scholarly journals The influence of composition on the functionality of hybrid CuO–ZnO–Al2O3/HZSM-5 for the synthesis of DME from CO2 hydrogenation

RSC Advances ◽  
2018 ◽  
Vol 8 (53) ◽  
pp. 30387-30395 ◽  
Author(s):  
Yubing Hu ◽  
Yajing Zhang ◽  
Jie Du ◽  
Chunyan Li ◽  
Kangjun Wang ◽  
...  
Keyword(s):  
Catalytic Performance ◽  
Acid Sites ◽  
Weak Acid ◽  
Co2 Hydrogenation ◽  
Chemical State

The introduction of Al2O3 increased the number of weak acid sites, altered the copper chemical state and improved the catalytic performance and stability consequently.

Efficient conversion of cotton stalks over a Fe modified HZSM-5 catalyst under microwave irradiation

RSC Advances ◽  
2016 ◽  
Vol 6 (34) ◽  
pp. 28532-28537 ◽  
Author(s):  
Xiangjin Kong ◽  
Xiaole Li ◽  
Shuxiang Wu ◽  
Xin Zhang ◽  
Junhai Liu
Keyword(s):  
Microwave Irradiation ◽  
Catalytic Performance ◽  
Acid Sites ◽  
Weak Acid ◽  
Cotton Stalk ◽  
Efficient Conversion ◽  
Fe Species ◽  
Cotton Stalks ◽  
Bio Oil

Doped amounts of Fe species to HZSM-5 distinctly improved the catalytic performance of the catalyst for the liquefaction of cotton stalk to bio-oil due to the enhanced total and weak acid sites.

Synthesis and Catalytic Application of Mesoporous Molecular Sieves MCM-41 Containing Niobium and Tantalum

2007 ◽  
Vol 124-126 ◽  
pp. 1761-1764 ◽  
Author(s):  
Hun Jung ◽  
Kwang Deog Jung ◽  
Oh Shim Joo ◽  
Sun Jin Kim
Keyword(s):  
Vapor Phase ◽  
Molecular Sieves ◽  
Catalytic Performance ◽  
Acid Sites ◽  
Weak Acid ◽  
Beckmann Rearrangement ◽  
Mesoporous Molecular Sieves ◽  
Cyclohexanone Oxime ◽  
Catalytic Application ◽  
Mcm 41

Niobium- and tantalum-containing mesoporous molecular sieves MCM-41 have been synthesized, and applied as a catalyst for vapor phase Beckmann rearrangement of cyclohexanone oxime to ε-caprolactam. NbMCM-41 catalyst exhibited high catalytic performance in the vapor phase Beckmann rearrangement of cyclohexanone oxime. The oxime conversions were almost 100% and the lactam selectivities were around 80%. The lactam selectivities of NbMCM-41 catalyst were higher than those of AlMCM-41 catalyst. However, TaMCM-41 catalyst exhibited lower catalytic performance than AlMCM-41 catalyst, and it was fast deactivated with time. These results may be due to the acidity difference among the catalysts. The results from NH3-TPD showed that NbMCM-41 catalyst possessed weak and medium acid sites, while TaMCM-41 catalyst possessed only very weak acid sites. AlMCM-41 catalyst also exhibited only weak acid sites.

scholarly journals Facile and Rapid Synthesis of Durable SSZ-13 Catalyst Using Choline Chloride Template for Methanol-to-Olefins

2021 ◽  
Author(s):  
xiongchao Lin ◽  
Sasha Yang ◽  
Xiaojia Li ◽  
Caihong Wang ◽  
Yonggang Wang
Keyword(s):  
Conversion Rate ◽  
Choline Chloride ◽  
Catalytic Performance ◽  
Acid Sites ◽  
Weak Acid ◽  
Soft Template ◽  
Lower Amount ◽  
Rapid Synthesis ◽  
Light Olefin ◽  
Hexagonal Ring

