CATALYSIS TODAY
·
2016
·
IF 4.312
Xuesong Liu,Xiaodong Wu,Duan Weng,Zhichun Si,Rui Ran
Cu-modified SAPO-34 molecular sieves with different Cu loading amounts were prepared by ion-exchange and impregnation methods. Both series of catalysts were hydrothermally treated at 750 °C in 10 vol% H 2 O/air for 24 h. The catalysts were characterized by inductively coupled plasma optical emission spectrometry (ICP-OES), electron paramagnetic resonance (EPR), X-ray photoelectron spectroscopy (XPS), H 2 temperature-programmed reduction (H 2 -TPR), NH 3 temperature-programmed desorption (NH 3 -TPD) and diffused reflectance infrared flourier transform spectroscopy (DRIFTS). All the fresh catalysts show high activity toward the selective catalytic reduction of NO x with NH 3 (NH 3 -SCR) at low temperatures regardless of preparation method. Generally, the hydrothermal aging shifts the operation window of the catalysts towards high temperatures. The improvement in high-temperatures activity is attributed to the migration of surface CuO clusters into the ion-exchanged sites as isolated Cu 2+ during ageing, which suppresses the competitive oxidation of NH 3 . The loss of low-temperatures activity is also related to the decrease in the amount of active surface CuO clusters, inhibiting the oxidation of NO to NO 2 and fast SCR reaction. Interestingly, the amount of Lewis acid sites increase linearly with the increasing isolated Cu 2+ , while the Brønsted acidity is weakened.
研究领域:
催化化学
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环境科学
✓ 已验证
DOI
高影响因子
MICROPOROUS AND MESOPOROUS MATERIALS
·
2020
·
IF 4.551
Chao Sun,Aijuan Zhao,Yaquan Wang,Ziyang Wang,Jingjing Zhao,Taotao Zhao,Wenrong Liu,Mingxue Shi,Jiaxin Lu,Shuhui Wu,Lingzhen Bu
Hierarchical SAPO-34 aggregates were hydrothermally synthesized with the assistance of organosilane N-[3-(Trimethoxysilyl)propyl]ethylenediamine (TPED), during which the morpholine was used as the template. The resultant products were characterized by XRD , SEM, ICP-OES, NH 3 -TPD, N 2 adsorption-desorption and TGA , and a possible formation mechanism was proposed. As the amount of added TPED varies, the morphologies, compositions and acid properties of the resultant hierarchical SAPO-34 aggregates differ. The hierarchical SAPO-34 aggregates possessed higher external surface areas, lower Si content, weaker strength and lower concentration in the strong acid sites than the conventional SAPO-34. The investigation of formation process showed that the addition of the TPED had a pivotal role for the formation of hierarchical SAPO-34 aggregates. Compared to conventional SAPO-34, the hierarchical SAPO-34 aggregates exhibited a significant improvement in methanol to olefin reaction (MTO) reactions due to their hierarchical structure and mild acid properties.
研究领域:
材料科学
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催化化学
✓ 已验证
产品关联
DOI
高影响因子
Inorganic Chemistry Frontiers
·
2023
·Vol. 10
·期 13
·3874-3883
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IF 7
Xiaosi Zhang,Miao Yang,Ye Wang,Caiyi Lou,Shutao Xu,Peng Tian,Zhongmin Liu
Seed-assisted synthesis shows great potential to modify the properties of inorganic microporous materials and enhance synthetic efficiency. However, the understanding of the related mechanism is insufficient, especially in silicoaluminophosphate (SAPO) molecular sieve systems. In this work, the seed-assisted synthesis of SAPO-34, an important industrial methanol-to-olefins (MTO) catalyst with CHA topology, was investigated by using various seeds with different structures, compositions and morphologies. It reveals that both double 6-ring (d6r) units and complex Si environments are key features for a highly effective SAPO seed, which may provide small fragments containing complete or broken d6r units with Si–O–Al domains after the dissolution of seeds and thus derive the nucleation and crystallization of SAPO-34. Moreover, small crystal size and high Si content are positive factors for a qualified SAPO seed. Heteronuclear seeds, such as SAPO-18, SAPO-35 and SAPO-56, have been found to be effective for the synthesis of SAPO-34 with improved MTO catalytic performance. For SAPO materials without d6r units, their effect strongly depends on the growth solution and there is no preferential phase selectivity for SAPO-34. These findings could prompt the efficient synthesis and property control of SAPO molecular sieves.
