Sulfate Resistance Research Articles

Significant Enhanced SO2 Resistance of Pt/SiO2 Catalysts by Building the Ultrathin Metal Oxide Shell for Benzene Catalytic Combustion.

A noble metal catalyst shows excellent low-temperature oxidation activity in the catalytic combustion of benzene but has the problem of SO2 poisoning. We all know that SO2 easily competes with the reactant molecules for adsorption of the active site and has electronic effects on the active site to deactivate the catalyst. Therefore, the sulfur resistance of catalysts is the key problem to be solved in the process of catalytic combustion of benzene. Herein, the Pt/SiO2 catalyst with an ordered mesoporous structure was prepared by a one-step hydrothermal method, and MgO, ZnO, and MnOx were, respectively, coated on the surface of Pt/SiO2 as ultrathin shells to improve the sulfur resistance of Pt/SiO2. We observed that the sulfur resistance of the Pt/SiO2 catalyst was significantly improved due to the protective effect of the metal oxide shell. By comparing the three core-shell catalysts, it was found that the Pt/SiO2@MnOx catalyst coated with a MnOx shell had the best performance. The reason was that the MnOx shell not only protected the Pt active site but also had a good electron transfer effect on the core Pt, so it could effectively avoid the rapid adsorption poisoning of SO2 on the active Pt0 site. In addition, it was verified that the excellent redispersion of MnOx species in a SO2 atmosphere could increase the low-temperature oxidation activity of the Pt/SiO2@MnOx catalyst. Meanwhile, in situ DRIFT results also confirmed that the MnOx shell could significantly promote the oxidation of benzene molecules in the SO2 atmosphere.

Depth investigation of the regulation mechanism of SiO2 on the denitrification performance and sulfur resistance of MnCe/Ti SCR catalyst

The “deep peaking” of coal-fired units presents great challenges for SCR catalysts’ de-NOx activity at wide temperatures. Mn-based catalysts have good de-NOx activity at low temperatures, but their poor sulfur resistance is one of the key issues affecting industrial applications. In this study, the effects of SiO2 doping on the denitrification, sulfur resistance, and physicochemical performance of the MnCe/Ti catalyst were investigated. The results showed that SiO2 improved the de-NOx activity of catalysts at high temperatures and enhanced SO2/H2O resistance at wide temperatures. Under short reaction time conditions, the MnCe/Ti0.9Si0.1 catalyst exhibited the highest NO conversion rate at 400 °C, which was 33% higher than that of the MnCe/Ti catalyst. The NO conversion rates of Si-doped MnCe/Ti catalysts increased rapidly to over 85% (65% of the MnCe/Ti catalyst) as the reaction temperature increased from 200 °C to 250 °C under SO2-containing atmosphere due to the promoting effects of SiO2 on the decomposition of ammonium bisulfate. MnCe/Ti0.7Si0.3 catalyst exhibited the optimal sulfur and H2O resistance, with NO conversion rate higher than 85% with 600 min under SO2/H2O-containing atmospheres. SiO2 inhibited the crystallization of anatase TiO2, and increased the specific surface area to 306.60 m2/g. Additionally, the ratios of Mn4+/Mnn+ and Ce3+/Cem+, and the surface adsorbed oxygen and weak-medium acid amount also increased due to the multiple interactions between the TiO2-SiO2 and Mn/Ce, resulting in the higher de-NOx activity. Compared with the MnCe/Ti catalyst, Si-doped MnCe/Ti catalysts have lower SO2(g) adsorption amount and the sulfation of Mn, and higher SO3(a) desorption performance, resulting in better sulfur resistance at wide temperatures.

