Search

Abstract Background The transition from fossil-derived jet fuels to sustainable aviation fuels represents one of the most viable strategies to decarbonize air transport and mitigate CO2 emissions generated by fossil fuel combustion. In the present investigation, a catalytic hydroprocessing upgrading approach was used to transform Yellow Dodolla oil—one of the most prominent inedible Brassica carinata vegetable oils (indigenous to Ethiopia)—into bio-jet fuel. Methods The feedstock was upgraded to jet fuel through catalytic hydroprocessing under elevated hydrogen pressure (21 bar), varying temperatures (300 and 500 °C), and employing supported carbon-coated mesoporous and crystalline nanocatalysts (β-Mo2C/AlPO4-18, Ni3C/AlPO4-18, and WC/AlPO4-18) in a laboratory-scale continuous three-phase fixed-bed reactor system. Other variables, such as the volumetric flow rate of oil feedstock, volumetric flow rate of hydrogen gas, hydrogen gas-to-oil ratio, catalyst-to-oil ratio, liquid hourly space velocity, weight hourly space velocity, and residence time, were maintained constant throughout the experimental procedure. Subsequent to an in-depth evaluation of catalytic performance parameters (conversion, selectivity, yield, and deoxygenation rate), a detailed characterization of the liquid phase products was undertaken to explore their most significant properties. Results The analysis results demonstrated that the catalytic hydroconversion of the feedstock resulted in a conversion range of 71.57–79.76 wt.%, with the highest conversion of 79.76 wt.% achieved by Ni3C/AlPO4–18 at the maximum temperature. Moreover, the rate of deoxygenation varied from 8.08 to 11.67 wt.% at 300 °C, with nickel catalyst reaching the maximum rate, while it sharply rose to vary from 57.31 to 96.67 wt.% using molybdenum as the temperature increased to 500 °C. It was also discovered that in comparison to bio-gasoline (2.63–8.72 wt.%) and biodiesel (1.18–4.58 wt.%), bio-jet fuel (C8–C16) had noticeably higher yields (23.34–27.31 wt.%), selectivity (37–45 wt.%), and a superb hydrocarbon product distribution (C9–C16) at the maximum temperature, with WC/AlPO4-18 producing the highest yields and selectivity of jet fuel. The characterization results revealed that the hydrocracked liquid products possessed virtually identical physicochemical properties, chemical compositions, hydrogen-to-carbon atomic ratios (1.90–1.92), oxygen-to-carbon atomic ratios (0.002–0.030), and gravimetric energy densities (41.35–42.89 MJ kg−1) to those of conventional jet fuels. Conclusions The conclusions of the study demonstrated that the non-food Yellow Dodolla oil was successfully hydrocracked into sustainable aviation fuel using AlPO4-18 supported metal carbide catalyst nanoparticles under the right reaction conditions and reactor system, potentially supporting the significant efforts of the aviation industry to lower its carbon footprint.

Background: The transition from fossil-derived jet fuels to sustainable aviation fuels represents one of the most viable strategies to decarbonize air transport and mitigate CO2 emissions generated by fossil fuel combustion. In the present investigation, a catalytic hydroprocessing upgrading approach was used to transform Yellow Dodolla oil—one of the most prominent inedible Brassica carinata vegetable oils (indigenous to Ethiopia)—into bio-jet fuel. Methods: The feedstock was upgraded to jet fuel through catalytic hydroprocessing under elevated hydrogen pressure (21 bar), varying temperatures (300 and 500 °C), and employing supported carbon-coated mesoporous and crystalline nanocatalysts (β-Mo2C/AlPO4-18, Ni3C/AlPO4-18, and WC/AlPO4-18) in a laboratory-scale continuous three-phase fixed-bed reactor system. Other variables, such as the volumetric flow rate of oil feedstock, volumetric flow rate of hydrogen gas, hydrogen gas-to-oil ratio, catalyst-to-oil ratio, liquid hourly space velocity, weight hourly space velocity, and residence time, were maintained constant throughout the experimental procedure. Subsequent to an in-depth evaluation of catalytic performance parameters (conversion, selectivity, yield, and deoxygenation rate), a detailed characterization of the liquid phase products was undertaken to explore their most significant properties. Results: The analysis results demonstrated that the catalytic hydroconversion of the feedstock resulted in a conversion range of 71.57–79.76 wt.%, with the highest conversion of 79.76 wt.% achieved by Ni3C/AlPO4–18 at the maximum temperature. Moreover, the rate of deoxygenation varied from 8.08 to 11.67 wt.% at 300 °C, with nickel catalyst reaching the maximum rate, while it sharply rose to vary from 57.31 to 96.67 wt.% using molybdenum as the temperature increased to 500 °C. It was also discovered that in comparison to bio-gasoline (2.63–8.72 wt.%) and biodiesel (1.18–4.58 wt.%), bio-jet fuel (C8–C16) had noticeably higher yields (23.34–27.31 wt.%), selectivity (37–45 wt.%), and a superb hydrocarbon product distribution (C9–C16) at the maximum temperature, with WC/AlPO4-18 producing the highest yields and selectivity of jet fuel. The characterization results revealed that the hydrocracked liquid products possessed virtually identical physicochemical properties, chemical compositions, hydrogen-to-carbon atomic ratios (1.90–1.92), oxygen-to-carbon atomic ratios (0.002–0.030), and gravimetric energy densities (41.35–42.89 MJ kg−1) to those of conventional jet fuels. Conclusions: The conclusions of the study demonstrated that the non-food Yellow Dodolla oil was successfully hydrocracked into sustainable aviation fuel using AlPO4-18 supported metal carbide catalyst nanoparticles under the right reaction conditions and reactor system, potentially supporting the significant efforts of the aviation industry to lower its carbon footprint. [ABSTRACT FROM AUTHOR]

