration had a sharp peak and differed significantly from that of toluene. Three‐dimensional computational fluid dynamics (CFD) analysis incorporating practical ethyl acetate emission models reproduced the external and internal emission characteristics of leaked ethyl acetate on the mortar material. The models showed reasonable agreement with the experimental data.

Colorimetric sensors are widely used because of their inherent advantages including accuracy, rapid response, ease-of-use, and low costs; however, they usually lack reusability, which precludes the continuous use of a single sensor. We have developed a threshold-responsive colorimetric system that enables repeated analyte measurements by a single colorimetric sensor. The threshold responsive algorithm automatically adjusts the sensor exposure time to the analyte and measurement frequency according to the sensor response. The system registers the colorimetric sensor signal change rate, prevents the colorimetric sensor from reaching saturation, and allows the sensor to fully regenerate before the next measurement is started. The system also addresses issues common to colorimetric sensors, including the response time and range of detection. We demonstrate the benefits and feasibility of this novel system, using colorimetric sensors for ammonia and carbon dioxide gases for continuous monitoring of up to (at least) 60 detection cycles without signs of analytical performance degradation of the sensors. [ABSTRACT FROM AUTHOR]

Assuming the leakage of hazardous liquid chemicals in factories and chemical plants caused by natural disasters or human error, it is important to precisely estimate exposure risk and design appropriate evacuation plans and risk‐reduction measures. The exposure risk of indoor residents to leaked chemicals may be estimated using direct measurements or theoretical/numerical estimations of gas‐phase concentrations. Although mathematical models of gas‐phase concentration in the workplace are essential for predicting exposure concentrations at the design stage, practical models have not yet been fully established. We previously proposed practical numerical models to assess indoor gas‐phase concentration distributions after the accidental leakage of liquid chemicals using liquid toluene as a representative hazardous chemical. In this study, the leakage of liquid ethyl acetate, a commonly used organic solvent, into mortar flooring was reproduced in a small test chamber, and numerical analysis was performed. The results showed that the time history of the chamber exhaust concentration had a sharp peak and differed significantly from that of toluene. Three‐dimensional computational fluid dynamics (CFD) analysis incorporating practical ethyl acetate emission models reproduced the external and internal emission characteristics of leaked ethyl acetate on the mortar material. The models showed reasonable agreement with the experimental data. [ABSTRACT FROM AUTHOR]

A study is performed of the effect of forces of different natures have on ion exchange in classical systems that are polymeric ion exchangers in aqueous solutions. A canonical form of the interaction energy is introduced in which the main contribution is made by electrostatic energy. A theoretical analysis is made of experimental data on the electrical conductivity of ion-exchange membranes, allowing for the nature of internal diffusion. A description is given of the dependence of local permittivity on the interionic distance, which is considered when establishing the configuration of ions and water in the region of interaction. The electrostatic potentials of some strong ion exchangers are determined. [ABSTRACT FROM AUTHOR]

Enzyme—metal hybrid catalysts bridge the gap between enzymatic and heterogeneous catalysis, which is significant for expanding biocatalysis to a broader scope. Previous studies have demonstrated that the enzyme—metal hybrid catalysts exhibited considerably higher catalytic efficiency in cascade reactions, compared with that of the combination of separated enzyme and metal catalysts. However, the precise mechanism of this phenomenon remains unclear. Here, we investigated the diffusion process in enzyme—metal hybrid catalysts using Pd/lipase-Pluronic conjugates and the combination of immobilized lipase (Novozyme 435) and Pd/C as models. With reference to experimental data in previous studies, the Weisz—Prater parameter and efficiency factor of internal diffusion were calculated to evaluate the internal diffusion limitations in these catalysts. Thereafter, a kinetic model was developed and fitted to describe the proximity effect in hybrid catalysts. Results indicated that the enhanced catalytic efficiency of hybrid catalysts may arise from the decreased internal diffusion limitation, size effect of Pd clusters and proximity of the enzyme and metal active sites, which provides a theoretical foundation for the rational design of enzyme-metal hybrid catalysts. [ABSTRACT FROM AUTHOR]

Colorimetric sensors are widely used because of their inherent advantages including accuracy, rapid response, ease-of-use, and low costs; however, they usually lack reusability, which precludes the continuous use of a single sensor. We have developed a threshold-responsive colorimetric system that enables repeated analyte measurements by a single colorimetric sensor. The threshold responsive algorithm automatically adjusts the sensor exposure time to the analyte and measurement frequency according to the sensor response. The system registers the colorimetric sensor signal change rate, prevents the colorimetric sensor from reaching saturation, and allows the sensor to fully regenerate before the next measurement is started. The system also addresses issues common to colorimetric sensors, including the response time and range of detection. We demonstrate the benefits and feasibility of this novel system, using colorimetric sensors for ammonia and carbon dioxide gases for continuous monitoring of up to (at least) 60 detection cycles without signs of analytical performance degradation of the sensors.

