scholarly journals Improvement of Lifetime Using Transition Metal-Incorporated SAPO-34 Catalysts in Conversion of Dimethyl Ether to Light Olefins

2013 ◽  
Vol 2013 ◽  
pp. 1-9 ◽  
Author(s):  
Hyo-Sub Kim ◽  
Su-Gyung Lee ◽  
Young-Ho Kim ◽  
Dong-Hee Lee ◽  
Jin-Bae Lee ◽  
...  
Keyword(s):  
Transition Metal ◽  
Transition Metals ◽  
Hydrothermal Method ◽  
Dimethyl Ether ◽  
Acid Sites ◽  
Weak Acid ◽  
Mas Nmr ◽  
Light Olefins ◽  
Structural Arrangement ◽  
Acidic Sites

Transition metal (Mn, Fe, or Ni) incorporated SAPO-34 (MeAPSO-34) nanocatalysts were synthesized using a hydrothermal method to improve the catalytic lifetime in the conversion of dimethyl ether to light olefins (DTO). The structures of the synthesized catalysts were characterized using several methods including XRD, SEM, BET,29Si-MAS NMR, and NH3-TPD techniques. Although the structure of the MeAPSO-34 catalysts was similar to that of the SAPO-34 catalyst, the amount of weak acid sites in all MeAPSO-34 catalysts was markedly increased and accompanied by differences in crystallinity and structural arrangement. The amount of weak acid sites decreased in the following order: NiAPSO-34 > FeAPSO-34 > MnAPSO-34 > SAPO-34 catalyst. The MeAPSO-34 catalysts, when used in the DTO reaction, maintained DME conversion above 90% for a longer time than the SAPO-34 catalyst, while also maintaining the total selectivity above 95% for light olefins. In addition, the NiAPSO-34 catalyst showed the longest catalytic lifetime; the lifetime was extended approximately 2-fold relative to the SAPO-34 catalyst. Therefore, the increase in the catalytic lifetime is related to the amount of weak acidic sites, and these sites are increased in number by incorporating transition metals into the SAPO-34 catalyst.

Reaction Characteristic of MeAPSO-34 (Me=Mn, Co) Catalysts for Olefins Production from Dimethyl Ether

2012 ◽  
Vol 550-553 ◽  
pp. 416-419
Author(s):  
Young Ho Kim ◽  
Su Gyung Lee ◽  
Eun Jee Kang ◽  
Hyo Sub Kim ◽  
Chu Sik Park
Keyword(s):  
Dimethyl Ether ◽  
Strong Acid ◽  
Acid Sites ◽  
Coke Deposition ◽  
Light Olefins ◽  
Co Catalysts ◽  
Strong Acid Sites ◽  
Reaction Characteristic ◽  
Catalyst Lifetime

In DME to olefins (DTO) reaction, SAPO-34 catalyst with CHA structure is well known to be one of the catalysts with good performance. However, the SAPO-34 catalyst is easily deactivated due to coke deposition during DTO reaction. In this study, MeAPSO-34 catalysts (Me=Mn, Co) were prepared for the increase of the catalyst lifetime and their properties have been characterized by XRD and SEM. The DTO reaction was carried out over the MeAPSO-34 catalysts, and the results were compared with the SAPO-34 catalyst. The lifetime of MeAPSO-34 catalysts with high DME conversion and selectivity of light olefins was prolonged than that of the SAPO-34 catalyst. It may be concluded that the decrease of strong acid sites, which were responsible for the formation of coke, affect on the lifetime of the MeAPSO-34 catalysts. In addition, the CoAPSO-34 catalyst with a Co additive showed the best performance in terms of the catalytic lifetime and the selectivity to light olefins.

