Sulfated Catalysts Research Articles

Synthesis of waste cooking oil-based biodiesel via effectual recyclable bi-functional Fe2O3[sbnd]MnO[sbnd]SO42−/ZrO2 nanoparticle solid catalyst

The ferric–manganese doped sulfated zirconia nanoparticle solid acid catalyst was prepared through the impregnation reaction followed by calcination at 600°C for 3h. The characterization was performed using X-ray diffraction (XRD), Temperature programed desorption of NH3 (TPD-NH3/CO2), Thermal gravimetric analysis (TGA), Fourier Transform Infrared spectrometer (FT-IR), Brunner–Emmett–Teller (BET) surface area measurement, Energy dispersive X-ray spectroscopy (EDS), Transmission electron microscopy (TEM) and X-ray photoelectron spectroscopy (XPS). In addition, the dependence of the biodiesel yield on the reaction variables, such as reaction temperatures, catalyst loading, as well as the molar ratio of methanol/oil and reusability, were also investigated. The catalyst was reused six times without loss in its activity with the maximum yield of 96.5±0.02% achieved under the optimized conditions of the reaction temperature of 180°C; stirring speed of 600rpm, 1:20M ratio of oil to alcohol and 3wt/wt% catalyst loading. Additionally, the fuel properties of producing biodiesel from waste cooking oil were investigated and compared with those of the American and European standards.

Isomerization of light gasoline fractions: The efficiency of different catalysts and technologies

The experience gained from the industrial use of isomerization catalysts (chlorinated, zeolite, and sulfated oxides) at Russian plants is analyzed. Isomerization has been used in Russia since the late 1990s. Early technologies used zeolite catalysts. The subsequent development of isomerization followed two trends that employed chlorinated and sulfated oxide catalysts. In this work, the advantages and disadvantages of chlorinated catalysts are shown by citing specific examples. The main disadvantages are high sensitivity to water admixtures and sulfur compounds in the raw materials, along with side reactions that yield low octane products in C6 recycling. Sulfated oxide systems are free of such problems, as has been proved in the industrial use of SI-2 sulfated catalyst on different types of plants.

High-yield selective conversion of carbohydrates to methyl levulinate using mesoporous sulfated titania-based catalysts

Mesoporous sulfated-metal oxides and mixed-metal oxides prepared by a facile coprecipitation method employing titanium oxysulfate–sulfuric acid complex as a precursor of both titanium and sulfate are highly active and selective for direct methanolysis of carbohydrates to methyl levulinate. The most active sulfated TiO2–ZrO2 catalyst selectively converted fructose to methyl levulinate with a remarkably high yield (71%) after 1h at 200°C. Significant amounts of methyl levulinate were also obtained from sucrose (54%) and glucose (23%) after 1h at 200°C. The used catalyst was easily recovered and recycled without any loss of selectivity although activity decreased due to humin deposition on the surface. The spent catalysts were easily rejuvenated through calcination in air. The formation of ethers during dehydration was negligible suggesting that methanol can be recycled after distillation.

Studies on B sites in Fe-doped LaNiO3 perovskite for SCR of NOx with H2

A series of LaNi1−xFexO3 (x = 0.0, 0.2, 0.4, 0.7, and 1.0) perovskites were synthesized and characterized by X-ray diffraction (XRD), N2 physisorption, scanning electron microscopy (SEM), H2-temperature-programmed reduction (H2-TPR), and X-ray photoelectron spectroscopy (XPS). The perovskites were investigated for selective catalytic reduction of NOx by hydrogen (H2-SCR). It is shown that Fe addition into LaNiO3 leads to a promoted efficiency of NOx removal, as well as a high stability of perovskite structure. Moreover, easy reduction of Ni3+ to Ni2+ with the aid of appropriate Fe component mainly accounts for the enhanced activity. Meanwhile, deactivation of the sulfated catalysts is due to that sulfates mainly deposit on active Ni component while doping of Fe can protect Ni to some extent at the expense of partial sulfation.

