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WOS: 000324103300007, The influence of poly(ethylene glycol) (PEG) and synthesis temperature in the synthesis of SBA-15-SO3H was investigated to evaluate the catalytic activity in the esterification of propionic acid with methanol. The catalysts were characterized by means of surface and structure analyses; X-ray diffraction, FT-IR, scanning electron microscopy, Thermo-gravimetric and N-2 adsorption/desorption techniques. It was found that, by the addition of PEG, the surface area and porosity of SBA-15-SO3H increased, while the structure and size of mesopores remained unchanged. Nitrogen sorption measurements indicate that PEG introduces additional pores into the pore walls of SBA-15-SO3H. Thus, a simple way of improving the porosity of mesoporous SBA-15-SO3H was presented that could enhance transport of substrates through the porous system and allow the generation of stable mesoporous replicas, important for catalytic applications and also beneficial for replication and nanocasting purposes., Commission of Scientific Research Projects of Uludag University [UAP(F)-2011/69], This work was supported by The Commission of Scientific Research Projects of Uludag University, Project number: UAP(F)-2011/69.

Novel approach was developed towards the synthesis of heterogeneous mesoporous B-SBA-15-SO3H acid catalysts. That is: B-SBA-15 materials were hydrothermally synthesized by using three different boron sources (boric acid, trisiopropylborate and potassium borohydride) and then post-synthetically functionalized with sulfonic acid to test their catalytic activity for the esterification of propionic acid with methanol. Mesoporous and amorphous character of the materials as well as the incorporation of the boron into the framework were verified by XRD, N-2-adsorption/desorption, ICP-OES, SEM and FT-IR techniques. All of the boron incorporated acid catalysts showed better activity than pure SBA-15-SO3H for methyl propionate synthesis. Combining the advantageous of hydrothermal synthesis and post functionalization, the obtained B-SBA-15-SO3H catalysts should present versatile catalytic properties in terms of both catalytic activity and reusability. Boron incorporation and post functionalization encourage the structural configuration, since the grafted catalytically active groups may experience similar environments and be isolated from each other.

The magnetic-poly(divinylbenzene-4-vinylpyridine) [m-poly(DVB-4VP)] microbeads (average diameter: 180–212 μm) were synthesized by copolymerizing of divinylbenzene (DVB) with 4-vinylpyridine (4VP) and by mixing this copolymer with Fe 3 O 4 nanoparticles. The resultant material was characterized by N 2 adsorption/desorption, ESR, elemental analysis, scanning electron microscope (SEM) and swelling studies. After functionalized with sulfonic acid, m-poly(DVB-4VP-SO 3 H) was characterized by FT-IR and TGA analysis. The results showed that both of Fe 3 O 4 and –SO 3 H are bonded to the polymer successfully. N 2 adsorption/desorption isotherms of synthesized samples had the hysteresis behaviour associated with mesoporous materials (pore diameter: 3.73 nm). Sulfonic acid functionalized mesoporous m-poly(DVB-4VP-SO 3 H) has been demonstrated to have higher reactivity than commercially available solid acid catalysts for the conversion of propionic acid to methyl ester. The apparent activation energy was found to be 38.5 kJ mol −1 for m-poly(DVB-4VP-20%SO 3 H). The catalyst showed negligible loss of activity after four repetitive cycles.

Esterifications of n-amyl alcohol with propionic acid catalyzed by macroporous (Amberlyst-15) and microporous (Dowex 50 W and Amberlite IR-120) polymeric ion-ex6hange resins were carried out between 333-348 K. When these catalysts were used as commercially available, Amberlyst-15 was observed to be the most effective catalyst with respect to rate constants, but after drying it became the less effective one. The reaction rate increased with increase in catalyst concentration and reaction temperature. Stirrer speed and different mesh sizes had virtually no effect on the rate under the experimental conditions. The effect of divinylbenzene content was examined for the micro porous resin Dowex 50 W, and the results showed that the propionic acid conversion decreased as the divinylbenzene content was increased. The rate data were correlated with a second-order homogeneous reaction model. The apparent activation energies, reaction enthalpies and entropy values were calculated for each catalyst. Reaction monitoring is simple and fast by volumetric method and the reproducibility of this method was the order of +/- %2.54.

