FUEL
·
2023
·
IF 7.4
Kezhen Qian,Wenmin Tian,Siwei Yan,Wentao Li,Lijie Yin,Derun Guo,Zixu Yang,Dezhen Chen,Yuheng Feng
The effects of pretreatment and structure of zeolite on aromatization of high-density polyethylene (HDPE) and polypropylene (PP) over different Ga-promoted zeolites (HZSM-5, hierarchical HZSM-5, HY, Hβ, and USY) were investigated. Hydrogen reduction of Ga-promoted HZSM-5 resulted in a higher yield of alkenes during HDPE pyrolysis but did not lead to increased production of total aromatic hydrocarbons. The reduction and subsequent oxidation of Ga/Z5 led to the formation of GaO + species with high dehydrogenation activity. This resulted in a remarkable 65% yield of aromatics, with a BTEX (benzene, toluene ethylbenzene and xylene) overall yield of 60% and a selectivity of 90% of the liquid product. Increasing the Ga loading decreased the BTEX yield due to pore blockage and a decrease in the amount of Brønsted acid sites. The BTEX yield over Ga-promoted zeolites was found to be strongly related to the pore size of the zeolite, whereas its yield over the parent zeolite was not strongly dependent on the pore size. Diffusion of the cracking intermediates was found to have a more significant impact on the aromatization of PP than HDPE. The highest BTEX yield for HDPE was achieved with Ga-promoted HZSM-5, while Ga-promoted hierarchical HZSM-5 exhibited the highest BTEX yield for PP. Furthermore, Ga(1)/Hβ-Redox demonstrated remarkable selectivity (90%) towards ethylene and propylene in the gas phase, surpassing other zeolites (37%-68%).
研究领域:
化学工程
·
材料科学
✓ 已验证
DOI
高影响因子
JOURNAL OF ORGANIC CHEMISTRY
·
2024
·
IF 3.3
Yangxin Jin,Predrag V. Petrovic,Shuquan Huang,Shibdas Banerjee,Abhijit Nandy,Paul T. Anastas,Jason Chun-Ho Lam
Dehydrogenative aromatization (DA) of cyclic ketones is central to the development of functionalized aromatic precursors and hydrogen transfer–related technologies. Traditional DA strategies require precious metals with oxidants and are typically performed at high temperatures (100–150 °C) to overcome the high energy barrier of aliphatic C–H bond activation. Recently, a mild alternative approach based on I2 has been proposed to realize DA on substituted unsaturated cyclic ketones under ambient conditions. However, depending on the solvent, the product selectivity may vary between phenol ether and phenol, and the reaction mechanisms remain unclear. Herein, based on time-resolved proton nuclear magnetic resonance, DFT calculation, and mass spectrometric analyses, we established a unified mechanism to account for the product distribution. Through substrate scope and desorption electrospray ionization–mass spectrometry, we discovered the formation of a carbocation, which has been overlooked in previous studies. An expanded substrate scope study coupled with spectroscopic observation provided strong evidence to elucidate the formation mechanism and the location of the carbocation. With a renewed understanding of the mechanism, we achieved a phenolic product yield of 17–96% while controlling the selectivity. Moreover, some reactants could undergo DA in H2O, achieving 95–96% yield at below water-boiling temperature.
研究领域:
有机化学
·
催化化学
✓ 已验证
产品关联
DOI
PubMed
高影响因子
CATALYSIS LETTERS
·
2021
·Vol. 152
·期 5
·1372-1385
·
IF 3.186
Qiu Baocheng,Zhang Yakun,Zhang Yi
The rapid deactivation caused by coke deposits is the major obstacle to the ethane aromatization of Zn-based catalysts. We have successfully synthesized a Zn-embedded inside HZSM-5 crystal catalyst (Zn@HZSM-5) by hydrothermal synthesis using preformed Zn/SiO 2 as the only silicone source. Based on various characterization results, including in situ etching XPS, operando DRIFTS, as well as NMR, it is found that Zn(OH) + and [Zn–O–Zn] 2+ species are active sites for ethane aromatization for zinc-based catalysts, and their dynamic transformation significantly changes reaction performance of ethane dehydrogenation. For the Zn/HZSM-5 catalyst, the existence of a large number of [Zn–O–Zn] 2+ species causes higher initial ethane conversion and higher selectivity of aromatics, resulting in a large amount of coke deposits. Moreover, [Zn–O–Zn] 2+ species on the Zn/HZSM-5 catalyst fast transit to Zn(OH) + species and subsequently form the sintered ZnO species, leading to rapid deactivation. For the Zn@HZSM-5 catalyst, the embedded structure contributes to forming more Zn(OH) + species and delays the transformation of the Zn(OH) + species to [Zn–O–Zn] 2+ species, resulting in slowly increased selectivity of aromatics during the reaction. Therefore, the Zn@HZSM-5 catalyst realizes stable ethane conversion with dynamic selectivity. Graphic Abstract
