Low Temperature Dry Reforming Of Methane Research Articles

Anti-coking Ni-La2O3/SiO2 catalyst prepared by using a glycine-assisted impregnation method for low-temperature dry reforming of methane

Abstract The development of efficient Ni-based catalysts for low-temperature (≤600 °C) dry reforming of methane remains a challenge because of their susceptibility to carbon deposition. Herein, we report a Ni-La2O3/SiO2 catalyst prepared by using the glycine-assisted impregnation method. Small Ni nanoparticles were confined by La2O3 on the SiO2 support in the catalyst, which exhibited remarkable resistance to carbon deposition for the dry reforming of methane at 600 °C.

Immobilization of Ni on MOF-derived CeO2 for promoting low-temperature dry reforming of methane

The development of highly active catalysts for low-temperature dry reforming of methane (DRM) is of great importance for the utilization of CO2 and CH4. Herein, the MOF-derived CeO2-supported Ni (Ni/CeO2-M) catalyst was facilely and mildly prepared, and its catalytic performance for DRM reactions at 400–600 °C was explored and compared with commercial CeO2-supported Ni (Ni/CeO2-C). At 550 °C, the CO2 and CH4 conversions of Ni/CeO2-M are 40.1 % and 30.8 %, respectively, which are significantly higher than those of Ni/CeO2-C (27.3 % and 15.5 %, respectively). The analysis of covariance also shows that the conversions of CO2 and CH4 of Ni/CeO2-M are 8.90 % and 11.65 % higher than those of Ni/CeO2-C after eliminating the effect of temperature, respectively. After 10 h of DRM reaction, Ni/CeO2-M exhibits better resistance to carbon deposition and sintering than Ni/CeO2-C, and carbon deposition is related to the reaction temperature rather than the catalyst. Morphological analysis suggests that, unlike the serious Ni accumulation on Ni/CeO2-C, metallic Ni is uniformly immobilized on Ni/CeO2-M. The highly dispersed metallic Ni0 on Ni/CeO2-M facilitates the dissociation of CH4, and more oxygen vacancies facilitate the dissociation of CO2 into CO and active O. Therefore, Ni/CeO2-M exhibits better catalytic performance and is very promising for low-temperature DRM reactions.

La–Ce binary oxide catalysts for low-temperature dry reforming

A series of Ni-based catalysts supported by La–Ce binary oxide were synthesized by a one-pot microwave-assisted hydrothermal method. With fine-tuning of the La/Ce ratio and synthesis process, fabricated Ni/La–Ce catalysts showed comparable catalytic performance in low-temperature dry reforming of methane (DRM). With a La/Ce ratio of 1:4, the synthesized catalyst had optimal conversions of reactants but severe coke formation. When La/Ce ratio increased to 1:1, with declined DRM reactivity Ni/La–Ce catalyst showed great coke resistance. Different characterizations had been performed on the fresh and spent Ni/La–Ce catalyst to evaluate the correlations between structures and surface properties with the catalytic performance of catalysts. It was found that synthesis and carbonate species formed on the surface of La–Ce binary oxide played important roles in the DRM reaction. The La–Ce binary oxide had its intrinsic lattice configuration with La inserting into the CeO2 phases and proved its efficiency in low-temperature DRM reactions.

Synergy of Oxygen Vacancies and Ni0 Species to Promote the Stability of a Ni/ZrO2 Catalyst for Dry Reforming of Methane at Low Temperatures

