Solid Superacid Catalyst Research Articles

Copper-induced formation of Lewis acid sites enhancing sulfated zirconia catalyzed i-butane normalization

Sulfated zirconia (SO42-/ZrO2) has been reported as an efficient and stable solid superacid catalyst for normalizing i-butane to n-butane, and may potentially substitute Pt-based catalysts. In this work, sulfated zirconia with Cu addition (Cu-SO42-/ZrO2) is prepared through a one-step method and exhibits comparable performance to commercial Pt-Cl/Al2O3, with an i-butane average conversion of 43.8% and n-butane average selectivity as high as 86.1%, while maintaining a stable n-butane yield for up to 120 hours. The relationship between Cu-promoter-induced physicochemical properties and catalytic performance for sulfated zirconia catalysts is investigated in detail, with the help of XPS, NH3-TPD, pyridine-IR, and density functional theory calculation. A volcano-type relationship is found between Cu content and n-butane yield, where n-butane yield first increases from 32.23% to 37.71%, and then decreases to 29.56%, with the gradual increase of Cu content. The moderate Cu species additive is beneficial to release Zr Lewis acid site from sulfate and increase its Lewis acid density, which accounts for its excellent catalytic selectivity for i-butane normalization. The excess Cu promoter covers the exposed Zr Lewis active sites, leading to the decayed i-butane conversion. Therefore, Lewis active sites density is regarded as descriptor to corelate n-butane yield, accounting for the volcano relationship between Cu content and n-butane yield for Cu-SO42-/ZrO2. This work demonstrates the feasibility of Cu modification and provides insight into the promotion mechanism, which may be extended to other solid superacid catalysts beyond sulfated zirconia.

Production of biodiesel from waste culinary oil catalyzed by S2O82−/TiO2–SiO2 solid super-acid catalyst prepared with recovered TiO2 from spent SCR

Recovery and valorization of natural resources from waste materials are crucial for promoting sustainable development. In light of this, the present study explores the transesterification of waste culinary oil into biodiesel production using a silica-supported solid super-acid catalyst (S2O82−/TiO2–SiO2) prepared with recovered TiO2 from spent SCR. The synthesized materials were characterized through XRD, SEM-DES, XPS, FT-IR, NH3-TPD, and N2-BET analysis. Notably, the crystal structure of recovered TiO2 was not destroyed during the whole process. N2-BET analysis showed that the silica-supported catalyst significantly increased the specific surface area from 47.89 to 101.16 g/m2. The presence of superacid sites (Brønsted and Lewis acid sites) on the surface of the catalyst was confirmed by NH3-TPD and FT-IR analysis. The silica-supported catalyst (S2O82−/TiO2–SiO2) exhibited high catalytic activity for free fatty acid (FFA) about a conversion rate of 90.7 % under optimal reaction conditions: a reaction time of 4 h, at 180 °C with a 5 wt% catalyst loading, and a methanol-to-oil molar ratio of 12:1. The biodiesel production was confirmed by using FT-IR and 1HNMR techniques. Furthermore, the catalytic performance of the prepared catalyst was compared with other catalysts prepared from pure TiO2 reported in the literature. This approach showed a potential for sustainable biodiesel production by using low-cost solid acid catalyst synthesized from recovered materials.

Solid superacid catalysts promote high-performance carbon dots with narrow-band fluorescence emission for luminescence solar concentrators

Facile and efficient method for constructing carbon dots (CDs) with narrow full width at half maximum (FWHM) is a major challenge in the field, and researches on regulating the FWHM of CDs are also rare and scarce. In this work, we delved into the synthesis of CDs with narrow fluorescence emission FWHM (NFEF-CDs) in the m-phenylenediamine (m-PD)/ethanol system, utilizing solid superacid resin as catalyst with solvothermal method. The resulting NFEF-CDs exhibit a photoluminescent (PL) emission peak at 521 nm with a narrow FWHM of 41 nm, an absolute PL quantum yield (QY) of 80%, and display excitation-independent PL behavior. Through comprehensive characterization, we identified the protonation of edge amino on NFEF-CDs as the key factor in achieving the narrow FWHM. Subsequently, we validated the broad applicability of solid superacid resins as catalysts for synthesizing CDs with narrow FWHM in the m-PD/ethanol system. Finally, we utilized a self-leveling method to prepare NFEF-CDs film on the surface of poly(methyl methacrylate) (PMMA) substrate and investigated the solid-state fluorescence properties of NFEF-CDs as well as their performance as luminescence solar concentrator (LSC) for photovoltaic conversion. The results revealed that the as-prepared LSC exhibit an internal quantum efficiency (ηint) of 42.39% and an optical efficiency (ηopt) of 0.68%. These findings demonstrate the promising prospects of NFEF-CDs in the field of LSCs and provide a theoretical basis for their application in photovoltaic conversion.

