Nanomaterials for Hydrocarbon Exploration, Acid Gas Removal and Energy Devices
Tour, James M.
Doctor of Philosophy
This thesis discusses the synthesis and characterization of several different nanomaterials as well as their applications to oil and energy industries. The nanomaterials studied here include asphalt-derived high surface area activated porous carbon, commercial carbon black (CB), nanoporous metal compounds, graphene, and graphene nanoribbons (GNRs). Through proper design and functionalization, these nanomaterials exhibit interesting properties and their applications in hydrocarbon exploration, acid gas removal as well as energy devices are demonstrated. Firstly, the research activities toward the development of new absorbents for carbon dioxide (CO2) capture have been growing quickly. Despite the variety of existing materials with high surface areas and high CO2 uptake performances, the cost of the materials remains a dominant factor in slowing their industrial applications. In the first chapter we study preparation and CO2 uptake performance of highly porous carbon materials derived from a very inexpensive carbon source, asphalt. Carbonization of asphalt with potassium hydroxide (KOH) at high temperatures (600 - 750 ºC) yields asphalt-derived porous carbon materials (A-PC) with high surface areas of up to 2780 m2 g-1 and high CO2 uptake performance of 21 mmol g-1 or 93 wt% at 30 bar and 25 ºC. Furthermore, nitrogen doping and reduction with hydrogen yields active N-doped materials (A-NPC and A-rNPC) containing up to 9.3% nitrogen, making them nucleophilic porous carbons with further increase in CO2 uptake to 26 mmol g-1 or 114 wt% at 30 bar and 25 ºC for A-rNPC. This is the highest reported CO2 uptake among the family of the activated porous carbonaceous materials. The CO2 is released and the asphalt material is regenerated when the pressure is returned to 1 bar. Thus the porous carbon materials from asphalt have excellent properties for reversibly capturing CO2 at the well-head during the extraction of natural gas, a naturally occurring high pressure source of CO2. Through a pressure swing sorption process, the asphalt-derived material is a reversible capture medium that is highly efficient and very inexpensive. Secondly, crude oil is called as “sour” crude oil when the total sulfur level is larger than 0.5 %. The sour crude oil is corrosive to the oil production and transportation facilities and toxic to human health. Among these sulfur species, H2S is the one of main impurities in sour crude. Therefore it is important to develop a method to accurately measure the sulfur content which may help geologists evaluate the quality of the crude oil before large scale extraction. In the second chapter, we study polyvinyl alcohol functionalized carbon black (PVA-CB) nanoparticles which are stable under high temperature and high salinity conditions. After further being functionalized with H2S-sensitive fluorescence probe, the probe molecule-PVA-CB (FB-PVA-CB) can be used to determine the H2S content in H2S-containing oil in porous rock based on the fluorescent enhancement of the H2S-sensitive addends. Thirdly, a flexible 3-dimensional (3-D) nanoporous NiF2-dominant layer on poly(ethylene terephthalate) has been developed. The nanoporous layer itself can be freestanding without adding any supporting carbon materials or conducting polymers. By assembling the nanoporous layer into two-electrode symmetric devices, the inorganic material delivers battery-like thin-film supercapacitive performance with a maximum capacitance of 66 mF cm-2 (733 F cm-3 or 358 F g-1), energy density of 384 Wh kg-1 and power density of 112 kW kg-1. Flexibility and cyclability tests show that the nanoporous layer maintains its high performance under long-term cycling and different bending conditions. The fabrication of the 3-D nanoporous NiF2 flexible electrode could be easily scaled. Fourthly, in its monolayer form, graphene is a one-atom-thick two-dimensional material with excellent electrical, mechanical and thermal properties. Large-scale production of high-quality graphene is attracting an increasing amount of attention. Chemical vapor and solid deposition methods have been developed to grow graphene from organic gases or solid carbon sources. Most of the carbon sources used were purified chemicals that could be expensive for mass production. In this work, we have developed a less expensive approach using six easily obtained, low or negatively valued raw carbon-containing materials used without pre-purification (cookies, chocolate, grass, plastics, roaches, and dog feces) to grow graphene directly on the backside of a Cu foil at 1050 °C under H2/Ar flow. The non-volatile pyrolyzed species were easily removed by etching away the frontside of the Cu. Analysis by Raman spectroscopy, X-ray photoelectron spectroscopy, ultraviolet-visible spectroscopy and transmission electron microscopy indicates that the monolayer graphene derived from these carbon sources is of high quality. Fifthly, the preparation of polymer-functionalized graphene nanoribbons (PF-GNRs) in a one-pot synthesis is described. Multiwalled carbon nanotubes (MWCNTs) were intercalated by potassium under vapor- or liquid-phase conditions, followed by addition of vinyl monomers, resulting in PF-GNRs. Scanning electron microscopy, thermogravimetric mass spectrometry and X-ray photoelectron spectroscopy were used to characterize the PF-GNRs. Also explored here is the correlation between the splitting of MWCNTs, the intrinsic properties of the intercalants and the degree of defects and graphitization of the starting MWCNTs. The PF-GNRs could have applications in conductive composites, transparent electrodes, heat circuits and supercapacitors.