Methane Selectivity Research Articles

Single atom Rh-sensitized SnO2 via atomic layer deposition for efficient formaldehyde detection

Single atom catalysts (SACs) have demonstrated great potential in detection of toxic volatile organic compounds (VOCs) because of their high catalytic efficiency and unique electronic and chemical properties. In this study, we report an extremely sensitive and selective formaldehyde gas sensor based on single atom Rh-sensitized SnO2 nanoparticles prepared by atomic layer deposition (ALD). Gas sensing investigations demonstrate that the SnO2/Rh sensor has a response of 36.3 to 20 ppm formaldehyde, showing a nearly 23-fold enhancement over pure SnO2, as well as high sensitivity, fast response-recovery time (4–29 s) and excellent selectivity. DFT calculations reveal that the atomic Rh dramatically increases the adsorption and charge transfer between formaldehyde molecules and SnO2. By using the developed sensor, a portable formaldehyde detection device has been designed, which indicates a great prospect of our strategy in practical sensors.

Electronic-supply crystal facet guiding enhancement of interfacial charge transfer in homologous covalent heterojunction NiO/Ni-BDC for efficient photocatalytic CO2 reduction

Heterojunction engineering has been an effective strategy to improve separation of charge carriers and photocatalytic activity of semiconductor photocatalysts. Where and how to build effective interface connections for facilitating interface charge migration has always been the key to the construction of high-performance heterojunction. Here, a series of covalently linked homologous heterojunction photocatalysts NiO(111)/Ni-BDC (Ni-BDC = Ni3(BDC)2(OH)2(H2O)4; H2BDC = terephthalic acid) were fabricated by H2BDC in-situ etching octahedral NiO(111) and fully characterized, which were used for photocatalytic reduction of CO2 (pCO2RR) into CH4 and CO. The NiO(111)/Ni-BDC-3 with a proper component proportion and etching degree exhibited an optimal pCO2RR performance with an electron consumption rate (Rele) of 222.68 μmol·g−1·h−1, an excellent CH4 production rate of 21.32 μmol‧g−1‧h−1 and a 76.6% CH4 selectivity, being far superior to most oxide/inorganic semiconductor and oxide/MOF heterojunctions. Comprehensive investigations with extensive photoelectric characterizations, control experiments and DFT calculations based on the homologous NiO(100)/Ni-BDC and non-homologous NiO(100)-Ni-BDC heterojunctions demonstrated that the excellent photocatalytic activity and methane selectivity of NiO(111)/Ni-BDC-3 could be attributed to two points: i) The homologous coordination etching forms a full range of interfacial covalent connections to promote tight MOF-semiconductor integration, yielding a large number of atomic-level electron transfer channels to accelerate the interfacial charge transfer; ii) the alternating polar Ni-O-Ni layer arrangement in NiO(111) crystal facet induces high-throughput electron supply and the enhanced surface charge density effectively promotes the 8-electron reduction process of methane production. Additionally, the durability of NiO(111)/Ni-BDC-3 and the possible charge-transfer mechanisms were also systematically investigated.

Ni-TiO2 catalysts derived from metal-organic framework for efficient photo-thermal CO2 methanation

Catalytic reduction of CO2 to high value-added chemicals such as methane is crucial in the development of renewable energy and waste disposal. Photo-thermal CO2 methanation has been received great attention, because the synergistic effect of photo and thermal lead to efficient CO2 reduction at low temperature. Herein, we reported the synthesis of Ni nanoparticles (NPs) supported on TiO2 (Ni-TiO2) derived from MIL-125 (Ti-MOFs) for photo-thermal CO2 methanation. The nanoparticle sizes and electron densities of metallic Ni, defects and chemical properties, photo-thermal and photo-electric characteristics of the catalysts have been systematically characterized by XRD, TEM, CO2/H2-TPD, XPS, photoluminescence and photocurrent. For the Ni-TiO2, the conversion of CO2 was 56 % under the full spectrum irradiation (1200 mW/cm2) at 325 °C, which was about 1.8 times of that without light irradiation. The selectivity of methane nearly 99 % with a production rate was 95.7 mmol/(gcat∙h), which was about 2.7 times of that without light irradiation. Meanwhile, the catalysts showed excellent stability without any activity decay during the four cycles testing (32 h). The main reasons for the high catalytic performance for photo-thermal CO2 methanation were attributed to the uniform distribution of Ni NPs with synergistic effect of large specific surface area of TiO2 with abundant moderate strength alkaline sites. In addition, good photo-thermal and photo-electric conversion ability make the catalysts possess more photo-generated charge carriers and reduce its recombination.

