Ni-based Catalysts Research Articles

Dry Reforming of Methane over Pyrochlore-Type La2Ce2O7-Supported Ni Catalyst: Effect of Particle Size of Support.

The properties of supports (such as oxygen vacancies, oxygen species properties, etc.) significantly impact the anti-carbon ability due to their promotional effect on the activation of CO2 in dry reforming of methane (DRM). Herein, pyrochlore-type La2Ce2O7 compounds prepared using co-precipitation (CP), glycine nitrate combustion (GNC) and sol-gel (S-G) methods, which have highly thermal stability and unique oxygen mobility, are applied as supports to prepare Ni-based catalysts for DRM. The effect of the calcining temperature (500, 600 and 700 °C) on La2Ce2O7(CP) has also been investigated. Based on multi-technique characterizations, it is found that the synthesis method and calcination temperature can influence the particle size of the La2Ce2O7 support. Changes in particle size strongly modulate the pore volume, specific surface area and numbers of surface oxygen vacancies of the La2Ce2O7 support. As a result, the distribution of supported Ni components is affected due to the different metal-support interaction, thereby altering the activity of the catalysts for cracking CH4. Moreover, the supports' abilities to adsorb and activate CO2 are also adjusted accordingly, accelerating the removal of the carbon deposited on the catalysts. Finally, La2Ce2O7(CP 600) with an appropriate particle size exhibits the best catalytic activity and stability in DRM.

Enhanced electrochemical oxidation of 5-hydroxymethylfurfural over tailored nickel nanoparticle assembly

Nickel-based materials are promising electrocatalysts for anodic oxidation of 5-hydroxymethylfurfural (HMF) to value-added 2, 5-furandicarboxylic acid (FDCA). However, their catalytic efficiency is impeded by the sluggish phase transformation of Ni(II) hydroxide to the active Ni(III) oxyhydroxide. Herein, we demonstrate for the first time that the phase transformation kinetics and the HMF oxidation activity of nickel nanoparticles can be modulated by creating self-assemblies with different particle aggregation structures: ordered nanoarrays, disordered nanoarrays, and random aggregates. Notably, the nanoparticle assembly featuring an ordered nanoarray structure exhibits the highest activity, achieving 99.8 % HMF conversion and 99.2 % FDCA yield at 1.36 V. In situ Raman spectroscopy and electrochemical analysis reveal that the ordered nanoarray effectively accelerates the transformation kinetics, attributed to the reduced dehydrogenation barrier of Ni(II) hydroxide as confirmed by density functional theory calculations. This work contributes new insights into the structure-performance relationship of Ni-based catalysts, offering valuable guidance for designing high-performing electrocatalysts.

Enhanced Methane Dry Reforming with Ni/SiO2 Catalysts Featuring Hierarchical External Nanostructures

Global energy demand escalates the interest in effective and durable catalytic systems for the dry reforming of methane (DRM), a process that converts CO2/CH4 into H2/CO syngas. Porous silica-supported nickel (Ni) catalysts are recognized as a promising candidate due to robust DRM activity associated with the confinement of Ni particles in the mesopores that reduces the catalyst deactivation by carbon byproduct deposits and sintering of active Ni sites. However, the small-sized pore configurations in the mesoporous catalysts hinders the fast mass transfer of reactants and products. A unique combination of the hierarchical nanostructure with macro–mesoporous features of the support is adopted to enhance the catalytic performance via the dual effect of the efficient mass transfer and minimized sintering issue. This study delves into the influence of SiO2 geometry and pore structure on the catalytic performance of Ni-based catalysts. Three types of porous silica supports were synthesized through various methods: (a) hydrothermal-assisted sol–gel for dendritic mesoporous silica (DMS), (b) spray-pyrolysis-assisted sol–gel for spray evaporation-induced self-assembly (EISA) silica, and (c) oven-assisted sol–gel for oven EISA silica. Among the prepared catalysts the hierarchical external nanostructured Ni/DMS showed the superior CH4 and CO2 conversion rates (76.6% and 82.1%), even at high space velocities (GHSV = 360 L∙g−1·h−1). The distinctive macro–mesoporous geometry effectively prevents the sintering of Ni particles and promotes the smooth diffusion of the reactants and products, thus improving catalytic stability over extended reaction periods (24 h). This research highlights the significant impact of macro–mesoporosity revealed in DMS support catalysts on the physicochemical properties of Ni/DMS and their crucial role in enhancing DRM reaction efficiency.

