Sulfated Catalysts Research Articles

Gas phase sulfation of ceria-zirconia solid solutions for generating highly efficient and SO2 resistant NH3-SCR catalysts for NO removal

A series of ceria-zirconia solid solutions (CexZr1-xO2) were prepared by co-precipitation method and then sulfated with SO2 + O2 at 200 °C. Subsequent testing with the selective catalytic reduction of NO by NH3 (NH3-SCR) showed that the activity of the sulfated CexZr1-xO2 catalysts oxide catalysts exhibited a volcano-type tendency with increasing Zr content. Furthermore, the sulfated Ce0.6Zr0.4O2 catalyst showed the most desirable NH3-SCR activity at 250-300 °C, and exhibited much better SO2 resistance at 250 °C. Detailed characterization results demonstrated that Ce0.6Zr0.4O2 could adsorb more surface sulfate species and then produce more stable acid sites than pure CeO2 at 200 °C. After sulfation treatment, more Ce3+ and oxygen vacancies were formed on the surface of Ce0.6Zr0.4O2. In situ diffuse reflectance infrared Fourier transform spectroscopy (in situ DRIFTS) experiments suggested that the nitrates species deposited on the surface of as-prepared Ce0.6Zr0.4O2, which showed no reactivity, could barely deposit on the same sample after sulfation. While, the sulfated Ce0.6Zr0.4O2 had more reactive acid sites to participate in the NH3-SCR and the reaction proceeded via Eley-Rideal mechanism. This work proved that sulfation treatment could be used in designing an efficient cerium-zirconium based NH3-SCR catalyst with great application prospect.

A partial sulfidation approach that significantly enhance the activity of FeCo layered double hydroxide for oxygen evolution reaction

We report a partial sulfidation approach that effectively boosts the OER activity of FeCo-layered double hydroxides (LDH). It is found that the mild sulfurized FeCo-LDH nanosheets using Na2S converted a portion of their surface metal-hydroxide bonds to metal-sulfur (-hydrosulfide) bonds without significantly altering their crystal structure. The sulfidation degree is controlled by Na2S concentration for obtaining a moderately surface electronic configurations. Benefits from the regulated electronic configurations, the sulfurized FeCo-LDH nanosheets only require an overpotential of 281 mV to produce oxygen at 10 mA cm−2 and their Tafel slope is 51.8 mV dec−1, which are both lower than the 348 mV and 72.7 mV dec−1 of pristine FeCo-LDH nanosheets. The sulfurized catalysts have sustained 12 h of operation without notable activity loss. This work can provide new insights into understanding the roles of metal-sulfur bonds for OER and offer an attractive strategy to design low cost but efficient OER catalysts.

Catalyst Effect on Grout Composition of Microalgae Biomass Hydrothermal Liquefaction Products

Hydrothermal liquefaction (HTL) of microalgae biomass over an aluminum oxide catalyst with an isomerization component in the neutral and sulfated forms was studied. Gas-chromatographic — mass-spectrometric analysis of the products led to conclusions about the effect of catalyst composition on the gasoline-fraction group composition of the processed bio-oil. The contents of isoalkanes and aromatic hydrocarbons increased whereas the concentrations of S-, 0-, and N-containing components decreased in the HTL products if a catalyst was used. The yield of water-soluble side products also decreased. Sulfated catalysts had greater effects than neutral catalysts on the group composition.

Effects of anaerobic SO2 treatment on nano-CeO2 of different morphologies for selective catalytic reduction of NOx with NH3

Tuning surface acidity is a common strategy to improve the reactivity of Ce-based materials for selective catalytic reduction (SCR) of NOx with NH3. Traditionally, it is achieved by wet impregnation of sulfate species or treatment under an atmosphere of sulfur dioxide and oxygen. However, the two methods do not bring any change to the electronic state of CeO2, and Ce4+ ions which cause undesired side reactions are largely retained on the surface. Herein, we report a sulfation strategy that can tune the surface acid sites and regulate the electronic state of nano-CeO2. Using SO2 as reducible gas for surface sulfation, we prepared sulfated CeO2 (S-CeO2) catalysts of different morphologies and tested them for the NH3-SCR reaction. The characterization results revealed that the interaction between SO2 and nano-CeO2 is obviously affected by ceria morphology. Among the sulfated catalysts, that with rod morphology (S-CeO2-Rod) shows the highest NOx conversion, and exhibits superior sulfur and water tolerance. The excellent SCR activity of S-CeO2-Rod is attributed to the enrichment of oxygen vacancies and surface Ce3+ ions as a result of the abundant presence of sulfate species.

