Low-temperature System Research Articles

Frictional Losses of Ring Pack in SI and HCCI Engine

The vast majority of research dedicated to enhancing the homogenous charge compression ignition (HCCI) low-temperature combustion system is focused on improving controllability, efficiency and emissions. This article aims to assess the impact of HCCI combustion on the operation of the piston ring system. Utilizing the measured pressures in the combustion chamber of a single-cylinder research engine operating in spark ignition (SI) and HCCI modes at various loads, simulations were carried out using an advanced ring pack model. This model integrates the gas flow, ring dynamics and ring mixed lubrication models. Simulations revealed that differences in the pressure above the piston between the HCCI and SI combustion significantly influence ring pack performance. The predicted energy losses due to the friction of piston rings against the cylinder liner are up to 5% higher in the HCCI engine than in the SI engine. This identified drawback diminishes the advantages of the HCCI engine resulting from higher thermal efficiency, and efforts should be made to minimize this negative impact.

Techno-economic feasibility & environmental sustainability of producing nutritionally enhanced snack foods from agro-food byproducts using supercritical CO2-based extrusion

This study evaluated the economic feasibility and environmental sustainability of producing nutritionally superior snacks on an industrial scale by supercritical fluid extrusion (SCFX) using milk protein concentrate (MPC81-AP) or starch (Starch-AP)-based formulations enriched with apple pomace powder. Selected nutrient contents and antioxidant attributes were also studied to highlight the nutritional qualities of the final products. For large-scale implementation using a low-temperature (85°C) and low-shear SCFX system, capital budgeting, breakeven point, and profitability ratios were determined. During a standard 12-hour production run, a substantial margin of safety of 29.03% and a breakeven point of 0.71 years were estimated, indicating resilience against potential losses and a swift return on investment. The projected prices for MPC81-AP and Starch-AP-based products were $30.13/kg (Similar market snacks, $32-65/kg) and $26.29/kg, respectively. In summary, both formulations exhibited superior nutritional qualities, better gross profit margins and return on investment with environmentally sustainability, compared with the conventional extrudate snack foods available in the market today.

Experimental Investigation of a Low-Temperature Three-Circuit Cooling System for an Electric Motor under Varying Loads

This study investigates a low-temperature three-circuit cooling system for a 55 kW industrial electric motor. The cooling system provides an increase of the power-to-dimension ratio by 63%, together with an improvement in motor performance. The three-circuit cooling system includes water cooling of the housing and stator and air-cooling of the motor’s interior. The test results show that the motor efficiency was maintained in the range between 92.5 and 94.5%, with respect to the motor’s power. With power increases up to 90 kW, a winding temperature of 67 °C was observed during three hours of operation. This advancement is particularly valuable for vehicles, ships, and aircraft applications, where maximizing power within limited space is crucial. An analysis of the experimental data showed that the cooling system operates at an average efficiency of 79.2%, indicating that roughly 20% of heat was accumulated in the rotor. This leads to a gradual temperature rise, particularly in the rotor, posing a risk of overheating and failure during motor overloads above 90 kW. Enhancing the cooling efficiency within the motor’s interior can be achieved by incorporating extra heat exchangers, implementing evaporative heat transfer, and employing water-cooling circuits at lower temperatures. This, in turn, can boost the electric motor’s power-to-dimension ratio.

Performance and mechanism analysis of sludge-based biochar loaded with Co and Mn as photothermal catalysts for simultaneous removal of acetone and NO at low temperature.

Replacing NH3 in NH3-SCR with VOCs provides a new idea for the simultaneous removal of VOCs and NOx, but the technology still has urgent problems such as high cost of catalyst preparation and unsatisfactory catalytic effect in the low-temperature region. In this study, biochar obtained from sewage sludge calcined at different temperatures was used as a carrier, and different Co and Mn injection ratios were selected. Then, a series of sludge-based biochar (SBC) catalysts were prepared by a one-step hydrothermal synthesis method for the simultaneous removal of acetone and NO in a low-temperature photothermal co-catalytic system with acetone replacing NH3. The characterization results show that heat is the main driving force of the reaction system, and the abundance of Co and Mn atoms in high valence states, surface-adsorbed oxygen, and oxygen lattice defects in the catalyst are the most important factors affecting the performance of the catalyst. The performance test results showed that the optimal pyrolysis temperature of sludge was 400 °C, the optimal dosing ratio of Co and Mn was 4:1, and the catalyst achieved 42.98% and 52.41% conversion of acetone and NO, respectively, at 240 °C with UV irradiation. Compared with the pure SBC without catalytic effect, the SBC loaded with Co and Mn gained the ability of simultaneous removal of acetone and NO through the combined effect of multiple factors. The key reaction steps for the catalytic conversion of acetone and NO on the catalyst surface were investigated according to the Mars-van Krevelen (MvK) mechanism, and a possible mechanism was proposed. This study provides a new strategy for the resource utilization of sewage sludge and the preparation of photothermal catalysts for the simultaneous removal of acetone and NO at low cost.