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. [ABSTRACT FROM AUTHOR]

The need to increase bio-oil yield from biomass and enhance its fuel properties has driven research into optimizing the pyrolysis process. This study investigated the influence of three key process parameters—temperature, heating rate, and nitrogen flow rate—on the pyrolysis of elephant grass (Pennisetum purpureum) in a fixed-bed reactor. Response surface methodology was used to study the impact of the aforementioned variables on bio-oil yield to improve its production efficiency. Proximate analysis of the biomass revealed 79.24 wt% volatile matter, 14.22 wt% fixed carbon, and 5.86% ash, with ultimate analysis showing 45.44% carbon, 5.59% hydrogen, and 40.95% oxygen. The high volatile matter content and favourable carbon and hydrogen percentages indicate that elephant grass is a viable energy source due to its potential for high bio-oil yield and energy content. The resulting bio-oil exhibited a higher heating value of 20.9 MJ/kg, indicating its suitability for various heating applications. A second-order regression model was developed for bio-oil yield, with optimal conditions identified as a temperature of 550°C, a heating rate of 17°C/min, and a nitrogen flow rate of 6 ml/min. The study achieved an optimal bio-oil yield of 59.03 wt%, and the model's high R ² value of 0.8683 from analysis of variance analysis confirmed its predictive accuracy. This research highlights elephant grass as a sustainable feedstock for bio-oil production, offering valuable insights into optimizing pyrolysis conditions to enhance bio-oil yield, thus advancing biofuel technology. [ABSTRACT FROM AUTHOR]

Hydrogen is gaining prominence in global efforts to combat greenhouse gas emissions and climate change. While steam methane reforming remains the predominant method of hydrogen production, alternative approaches such as water electrolysis and methane cracking are gaining attention. The bridging technology – methane cracking – has piqued scientific interest with its lower energy requirement (74.8 kJ/mol compared to steam methane reforming 206.278 kJ/mol) and valuable by-product of filamentous carbon. Nevertheless, challenges, including coke formation and catalyst deactivation, persist. This review focuses on two main reactor types for catalytic methane decomposition – fixed-bed and fluidised bed. Fixed-bed reactors excel in experimental studies due to their operational simplicity and catalyst characterisation capabilities. In contrast, fluidised-bed reactors are more suited for industrial applications, where efforts are focused on optimising the temperature, gas flow rate, and particle characterisation. Furthermore, investigations into various fluidised bed regimes aim to identify the most suitable for potential industrial deployment, providing insights into the sustainable future of hydrogen production. While the bubbling regime shows promise for upscaling fluidised bed reactors, experimental studies on turbulent fluidised-bed reactors, especially in achieving high hydrogen yield from methane cracking, are limited, highlighting the technology's current status not yet reaching commercialisation. • Two main mechanisms in CDM reactions: free-radical, vapour-liquid-solid (VLS) model. • Catalysts can deactivate due to coke formation from filamentous carbon encapsulation. • Fixed-bed reactors help gather experimental data for catalyst characterisation. • Fluidised-bed reactors are optimised via temperature, flow and particle adjustments. • Bubbling and turbulent regimes: strong potential in upscaling fluidised-bed reactors. [ABSTRACT FROM AUTHOR]

The byproduct "bio-char" produced by the pyrolysis process was characterized to investigate the properties and its appropriateness for energy application. The pyrolysis reaction was carried out at 300, 350, 400, and 450 °C and 1-h reaction holding time. The analytical techniques TGA/DTG, FT-IR, XRD, SEM, CHNS, and BET were used for the characterization of the different bio-char properties. Results showed that the carbon content in rice straw bio-char increased from 42.20 to 45.33%, with increasing pyrolysis temperatures from 300 to 450 °C. CHNS, XRD, FT-IR, and TGA analysis showed that the bio-char aromatic structure was rich in carbon and it demonstrated higher bio-char carbon stability at 450 °C. With increase in temperature from 300 to 450 °C, the specific surface area of the bio-chars was enhanced (1.17 to 6.60 m2/g). At higher temperatures, biomass macromolecules decomposed completely and bio-char became more porous in nature with voids created within the bio-char matrix. During the pyrolysis of the rice straw biomass, the sharp peaks of the crystalline structure were destroyed and less intensity broader peak appeared in the pyrolysis derived bio-chars. The atomic ratio of H/C and O/C decreased with increase in pyrolysis temperature from 300 to 450 °C. These low values indicate that the reaction temperature promoted the loss of oxygen and hydrogen. [ABSTRACT FROM AUTHOR]

This paper presents the results of investigations into the pyrolysis of waste polypropylene in a laboratory fixed-bed batch reactor. The experiments were designed and verified in such a way as to allow the application of the response surface methodology (RSM) in the development of an empirical mathematical model that quantifies the impacts mentioned above. The influence of the mass of the raw material (50, 100, and 150 g) together with the reactor temperature (450, 475, and 500 °C) and the reaction time (45, 50 and 75 min) was examined. It has been shown that the mass of the raw material, i.e., the filling volume of the reactor, has a significant influence on the pyrolysis oil yield. This influence exceeds the influence of reactor temperature and reaction time. This was explained by observing the temperature change inside the reactor at three different spots at the bottom, middle, and top of the reactor. The recorded temperature diagrams show that, with greater masses of feedstock, local overheating occurs in the middle part of the reactor, which leads to the overcracking of volatile products and, from there, to an increased formation of non-condensable gases, i.e., a reduced yield of pyrolytic oil. [ABSTRACT FROM AUTHOR]

