scholarly journals Methanol Dehydration to Dimethyl Ether over Modified γ-Al2O3 with Acid, Base and Zeolite (NaA and NaX)

2020 ◽  
Vol 20 (2) ◽  
pp. 109
Author(s):  
Maria Ulfah ◽  
Hendra Suherman ◽  
Melia Laniwati ◽  
IGBN Makertihartha ◽  
Subagjo Subagjo
Keyword(s):  
Surface Acidity ◽  
Fixed Bed ◽  
Strong Acid ◽  
Acid Sites ◽  
Weak Acid ◽  
Fixed Bed Reactor ◽  
Methanol Dehydration ◽  
Zeolite Nax ◽  
Zeolite Naa ◽  
Strong Acid Sites

The effect of acids, bases, zeolite NaA and zeolite NaX impregnation to g-Al2O3 on the catalyst characteristics and activity against methanol dehydration reaction were investigated. The catalyst characteristics include N2 physisorption, X-ray diffraction (XRD), and temperature-programmed desorption of ammonia (NH3-TPD) in addition to catalytic dehydration of methanol performed in a micro fixed-bed reactor at 270°C and 1 atm. The results of XRD characterization showed no changes related to the modification of alumina over acids, bases, and zeolite NaA and zeolite NaX. Therefore, the modification did not have any effect on the crystalline structure of alumina. The textural and surface acidity of g-Al2O3 changed post addition of acids, bases, zeolite NaA and zeolite NaX. NH3-TPD analysis results demonstrated that synthesized g-Al2O3 has three types of acid sites: weak, medium, and strong; however, the weak acid sites were not observed on alumina catalysts modified phosphate, KOH, zeolite NaA, and zeolite NaX. Furthermore, the concentration of strong acid sites increased in the catalyst containing KOH. The catalytic test results showed that the untreated g-Al2O3 catalyst gave prominent activity in dehydration of methanol compared to the treated catalyst following the number and strength of acid sites. 

Reaction Mechanism for CCl2F2 Catalytic Decomposition over MoO3/ZrO2

2013 ◽  
Vol 295-298 ◽  
pp. 326-330 ◽  
Author(s):  
Tian Cheng Liu ◽  
Yu Jiao Guo ◽  
Ping Ning ◽  
Ming Long Yuan
Keyword(s):  
Reaction Mechanism ◽  
Main Product ◽  
Solid Acid ◽  
Fixed Bed ◽  
Catalytic Decomposition ◽  
Strong Acid ◽  
Acid Sites ◽  
Fixed Bed Reactor ◽  
Surface Intermediate ◽  
Strong Acid Sites

Catalytic hydrolysis decomposition of dichlorodifluoromethane (CCl2F2) in the presence of water vapor and oxygen was studied over a series of solid acids using a fixed-bed reactor. Solid acid MoO3/ZrO2 displayed the highest activity, over which the conversion of CCl2F2 reached 100 % at 250 °C. CO2 was the main-product and the selectivity to CClF3 remained lower than 28.0 %. CO was not detected as by-product. The decomposition activity depended on the calcination temperature and the ZrO2 content. The activity of solid acid MoO3/ZrO2 correlates well with its specific surface area and the amount of medium-strong acid sites on the surface. To explain the reaction mechanism for CCl2F2 catalytic decomposition over MoO3/ZrO2, a surface intermediate, Osurface-CF2-Osurface is proposed.

Coke on Zn/Hβ Catalyst in Ethanol to Propylene

2014 ◽  
Vol 962-965 ◽  
pp. 719-722
Author(s):  
Wen Ting Qu ◽  
Ting Bai ◽  
Feng Wang ◽  
Xi Ling Liu ◽  
Xin Zhang
Keyword(s):  
Physicochemical Properties ◽  
Continuous Flow ◽  
External Surface ◽  
Fixed Bed ◽  
Strong Acid ◽  
Acid Sites ◽  
Fixed Bed Reactor ◽  
Isothermal Adsorption ◽  
Strong Acid Sites ◽  
Adsorption Desorption

Coke on Zn/Hβ catalyst in ethanol to propylene was studied in continuous-flow fixed-bed reactor. The physicochemical properties of these fresh and used catalysts were characterized by NH3-TPD, N2 isothermal adsorption-desorption and TPO. These results showed that the medium and strong acid sites might be responsible for the production of coke and coke mainly deposited on external surface and microporous mouth. In addition, the coke might be consisted of soft coke and hard coke.

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.

