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Two sets of Fe-modified Ni/γ-Al 2 O 3 catalysts were prepared and tested in partial oxidation of methane. In one set, Fe was co-impregnated on the surface (NiFe) and in the other set Fe was incorporated in the support bulk (Ni/Fe). The two types showed significantly different coking resistance and performance. While Fe well dispersed in the support bulk significantly enhanced coking resistance, Fe co-impregnated with Ni on the surface enhanced the rate of coke deposition on the catalysts' surfaces. The impact of Fe in the Ni/Fe catalysts is referred to its partially reduced ions (Fe2+) in redox reactions, and to the Ni-support strong interaction retarding the coke formation pathways. On the contrary, carbon formation on the NiFe catalysts is referred to the formation of Ni–Fe alloy particles which may block Ni active sites and can promote cracking of methane as well as CO molecules resulting in higher rates of coking. [Display omitted] • NiFe/γ-Al 2 O 3 and Ni/γ-Al 2 O 3 –Fe were compared in partial oxidation of methane. • Catalysts modified with Fe in the support showed superior coking resistance. • Catalysts with Fe co-impregnated on the surface showed considerable coking. • Coking resistance was referred to redox impact of Fe2+ and Ni-support interactions. • Formation of NiFe alloy and FeAl 2 O 4 in the support enhanced coke formation. [ABSTRACT FROM AUTHOR]

The purpose of this study is to demonstrate the potential of ceramic tile dust (CTD)-derived ZSM-5 zeolite (CZ) and its monodispersed composite with metal oxides (MgO and Fe2O3) in the catalytic pyrolysis of hyphaene thebaica shell (HTS). The HTS was pyrolysed in a Fixed-bed reactor at 400–600 °C, and 100–300 mL/min N2 flowrate. The maximum bio-oil production of 32 % was obtained at 500 °C and 150 mL/min N2 flowrate, with bio-oils containing 50 % acid and octadecenoic acids, as well as esters, phenols, aldehydes, ketones, ethers, aromatics, and hydrocarbons. A carboxymethyl cellulose templating agent was employed for the mesoporous zeolite synthesis from CTD. This resulted in the mesoporous zeolite with a predominant ZSM-5 crystal phase, exhibiting pore diameters ranging from 1.8-6 nm, 229 m2/g surface area and 1145 μmol/g total acidity. The catalytic pyrolysis of HTS was conducted using the ZSM-5 zeolite (CZ) and metal-oxide (MgO, Fe2O3, and Fe2O3/FeO) modified CZ, as monodispersed composite catalysts. Under best thermal pyrolysis conditions, CZ-Fe2O3, CZ-MgO, and CZ-Fe2O3/MgO demonstrated 22–23 % bio-oil yields. Notably, the CZ-Fe2O3/MgO catalyst exhibited the highest hydrocarbon yield at 16 %, while the CZ-MgO favoured the production of phenolics, esters, and alcohols. CZ-MgO also displayed the highest coking level at 7.5 %, indicating faster deactivation than the other catalysts. The synthesised catalysts exhibited remarkable catalytic activity, resulting in a notable improvement in the quality of bio-oils obtained from the intermediate pyrolysis of hyphaene thebaica shells in a fixed-bed reactor.

Thermal conversion of vacuum tower bottoms (VTB) and its narrow‐cut distillation fractions were studied at 530°C between 0.1 and 2 MPa pressure to assess the effect of the reaction pressure on coking. Coke yield in the VTB conversion increased with pressure, which was found to be mostly due to the enhanced coking of the 700°C+ narrow cut. The microcarbon residue in the liquid remained unaffected. The yield of products with a boiling point below 510°C, including distillate and by‐product lights, decreased with the pressure increase. The trend was a cumulative effect of the increased yields from the VTB cuts boiling below 635°C and the decreased yields from the heavier cuts. Admixing different VTB cuts into the VTB feed resulted in the weighted average changes with no synergistic or antagonistic effects. [ABSTRACT FROM AUTHOR]

Abstract Paramos, unique and biodiverse ecosystems found solely in the high mountain regions of the tropics, are under threat. Despite their crucial role as primary water sources and significant carbon repositories in Colombia, they are deteriorating rapidly and garner less attention than other vulnerable ecosystems like the Amazon rainforest. Their fertile soil and unique climate make them prime locations for agriculture and cattle grazing, often coinciding with economically critical deposits such as coal which has led to a steady decline in paramo area. Anthropic impact was evaluated using multispectral images from Landsat and Sentinel over 37 years, on the Guerrero and Rabanal paramos in central Colombia which have experienced rapid expansion of mining and agriculture. Our analysis revealed that since 1984, the Rabanal and Guerrero paramos have lost 47.96% and 59.96% of their native vegetation respectively, replaced primarily by crops, pastures, and planted forests. We detected alterations in the spectral signatures of native vegetation near coal coking ovens, indicating a deterioration of paramo health and potential impact on ecosystem services. Consequently, human activity is reducing the extent of paramos and their efficiency as water sources and carbon sinks, potentially leading to severe regional and even global consequences.

Paramos, unique and biodiverse ecosystems found solely in the high mountain regions of the tropics, are under threat. Despite their crucial role as primary water sources and significant carbon repositories in Colombia, they are deteriorating rapidly and garner less attention than other vulnerable ecosystems like the Amazon rainforest. Their fertile soil and unique climate make them prime locations for agriculture and cattle grazing, often coinciding with economically critical deposits such as coal which has led to a steady decline in paramo area. Anthropic impact was evaluated using multispectral images from Landsat and Sentinel over 37 years, on the Guerrero and Rabanal paramos in central Colombia which have experienced rapid expansion of mining and agriculture. Our analysis revealed that since 1984, the Rabanal and Guerrero paramos have lost 47.96% and 59.96% of their native vegetation respectively, replaced primarily by crops, pastures, and planted forests. We detected alterations in the spectral signatures of native vegetation near coal coking ovens, indicating a deterioration of paramo health and potential impact on ecosystem services. Consequently, human activity is reducing the extent of paramos and their efficiency as water sources and carbon sinks, potentially leading to severe regional and even global consequences. [ABSTRACT FROM AUTHOR]

