查找使用阿拉丁产品的科研文献

Hierarchical Molecular Highway Architectures in SAPO-34 Single Crystals Boost Methanol-to-Olefins Catalytic Performance

Chun-Mu Guo,Ming-Hui Sun,Zhan Liu,An-Kang Jiang,Bo Ye,Chang Xu,Xiao-Yu Yang,Bao-Lin Sun,Ying Jiang,Wei Wu,Xiao-Yun Li,Yu Li,Li-Hua Chen,Bao-Lian Su

The persistent challenge of catalyst deactivation in methanol-to-olefins (MTO) conversion, primarily arising from restricted molecular transport and subsequent coke accumulation in conventional microporous SAPO-34 zeolites, necessitates innovative structural solutions. Herein, we demonstrate a synthesis strategy that employs sucrose-derived carbon as a hard template combined with vapor-phase transport to fabricate hierarchical SAPO-34 single crystals, thereby overcoming the low crystallinity and poor pore connectivity that have previously plagued hierarchical SAPO-34 zeolites. This intracrystalline hierarchical architecture with highly interconnected pores demonstrates molecular highway functionality and exhibits a 77.5% increase in propylene diffusion coefficient compared to conventional samples. Such hierarchical molecular highway architecture effectively regulates coke distribution within SAPO-34 crystals during MTO reactions. The optimized hierarchical SAPO-34 exhibits a 505 min operational lifetime, a 3.3-fold enhancement in catalytic durability over traditional microporous systems. Our findings establish a materials design paradigm for overcoming diffusion-reaction trade-offs in zeolite catalysis, with implications extending beyond conventional MTO processes.

Zeolite/polyimide mixed-matrix membranes with enhanced natural gas purification performance: Importance of filler structural integrity

Xi Chen,Nana Wang,Guining Chen,Zhenggang Wang,Gongping Liu,Rongfei Zhou,Wanqin Jin

Mixed-matrix formulation is a promising method to overcome permeability-selectivity trade-off of polymers with incorporation of fillers with well-defined nanopores . The filler properties play a key role in determining the performance of mixed-matrix membrane (MMM). In this work, for the first time, we explored the critical effect of filler structural integrity on separation performance of MMM. Typically, micron as-synthesized, submicron as-synthesized and submicron ground SAPO-34 zeolites were incorporated into 6FDA-DAM polyimide , respectively. The interface compatibility between two phases was ensured by (3-aminopropyl) trimethoxysilane (APTMS) modification on SAPO-34 fillers. It was found that the directly synthesized micron and submicron fillers contributed to enhance the CO 2 /CH 4 separation performance whereas the submicron ground filler lowered the CO 2 permeability. Notably, incorporating 30 wt% micron as-synthesized SAPO-34 into 6FDA-DAM enhanced the CO 2 permeability by 68% and CO 2 /CH 4 by 37%, surpassing the performance upper-bound. Moreover, the hydrogen bonding between the filler and polymer matrix endowed the membrane with outstanding plasticization resistance with CO 2 partial pressure up to 20 bar. Adsorption isotherms and Maxwell model prediction revealed that the filler transport properties could be significantly affected by commonly-used methods of reducing the filler size. A decreased structural integrity was identified in the sequence of micron as-synthesized, submicron as-synthesized and submicron ground fillers. This work highlights the importance of a careful balance between structural integrity and crystal size of filler, and reliable routes to obtain nanofillers with desirable structural integrity as pursuing high-performing MMM toward practical application.

Silicon-Tuned Acidity in Nanoporous SAPO-34 for Enhanced Copper Dispersion and Methane-to-Methanol Conversion

