scholarly journals Silver-Modified Nano Mordenite for Carbonylation of Dimethyl Ether

Catalysts ◽  
2021 ◽  
Vol 11 (2) ◽  
pp. 197
Author(s):  
Qijia Lu ◽  
Weixin Qian ◽  
Hongfang Ma ◽  
Haitao Zhang ◽  
Weiyong Ying
Keyword(s):  
Ion Exchange ◽  
Dimethyl Ether ◽  
Methyl Acetate ◽  
Co Adsorption ◽  
Acid Sites ◽  
Membered Ring ◽  
27Al Nmr ◽  
Site Distribution ◽  
Adsorption Performance ◽  
Adsorption Desorption

Mordenite (H-MOR) catalysts were synthesized by a hydrothermal method, and silver-modified mordenite (Ag-MOR) catalysts were prepared by ion exchange with AgNO3 at different concentrations. The performance of these catalysts in the carbonylation of dimethyl ether (DME) to methyl acetate (MA) was also evaluated. The catalysts were characterized by Ar adsorption/desorption, XRD, ICP-AES, SEM, HRTEM, 27Al NMR, H2-TPR, NH3-TPD, Py-IR, and CO-TPD. According to the characterization results, Ag ion exchange sites were mainly located in the 8-membered ring (8-MR) channels of Ag-MOR; evenly dispersed Ag2O particles were also present. The acid site distribution was changed by the modification of Ag, and the amount of Brønsted acid sites increased in 8-MR and decreased in 12-MR. The CO adsorption performance of the catalyst significantly increased with the modification of Ag. These changes improved the conversion and selectivity of the carbonylation of DME. Over 4Ag-MOR in particular, DME conversion and MA selectivity reached 94% and 100%, respectively.

scholarly journals Reaction mechanism of dimethyl ether carbonylation to methyl acetate over mordenite – a combined DFT/experimental study

2017 ◽  
Vol 7 (5) ◽  
pp. 1141-1152 ◽  
Author(s):  
D. B. Rasmussen ◽  
J. M. Christensen ◽  
B. Temel ◽  
F. Studt ◽  
P. G. Moses ◽  
...  
Keyword(s):  
Experimental Study ◽  
Dimethyl Ether ◽  
Density Functional ◽  
Methyl Acetate ◽  
Flow Reactor ◽  
Reaction Path ◽  
Fixed Bed ◽  
Density Functional Theory Calculations ◽  
Membered Ring ◽  
Functional Theory

Dimethyl ether carbonylation to methyl acetate over mordenite was studied theoretically with density functional theory calculations and experimentally in a fixed bed flow reactor. A new reaction path to methyl acetate entirely in the 8 membered ring was discovered.

Sorption of dimethyl ether on silica gel

1970 ◽  
Vol 48 (1) ◽  
pp. 13-16 ◽  
Author(s):  
E. Robinson ◽  
R. A. Ross
Keyword(s):  
Dimethyl Ether ◽  
Hysteresis Loops ◽  
Acid Sites ◽  
Silica Gels ◽  
Hydrogen Bond Formation ◽  
Heats Of Adsorption ◽  
Heat Treated ◽  
Ether Oxygen ◽  
Initial Adsorption ◽  
Adsorption Desorption

The adsorption of dimethyl ether has been studied at its boiling point on a range of silica gels by measurement of adsorption/desorption isotherms and isothermal calorimetric heats of adsorption. Data were determined on gels heat treated at 240, 500, 700, and 900 °C and also on gels impregnated with 0.274% w/w aluminum. On 240 °C gels, heats of adsorption varied from around 20 through 12 to 7 kcal/mole at θ = 0.01, 0.50, and 0.90, respectively. Hysteresis loops are analyzed and the initial adsorption trends explained by hydrogen bond formation between the ether oxygen and surface hydroxy groups. The enhanced amounts of ether adsorbed after aluminum impregnation are explained by the creation of either Brønsted acid sites on gels treated at 240 °C or Lewis acid sites on gels treated at the highest temperatures.