The task of the study was to test new demulsifying compositions for high pyrolysis coal tars originally intended for separating emulsions based on heavy petroleum oils. Coal tars with a specific gravity of 1.243–1.261 were investigated and light coal tar with a specific gravity of 1.185 was used for comparison. Demulsifying compositions for heavy media were prepared on the basis of Dissolvan (Clariant) reagents, "PM" demulsifier was used as a main indicative reagent for breaking of light coal tar emulsions. To determine the efficiency of dewatering a "bottle test" was applied, Fourier transform infrared spectroscopy analysis of the distillate residues was performed to determine the functional group of potential stabilizers. The composition of the mineralized and dispersed solid stabilizers was determined by X-ray fluorescence (XRF) spectrometry. The results showed that for the heavy coal tar emulsions, some compositions based on oxalkylated resin showed high activity and separated up to 17–19% of water, in contrast to the indicative demulsifier 0–3%. An attempt has been made to investigate the mineral composition of emulsion stabilizers transferred into the water part and remaining in the coal tar (sludge). The results of XRF spectrometry suggested that Zn-pyridine compounds are the most likely hydrophile stabilizers of heavy coal tar emulsions. [ABSTRACT FROM AUTHOR]

Metal/biochar catalyst features with the advantages for easy recovery of chemical energy of biochar carrier and metal species via simply combustion. Another unique feature of biochar carrier is intrinsic inorganic species, which might also interact with metal species in resulting catalyst. This was investigated herein by synthesis of the Ni/biochar with rice husk-derived biochar carrier pretreated with NaOH for removal of SiO 2 and evaluation of the resulting catalysts in steam reforming of glycerol. The solid phase reactions between NaOH and biochar (mass ratio: 2) plus subsequent washing removed 94.6% of ash (mainly SiO 2). This formed Ni/biochar of fragmented surface with specific surface area increasing from 207.8 to 457.4 m2g-1 and simultaneously increasing mesopore percentage from 15.5% to 24.0%. NaOH treatment also effectively removed significant portion of both Lewis and Brønsted acidic sites but created abundant alkaline sites. These drastically enhanced nickel dispersion and activity for steam reforming. In-situ IR characterization suggested enhanced adsorption/activation of CO 2 and H 2 O over Ni/biochar treated with NaOH (Ni/biochar-NaOH), which mitigated accumulation of coke precursors bearing C O or C C via accelerated gasification reactions. This led to the reduced amount of coke (mass ratio to catalyst) from 193.4% to 94.7% over Ni/biochar treated with 2-fold of NaOH or to 111.3% over Ni/biochar treated with 1-fold of NaOH. The coke formed was mainly catalytic type in form of carbon nanotube over Ni/biochar-NaOH. The superior resistivity to coking originated from developed pores, enhanced Ni dispersion and abundant alkaline sites from the NaOH treatment. [Display omitted] • NaOH treatment removes SiO 2 in rice husk-biochar and creates developed pores. • NaOH treatment brings abundant alkaline sites while removes Lewis and Brønsted acidic sites. • NaOH treatment enhances Ni dispersion in Ni/biochar and activity for reforming. • NaOH treatment enhances activation of CO 2 /H 2 O, promoting gasification of coke precursors bearing C O/C C. • NaOH pretreatment effectively increases resistivity of Ni/biochar to coking. [ABSTRACT FROM AUTHOR]

In oil refining, it is a priority to intensify coking. The coking of heavy petroleum residues permits the production of coke with different types of microstructure. That is of great industrial importance. The quality and yield of petroleum coke depend on the composition of the raw materials employed and on the coking conditions. This article describes the functional structure of software that employs statistical analysis of experimental data in the synthesis of polynomial regression models capable of predicting how the yield and microstructure of petroleum coke depend on the coking conditions and the properties of the initial hydrocarbons. The models are verified by using the Fisher test for statistical analysis of calculation results and data derived from a series of experiments conducted by means of the pilot coking plant in the Department of Petrochemical and Coal-Chemical Production Technology at Saint Petersburg State Institute of Technology. Testing at the Institute's world-class laboratory has confirmed the performance of the software and its suitability for research at oil refineries with coking systems. [ABSTRACT FROM AUTHOR]

Various types of raw materials, including plant precursors, coal raw materials, solid fuel combustion residues, coal mining waste, coke fines, and others, are used for the production of porous carbon materials. One important type of porous carbon materials is microporous sorbents, which have a high volume of micropores. These pores provide carbon materials with the ability to effectively adsorb low-molecular-weight gases and possess molecular sieving properties, allowing their use in gas separation processes. The main method of increasing the porosity of sorbents and reducing pore sizes is the activation of sorbents at high temperatures using inert gases. This process increases the activity, capacity, and specific surface area of sorbents. The specific surface area of solid bodies plays a key role in their sorption properties at low and medium pressures. The use of activating agents, such as water vapor, in the thermal treatment processes of carbonaceous materials is a promising method for obtaining porous carbon materials. [ABSTRACT FROM AUTHOR]

The present work is focused on nickel catalysts supported on La2O3-CeO2 binary oxides without and with the addition of Cu to the active component for the dry reforming of methane (DRM). The catalysts are characterized using XRD, XRF, TPD-CO2, TPR-H2, and low-temperature N2 adsorption–desorption methods. This work shows the effect of different La:Ce ratios (1:1 and 9:1) and the Cu addition on the structural, acid base, and catalytic properties of Ni-containing systems. The binary LaCeOx oxide at a ratio of La:Ce = 1:1 is characterized by the formation of a solid solution with a fluorite structure, which is preserved upon the introduction of mono- or bimetallic particles. At La:Ce = 9:1, La2O3 segregation from the solid solution structure is observed, and the La excess determines the nature of the precursor of the active component, i.e., lanthanum nickelate. The catalysts based on LaCeOx (1:1) are prone to carbonization during 6 h spent on-stream with the formation of carbon nanotubes. The Cu addition facilitates the reduction of the Cu-Ni catalyst carbonization and increases the number of structural defects in the carbon deposition products. The lanthanum-enriched LaCeOx (9:1) support prevents the accumulation of carbon deposition products on the surface of CuNi/La2O3-CeO2 9:1, providing high DRM activity and an H2/CO ratio of 0.9. [ABSTRACT FROM AUTHOR]

