FUEL
·
2020
·
IF 5.578
Ruonan Zheng,Dong Liu,Junshi Tang,Qiang Song,Qiang Yao
Coke formation during the process of in-situ combustion is affected by clay minerals, among which montmorillonite shows the most significant effect. A fixed-bed reactor was used to conduct the thermal conversion experiments of heavy oil and model compounds to reveal the mechanism of montmorillonite affecting the coke formation. Under the inert atmosphere, in the presence of montmorillonite, the temperature at which aromatic C–C groups of coke appeared decreased from 500 °C to 450 °C and polymers were formed when toluene was heated, indicating that montmorillonite catalyzed aromatization and polymerization, respectively. The increase in the supporter surface area promoted the formation of coke from pyrolysis by shortening the induction of coking. Under the oxidizing atmosphere, in the presence of montmorillonite, the initial temperature of O 2 consumed by heavy oil decreased from 270 °C to 250 °C, indicating that montmorillonite catalyzed oxygen-adding reaction. The temperature of CO x released by acetaldehyde and acetic acid decreased, and the release amounts increased, indicating that montmorillonite catalyzed decarbonylation and decarboxylation. Polymers were formed when acetaldehyde, acetic acid, ethanol, and acetone were heated, indicating that montmorillonite catalyzed polycondensation. When the oil mass fraction in the sample was within 18%, further increase in the supporter surface area did not affect the formation of coke from oxidation. The catalysis of montmorillonite was the main mechanism affecting coke formation during the thermal conversion of heavy oil under the inert and oxidizing atmospheres.
研究领域:
石油工程
·
化学工程
✓ 已验证
产品关联
DOI
高影响因子
FUEL
·
2024
·
IF 6.7
Ji Mi,Peilun Wang,Hongshang Wang,Chongkun Shao,Zhiyuan Yuan,Jingkai Ma,Yongsheng Guo,Xufeng Lin,Wenjun Fang
Endothermic hydrocarbon fuels (EHFs) with high heat sink have revolutionized the thermal management technology of hypersonic aircraft over the past decades. In this work, highly stable quasi-homogeneous systems as a novel type of potential EHFs are introduced by dispersing water-rich multifunctional nanospheres in hydrocarbons. Studies conducted using cryo-transmission electron microscopy, dynamic light scattering and small-angle X-ray scattering have demonstrated that nanospheres with diameter less than 100 nm can be solubilized into hydrocarbons to form semi-transparent systems. They resist phase separation, remain stable under extreme centrifugal forces (exceeding 8000 RCF), and have low freezing points (subcooling temperature below −40 °C). In these quasi-homogeneous systems, the amphiphilic macromolecules within the multifunctional nanospheres serve dual roles: they stabilize the nanospheres and initiate the thermal cracking of the fuel, while the water component mitigates coking tendencies and contributes to the high heat sink. Ultimately, this novel fuel can achieve up to 19 % improvement in heat sink (from 3.42 MJ·kg −1 to 4.05 MJ·kg −1 at 3.5 MPa) and a 96.8 % reduction in coke formation (at 700 °C) with only a 9 % loss in volumetric heat value, without the need of catalysts.
研究领域:
材料科学
·
航空工程
✓ 已验证
产品关联
DOI
高影响因子
ENERGY & FUELS
·
2018
·
IF 3.024
Ruonan Zheng,Jingjun Pan,Lijuan Chen,Junshi Tang,Dong Liu,Qiang Song,Long Chen,Qiang Yao
In situ combustion is an enhanced method to recover heavy oil. The formation and oxidation of coke are crucial to promote the combustion front. Heavy oil from China and montmorillonite, a major type of clay, were used as samples in this study. The thermogravimetric analyzer (TGA) was applied to temperature-programmed oxidation/pyrolysis experiments to study the effect of montmorillonite on the thermal conversion characteristics of heavy oil. A fixed-bed reactor was then used to obtain coke and study the effect of montmorillonite on coke properties. The characteristic temperatures of thermal conversion decreased with montmorillonite in the oxidizing atmosphere but remained unaffected in the pyrolysis atmosphere. The fuel deposition increased in both atmospheres because of montmorillonite’s strong adsorption. In the oxidizing atmosphere, the presence of montmorillonite obviously promoted the progress of coke formation and increased coke yield. The content of O was increased, and the contents of C and H were decreased in coke. The oxidation activity of coke was improved, while trailing occurred due to the blocking in the pore structures of the montmorillonite skeleton. In the pyrolysis atmosphere, the presence of montmorillonite did not influence the coke formation temperature but increased the coke yield. The content of C was increased and the contents of H and O were decreased in coke. Coke oxidation activity was reduced with the more serious trailing phenomenon. Montmorillonite significantly affected coke formation through its strong adsorption to polar components in heavy oil in both atmospheres and obvious catalysis on dehydrogenation as an acid catalyst in the pyrolysis atmosphere, while it enhanced the oxygenation due to its large surface area and catalyzed polycondensation in the oxidizing atmosphere.