Most common adsorbents in research reports are powdered two-dimensional carbon materials, including powdered activated carbon and graphene, which tend to be lost during water treatment and cause secondary contamination. In this work, a hydrogel composed of three-dimensional graphene-doped acidified multiwalled carbon nanotubes (3DG/A-MWCNTs) was synthesized. The hydrogels with large specific surface areas and defect structures exhibited outstanding integration, compressive capacity, and negligible loss. The as-obtained material was added to a column as a continuous fixed-bed reactor (FBR). The 3DG/A-MWCNTs packed in the FBR exhibited superior adsorption and peroxymonosulfate (PMS) activation to achieve 56.2% naproxen (NPX) removal efficiency after 1150 min. The operation parameters were systematically optimized including the PMS concentration, initial pH, coexisting anions, bed height, and hydraulic retention time. Significantly, quenching, electron paramagnetic resonance, and electrochemical tests were used to demonstrate that reactive oxygen species (SO4•–, •OH, O2•–, and 1O2) and electron transfer were involved in NPX degradation. The presence of active sites, oxygen vacancies, electron-rich, oxygen-containing functional groups, and defect structures within 3DG/A-MWCNTs promoted their preeminent catalytic activity. The FBR maintains a removal efficiency of 66.2% for NPX after six repetitions and exhibits excellent purification ability for various pollutants and actual surface water. These results suggest that FBR performs well in practical applications. Overall, this study expands the environmental application of three-dimensional graphene and provides promising metal-free carbon materials for eliminating refractory contaminants in continuous flow mode by using adsorption and PMS-based advanced oxidation processes. [ABSTRACT FROM AUTHOR]

The global occurrence of micropollutants in water bodies has raised concerns about potential negative effects on aquatic ecosystems and human health. EU regulations to mitigate such widespread pollution have already been implemented and are expected to become increasingly stringent in the next few years. Catalytic wet peroxide oxidation (CWPO) has proved to be a promising alternative for micropollutant removal from water, but most studies were performed in batch mode, often involving complex, expensive, and hardly recoverable catalysts, that are prone to deactivation. This work aims to demonstrate the feasibility of a fixed-bed reactor (FBR) packed with natural magnetite powder for the removal of a representative mixture of azole pesticides, recently listed in the EU Watch Lists. The performance of the system was evaluated by analyzing the impact of H2O2 dose (3.6–13.4 mg L−1), magnetite load (2–8 g), inlet flow rate (0.25–1 mL min−1), and initial micropollutant concentration (100–1000 µg L−1) over 300 h of continuous operation. Azole pesticide conversion values above 80% were achieved under selected operating conditions (WFe3O4 = 8 g, [H2O2]0 = 6.7 mg L−1, flow rate = 0.5 mL min−1, pH0 = 5, T = 25 °C). Notably, the catalytic system showed a high stability upon 500 h in operation, with limited iron leaching (< 0.1 mg L−1). As a proof of concept, the feasibility of the system was confirmed using a real wastewater treatment plant (WWTP) effluent spiked with the mixture of azole pesticides. These results represent a clear advance for the application of CWPO as a tertiary treatment in WWTPs and open the door for the scale-up of FBR packed with natural magnetite. [ABSTRACT FROM AUTHOR]

It is well known that calcium oxide (CaO) has better catalytic efficiency than most heterogeneous catalysts in many transesterification reactions. However, the gradual deactivation problem prevents its large-scale application in industry. In this paper, the deactivation mechanism of CaO in a fixed-bed reactor is investigated based on the transesterification reaction of propylene carbonate and methanol. The leaching amount of CaO during the reaction was estimated by the concentration of Ca in the products. The pretreated and recovered catalysts were characterized by FT-IR, XRD, TG-MS and SEM-EDS. It is evident from experiments and characterization that the deactivation process of CaO is accompanied by the leaching of calcium species and the generation of CaCO3, which are also verified by DFT calculations. At high temperature and high weight hourly space velocity, the deactivation was attributed to the formation of dense CaCO3 shell, which prevents the contact between the feedstock and the active species inside.

The Fischer-Tropsch synthesis converted hydrogen and carbon monoxide into linear hydrocarbons as liquid fuel. Iron and cobalt were used as polymerization catalyst, that impregnated on HZSM-5. The Fe-Co/HZSM-5 could be applied as bifunction catalyst which combined polymerizing synthesis gas and long chain hydrocarbon cracking for making biofuel. The objective of this study is observing the effect of temperature and composition of iron and cobalt combination, supported by HSZM-5 (Fe-Co/HZSM-5) catalyst on fuel product composition. The results obtained from this study would be used to find optimum condition for various iron and cobalt ratio in the catalyst. The mesoHZSM-5 was prepared from ammonium ZSM-5 over calcination, desilication, and dispersion. The mixed solution consisted of Co(NO3)2.6H2O and Fe(NO3)3.9H2O were used as precursor for incipient wetness impregnation on HZSM-5. The catalyst performance was observed in a continuous fixed bed reactor using Fe-Co/meso-HZSM-5 catalyst with synthesis gas at various composition iron and cobalt ratio (10-40 % wt. Fe in Co), various temperature (225-275 °C) at 20 bars. All catalysts were reduced in situ in the reactor. The 10Fe-90Co/mesoHZSM-5 catalyst was more suitable for FTS at 250 °C with alkane (20.49 %) as the main product and alcohol as the by-product (79.51 %). The others catalysts composition of 20-40 % Fe (by weight) in Fe-Co were more suitable for FTS at 225-250°C because under these conditions, alkanes as the main product were obtained in relatively higher compositions compared to other compounds. The mechanism of paraffins, olefins, aldehydes and alcohols formation in this FTS reaction followed the hydrogen assisted CO dissociation with CO-insertion mechanism. [ABSTRACT FROM AUTHOR]