Yihang Jiang,Xia Zhang,Wenzhi Li,Liang Yuan

Low-concentration coalbed methane, an underused energy resource, poses environmental risks due to its potent greenhouse effect upon direct atmospheric release, creating an urgent need for efficient utilization. Converting methane to methanol offers a viable solution to this challenge. This research examines how the silicon content affects the catalytic activity of Cu/SAPO-34 in the continuous direct oxidation of methane into methanol. Yield and selectivity of methanol exhibit a distinct volcano-shaped dependence on silicon content, among which Cu/SA2 showed excellent activity and selectivity, achieving a space-time yield of methanol 293.6 ± 5.9 μmol/(gcat·h) and selectivity 78.9% ± 1.5%. Silicon content tunes SAPO-34’s acid site distribution and silicon coordination environment, which govern copper species anchoring during solid-state ion exchange. Moderate silicon content promotes the optimized dispersion of copper species, effectively enhancing the content of isolated Cu2+ active sites. In situ DRIFTS elucidates the methane activation mechanism involving Cu(I)-methyl intermediates, along with the critical role of trace oxygen (1000 pm) and water vapor in promoting the catalytic redox cycle of the active sites. This work clarifies the zeolite composition–activity relationship, guiding rational design of high-performance catalysts for methane valorization.

Low-cost organosilane-assisted synthesis of hierarchical SAPO-34 with improved stability in methanol-to-olefins reaction

Panpan Zhai,Yapeng Li,Zhipan Liu,Zhanling Ma,Dehua Wang,Beibei Gao

A series of hierarchical SAPO-34 molecular sieves were successfully synthesized through the organosilane-assisted method, employing low-cost 3-aminopropyltriethoxysilane (APTES) as a mesoporous template and partial silica source. The influence of APTES content on the crystallinity, pore structures, acidity, and catalytic performance of the products in the methanol-to-olefins (MTO) reaction was systematically investigated by XRD, XRF, SEM, N 2 adsorption-desorption, NH 3 -TPD measurements and a fixed-bed reactor. It revealed that the introduction of APTES created mesopores and simultaneously modulated the acidic properties, notably reducing both the strength and density of strong acid sites. Compared to the conventional microporous SAPO-34-C, the hierarchical SAPO-34 catalysts, particularly SAPO-34-0.1, demonstrated a superior catalytic lifetime and enhanced selectivity to light olefins in the MTO reaction. This performance enhancement could be attributed to their hierarchical pore systems and the moderated acidities. However, excessive APTES addition (SAPO-34-0.2) led to a decline in crystallinity and a consequent reduction in catalytic stability.

CO2 hydrogenation to light olefins on ZnO-ZrO2/SAPO-34 tandem catalysts: optimize the Zn/Zr ratio

Yi Xiang,Zidan Mei,Lulu Zhou,Yue Li,Yongdong Chen

The hydrogenation of CO2 to light olefins is a promising method for CO2 resource utilization. Tandem catalysts composed of metal oxides and zeolites have been widely studied for the hydrogenation of CO2 to light olefins, but there are bottleneck problems in terms of CO2 conversion and light olefins yield. ZnO-ZrO2 catalyst is extensively employed in CO2 hydrogenation because of its excellent stability at high temperatures, but there is still a "seesaw" problem between the CO2 conversion and light olefins selectivity. In addition, the synergetic effect between Zn and Zr sites on the reaction process remains unclear. In this work, a series of ZnO-ZrO2 catalytic materials with various Zn: Zr ratios were synthesized by co-precipitation, and the interaction between Zn and Zr could be regulated by altering the Zn: Zr ratio. XRD and TEM results confirmed the successful synthesis of ZnO-ZrO2 composite oxide and the existence of a certain interaction between Zn and Zr. CO2-TPD, H2-TPR and XPS results indicated that the interaction between Zn and Zr could improve the hydrogenation capacity of the catalyst and also induce the generation of abundant oxygen vacancies to effectively promote the adsorption and activation of CO2. Catalytic performance results showed that ZnO-ZrO2(1:4)/SAPO-34 exhibits the best CO2 to light olefins activity with a CO2 conversion rate of 26.4% and a C2=-C4=selectivity of 72.6%. This work provides a feasible strategy for rational designing and optimizing of CO2 hydrogenation catalyst.

