Stirred Batch Reactor Research Articles

Biosorption of thorium onto Chlorella Vulgaris microalgae in aqueous media

Thorium biosorption by a green microalga, Chlorella Vulgaris, was studied in a stirred batch reactor to investigate the effect of initial solution pH, metal ion concentration, biomass dosage, contact time, kinetics, equilibrium and thermodynamics of uptake. The green microalgae showed the highest Th adsorption capacity at 45 °C for the solution with a thorium concentration of 350 mg L−1 and initial pH of 4. The amount of uptake raised from 84 to 104 mg g−1 as the temperature increased from 15 to 45 °C for an initial metal concentration of 75 mg L−1 at pH 4. Transformation Infrared Spectroscopy (FTIR) was employed to characterize the vibrational frequency changes for peaks related to surface functional groups. Also, the scanning electron microscope (SEM) and energy-dispersive X-ray spectroscopy (EDX) were used to determine the morphological changes and elemental analysis of the biosorbent before and after the sorption process. The Langmuir isotherm was in perfect agreement with the equilibrium empirical data of thorium biosorption and the highest sorption capacity of the Chlorella Vulgaris microalgae was determined as 185.19 mg g−1. Also, the results of kinetic studies show that the thorium biosorption process follows a pseudo-second-order kinetic model. The negative value of ΔG0 indicates spontaneity and the positive values of ΔH0 indicate the endothermic nature of the adsorption process.

Effective Ethyl Carbamate Prevention in Red Wines by Treatment with Immobilized Acid Urease.

Climate change poses several challenges in the wine industry, including increasing risks related to chemical food contaminants such as biogenic amines and ethyl carbamate (EC). In this work, we focused on urea removal in red wines by immobilized acid urease aiming at limiting EC formation during wine storage. By considering separable kinetics of catalyst deactivation and urea hydrolysis, it was possible to model the time course of urea removal in repeated uses in stirred batch reactors. Treatments based on immobilized urease of red wine enriched with 30 mg/L of urea allowed the reduction in the contaminant concentration to <5 mg/L. After 28.5 h of treatment, the observed urea level was reduced to about 0.5 mg/L, corresponding to a decrease in the potential ethyl carbamate (PEC) from 1662 μg/L to 93 μg/L, below the level of the non-enriched wine (187 μg/L). As a comparison, when treating the same wine with the free enzyme at maximum doses allowed by the EU law, urea and PEC levels decreased to only 12 mg/L and 415 μg/L respectively, after 600 h of treatment. These results show that, for red wines, urease immobilization is an effective strategy for urea removal and, thus, effective reduction in ethyl carbamate as a process contaminant. This study provides the scientific background for the future scaling-up of the process at an industrial level.

Sulfured FeMo carbides and nitrides catalysts upgrade extra heavy crude oil quality

In the context of the energy transition scenario, effective sulfur management is crucial. Enhancing the quality of extra heavy crude oil (EHCO) through catalytic processes, specifically hydrotreatment, is essential for reducing pollutant emissions like SOx into the atmosphere. Traditional hydrotreatment, utilizing MoS2-based catalysts typically on Al2O3 support, faces challenges with EHCO due to its elevated S and N content, which hampers catalyst efficiency. Metal carbides and nitrides exhibit promising electronic structures that confer resistance to deactivation in the presence of heteroatoms. This study compares the catalytic performances of Fe-promoted Mo sulfides, carbides, and nitrides (FeMoS(C,N)) in the thiophene hydrodesulfurization (HDS) reaction, serving as a model molecule for sulfur removal. Subsequently, we investigate the upgrading of a Venezuelan EHCO in terms of pollutant reduction, API gravity, and feedstock aromaticity. Catalysts were prepared from oxide precursors, varying the (Fe/(Fe+Mo)) atomic ratios (x = 0.00, 0.10, 0.33, 0.50, and 1.00), employing a temperature-programmed reaction protocol. Catalytic upgrading of EHCO was conducted in a stirred batch reactor, and the results were compared with a commercial CoMo-based catalyst. FeMoC(N) outperformed the commercial catalyst in sulfur removal. The elemental composition and nitrogen content of the feed remained constant; however, the sulfur content of asphaltenes decreased. Furthermore, the API gravity of crude oil increased when employing FeMoS and FeMoN catalysts, except with FeMoC, possibly linked to dealkylation reactions and the enrichment of lighter fractions with alkanes. FeMoN increased asphaltene aromaticity, while FeMoC decreased it. These results highlight the promise of FeMoC(N) as catalysts for HDS and upgrading heavy feedstocks.

