Sulfated Catalysts Research Articles

Efficient NOx Reduction against Alkali Poisoning over a Self-Protection Armor by Fabricating Surface Ce2(SO4)3 Species: Comparison to Commercial Vanadia Catalysts.

Resolving severe deactivation by alkali metals for selective catalytic reduction of NOx with NH3 (NH3-SCR) is challenging. Herein, surface Ce2(SO4)3 species as a self-protection armor originally exhibited antipoisoning of potassium over ceria-based catalysts. The self-protection armor was also effective for other alkali (Na), alkali-earth (Ca), and heavy (Pb) metals, considerably resolving the deactivation of ceria-based SCR catalysts in practical applications. The catalytic activity tests indicated that the presence of ∼0.8 wt % potassium did not deactivate sulfated CeO2 catalysts, yet commercial V2O5-WO3/TiO2 catalysts almost lost the NOx conversions. Potassium preferably bonded with surface sulfates to form K2SO4 accompanied with the majority of surface Ce2(SO4)3 over sulfated CeO2 catalysts, but preferably coupled with active vanadia to generate inactive KVO3 species over V2O5-WO3/TiO2 catalysts. Such an active Ce2(SO4)3 species facilitated the adsorption and reactivity of NH3 and NOx, enabling ceria catalysts to maintain high catalytic efficiency in the presence of potassium. Conversely, the introduction of potassium into V2O5-WO3/TiO2 catalysts caused a considerable loss of surface acidity, hindering catalyst reactivity during the SCR reaction. The self-protection armor of Ce2(SO4)3 species may open a promising pathway to develop efficient ceria-based SCR catalysts with strong antipoisoning ability.

Chemical Recycling of Used PET by Glycolysis Using Niobia-Based Catalysts.

Plastic production has steadily increased worldwide at a staggering pace. The polymer industry is, unfortunately, C-intensive, and accumulation of plastics in the environment has become a major issue. Plastic waste valorization into fresh monomers for production of virgin plastics can reduce both the consumption of fossil feedstocks and the environmental pollution, making the plastic economy more sustainable. Recently, the chemical recycling of plastics has been studied as an innovative solution to achieve a fully sustainable cycle. In this way, plastics are depolymerized to their monomers or/and oligomers appropriate for repolymerization, closing the loop. In this work, PET was depolymerized to its bis(2-hydroxyethyl) terephthalate (BHET) monomer via glycolysis, using ethylene glycol (EG) in the presence of niobia-based catalysts. Using a sulfated niobia catalyst treated at 573 K, we obtained 100% conversion of PET and 85% yield toward BHET at 195 °C in 220 min. This approach allows recycling of the PET at reasonable conditions using an inexpensive and nontoxic material as a catalyst.

Highly active and stable oxygen vacancies via sulfur modification for efficient catalysis in lithium–sulfur batteries

Sulfur modification stabilizes oxygen vacancies at the surface through an “anchor vacancies” method and aids in accelerating the conversion of lithium polysulfides, thereby enhancing both the activity and stability of lithium–sulfur catalysts.

Synthesis, Characterisation and Catalytic Evaluation of Castor Oil-Templated Mesoporous Sulfated Solid Acid Catalysts for Esterification Reaction

