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Author: search.filters.author.Assawasaengrat, PornsawanSubject: search.filters.subject.Acid catalyst

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    Methanol dehydration to dimethyl ether over strong-acid-modified diatomite catalysts
    (2016-11-01)
    Pranee, Watcharakorn
    ;
    Neramittagapong, Sutasinee
    ;
    Assawasaengrat, Pornsawan
    ;
    Neramittagapong, Arthit
    Dimethyl ether synthesis via methanol dehydration over strong-acid-modified (with sulfuric, hydrochloric and nitric acid) diatomite (DM) catalysts was conducted in a fixed-bed reactor with elevated temperature reaction from 250 to 350°C. The modified DM catalysts were characterized by using X-ray diffraction, scanning electron microscopy, fourier transform infrared spectroscopy, fourier transform Raman spectroscopy, temperature-programmed desorption of ammonia, temperature-programmed of carbon dioxide, thermal gravimetric analysis, and solid-state 27Aluminum magic angle spinning/nuclear magnetic resonance spectroscopy. It was found that sulfuric-acid-modified DM catalyst yielded the highest DME selectivity (~99%). It was also revealed that methanol conversion depended on Al ions. The methanol conversion increased with Al<sup>(IV)</sup> but decreased with Al<sup>(V)</sup> and Al<sup>(VI)</sup>.
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    Dimethyl ether synthesis from methanol over diatomite catalyst modified using nitric acid treatment
    (2016-08-02)
    Pranee, Watcharakorn
    ;
    Neramittagapong, Sutasinee
    ;
    Assawasaengrat, Pornsawan
    ;
    Neramittagapong, Arthit
    Dimethyl ether synthesis from methanol over diatomite catalysts modified using nitric acid was investigated. The catalytic performance of diatomite was tested in a fixed-bed reactor under atmospheric pressure and within the temperature range of 250–350°C. It was discovered that high acidity of the catalyst yielded a higher methanol conversion rate. Moreover, it was revealed that the acidity of the catalyst surface was controlled by Al<sup>(IV)</sup> ions whereas basicity of the catalyst surface was determined by Al<sup>(V)</sup> and Al<sup>(VI)</sup> ions. From this finding, the authors were able to propose the mechanism of DME synthesis from methanol over treated diatomite.
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    Dimethyl ether synthesis via methanol dehydration over BEA zeolite from bagasse fly ash with zircronium- and nickel-ion exchange
    (2014-01-01)
    Pranee, Watcharakorn
    ;
    Assawasaengrat, Pornsawan
    ;
    Neramittagapong, Arthit
    ;
    Intarachit, Sasitorn
    ;
    Neramittagapong, Sutasinee
    The synthesis of dimethyl ether via methanol dehydration has been carried out over Beta zeolite (BEA) and ion-exchanged Beta zeolite from bagasse fly ash using hydrothermal method. The reactions were taken place in a fixed-bed reactor. The effects of nickel and zirconium ionexchanged of BEA were investigated. Ni-BEA zeolite exhibited high methanol conversion rate and DME-resultant upon the reaction temperature from 200 to 225°C with equilibrium-limiting condition over 225°C; Furthermore, the Ni-BEA zeolite presented the best stable activity at 225°C over 1,200 minute. The Ni-BEA zeolite has also been interesting as a zeolite which suited to be one role importance to improve the properties for methanol dehydration to dimethyl ether. © (2014) Trans Tech Publications, Switzerland.
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    Dimethyl ether synthesis via methanol dehydration over diatomite catalyst modified using hydrochloric acid
    (2014-01-01)
    Pranee, Watcharakorn
    ;
    Assawasaengrat, Pornsawan
    ;
    Neramittagapong, Arthit
    ;
    Neramittagapong, Sutasinee
    The synthesis of dimethyl ether via methanol dehydration has been carried out over untreated-diatomite catalyst (DM) and hydrochloric acid modified treatment on diatomite catalyst (DMHC). The reactions were carried out in a fixed-bed reactor. The effects of hydrochloric acid modifications of diatomite on its catalytic performance were studied. The characterization such as XRD, SEM, FT-IR and FT-Raman had no deformation after HCl-modified treatment on catalysts. DMHC catalyst apparently gave the higher methanol conversion rate than DM due to the acidity while the selectivity of dimethyl ether from 250 to 350°C was slightly changed. The acidity was depended upon Al<sup>(IV)</sup> ions; nevertheless, both Al<sup>(V)</sup> and Al<sup>(VI)</sup> were affected and hence increasing the basic active sites. Not only was the competitively catalytic methanol dehydrogenation preferred with basic condition but also methanol-blocking water molecule interaction was the unwanted reaction. In this investigation, the chemical-bond arrangements of silicon and aluminium ions were proposed with solid MAS/NMR. The DMHC catalyst exhibited better DME yield than the DM catalyst, and it could be used as a selective catalyst for DME synthesis from methanol. © (2014) Trans Tech Publications, Switzerland.