Light Hydrocarbon Separations Using Porous Organic Framework Materials

Light hydrocarbons (C₁–C₃) are used as basic energy feedstocks and as commodity organic compounds for the production of many industrially necessary chemicals. Due to the nature of the raw materials and production processes, light hydrocarbons are generated as mixtures, but the high-purity single-component products are of vital importance to the petrochemical industry. Consequently, the separation of these C₁–C₃ products is a crucial industrial procedure that comprises a significant share of the total global energy consumption per year. As a complement to traditional separation methods (distillation, partial hydrogenation, etc.), adsorptive separations using porous solids have received widespread attention due to their lower energy costs and higher efficiency. Extensive research has been devoted to the use of porous materials such as zeolites and metal-organic frameworks (MOFs) as solid adsorbents for these key separations, owing to the high porosity, tunable pore structures, and unsaturated metal sites present in these materials. Recently, porous organic framework (POF) materials composed of organic building blocks linked by covalent bonds have also shown excellent properties in light hydrocarbon adsorption and separation, sparking interest in the use of these materials as adsorbents in separation processes. This Minireview summarizes the recent advances in the use of POFs for light hydrocarbon separations, including the separation of mixtures of methane/ethane, methane/propane, ethylene/ethane, acetylene/ethylene, and propylene/propane, while highlighting the relationships between the structural features of these materials and their separation performances. Finally, the difficulties, challenges, and opportunities associated with leveraging POFs for light hydrocarbon separations are discussed to conclude the review.     

Toward efficient catalysts for electrochemical CO2 conversion to C2 products

With impressive progress in carbon capture and renewable energy, carbon dioxide (CO₂) conversion into useful chemicals has become a potential tool against climate change. Electrochemical CO₂ conversion into C₂ products (ethylene and ethanol) is an especially economically promising approach and an active research area. Nonetheless, catalyst layer design for CO₂ conversion is challenging because of the complex CO₂-to-C₂ reaction pathways. In this review, we highlight key ideas in catalyst layer design for CO₂ conversion to C₂ in the past few years. We identify three fundamental principles to control catalyst selectivity—local CO₂ and CO concentration, local pH, and intermediate–catalyst interaction. To achieve these goals, we introduce design strategies for both catalytic materials and overall catalyst layer morphology.     

Catalytic efficiency of some novel nanostructured heterogeneous solid catalysts in pyrolysis of HDPE

In the present study, the catalytic conversion of high density polyethylene (HDPE) to useful products has been investigated in the presence of BaTiO₃ based catalysts in a micro steel reactor at 350 °C and 30 min reaction time. The catalysts, including BaTiO₃, Pb/BaTiO₃, Co/BaTiO₃ and Pb–Co/BaTiO₃ were prepared in the laboratory by reactive calcination method and characterized by Scanning Electron Microscopy (SEM), Energy Dispersive X-rays (EDX), Surface Area Analyzer (SAA) and X-rays Diffractometry (XRD). The product yields (over all yields and yields of liquid, gas and coke/residue) as a function of individual catalyst concentration was studied. The result indicated a promising effect of the catalysts used on conversion to liquid products and their composition in term of carbon range (C₆ – >C₃₀) & hydrocarbon group types (paraffin's, olefins, naphthenics, and aromatics). Among the catalysts used, Pb–Co/BaTiO₃ gave the maximum yield of liquid products (86%) when used in 1 wt % loading. The same catalyst gave the average yield (20–25%) of different range hydrocarbons i.e. C₆–C₁₂, C₁₃–C₁₆, C₁₇–C₂₀ and C₂₀–C₃₀. Inversely, the un-doped BaTiO_3, favored the formation of C₆–C₁₂ and C₁₃–C₁₆ range hydrocarbons, whereas Pb doped BaTiO₃ and Co doped BaTiO₃ enhanced the yield of C₁₃–C₁₆, and C₂₀–C₃₀ range hydrocarbons. Regarding the hydrocarbon group types, all catalysts significantly increased the formation of paraffins and reduced olefins and naphthenes.     