In bio-refinery and other catalytic reactions, heterogeneous catalysts confer advantage over homogenous catalysts due to minimized recovery and separation costs. However, templating surfactant and solid support for the synthesis of heterogeneous catalysts ought to consider their cheap sources and environmentally friendliness for their sustainable use. Thus, with the vision to make the process significantly benign, in the present work, solid acids were synthesised from renewable sources (castor oil as surfactant and rice husk as the source of silica). The synthesised castor oil-templated mesoporous sulfonic acid modified catalysts (SO3H-MTS and SO3H-MT-RHS) were characterised and evaluated for catalytic esterification of acetic acid (C2), hexanoic acid (C6), lauric acid (C12), palmitic acid (C16), and ricinoleic acid (C18) with butanol at 110 °C. Physicochemical properties of the synthesised materials were characterised by nitrogen porosimetry, X-ray powder diffraction, thermogravimetry, X-ray Photoelectron Spectroscopy (XPS), and Diffuse Reflectance Infrared Fourier Transform Spectroscopy (DRIFTS). The porosimetric analysis of the synthesised materials revealed a type IV adsorption-desorption isotherm reminiscent of the mesoporous structures. The surface area of the synthesised materials decreased upon functionalisation by sulfonic group. The DRIFTS and XPS confirmed the attachment of sulfonic functional group on the synthesised materials. Evaluation of the catalytic performance of the synthesized materials was determined through analysis of carboxylic acid conversions using gas chromatographic technique. SO3H-MTS gave higher acid conversions compared to SO3H-MT-RHS. The sulfated solid acid catalysts showed good catalytic activity on the esterification with conversion ranging from 96-37% for C2-C18 with butanol at 110 °C within 6 h. Such castor oil-templated mesoporous sulphated solid acid catalysts can therefore be applied in biodiesel production upon process optimisation.

Supported Metal Sulfate Catalysts FexZny/SiO2 for Selective Dimerization of Isobutene in Mixed C4 to Isooctenes

AbstractIsobutene dimerization is an important route to properly utilize mixed C4 and further produce isooctane with a high‐octane number to replace MTBE in gasoline. A highly selective catalyst, which is effective for isobutene dimerization but ineffective for other olefins in the C4 mixture, is necessary for industrial implementation. In this work, a series of supported metal sulfate catalysts FexZny/SiO2 were prepared and characterized by XRD, SEM, N2 physical adsorption‐desorption, NH3‐TPD, Py‐FTIR, and XPS. Fe0.2Zn1.8/SiO2 can achieve isobutene conversion up to 89 % with 0 % conversion of n‐butene, and the selectivity of isooctenes (C8=) product is 57 % (10 h on stream). Furthermore, isobutene conversion can sustain above 80 % after 50 h. It is found that these supported catalysts contain Zn2+, Zn+, Fe3+, and Fe2+ species, and there is a synergetic effect between Zn2+ and Fe2+. Zn2+ is beneficial to improve the conversion of isobutene, and Fe2+ facilitates the formation of C8=, resulting in a high C8= yield.

Synthesis of sulfated titanium dioxide catalyst for sorbitol dehydration to isosorbide

The use of titania (TiO2) or sulfated titania (SO42-/TiO2) catalysts with different calcination temperatures was studied to study the influence of phase structure on the dehydration of sorbitol to isosorbide. The unsulfated titania calcination temperature and the acid density of the sulfated catalysts significantly influenced catalytic performance. The anatase-phase catalyst calcined at 400 °C and sulfated with 0.1 M sulfuric acid showed excellent performance, full sorbitol conversion, and an isosorbide yield of about 61 % was achieved. This work provides insight into optimizing the phase structure of sulfated catalysts for isosorbide production.

Pyrolytic Depolymerization Mechanisms for Post-Consumer Plastic Wastes

Fast pyrolysis of five post-consumer plastic waste materials was studied using pyrolysis coupled with gas chromatography/mass spectrometry (Py-GC/MS) technique. Prescription medicine bottles, landfill liners, and one type of industrial plastic waste represented polyolefin-based polymers, whereas packaging material represented polystyrene, and other industrial plastic waste represented polyurethane. The noncatalytic and catalytic degradation mechanisms of all five post-consumer plastic wastes were elucidated. The noncatalytic pyrolysis experiments were conducted at a temperature of 600 °C for a residence time of 5 min. For catalytic pyrolysis, a spent FCC catalyst was utilized for polystyrene, a sulfated zirconia-based catalyst was utilized for polyurethane, and a Y-zeolite catalyst was used for polyolefinic plastic waste. The results suggested that the thermal reaction has higher monomeric and oligomeric selectivity than the catalytic reaction. Results from the catalytic runs showed that the addition of catalysts greatly influences product compositions and has a significant effect on the selectivity of a specific compound. One of the plastic wastes, landfill liner, was selected for a batch scale pyrolysis at 420–440 °C using Y-zeolite as a catalyst to demonstrate the product properties and potential use of the liquid product formed. The complete product distribution of plastic crude oil was performed followed by distillation to produce aviation range fuel. The fuel properties of aviation range fuel were examined, and results suggested that the fuel fraction can be easily blended with commercially available fuels for direct applications.

