Showing papers on "Hydrocarbon published in 2009"

High-Rate Solar Photocatalytic Conversion of CO2 and Water Vapor to Hydrocarbon Fuels

Abstract: Efficient solar conversion of carbon dioxide and water vapor to methane and other hydrocarbons is achieved using nitrogen-doped titania nanotube arrays, with a wall thickness low enough to facilitate effective carrier transfer to the adsorbing species, surface-loaded with nanodimensional islands of cocatalysts platinum and/or copper. All experiments are conducted in outdoor sunlight at University Park, PA. Intermediate reaction products, hydrogen and carbon monoxide, are also detected with their relative concentrations underlying hydrocarbon production rates and dependent upon the nature of the cocatalysts on the nanotube array surface. Using outdoor global AM 1.5 sunlight, 100 mW/cm(2), a hydrocarbon production rate of 111 ppm cm(-2) h(-1), or approximately 160 microL/(g h), is obtained when the nanotube array samples are loaded with both Cu and Pt nanoparticles. This rate of CO(2) to hydrocarbon production obtained under outdoor sunlight is at least 20 times higher than previous published reports, which were conducted under laboratory conditions using UV illumination.

Evaluation of Butyl Rubber as Sorbent Material for the Removal of Oil and Polycyclic Aromatic Hydrocarbons from Seawater

Abstract: Ecological disasters resulting from oil spills have created a great need to find more efficient materials for oil spill cleanup This research highlights the use of a novel macroporous polymeric material based on butyl rubber (BR) as a sorbent in an oil spill cleanup The sorption capacity of BR for crude oil and petroleum products is 15−23 g g−1 as compared to the value of 10−16 g g−1 obtained using a nonwoven polypropylene (PP), a widely used commercial oil sorbent BR sorbent is reusable after simple squeezing and its continuous sorption capacity for crude oil is 76 g g−1 in each cycle, about 3 times the capacity of the PP sorbent BR sorbents also remove efficiently polycyclic aromatic hydrocarbons (PAHs) such as acenaphthene and pyrene from seawaters The results suggest that the rubber sorbents are a better alternative to the widely used PP sorbents by improving the efficiency of oil sorption and the reusability of the sorbent

Bio-oil upgrading over platinum catalysts using in situ generated hydrogen

Abstract: The liquid phase upgrading of a model bio-oil was studied over a series of supported Pt catalysts. Pt/Al 2 O 3 showed the highest activity for deoxygenation, the oxygen content of the model oil decreasing from an initial value of 41.4 wt% to 2.8 wt% after upgrading. GC–MS analysis of the oil showed it to be highly aromatic, the major components corresponding to alkyl-substituted benzenes and cyclohexanes. CO 2 was formed as the major gaseous product, together with lower yields of H 2 and C 1 –C 6 hydrocarbons. Based on the product distribution, a reaction scheme is proposed in which light oxygenates predominantly undergo reforming to CO 2 and H 2 , with C–O bond breaking/hydrogenation (to afford alkanes) as a minor pathway. In a parallel process, aromatics undergo C–O cleavage/hydrogenation, affording benzenes and cyclohexanes. The highly alkylated nature of the products appears to be a consequence of the acidic nature of the reaction medium, favoring the occurrence of aromatic electrophilic substitution reactions.

Effects of molecular structure on aerosol yields from OH radical-initiated reactions of linear, branched, and cyclic alkanes in the presence of NOx.

Abstract: The effect of hydrocarbon molecular structure on the measured yield and volatility of secondary organic aerosol (SOA) formed from OH radical-initiated reactions of linear, branched, and cyclic alkanes in the presence of NOx was investigated in an environmental chamber. SOA yields from reactions of homologous series of linear and cyclic alkanes increased monotonically with increasing carbon number due to the decreasing volatility of the parent alkanes and thus the reaction products. For a given carbon number, yields followed the order cyclic > linear > branched, a trend that appears to be determined primarily by the extent to which alkoxy radical intermediates decompose and the nature of the resulting products, with parent alkane volatility being of secondary importance. The trend was investigated quantitatively by correlating SOA yields with the fraction of OH radical reactions that lead to alkoxy radical decomposition (the remainder isomerize), calculated using structure−reactivity relationships. For alk...