Study on Preparation and Catalytic Properties of Pd/γ-Al2O3 Catalysts in One-Step Synthesis of Dimethyl Ether

2011 ◽  
Vol 66-68 ◽  
pp. 1404-1409 ◽  
Author(s):  
Rui Zhi Chu ◽  
Zhong Cai Zhang ◽  
Ya Fei Liu ◽  
Xian Liang Meng ◽  
Zhi Min Zong ◽  
...  
Keyword(s):  
Dimethyl Ether ◽  
Catalytic Performance ◽  
Acid Sites ◽  
Co Conversion ◽  
Dimethyl Ether Synthesis ◽  
Acidic Sites ◽  
One Step ◽  
Space Time Yield ◽  
Ether Synthesis ◽  
Synthesis Of Dimethyl Ether

A series of Pd/γ-Al2O3 catalysts with different additons of Pd were prepared by impregnation. The effect of calcination condition and Pd loading on catalytic performance of catalysts for one-step dimethyl ether synthesis has been investigated. The physic-chemical performance and structure of Pd/γ-Al2O3 catalysts were characterized by CO-TPD, TGA and nitrogen physisorption. The results show that the dispersion of Pd and the amount of adsorbration on the CO-bridge of Pd could be increased to by the moderate microwave heating on the catalysts, and the catalyst performance can be improved. But a large number of surface acidic sites of Pd/γ-Al2O3 are covered by highly fragmented Pd-grain, it causes DME selectivity reduced. And the excessive Pd can reduce the samples’ surface acid, decrease the dispersion of the metal Pd and block up the pore of γ-Al2O3. The CO conversion rate and DME space-time yield could reach 60.1% and 28.76 mmol·g-1·h-1 respectively at 2% Pd loading, at this time Pd/γ-Al2O3 has a high Pd activity surface and ideal acid sites.

scholarly journals Dimethyl Ether to Olefins over Modified ZSM-5 Based Catalysts Stabilized by Hydrothermal Treatment

Catalysts ◽  
2019 ◽  
Vol 9 (5) ◽  
pp. 485 ◽  
Author(s):  
Maria Magomedova ◽  
Ekaterina Galanova ◽  
Ilya Davidov ◽  
Mikhail Afokin ◽  
Anton Maximov
Keyword(s):  
Steady State ◽  
Hydrothermal Treatment ◽  
Dimethyl Ether ◽  
Formation Rate ◽  
Reaction Rates ◽  
Product Formation ◽  
Acid Sites ◽  
Weak Acid ◽  
Main Reaction ◽  
Reaction Products

The reaction of dimethyl ether to olefin over HZSM-5/Al2O3 catalysts modified by Zr and Mg and stabilized by hydrothermal treatment has been studied. Regardless of the introduction method and the nature of the metal, the dependence of the key products selectivity on X(DME) over hydrothermally treated steady-state catalysts does not change, and the experimental points are described by the same curves. Metal introduction and the corresponding changes in the acid sites distribution do not change the ratio of main reaction rates, only the absolute values of the formation rate of the products are changed. Zr doping leads to the greatest activity in the DME conversion due to an equable decrease in the total acidity of the sample. On the other hand, the Mg-modified sample has a higher amount of weak acid sites, which reduces activity. At low DME conversion, methanol is one of the primary reaction products which formed from DME simultaneously with propylene in alkene cycle. At high DME conversion, the methanol acts as a main reagent which leads to ethylene formation in the arene cycle. Based on the results, the role of the metal in the reaction chemistry is considered and the mechanism of product formation from DME over steady-state catalyst is proposed, which describes both the participation of DME and the methanol produced.

scholarly journals CuO-In2O3 Catalysts Supported on Halloysite Nanotubes for CO2 Hydrogenation to Dimethyl Ether

Catalysts ◽  
2021 ◽  
Vol 11 (10) ◽  
pp. 1151
Author(s):  
Alexey Pechenkin ◽  
Dmitry Potemkin ◽  
Maria Rubtsova ◽  
Pavel Snytnikov ◽  
Pavel Plyusnin ◽  
...  
Keyword(s):  
Dimethyl Ether ◽  
Space Velocity ◽  
Halloysite Nanotubes ◽  
Acid Sites ◽  
Co2 Conversion ◽  
X Ray Diffraction ◽  
Transition Electron Microscopy ◽  
Hydrogenation Of Co2 ◽  
Acidic Sites ◽  
Temperature Programmed