Sulfur trioxide (SO 3) is one of the major air pollutants in the flue gas of Fluid catalytic cracking (FCC) units during the regeneration process in refineries. However, it is difficult to remove SO 3 with the existing desulfurization systems. Nowadays, alkaline adsorbent spraying technology has been a promising method to remove SO 3. However, there is no relevant application research in the field of FCC regeneration flue gas. Therefore, in this paper, The SO 3 removal characteristics from FCC flue gas by activated carbon modified red mud adsorbent were studied, including modification method, reaction temperature and flue gas components. Combined with characterization analysis of adsorbents, the mechanism of SO 3 removal was studied. It was found that when the AC mass ratio is 10% and modification temperature is 400 ℃, the best LBRMAC adsorbent was achieved. When particle size is 0.096–0.125 mm and reaction temperature is 400 ℃, the highest SO 3 adsorption efficiency is up to 83.4%. The addition of NO has little influence on the adsorption efficiency of SO 3. The addition of SO 2 leads to competitive adsorption between SO 3 and SO 2 , resulting in a rapid decline in the removal efficiency of SO 3. Meanwhile, the characterization analysis proves that the SO 3 adsorption process mainly include chemical kinetics control stage and product layer diffusion stage. • Best modification of LBRMAC was achieved when the AC mass ratio is 10%. • Reaction temperature of 400 ℃ is optimal for SO 3 adsorption. • Particle size and SO 3 concentration have effects on SO 3 adsorption except NO. • There exists competitive adsorption between SO 2 and SO 3. • Chemical kinetics control stage and product layer diffusion stage mainly dominate SO 3 adsorption. [ABSTRACT FROM AUTHOR]

Pyrolysis is a method used for the thermochemical conversion of biomass and agro wastes into three major by-products namely, biochar, bio-oil, and biogas in the absence of oxygen. Global waste generation is increasing at an alarming rate. Palm kernel shell (PKS) is among the palm wastes accumulating in many palm oil mills around the globe with the attendant problems in waste management. The utilization of coal for energy generation is more expensive and not environmentally friendly. Bio-oil refineries and industries require the utilization of minimum resources (input) to achieve optimal response (output) in the production process. However, more than 30% of the energy content derivation from the pyrolysis process is wasted due to nonoptimization of the process parameters. This study investigated the optimization of the product yields of the pyrolysis of PKS in a fixed-bed batch reactor using response surface methodology (RSM). Masses of 1 kg, 2 kg, and 3 kg were pyrolyzed in batches at process temperature variations of 200 °C, 300 °C, 400 °C, and 500 °C. Design Expert 12 software (Version 12.0.3.0 Stat-Ease Inc. MN, USA) and Analysis of Variance (ANOVA) were used for the statistical analysis. Lack-of-fit, adjusted, and predicted multiple correlation coefficients and coefficient of variation of the different polynomial models were compared to select the best-fitting polynomial model. The optimal feedstock parameters were 2.66 kg of PKS and 410.0 °C process temperature. The predicted results were 0.986 kg of biochar, 1.205 kg of bio-oil, 0.481 kg of biogas, 1116.5 cm3 of bio-oil, and 140.6 minutes. The experimental results were 0.894 kg of biochar, 1.316 kg of bio-oil, 0.498 kg of biogas, 1208.9 cm3 of bio-oil, and at 162.8 minutes through validation. The validated quadratic model was suitable for the optimization and RSM is a numerical, statistical, and mathematical tool for modeling and optimization of the pyrolysis process in a fixed-bed batch reactor. [ABSTRACT FROM AUTHOR]

Hydrocracking of Crude Palm Oil (CPO) in fixed-bed reactor was studied using a six-lump computational fluid dynamics (CFD) model. The experiment was conducted in the reactor at the temperatures of 673-773 K with CPO flow rates between 60 and 300 g/h. The predictive modeling of CPO cracking demonstrated a strong correlation with the experimental data. CFD simulation investigated the influence of input flow rates and temperatures on species mass fraction and product yield in the reactor. At the lowest input flow rate, the highest results of diesel (31.7 %), kerosene (17.1 %), gasoline (7.62 %), and gas (3 %) were produced. As CPO flow rate increased from 60 to 300 g/h, the concentration of CPO in the reactor increased while the concentration of the desired products decreased at the reactor outlet. The highest total oil fraction was obtained at 773 K and a 60 g/h flow rate with oil fraction value of 59.42 %. • Experimental and CFD modeling of CPO hydrocracking in a fixed bed reactor. • A CFD model with a 6-lump kinetic scheme of CPO hydrocracking was developed. • Axial hydrodynamics and reaction kinetics were examined via the CFD model. • Predicted gas velocity and temperature are similar trends to experimental data. • CFD simulations predicted biofuel yield in the reactor with an error 11 %. [ABSTRACT FROM AUTHOR]

