The Infona portal uses cookies, i.e. strings of text saved by a browser on the user's device. The portal can access those files and use them to remember the user's data, such as their chosen settings (screen view, interface language, etc.), or their login data. By using the Infona portal the user accepts automatic saving and using this information for portal operation purposes. More information on the subject can be found in the Privacy Policy and Terms of Service. By closing this window the user confirms that they have read the information on cookie usage, and they accept the privacy policy and the way cookies are used by the portal. You can change the cookie settings in your browser.
To clarify the growth behavior of zeolite crystals under hydrothermal synthesis conditions, the growth process of ZSM-5 type zeolite crystals was studied using two kinds of in situ observation apparatus. Direct observation of ZSM-5 crystals from amorphous gels during steaming and silicalite crystals from clear aqueous solutions was performed. During the stationary growing stage, a constant rate...
Copolymers prepared from one acrylic monomer containing a carboxy group, one acrylic and/or vinyl monomer containing no carboxy groups, and one ethylenically unsaturated monomer containing a polyoxyethylene group and a hydrophobic fatty C 12-40 chain are used as dispersing agents in the preparation of stable aqueous suspensions of zeolites. The suspensions are...
The separation method involves (1) an extraction process using supercritical carbon dioxide; (2) an adsorption process using zeolite Y for selective adsorption of 2.7-dimethylnaphthalene.
Chemical procedures based on selective dissolution and compleximetric analysis have been developed to provide a simple but informative method for following the course of a high-silica zeolite synthesis reaction. For a dilute Na, TPA-ZSM-5 system, it is shown that amorphous precursor material converts quantitatively into crystalline zeolite product via a solution-mediated reaction-crystallization...
The process involves passing a stream of 100 volume ppm CO-containing air or N through a bed of CO-selective adsorbent at a temperature <150 K. The adsorbent is a Ca-exchanged zeolite X, zeolite 5A, or zeolite 13X. The adsorbent is regenerated by heat treatment.
Synchrotron powder X-ray diffraction (PXRD) data for calcined AIPO 4 -52 were refined in space group P31c using the Rietveld method. The previously proposed topology (AFT), an ABC six-ring structure type with an AABBCCAACCBB stacking sequence, was confirmed. The refined unit cell dimensions are a = b = 13.715 (1) and c = 29.676 (3) . Possible causes for peak broadening in the synchrotron...
Following an earlier study of controlled monolithic crystal growth in a semicontinuous reactor system, the present report is concerned with the effect of allowing the nucleation rate to rise. The initial result is a broadening of the crystal size distribution; however, under suitable conditions at highly enhanced nucleation rates a product morphology of high surface area polycrystalline aggregates...
The synthesis of zeolites from gels containing silica, alumina, potassium and/or sodium hydroxide or chloride, diethanolamine, and water was studied. Zeolites Theta-1, ZSM-5, ferrierite, and mordenite, and the dense phase cristobalite, were produced by varying the SiO 22 O 3 ratio, the alkalinity and the alkali metal cation. The effect of varying the SiO 22 O ...
We report the high-temperature/high-pressure synthesis and single-crystal structure of Cs 3 HTi 4 O 4 (SiO 4 ) 3 4H 2 O, which is a synthetic isostructure of the mineral species pharmacosiderite. The Cs 3 HTi 4 O 4 (SiO 4 ) 3 4H 2 O framework is built up from TiO 6 octahedra, sharing faces to form...
It is shown that the hydrothermal synthesis of aluminum-free chromosilicate results in the formation of crystalline zeolite with the ZSM-5 structure and some Cr 3+ ions substitutes isomorphically for Si 4+ ions in the lattice of as-made samples. After oxidative calcination most chromium ions aggregate in α-Cr 2 O 3 microcrystals on the outer surface of the...
Ferrisilicalite and FAPO-5 were synthesized hydrothermally with iron contents from 0.1 to 1% on a molar basis and investigated by X-ray diffraction and electron spin resonance (e.s.r.) in the as-synthesized, oxidized, and reduced forms. The amount of Fe in the solid, the degree of crystallinity, and the Fe 3+ e.s.r. signal intensity all increase with synthesis time in the same manner,...
The adsorption of benzene is followed by infrared spectroscopy. A detailed study in the rangepp 0 from 0 to 10 -4 is extended further topp 0 = 0.5. It shows that about two molecules of benzene per unit cell strongly interact with cations for pp 0 = 10 -4 . At higher benzene loadings the excess of aromatic is simply filling the pores. No significant...
The crystal structure of dehydrated NaX, composition Na 88 Al 88 Si 104 O 384 , a 0 = 25.099(5) , has been determined using single-crystal X-ray diffraction methods and refined in space group Fd3. Diffraction symmetry and refined T -- O distances indicate substantial ordering of Si and Al in the T sites. All Na + cations...
Decasils are a new order-disorder family of porous structures. All ordered and disordered decasil structures are built from one-dimensional chain-like basic building units that can be connected in different ways. Three simplest ordered framework structures of this family are possible: decasil types A, B, and C. Al decasil types possess cage-like voids that share 8MR pore openings to give a one-dimensional...
Highly crystalline MnAPO-20 and CoAPO-20 have been prepared at previously unreported substitution levels using tetrahedral tetrahalometallates. X-ray diffraction and infrared spectroscopy indicate that framework substitution of manganese and cobalt has taken place. Samples have also been studied using X-ray fluorescence, scanning electron microscopy, thermogravimetric analysis, and a Gouy balance...
The synthesis of zeolites from gels comprising silica, alumina, potassium and/or sodium hydroxide or chloride, diethanolamine, and water has been studied previously, and several zeolites including Theta-1 and ZSM-5 were synthesized. Diethanolamine was considered to have both a pore-filling role and charge-compensatory role (if the amine group was protonated), and hence its overall effectiveness as...
Four gels of initial compositions 8 TAABr:Al 2 O 3 :90 SiO 2 :1,000 H 2 O (gel I), 8 TAAOH:Al 2 O 3 :90 SiO 2 :1,000 H 2 O (gel II), 2 TAAOH:Al 2 O 3 :200 H 2 O (gel III), and 8 TAABr:4.5 Na 2 O:Al 2 O 3 :90 SiO 2 : 1,000 H 2 O (gel IV) were prepared and dried at 363 K (TAA...
CO 2 reduction on reduced titanium silicalite (TS-1) with photoirradiation in the presence of H 2 was investigated in a closed circulation system. CO 2 was reduced to give CH 4 under u.v. irradiation, which TS-1 absorbs. The amount of the carbon species on TS-1 after photoirradiation indicated that all Ti atoms in the framework may act as a photocatalytic site. Infrared...
Ammonia was used as a probe molecule to study the acid properties of NaH-mordenites. Ammonia reaches all acid sites in both large and narrow channels. The concentration of Bronsted sites (SiOHAl groups) and of Lewis acid sites was followed as a function of the Na/H exchange degree and the calcination temperature (extent of dehydroxylation). In NaH-mordenites of exchange degrees lower than 80%, the...
Set the date range to filter the displayed results. You can set a starting date, ending date or both. You can enter the dates manually or choose them from the calendar.