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Study on the Catalysts and Reaction Conditions for Natural Gas Direct Conversion to Ethene

Author: WangKai
Tutor: JiShengFu
School: Beijing University of Chemical Technology
Course: Chemical Engineering and Technology
Keywords: monolithic catalyst methane oxidative coupling autothermal catalyst bed
CLC: TQ221.211
Type: PhD thesis
Year: 2009
Downloads: 214
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Abstract


The declining reserves of crude petroleum have led to a great interest for more efficient utilization of the aboundant natural gas resources.It has been considered that the oxidative coupling of methane（OCM） to ethane is a promising route for the direct conversion of natural gas.In this study,we studied the catalytic performance of the supported catalysts and monolithic catalysts for the OCM reaction.We also studied the effect of reaction conditions on the catalytic performance in the OCM reaction.The main research works and results are listed as follows:The Na-W-Mn catalysts were prepared using SiO2 or SBA-15 as support, respectively.The effects of Ce,La,Bi,Sr,and Zr additives on the OCM catalytic properties were studied.The study results indicated that the OCM catalytic peroformace of the catalysts using SBA-15 as support was higher than the catalysts using SiO2 as support.The different transition metal doping has different degrees of change in the Na-W-Mn catalysts for the OCM reaction.Adding Ce to Na-W-Mn catalysts could improve the OCM catalytic performance of the Na-W-Mn catalysts. The 5%Na2WO4-2%Mn/SBA-15/Al2O3/FeCrAl and 5%Na2WO4-2%Mn /SiO2/D（dichroite） monolithic catalyst modified with different additives and Li/MgO/Al2O3/FeCrAl monolithic catalysts were prepared and the OCM catalytic properties of these catalysts were studied.For the 5%Na2WO4-2%Mn /SBA-15/Al2O3/FeCrAl monolithic catalysts,the 1%K modified monolithic catalyst exhibited the best the OCM catalytic performance.The addition of alkali metal potassium had changed the over style of acid-base properties of the monolithic catalyst,resulting in the improvement of the OCM catalytic performance.For the Li/MgO/Al2O3/FeCrAl catalysts,the OCM catalytic performance increased with higher Li content and reached the maximum at 5.0%Li/MgO/Al2O3/FeCrAl catalysts.Further increasing Li content,the OCM catalytic performance decreased significantly.For the 5%Na2WO4-2%Mn/SiO2/D monolithic catalysts modified with different promoter,the 4%Ce modified catalyst showed the best OCM catalytic performance.The OCM catalytic performance on the mixed particle and monolithic catalyst bed was studied.The results indicated that the catalysts bed in which the upper is particle catalyst and the lower is monolithic catalyst along feed direction,could enhance the selectivity of ethene product.In addition,the direct coupling of oxidative coupling of methane and oxidative dehydrogenation（ODH） of ethane with CO2 reaction was successful in our experiments.Under the experimental conditions,the catalysts bed in which the upper is Na-W-Mn particle catalyst for OCM reaction and the lower is 5%Cr/SBA-15/Al2O3 /FeCrAl monolithic catalyst for ODH reaction was benefit to enhance the selectivity and yield of ethene production in the coupling reaction.A series of carbonate/La2O3,carbonate/ZrO2,and carbonate/Sm2O3 catalysts were prepared by wet mixing method.The catalytic activity for the low temperature or autothermal oxidative coupling of methane was evaluated in a fixed-bed micro-reactor.The results showed that these catalysts had excellent catalytic performance of low temperature or autothermal OCM reaction.For the lanthanum based catalysts,under the VCH4:VO2=2.0, GHSV=18000 mL·g-1·h-1 reaction conditions,the 10%BaCO3/La2O3 catalyst could hold 230 h autothermal OCM reaction.The 30.12%CH4 conversion and 41.9%C2 hydrocarbon selectivity were obtained in the autothermal stability OCM reaction.For the zirconium based catalysts,the 7.5%BaCO3/ZrO2 catalyst showed the best low temperature OCM catalytic performance.For the samarium based catalysts,5%SrCO3/Sm2O3 catalyst showed the best autothermal OCM catalytic performance.During the 82h autothermal stability test,CH4 conversion and C2 hydrocarbon selectivity were 31.4%and 39.5%, respectively.

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CLC: > Industrial Technology > Chemical Industry > Basic Organic Chemistry Industry > The production of aliphatic compounds ( acyclic compounds) > Aliphatic hydrocarbons > Unsaturated lipid hydrocarbon > Monoolefins > Ethylene
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