Research Progress on Sulfur Deactivation and Regeneration over Cu-CHA Zeolite Catalyst

Benefiting from the exceptional selective catalytic reduction of NOx with ammonia (NH3-SCR) activity, excellent N2 selectivity, and superior hydrothermal durability, the Cu2+-exchanged zeolite catalyst with a chabazite structure (Cu-CHA) has been considered the predominant SCR catalyst in nitrogen oxide (NOx) abatement. However, sulfur poisoning remains one of the most significant deterrents to the catalyst in real applications. This review summarizes the NH3-SCR reaction mechanism on Cu-CHA, including the active sites and the nature of hydrothermal aging resistance. On the basis of the NH3-SCR reaction mechanism, the review gives a comprehensive summary of sulfate species, sulfate loading, emitted gaseous composition, and the impact of exposure temperature/time on Cu-CHA. The nature of the regeneration of sulfated catalysts is also covered in this review. The review gives a valuable summary of new insights into the matching between the design of NH3-SCR activity and sulfur resistance, highlighting the opportunities and challenges presented by Cu-CHA. Guidance for future sulfur poisoning diagnosis, effective regeneration strategies, and a design for an efficient catalyst for the aftertreatment system (ATS) are proposed to minimize the deterioration of NOx abatement in the future. Finally, we call for more attention to be paid to the effects of PO43- and metal co-cations with sulfur in the ATS.

Facile One Pot Synthesis of Acridinediones Using Caffeine Hydrogen Sulfate Catalyst and Their Antimicrobial Evaluation

A facile approach for the synthesis of bioactive acridinedione analogs using dimedone, aryl aldehydes, and ammonium acetate was developed using caffeine hydrogen sulfate catalyst in ethanol and water (2:1) solvent mixture at room temperature. The significant advantages of this procedure are efficient and simple method, ambient conditions, short reaction time (5–30 min), simple workup, easily recoverable catalyst, broad substrate scope and good yields (45–80%). Being water soluble, the catalyst was easily recovered by water and reused up to 4 runs. Moreover, the antimicrobial profile of synthesized derivatives was performed against different bacterial and fungal strains using broth microdilution method. Most of the synthesized derivatives exhibited significant activity against bacterial and fungal strains compared to standard. Compounds 4e (31.25 µg/mL and 31.25 µg/mL) and 4g (31.25 µg/mL and 62.5 µg/mL) were found the most active against E. coli. and S. aureus respectively with good MIC values. Compound 4f and 4j displayed the highest antifungal activity against A. niger with 31.25 µg/mL MIC value.

Parametric and kinetic study of simultaneous esterification and transesterification of model waste sunflower oil by using zirconium sulfate catalyst

Parametric and kinetic study of simultaneous esterification and transesterification of model waste sunflower oil by using zirconium sulfate catalyst

Epoxidation of soybean oil over titanium or niobium incorporated SBA-15 and sulfated lanthanum titania silicate catalysts