Deoxygenation of fatty acid esters in aqueous phase using in-situ generated H 2 has emerged as a promising approach to producing sustainable diesel-like hydrocarbons. In this study, we employed a solvothermal method to synthesize novel Ni–Sn metal–organic frameworks (MOFs) with a homogeneous distribution of Ni and Sn elements. Subsequently, various Ni–Sn intermetallic compounds (IMCs) encapsulated with a porous carbon layer (<3 nm) (Ni–Sn IMC@C) were prepared through the facile pyrolysis of metal–organic frameworks under a controlled N 2 atmosphere. Applying methyl palmitate as model reactant and methanol as hydrogen donor, Ni 3 Sn 2 IMC@C gives approximately 100% conversion and 93% yield towards n-C 15 and n-C 16 alkanes at 330 °C, without significant deactivation during the recycling for five times. The deoxygenation pathway is dominated by decarbonylation (DeCO) on Ni–Sn IMCs. In Ni–Sn IMCs, the oxophilic nature of Sn, along with its charge transfer with Ni, enhances the adsorption of an η2(C, O)-aldehyde configuration. The strategic isolation of adjacent Ni by Sn effectively inhibits methanation and C–C bond hydrolysis, reducing H 2 consumption and increasing carbon yield. Moreover, the ultrathin porous carbon encapsulation not only prevents the loss and sintering of Ni 3 Sn 2 IMC under harsh hydrothermal condition but also mitigates mass transfer limitation. Surface oxidation of Ni 3 Sn 2 IMC, particularly the formation of SnO 2 , is detrimental to deoxygenation. Additionally, Ni 3 Sn 2 IMC@C exhibits high hydrocarbon yields (>89.6%) in in-situ aqueous phase deoxygenation of methyl laurate, methyl stearate and methyl oleate. These findings highlight the remarkable potential of MOF-derived catalysts for hydrothermal deoxygenation. Efficient and robust ultrathin porous carbon encapsulated Ni–Sn intermetallic compounds are innovatively designed to suppress the sintering and loss of active components with low diffusion resistance for in-situ aqueous phase deoxygenation of fatty acid methyl esters to diesel-like hydrocarbons. [Display omitted] • Ni–Sn bimetallic MOF-74 was synthesized via a one-pot solvothermal process. • Ultrathin carbon-coated Ni–Sn IMCs derived from MOF-74 have low transfer limitations. • Ni–Sn IMC@C have excellent stability under harsh hydrothermal condition. • C–C bond hydrogenolysis and methanation are suppressed on Ni–Sn IMCs. • Yield of hydrocarbons reaches above 93 % on Ni 3 Sn 2 IMC@C. [ABSTRACT FROM AUTHOR]

Mass transfer usually affects the rate of chemical reactions in coal. The effect of internal diffusion on char gasification with CO2 in the temperature range from 1123 K to 1273 K was investigated via thermogravimetric analysis and assessment of char morphology features. The results revealed that the effect of internal diffusion on the initial reaction rate was more significant with an increase of particle size, due to the concentration gradient of the gasification agent within the solid particles. In the early stage of gasification, the generation of new micropores and the opening of closed pores led to an increase in specific surface area. As the reaction proceeded, the openings were gradually expanded and the specific surface area continued to increase. However, with further reaction, disappearance of edge pores, melting and collapse of the pore structure led to a decrease in specific surface area. The intrinsic activation energy and reaction order based on the nth-order model were 157.67 kJ·mol−1 and 0.36, respectively. Thus, temperature zones corresponding to chemical reaction and diffusion control were identified. Moreover, the calculated effectiveness factor provided a quantitative estimation of internal diffusion in the initial stage. [ABSTRACT FROM AUTHOR]