Sulfate resistance and degradation mechanism of basalt fiber modified graphite tailings cement-based materials

This paper delves into the modification mechanism and deterioration mechanism of basalt fiber (BF) on the sulfate resistance of graphite tailings (GT) cement-based materials. Initially, the comprehensive properties of basalt fiber modified graphite tailings cement mortar (BFM-GTCM) under different sulfate cycles, such as apparent morphology, water absorption and mechanical characteristics were investigated. Subsequently, the relationship between the evolution of microstructure, interface stability, pore structure, chemical composition and functional groups of BFM-GTCM and its resistance to sulfate erosion under different cycles was revealed by various microscopic characterization and analysis methods (SEM/XRD/MIP/FTIR/DSI). Simultaneously, a corrosion coefficient-pore structure relationship model was also put forth based on multivariate regression theory, and the mechanism enhancing BFM-GTCM resistance to sulfate attack was investigated. The results demonstrated that a suitable blend of BF and GT can prevent sulfate ion penetration, significantly slow down the generation of corrosion products (AFt and gypsum) in cement mortar during sulfate attack, postpone the occurrence of new cracks and the growth of existing ones, improve pore structure, and significantly lessen the degree of durability degradation of BF-GTCM. Among them, 0.3% BF addition and 20% GT replacement was the ideal ratio.

Analysis of the properties of recycled aggregates concrete with lime and metakaolin

In recent years, the use of alternative materials in cementitious systems has attracted considerable interest due to their potential for augmenting the durability and performance of concrete. This research is investigating the use of three such materials as partial cement replacements in concrete: Recycled Concrete Aggregate (RCA), Limestone, and Metakaolin. RCA is a byproduct of the demolition of concrete structures that can be recycled as aggregate. Incorporating RCA into concrete reduces the environmental impact of waste disposal and reduces the carbon burden. Due to its pozzolanic properties, limestone, a sedimentary rock composed primarily of calcium carbonate, can be used as a substitute for cement. By substituting a portion of cement with limestone, the cement manufacturing process can substantially reduce carbon dioxide emissions. Metakaolin, a thermally treated form of kaolin clay, is yet another alternative material with pozzolanic properties. When used as a partial cement replacement, metakaolin increases the concrete’s strength, durability, and chemical resistance. It also contributes to lowering hydration heat and mitigating alkali-silica reactions, thereby enhancing the durability of concrete structures. In this investigation, cement is replaced by limestone powder which is varied from 0% to 50% and the addition of metakaolin of 20% in every mix design. RCA is also incorporated in the mix design as a replacement for coarse aggregate by 20%. In the experimental investigation, various tests were conducted on each mix slump test, density, compressive strength, sulphate attack, mass loss, x-ray diffraction (XRD), and scanning electron microscope (SEM). After the investigation, the compressive strength improved by 15.07%, when metakaolin was added, and when LS was used to replace 10% of the cement, the compressive strength increased by 13.49%. The features of the combinations were negatively impacted when more cement was substituted. Following an investigation of hydration products, filler and dilution effects were found, both of which have the potential to be connected to improved mix quality. A mix that contains 20% metakaolin and 10% limestone powder may be considered the ideal mix owing to its superior strength and sulphate resistance when compared to normal concrete. It consists of less effect on slump value and density, the compressive strength was increased, and minimum mass loss after the sulphate attack. M3 mix best performer among all mix designs. It shows that the mix design with 20% metakaolin and 10% limestone powder is best-suitable for future recommendations.

Hydration characteristics, structure evolution of marine cement composites with high durability modified by colloidal nano-silica for low carbon footprints

The porous structure of cement composites provides channels for the invasion of chloride ions in marine environment, which limits their service life and low carbon footprints. Colloidal nano-silica (CNS) with the particle size of 10–30 nm theoretically can refine the pore structure, block the chloride ion transport channel. Thus, it is beneficial to improve the service life of cement composites and reduce the consumption of cement and carbon dioxide emission. In this paper, the CNS was introduced to partially replace high sulfate resistance Portland cement (HSRPC) preparing HSRPC-CNS composite. The hydration characteristics, strength property, porous structure and chloride ion resistance were investigated. The results revealed that the addition of CNS was effective in improving the properties of HSRPC-CNS composite, and the most suitable content of CNS was 3 wt%. In this case, the hydration process of HSRPC-CNS composite was accelerated, and the 28-days compressive strength increased by 12.26%. Additionally, as the CNS content increases to 3 wt%, the porosity and chloride diffusion coefficient decreased by 32.39% and 41.99%, respectively. Therefore, CNS can be used as a sustainable nano additive that improved compactness, alleviated chloride ion permeability and reduced carbon dioxide emissions in HSRPC-based composites.