研究领域:
石油工程
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化学工程
✓ 已验证
产品关联
DOI
高影响因子
COMBUSTION AND FLAME
·
2016
·
IF 4.168
Huiyan Zhang,Yun Wang,Shanshan Shao,Rui Xiao
Catalytic conversion of furfural to olefins and aromatics was conducted over ZSM-5 in a fixed-bed reactor. The effects of temperature, weight hourly space velocity and partial pressure on the yield and selectivity of products were investigated and the coked catalysts were characterized. The kinetics of furfural catalytic conversion including catalyst deactivation caused by coke deposition was built. The results showed that the main products of furfural catalytic conversion were aromatics, olefins, furan and coke. High temperature, high partial pressure and low WHSV promoted the formation of olefins and aromatics. The catalytic reaction pathway was speculated to be the decarboxylation of furfural to form furan, with further reactions to form olefins and aromatics. The amount of coke deposited on the catalyst increased with increasing reaction time. The surface area and acidity of catalysts declined as coke formed on the acid sites and blocked the pore channels, which led to the decrease of olefin and aromatic yields. Finally, a kinetic model considering coke deposition had been built based on the above reaction pathway to properly predict the product distribution.
研究领域:
化学工程
·
催化科学
✓ 已验证
产品关联
DOI
高影响因子
JOURNAL OF ANALYTICAL AND APPLIED PYROLYSIS
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2018
·
IF 3.468
Changsong Hu,Huiyan Zhang,Rui Xiao
In order to inhibit the coke formation on the external surface of HZSM-5 during catalytic fast pyrolysis (CFP) of biomass, core-shell structured HZSM-5@silicalite-1 zeolite catalysts were hydrothermally synthesized through the growth of silicalite-1 along the surface of a commercial HZSM-5. The catalyst characterization results indicate that silicalite-1 outer shell layer was successfully formed on the HZSM-5 core particles. Silicalite-1 coating was proved to be effective to reduce the external acidity as well as keep the internal acidity and channel patency of core HZSM-5 by catalytic probe reactions. The catalytic performances of HZSM-5@silicalite-1 samples in CFP of biomass were investigated using a bench-scale continuous feeding two-stage fluidized-bed/fixed-bed combination reactor. The results show that the productions of olefins and BTX were promoted (especially BTX), while the formations of catalyst coke and PAHs were significantly inhibited after silicalite-1 coating.
研究领域:
化学工程
·
能源科学
✓ 已验证
产品关联
DOI
高影响因子
INDUSTRIAL & ENGINEERING CHEMISTRY RESEARCH
·
2022
·
IF 4.326
Qiao Chen,Lidan Deng,Zewei Wu,Fang Wang,Xingmao Jiang
Propane dehydrogenation is one of the most admired technologies for propylene production. However, the development of an active and stable catalyst presents a significant challenge. In this study, Pt–Ga/SBA-15 catalysts were prepared via coimpregnation, followed by H2 reduction, and applied in propane dehydrogenation. The Pt–Ga/SBA-15 catalyst with a Ga/Pt molar ratio of 1 exhibited a high propane conversion of up to 60% and high selectivity toward propylene of 98.2% at 550 °C for 10 min, with a propane conversion of 51.6% and propylene selectivity of 99.5% after reaction for 25 h. The physicochemical properties characterized using N2 physisorption, XRD, TEM, XPS, CO chemisorption, and in situ CO–DRIFT spectroscopy reveal that the Pt–Ga alloy nanoparticles were formed on the SBA-15 support after direct reduction with H2. The study of coke formation via temperature-programmed oxidation showed that a large amount of coke was deposited over the support of spent Pt–Ga/SBA-15 catalyst, indicating coke mobility from the active sites to the supports and its contribution to catalyst stability. The activities of spent catalysts could be almost completely recovered via reduction regeneration, during which Pt–Ga alloy retains the original geometrical and electronic structure well. The dilution of Pt ensembles due to the addition of Ga, e.g., Pt–Ga alloy formation, plays an important role in enhancing the catalytic performance for propane dehydrogenation.
