Showing papers on "Hydrocarbon published in 2021"

Selective capture of carbon dioxide from hydrocarbons using a metal-organic framework.

Abstract: Efficient and sustainable methods for carbon dioxide capture are highly sought after. Mature technologies involve chemical reactions that absorb CO2, but they have many drawbacks. Energy-efficient alternatives may be realised by porous physisorbents with void spaces that are complementary in size and electrostatic potential to molecular CO2. Here, we present a robust, recyclable and inexpensive adsorbent termed MUF-16. This metal-organic framework captures CO2 with a high affinity in its one-dimensional channels, as determined by adsorption isotherms, X-ray crystallography and density-functional theory calculations. Its low affinity for other competing gases delivers high selectivity for the adsorption of CO2 over methane, acetylene, ethylene, ethane, propylene and propane. For equimolar mixtures of CO2/CH4 and CO2/C2H2, the selectivity is 6690 and 510, respectively. Breakthrough gas separations under dynamic conditions benefit from short time lags in the elution of the weakly-adsorbed component to deliver high-purity hydrocarbon products, including pure methane and acetylene.

One-step Ethylene Purification from an Acetylene/Ethylene/Ethane Ternary Mixture by Cyclopentadiene Cobalt-Functionalized Metal-Organic Frameworks.

Abstract: The separation of ethylene (C2 H4 ) from a mixture of ethane (C2 H6 ), ethylene (C2 H4 ), and acetylene (C2 H2 ) at normal temperature and pressure is a significant challenge. The sieving effect of pores is powerless due to the similar molecular size and kinetic diameter of these molecules. We report a new modification method based on a stable ftw topological Zr-MOF platform (MOF-525). Introduction of a cyclopentadiene cobalt functional group led to new ftw-type MOFs materials (UPC-612 and UPC-613), which increase the host-guest interaction and achieve efficient ethylene purification from the mixture of hydrocarbon gases. The high performance of UPC-612 and UPC-613 for C2 H2 /C2 H4 /C2 H6 separation has been verified by gas sorption isotherms, density functional theory (DFT), and experimentally determined breakthrough curves. This work provides a one-step separation of the ternary gas mixture and can further serve as a blueprint for the design and construction of function-oriented porous structures for such applications.

Deconstruction of high-density polyethylene into liquid hydrocarbon fuels and lubricants by hydrogenolysis over Ru catalyst

Abstract: Summary Polyethylene (PE) is the most popular plastic globally, and the widespread use of plastics has created severe environmental issues. High energy consumption in the current process makes its recycling a challenging problem. In our report, the depolymerization of high-density PE was conducted in various liquid-phase solvents with the Ru/C catalyst under relatively mild conditions. The maximum yields of the jet-fuel- and lubricant-range hydrocarbons were 60.8 and 31.6 wt %, respectively. After optimization of the reaction conditions (220°C and 60 bar of H2), the total yield of liquid hydrocarbon products reached approximately 90 wt % within only 1 h. The product distribution could be tuned by the H2 partial pressure, the active-metal particle size, and the solvents. The solvation of PE in the different solvents determined the depolymerization reaction kinetics, which was confirmed by the molecular dynamics simulation results.

Effective radiative forcing from emissions of reactive gases and aerosols – a multi-model comparison

Abstract: . This paper quantifies the effective radiative forcing from CMIP6 models of the present-day anthropogenic emissions of NOx, CO, VOCs, SO2, NH3, black carbon and primary organic carbon. Effective radiative forcing from pre-industrial to present-day changes in the concentrations of methane, N2O and halocarbons are quantified and attributed to their anthropogenic emissions. Emissions of reactive species can cause multiple changes in the composition of radiatively active species: tropospheric ozone, stratospheric ozone, secondary inorganic and organic aerosol and methane. We therefore break down the ERFs from each emitted species into the contributions from the composition changes. The 1850 to 2014 mean ERFs are 1.1 ± 0.07 W m−2 for sulfate, −0.24 ± 0.01 W m−2 for organic carbon (OC), and 0.15 ± 0.04 W m−2 for black carbon (BC), and for the aerosols combined it is −0.95 ± 0.03 W m−2. The means for the reactive gases are 0.69 ± 0.04 W m−2 for methane (CH4), 0.06 ± 0.04 W m−2 for NOx, −0.09 ± 0.03 W m−2 for volatile organic carbons (VOC), 0.16 ± 0.03 W m−2 for ozone (O3), 0.27 W m−2 for nitrous oxide (N2O) and −0.02 ± 0.06 W m−2 for hydrocarbon (HC). Differences in ERFs calculated for the different models reflect differences in the complexity of their aerosol and chemistry schemes, especially in the case of methane where tropospheric chemistry captures increased forcing from ozone production.

