Stirring Speed Research Articles

Optimization of Tantalite Ore Dissolution Using Hydrofluoric-sulphuric Acid and Shrinking Core Model

Aim: This study investigates the dissolution of tantalite mineral from granitic pegmatite in Okpella, Northern Edo State, Nigeria. Study Design: Elemental and mineral composition analysis of tantalite ore sample from Okpella was carried out using X-ray fluorescence and X-ray diffraction. Response Surface Methodology (RSM) and the shrinking core model were used in designing the study while the effects of temperature, stirring speed, particle diameter, and mixed acids concentrations were investigated in the dissolution rates of the mineral. Duration of Study: 50 experimental runs were designed using RSM Central Composite Design (CCD) to optimize variables including HF concentration (1-8 M), H2SO4 concentration (0.5-3 M), temperature (32-82°C), stirring speed (0-500 rpm), and particle size (0.1-0.3 mm), with a constant contact time of 240 minutes. Methodology: Pulverized tantalite samples (0.1-0.3 mm) were reacted with varying concentrations of hydrofluoric and sulphuric acids (1-8 M and 0.5-3.0 M, respectively) for 240 minutes, with stirring speeds between 0-500 rpm and temperatures from 32 to 82°C. The mixture was stirred in a water bath with 50 ml of mixed acids solution and 2 g of ore. After the reaction, the solution was decanted, and the residual ore was washed, dried at 60 °C, and weighed. The difference between the initial and final weights indicated the amount of undissolved tantalite ore. Results: Ore characterization results revealed high concentration of tantalum (34.17%), iron (12.55%), niobium (8.38%), and titanium (6.01%), with other elements present in smaller amounts. Optimal conditions were found to be 8 M HF, 0.5 M H2SO4, 82°C, 500 rpm stirring speed, and 0.1 mm particle size, resulting in 97.28% dissolution of tantalite ore. Regression analysis demonstrated model robustness with an F-value of 16.70 and a P-value of 0.0001, indicating HF concentration and stirring speed as the most impactful factors. The model’s R² value of 0.9201 and adjusted R² of 0.8650 confirm its predictive accuracy. Analysis using the shrinking sphere model showed that film diffusion control is the primary limiting step with t/τ=0.999, while reaction control resulted in slightly lower conversion with t/τ=0.973, highlighting film diffusion as the main constraint but with high conversion efficiency. Conclusion: The findings from this investigation not only reveal the dissolution of tantalite ore through a detailed experimental approach, identifying optimal conditions -8 M HF, 0.5 M H2SO4, 82 oC, 500 rpm stirring speed and 0.1 mm particle size- that achieve a 97.28% dissolution, but they also enhance our understanding of mineral processing. These understanding are crucial for mineral dissolution up scaling technologies in industrial applications, which will potentially leads to a more efficient extraction method that could significantly reduce costs and environmental impacts in the mining sector. This research could drive advancements in sustainable resource recovery and contribute to sourcing of critical minerals.

Electrolyte Solution Stirring Effect on Deposition Rate, Crystallographic Orientation, and Electrochemical Behaviour of Ni Film

Abstract Stirring the electrolyte meanwhile electrodeposition process is running may influence the properties of the forming films. In this work, the electrodeposition of copper (Cu) over aluminium (Al) alloy was performed. Subsequently, the electrodeposition of nickel (Ni) onto the formed Cu layer was conducted. In order to enhance the films properties, some various stirring speeds then are implied on the plating solution of the Ni electrodeposition process. The synthesized of Ni films were analysed by means of both X-ray diffraction (XRD) and a potentiostat equipment. The sample made shows different physical properties before and after electrodeposition based on sample weighed to examine the deposition rate. XRD patterns confirmed that all samples have a face-centered cubic (fcc) crystal structures with a space group of Fm-3m. Stirring speed play an important role of an inverse relationship with deposition rate, crystallite size, lattice strain, and corrosion rate. The sample that was made using the highest stirring speed yield a better corrosion resistance at around 0.239 mmpy due to less lattice strain.