Molybdenum-doping promoted surface oxygen vacancy of CeO2 for enhanced low-temperature CO2 methanation over Ni-CeO2 catalysts

It is challenging to improve the low-temperature activity of Ni-based catalyst for the CO2 methanation reaction. In this study, a molybdenum-doped cerium oxide supported Ni catalyst (Ni/MoCe) was constructed, and it showed remarkable CO2 methanation performance at low temperatures (<300 °C). Structural analysis revealed that the incorporation of Mo into the CeO2 lattice could enrich the surface oxygen vacancies, reduce the particle size of Ni species and enhance the metal-support interaction. The Ni/MoCe demonstrated a faster HCOO* pathway for the conversion of CO2 to CH4 compared with Ni/CeO2. Besides, the rich surface oxygen vacancies in Ni/MoCe facilitated the adsorption form of bidentate carbonates and the enhanced Ni-CeO2 interaction reduced the approach resistance of active H species from Ni for subsequent hydrogenation process. This work proves that Mo doping is an effective vacancy engineering strategy to design high-performance heterogeneous catalysts for CO2 hydrogenation.

Thermally stable Ni foam-supported inverse CeAlOx/Ni ensemble as an active structured catalyst for CO2 hydrogenation to methane

Nickel is the most widely used inexpensive active metal center of the heterogeneous catalysts for CO2 hydrogenation to methane. However, Ni-based catalysts suffer from severe deactivation in CO2 methanation reaction due to the irreversible sintering and coke deposition caused by the inevitable localized hotspots generated during the vigorously exothermic reaction. Herein, we demonstrate the inverse CeAlOx/Ni composite constructed on the Ni-foam structure support realizes remarkable CO2 methanation catalytic activity and stability in a wide operation temperature range from 240 to 600 °C. Significantly, CeAlOx/Ni/Ni-foam catalyst maintains its initial activity after seven drastic heating-cooling cycles from RT to 240 to 600 °C. Meanwhile, the structure catalyst also shows water resistance and long-term stability under reaction condition. The promising thermal stability and water-resistance of CeAlOx/Ni/Ni-foam originate from the excellent heat and mass transport efficiency which eliminates local hotspots and the formation of Ni-foam stabilized CeAlOx/Ni inverse composites which effectively anchored the active species and prevents carbon deposition from CH4 decomposition.

Nickel perovskite catalysts for ammonia decomposition: DFT calculations and microreaction kinetics

Combining policy guidance, catalyzing ammonia decomposition to produce hydrogen is a new concept for hydrogen energy supply. Alkaline carriers can effectively improve the ammonia decomposition activity on the catalyst by adjusting the dispersion of nickel (Ni) and controlling the size of Ni. However, the activity of Ni-based perovskite catalysts does not seem to be entirely affected by the above factors. Exploring the mechanism of Ni and perovskite alkaline carrier surfaces through theoretical calculations provides deeper theoretical guidance for ammonia (NH3) decomposition. This study uses periodic density functional theory calculation methods to investigate the reaction paths and energy distribution of monomeric ammonia and dimeric ammonia on a nickel-doped barium zirconate (Ni/BaZrO3) catalyst. Molecular dynamics simulations, Bader charge analysis, and density of states assist in understanding the adsorption states of NH3 and the catalytic decomposition mechanism. The energy barriers for N-H bond breaking and nitrogen generation reactions of Ni clusters loaded on the BaZrO3 surface (Ni4/BaZrO3) were compared and analyzed. The results show that Ni/BaZrO3 is more conducive to ammonia decomposition, with a maximum reaction barrier of 0.90 eV. The catalytic activity of the catalyst under oxygen vacancy conditions was further examined. By comparing the mechanisms of dimeric ammonia decomposition on the clean catalyst surface and the oxygen vacancy catalyst surface, it was found that the presence of oxygen vacancies facilitates ammonia decomposition, but Ni doping provides more effective assistance for N-H bond breaking. The rate constant for ammonia decomposition was calculated using transition state theory. This work not only provides theoretical references for the decomposition mechanism of NH3 in Ni-based perovskite materials but also provides kinetic data for the kinetic modeling of NH3 decomposition.

