Reversed ethane/ethylene adsorption in a metal–organic framework via introduction of oxygen

Separation of ethane from ethylene is a very important but challenging process in the petrochemical industry.Finding an alternative method would reduce the energy needed to make 170 million tons of ethylene manufactured worldwide each year.Adsorptive separation using C2H6-selective porous materials to directly produce high-purity C2H4 is more energy-efficient.We herein report the"reversed C2H6/C2H4 adsorption"in a metal–organic framework Cr-BTC via the introduction of oxygen on its open metal sites.The oxidized Cr-BTC(O2)can bind C2H6 over C2H4 through the active Cr-superoxo sites,which was elucidated by the gas sorption isotherms and density functional theory calculations.This material thus exhibits a good performance for the separation of 50/50 C2H6/C2H4 mixtures to produce 99.99%pure C2H4 in a single separation operation.

Numerical Study on Laminar Burning Velocity and Flame Stability of Premixed Methane/Ethylene/Air Flames

A numerical study on premixed methane/ethylene/air flames with various ethylene fractions and equivalence ratios was conducted at room temperature and atmospheric pressure. The effects of ethylene addition on laminar burning velocity, flame structure and flame stability under the condition of lean burning were investigated. The results show that the laminar burning velocity increases with ethylene fraction, especially at a large equivalence ratio. More ethylene addition gives rise to higher concentrations of H, O and OH radicals in the flame, which significantly promotes chemical reactions, and a linear correlation exists between the laminar burning velocity and the maximum H + OH concentration in the reaction zone. With the increase of ethylene fraction, the adiabatic flame temperature is raised, while the inner layer temperature becomes lower, contributing to the enhancement of combustion. Markstein length and Markstein number, representative of the flame stability, increase as more ethylene is added, indicating the tendency of flame stability to improve with ethylene addition.

Mn-doped SrCoO_(3-δ) Perovskite Oxides for Ethylene Production via Chemical Looping Oxidative Dehydrogenation of Ethane

Chemical looping oxidative dehydrogenation (CL-ODH) is an economically promising method for convertingethane into higher value-added ethylene utilizing lattice oxygen in redox catalysts, also known as oxygen carriers. Inthis study, perovskite-type oxide SrCoO_(3-δ) and B-site Mn ion-doped oxygen carriers (SrCo_(1-x)MnxO_(3-δ), x=0.1, 0.2, 0.3)were prepared and tested for the CL-ODH of ethane. The oxygen-deficient perovskite SrCoO_(3-δ) exhibited high ethyleneselectivity of up to 96.7% due to its unique oxygen vacancies and lattice oxygen migration rates. However, its low ethyleneyield limits its application in the CL-ODH of ethane. Mn doping promoted the reducibility of SrCoO_(3-δ) oxygen carriers,thereby improving ethane conversion and ethylene yield, as demonstrated by characterization and evaluation experiments.X-ray diffraction results confirmed the doping of Mn into the lattice of SrCoO_(3-δ), while X-ray photoelectron spectroscopy(XPS) indicated an increase in lattice oxygen ratio upon incorporation of Mn into the SrCoO_(3-δ) lattice. Additionally, H2temperature-programmed reduction (H2-TPR) tests revealed more peaks at lower temperature reduction zones and a declinein peak positions at higher temperatures. Among the four tested oxygen carriers, SrCo0.8Mn0.2O_(3-δ) exhibited satisfactoryperformance with an ethylene yield of 50% at 710 °C and good stability over 20 redox cycles. The synergistic effect of Mnplays a key role in increasing ethylene yields of SrCoO_(3-δ) oxygen carriers. Accordingly, SrCo0.8Mn0.2O_(3-δ) shows promisingpotential for the efficient production of ethylene from ethane via CL-ODH.

Ethane Chemical Looping Oxidative Dehydrogenation to Ethylene over Co_(2)O_(3)(Fe_(2)O_(3),NiO)/LaCoO_(3) Oxygen Carriers