Study on the effect of particles in oilfield produced water on the deposition process of CaCO3

In crude oil production, scale deposition significantly reduces production output and elevates operational costs, posing a severe threat to production safety. While chemical methods have been extensively explored for the scaling and inhibition of inorganic salts, the inorganic scaling triggered by solid particle scaling in complex oilfield water has largely been overlooked. This study involves the introduction of particles into a supersaturated CaCO3 solution, utilizing static scale inhibition and conductivity techniques to examine their influence on the scaling process and crystallization rate. It is evident that solid particles expedite the deposition process of CaCO3. Moreover, the deposition rate of CaCO3 is influenced by factors such as the solid particle content, particle size, and stirring speed. It is noteworthy that the presence of solid particles solely impacts the formation rate of CaCO3 crystals, without altering the total deposition. Specifically, under conditions of 70°C, 250/min stirring speed, and 0.08% SiO2 addition, the deposition rate of CaCO3 is enhanced by 13.5%. The nucleus growth rate constant increases from 11.10 × 10-3min-1 to 14.52 × 10-3min-1 and the crystal growth rate constant increases from 3.02 × 10-3min-1 to 3.36 × 10-3min-1 at most. Observations made through scanning electron microscopy (SEM) and polarized light microscopy reveal that scaling occurs predominantly on the added solid particles in later stages, indicating that solid particles in supersaturated solutions serve as crystal nuclei, inducing the growth of CaCO3 crystals and thus accelerating scaling. This research provides valuable insights for the study of scaling in complex water environments.

Extraction of Anacardium occidentale: a kinetic, thermodynamic, phytochemical identification, and antibacterial study

Cashew tree biomass, Anacardium occidentale, represents an underutilized part of the plant and could have great potential for application in several areas, such as bioengineering, food science, and chemical. The stirred bed process was optimized to produce extracts from Anacardium occidentale stem bark (SBAo) and leaves (LAo) for bactericide purposes. Variables as alcohol content, stirring speed (SS), particle size (PS), solid-to-solvent ratio (S/S), temperature, and extraction time were evaluated. Subsequently, kinetic, thermodynamic and diffusivity fittings of the data were performed using different nonlinear models (Peleg, 2nd order, Elovich, power law, and Fick’s 2nd law) applied to the yield curves. Extracts were characterized by Fourier-transform infrared (FTIR) spectroscopy, total phenolic content (TPC), total flavonoid content (TFC), trolox equivalent antioxidant capacity (TEAC), and ultra-high resolution mass spectrometry (UHRMS) techniques for qualitative and quantitative determination of the phytochemicals. The optimized operating conditions obtained were ethanol in solvent at 70%, PS < 45 μm, 1200 rpm SS, 1/10 S/S ratio, and extraction time of 1 h at 50 ºC. The 2nd order kinetic model was the one that presented the best fits: SBAo (R2 > 0.9893 and RMSE < 3.4293) and LAo (R2 > 0.9985 and RMSE < 3.1117). Both A. occidentale extracts showed high levels of polyphenols and flavonoids, such as anacardic acid. Finally, the optimized extracts showed antibacterial susceptibility, with larger halos against S. aureus, 0.88± 0.07 mm (SBAo) and 0.45 ± 0.03 mm (LAo), in relation to E. coli, 0.80 ± 0.10 mm (SBAo) and 0.69 ± 0.08 mm (LAo).

Cationic dye remediation in water treatment with Lizardite–Rice Husk composite: A statistical physics approach

This study presents the development of a novel composite adsorbent, Lizardite-Rice Husk Composite (LRHC), synthesized from lizardite, a mineral derived from chromite ore waste, and rice husk, an agricultural byproduct. The primary objective was to evaluate the efficiency of LRHC in the adsorption of cationic dyes, Malachite Green (MG) and Methylene Blue (MB), from aqueous solutions. Systematic investigations were conducted to assess the influence of adsorbent mass, initial dye concentration, stirring speed, and contact time on adsorption performance. The results revealed that LRHC exhibited optimal adsorption capacities at pH values above 5, with MB and MG adsorption capacities reaching 309.75 mg/g and 51.43 mg/g, respectively. Adsorption equilibrium for MB was achieved within 30 min, indicating rapid dye uptake. Isotherm analysis demonstrated that the Temkin model best described MB adsorption, while the Freundlich model was more suitable for MG, with favorable Langmuir constants. Kinetic studies confirmed that the adsorption followed a second-order model, suggesting chemisorption as the rate-determining step. Intraparticle diffusion and mass transfer were identified as significant contributors to the adsorption process. Thermodynamic studies indicated that MB adsorption was spontaneous (ΔG° = −4.69 kJ/mol for the concentration of 50 mg/L at 298 K) and that MG adsorption was non-spontaneous (ΔG° = 1.52 kJ/mol for the concentration of 50 mg/L at 298 K), with spontaneity increasing at higher initial concentrations. Statistical physics modeling, particularly the monolayer model, provided detailed insights into the adsorption mechanisms and geometry. Furthermore, LRHC demonstrated excellent reusability, maintaining over 80% of its initial adsorption capacity after four regeneration cycles via a heterogeneous Fenton-like reaction. The combination of easy availability, cost-effectiveness, and environmental friendliness makes LRHC a superior adsorbent for the removal of cationic dyes compared to conventional alternatives. This research contributes novel insights into the design and application of composite adsorbents, offering a sustainable solution for water treatment and addressing significant environmental challenges.

