Catalysis by Heteropoly Compounds .XXII. Reactions of Esters and Esterification Catalyzed by Heteropolyacids in a Homogeneous Liquid-Phase Effects of the Central Atom of Heteropolyanions Having Tungsten as the Addenda Atom

Hu, Changwen; Hashimoto, Masato; Okuhara, Toshio; Misono, Makoto

doi:10.1006/jcat.1993.1288

Cited by 167 publications

(59 citation statements)

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“…And HPAs are well known as solid acids which are also active towards liquid phase esterification and transesterification (Hu et al, 1993), it is often used as catalyst in the food and chemical industry (Fujita et al, 2004). Among Keggin-type heteropolyacids H n [XM 12 O 40 ], PW 12 has been proved to be the strongest acid and be widely used in catalysis such as liquid phase esterification (Ramalinga et al, 2002).…”

Section: Introductionmentioning

confidence: 99%

Biodiesel production from high acid value waste frying oil catalyzed by superacid heteropolyacid

Cao

Chen

Zhai

et al. 2008

Biotech & Bioengineering

138

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Transesterification of waste cooking oil with high acid value and high water contents using heteropolyacid H3PW12O40 x 6H2O (PW12) as catalyst was investigated. The hexahydrate form of PW(12) was found to be the most promising catalyst which exhibited highest ester yield 87% for transesterification of waste cooking oil and ester yield 97% for esterification of long-chain palmitic acid, respectively. The PW12 acid catalyst shows higher activity under the optimized reaction conditions compared with conventional homogeneous catalyst sulfuric acid, and can easily be separated from the products by distillation of the excess methanol and can be reused more times. The most important feature of this catalyst is that the catalytic activity is not affected by the content of free fatty acids (FFAs) and the content of water in the waste cooking oil and the transesterification can occur at a lower temperature (65 degrees C), a lower methanol oil ratio (70:1) and be finished within a shorter time. The results illustrate that PW12 acid is an excellent water-tolerant and environmentally benign acid catalyst for production of biodiesel from waste cooking oil.

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Section: Introductionmentioning

confidence: 99%

Biodiesel production from high acid value waste frying oil catalyzed by superacid heteropolyacid

Cao

Chen

Zhai

et al. 2008

Biotech & Bioengineering

138

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“…In Figure 4.2.5-2(b), on the other hand, the esterification activity decreased with TOS and the initial and steady-state activities declined with an increase in humidity. The results indicate that water is detrimental to esterification activity because (1) water molecules competitively adsorb with reactants (methanol and acetic acid) on the proton sites blocking them for reaction; (2) water vapor decreases the strength of the acid sites (acidity) by surrounding proton sites with fixed anionic charges [Hu 1993]; and/or (3) water vapor favors the hydrolysis reaction (re-forming acetic acid from methyl acetate). …”

Section: Effect Of Humidity On Conductivity and Esterification Activimentioning

confidence: 99%

Final Technical Report: Effects of Impurities on Fuel Cell Performance and Durability

