FUEL
·
2023
·
IF 7.4
Wenrui Yan,Lu Liu,Liuru Liu,Quan Zhu,Bo Wang
The coking problem of hydrocarbon fuel pyrolysis is the key factor affecting the application of active cooling technology for high-speed aircraft. The purpose of this work is to investigate the coking inhibition performance and coking mechanism of using ammonia as an additive during the thermal cracking. In this study, the pyrolysis and coking characteristics of supercritical n-decane were experimentally studied using an electrically heated tube. ICP-OES (Inductively Coupled Plasma Optical Emission Spectrometer), GC–MS (Gas Chromatograph Mass Spectrometer), SEM (Scanning Electron Microscope), EDS (Energy Dispersive Spectroscopy), TPO (Temperature Programmed Oxidation), and Raman spectroscopy are applied to characterize the anti-coking performance of the additives. The results show that the additive hardly affects the cracking of the fuel under high-temperature conditions, but the coke mass deposited on the inner surface of the tube is significantly reduced, and the coking inhibition rate can reach 80% at 750 °C. The addition of additives reduced the graphitization degree and oxidative activity of the coke. The maximum oxidation temperature of the coke obtained at 750 °C was reduced by 145 °C, and the I D /I G value of the Raman spectroscopy peak-fitting was 3.29. The new mechanism of the effect of additives on the formation of coking precursors and the deposition of coke on the surface of the tube wall is proposed. Ammonia can react with Ni of the inner metal tube and radicals generated by fuel cracking to form a carbonized film, achieving the effect of inhibiting metal catalytic coking. Meanwhile, the amino radicals generated by ammonia dehydrogenation can regulate the coking reaction path by forming a stable p - π conjugate structure with unsaturated radicals. Therefore, the research will contribute to a deeper comprehension of the coking inhibition mechanism and the development of more effective coking inhibitors, providing new technical support for active cooling technologies.
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
POLYMER DEGRADATION AND STABILITY
·
2020
·
IF 4.032
Junchao Zhao,Yangyang Fu,Song Lu,Neng Tao,Zhitao Yin,Muhammad Usman Shahid,Heping Zhang
Perfluoro copolymers (PFCPs) with PFD (long chain -(CF 2 ) 7 CF 3 moiety) have a wide range of applications, such as hydrophobic and oleophobic modification of dry chemicals suppressants. However, high fluorine contents may produce much HF in thermal environments. In this study, a newly designed perfluoro copolymer (DPFCP) was synthesized and its application, pyrolysis and HF production were investigated. The pyrolysis of DPFCP could be divided into three stages, whereas the gas mainly released at the second stage, including CH 2 O, CO 2 , H 2 O, C x H y , C x H y F z , NH 3 , HF. A tube furnace was used to heating DPFCP to collect residual products and HF. The results indicated that HF was mainly produced under 370 °C.
研究领域:
材料科学
·
环境科学
·
化学工程
✓ 已验证
产品关联
DOI
高影响因子
Catalysts
·
2022
·Vol. 12
·期 11
·1383
·
IF 4.501
Wangyuan Zhang,Qi Li,Yongfei Li,Sanbao Dong,Sen Peng,Gang Chen
At present, the research on aquathermolysis catalysts mainly focuses on the catalytic effect of external catalysts on the reaction, ignoring the fact that external catalysts will form complexes with in situ inorganic minerals after entering the reservoir. In this paper, we investigated the effects of transition metal complexes as external catalysts and bentonite as in situ catalysts on aquathermolysis, respectively. Meanwhile, the aquathermolysis reaction co-catalyzed by external and in situ catalysts was further investigated. The results show that the transition metal complexes exhibited good co-catalysis with bentonite. The viscosity reduction rate can reach 73.47% at 200 °C and 4 h with 0.1 wt.% of catalyst (NAD–Zn) addition. The addition of ethanol under the same reaction conditions will further increase the viscosity reduction rate to 84.59%. The results of thermogravimetric analysis, component analysis and boiling range analysis of heavy oil show that the heavy components in heavy oil are cracked into light components after the aquathermolysis. The results of elemental analysis show that the heteroatoms in the heavy oil were removed and the quality of the crude oil was improved. The results of GC–MS analysis of the model compounds showed that the process of aquathermolysis was mainly through the cleavage of C–C, C–N and C–S bonds to crack the macromolecules into small molecules, and then achieve the effect of viscosity reduction. The main mechanism of catalyst action is the acidic center on the surface of the bentonite and the coordination bonds formed by the transition metal complexes with the heteroatoms.Keywords:heavy oil;catalytic aquathermolysis;viscosity reduction;co-catalyst;ethanol;mechanism
研究领域:
石油工程