Enhancing AsH3 Detoxification via Electron-Deficient [NiIII-OH (μ-O)] in a Nickel-Modified NaY Zeolite: A Pathway toward As0 Products.

The transformation of toxic arsine (AsH3) gas into valuable elemental arsenic (As0) from industrial exhaust gases is important for achieving sustainable development goals. Although advanced arsenic removal catalysts can improve the removal efficiency of AsH3, toxic arsenic oxides generated during this process have not received adequate attention. In light of this, a novel approach for obtaining stable As0 products was proposed by performing controlled moderate oxidation. We designed a tailored Ni-based catalyst through an acid etching approach to alter interactions between Ni and NaY. As a result, the 1Ni/NaY-H catalyst yielded an unprecedented proportion of As0 as the major product (65%), which is superior to those of other reported catalysts that only produced arsenic oxides. Density functional theory calculations clarified that Ni species changed the electronic structure of oxygen atoms, and the formed [NiIII-OH (μ-O)] active centers facilitated the adsorption of AsH2*, AsH*, and As* reaction intermediates for As-H bond cleavage, thereby decreasing the direct reactivity of oxygen with the arsenic intermediates. This work presents pioneering insights into inhibiting excessive oxidation during AsH3 removal, demonstrating potential environmental applications for recovery of As0 from toxic AsH3.

Artificial Heterointerfaces with Regulated Charge Distribution of Ni Active Sites for Urea Oxidation Reaction.

In contrast to the thermodynamically unfavorable anodic oxygen evolution reaction, the electrocatalytic urea oxidation reaction (UOR) presents a more favorable thermodynamic potential. However, the practical application of UOR has been hindered by sluggish kinetics. In this study, hierarchical porous nanosheet arrays featuring abundant Ni-WO3 heterointerfaces on nickel foam (Ni-WO3/NF) is introduced as a monolith electrode, demonstrating exceptional activity and stability toward UOR. The Ni-WO3/NF catalyst exhibits unprecedentedly rapid UOR kinetics (200mAcm-2 at 1.384V vs. RHE) and a high turnover frequency (0.456s-1), surpassing most previously reported Ni-based catalysts, with negligible activity decay observed during a durability test lasting 150 h. Ex situ X-ray photoelectron spectroscopy and density functional theory calculations elucidate that the WO3 interface significantly modulates the local charge distribution of Ni species, facilitating the generation of Ni3+ with optimal affinity for interacting with urea molecules and CO2 intermediates at heterointerfaces during UOR. This mechanism accelerates the interfacial electrocatalytic kinetics. Additionally, in situ Fourier transform infrared spectroscopy provides deep insights into the substantial contribution of interfacial Ni-WO3 sites to UOR electrocatalysis, unraveling the underlying molecular-level mechanisms. Finally, the study explores the application of a direct urea fuel cell to inspire future practical implementations.

