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Mechanism of Bi-Ni Phase Formation in a Microwave-Assisted Polyol Process.

ABSTRACT: Typically, intermetallic phases are obtained in solid-state reactions or crystallization from melts, which are highly energy and time consuming. The polyol process takes advantage of low temperatures and short reaction times using easily obtainable starting materials. The formation mechanism of these intermetallic particles has received little attention so far, even though a deeper understanding should allow for better synthesis planning. In this study, we therefore investigated the formation of BiNi particles in ethylene glycol in a microwave-assisted polyol process mechanistically. The coordination behavior in solution was analyzed using HPLC-MS and UV-Vis. Tracking the reaction with PXRD measurements, FT-IR spectroscopy and HR-TEM revealed a successive reduction of Bi3+ and Ni2+, leading to novel spherical core-shell structure in a first reaction step. Bismuth particles are encased in a matrix of nickel nanoparticles of 2?nm to 6?nm in diameter and oxidation products of ethylene glycol. Step-wise diffusion of nickel into the bismuth particle intermediately results in the bismuth-rich compound Bi3Ni, which consecutively transforms into the BiNi phase as the reaction progresses. The impacts of the anion type, temperature and pH value were also investigated.

SUBMITTER: Smuda M

PROVIDER: S-EPMC7607453 | biostudies-literature | 2020 Nov

REPOSITORIES: biostudies-literature

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Mechanism of Bi-Ni Phase Formation in a Microwave-Assisted Polyol Process.

Smuda Matthias M Damm Christine C Ruck Michael M Doert Thomas T

ChemistryOpen 20201001 11

Typically, intermetallic phases are obtained in solid-state reactions or crystallization from melts, which are highly energy and time consuming. The polyol process takes advantage of low temperatures and short reaction times using easily obtainable starting materials. The formation mechanism of these intermetallic particles has received little attention so far, even though a deeper understanding should allow for better synthesis planning. In this study, we therefore investigated the formation of ...[more]

PMID: 33163325

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Project description:To produce biodiesel cost-effective, low-cost, high free fatty acid (FFA) oil feedstock is desirable. But high FFA creates difficulty during the base-catalyzed transesterification process by yield loss due to the formation of soap. However, these problems are overcome by the use of an acid catalyst. The acid catalysts can directly convert both triglycerides and FFAs into biodiesel without the formation of soaps or emulsions. The shortcomings of mostly used inorganic acids are that they work well for esterification of FFA present in low-cost oil, but their kinetics for transesterification of triglycerides present in oils is considerably slower. Corrosion of equipment is another major problem associated with an inorganic acid catalyst. The usage of an organic acid catalyst of the alkyl benzene sulfonic type, like 4-dodecyl benzene sulfonic acid (DBSA) minimizes these disadvantages of inorganic acid-catalyzed transesterification. The aim of the present investigation was to reduce the reaction time of transesterification of triglycerides further by using microwaves as a heating source in the presence of DBSA catalyst to achieve higher conversions under mild operating conditions. To optimize the transesterification variables for the higher conversion of biodiesel, the response surface methodology was employed to design the experiment. By using the DBSA catalyst under microwave heating at a temperature of 76 °C, conversion close to 100% in only 30 min of reaction time was obtained using a 0.09 molar ratio of catalyst to oil and 9.0 molar ratio of methanol to oil. A modified polynomial model was developed and was adequately fitted with the experimental data and could be used for understanding the effect of various process parameters. The catalyst to oil molar ratio and reaction temperature created a stronger effect on the biodiesel production than that exhibited by the methanol to oil molar ratio. It was observed that the microwave heating process outperformed conventional heating, providing a rapid, easy method for biodiesel synthesis from triglycerides in the presence of DBSA, an organic acid catalyst. The produced biodiesel was of good quality, as all the properties were within the prescribed limits of the ASTM D6751 standard.

Dataset Information

Mechanism of Bi-Ni Phase Formation in a Microwave-Assisted Polyol Process.

Publications

Mechanism of Bi-Ni Phase Formation in a Microwave-Assisted Polyol Process.

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