查找使用阿拉丁产品的科研文献

Flowerlike hierarchical SAPO-5 molecular sieve composed of loosely aggregating uniformly primary nano-rods-like AFI crystals

Quanhua Wang,Sai Li,Yanchao Liu,Lichen Zhang,Jiajun Zheng,Binbin Fan,Shuwei Chen,Wenlin Li,Ruifeng Li

Flowerlike hierarchical SAPO-5 molecular sieve was fabricated by a hydrothermally dynamic crystallization route using tetrapropyl-ammoniuhydroxide as a single structure-directing agent. The hierarchical SAPO-5 reveals high crystallinity, and large external surface areas validated by the XRD and N 2 adsorption-desorption. SEM and TEM indicate that the flowerlike hierarchical SAPO-5 is composed of loosely stacked primary nanorods with average diameter of 20 nm. FT-IR and EDS analyses show that as increasing crystallization time, more and more Si species are incorporated into the AFI crystals. Moreover, it is found that a dynamic crystallization condition is very mandatory toward the synthesis of a novel-flowerlike SAPO-5.

Unusual roles of ceria as the support of a single-atom catalyst in hydroisomerization of n-heptane: Phase boundary acts as transport channels between different active centers

Hao Qin,Hui Wan,Guofeng Guan

Hydroisomerization of n-alkanes plays an important role in fuel and lubricants processing. Bifunctional catalysts with ultralow platinum loading have recently been reported successively for hydroisomerisation. Herein, the catalysts were prepared successfully with different methods to improve the catalytic performance. The conversion of 0.01%Pt1@CeOx/SAPO-11 prepared by co-calcination method (0.01%Pt1@CS-c) is 71.4%, 25% higher than the other prepared by precipitation method. The turnover frequency per active surface platinum site (TOFPt) of 0.01%Pt1@CS-c is as high as 13115 h –1 . Revealed by the X-ray photoelectron spectroscopy (XPS) results, the quality of phase boundary/intersurface between ceria and zeolite is found significantly different. The conjunction quality of phase boundary directly affects the spillover rate of intermediate species, which further leads to an apparent activity difference. In addition, the possible role of ceria in the reaction is discussed, rather than just as a carrier for the active metal atoms.

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

Polyacrylamide-assisted synthesis of highly dispersed Ni nanoparticles wrapped by SAPO-11 molecular sieves for enhanced alkane hydroisomerization performances

Xue-Feng Song,Xue-Man Wang,Yan Bing,Yu Fan

A novel polyacrylamide-assisted method for synthesizing the hierarchical SAPO-11-wrapped Ni catalyst was proposed. In this method, firstly, Ni 2+ ions from nickel salts were coordinated with nitrogen atoms in polyacrylamide (HPAM) to form a Ni 2+ -HPAM complex; then, Ni 2+ -HPAM was adsorbed on negative SAPO-11 crystals during the crystallization of SAPO-11, and Ni 2+ -HPAM was wrapped by SAPO-11 crystals with the growth of these crystals; finally, Ni 2+ -HPAM was transformed into NiO nanoparticles (about 2.5 nm) wrapped by SAPO-11 crystals after the HPAM was removed during calcination. This method obtained an in-situ Ni@SAPO-11 assembly with hierarchical pore structures and highly dispersed Ni metals. Compared with both Ni/SAPO-4.0 with the same Ni content synthesized by conventional impregnation and the Ni@SAC-4.0 in which Ni salt was introduced into SAPO-11 in situ without HPAM addition, the as-synthesized catalyst (Ni@SACH-4.0) exhibited a higher Ni dispersion with smaller Ni nanoparticles, and more mesopores and Brønsted (B) acid sites. Consequently, Ni@SACH-4.0 showed a higher C 10 isomer yield (78.2%) and a lower cracking selectivity (9.4%) than Ni/SAPO-4.0 and Ni@SAC-4.0.

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.

Tuning zeolite crystal size in bifunctional catalysts assembled on bio-SiO2 for enhanced CO2 hydrogenation to light olefins

Shui Yang,Jialing Song,Yihua Yue,Bin Chen,Sajid Ali,Kok Bing Tan,Jian Tian,Jiale Huang,Qingbiao Li,Guowu Zhan

CO 2 hydrogenation to high-value-added light olefins over bifunctional catalysts is a promising pathway toward achieving net zero emissions. Herein, a series of SAPO-34 zeolites (bio-SAPO-34) with consistent acid properties but different particle sizes ( e.g. , 170 nm, 610 nm, and 7.50 μm) were synthesized using rice husk as the sole silicon source. Meanwhile, the rice husk derived SiO 2 (bio-SiO 2 ) could serve as a platform to assemble SAPO-34 and ZnZrO x into a bifunctional catalyst. It was found that the bio-SAPO-34 with the smaller particle size resulted in higher selectivity of light olefins and better long-term stability. Especially, after integration with ZnZrO x , the bio-SAPO-34 with a particle size of 170 nm exhibited higher light olefins selectivity (89.6 vs. 58.5 %) and longer catalytic lifetime (1000 vs. 59 min), as compared to a particle size of 26.0 μm. Notably, the zero length column (ZLC) technique, N 2 physisorption, and thermogravimetric analyses revealed that reducing the particle size of bio-SAPO-34 significantly decreases the diffusion resistance of light olefins in zeolites by shortening the diffusion paths, thereby inhibiting the formation of coke and enhancing the catalytic stability. Moreover, the bio-SiO 2 platform acts as a light olefins diffusion promoter by decreasing the surface diffusion resistance between zeolite particles and significantly alleviating the coke formation.

Catalytic cracking of acidified oil and modification of pyrolytic oils from soap stock for the production of a high-quality biofuel

Xia Jiang,Feng Long,Qiaolong Zhai,Jiaping Zhao,Peng Liu,Junming Xu

Soap stocks are by-products obtained during the refining process of vegetable oil, and are mainly feedstocks to produce acidified oil. In this work, an efficient process was developed to convert soap stock into a high-quality biofuel with low impurity content. A combination of acidification and catalytic cracking reactions employed as pretreatment was investigated to decrease the impurity content in the soap stock feedstock for obtaining a value-added biofuel. A high olefin content (approximately 47%) pyrolytic oil was obtained during the pretreatment. For further improvement of the cold flow properties, hydro-isomerization of pyrolytic oil for the formation of iso-alkanes over the Ce–Pt/SAPO-11and Ce–Pt/ZSM-5 catalysts was then carried out. The isomerization reaction temperature could be decreased to 320 °C because of the approximately 47% olefin content. The cold filter plugging point (CFPP) of the resulting product could be obtained at −11 °C, and the sulfur content could be decreased to lower than 10 ppm, which could meet the EN and ASTM specifications.