Hydrogenation of CO2 relative to valuable chemical compounds such as methanol or dimethyl ether (DME) is an attractive route for reducing CO2 emissions in the atmosphere. In the present work, the hydrogenation of CO2 into DME over CuO-In2O3, supported on halloysite nanotubes (HNT) was investigated in the temperature range 200–300 °C at 40 atm. HNT appears to be novel promising support for bifunctional catalysts due to its thermal stability and the presence of acidic sites on its surface. CuO-In2O3/HNT catalysts demonstrate higher CO2 conversion and DME selectivity compared to non-indium CuO/HNT catalysts. The catalysts were investigated by N2 adsorption, X-ray diffraction, hydrogen-temperature programmed reduction and transition electron microscopy. The acid sites were analyzed by temperature programmed desorption of ammonia. It was shown that CuO/HNT was unstable under reaction conditions in contrast to CuO-In2O3/HNT. The best CuO-In2O3/HNT catalyst provided CO2 conversion of 7.6% with 65% DME selectivity under P = 40 atm, T = 250 °C, gas hour space velocity 12,000 h−1 and H2:CO2 = 3:1.

Intercalation of First Row Transition Metals inside Covalent-Organic Frameworks (COF): a Strategy to Fine Tune the Electronic Properties of Porous Crystalline Materials

2018 ◽  
Author(s):  
Srimanta Pakhira ◽  
Jose Mendoza-Cortes
Keyword(s):  
Transition Metal ◽  
Transition Metals ◽  
Electronic Properties ◽  
High Surface ◽  
Electronic Devices ◽  
High Surface Area ◽  
Main Role ◽  
Covalent Organic Frameworks ◽  
Porous Network ◽  
Crystalline Materials

<div>Covalent organic frameworks (COFs) have emerged as an important class of nano-porous crystalline materials with many potential applications. They are intriguing platforms for the design of porous skeletons with special functionality at the molecular level. However, despite their extraordinary properties, it is difficult to control their electronic properties, thus hindering the potential implementation in electronic devices. A new form of nanoporous material, COFs intercalated with first row transition metal is proposed to address this fundamental drawback - the lack of electronic tunability. Using first-principles calculations, we have designed 31 new COF materials <i>in-silico</i> by intercalating all of the first row transition metals (TMs) with boroxine-linked and triazine-linked COFs: COF-TM-x (where TM=Sc-Zn and x=3-5). This is a significant addition considering that only 187 experimentally COFs structures has been reported and characterized so far. We have investigated their structure and electronic properties. Specifically, we predict that COF's band gap and density of states (DOSs) can be controlled by intercalating first row transition metal atoms (TM: Sc - Zn) and fine tuned by the concentration of TMs. We also found that the $d$-subshell electron density of the TMs plays the main role in determining the electronic properties of the COFs. Thus intercalated-COFs provide a new strategy to control the electronic properties of materials within a porous network. This work opens up new avenues for the design of TM-intercalated materials with promising future applications in nanoporous electronic devices, where a high surface area coupled with fine-tuned electronic properties are desired.</div>

Bond-length distributions for ions bonded to oxygen: Metalloids and post-transition metals

2017 ◽  
Author(s):  
Olivier Charles Gagné ◽  
Frank Christopher Hawthorne
Keyword(s):  
Transition Metal ◽  
Transition Metals ◽  
Metal Ions ◽  
Bond Length ◽  
Lone Pair ◽  
Transition Metal Ions ◽  
Oxygen Lone Pair

Bond-length distributions are examined for thirty-three configurations of the metalloid ions and fifty-six configurations of the post-transition-metal ions bonded to oxygen. Lone-pair stereoactivity is discussed.

Bond-length distributions for ions bonded to oxygen: Metalloids and post-transition metals

2017 ◽  
Author(s):  
Olivier Charles Gagné ◽  
Frank Christopher Hawthorne
Keyword(s):  
Transition Metal ◽  
Transition Metals ◽  
Metal Ions ◽  
Bond Length ◽  
Lone Pair ◽  
Transition Metal Ions ◽  
Oxygen Lone Pair

Bond-length distributions are examined for thirty-three configurations of the metalloid ions and fifty-six configurations of the post-transition-metal ions bonded to oxygen. Lone-pair stereoactivity is discussed.

