Sulfated Catalysts Research Articles

KINETIC STUDY OF ESTERIFICATION CATALYZED WITH ALUMINUM SULFATE AIMED AT CONVERTING LEVULINIC ACID INTO METHYL LEVULINATE

Recycling lignocellulosic biomass is a sustainable alternative to the petrochemical industry since it allows the production of valuable, sustainable, and environmentally friendly chemical products, such as levulinic acid (LVA) and levulinate esters. Methyl levulinate (MLV), for example, has been assessed as a fuel additive with low toxicity, high lubricity, and flash point stability. In this respect, the present investigation details a kinetic study of methyl esterification catalyzed with aluminum sulfate aimed at converting levulinic acid into methyl levulinate. The reactions were carried out in a Parr Instruments stainless steel reactor to assess the effect of temperature (120, 140 and 160 °C) and reaction time (30, 60, 120 and 180 min) on LVA conversion into MLV, maintaining a constant LVA:methanol ratio of 1:8 and aluminum sulfate catalyst concentration of 0.04 mol.L-1. The maximum LVA-MLV conversion of 93.04 % was obtained at a temperature of 160 °C and reaction time of 60 minutes. The pseudo first-order kinetic model exhibited the best fit to the experimental data, with correlation coefficients (R²) greater than 0.96, and it was used to calculate activation energy, obtaining a value of 10.19 kcal.mol-1.

PRODUCTION OF MDP PANELS WITH YERBA MATE HARVEST RESIDUES

The quality of MDP panels produced with Pinus taeda wood particles mixed with yerba mate harvest residues was evaluated. Monolayer panels were produced with the addition of 0. 20. 40. 60. 80 and 100% proportion of yerba mate waste, with a nominal specific gravity of 0.65 g.cm-³, using 12% urea-formaldehyde resin, 0.5% paraffin and 2% ammonium sulfate catalyst. The panels were pressed for 10 minutes at a temperature of 140°C and pressure of 40 kgf/cm². The physical properties of apparent density, moisture content, water absorption and thickness swelling (2 and 24 hours) were evaluated, as well as the mechanical properties of static bending (MOR and MOE), internal bonding, screw withdrawal on the face and Janka hardness. There was a trend towards an increase in internal bonding with an increase in the proportion of yerba mate residue in the panels, but the opposite occurred for the other mechanical properties studied. Some physical properties such as water absorption and thickness swelling resulted in better performance when yerba mate particles were added. In view of this, it can be concluded that it is possible to produce panels with the addition of yerba mate up to 40% in the composition with yerba mate particles, without affecting the quality of the properties.

Optimization of furfural production from xylose over sulfated titanium-niobium mixed oxides catalyst in biphasic system

The present study investigates the use of SO42-/TiO2Nb2O5 (STNO) catalyst prepared through the modified sol-gel method in the process of xylose dehydration to furfural. The reaction was carried out in a biphasic solvent consisting of toluene and water. The catalyst used in this study was subjected to several characterization methods, including Fourier-transform infrared spectroscopy (FTIR), scanning electron microscopy (SEM), and X-ray diffraction (XRD). The textural properties of the catalyst were evaluated by conducting N2 adsorption and desorption measurements using the Brunauer-Emmett-Teller (BET) method. The impact of catalyst dosage, resident time, xylose concentration, and reaction temperature in the dehydration of xylose to produce furfural was explored. The study employed response surface methodology to identify the optimal operational parameters that would result in the highest furfural selectivity. At a reaction temperature of 150 °C and a reaction time of 180 min, a maximum conversion of xylose of 98 mol%, furfural selectivity of 74 mol%, and a furfural yield of 63 mol% was obtained. The activation energy for the synthesized catalyst was determined to be 26.7 KJ/mol. The results of this investigation show the great potential that sulfated titanium-niobium mixed oxides have in transforming biomass resources into value-added compounds.