Abstract In this study, a facile and rapid synthesis approach for SSZ-13 catalyst was proposed using choline chloride (CC) as template. The optimal synthesis condition was explored, and the catalytic performance for methanol-to-olefins (MTO) was examined. Results revealed that the appropriate ratio of soft template could meet the condition for rapid and ordered growth of catalyst crystals. Using environmentally friend and cheaper CC as template could greatly accelerate the formation of bi-hexagonal ring structure in SSZ-13 framework, and it could shorten the synthesis cycle to within 4 h. With a proper amount of CC addition (i.e., m(CC)/m(SiO2) = 0.14), uniform and homogeneously distributed cubic SSZ-13 crystals were obtained with relatively lower aggregation. The catalyst synthesized with m(CC)/m(SiO2)=0.14 demonstrated excellent porous features with a total specific surface area and mesopore volume of 641.706 m2.g-1 and 0.0377 cm3.g-1, respectively. The optimized strong and weak acid sites on the SSZ-13 were obtained by regulating the m(CC)/m(SiO2). As a typical acid catalytic reaction, the SSZ-13 catalyst with strong and weak acid sites exhibited bi-functional role. The lower amount of strong acid sites and larger amount of weak acid sites in the synthesized catalyst were conducive to the catalytic performance for MTO under relatively lower reaction temperature (450 oC). Consequently, the synthesized SSZ-13 showed a better conversion rate and lifetime than that of purchased one. The methanol conversion rate using synthesized catalyst was maintained over 95% within 120 min, and its lifetime was achieved to 172 min. The appropriate acidity and well-developed pore structure of synthesized SSZ-13 could slow down the carbon deposition rate and significantly increase the lifetime of the catalyst. Moreover, the initial selectivity of light olefin could maintain above 50% within 160 min. Eventually, the desirable features of synthesized SSZ-13 catalyst were thought be with good potential for industrial application.

scholarly journals Glycerol Hydrogenolysis to 1,2-Propanediol over Novel Cu/ZrO2 Catalysts

Catalysts ◽  
2022 ◽  
Vol 12 (1) ◽  
pp. 72
Author(s):  
Giuseppina Luciani ◽  
Giovanna Ruoppolo ◽  
Gianluca Landi ◽  
Valentina Gargiulo ◽  
Michela Alfè ◽  
...  
Keyword(s):  
Batch Reactor ◽  
Metal Organic Framework ◽  
Sol Gel ◽  
Catalytic Performance ◽  
Acid Sites ◽  
Weak Acid ◽  
Copper Deposition ◽  
Biodiesel Production ◽  
Preparation Methods ◽  
Glycerol Hydrogenolysis

Glycerol is the main by-product of biodiesel production; its upgrading to more valuable products is a demanding issue. Hydrogenolysis to 1,2-propanediol is one of the most interesting processes among the possible upgrading routes. In this study, we propose novel copper/zirconia catalysts prepared by advanced preparation methods, including copper deposition via metal–organic framework (MOF) and support preparation via the sol–gel route. The catalysts were characterized by N2 physisorption, X-ray diffraction, Scanning Electron Microscopy, H2-TPR and NH3-TPD analyses and tested in a commercial batch reactor. The catalyst prepared by copper deposition via MOF decomposition onto commercial zirconia showed the best catalytic performance, reaching 75% yield. The improved catalytic performance was assigned to a proper combination of redox and acid properties. In particular, a non-negligible fraction of cuprous oxide and of weak acid sites seems fundamental to preferentially activate the selective pathway. In particular, these features avoid the overhydrogenolysis of 1,2-propanediol to 1-propanol and enhance glycerol dehydration to hydroxyacetone and the successive hydrogenation of hydroxyacetone to 1,2-propanediol.

Microwave hydrothermal synthesis, characterisation, and catalytic performance of Zn1−x MnxO in cellulose conversion

2014 ◽  
Vol 68 (9) ◽  
Author(s):  
Maria Bernardi ◽  
Vinícius Araújo ◽  
Caue Ribeiro ◽  
Waldir Avansi ◽  
Elson Longo ◽  
...  
Keyword(s):  
Catalytic Properties ◽  
Catalytic Performance ◽  
Acid Sites ◽  
Weak Acid ◽  
Spherical Nanoparticles ◽  
Hydrothermal Route ◽  
Cellulose Conversion ◽  
Microwave Assisted ◽  
Microwave Hydrothermal ◽  
Plate Morphology