Enzymatic Synthesis of Prebiotic Carbohydrates from Lactose: Integration of Osmotic Membrane Distillation with Batch Reactor System

AbstractThis study aimed to enhance galactooligosaccharide (GOS) yield by maintaining high lactose concentration levels using osmotic membrane distillation (OMD) throughout the synthesis. The main problem influencing GOS yield during transgalactosylation is the decrease of lactose concentration over extended reaction periods. By integrating OMD with a continuous stirred batch reactor, water was progressively removed from the reaction medium. Compared to a standard batch reactor, the OMD-integrated system not only increased GOS yield by a maximum of 20.1% but also reduced the time needed for equivalent lactose conversion about 15–90 min. This integration particularly boosted the formation of longer-chain GOS. A consistent GOS yield of 67% was achieved, with up to 28% lactose conversion, surpassing the non-integrated reactor’s performance. The proposed reactor design shows promise for enhancing GOS production efficiency while concurrently concentrating the reaction medium in a single step.

Indirect mineral carbonation of recycled concrete aggregate: Enhancing calcium extraction using a packed bed reactor

Mineral carbonation of industrial residues is gaining increasing interest, with the first pilot and industrial-scale applications being implemented. The process offers a low-risk, easily available solution for permanent carbon dioxide storage while concurrently valorising industrial wastes. This work investigates the indirect mineral carbonation of recycled concrete aggregate (RCA), in which calcium is first leached from the RCA into an aqueous ammonium nitrate (AN) solution, followed by carbonation to yield high-purity precipitated calcium carbonate. The study focuses on the first step, calcium dissolution, which traditionally takes place in a stirred batch reactor (SBR). However, SBRs often encounter solubility constraints, leading to low calcium extraction yields. In this investigation, we explore the application of a packed bed reactor (PBR) and demonstrate its superior performance, resulting in a calcium extraction enhancement of 27% to 55% relative to SBRs, across AN concentrations ranging from 0.25 to 2.0 mol/kg, at 25 °C and atmospheric pressure. The PBR’s superior performance can be attributed to the more compact design, enabling longer dissolution times, and to the continuous supply of fresh solvent, effectively reducing solubility limitations. The impact of key operating parameters (AN concentration, liquid flow rate and extraction time) are systemically assessed experimentally, accurately modelled using a shrinking-core model, and illustrated in process performance maps. Furthermore, this research highlights the significance of ammonium nitrate recovery from the wet solids after filtration to ensure the process’s environmental viability. The packed bed reactor (PBR) functions as an integrated filter, facilitating the straightforward recovery of 80% of the trapped ammonium nitrate solution through simple water flushing. In conclusion, the utilisation of PBRs in indirect mineral carbonation presents an innovative and efficient approach for enhancing calcium extraction while addressing environmental concerns through ammonium nitrate recovery. The applicability of PBRs extends beyond recycled concrete aggregates, and could also be successfully applied for other coarse industrial residues such as steel slags.

Bromine generation on various photoanodes: α-Fe2O3, Fe2TiO5, WO3 and TiO2

The competitive photoelectrochemical reactions bromide vs. water (photo)oxidation in an acidic medium (pH = 1.7) were studied on four semiconducting oxides viz. hematite (α-Fe2O3), pseudobrookite (Fe2TiO5), tungsten trioxide (WO3) and titanium dioxide (TiO2). The experiments were carried out with thin film electrodes on conductive substrates (FTO/glass) in a vigorously stirred batch reactor under AM1.5 irradiation. Electrical bias was applied to the electrodes, exclusively promoting valence band processes leading to oxidative pathways. The initial Faradaic efficiency (FE0) for bromine generation was determined by chemical analysis (UV-Vis absorbance) of the electrolytes. The semiconducting materials used as photoanodes showed a similar ability to oxidize bromide to bromine. For 0.02 M sodium bromide, a Faradaic efficiency of 100% was obtained for α-Fe2O3, WO3 and TiO2, while the highest value for pseudobrookite was 90%. From further analysis, as to competition kinetics, the ratio of the rate constants of water oxidation and bromide oxidation, vH2O / kox, was estimated. α-Fe2O3 was the most successful compound among the studied semiconductors.