Thermodynamic data of a promising cathode material NaV6O15 and its synthesis/decomposition thermodynamic analysis

Sodium-ion batteries have emerged as a promising alternative to lithium-ion batteries due to their lower cost and similar electrochemical properties. The development of high-capacity and long-life electrode materials is crucial for advancing sodium-ion battery research. A significant amount of research has been conducted on the electrochemical properties of NaV6O15, however, there remains a dearth of data on its thermodynamic properties. Herein, NaV6O15 was synthesized using the solid-phase sintering method and thoroughly characterized. Thermodynamic data in the temperature ranges of 298.15–900 K, 15–303 K, and 573–873 K were determined using the Neumann-Kopp rule, low-temperature physical property measurement system, and MHTC 96 line, respectively. The heat capacity equation of NaV6O15 was derived and its enthalpy, entropy, and Gibbs free energy (298.15–800 K) were calculated. Moreover, the thermodynamics of NaV6O15-related formation and decomposition reactions were analyzed. The obtained heat capacity equation of NaV6O15 was Cp=517.05524+0.08612T−1.25053×107T−2(J/mol·K)(298.15∼873K). This study addresses the thermodynamic knowledge gaps of NaV6O15 and provides valuable insights for its preparation and decomposition in manufacturing processes.

A novel thermal management for PEM fuel cell stack combining phase change materials with liquid cooling under low temperature condition

In this study, a low-temperature thermal management system (TMS) that combines a phase-change material (PCM) with liquid cooling for the cold start of a proton exchange membrane fuel cell (PEMFC) is introduced. The proposed system effectively utilizes the waste heat generated during the fuel cell operation to heat the PCM. After shutdown, the heat released during the PCM phase change process is transferred to the stack via a coolant pump, thus maintaining the stack temperature above the minimum startup threshold. A comprehensive thermal model of the proposed system is established and validated using numerical simulations. The temperature variations within the stack were evaluated under various environmental conditions, material properties, and coolant- pump control parameters. The results demonstrate that the TMS can sustain the stack temperature above 0 °C for 63.36 h in an environment at −20 °C. Furthermore, compared with passive thermal management, the proposed system has better temperature uniformity and an 11.71 % reduction in the stack startup time at 0 °C due to the proper loop design, which prevents the PCM from absorbing heat from the stack. This study provides innovative solutions to address the challenges associated with cold starts and is a valuable reference for future TMS designs.

Design of polarization converter based on dynamical cross-polarized amplitude modulation of superconducting NbN metasurface

In this paper, we innovatively employ superconducting material niobium nitride (NbN) into the polarization converter, designing a C-shape split resonant ring (SRR) polarization converter that works in the frequency range from 0.21 THz to 0.39 THz with a relative bandwidth of 60 % and the polarization conversion ratio (PCR) is more than 90 % in the superconducting state. The employment of NbN also brings dynamic modulation characteristic of cross-polarized amplitude. The cross-polarized amplitude reaches the maximum of −1 dB at 4.5 K, and decreases to the minimum of −10 dB at 16 K. Meanwhile, focusing on the output purity of cross-polarized amplitude at different temperatures, PCRs are more than 80 % in the frequency range of 0.25 to 0.33 THz. The characteristic is validated in the form of composite beam splitters. The simulation results show that the beam intensity controlled by NbN module decreases with the increase of temperature, achieving a switch in the number of beams. Variation trend is in a good agreement with the decreasing trend of cross-polarized amplitude of the polarization converter. This structure probably provides a new idea for the design of dynamically tuned polarization converter and expands the application of NbN which is beneficial for integration in low-temperature systems.