Carbon deposition as a deactivation mechanism of cobalt-based Fischer-Tropsch synthesis catalysts under realistic conditions

Abstract: Deactivation of cobalt-based Fischer–Tropsch synthesis (FTS) catalysts by carbonaceous species has been previously postulated. This mechanism, however, is difficult to prove due to the presence of long chain hydrocarbon wax product and the potential accumulation of inactive carbon on the catalyst support. Furthermore, due to the slow build-up of low quantities of inactive carbon with time on stream, the investigation of carbon deposition necessitates the use of data from extended FTS runs. In this study, the formation of carbon deposits on samples of a Co/Pt/Al2O3 catalyst, taken from a 100-barrel/day slurry bubble column reactor operated over a period of 6 months at commercially relevant FTS conditions is reported. The spent catalysts were wax extracted in an inert environment and the amount, nature and location of carbon deposits were then studied using temperature programmed hydrogenation and oxidation (TPH/TPO), energy filtered transmission electron microscopy (EFTEM), high sensitivity low energy ion scattering (HS-LEIS) and hydrogen chemisorption. TPH/TPO showed that there is an increase in polymeric carbon with time on stream which may account for a part of the observed long-term catalyst deactivation. Carbon maps from EFTEM as well HS-LEIS data show that the polymeric carbon is located both on the alumina support and cobalt. Although there is clearly an interplay of various deactivation mechanisms which may also include sintering, poisoning and cobalt reconstruction, the evidence presented shows that the polymeric carbon on the metal may be linked with a part of the longer term catalyst deactivation.

Decomposition of hydrocarbons to hydrogen and carbon

Abstract: This review assesses technologies and catalysts pertaining to the catalytic decomposition of hydrocarbons for the CO2-free generation of hydrogen for fuel cell applications through a single-step cracking (decomposition, decarbonization, dehydrogenation, pyrolysis, splitting, or dissociation) of hydrocarbons. It discusses and systematically categorizes the options for hydrocarbon decomposition to hydrogen and carbon. This decomposition helps to reduce green house gases by co-producing valuable carbon products such as carbon black or graphite-like carbon (carbon nanotubes or carbon filaments). The catalytic approach comprises metal and carbon-based catalysts while plasma-based decomposition depends on thermal or non-thermal methods. Almost all the proposed processes are applicable to a variety of gaseous and liquid hydrocarbon fuels, and some of these processes can potentially produce a stream of high-purity hydrogen. There have been successful attempts to use catalysts to reduce the maximum temperature of the thermal decomposition of hydrocarbons. Common catalysts used are noble and transition metals such as Ni, Fe, Pd, Co, Mo, etc., supported on high surface area ceramic substrates such as A12O3 and SiO2, etc. Several other publications disclose the use of carbon-based materials as catalysts for decomposition of hydrocarbons into H2 and carbon. The other non-catalytic decomposition methods include non-thermal low-temperature plasmas such as RF (radio frequency), dc (direct current) generators, microwave plasmatrons, and arc plasma jet.

Method and composition for enhanced hydrocarbons recovery

Abstract: A method of treating a hydrocarbon containing formation is described. The method may include providing a hydrocarbon recovery composition to the hydrocarbon containing formation. Hydrocarbons in the hydrocarbon containing formation may interact with the hydrocarbon recovery composition. The hydrocarbon recovery composition may include an aliphatic anionic surfactant and an aliphatic nonionic additive. In some embodiments, an aliphatic anionic surfactant may be branched. In other embodiments, an aliphatic nonionic additive may be branched.

Effects of oxidative modification of carbon surface on the adsorption of sulfur compounds in diesel fuel