Analysis of Mixing Efficiency in a Stirred Reactor Using Computational Fluid Dynamics

Lead recycling is very important for reducing environmental pollution risks and damages. Liquid lead is recovered from exhaust batteries inside stirred batch reactors; the process requires melting to be cleaned. Nevertheless, it is necessary to establish parameters for evaluating mixing to improve the efficiency of the industrial practices. Computational fluid dynamics (CFD) has become a powerful tool to analyze industrial processes for reducing operating costs, avoiding potential damages, and improving the equipment’s performance. Thus, the present work is focused on simulating the fluid hydrodynamics inside a lead-stirred reactor monitoring the distribution of an injected tracer in order to find the best injection point. Then, different injected points are placed on a control plane for evaluation; these are evaluated one by one by monitoring the tracer concentration at a group of points inside the batch. The analyzed reactor is a symmetrical, vertical batch reactor with two geometrical sections: one cylindrical body and a semi-spherical bottom. Here, one impeller with four flat blades in a shaft is used for lead stirring. The tracer concentration on the monitoring points is measured and averaged for evaluating the efficiency inside the tank reactor. Hydrodynamics theory and a comparison between the concentration profiles and distribution of tracer curves are used to demonstrate both methods’ similarities. Then, the invariability of the tracer concentration on the monitoring points is adopted as the main parameter to evaluate the mixing, and the best injection point is found as a function of the shortest mixing time. Additionally, the influence of the impeller rotation speed is analyzed as an additional control parameter to improve industrial practices.

Hydrothermal liquefaction of oil-palm-derived lignin to bio-oils for use as antioxidants in biodiesel

Lignin extracted from oil palm empty fruit bunch (EFB) fibers was used to produce a phenolics-rich bio-oil via hydrothermal liquefaction in pure water, or an ethanol–water (1:1 v v−1) solvent system, in a stirred batch reactor. The effects of liquefaction temperature (200–300 °C), pressure (10–40 bar), reaction time (0.5–3 h), solvent-to-lignin mass ratio (5–20), and the type of gas (N2, H2, CO2) in the reactor headspace were investigated on the yield and antioxidant properties of the bio-oil. The bio-oil and other products were characterized in detail. The conditions for obtaining a high yield of a bio-oil with a maximum phenolics content and the antioxidant activity were the following: ethanol–water solvent system with a solvent-to-lignin mass ratio of 10, 250 °C, 40 bar, H2 in the headspace, and a reaction time of 2 h. The bio-oil product contained multiple phenolics compounds, and proved to be an effective antioxidant additive in biodiesel made from palm oil. The bio-oil produced under the above specified conditions was a superior antioxidant than butylated hydroxytoluene (BHT), an oxidant used commercially. The bio-oil produced using water as the solvent instead of ethanol–water, was a less effective antioxidant.