·
催化化学
✓ 已验证
DOI
高影响因子
POLYMER DEGRADATION AND STABILITY
·
2018
·
IF 3.193
Lidong Feng,Songyang Feng,Xinchao Bian,Gao Li,Xuesi Chen
In order to obtain the mechanisms of the pyrolysis reaction that poly (lactic acid) (PLA) gives lactide in the presence of Sn, the four types of low molecular weight PLAs (L-PLA) with different end-groups were prepared, including HO-L-PLA-COOH, R-L-PLA-OH, R-L-PLA-COOH, and R-L-PLA-R, and depolymerized by thermogravimetry at different heating rates. As for the pyrolysis reactions of the L-PLAs, their activation energy ( E a ) were estimated by the several isoconversional model-free methods and their kinetic models were also explored by the Malek method. The random degradation behavior of L-PLAs was determined by the plots of ln { − ln [ 1 − ( 1 − w ) 0.5 ] } vs. 1/T for experimental data from TG for L-PLAs and model reactions. The experimental results showed that the E a values and the possible kinetic models for the pyrolysis reactions of the L-PLAs were different due to the different end-groups and thereof the mechanisms for the pyrolysis reactions of PLA that give lactide were proposed under the catalysis of Sn. The pyrolysis reactions of R-L-PLA-OH and R-L-PLA-R trend to be controlled by a single kinetic model. The pyrolysis reactions of HO-L-PLA-COOH and R-L-PLA-COOH are more complex and controlled by not less than two kinetic processes. The pyrolysis reaction of PLA selectively produces lactide through the unzipping and intramolecular transesterification reactions, including the backbiting reaction caused by the Sn-carboxylate and Sn-alkoxide chain ends, which are directly formed from the hydroxyl and carboxyl end-groups of PLA, and the lactide selective elimination at the random position of the polymeric backbone.
研究领域:
材料科学
·
化学工程
✓ 已验证
DOI
高影响因子
FUEL
·
2023
·
IF 7.4
Yu Feng,Huihang Zhang,Deming Zhang,Fuqiang Chen,Xinhai Xu,Jiang Qin,Yi Jiao
The cracking of on-board hydrocarbon fuels is a strong endothermic reaction and can provide an additional chemical heat sink in the cooling process of the hypersonic vehicle. However, the cooling capacity of current hydrocarbon fuels can hardly meet the cooling requirements of the hypersonic vehicle at higher flight speeds. Blending ethanol is an effective method to improve the chemical heat sink of hydrocarbon fuels, but the mechanism of ethanol on chemical heat sink is unclear. In this study, n-decane was selected as a model compound of hydrocarbon fuels to investigate the physical and chemical effect of ethanol on the chemical heat sink of n-decane cracking by analyzing the chemical reactions involved through experimental study and chemical dynamic simulation. The results indicate that there is an optimum ethanol blend ratio to achieve the maximum chemical heat sink. The carbon monoxide methanation reaction which is an exothermic reaction can deteriorate endothermic process at 300–375 °C. With ethanol blending ratio above 20 wt%, ethanol vaporization deteriorates chemical heat sink by reducing the residence time in the temperature range of 225–250 °C. Pressure can suppress the reduction of residence time caused by ethanol evaporation and also suppress the positive reaction of ethanol cracking. The kinetic model of ethanol and n-decane mixture cracking was established. The calculated results verify that ethanol cracking ( C 2 H 5 OH =CO+ C H 4 + H 2 ) and methane cracking ( C H 4 =C+ 2H 2 ) are dominant reactions in ethanol-assisted n-decane thermal cracking below 475 °C.
研究领域:
能源科学
·
化学工程
·
航空航天工程
✓ 已验证
DOI
高影响因子
JOURNAL OF ANALYTICAL AND APPLIED PYROLYSIS
·
2024
·
IF 5.8
Qingguo Zhou,Zhongyang Luo,Feiting Miao,Kaige Wang,Liwen Du,Qian Qian
For the biomass hydropyrolysis vapor upgrading (HPVU) route to be widely adopted, comprehensive and in-depth research on the free radical mechanism involved and the catalysts' performance is essential. Nine kinds of doped catalysts based on Al 2 O 3 -TiO 2 -SiO 2 (ATS) as composite supports with different Co, Ni and Mo metal loadings were prepared. Changes in the content of free radicals during the pyrolysis of poplar wood under different sources of hydrogen have been observed by the use of electron paramagnetic resonance. The doped catalysts with high conversion efficiency and carbon deposition resistance were screened out. To validate the findings, product analysis and experimental verification under three different poplar pyrolysis routes(i.e., catalytic hydropyrolysis, hydropyrolysis vapor upgrading, and catalytic hydropyrolysis vapor upgrading) were conducted using a long-term continuous lab-scale HPVU system under different pressures. The study reported a carbon deposition of only 1.56 wt% on the catalyst，and the highest yield of C4 + hydrocarbons achieved was 23.81 wt%daf. Based on the observations, the evolution mechanism in the hydrogenation conversion of biomass to liquid fuels was analyzed.