AbstractWurtzite-type Zn1−x MnxO (x = 0, 0.03, 0.05, 0.07) nanostructures were successfully synthesised using a simple microwave-assisted hydrothermal route and their catalytic properties were investigated in the cellulose conversion. The morphology of the nanocatalysts is dopant-dependent. Pure ZnO presented multi-plate morphology with a flower-like shape of nanometric sizes, while the Zn0.97Mn0.03O sample is formed by nanoplates with the presence of spherical nanoparticles; the Zn0.95Mn0.05O and Zn0.93Mn0.07O samples are mainly formed by nanorods with the presence of a small quantity of spherical nanoparticles. The catalyst without Mn did not show any catalytic activity in the cellulose conversion. The Mn doping promoted an increase in the density of weak acid sites which, according to the catalytic results, favoured promotion of the reaction.

Crucial Role of Weak Acid Sites for Catalytic Performance of Zeolites in Ethyl tert-butyl Ether Synthesis

2017 ◽  
Vol 204 (8) ◽  
pp. 937-941 ◽  
Author(s):  
N. V. Vlasenko ◽  
Yu. N. Kochkin ◽  
A. M. Puziy ◽  
P. E. Strizhak
Keyword(s):  
Crucial Role ◽  
Catalytic Performance ◽  
Acid Sites ◽  
Weak Acid ◽  
Butyl Ether ◽  
Tert Butyl ◽  
Ether Synthesis

scholarly journals Facile and Rapid Synthesis of Durable SSZ-13 Catalyst using Choline Chloride Template for Methanol-to-Olefins Reaction

Catalysts ◽  
2021 ◽  
Vol 11 (10) ◽  
pp. 1250
Author(s):  
Xiongchao Lin ◽  
Sasha Yang ◽  
Xiaojia Li ◽  
Caihong Wang ◽  
Yonggang Wang
Keyword(s):  
Choline Chloride ◽  
Strong Acid ◽  
Methanol Conversion ◽  
Catalytic Performance ◽  
Acid Sites ◽  
Weak Acid ◽  
Rapid Synthesis ◽  
Light Olefin ◽  
Mto Reaction ◽  
Strong Acid Sites

In the current study, a facile and rapid synthesis approach for a SSZ-13 catalyst using choline chloride (CC) as a template was proposed, and the catalytic performance for the methanol-to-olefins (MTO) reaction was examined. With a proper amount of CC addition (i.e., m(CC)/m(SiO2)=0.14), uniform and homogeneously distributed cubic SSZ-13 crystals were obtained within 4 h with lower aggregation. The synthesized catalyst demonstrated excellent porous features with a total specific surface area and mesopore volume of 641.71 m2·g−1 and 0.04 cm3·g−1, respectively. The optimized strong and weak acid sites on SSZ-13 were obtained by regulating the m(CC)/m(SiO2) ratio. The less strong acid sites and a larger amount of weak acid sites in the synthesized catalyst were conducive to the catalytic performance of the MTO reaction under a lower reaction temperature (450 °C). The appropriate acidity and well-developed pore structure of synthesized SSZ-13 could also slow down the carbon deposition rate and, thus, significantly improve the catalytic lifetime of the catalyst. The methanol conversion rate and initial selectivity of light olefin using the synthesized catalyst could maintain over 95% and 50%, respectively, and a lifetime of 172 min was achieved. Although the low olefin selectivity of the synthesized SSZ-13 catalyst was slightly lower than that of the purchased one, its desirable features were thought to have good potential for industrial application.

Conversion of Multicyclic Hydrocarbons to Mono-Aromatic Hydrocarbons Over CoMo/Zeolite Socony Mobil-5 Catalysts

2021 ◽  
Vol 21 (7) ◽  
pp. 3819-3823
Author(s):  
Huiji Ku ◽  
Seung Kyo Oh ◽  
Kyuri Kim ◽  
Young-Kwon Park ◽  
Jong-Ki Jeon
Keyword(s):  
Fixed Bed ◽  
Chemical Properties ◽  
Strong Acid ◽  
Catalytic Performance ◽  
Acid Sites ◽  
Weak Acid ◽  
Fixed Bed Reactor ◽  
Nanoporous Structure ◽  
Bead Type ◽  
Catalytic Cracking Reaction

