Hydrocarbon

About: Hydrocarbon is a research topic. Over the lifetime, 27606 publications have been published within this topic receiving 458598 citations.

The roles of subsurface carbon and hydrogen in palladium-catalyzed alkyne hydrogenation.

Abstract: Alkynes can be selectively hydrogenated into alkenes on solid palladium catalysts. This process requires a strong modification of the near-surface region of palladium, in which carbon (from fragmented feed molecules) occupies interstitial lattice sites. In situ x-ray photoelectron spectroscopic measurements under reaction conditions indicated that much less carbon was dissolved in palladium during unselective, total hydrogenation. Additional studies of hydrogen content using in situ prompt gamma activation analysis, which allowed us to follow the hydrogen content of palladium during catalysis, indicated that unselective hydrogenation proceeds on hydrogen-saturated β-hydride, whereas selective hydrogenation was only possible after decoupling bulk properties from the surface events. Thus, the population of subsurface sites of palladium, by either hydrogen or carbon, governs the hydrogenation events on the surface.

Dehydrogenation and aromatization of methane under non-oxidizing conditions

Abstract: The dehydrogenation and aromatization of methane on modified ZSM-5 zeolite catalysts has been studied under non-oxidizing conditions with a fixed bed continuous-flow reactor and with a temperature programmed reactor. The results show that benzene is the only hydrocarbon product of the catalytic conversion of methane at high temperature (973 K). The catalytic activity of ZSM-5 is greatly improved by incorporating a metal cation (Mo or Zn). H2 and ethene have been directly detected in the products with a mass spectrometer during TPAR. A carbenium ion mechanism for the activation of methane is suggested.

Adsorption of polycyclic aromatic hydrocarbons by carbon nanomaterials.

Abstract: Carbon nanomaterials are novel manufactured materials, having widespread potential applications. Adsorption of hydrophobic organic compounds (HOCs) by carbon nanomaterials may enhance their toxicity and affect the fate, transformation, and transport of HOCs in the environment. In this research, adsorption of naphthalene, phenanthrene, and pyrene onto six carbon nanomaterials, including fullerenes, single-walled carbon nanotubes , and multiwalled carbon nanotubes was investigated, which is the first systematic study on polycyclic aromatic hydrocarbons (PAHs) sorption by various carbon nanomaterials. All adsorption isotherms were nonlinear and were fitted well by the Polanyi−Manes model (PMM). Through both isotherm modeling and constructing “characteristic curve”, Polanyi theory was useful to describe the adsorption process of PAHs by the carbon nanomaterials. The three fitted parameters (Q0, a, and b) of PMM depended on both PAH properties and the nature of carbon nanomaterials. For different PAHs, adsorpt...

Adsorption of polar and nonpolar organic chemicals to carbon nanotubes.

Abstract: Understanding adsorptive interactions between organic contaminants and carbon nanotubes is critical to both the environmental application of carbon nanotubes as special adsorbents and the assessment of the potential impact of carbon nanotubes on the fate and transport of organic contaminants in the environment. The adsorption of organic compounds with varied physical−chemical properties (hydrophobicity, polarity, electron polarizability, and size) to one single-walled carbon nanotube (SWNT) and two multiwalled carbon nanotubes (MWNTs) was evaluated. For a given carbon nanotube, the adsorption affinity correlated poorly with hydrophobicity but increased in the order of nonpolar aliphatic < nonpolar aromatics < nitroaromatics, and within the group of nitroaromatics, the adsorption affinity increased with the number of nitro-functional groups. We propose that the strong adsorptive interaction between carbon nanotubes and nitroaromatics was due to the π−π electron-donor–acceptor (EDA) interaction between nitr...

Organic aerosol formation from the oxidation of biogenic hydrocarbons

Abstract: A series of outdoor chamber experiments has been used to establish and characterize the significant atmospheric aerosol-forming potentials of the most prevalent biogenic hydrocarbons emitted by vegetation. These compounds were also studied to elucidate the effect of structure on aerosol yield for these types of compounds. Because oxidation products partition between the gas and aerosol phases, the aerosol yields of the parent biogenic hydrocarbons depend on the concentration of organic aerosol into which these products can be absorbed. For organic mass concentrations between 5 and 40 µg m^(-3), mass-based yields in photooxidation experiments range from 17 to 67% for sesquiterpenes, from 2 to 23% for cyclic diolefins, from 2 to 15% for bicyclic olefins, and from 2 to 6% for the acyclic triolefin ocimene. In these photooxidation experiments, hydroxyl and nitrate radicals and ozone can contribute to consumption of the parent hydrocarbon. For bicyclic olefins (α-pinene, β-pinene, Δ^3-carene, and sabinene), experiments were also carried out at daytime temperatures in a dark system in the presence of ozone or nitrate radicals alone. For ozonolysis experiments, resulting aerosol yields are less dependent on organic mass concentration, when compared to full, sunlight-driven photooxidation. Nitrate radical experiments exhibit extremely high conversion to aerosol for β-pinene, sabinene, and Δ^3-carene. The relative importance of aerosol formation from each type of reaction for bicyclic olefin photooxidation is elucidated.