Hydrogen production from natural gas or biogas, at different purity levels, has emerged as an important technology with continuous development and improvement in order to stand for sustainable and clean energy. Regarding biogas, which can be obtained from multiple sources, hydrogen production through the steam reforming of methane is one of the most important methods for its energy use. In that sense, the role of catalysts to make the process more efficient is crucial, normally contributing to a higher hydrogen yield under milder reaction conditions in the final product. The aim of this review is to cover the main points related to these catalysts, as every aspect counts and has an influence on the use of these catalysts during this specific process (from the feedstocks used for biogas production or the biodigestion process to the purification of the hydrogen produced). Thus, a thorough review of hydrogen production through biogas steam reforming was carried out, with a special emphasis on the influence of different variables on its catalytic performance. Also, the most common catalysts used in this process, as well as the main deactivation mechanisms and their possible solutions are included, supported by the most recent studies about these subjects. [ABSTRACT FROM AUTHOR]

Three γ-Al2O3 supports were prepared by hydrothermal method, and PtSn/Al2O3 catalysts were prepared by sequential impregnation for propane dehydrogenation. The catalyst was characterized by TEM, PXRD, H2-TPR, and other characterization methods. The effects of different morphologies of PtSn/Al2O3 catalysts on the dehydrogenation performance and coking of propane were investigated. The results show that the exposed crystal planes of three morphologies of Al2O3 support are different, which makes the Lewis acid content on the support surface and the interaction of active metals on the support different, thus affecting the catalytic performance of the catalyst and coking carbon. Different morphologies of γ-Al2O3 expose different crystal planes, change the Lewis acid content on the surface of the support, and regulate the interaction between active metals and support, thus affecting propane dehydrogenation performance and catalyst coking. [ABSTRACT FROM AUTHOR]

Purposes Methane dehydroaromatization (MDA) is a frontier topic in the field of natural gas chemical industry. Methods Mo/commercial-HZSM-5, Mo/nano-HZSM-5, and Mo/hollow capsule HZSM-5 were synthesized by using a conventional wet impregnation strategy. The samples were characterized by ICP, XRD, BET, SEM, TEM, NH3-TPD, and XPS, and tested in MDA reaction. The properties of carbonaceous species were measured by TG and TPO techniques. The carbon cycle path was investigated through periodic 12CH4/13CH4 isotope switch pulse experiment over Mo/hollow capsule HZSM-5 catalyst during MDA reaction. Findings The active carbonaceous species located inside the pores could take part in the formation of benzene. Among these three Mo-based catalysts, the Mo/hollow capsule HZSM-5 showed higher CH4 conversion and aromatic yield, as well as superior catalytic lifespan. Compared to Mo/nano-HZSM-5 in zeolite particle size and acidity, Mo/hollow capsule HZSM-5 with lower deactivation rate is attributed enhanced gas molecules diffusion in its hollow capsule structure.

This comprehensive review explores recent catalyst advancements for the hydrodeoxygenation (HDO) of aromatic oxygenates derived from lignin, with a specific focus on the selective production of valuable aromatics under moderate reaction conditions. It addresses critical challenges in bio-crude oil upgrading, encompassing issues related to catalyst deactivation from coking, methods to mitigate deactivation, and techniques for catalyst regeneration. The study investigates various oxygenates found in bio-crude oil, such as phenol, guaiacol, anisole, and catechol, elucidating their conversion pathways during HDO. The review emphasizes the paramount importance of selectively generating arenes by directly cleaving C–O bonds while avoiding unwanted ring hydrogenation pathways. A comparative analysis of different bio-crude oil upgrading processes underscores the need to enhance biofuel quality for practical applications. Additionally, the review focuses on catalyst design for HDO. It compares six major catalyst categories, including metal sulfides, transition metals, metal phosphides, nitrides, carbides, and oxides, to provide insights for efficient bio-crude oil upgrading toward sustainable and eco-friendly energy alternatives. [ABSTRACT FROM AUTHOR]

Coking is still a major cause of catalyst deactivation in catalytic methane reforming processes. In this work, doping the support of Ni/γ-Al 2 O 3 catalysts with iron to provide redox functionality was found to significantly enhance coking resistance in methane partial oxidation. Catalysts with well-dispersed Fe3+ in the support, with Fe mass% in the range of 1.1–15.2 were prepared and tested in reactions at 700 °C. The catalyst with 3.2% Fe in the support showed negligible crystalline carbon at a coking rate of 9.0 × 10−6 g c g−1 catalyst h−1 compared with its Fe-free counterpart that showed a coking rate of 7.7 × 10−4 g c g−1 catalyst h−1. On the other hand, ≥10% Fe resulted in the formation of FeAl 2 O 4 and Fe0 that promoted considerable coking. The unique influence of iron was referred to the role of the dispersed Fe2+, which is dominant upon reduction, in promoting a redox cycle that allow the oxidation and removal of carbon. [Display omitted] • Fe molar concentrations up to 5% gave well-dispersed Fe2+ in reduced alumina. • Molar concentrations of Fe ≤ 5% in the support showed significant coking resistance. • High Fe contents resulted in FeAl 2 O 4 and Fe0 that considerably enhanced coking. • Redox functionality of Fe2+ in the support promoted carbon oxidation and removal. [ABSTRACT FROM AUTHOR]

Fuel flexibility is one of the significant advantages of solid oxide fuel cells (SOFCs). The utilization of methane in SOFCs can not only reduce fuel costs, but also greatly expand its application scenarios, which is of great significance to the commercial development of SOFCs. However, when methane is directly used, Ni-based cermet anode suffers from coking, which seriously affects the durability of the cell. To alleviate the coking issue, a reforming layer outside the Ni-based anode-supporter was proposed in this study, and Ba 0.9 (Zr 0.8 Y 0.2) 1- x Ni x O 3-δ (BZYNi x , x = 0.05, 0.1, 0.15 and 0.2) was used as reforming layer material. Among BZYNi x catalysts, BZYNi 0.2 exhibited excellent catalytic activity toward dry reforming of methane, and methane conversion was as high as 85% at 750 °C. The excellent catalytic durability and coking-resistance of BZYNi 0.2 were also confirmed. When BZYNi 0.2 reforming layer was applied, the single cell fueled with CH 4 –CO 2 fuel showed significantly improved electrochemical performance, durability and coking-resistance. The utilization of BZYNi 0.2 reforming layer provides guidance for solving the coking issue of SOFC cermet anodes when fueled with hydrocarbon. • DRM catalytic activities of BZYNi x with different Ni doping content was explored. • A Ba 0.9 (Zr 0.8 Y 0.2) 0.8 Ni 0.2 O 6-δ reforming layer was added outside the anode support. • Enhanced performance and durability of RSC were observed when fueled with CH 4 –CO 2. [ABSTRACT FROM AUTHOR]

