Heterogeneous Acid Research Articles

Biodiesel Production from Waste Cooking Oil via β-Zeolite-Supported Sulfated Metal Oxide Catalyst Systems.

Waste cooking oil (WCO) is a readily available and cheap feedstock for biodiesel production. However, WCO contains high levels of free fatty acids (FFAs), which negatively impact the biodiesel yield if homogeneous catalysts are used. Heterogeneous solid acid catalysts are preferred for low-cost feedstocks because the catalysts are highly insensitive to high levels of FFA in the feedstock. Therefore, in the present study, we synthesized and evaluated different solid catalysts, pure β-zeolite, ZnO-β-zeolite, and SO42-/ZnO-β-zeolite for the production of biodiesel using WCO as feedstock. The synthesized catalysts were characterized by Fourier transform infrared spectroscopy (FTIR), pyridine-FTIR, N2 adsorption-desorption, X-ray diffraction, thermogravimetric analysis, and scanning electron microscopy, while the biodiesel product was analyzed using nuclear magnetic resonance (1H and 13C NMR) and gas chromatography-mass spectroscopy. The results revealed that the SO42-/ZnO-β-zeolite catalyst showed excellent catalytic performance for simultaneous transesterification and esterification of WCO, with a higher percentage conversion than the ZnO-β-zeolite and pure β-zeolite catalyst, due to the large pore size and high acidity. The SO42-/ZnO-β-zeolite catalyst exhibits 6.5 nm pore size, a total pore volume of 0.17 cm3/g, and high surface area of 250.26 m2/g. Experimental parameters such as catalyst loading, methanol:oil molar ratio, temperature, and reaction time were varied in order to establish the optimal parameters. The highest WCO conversion of 96.9% was obtained using the SO42-/ZnO-β-zeolite catalyst under an optimum reaction condition of 3.0 wt % catalyst loading, 200 °C reaction temperature, and 15:1 molar ratio of methanol to oil in 8 h reaction time. The WCO-derived biodiesel properties conform to the ASTM6751 standard specification. Our investigation of its kinetics revealed that the reaction follows a pseudo first-order kinetic model, with an activation energy (Ea) of 38.58 kJ/mol. Moreover, the stability and reusability of the catalysts were evaluated, and it was found that the SO42-/ZnO-β-zeolite catalyst exhibited good stability, giving a biodiesel conversion of over 80% after three synthesis cycles.

Hydrogel-based heterogeneous-acid-catalysts for converting carbohydrates into the platform chemical: 5-hydroxymethylfurfural

Background5-hydroxymethylfurfural (5-HMF) is a significant platform chemical with the potential to be converted into hydrocarbon biofuels. Herein, a facile and reusable catalyst was investigated to synthesize 5-HMF from monosaccharides in a green solvent medium following eight green chemistry principles. MethodsA hydrogel-based heterogeneous acid catalyst was synthesized through photoreaction to determine its ability to dehydrate fructose in the invert sugar syrup into 5-HMF. The main structure of the hydrogel catalyst was formed with polyethylene glycol diacrylate (PEGDA), and this backbone structure was modified by 3-sulfopropyl methacrylate potassium salt (3SMP) and further acidified by 3M HCl to form PEGDA-3SMP-H with 32.54 mmole/g of H+ amount on the catalyst. Significant findingsWith the PEGDA-3SMP-H catalyst, fructose conversion of 85.80% with a 5-HMF yield of 46.99% could be attained at 120°C for a 24 h reaction time in an aqueous medium with the co-solvent gamma-butyrolactone (GBL), which is considered a green solvent medium. PEGDA-3SMP-M (M=metal) hydrogel catalyst was synthesized using 8 different metal ions fixed on the 3SMP through ion exchange. The catalytic ability sequence for synthesized hydrogel catalysts followed H+> Cr3+> Cu2+> Al3+> Ni2+> Co2+ > Cu+> Fe3+> Fe2+ for 5-HMF formation. The 5-HMF yield was improved with consecutive cycles of using a regenerated PEGDA-3SMP-H catalyst. In the first cycle, the 5-HMF yield was 36.86%; in the second and third cycles, it was 39.39% and 41.49%, respectively. The prepared heterogeneous catalyst is preferred in terms of industrial applications owing to its facile synthesis, recyclability, stability, simple separation method, low equipment corrosion, and minimization of final product contamination with acid catalysts.