Ethane chemical looping oxidative dehydrogenation(CL-ODH)to ethylene is a new technology for converting ethane to ethylene.In the current study MeO/LaCoO_(3)(MeO=Fe_(2)O_(3),NiO or Co_(2)O_(3))composite metal oxides were prepared via citrate gel and impregnation methods,and used as oxygen carriers for CL-ODH.X-ray diffraction results indicated that all oxygen carriers had a perovskite structure even after eight redox cycles.Under a reaction temperature of 650°C,a reaction pressure of 0.1 MPa,and a weight hourly space velocity(WHSV)of 7500 mL/(g·h),ethane conversion over Co_(2)O_(3)/LaCoO_(3) reached 100%and ethylene selectivity reached 60%,both of which were better than corresponding values attained over Fe_(2)O_(3)/LaCoO_(3) and NiO/LaCoO_(3).Ethylene selectivity remained stable for 80 cycles over Co_(2)O_(3)/LaCoO_(3),then decreased gradually after 80 cycles.X-ray photoelectron spectroscopy results and evaluation results indicated that lattice oxygen and O_(2)2-had a direct relationship with ethane conversion and ethylene selectivity.Co_(2)O_(3)/LaCoO_(3) exhibited a strong capacity to release and absorb oxygen,mainly due to interaction between Co_(2)O_(3) and LaCoO_(3).

Ca_(2)MnO_(4)-layered perovskite modified by NaNO_(3)for chemical-looping oxidative dehydrogenation of ethane to ethylene

Chemical-looping oxidative dehydrogenation(CL-ODH)is a process designed for the conversion of alkanes into olefins through cyclic redox reactions,eliminating the need for gaseous O_(2).In this work,we investigated the use of Ca_(2)MnO_(4)-layered perovskites modified with NaNO_(3) dopants,serving as redox catalysts(also known as oxygen carriers),for the CL-ODH of ethane within a temperature range of 700-780℃.Our findings revealed that the incorporation of NaNO_(3) as a modifier significantly-nhanced the selectivity for-thylene generation from Ca_(2)MnO_(4).At 750℃and a gas hourly space velocity of 1300 h^(-1),we achieved an-thane conversion up to 68.17%,accompanied by a corresponding-thylene yield of 57.39%.X-ray photoelectron spectroscopy analysis unveiled that the doping NaNO_(3) onto Ca_(2)MnO_(4) not only played a role in reducing the oxidation state of Mn ions but also increased the lattice oxygen content of the redox catalyst.Furthermore,formation of NaNO_(3) shell on the surface of Ca_(2)MnO_(4) led to a reduction in the concentration of manganese sites and modulated the oxygen-releasing behavior in a step-wise manner.This modulation contributed significantly to the enhanced selectivity for ethylene of the NaNO_(3)-doped Ca_(2)MnO_(4) catalyst.These findings provide compelling evidence for the potential of Ca_(2)MnO_(4)-layered perovskites as promising redox catalysts in the context of CL-ODH reactions.

Boosting kinetic separation of ethylene and ethane on microporous materials via crystal size control

The adsorptive separation of C_(2)H_(4)and C_(2)H_(6),as an alternative to distillation units consuming high energy,is a promising yet challenging research.The great similarity in the molecular size of C_(2)H_(4)and C_(2)H_(6)brings challenges to the regulation of adsorbents to realize efficient dynamic separation.Herein,we reported the enhancement of the kinetic separation of C_(2)H_(4)/C_(2)H_(6)by controlling the crystal size of ZnAtzPO_(4)(Atz=3-amino-1,2,4-triazole)to amplify the diffusion difference of C_(2)H_(4)and C_(2)H_(6).Through adjusting the synthesis temperature,reactant concentration,and ligands/metal ions molar ratio,ZnAtzPO4 crystals with different sizes were obtained.Both single-component kinetic adsorption tests and binary-component dynamic breakthrough experiments confirmed the enhancement of the dynamic separation of C_(2)H_(4)/C_(2)H_(6)with the increase in the crystal size of ZnAtzPO_(4).The separation selectivity of C_(2)H_(4)/C_(2)H_(6)increased from 1.3 to 98.5 with the increase in the crystal size of ZnAtzPO_(4).This work demonstrated the role of morphology and size control of adsorbent crystals in the improvement of the C_(2)H_(4)/C_(2)H_(6)kinetic separation performance.

Selective oxidative dehydrogenation of ethane to ethylene over a hydroxylated boron nitride catalyst

Boron nitride containing hydroxyl groups efficiently catalysed oxidative dehydrogenation of ethane to ethylene,offering rather high selectivity（95%） but only small amount of CO2 formation（0.4%） at a given ethane conversion of 11%.Even at high conversion level of 63%,the selectivity of ethylene retained at 80%,which is competitive with the energy-demanding industrialized steam cracking route.A long-term test for 200 h resulted in stable conversion and product selectivity,showing the excellent catalytic stability.Both experimental and computational studies have identified that the hydrogen abstraction of B-OH groups by molecular oxygen dynamically generated the active sites and triggered ethane dehydrogenation.