Rational design of the double hydrogen-bonds sites in IL@MOF composites for efficient and selective formaldehyde capture

Long-term exposure to volatile organic compounds (VOCs) represented by formaldehyde (HCHO) poses a serious threat to human health. However, traditional adsorption materials cannot meet the needs of efficient and selective formaldehyde capture because of the weak host-guest interaction. Herein, a double hydrogen-bonds strategy was proposed to boost the HCHO affinity by rich -NH3Cl sites in ionic liquids (ILs) named carbamide chloride ([CAM][Cl]). In order to fully expose these sites, MIL-101(Cr), as a kind of mesoporous metal-organic frameworks (MOFs) with large porosity, was used to construct the IL@MOF composites. As expected, the resulting [CAM][Cl]@MIL-101(Cr)-15% exhibits high HCHO uptake of 9.53 mmol·g−1, which is 2.3-fold higher than that in MIL-101(Cr) (4.10 mmol·g−1). Surprisingly, breakthrough experiments reveal that the HCHO concentration can be reduced from 800 ppm at the inlet to less than 1 ppb at the outlet within a time range of up to 1636 min·g−1, achieving efficient deep HCHO removal even under humidity conditions. Mechanism researches prove that the double hydrogen-bonding (Hδ+(-NH3Cl)···Oδ−(HCHO)) interactions play a significant role for the HCHO adsorption of [CAM][Cl]@MIL-101(Cr). More importantly, this work not only reports an adsorbent with excellent HCHO capture performance, but also innovatively highlights the important of double hydrogen-bonds for HCHO capture.

Enhancing Kerosene Selectivity of Fischer-Tropsch Synthesis by Periodical Pore Drainage Via Hydrogenolysis

Accumulation of wax inside the catalyst pores during transient cobalt-catalyzed Fischer-Tropsch synthesis (FTS) leads to unfavorable product distribution and low activity by imposing internal mass transfer limitations. The condensation of paraffin severely changes the apparent product stream that actually leaves the reactor before the catalyst pores are filled completely and the steady state is reached. Thus, the product distribution of the transient FTS is less complex than expected in comparison to the steady-state FTS and increasingly consists of hydrocarbons (HCs) with an average chain length in the range of kerosene (C<sub>9</sub>-C<sub>17</sub>). So, in order to prevent FTS from reaching a steady state, the pores are drained periodically by hydrogenolysis (HGL). The alternating HGL is realized by a switch from syngas (H<sub>2</sub>, CO) to pure hydrogen at a reaction temperature in the range of 210°C to 240°C. The alternating process leads to an improvement in kerosene selectivity of 48%, 37%, and 28% at 210°C, 220°C and 240°C, respectively. Furthermore, the influence of temperature on the hydrogenolysis of long-chain HCs was experimentally investigated. It was found that temperature affects methane selectivity severely. A high hydrogenolysis temperature is favorable as this leads to a severely decreased overall methane selectivity and, thus to a higher production rate of alkanes within the carbon number range of 9 to 17.