HnRNP Pathologies in Frontotemporal Lobar Degeneration

Frontotemporal dementia (FTD) is the second most common form of young-onset (<65 years) dementia. Clinically, it primarily manifests as a disorder of behavioural, executive, and/or language functions. Pathologically, frontotemporal lobar degeneration (FTLD) is the predominant cause of FTD. FTLD is a proteinopathy, and the main pathological proteins identified so far are tau, TAR DNA-binding protein 43 (TDP-43), and fused in sarcoma (FUS). As TDP-43 and FUS are members of the heterogeneous ribonucleic acid protein (hnRNP) family, many studies in recent years have expanded the research on the relationship between other hnRNPs and FTLD pathology. Indeed, these studies provide evidence for an association between hnRNP abnormalities and FTLD. In particular, several studies have shown that multiple hnRNPs may exhibit nuclear depletion and cytoplasmic mislocalisation within neurons in FTLD cases. However, due to the diversity and complex association of hnRNPs, most studies are still at the stage of histological discovery of different hnRNP abnormalities in FTLD. We herein review the latest studies relating hnRNPs to FTLD. Together, these studies outline an important role of multiple hnRNPs in the pathogenesis of FTLD and suggest that future research into FTLD should include the whole spectrum of this protein family.

Synthesis of acidic modified UiO‐66 by concentrated sulphation form and its application in the production of fatty acids ethyl esters

AbstractIn this article, UiO‐66 metal–organic frameworks containing structural modifications were synthesized and characterized to increase acidic surface behaviour for application in heterogeneous acid catalysis to produce fatty acid ethyl esters (FAEE) from degummed soybean oil. The solvothermal route synthesized UiO‐66, and the post‐synthesis acid modifications were done by sulphation reaction in strong acidic medium. The synthesized materials were characterized by physicochemical techniques such as X‐ray diffraction (XRD), C‐ray fluorescence (XRF), scanning electron microscopy (SEM), energy dispersive spectroscopy (EDS), Fourier transform infrared spectrometer (FTIR), and N2 physisorption, observing a strong structural modification of the original UiO‐66, but no signal of sulphated ZrO2 was presented. However, the acidic characteristics on the material's surface were increased. A central compound centred on face 23 experiments design was carried out to evaluate three essential reaction variables: temperature, time, and alcohol/oil ratio, obtaining an optimized fit for the UiO‐66‐S35 of temperature at 140°C, time of 3 h, and molar ratio of 16. The optimized statistical adjustment was applied in the reuse cycles assays in three catalyst cycles, reaching the maximum yield of 95% in FAEE, keeping the catalyst active at the end of 3 cycles.

Manufacturing, properties and selected applications of invert sugar syrups

Invert sugar syrups are mixtures of equal parts glucose and fructose, which are produced by hydrolysis of sucrose. They are characterised by a neutral sweet taste and do not lead to foam or floc formation in applications. Invert sugar syrups are microbiologically more stable than sucrose solutions due to their reduced water activity and the increased osmotic pressure. They are water-clear, odourless and allow easy and safe processing. These are used, for example, in the beverage, confectionery, tobacco and animal feed industries. In Germany alone, more than 10,000 t of invert sugar syrup are used annually for winter feeding of honeybees. The production takes place in batch or continuously running processes on the scale of the tonnes using homogeneous, heterogeneous acid or even enzymatic catalysis, whereby the molecular incorporation of water increases the amount of sugar, i.e., a mass increase of about 5% takes place. Many invert sugar syrup products can be produced, depending on the degree of inversion. One very important invert sugar syrup product in Germany in terms of quantity has a dry substance of 72.7% and an inversion degree of 66%.