Effect of autotransformation on the layer charge of smectites determined by the alkylammonium method

Clay Minerals ◽  
1997 ◽  
Vol 32 (4) ◽  
pp. 623-632 ◽  
Author(s):  
M. Janek ◽  
P. Komadel ◽  
G. Lagaly
Keyword(s):  
Aqueous Dispersion ◽  
Strong Acid ◽  
Acid Sites ◽  
Weak Acid ◽  
Layer Charge ◽  
Exchange Method ◽  
Density Distributions ◽  
Titration Curves ◽  
The Mean ◽  
Strong Acid Sites

AbstractHydrogen-forms of <2 µm fractions of six bentonites of various Fe contents were prepared by H+→OH-→H+ ion exchange using resins. Potentiometric titration curves revealed that the number of strong acid sites varied and accounted for 60-95% of the total acidity in the freshly prepared H-forms. The number of strong acid sites decreased and that of the weak acid sites increased on ageing. The process of autotransformation in aqueous dispersion at 90~ was completed within four days. Layer-charge distributions of all samples were inhomogeneous with layer charges from 0.25-0.39 Eq/unit O10(OH)2. Oxalate pretreatment of the samples resulted in changes in the layer-charge distribution due to the removal of readily soluble phases which may have blocked exchange sites. After autotransformation, the alkylammonium exchange method revealed inhomogeneous charge density distributions; the fraction of layers of the highest charge decreased. Comparison of total CEC obtained from potentiometric curves and interlamellar CEC calculated from the mean layer charge confirmed attack of protons from particle edges. However, for several samples the structural attack may also occur from the interlayer space. Autotransformation of the Hsmectites decreased the mean layer charge. Protons probably attack the Mg(O,OH)6 octahedra preferentially during the autotransformation.

Effect of Hydrothermal Conditions on Isomerization Activity of Pt/SO42--ZrO2

2010 ◽  
Vol 132 ◽  
pp. 183-191
Author(s):  
Juan Juan Zhang ◽  
Yue Qin Song ◽  
Xiao Long Zhou ◽  
Cheng Lie Li ◽  
Jin An Wang ◽  
...  
Keyword(s):  
Sulfur Content ◽  
Crystalline Structure ◽  
Fixed Bed ◽  
Strong Acid ◽  
Acid Sites ◽  
Zirconium Hydroxide ◽  
Fixed Bed Reactor ◽  
Isomerization Reaction ◽  
Hydrothermal Conditions ◽  
Hydrous Zirconia

Pt/SO42--ZrO2 catalysts (PSZ) were prepared by using a series of hydrous zirconia as support synthesized via a hydrothermal method. The catalytic performances of these catalysts were evaluated in the n-hexane isomerization in a fixed bed reactor. The crystalline structure, acidity, reduction properties, textural texture, and sulfur content were characterized by XRD, NH3-TPD, H2-TPR, N2 adsorption and thermal analysis. The experimental results indicated that the hydrothermal ageing of zirconium hydroxide led to great changes in the crystalline structure of hydrous zirconia support, sulfur content, and the acidity of PSZ. The abundant strong acid sites and high sulfur content were essential but insufficient to achieve a PSZ catalyst with high isomerization activity. Too weak or too strong interaction between sulfur species and zirconia in the catalysts was unfavorable to the isomerization reaction. The presence of considerable sulfate species interacting moderately with zirconia was crucial to high isomerization activity.

scholarly journals Catalytic Rapid Pyrolysis ofQuercus variabilisover Nanoporous Catalysts

2015 ◽  
Vol 2015 ◽  
pp. 1-6 ◽  
Author(s):  
Hyeon Koo Kang ◽  
In-Gu Lee ◽  
Kyong-Hwan Lee ◽  
Beom-Sik Kim ◽  
Tae Su Jo ◽  
...  
Keyword(s):  
Oil Quality ◽  
Strong Acid ◽  
Abundant Species ◽  
Acid Sites ◽  
Weak Acid ◽  
Nanoporous Materials ◽  
Bio Oil ◽  
Strong Acid Sites ◽  
Rapid Pyrolysis ◽  
Mcm 41

Catalytic rapid pyrolysis ofQuercus variabilis, a Korean native tree species, was carried out using Py-GC/MS. Mesoporous MFI, which has both nanopores and micropores, and three nanoporous materials, Al-MCM-41, Al-SBA-15, andγ-Al2O3, were used as the catalyst. The acid sites of mesoporous MFI were strong Brønsted acid sites, whereas those of nanoporous materials were mostly weak acid sites. The composition of the product bio-oil varied greatly depending on the acid characteristics of the catalyst used. Phenolics were the most abundant species in the bio-oil, followed by acids and furanics, obtained over Al-MCM-41 or Al-SBA-15 with weak acid sites, whereas aromatics were the most abundant species produced over mesoporous MFI with strong acid sites, followed by phenolics. Aromatics, phenolics, and furanics are all important chemicals contributing to the improvement of bio-oil quality.