Effect of low-calcium fly ash inclusion on long-term mechanical properties and durability of ground granulated blast furnace slag-based cement-free mortars

The present study focused on fabricating cement-free mortar based on ground granulated blast furnace slag incorporating low-calcium fly ash as precursors in an alkaline solution of sodium hydroxide and sodium silicate. The main purposes of the study were not only to find the optimum mixture proportions to confirm the fly ash role in contributing to the long-term mechanical properties and durability but also to expand the use of fly ash in cement-free binders based on ground granulated blast furnace slag. The ground granulated blast furnace slag was replaced with fly ash in the cement-free mortar at various levels of 30, 40, 50, 60, and 70% by mass. The cement-based sample as a control sample was prepared for comparison purposes. Results showed that the cement-free mortar samples with fly ash had the more superior long-term mechanical properties (i.e. flexural and compressive strengths and volumetric compaction via ultrasonic pulse velocity test) and durability (i.e. total charge passed via rapid chloride penetration test and sulfate resistance via length change of samples exposed to sulfate solution), lower water absorption and porosity, and denser microstructure than the control sample up to 120 days. The 40% replacement of ground granulated blast furnace slag by fly ash as an auxiliary source of alumina and silica was the optimum ratio in enhancing the long-term mechanical properties and durability of the cement-free mortar samples, which is in agreement with reducing the porosity and water absorption. The results of the environmental analysis indicate that using cement-free mortar samples has much lower environmental impacts. The cement-free mortar sample using 60% ground granulated blast furnace slag and 40% fly ash is found as an optimal mixture in terms of technical and environmental features.

Investigation of physical and mechanical properties of nanocarbon black-added lightweight UHPC

The high specific density of concrete significantly increases the dead load in buildings. Using pumice, which is a volcanic material, as an aggregate in concrete decreases the concrete's density. However, pumice causes a decrease in the mechanical properties of concrete owing to its porous structure. The improvement of the mechanical properties of concrete can provide material savings by reducing the cross-sections of the structural elements to be used in buildings. Ultra-high-performance concrete, which has been an important subject of studies in recent years, is an important construction material for civil engineering. In this study, the physical and mechanical properties of lightweight ultra-high-performance concrete (LW-UHPC) with pumice additive were investigated. Nanocarbon black was added to the mixture as 5, 10 and 15% of the cement weight. Significant increases were observed in the mechanical properties of nanocarbon black-added concrete. The addition of nanocarbon black to concrete at a certain ratio increased the compressive strength and flexural strength of concrete by 9.9% and 10.6%, respectively. In addition, it was observed that the sulfate resistance increased in direct proportion to the increase in the amount of nanocarbon black.

Life Testing and Redox Cycling of Ni- and Ru-Doped Strontium Iron Titanate Exsolution Fuel Electrodes in Electrolyte-Supported Solid Oxide Cells