An important category of glycerol derivatives, having multiple practical applications, are its esters with acetic acid (acetates or acetins). The most common preparation method of glycerol acetates is the direct esterification of glycerol with acetic acid in presence of acid catalysts. In this work is investigated the liquid phase glycerol esterification with acetic acid, catalyzed by the commercial Purolite CT-275 ion exchange resin. In this aim, there were performed batch experiments, in a stirred autoclave reactor, at initial acetic acid to glycerol molar ratios between 4 and 9 and temperatures between 70 and 110 °C. The experimental data were used to develop a kinetic model, based on the Langmuir Hinshelwood theory. The components activities, involved in the calculation of the reaction rates, were evaluated by the UNIFAC Dortmund method. The proposed kinetic model predicts with good accuracy the products distribution dependencies on the reactants molar ratio and reaction temperature. The calculated values of the Weisz-Prater criteria evidenced influences of the internal diffusion on the esterification process kinetics, over an initial reaction time interval. The proposed kinetic model is directly utilizable in the commercial process analysis and design calculations. • Initial reactants molar ratio has an important influence on the product yields. • It was developed a process kinetic model in component activities. • The internal diffusion of glycerol has limitation influence on process kinetics over an incipient time interval. [ABSTRACT FROM AUTHOR]

The pretreatment and effective utilization of carbonaceous gold ore is of significant to refractory gold resources. In this work, the calcination kinetics was employed to investigate the relationship between phase transformation and structure evolution of carbonaceous gold ore during roasting process. Mechanism functions were determined and the fact that roasting process was controlled by chemical reaction in the initial 90 min and dominated by internal diffusion as time reached to 120 min was uncovered. In addition, the apparent activation energies for initial and latter roasting stage were 212.11 kJ·mol ^−1 and 163.73 kJ·mol ^−1 , respectively. Combined with the analysis of phase transformation and structure evolution, the removal of carbonaceous matter and appearance of new tiny pores contributed to the change of calcination kinetics. Moreover, phase transformation and structure evolution were beneficial for elevating Au recovery during leaching experiment. These findings helped to understand the mechanism of carbonaceous minerals during roasting and provided new insight for the utilization of refractory gold resource.

Pristine biochar (PBC) is flourishing in adsorptive oxidation for pollutants remediation as an alternative to carbon adsorbents derived from coal/petroleum carbon sources, multistep, and hash synthesis. However, it is widely overlooked for aqueous S2- remediation because the rational design of biochar with proper conductive and porous structure is challenging. Cobalt or iron ion was impregnated in biomass to produce biochar with different porous and conductive structures and explore S2- adsorptive oxidation mechanism. Finding suggests cobalt and iron ions facilitate biomass decomposition to remove volatile matter, which transforms them into elemental cobalt (Co0) or magnetite (Fe 3 O 4) on biochars (BC-Co) or (BC-Fe) and improves the porous structure. BC-Co benefitted from superior mesopores to adsorb S2- 2.4 and 35 times faster than PBC and BC-Fe, achieving 811 ± 146 mg-S2-/g maximum capacity. BC-Fe removed S2- far less than PBC because Fe 3 O 4 on its surface blocked S2- diffusion channel to the active site. It is postulated that S2- was removed from water via external and internal diffusion and adsorption and oxidation at active sites. S2- diffuses from bulk liquid to film near the biochar pore and into the pores via pore and surface diffusion to the active site, where it is adsorbed and oxidized to elemental sulfur or sulfate by quinone, semiquinone, or hydroxyl radicals at the wall of biochars. This study has documented fundamental information for developing mesoporous electroactive biochar for contaminant removal. [Display omitted] • CO2+ dehydrate hydroxyl groups on biomass to produce mesopore biochar. • Fe3+ facilated a more conductive but less porous biochar. • BC-Co had a superior S2- uptake capacity, separability, and regenerative performance. • Fe 3 O 4 on carbon matrix donate and accept electrons due to presence of Fe2+ and Fe3+cycles. • Fe 3 O 4 blocked S2- diffusion channel to actve abd reduced BC-Fe sorption capacity. [ABSTRACT FROM AUTHOR]