Hydrothermal Modification Effect on the Catalyst for Etherification

2013 ◽  
Vol 805-806 ◽  
pp. 1368-1375
Author(s):  
Xi Ming Yan ◽  
Ming Ke ◽  
Zhao Zheng Song
Keyword(s):  
Active Component ◽  
Fixed Bed ◽  
Strong Acid ◽  
Weak Acid ◽  
Fixed Bed Reactor ◽  
Total Acid ◽  
Surface Areas ◽  
Hydrothermal Modification ◽  
Different Temperatures ◽  
Loading Amount

Etherification of isoamylene with methanol has been carried out over the γ-Al2O3/Hβ catalyst in a fixed bed reactor, catalysts were hydrothermal modified at different temperatures and time. The results show that the appropriate loading amount of active component Hβ is 20%; Hydrothermal modification is an effective way to improve the etherification activity, When γ-Al2O3/20%Hβ catalyst was hydrothermal modified at 573K for 3 hours, the isoamylene conversion is the highest, reach up to 51.95%, about 25% higher than the untreated one. From results of BET, XRD, and NH3-TPD characterization can be seen that hydrothermal modification does not change crystalline structure of the catalyst, but specific surface areas decrease together with pore volume and pore size increase, it also reduced the total acid volume of catalyst and improved the surface acid distribution of weak acid and strong acid.

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.

scholarly journals Acidity effects of K promoted Co-based catalyst with NH4OH addition of the impregnation solution for Fischer-Tropsch synthesis

2019 ◽  
Vol 268 ◽  
pp. 07001
Author(s):  
Zaky Al Fatony ◽  
Yosi Febriani ◽  
IGBN Makertihartha ◽  
Melia Laniwati Gunawan ◽  
Subagjo
Keyword(s):  
Catalyst Activity ◽  
Fixed Bed ◽  
Product Distribution ◽  
Acid Sites ◽  
Weak Acid ◽  
Tropsch Synthesis ◽  
Fixed Bed Reactor ◽  
Impregnation Method ◽  
Fischer Tropsch ◽  
Fischer Tropsch Synthesis

Fischer-Tropsch synthesis (FTS) with cobalt-based catalyst has been developed to produce wax as a feedstock for further catalytic cracking. During catalyst preparation, NH4OH was added to the salt nitrate precursor to investigate the influence on catalyst acidity. Catalysts were prepared by the dry impregnation method and characterized by XRD, BET and NH3-TPD analyses. These properties were correlated with activity and selectivity of the catalyst. Activity tests showed CO and H2 conversion were in the range of 36.4% to 80.3% and 34.2% to 74.1% respectively. The cobalt particle size measurements exhibited 7.6-8.5 nm. The presence of weak acid sites on catalyst with large surface area and pore size is mainly responsible for obtaining high yields of C5+ hydrocarbon due to suppression of cracking properties. The product distribution showed a higher selectivity to C5+ in the range of 53.57% to 96.5%. In this study, FTS was evaluated by using fixed-bed reactor at 20 bar, 250 C, and WHSV of 1500 ml/g.cat/h-1.

scholarly journals Tungsten Oxide-Modified SSZ-13 Zeolite as an Efficient Catalyst for Ethylene-To-Propylene Reaction

Catalysts ◽  
2021 ◽  
Vol 11 (5) ◽  
pp. 553
Author(s):  
Mansurbek Urol ugli Abdullaev ◽  
Sungjune Lee ◽  
Tae-Wan Kim ◽  
Chul-Ung Kim
Keyword(s):  
Tungsten Oxide ◽  
Fixed Bed ◽  
Acid Sites ◽  
Fixed Bed Reactor ◽  
Incipient Wetness Impregnation ◽  
Impregnation Method ◽  
Efficient Catalyst ◽  
X Ray ◽  
Propylene Selectivity ◽  
Temperature Programmed

Among the zeolitic catalysts for the ethylene-to-propylene (ETP) reaction, the SSZ-13 zeolite shows the highest catalytic activity based on both its suitable pore architecture and tunable acidity. In this study, in order to improve the propylene selectivity further, the surface of the SSZ-13 zeolite was modified with various amounts of tungsten oxide ranging from 1 wt% to 15 wt% via a simple incipient wetness impregnation method. The prepared catalysts were characterized with several analysis techniques, specifically, powder X-ray diffraction (PXRD), Raman spectroscopy, temperature-programmed reduction of hydrogen (H2-TPR), temperature-programmed desorption of ammonia (NH3-TPD), inductively coupled plasma-atomic emission spectroscopy (ICP-AES), and N2 sorption, and their catalytic activities were investigated in a fixed-bed reactor system. The tungsten oxide-modified SSZ-13 catalysts demonstrated significantly improved propylene selectivity and yield compared to the parent H-SSZ-13 catalyst. For the tungsten oxide loading, 10 wt% loading showed the highest propylene yield of 64.9 wt%, which was 6.5 wt% higher than the pristine H-SSZ-13 catalyst. This can be related to not only the milder and decreased strong acid sites but also the diffusion restriction of bulky byproducts, as supported by scanning transmission electron microscopy-energy dispersive X-ray spectroscopy (STEM-EDS) observation.

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