研究领域:
能源科学
·
催化化学
✓ 已验证
产品关联
DOI
高影响因子
FUEL
·
2022
·
IF 8.035
Zengtong Deng,Syed Shatir A. Syed-Hassan,Yuanjing Chen,Long Jiang,Jun Xu,Song Hu,Sheng Su,Yi Wang,Jun Xiang
Bio-oil can be converted to chemicals, carbon material, or syngas by various thermochemical processes which are always preceded with the pyrolysis step. In bio-oil pyrolysis, coke formation is almost inevitable, causing difficulties for further processing. In this study, bio-oil was mixed with Ni/Al 2 O 3 before it was fed for pyrolysis. Interesting results were observed whereby the effect of Ni/Al 2 O 3 mixing on coke formation shifted from promoting to inhibiting with increasing pyrolysis temperature. When the temperature was higher than 700 °C, contrary to the cases without mixing, the apparent decreases in coke yield were observed (e.g., the coke yield decreased by 10% at 800 °C). Comparative studies on bio-oil and its lignin-derived oligomer fraction indicated that the catalytic cracking of small molecules could enhance the formation of hydrogen radicals, which promoted thermal decomposition of lignin-derived oligomers, thus inhibiting coke formation via polymerization.
研究领域:
能源科学
·
催化化学
✓ 已验证
产品关联
DOI
高影响因子
FUEL
·
2023
·
IF 7.4
Bo Wang,Wenrui Yan,Xianlong Gong,Quan Zhu
Coking during the endothermic hydrocarbon fuel pyrolysis is a key issue that needs to be solved in the development of regenerative cooling technology for high-speed aircrafts. The compounds containing hydroxyl groups are developed to inhibit coking by regulating coking pathway during the thermal cracking of hydrocarbon fuels. Pyrolytic deposition experiments of n -decane with additives were performed using the method of electrical heating. The anti-coking performance of the additives was characterized by means of gas chromatograph–mass spectrometer (GC–MS), scanning electron microscopy (SEM), temperature programmed oxidation (TPO) and Raman spectroscopy. The results showed that the degree of cracking is reduced at low fuel temperature due to the dilution of the additives, and the additives do not affect the fuel cracking as the fuel temperature increased. With the function of additives, the masses of filamentous and amorphous coke were decreased. A possible mechanism for the additives inhibiting coking has been proposed. The additives containing hydroxyl groups can block the initial coking reaction path to inhibit coking at the source. In general, the hydroxyl radicals released by the additives oxidize the coking precursors to prevent its further growth, and react with the substrate to form particulate matters serving as passivation coating, inhibiting the bulk phase coking and metal catalytic coking simultaneously. This work provides significant ideas for inhibiting coking by regulating coking reaction pathways.
研究领域:
化学工程
·
航空航天材料科学
✓ 已验证
产品关联
DOI
高影响因子
JOURNAL OF ANALYTICAL AND APPLIED PYROLYSIS
·
2023
·
IF 6
Feng Wang,Zheng Zhang,Ying Yang,He Liu,Kun Chen,Zongxian Wang,Aijun Guo
The factors leading to olefinic hydrogen signal shielding in the 1 H NMR spectra of thermally cracked vacuum residue (VR) and its heavy fractions were revealed using a series of model compound systems, and the effect of olefinic hydrogen signal shielding on the determination of olefinic hydrogen content was elucidated. There were two main factors leading to the olefinic hydrogen signal shielding in the 1 H NMR spectra of olefins in heavy fractions, i.e. intramolecular and intermolecular. For the olefin itself in heavy fractions, the chemical shift of the olefinic hydrogen closest to the aromatic ring was in the aromatic region rather than the olefinic region due to the π-π conjugation effect between the double bond and the intramolecular aromatic ring. Notably, the response intensity of the olefinic hydrogen signal could be weakened or even disappear due to the suppressive effect of the intermolecular aromatic structures in other polycyclic aromatic hydrocarbons (PAHs), while alkanes and monocyclic aromatics had little effect on the olefinic hydrogen signal response. Although the olefinic hydrogen signal was detected merely at about 5.30 ppm in the 1 H NMR spectra of heavy fractions, these olefinic structures may be predominantly of the R─CH═CH 2 type rather than the R─CH═CH─R′ type. More importantly, the measured olefinic hydrogen content of thermally cracked VR and its heavy fractions may be considerably lower than the actual content, with the measured content being only about 30–40 % of the actual content. This is mainly due to the weakening and disappearance of the olefinic hydrogen signal, coupled with the fact that the integral area of the possible olefinic hydrogen signal in the aromatic region was overlooked when calculating the total integral area of the olefinic hydrogen signal in the 1 H NMR spectrum.