Recently perovskite materials have gained much attention as potential candidates for solid oxide cell (SOC) fuel electrodes due to their advantages of redox stability, coking resistance and sulfur resistance over their cermet counterparts. Enhanced electrochemical performance has also been observed for some of these perovskite materials resulting from exsolution, where nano-sized metal particles are formed on the material surface under reducing conditions. However, the degradation mechanism of these perovskite fuel electrodes has yet to be fully understood and the relationship between their long-term stability and operating envrionments (fuel-cell/electrolysis, fuel compositions, redox cycles, operating pressure, etc.) has not been fully investigated.Here, life tests were conducted in open-circuit and reversible operation at 850oC on electrolyte-supported symmetric and full cells with Ni and Ru-doped strontium iron titanate (Sr0.95Ti0.3Fe0.63Ni0.07O3 and Sr0.95Ti0.03Fe0.63Ru0.07O3) as fuel electrodes (SrTi0.3Fe0.6Co0.1O3 used as the air electrode in the full cells). For both materials, higher degradation rate was observed when operated with 97% H2 + 3% H2O compared with 50% H2 + 50% H2O as fuel; an increase in ohmic resistance and gas adsorption/desorption resistance contributed to most of the degradation observed. STFN also showed higher degradation rates than STFRu in both fuel compositions. Exsolution from both compositions was confirmed by scanning electron microscopy (SEM) and scanning transmission electron microscopy (STEM) with both fuel compositions and in situ X-ray Diffraction (XRD) showed the simultaneous perovskite to Ruddlesden-Popper (RP) phase transformation. The faster perovskite-RP phase transformation is believed to be responsible for the higher degradation rates observed for cells using fuel electrode materials with less stable perovskite structure (STFN over STFRu) and tested in more reducing fuel compositions (97% H2 over 50% H2). Moreover, redox cycles were introduced for STFN and STFRu during life tests and partial performance recovery was observed; in situ XRD and SEM microstructural analysis suggests that the recovery resulted from a transformation from RP back to perovskite for both materials. Finally full cell reversible operation durability tests (6 hrs each in fuel cell and electrolysis modes at 0.8 A/cm2) conducted at 850oC with 50% H2 + 50% H2O as fuel at 1 atm showed reasonably good stability over 1000 h. Initial reversible life testing at 3 atm operating pressure showed higher degradation rates, and the possible reasons for this will be discussed.

Copper-ceria catalysts with improved water and sulfur resistance: Computational design and structural optimization

Copper species dispersed on ceria have emerged as promising catalysts for various energy and environmental applications. However, the presence of water vapor in the actual application environment can significantly hinder the catalyst activity. Flame-synthesized catalysts have been found to possess good water resistance as well as strong mercury oxidation and sulfur resistance. In this study, two types of copper-cerium binary structures were compared: Cu/CeO2 and CuO/CeO2, which represent highly dispersed copper on the CeO2 lattice surface (the main structure of the flame-synthesized catalyst) and CuO clusters supporting on the CeO2 lattice (the main structure of catalyst synthesized by impregnation methods), respectively. The adsorption energies of SO2, H2O, and Hg0 over these structures were studied by density functional theory calculations. The results revealed that Cu-O2/CeO2 (Cu/CeO2 with absorbed O2) had the highest Hg0 adsorption energy (−81.4 kJ/mol), followed by CuO/CeO2 (−13.1 kJ/mol) and CeO2 (−4.4 kJ/mol). Both Cu-O2/CeO2 and CuO/CeO2 showed improved sulfur resistance compared to CeO2, because SO2 was preferentially absorbed on copper sites, protecting the active sites on the CeO2 surface·H2O was absorbed and hydrolyzed into hydroxyl groups on the surfaces of all structures. The hydrolysis process consumed active oxygen on the CeO2 surface for CeO2 and CuO/CeO2, but consumed oxygen absorbed from the surrounding air for Cu-O2/CeO, leading to its best water resistance among the three. This finding opens up possibilities for the development of highly efficient and water-resistant catalysts.

A comprehensive investigation on sulphate resistance of geopolymer recycled concrete: Macro and micro properties