Abstract: This work examines the effects of modification of activated carbons (ACs) by HNO 3 oxidation and gas-phase O 2 oxidation, respectively, on the liquid-phase adsorption of sulfur compounds in diesel fuel. The adsorption characteristics of the oxidized and the original AC samples were evaluated in a fixed-bed flow system by using a model diesel fuel containing 400 parts per million by weight (ppmw) of sulfur as thiophenic compounds and 10 wt% of aromatics in a paraffinic solvent. The pore structure and surface properties of the AC samples were characterized by N 2 adsorption, SEM, FTIR, XPS and surface pH measurements. The adsorptive selectivity factor of the AC samples increases in the order of benzothiophene (BT) ≈ naphthalene (Nap) 3 oxidation was an efficient method in improvement of the adsorption performance of the AC for sulfur compounds. The improved adsorption performance upon the HNO 3 oxidation can be attributed mainly to an increase in the acidic oxygen-containing functional groups. However, the improved adsorption capacity upon oxidation is unlikely due to an increase in mesoporous or microporous surface/volume, although such attribution might have been inferred from the literature. An excellent correlation between the concentration of the surface oxygen-containing functional groups and the adsorption capacity per unit area as well as a good relationship between the adsorption capacity and the surface pH value were observed in this work, which suggest that the adsorption of the sulfur compounds over AC from the liquid hydrocarbon fuel may involve an interaction of the acidic oxygen-containing groups on AC with the sulfur compounds.

Aromatic Hydrocarbons of Mineral Oil Origin in Foods: Method for Determining the Total Concentration and First Results

Abstract: An online normal phase high-performance liquid chromatography (HPLC)-gas chromatography (GC)-flame ionization detection (FID) method was developed for the determination of the total concentration of the aromatic hydrocarbons of mineral oil origin with up to at least five rings in edible oils and other foods. For some samples, the olefins in the food matrix were epoxidized to increase their polarity and remove them from the fraction of the aromatic hydrocarbons. This reaction was carefully optimized, because also some aromatics tend to react. To reach a detection limit of around 1 mg kg(-1) in edible oils, an off-line enrichment was introduced. Some foods contained elevated concentrations of white paraffin oils (free of aromatics), but the majority of the mineral oils detected in foods were of technical grade with 20-30% aromatic hydrocarbons. Many foods contained mineral aromatic hydrocarbons in excess of 1 mg kg(-1).

Selective Adsorption for Removal of Nitrogen Compounds from Liquid Hydrocarbon Streams over Carbon- and Alumina-Based Adsorbents

Abstract: In order to explore the adsorptive denitrogenation of liquid hydrocarbon streams for producing ultraclean fuels, the adsorption performance of seven representative activated carbon samples and three activated alumina samples was evaluated in a batch adsorption system and a fixed-bed flow adsorption system for removing quinoline and indole from a model diesel fuel in the coexistence of sulfur compounds and aromatics. Different adsorbents show quite different selectivity toward basic and nonbasic nitrogen compounds (quinoline and indole) and sulfur compounds (dibenzothiophene and 4,6-dimethyldibenzothiophene). The activated carbons generally show higher capacity than activated alumina samples for removing the nitrogen compounds. The adsorption capacity and selectivity of the activated carbons for nitrogen compounds were further correlated with their textural properties and oxygen content. It was found that (1) the microporous surface area and micropore volume are not a key factor for removal of the nitrogen...

Shock-tube study of the ignition of methane/ethane/hydrogen mixtures with hydrogen contents from 0% to 100% at different pressures

Abstract: The ignition delay times of diluted hydrogen/reference gas (92% methane, 8% ethane)/O2/Ar mixtures with hydrogen contents of 0%, 40%, 80% and 100% were determined in a high-pressure shock tube at equivalence ratios ϕ = 0.5 and 1.0 (dilution 1:5). The temperature range was 900 K ⩽ T ⩽ 1800 K at pressures of about 1, 4 and 16 bar. The reference gas and the 40% hydrogen/60% reference gas data showed typical characteristics of hydrocarbon systems and can be represented by: τ ign / μ s = 10 - 2.75 ± 0.13 exp ( 20 , 450 ± 442 K / T ) ( p / bar ) - 0.51 ± 0.02 ϕ 0.59 ± 0.06 ( reference gas ) and τ ign / μ s = 10 - 2.07 ± 0.09 exp ( 16 , 350 ± 299 K / T ) ( p / bar ) - 0.49 ± 0.02 ϕ 0.75 ± 0.06 ( 40 % H 2 / reference gas ) . The pure hydrogen data exhibit a more complex pressure dependence with the 16 bar values having the slowest ignition delay times at lower temperatures and the fastest ignition delay times at higher temperatures. No dependence on the equivalence ratio was observed. The 80% hydrogen/20% reference gas data display characteristics of hydrocarbon and hydrogen systems. The comparison of the measurements to MPFR-CHEMKIN II simulations with different mechanisms shows that the predictions of all tested mechanisms with the exception of the GRI3.0 agree well with the experimental values for reference gas, 40% hydrogen/60% reference gas and partly for 80% hydrogen/20% reference gas and 100% hydrogen. None of the mechanisms can represent the observed reduction of the activation energy at low temperatures of pure hydrogen and of 80% hydrogen/20% reference gas at p ⩾ 4 bar. The literature mechanisms which were developed for H2 or for mixtures with a dominating H2 subsystem cannot predict the observed reduction of the activation energies, either.