S2O82−/CeO2 Solid Superacid Catalyst Prepared by Radio-Frequency Plasma-Assisted Hydrothermal Method

CeO2 was prepared using a hydrothermal method, modified by radio-frequency plasma in the form of glow discharge, and then the solid superacid S2O82−/CeO2 was prepared by the impregnation method. A series of properties such as pore structure was characterized by N2 adsorption–desorption experiments, surface morphology was characterized by TEM, crystal phase was characterized by XRD, and surface acidity of the catalyst was characterized by Py-IR and Hammett titration. The methyl esterification reaction of tryptophan was used to evaluate the activity of the solid superacid. The results showed that the catalyst modified by radio-frequency plasma had a larger specific surface area, more surface oxygen vacancies, smaller particle size, and higher total acid content. The yield of tryptophan methyl ester reached a higher level of 94.5% (150 °C, 1 MPa, 2 h), catalyzed by the modified S2O82−/CeO2. This work verified the feasibility of plasma technology in the field of catalytic activity enhancement of solid superacid.

Preparation, characterization, and catalytic properties of SO42-/SnO2-Hangjin2#Clay solid superacid catalyst

A new sulfate oxide solid acid catalyst SO42-/SnO2-Hangjin2# clay was compounded with Hangjin2#clay, activated by sulfuric acid, as a carrier. In the catalysis of Xanthoceras sorbifolium Bunge, using the yield of oil and methanol synthesis of biodiesel as an index, the effect of SO42-/SnO2–Hangjin2#clay and the preparation conditions on the activity of solid acid were investigated. The variables included in the optimization process were concentration of Sn, impregnation sulfuric acid concentration, and calcination temperature. The optimal conditions were found as 0.4 M SnCl4, 3.0 M H2SO4 impregnation, and 350 °C calcination temperature. The catalyst was examined by scanning electron microscope, X-ray diffraction meter, Fourier transform infrared spectroscopy, surface area, and thermal weight analysis. The results showed that the introduction of Hangjin2#clay in the SO42--SnO2 solid acid catalyst improves its catalytic activity.

Novel S2O82−/Fe-ZrO2 solid superacid catalyst combined with O2-Ac2O for highly efficient catalytic nitration of 1-nitronaphthalene with NO2 to 1,5-dinitronaphthalene

Novel S2O82−/Fe-ZrO2 solid superacid catalyst combined with O2-Ac2O for highly efficient catalytic nitration of 1-nitronaphthalene with NO2 to 1,5-dinitronaphthalene

TiO2/SO42− Solid Superacid Catalyst Prepared by Recovered TiO2 from Waste SCR and Its Application in Transesterification of Ethyl Acetate with n-butanol

TiO2/SO42− Solid Superacid Catalyst Prepared by Recovered TiO2 from Waste SCR and Its Application in Transesterification of Ethyl Acetate with n-butanol

Sulfate-enhanced low-temperature activity of Pt/γ-Al2O3 for landfill gas deoxygen

Deoxygen is a crucial step for landfill gas (LFG) recycling and purification. Pt/γ-Al2O3 is the most active catalyst for LFG deoxygen via catalytic methane oxidation. It is challenging but significant to further improve the performance of this type of catalyst. In regard of homogeneous and heterogeneous activation of methane by superacids, here we demonstrate LFG deoxygen via catalytic methane oxidation using a solid superacid catalyst, Pt/SO42-/Al2O3, synthesized using pre-sulfated γ-Al2O3 support by impregnated with sulfuric acid. In comparison to Pt/γ-Al2O3, Pt/SO42-/Al2O3 catalysts exhibit exceptionally improved activity and minimum complete O2 conversion at a temperature of 264 ℃, a decrease of about 51 ℃. This value is superior to the state-of-the-art Pt-based deoxygen catalysts. Characterizations and theoretical calculations indicate that sulfation enhances the amount of acid sites on γ-Al2O3 support and induces electron deficiency of the supported Pt species (+0.28|e|), thus boosting the low-temperature activity. Furthermore, the Pt/SO42-/Al2O3 catalyst maintained its initial activity after six runs without any detectable coke deposition. This discovery offers simple and effective strategies to precisely design higher performance application-oriented Pt based deoxygen catalysts.

