Separable Solid Acid Research Articles

High-efficiency synthesis of 5-hydroxymethylfurfural and 2,5-diformylfuran from fructose over magnetic separable catalysts

In this work, a sulfonic acid-functionalized magnetic separable solid acid (Fe3O4@SiO2-SO3H) was synthesized, characterized, and tested for fructose conversion to 5-hydroxymethylfurfural (HMF). Results indicated that the prepared catalyst had a good efficacy for fructose dehydration to HMF due to its larger specific surface area, appropriate acid amount and homogeneous acid distribution. The maximum HMF yield of this work was 96.1 mol%. It was obtained at 120 °C for 1.5 h with 100 mol% fructose conversion. More importantly, the produced HMF could be further in-situ oxidized into 2,5-diformylfuran (DFF) after the replacing of the Fe3O4@SiO2-SO3H with a ZnFeRuO4 catalyst, and the highest DFF yield of 90.2 mol% (based on initial fructose) was obtained after reaction another 8.5 h. The production of DFF from fructose through the above two consecutive steps avoids the intermediate HMF separation, which saves time and energy. In addition, both Fe3O4@SiO2-SO3H and ZnFeRuO4 catalysts exhibited satisfied stability in the recycling experiments, which can be reused at least for five times with the HMF and DFF yield loss<5.3% and 3.3%, respectively. Finally, the plausible reaction mechanisms for fructose conversion to HMF or DFF over Fe3O4@SiO2-SO3H or/and ZnFeRuO4 catalysts were also proposed in this work.

Fabrication of new magnetite based sulfonic-phosphotungstic dual-acid catalyst for catalytic acetalization of benzaldehyde with ethylene glycol

A new sulfonic-phosphotungstic dual-acid hybrid catalyst based on silica coated magnetite nanoparticles (SCMNPs) containing two types of Bronsted acidic sites i.e. sulfonic acid (–SO3H) and phosphotungstic acid (HPW) groups, was prepared with chemical and electrostatic interactions of these acidic functional moieties with piperazine-grafted propylsilyl spacer groups. Physicochemical techniques including FT-IR spectroscopy, elemental analysis and inductively coupled plasma-optical emission spectroscopy (ICP-OES), vibrating sample magnetometry (VSM), X-ray diffraction (XRD), energy dispersive X-ray (EDX) analysis, scanning electron microscopy (SEM), and transmission electron microscopy (TEM) were used to characterize the prepared solid acid catalyst. Acetalization reaction between benzaldehyde and ethylene glycol was done to investigate the catalytic activity of prepared catalyst and 97% conversion toward acetal production was reached in short reaction time. The lower conversion was also achieved for the same catalyst without any HPW species, demonstrated the positive role of the second acidic sites on progression of this reaction. In addition, this easily separable solid acid catalyst reused for four runs with no observable loss in benzaldehyde conversion.

분리 가능한 고체 산촉매를 통한 신갈나무 내 헤미셀룰로오스 분해 연구

분리 가능한 고체 산촉매를 통한 신갈나무 내 헤미셀룰로오스 분해 연구

분리 가능한 silica 계열 고체 산촉매를 통한 목질계 바이오매스의 가수분해 연구

분리 가능한 silica 계열 고체 산촉매를 통한 목질계 바이오매스의 가수분해 연구

Octyl and propylsulfonic acid co-fixed Fe3O4@SiO2 as a magnetically separable, highly active and reusable solid acid catalyst in water

Modifications of propylsulfonic acid-fixed Fe3O4@SiO2 with three organosilanes (C2, C8, and phenyl) were investigated to develop a magnetically separable solid acid catalyst active for hydrolysis of ethyl acetate in excess water. Among the organosilanes, triethoxy(octyl)silane was the best modifier for improvement in catalytic activity, with activity of approximately twice that of the unmodified catalyst. The catalytic activity was comparable to those of Cs2.5H0.5PW12O40 and H3PW12O40 anchored on hydrophobic SBA-15 if compared per acid sites, though the acid strength of sulfonic acid was much weaker than that of H3PW12O40. High hydrophobicity over the surface and around the acid sites created by the octyl group was responsible for the high catalytic activity and the high stability in water. In addition to the improvement in catalytic activity, modification with the octyl group provided high stability for repeated uses of the catalyst in the reaction and there was little decrease in activity over at least four reuses. The catalyst was easily separated from the reaction solution by application of an external magnetic field.