研究领域:
催化化学
·
材料科学
✓ 已验证
产品关联
DOI
高影响因子
Polymers
·
2019
·Vol. 11
·期 7
·1119
·
IF 3.164
Yu Ji,Qiang Yao,Yueying Zhao,Weihong Cao
To gain an insight of the chemistry in the alkali-promoted aromatization of oxygen-containing heavily aromatic polymers or biomass; thermal degradations of sodium phenolates with different substituents have been investigated. The -ONa group strongly destabilizes the phenolates. The thermal stability of phenolates is largely in parallel with bond strengths of Ar substituents. De-substituents and the removal of aromatic hydrogens are dominant reactions in the main degradation step. CO is formed only at a very late stage. This degradation pattern is completely different from that of phenol. To account for this distinctive decomposition; a mechanism involving an unprecedented formation of an aromatic carbon radical anion generated from the homolytic cleavage of Ar substituent (or Ar–H) in keto forms has been proposed. The homolytic cleavage of Ar substituent (or Ar–H) is facilitated by the strong electron-donating ability of the oxygen anion. A set of free-radical reactions involved in the alkali-catalyzed aromatization have been established.Keywords:phenolate;thermal degradation;radical anion;aromaticity;aromatization
研究领域:
化学
·
催化反应
✓ 已验证
产品关联
DOI
PubMed
高影响因子
FUEL
·
2021
·
IF 6.609
Tao Pan,Sida Ge,Mengnan Yu,Yana Ju,Ran Zhang,Pei Wu,Kuanyu Zhou,Zhijie Wu
Zn modified ZSM-5 zeolite supported Ni bifunctional catalysts were prepared by in-situ hydrothermal synthesis (Zn-Ni-ZSM-5), co-impregnation method (Zn-Ni/ZSM-5) as well as combining in-situ hydrothermal synthesis of Zn-ZSM-5 and sequential impregnation of Ni (Ni/Zn-ZSM-5) and used for the selective converting olefin to aromatics applicable for FCC gasoline hydro-upgrading. The Lewis (L) acid sites generated by ZnOH + species and hydrogenation active sites from Ni 0 species were varied with preparation method, in which their locations at the external surface or micropores of zeolite changed the acid properties of catalysts. Comparing to the Zn-Ni/ZSM-5 from the co-impregnation method, direct in-situ hydrothermal method could incorporate Zn and Ni species within zeolite, which makes the strong interaction between the metal species and the framework Al to form medium-strong L acids (ZnOH + /NiOH + ). This leads to the decrease of ratio of Brønsted acid sites to L acid sites (B/L) from 0.40 to 0.12 and the difficulty in reducing of Ni cations to Ni 0 from 57% to 30% Ni 0 percent. Ni/Zn-ZSM-5 sample prepared by incorporating Zn species into micropores and sequential depositing Ni species at the external surface of zeolite possesses a low B/L ratio similar to Zn-Ni-ZSM-5 (0.20 versus 0.12) but a much higher Ni 0 percent (52% versus 30%). Zn-Ni-ZSM-5 shows closer intimacy between Zn and Ni species comparing to Zn-Ni/ZSM-5 and Ni/Zn-ZSM-5. For the 1-hexene aromatization, the formed iso -alkene at acid sites was quickly saturated to iso -alkanes by the adjacent Ni 0 particles over Ni-Zn-ZSM-5 catalyst in hydrogen steam. However, the location of aromatization active sites (ZnOH + , L acid sites) in micropores and hydrogenation active sites (Ni 0 species) on external surface of Ni/Zn-ZSM-5 makes the tandem conversion of n-alkene → iso -alkene → aromatics, rather than the n-alkene → iso -alkene → iso -alkane. Thus, Zn-Ni-ZSM-5 with close intimacy of ZnOH + and Ni 0 particles shows a high iso -alkane selectivity (27.9% iC 4 + ), while Ni/Zn-ZSM-5 exhibits a high aromatics selectivity (39.6 %) in the conversion of 1-hexene in hydrogen steam. Similar results have also found in the conversion of n-heptane. Here, the control of the intimacy of Zn and Ni in ZSM-5 zeolites has been realized to be a good protocol to adjust the selective conversion of olefins/alkanes to aromatics versus iso -alkanes.