As a potential alternative to ordinary Portland cement concrete (OPC), geopolymer recycled concrete (GRC) is provided with great research value as it not only significantly reduces carbon dioxide (CO2) emissions but also promotes the resourceful use of construction and demolition waste (CDW). However, concrete is frequently subjected to extreme circumstances such as sulphate attack during service. To comprehensively explore the structural and performance damage mechanisms of GRC caused by sulphate assault, this study is conducted to erode GRC specimens with recycled aggregate (RA) replacement rate of 0%, 30%, 50%, 70% and 100% by using magnesium sulphate solution with 10% mass fraction. The macroscopic properties of GRC subjected to sulphate attack are examined, including mass loss rate, relative modulus of elasticity and compressive strength. The microstructure and phase evolution of GRC subjected to sulphate attack is analyzed by SEM, EDS and XRD. The micro-mechanical properties of interfacial transition zones (ITZs) in GRC are measured by nanoindentation. The results show that there is no loss of mass in all GRC specimens throughout the erosion age, and the relative dynamic elastic modulus of GRC first increases and then decreases. GRC with 30% RA substitution rate has the best resistance to sulphate attack. The degradation of GRC by sulphate attack is closely related to its internal structural changes. The deterioration of the micromechanical properties of three ITZs by sulphate erosion is not significant, which indicates the RA has favorable performances with geopolymer binder contributing to excellent resistance of GRC to sulfate attack. In addition, a prediction model for the evolution of GRC resistance to sulfate erosion with erosion age for different RA substitution rates is developed, which provides a theoretical guidance for the application of GRC.

Insight into the mechanisms of activity promotion and SO2 resistance over Fe-doped Ce-W oxide catalyst for NOx reduction

Ceria-based catalysts for the selective catalytic reduction of NOx with NH3 (NH3-SCR) are always subject to deactivation by sulfur poisoning. In this study, Fe-doped Ce-W mixed oxides, which were synthesized by the co-precipitation method, improved the SCR activity and SO2 durability at low temperatures of undoped Ce-W oxides. The improved low-temperature activity was mainly due to the enhancement of redox properties at low temperatures and more active oxygen species, together with the adsorption and activation of more abundant NOx species, facilitating the “fast SCR” reaction. In the presence of SO2, doping with Fe species effectively prevented sulfate deposition on the CeW catalyst, due to the interaction between Fe, Ce, and W species inducing electron transfer among different metal sites and altering the electron distribution. The competitive adsorption behavior between NO and SO2 was changed by Fe doping, in which the adsorption and oxidation of SO2 were restrained. Besides, the elevated NO oxidation accelerated the decomposition of ammonium bisulfate, causing the SCR reaction to not be greatly suppressed. Hence, Fe-doped Ce-W oxides catalysts showed excellent sulfur resistance. This study provides an in-depth understanding of efficient Ce-based catalysts for SO2-tolerance strategies.

Effect of additives on sulfur resistance of catalytic filter material during denitrification and synergistic decomposition of 1,2-DCBz.

Modified Mn-Ce/P84 catalytic filter material can be used to achieve high removal efficiency of NOx and 1,2-DCBz in bag-filtering dust precipitator synergistic removal of multiple pollutants. However, the presence of SO2 in the actual industrial flue gas has an adverse impact on the catalytic performance of the catalytic filter material. In this paper, a kind of Mn-Ce catalytic filter material was prepared by the impregnation method, which was modified by Fe, Cu, and Co, respectively. As a result, the sulfur resistance of the catalytic filter material was improved. The change of catalytic activity of the three kinds of modified catalytic filter material at different concentrations was compared in the SO2 flue gas fixed bed system. And the modified catalytic filter materials were characterized by SEM, BET, XPS, XRD, and H2-TPR. When the temperature was over 80 °C, different concentrations of SO2 were injected into the simulated flue gas to test the denitrification activity of the catalytic filter material. The results showed that under the low SO2 concentration of 150 ppm, the denitrification activity and 1,2-DCBz activity of Fe, Co, and Cu-modified filter material were increased, and the sulfur resistance of Fe was better under the flue gas conditions of 300 ppm and 450 ppm SO2. Under the condition of 450 ppm SO2 and 200 °C reaction, 93.4% denitrification efficiency and 96.1% 1,2-DCBz removal efficiency could be achieved by using modified Fe-Mn-Ce catalytic filter material.

