C2 Hydrocarbons Research Articles

Highly active and selective Li/MgO catalysts for methane transformation to C2 hydrocarbons: experimental and DFT study

Oxidative coupling of methane to C2 hydrocarbons.

Maximizing the catalytic performance of FER zeolite in the methanol-to-hydrocarbon process by manipulating the crystal size and constructing a bifunctional system

An unprecedented catalyst lifespan was accomplished with a preferential selectivity for C4–C7 hydrocarbons by combining Y2O3 with a unique flake-shaped FER zeolite with optimized physicochemical properties.

Исследование примесного состава тетрафторида германия методом хромато-масс-спектрометрии

For the first time, the impurity composition of GeF4 with a natural content of isotopes and isotopically enriched was studied by chromato-mass spectrometry using adsorption capillary columns. For the identification and determination of impurity substances, their preliminary cryogenic concentration is proposed. Information on the impurity composition of germanium tetrafluoride of various isotopic composition has been expanded. The presence of permanent gases, limiting and unsaturated C3–C9 hydrocarbons, freons, alkylfluorosilanes, fluorochlorogermanes, silicon tetrafluoride, germanium tetrachloride. A total of 32 impurity substances were identified, 29 of which were discovered for the first time.

Effect of biomass ash on preventing aromatization of olefinic cracking products in dual fluidized bed systems

In this work, the effect of ash activated olivine on olefinic products cracking and aromatization was assessed. The experiments were carried out in the Chalmers 2–4 MWth dual fluidized bed gasifier, where the feedstock was cracked using steam as fluidization agent, at a reaction temperature of ca. 780–790 °C. Three activation states of the olivine, representing three consecutive days of the campaign, were evaluated. The changes of the permanent gas composition along with the reduction in aromatic species with the time of exposure to biomass ash demonstrate a clear effect of the ash activated olivine on the conversion of olefinic cracking products. The ash activation of the olivine clearly promoted the reactions involving steam. As a consequence, higher yields of permanent gases, mainly H2, CO and CO2, were produced at expenses of the yields of the total aromatic compounds and C4 hydrocarbons and larger. It is concluded that the biomass ash activated olivine promotes the steam reforming path of the C4 and larger hydrocarbon fragments, while avoiding the alternative aromatization route. The results presented here provide useful insights on the opportunities and limitations of ash activated materials in DFB systems when steam cracking linear hydrocarbon feedstocks, e.g., polyolefin-based materials.

One-Step Carbothermal Reduction Synthesis of Metal-Loaded Biochar Catalyst for In Situ Catalytic Upgrading of Plastic Pyrolysis Products

A novel biochar-supported metal catalyst was prepared in this study using a one-step carbothermal reduction synthesis method for the catalytic pyrolysis of plastics. Several catalysts with different metals (Cu, Fe, Ni, and Ru) loaded on three biochar supports from lignin, soybean straw, and Chlorella vulgaris were evaluated using XRD, FTIR, NH3-TPR, and TEM. Zerovalent metal nanoparticles, including Ni, Cu, and Ru, and various functional groups were observed on the biochar surface. The chemical selectivities of gasoline hydrocarbons (C4–C12 hydrocarbons) reached 76.2% with a remarkable catalytic cracking effect of Ni/lignin biochar on low density polyethylene (LDPE). Catalytic performance was comparable to that of the Ru-based catalyst, which contributed to 85.6% of gasoline hydrocarbons. The Ni/lignin catalytic cracking of plastic waste simulated by LDPE, polypropylene (PP), and polystyrene (PS) showed a maximum selectivity of 87.9% for C4–C12 hydrocarbons and yields of 78.1 mg/g for benzene, toluene, and xylene (BTX). The mechanism related to the cleavage of long chain radicals of polyethylene, polypropylene, and polystyrene as well as the aromatization of aliphatics were proposed.