Improving the anti-coking ability in the Ni-M(M = Ce, Zr, Co)@SiO2 yolk-shell catalysts for dry reforming of methane

Dry methane reforming (DRM) represents a highly promising approach to greenhouse gas conversion (CO2 and CH4) to valuable byproducts. However, severe carbon deposition and catalyst deactivation inhibit large-scale applications. The work designed new catalysts with a yolk-shell structure using the water-in-oil microemulsion method. The catalysts were composed of a yolk-shell structure, with Ni-M as the active point and silica as the shell. The catalytic performance evaluation indicates that the Ni-M @SiO2 catalysts show higher CH4 and CO2 conversion compared with the Ni@SiO2 and conventional catalysts at 750 ℃, suggesting the yolk-shell structure and added M species enhance the DRM activity. The XRD, HRTEM, XPS, BET, H2-TPR, and CO2-TPD analysis confirmed the existence of yolk-shell configuration and evident electronic effect among Ni, M species, and SiO2. The long term measurements indicate that the added M species also bring higher carbon deposition tolerance for DRM, where Ni-Ce@SiO2 and Ni-Zr@SiO2 exhibit good structural and catalytic stability for DRM over 100 h. Through XRD, TEM, and TGA characterizations of the exhausted catalysts, it is determined that the coke deposition resistance of the catalyst is improved as a result of increased oxygen mobility and enhanced Ni dispersion on the catalytic surface, both of which are enhanced by the added Ce species. The structural analysis of the spent catalysts indicates that the tolerance of carbon deposition is improved by the yolk-shell samples. This study can offer valuable insights for the development of Ni-based catalysts with exceptional carbon deposition capability for DRM.

Ni-Based Catalysts for CO2 Methanation: Exploring the Support Role in Structure-Activity Relationships.

The catalytic hydrogenation of CO2 to methane is one of the highly researched areas for the production of chemical fuels. The activity of catalyst is largely affected by support type and metal-support interaction deriving from the special method during catalyst preparation. Hence, we employed a simple solvothermal technique to synthesize Ni-based catalysts with different supports and studied the support role (CeO2, Al2O3, ZrO2, and La2O3) on structure-activity relationships in CO2 methanation. It is found that catalyst morphology can be altered by only changing the support precursors during synthesis, and therefore their catalytic behaviours were significantly affected. The Ni/Al2O3 with a core-shell morphology prepared herein exhibited a higher activity than the catalyst prepared with a common wet impregnation method. To have a comprehensive understanding for structure-activity relationships, advanced characterization (e. g., synchrotron radiation-based XAS and photoionization mass spectrometry) and in-situ diffuse reflectance infrared Fourier transform spectroscopy experiments were conducted. This research opens an avenue to further delve into the role of support on morphologies that can greatly enhance catalytic activity during CO2 methanation.

Hydrogen-donating behavior and hydrogen-shuttling mechanism of liquefaction solvents under Fe- and Ni-based catalysts

The H-donating solvent plays a crucial role in both oil yield and products distribution during direct coal liquefaction. Meanwhile, liquefaction catalyst significantly influences the H-donating behavior of the solvent and the pathways of hydrogen transfer. In view of insufficient understanding on the impact of catalysts on H-donating behavior of solvent and hydrogen transfer pathways in direct liquefaction, in this study, non-H-donating solvents including naphthalene, 1-methylnaphthalene and pyrene (Py) and H-donating solvents including tetralin (THN) and 9,10-dihydroanthracene (DHA) were chosen as the solvents. The Shenhua nano-sized Fe-based and the prepared Ni/Al2O3 catalysts were used to investigate their effect on H-donating behavior of the solvent and H-shuttling mechanism. Results show that liquefaction solvent obviously affects coal conversion and products distribution no matter Fe-based or Ni-based catalyst was used. When non-H-donating solvent is used as liquefaction solvent, coal conversion is lower than that with THN or DHA as solvent. The addition of Py to THN as solvent improves the utilization of effective hydrogen in non-catalytic liquefaction, which is ascribed to hydrogen transfer effect of Py; however, hydrogen transfer mainly occurs through direct combination of gaseous H2 with radicals generated from coal pyrolysis in presence of Fe-based catalyst, with minimal shuttle action of solvent hydrogen. On the contrary, the Ni-based catalyst aids in enhancing the hydrogen shuttle effect of the solvent, and the hydrogen transfer path primarily involves H2 to solvent and then to coal, which is ascribed to good hydrogenation ability of Ni-based catalyst. Under the action of Fe-based catalyst, DHA as liquefaction solvent exhibits lower H-donating capability compared to THN, and approximately 65% of total hydrogen consumption is effectively utilized for coal liquefaction, along with about 35% of total hydrogen consumption for the hydrogenation, ring opening, and side-chain scission reactions of DHA. However, about 96% of total hydrogen consumption is effectively utilized for coal liquefaction when THN used as solvent, indicating that THN as liquefication solvent is more conducive to the transfer of gaseous hydrogen to free radical fragments from coal pyrolysis compared to DHA.

