FUEL
·
2023
·
IF 7.4
Xin Guo,Zhiyong Ding,Na Kang,Liu Yang,Yuanjiang Wang,Cheng Zhang,Zhaoqiang Li,Tiantian Zhang,Yan Wang,Yu Wang,Hao Qu
The zeolite-based catalyst is a promising option for the selective catalytic reduction (SCR) of nitrogen oxides (NO x ) due to its low toxicity. However, the challenge lies in its low-temperature activity. This study developed a multi-component catalytic system consisting of Ce/Mn/Cu-loaded Beta zeolite to reduce NO x . With fixed contents of Cu and Mn, we investigated the NH 3 -SCR process and the mechanism of action of the rare-earth species (i.e., Ce) in the system. Upon optimization of the content of Ce, the Ce/Mn/Cu-loaded Beta zeolite demonstrated enhanced low-temperature activity compared to samples loaded with Cu or Cu/Mn in the temperature range of 150–250 °C. When Ce was loaded in an appropriate proportion, it regulated the oxidation state of Cu, optimizing active adsorption species for NO and strengthening the strength of Brønsted acid sites in the catalyst. These synergetic effects led to improved NH 3 -SCR catalytic performance. This study can contribute to a better understanding of multiple metal-loaded zeolites in the NH 3 -SCR process and inform future design of Beta-type catalysts.
研究领域:
催化化学
·
环境科学
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产品关联
DOI
高影响因子
APPLIED CATALYSIS A-GENERAL
·
2021
·
IF 5.706
Juan Ye,Chenyu Chen,Ying Zheng,Dan Zhou,Yunzhen Liu,Denglong Chen,Liufang Ni,Gang Xu,Fanan Wang
The selective one-pot synthesis of lactic acid (LA) from cellulose, and further the raw biomass, on heterogeneous catalysts is the key point for the development of biorefinery technology. Herein, we reported an yttrium (Y) modified siliceous Beta zeolites catalyst via two-step post-synthesis for highly efficient conversion of cellulose to LA. Under condition of 220 °C and 2 MPa N 2 , the cellulose could be transformed to LA with a yield of 49.2 % within 30 min, and the substrate can be extended to various raw biomass. It was demonstrated that the dealumination and modification of Y can efficiently modulate the acidity on the surface of zeolite. The dehydration products HMF and other derivatives were suppressed, and the yield of LA was correlated in line with the acid amount, which were attributed to the increased Lewis acidity originated by Y incorporation. These results contribute to the development of the green and efficient synthesis of bio-chemicals.
研究领域:
生物化学
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催化化学
·
可再生资源
✓ 已验证
DOI
高影响因子
MATERIALS CHEMISTRY AND PHYSICS
·
2022
·
IF 4.778
Xiaomei Yang,Xu Chen,Bin Lv,Yunlai Su,Lipeng Zhou
Sn-Beta zeolite is an excellent catalyst for the transformation of biomass derived carbohydrates. However, the long synthesis time restricted its application. Here, alkaline (earth) salt was used as promoter to accelerate the crystallization of Sn-Beta. Different alkaline (earth) salts and the amount of MgCl 2 were investigated. The properties of the synthesized samples were characterized by various techniques and compared with Sn-Beta, and the catalytic performance was investigated for the conversion of glucose to methyl lactate (MLA). The results indicate that a small amount of alkaline (earth) salt, especially MgCl 2 , promoted dramatically the crystallization of Sn-Beta. The full crystallization time was shortened from 15 d to 5 d with the aid of MgCl 2 ( n Mg / n Sn of 1.0) for Sn-Beta with n Si / n Sn of 100. Sn 4+ cations were incorporated into the framework sites, while Mg 2+ cations replaced the protons of silanol defects. Mg–Sn-Beta with strong Lewis acid sites and less silanols showed high activity and selectivity for glucose conversion to MLA. The yield of MLA is 20% over the fully crystallized Sn-Beta at 120 °C for 15 h and glucose concentration of 3.1 wt%, which increased significantly to 44% over the fully crystallized 1 Mg–Sn-Beta. Furthermore, Mg–Sn-Beta is stable and recyclable.
