Alkali Zeolite Research Articles

Occurrence of analcime in the middle Jurassic coal from the Dongsheng Coalfield, northeastern Ordos Basin, China

This paper describes the occurrence of significant authigenic analcime (NaAlSi2O6·H2O) in the middle Jurassic coal from the northeastern Ordos Basin and discusses its origin. Twelve coal samples from borehole ZK31-19 in the Dongsheng Coalfield were collected and analyzed. The coals are characterized by a low-medium ash yield, high volatile matter and low sulfur contents. The major-element oxides in the studied coals are mostly at similar or much lower concentrations compared to the averages for Chinese coals. Similarly, most trace elements are depleted or in concentrations close to the respective averages for world low-rank coals. Based on Seredin-Dai's classification, the REY (rare earth elements and Y) in the coal mainly display N- and H-type distribution patterns, with no Ce and Eu anomalies. Coal sample ZK31-19-12 from the lower Zhiluo Formation contains analcime up to 23 wt%, with a high Na2O concentration of 1.23% (both on a whole-coal basis). The analcime occurs as lath, as subhedral granular crystals in fissures or pores and as anhedral crystals in the organic matrix. Furthermore, significant analcime has also been observed by SEM in coal from the upper Yan'an Formation (sample ZK31–19-10), which mainly occurrs as anhedral crystals. No evidence of analcime forming from precursors of volcaniclastic material, alkali zeolites or other silicates was detected, therefore, it is deduced that the analcime in the studied coals formed by authigenic precipitation. The Na2O content in the studied coal seams displays a vertical variation different from that of the ash yield (Ad) and those of the detrital-dominated elements, such as SiO2, Al2O3, TiO2, Zr, Nb and Th, indicating a different origin of Na compared with other detrital materials of terrigenous origin. Combined with the evidence of the obvious Na peak in authigenic amorphous material and gypsum mineral by SEM, it can be inferred that the source of Na may derive from the fluids. The paleoclimatic change (from subtropical warm and humid to semi-arid and arid hot, during the deposition period of the Yan'an to the Zhiluo Formation) may provide favorable conditions for analcime authigenesis, leading to its abundant precipitation in the lower Zhiluo Formation and its limited occurrence in the upper Yan'an Formation. Such paleoclimatic change is also significant for the U mineralization in the lower Zhiluo Formation.

Zeolites in Mafic Pyroclastic Rocks from the Sandikli-Afyonkarahisar Region, Turkey

AbstractGeologic mapping and crystal-chemical analysis of Middle-Upper Miocene volcanics in the Sandıklı-Afyonkarahisar region of Turkey, coupled with published zeolite analyses has revealed that western Turkey hosts unique zeolitic mineral assemblages with distinct paragenetic sequences. The present investigation focused on pyroclastic deposits, including low to intermediate potassic trachytic/trachyandesitic tuffs (LPT) and high potassic tephriphonolitic, tephritic, and trachybasaltic tuffs (HPT), each of which contains various styles of zeolites. Optical petrography, X-ray powder diffraction, and chemical analyses have revealed varying degrees of lithification, probably related to differences in initial emplacement temperature, depositional mechanism and thickness, chilling rate, and extent of mafic composition. Zeolitization was further influenced by meteoric flushing in a hydrologically open system. Chabazite in the LPT from the Selçik area occurs extensively as coatings and infillings of pores. Phillipsite in the HPT found in the Ballık, Küfeke, and Ömerkuyu areas dominates the assemblage and is accompanied by chabazite and minor amounts of analcime. Analcime was probably generated by alteration of leucite which is found as a pyrogene mineral. Alkali zeolites or Ca-bearing zeolites formed as a consequence of the addition of Ca and/or the removal of Na (i.e. dissolution of analcime). The paragenetic sequence may be described as: analcime/phillipsite → chabazite → calcite. The characterization of these assemblages may lead to better exploitation strategies for natural zeolitic resources in the region.

Selective Nitration of Chlorobenzene by NO2 in the Alkali Zeolite NaZSM-5

Chlorobenzene was reacted with NO2, in the initially acid-free zeolite NaZSM-5, to yield para-chloronitrobenzene exclusively. The precursors were loaded sequentially into self-supporting pellets of the zeolite, contained within a stainless steel cell, from the gas phase. The reaction proceeds spontaneously at room temperature. It is, however, very temperature dependent and effectively ceases at zero degrees Celsius. The reaction was monitored in situ using FT-IR. The active nitrating agent is formed from the partial electron donation by the NO2 to the Na+ cations present in the zeolite lattice. Under the reaction conditions, chlorobenzene is not readily mobile through the pore system; thus, only the molecules adsorbed near a cation site react to form para-chloronitrobenzene.