Stepwise pyrolysis of macerals

Kerogen separates which consist predominantly of single maceral types at maturity levels lower than 0.7% vitrinite reflectance (R ₀) were pyrolysed in a single step and stepwise between 50 and 600°C. The total hydrocarbon yield and the yield of hydrocarbon gases (C₁−C₄) were determined along with the detailed composition of the gaseous fraction (C₁−C₄ alkanes and alkenes) and the C₅₊-fraction. The distribution of hydrocarbons, particularly in the C₁−C₃ range and the alkene/alkane ratio are useful as specific indicators for the various maceral types. The residue was analysed by reflected white light and fluorescence microscopy. The different types of reactive macerals i.e. algae, altered algae, particulate liptinites, amorphous liptinites and amorphous humic matter are transformed into particular types of inertinite. The reconstruction of the original maceral composition from its residue after katagenesis in a natural assemblage seems however difficult, due to the small amount of residue of the reactive macerals and the presence of original inertinite. Qualitative and quantitative data derived from these pyrolysis experiments may be useful on a comparative basis for the prediction of hydrocarbon generation by these maceral groups during katagenesis. Dedicated to Professor Lisa Heller-Kallai on the occasion of her 65^th birthday     

Degradation of Aqueous Pentadecane Emulsion by an Anodic Microdischarge: 4. Gaseous Products

The composition of hydrocarbon and other gases produced during the treatment of a pentadecane emulsion in water with a microdischarge at an aluminum valve anode was studied. It was shown that the power yields of C₁–C₅ hydrocarbon gases and CO do not depend on the emulsion concentration in the liquid phase. The mechanism of formation of gaseous products is discussed.     

Conversion of hydrocarbon gases in dielectric barrier discharge in the presence of water

The conversion of C₁–C₄ hydrocarbons into gaseous and liquid products in a dielectric barrier discharge plasma in the presence of water has been studied. The formation of a deposit on the electrode surface is prevented by introducing water in the liquid state into a gaseous hydrocarbon stream, a finding that has been confirmed by IR spectroscopic study of the electrode surface. Hydrogen and C₂₊ hydrocarbons have been detected among the gaseous products of conversion, the liquid products being represented by C₆–C₁₀₊ alkanes. The total liquid products have amounted to 13.4, 26.0, or 36.6% for the methane, propane, or n-butane conversion, respectively. A 10% propane or butane admixture to methane increases the yield of the liquid products to make 22.0 and 31.7% for the methane–propane and the methane–butane mixture, respectively.     

Chemical catalysed recycling of waste polymers: Catalytic conversion of polypropylene into fuels and chemicals over spent FCC catalyst in a fluidised-bed reactor

Polypropylene (PP) was pyrolysed over spent FCC commercial catalyst (FCC-s1) using a laboratory fluidised-bed reactor operating isothermally at ambient pressure. The influence of reaction conditions including catalyst, temperature, and ratio of polymer to catalyst feed and flow rates of fluidising gas was examined. The yield of gaseous and liquid hydrocarbon products at 390 °C for spent FCC commercial catalyst (87.8 wt%) gave much higher yield than silicate (only 17.1 wt%). Greater product selectivity was observed with FCC-s1 as a post-use catalyst with about 61 wt% olefins products in the C₃-C₇ range. The selectivity could be further influenced by changes in reaction conditions. Valuable hydrocarbons of olefins and iso-olefins were produced by low temperatures and short contact times used in this study. It is also demonstrated that a post-use catalyst system under appropriate conditions the resource potential of polymer waste can be economically recovered and also can address the recycling desire to see an alternative to solve a major environment problem.     

Flash Pyrolysis of Lakhara Lignite Utilizing Effective Radical Transfer

Flash pyrolysis of raw and tetralin treated coal samples were carried out in nitrogen atmosphere. Two representative coal samples from Lakhra coalmines labeled Lakhra‐3 (L3) and Lakhra‐6B (L6B) were pyrolyzed in their raw state and after treatment with tetralin. Initial experiments were carried out at 700 °C with 2 milligrams of 80 mesh size samples. The main hydrocarbon products detected from both samples were methane, ethylene, ethane, propane, butane, pentane, benzene, toluene and xylene (BTX). The ratio of the total hydrocarbon yield from L3 and L6B raw samples is 1:1.49, respectively, while the relative yield of aliphatic C₁‐C₅ straight chain products to BTX are 7.65:5.49. Theses differences in product yields clearly indicate the compositional variation between the two samples. The total hydrocarbon yield (C₁‐C₅ +BTX) of tetralin swollen L3 coal and L6B coal was larger than the raw coal at all temperatures, and larger by 50.6% and 32.6%, respectively, at 700 °C. The treatment of coal samples has a more pronounced effect on BTX yield than C₁‐C₅ aliphatic hydrocarbons. BTX yield of tetralin treated L3 coals at 700 °C was 3.5 times higher while for L6B coal the BTX yield was 2.1 times higher than the raw samples. These significant increases in hydrocarbons yields can be explain in terms of the suppression of the cross‐linking reactions of coal fragments due to the penetration of tetralin in to the micropores of coal, as well as the effective H radicals transfer from tetralin to coal fragments during pyrolysis.     