Hydro-Pyrolysis and Catalytic Upgrading of Biomass and Its Hydroxy Residue Fast Pyrolysis Vapors

Fast pyrolysis of Miscanthus, its hydrolysis residue and lignin were carried with a pyrolysis-gas chromatography/mass spectrometry (Py-GC/MS) followed by online vapor catalytic upgrading with sulfated ZrO2, sulfated TiO2 and sulfated 60 wt.% ZrO2-TiO2. The most evident influence of the catalyst on the vapor phase composition was observed for aromatic hydrocarbons, light phenols and heavy phenols. A larger amount of light phenols was detected, especially when 60 wt.% ZrO2-TiO2 was present. Thus, a lower average molecular weight and lower viscosity of bio-oil could be obtained with this catalyst. Pyrolysis was also performed at different pressures of hydrogen. The pressure of H2 has a great effect on the overall yield and the composition of biomass vapors. The peak area percentages of both aromatic hydrocarbons and cyclo-alkanes are enhanced with the increasing of H2 pressure. The overall yields are higher with the addition of either H2 or sulfated catalysts. This is beneficial as phenols are valuable chemicals, thus, increasing the value of bio-oil. The results show that the hydrolysis residue has the potential to become a resource for phenol production.

Understanding the deposition and reaction mechanism of ammonium bisulfate on a vanadia SCR catalyst: A combined DFT and experimental study

The deactivation of NH3-selective catalytic reduction (SCR) catalysts due to NH4HSO4 deposition at low temperatures (< 300 °C) is still a significant challenge. In this work, we present a comprehensive mechanism describing the formation, deposition, and reaction of NH4HSO4 on a V2O5/TiO2 catalyst using a combination of theoretical and experimental methods. The results show that NH4HSO4 is mainly formed in the gas phase through the nucleation of SO3, H2O, and NH3 and then deposits onto the catalyst surface. The decomposition of NH4HSO4 on the surface of the V2O5/TiO2 catalyst consists of two steps: NO is reduced by the NH4+ of NH4HSO4 forming N2 and H2O by transferring an electron to the adjacent vanadium site, followed by a reoxidation of the reduced vanadium site by either O2 or NO2. At low temperatures, due to the weak reoxidizing ability of O2, the reaction of NH4HSO4 with NO in the NO/O2 mixture is rather slow. Adding NO2 can remarkably enhance the decomposition of NH4HSO4 on the catalyst surface. Our results reveal that the rate-determining step of the reaction between NH4HSO4 and NO/O2 is the reoxidation of the reduced vanadium site and that NO2 is a better reoxidizing agent than O2, which has been confirmed by X-ray photoelectron spectroscopy analysis and the designed transient response method experiments. Finally, the catalyst sulfur tolerance test has proven that the commercial V2O5-WO3/TiO2 catalyst can successfully maintain its long-term activity for NOx reduction in SO2-contained flue gas at 250 °C due to the rapid decomposition of deposited NH4HSO4 on the catalyst surface by the NO/NO2 mixture.

Dehydration of Glycerol to Acrolein over Sulfated Iron Oxide Catalysts

The problem of disposal of glycerol, the main waste product in the production of biodiesel, has been explored. It has been shown that cheap catalysts on the basis of iron(III) oxide can be use for mediating the transformation of glycerol to acrolein—an important intermediate product of industrial organic synthesis. The influence of external factors on the process of dehydration of glycerol to acrolein has been examined.

Examining a catalyst sample for demercaptanization process

This paper studies the results of experimental analysis on the demercaptanization of various crude distillation products by using a catalyst that was produced by Caravan sulfur catalyst company (CSC). This process is very important due to the removal of sulfur compounds and the most of desulfurization is carried out in a catalytic manner. According to the analysis, this catalyst is suitable for use in demercaptanization processes with 10% caustic solution.