Metal–organic framework-assisted synthesis of SAPO-34 with enhanced catalytic performance for the methanol-to-olefins reaction

Zhang Liheng,Miao Huaibin,Li Fangfei

Microporous SAPO-34 molecular sieves are prone to rapid deactivation due to coke deposition in the methanol-to-olefins (MTO) reaction, primarily because of diffusion limitations. To address this issue, we propose a metal–organic framework (MOF)-assisted one-step hydrothermal synthesis strategy. For the first time, UiO-66 is introduced into the SAPO-34 synthesis system, successfully constructing SAPO-34 crystals with a stepped, special morphology. The results indicate that the addition of UiO-66 causes the samples to gradually aggregate and stack, forming an abundant hierarchical pore structure. Meanwhile, Zr species are incorporated into the molecular sieve framework, which effectively modulates the acidic properties by significantly reducing the strength of the strong acid sites. When applied to the MTO reaction, the UiO-66-modified SAPO-34 exhibits a significantly prolonged catalytic lifetime and enhanced selectivity towards light olefins (ethylene and propylene) compared to the unmodified SAPO-34. This enhanced performance is attributed to the abundant hierarchical pores providing rapid diffusion channels, and the reduced acid strength retarding coke deposition. This study provides a new design strategy for the one-step construction of hierarchical pore structures coupled with the introduction of metal species to regulate acidity.

Toward Solvent Development for Industrial CO2 Capture by Optimizing the Catalyst–Amine Formulation for Lower Energy Consumption in the Solvent Regeneration Process

Xiayi Hu,Qian Yu,Yuanyuan Cui,Juntao Huang,Elenica Shiko,Yefeng Zhou,Zhaogang Zeng,Yang Liu,Rui Zhang

The main issue for the development of CO2 capture in industry is its high energy cost. In this work, the regeneration of the chemical solvent 3-(diethylamino)propylamine (DEAPA) with or without catalyst was studied to further reduce the energy consumption. Three different catalysts (SAPO-34, MCM-41, and SO42–/TiO2) were applied into the DEAPA system to enhance the energy efficiency by lowering the heat cost per mole of CO2 released in a CO2 stripping process. The results show that solely DEAPA (without catalyst) can increase the CO2 desorption rate by 37.28%, increase the cyclic capacity by 38.02%, and reduce the heat duty by 14.85% compared to 5 M monoethanolnamine (MEA). In addition, for the catalyst–DEAPA systems, DEAPA-SAPO-34, DEAPA-MCM-41, and DEAPA-SO42–/TiO2 could lower the heat duty by 33.08%, 27.79%, and 22.41%, respectively, relative to 5 M MEA. The SAPO-34 catalyst also shows a better efficiency for increasing the CO2 desorption rate and cyclic capacity compared to the other two catalysts used. Moreover, a possible catalytic mechanism for CO2 desorption from the DEAPA–catalyst system is proposed based on the results from catalyst characterization. Through comparing the parameters of each catalyst, it can be inferred that the mesopore surface area (MSA) and the total acid sites (TAS) are the critical factors for an efficient catalyst. The combination of MAS*TAS could especially act as a key value to evaluate the performance of a catalyst for catalytic CO2 desorption.

Low-temperature SCR of NOx by NH3 over MnOx/SAPO-34 prepared by two different methods: a comparative study

Chenglong Yu,Lifu Dong,Feng Chen,Xiaoqing Liu,Bichun Huang

Comparative studies of ethanol to propylene over HZSM-5/SAPO-34 catalysts prepared by hydrothermal synthesis and physical mixture

Chao Duan,Xin Zhang,Rui Zhou,Yuan Hua,Li Zhang,Jie Chen

HZSM-5/SAPO-34 catalysts were prepared by physical mixture (named as ZS(m)-MM-n) and hydrothermal synthesis (named as ZS(m)-HS-n), respectively. Ethanol to propylene over these as-prepared catalysts was investigated under different reaction conditions. In addition, the physicochemical properties of these catalysts were characterized by AAS , XRD , N2 isothermal adsorption–desorption, SEM , NH3-TPD and TPO . The catalytic reactivity of HZSM-5/SAPO-34 catalyst was strongly dependent on its preparation method and composition as well as the reaction conditions. ZS(25)-MM-4 (HZSM-5/SAPO-34   =   4, weight ratio; HZSM-5 with Si/Al2   =   25 molar ratio) in isothermal fixed-bed reactor showed the highest propylene yield of ca. 34.5% among these catalysts and the poor catalytic stability. The use of nonisothermal fixed-bed reactor with the temperature configuration (2) significantly improved the catalytic stability of ZS(25)-MM-4. Synergetic effect of HZSM-5 with SAPO-34 occurred in HZSM-5/SAPO-34 catalyst, which modified its properties and catalytic reactivity. The concentration and the strength distribution of acid sites were closely relative to the catalytic reactivity of HZSM-5/SAPO-34 catalyst. For achieving the high yield of propylene, it was necessary that HZSM-5/SAPO-34 catalyst had the moderate concentration and strength distribution of acid sites.