The combined addition of citric and aromatic organic acids to an acid soil prolongs phosphorus availability

AbstractThe role of organic acids (both aliphatic and aromatic) in increasing soil P availability is well established. However, the effect of the combined addition of aliphatic and aromatic organic acids on soil P availability is not well studied, which is particularly important when assessing the efficacy of heterogeneous natural organic acid sources, such as compost and biochar, on soil P availability based on their total abundance of organic acid compounds. In this study, some naturally occurring aliphatic (oxalic and citric) and aromatic (benzoic, 4‐hydroxybenzoic, and protocatechuic) organic acids were incubated with an acidic soil for up to 110 days and their effect on soil P availability (Olsen extractable P) and phosphorus buffering capacity (PBC) were studied. The aliphatic and aromatic organic acids were added as individual and combined treatments. The experimental results suggested that aliphatic organic acids were more effective in increasing Olsen extractable P and decreasing soil PBC when compared to aromatic organic acids. The effect of citric acid on increasing soil P availability was prolonged when applied in combination with aromatic organic acids. The contrasting chemical nature and complementary effect between aliphatic and aromatic organic acids were suggested as the reason for this phenomenon.

Preparation and characterization of a novel efficient catalyst based on molybdenum oxide supported over graphene oxide for biodiesel synthesis

In this study, a new catalyst for heterogeneous acid based on molybdenum oxide (MoO3) supported over graphene oxide (GO) was synthesized and applied in simultaneous esterification-transesterification reactions using waste cooking oil (WCO) to obtain biodiesel. In the catalyst synthesis, the GO support was synthesized from graphite oxidation, followed by wet MoO3 impregnation. The MoO3/GO catalyst was characterized by Surface Acidity, Thermogravimetric Analysis (TG/DTG), X-ray Diffraction (XRD), Fourier Transformation Infrared Spectroscopy (FTIR), Scanning Electron Microscope (SEM) and Energy Dispersion X-ray Spectroscopy (EDS). The application of the catalyst in the conversion of WCO into biodiesel had as parameters reaction temperature (120.0–160.0 °C), reaction time (1.0–5.0 h), catalyst loading of (2.0–10.0%) and methanol:oil molar ratio of (25:1–45:1). The results of the catalytic tests showed the best condition of biodiesel synthesis was 140.0 °C reaction temperature, 5.0 h of reaction time, 6.0% catalyst loading and 35:1 methanol:oil molar ratio, leading to a biodiesel with ester content of 95.6%. The catalyst showed good recovery and excellent catalytic performance in the reuse study, producing biodiesel with ester content above 70.0% after 5 reaction cycles. Thus, this study shows a promising new catalyst of heterogeneous acid with high catalytic activity and applicability in the biodiesel synthesis process.

An Evaluation of Glycerol Acetalization with Benzaldehyde over a Ferromagnetic Heteropolyacid Catalyst

Tungstophosphoric acid (H3PW12O40) supported on silica-coated magnetite nanoparticles has been prepared and used as a heterogeneous acid catalyst (Fe3O4@SiO2@HPW) in the condensation of benzaldehyde (B) with glycerol (Gly) for the production of cyclic acetals. Physicochemical techniques, including scanning electron microscopy (SEM), transmission electron microscopy (TEM), Fourier-transform infrared spectrometry (FTIR), X-ray diffraction (XRD), thermogravimetric analysis (TGA), and N2 physisorption were used to characterize the prepared catalyst. The effect of glycerol/benzaldehyde molar ratio (1/1 to 1/1.2), temperature (80–120 °C), and catalyst amount (1–5%) on glycerol conversion and the selectivity in main reaction products: benzoic acid, 2-phenyl-1,3-dioxolan-4-yl)methanol, 2-Phenyl-1,3-dioxan-5-ol, 2-phenyl-1,3-dioxolane, and methyl 2-hydroxy-3-phenylpropanoate was studied to evaluate the catalytic activity of the prepared Fe3O4@SiO2@HPW catalyst. The optimization of these process parameters was conducted using Box–Behnken design (BBD). Using the BBD methodology, the optimal parameters (120 °C, 1:1.15 glycerol: benzaldehyde, 5% catalyst) were determined, for a glycerol conversion of and cyclic acetals yield of 85.95% and 78.36%, respectively. The catalyst also exhibits excellent activity for glycerol acetalization with other aromatic aldehydes such as cinnamaldehyde, p-methyl-benzaldehyde, p-hydroxy-benzaldehyde, and vanillin.