Construction of multi-porous Ni-based monolithic catalyst by combining wood carbon and SBA-15 for strengthening CO2 methanation

Monolithic catalysts meet the needs of practical application compared with powder catalysts. In this work, we constructed a Ni-based monolithic catalyst (Ni/SAB-15/WWC) by in situ growth of rod-like mesoporous SBA-15 in the microchannels of wood carbon. The small Ni-based nanoparticles (∼5.3 nm) were uniformly dispersed into the mesoporous channels via a post-loading method. The monolithic Ni/SAB-15/WWC catalyst with a multilevel porous structure could provide a laminar gas flow on the surface of Ni active sites, increasing the low-temperature activity and high-temperature durability of CO2 methanation. The Ni/SAB-15/WWC with low Ni loading (∼2%) displayed superior CO2 methanation catalytic performance in terms of low-temperature activity and CH4 selectivity compared with the powder Ni/SAB-15 with high Ni loading (∼15 %). The combination of wood carbon and mesoporous materials is an innovative strategy for the design monolithic catalysts with low metal loading and excellent catalytic performance.

Cu Promoted the Dynamic Evolution of Ni-Based Catalysts for Polyethylene Terephthalate Plastic Upcycling.

Upcycling plastic wastes into value-added chemicals is a promising approach to put end-of-life plastic wastes back into their ecocycle. As one of the polyesters that is used daily, polyethylene terephthalate (PET) plastic waste is employed here as the model substrate. Herein, a nickel (Ni)-based catalyst was prepared via electrochemically depositing copper (Cu) species on Ni foam (NiCu/NF). The NiCu/NF formed Cu/CuO and Ni/NiO/Ni(OH)2 core-shell structures before electrolysis and reconstructed into NiOOH and CuOOH/Cu(OH)2 active species during the ethylene glycol (EG) oxidation. After oxidation, the Cu and Ni species evolved into more reduced species. An indirect mechanism was identified as the main EG oxidation (EGOR) mechanism. In EGOR, NiCu60s/NF catalyst exhibited an optimal Faradaic efficiency (FE, 95.8%) and yield rate (0.70 mmol cm-2 h-1) for formate production. Also, over 80% FE of formate was achieved when a commercial PET plastic powder hydrolysate was applied. Furthermore, commercial PET plastic water bottle waste was employed as a substrate for electrocatalytic upcycling, and pure terephthalic acid (TPA) was recovered only after 1 h electrolysis. Lastly, density functional theory (DFT) calculation revealed that the key role of Cu was significantly reducing the Gibbs free-energy barrier (ΔG) of EGOR's rate-determining step (RDS), promoting catalysts' dynamic evolution, and facilitating the C-C bond cleavage.