Yttrium Oxide Supported La2O3 Nanomaterials for Catalytic Oxidative Cracking of n-Propane to Olefins

La2O3 nanorods were prepared by simple hydrothermal synthesis method. Yttrium oxide (1, 3, 5 and 7 wt%) supported La2O3 and SO42− incorporated La2O3 nanorods were prepared impregnation method and used as catalysts in oxidative cracking of n-propane. The pure La2O3 nanorods exhibited 15% n-propane conversion with 22% olefins (ethane and propene) selectivity. Considerable improvement in n-propane conversion was observed in case of 3 wt% yttrium oxide supported on La2O3 nanorods (25% conversion of n-propane and 36% selectivity to olefins) at reaction temperature of 550 °C. Interestingly, 5 wt% yttrium oxide supported 10 wt% SO42−/La2O3 nanorod sample exhibited superior performance in n-propane conversion (42%) and olefins selectivity (54%). The yttrium oxide loading and sulfation of La2O3 nanorods influenced the catalytic activity. The characterization of synthesized nanomaterials was performed using elemental analysis, XRD, FT-IR, N2-physisorption, SEM, XPS and H2-TPR techniques. The obtained results indicated that yttrium oxide was highly dispersed over the La2O3 nanorods because of strong interaction between the two rare earth metal oxides. Additionally, deposition of yttrium oxide to sulfated La2O3 nanorods increased the surface area and the amount of Lewis acid sites (for the activation of n-propane) on La2O3 nanorods. Yttrium oxide supported sulfated La2O3 catalyst showed no deactivation during the 24 h of reaction and without coke formation.

A core-shell SO4/Mg-Al-Fe3O4 catalyst for biodiesel production

Catalytic transesterification of triglycerides and esterification of free fatty acids underpins sustainable biodiesel production, wherein efficient heterogeneous catalysts are sought to replace mineral acids. A robust, magnetic core-shell SO4/Mg-Al-Fe3O4 catalyst was synthesised by stepwise co-precipitation, encapsulation, and surface functionalisation. The resulting magnetically-separable catalyst has a surface area of 123 m2 g−1, uniform 6.5 nm mesopores, and a high total acid site loading of 2.35 mmol g-1. Optimum conditions for the (trans)esterification of waste cooking oil (WCO) over the sulfated solid acid catalyst were 95 °C, a methanol:WCO molar ratio of 9:1, and 300 min reaction to achieve 98.5% FAME yield. Esterification of oleic acid to methyl oleate resulted in an 88% yield after 150 min under the same reaction conditions. The magnetic solid acid catalyst exhibited good thermal and chemical stability and enabled facile catalyst separation post-reaction and the production of high quality biodiesel.

Selective Catalytic Reduction of NOx with NH3 by Using Novel Catalysts: State of the Art and Future Prospects

Selective catalytic reduction with NH3 (NH3-SCR) is the most efficient technology to reduce the emission of nitrogen oxides (NOx) from coal-fired industries, diesel engines, etc. Although V2O5-WO3(MoO3)/TiO2 and CHA structured zeolite catalysts have been utilized in commercial applications, the increasing requirements for broad working temperature window, strong SO2/alkali/heavy metal-resistance, and high hydrothermal stability have stimulated the development of new-type NH3-SCR catalysts. This review summarizes the latest SCR reaction mechanisms and emerging poison-resistant mechanisms in the beginning and subsequently gives a comprehensive overview of newly developed SCR catalysts, including metal oxide catalysts ranging from VOx, MnOx, CeO2, and Fe2O3 to CuO based catalysts; acidic compound catalysts containing vanadate, phosphate and sulfate catalysts; ion exchanged zeolite catalysts such as Fe, Cu, Mn, etc. exchanged zeolite catalysts; monolith catalysts including extruded, washcoated, and metal-mesh/foam-based monolith catalysts. The challenges and opportunities for each type of catalysts are proposed while the effective strategies are summarized for enhancing the acidity/redox circle and poison-resistance through modification, creating novel nanostructures, exposing specific crystalline planes, constructing protective/sacrificial sites, etc. Some suggestions are given about future research directions that efforts should be made in. Hopefully, this review can bridge the gap between newly developed catalysts and practical requirements to realize their commercial applications in the near future.