Investigation on the catalysis performance of metal-doped zeolites on ring-opening acidolysis reaction

Metal-incorporated zeolites as heterogeneous Lewis acid were applied in the ring-opening acidolysis of ethylene oxide with acrylic acid to prepare 2-hydroxyethyl acrylate (HEA). The catalysis characteristics, including Lewis acid strength and internal mass transfer resistance, were systematically investigated to facilitate the rational design of zeolite catalysts. Through modifying the Lewis acid strength of zeolites via different metals (Sn, Zr and Ti) incorporation and the internal mass transfer resistance of zeolites from the particle size, pore diameter or pore structure, it was found that the increased Lewis acidity can accelerate both the main and side reactions, resulting in the high activity but low selectivity of zeolite catalysts; the enhanced internal diffusion was the key to limiting subsequent cascade alcoholysis side reactions as well as the decline of catalytic performance. Based on these findings, Zr-containing zeolites featured with moderate Lewis acidity and uniform intracrystalline mesoporosity were designed and prepared, presenting excellent catalysis and recycling performance. These results demonstrated the great potential of the developed zeolite catalysts for the green synthesis of HEA as well as the similar ring-opening acidolysis of epoxides.

Oxidized pectin modified by sulfonic acid groups as a bio-derived solid acid for the synthesis of 1-amidoalkyl-2-naphthols

The widespread use of homogeneous acids faces enormous environmental problems due to their corrosive nature and recovery issues. On the other hand, developing heterogeneous catalysts with high acid content and benign nature is challenging. Thus, pectin was selected as a cost-effective and eco-friendly support material for preparing a solid acid with high Brønsted acidity. Therefore, pectin was first oxidized by NaIO4 to produce oxidized pectin (OPec) with aldehyde groups as additional sites to effectively anchor melamine (Mel) and chlorosulfonic acid (SA). After oxidation, the dialdehyde content (Ac) was found to be 53.2%. Then, the as-produced OPec-Mel-SA was compared with the catalyst based on non-oxidized pectin (Pec-Mel-SA) to ensure the positive effect of oxidation on the catalytic activity and morphology. Field emission scanning electron microscopy (FESEM) images revealed that OPec-Mel-SA is more ordered with fewer aggregated particles relative to Pec-Mel-SA. The results of energy dispersive X-Ray analysis (EDX) indicated a higher sulfur content for OPec-Mel-SA than Pec-Mel-SA. Moreover, BET (Brunauer-Emmet-Teller) analysis showed a higher SBET and pore volume for OPec-Mel-SA. The higher acidity of OPec-Mel-SA over Pec-Mel-SA nanoparticles was confirmed by titration and Hammet acidity function (H0) studies using H2SO4 as a benchmark. Accordingly, the OPec-Mel-SA nanoparticles presented a higher catalytic activity compared to Pec-Mel-SA for the three-component synthesis of 1-amidoalkyl-2-naphthols from aldehyde, 2-naphthol, and benzamide, under solvent-free conditions. As a bio-inspired and metal-free heterogeneous solid acid, the OPec-Mel-SA nanoparticles were reusable and highly stable for at least five runs.

Simple Synthetic Approach to N-(Pyridin-2-yl)imidates from Nitrostyrenes and 2-Aminopyridines via the N-(Pyridin-2-yl)iminonitriles as Intermediates.

A facile, green, synthetic protocol of several substituted N-(pyridin-2-yl)imidates from nitrostyrenes and 2-aminopyridines via the corresponding N-(pyridin-2-yl)iminonitriles as intermediates is reported. The reaction process involved the in situ formation of the corresponding α-iminontriles under heterogeneous Lewis acid catalysis in the presence of Al2O3. Subsequently, α-iminonitriles were selectively transformed into the desired N-(pyridin-2-yl)imidates under ambient conditions and in the presence of Cs2CO3 in alcoholic media. Under these conditions, 1,2- and 1,3-propanediols also led to the corresponding mono-substituted imidates at room temperature. The present synthetic protocol was also developed on one mmol scale, providing access to this important scaffold. A preliminary synthetic application of the present N-(pyridin-2-yl)imidates was carried out for their facile conversion into the N-heterocycles 2-(4-chlorophenyl)-4,5-dihydro-1H-imidazole and 2-(4-chlorophenyl)-1,4,5,6-tetrahydropyrimidine in the presence of the corresponding ethylenediamine and 1,3-diaminopropane.