Insight into the strong Brönsted acid sites on isolated WOx-modified Pt/zirconium phosphate for glycerol efficient hydrodeoxygenation

Brönsted acidity of Pt/WOx-based catalysts is crucial to efficient activation of C–OH bond in glycerol. Constructing strong Brönsted acidic sites (BAs) on catalysts is highly desired for efficient transformation of glycerol. Motivated by the source of Brönsted acidity in phosphotungstic acid, strong BAs were constructed on isolated WOx-modified Pt/zirconium phosphate (ZrPO4). Various characterizations confirm that the strong BAs on Pt-WOx/ZrPO4 are derived from the distinctive local structure of isolated W (V) oxides upon interacted with phosphate anion and zirconium center of ZrPO4 through O–W–O groups. In addition, the strong Brönsted acidity of Pt-WOx/ZrPO4 contributes to the efficient C–OH activation and producing 46.2% of C3 hydrocarbons in yield in glycerol hydrodeoxygenation, which is superior to that over other reported Pt/WOx catalysts. This work provides a strategy of fabricating strong BAs on solid catalysts and deep insight into the source of its Brönsted acidity for efficient transformation of C–OH in polyols.

СОПОСТАВЛЕНИЕ ЭФФЕКТИВНОСТИ РАЗДЕЛЯЮЩИХ АГЕНТОВ В ПРОЦЕССЕ ВЫДЕЛЕНИЯ ДИВИНИЛА ИЗ БУТЕН-ДИВИНИЛЬНОЙ ФРАКЦИИ (БДФ) МЕТОДОМ ЭКСТРАКТИВНОЙ РЕКТИФИКАЦИИ

Comparison of the relative volatility of C4 hydrocarbons with respect to divinyl in the presence of various separating agents was made

Slow Pyrolysis of Quercus cerris Cork: Characterization of Biochars and Pyrolysis Volatiles

Waste cork granules of Quercus cerris bark were subjected to isothermal and non-isothermal slow pyrolysis. The heat of the reaction, as well as the yields and properties of biochar, bio-oil, and pyrolysis gas were investigated by thermogravimetric analysis, FT-IR, CHN elemental analysis, higher heating value (HHV) determinations, scanning electron microscopy (SEM), and gas chromatography (GC). The slow pyrolysis was carried out in a semi-batch reactor using an isothermal or a non-isothermal dynamic approach. The results demonstrated that isothermal or non-isothermal slow pyrolysis of cork is a slightly exothermic reaction that produces biochars. The elemental analysis results indicated that non-isothermally produced chars have similar fuel properties compared to isothermally produced chars. The FT-IR results showed that cork suberin undergoes a higher degree of degradation in isothermal chars and aromatization begins in the char structure. Bio-oils are also produced and they consist of C5–C12 hydrocarbons with C8 carbon compounds making up the main fraction. Lighter components, mainly C1–C2 hydrocarbons are collected in the gas phase. The overall results indicate a possible reduced-cost route for the production of cork-based biochars by using non-isothermal slow pyrolysis.

Mechanism study on gliding arc (GA) plasma reforming: Unraveling the decisive role of CH4/CO2 ratio in the dry reforming reaction

AbstractAiming at understanding the role of CH4/CO2 ratio on gliding arc (GA)‐based dry reforming of methane (GA‐DRM), the GA‐DRM at CH4/CO2 ratio range of 0.11 to 1 was studied with kinetics simulation. The radicals of H, OH, and CH3 are identified as the main reactive species to induce the reactant conversion and product formation in GA‐DRM. The increase of CH4/CO2 raises the concentrations of H and CH3 and reduces the OH concentration. Subsequently, the CH4/CO2 ratio regulates the main reaction routes of GA‐DRM. The dehydrogenation coupling reaction enhances with CH4/CO2 and thus raises the selectivities of C2 hydrocarbons. The OH‐induced reactions for OH to H2O weaken with CH4/CO2, thereby increasing the H2 selectivity.