Highly Selective Adsorption of Carbon Dioxide over Acetylene in an Ultramicroporous Metal–Organic Framework

Abstract: Separating carbon dioxide from fuel gases like hydrocarbons by physical adsorbents is industrially important and more energy-efficient than traditional liquid extraction or cryogenic distillation methods. It is very important while very challenging to develop CO2 -selective adsorbents, considering CO2 is less polarizable than light hydrocarbon molecules, particularly those simultaneously with almost identical molecular dimensions and physical properties, such as acetylene. Herein, an ultramicroporous metal-organic framework constructed from copper(II) and 5-fluoropyrimidin-2-olate, termed Cu-F-pymo, is carefully studied under different activations for inverse separation of CO2 from C2 H2 . The partially desolvated Cu-F-pymo can exclusively capture CO2 over C2 H2 with very high selectivity exceeding 105 under ambient conditions, the highest ever reported. Sorption experiments and modeling studies reveal that such molecular sieving effect is attributed to the suppression of C2 H2 adsorption from the blockage of the preferential sites for C2 H2 by residual water molecules. The inverse separation is further confirmed by column breakthrough studies given that highly pure acetylene (>99.9%) can be directly harvested from the gas mixture. Cu-F-pymo also shows remarkable stability under harsh conditions.

Thermal and catalytic pyrolysis of waste polypropylene plastic using spent FCC catalyst

Abstract: Waste polypropylene plastic (WPP) is an enormous volume of plastics in the landfill in Nigeria. It causes serious environmental problems, such as reduced landfill space and pollution. We made WPP plastic undergo pyrolysis using a batch reactor subjected to temperatures variation of 300 °C, 350 °C, 375 °C, 400 °C, and the spent fluid catalytic cracking (FCC) catalyst used were 5, 7.5, and 10 wt% catalyst. We heated the reactor at a rate of 15 °C/min. until it reaches the pyrolysis temperature of 400 °C at atmospheric pressure. We investigated the influence of the FCC catalyst, reaction temperatures, and catalyst to plastic ratio. We characterized the pyrolysis liquid oil using density, pour point, API gravity, flash point, viscosity, calorific value, carbon residue, ATSM distillation, and GC–MS. The thermal pyrolysis produced maximum liquid oil (83.3 wt%) with gases (13.2 wt%), and char (3.0 wt%), while the catalytic pyrolysis using 0.1 catalyst to plastic ratio decreased the liquid oil yield (77.6 wt%), and char (2.7 wt%), with an increase in gases (19.7 wt%). The GC–MS results of the catalytic pyrolysis of liquid oil showed that the liquid fractions comprised a wide range of hydrocarbon, mainly distributed within C4 to > C17. The paraffin, olefins, naphthalene, and aromatics yield were 30.83%, 44.6%. 19.44%, and 5.13%, respectively. The liquid oil’s fuel properties were like that of gasoline and diesel.

Cobalt-Catalyzed Intermolecular C-H Amidation of Unactivated Alkanes.

Abstract: Alkanes are an abundant and inexpensive source of hydrocarbons; thus, development of new methods to convert the hydrocarbon feedstocks to value-added chemicals is of high interest. However, it is challenging to achieve such transformation in a direct and selective manner mainly due to the intrinsic inertness of their C-H bonds. We herein report a tailored Cp*Co(III)(LX)-catalyzed efficient and site-selective intermolecular amidation of unactivated hydrocarbons including light alkanes. Electronic modulation of the cobalt complexes led to the enhanced amidation efficiency, and these effects were theoretically rationalized by the FMO analysis of presupposed cobalt nitrenoid species. Under the current cobalt protocol, a secondary C-H bond selectivity was observed in various nonactivated alkanes to reverse the intrinsic tertiary preference, which is attributed to the steric demands of the cobalt system that imposes difficulties in accessing tertiary C-H bonds. Experimental and computational studies suggested that the putative triplet Co nitrenoids are transferred to the C-H bonds of alkanes via a radical-like hydrogen abstraction pathway.