Influence of the Copper Content of De-SOx Catalyst on Performance

AbstractA series of the Cu/MnMgAl mixed oxides were prepared by using the acid-processed gelatin method, characterized by Brunauer-Emmett-Teller (BET), X-ray diffraction (XRD), Fourier transform infrared (FT-IR), and transmission electron microscopy (TEM) techniques and applied as sulfur transfer catalysts under conditions similar to those of fluid catalytic cracking (FCC) units. The analysis of the SO2 abatement curves as a function of the copper content indicates that the reaction mechanism of SO2 uptake depends on two reversible surface processes (the chemisorptions of SO2 and its oxidation by copper ions) and a nearly irreversible process (bulk diffusion of the sulphate species). The results also show that the mixed oxides catalysts achieve the highest oxidative rate when they contain 11.1% (mol) copper (sample 10Cu/MnMgAl).

Ordered mesoporous carbon supported ferric sulfate: A novel catalyst for the esterification of free fatty acids in waste cooking oil

Ordered mesoporous carbon (OMC) supported ferric sulfate (FS) catalysts were prepared by impregnation, and their catalytic activity for the esterification of the free fatty acids (FFAs) in waste cooking oil (WCO) with methanol was evaluated. The FS/OMC catalysts were characterized by N2 adsorption–desorption, powder X-ray diffraction and transmission electron microscopy. The results indicated that catalysts retained the ordered mesoporous structure, and the FS was well dispersed on the surface of the OMC. The FT-IR spectrum of pyridine adsorbed on the FS/OMC catalysts showed the presence of strong Lewis acid sites on the surface of the catalysts. The FS/OMC catalysts exhibited excellent catalytic performances for FFA esterification. In addition, the process variables that influence the esterification of FFAs, such as the FS loading, the amount of catalyst, the molar ratio of methanol to FFAs, the reaction temperature and the reaction time, were investigated and optimized. The FS/OMC catalysts are reusable and maintained their original catalytic activities after six uses.

Benzylation of benzene by benzyl chloride over silica-supported iron sulfate catalysts

The silica-supported Fe-containing catalysts prepared using FeSO4 as a precursor exhibit high activity toward the reaction of benzene with benzyl chloride.

Decarbonylation of Lactic Acid to Acetaldehyde over Aluminum Sulfate Catalyst

Decarbonylation of lactic acid to acetaldehyde over several solid catalysts was investigated. Among the tested catalysts, aluminum sulfate has an excellent activity. In order to further understand the main reason which influenced the catalytic activity, NH3-TPD was used to estimate the acidity of the catalyst. According to the total acid amount, aluminum sulfate has a moderate amount. Heteropolyacids have strong acidity which caused serious carbon deposition on the surface of catalysts, resulting in a rapid deactivation of catalysts. Besides, FT-IR, XRD, and SEM were also utilized to characterize the fresh catalysts and the used. As for the aluminum sulfate catalyst, an evident adsorption band occurs in 2970 cm–1, suggesting a formation of poly lactate on the surface of the catalyst, and led to deactivation of the catalyst. Other parameters such as reaction temperature, lactic acid concentration, and LHSV (liquid hourly space velocity) were also discussed. Inspiringly, at high LHSV, lactic acid was efficiently converted to acetaldehyde via a decarbonylation reaction. As for stability and the recovery of aluminum sulfate, deactivation of the catalyst belongs to temporary deactivation caused by poly lactate covering the active sites of the catalyst, and only at simple calcination under the air atmosphere, the catalyst may be compeletely regenerated. Under the optimal reaction conditions, conversion of lactic acid achieved 100%, and the selectivity of acetaldehyde achieved 92.1% at 380 °C over the aluminum sulfate catalyst.