Optimization of operating conditions of an internal combustion engine used as chemical reactor for methane reforming using ozone as an additive

Internal combustion engines can be used as chemical reactors exploiting the high temperature and pressure as well as short residence time for chemical conversion. For instance, methane and CO2 can be efficiently converted to H2 and CO (syngas). The process can be boosted by additives such as dimethyl ether (DME). In this paper, the focus is on optimizing the operating conditions for the use of ozone, O3, as an alternative fuel additive for dry reforming of methane. Furthermore, methane can be converted to C2 hydrocarbons, which is also studied numerically to find optimized operating conditions, again using O3 as an additive. The engine is modelled as a single-zone batch reactor under ideal gas assumptions with a variable volume profile. An elementary-step reaction mechanism consisting of 749 reactions among 132 species and including O3 chemistry was used for the simulations. CO2 conversion of over 70% is possible using O3 as an additive, whereas the maximum achievable using DME was around 50%. The optimized yield of C2H4 is higher with O3 as an additive as compared to DME, at all the inlet gas temperatures, whereas it is lower for CH2O and comparable for C6H6 and CH3OH.

Substituent Engineering-Enabled Structural Rigidification and Performance Improvement for C2/CO2 Separation in Three Isoreticular Coordination Frameworks.

Construction of porous solid materials applied to the adsorptive removal of CO2 from C2 hydrocarbons is highly demanded thanks to the important role C2 hydrocarbons play in the chemical industry but quite challenging owing to the similar physical parameters between C2 hydrocarbons and CO2. In particular, the development of synthetic strategies to simultaneously enhance the uptake capacity and adsorption selectivity is very difficult due to the trade-off effect frequently existing between both of them. In this work, a combination of the dicopper paddlewheel unit and 4-pyridylisophthalate derivatives bearing different substituents afforded an isoreticular family of coordination framework compounds as a platform. Their adsorption properties toward C2 hydrocarbons and CO2 were systematically investigated, and subsequent IAST and density functional theory calculations combined with column breakthrough experiments verified their promising potential for C2/CO2 separations. Furthermore, the substituent engineering endowed the resulting compounds with simultaneous enhancement of uptake capacity and adsorption selectivity and thus better C2/CO2 separation performance compared to their parent compound. The substituent introduction not only mitigated the framework distortion via fixing the ligand conformation for establishment of better permanent porosity required for gas adsorption but also polarized the framework surface for host-guest interaction improvement, thus resulting in enhanced separation performance.

Effect of different oxygen species on the oxidative coupling of methane over TiO2 catalysts

TiO2 is widely used in oxidative coupling of methane (OCM) reaction because of its low cost, reducibility and nontoxicity, but pure TiO2 has poor activity on methane activation. Density functional theory with an additional Hubbard-like parameter (DFT + U) was used to research OCM reaction on Ir/TiO2(001), Pt/TiO2(001) and Mn/TiO2(001) catalysts to explore catalysts with high activity and C2 hydrocarbon selectivity. The results indicate that Ir, Pt and Mn doping can significantly improve the activity of lattice oxygen and reduce the activation energy of methane dissociation. Additionally, the evolution of oxygen species on Ir/TiO2(001) Pt/TiO2(001) and Mn/TiO2(001) catalysts show that the lattice oxygen species and peroxide species have the strongest activity to activate methane. However, the superoxide species has the worst activity. Furthermore, the formation paths of ethane and ethylene were researched on Ir/TiO2(001), Pt/TiO2(001) and Mn/TiO2(001) surfaces. And we expect that Ir/TiO2(001) is effective for catalyzing OCM reaction.