CO2 methanation on γ-Al2O3 nanoparticles from waste aluminium: Effect of Ba promoter on sulfur impurities

The inferior activity of γ-Al2O3 (GAL1) from the waste aluminium for CO2 methanation was improved using Ba promoter. Ba promoted CO2 conversion to ∼82% with 100% methane selectivity at 400 °C (Ni-Ba/GAL1), compared to ∼10% conversion without Ba (Ni/GAL1). Acid digestion of waste aluminium formed residual Al2(SO4)3 at ∼0.5% atomic weight, forming the detrimental NiAl2O4 under reaction conditions. Ba inhibited NiAl2O4 formation by producing BaAl2O4, increasing Ni-Ba/γ-Al2O3 stability for 50 h at 400 °C. In-situ DRIFTS analysis revealed that NiAl2O4 caused CO2 methanation via CO2 dissociation into CO, followed by high temperature hydrogenation to CH4. Ba promotes catalytic activity and stability of alumina with sulfur impurities by maintaining Nio oxidation states to catalyze CO2 hydrogenation to formate at low temperatures, producing a high methane yield. In addition to transforming waste aluminium into a valuable material, investigation on γ-Al2O3 catalytic activity expands its potential use as a catalyst for CO2 methanation.

Effect of morphology and structure of CuTCPP nanomaterials on the electrocatalytic CO2 reduction to methane and ethylene

The effect of Cu–N4, Cu–O4 and/or –COOH sites on the electrocatalytic CO2 reduction (ECR) activity and selectivity is rarely evaluated together and directly confirmed through the morphology and structure dependence of ECR performance. Here, the ECR performance of CuTCPP nanoparticles, nanorods, nanosheets and nanoflowers are systematically investigated. The experimental results show that their total ECR activity is nanoflowers > nanosheets > nanoparticles > nanorods. CuTCPP nanosheets with more Cu−N4 sites exposed showed the best ethylene selectivity of 40.6 % at –1.2 V vs. RHE. CuTCPP nanoflowers with more Cu−O4 sites were more stable than the nanosheets, showing 61.0 % methane selectivity at –1.3 V vs. RHE. A series of characterizations reveal that Cu−O4 is mainly responsible for methane production, while Cu–N4 is the main active site for ethylene production and its synergy with Cu–O4 or –COOH groups can improve the ethylene selectivity.

The Influence of the Reaction Conditions on the Photocatalytic Gas‐Phase Conversion of Methanol with Water Vapor over Pt/SrTiO3 in a Continuously Operated Flow Reactor

AbstractContinuous methanol photooxidation in the gas phase is a promising method to produce valuable chemicals like formaldehyde or methyl formate in addition to hydrogen under mild conditions. The influence of the reaction conditions on the selectivity of methanol oxidation to formaldehyde is studied using a heated flat‐plate flow photoreactor illuminated by an LED array (λmax = 368 nm) and Pt‐modified SrTiO3. A combination of online analytical methods allowed to quantify all gaseous products during extended time‐on‐stream (> 48 h TOS). The selectivity to formaldehyde is found to be primarily determined by the residence time and the process temperature. At a low methanol to water ratio, methanol conversion and evolution of CO2 are favored, whereas the light intensity primarily influenced the apparent quantum yield from 5.1 to 1.8% at 9.36 to 52.93 mW cm−2, respectively, and the methanol conversion thus determining the economic efficiency of the process. Operation temperatures higher than 110 °C resulted in a strong deactivation of the catalyst while simultaneously the formation of CO at the expense of formaldehyde selectivity is favored. This study demonstrates the importance of understanding the influence of relevant reaction conditions and the potential of selective photocatalytic gas‐phase oxidation of small molecules.

Solar-Driven Reforming of Methane and Nitrogen to Methanol and Ammonium on Iron-Modified Zeolite under Ambient Conditions in Water.

Artificial photosynthesis from selective methane oxidation or nitrogen reduction to value-added chemicals provides a promising pathway for the sustainable chemical industry, while still remaining a great challenge due to the extreme difficulty in C-H and N≡N bond cleavage under ambient conditions. Catalysts that can cocatalyze these two reactions simultaneously are rarely reported. Here, Fe-ZSM-5 with highly dispersed extra-framework Fe-oxo species enables efficient and selective photocatalytic conversion of methane and nitrogen to coproduce methanol and ammonia using H2O as the redox reagent under ambient conditions. The optimized Fe-ZSM-5 photocatalyst achieves up to 0.88 mol/molFe·h of methanol products with 97% selectivity. Meanwhile, the productivity of ammonia is 0.61 mol/molFe·h. In situ EPR and DRIFT studies disclose that water serves as a redox reagent to provide hydroxyl radicals for methane oxidation and protons for nitrogen hydrogenation. Quantum chemical calculations revealed that Fe-oxo species play a significant role in the coactivation of methane and nitrogen molecules, which lowers the energy barriers of rate-determining steps for methanol and ammonia generation.