Effect of NaX Zeolite Mass and Baffle Presence on Copper Sorption

Sorption is often conducted in stirred batch reactors without assessing the impact of mixing on yield and costs. Operating the mixing in the batch reactor at a state of complete suspension, &amp;lt;i&amp;gt;i.e.&amp;lt;/i&amp;gt;, at just suspended impeller speed, &amp;lt;i&amp;gt;N&amp;lt;/i&amp;gt;&amp;lt;sub&amp;gt;JS&amp;lt;/sub&amp;gt;, is a compromise between these conflicting goals. Therefore, copper sorption on NaX zeolite using a pitched blade turbine was conducted in both baffled and unbaffled batch reactors at &amp;lt;i&amp;gt;N&amp;lt;/i&amp;gt;&amp;lt;sub&amp;gt;JS&amp;lt;/sub&amp;gt;. Maintaining constant impeller to reactor diameter ratio (&amp;lt;i&amp;gt;D&amp;lt;/i&amp;gt;/&amp;lt;i&amp;gt;d&amp;lt;/i&amp;gt;&amp;lt;sub&amp;gt;T&amp;lt;/sub&amp;gt; = 0.32), and impeller off-bottom clearance (&amp;lt;i&amp;gt;C/H&amp;lt;/i&amp;gt; = 0.33), kinetic sorption experiments were performed. Besides kinetic sorption experiments and the kinetic analysis of data obtained, to gain insight into the hydrodynamic behaviour of the system, transient multiphase computational fluid dynamics simulations (CFD) were performed.&lt;br /&gt; The &amp;lt;i&amp;gt;N&amp;lt;/i&amp;gt;&amp;lt;sub&amp;gt;JS&amp;lt;/sub&amp;gt; speed is related to the particle settling speed, wherein a higher zeolite suspension mass concentration requires a greater NJS speed, resulting in increased energy consumption. The differences in &amp;lt;i&amp;gt;N&amp;lt;/i&amp;gt;&amp;lt;sub&amp;gt;JS&amp;lt;/sub&amp;gt; speeds for the investigated zeolite suspension mass concentrations were found to be insubstantial, and therefore, the increase in mixing intensity for the tested systems was not deemed significant. Regardless of the zeolite mass used, the values of &amp;lt;i&amp;gt;N&amp;lt;/i&amp;gt;&amp;lt;sub&amp;gt;JS&amp;lt;/sub&amp;gt; and &amp;lt;i&amp;gt;P&amp;lt;/i&amp;gt;&amp;lt;sub&amp;gt;JS&amp;lt;/sub&amp;gt; (mixing power consumption) were consistently higher in the unbaffled reactor. The hydrodynamic conditions employed were found to have no significant effect on the maximum amount of copper sorbed or process efficiency, but was significantly affected by zeolite mass. The kinetics were affected by both, and, generally, sorption occurred faster in the unbaffled reactor.

Screening Electrochemical Phosphorous Recovery Conditions in Real and Synthetic Wastewater Streams

The recovery of phosphorus (P) from wastewater via electrochemical precipitation is a promising route to improved nutrient recovery due to its ability to be coupled with current wastewater treatment processes, the viability of both small- and large-scale implementation (allowing for dispersed nutrient recovery systems), and utilization of electrons as an energy source (as opposed to chemically induced precipitation). In this talk, electrochemical P recovery from real and synthetic wastewater will be demonstrated, discussed, and contrasted. This study highlights the viability of electrochemical P recovery by considering waste stream composition, energetics of separation, and analyses of recovered products.Specifically, both synthetic and real wastewater was tested under similar stirred batch reactor conditions with various mass transfer conditions, electrode types, and applied potentials. The reactor solution chemistry was based upon an analysis of three real waste streams and time series analyses were used to compare the transient stream conditions to conditions used in P recovery studies. Additionally, materials characterization was performed on the product of various recovery conditions and the implications of reactor conditions are discussed.

Electrochemical Phosphorous Recovery from Wastewater: Modeling & Scale-up Considerations

The prospect of electrifying the recovery of valuable nutrients from waste streams is of great interest in the effort of reducing the overall energy consumption and environmental impact of nutrient usage. Currently, many electrochemical precipitation technologies exist, and some have shown energy consumption values on par with implemented nutrient recovery technologies (both gravimetric for specified products and volumetric for waste stream handling). However, electrochemical precipitation technologies are at low-to-intermediate Technology Readiness Levels (TRLs) and need to be optimized and scaled to determine the feasibility of implementing them industrially. This presentation discusses necessary considerations for modeling and scaling electrochemical precipitation technologies from the perspective of phosphorus (P) recovery.Two specific modeling tools were used to study P recovery as struvite. Mass transport and electrochemical phenomenon were modeled using COMSOL within a stirred batch reactor format. The COMSOL modelling yields valuable information about limiting conditions, spatial distribution of dissolved species concentrations, and the effects of various reactor conditions (e.g., stirring or applied potential). Next, the precipitation of struvite under various solution conditions is discussed with respect to a thermodynamic model of precipitation developed using OLI Flowsheets. The precipitation study is then discussed with respect to modeled reactor conditions to ascertain information relevant to scaling electrochemical P precipitation. Figures of Merit (FOM) useful in scaling electrochemical reactions are highlighted to alleviate the dependence on the reactor design used for modelling, enabling a transfer of information to other reactor formats.

