123-86-4Relevant articles and documents
Characterization of HNbMoO6, HNbWO6 and HTiNbO 5 as solid acids and their catalytic properties for esterification reaction
He,Li,Tang,Yang,Li,Li,Li
, p. 145 - 152 (2012)
HTiNbO5, HNbMoO6·H2O and HNbWO 6·1.5H2O were prepared by proton-exchange of the precursors KTiNbO5, LiNbMoO6 and LiNbWO6, respectively, which were synthesized by a solid-state reaction method. The morphology and the micro-structure were characterized by means of scanning electron microscope (SEM), transmission electron microscope (TEM), powder X-ray diffraction (XRD) and Fourier-transform infrared spectroscopy (FT-IR). NH 3 temperature-programmed desorption (NH3-TPD) was used to measure the acidic properties of the samples. The Sanderson electronegativity and Kataoka′s bond strength theory were also applied to investigate the acid properties of the as-prepared samples. Finally, their catalytic activities were evaluated through catalyzing the liquid-phase esterification reaction of acetic acid and n-butanol to form n-butyl acetate. It has been revealed that H+ ions existed in different forms and interaction modes with MO bond in the solid acids. The acid strength for these as-prepared samples follows the order HNbMoO6·H2O > HNbWO6·1. 5H2O > HTiNbO5. In this work, HNbMoO 6·H2O presents an excellent catalytic activity for the esterification reaction, while HNbWO6·1.5H2O and HTiNbO5 have little catalytic activity. The result suggested that the catalytic activity of the layered solid acid for the esterification reaction was mainly controlled by gallery height.
A facile synthesis of vanadium phosphate: An efficient catalyst for solvent free esterification of acetic acid
Parida,Behera, Gobinda Chandra
, p. 197 - 204 (2010)
This paper reports the facile synthesis of vanadium phosphate (VPO) by the decomposition of VOHPO4?0.5H2O which was prepared by reduction of dihydrate VOPO4?2H2O with isobutanol. The material was promoted with aluminum by impregnation method. The catalysts were unambiguously characterized by N2 adsorption-desorption, XRD, FT-IR techniques, UV-Vis DRS and the total amount of the acidity of the catalysts was estimated by NH3-TPD. The catalytic activities were checked in the heterogeneous catalytic esterification of acetic acid with 1° alcohol (n-butanol) in a solvent free medium. The optimization of reaction was carried out by varying temperature from 75 to 150 °C, molar ratio (butanol:acetic acid) from 1:1 to 1:4. Under optimum conditions, the catalytic esterification runs revealed a significant effect of the VPO giving 62% conversion with 100% selectivity to butyl acetate.
PHASE TRANSFER CATALYSTS POLYETHYLENE GLYCOLS IMMOBILIZED ONTO METAL OXIDE SURFACES
Sawicki, Robert A.
, p. 2249 - 2252 (1982)
Catalysts prepared by reacting polyethylene glycol and polyethylene glycol monomethyl ether with both alumina and silica gel were found to be effective phase transfer agents in displacement and oxidation reactions.
Facile synthesis of dodecatungstophosphoric acid @ TiO2 pillared montmorillonite and its effectual exploitation towards solvent free esterification of acetic acid with n-butanol
Bishwa Bidita Varadwaj,Parida
, p. 1476 - 1483 (2011)
An acid activated montmorillonite, treated with organic cationic surfactant, i.e. cetyltrimethylammonium bromide (CTAB), was used as a template to prepare TiO2 pillared montmorillonite taking titanium ethoxide as titania precursor in hydrochloric acid environment. The pillared montmorillonite was further promoted by dodecatungstophosphoric acid impregnation. The as prepared materials were characterized by various spectroscopic and analytical characterization techniques. The catalyst was employed towards a solvent free esterification of acetic acid with n-butanol. The catalyst showed excellent results with 88% conversion and 100% butyl acetate selectivity. It can be recovered and reused readily, making product isolation and catalyst reuse simple.
Modulation of starch nanoparticle surface characteristics for the facile construction of recyclable Pickering interfacial enzymatic catalysis
Qi, Liang,Luo, Zhigang,Lu, Xuanxuan
, p. 2412 - 2427 (2019)
In this work, maize starch (MS) was successively modified via an esterification reaction with acetic anhydride (AA) and phthalic anhydride (PTA). Combined with the gelatinization-precipitation process, the formed starch nanoparticles at an AA/PTA ratio of 2 (MS-AP (2)) and 3 (MS-AP (3)) had similar regular spheres but distinct surface characteristics. In order to enhance the activity of lipase B from Candida antarctica (CALB) in an organic solvent, we designed an oil-in-water (o/w) and a water-in-oil (w/o) Pickering interfacial catalytic system simultaneously by utilizing MS-AP (2) and MS-AP (3) as robust Pickering emulsion stabilizers. Impressively, during the esterification of 1-butanol and vinyl acetate, the specific activity of CALB in the o/w (0.0843 U μL-1) or w/o (0.0724 U μL-1) Pickering interfacial catalytic system was much higher than that of free enzymes in the monophasic (0.0198 U μL-1) and biphasic (0.0282 U μL-1) system. Moreover, after preliminarily elaborating mass transfer discrepancies between the o/w and w/o Pickering interfacial catalytic systems and calculating their mass transfer resistance, we clarified the effects of the location of these two phases on the catalytic capacity of the Pickering emulsion. Impressively, both Pickering interfacial catalytic systems exhibited high effectiveness in product separation. It was found that the w/o Pickering emulsion enabled the organic product to be facilely isolated through a simple decantation, while the o/w Pickering emulsion achieved similar results after adjusting the system temperature. The bio-based nanomaterials and simple protocol, in conjunction with the stability to simultaneously achieve high catalysis efficiency and excellent recyclability, makes us believe that this starch nanoparticle-based Pickering interfacial catalytic system is a promising system for meeting the requirements of green and sustainable chemistry.