Abstract Polyoxymethylene dimethyl ethers (PODE n , CH 3 O(CH 2 O) n CH 3 , where n ≥ 1) are environmentally friendly diesel fuel additives because they can significantly reduce the emission of engine exhaust during combustion. It is an efficient way to synthesize PODE n from dimethoxymethane (DMM) and paraformaldehyde (PF) over solid acid catalysts. The synthesis process consisted of two steps: the depolymerization of PF and the polymerization of PODE n. In this work, the first step was proved to be the rate-determining step by analyzing the product distribution and the rate of reactions with and without PF. NKC-9 resins of different size were used to prove that the internal diffusion in catalyst was a key factor to affect the depolymerization process. The SO 4 2−/TiO 2 and SO 4 2−/TiO 2 -ZrO 2 catalysts were used to further prove that the catalysts with larger pores were more active for the synthesis of PODE n. Graphic abstract Comparison between reactions with and without paraformaldehyde. Unlabelled Image Highlights • Synthesis of PODE n from DMM and paraformaldehyde (PF) was studied. • Depolymerization of paraformaldehyde was identified as the rate-determining step. • Internal diffusion was a key factor affecting the rate-determining step. • Catalyst with smaller particle size and larger pore size had much higher activity. [ABSTRACT FROM AUTHOR]

A shrinking-layer model by modification of classical shrinking-core model was developed based on cell wall multi-layered structure for delignification of sugarcane bagasse with sulfuric acid (SA) catalyzed atmospheric acetic acid (AA) fractionation. The general model for overall rate of delignification was obtained and further employed to evaluate the mass transfer effects on delignification. It was found that the external diffusion could be neglected under the studied fractionation conditions, while the internal diffusion appeared to play an important role. The effective diffusion coefficient for lignin within the biomass was estimated as 6.7 × 10 −14 –1.6 × 10 −12  m 2 /s depending on temperature, solid content in the system and molecular weight of lignin. However, surface reaction also seems to be a limiting step to the overall rate of delignification. At the early stage of delignification, both internal diffusion and reaction were controlling steps, while at the late stage reaction seems to be the controlling step. [ABSTRACT FROM AUTHOR]

Mass transfer plays a significant role in a sensor's performance, because the substrate can be detected only when it contacts with the active catalytic surface. In this work, cuprous oxide mesoporous nanospheres (Cu2O MPNS) with different pore size distributions are fabricated and applied as electrocatalysts for glucose detection. The small pore Cu2O (SP-Cu2O, mean pore size of 5.3 nm) and large pore Cu2O (LP-Cu2O, mean pore size of 16.4 nm) spheres are prepared by the template method and an etching treatment. The obtained two kinds of Cu2O MPNS exhibit high porosity with a similar specific surface area of 61.2 and 63.4 (m2·g-1), respectively. The prepared Cu2O MPNS are used to construct an electrochemical non-enzymatic glucose sensor. The results show that the LP-Cu2O exhibits better performance than SP-Cu2O, which illustrates that the internal diffusion takes a great impact on the performance of the sensor. The LP-Cu2O modified electrode possesses a high and reproducible sensitivity of 2116.9 μA mM-1·cm-2 at the applied potential of 0.6 V with a wide detection range of 0.003-7.8 mM and a low detection limit of 0.42 μM. [ABSTRACT FROM AUTHOR]

The modeling and simulation of hydrotreating (HDT) reactors can provide relevant information about optimal operating conditions, reactor design and formulation of catalysts to achieve cleaner fuels. This study developed a phenomenological model to estimate the kinetic parameters for the HDT process using the design of experiments technique. The catalytic tests were carried out in a bench-scale unit with diesel as feedstock under similar conditions to those of the industrial units and commercial nickel-molybdenum on alumina (NiMo/γ-Al 2 O 3 ) as catalyst. The reactor temperature was varied from 330 to 380 °C and liquid hourly space velocity (LHSV) from 0.5 to 1.5 h −1 , keeping constant hydrogen to oil ratio (H 2 /oil) and pressure at 800 std m 3 /m 3 and 90 bar, respectively. The unknown parameters are estimated from experimental data by minimization of the unweighted least-squares function, using a non-linear optimization method (complex algorithm). The proposed model was able to reproduce different operating conditions with good adjustment and accuracy. Relative deviations below 4% for the experimental data and model prediction were achieved. Statistical parameters, p values, and confidence intervals confirmed the good quality of the estimated kinetic parameters. Internal diffusion resistances were present during hydrodesulfurization (HDS) and hydrodenitrogenation (HDN) reactions. The hydrogen consumption for HDS was higher than for HDN reaction. Finally, the proposed experimental design with 12 catalytic tests was satisfactory to obtain the desired results in a reliable way. [ABSTRACT FROM AUTHOR]