Aqueous‐phase reforming of model compounds of wet biomass to hydrogen on alumina‐supported metal catalysts

AbstractCatalytic aqueous‐phase reforming (APR) of wet biomass such as microalgae and activated sludge is a potential technique for the production of H2‐rich gaseous products. In the present work, model compounds such as ethylene glycol, xylose and alanine were selected as representatives of the polyols, carbohydrates and proteins in wet biomass. APR trials were performed in a stirred batch reactor using commercial Pt/Al2O3 and Ru/Al2O3 catalysts. The reforming reactions were investigated at different conditions: temperature (T), 498 to 518 K, feed concentration, 1 to 5 wt. %, catalyst loading (ω), 2 to 6 kg/m3, and reaction time (t), 1 to 6 h. The commercial Pt/Al2O3 catalyst exhibited higher reforming activity. The influence of reaction parameters on turnover frequency (TOFH₂), hydrogen yield (Y‐H2) and carbon‐to‐gas conversion (C to G conversion) was studied. The values of TOFH₂ for Pt/Al2O3 were measured at T = 518 K, ω = 2 kg/m3 and t = 3 h using 1 wt% feed and these values were 19.2, 4 and 6 1/min for ethylene glycol, xylose and alanine. The values of TOFH₂ over Ru/Al2O3 under identical conditions were: ethylene glycol–12.4, xylose–1.4 and alanine–5.4 1/min. The activation energies for H2 production from ethylene glycol, xylose and alanine over Pt/Al2O3 and Ru/Al2O3 catalysts were determined. APR of the mixture of model compounds was also studied over laboratory‐made Pt/Al2O3 and Ru/Al2O3 catalysts at the optimum reaction conditions. Thus, this work has provided crucial insights into the production of H2 from model compounds of wet biomass using Al2O3‐supported catalysts.

Performance of trembesi seed (Samanea saman) on tempeh wastewater treatment (a case study in Semanan Tempeh Industry), West Jakarta

Tempeh wastewater contains organic matter, TSS, and high turbidity, which negatively impact if discharged directly into water bodies. The use of biocoagulant from trembesi seeds to treat wastewater is considered more environmentally friendly, easy to find, and affordable. The purpose of this research is to determine how effective trembesi seeds are as a coagulant in removing turbidity, Total Suspended Solid (TSS), Biochemical Oxygen Demand (BOD), and Chemical Oxygen Demand (COD) from tempeh wastewater in a batch-stirred reactor. Jar test with dose variations of 10-700 mg/L, finding the optimum stirring duration for coagulation at 200 rpm with time intervals of 1-3 minutes and for flocculation at 80 rpm with time intervals of 15, 30, and 45 minutes. The findings show that using a coagulant concentration of 500 mg/L resulted in a 63% reduction in turbidity. The optimum coagulation duration is 2 minutes and flocculation is 30 minutes. BOD initially at 1,245 mg/L decreased by 78% to 273 mg/L. COD initially at 6,400 mg/L decreased by 40% to 3,840 mg/L. TSS initially at 609 mg/L decreased by 66% to 205 mg/L. The percentage of allowance for BOD, COD, TSS, and turbidity using a reactor is 68%, 35%, 58%, and 70%. From these results it can be said that trembesi seed coagulant is effective in removing BOD, COD, TSS, and turbidity in tempeh wastewater.

Production of crude oil from industrial wastes and wastewaters by hydrothermal liquefaction

Hydrothermal Liquefaction (HTL) is a promising thermochemical treatment suitable for the valorization of a wide variety of organic wastes and wastewaters. Many research studies have demonstrated the suitability of HTL to produce bio-oil from biomass wastes, but few works have focused on the application of HTL to industrial wastes and wastewaters. The objective and novelty of this work are the study of HTL suitability over a specific selection of industrial residues that present notable drawbacks when treated by conventional waste management methods, including technical problems or high costs. Most of the wastes presented poor results from the technical or energetical point of view. However, liquid surfactant wastewaters were successfully treated by HTL at 300ºC and 100 bar in a 300 mL stirred batch reactor, producing a crude oil yield of around 16%, with a High Heating Value (HHV) of up to 30 MJ/kg. The composition and quality of the crude oils obtained have also been determined and compared against conventional biomass fuels.Graphical abstract