Preparation of Ni/YSZ Catalysts for Application of Solid Oxide Electrolysis Cell Methanation

Co-electrolysis of CO2 and steam using solid oxide electrolysis cells (SOECs) is a major focus of the CO2 conversion. Furthermore, SOECs have the potential to drive high value-added products with reduced carbon footprint. For example, the syngas (mixture of CO and H2) can be produced by SOEC-driven co-electrolysis of CO2 and steam, and utilized in the Fischer-Tropsch (FT) process for the synthesis of artificial hydrocarbon. The artificial hydrocarbons would be environmentally friendly fuels when CO2 is obtained from carbon capture and storage (CCS) technology. The Ni-based cermet, such as Ni with yttria-stabilized zirconia (Ni/YSZ), is a typical material of SOEC device, and Ni has been found to be an active catalyst for CH4 production (methanation). Therefore, use of the Ni/YSZ has potential to directly convert CO2 and H2O to CH4. In the catalytic process, the activity, selectivity and durability of the Ni/YSZ catalyst are significantly influenced by the structural property of Ni and YSZ, which is varied by the Ni loading and calcination conditions in addition to the studied reaction conditions. The preparation of Ni/YZS catalyst with high performance in co-electrolysis and methanation is still challenging.Herein, the preparation of the Ni/YSZ catalysts with enhanced activity in SOEC methanation was studied. The Ni/YSZ catalysts were prepared by wet impregnation, one of the catalyst preparation methods, and characterized by several conventional methods. Effects of Ni loading and calcination conditions on the performance of Ni/YSZ catalysts were examined by CO2 methanation. A Ni/YZS catalyst gave a high CO2 conversion of 86% and a high methane selectivity at around 300 ºC under ambient pressure. With Ni/YSZ prepared using the optimized method, we are planning to prepare tubular cells and evaluate their activity in SOEC methanation.

RuNi/MMO Catalysts Derived from a NiAl-NO3-LDH Precursor for CO Selective Methanation in H2-Rich Gases

CO selective methanation (CO-SMET) is a promising method for deep CO removal from H2-rich gases. In this study, a series of RuNi/MMO catalysts are prepared using the support MMO-N derived from NiAl-NO3-LDHs, which was prepared from NiAl-CO3-LDHs via an acid–alcohol ion-exchange reaction. The prepared catalysts were characterized by XRD, SEM, TEM, XPS, H2-TPR, CO-TPD, CO2-TPD, NH3-TPD, and TG. The RuNi/MMO-N catalyst demonstrated excellent CO-SMET performance, successfully reducing the CO to less than 10 ppm with a selectivity greater than 50% in a reaction temperature window ranging from 180 °C to 260 °C. Compared with similar catalysts derived from NiAl-CO3-LDHs, the exceptional CO-SMET capability of the RuNi/MMO-N catalyst is suggested to be associated with a more effective hydrogen spillover, a larger number of electron-rich Ni sites, and a higher density of acid sites on the surface of RuNi/MMO-N, which are conducive to CO adsorption and the inhibition of CO2 methanation.