Catalytic Hydrothermal Liquefaction of Algae for Production of Bio-oil with Solid Superacid Catalyst SO42−/ZrO2

Catalytic Hydrothermal Liquefaction of Algae for Production of Bio-oil with Solid Superacid Catalyst SO42−/ZrO2

Sulfated tin oxide (SO4−2/SnO2): an efficient heterogeneous solid superacid catalyst for the facile synthesis of 2,3-dihydroquinazolin-4(1H)-ones

Sulfated tin oxide (SO4−2/SnO2): an efficient heterogeneous solid superacid catalyst for the facile synthesis of 2,3-dihydroquinazolin-4(1H)-ones

Zn(OAc)2.2H2O-Catalyzed C3-alkylation and O-alkylation of 4-Hydroxycoumarin derivatives

or the C3-alkylation and O-alkylation of 4-hydroxycoumarins with benzylic, allylic, and corresponding acetates, respectively, under neat conditions at 60 0C with high product yield, Zn(OAc)2.2H2O has been found to be an effective reusable solid superacid catalyst.

Synthesis of Bioactive 1,4‐DHPs Using Sulfated Tin Oxide as an Efficient Solid Superacid Catalyst

AbstractA novel synthetic approach is formulated for the synthesis of 1,4‐dihydropyridine derivatives via one pot condensation of aromatic aldehydes, β‐keto esters, and ammonium hydroxide by using prepared STO as solid super acid heterogenous catalyst in ethanol at reflux condition. The synthesized sulfated tin oxide is confirmed by FTIR, XRD, and SEM EDX. The surface area of the catalyst is measured using BET plots. The reactions are optimized for different solvents and loading of catalyst. The yields of all 1,4‐dihydropyridine derivatives are observed in the range of 80–92%. All the synthesized DHPs are authenticated by spectral analysis. The use of environmentally benign catalyst, good atom economy, low cost and ease of work up makes this exercise efficient and sustainable.

Deep oxidative desulfurization by sulfated alumina catalyst using ferrate (Fe(VI)) oxidant derived from scrap iron

A new efficient and environmentally friendly approach using ferrate (Fe (VI)) and SO42−/γ-Al2O3 solid super-acid catalyst was proposed for deep oxidative desulfurization in this work. Fe (VI) was produced via electrolyzing of scrap iron as an affordable industrial feed. The SO42−/γ-Al2O3 catalysts were synthesized by impregnation method and then characterized by XRF, XRD, BET, N2-adsorption desorption, SEM-EDX, FTIR, and NH3-TPD analysis. Relatively, impacts of reaction temperature and tetra butyl ammonium chloride (TBAC) as a mass transfer agent on dibenzothiophene (DBT) oxidation ability of ferrate, was positive; however, a very more significant promotion in the ferrate performance was achieved using the SO42−/γ-Al2O3 catalyst. It can be interpreted that acidic sites of this catalyst were beneficial for generating protonated ferrates as strong oxidant reagents. However, a high amount of sulfuric acid concentration during impregnation, was not in favor of its catalytic effects. It led to aggregation of sulfate over the catalyst surface which induced a low dispersion and decreased acidic sites. The best efficiency of DBT elimination by ferrate was found to be 91.7% at temperature of 40°C by 0.2g/mL of SO42−/γ-Al2O3 catalyst at 3wt.% S loading. Accumulations of impurities on the catalyst during ODS reaction caused a slight reduction in the catalyst performance after 4 consecutive recycling.

Novel WO3/SO42--ZrO2–TiO2 double bridge coordination catalyst hfor oxidation of cyclohexene

A solid super acid WO3/SO42--ZrO2–TiO2 catalyst was prepared with adjustable acidity via double bridge connection strategy for oxidation of cyclohexene (CHE) to adipic acid (AA). XRD, SEM and N2 adsorption-desorption isotherm indicated that WO3 was successfully decorated and was highly dispersed on SO42--ZrO2–TiO2 surface. An obvious stretching vibration peak (1125-1055 ​cm−1) in FT-IR illustrated that connection effect between SO42− and ZrO2–TiO2 was double bridge connection. NH3-TPD profile appeared a strong acid center peak (516 ​°C), while this center of solid super acid catalyst could reduce decomposition rate of H2O2 directly, and increase reaction time between CHE and H2O2 meanwhile. The marked catalytic performance was attributed to the synergistic effect between WO3 and SO42--ZrO2–TiO2. DFT calculation was employed to further analyze reaction process and system energy.