Solar Energy and Climate Change

Modern solar energy is based on photothermal, photovoltaic and hybrid solar radiation conversion and passive capture of solar radiation. Photothermal conversion of solar radiation takes place in low-temperature, medium-temperature, and high-temperature photoconversion systems. Flat collectors with water and air are used for low-temperature conversion of solar radiation. Solar concentrators are used for medium-temperature conversion of solar radiation. Concentrators with heliostatic fields and parabolic reflectors of solar radiation are used for hightemperature conversion of solar radiation. Solar cells made of different materials are utilized for the photovoltaic conversion of solar radiation. Stand-alone and photovoltaic systems connected to the electricity distribution network are used to supply consumers with electricity. Fixed tilt, single or dual-axis tracking solar power plants are designed with the aim to generate a larger amount of electricity. Hybrid solar collectors are used for the simultaneous conversion of solar radiation into heat and electricity. For passive capture of solar radiation, individual residential and other buildings are used, which are built in accordance with the principles of solar architecture. Solar energy uses mainly environment-friendly materials, except toxic As and Cd in GaAs and CdTe solar cells. Devices used in solar energy do not emit harmful substances and do not have an adversary impact on climate change.

Methyl and Ethyl Ethers of Glycerol as Potential Green Low-Melting Technical Fluids.

The study is dedicated to the consideration of lower alkyl ethers of glycerol as potential components of low-melting technical fluids (e.g., heat transfer fluids, hydraulic fluids, aircraft de-icing fluids, etc.). Four isomeric mixtures of glycerol ethers (GMME-monomethyl; GDME-dimethyl; GMEE-monoethyl; GDEE-diethyl) were synthesized from epichlorohydrin and methanol/ethanol in the presence of sodium and subjected to detailed characterization as pure compounds and as aqueous solutions (30-90 vol%). The temperature and concentration dependencies of density, viscosity, cloud point, boiling range, specific heat capacity, thermal conductivity, and rubber swelling were obtained. On the basis of the data obtained, a comparison was made between the aqueous solutions of glycerol ethers and of other common bases for low-melting liquids (glycerol, ethylene glycol, and propylene glycol). Pure glycerol ethers could potentially be used as technical fluids in a very wide temperature range-from -114 to 150 °C. It was further demonstrated that in low temperature applications (e.g., in low-temperature chiller systems) the glycerol-ether-based aqueous heat transfer fluids could provide enhanced efficiency when compared to the glycerol- or propylene-glycol-based ones due to their lower viscosities and favorable environmental properties.

Influence of storage conditions, packaging, post-harvest technology, nanotechnology and molecular approaches on shelf life of microgreens

Microgreens have achieved importance recently due to their high nutritive value, easiness of cultivation and year round availability. However, being very tender and having high moisture content, their shelf life is too short. Studies show that the physical quality, chemical quality and shelf life deterioration in post harvest of micro greens can be improved with effective storage conditions, packaging matters, nanoparticle application, physiological treatments and molecular approaches. Low ambient or storage temperature and effective storage system improve and sustain the shelf life, and quality and restrict microbial activity in micro greens. Packaging with bioplastic clamshell, cardboard clamshell, bioplastic pouch, kraft paper box, or classified polymer upgrades the shelf life and reduce antimicrobial activity under controlled temperature. The interventions with nanoparticles such as nano packaging, nano coatings and nano bubble modify the shelf life and quality and forbids microbial outbreak, solvent discharge and unstable gaseous exchange. The real time signal processing nano sensor technology can detect pesticides, pathogens, toxic materials, contaminants, and microbes in microgreens. The emission of light emitting diodes with stable ratio of wavelength extends shelf life. High carbon dioxide and low oxygen pressure at 5 °C temperature exhibits control respiration rate and prolonged shelf life. The standard packaging materials and post harvest technology may be recognized for extending shelf life and quality in harvested microgreens. The integration of molecular tools can be used to screen genome, replication, transcription, translation, post translation and gene regulation for shelf life improvement and desired traits.

Synthesis of Multifunctional Mn3O4-Ag2S Janus Nanoparticles for Enhanced T1-Magnetic Resonance Imaging and Photo-Induced Tumor Therapy.