Enhanced ethane/ethylene separation based on metal regulation in zeolitic imidazolate frameworks

The acquisition of polymer-grade(≥99.95%)C_(2)H_(4) poses a challenge due to the presence of ethane(C_(2)H_(6))having similar physical and chemical properties.Consequently,the one-step purification of C_(2)H_(4) becomes a crucial and demanding process.In this study,we synthesized ZIF-78 with a GME configuration using different metal sources(Zn,Co).Both substances have been identified as ethane-selective adsorbents with excellent thermal stability.The Brunauer Emmett Teller(BET)surface area of ZIF-78-Co(748 m^(2)/g)surpasses that of ZIF-78-Zn(585 m^(2)/g),and the former exhibits a higher Q_(st) value for C_(2)H_(6),resulting in enhanced adsorption capacity for C_(2)H_(6)(50.61 cm^(3)/g)and selectivity for C_(2)H_(6)/C_(2)H_(4)(1.71)compared to ZIF-78-Zn(48.97 cm^(3)/g,1.46)at 298 K and 1 bar.Grand Canonical Monte Carlo(GCMC)calculations indicate that C_(2)H_(6) has a stronger interaction with the ZIF-78-Co framework.Breakthrough experiments for the C_(2)H_(6)/C_(2)H_(4)(50:50,V/V)mixture at 298 K and 1 bar demonstrate that ZIF-78-Co achieves separation in approximately 5 min/g,outperforming ZIF-78-Zn.And the separation time for ZIF-78-Co in the C_(2)H_(6)/C_(2)H_(4)(10:90,V/V)mixture is 9 min/g.Furthermore,ZIF-78-Co exhibits excellent structural stability,thermal stability,water stability,and acid-base stability.Therefore,it holds promising prospects for practical industrial separation.Additionally,we hope that our findings inspire further experimentation on alternative metal ethane adsorbents.

Surface Acidity/Basicity and Catalytic Reactivity of CeO2/7-Al2O3 Catalysts for the Oxidative Dehydrogenation of Ethane with Carbon Dioxide to Ethylene

Dehydrogenation of ethane to ethylene in CO_2 was investigated overCeO_2/γ-Al_2O_3 catalysts at 700℃ in a conventional flow reactor operating at atmosphericpressure. XRD, BET and microcalori-metric adsorption techniques were used to characterize thestructure and surface acidity/basicity of the CeO_2/γ-Al_2O_3 catalysts. The results show that thesurface acidity decreased while the surface basicity increased after the addition of CeO_2 toγ-Al_2O_3. Accordingly, the activity of the hydrogenation reaction of CO_2 increased, which mightbe responsible for the enhanced conversion in the dehydrogenation of ethane to ethylene. The highestethane conversion obtained was about 15% for the 25%CeO_2/γ-Al_2O_3. The selectivity to ethylenewas high for all the CeO_2, γ-Al_2O_3 and CeO2/γ-Al_2O_3 catalysts.

Promoted catalytic performances of highly dispersed V-doped SBA-16 catalysts for oxidative dehydrogenation of ethane to ethylene

V-doped SBA-16 catalysts (V-SBA-16) with 3D nanocage mesopores have been successfully synthesized by a modified one-pot method under weak acid condition. The obtained materials were characterized by means of small angle XRD, N2adsorption–desorption, TEM, UV–Vis and UV-Raman spectroscopy. These characterization results indicated that well-order mesoporous structures were maintained even at higher vanadium loadings and high concentration of VOxspecies were incorporated into the framework of SBA-16 support. The catalytic performances of V-SBA-16, V/SBA-16 and V/SiO2catalysts were comparatively investigated for the oxidative dehydrogenation of ethane to ethylene. The highest selectivity to ethylene of 63.3% and ethylene yield of 25.6% were obtained over 1.0V-SBA-16 catalyst. The superior catalytic performance of V-SBA-16 catalysts could be attributed to the presence of isolated framework VOxspecies, the unique structure of SBA-16 support and weak acidity. Moreover, V/SiO2catalyst exhibited relatively poor catalytic activity duo to the formation of V2O5nanoparticles on the surface of SiO2support and the low dispersion of VOxspecies. These results indicated that the catalytic performances of the studied catalysts were strongly dependent on the vanadium loading, the nature and neighboring environment of VOxspecies and the structure of support. © 2016