Investigations on the removal of phosphate and nitrate using a mixture of cactus and Moringa seed powder via RSM techniques

Humans utilize water for a variety of purposes, which needs the treatment. The study explores the use of blended cactus and Moringa seed powder as coagulants to reduce phosphate and nitrate levels in surface water. Samples was collected from the Kitto River in the Oromiya region, Jimma, Ethiopia, were analyzed using various tools. A jar test was used to investigate the study using blended powder of cactus and Moringa under different operating parameters. In this study, pH (5−9), settling time (30–50 min), stirring speed (40–50 rpm), and dosage ratio (50 %C to 50 %M, 25 % C to 75 %M, and 75 % C to 25 % M) were used to analyze the removal % of NO3-, and PO43-. The highest removal efficiency was achieved with a dosage ratio of 3 (75 % M: 25 % C), a pH of 7, a settling time between 40 to 50 min, and a stirring speed of less than 50 rpm. The removal efficiencies closely matched the predicted values (92.6 %, 88.31 %) and actual values (99.46 %, 92.32 %) for PO43- and NO3- respectively. Hence, the finding showed that blended cactus with Moringa seed increases the effectiveness of phosphate and nitrate reduction.

Formulation Optimization and Evaluation of Patented Solid Lipid Nanoparticles of Ambrisentan for Pulmonary Arterial Hypertension.

Ambrisentan is a new endothelin receptor antagonist extensively used to manage pulmonary or pulmonary arterial hypertension. The therapeutic efficacy of Ambrisentan is limited due to its reduced solubility, higher log P (3.4), and thus less bioavailability. The recent investigation was concentrated on the improvement of solubility, and bioavailability of Ambrisentan for the therapy of hypertension via solid lipid nanoparticles (SLN) administered orally. XRD evaluated the compatibility of Ambrisentan with lipids with FTIR, DSC, and crystalline nature. The SLN was developed by High-pressure homogenization method. The Glyceryl monostearate and Tween 80 indicated the highest solubility, hence selected. The optimization was performed with Box-Behnken Design considering the concentration of GMS (X1), Tween 80 (X2), stirring speed (X3) as independent factors and particle size (Y1), entrapment efficiency (Y2) as dependent factors. The Patents on the SLN are Indian 202321053691, U.S. Patent, 10,973,798B2, U.S. Patent 10,251,960B2, U.S. Patent 2021/0069121A1 and U.S. Patent 2022/0151945A1. The optimized batch F1 showed particle size (130 nm), ZP (-18.9 mV), and entrapment efficiency (85.73 %). The dual release pattern (prompt and sustained) was achieved with the SLNloaded Ambrisentan for about 24 hours. The lyophilized sample was subjected to SEM, which also revealed a spherical shape of a colloidal dispersion with a particle size of 126 nm. Hence, the F1 batch is highly recommended for solid oral delivery and also for the pilot-plant scale-up. A marked improvement in the solubility and dissolution of Ambrisentan was attained with the SLN. Moreover, the sustained delivery via the oral route enabled the patient's comfort, compliance, and therapeutic efficacy.