The global burden of cancer is increasing rapidly, and nanomedicine offers promising prospects for enhancing the life expectancy of cancer patients. Janus nanoparticles (JNPs) have garnered considerable attention due to their asymmetric geometry, enabling multifunctionality in drug delivery and theranostics. However, achieving precise control over the self-assembly of JNPs in solution at the nanoscale level poses significant challenges. Herein, a low-temperature reversed-phase microemulsion system was used to obtain homogenous Mn3O4-Ag2S JNPs, which showed significant potential in cancer theranostics. Structural characterization revealed that the Ag2S (5-10 nm) part was uniformly deposited on a specific surface of Mn3O4 to form a Mn3O4-Ag2S Janus morphology. Compared to the single-component Mn3O4 and Ag2S particles, the fabricated Mn3O4-Ag2S JNPs exhibited satisfactory biocompatibility and therapeutic performance. Novel diagnostic and therapeutic nanoplatforms can be guided using the magnetic component in JNPs, which is revealed as an excellent T1 contrast enhancement agent in magnetic resonance imaging (MRI) with multiple functions, such as photo-induced regulation of the tumor microenvironment via producing reactive oxygen species and second near-infrared region (NIR-II) photothermal excitation for in vitro tumor-killing effects. The prime antibacterial and promising theranostics results demonstrate the extensive potential of the designed photo-responsive Mn3O4-Ag2S JNPs for biomedical applications.

Multi-criteria comparison of various drinking water installations for low-temperature supply systems in apartments

Rules to prevent from legionnaires disease gain importance as the building sector, esp. multi-family houses, needs to be decarbonized with temperature sensitive heat pumps. As legionella grow often in the peripheries of the pipe networks, we carried out dynamic simulations with TRNSYS of four different piping designs with composite pipes inside a reference apartment (T-piece, in-series, ring and a mix of T-piece for potable hot water (PWH) and ring for potable cold water (PWC)). We applied PWH and PWC tapping profiles for each tap, investigated two different supply temperatures of potable hot water 60 °C and 45 °C, and compared the results using hygienic, comfort and energy efficiency performance indicators. Based on the indicators and the boundary conditions used, classical T-piece and the mix installation show the best results, followed by series and ring, especially when using decentral water heaters with 45 °C.

Scalable façade-integrated PVT-systems for upward extensions in the urban context

This article presents a building concept, realised in a timber demonstration house. It is characterized by vertical, façade-integrated PVT collectors and a newly developed active layer as low-temperature storage system. We developed a scalable and transferable energy system design. Especially for multi-storey additions, where the roof area does not grow with the floor space, the concept increases - very much needed - power and energy density in urban areas. The novelty of the presented concept is the sole reliance on vertically mounted PVT-Panels as a heat source, without any seasonal energy storage (e.g., ice storage or geothermal) in combination with the active layer storage below the underfloor heating. Together they allow scaling of energy storage and solar gains with the usable space in the urban context of adding floors to existing buildings.

Environmental impact and thermodynamic comparative optimization of CO2-based multi-energy systems powered with geothermal energy

The continuous increase in global population and energy demands has enhanced the use of fossil fuels. The evident climate change effect in recent years has brought about the necessity to reduce fossil fuels. Hence, there exists an aggregate problem of meeting energy demands and reducing carbon emissions. Renewable energy sources have been proffered as the probable solution; however, multi-energy systems are effective options/alternatives to solving this problem. In recent literature, geothermal energy has been proposed as a renewable energy source that can continuously meet energy demands. However, there exists a significant gap in literature about the most viable temperature range for geothermal energy applications in multi-energy systems. In this study, two innovative CO2-based systems namely, high-temperature geothermal multi-energy system (HTGMES) and low-temperature geothermal multi-energy system (LTGMES) are designed, modelled, analyzed, and compared using a thermodynamic approach. While the HTGMES is modelled to predominantly use CO2 as a working fluid, a novel modified absorption system is integrated with the LTGMES. The two systems are modelled to produce electricity, cooling/refrigeration effect, space heating, hydrogen, and hot water. The energy, exergy environmental, exergy destruction, and exergoeconomic methodology is used to evaluate the performance of the innovative GMESs. Also, multi-objective optimization of the HTGMES and the LTGMES is carried out in a bid to minimize the total product unit cost and maximize overall exergy efficiency. The environmental impact analysis of the proposed system is presented considering CO2 mitigation. The results from analyses showed that the overall energetic and exergetic efficiencies in steady state are 44. 22 % and 33.5 % for the HTGMES and 45.40% and 32.9 % for the LTGMES. The optimized LCOE, LCOC, and LCOH based on the total unit cost are 0.0573 $/kWh, 0.1833 $/kWh, and 11.59 $/kg for the HTGMES; 0.0323 $/kWh, 0.0032 $/kWh, and 11.9$/kg for the LTGMES. Furthermore, the optimized exergetic performance showed that the LTGMES can achieve as high as 64.54 % and 40.96 % energy and exergy efficiency.