A high-surface-area mesoporous sulfated nano-titania solid superacid catalyst with exposed (101) facets for esterification: facile preparation and catalytic performance

In this paper, a high-surface-area mesoporous sulfated nano-titania exposed with (101) facets was prepared by a simple hydrothermal method without any template followed by surface sulfate modification. The physicochemical properties of the as-prepared catalyst were well characterized by X-ray diffraction (XRD), transmission electron microscopy (TEM), high resolution transmission electron microscopy (HRTEM), scanning electron microscopy (SEM), Raman spectroscopy (Raman), Fourier transform infrared spectroscopy (FTIR), N2 adsorption–desorption isotherms, temperature programmed desorption of NH3 (NH3-TPD), X-ray photoelectron spectroscopy (XPS) and pyridine adsorption infrared spectroscopy. The BET surface area of sulfated nano-titania with exposed (101) facets was 121 m2 g−1. Well dispersed bidentate sulfate groups were linked to the exposed (101) facets of anatase nano-titania. Acid sites with moderate- and superacidic strength formed in the sulfated titania catalyst. Also, the as-prepared sulfated sample possessed both Lewis and Bronsted acid sites. The catalytic activity of sulfated nano-titania with exposed (101) facets was evaluated using the esterification reaction between acetic acid and n-butanol. It was found that the yield of butyl acetate increased to about 92.2% in the presence of the catalyst. Compared with the exposed (001) facets, the exposed (101) facets showed better catalytic activity of sulfated TiO2 in esterification. The effects of different reaction conditions were discussed in detail. Additionally, the as-prepared sulfated sample could be efficiently recycled and regenerated by simple soaking in sulfuric acid followed by calcination.

Esterification of levulinic acid with ethanol over sulfated Si-doped ZrO2 solid acid catalyst: Study of the structure–activity relationships

Esterification of levulinic acid with ethanol to produce ethyl levulinate was examined by using sulfated Si-doped ZrO2 solid acid catalysts with enlarged surface areas and the relationships between the structural properties and catalytic performances were investigated. Structures of the catalysts were verified by XRD, nitrogen physisorption, FE-SEM, UV–vis and FTIR measurements. Acidity of the catalysts that substantially affect the catalytic activity was evaluated by NH3-TPD measurement. Incorporation of Si atom into the lattice structure of ZrO2 (up to 30mol% Si per Zr atom) afforded high-surface-area SiO2-ZrO2 mixed oxides, and their sulfated forms provided increased numbers of sulfate anions and the associated acid sites. Several distinct correlations were found between the structural properties/acidities and catalytic activities, which suggested that (i) the number of accessible active acid sites and (ii) the accessibility of the organic reactants to the active sites play crucial roles in determining the overall activity. Among the catalysts tested, sulfated Si-doped ZrO2 with optimum Si content (5.0–10mol% Si per Zr) was found to be the best catalyst, the activity of which was far superior to that of the conventional sulfated ZrO2. In addition, direct conversion of cellulosic sugars (glucose and fructose) into levulinate esters was also examined, in view of their practical applications in acid-catalyzed biomass conversion processes.

Synthesis of ethyl levulinate as fuel additives using heterogeneous solid superacidic catalysts: Efficacy and kinetic modeling

Esters of levulinic acid, which is biomass derived, are used as oxygenated additives in fuels, flavoring and fragrance industry or as blending components in biodiesel. A series of sulphated metal oxide catalysts were prepared and their activities were tested in the synthesis of ethyl levulinate as the model compound, among which UDCaT-5 (mesoporous super acidic zirconia modified catalyst) was the most active and robust catalyst. The effects of various parameters were studied in a batch reactor to establish kinetics and mechanism of reaction under optimized conditions. The reaction follows Langmuir–Hinshelwood–Hougen–Watson mechanism involving weak adsorption of the reactants and products. The apparent energy of activation was found to be 9.00kcal/mol for ethyl levulinate. Several other alkyl levulinates were produced from esterification of levulinic acid with different alcohols using UDCaT-5. The use of solid acid catalyst made the process environmentally benign. The catalyst was reused up to four runs including the fresh one. A green and effective route for conversion of biobased levulinic acid into valuable esters is established.