Adsorptive potential of apricot (Prunus Armeniaca) stone in the removal of Cr (VI) and Fe (II) ions from Aquatic Systems: Kinetic and isothermal investigations

Biogenic adsorbents have emerged as a promising alternative to the traditional remediation techniques of heavy-metals contaminated water treatment. Using apricot (Prunus Armeniaca) stone as a naturally derived adsorbent, the current study provides a comprehensive analysis of the kinetic and isothermal characteristics associated with Cr (VI) and Fe (II) ion adsorption. The results show that 0.5 mg of the adsorbent removed approximately 90 % of Cr (VI) and Fe (II) ions from 100 ppm solutions within 120 min at 298 K at 300 rpm stirring speed. Equilibrium was attained within 90 to 120 min, with a significant increase in the removal percentage observed in the first 30–40 min for both metals compared to the subsequent 80–90 min. The optimal pH conditions for adsorption were determined to be acidic (pH = 1.5) for Cr (VI) and neutral (pH = 7) for Fe (II). The adsorption kinetics followed a pseudo-second order model, while the isothermal equilibrium data best fit the Freundlich model over the Langmuir model. Moreover, the thermodynamic parameters, including ΔG°, ΔH°, and ΔS°, indicated that the sorption process is spontaneous, feasible, and endothermic. The response surface methodology (RSM) analysis showed a high level of accuracy in predicting the percent removal. These findings illustrate the effectiveness of apricot stone as a low-cost and environmentally conscious adsorbent, contributing to the development of sustainable water treatment technologies.

Design and Test of Potato Seedling Killing and Residual Film Recycling Integrated Machine

Plastic film mulching technology can effectively enhance crop yield and quality, and the use of mulch has been increasing in recent years; however, the problem of mulch residue is worsening due to the large amount of recycling work and slow natural degradation. In this study, a potato seedling killing and residual film recycling machine is designed to provide good working conditions for potato harvesters before harvesting in response to the problems of difficult separation of film tangles, the low net rate of recycling due to the mixing of residual film with soil, and the high soil content in residual film recycling operations in northwest China. The machine is based on the potato monoculture and double row planting mode in Gansu area. This paper puts forward the overall design scheme and carries out the theoretical analysis and parameter determination of the key components, such as the seedling killing device, the film surface cleaning device, the film unloading device, and so on. Using EDEM software to carry out the virtual simulation test and Design-Expert13 to analyze the test results, we determined the optimal working scheme for the machine, with a forward speed of 0.8 m/s, a film gap of 125 mm, and a spiral stirrer speed of 600 r/min. Based on a field test for verification, the test results show that the machine’s residual film recovery rate was 83.3%, the impurity rate was 3.8%, and the rate of injury to the potatoes was 1.4%. The machine meets the requirements of national and industry standards, and it can simultaneously realize straw crushing, film surface cleaning, residual film recycling, and hydraulic film unloading operations, with better operating results and while reaching the expected results. It can also provide a reference for the design and testing of a seeding and residual film recycling machine.

WITHDRAWN: rGO@CaO/NiO as a bifunctional heterogeneous nanocatalyst for high-quality biodiesel production from degraded waste oil by microwave-assisted: Diesel engine parameters assessment

In this research, a highly effective rGO@CaO/NiO bifunctional nanocatalyst was synthesized and utilized for the generation of biodiesel from degraded waste oil (DWO) through microwave assistance. A comprehensive analysis was conducted to assess the catalyst structure, revealing a notable specific surface area with significant surface characteristics for the rGO@CaO/NiO bifunctional nanocatalyst. The maximum biodiesel yield was achieved 97.46% under optimum conditions including methanol to oil ratio of 11.1 mol/mol, catalyst content of 3 wt.%, microwave time of 7.5 min, and stirring speed of 700 rpm. The catalyst's reusability was demonstrated through multiple cycles, maintaining high stability and consistent biodiesel yield over seven iterations. The activation energy and exponential factor for the conversion of DWO to biodiesel were determined as 30.91 kJ/mol and 2.3×104 min-1, respectively. The physical attributes of DWO-derived biodiesel revealed that they fall within the ASTM D6751 standard range. The impact of adding biodiesel to petrodiesel/biodiesel blends at various torques on the emission of key pollutants (CO, NOx, CO2, and UHC) and engine performance (BP, EGT, BTE, and BSFC) was investigated, yielding promising results. The rGO@CaO/NiO appears as a superior choice for biodiesel production, offering exceptional reusability, and significant biodiesel efficiency achieved within a short reaction time.

Production and Optimization of Xylanase Enzyme from Bacillus cereus by Submerged Fermentation Method

Three strains of Bacillus cereus were isolated from soil samples in this study in an effort to enhance the circumstances for the production of xylanase by the bacteria. The bacteria released extracellular xylanase throughout the submerged fermentation process. In a 250 ml conical flask, the whole fermentation process was conducted at 150 rpm stirring speed. The highest amount of xylanase synthesis was demonstrated by the isolated strains at 45°C, 48 hours of incubation, pH 5, 1.5% oat splet xylan base concentration, lactose carbon source, and beef extract source.