RETRACTED: Graphene supported magnetically separable solid acid catalyst for the single step conversion of waste cooking oil to biodiesel

Abstract Conversion of vegetable oils to biodiesel typically involves the use of highly corrosive acids or bases as catalysts. Solid catalysts can be used to avoid the use of corrosive mineral acids/bases and they have the possibility of reuse. Development of a highly active solid acid based on graphene oxide that can be recovered using magnetic seperation and reactivated by simple washing is reported here. High catalytic activity of the iron oxide supported on sulphonated graphene oxide (GO-Fe 2 O 3 SO 3 H) was established for the esterification of oleic acid as well as single step biodiesel production from waste cooking oil (WCO) using ethanol. Catalytic activity of GO-Fe 2 O 3 SO 3 H was higher than GO, GO-SO 3 H as well as GO-Fe 2 O 3 . Thorough characterization of the prepared catalysts was done using a number of spectroscopic, thermal and microscopic techniques. Complete conversion of oleic acid to its ethyl ester could be done in 4 h, at 100 °C using 5 (% by wt.) of the catalyst. Moreover, single step conversion of WCO to biodiesel could be achieved at 90 °C in 6 h using 5 wt % of the catalyst. The catalyst was reclaimed by magnetic separation and reused upto 7 cycles without any significant loss of activity.

Fe 3 O 4 @SiO 2 ‐SO 3 H nanocomposites: an efficient magnetically separable solid acid catalysts for esterification reaction

Fe3O4@SiO2-SO3H nanocomposites were successfully synthesised as the efficient magnetically separable solid acid catalysts for an esterification reaction. The resultant catalysts were characterised by X-ray diffraction, scanning electron microscopy, transmission electron microscopy, Fourier-transform infrared spectroscopy, vibrating sample magnetometer (VSM), and nitrogen physical adsorption analyses [Brunauer–Emmett–Teller (BET) theory]. The catalytic activities of as-prepared Fe3O4@SiO2-SO3H nanocomposites were also investigated for the esterification of n-butyl acetate and isoamyl acetate. The acid esterification rate was confirmed by gas chromatography. The results showed that the Fe3O4@SiO2-SO3H nanocomposites can be as candidate cataysts for the concentrated H2SO4 for the esterification reaction of n-butyl alcohol or isoamyl alcohol. More importantly, the magnetic catalysts can be easily separated from the reaction system by a magnetic bar and reused at least three recycles without significant degradation of their activities.

Magnetic nanoparticles-supported tungstosilicic acid: as an efficient magnetically separable solid acid for the synthesis of benzoazoles in water

The magnetic nanoparticles-supported tungstosilicic acid (TSAMNP) was found to be a highly efficient solid acid for the synthesis of benzoazoles in water. TSAMNP catalyst was achieved by the immobilization of tungstosilicic acid [H4(W12SiO40)] species on the silica core–shell magnetic nanoparticles (Fe3O4@SiO2). A variety of aldehydes were successfully condensed with 1,2-diaminobenzene, 2-aminophenol and 2-aminothiophenol in water as a green solvent to synthesize benzoazoles in good-to-excellent yields. TSAMNP catalyst was easily separated from the reaction mixture and reused several times without any loss of efficiency.