The influence of intraphase diffusion on the oxidation of toluene over manganese-based oxide, MnFeOx, under isothermal conditions was investigated. The one-dimensional (1D) heterogeneous model was developed to explain the experimental results. The model can be applied under certain operating conditions, i.e. conditions with negligible resistance to external mass transfer. The article describes the numerical solution of the equations of the proposed model. The relevance of the 1D heterogeneous model compared to the 1D pseudohomogeneous model was also emphasized. Validation of the proposed models was carried out by comparing with experimentally measured results. Both models were found to describe the experimental system studied quite well, with the 1D heterogeneous model providing better insight into the relationship between the rate of chemical reaction and the rate of intraphase diffusion. [ABSTRACT FROM AUTHOR]

This paper deals with the proposition of a kinetic model for the direct synthesis of DME via CO2 hydrogenation in view of the necessary optimization of the catalytic system, reactor design, and process strategy. Despite the fact that DME synthesis is typically treated as a mere combination of two separated catalytic steps (i.e., methanol synthesis and methanol dehydration), the model analysis is now proposed by taking into account the improvements related to the process running over a hybrid catalyst in a rational integration of the two catalytic steps, with boundary conditions properly assumed from the thermodynamics of direct DME synthesis. Specifically, the CO2 activation step at the metal–oxide interface in the presence of ZrO2 has been described for the first time through the introduction of an ad hoc mechanism based on solid assumptions from inherent studies in the literature. The kinetic modeling was investigated in a tubular fixed-bed reactor operating from 200 to 260 °C between 1 and 50 bar as a function of a gas hourly space velocity ranging from 2500 to 60,000 NL/kgcat/h, in a stoichiometric CO2/H2 feed mixture of 1:3 v/v. A well-detailed elementary mechanism was used to predict the CO2 conversion rate and identify the key reaction pathways, starting with the analysis of the implicated reactions and corresponding kinetic mechanisms and expressions, and finally estimating the main parameters based on an appropriate modeling of test conditions. [ABSTRACT FROM AUTHOR]

Copyright of Low-Carbon Chemistry & Chemical Engineering is the property of Low-Carbon Chemistry & Chemical Engineering Editorial Office and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

This paper presents the results of investigations on the pyrolysis of tyre waste in a laboratory fixed-bed batch reactor. The results regarding the influence of either the reaction temperature (425, 450, 475, and 500 °C) and the flow of the inert gas (0, 100, 300, and 500 mL/min) on product yield (referred to as pyrolysis of waste tyres) are also considered and discussed. On the basis of the abovementioned findings, the most appropriate experimental conditions were selected to contribute to a higher yield of pyrolysis oil. The sample of pyrolysis oil obtained from the experiments carried out in the selected optimal conditions (reaction time 120 min, temperature 450 °C and the inert gas flow of 100 mL/min) was subjected to calorimetric and infrared spectroscopy analysis. [ABSTRACT FROM AUTHOR]

The E. coli inactivation using hydrogen peroxide (H2O2) and cobalt ferrite granulated catalyst was investigated in a fixed-bed flow reactor. CoFe2O4 catalyst was synthesized by the co-precipitation method, granulated, and annealed at 1150°C. X-ray diffraction analysis was used to identify the crystal structure of the catalyst. CoFe2O4 catalyst demonstrates good catalytic activity for bacteria inactivation in the presence of H2O2. An increase in the hydrogen peroxide concentration increases the inactivation efficiency. The reactor demonstrates the E. coli inactivation of 99.94% at the H2O2 hydrogen peroxide concentration of 15 mM and initial bacterial concentration of 6·103 CFU/L. The water disinfection using a fixed-bed reactor demonstrates the broad prospects for industrial use.

Copyright of Low-Carbon Chemistry & Chemical Engineering is the property of Low-Carbon Chemistry & Chemical Engineering Editorial Office and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Herein, a preparation of a mixed-phase titanium dioxide (TiO2) thin layer on glass beads was developed using the modified spray method. This approach was determined to be affordable and easy to operate. Optimum conditions were investigated for the photodegradation of wastewater generated from textile dyeing by TiO2-coated glass beads as a catalyst using the central composite design (CCD). An increase in the direct dye photodegradation rate was observed at lower direct dye concentrations when TiO2 dosages were increased, and the initial pH value was decreased. The optimal conditions involving TiO2 dosage, pH, UV intensity, and dye concentrations were 3 g/L, 5.0, 3000 µW/cm2, and 50 mg/L, respectively, when administered at ambient temperatures. For the batch experiments, the direct dye removal efficiency at 93.7% was achieved within 24 h. The average direct dye removal efficiency was 67.8% and could be up to 80.2% when using a fixed-bed photocatalysis reactor during 30 d of continuous operation. The reused catalyst's degradation efficiency was not significantly changed, indicating its capability for repeated reuse and the excellent stability of immobilized TiO2 onto the glass beads. This study additionally found that high temperatures could increase the efficiency of color removal. [ABSTRACT FROM AUTHOR]

Copyright of Environmental Science & Technology (10036504) is the property of Editorial Board of Environmental Science & Technology and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