CrOx modified particles size and electronic density of Ni catalyst on ZSM-23 for enhanced hydroisomerization performance of long-chain n-alkanes

CrOx-doped Ni catalysts with different Ni/Cr mass ratios on ZSM-23 (NimCrn/ZSM-23) were synthesized using a simple initial wet impregnation method. The influence of CrOx on Ni in the NimCrn/ZSM-23 catalysts was investigated by combining XPS, IR-CO, H2-TPR, TEM, and EDX mapping. The obtained results suggested that an intimate contact was formed between Ni and CrOx in the catalysts. The CrOx-modified NiOx species strongly interacted with ZSM-23, facilitating the formation of small sized Ni nanoparticles. Meanwhile, the electronic density around Ni on the catalyst was increased due to the presence of adjacent CrOx. The reaction rate and TOFs over Ni2.0Cr2.0/ZSM-23 (1.13 × 10-2 mol•g-1•h−1 and 6.8 × 10-2 s−1) are much higher than over Ni2.0/ZSM-23 (0.88 × 10-2 mol•g-1•h−1 and 6.2 × 10-2 s−1) in the n-hexadecane hydroisomerization, illustrating the promotion of CrOx in the Ni-based catalyst. The Ni2.0Cr2.0/ZSM-23 catalyst exhibited the highest iso-hexadecanes yield of 82.9 %, as compared to Pt/ZSM-23 catalyst (78.9 %).

Industrial waste-based Ni-catalysts for ammonia decomposition to produce clean hydrogen

The high mineral containing solid waste materials generated during aluminum production currently lacks any practical application. In this work, the potential of solid waste with/without additional nickel loading (10 to 20 wt%) was investigated as an active catalyst for low temperature ammonia decomposition to produce high purity hydrogen. The X-ray diffraction (XRD) analysis of the samples reveals that iron oxide was the primary component of solid waste with the ability to catalyze the ammonia decomposition reaction. The reducibility, metal support interaction and catalytic activity of the solid waste supported Ni-based catalysts were correlated by the reduction kinetics of the catalysts using temperature-programmed reduction (H2-TPR) data and nucleation/nuclei growth models. Based on the statistical indicators, it was concluded that the random nucleation model describes catalyst reduction adequately. The estimated activation energy for the reduction of the solid waste itself was significantly higher (108.5 kJ/mol) than that of solid waste supported catalyst containing 10 wt% Ni (86.6 kJ/mol). The increase in nickel loading also slightly decreased the activation energy of catalyst reduction, indicating an improvement in the reducibility of the nickel-containing catalysts. These reduction behaviors were also reflected in the ammonia decomposition reaction in a flow reactor. The addition of nickel onto the solid waste resulted in the creation of additional active nickel sites. Consequently, the nickel loaded solid waste supported catalysts exhibited significant improvements in ammonia decomposition activity. Among the three solid waste supported Ni-based catalysts, the catalyst containing 15 wt% Ni displayed the highest activity, that also remained unchanged over extended period, indicating the catalyst stability.

Reduced Siderite Ore Combined with Magnesium Oxide as Support Material for Ni-Based Catalysts; An Experimental Study on CO2 Methanation

Ni-based catalysts play a fundamental role in catalytic CO2 methanation. In this study, the possibility of using siderite ore as a catalyst or catalytic support material for nickel-based catalysts was investigated, aiming at the exploitation of an abundant natural resource. The catalytic performance of Ni-based catalysts with reduced siderite ore as a support was evaluated and compared to MgO as a support material. MgO is known as an effective support material, as it provides access to bifunctional catalysts because of its basicity and high CO2 adsorption capacity. It was shown that undoped and Ni-doped reduced siderite ore have comparable catalytic activity for CO2 hydrogenation (20−23%) at 648 K, but show limited selectivity toward methane (&lt;20% for sideritereduced and 60.2% for Ni/sideritereduced). When MgO was added to the support material (Ni/sideritereduced/MgO), both the CO2 conversion and the selectivity toward methane increased significantly. CO2 conversions were close to the thermodynamic equilibrium, and methane selectivities of ≥99% were achieved.

