Authors:Anne Garrido Pedrosa, M. Souza, A. Silva, Dulce Melo, and A. Araujo
The study of the incorporation
of rare earth elements as additives in Y zeolites is a very interesting field
of research, mainly by its potential application as additives in catalytic
cracking process. In this work was studied the thermal and structural properties
of cerium, holmium and samarium supported on HZSM-12 zeolite. The obtained
materials were characterized by X-ray diffraction (XRD), infrared spectroscopy
(FTIR), nitrogen adsorption, thermogravimetry (TG/DTG), differential scanning
calorimetry (DSC) and differential thermal analysis (DTA). TG/DSC/DTA analyses
showed that the dehydration temperatures of RE/HZSM-12 zeolites (RE=Ce, Ho, Sm) increase in relation to pure HZSM-12.
The acid properties were investigated by pyridine thermo desorption via TG.
The results showed two events of mass loss attributed to elimination of pyridine
adsorbed on the weak+medium acid sites and on the strong acid sites.
Authors:I. Ferino, R. Monaci, E. Rombi, and V. Solinas
Interaction between 1-methylnaphthalene and alkali-metal X and Y zeolites has been investigated using TPD. All spectra show
only a single peak, the temperature of which changes with the nature and amount of the alkali-metal cation and the Si/Al ratio
of the faujasite. A correlation between peak temperature and average charge of structural oxygen atoms of the zeolite is shown.
On the basis of the atomic charge distribution in the 1-methylnaphthalene molecule, it is, suggested that adsorption is initiated
by interaction between the alkali-metal cation and the carbon atom of the methyl group. Simultaneously, an interaction involving
hydrogens atoms of the aromatic rings and structural oxygen atoms of the zeolite occurs, except for X samples containing high
amounts of large alkali-metal cations.
Zeolite catalysts are widely used in oil refinery and petrochemical industries. Fluid catalytic cracking (FCC) catalysts used
in a refinery consist of Y zeolite, a silica-alumina matrix and a binder. In this study, spent FCC catalysts were prepared
by cracking sour imported heavy gas oil (SIHGO) in a microactivity test unit. The total amount of coke and the hydrogen-to-carbon
ratio (H/C) in the coke for spent FCC catalysts contaminated with metals were determined using temperature-programmed oxidation
(TPO). Total H/C ratios of the coke on FCC catalysts were found to be in the range of 0.4 to 1, indicating the majority of
the coke consists of polyaromatic species. H/C ratio decreased with increasing coke contents on the catalysts. This ratio
was found to be higher for the catalyst with high metal concentration compared to the catalyst with relatively low metal concentration.
The high H/C ratio for highly contaminated FCC catalyst was attributed to the formation of hydrogen rich coke by hydrogenation
reactions catalyzed by the contaminant metals on the catalyst. After hydrogen pretreatment both coke amount and H/C ratio
decreased significantly. This was due to the decrease in the hydrogenation activities of the contaminant-metals in their reduced
Four different samples of NdX, NdY, NdNH4X and NdNH4Y-zeolites were prepared by ionexchange methods. DTA and XRD analyses have been carried out for the samples. The thermally activated zeolites were irradiated by 1.5 and 10.0 Mrad -rays. The catalytic activities of these samples were tested in dehydration of isopropanol. The results of DTA indicated that all samples showed endothermic peaks at about 215 °C related to the release of physically adsorbed water and exothermic peaks at 850–950 °C indicating the collapses of the zeolite. The X-ray analysis revealed that the exchange of sodium by neodymium or ammonium followed by neodymium ions did not change the crystal structure but some decrease in the crystallinity was observed. The catalytic activities of these zeolites were measured in dehydration of isopropanol as a function of temperature. It was found that the activity of the prepared Nd-zeolites depends on the crystallinity of zeolites and on the condensation products formed on catalyst surface. However, the irradiated samples exhibited higher catalytic activities in isopropanol conversion than the unirradiated ones. The observed higher activity for irradiated samples was attributed to the increase of the number of acidic centers responsible for dehydration of alcohols. These centers were formed as a result of the formation of tricoordinate aluminium atoms in -irradiated zeolites.
A series of rare earth zeolites of types X and Y were prepared by cation exchange. Thermal analysis curves (TG/DTA) were employed to estimate the structural changes in the zeolite framework. Analogous investigations were carried out by independent methods such as XRD and IR spectroscopy. The results indicate increased thermal stability on the replacement of sodium by rare earth. Partial replacement of rare earth by ammonium/hydrogen enhances the thermal stability. The type Y zeolites are more stable than those of X type.
industries [ 34 , 35 ]. One of the remarkable catalytic reactions of monoterpenes is the epoxidation of limonene to limonene oxide, used to treat rhinitis. It has previously been reported that the Yzeolite-entrapped Mn(III) complex with tetra(4- N
Authors:Cleanio L. Lima, Hélvio S. A. de Sousa, Santiago J. S. Vasconcelos, Josué M. Filho, Alcemira C. Oliveira, Francisco F. de Sousa, and Alcineia C. Oliveira
Catalyst preparation and characterization
Catalysts prepared from ZSM-5, FAU type Y, AlSBA-15, and γ-Al 2 O 3 were obtained by the appropriate methodology [ 4 – 6 , 18 ].
Faujasite type Yzeolite was prepared by using a silica source
Authors:Yue Yao, Jianhong Wang, Yanyan Deng, and Jun Wang
include SAPO molecular sieves [ 6 , 7 ], Yzeolite [ 8 , 9 ], β zeolite [ 10 , 11 ], SO 4 2− /ZrO 2 [ 12 , 13 ] and heteropolyacids [ 14 , 15 ], among which, the three-dimensional 12-membered ring β zeolite is known as one of the most effective