研究领域:
催化化学
·
生物质转化
✓ 已验证
DOI
高影响因子
Catalysis Science & Technology
·
2021
·Vol. 12
·期 2
·652-663
·
IF 6.119
Chuanyu Yang,Zhongwen Dong,Weifeng Chu,Yanan Wang,Dongpu Zhao,Fucun Chen,Wenjie Xin,Xiangxue Zhu,Shenglin Liu,Longya Xu
A series of beta zeolite catalysts with controllable particle sizes and similar Si/Al ratios were prepared by introducing imidazole (IMD) into the synthesis system and used for liquid-phase transalkylation of diethylbenzene (DEB) with benzene (Bz). The beta zeolite catalyst prepared with an IMD/SiO2 molar ratio of 0.5 possessed the smallest particle size (mean particle size of 119 nm) and the highest DEB conversion of 79.16% under the reaction conditions: 260 °C, 4.0 MPa, WHSV (diethylbenzene) of 2.0 h−1, W(benzene)/W(diethylbenzene) of 3/1, time on stream of 5 h. Then, to elucidate the catalytic roles of acid sites with different strengths, types and positions in beta zeolite in the transalkylation reaction, we carried out Na+ loading on the prepared beta zeolite to eliminate strong acid sites and poisoned the Brønsted acid sites and external acid sites by using 2,4-dimethylquinoline (2,4-DMQ) and triphenylphosphorus (TPP) as toxic reagents, respectively. The results suggested that the moderate and strong Brønsted acid sites of beta-IMD0.5 were the active sites for the liquid-phase transalkylation of DEB with Bz and their utilization rate showed a trend of increasing first and then decreasing. Significantly, 31% of the external Brønsted acid sites of beta-IMD0.5 contributed 81% of DEB conversion. The external acid sites had more contribution to the reaction due to the short diffusion path and fine accessibility.
研究领域:
催化化学
·
材料科学
✓ 已验证
DOI
高影响因子
APPLIED CATALYSIS A-GENERAL
·
2019
·
IF 4.63
Meng Xia,Zheng Shen,Shaoze Xiao,Bo-yu Peng,Minyan Gu,Wenjie Dong,Yalei Zhang
The direct catalytic transformation of raw lignocellulosic biomass into valuable chemicals is of great significance for sustainable production. This work reports the combination of a transition metal chromium with tin in Beta zeolites to efficiently catalyse the conversion of Miscanthus into lactic acid with a yield of 33.4% and a selectivity of 53.2%. On the basis of experiment and kinetic studies , chromium and tin were beneficial for the retro-aldol condensation and isomerization of carbohydrates, respectively. The acidity of the catalyst was investigated based on important insight into the synergetic catalytic mechanism. The strong Lewis acidity possessed by the transition metals was remarkably advantageous for catalysing the retro-aldol fragmentation reaction, while the relatively weak Lewis acidity of the tin species was considered a dominant factor in the isomerization reaction. The coupling of multifunctional active sites provided a new director for the transformation towards lactic acid formation.
研究领域:
催化化学
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可再生资源转化
✓ 已验证
产品关联
DOI
高影响因子
COLLOIDS AND SURFACES A-PHYSICOCHEMICAL AND ENGINEERING ASPECTS
·
2024
·
IF 4.9
Weimin Zhang,Wenming Hao,Yanni Guo,Jinghong Ma,Ruifeng Li
Even though cetyltrimethylammonium bromide (CTAB) has been successfully used in the surfactant-templating system to create the mesostructured zeolites , the formation mechanism of the pore structure still remains elusive. Here, we investigated the sol-gel and structure evolution in the hierarchical zeolite Beta synthesis focusing on the role of CTAB in a dual templating system. It is found that the induction period was prolonged and the Ostwald ripening was retarded by the presence of CTAB in crystallization . CTAB was involved in the synthesis and incorporated within the solid phase at the first stage when mesopores were formed. However, the incorporated CTAB was released later into the solution when the crystallized microporous structure was developed. The thermogravimetric analysis revealed that CTA + cation worked both as structure directing agent (SDA) for micropores and mesoporogen for the secondary lager pores in the matrix of hierarchical zeolite Beta. Moreover, CTA + competed with tetraethylammonium cation (TEA + ) to work as the SDA for micropores, with a decrease of the total amount of CTA + and TEA + when the concentration of CTAB in the synthesis solution was increased. It is anticipated that the understanding of the role of CTAB in the sol-gel and structure evolution in the hierarchical zeolite Beta synthesis process can provide a basis for designing the synthesis of hierarchical zeolites.