In coal coking, volatile products are liberated. As a result, deposits of pyrocarbon (graphite) are formed on the walls and roof of the coke ovens. Those deposits may obstruct the extraction of coke cake. By identifying the parameters with the greatest effect on the formation of pyrocarbon, its growth in the coke ovens may be more accurately monitored, and hence the coke plant's stock of coke ovens may be better maintained. The influence of the following factors on the rate of pyrocarbon formation is investigated: the metamorphic development of the coal; its moisture content; and its granulometric composition. [ABSTRACT FROM AUTHOR]

The integrated carbon capture and conversion (ICCC) is a promising catalytic process to produce syngas from CO2 and CH4 via a combined separation and reactor unit. Besides, its performance can fluctuate from the inconsistent feed ratio resulting from the flue gas unit. Herein, the Ratings concept based on density functional theory (DFT) is applied to overcome these problems in a two‐step protocol: (i) catalyst identification, which designates the catalyst characteristics and predicts performance based on reactivity (RT−R) and stability (RT−S) Ratings calculated based on activation energies obtained either from experiments or DFT, and (ii) catalyst optimization that optimized a catalyst's performance via the determination of new operating condition accounted for its deactivation over time. Moreover, temperature and feed ratio sensitivity were investigated, revealing that most catalysts are more sensitive to temperature change than the feed ratio. [ABSTRACT FROM AUTHOR]

Ethylene is a key molecule in the chemical industry and it can be obtained through the catalytic dehydrogenation of ethane. Pt‐based catalysts show high performance toward alkane dehydrogenation, but suffer from coke formation and sintering that deactivate the catalyst. Ge was recently discovered to be a promising alloying element that suppresses deactivation of Pt while preserving its catalytic activity toward alkane dehydrogenation. This work explores the effect of the Ge content in supported PtGe cluster alloys, on the activity toward ethane dehydrogenation, selectivity against deeper dehydrogenation and coking, and sintering resistance. The model proposed herein is a tetrameric Pt cluster supported on magnesia, with varying amounts of added Ge. The phase diagram for these clusters was computed using global optimization at the density functional theory level, and under the paradigm of a statistical ensemble of many states populated by clusters at catalytic temperatures. The phase diagram shows that various Ge contents should be synthetically accessible, with Pt4Ge/MgO and Pt4Ge4/MgO being the most likely phases. The subsequent adsorption and mechanistic studies show that the clusters with the 1 : 4 Ge to Pt ratio (Pt4Ge/MgO) feature the largest resistance to sintering and best selectivity in the ethane dehydrogenation toward ethylene. Clusters without Ge are too active and easily coke, whereas clusters with higher Ge content start losing the catalytic activity toward ethane dehydrogenation. Thus, Ge concentration is a lever of control of Pt cluster stability and selectivity, and of cluster catalyst design. The effect of the Ge concentration on the cluster properties is explained on the basis of the electronic structure. [ABSTRACT FROM AUTHOR]

Nickel-based catalysts used for dry reforming of methane (DRM) suffer from coking and sintering, which hinders the broad application of the process in the industry. Thermogravimetric analysis was employed to investigate coking on a commercial nickel catalyst with an anti-coking additive (CaO). It was found that the catalyst sintered at temperatures between 850 and 900 °C, which resulted in permanent catalyst deactivation. For the tested Ni/CaO–Al 2 O 3 catalyst, the coking and carbon gasification rates are equal at the temperatures of 796–860 °C, depending on the heating rate (5–20 K/min). Significant differences in the temperatures related to the maxima on TG curves for various heating rates follow from DRM kinetics. This work reveals that the coking rate is lower at higher temperatures. After 50 min, the weight gains amount to about 20% and 40% at 800 °C and 600 °C, respectively. Lower sample weight gains were observed at higher temperatures for a methane decomposition reaction over the Ni/CaO catalyst, unlike for the second tested catalyst – activated carbon. For the nickel catalyst, the reaction order for methane decomposition is 0.6 in the temperature range 640–800 °C, while the sign of the activation energy changes at 700 °C. The elaborated kinetic equation predicts the initial CH 4 decomposition rate with 15% accuracy. [Display omitted] • Thermogravimetric analysis of dry reforming of CH 4 on a commercial Ni/CaO catalyst. • The higher the temperature, the lower the coking rate on the Ni/CaO catalyst. • Reaction order for CH 4 decomposition on the Ni/CaO catalyst is 0.6. • The sign of the activation energy for CH 4 decomposition reaction changes at 700 °C. • Elaborated kinetic equation predicts CH 4 decomposition rate with 15% accuracy. [ABSTRACT FROM AUTHOR]

[Display omitted] • An impregnation-complexation method was proposed to selectively control the Ni species. • A systematic identification of dehydrogenation active sites was established based on in situ FTIR experiments. • NiO x /Al 2 O 3 catalysts were developed with high propylene selectivity and low coke yield. Propane dehydrogenation (PDH) is a vital petrochemical process. As an alternative to Pt and Cr-based catalysts, Ni-based catalysts used in PDH, however, exhibit low propylene selectivity with severe coking. This work aims to understand the role of different Ni species in PDH and achieve high propylene selectivity by inhibiting coking. Specifically, we obtained NiO x /Al 2 O 3 catalysts with solely tetrahedrally coordinated Ni2+ (NiIV) by selectively removing microcrystalline NiO x using the impregnation-complexation strategy. The Niσ+ species derived from NiIV exhibited high propylene selectivity (∼88 %) and low coke yield (2.26 %) in PDH. In contrast, reducing microcrystalline NiO x to Ni0 resulted in high methane selectivity and high coke yield (14.90 %). Theoretical calculations and experimental results indicate that this difference is attributed to the faster propylene desorption from Niσ+ as compared to that from Ni0. Therefore, catalysts with well-confined Niσ+ are selective in PDH. This study offers a rational strategy for designing Ni-based PDH catalysts. [ABSTRACT FROM AUTHOR]