π-Complexation Mesoporous Adsorbents Cu-MCM-48 for Ethylene-Ethane Separation

Copper incorporated MCM-48 molecular sieve adsorbents with different Cu content have been hydrothermally synthesized. The samples have been characterized by various physicochemical methods, including X-ray diffraction （XRD）, nitrogen adsorption （N2） and X-ray photoelectron spectroscopy （XPS）. The results reveal that Cu-MCM-48 with mass fraction of copper up to 10 % can still retain the uniform mesoporous framework of MCM-48. The copper in the framework of MCM-48 was easily auto-reduced to Cu（I） in N2 at high temperature, which did not alter the mesoporous structure of MCM-48. The adsorption equilibrium isotherms of ethylene and ethane on these molecular sieve adsorbents have been measured at 30℃. At 100 kPa, the adsorption capacities of ethylene on 5Cu-MCM-48 and 10Cu-MCM-48 are higher than those on MCM-48. The 10Cu-MCM-48 molecular sieve adsorbent has a higher selective adsorption ratio of ethylene to ethane, the separation factor is 3.8, and the amount of ethylene adsorbed is 11.1 ml·g ^-1.

Synergistic Effects of Nitrogen Amendments and Ethylene on Atmospheric Methane Uptake under a Temperate Old-growth Forest

An increase in atmospheric nitrogen （N） deposition can promote soil acidification, which may increase the release of ethylene （C2H4） under forest floors. Unfortunately, knowledge of whether increasing N deposition and C2H4 releases have synergistic effects on soil methane （CH4） uptake is limited and certainly deserves to be examined. We conducted some field measurements and laboratory experiments to examine this issue. The addition of （NH4）2SO4 or NH4Cl at a rate of 45 kg N ha-1 yr-1 reduced the soil CH4 uptake under a temperate old-growth forest in northeast China, and there were synergistic effects of N amendments in the presence of C2H4 concentrations equal to atmospheric CH4 concentration on the soil CH4 uptake, particularly in the NH4Cl-treated plots. Effective concentrations of added C2H4 on the soil CH4 uptake were smaller in NH＋4 -treated plots than in KNO3-treated plots. The concentration of ca 0.3 μl C2H4 L-1 in the headspace gases reduced by 20% soil atmospheric CH4 uptake in the NH4Cl-treated plots, and this concentration was easily produced in temperate forest topsoils under short-term anoxic conditions. Together with short-term stimulating effects of N amendments and soil acidification on C2H4 production from forest soils, our observations suggest that knowledge of synergistic effects of NH＋4 , rather than NO3- , amendments and C2H4 on the in situ soil CH4 uptake is critical for understanding the role of atmospheric N deposition and cycling of C2H4 under forest floors in reducing global atmospheric CH4 uptake by forests. Synergistic functions of NH4＋ -N deposition and C2H4 release due to soil acidification in reducing atmospheric CH4 uptake by forests are discussed.

Study of Adsorptive Ethylene/Ethane Separation with Ag^+-Exchanged Resins via π-Complexation

Ag^+-exchanged resins are prepared and studied for ethylene/ethaneseparation by adsorption. On Ag^+-exchanged S9, at 25 deg. C and0.1013 Mpa, the equilibrium adsorbed amount for C_2H_4 is 0.992 mmol·g^-1, and The adsorption ratio for C_2H_4/C_2H_6 is 3.56. Theadsorption capacity can be restored almost completely at 25 deg. CAnd 75 deg. C, and the desorption residual amount is less than 0.01mmol·g^-1. For the adsorption consisting of physical Adsorption andπ-complexation with energy heterogeneity, the equilibrium data arecorrelated with Langmuir- Freundlich isotherm equation.

Effect of methane co-feeding on the selectivity of ethylene produced from oxidative dehydrogenation of ethane with CO_2 over a Ni-La/SiO_2 catalyst

A Ni-La/SiO2 catalyst was prepared through the incipient wetness impregnation method and tested in the oxidative dehydrogenation of ethane （ODHE） with CO2. The fresh and used catalysts were characterized by XRD and SEM techniques. The Ni-La/SiO2 catalyst exhibited catalytic activity for the oxidative dehydrogenation of ethane, but with low ethylene selectivity in the absence of methane. The selectivity to ethylene increased with increasing molar ratio of methane in the feed. The carbon deposited on the catalyst surface in the sole ODHE with CO2 was mainly inert carbon, while much more filamentous carbon was formed in the presence of methane. The filamentous carbon was easy to be removed by CO2, which might play a role in improving the conversion of ethane to ethylene. The introduction of methane might affect the equilibrium of the CO2 reforming of ethane and the ODHE with CO2. As a consequence, the synthesis gas produced from CO2 reforming of methane partly inhibited the reaction of ethane and promoted the ODHE with CO2, thus increasing the selectivity of ethylene.