Esterification of acetic acid with n-Butanol using vanadium oxides supported on γ-alumina
Mitran, Gheorghita,Makó, éva,Rédey, ákos,Marcu, Ioan-Cezar
, p. 793 - 798 (2012)
Esterification of acetic acid with n-Butanol has been studied in a heterogeneous reaction system using two γ-alumina-supported vanadium oxide catalysts with different V loadings, which were prepared by the impregnation of a precipitated alumina. The alumina support and the supported catalysts were characterized using X-ray diffraction, N2 adsorption, EDX analysis and NH3-TPD techniques. The effects of the reaction time, of the molar ratio of the reactants, of the speed of agitation and of the mass fraction of the catalyst on the catalytic properties were studied. In the presence of the supported catalyst containing 10 wt % V2O5 (10V-Al2O3 sample) the conversion reached 87.7% after 210 min of reaction at 100 °C with an n-Butanol-to-acetic acid mole ratio equal to one. The conversion as well as the total acidity measured by TPD of NH 3 increased in the following order: Al2O3 2O3 (5 wt % V2O5/Al 2O3) 2O3. In all cases the reaction was completely selective to n-butyl acetate. Nevertheless, a loss in catalytic activity after three reaction cycles with 10 V2O 5-Al2O3 catalyst was observed.
Polymers as reagents and catalysts. Part 28. The effect of polymer catalyst structure on the esterification of acids
Zupan,Segatin
, p. 597 - 609 (1991)
Crosslinked sulphonated polystyrene (Dowex 20 M) and various salts of crosslinked co-poly[styrene-4-vinylpyridine] with hydrogen halides were used as solid catalysts in investigations of the conversion of acids to esters. The role of the structure of the acid (acetic acid, benzoic acid), solvent (n-octane, toluene, n-butanol) and reaction temperature in the presence of polymer supported catalyst was tested in the reaction with n-butanol. Sulphonated crosslinked polystyrene (3a) was the most active catalys, similar activity was found with crosslinked co-poly[styrene-4-vinyl(pyridinium chloride)], while catalysts bearing a fluoride (3b) and iodide (3e) function were almost unreactive. The important role of co-solvents was also established.
One-step synthesis of a novel carbon-based strong acid catalyst through hydrothermal carbonization
Xiao, Huiquan,Guo, Yingxue,Liang, Xuezheng,Qi, Chenze
, p. 929 - 932 (2010)
A novel carbon-based strong acid catalyst was synthesized through the one-step hydrothermal carbonization of furaldehyde and p-toluenesulfonic acid (PTSA) in aqueous solution at 180 °C for only 4 h. The novel carbonbased solid acid possessed high acidity, and the catalytic activities were investigated by esterification and oxathioketalization. The results showed that the novel catalyst demonstrated much greater activity than the traditional solid acids and was comparable to sulfuric acid. The onestep method provides an efficient procedure for the synthesis of various functionalized carbons by one-step hydrothermal carbonization. Springer-Verlag 2010.
A Convenient Synthesis of Isotopically Labelled Anthraquinones, Chrysophanol, Islandicin, and Emodin. Incorporation of Chrysophanol into Tajixanthone in Aspergillus variecolor
Ahmed, Salman A.,Bardshiri, Esfandiar,Simpson, Thomas J.
, p. 883 - 884 (1987)
Cycloaddition reactions of labelled 6-methoxy-3-methyl-2-pyrone (1) with naphthoquinones provide the common fungal anthraquinones, chrysophanol (2), islandicin (3), and emodin (4) suitably labelled for biosynthetic studies, as demonstrated by synthesis and incorporation of chrysophanol into the xanthone metabolite, tajixanthone (17) in Aspergillus variecolor.
Tailoring ionic liquid catalysts: Structure, acidity and catalytic activity of protonic ionic liquids based on anionic clusters, [(HSO4)(H 2SO4)x]- (x = 0, 1, or 2)
Matuszek, Karolina,Chrobok, Anna,Coleman, Fergal,Seddon, Kenneth R.,Swadzba-Kwasny, Malgorzata
, p. 3463 - 3471 (2014)
Aiming at inexpensive Bronsted-acidic ionic liquids, suitable for industrial-scale catalysis, a family of protonic ionic liquids based on nitrogen bases and sulfuric acid has been developed. Variation of the molar ratio of sulfuric acid, ?H2SO4, was used to tune acidity. The liquid structure was studied using 1H NMR and IR spectroscopies, revealing the existence of hydrogen-bonded clusters, [(HSO4)(H2SO4)]?, for ?H2SO4 0.50. Acidity, quantified by Gutmann Acceptor Number (AN), was found to be closely related to the liquid structure. The ionic liquids were employed as acid catalysts in a model reaction; Fischer esterification of acetic acid with 1-butanol. The reaction rate depended on two factors; for ?H2SO4 0.50, the key parameter was acidity (expressed as AN value), while for ?H2SO4 0.50 it was the mass transport (solubility of starting materials in the ionic liquid phase). Building on this insight, the ionic liquid catalyst and reaction conditions have been chosen. Conversion values of over 95% were achieved under exceptionally mild conditions, and using an inexpensive ionic liquid, which could be recycled up to eight times without diminution in conversion or selectivity. It has been demonstrated how structural studies can underpin rational design and development of an ionic liquid catalyst, and in turn lead to a both greener and economically viable process.