Enhancement of Succinic Acid Production by Actinobacillus succinogenes in an Electro-Bioreactor

This work examines the electrochemically enhanced production of succinic acid using the bacterium Actinobacillus succinogenes. The principal objective is to enhance the metabolic potential of glucose and CO2 utilization via the C4 pathway in order to synthesize succinic acid. We report on the development of an electro-bioreactor system to increase succinic acid production in a power-2-X approach. The use of activated carbon fibers as electrode surfaces and contact areas allows A. succinogenes to self-initiate biofilm formation. The integration of an electrical potential into the system shifts the redox balance from NAD+ to NADH, increasing the efficiency of metabolic processes. Mediators such as neutral red facilitate electron transfer within the system and optimize the redox reactions that are crucial for increased succinic acid production. Furthermore, the role of carbon nanotubes (CNTs) in electron transfer was investigated. The electro-bioreactor system developed here was operated in batch mode for 48 h and showed improvements in succinic acid yield and concentration. In particular, a run with 100 µM neutral red and a voltage of −600 mV achieved a yield of 0.7 gsuccinate·gglucose−1. In the absence of neutral red, a higher yield of 0.72 gsuccinate·gglucose−1 was achieved, which represents an increase of 14% compared to the control. When a potential of −600 mV was used in conjunction with 500 µg∙L−1 CNTs, a 21% increase in succinate concentration was observed after 48 h. An increase of 33% was achieved in the same batch by increasing the stirring speed. These results underscore the potential of the electro-bioreactor system to markedly enhance succinic acid production.

Pengaruh Suhu Ekstraksi dan Kecepatan Pengadukan terhadap Karakteristik Crude Ekstrak Stevia

Stevia is a natural sweetener that is 250-300 times sweeter than sucrose and is low in calories. Stevia sweeteners are obtained from the extraction of stevia leaves. This study aims to determine the effects of temperature and stirring speed on the characteristics of crude stevia extract (yield, brix value, and IR spectrum). Maceration extraction was conducted with 70% ethanol for 1 hour, varying the temperature (28 ℃, 40 ℃, 55 ℃) and stirring speed (0 rpm, 50 rpm, 100 rpm, 150 rpm). The results showed that a temperature of 40 ℃ produced the highest yield at each stirring speed. The yield increased with the increase in stirring speed at each extraction temperature. The highest brix value was obtained at 55 ℃ and a stirring speed of 150 rpm. The IR spectrum results showed that the functional groups in the crude stevia extract were almost identical to those in commercial stevia.

Transesterifikasi In Situ Minyak Biji Pepaya Menggunakan Ko-pelarut Tetrahidrofuran: Pengaruh Waktu Reaksi dan Penggunaan Katalis Natrium Hidroksida

The papaya seed oil is a non-food oil that can be used as raw material for biodiesel. The transesterification process using oil as raw material requires long process stages so it is not efficient. In situ transesterification with a co-solvent is an alternative to overcome this problem. This research aims to obtain optimum conditions for the in situ transesterification reaction of papaya seed oil with THF co-solvent. The research operating conditions included stirring speed 450 rpm, reaction at room temperature, oil:methanol molar ratio = 1:101.39, catalyst:oil molar ratio = 0.5:1, oil:THF molar ratio = 1: 67.85, reaction time are 3, 8, 13, 18, 23, 28 minutes and reactions with and without a NaOH catalyst. The best research conditions were obtained in the in situ transesterification reaction of papaya seed oil with THF co-solvent using a NaOH catalyst at a reaction time of 33 minutes, producing a crude yield of 74.38% and methyl esters concentration of 98,036.4 ppm and physical properties of biodiesel that met SNI 7182-2015, namely density 0.89 g/mL and acid number 0.44 mg KOH/g sample.

Comprehensive Evaluation of Process Parameters in the Green Synthesis of Iron Oxide Nanoparticles Using Moringa olifera extract.