Liquid-phase epoxidation of alkenes and hydroxylation of phenol were carried out using TS-1 titanosilicate as a catalyst with the particle sizes ranging from 0.15 up to 25 µm. Experimental reaction rates as measured on the smallest catalyst particles were found to be free of mass transfer influence. This makes it possible to describe quantitatively the internal diffusion effects for large-size grains, so as to evaluate the values of reagent diffusion coefficients within the catalyst pores. Graphical Abstract: [ABSTRACT FROM AUTHOR]

Based on the porous structure of coal, a coupled thermal decomposition model is developed to describe the coal pyrolysis process more fully and truly. It not only incorporates specific surface change in reaction rate during conversion, but also couples chemical reaction rate happened on pore surfaces with internal diffusion rate of the gaseous product. To validate the applicability of the model, three kinds of coal pyrolysis experiments were carried out. The results show that the model is suitable for all the three stages of coal pyrolysis, which realizes the unification of mechanisms in low-, middle- and hightemperature stages. One set of activation energy and pre-exponential factor is calculated for each stage of coal pyrolysis according to the slope and intercept of the corresponding fitting line. With these kinetic parameters, the numerical solution of this model is obtained. Compared the numerical solution with experimental values, the good agreement between them is observed, which validates the reliability of the model. [ABSTRACT FROM AUTHOR]

Coprocessing of bio-oil and petroleum fraction is a prospective way of bio-oil upgrading. The upgrading is a complex combination of kinetic and transport processes. An overall kinetic model was developed considering the internal diffusion and the catalyst deactivation in this paper. First, the parameters of intrinsic kinetics model were calculated by the experimental data obtained in a fixed-bed reactor with a fine powder catalyst particle (0.32 mm). Using the intrinsic kinetic parameters and gas–solid catalysis theory, an effectiveness factor model was developed to evaluate the effect of internal diffusion on coprocessing. Then the kinetic model rB=a×η×rB0was established based on the effectiveness factor model and the deactivation rate equation. The effectiveness factor η and liquid yields at different reaction conditions predicted by this kinetic model agreed closely with the experimental results. [ABSTRACT FROM PUBLISHER]

Packed bed reactors are often used for catalyst screening studies due to their simple construction and ease of operation. The use of gold nanoparticles for partial oxidation reactions of alcohols has arisen interest of the scientific community. A model was generated to explain the experimentally observed reactor behavior (conversion of alcohol, yields of products) in the alcohol oxidation over gold nanoparticles. The model for this gas-phase heterogeneously catalyzed multi-reaction system consisted of the dynamic mass and energy balances and Langmuir–Hinshelwood–Hougen–Watson, Mars van Krevelen or Power law expressions for the reaction kinetics. Fluid flow was described with convection and dispersion terms. A semi-empirical pressure drop correlation was used. This resulted in a rapidly running model by reducing the problem size significantly. Powerful gPROMS Modelbuilder software was used as the model development, simulation and parameter estimation platform. The primary task was to punctually define and solve the complete set of equations (Partial Differential Equations (PDEs) together with algebraic equations). The modeling effort focused on the selection of the complete set of equations to adjust the degrees of freedom 0 and on the simultaneous solution of the whole set. Numerical method of lines was applied to convert the partial differential equations to ordinary ones. All reactions were assumed to take place on evenly distributed active sites of the porous catalyst particles. The dynamic mass balances consisting of internal diffusion and surface reaction within the porous particles were solved simultaneously with the mass and energy balances of the whole reactor. The axial and radial concentration and temperature profiles inside the reactor and the concentration profiles within the particles were then obtained results. Starting from experiments performed at T = 125–250 °C, p = 1 atm and superficial gas velocity of 0.03 m/s, a parameter estimation analysis was conducted. After the parameter estimation, the calculated alcohol conversion and yields of the main products (acetaldehyde and acetic acid) followed relatively closely the experimentally observed ones. The estimated parameters were the rate constants and the activation energies and the adsorption parameters (with LHHW kinetics, Mars van Krevelen kinetics) and reaction orders of oxygen (Power law kinetics). Simulation studies were done to show how feed temperature and catalyst loading influenced the results and how the Peclet number reflected on obtained results. [ABSTRACT FROM AUTHOR]