Acid monolayer functionalized iron oxide nanoparticles as catalysts for carbohydrate hydrolysis

Superparamagnetic iron oxide nanoparticles were functionalized with a quasi-monolayer of 11-sulfoundecanoic acid and 10-phosphono-1-decanesulfonic acid ligands to create separable solid acid catalysts. The ligands are bound through carboxylate or phosphonate bonds to the magnetite core. The ligand-core bonding surface is separated by a hydrocarbon linker from an outer surface with exposed sulfonic acid groups. The more tightly packed monolayer of the phosphonate ligand corresponded to a higher sulfonic acid loading by weight, a reduced agglomeration of particles, a greater tendency to remain suspended in solution in the presence of an external magnetic field, and a higher catalytic activity per sulfonic acid group. The particles were characterized by thermogravimetric analysis (TGA), transmission electron microscopy (TEM), potentiometric titration, diffuse reflectance infrared Fourier transform spectroscopy (DRIFTS), inductively coupled plasma optical emission spectrometry (ICP-OES), and dynamic light scattering (DLS). In sucrose catalysis reactions, the phosphonic–sulfonic nanoparticles (PSNPs) were seen to be incompletely recovered by an external magnetic field, while the carboxylic–sulfonic nanoparticles (CSNPs) showed a trend of increasing activity over the first four recycle runs. The activity of the acid-functionalized nanoparticles was compared to the traditional solid acid catalyst Amberlyst-15 for the hydrolysis of starch in aqueous solution. Catalytic activity for starch hydrolysis was in the order PSNPs > CSNPs > Amberlyst-15. Monolayer acid functionalization of iron oxides presents a novel strategy for the development of recyclable solid acid catalysts.

Advances in liquid-phase organic reactions using heteropolyacid and clay

Zinc ion-exchanged smectite clays, particularly Fe-containing nontronite clays, were effectively applied as insoluble, readily recoverable solid acid catalysts to liquid-phase Friedel-Crafts reactions. Mesoporous montmorillonite K10 and FSM-16 catalyzed the condensation of aldehydes and pyrroles to give porphyrin precursors more efficiently than the conventional homogeneous acids such as BF 3 etherate. 12-Tungstophosphoric acid could be included in silica matrix by means of sol-gel technique that involves hydrolysis of ethyl orthosilicate to give an insoluble and easily separable solid acid catalyst. The silica-included heteropolyacid was thermally more stable than an ion-exchange resin catalyst such as Amberlyst-15, and catalyzed the hydrolysis of ethyl acetate in the liquid-phase more efficiently than the resin, H-ZSM-5 and even more than aqueous heteropolyacid.

Recent advances in liquid-phase organic reactions using heteropolyacid and clay

ecent advances in liquid-phase organic reactions over solid acids are described based on the catalyses of acidic clays and silica-included heteropoly compounds. Zinc ion-exchanged smectite clays, particularly nontronite clays, were effectively applied as insoluble, readily recoverable solid acid catalysts to liquid-phase Friedel-Crafts reactions. Montmorillonite K10 catalyzes the synthesis of alkylporphyrin derivatives from aliphatic aldehydes and pyrroles more efficiently than the conventional homogeneous acids such as BF3 etherate. 12-Tungstophosphoric acid and its acidic Cs salt could be included in a silica matrix by means of sol-gel technique involving hydrolysis of ethyl orthosilicate forming insoluble and easily separable solid acid catalysts. These silica-included heteropoly compounds were thermally more stable than an ion-exchange resin catalyst such as Amberlyst-15, and catalyzed the hydrolysis of ethyl acetate in the liquid phase more efficiently than the resin, H-ZSM-5 and even than aqueous heteropolyacid.

Silica-included heteropoly compounds as solid acid catalysts

12-Tungstophosphoric acid (H 3PW 12O 40) and its acidic cesium salt (Cs 2.5H 0.5PW 12O 40), which readily dissolve or disperse as a colloid in water or in highly polar organic media, could be immobilized into a silica matrix by means of a sol-gel technique. This involves the hydrolysis of ethyl orthosilicate to afford insoluble and easily separable solid acid catalysts. The silica-included heteropoly compounds thus obtained were porous materials with mesopores and large surface areas, and were thermally more stable than the acidic ion-exchange resin Amberlyst-15. They effectively catalyzed the hydrolysis of ethyl acetate in the liquid phase owing to their strong acidity. Their turnover frequencies were larger than those of Amberlyst-15 and H-ZSM-5. H 3PW 12O 40, when included in a silica matrix, showed higher catalytic activity than as an aqueous solution.