Coprocessing of Waste Plastic and Hydrocarbons over MFI (HZSM‐5)

The thermal and catalytic degradation of high‐ and low‐density polyethylene (HDPE and LDPE, respectively) and waste plastic film (polyethylene‐based plastic wastes) were analyzed through simultaneous thermogravimetry and differential scanning calorimetry in inert atmosphere. Catalytic degradation was performed using MFI (HZSM‐5) zeolites. Although the catalyst induces a large decrease of the degradation temperature for polyethylene, it has a smaller effect on the waste plastic (WP) degradation temperature. To check the activity of the catalyst after its use in the WP degradation, experiments were conducted with fresh HDPE which confirmed a significant loss of catalytic activity. Mixtures of WP with large paraffin were also analyzed (nC₅₀). The results show that the presence of the hydrocarbon in the mixture grants some protection to the catalyst, allowing it to retain part of its activity during the process even in the presence of the waste contaminants. These findings suggest that larger hydrocarbon: waste plastic ratios promote higher protection to deactivation and that WP coprocessing with oil is feasible. Gas chromatography was used to analyze the products formed in the catalytic degradation of the WP in the presence C₅₀ hydrocarbon at a ratio of 1:12, consisting mostly of light products in the range of C₂ to C₈ hydrocarbons.     

Novel C9 and C11 Hydrocarbons from the Brown Alga Cutleria multifida; Sigmatropic and Electrocyclic Reactions in Nature. Part VI

In addition to the known C₁₁H₁₆ hydrocarbons multifidene ( 4 ), aucantene ( 2 ), and ectocarpene ( 5 ), the marine brown alga Cutleria multifida produces trace amounts of the C₉H₁₂ hydrocarbon 7-melhylcycloocta-1,3,5-triene ( 8 ) and its valence tautomer 7-methylbicyclo[4.2.0]octa-2,4-diene, A second novel C₉H₁₂ hydrocarbon is 6-vinyicyclo-hepta-1,4-diene ( 9 ), a lower homologue of ectocarpene ( 5 ). Among the C₁₁H₁₆ hydrocarbons, 7-((1E/Z)-prop-l-enyl)cycloocta-1,4-diene ( 10 / 11 ) is found for the first time. The structure of all new products is confirmed by synthesis and spectroscopic data. The biosynthesis of the new hydrocarbons 8 – 11 is obviously linked to the pathways which lead to the major products giffordene ( 7 ), (6S)-ectocarpene ((6S)- 5 ), and (4R,5R)-aucantene ((4R,5R)- 2 ). Consecutive reactions of certain thermolabile primary products proceed via electrocyclic ring closure, 3,3-sigmatropic rearrangement, or a 1,7-sigmatropic H-shift.     

Corannulene Chalcogenides

The introduction of chalcogen atoms into a polycyclic aromatic hydrocarbon structure is an established method to tune material properties. In the context of corannulene (C₂₀H₁₀), a fragment of fullerene C₆₀, such structural adjustments have given rise to an emerging class of functional and responsive molecular materials. In this minireview, our aim is to discuss the synthesis and properties of such chalcogen (sulfur, selenium, and tellurium) derivatives of corannulene.     

Verification of the interstitial carbide hydrolysis mechanism by a radioanalytical method

The hydrolytic products of manganese carbide Mn₇C₃ are hydrogen and a number of paraffins of the series CH₄, C₂H₆, C₃H₈, etc., whose concentrations characteristically decrease with increasing number of carbon atoms in the hydrocarbon molecule. A radioanalytical method applied after Mn₇C₃ hydrolysis by tritium, oxide has revealed that an analogous series of olefins in trace concentrations is formed as well. It has been confirmed that the sum of the concentrations of hydrocarbons higher than C₄ corresponds to the trend of the series. A stoichiometric and structurally consistent radical mechanism of Mn₇C₃ hydrolysis is proposed as derived from the composition of the hydrolytic products. The initial components of the radical reactions could be CH ₂ ^¨ and CH ₃ ^· radicals. The statisical and combinatorial aspects of the mechanism are also discussed.     