Low-temperature dry reforming of methane (DRM) can avoid the sintering of nickel and reduce the cost of the process. However, inefficient activation of CO2 and oxidization of Ni0 hamper the catalytic performance of Ni-based catalysts at low temperatures. Herein, a Ni/ZrO2 catalyst was prepared and used in the DRM reaction, which exhibited stable activity at low temperatures (400, 320 and 300 °C) for 10 h, with CH4 and CO2 turnover frequencies of 0.26 and 0.18 s–1 at 320 °C, respectively. The presence of Ni0 species and oxygen vacancies promotes the activation of CO2 at 300 °C, proved by CO2 temperature-programmed oxidation (CO2-TPO). Combined with O2 temperature-programmed decomposition (O2-TPD), C18O2-DRM, in situ X-ray photoelectron spectroscopy (XPS), and diffuse reflectance infrared Fourier transform spectroscopy (DRIFTS) results, after CH4 decomposition on the Ni0 site, the resultant C would react with nearby surface oxygen species and lattice oxygen species of ZrO2, forming CO and an oxygen vacancy. The oxygen vacancy nearby Ni0 species with more electron transfer would promote the activation of CO2. This work highlights the importance of CO2 activation and emphasizes the key role of the synergistic effect between Ni0 species and the oxygen vacancy in enhancing the stability of catalysts over low-temperature DRM reactions.

Microwave-assisted hydrothermal synthesis of Ru/CeO2 catalyst for efficient and stable low-temperature dry reforming of methane

As the widely applied catalysts in dry reforming of methane (DRM), Ni-based catalysts typically suffer from severe coke formation on the catalyst leading to the deactivation of the catalyst. Meanwhile, with great trends of reducing the operating temperature for DRM reactions, the Ni-based catalysts can’t exhibit comparable reactivity in low-temperature DRM reactions. To reduce coke formation and achieve better reactivity at low temperatures, a novel Ru/CeO2 catalyst was synthesized through a microwave-assisted hydrothermal method and exploited in a low-temperature DRM reaction in a fixed bed reactor. It exhibited comparable activity of above 58 % CH4 and 71 % CO2 conversion with above 0.85 H2/CO ratio for over 120 h at 600 °C. Moreover, it remained stable without obvious coke deposition on the catalyst after the long-term experiment. The characterizations by XRD, XPS, HAADF-STEM, FTIR and some temperature-programmed experiments indicated that microwave irradiation and the introduction of glucose played important roles in achieving great thermal stability and better DRM reactivity of Ru/CeO2. Ru, as the active metal compared with Ni, exhibited moderate CH4 dissociation ability leading to excellent coke resistance. The novel Ru/CeO2 catalyst with high DRM reactivity, simple synthesis method and great coke resistance in this work offers a new opportunity for the commercialization of low-temperature DRM reaction.

Carbon-confined Ni based catalyst by auto-reduction for low-temperature dry reforming of methane

Producing syngas from dry reforming of methane is fascinating but challenging because of coking and sintering. Here, carbonising Ni based catalysts by auto-reduction are fabricated and applied to low-temperature DRM reaction. The catalytic structure–function relationship including the effects of carbonising temperature on carbon structure is investigated and rendered in detail. Ultimately, the carbon-confined catalysts boost DRM reaction at a relatively low temperature of 600 °C and effectively convert greenhouse gases to syngas. The carbon layers obtained by carbonising metal–organic frameworks (MOFs) precursor act as a shell protecting fine Ni nanoparticles (NPs) from reaction-induced reshaping, agglomeration, and coking. This work not only identifies an energy-conserving process for the utilization of greenhouse gases, but also reveals the sintering and coking can be restricted by carbon confinement effect.

Facile integration of core–shell catalyst and Pd-Ag membrane for hydrogen production from low-temperature dry reforming of methane

Dry reforming of methane (DRM) is an important way of conversion of CH4 and CO2, two greenhouse gases, for the production of hydrogen. In this study, a catalytic membrane reactor combining an ultra-thin Pd-Ag alloy membrane with a coke-resistant Ni-SiO2@CeO2 core–shell catalyst was developed for high yield hydrogen production from DRM. The performance of membrane in the presence of gases such as CO, CO2 and CH4 was evaluated, and very little reduction in H2 flux (∼2.5 %) was observed in the presence of these gases at the relevant reaction conditions. The catalyst was tested for DRM reaction in both fixed bed reactor (FBR) and catalytic membrane reactor (CMR) to evaluate its performance at different reaction conditions. In a catalytic membrane reactor, the removal of hydrogen resulted in 1.5 times higher methane conversion compared to the calculated conversion at thermodynamic equilibrium at the used reaction conditions when hydrogen is not removed from the reaction mixture. Around 70 % of the produced H2 was recovered from the reaction stream, by virtue of the high H2 flux through the ultra-thin Pd-Ag membrane. Further, the competing reverse water gas shift reaction, that consumes the produced H2, was drastically suppressed by using membrane reactor. The suppression of reverse water gas shift reaction (RWGS) in CMR was confirmed by analyzing downstream gases using gas chromatography mass spectrometer, the result showed significantly lower H2O content for CMR than FBR. Thus, the coupling of ultra-thin membrane with a core shell catalyst synergistically improved the performance of the dry reforming of methane.