Conversion of Biomass-Derived Tars in a Fluidized Catalytic Post-Gasification Process

The present study deals with the development, characterization, and performance of a Ni-based catalyst over a ceria-doped alumina support as a post-gasification step, in the conversion of biomass-derived tars. The catalysts were prepared using the incipient wetness technique and characterized chemically and physically using NH3-TPD, CO2-TPD, H2-TPR, XRD, Pyridine-FTIR, N2 physisorption, and H2-Pulse Chemisorption. It was observed that the 5 wt% CeO2 reduced the strong and very strong acid sites of the alumina support and helped with the dispersion of nickel. It was noticed that the nickel crystallite sizes and metal dispersion remained unchanged as the nickel loading increased. The performance of the catalysts was studied in a mini-fluidized CREC Riser Simulator at different temperatures and reaction times. The selected tar surrogate was 2-methoxy-4-methylphenol, given its functional group similarities with lignin-derived tars. A H2/CO2 gas blend was used to emulate the syngas at post-gasification conditions. The obtained tar surrogate conversion was higher than 75%, regardless of the reaction conditions. Furthermore, the catalysts used in this research provided an enhancement in the syngas product composition when compared to that observed in the thermal experiments. The presence of hydrocarbons greater than CH4 (C1+) was reduced at 525 °C, from 96 ± 3% with no catalyst, to 85 ± 2% with catalyst and steam, to 68 ± 4% with catalyst and steam-H2/CO2. Thus, the catalyst that we developed promoted tar cracking, tar reforming, and water-gas shift reactions, with a H2/CO ratio higher than 3.8, providing a syngas suitable for alcohol synthesis.

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.

Catalyst Screening and Optimization Condition of Green Solvent for BHD Production using Ni-based Catalysts

The high production costs associated with bio-hydrogenated diesel (BHD) have posed a major challenge. Considering this, the present research focused on the production of green solvents at lower pressures as a potential solution. Specifically, the synthesis of various catalysts, namely Ni/γ-Al2O3, Ni/C, NiMo/γ-Al2O3, NiMo/SiO2TiO2, and NiMo/C, was conducted to facilitate the hydrodeoxygenation reaction of methyl laurate into cyclohexane, leading to conversion into dodecane. The resulting green solvent was analyzed using GC-FID and GC-TCD techniques. Among the five catalysts tested, NiMo/C demonstrated superior performance, achieving a conversion rate of 64.61%, selectivity of 62.46%, and yield of 44.98%. The gas analysis conducted using GC-TCD revealed the production of carbon monoxide, methane, and carbon dioxide, aligning with the dodecane pathway theory. Further analysis of the NiMo/C catalyst was conducted using SEM, BET, and XRD techniques, while the Design of Expert program was used to identify more favorable conditions for dodecane production. Through this optimization process, significant improvements were achieved, resulting in a conversion rate of 98.26%, selectivity of 66.82%, and yield of 65.66% at 320 °C and 28 bar, with a reaction time of 6 h.

Thermochemical conversion of silkworm by-product into syngas

This study explored the valorisation of silkworm by-product, a major by-product of the silk industry (sericulture), which amounts to 16 million tonnes annually. The focus was on transforming waste into energy resources through pyrolysis under CO2 conditions. In one-stage pyrolysis, the evolution of syngas under N2 was found to be comparable to that under CO2. A notable allocation of carbon to biocrude rather than syngas was observed. The two-stage pyrolysis resulted in increased syngas production. However, achieving a homogeneous reaction between CO2 and the volatiles liberated from silkworm byproduct proved challenging. Indeed, the reaction kinetics governing CO2 reactivity was not fast although the temperature windows of the reaction were aligned in the two-stage pyrolysis. To address this issue, pyrolysis was performed using a Ni-based catalyst to expedite the reaction kinetics. Consequently, syngas formation, particularly CO formation, was significantly enhanced under CO2 conditions compared to that under N2 conditions. The syngas yield under CO2 was 36.42 wt% which was 2-fold higher than that of N2. This suggested the potential of CO2 altering the carbon distribution from biocrude to syngas. This strategy would contribute to the establishment of sustainable production of silk by converting sericulture by-product into energy/chemical resources.