Relationships between structures of surfactants and their anti-hygroscopicity performance of ammonium nitrate particles

The coating processing condition was used for the research of coating ammonium nitrate particles by means of the surfactants as coating materials which have the same polar heads with different non-polar straight hydrocarbon tails or the same non-polar straight hydrocarbon tails with different polar heads, in order to investigate the relationships between structures of surfactants and their anti-hygroscopicity used in ammonium nitrate particles coated. Furthermore, the relationships and possibly mechanism were analyzed and discussed based on both the experimental results and the selected coating processing, basic property of materials and behaviors of material in coating processes. The experimental results indicated that, the anti-hygroscopicity performance of C₁₆-alchol and C₁₈-acid were best ones within the all groups of selected surfactants with polar heads. The best declines of hygroscopicity of ammonium nitrate particles coated were 29.26% for C₁₆-alcohol and 24.0% for C₁₈-acid. And for the later, the anti-hygroscopicity performance of C₁₈-acid and C₂₀-acid were best ones within the all groups of selected surfactants with longer tails, and that of C₁₆-alcohol and C₁₄-amine were best ones with shorter tails, their best declines were 24.0%, 20.39%, 29.26% and 18.6%, respectively. The mechanism analysis results indicated that the decline of hygroscopicity were influenced by both the coating processing condition and the material properties, such as the polarity, hydroscopicity, solublity in solves and especially the surfactivity of the used surfactants, and the later, i.e. the material properties would play an important role when the processing condition and solvent used in coating ammonium nitrate particles were fixed. Therfore, the property of coating materials which are depending on their structures and the bahaviours of coating material molecules in coating processes dominated commonly and ultimatly anti-hydroscopicity of coated ammonium nitrate particles, under a selected coating processing condition. This work provides new insights on understanding the relationship between structure of surfactants and anti-hygroscopicity performance to further improve the anti-hygroscopicity performance of ammonium nitrate particles.     

Radical copolymerization of the C9 hydrocarbon fraction of liquid pyrolysis products with maleic anhydride

Radical copolymerization of the C₉ hydrocarbon fraction of liquid pyrolysis products with maleic anhydride was studied. The influence of reaction conditions on the copolymer yield, its molecular mass, and maleic anhydride content was elucidated. Hydrophilic products showing promise as modifying additives to paper stock, binding agents, dispersants, and compatibilizers were prepared.     

复合催化剂上CO2加氢合成C2烃类

介绍了由CO₂+H₂合成C2⁺烃的几种复合催化剂体系的研究进展，比较和评价了复合催化剂体系的活性和选择性及对C2⁺烃类生成的影响。着重于复合催化剂体系对C4⁺烃的生成及产物分布的影响并简述反应机理。     

Desorption due to charge exchange in low-energy collisions of organofluorine ions at solid surfaces

Collisions of organofluorine ions at a metal surface result in efficient emission of adsorbate species as gas-phase ions. The experiments are done at 120° scattering angle in a hybrid (BQ) mass spectrometer; the primary ions, mass-selected by a magnetic sector (B), are allowed to collide with a target at a selected kinetic energy in the tens of eV range and the emitted ions are mass-analyzed using a quadrupole mass filter (Q). It is proposed that the impinging ions undergo neutralization accompanied by desorption of hydrocarbon ions and that the amount of internal energy deposited in the desorbed ions is strongly dependent on the collision energy and affects their degree of fragmentation. Competing processes include reflection and fragmentation of the colliding particle, along with such ion/adsorbate reactions as hydrogen atom abstraction by the fluorinated ion. Small even-electron ions, such as [CHF₂]⁺ and [C₂H₂F]⁺ are more effective in promoting chemical sputtering of the surface adsorbate as compared to larger ions (e.g. [C₃F₅]⁺) and odd-electron ions (e.g. [C₂F₄]⁺˙ and [C₂HF₂]⁺˙). At low energies some odd-electron fluorinated ions undergo collision without any secondary ions being emitted from the surface. In these cases the parent ions are apparently neutralized, but without sufficient energy transfer to cause hydrocarbon ion desorption. Non-fluorinated organic ions yield fragment ions and ion/surface reaction products under the condition of these experiments, but do not cause significant desorption of hydrocarbon ions.     