Glycine-assisted preparation of highly dispersed Ni/SiO2 catalyst for low-temperature dry reforming of methane

Ni-based catalysts have been widely studied in reforming methane with carbon dioxide. However, Ni-based catalysts tends to form carbon deposition at low temperatures (≤600 °C), compared with high temperatures. In this paper, a series of Ni/SiO2-XG catalysts were prepared by the glycine-assisted incipient wetness impregnation method, in which X means the molar ratio of glycine to nitrate. XRD, H2-TPR, TEM and XPS results confirmed that the addition of glycine can increase Ni dispersion and enhance the metal-support interaction. When X ≥ 0.3, these catalysts have strong metal-support interaction and small Ni particle size. The Ni/SiO2-0.7G catalyst has the best catalytic performance in dry reforming of methane (DRM) test at 600 °C, and its CH4 conversion is 3.7 times that of Ni/SiO2-0G catalyst. After 20 h reaction under high GHSV (6 × 105 ml/gcat/h), the carbon deposition of Ni/SiO2-0.7G catalyst is obviously lower than that of Ni/SiO2-0G catalyst. Glycine-assisted impregnation method can enhance the metal-support interaction and decrease the metal particle size，which is a method to prepare highly dispersed and stable Ni-based catalyst.

Low-temperature dry reforming of methane tuned by chemical speciations of active sites on the SiO2 and γ-Al2O3 supported Ni and Ni-Ce catalysts

The cognition of active sites in the Ni-based catalysts plays a vital role and remains a huge challenge in improving catalytic performance of low temperature CO2 dry reforming of methane (LTDRM). In this work, typical catalysts of SiO2 and γ-Al2O3 supported Ni and Ni-Ce were designed and prepared. Importantly, the difference in the chemical speciations of active sites on the Ni-based catalysts is revealed by advanced characterizations and further estimates respective catalytic performance for LTDRM. Results show that larger [Nin0] particles mixed with [Ni-O-Sin]) species on the Ni/SiO2(R) make CH4 excessive decomposition, leading to poor activity and stability. Once the Ce species is doped, however, superior activity (59.0% CH4 and 59.8% CO2 conversions), stability and high H2/CO ratio (0.96) at 600 °C can be achieved on the Ni-Ce/SiO2(R), in comparison with other catalysts and even reported studies. The improved performance can be ascribed to the formation of integral ([Nin0]-[CeIII-□-CeIII]) species on the Ni-Ce/SiO2(R) catalyst, containing highly dispersed [Nin0] particles and rich oxygen vacancies, which can synergistically establish a new stable balance between gasification of carbon species and CO2 dissociation. With respect to Ni-Ce/γ-Al2O3(R), the Ni and Ce precursors are easily captured by extra-framework Aln-OH groups and further form stable isolated ([Nin0]-[Ni-O-Aln]) and [CeIII-O-Aln] species. In such a case, both of them preferentially accelerate CO2 adsorption and dissociation, causing more carbon deposition due to the disproportionation of superfluous CO product. This deep distinguishment of chemical speciations of active sites can guide us to further develop new efficient Ni-based catalysts for LTDRM in the future.