研究领域:
分析化学
·
石油化学
·
有机化学
·
光谱学
·
能源化学
✓ 已验证
DOI
高影响因子
INTERNATIONAL JOURNAL OF HYDROGEN ENERGY
·
2020
·
IF 4.939
Zhaowei Li,Xiaosong Yang,Yingxiang Han,Long Rong
The conversion of biomass to produce high-valued chemical aromatic intermediates such as benzene (B), toluene (T), ethylbenzene (E), xylene (X), naphthalene (N) has attached booming interests. Herein, in order to obtain BTEXN aromatics on the hydrocracking of Jatropha oil, several LaNiMo/ZSM-5 catalysts (La loading from 0.5 to 15 wt%) by alkali treatment and metal impregnation methods were synthesized and investigated. Fundamentally, we found the alkali treatment engendered more mesoporosity to ZSM-5 and resulted in higher catalytic activity . It bears emphasis that further metal impregnated catalyst NiMo/ZSM-5 could improve the aromatics yield due to the increase of metal active sites and acidity sites. Besides, we noted that La loading had positive effects on coke reduction, catalytic stability and catalyst lifetime. To sum up, results confirmed the favorable 1 wt% La–NiMo/ZSM-5 had maximum 75 wt% BTEXN yield, longer catalyst lifetime for 100 h and decreased carbon deposits by 1.11%.
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
Journal of Cleaner Production
·
2019
·
IF 6.395
Nan Zhou,Yifan Wang,Denghui Yao,Shikai Li,Jiajie Tang,Da Shen,Xiaoyu Zhu,Liyang Huang,Mei-e Zhong,Zhi Zhou
The enhancement of surface functional groups of biochar is essential to improving the biochar contaminant adsorption. Current pyrolysis methods that are accompanied by activation are energy consuming and costly. Herein, a novel wet-pyrolysis system that was carried out in open air, with simultaneous conversion and modification to produce an effective biochar adsorbent, is described. Within this system, the surface of the biochar was oxidized partially to produce sufficient functional groups at the surface, whereas carbonization of the biomass (miscanthus sacchariflora) occurs under an acidic catalyst. The characteristic results confirmed the attachment of abundant surface functional groups, including hydroxyl and carboxyl groups , which increased in content with the ongoing reaction time. Neutralization with sodium carbonate removed the hydrogen bonds and enhanced the adsorption properties. The biochar that was obtained by using this technique exhibited an excellent cadmium adsorption capacity of 197 mg .g −1 and a high removal efficiency of 99%. Analysis of the Cd-loaded biochar indicated that adsorption occurred via ion exchange, and formed cadmium complexes. It could be concluded that this novel wet-pyrolysis system is a promising approach to produce biochar efficiently and cost-effectively for heavy-metal remediation.
研究领域:
环境科学
·
土壤学
✓ 已验证
产品关联
DOI
高影响因子
INDUSTRIAL CROPS AND PRODUCTS
·
2024
·
IF 5.6
Penghui Wang,Junran Pang,Hua Zhang,Huiyun Liao,Dangan Xiong,Longjie Zhu,Dong Xue,Min You,Yukun Liu,Jiang Li,Shuang Li,Xiaoyan Tan,Zheng Yao,Bo Chi,Junzhang Wu
In order to encourage effective recycling of tobacco resources in the industry and successfully enhance the quality of reconstituted cut stems (GS30). This study investigates the thermal, structural, and material composition of GS30. It was found that compared with high-quality tobacco leaves and cut stems, the contents of important macromolecules including cellulose, hemicellulose and lignin in GS30 were 21.74 ± 1.14 %, 3.66 ± 0.56 %, and 1.69 ± 0.46 % respectively. Its content is smaller than that of blank cut stems but similar to high-quality tobacco leaves. The important macromolecular structures were further analyzed for their surface morphology and crystal structure using FTIR, XRD, SAXS, and SEM. After analyzing the thermal cracking behavior of GS30 through PY-GC-MS, it was found that GS30 has four weight loss stages and thermal cracking releases near 30 types of aroma substances, showing obvious advantages in releasing aromatic gases. This demonstrates that the structure of GS30 obtained from secondary processing of discarded tobacco leaves is loose and easy to burn and decompose, which can effectively reduce the release of cigarette tar.
研究领域:
烟草科学
·
材料科学
·
分析化学
✓ 已验证
产品关联
DOI
高影响因子
危险品化学品经营许可证（带存储）