Effect of doping fulllerene soots with metals on the conversion of methane into higher hydrocarbons

We have previously demonstrated that fullerene soots catalyze hydrogen-transfer reactions that are useful for hydrocarbon processing, including conversion of methane into higher hydrocarbons. In this paper we describe the effect of doping fullerene soot with alkali and transition metals for converting methane and other light hydrocarbons. The fullerene soot was found to lower the temperature threshold for methane activation compared to other carbons; however, the selectivity to C₂ hydrocarbons was quite low (20%). In contrast, when the soot was doped with metals such as Mn or K, the overall yield of hydrocarbons increased and selectivities as high as 80% were achieved. When potassium was used as a dopant, the selectivity to C₃ and C₄ hydrocarbons also increased.     

Formation of C1–C5 Hydrocarbons from CCl4 in the Presence of Carbon-Supported Palladium Catalysts

Along with hydrodechlorination, the formation of C₁ and higher hydrocarbons takes place in a flow system in the presence of catalysts containing 0.5–5.0% Pd supported on a Sibunit carbon carrier at 150–230°C. In the entire range of conditions examined, the reaction products are primarily methane, C₂–C₄ hydrocarbon fractions, and C₅ traces. The catalysts are stable in operation, and a high conversion of CCl₄ was retained for a long time interval. The nonselective formation of linear and branched hydrocarbons is indicative of a radical mechanism of the process.     

Influence of Helium on the Conversion of Methane and Carbon dioxide in a Dielectric Barrier Discharge

We have studied the production of synthesis gas and other hydrocarbons in a dielectric barrier discharge using mixtures of helium, methane and carbon dioxide. It was found that helium has a significant influence on the discharge, decreasing the breakdown voltage and increasing the rate of conversion of CH₄ and CO₂. However it also decreases the selectivities and the range of stable operating conditions for the discharge. The main products obtained were H₂, CO, C₂H₆ and C₃H₈ but traces of other hydrocarbon, carbon deposition and the formation of condensable products were also detected. The rate of conversion and conversion abilities were obtained by fitting the conversion results to a model.     

Gas sorption,diffusion, and permeation in poly(dimethylsiloxane)

The permeability of poly(dimethylsiloxane) [PDMS] to H₂, O₂, N₂, CO₂, CH₄, C₂H₆, C₃H₈, CF₄, C₂F₆, and C₃F₈, and solubility of these penetrants were determined as a function of pressure at 35 °C. Permeability coefficients of perfluorinated penetrants (CF₄, C₂F₆, and C₃F₈) are approximately an order of magnitude lower than those of their hydrocarbon analogs (CH₄, C₂H₆, and C₃H₈), and the perfluorocarbon permeabilities are significantly lower than even permanent gas permeability coefficients. This result is ascribed to very low perfluorocarbon solubilities in hydrocarbon‐based PDMS coupled with low diffusion coefficients relative to those of their hydrocarbon analogs. The perfluorocarbons are sparingly soluble in PDMS and exhibit linear sorption isotherms. The Flory–Huggins interaction parameters for perfluorocarbon penetrants are substantially greater than those of their hydrocarbon analogs, indicating less favorable energetics of mixing perfluorocarbons with PDMS. Based on the sorption results and conventional lattice solution theory with a coordination number of 10, the formation of a single C₃F₈/PDMS segment pair requires 460 J/mol more energy than the formation of a C₃H₈/PDMS pair. A breakdown in the geometric mean approximation of the interaction energy between fluorocarbons and hydrocarbons was observed. These results are consistent with the solubility behavior of hydrocarbon–fluorocarbon liquid mixtures and hydrocarbon and fluorocarbon gas solubility in hydrocarbon liquids. From the permeability and sorption data, diffusion coefficients were determined as a function of penetrant concentration. Perfluorocarbon diffusion coefficients are lower than those of their hydrocarbon analogs, consistent with the larger size of the fluorocarbons. © 2000 John Wiley & Sons, Inc. J Polym Sci B: Polym Phys 38: 415–434, 2000