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Carbon dioxide reforming of dimethyl ether using γ-Al 2 O 3 load Ni, La Catalysts

Author: MaZhong
Tutor: JiangZuoZhong
School: Shanghai Jiaotong University
Course: Chemical Engineering and Technology
Keywords: Carbon dioxide DME Hydrogen Nickel Lanthanum Restructuring
CLC: TQ116.2
Type: Master's thesis
Year: 2012
Downloads: 51
Quote: 0
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Abstract


DME is a clean fuel, is expected to replace the traditional motor fuels in order to achieve high efficiency and low emissions. At the same time a large number of studies have shown that adding a certain amount of hydrogen gas engine can effectively improve the combustion properties of DME. However, the storage and transport of hydrogen present a problem that can not directly carry and store car hydrogen. The fuel reformer gas recirculation technology compared to this problem provides a good solution. At the same time, DME high hydrogen to carbon ratio, high energy density and non-toxicity and other characteristics make it a promising reformer producing hydrogen fuel, while carbon dioxide is a greenhouse gas. So the carbon dioxide reforming of dimethyl ether is hydrogen and reduce carbon dioxide emissions of the green line. Since DME engine exhaust contains amounts of carbon dioxide and dimethyl ether, carbon dioxide so DME reforming hydrogen car is excellent utilization of the reformed gas combustion and exhaust gas recirculation reduction technology in order to improve combustion efficiency and improved engine its emissions of key technologies. However, to date, dimethyl ether, carbon dioxide reforming reaction has not been reported. In this paper, carbon dioxide reforming reaction of dimethyl ether as an object of study, carried out on the reaction thermodynamics analysis; studied Ni / γ-Al 2 O 3 and Ni / La 2 O 3 / γ-Al 2 O 3 catalysts for carbon dioxide reforming reaction of DME activity; preliminary study of La 2 O 3 / γ-Al 2 O 3 catalyst for dimethyl ether carbon dioxide reforming reaction activity, in order for the car DME hydrogen technology provides a new feasible ways and theoretical research base. This resultant main conclusions are: 1. According to thermodynamic calculation results show that the carbon dioxide reaction DME theoretical critical temperature of 481.9K, while experimental results show that the reaction can indeed occur in practice. 2 In the blank experiment, dimethyl ether cleavage of a certain high temperature occur, and dimethyl ether in the three catalysts used in this study the cleavage reaction is a catalytic cracking process, rather than a simple pyrolysis. Acid carrier γ-Al 2 O 3 dimethyl ether carbon dioxide reforming reaction and the thermal cracking reaction has some activity, the reaction temperature is 650 ℃, the selectivity of hydrogen respectively 52.2% and 53.0%, carbon monoxide 35.6% and the selectivity was only 36.2%, but in the carbon dioxide reforming reaction conversion rate was 24.0%. Carrier activity may be due to poor stability caused serious coke. (3) We investigated Ni / γ-Al 2 O 3 carbon dioxide reforming catalyst DME catalytic activity. Reduction pretreatment on Ni / γ-Al 2 O 3 catalyst activity results indicate that at lower temperatures (550 ℃), the reduction of hydrogen pretreatment reduced selectivity, but to improve the conversion rate of carbon dioxide, 650 ℃, the reduction activity of the catalyst pretreatment no effect, but improved resistance to coking of the catalyst performance. The optimum loading of the catalyst Ni Nickel is 10wt.%; Raw material gas in the best ratio of: nCO 2 : nDME = 1, when the increased amount of carbon dioxide, the carbon deposition rate of the catalyst obtained a reduced, but can not improve the selectivity of hydrogen product; reaction conversion of the starting material and product selectivity are increased as the reaction temperature and improved, wherein the reaction temperature is higher than 550 ℃ conversion of DME reached 100%. Ni loading of 10wt.%, NCO 2 : nDME = 1, the reaction temperature was 650 ℃ under the conditions of the reduction catalyst without pretreatment, the hydrogen selectivity of 70.9%, carbon monoxide selection sex was 60.6%, the selectivity of methane byproduct as low as 15.7%, raw carbon dioxide conversion rate 70.1%. According to the catalyst XRD, H 2 -TPR and XPS results showed that the catalyst mainly NiO and Ni in NiAl 2 O 4 phase. The reduction catalyst pretreated elemental Ni-Ni highly dispersed on the support, the catalyst still present after the reaction of elemental Ni and NiO4. Order to further improve catalyst performance, of the rare-earth doped La, Ni / La 2 < / sub> O 3 / γ-Al 2 O 3 catalyst on the reaction activity. The results show that, La doping elements help to improve the catalyst performance and low resistance to coking reaction performance. At low temperature (550 ℃), reducing the activity of the catalyst pretreatment has a great influence, the longer the pre-reduction catalyst of low activity platform longer. 550 ℃ and the optimum catalytic reaction temperature; increased levels of carbon dioxide in the feed gas can not only reduce the rate of catalyst coking, and can improve the stability of the catalyst. At 650 ℃ without reduction pretreatment, material ratio is 1, the catalyst loading was 10wt.% Ni and 6wt.% La 2 O 3 , selectivity of 72.1% hydrogen, 57.3% carbon monoxide selectivity, by-product methane selectivity was 13.1% DME conversion was 100% conversion of carbon dioxide was 69.8%. Ni catalyst still NiO and NiAl 2 O 4 phase exists, and Ni / γ-Al 2 O 3 The difference is that the catalyst after the reaction of elemental Ni catalyst does not appear the five paper a preliminary study La 2 O 3 / γ-Al 2 O 3 catalysts for carbon dioxide reforming of dimethyl ether catalytic activity and found that: γ-Al 2 O 3 load individual rare earth elements La also has activity in this reaction. At 650 ℃, the reduction pretreatment did not affect the activity of the catalyst. 550 ℃ when the catalytic activity is higher than 650 ℃. Lanthanum a loading of 20wt.% Catalytic activity than the loading of 10wt.%. At 650 ℃, without pre-reduction, the raw material ratio of 1:00, La loading of 10wt.%, The selectivity of 74.3% hydrogen, 62.3% CO selectivity, 12.2 selectivity to methane by-product % DME conversion was 100%, 68.5% conversion of carbon dioxide. 6 compared on three catalysts at 650 ℃ and 550 ℃ activity data to restore pretreatment on Ni / γ-Al 2 O 3 catalyst activity affecting results, Ni metal can promote the conversion of carbon dioxide, the rare earth element La can reduce the formation of methane by-product.

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