Oxidation of CO and slipped NH3 over a WS2-Loaded Pt/TiO2 catalyst with an extended reaction temperature range

The recent tightening of emission regulations aims to reduce the release of CO and slipped NH3 with industrial flue gas, necessitating the development of improved CO and NH3 oxidation catalysts, as conventional Pt catalysts are easily poisoned by the SO2 present in flue gas. In particular, the reaction temperature range of existing Pt/TiO2 catalysts and their resistance to sulfur poisoning can be improved by enhancing Pt dispersion through modification with WS2. This study examined the ability of WS2-doped Pt/TiO2 catalysts prepared using different WS2 loadings (3.6 and 5 wt%) at various calcination temperatures (300, 400, and 500 °C) to promote the oxidation of CO and NH3 in the absence and presence of SO2. The partial conversion of WS2 to WO3 at high calcination temperatures is found to be of key importance for securing high catalyst performance. The optimal catalyst exhibits high oxidation activity and sulfur resistance at low temperatures, achieving CO and NH3 oxidation efficiencies of ≥85% and 100%, respectively, at an SO2 content of 100 ppm and 280 °C.

Design Sr, Mn-doped 3DOM LaCoO3 perovskite catalysts with excellent SO2 resistance for benzene catalytic combustion

Anti SO2 poisoning is a major scientific challenge in the field of VOCs catalytic combustion. To enhance sulfur resistance of 3DOM LaCoO3 perovskite catalysts, the strontium (Sr) and manganese (Mn) elements were doped to regulate and control its microstructure and electronic valence states of active metals. The macropore structure is constructed to accelerate the adsorption and diffusion of benzene and intermediate species and promote the deep oxidation in ordered macropores. Surprisingly, we observed that the co-doping of Sr and Mn components resulted in the superior catalytic performance for benzene catalytic combustion. Especially, the sulfur resistance of LaCoO3 catalyst was significantly improved due to the doping of Sr and Mn species. Through various characterizations, it is discovered that the doping of Mn component in 3DOM LaCoO3 perovskite catalyst could promote the formation of active Co3+ species due to the excellent redox properties between Mn&+ and Co&+ species (Mn4++Co2+→Mn3++Co3+), while the co-doping of Sr and Mn elements could produce and form some new active species. On one hand, Sr and Mn may act as an electron promoter to increase the concentration of Co3+ and Oads. On the other hand, Sr and Mn can act as a structure promoter to enhance the specific surface area and promote the dispersion of active Co species. The research provides valuable reference for the development of highly efficient catalysts for the industrial degradation of benzene.

Tribological properties and sulfuric acid corrosion resistance of laser clad CoCrFeNi high entropy alloy coatings with different types of TiC reinforcement

CoCrFeNi, directly added TiC (D-TiC) and in-situ synthesized TiC (I-TiC) reinforced CoCrFeNi high entropy alloy coatings (HEACs) were prepared on the surface of 316 stainless steel (SS) by laser cladding (LC). The HEACs all achieved a dense and uniform structure, the TiC distributed at the grain boundaries (GBs) reduced the dilution rate of the HEACs, and the I-TiC composite coating realised a fine and diffuse distribution of the reinforcing phase compared to the D-TiC HEAC. The introduction of TiC dramatically refined the grain size of HEA system and inhibited the formation of high angle grain boundaries (HAGBs), with the average grain size decreasing from 23.6 µm in the TiC-free HEAC to 12.3 µm in D-TiC HEAC and 9.3 µm in I-TiC HEAC, and the proportion of low angle grain boundaries (LAGBs) of D-TiC and I-TiC composite coatings was even as high as 64.8% and 70.4%. As a result, the density of geometrically necessary dislocations (ρGND) in TiC-containing coatings also increased greatly, and ρGND in CoCrFeNi, D-TiC and I-TiC HEACs were 0.55 × 1015, 1.08 × 1015 and 1.27 × 1015 m−2, respectively. The highest average microhardness values of 420.2 ± 6 HV0.2 was achieved with I-TiC HEAC, which relied on TiC precipitation in a nucleation-growth mode. In electrochemical corrosion tests, the introduction of TiC also provided additional channels for ion diffusion. The ordered and dense passivation film of the I-TiC composite coating impeded sulfuric acid attack effectively, with an Icorr value of only 2.28 × 10−2 ± 0.8 μA/cm2, which was less than that of the substrate as well as the other two HEACs. In both dry sliding friction and wear and corrosive wear experiments, abrasive wear was the dominant wear pattern of I-TiC HEAC due to the increase in local stresses caused by the "point-to-point" contact between the TiC particles and the friction pair. Thanks to the diffuse and homogeneous distribution of the TiC reinforcing phase, I-TiC HEAC exhibited the best tribological performance in both dry sliding friction and wear or corrosive wear experiments with specific wear rates as low as 0.05 mm3/Nm in air and 0.06 mm3/Nm in sulfuric acid.