Direct liquefaction performance of sub-bituminous coal from Hefeng by solid super acids and pyrolysis kinetic analysis of the corresponding residue

Highly active, recyclable, and reusable supported super-acid catalyst is of great significance for improving coal liquefaction performance and liquefaction conditions and realizing comprehensive utilization of coal resources. Solid super-acid catalysts were prepared by impregnation method with trifluoromethanesulfonic acid (TFMSA) supported on different carriers (ZrO2, Al2O3, SiO2, and ZSM-5). Hefeng sub-bituminous coal (HFSB) was used as raw material to investigate the liquefaction effect of the catalysts. Composition, structure, acidity property of the catalysts were analyzed by EDS, XRD, and NH3-TPD methods, and direct coal liquefaction performance of the catalysts was performed, and TG-DTG characterization was used to evaluate the pyrolysis behavior of the liquefaction residue. Results showed that activity of the four supported solid super-acid catalysts was followed by TFMSA/ZrO2, TFMSA/ZSM-5, TFMSA/Al2O3, and TFMSA/SiO2, with coal conversions of 84.20 %, 78.40 %, 76.67 % and 73.23 %, and oil yields of 67.16 %, 62.53 %, 61.15 %, and 58.41 %, respectively. The Coast-Redfern method was used to analyze the pyrolysis kinetics of the four coal liquefaction residues (R-ZrO2, R-ZSM-5, R-Al2O3, and R-SiO2). Results presented that, in low temperature range (200−530 ℃), except R-SiO2, the pyrolysis process of residues conforms to the third-order reaction. And in high temperature range (530−850 ℃), the four-order reaction is more suitable for the four residues. The pyrolysis activation energy of R-ZrO2 is lower at low temperature region (16.822 kJ/mol), while R-Al2O3 presents lower activation energy at high temperature range (45.494 kJ/ mol).

Synthesis of bio-additive fuels from glycerol acetalization over a heterogeneous Ta/W mixed addenda heteropolyacid catalyst

The heterogeneous heteropolyacid-catalyzed acetalization of glycerol with acetone was investigated under solvent-free conditions. In this work, the calcined Ta/W mixed addenda heteropolyacid catalyst ({H20}-355) was employed as a solid acid catalyst and showed much higher activity than these soluble Keggin-type catalysts in the acetalization of glycerol with acetone due to its superacidity (H0 = −12.95). Meanwhile, it showed high stability in catalytic recycles and extended for acetalization of glycerol with the other aldehydes and ketones. Based on the catalyst characterization by X-ray diffraction (XRD), scanning electron microscopy (SEM), 31P NMR spectra, FT-IR spectra, pyridine-absorbed FT-IR, and Hammett acidity functions (H0) by UV–vis spectroscopy, it was found that the acidic strength of the Ta/W mixed addenda heteropolyacid was highly dependent on the contents of crystalline water that could be tuned by calcination temperature. Notably, the solid superacid catalyst {H20}-355 was swollen by acetone, exhibiting an interesting “pseudo-liquid” behavior, which served as a microreactor and facilitated the reaction. Furthermore, after the acetalization reaction of glycerol with furfural (98% yield of acetal) on {H20}-355 catalyst, the furan ring of the acetal products can be hydrogenated sequentially into dioxolane or dioxane with Pd/C catalyst under room temperature condition without the need of any isolation procedure.

Hydrodeoxygenation of Lignin‐Derived Monomers and Dimers over a Ru Supported Solid Super Acid Catalyst for Cycloalkane Production

AbstractThe monomers and dimers produced via lignin depolymerization are a promising alternative to transportation fuels after hydrodeoxygenation (HDO). However, these compounds contain numerous oxygen‐containing functional groups that are strongly bonded to aromatic rings. Therefore, the conventional HDO of lignin‐derived compounds faces serious problems of catalyst deactivation due to coke deposition and low hydrocarbon yields. A metal–solid super acid catalyst, i.e., Ru(SO42−)/ZrO2–CeO2, is synthesized, characterized, and evaluated for the HDO of various lignin‐derived monomers and dimers in a biphasic n‐dodecane/H2O system. A high cyclohexane yield of 98.5% is obtained by the HDO of phenol performed at 200 °C and 5 MPa. The “hydrated” configuration can be formed between the hydrogenation intermediates and H2O on the Ru sites. In addition, the anionic vacancies of ZrO2–CeO2 can be occupied by H− derived from the heterolytic cleavage of H2, leading to the formation of metal hydrides. The strong acidity of SO42−/ZrO2–CeO2 is beneficial for the subsequent deoxygenation of the hydrotreated products. In addition, the biphasic system can minimize the side reactions induced by the strong acidity of the catalyst. The catalytic system also exhibits a good catalytic performance for the HDO of other lignin‐derived monomers and dimers to produce cycloalkanes.

