Sulfonic Acid-functionalized SBA-15 Research Articles

Beta zeolite as an efficient catalyst for the synthesis of diphenolic acid (DPA) from renewable levulinic acid

The solvent-free production of diphenolic acid (DPA) from levulinic acid (LA) and phenol is studied using readily accessible commercial acid zeolites like Beta, ZSM-5 and USY. Acid zeolites are cost-effective catalysts, and they are herein benchmarked against the sulfonic acid resins Amberlyst-15 and Nafion®, and sulfonic acid-functionalized SBA-15 silicas. Beta zeolite with a moderate aluminum content (H-Beta 19, Si/Al=23) presents the best catalytic performance, owing to the right combination of the shape selectivity effect conferred by the BEA structure, and the adequate balance of acidity (Al content and speciation). The optimization of the reaction conditions is tackled by the response surface methodology using as optimization factors the temperature, the PhOH:LA molar ratio, and the catalyst loading. Thus, under the optimized reaction conditions (12 mmol LA, 140 ᵒC, 0.30 g catalyst loading, PhOH:LA = 6:1 mol), over 70% yield to DPA with LA conversion around 77% is obtained after 72 h. Despite the catalyst shows a progressive activity decay in successive uses because of fouling, removal of the formed organic deposits by calcination in air allows restoring the starting catalytic performance.

Sulfonic Mesostructured SBA-15 Silicas for the Solvent-Free Production of Bio-Jet Fuel Precursors via Aldol Dimerization of Levulinic Acid

Sulfonic acid-functionalized mesostructured silicas have been evaluated in the solvent-free aldol dimerization of biomass-derived levulinic acid into bio-jet fuel precursors. These compounds produce branched alkanes in a subsequent hydrodeoxygenation process, with suitable properties for being a renewable alternative to conventional fossil aviation fuels. The combination of activity and selectivity toward the desired condensation products achieved over sulfonic acid-functionalized SBA-15 materials is superior to those displayed by other commercial solid acid catalysts. Enhanced textural properties provided by the mesoporous SBA-15 support contribute to such improved catalytic performance. The strength and loading of the mesoporous silica-supported sulfonic acid moieties are also important factors affecting the catalytic performance of the materials. Reaction conditions (temperature, time, and catalyst loading) have been optimized for propylsulfonic acid-functionalized mesostructured silica (Pr-SBA-15) by means of a response surface methodology, leading to a maximum yield to levulinic acid dimerization products of 58.4% (145 °C, 0.15 g of catalyst, 24 h, no solvent). Under these reaction conditions, conversion of levulinic acid is 61.1%, indicating excellent selectivity toward bio-jet fuel precursors. A small catalytic activity decay has been detected in reutilization experiments, attributed to the formation of organic deposits onto the catalyst surface. A mild acid washing of the catalyst allowed a significant recovery of the initial activity.

Sulfonic Acid-Functionalized SBA-15 as Strong Cation-Exchange Sorbent for Solid-Phase Extraction of Atropine and Scopolamine in Gluten-Free Grains and Flours.

A novel method was developed and applied to the determination of the most representative tropane alkaloids (TAs), atropine and scopolamine, in gluten-free (GF) grains and flours by HPLC-MS/MS. Accordingly a suitable sample treatment procedure based on solid-liquid extraction (SLE) and followed by strong cation-exchange solid-phase extraction (SCX-SPE) was optimized. SBA-15 mesostructured silica functionalized with sulfonic acids was evaluated as sorbent. The proposed method was fully validated in sorghum flour showing good accuracy with recoveries in the range of 93–105%, good linearity (R2 > 0.999) and adequate precision (RSD < 20%). Low method quantification limits (MQL) were obtained (1.5 and 2.4 µg/kg for atropine and scopolamine, respectively) and no matrix effect was observed thanks to the extraction and clean-up protocol applied. The method was applied to 15 types of GF samples of pseudocereals (buckwheat, quinoa and amaranth), cereals (teff, corn and blue corn, sorghum and millet) and legumes (red and green lentil, chickpea and pea). Atropine was found above the MQL in eight of them, with values between 7 and 78 µg/kg, while scopolamine was only found in teff flour, its concentration being 28 µg/kg. The method developed is an interesting tool for determining TAs in a variety of samples of GF grains and flours.