In this study 4 different acid catalysts were prepared and mixed with commercial CZA catalysts and investigated in direct DME synthesis. Some of the used acid catalysts were not investigated in the literature therefore the work involves novelty. In a fixed-bed reactor, dimethyl ether (DME) was synthesized from the synthesis gas on two catalysts from, natural clinoptilolite and zeolite catalysts. The clinoptilolite (HK and DK) and two (HZSM5(117) and HZSM5(360)) catalysts mixed with commercial CuO/ZnO/Al 2 O 3 (CZN) catalysts. The catalysts were also characterized by analytical chemistry techniques such as XRD, BET, TGA, and FTIR. Four different catalysts (HK, DK, HZSM5(117) and HZSM5(360)) and CZA catalysts were mixed at a ratio of 3/1, respectively, and studies were carried out in a fixed-bed reactor. Four different catalyst composition activity tests were made at temperatures 250, 275, and 300 °C. At the same time, the pressure was 30 and 40 bar and four different times (30, 60, 90, and 120 min). The composition of the gases fed to the system for DME was adjusted to N 2 /CO 2 /CO/H 2 = 36/10/18/36 by volume. DME selectivity (S DME) and total carbon (X C) conversion were calculated for each condition. The experimental results showed that the highest DME selectivity of 96.50% was observed in the reaction of the DK + CZA catalyst mixture at 250 °C and 30 min at 40 bar. In addition, high DME selectivity was obtained in all reactions of DK + CZA and HK + CZA catalyst compositions at three different temperatures. The highest DME selectivity obtained is 89.69% for the reaction of the HK + CZA catalyst mixture at 300 °C and 60 min at 30 bar. Experimental results gave insights into Dimethyl ether synthesis from syngas on clinoptilolite zeolite and HZSM5-based hybrid catalysts in a fixed-bed reactor. • Dimethyl ether was synthesized from the synthesis gas on clinoptilolite and zeolite catalysts in a fixed-bed reactor. • Experimental results gave valuable insights on Dimethyl ether synthesis from syngas on clinoptilolite zeolite. • The clinoptilolite based catalysts and H-ZSM5(117) and H-ZSM5(360) catalysts mixed with commercial CuO/ZnO/Al2O3 catalysts. • The highest DME selectivity of 96.50% was obtained in the reaction of the DK + CZA catalyst mixture at 250 °C and 30 min. • The highest DME selectivity was 89.69% for the reaction of the HK + CZA catalyst mixture at 300 °C and 60 min and 30 bar. [ABSTRACT FROM AUTHOR]

Sulfur dioxide, which comes from the flue gas emitted by the steel and coal power industries, is extremely harmful to humans and the natural environment. Due to its high efficiency and economy, dry fixed-bed desulfurization technology and Ca-based adsorbents have attracted wide attention. In this paper, a detailed outline of the process of the fixed-bed reactor, performance indexes, economic value, recent research, and industrial applications of the dry fixed-bed desulfurization process was summarized. The classification and properties, preparation method, desulfurization mechanism, and influencing factors of Ca-based adsorbents were discussed. This review indicated the challenges in the commercialization of dry Ca-based fixed-bed desulfurization and demonstrated the possible solutions. It is beneficial to promote industrial application by improving the utilization efficiency of Ca-based adsorbent, reducing the amount of adsorbent and operation cost, and developing ideal regeneration methods. [ABSTRACT FROM AUTHOR]

[Display omitted] • Coke precursors in O-containing organics reforming hardly penetrate catalyst bed. • Coke precursors from hexane/toluene easily penetrate two layers of catalysts. • O-containing intermediates are converted quickly while *C x H y from hydrocarbons is not. • Reforming of hexane/toluene produces much more coke than that from acetic acid/acetone/ethanol. • Coke from O-containing organics is more aliphatic while more aromatic from hexane/toluene. In steam reforming of organics in a fixed-bed reactor, catalyst particles in varied location of catalyst bed will experience different history of contacting with reactants/products. This may affect accumulation of coke in varied section of catalyst bed, which are investigated in steam reforming of some typical oxygen-containing organics (acetic acid, acetone and ethanol) and hydrocarbons (n -hexane and toluene) in a fixed-bed reactor with double layers of catalyst bed for investigating coking depth at 650 °C over Ni/KIT-6 catalyst in this study. The results indicated that the intermediates derived from the oxygen-containing organics in steam reforming could hardly penetrate the upper-layer catalyst to form coke in the lower-layer catalyst. In converse, they reacted quickly over the upper-layer catalyst via gasification or coking, forming coke almost exclusively in the upper-layer catalyst. The hydrocarbon intermediates from the dissociation of hexane or toluene could easily penetrate and reach the lower-layer catalyst to form even more coke therein than the upper-layer catalyst. The characterization showed that the insufficient gasification of *C x H y species led to their aggregation/integration to form more aromatic coke, especially from n -hexane. The aromatic-ring containing intermediates from toluene tended to integrate with *OH species to form ketones that further involved in coking, forming coke of less aromatic nature than that from n -hexane. Steam reforming of oxygen-containing organics also produced oxygen-containing intermediates and coke of higher aliphatic nature, lower carbon to hydrogen (C/H) ratio, lower crystallinity and thermal stability. [ABSTRACT FROM AUTHOR]