Synthesis and evaluation of the cobalt-promoted NiO/CaO.2Al2O3 catalysts in CO2 methanation reaction: Effect of different promoters

This work is concentrated on designing of CO2 methanation process over nickel-based catalysts doped by different promoters (CuO, Cr2O3, Co3O4, Fe2O3, and MnO2) supported on CaO.2Al2O3 powder. The CaO-Al2O3 powder was fabricated by mechanochemical method, and catalysts were synthesized via a wet impregnation procedure. The characterization properties of all samples were tested by XRD, BET, TPR, FESEM, and EDS-mapping analyses. The optimum amount of NiO was selected at 10 wt% along with CaO:Al2O3 as support with the molar ratio of 1:2. The Co-doped catalyst showed the lowest pore size (9.4 nm) and the highest surface area (106 m2.g−1) among the promoted catalysts. The results exhibited that the Co3O4(3)-NiO(10)/CaO.2Al2O3 catalyst possessed superior catalytic performance in the CO2 methanation reaction. The results illustrated that the increase in cobalt oxide percentage up to 3 wt% improved catalytic performance. However, further augmentation in the Co3O4 from 3 to 7 wt% diminished the specific surface area. According to the performance tests, carbon dioxide conversion and methane selectivity were 83.1% and 99.5% at 450 °C under operating conditions (GHSV = 18,000 ml.gcat−1.h−1 and H2:CO2 = 4:1) over this catalyst. The processing conditions including calcination temperature, reduction temperature, GHSV, feed ratio, and long-term stability test were also examined over the selected catalyst. Outcomes revealed that CO2 conversion increased with a decrement in calcination temperature from 650° to 450°C. Also, chosen catalyst reduced at 650 °C showed the highest performance. Besides, catalytic performance enhanced by raising feed ratio (H2:CO2) from 2:1 to 5:1 and decreased with augmentation of GHSV from 12,000 to 30,000 ml.gcat−1.h−1. Moreover, Co3O4(3)-NiO(10)/CaO.2Al2O3 catalyst possessed high stability during 14 h time on stream.

Elemental Fe conditioning for the synthesis of highly selective and stable high entropy catalysts for CO2 methanation

High entropy oxides (HEOs) with high stability and designability have demonstrated excellent catalytic performance in CO2 hydrogenation. However, it is challenging to combine high methane selectivity and high stability of HEOs using an equimolar design strategy. In this study, a non-equimolar design strategy was used to fix the Cr, Co, Mn and Ni elements and adjust different Fe molar amounts to prepare a highly crystalline HEO at 900 °C. After H2 reduction, the catalyst (HEO-4-900/H2) achieved 72.9% CO2 conversion and 98.8% methane selectivity at atmospheric pressure and 400 °C, and maintained a high methane selectivity of over 97% after 100 h stability test. The catalytic activity was influenced by the amount of Fe. Increasing the amount of Fe could precisely regulate the crystallinity and oxygen defects of the crystal, improve the catalyst stability, reduce the interaction between the Co-Ni alloys and HEOs, and allow the catalyst to contain more Co-Ni active sites and more abundant oxygen vacancies. This study demonstrates the considerable potential of HEOs for CO2 methanation, and provides a new design idea for further stimulating highly active CO2 methanation HEOs catalysts.

Syngas to FCC-like gasoline range hydrocarbons with upgraded light olefin selectivity catalyzed by readily synthesized Fe-MOF

The global trend toward sustainability is due to the growing demand for synthetic chemicals and fuels relying on fossil crude oil with the associated concerns of climate change. The Fischer-Tropsch synthesis (FTS) process is a key sustainable pathway for supplying light olefins, gasoline, and other petrochemicals using green hydrogen and energy. Here we report a simple, green, cost-effective synthesis strategy to prepare an iron-based metal–organic framework (Fe-BTC MOF) at room temperature with a remarkable porous structure analogous to the commercially available Basolite F300. The catalyst shows a 97% syngas conversion to gasoline-range hydrocarbons (C5-C12) at high temperatures, with a selectivity of 48.3%, yield of 28%, low methane selectivity (15.5%) and low C13+ selectivity (1%). In addition, the catalyst is 29% selective to light olefin (C2-C4=), yielding 17%, besides an olefin/paraffin ratio (O/P) of 4.3 with 81% olefin selectivity of the C2-C4 fraction. The resulting gasoline is equivalent to gasoline produced by Fluid Catalytic Cracking (FCC) of crude oil. The highest C5-C12 selectivity reached 63.6%, yielding 12% at 29% CO conversion. The Fe-BTC/C catalyst showed excellent stability for time on stream >100 h and a high gas hourly space velocity (GHSV) value of 20000 mL g-1cat h−1 with an Fe-time yield of 165 µmolCO g-1Fe s−1. The prepared Fe-BTC catalyst, with a 2-fold larger pore volume than the previously prepared Fe-MIL-88B catalyst, has a higher olefin production capability by 2-fold, 7-fold higher O/P for the light fraction and 2.3-fold higher C5+ selectivity. The sustainable synthesis of catalysts with improved porous structure may significantly foster FTS technology for being economically practical to be scaled up and commercialized for national fuel and olefin production projects.