研究领域:
材料科学
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催化化学
✓ 已验证
DOI
高影响因子
Catalysts
·
2018
·Vol. 9
·期 1
·16
·
IF 3.465
Yuehong Yu,Jiaxiang Qin,Min Xiao,Shuanjin Wang,Dongmei Han,Yuezhong Meng
Introducing mesopores into the channels and cages of conventional micropores CHA (Chabazite) topological structure SAPO-34 molecular sieves can effectively improve mass transport, retard coke deposition rate and enhance the catalytic performance for methanol to olefins (MTO) reaction, especially lifetime and olefins selectivity. In order to overcome the intrinsic diffusion limitation, a novel CO2-based polyurea copolymer with affluent amine group, ether segment and carbonyl group has been firstly applied to the synthesis of SAPO-34 zeolite under hydrothermal conditions. The as-synthesized micro-mesoporosity SAPO-34 molecular sieve catalysts show heterogeneous size distribution mesopores and exhibit slightly decrease of BET surface area due to the formation of defects and voids. Meanwhile, the catalysts exhibit superior catalytic performance in the MTO reaction with more than twice prolonged catalytic lifespan and improvement of selectivity for light olefins compared with conventional microporous SAPO-34. The methodology provides a new way to synthesize and control the structure of SAPO-34 catalysts.Keywords:molecular sieves;SAPO-34;MTO;CO2-based polyuria;mesoporogen
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
FUEL
·
2022
·
IF 8.035
Xiaohe Wang,Hongwei Chen,Maosheng Zhang,Chaoran Wang,Yufei Wang,Pu Bai,Libo Li,Wenfu Yan
Silicoaluminophosphate (SAPO) zeolites as one of the most important members of zeolitic materials, providing equally high adsorption capacity of CO 2 as aluminosilicate zeolites, can be used as promising candidate materials for selective adsorption and separation of CO 2 . In this work, desirable from both economic and environmental viewpoints, a green and cost-effective one step synthesis strategy of K-SAPO-34 zeolite was developed in a wholly inorganic system under hydrothermal conditions. The pure K-SAPO-34 crystals can be obtained in a wide range of initial gel compositions. The as-synthesized K-SAPO-34 has high proportion of framework Si (Si / (Si + Al + P) = 0.37) and framework charge density ((Al – P) / (Si + Al + P) = 0.36). Because the presence of silica islands in K-SAPO-34 framework leads to a decrease in the number of extra framework cations per unit cell, the K-SAPO-34 in this work has a high CO 2 adsorption capacity (64.1 cm 3 /g) than the conventional K-SAPO-34 prepared by ion-exchange (1.9 cm 3 /g). Moreover, the K-SAPO-34 in this work has a superior separation performance for CO 2 /N 2 and CO 2 /CH 4 .
研究领域:
材料科学
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环境科学
✓ 已验证
DOI
高影响因子
SEPARATION AND PURIFICATION TECHNOLOGY
·
2024
·
IF 8.1
Ying Wang,Fei Liu,Mengqin Yao,Jun Ma,Shuo Geng,Jianxin Cao,Xiaodan Wang
Promoting the efficient formation of methanol intermediates during CO 2 hydrogenation to lower olefins plays a decisive role in improving the catalytic performance of a tandem catalyst. In this study, a series of chromium (Cr)-modified gallium–zirconium oxides with the formula GaCrZrO x (y%) were prepared via the sol–gel method. The characterization and experimental results show that the addition of moderate amounts of Cr not only facilitates the formation of more oxygen vacancies on the surface of GaZrO x but also strengthens the adsorption and activation ability of CO 2 and H 2 , thereby promoting the generation of formate and methoxy intermediates. After coupling with SAPO-34 zeolite, the methanol intermediate produced on GaCrZrO x (y%) is rapidly converted into lower olefins. This integration manner oxide and zeolite catalysts is particularly important for catalytic performance because an appropriate affinity between components can induce the formation of methanol intermediates via the kinetic effect, which limits the reverse water–gas shift reaction at high temperature. The GaCrZrO x (3.0 %)/SAPO-34 tandem catalyst synthesized via grinding and mixing at 390 °C and 3 MPa exhibits remarkable stability and catalytic performance, achieving a CO 2 conversion close to 30 %, a lower olefin selectivity of 85.8 %, and a lower olefin yield of 11.7 %.