Dual-Temperature Crystallization Synthesis of Secondary-Growth SAPO-34 Molecular Sieve with Adjusted Silicon Content for Superior MTO Catalysis

Zhang Haijun,Li Yuwei,Zheng Yulong,Chen Lei,Yang Gang

Based on the dual-temperature method (100 ℃ for 6 h and then 200 ℃ for 12 h), the novel surface modification strategy involving secondary growth with the pre-synthesized nano-flake SAPO-34 seeds is presented for the synthesis of hierarchical pore SAPO-34. The effective regulation of the silicon content in the initial gel modulated the pore architecture and the acid strength of the SAPO-34 product. The optimized catalyst demonstrated a superior selectivity for the light olefins and a suppression of the coke deposition, leading to a prolonged catalytic lifetime. The catalytic performance showed a trend of first increasing and then decreasing with the silicon content. The optimal catalyst demonstrated an excellent selectivity of 95.88% and an extended lifetime of 600 min. Graphical The alternative text for this image may have been generated using AI.

Construction of Cu-SSZ-13@SAPO-34 selective catalytic reduction catalyst: Multifunctional protective shell against hydrothermal aging and chemical poisoning

Yang Gao,Yue Ma,Letong Yang,Xiaodong Wu,Rui Ran,Yanyang Yu,Duan Weng

Cu-SSZ-13, a Cu-exchanged zeolite, has been applied as a NO x selective catalytic reduction (SCR) catalyst for diesel aftertreatment, but improving its durability remains a challenge. To address this issue, a core–shell Cu-SSZ-13@SAPO-34 catalyst was prepared by a microwave-assisted hydrothermal method. The evolution of copper species and zeolite framework during high-temperature hydrothermal aging, potassium poisoning and sulfur poisoning, as well as the impacts on SCR performance, was explored. Cu 2+ ions detached by hydrothermal aging could migrate from the Cu-SSZ-13 core to the SAPO-34 shell and be reactivated, owing to the close interface contact between the zeolites. When exposed to chemical poisoning by K + and SO 2 , the SAPO-34 shell effectively shielded the Cu-SSZ-13 core. Thus, more active Cu 2+ ions could be preserved to maintain the SCR performance of the catalyst.

Seeds Promoted Interzeolite Transformation of USY and Fumed Silica to Long-Lifetime SSZ-13 Catalysts in Methanol-to-Olefins Reaction via a Grinding Route

Hao Zongyi,Niu Li,Long Xuefeng,Li Hongwei,Wang Dongliang,Ji Dong,Zhao Xinhong

Abstract Two different seed crystals (K–CHA and nano-scaled SAPO-34) were used to promote the rapid interzeolite conversion of USY and fumed silica to pure SSZ-13 zeolite phase via a grinding route. The results show that both seeds can shorten the crystallization time of SSZ-13 zeolite to 24h, which is much shorter than the syntheses in the absence of seeds. The phase purity, morphology, textural parameters, elemental compositions and acid properties of two typical H–SSZ-13 samples with seeds were analyzed by XRD, SEM, N 2 physisorption, EDS and NH 3 –TPD techniques in detail, and compared with the sample without seeds and a reference sample. The results indicate that the introduction of seeds can effectively modify the acid properties of H–SSZ-13, especially their medium strong acid sites. The methanol-to-olefins (MTO) reaction was employed as a probe to evaluate the catalytic stability of above four H–SSZ-13 catalysts. The results reveal that the catalytic lifetime of the two catalysts using seeds is much longer than that of the one without seeds and the reference sample H–SSZ-13–RS. It was speculated that the appropriate concentration of medium strong acid sites may play a pivotal role in prolonging their catalytic lifetime. Here our findings may throw light on the rational design of long-lifetime H-SSZ-13 catalysts in the MTO reaction.