Effect of interstitial carbon atoms in core-shell Ni3ZnC0.7/Al2O3 catalyst for high-performance dry reforming of methane

Dry reforming of methane (DRM) on Ni-based catalysts provides an economically and environmentally pivotal route to generate synthesis gas. However, coke formation on Ni surface by the growth of carbon atoms is the main reason for catalyst deactivation and reactor blockage. Here, we propose a reaction-induced method to incorporate and store active carbon atoms into nickel octahedral sites in core-shell Ni3ZnC0.7/Al2O3. This strategy can fundamentally avoid C−C bond formation and feasible oxidation of Ni3ZnC0.7 in low-temperature DRM under CO2-rich condition. About 2 nm of thin-layer Al2O3 encapsulated Ni3ZnC0.7 is explored as the carbon reservoir to accommodate sufficient interstitial carbon atoms, and less than 5% Ni3Zn was observed under CH4/CO2 < 1/1 for 100 h. The dynamic balance of carbon atom storage and conversion in robust Ni3ZnC0.7 contributes to the enhanced activity, stability, coke and oxidation resistance, and distinct reaction pathway in low-temperature DRM.

In situ study of low-temperature dry reforming of methane over La2Ce2O7 and LaNiO3 mixed oxides

Dry reforming of methane (DRM) is a promising process to generate synthetic gas with a low H2/CO ratio. The main issues in DRM are the deposition of carbon over the catalyst and active metal sintering. Pyrochlores and perovskites are stable materials with properties that can overcome these challenges due to the presence of well dispersed active metal and oxygen vacancies. La2Ce2O7 and LaNiO3 mixed oxides containing 5 wt% of nickel were synthesized by modified Pechini and hydrothermal methods. The reduction of the La2Ce2O7 and LaNiO3 mixed materials was followed by in situ X-ray diffraction, ambient pressure X-ray photoelectron spectroscopy (APXPS), and X-ray absorption near edge structure. An oxygen-deficient perovskite La2Ni2O5 was identified already at room temperature. Both catalysts were stable during the performance test at low-(600 °C) and high-(850 °C) temperature DRM reaction, thanks to a negligible carbon accumulation on the catalyst surface. The high amount of electrophilic oxygen species, oxygen vacancies and basic sites detected correlates with the high catalytic activity. The material synthesized by hydrothermal method showed the highest conversion and yield. The better performance in this catalyst was related to higher amount of intermediate basic sites, oxygen vacancies and greater interaction between nickel and cerium. The reaction mechanism proposed in these materials takes into account the intermediates CHx and adsorbed O/OH, which were observed by means of APXPS.

Ni-CeO2/SBA-15 Catalyst Prepared by Glycine-Assisted Impregnation Method for Low-Temperature Dry Reforming of Methane

Developing low-temperature nickel-based catalysts with good resistance to coking and sintering for dry reforming of methane (DRM) is of great significance. In this work, Ni (5 wt%) and CeO2 (5 wt%) were supported on SBA-15 porous material by glycine-assisted impregnation method to obtain Ni-CeO2/SBA-15-G catalyst. XRD and TEM results showed that the addition of glycine can effectively promote the dispersion of NiO and CeO2 in the pores of SBA-15. H2-TPR and XPS results confirmed the formation of stronger metal-support interaction. In addition, after the addition of glycine, the NixCe1−xOy solid solution content was increased significantly, meanwhile, the Ce3+ concentration was increased from 31% to 49%, accompanied by more oxygen vacancies and generation of active oxygen species. For the above reasons, Ni-CeO2/SBA-15-G had better catalytic performance in the low-temperature DRM test (20 h, 600 °C) with high GHSV (600,000 mL/gcat/h), its CH4 conversion after reaction of 20 h was 2 times that of Ni-CeO2/SBA-15-C catalyst prepared by a conventional impregnation method. TGA-DTA test also proved that Ni-CeO2/SBA-15-G almost completely eliminated carbon deposition. The above advantages of the Ni-CeO2/SBA-15-G catalyst may have originated from the complexation of glycine with metal cations and can prevent them from gathering.