Efficient Production of Medium-Chain Structured Phospholipids over Mesoporous Organosulfonic Acid-Functionalized SBA-15 Catalysts

It is highly desirable that efficient recoverable heterogeneous catalysts should be developed to replace the costly biocatalysts used in producing structured phospholipids (SPLs) with medium-chain fatty acids (MCFAs). Thus, mesoporous propyl and phenyl sulfonic acid-functionalized SBA-15 materials synthesized via surface modification methods were investigated for the soybean lecithin interesterification with methyl caprate or caprylate. The physicochemical properties of the synthesized solid acids were deeply studied by small-angle X-ray diffraction, scanning electron microscopy, transmission electron microscopy, Fourier transform infrared and pyridine adsorption, etc. to build the possible structure–performance relationships. The results revealed that amounts of organosulfonic acid groups were successfully grafted onto the SBA-15 support, and most of the surface acid sites contained in the as-prepared organic–inorganic hybrid samples were assigned as strong Brӧnsted acid sites. Notably, the functionalized SBA-15 materials exhibited promising catalytic behaviors in producing MCFA-enriched SPLs under mild conditions (40 °C, 6 h) when compared with commercial Amberlyst-15 and typical phospholipases or lipases, mostly due to their high surface area, ordered structure and adequate Brӧnsted acid sites. Besides, the as-prepared materials could be easily recycled five times without obvious deactivation. This work might shed light on alternative catalysts for SPL production instead of the costly enzymes.

Catalytic Applications of Large Pore Sulfonic Acid-Functionalized SBA-15 Mesoporous Silica for Esterification

Abstract We report the preparation of pore expanded and sulfonic acid functionalized mesoporous silica catalysts by using different kinds of swelling agents such as 1,3,5-trimethyl benzene (TMB), n-decane (D), n-tridecane (TD), and n-hexadecane (HD) at two different ratios of swelling agent/surfactant. Non-swelled mesoporous silica catalyst, SBA-15-SO3H, was also prepared for comparison. The performance of the sulfonic acid functionalized solid acid catalysts by using one-pot synthesis procedure was evaluated in terms of their catalytic activity in the esterification of propionic acid with methanol. The catalysts have been characterized by X-ray diffraction to investigate the phase transition between the hexagonally packed arrangement of cylindrical pores and mesocellular silica foams (MCF), and N2 adsorption/desorption technique in terms of pore size and distributions. It was concluded from the XRD and N2 adsorption/desorption analyses that hexagonally packed and cylindrical pore structure is maintained only for low ratio of swelling agent/surfactant and the increase of the dimension of a template micelle is accompanied by an increase in structural disruption, which was attributed to the phase transition from highly ordered hexagonal arrangement to mesocellular foam (MCF) phase with large nodded pore structures rather than cylindrical pores. Among the different swelling agents, TMB and D were found to be effective for the increase in pore diameter (up to 8 and 7.8 nm), whereas, TD and HD (6.6 nm) are effective to maintain the ordered X-ray diffraction patterns resulting mesoporous materials without giving enlargement of pore diameter in comparison with TMB and D. Pore expanded catalysts, SBA-15-SO3H-TMB-0.1 and SBA-15-SO3H-D-0.1, exhibit 68 and 43% enhancement in turnover frequency toward propionic acid methanol esterification, respectively, over non-swelled SBA-15-SO3H, despite possessing similar acid strengths. The increased activity especially for SBA-15-SO3H-TMB-0.1 and SBA-15-SO3H-D-0.1 likely reflects the accessibility to the active sulfonic acid sites as well as acidity.

Intraparticle Diffusional versus Site Effects on Reaction Pathways in Liquid-Phase Cross Aldol Reactions.

Chemo- and regioselectivity in a heterogeneously catalyzed cross aldol reaction were directed by tuning the nature of the sites, textural properties, and reaction conditions. Catalysts included sulfonic acid-functionalized resins or SBA-15 with varying particle size or pore diameter, H-BEA zeolites, and Sn-BEA zeotype; conditions were 25 °C to 170 °C in organic media. Benzaldehyde and 2-butanone yielded branched (reaction at -CH2 - of butanone) and linear (reaction at -CH3 ) addition and condensation products; and fission of the branched aldol led to β-methyl styrene and acetic acid. Strong acids promoted the dehydration step, and regioselectivity originated from preferred formation of the branched aldol. Both, resins and functionalized SBA-15 materials yielded predominantly the branched condensation product, unless particle morphology or temperature moved the reaction into the diffusion-limited regime, in which case more fission products were formed, corresponding to Wheeler Type II selectivity. For H-form zeolites, fission of the branched aldol competed with dehydration of the linear aldol, possibly because weaker acidity or steric restrictions prevented dehydration of the branched aldol.

Synthesis of polyoxymethylene dimethyl ethers catalyzed by sulfonic acid-functionalized mesoporous SBA-15

Sulfonic acid-functionalized mesoporous SBA-15 with different sulfur loading was synthesized and used to investigate the catalytic performance for PODEn synthesis.