Liquid metals are largely unexplored as catalytic media for biomass conversion. Unlike conventional solid-state catalysts which are prone to deactivation, liquid metals, i.e., low-melting metals operated above their melting point, can show resilience against coking, high thermal conductivity, and enhanced liquid-solid contact between catalyst and biomass feedstocks. This promise motivated the present investigation of liquid metals as catalysts for cellulose pyrolysis. Bismuth, tin, and indium were selected as liquid metal candidates, and their impact on cellulose devolatilization kinetics is studied via thermogravimetric analysis. The results indicate that all three metals show catalytic activity, with bismuth catalyzing volatiles formation, while indium and tin enhance char formation. Quantitative analysis of liquid product reveals that bismuth is selective to dehydration and functional rearrangement reactions, leading to anhydro sugars and functionalized furans formation. In contrast, indium and tin are selective towards dehydration, fragmentation reactions, and Diels Alder chemistry, leading to formation of C2-C4 fragments and aromatic compounds, as further confirmed via infrared spectroscopic analysis of the obtained chars. Finally, the Sn and Bi liquid metals' stability against deactivation via coking is examined against conventional solid-state zeolite catalyst through multiple cellulose pyrolysis runs in the thermogravimetric analyzer (TGA) with the same batch of catalyst. While ZSM-5 zeolite catalyst's activity and selectivity declined and approached non-catalytic sand results (both the TGA curve and the liquid product distribution) within the first few runs, both Sn and Bi fairly maintained their robustness against coking for the conducted durability runs. Overall, the results show significant promise for this new class of catalysts for biomass pyrolysis. [Display omitted] • Low-melting liquid metals catalytic activity for cellulose pyrolysis was explored. • Bismuth is selective towards dehydration and isomerization reactions. • Tin and indium catalyze reactions that mainly yield in char. • Tin and indium are selective towards C2-C4 fragments and aromatic alcohols. • Unlike solid catalysts, liquid metals show robustness against coking deactivation. [ABSTRACT FROM AUTHOR]

• TGA and GC enable complementary studies of catalytic decomposition of CH 4 (CDM). • Thermal (non-catalytic) decomposition of CH 4 presents a significant source of H 2. • Reaction order with respect to CH 4 is 0.6 for CDM on the investigated Fe/C catalyst. • Activation energy is approximately 71 kJ/mol for CDM on the investigated catalyst. • Repeated regeneration of the Fe/C catalyst with CO 2 does not cause its deactivation. Methane pyrolysis (MP) is one of enabling technologies in the economy transition from fossil to renewable fuels. Although the technology has its undoubted advantages, the cost of producing hydrogen with MP is still higher than that using Steam Methane Reforming (SMR). Remote and contactless catalyst heating by microwaves can significantly intensify methane pyrolysis and reduce these costs. One of the catalysts that can be utilized in the microwave-assisted MP is the Fe/C catalyst. The current work presents a reference study of the MP kinetics on the dedicated Fe/C catalyst under conventional (non-microwave) heating. The kinetic data determined in this work are necessary for appropriate modelling and design of the microwave-assisted MP reactor. Experiments were carried out using thermogravimetric analysis coupled with gas chromatography. The reaction order with respect to methane and the activation energy were found to be 0.6, and 71 kJ/mol, respectively. The effects of CO 2 concentration and temperature on the regeneration of the catalyst were also demonstrated. [Display omitted] [ABSTRACT FROM AUTHOR]

This comprehensive review explores recent catalyst advancements for the hydrodeoxygenation (HDO) of aromatic oxygenates derived from lignin, with a specific focus on the selective production of valuable aromatics under moderate reaction conditions. It addresses critical challenges in bio-crude oil upgrading, encompassing issues related to catalyst deactivation from coking, methods to mitigate deactivation, and techniques for catalyst regeneration. The study investigates various oxygenates found in bio-crude oil, such as phenol, guaiacol, anisole, and catechol, elucidating their conversion pathways during HDO. The review emphasizes the paramount importance of selectively generating arenes by directly cleaving C–O bonds while avoiding unwanted ring hydrogenation pathways. A comparative analysis of different bio-crude oil upgrading processes underscores the need to enhance biofuel quality for practical applications. Additionally, the review focuses on catalyst design for HDO. It compares six major catalyst categories, including metal sulfides, transition metals, metal phosphides, nitrides, carbides, and oxides, to provide insights for efficient bio-crude oil upgrading toward sustainable and eco-friendly energy alternatives.

The switch from a carbon-based to a hydrogen-based economy requires environmentally friendly methods for hydrogen production. CO2-reforming of methane promises to be a greener alternative to steam-methane reforming, which accounts for the majority of hydrogen production today. For this dry process to become industrially competitive, challenges such as catalyst deactivation and degradation through coke formation must be better understood and ultimately overcome. While bulk characterisation methods provide a wealth of useful information about the carbon formed during coking, spatially resolved techniques are required to understand the type and extent of degradation of supported catalyst particles themselves under coking conditions. Here, lab-based X-ray nano-computed tomography, in conjunction with a range of complementary techniques, is utilised to understand the effects of the nickel-to-cobalt ratio on the degradation of individual supported catalyst particles. Findings suggest that a bimetallic system greatly outperforms monometallic catalysts, with the ratio between nickel and cobalt having a significant impact on the type and quantity of the carbon formed and on the extent of supported catalyst breakdown.

Surface carbon deposits deactivate Ni and Co catalysts in reactions involving hydrocarbons and COx. Electronic properties, adsorption energies of H, C, and CHx species, and the energetics of the hydrogenation of surface C atom to methane are studied for (100) and (111) surfaces of monometallic Ni and Co, and bimetallic NiCo. The bimetallic catalyst exhibits a Co→Ni electron donation and a concomitant increase in the magnetization of Co atoms. The CHx species resulting from sequential hydrogenation are more stable on Co than on Ni atoms of the NiCo surfaces due to more favorable (C-H)–Co agostic interactions. These interactions and differences between Co and Ni sites are more significant for (111) than for (100) bimetallic surfaces. On (111) surfaces, CH is the most stable species, and the first hydrogenation of C atom exhibits the highest barrier, followed by the CH3 hydrogenation steps. In contrast, on (100) surfaces, surface C atom is the most stable species and CH2 or *CH3 hydrogenations exhibit the highest barriers. The Gibbs free energy profiles suggest that C removal on (111) surfaces is thermodynamically favorable and exhibits a lower barrier than on the (100) surfaces. Thus, the (100) surfaces, especially Ni(100), are more prone to C poisoning. The NiCo(100) surfaces exhibit weaker binding of C and CHx species than Ni(100) and Co(100), which improves C poisoning resistance and lowers hydrogenation barriers. These results show that the electronic effects of alloying Ni and Co strongly depend on the local site composition and geometry. [ABSTRACT FROM AUTHOR]