Goodwin¹,

Colón-Mercado²,

Hongsirikarn³

et al. 2011

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EXECUTIVE SUMMARYThe main objectives of this project were to investigate the effect of a series of potential impurities on fuel cell operation and on the particular components of the fuel cell MEA, to propose (where possible) mechanism(s) by which these impurities affected fuel cell performance, and to suggest strategies for minimizing these impurity effects. This project was carried out primarily at Clemson University and the Savannah River National Lab. Fuel cell investigations were done at SRNL while all investigations of the MEA components were carried out at Clemson. Meetings took place weekly at Clemson University and at SRNL with the respective project participants. Joint meetings between researchers at Clemson and SRNL took place quarterly, on average. In addition, frequent communications among project participants took place via e-mail and telephone discussions. On other occasions the researchers met with the technical staff of John Deere for discussions. At least one member of our team routinely participated in the DOE-Sponsored Joint Hydrogen Quality Task Force Meetings (usually conducted monthly).The nature and concentrations of impurities investigated and their impact on fuel cell performance and individual components are given in the table below. The negative effect on Pt/C was to decrease hydrogen surface coverage and hydrogen activation at fuel cell conditions. The negative effect on Nafion components was to decrease proton conductivity, primarily by replacing/reacting with the protons on the Bronsted acid sites of the Nafion.Even though already well known as fuel cell poisons, the effects of CO and NH 3 were studied in great detail early on in the project in order to develop methodology for evaluating poisoning effects in general, to help establish reproducibility of results among a number of laboratories in the U.S. investigating impurity effects, and to help establish lower limit standards for impurities during hydrogen production for fuel cell utilization.New methodologies developed included (1) a means to measure hydrogen surface concentration on the Pt catalyst (HDSAP) before and after exposure to impurities, (2) a way to predict conductivity of a Nafion membranes exposed to impurities using a characteristic acid catalyzed reaction (methanol esterification of acetic acid), and, more importantly, (3) application of the latter technique to predict conductivity on Nafion in the catalyst layer of the MEA. H 2 -D 2 exchange was found to be suitable for predicting hydrogen activation of Pt catalysts.Using a combination of standard catalyst characterization techniques, a structure sensitive catalytic reaction technique (cyclopropane hydrogenolysis), and reaction and transport modeling led to the finding that in the catalyst layer (essentially Nafion/Pt/C) the following best describes the structure. Pt is highly dispersed on the C support, but primarily in the meso-and macropores. The Nafion (ca. 30 wt%) resides primarily on the external surface of the C support where it blocks significant numbers ...

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“…Tungstosilicic acid (H 4 SiW 12 O 40 ) was synthesized as described in literature (Hu et al, 1993) and examined by IR spectra. The IR (infrared) spectra were obtained using an IMP 410 IR spectrometer (Nicolet, USA).…”

Section: Materials and Measurementsmentioning

confidence: 99%

Synthesis of acetals and ketals catalyzed by tungstosilicic acid supported on active carbon

Shui-jin

Sun

2005

J Zheijang Univ Sci B

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Catalytic activity of activated carbon supported tungstosilicic acid in synthesizing 2-methyl-2-ethoxycarbonylmethyl-1,3-dioxolane, 2,4-dimethyl-2-ethoxycarbonylmethyl-1,3-dioxolane, cyclohexanone ethylene ketal, cyclohexanone 1,2-propanediol ketal, butanone ethylene ketal, butanone 1,2-propanediol ketal, 2-phenyl-1,3-dioxolane, 4-methyl-2-phenyl-1,3-dioxolane, 2-propyl-1,3-dioxolane, 4-methyl-2-propyl-1,3-dioxolane was reported. It has been demonstrated that activated carbon supported tungstosilicic acid is an excellent catalyst. Various factors involved in these reactions were investigated. The optimum conditions found were: molar ratio of aldehyde/ketone to glycol is 1/1.5, mass ratio of the catalyst used to the reactants is 1.0%, and reaction time is 1.0 h. Under these conditions, the yield of 2-methyl-2-ethoxycarbonylmethyl-1,3-dioxolane is 61.5%, of 2,4-dimethyl-2-ethoxycarbonylmethyl-1,3-dioxolane is 69.1%, of cyclohexanone ethylene ketal is 74.6%, of cyclohexanone 1,2-propanediol ketal is 80.1%, of butanone ethylene ketal is 69.5%, of butanone 1,2-propanediol ketal is 78.5%, of 2-phenyl-1,3-dioxolane is 56.7%, of 4-methyl-2-phenyl-1,3-dioxolane is 86.2%, of 2-propyl-1,3-dioxolane is 87.5%, of 4-methyl-2-propyl-1,3-dioxolane is 87.9%.

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Catalysis by Heteropoly Compounds .XXII. Reactions of Esters and Esterification Catalyzed by Heteropolyacids in a Homogeneous Liquid-Phase Effects of the Central Atom of Heteropolyanions Having Tungsten as the Addenda Atom

Cited by 167 publications

References 0 publications

Biodiesel production from high acid value waste frying oil catalyzed by superacid heteropolyacid

Biodiesel production from high acid value waste frying oil catalyzed by superacid heteropolyacid

Final Technical Report: Effects of Impurities on Fuel Cell Performance and Durability

Synthesis of acetals and ketals catalyzed by tungstosilicic acid supported on active carbon

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