Mechanical milling promotes the preparation of catalyst lanthanum dodecyl sulfate and green solvent-free grinding for synthesis of N-heterocyclic derivatives

The lanthanum dodecyl sulfate catalyst (La(DS)3) was synthesized using a solvent-free mechanical ball method and applied in the preparation of solvent-free N-heterocyclic compounds. The preparation of the La(DS)3 catalyst and the synthesis of C-N bond series compounds only require brief ball milling of the mixed material at room temperature. Various analyses such as SEM, HRTEM, XRD, AFM, FT-IR, XPS, TGA, and DFT were conducted, which showed that the catalyst material synthesized by mechanical ball milling exhibited superior catalytic activity, thermal stability, and cyclic life compared to similar materials synthesized in an aqueous phase. The solvent-free catalytic synthesis of quinoxaline, dihydroacridin-1(2H)-one, and bis(indolyl)methanes derivatives achieved excellent target yields. Furthermore, the catalyst could be reused at least seven times without a significant decrease in activity after simple treatment. The catalyst also demonstrated gram scale scaling up in the model reaction. It exhibited weak hydrophilicity and a stable network-like layered nanostructure.

Insight into catalytic effects of alkali metal salts addition on bamboo and cellulose pyrolysis

Alkali metal compounds have vital influence on biomass pyrolysis conversion. In this study, cellulose, and bamboo catalytic pyrolysis with different alkali metal salts catalysts (KCl, K2SO4, K2CO3, NaCl, Na2SO4, and Na2CO3) were investigated in the fixed-bed reaction system. The effects of cations (K+ and Na+) and anions (Cl-, SO42−, and CO32-) on the evolution properties of biochar, bio-oil, and gas products were explored under both in-situ and ex-situ catalytic pyrolysis. Results showed that alkali metal salts facilitated the yields of biochar and gases at the expense of that of bio-oil. Alkali metal chloride and sulfate showed a weaker catalytic effect, while alkali metal carbonate greatly promoted the generation of gas products and increased the condensation degree of biochar. With the addition of K2CO3 and Na2CO3, cyclopentanones content was over 50% from cellulose catalytic pyrolysis, and phenols content (mainly alkylphenols) reached over 80% from bamboo catalytic pyrolysis. Moreover, solid-solid catalytic reactions with K2CO3 and Na2CO3 catalysts had an important role in strikingly promoting conversion of pyrolysis products, and the solid-solid and gas-solid catalytic reactions with alkali metal carbonate catalysts were stronger than those with alkali metal chloride and sulfate catalysts. Furthermore, the possible catalytic pyrolysis mechanism of alkali metal salts on biomass pyrolysis was proposed, which is important to the high-value utilization of biomass.

Kinetics of heterogeneous ammonia sulfite oxidation in wet desulfurization with cobalt sulfate catalyst

Kinetics of heterogeneous ammonia sulfite oxidation in wet desulfurization with cobalt sulfate catalyst

Catalyst–sulfur bidirectional stimulation to accelerate redox kinetics for high-performance cryogenic lithium-sulfur batteries

The development of cryogenic lithium-sulfur batteries (LSBs) suffers from the sluggish reaction kinetics and the shuttle effect of polysulfide. In order to accelerate the redox process and improve the utilization rate of elemental sulfur at the low temperature, we first propose catalyst–sulfur bidirectional stimulation to accelerate redox kinetics for high-performance cryogenic LSBs. Theoretical calculation and experimental results suggest that the selenium-doped MoS2 (SeDMoS2) catalyst can not only effectively capture and anchor polysulfide but also can interact with the sulfur species to stimulate each other, thus boosting the low-temperature kinetics and optimizing the cryogenic capacity. Quite impressively, with the assistance of the bidirectional stimulation between the SeDMoS2 catalyst and sulfur, the LSB can deliver a high initial capacity of 732 mAh g−1, and only ∼0.3% of the capacity is attenuated per cycle during 100 cycles at the low temperature of −40 °C. This strategy throws light on the further development of high-capacity cryogenic LSBs and points the way to explore other low-temperature metal batteries.

New Approach to Ultrafast Oxidative Desulfurization in the Presence of Sulfated Alumina-Based Catalysts

New Approach to Ultrafast Oxidative Desulfurization in the Presence of Sulfated Alumina-Based Catalysts

Promotional effect of aluminum doping on the sulfated Fe2O3 catalyst in selective catalytic reduction of NO with NH3

Promotional effect of aluminum doping on the sulfated Fe2O3 catalyst in selective catalytic reduction of NO with NH3

Influence of organic sulfur gas-phase sulfation on the NH3-SCR activity of CeO2 catalyst: The competitive adsorption and conversion of CS2 and COS at a low hydrolysis temperature