Electrocatalytic Reduction of CO2 to C1 Compounds by Zn-Based Monatomic Alloys: A DFT Calculation

Electrocatalytic reduction of carbon dioxide to produce usable products and fuels such as alkanes, alkenes, and alcohols, is a very promising strategy. Recent experiments have witnessed great advances in precisely controlling the synthesis of single atom alloys (SAAs), which exhibit unique catalytic properties different from alloys and nanoparticles. However, only certain precious metals, such as Pd or Au, can achieve this transformation. Here, the density functional theory (DFT) calculations were performed to show that Zn-based SAAs are promising electrocatalysts for the reduction of CO2 to C1 hydrocarbons. We assume that CO2 reduction in Zn-based SAAs follows a two-step continuous reaction: first Zn reduces CO2 to CO, and then newly generated CO is captured by M and further reduced to C1 products such as methane or methanol. This work screens seven stable alloys from 16 SAAs (M = Fe, Ru, Os, Co, Rh, Ir, Ni, Pd, Pt, Cu, Ag, Au, V, Mo, Ti, Cr). Among them, Pd@Zn (101) and Cu@Zn (101) are promising catalysts for CO2 reduction. The reaction mechanisms of these two SAAs are discussed in detail. Both of them convert CO2 into methane via the same pathway. They are reduced by the pathway: *CO2 → *COOH → *CO + H2O; *CO → *CHO → *CH2O → *CH3O → *O + CH4 → *OH + CH4 → H2O + CH4. However, their potential determination steps are different, i.e., *CO2 → *COOH (ΔG = 0.70 eV) for Cu@Zn (101) and *CO → *CHO (ΔG = 0.72 eV) for Pd@Zn, respectively. This suggests that Zn-based SAAs can reduce CO2 to methane with a small overpotential. The solvation effect is simulated by the implicit solvation model, and it is found that H2O is beneficial to CO2 reduction. These computational results show an effective monatomic material to form hydrocarbons, which can stimulate experimental efforts to explore the use of SAAs to catalyze CO2 electrochemical reduction to hydrocarbons.

Separation of trans-1, 3‑butadiene from C4 hydrocarbons mixtures by metal organic framework: A molecular dynamics simulation investigation

Separation of C4 hydrocarbons, particularly trans-1, 3‑butadiene (t-C4H6) from other C4 hydrocarbons mixtures such as 1‑butene (n-C4H8), isobutene (i-C4H8) and n-butane (n-C4H10) is extremely important in the oil and gas processing industry. We have performed extensive molecular dynamics simulation to explore the possibility of using the metal–organic framework (ZIF-71) as a host for the separation of C4 hydrocarbon from their mixtures. From the self-diffusion coefficient value, we show that even at room temperature ZIF-71 is an excellent host to separate trans-1, 3‑butadiene (t-C4H6) from the other C4 hydrocarbons. It is also observed that at the appropriate thermodynamics conditions all the C4 molecules can be individually separated from their mixtures by using only ZIF-71 metal organics framework.

Relative sensitivity of hydrodynamic, thermodynamic, and chemical processes for simulating the buoyant multiphase plume and surfacing flows of an oil and gas blowout

Deepwater hydrocarbon releases experience complex chemical and physical processes. To assess simplifications of these processes on model predictions, we present a sensitivity analysis using simulations for the Deepwater Horizon oil spill. We compare the buoyant multiphase plume metrics (trap height, rise time etc), the hydrocarbon mass flowrates at the near-field plume termination and their mass fractions dissolved in the water column and reaching the water surface. The baseline simulation utilizes a 19-component hydrocarbon model, live-fluid state equations, hydrate dynamics, and heat and mass transfer. Other simulations turn-off each of these processes, with the simplest one using inert oil and methane gas. Plume metrics are the least sensitive to the modeled processes and can be matched by adjusting the release buoyancy flux. The mass flowrate metrics are more sensitive. Both liquid- and gas-phase mass transfer should be modeled for accurate tracking of soluble components (e.g. C1 − C7 hydrocarbons) in the environment.