The role of Cu:Co composition in bi‐metallic Cu‐Co/ZnAl2O4 catalysts on higher alcohol synthesis (HAS) was investigated at H2:CO = 4. The addition of Cu strongly facilitated Co reduction upon catalyst activation and suppressed coke deposition during HAS. Formation of predominantly hydrocarbons and higher alcohols was observed on the bi‐metallic catalysts. Co/ZnAl2O4 produced mainly CH4 and Cu/ZnAl2O4 mainly CH3OH, while at Cu:Co = 0.6 the best ethanol selectivity of 4.5 % was reached. The microstructure of the spent catalysts confirmed a close interaction of Cu and Co. [ABSTRACT FROM AUTHOR]

A method is proposed for producing coke from distilled coal tar fractions. The influence of heat treatment of the tar fractions on the coke yield is investigated. The physicochemical characteristics of the coke produced from the tar fraction boiling above 280°C are investigated. [ABSTRACT FROM AUTHOR]

Summary: The thermal cracking characteristic of an in‐house prepared plant‐derived hydrogenated carene (H‐Carene) fuel is examined above its critical temperature and pressure. The experiments were performed for a wide range of temperatures between 450°C and 650°C at 40 bar pressure in a tubular flow reactor. At 650°C and 40 bar pressure, the conversion of the H‐Carene fuel is about 40%, and the estimated value of chemical heat sink capacity is 488 kJ/kg of fuel. The aptness of triethylamine (TEA) as an initiator to improve the heat sink capacity of the H‐Carene fuel is also examined. The investigation showed that the initiator improved the fuel conversion and endothermicity. The endothermic heat sink capacity of the H‐Carene increased by about 28% at 650°C with 5% (by weight) of TEA. It is noted that the sensitivity of temperature on the coke formation rate is higher than the initiator sensitivity for a similar range of the conversion change. The thermal cracking of H‐Carene follows a first‐order kinetic model, and the estimated value of the apparent activation energy of the H‐Carene cracking reaction is about 95 kJ/mol. The work shows that the heat sink capability of the plant‐derived H‐Carene fuel is comparable with JP‐7, a petroleum‐derived fuel. Novelty Statement: The manuscript presented the cracking characteristics of hydrogenated carene under supercritical conditions emphasizing various features like detailed characterization, feed conversion, product distribution, cooling capacities, coke deposition rate, cracking kinetics, and so on. It also highlighted the suitability of an amine‐based initiator to enhance the endothermicity of the fuel. The study is unique and not found in any article which addressed the above aspects altogether. [ABSTRACT FROM AUTHOR]

The VO X /Al 2 O 3 is known as an active catalyst in the propane dehydrogenation, however, with poor stability due to the severe coking problem. In this study, the VO X /Al 2 O 3 catalyst was modified by boric acid, and the catalyst exhibited significantly improved stability and less coke deposition than the unmodified counterpart. The experimental results and theoretical modeling (DFT) suggested that the boron decreased the polymerization degree of VO X species, generated a high proportion of isolated vanadium species that reduced the initial activity but enhanced the stability of VO X /Al 2 O 3 catalyst. Boron interacted with Al and V forming B-O-Al and B-O-V bonds, which significantly reduced the amounts of both Brønsted and Lewis acid sites, alleviating the coke deposition rate on the catalyst surface. The boron on VO X /Al 2 O 3 promoted the desorption of propylene that inhibited further cracking and its polymerization, thus improving the propylene selectivity and catalyst stability. [Display omitted] • Boric acid modification improves the stability of the VO X / Al 2 O 3 catalyst. • Boron reduces the VO X polymerization degree and produces isolated vanadium sites. • Boron reduces the number of Brønsted and Lewis acid sites. • Boron promotes the propylene desorption, inhibiting polymerization and cracking. [ABSTRACT FROM AUTHOR]

The characteristics of synthetic and industrial coal-tar pitch samples are investigated. The characteristics of the corresponding pitch cokes are compared. Three materials are considered: synthetic low-temperature pitch based on coal-tar distillate; and medium and high-temperature industrial coal-tar pitches from different Russian producers. The influence of the pitch composition on the properties of the pitch coke is determined. [ABSTRACT FROM AUTHOR]

The change in composition of coke oven gas on removing hydrogen is calculated. The influence of this process on the combustion products is determined. The variation in concentration of the coke oven gas's components as hydrogen is removed is studied. The influence of the hydrogen content on the calorific value of coke oven gas and hence on its consumption in coke production and on the toxic emissions to the atmosphere is shown. [ABSTRACT FROM AUTHOR]

Ni is regarded as active site for provoking urea oxidation reaction (UOR); nevertheless, monometallic Ni-based catalysts can not possess sufficiently high performance owing to poisoning susceptibility of Ni towards carbonaceous intermediates and the poor electrical conductivity. In response, NiS x -VS 4 -C is synthesized via a facile glycerol coking strategy in hydrothermal system. It is found that NiS x -VS 4 -C is composed of many nanoparticles with a relatively small size (approximately 70 nm). Besides acting as the precursor of carbon, glycerol can regulate the morphology and structure of catalysts, and promote the formation of vacancy defects. Using as catalyst for UOR, a specific current activity of 652 mA cm−2 mg−1 for NiS x -VS 4 -C can be achieved at 0.52 V (vs. Hg/HgO), which is much higher than that for NiS x or VS 4 synthesized in glycerol solution. Glycerol coking is important for boosting catalytic activity. NiS x -VS 4 -C synthesized in glycerol solution exhibits much better catalytic activity than that synthesized in other alcohol solutions. Potential dependent impedance analyses reveal that urea indirect electro-oxidation mechanism should be mainly obeyed when NiS x -VS 4 -C is employed as catalyst. Both Ni and V with high chemical valence are active sites, where Ni species is mainly in charge of the oxidation of amine intermediate and V species is mainly in charge of the oxidation of CO intermediate. Carbon, especially graphitized phase, will significantly enhance the electrical conductivity and accelerate the charge transfer process. Therefore, constructing dual active sites and enhancing electrical conductivity via polyalcohol coking provide promising strategies for Ni-based catalysts towards UOR. [Display omitted] • NiS x -VS 4 -C is synthesized via a facile glycerol coking strategy in hydrothermal system. • NiS x -VS 4 -C exhibits superior catalytic performance towards UOR. • Ni species can facilitate the oxidation of ammine intermediate. • V species can facilitate the oxidation of CO intermediate. • The existence of carbon plays a vital role in promoting the charge transfer process. [ABSTRACT FROM AUTHOR]