One-Step Solvothermal Synthesis of Ni Nanoparticle Catalysts Embedded in ZrO2 Porous Spheres to Suppress Carbon Deposition in Low-Temperature Dry Reforming of Methane

Ni nanoparticle catalysts embedded in ZrO2 porous spheres and ZrO2 porous composite spheres, SiO2-ZrO2, MgO-ZrO2, and Y2O3-ZrO2, with 83−115 nm diameter and 167–269 m2/g specific surface area were prepared by a one-pot and one-step solvothermal reaction from precursor solutions consisting of Ni(NO3)2‧6H2O, Zr(OnBu)4, and acetylacetone in moist ethanol combined with either Si(OEt)4, magnesium acetylacetate, or Y(OiPr)3. The obtained Ni catalysts have high specific surface areas of 130–196 m2/g, even after high-temperature reduction by H2 at 450 °C for 2 h. They were utilized as catalysts for low-temperature dry reforming of methane (DRM) at 550 °C to suppress carbon deposition on Ni nanoparticles. The Ni catalysts embedded in SiO2-ZrO2 and Y2O3-ZrO2 demonstrated high catalytic activity and long stability in the reaction. Moreover, carbon deposition on Ni nanoparticles in the DRM reaction was effectively suppressed in when using the SiO2-ZrO2 and Y2O3-ZrO2 composites.Graphical abstract

Microwave-Assisted Hydrothermal Synthesis of Ru/Ceo2 Catalyst for Efficient and Stable Low-Temperature Dry Reforming of Methane

Microwave-Assisted Hydrothermal Synthesis of Ru/Ceo2 Catalyst for Efficient and Stable Low-Temperature Dry Reforming of Methane

Microwave-Assisted Hydrothermal Synthesis of Ru/Ceo2 Catalyst for Efficient and Stable Low-Temperature Dry Reforming of Methane

Microwave-Assisted Hydrothermal Synthesis of Ru/Ceo2 Catalyst for Efficient and Stable Low-Temperature Dry Reforming of Methane

Support Induced Effects on the Ir Nanoparticles Activity, Selectivity and Stability Performance under CO2 Reforming of Methane.

The production of syngas (H2 and CO)—a key building block for the manufacture of liquid energy carriers, ammonia and hydrogen—through the dry (CO2−) reforming of methane (DRM) continues to gain attention in heterogeneous catalysis, renewable energy technologies and sustainable economy. Here we report on the effects of the metal oxide support (γ-Al2O3, alumina-ceria-zirconia (ACZ) and ceria-zirconia (CZ)) on the low-temperature (ca. 500–750 °C) DRM activity, selectivity, resistance against carbon deposition and iridium nanoparticles sintering under oxidative thermal aging. A variety of characterization techniques were implemented to provide insight into the factors that determine iridium intrinsic DRM kinetics and stability, including metal-support interactions and physicochemical properties of materials. All Ir/γ-Al2O3, Ir/ACZ and Ir/CZ catalysts have stable DRM performance with time-on-stream, although supports with high oxygen storage capacity (ACZ and CZ) promoted CO2 conversion, yielding CO-enriched syngas. CZ-based supports endow Ir exceptional anti-sintering characteristics. The amount of carbon deposition was small in all catalysts, however decreasing as Ir/γ-Al2O3 > Ir/ACZ > Ir/CZ. The experimental findings are consistent with a bifunctional reaction mechanism involving participation of oxygen vacancies on the support’s surface in CO2 activation and carbon removal, and overall suggest that CZ-supported Ir nanoparticles are promising catalysts for low-temperature dry reforming of methane (LT-DRM).

Yolk–Shell Pt-NiCe@SiO2 Single-Atom-Alloy Catalysts for Low-Temperature Dry Reforming of Methane

Herein, we report a highly carbon resistant nanotubular yolk–shell Pt-NiCe@SiO2 single-atom-alloy (SAA) catalyst for low-temperature dry reforming of methane (DRM). A synergetic combination of the confined yolk–shell morphology and Pt–Ni SAA structures prevents carbon formation and provides excellent catalyst stability. The confined morphology of the yolk–shell structures can impede carbon deposition due to the facile CO desorption from the surface. Carbon formation can be further minimized by 0.25 wt % Pt promotion, showing an excellent stability for 120 h during DRM at 500 °C. The enhanced stability of the Pt0.25-NiCe@SiO2 catalyst can be attributed to the atomically dispersed Pt on the yolks forming Pt–Ni SAA structures encapsulated by a nanotubular SiO2 shell. The Pt–Ni SAA facilitates Pt–Ni interactions and enhances the reducibility of the Ni species, which further suppresses carbon formation during DRM. The developed bifunctional catalyst exhibits excellent resistance to coking by decreasing the effect of both main carbon formation reactions: i.e., CO disproportionation and CH4 decomposition. When the Pt loading is increased above 0.25 wt %, Pt nanoparticles form, leading to oligomerization of C–H species. Our results show that advantageous effects of both confined morphology and Pt–Ni SAA structures can lower the operating temperature of DRM without showing any catalyst deactivation.