Reaction characteristics of maximizing light olefins and decreasing methane in C5 hydrocarbons catalytic pyrolysis

When converting C5 hydrocarbons to light olefins by catalytic pyrolysis, the generation of low value-added methane will affect the atomic utilization efficiency of C5 hydrocarbons. To improve the atomic utilization efficiency, different generation pathways of light olefins and methane in the catalytic pyrolysis of C5 hydrocarbons were analyzed, and the effects of reaction conditions and zeolite types were investigated. Results showed that light olefins were mainly formed by breaking the C2–C3 bond in the middle position, while methane was formed by breaking the C1–C2 bond at the end. Meanwhile, it was discovered that the hydrogen transfer reaction could be reduced by about 90% by selecting MTT zeolite with 1D topology and FER zeolite with 2D topology under high weight hourly space velocity (WHSV) and high temperature operations, thus leading to the improvement of the light olefins selectivity for the catalytic pyrolysis of n-pentane and 1-pentene to 55.12% and 74.60%, respectively. Moreover, the fraction ratio of terminal C1–C2 bond cleavage was reduced, which would reduce the selectivity of methane to 6.63% and 1.83%. Therefore, zeolite with low hydrogen transfer activity and catalytic pyrolysis process with high WHSV will be conducive to maximize light olefins and to decrease methane.

Reduced TiO2 quantum dots/graphene for solar light driven CO2 reduction into precisely controlled C1 vs C2 hydrocarbon products without noble Co-catalyst

Photocatalytic CO2 reduction is a logical approach to overcome the energy crisis as well as to curb the anthropogenic CO2 emission by converting atmospheric CO2 with water vapour under irradiation into hydrocarbon fuels. Herein, for the first time, a noble metal-free photocatalyst comprised of reduced TiO2 quantum dots (TQDs) dispersed over graphene sheets has been successfully synthesized and employed for this reaction. EELS investigation reveals the addition of graphene has imparted oxygen vacancies inside TQDs, which in turn helps to enhance broad solar light absorption. TRPL spectroscopy revealed a prolonged charge separation in the heterostructure. Depending on graphene content, the ratio of the products has been changed; CH4:C2H6 from 3.41:1 to 1:1.62. The optimized sample exhibits 2.8- and 3.7-fold increment of CH4 and C2H6 yields compared to TQDs. Under the continuous mode, the photocatalyst has shown excellent stability of 72 h.

The Role of Adsorbed and Lattice Oxygen Species in Product Formation in the Oxidative Coupling of Methane over M2WO4/SiO2 (M = Na, K, Rb, Cs)

MnOx–Na2WO4/SiO2 is one of the best-performing catalysts in the oxidative coupling of methane (OCM) to C2 hydrocarbons (C2H6 and C2H4). The current mechanistic concepts related to the selectivity to the desired products are based on the involvement of crystalline Mn-containing phases, the molten Na2WO4 phase, surface Na–WOx species, and the associated lattice oxygen. Using in situ X-ray diffraction, operando UV–vis spectroscopy, spatially resolved kinetic analysis of product formation in steady-state OCM tests, and temporal analysis of products with isotopic tracers, we show that these phases/species are not categorically required to ensure high selectivity to the desired products. M2WO4/SiO2 (M = Na, K, Rb, Cs) materials were established to perform similarly to MnOx–Na2WO4/SiO2 in terms of selectivity–conversion relationships. The unique role of the molten Na2WO4 phase could not be confirmed in this regard. Our alternative concept is that the activity of M2WO4/SiO2 and product selectivity are determined by the interplay between the lattice oxygen of M2WO4 and adsorbed oxygen species formed from gas-phase O2. This lattice oxygen cannot convert CH4 to C2H6 but oxidizes CH4 exclusively to CO and CO2. Adsorbed monoatomic oxygen species reveal significantly higher reactivity toward overall CH4 conversion and efficiently generate CH3 radicals from CH4. These reactive intermediates couple to C2H6 in the gas phase and are oxidized, to a lesser extent, by the lattice oxygen of M2WO4 to CO and CO2. Adsorbed diatomic oxygen is involved in the direct CH4 oxidation to CO2. The electronegativity of alkali metal in M2WO4 was established to affect the catalyst ability to generate adsorbed oxygen species from O2. This knowledge opens the possibility to influence product selectivity by controlling the coverage by adsorbed and lattice oxygen via reaction conditions or catalyst design.