Supported L-pyrrolidine-2-carboxylic acid-4-hydrogen sulphate on silica gel as an economical and efficient catalyst for the one-pot preparation of for the one-pot preparation of β-acetamido ketones via a four-component condensation reaction

An efficient, one-pot, four-component condensation of aldehydes, acetophenone (or propiophenone), acetyl chloride and acetonitrile in the presence of catalytic amounts of L-pyrrolidine-2-carboxylic acid-4-hydrogen sulphate (supported on silica gel), a green and non-toxic catalyst, is described for the preparation of β-acetamido ketones in good to excellent yields. An efficient multi-component procedure, catalysed by L-pyrrolidine-2-carboxylic acid-4-hydrogen sulphate (supported on silica gel), as green and non-toxic catalyst, has been applied for the preparation of β-acetamido ketones under reflux conditions.

Catalytic dehydration of fructose to 5-hydroxymethylfurfural over a mesoscopically assembled sulfated zirconia nanoparticle catalyst in organic solvent

This work prepared a series of novel assembled sulfated zirconia nanoparticle catalysts which were first applied in carbohydrate conversion.

Conformal sulfated zirconia monolayer catalysts for the one-pot synthesis of ethyl levulinate from glucose.

Here we describe a simple route to creating conformal sulphated zirconia monolayers throughout an SBA-15 architecture that confers efficient acid-catalysed one-pot conversion of glucose to ethyl levulinate.

Hydrothermal stability of MOx-Ce0.75Zr0.25O2 catalysts for NOx reduction by ammonia

Various acidic components (MOx: phosphate, sulfate, tungstate and niobate) were loaded on Ce0.75Zr0.25O2 powders by an impregnation method. The as-prepared catalysts were hydrothermally treated at 760 °C for 48 h in air containing 10 vol.% H2O to obtain the aged catalysts. The catalysts were characterized by X-ray diffraction, Fourier transform infrared spectroscopy, H2 programmed-reduction, NH3 adsorption and deNOx activity measurements. The results showed that, among the catalysts investigated, the phosphated Ce0.75Zr0.25O2 catalyst showed the highest hydrothermal stability. The remained high acidity of the phosphated catalyst with moderate redox property helped to maintain the excellent NH3-SCR activity of hydrothermally aged catalyst. Cerium tungstate led to the poor redox property of the tungstated catalyst although the acidity of catalyst was still high. The decomposition of sulfates at temperatures higher than 600 °C restrained the usage of sulfated catalysts in high temperature conditions. The overall dehydration of niobate to niobium oxides led to the low acidity of hydrothermally aged Nb2O5-Ce0.75Zr0.25O2 catalyst.

Mild Hydrosulfenylation of Olefins under Neutral Conditions Using a Defined NHC-Ligated Iron–Sulfur Catalyst

A defined NHC-Fe–S complex proved to be an efficient catalyst for the selective hydrosulfenylation of α,β-unsaturated ketones or vinylnitriles. A wide range of different aliphatic thiols were transferred in this atom-economic reaction into the corresponding thioethers. Mild reaction conditions, equimolar amounts of substrates, low catalyst loadings, and mild reaction conditions are characteristic for this transformation.

FTIR study of β-picoline and pyridine-3-carbaldehyde transformation on V–Ti–O catalysts. The effect of sulfate content on β-picoline oxidation into nicotinic acid

Surface complexes of β-picoline, 3-pyridine-carbaldehyde and nicotinic acid on 20wt.% V2O5/TiO2 catalysts containing 0.07 and 6.3lwt.% SO42− were studied by FTIR spectroscopy and temperature programmed reaction technique. The water (both H2O and D2O), pyridine and β-picoline were used as molecular probes for identification of surface acidity and the structure of sulfate species. Both samples possess Lewis and Brönsted acidic sites. β-Picoline, 3-pyridine-carbaldehyde and nicotinic acid form surface complexes of similar structure on both studied catalysts. But high sulfated catalyst contains stronger Brönsted sites in greater amount. It leads to the formation of stronger bound surface complexes of β-picoline, 3-pyridine-carbaldehyde and nicotinic acid. The strongly bound surface complexes are transformed into by-products (COx, pyridine and 3-cyanopyridine). It resulted in substantial reduction of nicotinic acid yield.