Production of Alkyl Levulinates from Carbohydrate-Derived Chemical Intermediates Using Phosphotungstic Acid Supported on Humin-Derived Activated Carbon (PTA/HAC) as a Recyclable Heterogeneous Acid Catalyst

This work reports a straightforward and high-yielding synthesis of alkyl levulinates (ALs), a class of promising biofuel, renewable solvent, and chemical feedstock of renewable origin. ALs were prepared by the acid-catalyzed esterification of levulinic acid (LA) and by the alcoholysis of carbohydrate-derived chemical platforms, such as furfuryl alcohol (FAL) and α-angelica lactone (α-AGL). Phosphotungstic acid (PTA) was chosen as the solid acid catalyst for the transformation, which was heterogenized on humin-derived activated carbon (HAC) for superior recyclability. Using HAC as catalyst support expands the scope of valorizing humin, a complex furanic resin produced inevitably as a side product (often considered waste) during the acid-catalyzed hydrolysis/dehydration of sugars and polymeric carbohydrates. Under optimized conditions (150 °C, 7 h, 25 wt.% of 20%PTA/HAC-600 catalyst), ethyl levulinate (EL) was obtained in an 85% isolated yield starting from FAL. Using the general synthetic protocol, EL was isolated in 88% and 84% yields from LA and α-AGL, respectively. The 20%PTA/HAC-600 catalyst was successfully recovered from the reaction mixture and recycled for five cycles. A marginal loss in the yield of ALs was observed in consecutive catalytic cycles due to partial leaching of PTA from the HAC support.

Macroscopic shaping of coordination polymer via crystal–glass phase transformation as monolithic catalyst for efficient catalyst recovery

To circumvent the difficult processability and recovery of catalytic materials in powder form, we herein report macroscopic shaping of 1D coordination polymer consisting of zinc ions, orthophosphate, and benzimidazole, namely ZnPBIm, motivated by the crystal–glass phase transformation. Glassy ZnPBIm monoliths with different shapes and sizes were prepared via a melt-quench process without using the secondary component. As a heterogeneous acid catalyst, the glassy ZnPBIm monoliths contribute to the esterification of levulinic acid with ethanol at 100 °C with recyclability for at least three consecutive cycles, and over 90% of catalyst mass was recovered. The macroscopic shape of the monoliths was retained after 24 h of reaction. Surface crystallization of glassy ZnPBIm was induced by the presence of water during esterification, and the glass domain serves as a macroscopic support for the crystallized domain.

A novel heterogeneous acid–base nano-catalyst designed based on graphene oxide for synthesis of spiro-indoline-pyranochromene derivatives

Nano graphene oxide/3-aminopyridine has been introduced as a new, efficient and robust heterogeneous organic catalyst for synthesis of spiro-indoline-pyranochromene derivatives. Nano graphene oxide/3-aminopyridine was provided in an easy and green way from GO. Firstly, graphene oxide (GO) was synthesized and then 3-aminopyridine was immobilized with covalent bonds on its surface as a nitrogenous organic compound, in this step we didn’t use any organic or toxic substance. This bonding was easily performed due to the presence and reactivity of the epoxy groups in the GO structure. Because of its vast-surface nano-layers, GO could be effective in appropriate dispersion of 3-aminopyridine on its surface and increasing the catalyst performance. The new catalyst was analysed using different microscopic and spectroscopic techniques such as Fourier-transform infrared (FT-IR), field emission scanning electron microscope (SEM), energy-dispersive X-ray spectroscopy (EDS), X-ray diffraction (XRD) and thermogravimetric analysis (TGA). Our results showed that the distance between GO plates was increased in the presence of the modifying agent. This is due to the placement of the organic compound between the GO sheets. Finally, the ability of our new nano-catalyst in the synthesis of some spiro-indoline-pyranochromene and dihydropyranochromene derivatives was evaluated and acceptable results were obtained. Eight analogous of spiro-indoline-pyranochromene (4a-4 h) were synthesized in high yields and characterized. Using 3-aminopyridine as an organic and efficient catalyst, its stabilization by a simple method on GO, recycling of the catalyst up to 7 times and obtaining a highly pure product were the points that made the present work more attractive.Graphical