Controllable CO adsorption determines ethylene and methane productions from CO2 electroreduction

Abstract: Among all CO2 electroreduction products, methane (CH4) and ethylene (C2H4) are two typical and valuable hydrocarbon products which are formed in two different pathways: hydrogenation and dimerization reactions of the same CO intermediate Theoretical studies show that the adsorption configurations of CO intermediate determine the reaction pathways towards CH4/C2H4 However, it is challenging to experimentally control the CO adsorption configurations at the catalyst surface, and thus the hydrocarbon selectivity is still limited Herein, we seek to synthesize two well-defined copper nanocatalysts with controllable surface structures The two model catalysts exhibit a high hydrocarbon selectivity toward either CH4 (83%) or C2H4 (93%) under identical reduction conditions Scanning transmission electron microscopy and X-ray absorption spectroscopy characterizations reveal the low-coordination Cu0 sites and local Cu0/Cu+ sites of the two catalysts, respectively CO-temperature programed desorption, in-situ attenuated total reflection Fourier transform infrared spectroscopy and density functional theory studies unveil that the bridge-adsorbed CO (COB) on the low-coordination Cu0 sites is apt to be hydrogenated to CH4, whereas the bridge-adsorbed CO plus linear-adsorbed CO (COB + COL) on the local Cu0/Cu+ sites are apt to be coupled to C2H4 Our findings pave a new way to design catalysts with controllable CO adsorption configurations for high hydrocarbon product selectivity

Design of Cobalt Fischer–Tropsch Catalysts for the Combined Production of Liquid Fuels and Olefin Chemicals from Hydrogen-Rich Syngas

Abstract: Adjusting hydrocarbon product distributions in the Fischer-Tropsch (FT) synthesis is of notable significance in the context of so-called X-to-liquids (XTL) technologies. While cobalt catalysts are selective to long-chain paraffin precursors for synthetic jet- and diesel-fuels, lighter (C10-) alkane condensates are less valuable for fuel production. Alternatively, iron carbide-based catalysts are suitable for the coproduction of paraffinic waxes alongside liquid (and gaseous) olefin chemicals; however, their activity for the water-gas-shift reaction (WGSR) is notoriously detrimental when hydrogen-rich syngas feeds, for example, derived from (unconventional) natural gas, are to be converted. Herein the roles of pore architecture and oxide promoters of Lewis basic character on CoRu/Al2O3 FT catalysts are systematically addressed, targeting the development of catalysts with unusually high selectivity to liquid olefins. Both alkali and lanthanide oxides lead to a decrease in turnover frequency. The latter, particularly PrO x , prove effective to boost the selectivity to liquid (C5-10) olefins without undesired WGSR activity. In situ CO-FTIR spectroscopy suggests a dual promotion via both electronic modification of surface Co sites and the inhibition of Lewis acidity on the support, which has direct implications for double-bond isomerization reactivity and thus the regioisomery of liquid olefin products. Density functional theory calculations ascribe oxide promotion to an enhanced competitive adsorption of molecular CO versus hydrogen and olefins on oxide-decorated cobalt surfaces, dampening (secondary) olefin hydrogenation, and suggest an exacerbated metal surface carbophilicity to underlie the undesired induction of WGSR activity by strongly electron-donating alkali oxide promoters. Enhanced pore molecular transport within a multimodal meso-macroporous architecture in combination with PrO x as promoter, at an optimal surface loading of 1 Prat nm-2, results in an unconventional product distribution, reconciling benefits intrinsic to Co- and Fe-based FT catalysts, respectively. A chain-growth probability of 0.75, and thus >70 C% selectivity to C5+ products, is achieved alongside lighter hydrocarbon (C5-10) condensates that are significantly enriched in added-value chemicals (67 C%), predominantly α-olefins but also linear alcohols, remarkably with essentially no CO2 side-production (<1%). Such unusual product distributions, integrating precursors for synthetic fuels and liquid platform chemicals, might be desired to diversify the scope and improve the economics of small-scale gas- and biomass-to-liquid processes.

Extra-Heavy Oil Aquathermolysis Using Nickel-Based Catalyst: Some Aspects of In-Situ Transformation of Catalyst Precursor

Abstract: In the present work, we studied the catalytic performance of an oil-soluble nickel-based catalyst during aquathermolysis of oil-saturated crushed cores from Boca de Jaruco extra-heavy oil field. The decomposition of nickel tallate and some aspects of in-situ transformation of the given catalyst precursor under the steam injection conditions were investigated in a high-pressure batch reactor using XRD and SEM analysis methods. The changes in physical and chemical properties of core extracts after the catalytic aquathermolysis process with various duration were studied using gas chromatography for analyzing gas products, SARA analysis, GC-MS of saturated and aromatic fractions, FT-IR spectrometer, elemental analysis, and matrix-activated laser desorption/ionization (MALDI). The results showed that nickel tallate in the presence of oil-saturated crushed core under the injection of steam at 300 °C transforms mainly into nonstoichiometric forms of nickel sulfide. According to the SEM images, the size of nickel sulfide particles was in the range of 80–100 nm. The behavior of main catalytic aquathermolysis gas products such as CH4, CO2, H2S, and H2 depending on the duration of the process was analyzed. The catalytic upgrading at 300 °C provided decrease in the content of resins and asphaltenes, and increase in saturated hydrocarbon content. Moreover, the content of low-molecular alkanes, which were not detected before the catalytic aquathermolysis process, dramatically increased in saturates fraction after catalytic aquathermolysis reactions. In addition, the aromatics hydrocarbons saturated with high molecular weight polycyclic aromatic compounds—isomers of benzo(a)fluorine, which were initially concentrated in resins and asphaltenes. Nickel sulfide showed a good performance in desulfurization of high-molecular components of extra-heavy oil. The cracking of the weak C–S bonds, which mainly concentrated in resins and asphaltenes, ring-opening reactions, detachment of alkyl substitutes from asphaltenes and inhibition of polymerization reactions in the presence of catalytic complex reduced the average molecular mass of resins (from 871.7 to 523.3 a.m.u.) and asphaltenes (from 1572.7 to 1072.3 a.m.u.). Thus, nickel tallate is a promising catalyst to promote the in-situ upgrading of extra-heavy oil during steam injection techniques.