Sulfonic acid functionalized poly(ethylene glycol dimethacrylate-1-vinyl-1,2,4-triazole), poly(EGDMA-VTAZ-SO 3 H), is evaluated in the esterification of lactic acid with methanol. From nitrogen physisorption data, high surface area (220 m 2 /g) and type IV isotherm are obtained. Conversion measurements indicate a stronger interaction of poly(EGDMA-VTAZ-20%SO 3 H) with water molecules than that occurring in poly(EGDMA-VTAZ-10%SO 3 H). Hence, the higher catalytic activity of poly(EGDMA-VTAZ-10%SO 3 H) is related to the more hydrophobic microenvironment of –SO 3 H sites, which reduces the acid site deactivation associated with adsorption of water generated during the reaction. Moreover, apparent activation energy is found to be 48.02 kJ mol −1 , which can be comparable with the literature values.

WOS: 000301320500021, PubMed ID: 22197058, Mesoporous silica SBA-15 has been synthesized and functionalized by one-step synthesis method to widen their various application possibilities. In this study, phenyltrimethoxysilane (PTMS), 3-mercapto-propyltrimethoxysilane (MPTMS) and trimethoxypropylsilane (TMPS) were used as silane precursors for the functionalization, and after treated with HCl solution, their catalytic activities were evaluated in the lactic acid-methanol esterification. The presence of anchoring of functional groups on SBA-15 was proved by XRD, FT-IR, BET surface area and pore size distributions. Good catalytic activity was observed especially for SBA-15-SO3H-MPTMS, and the catalytic activity order was determined as follows: SBA-15SO(3)H-MPTMS > SBA-15-TMPS > SBA-15-PTMS, which is directly associated with the surface area, pore size and pore volume. As compared with homogeneous catalyst, SBA-15-SO3H-MPTMS heterogeneous catalyst shows remarkable performance, such as separation, recovery and reusability

Sulfonic acid functionalized poly (ethylene glycol dimethacrylate-1-vinyl-1,2,4-triazole), poly (EGDMA–VTAZ–SO3H) (average diameter 1.0–1.5 mm), was found to be efficient solid acid catalyst for the esterification of methanol and propionic acid under heterogeneous reaction conditions. The pristine polymer, poly (EGDMA–VTAZ), was produced by suspension polymerization and then proton-conducting polymer was obtained by blending of poly (EGDMA–VTAZ) with different percentage of H2SO4 solutions. The protonation of aromatic heterocyclic rings was proved with Fourier-transform infrared spectroscopy (FT-IR). Thermo gravimetric (TG) analysis showed that the catalyst is thermally stable up to 573 K. The surface morphology of the catalyst was characterized by scanning electron microscopy (SEM). Poly (EGDMA–VTAZ–SO3H) beads can be regenerated and reused, so this provides a potential application. It has a rate constant which exceeds that of Amberlyst-15 by a factor of about four at 333 K. As for the reaction equilibrium constant (Ke), which is independent of temperature ranging from 318 to 343 K, was determined to be 3.16. The apparent activation energy was found to be 41.6 kJ mol−1 for poly (EGDMA–VTAZ–SO3H).

This paper describes the application of LFER in the form of Taft correlation to understand the mechanism of the esterification of propanoic acid with different alcohols over heterogeneous catalyst, Dowex 50Wx4. The rate constant (k1) in the rate equation decreases with change of alcohols in the order methanol, ethanol, n-propyl, n-butyl, n-pentyl, iso-butyl, iso-propyl and sec-butyl (2-buthanol). The reaction of propanoic acid with alcohols fits the Taft equation, log k1/kCH3= 1.0061 Es- 0.0012, which implies that the steric effect of the substituent governs that reaction and the mechanism is similar between the different alcohols. The experimental results were modelled according to a simple second-order model. It was found that the equilibrium constant of this reaction does not depend on the structure of the organic alcohols, and has for 333 K the value 4.04.

Summary Esterification of methyl alcohol with acetic acid catalysed by commercially available polymeric ion-exchange resins Amberlyst-15, Dowex 50W and Amberlite IR-120 was carried out in the temperature ranging between 323–338K. Mesh sizes and divinylbenzene contents had virtually no effect on the rate the data of which were correlated with a second-order homogeneous reaction. The samples were analysed with gas chromatography, refractometry and volumetry. The reproducibilities were the order of ±2.89%, ±5.07% and the order of ±6.58% respectively for the volumetric, chromatographic and refractometric methods.