Iron oxide supported sulfated TiO2 nanotube catalysts for NO reduction with propane

Sulfated TiO2 nanotubes and a series of iron oxide loaded sulfated TiO2 nanotubes catalysts with different iron oxide loadings (1wt%, 3wt%, 5wt% and 7wt%) were prepared and calcined at 400°C. The physico-chemical properties of the catalysts were studied by using XRD, N2-physisorption, Raman spectroscopy, SEM-EDX, TEM, XPS, and pyridine adsorption using FTIR and H2-TPR techniques. It was observed that iron oxide was highly dispersed on the sulfated TiO2 nanotube support due to its strong interaction. The activity of these catalysts in the catalytic removal of NO with propane was also studied in the temperature range of 300–500°C. Highest activity (90% NO conversion) was observed with 5wt% iron oxide supported on sulfated TiO2 catalyst at 450°C. Selective catalytic reduction of NO activity of the catalysts was correlated with iron oxide loading, reducibility, and the Brönsted and Lewis acid sites of the catalysts. The catalyst also showed good stability under studied reaction conditions that no deactivation was observed during the 50h of reaction.

Improvement of Activity and SO2 Tolerance of Sn-Modified MnOx–CeO2 Catalysts for NH3-SCR at Low Temperatures

The performances of fresh and sulfated MnOx-CeO₂ catalysts for selective catalytic reduction of NOx by NH₃ (NH₃-SCR) in a low-temperature range (T < 300 °C) were investigated. Characterization of these catalysts aimed at elucidating the role of additive and the effect of sulfation. The catalyst having a Sn:Mn:Ce = 1:4:5 molar ratio showed the widest SCR activity improvement with near 100% NOx conversion at 110-230 °C. Raman and X-ray photoelectron spectroscopy (XPS) indicated that Sn modification significantly increases the concentration of oxygen vacancies that may facilitate NO oxidation to NO₂. NH₃-TPD characterization showed that the low-temperature NH₃-SCR activity is well correlated with surface acidity for NH3 adsorption, which is also enhanced by Sn modification. Furthermore, as compared to MnOx-CeO₂, Sn-modified MnOx-CeO₂ showed remarkably improved tolerance to SO₂ sulfation and to the combined effect of SO₂ and H₂O. In the presence of SO₂ and H₂O, the Sn-modified MnOx-CeO₂ catalyst gave 62% and 94% NOx conversions as compared to 18% and 56% over MnOx-CeO₂ at temperatures of 110 and 220 °C, respectively. Sulfation of SnO₂-modified MnOx-CeO₂ may form Ce(III) sulfate that could enhance the Lewis acidity and improve NO oxidation to NO₂ during NH₃-SCR at T > 200 °C.

Selective conversion of glycerol to acrolein over supported nickel sulfate catalysts

Supported nickel sulfate was proved to be an efficient catalyst for gas-phase dehydration of glycerol to acrolein at 340°C in the presence of oxygen. At a GHSV of glycerol of 873h−1, glycerol conversion over 17NiSO4-350 was still higher than 90% even after 10h of reaction, with selectivity to acrolein always higher than 70mol.%. It was demonstrated that Lewis acid sites were responsible for heavy compounds formation, and that Brønsted acid sites with medium and high strength were active sites for acrolein production from glycerol dehydration. The acidity of supported nickel sulfate was associated with one metastable structure, NiSO4·xH2O (0<x<1). Furthermore, not only nickel cations but also sulfate groups exhibited oxidizability during reactions, and loss of sulfur was the main reason for irreversible deactivation of supported nickel sulfate.