Promoting effect of Si on MnOx catalysts for low-temperature NH3-SCR of NO: Enhanced N2 selectivity and SO2 resistance

Manganese-based catalysts have excellent catalytic performance for the effective removal of NOx in low-temperature flue gas through selective catalytic reduction with NH3 (NH3-SCR). However, the catalysts suffer from poor SO2 resistance and N2 selectivity in the actual process, which still need to be solved. In this study, MnOx-SiO2 mixed oxide catalysts were designed and prepared by coprecipitation method to improve the SO2 resistance and N2 selectivity in NH3-SCR process. In the presence of 100 ppm SO2, MnOx-SiO2(0.72) catalyst showed excellent sulfur resistance with the conversion of NOx reached 95 % even after introducing SO2 for 8 h. The doping of SiO2 greatly improved the specific surface area and surface acidity of the catalyst, which was conducive to the adsorption of NH3. Meanwhile, the redox performance of the catalyst was decreased, improving the N2 selectivity. The study on the sulfur resistance mechanism revealed that the doping of SiO2 reduced the adsorption of SO2 on the surface of catalyst, protecting the active components and avoiding the accumulation of sulfates, thus achieving good sulfur resistance performance. This work provided an environmentally friendly NH3-SCR catalyst by inhibiting SO2 adsorption to have good catalytic performance and SO2 resistance.

Porous Fe-modified CuCeZr catalysts for simultaneous removal of NO and toluene at low-medium temperatures: Promoted activity and SO2 effect on the reaction process

Developing non-vanadium-based SCR catalysts with high performances for simultaneous removal of NO and toluene at low-medium temperatures remains a challenge in addressing SO2 poisoning. Herein, porous Fe-modified CuCeZr catalysts prepared via KIT-6 hard-templating method was conducted to investigate the simultaneous removal of NO and toluene at low-medium temperatures. A suite of experiments and characterizations was systematically used to probe into the effect of SO2 on the reaction process. The results indicated that porous Fe-modified CuCeZr displayed excellent performance for simultaneous removal of NO and toluene. The introduction of Fe into CuCeZr enhances both acid sites and redox properties via the redox cycle between Cu2++Ce3+↔Cu++Ce4+ and Fe3++Ce3+↔Fe2++Ce4+ redox cycle. Importantly, Fe incorporation leads to the formation of lattice defects and oxygen vacancies, generating abundant active sites that mitigate the detrimental effects of SO2 poisoning, and promote the efficient removal of NO and toluene simultaneously. Besides, a mechanism influence of SO2 on the reaction process for simultaneous removal of NO and toluene at low-medium temperatures was proposed. This mechanism has the potential to provide an effective solution for developing non-vanadium-based SCR catalysts with sulfur resistance.