Electro-assisted methane oxidation to formic acid via in-situ cathodically generated H2O2 under ambient conditions

Direct partial oxidation of methane to liquid oxygenates has been regarded as a potential route to valorize methane. However, CH4 activation usually requires a high temperature and pressure, which lowers the feasibility of the reaction. Here, we propose an electro-assisted approach for the partial oxidation of methane, using in-situ cathodically generated reactive oxygen species, at ambient temperature and pressure. Upon using acid-treated carbon as the electrocatalyst, the electro-assisted system enables the partial oxidation of methane in an acidic electrolyte to produce oxygenated liquid products. We also demonstrate a high production rate of oxygenates (18.9 μmol h−1) with selective HCOOH production. Mechanistic analysis reveals that reactive oxygen species such as ∙OH and ∙OOH radicals are produced and activate CH4 and CH3OH. In addition, unstable CH3OOH generated from methane partial oxidation can be additionally reduced to CH3OH on the cathode, and so-produced CH3OH is further oxidized to HCOOH, allowing selective methane partial oxidation.

Tailoring gas hydrate lattice dimensions for enhanced methane selectivity in biogas upgrading

Gas hydrates, specifically clathrate hydrates, have emerged as a potential separation medium for biogas containing methane (CH4) and carbon dioxide (CO2). However, the efficient separation of CH4 and CO2 remains challenging due to their similar cage occupation behavior within the hydrate structure. This study aimed to enhance CH4 selectivity by modifying the hydrate lattice to exclude CO2 from large cages and reduce the size of small cages through lattice engineering. To achieve this, tert-butyl alcohol (TBA) and trimethylene oxide (TMO) were employed as thermodynamic promoters, inducing strong and weak cage expansion, respectively. The results revealed that TMO hydrates, with their weak cage expansion, exhibited improved CH4 selectivity compared to TBA hydrates, which displayed strong cage expansion due to the larger size of TBA. Multi-stage separation experiments demonstrated that TMO hydrates required four unit stages, while TBA hydrates necessitated more than five unit stages to obtain purified CH4 (> 85%) from an initial gas mixture of CH4 (50%) and CO2 (50%). Additionally, TMO hydrates consistently exhibited higher separation factors than TBA hydrates in all unit stages. The findings emphasize the influence of the thermodynamic promoter's size on the separation performance of gas hydrates in separating CH4 from CH4 + CO2 mixtures. The study provides valuable insights into enhancing CH4 selectivity through lattice engineering and offers guidance in selecting suitable thermodynamic promoters for gas hydrate-based biogas upgrading applications.

Bioinspired microenvironment modulation of metal–organic framework-based catalysts for selective methane oxidation

Inspiration from natural enzymes enabling creationary catalyst design is appealing yet remains extremely challenging for selective methane (CH4) oxidation. This study presents the construction of a biomimetic catalyst platform for CH4 oxidation, which is constructed by incorporating Fe-porphyrin into a robust metal–organic framework, UiO-66, furnished with saturated monocarboxylic fatty acid bearing different long alkyl chains. The catalysts demonstrate the high efficiency in the CH4 to methanol (CH3OH) conversion at 50 °C. Moreover, the selectivity to CH3OH can be effectively regulated and promoted through a fine-tuned microenvironment by hydrophobic modification around the Fe-porphyrin. The long-chain fatty acids anchored on the Zr-oxo cluster of UiO-66 can not only tune the electronic state of the Fe sites to improve CH4 adsorption, but also restrict the amount of H2O2 around the Fe sites to reduce the overoxidation. This behavior resembles the microenvironment regulation in methane monooxygenase, resulting in high CH3OH selectivity.