This study focuses on analyzing the effects of the SiO2/Al2O3 ratio of a support on the physico-chemical properties of bead-type CoMo/HZSM-5 catalysts and on the catalytic performance during the hydrocracking reaction of PFO. CoMo/HZSM-5 catalysts were prepared by an incipient wetness method. Subsequently, binder-added catalysts were molded into the bead type catalysts. The N2 adsorption-dersorption results clearly indicate that the nanoporous structure was well developed in the bead-type CoMo/HZSM-5 catalyst. The CoMo/HZSM-5(30) catalyst not only possessed the highest number of acid sites but also showed the highest ratio of strong acid to weak acid sites. Moreover, the Lewis acid/Brönsted acid site ratio is highest with the CoMo/HZSM-5(30) catalysts. A hydrocracking reaction of PFO over the bead-type CoMo/HZSM-5 catalysts was conducted at 400 °C and under 40 atm in a fixed-bed reactor. The bead-type CoMo/HZSM-5(30) catalyst showed the highest BTXE yield with a sum of BTXE outcome of 43.0% in the catalytic cracking reaction of PFO, which is attributed to the synergistic combination of suitable acidity and hierarchical porosity.

Deep Eutectic Solvents with Multiple Weak Acid Sites for Highly Efficient, Reversible and Selective Absorption of Ammonia

2021 ◽  
pp. 118791
Author(s):  
Ning-Ning Cheng ◽  
Zi-Liang Li ◽  
Hong-Chao Lan ◽  
Wen-Long Xu ◽  
Wen-Jing Jiang ◽  
...  
Keyword(s):  
Deep Eutectic Solvents ◽  
Acid Sites ◽  
Weak Acid ◽  
Selective Absorption ◽  
Highly Efficient

scholarly journals Insight into Active Centers and Anti-Coke Behavior of Niobium-Containing SBA-15 for Glycerol Dehydration

Catalysts ◽  
2021 ◽  
Vol 11 (4) ◽  
pp. 488
Author(s):  
Katarzyna Stawicka ◽  
Maciej Trejda ◽  
Maria Ziolek
Keyword(s):  
Coke Formation ◽  
Catalytic Performance ◽  
Acid Sites ◽  
Silica Matrix ◽  
High Concentration ◽  
Active Centers ◽  
Acidic Sites ◽  
Glycerol Dehydration ◽  
Adsorption Desorption ◽  
Insight Into

Niobium containing SBA-15 was prepared by two methods: impregnation with different amounts of ammonium niobate(V) oxalate (Nb-15/SBA-15 and Nb-25/SBA-15 containing 15 wt.% and 25 wt.% of Nb, respectively) and mixing of mesoporous silica with Nb2O5 followed by heating at 500 °C (Nb2O5/SBA-15). The use of these two procedures allowed obtaining materials with different textural/surface properties determined by N2 adsorption/desorption isotherms, XRD, UV-Vis, pyridine, and NO adsorption combined with FTIR spectroscopy. Nb2O5/SBA-15 contained exclusively crystalline Nb2O5 on the SBA-15 surface, whereas the materials prepared by impregnation had both metal oxide and niobium incorporated into the silica matrix. The niobium species localized in silica framework generated Brønsted (BAS) and Lewis (LAS) acid sites. The inclusion of niobium into SBA-15 skeleton was crucial for the achievement of high catalytic performance. The strongest BAS were on Nb-25/SBA-15, whereas the highest concentration of BAS and LAS was on Nb-15/SBA-15 surface. Nb2O5/SBA-15 material possessed only weak LAS and BAS. The presence of the strongest BAS (Nb-25/SBA-15) resulted in the highest dehydration activity, whereas a high concentration of BAS was unfavorable. Silylation of niobium catalysts prepared by impregnation reduced the number of acidic sites and significantly increased acrolein yield and selectivity (from ca. 43% selectivity for Nb-25/SBA-15 to ca. 61% for silylated sample). This was accompanied by a considerable decrease in coke formation (from 47% selectivity for Nb-25/SBA-15 to 27% for silylated material).

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