研究领域:
化学工程
·
催化科学
✓ 已验证
DOI
高影响因子
CHINESE JOURNAL OF CATALYSIS
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2024
·
IF 15.7
Shuyi Li,Changle Mu,Nianqiu He,Jie Xu,Yanping Zheng,Mingshu Chen
ABSTRACT The surface structures of heterogeneous catalysts significantly impact catalytic performance, especially for structure-sensitive reactions. In this study, we employed surface techniques such as low-energy ion scattering spectroscopy, X-ray photoelectron spectroscopy, and Fourier transform infrared spectroscopy with CO as a probe (CO-FTIR) to investigate the surface dynamics of Rh/Al 2 O 3 catalysts for propane dehydrogenation (PDH). We observed a notable induction process for PDH on Rh/Al 2 O 3 catalysts, marked by significant variations in propane conversion, methane, and propylene selectivities. These changes were attributed to substantial coke formation. Aberration-corrected high-angle annular dark-field scanning transmission electron microscopy) and CO-FTIR revealed the coexistence of Rh nanoparticles , clusters, and single atoms on the surface. Through various dynamic quasi in-situ characterizations, we found that coke preferentially covered Rh clusters, thereby inhibiting C–C bond breaking and methane formation. Meanwhile, Rh single atoms were less affected by coke coverage and remained exposed as active and selective sites for PDH, favoring propylene production. This work underscores the sensitivity of PDH to the sizes of Rh species, with isolated Rh single atoms promoting propylene formation.
研究领域:
催化化学
·
材料科学
✓ 已验证
DOI
高影响因子
APPLIED CATALYSIS B-ENVIRONMENTAL
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2016
·
IF 8.328
Xinyu Li,Di Li,Hao Tian,Liang Zeng,Zhi-Jian Zhao,Jinlong Gong
This paper describes the design of a Ni/La 2 O 3 catalyst using La 2 O 2 CO 3 nanorod as a support precursor (denoted as Ni/La 2 O 3 -LOC) via a wet impregnation method for dry reforming of methane (DRM). The results showed that La 2 O 3 derived from the La 2 O 2 CO 3 precursor maintained its initial morphology upon thermal treatment and could highly disperse Ni particles on it. Additionally, the nanorod-shaped support could provide more medium-strength basic sites to facilitate CO 2 adsorption and activation on its surface. Consequently, the Ni/La 2 O 3 -LOC catalyst reached 70% of CH 4 conversion and 75% of CO 2 conversion at 700 °C after 50 h DRM reaction with a H 2 /CO ratio of 0.87. The enhanced metal-support interaction restricted the sintering of nickel particles under harsh reaction conditions. Coke evolution on the catalysts was also investigated to understand coke formation mechanism and the role of La 2 O 2 CO 3 in coke elimination. It has been found that nickel dispersion can affect distribution of coke and La 2 O 2 CO 3 on the surface of catalyst, both of which have a close relation with catalytic performance.
研究领域:
化学工程
·
催化材料科学
✓ 已验证
产品关联
DOI
高影响因子
ACS Omega
·
2021
·
IF 3.512
Wenke Wang,Jie Zhao,Dandan Jia,Zhaolin Fu,Enhui Xing,Zhongpeng Zhu,Rui Yan,Zhiping Tao,Yibin Luo,Xingtian Shu
The fast deactivation caused by serious formation of coke is a major challenge in catalytic isomerization of endo-tetrahydrodicyclopentadiene (endo-THDCPD) into exo-tetrahydrodicyclopentadiene (exo-THDCPD) over the HY zeolite. In order to suppress the coke formation for the isomerization process, the conventional HY zeolite was modified with Pt at 0.3 wt %. Then, the hydroisomerization of endo-THDCPD into exo-THDCPD was evaluated over a fixed-bed reactor. The catalytic stability of Pt/HY was greatly enhanced in comparison to that of the HY zeolite. The Pt/HY catalyst provided 97% endo-THDCPD conversion and 96% selectivity for exo-THDCPD without deactivation after 100 h. Moreover, the formation mechanism of coke on the HY zeolite during the isomerization process was proposed based on the results of the coke analysis. It was indicated that the coke was generated from the oligomerization and condensation of olefin species, which originated from the β-scission reaction or hydride transfer reaction of intermediates. The lower coke formation over Pt/HY was attributed to the lower amount of coke precursors, which could be hydrogenated by activated H2 over Pt sites. Therefore, Pt on Pt/HY and H2 were two crucial factors in efficiently enhancing the catalytic stability of the HY zeolite for this isomerization reaction.