Recipe for Fabricating Zeolite Ion Source for Plasma Probing

Alkali zeolite is often used as an ion source material owing to its easy extraction of alkali ions. In our laboratory, we fabricated zeolite containing a particular alkali species through a replacement reaction with sodium zeolite. In this paper, we present a simple mathematical model for describing this replacement reaction for making zeolite containing a particular alkali species. In this model, the fraction of alkali ions trapped in the zeolite lattice is expressed as a function of the numbers of substitution reactions in a concise recursion formula. This formula gives a simple estimation of efficiency for fabricating alkali zeolite in terms of the consumptions of time and chemicals.

Influence of the Chemical Composition upon Adsorption, Coadsorption, and Reactivity of Ammonia and Methanol on Alkali-Exchanged Zeolites

The interaction of ammonia and methanol with several alkali zeolites was studied by means of IR spectroscopy, mass spectrometry, and thermogravimetry. While ammonia adsorbed identically on all zeolites investigated, the adsorption complex of methanol subtly depended upon the concentration of lattice aluminum in the zeolite. This is attributed to the variation of the polarizability of the zeolite lattice induced by the varying chemical composition. With respect to the reaction of methanol with ammonia, the differences in the sorption of methanol led to variations in the reactivity of these zeolites toward the primary products monomethylamine and dimethyl ether. On zeolites with a high aluminum content, both products were formed in approximately equal concentrations, while with silicon-rich zeolites monomethylamine was the dominating product. With all alkali zeolites investigated methanol was significantly stronger adsorbed than ammonia.

Self-Condensation of n-Butyraldehyde over Solid Base Catalysts

The catalytic properties of various solid bases for self-condensation of n-butyraldehyde in liquid phase were studied to elucidate the factors governing the activity and selectivity. For alkaline earth oxide catalysts and γ-alumina catalyst, aldol condensation occurred, followed by Tishchenko-type cross-esterification of n-butyraldehyde with the dimer produced by the aldol condensation to form trimeric glycol ester. Alkali ion-modified alumina catalysts exhibited a high selectivity for the aldol condensation dimer, the trimeric glycol ester being formed tittle. Both basic and acidic sites on the surfaces of the alkaline earth oxides and γ-alumina were assumed to contribute to Tishchenko-type cross-esterification. The suppression of Tishchenko-type cross-esterification for alkali ion-modified alumina catalysts is due to the absence of acidic sites on the surfaces. The catalytic performances of alumina-supported magnesium oxide and alkali zeolite X were also examined. Alumina-supported magnesium oxide exhibited lower activity but higher selectivity to trimeric glycol ester than MgO. This catalytic feature was caused by the lower basicity and higher acidity on the surface of alumina-supported magnesium oxide as compared with MgO. The activity of alkali ion-exchanged zeolites was lowest among the catalysts examined in this study. The modification of zeolites with excess alkali ions improved the activity.

本邦油田地域の後期新生界海成層における弗石化作用

Zeolites found in the Late Cenozoic marine sediments of the Japanese oil producing regions are widely distributed in a vertical zonal arrangement. The zeolitization in these sediments is studied at eleven deep wells drilled in the regions. The strata in these wells have been deposited continuously under the marine environments until the Recent.The zeolite and albite zones are present at the various depth, and are oblique to the stratigraphic datums. The subsurface temperature at the top of each zeolite zone ranges from 42°C to 60°C for the clinoptilolite zone, 64°C to 112°C for the analcime zone, and 124°C to 152°C for the albite zone.From consideration of burial and thermal histories in these wells, the transformation temperature of the alkali zeolite reaction series decreases gradually with increase in geological time elapsed since sedimentation, and/or with increase in the effective heating time of HOOD and CASTANO (1975). For exsample, clinoptilolite is transformed into analcime at 62°C for the effective heating time of 5Ma, and at 105°C for 0.5Ma, approximately.The zeolitization is governed by not only the maximum temperature but also by the geological reaction time under the marine enviroments saturated with the sufficient cations (Na+) in interstitial water.