In this study, a simplified approach is proposed to realize the gas-phase sulfation of CS2 or/and COS at the hydrolysis temperature for further facilitating the NH3-SCR activity of CeO2 in diverse conditions. A low-temperature oxidation conversion process for the adsorbed CS2 or COS on cubic fluorite CeO2 surface is developed. It is found that the gas-phase sulfation of organic CS2 or/and COS at 50 °C enhances the mobility of lattice oxygen of cubic fluorite CeO2 and the concentration of oxygen defects for the sulfated CeO2 catalyst, but the kinds of organic COS/CS2 can regulate the formed types and quality of sulfur-containing species on the catalyst surfaces during the gas-phase sulfation. and the formed sulfates under the gas-phase sulfation of CS2 are more active than those of COS, and CeO2-CS2-50 °C-3 h presents the best mobility of lattice oxygen, the largest concentration of adsorbed oxygen and the best NH3-SCR activity. Furthermore, the competitive adsorption and conversion of CS2 and COS is disadvantageous for the formation of oxygen vacancies on the catalyst surfaces compared to single CS2 or COS. However, the long-time durability testing coupling re-cycle experiments can optimize the oxygen vacancy defects and increase the concentration of chemisorbed oxygen of the sulfated CeO2-CS2 + COS-50 °C-24 h catalyst via optimizing the oxidization of sulfur element to sulfur oxides or/and sulfates, thereby improves its NH3-SCR activity. And the sulfated CeO2 catalyst by the gas-phase sulfation of organic COS + CS2 presents a good stability for NH3-SCR reaction. This study specifies a novel approach to simplify the gas-phase sulfation process of CeO2 catalyst, which is valuable in promotion of the NH3-SCR activity of CeO2 and reduction of cost in experimental procedures.

Mercury removal performance of sulfated MnCe catalyst prepared by tobacco waste combustion synthesis

MnOx-CeO2 is a promising catalyst for Hg0 removal from coal flue gas at ∼150 °C but exhibits insufficient catalytic activity. Even though sulfation enhances the catalytic activity of MnOx-CeO2, gas-phase sulfation leads to SO2 poisoning and catalyst deactivation. In this study, we developed a liquid-phase sulfation strategy involving the direct combustion of cigarette butts soaked in a solution of sulfate and metal precursors to directly synthesize sulfated MnCe catalyst (SMC). SMC was characterized via N2 adsorption–desorption isotherms, SEM-EDS, XRD, XPS, and Hg-TPD. Both the MnCe catalyst and SMC exhibited good Hg0 oxidation efficiencies (66.46 % and 88.76 %, respectively) at 150 °C. The enhanced performance of SMC was attributed to the generation of abundant chemically adsorbed oxygen species on the SMC surface during sulfation. Moreover, the synergistic effect between the Ce4+ and Mn4+ species contributed to the improved catalytic performance of SMC. This strategy not only provides a one-step synthesis of sulfated catalysts but also has potential applications in Hg0 removal from coal flue gas in coal-fired power plants.

Microalgal synthesis of the biodiesel employing simultaneous extraction and esterification via heterogeneous catalyst

Within the realm of biorefinery, the third generation of biodiesel production relies on extracting oil from Algae to create renewable fuels. Algae cultivation can occur under precise laboratory conditions, making them a sustainable substitute for Fatty Acid Methyl Ester or biodiesel production. Through analysis of the simultaneous extraction and (trans)esterification process of Algae Chlorella Minutissima utilizing sulfated carbonaceous catalysts, scientists have discovered an efficient technique for producing biodiesel. Various parameters, such as catalyst loading, oil-to-methanol ratio, reaction temperature, and reaction time for FFA reduction and FAME yields, were studied and optimized. Results indicate that utilizing a 10 wt% catalyst loading and a 70:30 volumetric oil to methanol ratio can achieve 67.59 % FFA reduction and a biodiesel yield of 44 mL. This method of producing biodiesel can occur in a single-unit operation, leading to higher yields of renewable fuel at a reduced cost and energy consumption. Finally, the quality of the biodiesel produced met ASTM D6751 standards, confirming its suitability for use.

The influence of H2O or/and O2 introduction during the low-temperature gas-phase sulfation of organic COS + CS2 on the conversion and deposition of sulfur-containing species in the sulfated CeO2-OS catalyst for NH3-SCR.