Mesoporous heterogeneous catalysts were synthesized to develop environmentally benign catalysts for soybean oil's (Glycine max) epoxidation. The investigated materials were sulfated lanthanum doped titania silica xerogel (SO4/La-TiO2-SiO2), and Ti and Nb incorporated SBA-15 with two different silica/metal molar ratios of 10 and 20. Soybean oil epoxidation reactions were performed in tert-butanol by utilizing H2O2 as oxidant at 75 °C for 6 h. Product analysis was carried out by H NMR, FTIR, and analytical methods. Nb-SBA-15 catalysts yielded better conversion than Ti-SBA-15 catalysts owing to their high acidity. However, epoxide selectivity was found low for both catalyst groups due to water in the medium that promoted side reactions. Tert-butanol and ethyl acetate were studied as solvents, but employing ethyl acetate in the reactions triggered catalysts aggregation and deposition on the reactor surface. Stability tests indicated the robustness of Ti and Nb against leaching, whereas sulfur leaching was noted with SO4/La-TiO2-SiO2 catalyst. The most active Nb-SBA-15 (10) catalyst was also applied in the epoxidation of soybean-derived fatty acid methyl esters (FAME). The results showed that small-sized FAME molecules did not enhance the reaction rate. Reusability tests indicated that Nb-SBA-15 (10) was active in epoxidation for at least three cycles.

Monitoring the ambient oxidation of a NiMoSx/Al2O3 hydrotreating catalyst by a thermogravimetric method

The ambient oxidation of a liquid-sulfurized commercial NiMoSx/Al2O3 hydrotreating catalyst was monitored by a thermogravimetric (TG) method. Each mass loss stage in TG was indicative of different oxidation species formed during the ambient oxidation. The mass loss is indicative of the change of oxidation products and degree with the air exposure time. The results of TG were confirmed by other characterization techniques including X-ray diffraction (XRD), Fourier transform infrared (FT-IR) spectroscopy, X-ray photoelectron spectroscopy (XPS) and elemental analysis. Upon the ambient oxidation, molybdenum sulfide and nickel sulfide were converted into MoSxOy and NiSO4, respectively. Almost no MoO3 and NiO are observed and little sulfur loss occurred, even if the catalyst was exposed to air for 25 days. Both the carbonaceous deposition generated by the liquid-phase sulfurization and oxidation products could form passivation layers to preclude sulfides from deep oxidation. TG in air might be a rapid, low-cost and less sample consumption method for monitoring the oxidation of sulfurized catalysts.

Stability of novel eco-friendly sulfated metal oxide solid acid catalyst for esterification and condensation reaction

<h2>Abstract</h2> In this paper, the metal oxide supports and active component precursors of SO₄²⁻/M_xO_y solid acid were screened, and S₂O₈²‐⁻/Cr₂O₃-Fe₂O₃ (S₂-CrFe) was prepared. The NH₃-TPD results showed that the solid acids loaded with S₂O₈²⁻ had stronger acidity than those loaded with SO₄²⁻, and the mixture of the two metal oxides could adjust the acidity of the solid acids. The optimum conditions for the preparation of S₂-CrFe were as follows: the mass ratio of Cr₂O₃ to Fe₂O₃ was 1:1, the concentration of ammonium persulfate solution was 1 mol/L, and the calcination temperature was 550 °C. The yield of esterification catalyzed by the solid acid obtained under these conditions was 91.2%. The stability of the new solid acid was investigated, and it was found that S₂-CrFe was easy to be deactivated, so it was considered to be modified by organosilane and lanthanum oxide. The experimental results showed that after the modified solid acid was recycled for four times, the yield of ethyl acetate was more than 60%.

Hydrogenation of 1,3-pentadiene on modified Pd-containing catalysts

Activity and selectivity of alumina-supported palladium catalysts, particularly the sulfurized ones, in the hydrogenation of 1,3-pentadiene to pentenes were investigated. Preliminary sulfurizing of palladium catalysts considerably enhances the selectivity to olefins in a wide range of the H2 /diene molar ratio (from 2.5 to 10). Samples activated in H2 at elevated temperatures demonstrate a higher activity toward diene hydrogenation. Palladium catalysts are more active at low temperatures of the reaction; however, the earlier studied sulfurized Ni catalysts compare well with palladium ones in terms of their selectivity to olefins and productivity, and are more selective in an excess of hydrogen. Modification of palladium with chromium, silver or lithium increases the selectivity to olefins.

