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Methanol dehydration to dimethyl ether over strong-acid-modified diatomite catalysts
(2016-11-01)
Pranee, Watcharakorn
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Neramittagapong, Sutasinee
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Assawasaengrat, Pornsawan
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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(IV) but decreased with Al(V) and Al(VI).
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Methanol conversion to dimethyl ether over beta zeolites derived from bagasse fly ash
(2016-10-17)
Assawasangrat, Pornsawan
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Neramittagapong, Sutasinee
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Pranee, Watcharakorn
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Praserthdam, Piyasan
Catalytic performance of beta zeolites derived from bagasse fly ash for methanol dehydration to dimethyl ether, alternative fuel, was investigated. Amorphous silica extracted from bagasse fly ash, a tetraethylammonium hydroxide (TEAOH) were used as a precursor and a template for synthesis of beta-zeolites, respectively. Beta zeolites could be synthesized at a constant hydrothermal temperature of 135°C and a constant initial pressure of 3 bars under the nitrogen atmosphere. The crystallization time and Si/Al ratio were 48 h and 15, respectively. These conditions gave the highest crystallinity for beta zeolites with a crystal size of 0.51 μm as well as a Brunauer–Emmett–Teller surface area of 844 m2 g−1. Beta zeolites with the Si/Al ratios of 15.8 and 24.6 were used as catalysts for methanol conversion to dimethyl ether. Beta zeolites with the Si/Al ratios of 15.8 and 24.6 have the % yields of 84 and 60, respectively. According to the result of NH<inf>3</inf>-TPD, the beta zeolites with the Si/Al ratio of 15.8 showed higher acidity than beta zeolites with a Si/Al ratio of 24.6. Therefore, the beta zeolites with a Si/Al ratio of 15.8 were more efficiency in methanol conversion reaction than beta zeolites with a Si/Al ratio of 24.6.
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Dimethyl ether synthesis from methanol over diatomite catalyst modified using nitric acid treatment
(2016-08-02)
Pranee, Watcharakorn
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Neramittagapong, Sutasinee
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Assawasaengrat, Pornsawan
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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(IV) ions whereas basicity of the catalyst surface was determined by Al(V) and Al(VI) 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
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Assawasaengrat, Pornsawan
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Neramittagapong, Arthit
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Intarachit, Sasitorn
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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(IV) ions; nevertheless, both Al(V) and Al(VI) 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.
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