Herein, the typical components of blast furnace gas, including H2O and O2, were introduced to improve the NH3-SCR activity of the sulfated CeO2-OS catalyst during the gas-phase sulfation of organic COS + CS2 at 50 °C. The characterization results demonstrate that the introduction of O2 or H2O during gas-phase sulfation enhances the conversion of organic COS + CS2 on a cubic fluorite CeO2 surface and reduces the formation of sulfur and sulfates in the catalyst, but decreases the BET surface area and pore volume of the sulfated CeO2-OS catalyst. However, the introduction of O2 or H2O during the gas-phase sulfation increases the molar ratios of Ce3+/(Ce3+ + Ce4+) and Oβ/(Oα + Oβ + Oγ) on the sulfated CeO2-OS catalyst surface, thus promoting the formation of surface oxygen vacancies and chemisorbed oxygen, and these properties of the catalyst are further enhanced by the co-existence of O2 and H2O. Furthermore, the reduction of sulfates formed under the action of O2 or H2O decreases the weak acid sites of the sulfated CeO2-OS catalyst, but the few and highly dispersive sulfates present stronger reducibility, and the proportion of medium-strong acid sites of the catalyst increases. These factors help to improve the NH3-SCR activity of the sulfated CeO2-OS catalyst. Thus, there exists a synergistic effect of H2O and O2 introduction during gas-phase sulfation on the physical-chemical properties and catalytic performance of the sulfated CeO2-OS catalyst by organic COS + CS2 at 50 °C.

Synthesis of β-amino alcohols by ring opening of epoxides with amines catalyzed by sulfated tin oxide under mild and solvent-free conditions

One significant and elegant method for creating β-amino alcohols, which are useful intermediates for the synthesis of many different natural and synthetic pharmaceutical compounds, is to open the rings of epoxides with amines. When sulfated tin oxide catalyst (2 mol%) is present, epoxides can open their rings and react with amines to produce corresponding β-amino alcohols in good to high yields under mild circumstances. Under clean circumstances and in a short amount of time, the reaction demonstrated high regioselectivity and functioned well with both aromatic and aliphatic amines at room temperature.

(1‐10) Facet‐Dominated TiB2 Nanosheets with High Exposure of Dual‐Atom‐Sites for Enhanced Polysulfide Conversion in Li‐S Batteries

AbstractElaborate modulation of the highly active crystal facet emerges as an efficient strategy for enhancing the nanocrystalline catalytic activity. Herein, ultrathin TiB2 nanosheets with preferentially exposed (1‐10) facets are developed as highly efficient catalyst with enriched bonding and electrocatalytic sites in Li‐S batteries. Attributed to the highly equivalent exposure of Ti and B active sites on the (1‐10) surface, the (1‐10) facet‐dominated TiB2 nanosheets maximize the binding effect via Ti and B dual‐atom‐sites adsorption through Ti─S and B─S bonds. More importantly, experiments and theoretical calculations confirm the superb catalytic activity of (1‐10)TiB2 in facilitating the polysulfide conversion and Li2S decomposition, thereby markedly suppressing the shuttling effect and improving the redox kinetics. Consequently, excellent electrochemical properties are achieved in Li‐S batteries, which demonstrate a high discharge capacity of 1469 mAh g−1 at 0.2 C and maintain high capacity reversibility at 1 C with a low capacity decay rate of 0.048% over 500 cycles. Even under a sulfur loading of 5 mg cm−2, a prominent areal capacity of 4.86 mAh cm−2 is still attained. It is proposed that the crystal surface engineering provides a new path for the structure optimization of sulfur catalysts in Li‐S batteries.

Hierarchically Porous Sulfated Geopolymer Catalyst: Preparation and Performance Evaluation Towards Oxidative Denitrogenation

Hierarchically Porous Sulfated Geopolymer Catalyst: Preparation and Performance Evaluation Towards Oxidative Denitrogenation

Revisiting the role of sulfated oxides for the synthesis of pharmaceutically important heterocycles: Understanding, challenges, and future prospects

The development of sustainable catalytic processes is the requirement of the future to replace traditional protocols involving hazardous, non-green, non-benign reagents/solvents, and cost ineffectiveness. Metal and mixed metal oxides due to their redox properties make them potential substitutes for conventional homogeneous catalysts. The acidity can be enhanced further by the sulfation process to form sulfated oxides representing a new class of solid acid catalysts. This review is the revisiting of sulfated solid acid catalysts, with major emphasis on understanding, methods, applications, and their role in the syntheses of heterocycles of pharmaceutical importance. The present review also discusses factors affecting the acidity of the catalysts, possibilities of leaching in reaction media, methods of sulfation to arrest leaching, other challenges, and future prospects.