研究领域:
催化化学
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材料科学
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环境科学
✓ 已验证
产品关联
DOI
高影响因子
MICROPOROUS AND MESOPOROUS MATERIALS
·
2025
·
IF 4.7
Weijiong Dai,Zongqiang Liu,Jing Zhao,Yan Wang,Jiajun Zheng,Ruifeng Li
SAPO-34 zeolites with excellent selectivity towards to light olefins and highly catalytic stability are highly desirable. In this work, SAPO-34 zeolite (SAPO-34-S-F) featuring both significantly reduced crystal dimension and a hierarchical structure was synthesized for the first time through a seed-assisted strategy employing cost-effective triethylamine (TEA) as the only organic structure-directing agent (OSDA) in the NH 4 F-containing medium. The resulting SAPO-34 zeolite demonstrated exceptional catalytic performance in methanol-to-olefin (MTO) reaction, exhibiting a substantially increased catalytic lifetime of 525 min as well as an impressive light olefin selectivity of up to 83.7 %. These results significantly outperform those of conventional SAPO-34 zeolite with larger crystal dimension synthesized using TEA as OSDA, and SAPO-34 zeolite with similar crystal dimension synthesized without fluoride addition. Thermogravimetric analysis (TGA) of the spent catalysts revealed that SAPO-34-S-F possesses enhanced coke tolerance. Furthermore, in situ UV/Vis studies of the organic intermediates generated on zeolites during MTO reaction provided additional evidence for the excellent catalytic activity and stability of the SAPO-34-S-F sample. These findings offer important insights for the rational development of stable and high-efficiency SAPO-34 zeolite for MTO reaction.
研究领域:
材料科学
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催化化学
·
能源化工
✓ 已验证
产品关联
DOI
高影响因子
CATALYSIS LETTERS
·
2024
·
IF 2.3
Li Shengpeng,Cheng Shimin,Yuan Long,Tan Guangyu,Cheng Ying,Li Li,Li Yichen,Wang Chuang
In this study, nano-sheet SAPO-34 molecular sieves were synthesized using an aminothermal method. Triethylamine (TEA) was used as the major solvent and template, along with varying amounts of tetraethylammonium hydroxide (TEAOH). Physicochemical properties of the synthesized catalysts were characterized by techniques of XRD, SEM, BET, XRF, and NH 3 -TPD. As the amount of TEAOH increases, the composition of the product changes from a mixture of SAPO-5 and SAPO-34 to pure nano-sheet SAPO-34 molecular sieves. A TEAOH increment causes a reduction in crystallinity and particle size, as well as an increase in acid sites. Additionally, there is a non-linear relationship between the silicon content in molecular sieves and the amount of TEAOH added in the system. In the conversion of methanol to olefins using various SAPO-34 catalysts, the nano-sheet samples with the highest crystallinity and moderate acidity exhibited the longest lifetime and higher selectivity to C 2 = + C 3 = olefins. Graphical Abstract
研究领域:
材料科学
·
催化化学
✓ 已验证
产品关联
DOI
高影响因子
EUROPEAN JOURNAL OF INORGANIC CHEMISTRY
·
2019
·Vol. 2020
·期 3
·318-326
·
IF 2.578
Mingjian Luo,Mingxu Liu,Yadong Fu,Wenxin Chen,Baohui Wang,Guoliang Mao
Graphical Three-stage SAPO-34s have higher purity, smaller crystal size, more acidic sites, longer catalytic lifetime and better olefin selectivity. The crystallization mechanism and the relationship between properties and performance are discussed. Acidity and 2–4 nm mesopores have little effect on MTO performance, which mainly depends on the size and dispersity of the crystallites and the purity of SAPO-34. SAPO-34 zeolites were synthesized by one-, two-, and three-stage crystallization processes with fumed silica (FS), acidic silica sol (AS), basic silica sol (BS) and tetraethoxysilane (TEOS) as silicon sources. Properties of samples were characterized by XRD, SEM, EDX, N 2 -adsorption/desorption, NH 3 -TPD and 29 Si NMR. In contrast with one- and two-stage processes, the three-stage one favors the formation of SAPO-34s with higher purity, higher Si/Al ratio, smaller crystallite/crystal size, better dispersion and more acidic sites. Crystallization mechanism was proposed. It is supposed that three-stage process favors the formation of high supersaturated SBUs (secondary building units) and CBUs (composite building units) before nucleation. Thus massive nuclei are formed during nucleation and well-dispersed small size SAPO-34 crystals are formed in three-stage process. Three-stage SAPO-34s are longer catalytic lifetime and better olefin selectivity in MTO process. TEOS-3 has the best MTO performance. It was found that acidity of sample and mesopores in 2–4 nm range have little effect on the MTO performance of SAPO-34. Catalytic lifetime and olefin selectivity are mainly depending on the size of crystallites, the dispersity of crystallites, and the purity of SAPO-34.