Biodiesel Production through the Transesterification of Waste Cooking Oil over Typical Heterogeneous Base or Acid Catalysts

For the production of biodiesel from waste cooking oil with an acid value of 1.86 mg KOH/g, five heterogeneous catalysts—Ba(OH)2, CaO, MgO, ZnO, and AlCl3—were employed. To optimize the reaction parameters of each catalyst, the influence of crucial process variables, such as catalyst loading, methanol-to-oil ratio, and reaction duration, was investigated. In addition, the effect of acetone as a cosolvent toward the progress of biodiesel production and the reusability of the heterogeneous catalysts were also examined, and the data were statistically evaluated with a 95% confidence level. Ba(OH)2 performed exceptionally well, with a 92 wt.% biodiesel yield, followed by CaO with an 84 wt.% yield. However, none of the results for MgO, ZnO, or AlCl3 were adequate. In addition, regardless of the type of catalyst utilized, adding 20 vol.% acetone to the biodiesel manufacturing process led to an increase in output. Furthermore, every heterogeneous catalyst was reusable, but only Ba(OH)2 and CaO produced a significant yield until the third cycle. The other catalysts did not produce yields of any significance.

Cascade Catalysis for the Hydrogenation of Carbon Dioxide to Methyl Formate Using a Molecular Ru–Phosphine Complex and the Metal–Organic Framework UiO-66 as Heterogeneous Acid

The direct incorporation of CO2 into value-added base chemicals, such as methyl formate (MF), is a grand challenge to chemical science. In this work, a base-free cascade catalysis system is described to effectively convert carbon dioxide into MF. In the initial step a well-established Ru complex (i.e., RuHCl(dppm)2, dppm = 1,1-bis(diphenylphosphino)methane) is able to hydrogenate CO2 into formic acid, which subsequently undergoes a heterogeneous acid catalyzed esterification with methanol to selectively produce MF. Here, the small pore MOF UiO-66, a Zr-terephthalate, is identified as a promising heterogeneous acid and its Zr6 cluster is modified to understand the effect of Brønsted/Lewis acidity on the performance. Moreover, this heterogeneous acid catalyst could be reused for multiple times without significantly losing its activity.

An effective and eco‐friendly sonochemical multicomponent synthesis of trisubstituted imidazoles via modified silica‐coated cobalt ferrite nanoparticles by tungstic acid

This research is providing a method for the synthesis of 2,4,5‐trisubstituted imidazole derivatives based on pursuing the green chemistry principles. Therefore, a one‐pot multicomponent cyclocondensation reaction through aldehyde interaction with ammonium acetate and 1,2‐diketone was carried out in EtOH:H2O solvent under ultrasound irradiation. This protocol was utilized as an eco‐effective synthetic route by applying CoFe2O4@SiO2@(‐CH2)3OWO3H nanocomposite as a nanocatalyst. The stabilized tungstic acid on 3‐chloropropyl anchored to SiO2‐coated CoFe2O4 magnetic nanoparticles was designed, prepared, and applied as a recyclable heterogeneous acid catalyst to attain high product yields and short reaction times. The structure of nanocatalyst was confirmed by using Fourier transform infrared spectroscopy (FT‐IR), X‐ray diffraction (XRD), field emission scanning electron microscopy (FE‐SEM), energy dispersive spectroscopy (EDS), vibrating sample magnetometer (VSM), thermogravimetric analysis (TGA), and Brunauer–Emmett–Teller (BET) techniques, and the obtained organic derivatives were examined through melting point, FT‐IR, and 1H NMR analyses.