Hydration of DCPD over sulfonic acid-functionalized SBA-15 catalyst

Sulfonic acid-functionalized SBA-15 materials (SA-SBA-15) with ordered channeling pores were synthesized by one-pot co-condensation and used to catalyze the hydration of dicyclopentadiene (DCPD). The target product, cydecanol (DCPD-OH) has been used as a modifier for polyester or alkyd resin. Propylsulfonic acid functionalized SBA-15 was found to be more efficient than the silica gel counterpart or arylsulfonic acid functionalized material in catalyzing DCPD hydration to yield DCPD-OH. The DCPD conversion and DCPD-OH yield increased with the decrease in H2O/DCPD ratio. Optimal DCPD conversion and DCPD-OH selectivity were obtained with the molar composition of DCPD:H2O:H+-catalyst=1:30:0.1.

Heterogeneous Synthesis of Indole-2-Carboxylic Esters Via Bischler Cyclization Under the Catalysis of Sulfonic Acid-Functionalized SBA-15 Silicas

Phenylsulfonic acid-functionalized SBA-15 silica was found to be an efficient heterogeneous acid catalyst in Bischler cyclization for the synthesis of indole-2-carboxylic esters. Under the optimized conditions, a wide range of substituted 4-nitrobenzyl 3-hydroxy-2-(N-methyl-N-arylamino)-2-enoates could be smoothly transformed to the corresponding 4-nitrobenzyl indole-2-carboxylates in excellent yields (87–99 %). Moreover, the catalyst could be conveniently recovered and reused at least four times without significant loss of catalytic activity.

ChemInform Abstract: Sulfonic Acid‐Functionalized Mesoporous Silica (SBA‐Pr‐SO3H) as Solid Acid Catalyst in Organic Reactions

AbstractReview: 251 refs.

Transformation of non-edible vegetable oils into biodiesel fuels catalyzed by unconventional sulfonic acid-functionalized SBA-15

A real understanding of intrinsic acidity and catalytic property of unconventional and sulfonic acid-functionalized SBA-15 platelet catalysts synthesized with the aid of highly solvated Zr4+ salts (shortly termed SA-SBA-15-p) for transesterification of non-edible vegetable oils into biodiesel fuel (BDF) was reported, in comparison with conventional SBA-15 catalyst (shortly termed SBA-15-conv), unconventional SBA-15 platelet catalyst (shortly termed SBA-15-p) and commercial sulfonic resins of Amberlyst-15 and SAC-13. Thorough characterizations and catalytic study revealed that the content of fatty acid methyl ester (FAME) as the main component of BDF was increased in the order of SBA-15-conv<SAC-13<SBA-15-p<Amberlyst-15<5-25SA-SBA-15-p, which correlated closely with the loading, distribution, strength of acidic sites. Among them, the unconventional 15SA-SBA-15-p catalyst with proper loadings of propylsulfonic groups (1.15mmolS−1g−1) and superficial Zr4+ clusters (0.66mmolg−1) as a mixed solid Bronsted and Lewis acid, which had differential heat of NH3 adsorption in the range of 90–125kJmol−1, gave highest FAME content with low concentrations of byproducts, such as glycerides and free fatty acid (FFA). In addition to high water and FFA tolerance levels, the used 15SA-SBA-15-p catalyst could be easily regenerated by ethanol extraction and its high activity was maintain. By contrast, the SBA-15-conv catalyst without any Lewis and Bronsted acids had almost no activity in BDF synthesis. The unconventional SBA-15-p catalyst with superficial Zr4+ clusters as a pure solid Lewis acid gave a moderate FAME content accompanying with a high concentration of unreactive glycerides. Commercial sulfonic resins of Amberlyst-15 and SAC-13 with strongly phenylsulfonic and Nafion sulfonic groups as pure solid Bronsted acids gave moderate FAME contents accompanying with high concentrations of unreactive glycerides and unwanted FFA byproducts. Furthermore, they were significantly deactivated by water, FFA and regeneration treatment due to the poison and leaching of sulfonic groups and the decomposition of thermally unstable framework.