This study investigates the green synthesis of iron oxide nanoparticles using Moringa olifera ethanolic extract and evaluates the impact of various process parameters on their physicochemical characteristics. The parameters examined include synthesis time, temperature, pH, stirring speed (RPM), and the ratio of extract to iron precursors. The findings reveal that a lower proportion of the extract increases the entrapment efficiency of the nanoparticles. Specifically, batch ME3 (3:1 ratio) produced the smallest nanoparticles at 117.8 nm, with a drug release of 75.54% and the highest entrapment efficiency at 60.28%. Extending the synthesis time to three hours in batch TM3 resulted in a drug release of 74.23% and a particle size of 116.3 nm. Batch TEM1, synthesized at 70°C, showed the highest entrapment efficiency and a favorable drug release profile of 71.09%, with the smallest particle size of 105.24 nm, suggesting that higher synthesis temperatures favor smaller particle sizes. Adjusting the pH to 10 in batch PM3 achieved a drug release efficiency of 76.02%. Batch RM5, synthesized with a stirring speed of 750 RPM, demonstrated a particle size of 95.7 nm and a drug release of 78.26%, indicating that higher stirring rates produce smaller nanoparticles and enhance drug release. These results highlight the significance of optimizing synthesis conditions to produce nanoparticles with desired properties. The use of M. olifera extract as a sustainable reducing and stabilizing agent presents an environmentally friendly approach to nanotechnology. This method has potential applications in drug delivery systems and various other industries, emphasizing the importance of green synthesis in creating sustainable and efficient nanomaterials.

Production of Biodiesel Without Catalyst Separation with Palm Oil Interesterification Process Using Essential Oil Biocatalyst

The transesterification is a method commonly used in the production of biodiesel. Therefore, this study aimed to investigate interesterification reaction of palm oil with methyl acetate using essential oil biocatalyst, specifically focusing on eugenol and cajuput oil. The operating parameters were: 250 g of palm oil, a molar ratio of palm oil:methyl acetate of 1:6, a reaction temperature of 60ºC, a stirring speed of 300 rpm, a biocatalyst of 0.75 wt. % in relation to oil, and reaction times of 15, 30, 45, 60, and 75 min. The palm oil, methyl acetate and biocatalyst reacted in a three-necked flask as a reactor under operating conditions. Additionally, simulations were performed using ChemDraw Professional 15.0 to analyze the molecular behavior of the reacting compounds.

A novel bio-coagulation/co-digestion/pyrolysis scheme for banana pseudostem waste management: techno‑economic and sustainability approaches.

While several studies have focused on utilizing banana pseudostem waste (BPW) for wastewater treatment via bio-coagulation, this process still suffers from secondary pollution caused by the disposal of generated sludge. To avoid this pollution transfer issue, this study is the first to focus on the recyclability of post-coagulation sludge (PCS) to recover added-value products. For this purpose, BPW was used as a model bio-coagulant for the decontamination of laundry wastewater (LWW), followed by anaerobic digestion and pyrolysis schemes to recover biogas and biochar, respectively. In the first experiment, BPW succeeded in removing 55.44 ± 1.21%, 90.40 ± 3.09%, and 78.13 ± 2.44% of chemical oxygen demand (COD), turbidity, and surfactant, respectively, at the optimized condition (pH = 3.5, dosage = 2.34 g/L, stirring speed = 160.6 rpm, and settling time = 55.5 min). Inoculating the spent bio-coagulant with cattle manure (CM), with a mixing ratio of 1:1 (w:w), showed a biogas yield of 110.33 ± 6.02 mL/g COD. The synergetic effect of spent coagulant and microbes of CM was further validated by performing a COD mass balance, showing that about 31.52 ± 1.63% of CODfeed was converted to bio-CH4 (as COD). Further, the thermal treatment of digestate was successfully employed for biochar recovery at a yield of 0.58 ± 0.05 g biochar/g dry digestate. The study also revealed that the triple LWW treatment/biogas/biochar strategy could gain economic benefits with a payback period of 4.4 years. Hence, BPW could be used as a promising feedstock for pollution reduction, energy generation, and gaining profits.