Calcium looping process is a promising approach for CO2 capture from the flue gas of fossil fuel power plants and the cement industry. Even though the advantages of calcium‐based sorbents are low cost and high uptake capacity, they suffer from low durability during cycles. Modified sorbents were fabricated by adding alumina and zirconia and the mixture of alumina and zirconia to calcium oxide via the co‐precipitation method. The performance of synthesized sorbents in terms of stability and CO2 capture capacity were evaluated using a fixed bed reactor in various CO2 sorption/desorption cycles. The sorbents were fabricated by a co‐precipitation methodology using 10% binders (alumina and/or silica). X‐ray diffraction (XRD), BET/BJH, and scanning electron microscopy (SEM) were conducted for characterization of synthesized sorbents. CaO‐10% ZrO2 showed the best performance among the fabricated sorbents in terms of stability during 5 cycles and CO2 capacity (14 mmol CO2/g sorbent). The formation of CaZrO3 with a perovskite structure and high‐temperature resistance could be attributed to well performance of zirconia‐supported sorbent. On the other hand, no sign of aluminum zirconate formation was approved in XRD analysis for the fabricated sorbent using mixed binders of zirconia and alumina to enhance its stability during cycles. [ABSTRACT FROM AUTHOR]

Using a Ca(OH)2/CaO thermochemical heat storage system is an effective way to promote the utilization of renewable energy. However, poor thermal conductivity restricts the application of a widely used fixed-bed reactor. To improve the heat storage rate, the internal heating mode, which heats the reactant via the internal heating tube instead of the external wall, was adopted, and the heat storage process in the fixed-bed reactor was investigated numerically. The results show that the number and location of tubes have a significant impact on heat storage performance. Compared with the external wall heating mode, the optimized scheme of six internal heating tubes can shorten the reaction time by 21.78%. The temperature and reaction extent distribution reveal that as the reaction proceeds, the optimized scheme has a higher temperature and reaction extent. Additionally, the effects of different conditions, such as solid particle porosity, wall temperature, outlet pressure, and solid particle size, were also analyzed. The study demonstrates that increases in solid particle porosity, wall temperature, and solid particle size as well as a decrease in outlet pressure can improve the heat storage rate. [ABSTRACT FROM AUTHOR]

Continuous liquid-phase CO 2 cycloaddition to cyclic carbonate is successfully realized for the first time in a membrane dispersion enhanced fixed-bed reactor. The reactor system can be operated steadily for 100 h with a productivity of 15.9 g cyclic carbonate ·h−1·g cat.−1, more than ten times that of the traditional fixed-bed reactor. [Display omitted] • A membrane dispersion enhanced fixed-bed reactor system was constructed. • Continuous liquid-phase CO 2 cycloaddition to cyclic carbonate was realized. • The membrane dispersion enhancement could improve the product selectivity. • The cyclic carbonate yield remained at around 90 % during 100 h continuous run. • The catalyst and membrane showed good stability during the continuous operation. CO 2 cycloaddition is an effective approach to achieve high-value chemical products and mitigate greenhouse gas emissions. However, high-efficiency and continuous CO 2 cycloaddition keeps a significant challenge. Herein, continuous liquid-phase CO 2 cycloaddition to cyclic carbonate is successfully realized for the first time in a membrane dispersion enhanced fixed-bed reactor. The reactor system can be operated steadily for 100 h with a productivity of 15.9 g cyclic carbonate ·h−1·g cat.−1, more than ten times that of the traditional fixed-bed reactor. [ABSTRACT FROM AUTHOR]

[Display omitted] • Thermal decomposition was promoted at 250–283 °C and suppressed above 400 °C. • Char yield increased mainly from melting suppressing aliphatic carbon release. • The impact of plastic melting on the co-pyrolysis process was further clarified by HTSM. • The gas yields were increased by 3.2 %–12.0 %, particularly H 2 , CH 4 , C 2 H 4 , and C 2 H 6. • The underlying mechanism for the co-pyrolysis of plastics and paper was proposed. Plastics and paper are common components of municipal solid waste (MSW), making an in-depth understanding of their interactions essential for MSW thermal conversion. In this study, the co-pyrolysis behavior of plastic and paper was investigated. Firstly, the thermal decomposition characteristics were analyzed. Secondly, the pyrolytic behavior was elucidated in a fixed-bed reactor. Thirdly, the impact of plastic melting on co-pyrolysis was clarified. Results indicated that the thermal decomposition was accelerated between 250 °C and 283 °C, while temperatures above 400 °C resulted in inhibition. During fixed-bed pyrolysis, char yields (70.7–16.9 %) were increased by 4.0 %–12.7 %. This increase was mainly due to plastic melting, which contributed 8.6 % and increased aliphatic carbon content. Besides, PVC and PET exhibited a broader melting range > 500 °C. Bio-oil yields (25.5–70.6 %) were reduced by 3.4 %–12.4 %, primarily affecting aliphatic compositions. Gas yields (3.8–6.5 %) were reduced < 400 °C but increased with temperature, involving primarily H 2 , CH 4 , C 2 H 4 , and C 2 H 6. [ABSTRACT FROM AUTHOR]