Production of Jatropha biodiesel fuel over sulfonic acid-based solid acids

Sulfonic acid-functionalized platelet SBA-15 mesoporous silica with an acid capacity of 2.44mmol H(+) g-cat(-1) (shortly termed 15SA-SBA-15-p) was one-pot synthesized by co-condensation method. When applied as solid acid catalyst in synthesis of Jatropha biodiesel fuel (BDF), the 15SA-SBA-15-p catalyst showed higher activity and resistances to water and free fatty acid (FFA) than commercial sulfonic resins of Amberlyst-15 and SAC-13. For the continuous Jatropha BDF production, a steady 75-78wt% of fatty acid methyl ester (FAME) content was obtained over 15SA-SBA-15-p catalyst at 150°C for 75h, whereas the Amberlyst-15 and SAC-13 catalysts were quickly deactivated due to the decomposition of thermally unstable framework and serious leaching of sulfonic acids. More importantly, the quality, stability and cold flow characteristic of Jatropha BDF synthesized by 15SA-SBA-15-p catalyst were better than those synthesized by Amberlyst-15 and SAC-13 catalysts, making the blending with petro-diesel an easy task.

Sulfonic Acid-Functionalized Catalysts for the Valorization of Glycerol via Transesterification with Methyl Acetate

Sulfonic acid-functionalized mesostructured SBA-15 silicas have been demonstrated to be active for the catalytic transesterification of glycerol with methyl acetate to produce di- and triacetylglyc...

Synthesis and characterization of sulfonic acid-functionalized SBA-15 for adsorption of biomolecules

Sulfonic acid-functionalized SBA-15 mesoporous molecular sieve (SBA-15-SO 3H and SBA-15-po-SO 3H) were synthesized by two post-synthesis methods. The functionalized SBA-15 materials were characterized and used to investigate the adsorption behavior for proteins (bovine serum albumin and cytochrome c) and polypeptides (insulin and glucagon) in the static and dynamic processes. The adsorption conditions: including adsorption time, pH and ionic strength of sample solution were investigated in the static adsorption mode. Under optimal conditions, SBA-15-SO 3H and SBA-15-po-SO 3H had a maximum capacity for insulin of 430 and 451 mg/g and for glucagon of 1303 and 1094 mg/g, respectively. In addition, the two functionalized SBA-15 mesoporous materials showed selectively adsorption of proteins in the dynamic adsorption mode. Compared with SBA-15, the surface modification of SBA-15 was responsible for the selective adsorption of proteins and high adsorption capacity for some biomolecules. It indicated that the two functionalized materials could be used as adsorbents to immobilize or separate biomolecules.

Sulfonic acid-functionalized platelet SBA-15 materials as efficient catalysts for biodiesel synthesis

Sulfonic acid-functionalized platelet SBA-15 materials (SA-SBA-15-p) with ordered short mesochannels (150–350 nm) and acid capacities up to 1.2 mmol H+ g−1 were synthesized by one-pot co-condensation of tetraethyl orthosilicate (TEOS) and 3-mercaptopropyltrimethoxysilane (MPTMS) in the presence of appropriate amounts of Zr(IV) ions and H2O2. The SA-SBA-15-p materials were efficient catalysts for biodiesel synthesis through esterification of long chain carboxylic acids with methanol. The short-channel SA-SBA-15 materials showed higher catalytic activities than the conventional rod-like or fiber-like analogues, due to better molecular diffusion. Moreover, the used SA-SBA-15-p materials could be easily regenerated by ethanol extraction and the catalytic activities were retained after several recycle runs. In comparison to Amberlyst 15 resin, SA-SBA-15-p materials were superior considering the reaction rates per acid site because of the high accessibility of the sulfonic acid sites in the well-ordered large mesopores (ca. 7 nm) to the reactant molecules. Moreover, SA-SBA-15-p also showed better tolerance to small amounts of water in the reaction system than Amberlyst 15 resin.

Biodiesel production from crude palm oil using sulfonic acid-modified mesostructured catalysts

Biodiesel production from crude palm oil containing high percentage of free fatty acids over sulfonic acid-functionalized SBA-15 materials (propyl-SO 3H, arene-SO 3H, perfluoro-SO 3H) has been studied. The catalytic results showed that sulfonic acid-modified mesostructured materials were more active than conventional ion-exchange sulfonic resins (Amberlyst-36 and SAC-13) in the simultaneous esterification of free fatty acids and transesterification of triglycerides with methanol. The reusability of the catalysts was also investigated showing high stability for propyl-SO 3H and arene-SO 3H-modified mesostructured materials. In contrast, ionic-exchange sulfonic acid resins displayed low-conversion rates, being stronger this decay of activity in the second consecutive catalytic run. Interestingly, perfluorosulfonic acid-functionalized SBA-15 sample yielded a dramatic loss of activity indicating that Si–O–C bonding is not stable under the reaction conditions as compared with Si–C bond present in propyl-SO 3H and arene-SO 3H catalysts. Further functionalization of arene-SO 3H SBA-15 catalyst with hydrophobic trimethylsilyl groups enhanced its catalytic performance. This material was able to produce a yield to FAME of ca. 95% as determined by 1H NMR in 4 h of reaction with a moderate methanol to oil molar ratio (20:1), 140 °C and a catalyst concentration of 6 wt.% referred to starting oil.