Elucidating the nature and role of Cu species in enhanced catalytic carbonylation of dimethyl ether over Cu/H-MOR

2015 ◽  
Vol 5 (9) ◽  
pp. 4378-4389 ◽  
Author(s):  
Huimin Zhan ◽  
Shouying Huang ◽  
Ying Li ◽  
Jing Lv ◽  
Shengping Wang ◽  
...  
Keyword(s):  
Synergistic Effect ◽  
Dimethyl Ether ◽  
Methyl Acetate ◽  
Acid Sites ◽  
Bronsted Acid ◽  
Brønsted Acid Sites ◽  
Brönsted Acid ◽  
Brönsted Acid Sites ◽  
Catalytic Carbonylation

The synergistic effect of Cu0 and Brønsted acid sites remarkably facilitates the carbonylation of dimethyl ether to form methyl acetate.

scholarly journals Resolving the Acid Site Distribution in Zn-Exchanged ZSM-5 with Stimulated Raman Scattering Microscopy

Catalysts ◽  
2020 ◽  
Vol 10 (11) ◽  
pp. 1331
Author(s):  
Guillaume Fleury ◽  
Maarten B. J. Roeffaers
Keyword(s):  
Ion Exchange ◽  
Lewis Acid ◽  
Active Sites ◽  
Stimulated Raman Scattering ◽  
Acid Sites ◽  
Lewis Acid Sites ◽  
Site Distribution ◽  
Particle Level ◽  
The Impact ◽  
Brønsted And Lewis Acid

Zeolites are widely used acid catalysts in research and in industrial processes. The catalytic performance of these materials is affected by the nature and concentration of Brønsted and Lewis acid sites. The balance between these types of active sites—and thus the activity and selectivity of the zeolite—can be altered by the introduction of metal species, e.g., by ion exchange. Although the acidic properties of zeolites are routinely characterized by bulk-scale techniques, this ensemble-averaged approach neglects the local variations in the material. Insights into the distribution of active sites at the single-particle level are thus critical to better understand the impact of post-synthetic modifications on the zeolite acidity. In this contribution, we spatially resolve Brønsted and Lewis acid sites in protonated and Zn-exchanged ZSM-5 crystals. To this end, the vibrational modes of pyridine chemisorbed on active sites are mapped with stimulated Raman scattering (SRS) microscopy. The SRS images reveal sharp inter- and intra-particle heterogeneities in the distribution of Lewis acid sites introduced upon ion exchange, ascribed to local variations in the Al content. Besides assessing the impact of Zn exchange on the active site distribution in ZSM-5 crystals, this approach enables uniquely to map the distribution of Lewis acid sites in catalysts at the single-particle level.

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).

Synthesis and Characterization of Different γ-Al2O3 Nanocatalysts for Methanol Dehydration to Dimethyl Ether

2012 ◽  
Vol 10 (1) ◽  
Author(s):  
Seyyed Ya'ghoob Hosseini ◽  
Mohammad Reza Khosravi Nikou
Keyword(s):  
Dimethyl Ether ◽  
Solid Acid Catalyst ◽  
Fixed Bed ◽  
Operating Parameter ◽  
Textural Properties ◽  
Ammonia Solution ◽  
Precipitation Method ◽  
High Yield ◽  
Methanol Dehydration ◽  
Adsorption Desorption

Abstract A simple co-precipitation method was utilized to synthesize γ-Al2O3 catalysts using aluminum nitrate nonahydrate as the source of aluminum cations for methanol dehydration to dimethyl ether (DME). Different precipitating agents comprising ammonium carbonate, ammonium bicarbonate and ammonia solutions were used for preparation of the samples. The catalysts were characterized by XRD, FTIR, SEM, NH3-TPD and N2 adsorption-desorption techniques. The sample prepared by ammonia solution had the highest acidity among the synthesized catalysts. Also, N2 adsorption-desorption results showed suitable textural properties for all of the synthesized samples. Vapor phase dehydration of methanol to DME was performed in the fixed bed micro reactor over the synthesized catalysts and commercial one for comparison purposes. The effects of different characteristics of catalysts such as surface area, acidity, sintering factor and temperature as an operating parameter on performance of catalysts were investigated. The catalyst prepared by ammonia solution showed best catalytic activity due to the suitable textural properties and high amount of acidic sites. Also, the results showed that only high acid strength can’t result high yield of DME for a solid acid catalyst.

Cuprous Species Distribution over CuCl/NaY Dependent on Acidity and their CO Adsorption/desorption Performance Study

2021 ◽  
pp. 133763
Author(s):  
Dequan Fan ◽  
Shuchao Jiang ◽  
Kai Qiao ◽  
Shengzhong Zhang ◽  
Hongtao Wang ◽  
...  
Keyword(s):  
Species Distribution ◽  
Co Adsorption ◽  
Performance Study ◽  
Adsorption Desorption
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