Influence of Gas Feed Composition and Pressure on the Catalytic Conversion of CO2 to Hydrocarbons Using a Traditional Cobalt-Based Fischer−Tropsch Catalyst

Abstract: The hydrogenation of CO2 using a traditional Fischer−Tropsch Co−Pt/Al2O3 catalyst for the production of valuable hydrocarbon materials is investigated. The ability to direct product distribution was measured as a function of different feed gas ratios of H2 and CO2 (3:1, 2:1, and 1:1) as well as operating pressures (ranging from 450 to 150 psig). As the feed gas ratio was changed from 3:1 to 2:1 and 1:1, the production distribution shifted from methane toward higher chain hydrocarbons. This change in feed gas ratio is believed to lower the methanation ability of Co in favor of chain growth, with possibly two different active sites for methane and C2−C4 products. Furthermore, with decreasing pressure, the methane conversion drops slightly in favor of C2−C4 paraffins. Even though under certain reaction conditions product distribution can be shifted slightly away from the formation of methane, the catalyst studied behaves like a methanation catalyst in the hydrogenation of CO2.

Ethanol transformation over HFAU, HBEA and HMFI zeolites presenting similar Brønsted acidity

Abstract: Ethanol transformation into higher hydrocarbons in one step by heterogeneous acid catalysis was studied, under 350 °C and 30 bar of total pressure. A comparison was established among three zeolites (HFAU, HBEA and HZSM-5) having the same quantity of Bronsted acid sites but possessing different pore architectures. Large pore HFAU and HBEA zeolites gave mainly increasing yield of ethylene and diethyl ether with time-on-stream, due to the deactivation of the strongest acid sites and only a low quantity of C 3+ hydrocarbons. This was explained by a faster deactivation of large pore zeolites due to fast coke formation which rapidly eliminates strong Bronsted acid sites, required for the transformation of ethylene into higher hydrocarbons. These coke molecules were identified as being polyaromatic compounds. Medium pore zeolite HZSM-5 showed an important formation of C 3+ hydrocarbons (mostly C 5 –C 11 compounds) and very small amounts of ethylene and diethyl ether. For this zeolite, after 16 h reaction, there was still complete ethanol transformation into C 3+ hydrocarbons, even though a 55% loss of microporosity and 94% loss of Bronsted acidity were observed. On HZSM-5 the deactivation is slower and the formation of C 3+ hydrocarbons was observed even when the catalyst was saturated with coke molecules (high activity for the hydrogen transfer reactions). It could be possible, that for this zeolite, reaction occurs at the pore mouth of the channel.

Role of Surface Oxygen-Containing Functional Groups in Liquid-Phase Adsorption of Nitrogen Compounds on Carbon-Based Adsorbents

Abstract: The carbon-based adsorbents are promising for adsorptive denitrogenation (ADN) of liquid hydrocarbon streams. The objective of the present study is to develop a fundamental understanding of the rol...

Oil Recovery from Petroleum Sludge by Solvent Extraction

Abstract: Technical problems associated with sludge deposition in storage units of petroleum industries are enormous. The conventional methods of management are laborious and uneconomical; the hydrocarbon co...

Isolation of hydrocarbon degrading bacteria from soils contaminated with crude oil spills.

Abstract: A feasibility study was conducted to evaluate the capability of bacterial strains to degrade crude oil under in vitro conditions. Pseudomonas strain PS-I could degrade alkanes (70.69%) and aromatics (45.37%). Alkanes and aromatic fractions separated by column chromatography were analyzed by gas chromatography. In case of Pseudomonas strain PS-I, nC 17 /Pr, nC 18 /Ph ratios decreased from 2.5100 to 0.1232 and from 7.2886 to 0.3853, respectively. It was concluded that out of the isolated strains, Pseudomonas strain PS-I, PS-II and PS-III were comparatively better and potent hydrocarbon degraders. Pseudomonas strain PS-I was almost comparable with standard strain of Acinetobacter calcoaceticus in crude oil biodegradation potency.