The molecular diffusion of phenolics inside walnut pellicle fiber particles under solid-liquid extraction enhanced by ultrasound (US), orbital agitation (OA), impeller agitation (IA), and the combined microwave and impeller agitation (MW-IA) were explored. Numerical modeling considering the temperature-dependent diffusivity revealed that the internal diffusivity of phenolics was the highest under MW-IA and the lowest under OA. At 35 °C, IA (126.246 mg/g, t = 10 min) was more effective to strengthen the phenolic diffusivity than the US-39W (95.538 mg/g, t = 10 min). Due to the simultaneous enhancement of internal diffusivity and external dissolution, the MW-IA extraction reached equilibrium within 16 min, reaching the highest yield among all the treatments (176.944 mg/g). The extraction was then divided into the increasing and falling driving force periods. The comparison of phenolic diffusivity among MW-IA and IA roughly indicated that the proportion of non-thermal effect of microwave at 315 W was 889% higher than 189 W at the extraction equilibrium. Moreover, some soluble polyphenols, i.e. quercitrin and syringic acid, could be adsorbed by the cell wall after equilibrium. The correlations between any two soluble phenolics varied with the phenolic type, deducing that soluble phenolics may interact with each other either positively or negatively. Besides, the mining of phenolic data also indicated that intensive impeller agitation is a good substitution for ultrasonication to extract phenolics effectively. [Display omitted] • Solid-liquid extraction was modeled by a diffusion model with a temperature factor. • Diffusion was divided into the increasing and falling driving force periods. • Non-thermal effect of microwave at 315 W was 889% higher than 189 W at equilibrium. • Impeller agitation at a high temperature can be a substitute for ultrasound extraction. • Soluble polyphenols interact with each other either positively or negatively. [ABSTRACT FROM AUTHOR]

A generic approach was applied to develop a comprehensive Trickle Bed Reactor (TBR) model. The model was based on exact definition of the required equations and development of a program code (in gPROMS ModelBuilder environment) to solve them simultaneously. The model consisted of dynamic mass and energy balances in three phases of heterogeneously catalyzed reaction system. The fluid dynamics was expressed in simple terms (dispersion model, semi-empiric expressions for pressure drop and liquid hold-up) to guarantee a fast running program code. Even though a large number of articles have been published on the topic, only few of these studies penetrate into all details of the system. Most of them focus on the description of few selected physical phenomena. Including most or even all phenomena in a single model is seldom done. Most often, the published reactor models consider two dimensions only, because of mathematical simplicity (i.e. TBR axial and radial coordinates or only TBR axial coordinate and particle radius). Here an attempt was made to present a generic simulation model for tubular reactors working in non-isothermal three-phase systems (gas–liquid–solid) where three dimensions are simultaneously taken into account (TBR axial and radial coordinate and particle radius). All the model development and calculations were made by using the powerful software, which allows solving a large set of partial differential equations and algebraic equations. An example case study of hydrogenation of arabinose to arabitol on a ruthenium catalyst was included. [ABSTRACT FROM AUTHOR]

To improve the selectivity performance of CoMoS catalysts applied to the hydrodesulfurization (HDS) of fluid catalytic cracking (FCC) gasoline, a series of CoMoS/Al 2 O 3 catalysts was prepared with alumina of different pore structures, and their HDS performance was evaluated with a real FCC gasoline. This study indicated that CoMoS/Al 2 O 3 catalysts prepared with micro- or meso-porous alumina possessed high HDS activity but low selectivity, whereas macro-porous alumina enhanced the selectivity of CoMoS catalysts. The enhanced HDS selectivity was due to the tuning of the MoS 2 slabs and the weakening of the internal diffusion resistance. Based on the above results, the optimal CoMoS/Al 2 O 3 catalyst was prepared with the alumina of the tri-modal pore distribution at approximately 5–8 nm, 15–20 nm, and 90–100 nm. The optimal catalyst displayed a balanced HDS activity and selectivity in contrast to the reference catalyst prepared with K- and P-modified Al 2 O 3 . [ABSTRACT FROM AUTHOR]

