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Production of C4-C10 Hydrocarbons from CO₂, H₂O, CO, H₂ and CH₄ Utilizing DC Glow Discharges, Catalytic Rapid Temperature Pulsing in Micro-Scale Reactors.

Description: 
This thesis experimentally determines the feasibility to creating C4 to C10 hydrocarbons from CO2, CO, H2, H2O and CH4. This is done in two steps, the initial step is the formation of ethylene through DC electrical glow discharge at ambient pressure while the second step is through temperature pulse controlled ethylene polymerization. This took the form of a preliminary experimental investigation into two chemical species and three chemical species inlet feed dual needle-to-needle glow discharge micro-scale reactor and resulted in a final investigation of a multi-discharge needle-to-plate micro-scale reactor with a 3-component feed. This led into a proof-of-concept temperature pulse study whereby a resistive filament was coated with a Phillips ethylene polymerization catalyst and pulsed a set times to form hydrocarbon species in a continuous flow micro-scale reactor. The two-component dual DC glow discharge study began with an investigation of CH4 with H2 and CH4 with H2O. These two studies both resulted in the formation of a carbon filament across the discharge needles, causing a short and failure of the plasma. The needle was analytically determined via Energy Dispersive X-ray analysis to consist of 5% oxygen, 15% tungsten with the balance being carbon. Investigations including CO2 and H2 resulted in the formation of primarily CO and H2O, with only 2% CH4 selectivity. CO2 with H2O resulted in the formation of CO and H2 in what seemed to be a non-thermal form of the water-gas-shift reaction. CO with H2O similarly formed CO2 and H2 with a 1% selectivity towards CH4. These three combinations CO2-H2O, CO2-H2 and CO-H2O all favored what could be considered water-gas-shift products or reactants. The final experimental set was CO with H2 which resulted in a conversion between 6% and 1% but a 90% selectivity to CH4 and a 10% selectivity to C2 hydrocarbons. The primary route for forming hydrocarbon species, based on the experimental results, seemed to come from removing oxygen from carbon or hydrogen species. The highest ethylene selectivity was noted for CO and H2, which also had the lowest amount of oxygen in the feed gas. The outcome of the three-component dual DC glow discharge study was based on the results of the two-component study. The study removed several potential mixtures when considering CO2, CO, CH4, H2 and H2O feed components based on the results of the two-component study. Mixtures were set up to be a total of 5 parts, such as a 1:1:3 ratio of inlet species of 2:1:2 ratio of inlet species. The CO2-H2-CH4 inlet mixture produced primarily CO, H2O and carbon coke. The study had a high CO2 conversion of 80% and a high CH4 conversion of 95%. The CO2-CO-CH4 mixture was inconclusive due to carbon filament formation. The filament caused an electrical short and plasma failure. The CO2-CO-H2 inlet composition showed a maximum CO conversion of 40% and a nearly 100% selectivity to CO, with trace amounts of CH4, C2 and coke also being formed. The H2O-H2-CO composition showed a low CO conversion of 1% to 12% but high variability in selectivity with CH4 selectivity ranging from 1% to 99% and C2+ selectivity ranging from sub-1% to 24%. The major conversion spikes for C2 plus and CH4 selectivity occurred when more CO and H2 were fed in, with H2O being in lesser concentrations. The final H2-CO-CH4 feed had to be modified from the norm due to the speed at which filaments formed. The concentration of CH4 was lowered to be 2 to 8 mol% of the feed with the balance being 25 to 22 mol% CO and 73 to 68 mol% H2. The conversion was between 8% to 15% but showed a 40% to 82% selectivity to C2+ hydrocarbon species, with the balance being coke formation. Ultimately, the final hypothesis of oxygen inhibiting the formation of hydrocarbon species seemed consistent with the three-component study. The inclusion of methane also assisted in the formation of hydrocarbon species. The results of the multi-discharge DC glow discharge investigation showed that increasing the number of discharges did have a positive effect on the conversion of feed species and concentration of product species. The increased conversion showed a more muted effect in the presence of carbon dioxide, where increases in CO2 and H2 conversion were approximately 10% while selectivity towards methane increased by nearly 8%. The more dramatic effects were when noted when H2 and CO where in the presence of CH4. This resulted in an 18% increase in carbon conversion, a 23% increase in C2 selectivity and a 25% decrease in carbon coke formation. Supplemental investigations were done to show that residence time in the plasma had a strong effect on conversion, with 90 SCCM resulting in a conversion of 17% and 50 SCCM resulting in a conversion of 30%. The results of the temperature pulse-controlled ethylene polymerization investigation showed that little to no hydrocarbon species were removed from the surface if the temperature amplitude was below 70 ⁰C. Different on catalyst residence times resulted in the formation of longer chain hydrocarbons and a shift in the product hydrocarbon distribution. The results were confirmed by mass spectrometry and gas chromatography. The on catalyst residence time increased by approximately 4 to 5 minutes when comparing initial temperature pulses to subsequent temperature pulses. The concentration of hydrocarbon species out of the reactor slightly decreased as the chain length grew, with 1.43 mol% butene coming out of the reactor at 4.5 minutes but only 1.13 mol% decene coming out of the reactor at 24 minutes.
Type: 
Dissertation
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http://ir.library.oregonstate.edu?metadataPrefix=oai_dc&verb=GetRecord&identifier=ir.library.oregonstate.edu:1z40m162p
Repository Record Id: 
ir.library.oregonstate.edu:1z40m162p
Record Title: 
Production of C4-C10 Hydrocarbons from CO₂, H₂O, CO, H₂ and CH₄ Utilizing DC Glow Discharges, Catalytic Rapid Temperature Pulsing in Micro-Scale Reactors.
http://ir.library.oregonstate.edu/concern/graduate_thesis_or_dissertations/1z40m162p
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