The Effect of Rhodium (III) Sulfate and Clove Oil Catalysts on The Droplet Combustion Characteristics of Castor Oil

The Effect of Rhodium (III) Sulfate and Clove Oil Catalysts on The Droplet Combustion Characteristics of Castor Oil

Fenton oxidation and adsorption pretreatment for superior biogas recovery from biomethanated spent wash

A key task in alcohol distilleries is the effective treatment of biomethanated spent wash after biogas recovery. This colored washwater exhibits low biodegradability index (BI < 0.2), high chemical oxygen demand (30,000 < COD < 40,000 mg/L), and recalcitrance to aerobic treatment. In this work, pretreatment of biomethanated distillery wastewater by Fenton oxidation was proposed for improved biogas recovery. The effects of temperature, solution pH, and H2O2 dosage on the efficacy of the oxidation process were studied. Using ferrous sulfate catalyst (36 mg/L) for diluted wastewater (BOD5 = 81; COD = 400 mg/L), 54% reduction in COD was achieved within 1 h in acidic medium (pH = 3) at ambient temperature (T = 30 °C). Post-oxidation, the BI value improved (0.33). After subsequent adsorption over activated carbon (loading 5%) for 1 h, COD reduction (70%), and BI value (0.43) improved further. Upon anaerobic treatment with 1% acclimatized biomass, 1 Nm3 of biogas (47% CH4) was additionally formed per m3 of treated wastewater; without pretreatment, this value was 0.9 Nm3 (just 11% CH4). Lastly, aerobic treatment was performed and the results were encouraging: BI = 0.51 and COD reduction = 94%. Many oxidation products were identified and first-order kinetic plots were made to describe COD conversion kinetics. In this way, useful insight on a plausible technique for valorization of biomethanated washwater was provided.

Effects of regeneration conditions on sulfated CuSSZ-13 catalyst for NH3-SCR

To understand the role of regeneration conditions on sulfur-poisoned Cu/SSZ-13 catalysts for NH3-SCR, the physicochemical characterizations and NO2 conversions were investigated. The sulfur-poisoned Cu/SSZ-13 catalysts were treated at different conditions as a function of temperature and duration. TGA results revealed that regeneration at 500 °C only removed parts of sulfur spices and at 700 °C can completely remove all sulfur spices. The physical structural characterizations results illustrate that regeneration below 700 °C has no significant impact on CHA structure for Cu/SSZ-13 catalysts, while dealumination occurs on poisoned Cu/SSZ-13 when regeneration temperature is higher than 700 °C. EPR and H2-TPR results show that the sulfate decomposition and Cu migration reactions involved during regeneration and, as a result, the content of Cu2+ gradually increased as the extent of regeneration increased. The kinetics tests support that NOx conversion recovery is related to the content of Cu2+ increase during regeneration. Our study reveals that the optimum regeneration temperature is 700 °C, because severe dealumination at 750 °C inhibited Cu2+ amount increase.

Heterogeneous Esterification of Waste Cooking Oil with Sulfated Titanium Dioxide (STi)

In this work, a sulfated titanium dioxide (STi) catalyst obtained from a commercial TiO2 precursor was synthesized and characterized. The catalyst was sulfated by the simple impregnation method with H2SO4 and subsequently calcined at different temperatures. The synthesized catalyst was characterized by X-ray Diffraction (XRD), Energy-Dispersive Spectroscopy (EDS), and Scanning Electron Microscopy (SEM). The sulfated catalyst was thermally treated at different temperatures (100, 200, 400, and 600 °C) and evaluated in oleic acid esterification reactions by varying the concentration of the catalyst during the conversion of oleic acid to methyl oleate. The conversion was measured from the variation of the acid index (AI)° and free fatty acids (FFA) during the reaction. The STi catalyst obtained was compared with two homogeneous catalysts, H2SO4 and ferric sulfate [Fe2(SO4)3], evaluating the reaction time in the conversion, from which improvements in the reaction performance of the catalyst synthesized in this work were observed versus the two homogeneous catalysts mentioned earlier. Catalyst reuse cycles were also evaluated as well as their performance in the esterification of waste cooking oil. The best catalyst yields reached values close to 86% in a reaction time of 6 h.