研究领域:
化学工程
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材料科学
✓ 已验证
产品关联
DOI
高影响因子
APPLIED CATALYSIS B-ENVIRONMENTAL
·
2018
·
IF 11.698
Yueqing Wang,Guoqiang Ding,Xiaohai Yang,Hongyan Zheng,Yulei Zhu,Yongwang Li
The selective synthesis of furfural or hydroxymethylfurfural (HMF) from fructose on single catalyst (Beta zeolite, Hβ) is challenging task. However, in this study, selectivity of Hβ zeolite was discovered easily to tune by solvent effects. Strong solvent effects on the selectivity of fructose conversion were observed in different manners depending on the solvent used. It was shown that the coordinated state of framework aluminum, induced by solvent effects, has a major impact on the selectivity. The solvents with amide group were discovered to induce the reversible tetrahedral-octahedral framework aluminum transformation, but the configuration of aluminum was no influenced by other solvents such as γ-butyrolactone (GBL). Compared with other solvents, the GBL was not able to enhance turnover frequency (TOF) value of reaction but also suppress the degradation of furfural. Interestingly, a considerable yield of furfural (50.25%) was obtained combined with tetrahedral and octahedral framework aluminum active sites in GBL, while high selectivity of HMF (83.3%) was achieved in presence of single tetrahedral framework aluminum over Hβ in NMP.
研究领域:
催化化学
·
绿色化学
✓ 已验证
产品关联
DOI
高影响因子
CHEMICAL ENGINEERING JOURNAL
·
2025
·
IF 13.2
Yu Wang,Hang Zhang,Dingmei Han,Meiyu Liu,Binbin He,Yun Zu
Cobalt (Co)-based zeolite catalysts are promising alternatives to replace expensive Pt- and toxic Cr-based catalysts for direct propane dehydrogenation (PDH). However, identifying the interaction between Co species and surface Si-hydroxyls of siliceous zeolites has been an inevitable challenge to realize the controllable construction of the Co species as dehydrogenation sites. Herein, we have fabricated a series of Co/Si-Beta(m-n) catalysts by using the dealuminated Si-Beta zeolites with “on-purpose” quantifying different type of Si-hydroxyls, involving geminal silanols ( g -SiOH), vicinal silanols ( v -SiOH) and silanol nests ( n -SiOH). In comparison to ultra-small CoO x nanoparticles (< 1.0 nm) directly trapped by the n -SiOH structure, a moderate interaction was built between tetrahedrally-coordinated divalent CoO x nanoparticles (∼4.5 nm) and external n -SiOH structure, resulting from partial migration and aggregation of initial CoO x species preferentially captured with g -/ v -SiOH structures during H 2 reduction. Given this, a representative Co/Si-Beta(500–12) catalyst exhibited a high catalyst productivity of 29.22 mol/g-catalyst (the product of initial reaction rate and the inverse of deactivation coefficient) with about 96 % propylene selectivity. In-situ FTIR spectra further revealed that such superior PDH performance was attributable to the moderately interaction of defined Si-O-Co structure that could be conducive to form the 2-propyl intermediate product, supporting the production of propylene and H 2 . These findings provide a novel inspiration for the development and optimization of low-cost, ecofriendly and advanced PDH catalysts.
研究领域:
催化化学
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材料科学
✓ 已验证
产品关联
DOI
高影响因子
JOURNAL OF CHEMICAL TECHNOLOGY AND BIOTECHNOLOGY
·
2021
·Vol. 96
·期 8
·2238-2248
·
IF 3.174
Xiao-Yang Yue,Hui-Fang Ren,Chengming Wu,Jun Xu,Jifan Li,Chun-Ling Liu,Wen-Sheng Dong
BACKGROUND Methyl lactate is widely applied in the chemical, food, cosmetics and pharmaceutical industries. The conversion of carbohydrates over heterogeneous catalysts to methyl lactate is a promising environmentally benign process. RESULTS Hierarchical Sn-Beta zeolite (Sn-Beta) and corresponding bimetal-doped Beta zeolites (M-Sn-Beta; M = Zn, In, La, Ga, Ni) were prepared via a novel modified hydrothermal synthesis method to convert carbohydrates into methyl lactate. The introduction of Zn into Sn-Beta considerably improved the yield of methyl lactate from glucose, while for the catalysts containing In, La, Ga and Ni, such improvements were not observed. CONCLUSIONS A methyl lactate yield reaching up to 66.7% was obtained over Zn-Sn-Beta at 220 °C for 6 h. The enhanced catalytic performance was attributed to high Lewis acid density and strength, together with synergistic effects between framework Sn 4+ and Zn 2+ ions of Zn-Sn-Beta. Additionally, Zn-Sn-Beta demonstrated fructose and sucrose conversion into methyl lactate with yields of 68.4% and 70.0%, respectively. The Zn-Sn-Beta catalyst could be re-used at least five times with only a slight loss of methyl lactate yield. © 2021 Society of Chemical Industry (SCI).