The phenomenon of coking pressure is crucial for cokemaking both in respect of a safe coke oven battery operation and a proper quality of the produced coke. In spite of that, the mechanism of this phenomenon has not been clearly explained yet. The aim of the presented research was to clarify which of the phenomena most commonly mentioned in the literature on the subject, i.e., the reduced gas permeability of the plastic layer or the swelling of plasticized coal grains, is responsible for generating internal coking pressure. To that end, laboratory equipment was developed which enabled examining the pressure generated by the bed of plasticized coal grains under conditions of a varying possibility of its expansion. The results of the examinations suggest that the swelling phenomenon of plasticized coal grains is the direct cause of coking pressure, and the coking pressure strongly depends on the possibility of plastic layer expansion. The results confirm also the migration phenomenon of plasticized coal matter, especially towards the cool part of the charge as well as the possibility of compression of this part of coal charge. As a result of both these phenomena, it becomes possible for the plastic layer to expand, which results in a reduction of generated coking pressure. [ABSTRACT FROM AUTHOR]

[Display omitted] • H 2 regeneration of ZSM-5 coked in methanol-to-hydrocarbons reaction was studied. • H 2 restores >85% of activity and >30% of turnover capacity at 20–30 bar and ≤823 K. • Decoking of Al-rich ZSM-5 (Si/Al ∼ 14) removes >96% of coke under certain conditions. • H 2 treatment of Al-rich ZSM-5 removes both internal and external coke. • H 2 converts coke into light alkanes and aromatics instead of burning it into CO 2. Catalyst coking is one of the key challenges in hydrocarbons processing. Herein, we studied the potential of reacting coke deposits with hydrogen to regenerate the methanol–to–hydrocarbons (MTH) performance of archetypical ZSM-5 catalysts exhibiting low-to-medium Si/Al atomic ratios (14–39). The reactivation with hydrogen is substantially enhanced at elevated pressures (20–30 bar), restoring significant part of the MTH activity (>85%) and turnover capacity (>30%) at 753–823 K. Decoking is particularly efficient for the aluminum-rich catalyst, removing up to 96% of coke and attaining the performance comparable to conventional coke combustion. X-ray diffraction, Raman, infrared, nuclear magnetic resonance, and X-ray photoelectron spectroscopic analyses revealed that hydrogen eliminates internal and external coke from the catalyst with low Si/Al ratio, and internal coke from the silicon-richer materials. Hydrogen treatments yield light hydrocarbons (e. g., methane and ethane) and aromatics (e. g., methylated benzenes) offering thus a route for valorizing coke that can be exploited in other processes. [ABSTRACT FROM AUTHOR]

The specific branches of industry utilize needle coke, a carbon form with a highly anisotropic structure. Searching for novel raw materials for its production is now rigorously studied. In the present work, we use low-sulfur gasoil for this purpose, namely its high-boiling fractions. We study their chemical and physicochemical parameters with the set of physicochemical and spectral methods. The data of FT-IR and UV-Vis spectroscopies with a phenomenological method (that allows assessing average electronic structure parameters) indicate that the gas oil of the West Siberian origin contains polycyclic aromatic hydrocarbons (PAHs) with 3–5 condensed benzene rings. The maximum amount of PAHs with molecular masses of 400–600 a.u. is contained in the fractions with boiling points higher than 450 °C. According to the data of polarized-light optical microscopy, the higher boiling point of the gasoil fraction the higher anisotropy of the produced coke. This occurs as a result of an increase in the amount of PAHs capable of condensation with the formation of a mesophase. Thus, low-sulfur gas oils from thermally processed West Siberian oil are promising raw materials for the production of needle coke in delayed coking processes. [ABSTRACT FROM AUTHOR]

The catalyst coking and production of undesired products during the transformation of propane into propylene have been the critical challenges in the on purpose approach of propylene production. The mechanism contributing to this challenge was theoretically investigated through the analysis of cracking reaction routes. The study carried out employed the use of a density functional theory and cluster approach in order to understand the reactions that promote coking of the catalyst and in the search for the kinetic and thermodynamic data of the reaction mechanism involved in the process over Cr2O3. The ratedetermining step and feasible route that easily promote the production of small hydrocarbons like ethylene, methane, and many others were identified. The study suggests Cr-site substitution or co-feeding of oxygen can aid in preventing deep dehydrogenation in the conversion of propane to propylene. This information will help in improving the Cr2O3 catalyst performance and further increase the production yield.

The study involved a series of experiments on the coking of vacuum residue (VR) and of a mixture of carbon nanotubes (CNTs) and VR in an autoclave at 400–550°C. Using XRD, TEM, and electrical resistivity measurements, the properties of petroleum coke (petcoke) and CNT/petcoke composite were investigated and compared with those after calcination in an inert atmosphere at 1000–1100°C. It was found that the coking of a 2.5% CNT/VR mixture reinforces the petcoke with the CNTs. The CNT/petcoke composite exhibits a slightly higher crystallinity than the petcoke. However, the resistivity of the CNT/petcoke composite was found to be more than an order of magnitude lower than that of the petcoke. After high-temperature (1000–1100°C) calcination, the difference in resistivity between the petcoke and the 2.5% CNT/petcoke composite becomes substantially lower. This is associated with a resistivity drop in the petcoke itself, which approximates the resistivity of the carbon nanotubes. It was also identified that the high-temperature calcination reduces the sulfur content in the CNT/petcoke composite, and this reduction is more dramatic than that for the petroleum coke. [ABSTRACT FROM AUTHOR]