Decrease in the organic content of refinery wastewater by photocatalytic Fenton oxidation using iron-doped zeolite: Catalyst preparation, characterization, and performance

A Fe-exchanged zeolite photocatalyst was synthesized by applying an ion exchange method and used to examine the degradation of effluent from the petroleum industry. The exchanged zeolite catalyst was characterized by X-ray diffraction, X-ray fluorescence, Fourier-transform infrared spectroscopy, Naioatomic force microscopy, Brunauer-Emmett-Teller surface area, and Filed Emission Scanning Electron Microscopy-Energy Dispersive X-ray Spectrometer. Characterization of the catalyst confirmed its composition and phase but also showed a decrease in uniformity and crystallinity. The photocatalyst was tested under ultra-violet lamp irradiation for the removal of pollutants in wastewater from Iraqi petroleum refineries. Experiments were performed using a stirred batch reactor with an initial chemical oxygen demand of 492 mg/L. The exchanged zeolite was used as a catalyst and H2O2 was used as an oxidant. For synthetic wastewater, 99.84 % of organic pollutants were removed in 120 min. Chemical oxygen demand removal values were almost the same (85.29 and 81.67 %, respectively) for real wastewater obtained from the Dora Refinery and North Gas Company. Furthermore, the exchanged zeolite displayed excellent stability and low release of iron ions from the catalyst during the reaction (less than 11 mg/L). The catalyst was recycled five times with power consumption ranging from 691.18 to 826.96 kWh/kg COD.

Effect of light alkanes and aromatics on decalin dehydrogenation over noble metal catalysts: A new strategy for the development of naphthalene-based LOHCs

The use of the naphthalene/decalin pair as a liquid organic hydrogen carrier has gained increasing interest due to its high hydrogen loading capacity and industrial availability. However, a major challenge in its application is the fact that naphthalene is a solid at ambient conditions, leading to the solidification of the unloaded organic carrier. To address this limitation, small amounts of light organics, such as monoaromatics or cycloalkanes, can be added. In this study, we investigated the dehydrogenation of decalin over various supported precious catalysts (Pt, Pd, Rh, Ru; supported on both activated carbon and alumina) in a stirred batch reactor at 200 °C. Initial experiments were conducted with pure decalin, and we found that Pt/C provided the best performance. Subsequently, we studied the dehydrogenation of decalin in mixtures with different solvents (cyclohexane, methylcyclohexane, benzene, and toluene in the concentration range of 10–40% of the light hydrocarbon). Our results show that the addition of cycloalkanes did not affect the main reaction, while aromatic compounds exhibited weak inhibition. A Langmuir-Hinshelwood kinetic model has been proposed for predicting this behavior, taking into account the significant inhibitory impacts of naphthalene and, when present, the aromatic additive.

Response Surface Methodology for the Synthesis and Characterization of Bio-Oil Extracted from Biomass Waste and Upgradation Using the Rice Husk Ash Catalyst.

Rice husk ash (RHA), a low-cost biomaterial, was utilized to form bio-oil from pyrolysis in a batch-stirred reactor, followed by its upgradation using the RHA catalyst. In the present study, the effect of temperature (ranging from 400 to 480 °C) on bio-oil production produced from RHA was studied to obtain the maximum bio-oil yield. Response surface methodology (RSM) was applied to investigate the effect of operational parameters (temperature, heating rate, and particle size) on the bio-oil yield. The results showed that a maximum bio-oil output of 20.33% was obtained at 480 °C temperature, 80 °C/min heating rate, and 200 μm particle size. Temperature and heating rate positively impact the bio-oil yield, while particle size has little effect. The overall R2 value of 0.9614 for the proposed model proved in good agreement with the experimental data. The physical properties of raw bio-oil were determined, and 1030 kg/m3 density, 12 MJ/kg calorific value, 1.40 cSt viscosity, 3 pH, and 72 mg KOH/g acid value were obtained, respectively. To enhance the characteristics of the bio-oil, upgradation was performed using the RHA catalyst through the esterification process. The upgraded bio-oil stemmed from a density of 0.98 g/cm3, an acid value of 58 mg of KOH/g, a calorific value of 16 MJ/kg, and a viscosity 10.5 cSt, respectively. The physical properties, GC-MS and FTIR, showed an improvement in the bio-oil characterization. The findings of this study indicate that RHA can be used as an alternative source for bio-oil production to create a more sustainable and cleaner environment.