Conversion of Polyethylene Waste into Gaseous Hydrocarbons via Integrated Tandem Chemical-Photo/Electrocatalytic Processes.

Abstract: The chemical inertness of polyethylene makes chemical recycling challenging and motivates the development of new catalytic innovations to mitigate polymer waste. Current chemical recycling methods yield a complex mixture of liquid products, which is challenging to utilize in subsequent processes. Here, we present an oxidative depolymerization step utilizing diluted nitric acid to convert polyethylene into organic acids (40% organic acid yield), which can be coupled to a photo- or electrocatalytic decarboxylation reaction to produce hydrocarbons (individual hydrocarbon yields of 3 and 20%, respectively) with H2 and CO2 as gaseous byproducts. The integrated tandem process allows for the direct conversion of polyethylene into gaseous hydrocarbon products with an overall hydrocarbon yield of 1.0% for the oxidative/photocatalytic route and 7.6% for the oxidative/electrolytic route. The product selectivity is tunable with photocatalysis using TiO2 or carbon nitride, yielding alkanes (ethane and propane), whereas electrocatalysis on carbon electrodes produces alkenes (ethylene and propylene). This two-step recycling process of plastics can use sunlight or renewable electricity to convert polyethylene into valuable, easily separable, gaseous platform chemicals.

The development of bifunctional catalysts for carbon dioxide hydrogenation to hydrocarbons via the methanol route: from single component to integrated components

Abstract: Hydrocarbon utilisation results in the emission of a large amount of CO2, while crude oil as the conventional source of hydrocarbons will eventually be depleted These problems can both be potentially solved via a bifunctional catalytic system with integrated components that can directly convert CO2 into hydrocarbons There are two possible reaction pathways involved in this catalytic system, but compared to the reverse water gas shift-Fischer Tropsch synthesis (RWGS-FTS) route, the methanol route potentially has a higher selectivity of desired products due to its ability to overcome the restriction of the Anderson–Schulz–Flory (ASF) distribution The methanol route requires bifunctional catalysts consisting of metal/metal oxide and zeolite components The former is used to convert CO2 into methanol, whereas the latter is used to convert methanol into hydrocarbons This review first discusses the development of metal/metal oxide single component catalysts to enhance the hydrogenation of CO2, methanol selectivity, and methanol yield Next, the development of zeolite single-component catalysts for the methanol to hydrocarbon (MTH) reaction by minimising coke formation and tuning the hydrocarbon selectivity is discussed, and finally the development of integrated bifunctional catalysts via the methanol route is introduced Overall, although bifunctional catalytic systems can successfully achieve the desired product selectivity for all hydrocarbons, they suffer from high CO selectivity at a high operating temperature, which needs to be addressed to enhance the yield and selectivity of a specific hydrocarbon At this stage, it could not be confirmed if bifunctional catalytic systems can effectively decrease the CO2 content globally, while acting as an effective alternative hydrocarbon source until a complete life cycle analysis is conducted Nevertheless, it can be concluded that bifunctional catalytic systems demonstrate much better potential and benefits than separate multi-step catalysts in different reactors because under the same reaction conditions, bifunctional catalysts demonstrate higher CO2 conversion and lower CO selectivity than single metal/metal oxide catalysts and longer catalyst lifetimes than single zeolite catalysts, while maintaining selectivity for desired hydrocarbon products

Highly Durable C2 Hydrocarbon Production via the Oxidative Coupling of Methane Using a BaFe0.9Zr0.1O3−δ Mixed Ionic and Electronic Conducting Membrane and La2O3 Catalyst

Abstract: The oxidative coupling of methane (OCM) is an attractive technology for the production of ethane (C2H6) and ethylene (C2H4); and significant performance and efficiency gains as well as reduced carb...