Plasma-assisted synthesis of nano-sulfur adsorbent for efficient removal of mercury from flue gas

Adsorbents injection technology is one of the most promising strategies to control mercury emission from flue gas. However, existing literature has shown leaching risk of mercury and halogen from commercial halogen impregnated adsorbents. Therefore, we proposed a novel and convenient fabrication method for nano-sulfur adsorbent assisted with nonthermal plasma technology in order to address these issues. The morphology, number concentration and size distribution of as-obtained nano-sulfur particles was determined by High Resolution Transmission Electron Microscopy (HRTEM) and Scanning Mobility Particle Sizer (SMPS). The mercury adsorption experiments showed nano-sulfur adsorbent (removal efficiency: 88.2 %) was more effective than micron-sized elemental sulfur (less than 10 %). Furthermore, the chemical composition of elemental sulfur allotropes (S6, S7 and S8) was determined using High-performance Liquid Chromatography-Mass Spectrometry (HPLC-MS). It was found that nano-sulfur particles contained higher proportions of S6 (1.53 %) and S7 (1.29 %) allotropes, which are the active materials in elemental sulfur. To investigate the effects of adsorption temperature and simulated flue gas on the performance of nano-sulfur adsorbent, the optimal adsorption temperature of 110 °C was determined, indicating its suitability for coal-fired power plants equipped with a low-temperature electrostatic precipitator system. Additionally, it was observed that simulated flue gas had slight inhibitory effects on the adsorbent performance, with a reduction of approximately 5 % in Hg0 removal efficiency. In summary, this research proposed a novel method for synthesizing nano-sulfur adsorbent and revealed the differences in sulfur allotropes' reactions with mercury, thereby deepening our understanding of the mercury-sulfur reaction mechanism.

Flexible phase change materials for low temperature thermal management in lithium-ion batteries

The performance of Li-ion batteries can degrade dramatically at cold ambient temperatures. The excess heat generated during battery operation can be stored by PCMs and then released at low ambient temperatures to insulate the battery. However, PCMs inevitably suffer from easy leakage and poor adaptability. In this study, we prepared a novel Oct/SEBS composite PCM and applied it in a low-temperature Li-ion battery thermal management system. The prepared Oct/SEBS has good shape stability, a sufficiently high latent heat (187.7 J/g), and thermally induced flexibility properties. In addition, the BTMS containing CPCM can exhibit excellent thermal insulation performance, which can insulate the Li-ion battery for more than 30 min even at −20 °C and increase the discharge capacity from 3.78 Ah to 5.49 Ah, which is very beneficial for the operation of the Li-ion battery at low temperatures.

Modeling of a low-temperature gas treatment system

Objective. The main purpose of the work is: investigation of the effect of changes in technological parameters on the efficiency of the separation process and determination of optimal technological modes of operation of gas field X CNTS in the separation process.Method. The problem was solved in the KBC Petro-SIM computer program and the LTS model was built. To conduct the study, a model of the LTS was built in the KBC Petro-SIM computer program.Result. The results obtained with the help of it showed: with the current composition of the gas with a decrease in temperature for every 2oC, with other technological indicators being equal, the specific condensate yield increases in the range from 15 to 30%, and the lower the temperature, the higher this percentage. When the pressure on the throttle decreases by every 0.4 MPa, the condensate output increases, if the pressure drops below 1.8 MPa, the specific condensate output will begin to decrease, which is explained by the pressure drop below the maximum condensation line of the phase diagram. The change in gas flow within the design values did not affect the operation of low-temperature separation. At any available low temperature and high pressure at the inlet to the ILTS, the most optimal mode will be when the pressure after the throttle is maintained within 1.8 - 1.9 MPa. The maximum specific yield of gas condensate (48.21%) was obtained at a pressure at the inlet to the ILTS of 5.1 MPa, a temperature after the heat exchanger of minus 2oC and a pressure drop at the throttle of 3.05 MPa. As part of the numerical research, the following results were obtained: with an increase in the pressure at the inlet to the ILTC, the change in the specific output of the gas condensate is insignificant, but with this parameter it is possible to create a larger pressure drop on the throttle; with a decrease in the gas temperature at the outlet of the heat exchanger, the specific yield of the gas condensate will increase; with an increase in the pressure drop at the throttle, the specific output of the gas condensate increases until the pressure after the throttle reaches the range of values of 1.8 – 1.9 MPa. In this interval, the maximum specific condensate yield is achieved. With a further increase in the pressure drop on the throttle, the specific output of the gas condensate decreases. This is explained by the phenomenon of retrograde condensation, since the maximum condensation line is in the range of these pressures.Conclusion. Based on the results of the work, it was found that the developed software module can be used to solve the emerging series of problems. The results of the work show the suitability of the proposed method for practical purposes.