Sulfated Copper Oxide Catalyzed One-Pot Synthesis of N-Fused Benzimidazolo/Benzothiazolo Pyrimidines

A recyclable sulfated copper oxide catalyst in acetonitrile is effective for the synthesis of N-fused benzimidazolo/benzothiazolo pyrimidine derivatives by the reaction of 2-aminobenzimidazole/2-aminobenzothiazole, phenyl acetylene, and benzaldehydes. This method is a unified approach to assemble a wide variety of fused pyrmidines.

Biodiesel Production Through Waste Cooking Oil (WCO) Esterification Using Sulfated Alumina as Catalyst

Biodiesel produced from waste cooking oil (WCO) with initial free fatty acids (FFA) of 6.67 % through one-stage reaction (transesterification) and two-stage reaction (esterification followed by transesterification) had been studied. The esterification process was catalyzed by solid catalyst of synthesized sulfated alumina and transesterification reaction was catalyzed by NaOH. The objective of this research is to determine the optimum condition of biodiesel production from WCO using sulfated alumina catalysts by esterification reaction and to compare biodiesel yield using homogeneous catalysts of sulfuric acid with a heterogeneous catalyst of sulfated alumina. The results showed that the optimum conditions for esterification reactions using sulfated alumina catalyst is at the volume ratio of methanol/oil of 1.5, the amount catalyst of 1 wt %/v of oil at 1 hour reaction time. With the optimum condition, the maximum conversions of free fatty acid using a sulfuric acid and sulfated alumina catalyst were 90.4 % and 89.97 % respectively. The yield of biodiesel from waste cooking oil by two-stage transesterification process is 86.67 % and one-stage transesterification is 66.67 %.

Закономерности процесса пероксидно-ацетатной делигнификации недревесного цел- люлозосодержащего сырья в присутствии сернокислотного катализатора

Закономерности процесса пероксидно-ацетатной делигнификации недревесного цел- люлозосодержащего сырья в присутствии сернокислотного катализатора

Sulfated Ceria Catalyzed Synthesis of Imidazopyridines and Their Implementation as DNA Minor Groove Binders.

The small molecules that bind to DNA minor groove are considered as potential therapeutic agents to fight against many human diseases. They induce cell death by interfering with transcription, replication and progression of cell cycle. Herein, we report the synthesis of imidazopyridine-3-amines using sulfated ceria catalyst by employing Groebkee-Blackburne-Bienayme reaction. We evaluated the possible antiproliferative and antimycobacterial activity against A549 cells and Mycobacterium tuberculosis, respectively. Among the tested compounds, N-tert-butyl-2-(2-butyl-4-chloro-1H-imidazol-5-yl)-5,7-dimethylimidazo[1,2-a]pyridin-3-amine (4g) was identified as cytotoxic heterocycle and antimycobacterial agent. Molecular docking studies of the imidazopyridine derivatives revealed the consistent positioning in the minor groove with a tight shape fit between receptor and ligands. Therefore, we speculate that new imidazopyridines induce their pharmacological effect by targeting the minor groove of DNA.

Catalytic upgrading of volatiles from coal pyrolysis over sulfated carbon-based catalysts derived from waste red oil

Sulfated carbon-based catalysts, red oil-derived carbon materials (RDCMs), were prepared by the self-assembly process from industrial alkylation process waste red oil. The performance of catalysts on upgrading of coal pyrolysis volatiles was investigated in a two-stage fixed-bed reactor. Compared with activated carbon (AC) or char, RDCMs exhibited better performance in increasing the yield and fraction of light tar (boiling point <360 °C). The higher specific surface areas and relatively more defects for RDCMs promoted the conversion of more heavy tar into light tar. The high-content doped sulfur in RDCMs contributed to more oxidation reaction in the secondary reaction for producing gaseous products. The pyrolysis water could be activated on the sulfur functional group to form ·H and ·OH radicals, which were able to stabilize the larger radical fragments from tar cracking to form more oxygenated organic compounds. The yield and fraction of light tar after catalytic upgrading using RDCMs (10 wt% of the tested coal) at 500 °C were 7.9 wt% and 80.0%, respectively, which increased by 19.6% and 33.3% in comparison with that from coal pyrolysis without catalyst.