Preparation of Biscuit-Like SO2-₄/ZrO₂ Catalyst for Alkylation of o-Xylene with Styrene.

We present here a facile synthesis of SO2-₄/ZrO₂ solid superacid by impregnating the biscuit-like mesoporous ZrO₂ nanoparticles prepared by an emulsion combustion method directly into H₂SO₄ solution. The obtained solid acid catalyst was characterized by means of X-ray powder diffraction, transmission and scanning electron microscopy, thermogravimetry, Brunner-Emmet-Teller measurement, and infrared analysis. Its catalytic performance was examined by alkylation of o-xylene with styrene. The optimal catalytic formulation, obtained from the investigation of experimental conditions, was determined to be 5 wt% of catalyst loading with initial o-xylene/styrene molar ratio of 5 under reaction temperature at 120 °C for 120 min, achieving a 100% styrene conversion and a 93.3% 1-phenyl-1-xylyl ethane selectivity. The biscuit-like SO2-₄/ZrO₂ solid acid exhibited high catalytic activity and selectivity and excellent structural stability. This synthetic strategy for preparing the mesoporous SO2-₄ promoted ZrO₂ solid superacid catalyst is generalized and expected to be applied to other metal oxides.

Preparation and characterisation of ordered mesoporous SO42−/Al2O3 and its catalytic activity in the conversion of furfuryl alcohol to ethyl levulinate

A series of ordered mesoporous SO42−/Al2O3 (OMSA) solid super acid catalysts were prepared by evaporation-induced self-assembly (EISA) method, followed by sulphonation at different calcination temperatures (400°C-900 °C). The results of transmission electron microscopy (TEM) and small-angle X-ray diffraction (XRD) indicated that all of the OMSAs possessed ordered mesoporous structures. The N2-Brunauer–Emmett–Teller (N2-BET) results showed that the specific surface area of OMSAs could reach up to 160–380 m2/g, and the average pore diameters fall into the range between 8.6 and 9.8 nm. The temperature-programmed desorption of ammonia (NH3-TPD) characterisation proofed that the OMSAs contained super acid, and ammonia desorption by the super acid in the OMSA calcined at 600 °C reached 25.9 cm3/g STP. The pyridine adsorption infrared (Py-IR) indicated that all of the OMSAs consisted mainly of Lewis acids. The OMSA was used to catalyse furfuryl alcohol in the synthesis of ethyl levulinate (EL). The maximum yield (80.6%) was obtained in the reaction conducted at 200 °C for 3 h. The reusability of the catalyst was proofed after four times of reuse as its activity was maintained with a yield of 71.2%.

Application of Sulfated Tin (IV) Oxide Solid Superacid Catalyst to Partial Coupling Reaction of α-Pinene to Produce Less Viscous High-Density Fuel

Brønsted acid-catalyzed reactions of α-pinene have been studied because of their ability to produce various types of fragrance molecules. Beyond this application, dimeric hydrocarbon products produced from coupling reactions of α-pinene have been suggested as renewable high-density fuel molecules. In this context, this paper presents the application of a sulfated tin(IV) oxide catalyst for the partial coupling reaction of α-pinene from turpentine. Brønsted acid sites inherent in this solid superacid catalyst calcined at 550 °C successfully catalyzed the reaction, giving the largest yield of dimeric products (49.6%) at 120 °C over a reaction time of 4 h. Given that the low-temperature viscosity of the mentioned dimeric products is too high for their use as a fuel in transportation engines, lowering the viscosity is an important avenue of study. Therefore, our partial coupling reaction of α-pinene provides a possible solution as a considerable amount of the isomers of α-pinene still remained after the reaction, which reduces the low-temperature viscosity. On the basis of a comparison of the reaction products, a plausible mechanism for the reaction involving coinstantaneous isomerization and coupling reaction of α-pinene was elucidated.