研究领域:
催化化学
·
材料科学
✓ 已验证
产品关联
DOI
高影响因子
JOURNAL OF ORGANIC CHEMISTRY
·
2024
·
IF 3.3
Yan-Ling Liu,Xian-Chen He,Jie Gao,Ke-Rong Li,Kai Chen,Hao-Yue Xiang,Hua Yang
Herein, visible light-induced, nickel-catalyzed direct functionalization of the Hantzsch esters (HEs) with readily accessible alkyl bromides has been successfully achieved by taking advantage of HE as the reductant and substrate through an aromatization-dearomatization process. In this strategy, the single electron reduction of alkyl bromides by reactive Ni(I) species is essential for the success of this late-stage transformation. A wide range of 4-alkyl-1,4-dihydropyridines were rapidly assembled in moderate to good yields under mild conditions, rendering this photoinduced approach attractive for synthetic and medicinal chemistry.
研究领域:
有机化学
·
光化学
·
催化
·
合成方法学
·
药物化学
✓ 已验证
DOI
高影响因子
Catalysis Science & Technology
·
2019
·Vol. 10
·期 3
·835-843
·
IF 5.726
Yan Zhang,Shide Wu,Xia Xu,Heqing Jiang
Rapid deactivation by coke deposition is the main obstacle of ethane aromatization over Zn/ZSM-5. In this work, using the prepared nanosized Zn/HZSM-5, an almost threefold product yield and significantly improved stability were achieved in comparison with those of the microsized catalyst. XRD and XPS analyses indicated that a higher percentage of reactive [ZnOZn]2+ species was maintained during ethane aromatization over nano-Zn/HZSM-5 than micro-Zn/HZSM-5. In addition, the evolution of carbon deposits over nanosized and microsized Zn/ZSM-5 was investigated during prolonged ethane aromatization reaction using Raman spectroscopy and thermogravimetry measurements. Compared to the microsized catalyst, the nanosized zeolite facilitated the faster escape of light aromatics and the precursors of carbon deposits from the zeolite pores, thus suppressing the accumulation of coke deposits and improving the catalyst stability. Based on the nanosized Zn/HZSM-5, a protocol of isothermal reaction followed by regeneration was developed by periodically removing carbonaceous deposits, and an ∼25–35% product yield was achieved after 10 reaction–regeneration cycles.
研究领域:
催化化学
·
材料科学
✓ 已验证
DOI
高影响因子
Catalysts
·
2019
·Vol. 9
·期 11
·899
·
IF 3.444
Wei Xu,Lijing Gao,Guomin Xiao
Nano-sized HZSM-5 (n-HZSM-5) was synthesized and applied in the aromatization of glycerol. The effects of additives (carboxymethylcellulose sodium, NaCl, sodium alginate, etc.) on the chemical and physic properties of n-HZSM-5 during preparation were investigated. Metal modification was also investigated based on the synthesized n-HZSM-5. The results showed that the addition of carboxymethylcellulose sodium (CMC-Na), NaCl and sodium alginate (SA) led to forming smaller sizes of HZSM-5 and promoted the acid amounts of the catalysts, which increased its catalytic activities for obtaining BTX. The highest BTX yield of ~35% was obtained by SA derived n-HZSM-5, and the life of the catalyst were both obviously promoted by the additives with a highest of ~11 h by γ-(2,3-epoxypropoxy)propytrimethoxysilane (KH-560) derived n-HZSM-5. BTX yields could be improved by 40%by the addition of Zn and Cd in n-HZSM-5 while having little effect on the catalyst life.
研究领域:
催化化学
·
纳米材料科学
·
绿色化学
✓ 已验证
DOI
高影响因子
PETROLEUM SCIENCE AND TECHNOLOGY
·
2017
·
IF 0.655
Lanyu Xing,Zhenhao Wei,Zhenhao Wen,Xuedong Zhu
Hierarchical and conventional ZSM-5 zeolites were synthesized through steam-assisted crystallization approach using acid-treatment kaolin clay as the silica and aluminium sources. The samples were characterized by XRD, SEM, NH3-TPD, N2-physisorption and TG techniques. The results showed that hierarchical ZSM-5 had rich mesopores and bigger specific surface. In conversion of methanol to aromatics, hierarchical and conventional ZSM-5 zeolites showed higher selectivity for aromatics compared with commercial ZSM-5. Under the conditions of 450 °C, 0.15 MPa, the synthesized hierarchical ZSM-5 showed longest lifetime of 380 h, which was 2 and 6 times than those of conventional and commercial ZSM-5, respectively.