Durability Behaviours of Engineered Cementitious Composites Blended with Carbon Nanotubes against Sulphate and Acid Attacks by Applying RSM Modelling and Optimization

Chemical deterioration, including sulphate and acid attacks, is a major issue affecting the long-term durability of engineered cementitious composite (ECC) constructions that contact water from various sources, including groundwater, seawater, sewer water, and drinking water. This research enhances ECCs’ strength and resilience against chemical attack by combining cementitious composites with multiwalled carbon nanotubes (CNTs) and polyvinyl alcohol (PVA) fibre volume fractions using multiobjective optimization. The central composite design (CCD) of RSM was applied to generate thirteen mixes of different potential combinations of factors (multiwalled CNTs: 0.05% to 0.08%, PVA: 1–2%) and eight outcome responses were studied, although eight response models—six quadratic and two linear—were successfully designed and assessed using analysis of variance. The coefficients associated with R2 for all the models were exceptionally high, with values varying from 84 to 99 percent. The multiobjective optimization predicted the best outcomes and developed optimal values for both variables (CNTs: 0.05% and PVA: 1%). The results showed that, at 0.05% of CNTs in ECCs, an ultimate improvement of 23% in compressive strength was seen. Additionally, when CNTs are used to grow in the ECC matrix, the expansion owing to sulphate resistance and length change due to acid attack are both reduced. In addition, when the percentage of CNTs increases in ECCs, the weight loss and pH value owing to acid attack, as well as the rate of chloride permeability test results, are reduced. Furthermore, CNTs and PVA fibres with 0.05% and 1–1.5% concentrations offer optimal construction sector outcomes.

Mechanical and durability properties of alkali-activated slag/waste basalt powder mixtures

There are several studies investigating the feasibility of basalt powder as a precursor in alkali-activated cement production. The originality of this research lies in investigating the mechanical and durability features of alkali-activated mortars manufactured by partially substituting granulated blast furnace slag (GBFS) with waste basalt powder (WBP). In this study, 20% of GBFS was replaced with WBP, and high temperature (300 °C, 600 °C, and 900 °C) and magnesium sulfate (5% concentration) resistance of the manufactured mortars were investigated. The deteriorations of the mortars subjected to high temperature and magnesium sulfate were examined by compressive strength test, ultrasonic pulse velocity test, scanning electron microscopy analysis, and Fourier transform infrared spectroscopy analysis. The compressive strength of the mortar produced with 20% WBP substitution was 9.9% lower compared to the mortar containing 100% GBFS as the precursor. However, the performance of alkali-activated slag (AAS), known for its good resistance to high temperatures, did not decrease with the WBP substitution. The reduction in strength of both mortars after 900 °C was approximately 86%. No excessive changes were observed in the visual appearance and the compressive strength of the mortars after 3 months of exposure to magnesium sulfate. Microstructure analyses also revealed that WBP substitution had a limited effect on the high temperature and sulfate resistance of AAS.

Effect of precipitation variables on the performance of CeO2-based catalysts for waste-to-hydrogen

Waste-to-hydrogen technology, a future net-zero energy mix as a clean hydrogen source, is currently a research hotspot. To upcycle waste to high-value chemicals such as hydrogen, it is necessary to study customized catalysts for water-gas shift (WGS) reactions considering waste-derived synthesis gas. Herein, we aimed to enhance the physicochemical properties of CeO2 supported Pt catalysts by controlling the precipitation variables to develop a highly sulfur-tolerant WGS catalyst using waste-derived synthesis gas. The CeO2 support was prepared by the classic precipitation method. During precipitation, the precipitating agent was injected at different methods and rates. In the case of the normal titration method, the KOH solution was injected into the Ce precursor dissolved solution at rates of 5, 20, and 50 mL/min. In the case of the reverse titration method, the Ce precursor dissolved solution was injected into the KOH solution at rates of 5, 20, and 50 mL/min. The as-prepared Pt/CeO2 catalysts were applied to the WGS reaction with 500 ppm H2S. This work demonstrated that the titration method and titration rate affected the oxygen vacancy concentration and the active metal dispersion of the catalysts, respectively. And these properties worked in combination to determine the sulfur resistance of the catalysts. Subsequently, the high sulfur tolerance and catalytic performance of Pt/CeO2 catalyst prepared by normal titration method with the titration rate of 50 mL/min were due to the high Pt dispersion and concentration of oxygen vacancies.