Emission and chemistry of organic carbon in the gas and aerosol phase at a sub-urban site near Mexico City in March 2006 during the MILAGRO study

Abstract: . Volatile organic compounds (VOCs) and carbonaceous aerosol were measured at a sub-urban site near Mexico City in March of 2006 during the MILAGRO study (Megacity Initiative: Local and Global Research Objectives). Diurnal variations of hydrocarbons, elemental carbon (EC) and hydrocarbon-like organic aerosol (HOA) were dominated by a high peak in the early morning when local emissions accumulated in a shallow boundary layer, and a minimum in the afternoon when the emissions were diluted in a significantly expanded boundary layer and, in case of the reactive gases, removed by OH. In comparison, diurnal variations of species with secondary sources such as the aldehydes, ketones, oxygenated organic aerosol (OOA) and water-soluble organic carbon (WSOC) stayed relatively high in the afternoon indicating strong photochemical formation. Emission ratios of many hydrocarbon species relative to CO were higher in Mexico City than in the U.S., but we found similar emission ratios for most oxygenated VOCs and organic aerosol. Secondary formation of acetone may be more efficient in Mexico City than in the U.S., due to higher emissions of alkane precursors from the use of liquefied petroleum gas. Secondary formation of organic aerosol was similar between Mexico City and the U.S. Combining the data for all measured gas and aerosol species, we describe the budget of total observed organic carbon (TOOC), and find that the enhancement ratio of TOOC relative to CO is conserved between the early morning and mid afternoon despite large compositional changes. Finally, the influence of biomass burning is investigated using the measurements of acetonitrile, which was found to correlate with levoglucosan in the particle phase. Diurnal variations of acetonitrile indicate a contribution from local burning sources. Scatter plots of acetonitrile versus CO suggest that the contribution of biomass burning to the enhancement of most gas and aerosol species was not dominant and perhaps not dissimilar from observations in the U.S.

Physisorption and chemisorption of alkanes and alkenes in H-FAU: a combined ab initio–statistical thermodynamics study

Abstract: The sorption in H-FAU zeolite of C4-C12 n-alkanes, and linear and branched C2-C8 alkenes has been quantified up to 800 K by combining QM-Pot(MP2//B3LYP) with statistical thermodynamics calculations. The physisorption strength increases linearly with increasing carbon number by 8.5 kJ mol(-1) and does not depend on the detailed alkane or alkene structure. Van der Waals interactions are dominant in physisorption, but alkenes are additionally stabilized by 20 kJ mol(-1) by formation of a pi-complex. Protonation of an alkene leads to the formation of alkoxides, which are more stable than the physisorbed species. As for physisorption a linear relation between the chemisorption energy and the carbon number is obtained. Protonation energies are independent of the carbon number but depend on the type of CC double bond being protonated. The relative stability difference between the secondary and tertiary alkoxides is 15 kJ mol(-1) in favor of the former. Both physisorption and chemisorption are accompanied with entropy losses which increase linearly with the carbon number. A typical compensation effect is obtained: the stronger the stabilization of the sorbed species the more pronounced the entropy loss. For temperatures ranging from 0 to 800 K, all of the derived linear relations expressing the physisorption and/or chemisorption enthalpy and entropy of the alkanes and the alkanes as function of the carbon number are independent of temperature. A good agreement between calculated and experimental values for alkanes is obtained at 500 K.

The Hydrocarbon Pool in Ethanol-to-Gasoline over HZSM-5 Catalysts

Abstract: It is shown that the conversion of ethanol-to-gasoline over an HZSM-5 catalyst yields essentially the same product distribution as for methanol-to-gasoline performed over the same catalyst. Interestingly, there is a significant difference between the identity of the hydrocarbon molecules trapped inside the HZSM-5 catalyst when ethanol is used as a feed instead of methanol. In particular, the hydrocarbon pool contains a significant amount of ethylsubstituted aromatics when ethanol is used as feedstock, but there remains only methyl-substituted aromatics in the product slate.