研究领域:
化学工程
·
材料科学
✓ 已验证
产品关联
DOI
高影响因子
FUEL PROCESSING TECHNOLOGY
·
2023
·
IF 7.5
Ke Li,Mengxia Yan,Haili Wang,Lifen Cai,Ping Wang,Huimin Chen
As a typical high-efficient alkane aromatization catalyst, Pt/KL is prone to deactivation due to the sintering growth of Pt on the outer surface of KL and the channel blockage caused by carbon deposition , which is further exacerbated by the one-dimensional channel structure of KL. Therefore, a series of encapsulated catalysts combining the three-dimensional channel structure advantages of S-1 with the role of potassium are prepared and evaluated. It is shown that the encapsulated catalyst KPt@S-1-02 modified by moderate potassium exhibits extremely superior stability and no significant deactivation is observable after n-heptane aromatization for 180 h under harsh conditions. On the one hand, encapsulation structure enables a strong anti-agglomeration ability of Pt and the topological structure of S-1 endows the encapsulation catalysts less susceptible to channel blockage, which has been demonstrated by HAADF-STEM and N 2 -adsorption. On the other hand, characterizations involving NH 3 -TPD, CO-DRIFT and HAADF-STEM verify that the modification by an appropriate amount of K can inhibit acid sites of catalysts and improve Pt dispersion and electron density, thus enhance the stability of catalysts. However, excessive K can serve as weak acid sites, poison of active sites and inhibitor of H 2 adsorption on Pt surface, leading to deactivation of the catalyst.
研究领域:
催化化学
·
材料科学
✓ 已验证
产品关联
DOI
高影响因子
Journal of Energy Chemistry
·
2025
·
IF 14.9
Wenjun Chen,Yiyi Fan,Yue Liu,Xiaobin Xie,Fan Zhang
Converting waste plastics directly into valuable aromatic chemicals is a promising, cost-effective recycling strategy. Traditional zeolite-catalyzed cracking of polyolefins to produce aromatics often needs high temperatures and faces issues like low selectivity for liquid aromatics, separation difficulties, and rapid catalyst deactivation due to coking. To address this, a multifunctional Ni/HZSM-5 catalyst was developed to efficiently upgrade various polyolefins—including polyvinyl chloride—into gaseous alkanes (C 1 –C 5 ) and easily separable liquid aromatics (C 6 –C 12 ) at 400 °C, without added solvents or hydrogen. Aromatic products make up 57.1 wt% of total output, with more than 97.8% selectivity for the liquid phase and a BTX (benzene, toluene, and xylene) selectivity of 76.1%. The high activity and selectivity for aromatics stem from synergistic interactions between Ni nanoparticles (NPs) and acid sites in the zeolite, which promote selective C–C bond breaking and control hydrogenolysis and aromatization pathways. This synergy allows precise control over the distribution of products by carbon number and favors the formation of separable aromatics. Notably, the catalyst also prevents coking by hydrogenolyzing and hydrogenating reactive intermediates before they form stable graphite-like deposits. Consequently, Ni/ZSM-5 catalyst demonstrates excellent stability, maintaining consistent aromatics yield over 13 consecutive cycles and processing over 30 times its weight in plastics without regeneration. After regeneration, the activity of the catalyst was fully restored, highlighting its potential for industrial use. This work offers valuable insights for designing durable, high-activity catalysts, providing a practical route to improve plastic recycling technologies.
研究领域:
催化化学
·
化学回收
·
高分子化学
·
材料科学
·
环境科学
·
石油化学
✓ 已验证
产品关联
DOI
高影响因子
Advances in Materials Science and Engineering
·
2022
·Vol. 2022
·期 1
·7408284
·
IF 2.098
Zhenhao Wei,Yufan Ji,Yiping Huang,Jingjing Huang,Yunguo Huang,Changhai Yue,Junzhou Li,Mingwei Tang,Yunfang Liu,Hanfei Liu,Hao Zhu,Kai Zhu,Fan Yang,Xuedong Zhu
Zinc (Zn) and cerium (Ce) modified hierarchical ZSM-5 (HZ) catalysts were prepared by incipient wetness impregnation, and their catalytic performances in methanol to aromatics reaction were evaluated in a fixed-bed reactor operating at 400°C under 0.1 MPa and WHSV of 1.0 h −1 . The structure, acidity, and state of Zn species of the Zn/Ce modified HZ catalysts were investigated via several characterization techniques, including XRD, NH 3 -TPD, H 2 -TPR, nitrogen adsorption, and XPS. The results showed that the aromatization activity of 2 wt% Zn-modified HZ (2% Zn/HZ) could be significantly enhanced by loading 0.6 wt% Ce, which was mainly attributed to the increase in surface ZnOH + species. Moreover, it was found that Ce inhibited pore blockage caused by Zn. Consequently, compared to 2% Zn/HZ, 2% Zn-0.6% Ce/HZ exhibited higher aromatic selectivity and longer catalyst lifetime.
研究领域:
催化化学
·
材料科学
✓ 已验证
DOI
高影响因子
危险品化学品经营许可证（带存储）