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
ACS Sustainable Chemistry & Engineering
·
2021
·
IF 8.198
Qiang Yu,Yonghua Guo,Xiaoxia Wu,Zijun Yang,Hua Wang,Qingfeng Ge,Xinli Zhu
Ketonization reactions provide a feasible approach to remove oxygen and increase carbon chain length for conversion of biomass derived carboxylic acids. However, the reaction suffers from fast catalyst deactivation and low ketone selectivity. In this work, Lewis acidic heteroatom Ti-, Zr-, Ce-, and Sn-Beta zeolites were prepared using a two-step post-synthesis method and applied in vapor phase ketonization of propionic acid at 350 °C. Among these zeolites, Zr-Beta shows both the highest activity and selectivity. Characterizations indicate that Zr prefers the vacant tetrahedral site when the Zr content is < 7%, corresponding to the maximal fraction of vacant sites produced from dealumination of the parent H-Beta with a Si/Al ratio of 19. Extraframework Zr may also form at a Zr content ≥ 7%. The tetrahedrally coordinated framework Zr species (mainly in the structure of open sites) show Lewis acidic characteristic, and their density can be linearly correlated with the ketonization activity, indicating that these sites are active sites for ketonization. In contrast to rapid deactivation of H-Beta, the 7% Zr-Beta is stable for ketonization over 60 h, maintaining a conversion of ∼50% and a 3-pentanone selectivity > 96% at a space time of 2 h. The amount of coke deposition on Zr-Beta is about 1/3 of that on H-Beta, and the structure of Zr-Beta is preserved after 60 h of reaction. The results of this work indicate that Zr-Beta zeolite is a promising catalyst for ketonization with good stability and high selectivity toward ketone.
研究领域:
催化化学
·
生物质能
·
材料科学
✓ 已验证
产品关联
DOI
高影响因子
CELLULOSE
·
2019
·Vol. 26
·期 17
·9135-9147
·
IF 3.917
Zhou Shengqiang,Yang Xiaomei,Zhang Yali,Jiang Lingyun,Zhou Lipeng,Lu Tianliang,Su Yunlai
Abstract One-pot conversion of cellulose to valued-added platform chemicals such as alkyl levulinate is a promising and challenging process of biomass utilization due to the insolubility of cellulose in alcohol. In this work, commercial heteropoly acid combined with postsynthesized Sn-Beta zeolite was employed to transform cellulose to methyl levulinate (MLE) in one pot. The synergistic catalysis of the homogeneous strong Brønsted (B) acid and the solid strong Lewis (L) acid can effectively realize the depolymerization of solid cellulose and the subsequent isomerization, dehydration and hydration steps to MLE. 55% and 62% of MLE yields were obtained from α-cellulose and microcrystalline cellulose, respectively, at 160 °C for 10 h. Various carbohydrates besides cellulose can also be efficiently converted to MLE in high yields over the bifunctional catalyst system. The effects of the amount of B acid and L acid, the reaction temperature and time and the amount of cellulose on the production of MLE were investigated in detail. Finally, the reaction pathway of cellulose to MLE was revealed. Recyclability tests indicated that the binary catalyst can be reused without decrease of catalytic activity. Graphic abstract
研究领域:
生物质化学
·
催化化学
✓ 已验证
产品关联
DOI
高影响因子
Crystals
·
2018
·Vol. 8
·期 2
·73
·
IF 2.144
Yucun Cui,Zheng Yan,Mengli Li,Jie Zhu,Longfeng Zhu,Hong Yao,Xuebo Cao
We report a solvent-free synthesis of all silica Beta zeolite using a cheap organic template of tetraethylammonium bromide (TEABr). The method includes mixing, grinding and heating solid raw material in the absence of water solvent but the presence of zeolite seeds. The absence of water solvent significantly improves the efficiency of synthesis, while the addition of seeds remarkably enhances the crystallization rate. In addition, the use of a cheap organic template of TEABr greatly decreases the synthesis cost. The effects of the reaction compositions, including the molar ratios of NH4F/SiO2, TEABr/SiO2, and mass ratios of seeds to the silica, on the synthesis of the pure product were investigated using different temperature. Physicochemical characterizations, including XRD, SEM, TG and N2sorption, show that the zeolitic product has good crystallinity, uniform crystals, and high surface area.Keywords:zeolite;all silica Beta;solvent-free synthesis;tetraethylammonium bromide;cheap
研究领域:
材料科学
·
化学工程
✓ 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）