Carbon Nanomaterials for Detection, Assessment and Purification of Oil and Natural Gas
Tour, James M.
Doctor of Philosophy
This thesis studies several carbon nanomaterials. Their synthesis and characterization are studied as well as their potential applications to the oil industry. The carbon nanomaterials studied here include mesoporous carbon (CMK-3), sulfur- or nitrogen-doped porous carbon (SPC or NPC), and commercial carbon black (CB). Through appropriate functionalization, these carbon nanomaterials exhibit unique properties and their performances in detection, assessment as well as purification of oil and natural gas are studied and demonstrated. First, it was shown that amine-modified CMK-3 composites, polyethylenimine-CMK-3 (PEI-CMK-3) and polyvinylamine-CMK-3 (PVA-CMK-3) can be synthesized through in situ polymerization of amine species within the channels of the CMK-3. The synthesis process results in the entrapped amine polymers interpenetrating the composite frameworks of the CMK-3, improving the CO2 capture performance and recycle stability. CO2 uptake by the synthesized composites was determined using a gravimetric method at 30 °C and 1 atm; the 39% PEI-CMK-3 composite had ~12 wt% (3.1 mmol/g) CO2 uptake capacity and the 37% PVA-CMK-3 composite had ~13 wt% (3.5 mmol/g) CO2 uptake capacity. A desorption temperature of 75 °C was sufficient for regeneration. The CO2 uptake was the same when using 10% CO2 in a 90% CH4, C2H6 and C3H8 mixture, underscoring this composite’s efficacy for CO2 sequestration from natural gas. Secondly, nucleophilic porous carbons (SPC and NPC) were synthesized from simple and inexpensive carbon-sulfur and carbon-nitrogen precursors. A strong sorbate-sorbent interaction between CO2 and nucleophilic centers in the porous carbon was established using spectroscopic and heat of sorption data. Raman spectroscopy supports the assertion that the nucleophilic centers react with the CO2 to produce carbonate anions that further cause polymerization in the porous carbon channels to form poly(CO2) under much lower pressure than previously reported for such polymer formation. Once returned to ambient conditions, the poly(CO2) depolymerizes during the pressure swing, leading to a sorbent that can be easily regenerated without the thermal energy input that is required for traditional liquid phase sorbents. The synergy between the nucleophilic centers and the high surface area porous carbon produces a sorbent with high CO2 capacity, selectivity, and volumetric efficiency, so that the materials have potential to be used for CO2 removal from natural gas streams. As energy demand continues to increase, it is desirable to produce as much oil as possible from existing oil wells. Tracers have long been used to map entry/exit well correlations in the oil-field, but they do not provide any information about the environment between the entry and exit locations. Hence, the third part of this thesis will show that nanoparticles possessing functionalized carbon black (fCB) cores and sulfated polyvinyl alcohol (sPVA) addends can be designed to transport hydrocarbon detection molecules through subsurface rock formations. The sPVA-fCBs are stable under high-temperature and salinity conditions and are transported through a variety of oilfield rock types. A non-radioactive probe molecule that is easily detectable by mass spectrometry, triheptylamine (THA), was adsorbed onto the sPVA-fCBs. The THA was selectively released when the nanoparticles were passed through a column of isooctane-containing crushed rock, providing a path to both entry and exit correlations and a measure of oil content. This study simulates detection and quantitative analysis of the hydrocarbon content in downhole rock formations, which is a critically needed assessment in older oilfields. Crude oil is classified as “sour” when it contains a total sulfur content greater than 0.5%. Among these sulfur species, H2S is the one of main impurities in sour crude. The sour crude is toxic and corrosive to the materials of construction in pipelines and other holding and transportation vessels. Since the sulfur amount in a sample of crude depends on where it was found, if the concentration of the sulfur species in the subsurface could be accurately monitored, then geologists might be able to evaluate the quality of the crude before large scale extraction ensues. The last part of the thesis covers polyvinyl alcohol functionalized carbon black (PVA-CB). The particles have high stability under high temperature and salinity conditions, and they acts as a carrier to transport molecular cargo efficiently through simulated oilfield formations. After being functionalized with H2S-sensitive moieties, the functionalized PVA-CB can be pumped through H2S-containing oil and water in porous rock and the H2S content can be determined based on the fluorescent enhancement of the H2S-sensitive addends.