Biogasoline Obtained Using Catalytic Pyrolysis of Desmodesmus sp. Microalgae: Comparison between Dry Biomass and n-Hexane Extract

The present work deals with the production of hydrocarbons in the C5–C12 range obtained from the fast micropyrolysis of a laboratory-grown Desmodesmus sp. microalgae. It compares the properties of this specific fraction of hydrocarbons using or not using transition alumina catalysts during pyrolysis in experiments with both pure dried microalgae and its n-hexane extract. The microalgae were characterised using thermogravimetry (TG) and CHN analysis; the n-hexane extract was analysed through Fourier transform infrared spectroscopy (FTIR). The pyrolysis experiments were performed in a multi-shot pyrolyser connected online with a gas chromatograph coupled to a mass spectrometer (GC/MS). The composition of the C5–C12 fraction was compared to that of an industrial pyrolysis gasoline. The results of pyrolysis at 600 °C show that the alumina catalyst increases the quantity of C5–C12 hydrocarbon families when compared to purely thermal pyrolysis, representing about 40% of all the dry microalgae pyrolysis products. In the case of n-hexane extract, the C5–C12 area fraction corresponds to 33.5% of the whole products’ area when pyrolysis is conducted with an alumina catalyst. A detailed analysis shows that linear molecules, mainly unsaturated, are predominant in the products. Dry biomass formed more aromatic but less cyclic and alkylated molecules in relation to the n-hexane extract. Nitrogen products, essentially alkylated pyrroles, were produced in large quantities when dry biomass was used but were below the detection limit when pyrolysing the extracts. Thus, the extraction with hexane proved to be an effective way to remove nitrogen compounds, which are undesirable in fuels. The estimated low heating values of the present C5–C12 pyrolysis hydrocarbon fractions (between 43 and 44 MJ/kg) are quite comparable to the reported values for reformulated and conventional industrial gasolines (42 and 43 MJ/kg, respectively).

Retention performance of alumina porous layer open-tubular column coated with γ–alumina nanoparticles in the highly volatile hydrocarbons separation

An alumina porous layer open-tubular (Al2O3 PLOT) column coated with γ–alumina nanoparticles (20 nm) for highly volatile hydrocarbons (C1 to C5) separation was described. Relative to the coating of bulk alumina, this column was easily coated with dynamic method under 0.4 or 0.6 MPa for 0.53 mm or 0.32 mm capillary, respectively. And the thickness of coating layer could be tuned by repeating the coating process after column was dried and activated at 300 °C for 3 h. The effect of deactivation agents on the physicochemical properties of nano γ–alumina was characterized by X–ray diffraction (XRD) measurement and nitrogen adsorption–desorption isotherms. The influences of deactivation agents, film thickness, conditioning and column dimensions on the inertness, polarity, selectivity and elution order of C1 to C5 separation were investigated in detail. The crystallite structure and size of nano alumina were not affected by the deactivation agents and remained constant during the column making processes, whereas specific surface area, pore volume and average half pore width altered significantly. The specific surface area decreased to 125.4 m2 g–1 or 174.0 m2 g–1 and the average half pore size distributions decreased to 1.6–8.4 nm or 2.4–14.3 nm when it was deactivated with potassium chloride or sodium sulfate solution, respectively. The deactivation agents and its concentrations impacted significantly on the retention performance of column. The column deactivated with sodium sulfate solution exhibited stronger polarity and lower selectivity than which deactivated with potassium chloride solution although both columns showed good inertness. The length, internal diameter and film thickness of the column had less influence on the selectivity and resolution for C1 to C5 hydrocarbons separation, whereas the conditioning temperature and time had an obvious influence. The column had distinguished polarity and selectivity which was different from either bulk or commercial alumina columns. Typically, the hydrocarbons were baseline separated with resolutions ranging from 1.65 to 15.33 within 9 min under programmed temperature below 100 °C, and the tailing factors ranging from 1.02 to 1.07.