Bisphenol F Synthesis from Formaldehyde and Phenol over Zeolite Y Extrudate Catalysts in a Catalyst Basket Reactor and a Fixed-Bed Reactor

The objective of this study was to evaluate the applicability of zeolite Y as a catalyst for producing bisphenol F (BPF) from phenol and formaldehyde. Catalyst extrudates were prepared by extrusion after adding pseudoboehmite sol (PS) and Ludox (Lu) as alumina and silica binders, respectively. The compressive strength of the catalyst extrudates increased with the addition of Ludox. However, the formaldehyde conversion decreased as more Ludox was used as a binder, resulting in a decrease in the yield of BPF. This decrease is attributed to the reduction in the total amount of acid sites caused by the addition of Ludox. In this study, the Y_PS5_Lu5 catalyst was selected as the most suitable for BPF synthesis. In the BPF synthesis over the Y_PS5_Lu5 catalyst in a catalyst basket reactor, the optimum reaction temperature was determined to be 110 °C. The effect of stirring speed on the yield of BPF was found to be negligible in the range of 200 rpm to 350 rpm. The spent catalyst was able to recover a specific surface area and reaction activity similar to those of a fresh catalyst through regeneration in an air atmosphere at 500 °C. When the Y_PS5_Lu5 extruded catalyst was used in a continuous reaction in a fixed-bed reactor, there was no noticeable deactivation of the catalyst at low space velocities of the reactants. However, when the space velocity was increased to 18.0 h−1, catalyst deactivation was clearly observed. This suggests that periodic regeneration of the catalyst is inevitable in a continuous reaction using the Y_PS5_Lu5 extruded catalyst.

Valorisation of white wine lees: optimisation of subcritical water extraction of antioxidant compounds

This study explored the extraction of antioxidant compounds from white wine lees using subcritical water extraction (SWE). First, SWE was compared to extraction using conventional solvents mixed with water: 50 % methanol, 50 % ethanol and 50 % acetonitrile. The antiradical activity of the extract increased to 12.8 mg TE/g of extract dry matter (DM) using conventional solvents and to 29.2 mg TE/g DM with SWE, compared to the antiradical activity of dried lees, which was 5.7 mg Trolox Equivalent/g of dry matter (mg TE/g DM). Second, SWE conditions were optimised to obtain lees extracts with a high antioxidant activity by applying a Doehlert design and response surface methodology (RSM). The extraction parameters modulated during RSM optimisation were extraction time (t, 15 – 60 min), temperature (T, 100 – 250 °C) and stirring speed (S, 100 – 1000 RPM). Antioxidant activity was assessed using DPPH and FRAP tests, as well as by measuring the Oxygen Consumption Rate (OCR) of lees extracts. Temperature was found to be the main parameter that had a significant effect on antioxidant activity. The results of the RSM showed the optimal conditions (temperature, duration and speed) for attaining maximum antioxidant activity to be: 240 °C, 15 min and 550 RPM respectively. The best-known antioxidant compounds in white wine lees, Total Polyphenol Content (TPC), Glutathione (GSH) and Total Sulfhydryl groups (TSH) were also quantified. Extracts with the highest antioxidant capacity had the highest TPC and TSH concentrations. In conclusion, this study showed (i) that subcritical water extraction is a green process that has potential as an alternative to using conventional solvents for extracting white wine lees, (ii) the chemical components involved in their antioxidant capacity, and (iii) the potential of the lees for oenological and other industrial applications.

Research on the Phase Behavior of Multi-Component Thermal-Fluid-Heavy Oil Systems

Multi-component thermal luid technology optimizes development effects and has a strong adaptability, providing a new choice for the efficient development of heavy oil reservoirs. However, due to the significant differences between the phase behavior of multi-component thermal-fluid-heavy oil systems and conventional systems, and the lack of targeted and large-scale research, key issues such as the phase behavior of these systems are unclear. This research studies the phase behavior and influencing factors of emulsions and foamy oil in a multi-component thermal-fluid-heavy oil system through high-temperature and high-pressure PVT experiments, revealing the characteristics of the system’s special phase behavior. In the heavy oil emulsion system, the water content directly affects changes in the system’s phase state. The higher the temperature, the larger the phase transition point, and the two are positively correlated. As the stirring speed increases, the phase transition point first increases and then decreases. The amount of dissolved gas is negatively correlated with the size of the phase transition point, and dissolution can form foamy oil. In the heavy oil–foamy oil system, the dissolution capacity of CO2 is greater than that of multi-component gases, which is greater than that of N2. A high water content and high temperature are not conducive to the dissolution of multi-component gases. While an increase in stirring speed is beneficial for the dissolution of gases, there are limitations to its enhancement ability. Therefore, the development of multi-component thermal fluids should avoid the phase transition point of emulsions and promote the dissolution of multi-component gases.