Alkylation reactions over ion-exchanged molecular sieve zeolite catalysts. Part 3.—Alkylation of toluene and benzene with ethanol: consideration of the effects of initial coke formation on para selectivity

1983 ◽  
Vol 79 (2) ◽  
pp. 311 ◽  
Author(s):  
Brendan Coughlan ◽  
William M. Carroll ◽  
John Nunan
Keyword(s):  
Molecular Sieve ◽  
Coke Formation ◽  
Zeolite Catalysts ◽  
Alkylation Reactions

Para-directed aromatic reactions over shape-selective molecular sieve zeolite catalysts

1979 ◽  
Vol 101 (22) ◽  
pp. 6783-6784 ◽  
Author(s):  
N. Y. Chen ◽  
W. W. Kaeding ◽  
F. G. Dwyer
Keyword(s):  
Molecular Sieve ◽  
Zeolite Catalysts ◽  
Shape Selective

Analysis of Precursors of Carbon Deposition in Hydrogen Preparation by Fast Pyrolysis of Bio-Oil via Catalytic Steam Reforming

2012 ◽  
Vol 512-515 ◽  
pp. 338-342 ◽  
Author(s):  
Ping Lan ◽  
Li Hong Lan ◽  
Tao Xie ◽  
An Ping Liao
Keyword(s):  
Steam Reforming ◽  
Molecular Sieve ◽  
Carbon Deposition ◽  
Catalyst Activity ◽  
Coke Formation ◽  
Fast Pyrolysis ◽  
Bio Oil ◽  
Aldehydes And Ketones ◽  
Pyrolysis Of Biomass ◽  
Catalytic Steam Reforming

In the preparation of hydrogen, the bio-oil from pyrolysis of biomass must be further upgraded (catalytic steam reforming)SO as to improve its quality．However the catalyst used in the steam reforming reaction is easy to lose its activity due to being coked' SO that it is important to study the coke formation and its efects on the catalyst activity in the steam reforming process．Fourier Transform Infrared Spectroscopy were used to analyze the precursor of coke on the catalyst Ni/MgO-La2O3-Al2O3 used in steam reforming reaction and the mechanism of coking Was also discussed based on it．The results indicate that precursors of coke deposited inside the pore of the molecular sieve are mainly paraffin, alcohols, aldehydes and ketones, and aromatic compounds.

scholarly journals Perfomance of Chromium-Exchanged Zeolite Catalysts in the Combustion of Volatile Organic Compound Pollutants

2004 ◽  
Vol 4 (2) ◽  
pp. 66
Author(s):  
Ahmad Zuhairi Abdullah ◽  
Mohamad Zallani Abu Bakar ◽  
Subhash Bhatia
Keyword(s):  
Resonance Effect ◽  
Coke Formation ◽  
Fixed Bed ◽  
Space Velocity ◽  
Zeolite Catalysts ◽  
Long Run ◽  
Acetate Methyl ◽  
Beta Zeolites ◽  
Volatile Organic ◽  
High Metal

The activity and stability of chromium-exchanged beta (Cr-BEA),mordenite (Cr-MOR), and ZSM-5 (Cr-ZSM-5) zeolites of different Si/Alratios for volatile organic compounds (VOCS) combustion were reported. A fixed-bed catalytic reactor operated between 100 and 500°C and at a gas hourly space velocity (GHSV) of 32,000 h'! was used for the study. Methanol, ethyl acetate, methyl ethyl ketone, benzene, hexane, toluene, and xylene, all at 2,000 ppm, were selected as the VOC model compounds. Oxygenated VOCs were more reactive while showing good carton dioxide yield. Aromatics were more stable due to their resonance effect but the reactivity increased with the attachment of an electron donor group such as the methyl group. Cr-ZSM- 5(240) demonstrated the highest hydrothermal stability due to its high Si/Al ratio. Despite giving a high initial activity due to its high metal loading, Cr-BEA(25) was susceptible to coking in the long run. The high coke formation in mordenite and beta zeolites was attributed to their high acidity, interconnecting channels of different sizes, and relatively larger pore sizes. The coke that formed on Cr-ZSM-5(240) was more carbonaceous and oxidized at higher temperatures.

Investigating the properties and performance of 3A molecular sieves as an adsorbent to prevent coke formation in olefin dehydration process

2021 ◽  
Vol 0 (0) ◽  
Author(s):  
Zoya Moslempour ◽  
Sepehr Sadighi ◽  
Ali Dashti ◽  
Ali Ahmadpour
Keyword(s):  
Molecular Sieves ◽  
Molecular Sieve ◽  
Coke Formation ◽  
Chemical Properties ◽  
X Ray Diffraction ◽  
X Ray ◽  
Na Ions ◽  
Temperature Programmed ◽  
And Performance ◽  
Physical And Chemical

Abstract To study the affinity of 3A aluminosilicate adsorbents to prevent oligomerization of olefin molecules and forming green oil, physical and chemical properties of 3A molecular sieves are measured by using characterization techniques such as temperature-programmed desorption (TPD), nitrogen (N2) and water adsorptions, X-ray diffraction (XRD), X-ray fluorescence (XRF), crushing strength, and carbon dioxide (CO2) adsorption. Moreover, coke formation affinities of the understudy adsorbents are evaluated in a bench-scale system using 1-butene and 1,3-butadiene at temperatures of 220 and 260 °C, and outcomes are validated against the actual data gathered from an industrial scale olefin dehydration plant. Results confirm that the type of binder and the amount of ion exchange affect the performance of a 3A molecular sieve nominated for dehydrating olefinic streams. The binder with the least amount of acidity is preferred, and at least 35% of Na ions of the 4A zeolite should be exchanged with K ions to make it applicable for synthesizing an appropriate 3A molecular sieve. Furthermore, to control the oligomerization and inhibit green oil formation, the CO2 adsorption and acidity of Trisiv shape molecular sieves with the sizes of 1/4 inch should be less than 0.5 wt % and 1.7 mmol NH3/g, respectively. For extrudate shape with the sizes of 1/16 inch CO2 adsorption and acidity should be less than 0.2 wt % and 2.2 mmol NH3/g, respectively.

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