Commercial cylindrical mesoporous silica pellets (3 mm diameter by 3–6 mm length) were modified by coring the pellets and inserting a 1 mm diameter copper wire along the long axis of the pellet, to give a pseudo core–shell support. While there were negligible differences in the thermal conductance of the two supports, the volumetric thermal capacitance of the core–shell support was 4.1 times greater than the unmodified silica. Fischer–Tropsch synthesis (FTS) catalysts comprised of 16 wt% Co and 1.5 wt% Ru immobilized on the native pellets (control catalyst, CT) or on the core–shell support (CS-Cu catalyst) were prepared, placed in a tubular packed-bed reactor and reduced with H2 at 400 °C. The catalysts were conditioned for FTS (255 °C; 10 atm; H2/CO = 2; GSV 510 h−1) by cooling to 150 °C, changing to a syngas atmosphere, and slowly ramping to the run temperature of 255 °C over 8 h. Measurements of the catalyst bed temperature and furnace temperature during the activation and run time revealed frequent and large temperature spikes (∆T ~ 70 °C) in the CT bed, especially in the first 12 h of operation. In comparison, runs using the CS-Cu catalyst experienced fewer and less substantive temperature spikes (∆T ~ 30 °C). From the thermal data and the FTS productivity data, it was clear that the CT catalyst experienced a substantially greater degree to deactivation due to the thermal spikes than the CS-Cu catalysts. At similar conversions, the CS-Cu showed 50% greater productivity (gproduct/gCo–h) and a small but reproducible improvement in C5+ selectivity (52–55 wt%). Notably, the CS-Cu catalyst gave an appreciably smaller amount of the olefinic product (3 vs 15%). The thermal capacitance of the CS-Cu clearly moderates the negative consequences of local exotherms in the catalyst bed, especially during the activation phase of the FTS run. [ABSTRACT FROM AUTHOR]

Copyright of Inorganic Chemicals Industry is the property of Editorial Office of Inorganic Chemicals Industry and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

This paper represents a detailed techno-economic analysis of a typical commercial-scale catalytic decarboxylation process of naphthenic acids over HZSM-5 zeolite. Simulation of the process has been performed in ASPEN Plus®. The performance of the modeled unit was compared to experimental results data from a similar plant. Two models were developed for the proposed industrial plant based on continuous flow reactors; the first is based on a fluidized bed reactor, and it was modeled as a continuous stirred tank reactor (CSTR) unit, and the second is a semi-regenerative process that consists of three fixed-bed reactors with intermediate preheaters and are modeled as three plug flow reactors (PFR). The outcome of the economic analysis of the two proposed commercial scale reactors of a decarboxylation process of a capacity of 11,000 bbl/day showed that the CAPEX, including the total equipment cost for the fluidized bed reactor plant and semi-regenerative process plant, was $44,319,362 and $4,447,919, respectively. The annual operating cost for the fluidized bed plant and semi-regenerative process plant is 45,269,180 $/year and 1,771,839 $/year, respectively. Our results demonstrated that catalytic decarboxylation over HZSM-5 zeolite is economically feasible using a semi-regenerative process, and is a promising method for removing naphthenic acid. The insight obtained from this work can be used as a basis for more comprehensive future financial and risk modeling of the process. The cost estimated in this work was compared to the Khartoum refinery cost for the naphthenic acid corrosion mitigation system, with a saving of $29,459,528. [ABSTRACT FROM AUTHOR]

The article highlights the development of cheap affordable highly efficient catalytic oxidation system of harmful components of industrial flue gases of carbon graphite enterprises, its design features according to the parameters of furnace equipment, which will significantly improve the environmental safety of metallurgical and machine-building enterprises. The presented calculation and design solutions, in addition to carbon production, can be used in environmental protection technologies at other environmentally hazardous facilities to neutralize toxic emissions. The paper presents the calculation of the catalytic CO oxidation reactor made for the real flow rate of flue gases with temperature range 270-390 °C, which come out of the combustion chamber of the Riedhammer «first fire» kiln, heated by the flue gases. For such medium exothermic processes, mass and heat transfer between gas flow and the outer surface of the catalyst grains is sufficient intense. In this case for description of the catalytic process in the reactor is sufficient to use quasi-homogeneous single-phase model. The model of plug-flow reactor with a fixed bed of catalyst was used to calculate the flow parameters of the gas mixture through a reactor loaded with a composite zeolite-based manganese-oxide catalyst in the process of catalytic CO oxidation. The calculation results obtained using the software CHEMCAD 7.1.5 were almost identical to the previously made calculation. The peculiarity of the suggested solution was the use of the designed catalytic reactor for treatment of large volume of flue gases with low concentrations of CO at the companies of electrode carbon graphite production. [ABSTRACT FROM AUTHOR]

The results of a study of the pyrolysis of dried sewage sludge taken from a fixed-bed reactor of urban wastewater treatment plants are presented. The obtained experimental data made it possible to estimate the migration activity of heavy metals entering into the composition of the sewage sludge. Measurements were carried out for vanadium (V), chromium (Cr), cobalt (Co), nickel (Ni), copper (Cu), zinc (Zn), strontium (Sr), lead (Pb), rubidium (Rb), barium (Ba), zirconium (Zr), and arsenic (As). It is shown that the emission of heavy metals upon release of volatile substances during pyrolysis is characteristic for almost all of the studied elements, among which As, Rb, Co, and Ba are the elements having the highest migration activity. [ABSTRACT FROM AUTHOR]

In recent years, the catalyst pellets made of open‐cell metallic foams have been identified as a promising alternative in fixed‐bed reactors. A reliable modeling tool is necessary to investigate the suitability of different foam properties and the shapes of foam pellets. In this article, a workflow for a detailed computational fluid dynamics (CFD) model is presented, which aims to study the flow characteristics in the slender packed beds made of metal foam pellets. The CFD model accounts for the actual random packing structure and the fluid flow throughout the interstitial regions is fully resolved, whereas flow through the porous foam pellets is represented by the closure equations for the porous media model. The bed structure is generated using rigid body dynamics (RBD) and the influence of the catalyst loading method is also considered. The mean bed voidage and the pressure drop predicted by the simulations show good agreement with the experimental data. [ABSTRACT FROM AUTHOR]