研究领域:
催化化学
·
材料科学
·
石油化工
✓ 已验证
产品关联
DOI
PubMed
高影响因子
ACS Catalysis
·
2020
·
IF 12.35
Xianxian Shi,Yue Lin,Li Huang,Zhihu Sun,Yong Yang,Xiaohong Zhou,Evgeny Vovk,Xinyu Liu,Xiaohui Huang,Mei Sun,Shiqiang Wei,Junling Lu
Metal particle size plays essential roles in metal-catalyzed heterogeneous reactions. Reducing the particle size from a few nanometers down to atomically dispersed single atoms alters both the morphology and electronic property of the metal enormously, thus greatly modulating its catalytic performance. Detailed investigation of the particle size effect as well as taking account of a metal single-atom catalyst (SAC), the frontier in heterogeneous catalysis, can provide a deeper insight into structure–activity relations and facilitate the rational design of advanced metal catalysts. However, such studies have been rarely reported. Herein, Cu single atoms and nanoparticles with different sizes of about 3.4, 7.3, and 9.3 nm were synthesized on an alumina support using atomic layer deposition. Comprehensive microscopic and spectroscopic characterization shows that the Cu single atoms remain very stable and have 1+ valence state after reduction at 300 °C in hydrogen. In semihydrogenation of acetylene in excess of ethylene, we show that a decrease in the Cu particle size reduces the activity considerably but gradually improves both the ethylene selectivity and durability. In particular, the Cu SAC exhibits the highest ethylene selectivity of 91% at the complete conversion along with excellent long-term stability for at least 40 h, in sharp contrast with the rapid deactivation on Cu nanoparticle catalysts. In situ thermogravimetry measurements further reveal that coke formation on Cu1 SAC is significantly suppressed by up to ∼89% compared to that on the 9.3 nm Cu nanoparticle catalysts. In brief, our findings demonstrate that SACs can be promising candidates for selective hydrogenation reactions in terms of high selectivity and high coking resistance.
研究领域:
催化化学
·
材料科学
✓ 已验证
DOI
高影响因子
JOURNAL OF ANALYTICAL AND APPLIED PYROLYSIS
·
2025
·
IF 6.2
Feng Wang,Shouhui Jiao,Xiaoqi Zhang,Ying Yang,Xiaohan Jin,He Liu,Zongxian Wang,Aijun Guo
Although highly reactive olefinic species are abundant in thermally cracked oil, previous studies have predominantly focused on the macroscopic fouling effects of aliphatic olefins during transportation/storage. In contrast, the molecular-level mechanisms by which aromatic olefins promote coking during thermal conversion remained unclear. This work systematically investigated how aromatic olefins drive molecular growth and coke formation of heavy aromatic fractions. Thermal conversion experiments with vacuum residue (VR), resins (Re), and asphaltenes (Asp) mixed with olefin model compounds revealed that aromatic olefins accelerated coking compared to aliphatic olefins, with the coking-promoting effect intensifying as the number of aromatic rings in the molecule increased. At 410°C for 60 min, the addition of 5 wt% 9-vinylanthracene to VR increased the coke yield from 1.35 wt% to 5.72 wt%, versus 1.68 wt% with the addition of 5 wt% 1-octene. Similarly, the addition of 5 wt% 9-vinylanthracene elevated the coke yields for Re and Asp systems from 0.66 wt% and 41.28 wt% to 5.13 wt% and 50.84 wt%, respectively, compared to 1.08 wt% (Re) and 43.36 wt% (Asp) observed with the addition of 1-octene. Model compound system studies demonstrated that, aromatic olefins, unlike 1-octene, could further react with primary addition products formed by their initial co-addition with conventional aromatics, leading to the formation of secondary and high-order addition products. Notably, aromatic olefins exhibited increasing reactivity in continuous co-addition reactions as the number of aromatic rings increased. This was supported by 42.2 % high-order addition products detected in the toluene/9-vinylanthracene system versus 30.1 % in the toluene/styrene system. This study elucidated that aromatic olefin promoted molecular growth through continuous co-addition reactions, ultimately triggering phase separation and coke formation. The findings provided molecular-level insights into the adverse impacts of aromatic olefins on industrial processing of thermally cracked oil.
✓ 已验证
产品关联
DOI
高影响因子
BIORESOURCE TECHNOLOGY
·
2022
·
IF 11.889
Xiheng Kang,Jian Peng,Arthur J. Ragauskas,Xiaofei Ren,Chuanling Si,Shuangfei Wang,Xueping Song
The complexity of polysaccharide hydrothermal products increases the difficulty of exploring the formation of biochar, limiting the development of biochar. This work clarifies the completive effects of glucan’s main hydrolysates on biochar formation from three aspects: experimental, thermodynamic, and kinetic. The products distribution illustrates that 5-HMF, FA, and LA are mainly involved in the formation of biochar. Biochar mainly includes furan ring, ether group, and ester group by the analysis of magic-angle-spinning nuclear magnetic resonance, X-ray photoelectron spectroscopy, and elemental analysis. Combined experiments and density functional theory analysis, the etherification reaction of 5-HMF itself is most likely to occur and is key to form biochar, followed by the esterification of FA with 5-HMF, and then the etherification of 5-HMF and LA. The further verified experiments also manifest these results. This work will develop a foundation for exploring the complex formation mechanism of cellulose-based biochar.
研究领域:
化学
·
环境科学
·
生物质能
✓ 已验证
DOI
PubMed
高影响因子
危险品化学品经营许可证（带存储）