Li2S4 Anchoring Governs the Catalytic Sulfur Reduction on Defective SmMn2O5 in Lithium–Sulfur Battery

AbstractThe introduction of sulfur redox electrocatalysts has been considered to be an effective strategy to anchor polysulfides on the cathode and reduce the energy barriers of the reactions. Due to the complexity of sulfur redox reactions (SRR/SER), there exist few descriptors to correlate the catalytic performance and the underlying electronic structures of a given catalyst, which inhibits the development of lithium−sulfur catalysts. In this article, upon mullite oxide SmMn2O5 with various substitutional defects, density functional theory calculations are used to probe the structure–property relationships. It is found that there exists no scaling relationship among the polysulfide binding energies, indicating that the catalytic performance can be tuned by a key intermediate individually. Statistical analysis of various models with different S‐containing intermediates shows that only the Li2S4 binding energy has a linear correlation with the overpotential, showing the dominant role of Li2S4 anchoring to determine the catalytic performance. The electronic structure analysis combined with machine learning further quantitatively verifies the coeffect of charge transfer, electronegativity, and work function on the binding strength of the polysulfide Li2S4. This work provides a theoretical understanding of the complex SRR/SER mechanisms and sheds light on the rational design of a sulfur redox catalyst.

Sulfur/water resistance and regeneration of MnOx-CeO2/TiO2 catalyst for low-temperature selective catalytic reduction of NOx

Mn-based catalysts present a great prospect for application in selective catalytic reduction (SCR) of NOx with NH3 at low temperatures, due to their high low-temperature catalytic activity. However, poor resistance of Mn-based catalysts to SO2 and H2O restricts their industrial application. This paper investigates the SO2&H2O resistance of MnOx-CeO2/TiO2 catalyst and discusses the poisoning mechanism based on catalytic characterizations. The results indicate that MnOx-CeO2/TiO2 catalyst exhibit high tolerance to SO2 poisoning mainly because the surface sulfates are preferentially formed on Ce dopants so that protect the main active component (MnOx). Catalytic deactivation become more severe when SO2&H2O are simultaneously present, which implies that SO2&H2O exhibit a synergistic toxicity in poisoning catalyst. Interestingly, the presence of H2O can alleviate the formation of surface metal sulfates on catalyst to some extent, for the surface reactive oxygen species and the surface acid sites are preserved to fulfill the low temperature SCR reaction cycle. Thermal regenerations under different atmosphere (e.g., O2 and H2O) are conducted for the SO2 poisoned catalyst. Effective regeneration of the sulfated catalyst can be realized and their regeneration mechanisms are explored by utilization of several catalytic characterizations.

Superhydrophobic Ni-Reduced Graphene Oxide Hybrid Coatings with Quasi-Periodic Spike Structures.

Recently, sophisticated technologies are applied to design a certain surface nature that can have superhydrophobic properties. Thus, a simple spray technique was introduced to prepare a superhydrophobic surface using rGO with Ni-S system (rGO-Ni) by using NiSO4 catalyst under microwave irradiation at various reaction times of 5, 10, 20, and 30 min. The GO reduction was conducted at a fixed Ar/H2 ratio, a flow rate of 0.4 L/min, microwave power of 720 W, and a mass of 0.5 g. GO powder with nickel sulfate catalyst was treated under Ar/H2 (4:1) mixture for GO reduction, where Ar and H2 were expected to prevent the rebinding of oxygen released from GO. The result of XRD and Raman measurement confirms that rGO-Ni prepared at reaction time 20 min exhibit the highest reduction of GO and the presence of various Ni-S crystal structures such as NiS, NiS2, Ni3S2, and Ni3S4 due to decomposition of NiSO4. The rGO-Ni coating performance shows superhydrophobic nature with a contact angle of 150.1°. The AFM images show that the addition of nickel to rGO produces a quasi-periodic spike structure, which increases the superhydrophobicity of the r-GO-Ni coated glass with a contact angle of 152.6°. It is emphasized that the proposed simple spray coating using rGO-Ni provides a more favorable option for industry application in obtaining superhydrophobic surfaces.