Efficient integration of CO2 capture and conversion over a Ni supported CeO2-modified CaO microsphere at moderate temperature

Efficient integration of calcium-looping (CaL) and dry reforming of methane (DRM), termed as CaLDRM, into an isothermal process implemented on a bifunctional Ni-CaO based material is a promising technology to achieve CO2 capture and in-situ conversion to syngas, thereby allowing a win–win for environment and economy. The core of this technology is the employed material which should ensure both good CO2 capture capacity and significant catalytic activity at a temperature matching CaL and DRM. To this end, we synthesize a Ni supported porous CeO2-modified CaO microsphere to serve as the bifunctional material by a combination of template-assisted hydrothermal and impregnation method. This material successfully drives cyclic CO2 capture and conversion at the same temperature of 650 °C, i.e. simultaneously realizing high-temperature CaL and low-temperature DRM. The role of Ce on boosting the material performance originates from two aspects: on the one hand, the homogeneously mixed CeO2, as an activity promoter, enhances the CO2 affinity of CaO and the low-temperature activity of Ni, enabling higher CO2 capture and conversion capacities at 650 °C; on the other hand, it, as a structure stabilizer, improves the sinter resistance of CaO and the dispersion of Ni, maintaining the CaL kinetics and catalytic DRM activity. Following the premise of minimizing additive quantity, the bifunctional material constructed from the support with a Ca:Ce molar ratio of 85:15 shows stable CO2 uptake and syngas yield during the isothermal CaLDRM cycles at 650 °C, exceeding the performance of unmodified material by more than 2 times.

Improved Effect of Fe on the Stable NiFe/Al2O3 Catalyst in Low-Temperature Dry Reforming of Methane

Bimetallic catalysts with alloy structure have been extensively explored to tailor and boost the catalytic performance of the dry reforming of methane. Herein, NiFe/Al2O3 catalyst was designed from an aluminum gel with metal nitrate in a triblock copolymer solution by an evaporation-induced self-assembly process and calcination for the low-temperature dry reforming of methane (LT-DRM). The resultant NiFe/Al2O3 exhibited a large surface area of 203 m2 g–1 and porosity of 0.8 cm3 g–1. Bimetallic NiFe/Al2O3 promoted CH4 and CO2 conversion as well as the H2/CO ratio relative to monometallic Ni/Al2O3. CH4 and CO2 conversion on the NiFe/Al2O3 was 26.6 and 37.8% with a H2/CO ratio of 0.67 at 550 °C. Furthermore, NiFe/Al2O3 possessed good stability at 450 °C during LT-DRM reaction for 20 h. The Ni3Fe alloy structure is favorable for the resistance of oxidation and coke deposition. This work sheds light on the sophisticated design of the alloy structure of the bimetallic catalyst for efficient and stable catalytic performances.

NiYAl-Derived Nanoporous Catalysts for Dry Reforming of Methane

Dry reforming of methane can be used for suppressing the rapid growth of greenhouse gas emissions. However, its practical implementation generally requires high temperatures. In this study, we report an optimal catalyst for low-temperature dry reforming of methane with high carbon coking resistance synthesized from NiYAl alloy. A facile two-step process consisting of preferential oxidation and leaching was utilized to produce structurally robust nanoporous Ni metal and Y oxides from NiYAl4. The catalyst exhibited an optimal carbon balance (0.96) close to the ideal value of 1.0, indicating the optimized dry reforming pathway. This work proposes a facile route of the structural control of active metal/oxide sites for realizing highly active catalysts with long-term durability.