Experimental analysis of one and two-stage thermoelectric heat pumps to enhance the performance of a thermal energy storage

This experimental study demonstrates the possibility to enhance the performance of a low-temperature thermal energy storage system (∼160 °C) based on airflow heating using electrical heaters by including thermoelectric technology. An improvement of the 17 % on COP is reached by using an optimized thermoelectric heat pump system to preheat the airflow, consisting of three one-stage and three pyramidal two-stage thermoelectric heat pumps sequentially installed along the airflow that is heating.This research experimentally analyses and compares the COP of three different configurations of thermoelectric heat pumps: one-stage, square two-stage, and pyramidal two-stage thermoelectric heat pumps. The experimental study aims to characterize the operation of each configuration for heating an airflow of 16.5 m³/h at 25 °C as ambient temperature. To that purpose, the airflow inlet temperature, voltage supply, and voltage ratio between stages have been modified.The experimental results show that for 25 °C as inlet temperature the one-stage thermoelectric heat pump has the best performance with a maximum generated heat of 78 W. Whereas, a two-stage thermoelectric heat pump is required when the inlet temperature increases. At 40 °C as inlet temperature, the square two-stage configuration provides the best performance with a voltage ratio of 2, which reaches a COP of 3.29 generating only 20 W of heat. However, the pyramidal two-stage configuration is able to achieve the maximum heat outputs with a voltage ratio of 1, generating 172; 161; 149 and 138 W, with corresponding COP values of 1.17; 1.16; 1.14 and 1.11 for inlet temperatures of 25; 40; 55 and 70 °C. This configuration is the one that achieves the greatest COP values with high inlet temperatures.

Application Prospect of Monopolar Low-temperature Plasma Knife in Oral and Maxillofacial Surgery

Oral and maxillofacial surgery is primarily responsible for the treatment of oral and maxillofacial tumors, jaw fractures, maxillary sinusitis, and other temporomandibular joint diseases using surgical techniques. With improvements in living conditions and dietary changes, the demand for diagnosis and treatment in oral and maxillofacial surgery has been steadily increasing. Simultaneously, both patients and healthcare providers have higher expectations for intraoperative effectiveness and postoperative recovery. With the advancement of technology, surgical knives in oral and maxillofacial surgery have gradually transitioned from traditional physical blades to high-frequency electric scalpels. However, high-frequency electric scalpels have drawbacks, including substantial tissue damage, the generation of intraoperative smoke, electrode adhesion, imprecise cutting, and reliance on traditional surgical blades. This paper proposes the idea of using a monopolar low-temperature plasma knife in oral and maxillofacial surgery, with a focus on research utilizing the monopolar low-temperature plasma surgical system produced by Jingyi Medical (Host Model: PSG-60A; Electrode Model: PS-01) as an example. This equipment disrupts tissue molecular bonds through the low-temperature plasma layer formed around the knife tip, allowing for tissue cutting and separation. This approach significantly reduces tissue damage compared to traditional surgical blades and high-frequency electric scalpels, while also simplifying surgical procedures, improving cutting precision, and enhancing postoperative recovery. Through this research, it can be observed that the monopolar low-temperature plasma knife has significant potential for widespread application in oral and maxillofacial surgery.

Styrene removal by low-temperature catalytic oxidation using Mn2O3/Al2SiO5

Highly efficient catalytic oxidation for the removal of volatile organic compounds (VOCs) is commonly accompanied by considerable energy demand to conduct the reaction at high temperature. Therefore, the development of low-temperature catalytic oxidation systems based on metal oxides has attracted widespread interest. In this study, we have assessed the performance of Mn2O3/Al2SiO5 in catalyzing the oxidation of styrene. Tests were conducted in a fixed-bed reactor with different loadings of the supported catalyst under different operating conditions (concentration of styrene, oxygen availability, space velocity, and temperature). The characteristics of the catalyst and the reaction kinetics have been studied in detail. The best catalytic activity was achieved with 38 wt% Mn2O3/Al2SiO5, which gave 95% styrene conversion (T95) at 298 °C. A space velocity of 5000 h−1 provided sufficient reaction time and favored the oxidation of styrene. The absence of O2 significantly suppressed styrene conversion to 25.4%, but the presence of just 1% O2 substantially enhanced its catalytic oxidation. A lower reaction temperature of 282 °C led to reduced performance of the catalyst, such that only 20% styrene conversion was achieved, which was due in part to extensive carbon deposition.