Esterification of Free Fatty Acid in Palm Oil Mill Effluent using Sulfated Carbon-Zeolite Composite Catalyst

Free fatty acid esterification (FFA) in palm oil mill waste (POME) was carried out using a sulfonated carbon-zeolite composite catalyst. The catalyst is synthesized with carbon precursor obtained from molasses, which is adsorbed on the surface of the zeolite and then carbonized and sulfonated with concentrated H2SO4 to form a sulfonated carbon-zeolite catalyst composite, which will be used for the esterification catalyst and the optimization process for the esterification reaction is carried out using the response surface methodology (RSM) and experimental central composite design (CCD). Importantly, the observed independent variables were temperature, catalyst weight, and reaction time to produce fatty acid methyl ester (FAME) products. The catalyst was successfully synthesized, which was shown from the SEM characterization strengthened by the presence of a sulfate group in the FTIR results and the calculation results of high acidity properties. Optimization of FFA esterification with SCZ catalyst obtained optimal conditions with a temperature of 79oC, a catalyst weight of 3.00 g, and a reaction time of 134 minutes with a FAME product of 93.75%, considering that the viscosity of biodiesel is below that required by the API.

Highly efficient non-microwave instant heating synthesis of hexyl levulinate fuel additive enhanced by sulfated nanosilica catalyst

Highly active and recyclable sulfated silica nanocatalyst for the synthesis of hexyl levulinate (HL) is reported. The sulfated catalysts, Sn-BLA (n = 15 or 30 μL of H2SO4 added), are prepared via sulfation upon amorphous bamboo leaf ash (BLA) under non-microwave instant heating condition (100 °C, 1.5 h). The spectroscopy and microscopy results reveal that silica nanoparticles (28 nm) with Brӧnsted ( bisulfate group) and Lewis ( sulfate group) acid sites are produced upon sulfation treatment. The sulfur containing acid groups covalently bound on the mesosilica surface are very active in the esterification of levulinic acid and hexanol where S30-BLA presents excellent catalytic activity (95.2% conversion, 98.0% selective to HL) at 90 °C for 7 min, which is far more superior than the previously reported catalysts. The S30-BLA catalyst is reusable with slight decrease in catalytic activity after six consecutive runs, suggesting an economical and environment-friendly route to biomass utilization.

Synthesis and Characterization of Ni-WO3/Sulfated Zirconia Nano catalyst for Isomerization of N-Hexane and Iraqi Light Naphtha

This work deals with preparation of Sulfated Zirconia catalyst (SZ) for isomerization of n-hexane model and refinery light naphtha, as well as enhanced the role of promoters to get the target with the mild condition, stability, and to prevent formation of coke precursors on strong acidic sites of the catalyst. The prepared SZ catalysts were characterization by fourier transform infrared spectroscopy (FTIR), X-ray diffraction (XRD), Brunauer –Emmett-Teller (BET) surface area analysis, Thermogravimetric Analysis (TGA), Scanning Electron Microscope (SEM) and atomic force microscopy (AFM) Analyzer. The results illustrate that the maximum conversion and selectivity for n-hexane isomerization with Ni-WSZ and operating temperature of 150 °C was 80.1% and 96 % respectively .Other set of experimental with light naphtha , the results show that the maximum conversion and selectivity with Ni-WSZ and operating temperature of 150 °C was 73.6% and 74% respectively.