Electronic properties of quasi two-dimensional transition metals chalcogenides with low-dimensional magnetism

Doklady BGUIR ◽  
2020 ◽  
Vol 18 (7) ◽  
pp. 87-95
Author(s):  
M. S. Baranava ◽  
P. A. Praskurava
Keyword(s):  
Transition Metal ◽  
Transition Metals ◽  
Exchange Interaction ◽  
Electronic Properties ◽  
Metal Atom ◽  
Transition Metal Atom ◽  
Two Dimensional ◽  
Transition Metal Atoms ◽  
Ground Magnetic ◽  
Low Dimensional

The search for fundamental physical laws which lead to stable high-temperature ferromagnetism is an urgent task. In addition to the already synthesized two-dimensional materials, there remains a wide list of possible structures, the stability of which is predicted theoretically. The article suggests the results of studying the electronic properties of MAX3 (M = Cr, Fe, A = Ge, Si, X = S, Se, Te) transition metals based compounds with nanostructured magnetism. The research was carried out using quantum mechanical simulation in specialized VASP software and calculations within the Heisenberg model. The ground magnetic states of twodimensional MAX3 and the corresponding energy band structures are determined. We found that among the systems under study, CrGeTe3 is a semiconductor nanosized ferromagnet. In addition, one is a semiconductor with a bandgap of 0.35 eV. Other materials are antiferromagnetic. The magnetic moment in MAX3 is localized on the transition metal atoms: in particular, the main one on the d-orbital of the transition metal atom (and only a small part on the p-orbital of the chalcogen). For CrGeTe3, the exchange interaction integral is calculated. The mechanisms of the formation of magnetic order was established. According to the obtained exchange interaction integrals, a strong ferromagnetic order is formed in the semiconductor plane. The distribution of the projection density of electronic states indicates hybridization between the d-orbital of the transition metal atom and the p-orbital of the chalcogen. The study revealed that the exchange interaction by the mechanism of superexchange is more probabilistic.

Efficient Production of Light Olefin Based on Methanol Dehydration: Simulation and Design Improvement

2020 ◽  
Vol 23 ◽  
Author(s):  
S. Majid Abdoli ◽  
Mahsa Kianinia
Keyword(s):  
Dimethyl Ether ◽  
Flow Reactor ◽  
New Technology ◽  
Plug Flow ◽  
Light Olefins ◽  
Efficient Production ◽  
Actual Process ◽  
Light Olefin ◽  
Aspen Hysys ◽  
Improved Design

Background: Ethylene, propylene, and butylene as light olefins are the most important intermediates in the petrochemical industry worldwide. Methanol to olefins (MTO) process is a new technology based on catalytic cracking to produce ethylene and propylene from methanol. Aims and Objective: This study aims to simulate the process of producing ethylene from methanol by using Aspen HYSYS software from the initial design to the improved design. Methods: Ethylene is produced in a two-step reaction. In an equilibrium reactor, the methanol is converted to dimethyl ether by an equilibrium reaction. The conversion of the produced dimethyl ether to ethylene is done in a conversion reactor. Changes have been made to improve the conditions and get closer to the actual process design done in the industry. The plug flow reactor has been replaced by the equilibrium reactor, and the distillation column was employed to separate the dimethyl ether produced from the reactor. Result and Conclusion: The effect of the various parameters on the ethylene production was investigated. Eventually, ethylene is

Correlative experimental and theoretical characterization of transition metal doped hydroxyapatite nanoparticles fabricated by hydrothermal method

2021 ◽  
Vol 173 ◽  
pp. 110911
Author(s):  
Anastasia V. Sadetskaya ◽  
Natalia P. Bobrysheva ◽  
Mikhail G. Osmolowsky ◽  
Olga M. Osmolovskaya ◽  
Mikhail A. Voznesenskiy
Keyword(s):  
Transition Metal ◽  
Hydrothermal Method ◽  
Hydroxyapatite Nanoparticles ◽  
Theoretical Characterization ◽  
Metal Doped
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