In the coking of heavy tar at 450–550°C, the influence of added carbon nanotubes on the yield of petroleum coke is studied. The properties of the resulting coke–nanotube composite are determined. Electron-microscopic data show that, in coking a mixture of heavy tar and nanotubes, the petroleum coke is reinforced by carbon nanotubes. Adding carbon nanotubes to heavy tar decreases its sulfur content. The drop in sulfur content of the petroleum coke is associated with the transfer of sulfur to hydrogen sulfide and COS, which are removed with the gas phase. With increase in the content of carbon nanotubes in petroleum coke, the electrical resistance of the coke–nanotube composite declines. Adding 5% of carbon nanotubes to the heavy tar lowers the resistance of the coke produced by a factor of 20. [ABSTRACT FROM AUTHOR]

The importance of the dry reforming of methane (DRM) lies in its capability to upgrade two greenhouse gases (CH4 and CO2) into synthesis gas (CO and H2), which is one of the main building block for synthesizing hydrocarbons. However, the Ni-based catalysts for DRM reaction usually have a major catalytic stability drawback. This works aims to assess the catalytic activity and stability of two Ni-based catalysts obtained from hydrotalcite (HT) precursors (i.e., NiAl-HT and NiMgAl-HT). The precursors, calcined (-c), reduced (-R) and spent samples were characterized by a series of techniques to gain insight into the influence of MgO over Ni-based catalyst in the drying reforming of methane. An in-situ ageing cycle process to speed up the deactivation of hydrotalcite-derived catalysts showed that the NiMgAl-HTc-R catalyst displayed a higher activity and resistance to coke formation (stability) than NiAl-HTc-R because of the introduction of Mg into hydrotalcite structure in the catalyst precursor. The presence of this element enhances several factors involved in the stability of Ni-based catalysts for the DRM process such as the reducibility and textural features of the catalysts, size and dispersion of Ni0 nanoparticles and also maintains a good compromise between the acid and base properties of the solid catalysts. [ABSTRACT FROM AUTHOR]

Given that coal may be oxidized and the yield of ammonia and hydrogen sulfide cannot be predicted from the volatile matters, mathematical formulas describing the yield of the basic coking products as a function of the elemental composition of the initial stamped coal batch are derived. It is found that, with increase in the content of gas coal (and hence in the volatile matter) in the stamped batch, the coke yield declines, but there is a higher yield of tar, benzene, carbon dioxide, pyrogenetic moisture, and coke-oven gas. The yield of the basic coking products is found to be additive. Hence, the total yield for the enterprise may be calculated, taking account of the characteristics and proportions of stamped and unstamped batch. [ABSTRACT FROM AUTHOR]

Flow thermomechanics in reactive porous media is of importance in industry including the thermal processing of fossil fuel (coking understood as a slow pyrolysis) involving devolatilisation. On the way to provide a detailed description of the process, a multi-scale approach was chosen to estimate effective transport coefficients. For this case the Lattice Boltzmann method (LBM) was used due to its advantages to accurately model multi-physics and chemistry in a random geometry of granular media. After account for earlier studies, the paper presents description of the model with improved boundary conditions and a benchmark case. Results from meso-scale LBM calculations are presented and discussed regarding the spatial resolution and the choice of relaxation parameter along its influence on the accuracy compared with empirical formulae. Regarding the estimation of effective thermal conductivity coefficient it is shown that occurrence of devolatilization has a crucial effect by reducing heat transfer. Some quantitative results characterise the propagation of thermal front; also presented is the evolution of effective thermal conductivity. The work is a step forward towards a physically sound simulation of thermal processing of fossil fuel. [ABSTRACT FROM AUTHOR]

The maximum moisture content is found to depend on the nature of the coal and its metamorphic stage, characterized by the volatile matter, the vitrinite reflection coefficient, the carbon and hydrogen content, and the calorific value. On moving to smaller size classes, the maximum moisture content increases on account of the increase in specific surface. The maximum moisture content is practically independent of the coal's degree of oxidation and the chemical composition of the ash. The packing density is a maximum for dry coal and falls to a minimum at a moisture content of 6–10% (depending on the size class). The oxidation of coal is accompanied by increase in the total and analytical moisture content as a result of physical and chemical sorption at the surface of the coal particles. Increase in moisture content increases the coal's resistance to crushing, which results in nonuniform particle size and impaired coal mobility. The consequences of increased moisture content are increase in the heat required in coking; coke of poorer quality (less uniform piece size, lower mechanical strength, and increased porosity); and shorter working life of the coke ovens. [ABSTRACT FROM AUTHOR]

The possibility of classifying coal in terms of IR spectra and soft independent modeling of class analogy (SIMCA) is considered. The samples investigated are first divided into two basic classes: optimal blend; and the alternative set of other blends. Spectral classification may be useful in identifying the structural similarity of blends, so as to ensure stable coke quality. [ABSTRACT FROM AUTHOR]

The alarming global warming issue has sparked interest in researchers to mitigate greenhouse gas emissions via CO 2 reforming of CH 4 (CRM). Regrettably, the main drawback of CRM is catalyst deactivation because of coking and metal sintering. Therefore, exceptional resistance towards coking and sintering is crucial to formulate viable CRM catalysts. This article reviewed the latest development of nanosilica-based catalysts (mesoporous nanosilica, dendritic fibrous nanosilica, green nanosilica, and core@shell nanosilica) for CRM application. The physicochemical properties of nanosilica supports could be modulated by synthesis methods to improve their resistance towards coking and sintering. Furthermore, this review compiled the influence of catalytic properties of nanosilica supported catalysts, such as active metal dispersion, crystallite size, acid-basic properties, oxygen mobility, reducibility, porosity, and morphology on CRM. To conclude, nanosilica supports with strong metal-support interaction, homogeneous metal dispersion, appropriate crystallite size, and moderate acidity/basicity, exhibited satisfactory catalytic activity, thermal stability, and resistance towards coking and sintering. The fundamental study and depth understanding on this catalysis field is of worth in configuring robust catalysts for future industrial applications success of CRM reaction with superb activity and carbon resistance for CRM. [Display omitted] • Nanosilica supports are preferred due to their high thermal stability and porosity. • Type of nanosilica supports: mesoporous, dendritic fibrous, and core@shell. • Dendritic fibrous nanosilica has high accessible active sites and minor clogging. • Core@shell nanosilica has low internal diffusion resistance and confinement effect. • Coke management based on basic nature and oxygen storage capacity of the supports. [ABSTRACT FROM AUTHOR]