H-USY Zeolite Research Articles

Influences of zeolite structure on formation and location of coke: A 129Xe and 13C CP-MAS NMR study

129Xe and 13C CP-MAS NMR have been used to study coking and deactivation behavior of fouled H-beta, H-mordenite, H-ZSM-5 and H-USY zeolites during ethylbenzene disproportionation reaction. The nature and preferable location of coke are investigated for two different reaction severities, namely at low conversions (5–15 wt%) where only disproportionation reactions are expected to take place and high conversions (25–45 wt%) at which side reactions such as cracking may also occur. At low conversion, cokes are alkyl aromatic in nature and consist of both soft and hard cokes, whereas at high conversion only less volatile polyaromatic hard cokes are present. The preferred location of the carbonaceous residues is found to be strongly dependent on the reaction severity as well as the framework structure of the zeolitic catalysts.

Role of Lewis Acidity in the Deactivation of USY Zeolites during 2-Methylpentane Cracking

The role of strong Lewis acid sites in the deactivation of H-USY zeolite during 2-methylpentane cracking was investigated. NH3 adsorption microcalorimetry and FTIR of adsorbed NH3 were used to char...

Fluorination of USY and Modification of Its Catalytic Properties

A set of ultrastable Y zeolites with different amounts of framework and nonframework aluminum was prepared by fluorination of H-USY zeolite. The samples were characterized by chemical analysis, physical adsorption of nitrogen at low temperature and of pentane at room temperature, XRD,29Si, and27Al MAS NMR.n-Pentane isomerization has been studied mainly at 285°C, while the activation energy was measured on several samples. The fluorine treatment removed Al from the framework position and stabilized the zeolite structure. Hence, it decreases the number of Brønsted sites. Despite an increase in the amount of nonframework aluminum, the number of Lewis sites decreases; this means that the dispersion of the Lewis sites on the nonframework alumina particles decreases dramatically. The catalytic activity appears to be a direct function of both the number of Lewis and the number of Brønsted acid sites. These numbers being close to one another, it might be that the “acid site” is, in fact, a complex resulting from the interaction between the proton donor and an electron acceptor.

Zeolite-supported hydrodesulfurization catalysts prepared by ion exchange with Mo and Mo [sbnd]Ni sulfide clusters

Zeolites NaY, HUSY and KL were ion-exchanged with a cationic molybdenum sulfide cluster [Mo 3S 4(H 2O) 9] 4+ with incomplete cubane-type structure and a cationic nickel-molybdenum mixed sulfide cluster [Mo 3NiS 4Cl(H 2O) 9] 3+ with complete cubane-type structure. The UV-visible spectra and EXAFS analysis data exhibited that the structure of the molybdenum cluster was maintained after ion exchange. These zeolite catalysts showed activity for benzothiophene hydrodesulfurization; especially, involvement of Ni resulted in great enhancement of the hydrodesulfurization activity.

Synthesis of adamantane on zeolite catalysts

AbstractThe synthesis of adamantane from tetrahydrodicyclopentadiene on zeolites with different framework structures was studied. The adamantane yield on HY zeolites is higher than on HM and HZSM‐5 zeolites. Among various types of dealuminated HY zeolites the HEY and HUSY zeolites give higher adamantane yields than conventional HY zeolite. The changes in activity and selectivity of the main and side reactions are correlated with the acidity and the pore structure of the zeolites. To ion‐exchange the HY and HUSY zeolites with Ni2+ and La3+ cations may further improve the activity and selectivity of the zeolite catalysts.

Compounds responsible for the deactivation of H-USY zeolite during the alkylation of phenol with methanol

H-USY deactivates very rapidly during the alkylation of phenol with methanol at 200°C. The retention in the pores of compounds resulting from successive O- and C-alkylation of phenol (such as polymethylphenols and polymethylanisoles) is responsible for this deactivation. The retention of these compounds in the pores is not due to their steric blockage but to their low volatility and their strong adsorption.

Ion-exchanged ultrastable Y zeolites: II. Alkaline earth-exchanged zeolites

The preparation and structural characteristics of alkaline earth-exchanged ultrastable Y zeolites ( M II, H-USY) are described and discussed. M II, H-USY zeolites were prepared at different exchange pH. These materials have good crystallinity and stability. Their thermal stability decreases with increasing ionic radius of the alkaline earth metal. The Brønsted acidity shows a similar trend. However, the affinity for zeolitic sites increases with ionic radius. The infrared spectra of M II, H-USY zeolites in the OH stretching region and in the framework vibrational region are described. Pyridine adsorption experiments indicate the presence of both Brønsted and Lewis acidity. Steaming results in decrease of Brønsted acidity, shrinking in unit cell size, further dealumination of the zeolitic framework, and cationic migration.

Ion-Exchanged Ultrastable Y Zeolites. 3. Gas Oil Cracking over Rare Earth-Exchanged Ultrastable Y Zeolites

A series of lanthanum, cerium, and mixed rare earth exchanged ultrastable Y zeolites were prepared by methods described previously, mixed with 75-90Vertical Bar3< amorphous silica-alumina, and calcined or steam-treated prior to catalytic evaluation. Results for West Texas gas oil cracking at 493/sup 0/C in a pilot fluid catalytic cracking unit showed that rare earth, exchanged ultrastable Y (RE-USY) zeolites are more active than H-USY zeolites. They show good gasoline selectivity, lower coking rates, and higher olefin selectivity than ordinary RE-Y. The gasoline fractions obtained over RE-USY catalysts have a high content of aromatics, olefins, and cyclic allylic hydrocarbons compared with that formed over RE-Y; this is attributed to the lower acid site density in RE-USY. By varying the rare earth input into the zeolite, a series of yield-oriented catalysts can be prepared, each tailored to meet the demand of a particular segment of the refining industry.