研究领域:
材料科学
·
催化化学
✓ 已验证
产品关联
DOI
高影响因子
RSC Advances
·
2017
·Vol. 7
·期 60
·37787-37796
·
IF 3.108
Xuesong Liu,Xiaodong Wu,Duan Weng,Zhichun Si,Rui Ran
Cu/SAPO-34 catalysts were prepared by wet impregnation and ion-exchange methods, and both the catalysts were hydrothermally treated at 750 °C in 10 vol% H2O/air for 24 h. Subsequently, the as-received and hydrothermally treated catalysts were exposed to a sulfur poisoning treatment at 350 °C in 100 ppm SO2/10 vol% H2O/air for 24 h and examined for NOx conversion. Sulfur poisoning considerably decreased the NOx conversion efficiency of the catalysts at low temperatures. In contrast, it improved the high-temperature selective catalytic reduction (SCR) activities of the as-received catalysts. The ion-exchange-prepared catalysts displayed higher sulfur tolerance than the impregnation-prepared catalysts at 150–350 °C. The electron paramagnetic resonance, X-ray photoelectron spectroscopy, energy-dispersive X-ray spectroscopy and H2-temperature-programmed reduction results showed that sulfur poisoning significantly influenced the migration of the copper species and thereby the amount of active isolated Cu2+. More dispersed CuSO4 was produced on the ion-exchange-prepared catalysts than on the impregnation-prepared catalysts after sulfur poisoning. The dispersed CuSO4 showed considerably higher SCR activity than the crystalline CuSO4. Both the dispersed CuSO4 and remaining isolated Cu2+ determined the low-temperature SCR behavior of the sulfur-poisoned catalysts.
研究领域:
催化化学
·
环境科学
✓ 已验证
DOI
高影响因子
APPLIED SURFACE SCIENCE
·
2017
·
IF 3.387
Leiqing Hu,Jun Cheng,Yannan Li,Jianzhong Liu,Li Zhang,Junhu Zhou,Kefa Cen
Mixed matrix membranes with ionic liquids and molecular sieve particles had high CO 2 permeabilities, but CO 2 separation from small gas molecules such as H 2 was dissatisfied because of bad interfacial interaction between ionic liquid and molecular sieve particles. To solve that, amine groups were introduced to modify surface of molecular sieve particles before loading with ionic liquid. SAPO 34 was adopted as the original filler, and four mixed matrix membranes with different fillers were prepared on the outer surface of ceramic hollow fibers. Both surface voids and hard agglomerations disappeared, and the surface became smooth after SAPO 34 was modified by amine groups and ionic liquid [P 66614 ][2-Op]. Mixed matrix membranes with composites of amine-modified SAPO 34 and ionic liquid exhibited excellent CO 2 permeability (408.9 Barrers) and CO 2 /H 2 selectivity (22.1).
研究领域:
材料科学
·
环境工程
✓ 已验证
产品关联
DOI
高影响因子
Green Energy & Environment
·
2019
·
IF 0
Ge Li,Baodong Wang,Qi Sun,Wayne Qiang Xu,Ziran Ma,Hongyan Wang,Daojun Zhang,Jiali Zhou
A combined acid–alkali hydrothermal method was used to prepare fly ash –derived SAPO-34 molecular sieves from a thermal power plant in Inner Mongolia (China). The specific surface area of the prepared fly-ash-derived SAPO-34 molecular sieves was 579 m 2 g −1 , the total pore volume was about 0.27 cm 3 g −1 , and the pore size was 0.56 nm; the molar ratios of Al 2 O 3 :P 2 O 5 :SiO 2 were 1:0.86:0.45. Cu/SAPO-34 catalysts were prepared by impregnation of low-cost fly-ash-derived SAPO-34 molecular sieves as a support and tested in selective catalytic reduction with NH 3 (NH 3 -SCR). Powder X-ray diffraction (XRD), N 2 adsorption–desorption, X-ray photoelectron spectroscopy (XPS), H 2 temperature-programmed reduction (H 2 -TPR), NH 3 temperature-programmed desorption (NH 3 -TPD), electron paramagnetic resonance (EPR), nuclear magnetic resonance (NMR), X-ray fluorescence analysis (XRF) and scanning electron microscopy (SEM) were used for catalyst characterization and investigation of the relationships between the catalyst structure and the catalytic activity. The actual silica:alumina ratio of the molecular sieves did not increase with increasing Cu loading, indicating that increasing the Cu loading does not change the original structure of the SAPO-34 molecular sieves. The XRF and NMR results showed that replacement by Cu results in more Si islands. The molecular sieve acidity decreased because of the increased number of Si islands. The NH 3 -TPD results showed that for the Cu/SAPO-34 catalysts there was a low correlation between the low-temperature activity and the amount of acidic sites. SCR activity is closely related to the location of Cu. The 4.47Cu/SAPO-34 catalyst has the highest isolated Cu 2+ showed the highest NH 3 -SCR activities (> 90%) at 250–350 °C. This work opens up new avenues for recycling fly ash formed in coal-fired power plants (reducing environmental pollution) and developing low-cost SCR catalysts for NO x pollution control.
研究领域:
环境科学
·
材料科学
✓ 已验证
产品关联
DOI
危险品化学品经营许可证（带存储）