Enhanced conversion of syngas to high-quality diesel fuel over ZrO2 and acidized carbon nanotube bifunctional catalyst

Direct syngas conversion for diesel fuel becomes an attractive route for its possibility of utilizing non-petroleum carbon resources. However, there is a limited selectivity of around 36% for diesel hydrocarbons (C9-C22) via the conventional Fischer-Tropsch process due to the Anderson-Schulz-Flory (ASF) constraint. Herein, bifunctional catalysts composed of zirconium dioxide (ZrO2) dispersed on multi-walled carbon nanotubes (CNT) (ZrO2/CNT) were successfully designed and applied for direct conversion of syngas into diesel with selectivity far beyond the ASF limitation. At 350 °C with the pressure of 3 MPa, H2/CO of 2 and gas hourly space velocity of 2400 mL·h−1·gcat−1, ZrO2/CNT gave an unexceptionable C9-C22 selectivity of 50.74% at a single pass CO conversion of 43.86% compared with those (9.11% and 20.55%, respectively) of ZnO/CNT and those (14.07% and 25.76%, respectively) of ZnO-ZrO2/CNT. The iso/n-paraffin ratio in the C9-C22 reached up to 16. Moreover, after 100 h of operation, the catalyst still showed remarkable catalytic activity with CO conversion remaining at 40.61%, diesel hydrocarbon selectivity, and methane selectivity at 42.27% and 7.67%, respectively, while the by-product CO2 selectivity was also stable at about 3.77%.

Structure-Property Relationships for Nickel Aluminate Catalysts in Polyethylene Hydrogenolysis with Low Methane Selectivity.

Earth-abundant metals have recently been demonstrated as cheap catalyst alternatives to scarce noble metals for polyethylene hydrogenolysis. However, high methane selectivities hinder industrial feasibility. Herein, we demonstrate that low-temperature ex-situ reduction (350 °C) of coprecipitated nickel aluminate catalysts yields a methane selectivity of <5% at moderate polymer deconstruction (25-45%). A reduction temperature up to 550 °C increases the methane selectivity nearly sevenfold. Catalyst characterization (XRD, XAS, 27Al MAS NMR, H2 TPR, XPS, and CO-IR) elucidates the complex process of Ni nanoparticle formation, and air-free XPS directly after reaction reveals tetrahedrally coordinated Ni2+ cations promote methane production. Metallic and the specific cationic Ni appear responsible for hydrogenolysis of internal and terminal C-C scissions, respectively. A structure-methane selectivity relationship is discovered to guide the design of Ni-based catalysts with low methane generation. It paves the way for discovering other structure-property relations in plastics hydrogenolysis. These catalysts are also effective for polypropylene hydrogenolysis.

Applications of Metal-Organic Frameworks in Methane Storage

Metal-organic frameworks (MOFs) are a type of porous materials that are receiving a lot of attention for their application potential in gas storage and separation. Methane storage, in particular, is an active area of research due to its significance as a vital component of natural gas, which is used for heating, transportation, and electricity generation. MOFs offer a promising solution to the challenge of efficiently storing and transporting methane because of their enormous surface area and variable pore sizes, which can facilitate efficient and reversible methane adsorption. The development of MOFs for methane storage has the potential to revolutionize the energy industry by enabling more efficient and cost-effective storage and transportation of natural gas, thereby reducing greenhouse gas emissions and promoting the use of cleaner energy sources. New MOF materials are being created and characterized as part of this field's research., and the study of their adsorption properties uses both experimental and computational techniques as well as the understanding the underlying mechanisms that govern methane adsorption in these materials. Key areas of investigation include measuring methane uptake and selectivity, as well as studying the thermodynamics and kinetics of the adsorption process.