Application of nano hydrophobic sulfated mordenite as a novel catalyst for biodiesel production from neem seed-derived oil by electrochemical method

The sulfated mordenite catalyst was prepared using the impregnation method and underwent modification via sulfation. The hydrophobic sulfated mordenite as a novel catalyst was applied for biodiesel production from neem seed-derived oil (NSDO) by electrochemical method. The impact of various degrees of sulfation and operational parameters were examined, and it was found that Mordenite-0.5 M Sulfated, exhibited the most outstanding performance and was deemed the most suitable catalyst. In this way, the produced catalyst, with its hydrophobic property, caused the polar molecules of methanol and especially water to move away from its surface, and instead by bringing the free fatty acids (FFA) molecules closer to its surface. The catalyst's excellent efficiency resulted in a satisfactory outcome for the reaction under gentle circumstances. The highest efficiency of the process was obtained at 0.85 % with operating conditions of 6 wt% of the catalyst, potential of 10 V, MeOH/NSDO molar ratio of 10:1, and reaction duration of 1 h. The catalyst displayed remarkable performance and reusability, with a mere 15 % decrease in the reaction yield after five consecutive cycles. XRD, BET, FT-IR, EDX-Mapping, and NH3-TPD analyses examined the structure and acidity of the synthesized catalyst. Furthermore, to examine the quality of the biodiesel produced, physicochemical analyses were conducted following the standards set by ASTM. The obtained results were found to be entirely in line with the quality attributes of diesel fuel.

Mechanisms and Opportunities for Rational In Silico Design of Enzymes to Degrade Per- and Polyfluoroalkyl Substances (PFAS).

Per and polyfluoroalkyl substances (PFAS) present a unique challenge to remediation techniques because their strong carbon-fluorine bonds make them difficult to degrade. This review explores the use of in silico enzymatic design as a potential PFAS degradation technique. The scope of the enzymes included is based on currently known PFAS degradation techniques, including chemical redox systems that have been studied for perfluorooctanesulfonic acid (PFOS) and perfluorooctanoic acid (PFOA) defluorination, such as those that incorporate hydrated electrons, sulfate, peroxide, and metal catalysts. Bioremediation techniques are also discussed, namely the laccase and horseradish peroxidase systems. The redox potential of known reactants and enzymatic radicals/metal-complexes are then considered and compared to potential enzymes for degrading PFAS. The molecular structure and reaction cycle of prospective enzymes are explored. Current knowledge and techniques of enzyme design, particularly radical-generating enzymes, and application are also discussed. Finally, potential routes for bioengineering enzymes to enable or enhance PFAS remediation are considered as well as the future outlook for computational exploration of enzymatic in situ bioremediation routes for these highly persistent and globally distributed contaminants.

Promotional effect of H2O introduction on the NH3-SCR activity of the gas-phase sulfated CeO2 catalyst by organic CS2+COS: Influence of H2O concentration

Herein, as an indispensable key reactant for the hydrolysis of organic sulfur, H2O was firstly introduced to optimize the NH3-SCR activity of CeO2 by providing the adsorption and reaction spots of catalysis for organic CS2+COS during the low-temperature gas-phase sulfation. The results demonstrate that the introduction of 0.33 vol% H2O is beneficial to enhance the interaction between organic CS2+COS and cube fluorite CeO2, which not only increases the concentrations of Ce3+ ions, chemisorbed oxygen (Oβ) and oxygen vacancies on CeO2-CS2+COS surface, but also effectively enhances the redox cycle of Ce4+/Ce3+ ion pairs and the medium-strong acid sites of catalyst. These all help enhance the promotional effect of organic sulfur low-temperature gas-phase sulfation on the NH3-SCR activity of CeO2 and further improve NOx reduction over the CeO2-CS2+COS catalyst. However, the introduction of 5.0 vol% H2O shows a certain inhibitory effect due to the competitive adsorption of excess water and CS2+COS on the cube fluorite CeO2 surface, which weakens their interaction during the low-temperature gas-phase sulfation, thereby decreases the promotional effect of low concentration water introduction on the NH3-SCR activity of the CeO2-CS2+COS catalyst. Therefore, the results of this research provide a scientific reference for developing the NH3-SCR CeO2-based catalyst in practical applications.