Acidity of Sulfonic and Phosphonic Acid-Functionalized SBA-15 under Almost Water-Free Conditions

The hydrogen bond interaction of pyridine with sulfonic and phosphonic acid moieties at the surface of SBA-15 ordered mesoporous silica has been studied by a combination of solid-state NMR techniques. The composition of the materials is characterized by 29Si MAS NMR, the residual water content is inspected by 1H MAS NMR, and the hydrogen bond interactions are characterized by 15N CPMAS NMR at 130 K using pyridine-15N as a probe molecule. It is shown that (i) all acid moieties at the surface are accessible for pyridine; (ii) each sulfonic acid moiety interacts with one pyridine molecule; (iii) each phosphonic acid moiety can interact simultaneously with two pyridine molecules; (iv) for both materials the interaction of the acid moieties with the base results in proton transfer to pyridine. The observed proton-donating ability of the acid moieties depends on the presence of residual water. In contrast to nonfunctionalized SBA-15, the sulfonic acid-functionalized SBA-15 material contains about six water mole...

Mesoporous silica immobilized cobalt complex: An efficient catalyst for epoxides ring opening by aromatic amines under ambient conditions

Abstract Cobalt complex, CobpbH2Cl22H2O [where, bpbH2 = 1,2-bis(pyridine-2-carboxamido)benzene] immobilized onto sulfonic acid-functionalized SBA-15 molecular sieve (SBA-15-SO3-CobpbH2Cl22H2O) has been found to be an efficient catalyst for epoxide ring opening by amines. A variety of β-amino alcohols with nearly 100% regio- and stereo-selectivities were produced with excellent yields under ambient conditions and in an environmentally friendly manner.

Spectroscopic and catalytic properties of SBA-15 molecular sieves functionalized with acidic and basic moieties

SBA-15, grafted with Lewis acidic Ti 4+ ions and basic amines (imidazole, guanine or adenine) exhibited high catalytic activity in the cycloaddition of CO 2 to epoxides yielding selectively cyclic carbonate precursors of polycarbonates. In the second class of materials, the surface of SBA-15 was grafted with thiol or sulfonic acid functionalities. Mn(Salen)Cl was, then, covalently bound to these acidic groups. The resulting catalysts show enhanced chemo-, regio- and stereo-selective catalytic activity in the epoxidation of terpenes such as R-(+)-limonene, α-pinene and Δ-carene with molecular oxygen. The acid–base properties of these modified SBA-15 materials were investigated by temperature-programmed desorption and diffuse-reflectance infrared Fourier transform spectroscopy. Ammonia and pyridine were used as probe molecules for acidic sites and CO 2 for basic sites. Acidic Ti sites activated epoxides and the grafted basic amines activated CO 2. The simultaneous presence of both acidic and basic sites on amine/adenine-functionalized Ti-SBA-15 enabled synergistic enhancement in catalytic activity in the cycloaddition reaction of CO 2 to epoxides. When Mn(Salen)Cl was immobilized on thiol or sulfonic acid-functionalized SBA-15, the oxidation state of Mn decreased from +3 to +2. The organo-acidic functional groups (thiol or sulfonic acid) axially coordinated to Mn ions modified the electronic structure of Mn ions enhancing the activity and selectivity of Mn(Salen) complexes in aerial oxidation reactions.

Chemo-, regio- and stereo-selective aerial oxidation of limonene to the endo-1,2-epoxide over Mn(Salen)-sulfonated SBA-15

Mn(Salen) complexes immobilized on sulfonic acid-functionalized SBA-15 molecular sieves (SBA-15- pr-SO 3-Mn(Salen)) catalyze the Mukaiyama-type oxidation of R-(+)-limonene selectively to the 1,2-epoxide with molecular oxygen at 298 K (Salen = N, N-ethylenebis(salicylidenaminato)). The endo-diastereomer is formed with a diasteromeric excess of 39.8%. This catalyst exhibited higher catalytic activity than “neat” Mn(Salen) complexes directly supported on SBA-15 or zeolite-Y. A change in the oxidation state of Mn from +3 in the “neat” complex to +2 when immobilized on the sulfonated surface is a probable cause for the observed enhancement of catalytic activity. A part of the Mn complexes was leached out of the solid phase during the reaction.