Effect of Zeolite 5A Particle Size on Its Performance for Adsorptive Separation of Ethylene/Ethane

The adsorptive separation of ethylene from ethane exhibits a less energy-intensive-alternative technique with development potential among all processes for separation of ethylene/ethane currently. In this approach, zeolite 5 A with different particle sizes ranging from 3 340 nm to 440 nm was prepared by hydrothermal synthesis. The effect of particle size on the adsorptive separation performance of zeolite 5 A was investigated. The results show that the particle size has a significant effect on the ethylene IAST(Ideal Adsorbed Solution Theory) selectivity of zeolite 5 A. The zeolite 5 A with a particle size of 710 nm demonstrated the highest ethylene selectivity(5.6). The relatively high crystallinity of zeolite 5 A is in favor of massive adsorption capacities of ethylene and ethane.

A Green Process for High-Concentration Ethylene and Hydrogen Production from Methane in a Plasma-Followed-by-Catalyst Reactor

A green process for the oxygen-free conversion of methane to high-concentration ethylene and hydrogen in a plasma-followed-by-catalyst （PFC） reactor is presented. Without any catalysts and with pure methane used as the feed gas, a stable kilohertz spark discharge leads to an acetylene yield of 64.1%, ethylene yield of 2.5% and hydrogen yield of 59.0% with 80.0% of methane conversion at a methane flow rate of 50 cm^3/min and a specific input energy of 38.4 kJ/L. In the effluent gas from a stable kilohertz spark discharge reactor, the concentrations of acetylene, ethylene and hydrogen were 18.1%, 0.7% and 66.9%, respectively. When catalysts Pd-Ag/SiO2 were employed in the second stage with discharge conditions same as in the case of plasma alone, the PFC reactor provides an ethylene yield of 52.1% and hydrogen yield of 43.4%. The concentrations of ethylene and hydrogen in the effluent gas from the PFC reactor were found to be as high as 17.1% and 62.6%, respectively. Moreover, no acetylene was detected in the effluent gas. This means that a high concentration of ethylene and oxygen-free hydrogen can be co-produced directly from methane in the PFC reactor.

Experimental study of partially decoupled oxidation of ethane for producing ethylene and acetylene

With increasing amount of unconventional natural gas,the production of ethane,propane and other low alkanes continues to increase.In our previous works,a partially decoupled process(PDP) was proposed for conversion of ethane based on numerical simulations,which showed higher acetylene and ethylene selectivities than the original partial oxidation process.In the current work,the PDP of ethane for producing acetylene and ethylene was studied experimentally to verify the PDP concept.In the PDP of ethane,coke-oven gas or other cheap gas combusts with stoichiometric oxygen as heat carrier,and ethane is mixed with the heat carrier and undergoes pyrolysis at high temperatures.The jet-in-cross-flow(JICF) reactor was designed and manufactured to realize the PDP.A positioning device of 0.1 mm accuracy and a mass spectrometer were used to measure the spatial profiles of the species concentrations.The maximum combined yield(52.7%) of acetylene and ethylene was obtained even at the condition of heat loss,confirming that the PDP of ethane was advantageous over the partial oxidation process and at least comparable to the steam cracking process.

Oxygen-Free Conversion of Methane to Ethylene in a Plasma-Followed-by-Catalyst (PFC) Reactor

Oxygen-free conversion of methane to ethylene was investigated in a two-stage plasma-followed-by-catalyst （PFC） reactor. In the absence of catalyst, pulsed spark discharges and pulsed corona discharges were compared for methane conversion. The results showed that methane was mainly converted to acetylene, but pulsed spark discharges exhibited distinct advantages over the pulsed corona discharges in methane conversion. Thereby, pulsed spark discharges were employed and followed by Ag-Pd/SiO2 catalyst for achieving ethylene as a target product in the PFC reactor. Using the PFC reactor, a steady single-pass ethylene yield of 57% was obtained at a rate of methane conversion of 74%.

Complexation Properties and Synthesis of 1,2-Bis(2 ,2' -bipyridinyl)ethylene and 1,2-Bis(2,2' -bipyridinyl)ethane Ligands with Cu(I)

l,2-Bis(2,2'-bipyridinyl)ethylene(1) ligand was synthesized by Wittig-Horner reaction and 1, 2-Bis(2, 2'-bipyridinyl)ethane(2) ligand(which can be obtained via another route ) was prepared by hydrogenation of (1). The formation of complexes of (1) and (2) with copper (I) has been studied. The influence of the different bridge chains (CH =CH, CH2CH2) on complexation is discussed on the basis of 1H NMR spectra. Keywords Dipyridine aldehyde, Dipyridine derivative, Copper complex