Techno-Economic Analysis of Interesterification for Biodiesel Production

Interesterification is an alternative reaction for the production of fatty acid alkyl esters from triglycerides, a pathway that avoids unwanted byproduct formation. In this work, the technical and economic feasibility of soybean oil interesterification for biodiesel production on a commercial scale is assessed. The interesterification kinetics of triolein (model soybean oil) and methyl acetate using ferric sulfate as a heterogeneous acid catalyst are experimentally determined, and the results are used to parameterize a kinetic model. Process simulations are developed using Aspen Plus V11 for acid and alkaline heterogeneously catalyzed interesterification plants at varying production rates and methyl acetate-to-oil molar ratios (MAOMRs). At all production capacities and MAOMRs tested, the acid-catalyzed processes are found to have more favorable process energy consumption and profitability metrics compared to the alkaline-catalyzed processes. The most economically promising design operates at a production capacity of 30,000 metric tons/yr and an MAOMR of 10:1 with a net present value of $34 million after 20 years and a biodiesel breakeven price of $0.78/kg. This case has a process energy demand of 35,000 MJ/h, resulting in a process energy ratio of 0.25. This work indicates that interesterification shows commercial viability and is a promising alternative to transesterification for biodiesel production.

Aquivion® PFSA-based spray-freeze dried composite materials with SiO2 and TiO2 as hybrid catalysts for the gas phase dehydration of ethanol to ethylene in mild conditions.

Aquivion PFSA resin, a perfluorinated ion-exchange polymer, has been used as a heterogeneous strong acid catalyst for a range of reactions; however, the activity of this material is limited due to the extremely low surface area of the polymer. In this paper we described the one-step synthesis of Aquivion® PFSA-based hybrid materials using heterocoagulation and spray-freeze-drying of sols containing the precursor of the active phases. The intimated encapsulation of different nano-oxides, such as TiO2 and SiO2 in the superacid resin matrix was easily obtained using this technique and compared with similar catalysts prepared by the impregnation conventional route. The approach led to the preparation of porous micro-granules characterised by a high homogeneity in the phase distribution and high surface area. The prepared materials were active and selective for the gas phase dehydration of ethanol to ethylene in mild conditions. The increase of the porosity improved the activity of the composites, compared to the pure Aquivion® PFSA, and allowed to reduce the amount of the superacid resin. Moreover, the type of encapsulated oxide, TiO2 or SiO2, modified the improved performance of the catalysts, having TiO2 the higher efficiency for ethanol conversion and selectivity in ethylene at very low temperature.

KIT-5 Structural and Textural Changes in Response to Different Methods of Functionalization with Sulfonic Groups.

In this project, KIT-5 materials were effectively functionalized with sulfonic groups introduced by grafting or the co-condensation method and tested as heterogeneous solid acid catalyst. A co-condensation procedure leading to the stable, -SO3H functionalized KIT-5 materials was successfully established. Moreover, the influence of both synthesis methods on the structural and textural parameters, as well as surface chemistry, morphology, and catalytic activity of -SO3H/KIT-5 materials was thoroughly investigated. The syntheses with 3-mepkaptopropyltrimethoxysilane (MPTMS) acting as a modifying agent resulted in samples in which functional groups were introduced into the structure and/or onto the mesoporous silica surface. The oxidation stage of -SH to -SO3H groups was carried out under mild conditions, using a "green" oxidant (H2O2). The application of different functionalization techniques and the introduction of different amounts of modifying agent allowed for an evaluation of the influence of these parameters on the ordering of the mesoporous structure of KIT-5 materials. The applied methods of assessment of the physicochemical parameters (XRD, low-temperature N2 sorption, TEM) showed that, especially when the co-condensation method was applied, as the number of functional groups increased, the ordering of structure characteristic of KIT-5 decreased. On the other hand, the samples modified by grafting had a stable structure, regardless of the amount of introduced MPTMS. Test reactions carried out on the basis of Friedel-Crafts alkylation process showed that the synthesized materials can be considered promising acid catalysts in heterogeneous catalysis reactions.