Effects of plants’ structures on bioactive compounds extraction were rarely reported, which limited the research improvement of extraction efficiency from an intrinsic perspective. In this work, the structural properties of untreated and steam exploded fig leaves as well as their effects on flavonoids extraction were systematically studied. Results implied that internal diffusion became the limiting factor of flavonoids extraction from untreated fig leaf when liquid–solid ratio exceeded 75 mL/g-dry. After steam explosion pretreatment (0.2 MPa and 3 min), flavonoids yield extracted from fig leaf was increased by 55.9% compared with that from untreated fig leaf. However, more drastic steam explosion condition (0.4 MPa and 3 min) did not lead to higher flavonoids yield, which may be caused by the damage of flavonoids at high pretreatment temperature. A finite reaction model was proposed to demonstrate the mechanisms of flavonoids extraction from steam exploded fig leaf, and it was well consistent with the practical extraction. Therefore, steam explosion pretreatment with proper intensity should be a novel technology to enhance the extraction performance. [ABSTRACT FROM AUTHOR]

In this study, a macro-structured Pd catalyst supported on carbon nanofiber coated on cordierite monolith (Pd/CNF/TiO 2 /monolith) was employed for hydrogenation of 4-CBA. The effect of mass transfer on the catalyst performance was studied experimentally and the results are described using a simple kinetic model. The results were compared to Pd catalysts supported on activated carbon (Pd/AC) and on carbon nanofibers aggregates (Pd/CNF). Catalytic performance of the Pd/CNF/TiO 2 /monolith is similar to Pd/CNF and the Pd/AC with particles as small as 50 μm (Pd/AC50), whereas Pd/AC with larger support particles revealed a lower activity per Pd active surface site, due to internal mass transfer limitation. Also the selectivity to the intermediate hydrogenation product (4-HMBA), versus deep hydrogenation to p -TA, is clearly affected by internal mass transfer. Pd/AC with large particles (3000 μm) achieves a maximum yield to the intermediate product of only 35%, whereas all the other catalysts achieve typically 70%. Remarkably, the conversion level at which the maximum yield of the intermediate product is achieved is highest for the Pd/CNF/TiO 2 /monolith. This advantage is assigned to superior internal mass transfer properties, thanks to high porosity, low tortuosity and short diffusion length of the CNF layer. Clearly, the CNF/TiO 2 /monolith applied as a fixed bed outperforms slurry phase catalysts, abandoning the need of a filtration section. [ABSTRACT FROM AUTHOR]

The present paper deals with theoretical and experimental substantiation of the basic process laws of the sunflower cake extraction by unconventional solvent - ethyl alcohol. Industrial samples of sunflower cake in the form of granules and grits, for which the porosity parameters (porosity and filtration ratios) were defined, were subjected to the test. Physical model of the 8-step extractor, operating by the countercurrent irrigation principle was developed using a specially designed laboratory setup. The influence of some technological factors (duty of water, extraction time and oilseed material structure) on the sunflower oil extraction kinetics (original cake oil content variation in time) and miscella concentration at each extraction stage was experimentally found. Based on the experimental results, internal diffusion coefficient for ethanolic extraction of sunflower cake, depending on the porosity and filtration indicators was calculated using MathCad and MicrosoftExsel application package. It was shown that improved ethyl alcohol percolation in the granule is confirmed by the higher value of the coefficient of internal diffusion in the granule. The latter is about 2 times higher than that for the hexane extraction. New scientific data for the formulation of the values of process parameters for future technology were obtained. [ABSTRACT FROM AUTHOR]

This research addresses the theoretically neglected question of how the internal diffusion of inter-organizational systems (IOS) into a firm's activities and its external diffusion into the supply chain partners influence performance improvement. Drawing on the resource-based view, our research model posits that organizational and relational resources affect both internal and external diffusion, which in turn, influence performance improvement. Survey results from 187 managers in Korean and Chinese firms showed that while the impact of organizational resources on a firm's performance improvement was fully mediated by IOS diffusion, the diffusion partially mediates the impact of relational resources on performance improvement. This study also revealed a significantly different pattern of diffusion between Korean and Chinese firms, i.e. showing the impact of organizational and relational resources on a firm's performance through external diffusion of IOS are significantly greater in Korean firms, while the impact of internal diffusion was significantly greater in Chinese firms. In other words, Korean firms tend to externally diffuse IOS toward their business partners, while Chinese firms tend to internally diffuse IOS by deploying IOS from their partners. The implications of these findings for both research and practice are discussed. [ABSTRACT FROM AUTHOR]