Bifunctional metal-loaded micro-mesoporous zeolites for waste plastics conversion to high quality liquid product

A series of micro-mesoporous zeolitic catalysts synthesized using recrystallization of two different zeolites (HZSM-5 and beta) were impregnated with Pt and other notable metals. The resulting bifunctional catalysts were characterized and tested for the hydrocracking of a model municipal waste plastic mixture. Actual waste plastic mixture of the same composition was also employed for the comparison. The hydrocracking experiments were carried out in a Parr stirred batch reactor at 325, 350, and 375 °C. The other reaction conditions were fixed at the initial cold H2 pressure of 20 bar, reaction time of 60 min, and plastic to catalyst ratio of 20:1 by wt. The inclusion of the Pt metal has shown to increase the hydrocracking activity of the micro-mesoporous supports. The Pt micro-mesoporous ZSM-5 catalysts have shown the better activity while Pt micro-mesoporous beta catalysts have shown better selectivity towards liquid. The presence of Pt metal has also produced a better quality liquid product with fewer unsaturated hydrocarbons and results in lower coke formation as determined by the TGA analysis of the spent catalysts.

Zeolite NaX Mass and Propeller Agitator Speed Impact on Copper Ions Sorption

Sorption is often carried out in stirred batch reactors without any consideration of how much mixing is sufficient to avoid the effect of diffusion without compromising yield and cost due to overmixing. Therefore, the focus of this work was to study how the maximum sorption capacity, removal efficiency, kinetics and power consumption (P) of the studied process are affected by different mixing speeds, i.e., impeller speed/minimum impeller speed for complete suspension (N/NJS) ratio values and zeolite suspension mass concentrations. Experiments were conducted in a baffled reactor with the propeller at a standard off-bottom clearance. In addition to the experimental studies, numerical modelling approaches were carried out to investigate the sorption process using a transient multiphase computational fluid dynamics model and fitting selected kinetic models. The results show that an increase in zeolite mass leads to a slight increase in the NJS and consequently PJS. The impeller speed affects the velocities, power consumption, kinetics, final amount and removal efficiency of copper sorbed. The experimentally determined kinetic data fit Ritchie’s kinetic model well. However, for two experiments, performed at N/NJS ratios of 0.8 and 0.6, Mixed kinetic model fits better, suggesting that the second-order reaction is suppressed by diffusion. Due to the influence of diffusion, the experimentally determined sorption efficiency decreased from 59.377% to 54.486% and 46.372% for N/NJS ratios of 0.8 and 0.6, respectively.

Optimizing lactic acid production for agricultural wastes revalorization via sugars hydrothermal conversion with zirconia-based catalysts: response surface methodology

The hydrothermal conversion of a complex sugars solution comprising glucose, arabinose, and xylose with zirconia-based catalysts to produce lactic acid (LA) was studied. Catalysts were synthesized by a simple template-assisted sol–gel method. Alternative template removal procedures, such as refluxing ethanol extraction, were compared to the conventional direct calcination. The catalyst obtained after ethanol extraction (Z-Ex) reported the highest specific surface area (323 m2 g−1), total pore volume (0.21 cm3 g−1) and density of acid sites (1.111 µmol m−2), with a significant contribution of strong acid sites. On the other hand, template removal by thermal treatment transformed the hydrous zirconia into crystalline tetragonal phase, reducing the specific surface area and removing most of the acid sites. Catalytic tests were carried out in a stirred batch reactor, resulting Z-Ex the most selective towards LA production. A four-factor experimental design was performed for Z-Ex catalyst by varying temperature, reaction time, initial pressure, and catalyst/reactants ratio. Results were analyzed using the response surface methodology (RSM) to maximize the LA production. A molar yield of 61.2% towards LA and complete sugars conversion were reached at optimized operating conditions: 189 °C, 208 min, 0.5 g catalyst g−1 reactants, and 10 bar N2. Additionally, fitting models for main by-products molar yields (furans, glyceraldehyde, glycolic, formic, acetic, and levulinic acids) were obtained with good accuracy prediction. All responses were jointly studied to understand the reaction mechanisms involved in generation of intermediaries and undesired degradation products.Graphical Abstract