Secondary hydrothermal

Mongiorgi and Morandi (1970) secondary hydrothermal alteration of Al-saponite breccia associated with diabase, near Rossena, Italy. 

In this work, a secondary hydrothermal treatment is applied on MSU-Sfau to get a stable micro/meso composite stracture. The new material has a strong acidity and high surface area. When it is used as the support of the Pd-Pt catalyst, the catalyst shows a good activity in the hydrogenation of pyrene and a good sulfur tolerance during naphthalene hydrogenation. 

A composite micro/meso porous material has been prepared by a secondary hydrothermal treatment. The material shows bimodal pore system due to the formation of zeolite Y in mesoporous framework. When used as the support of a Pd-Pt catalyst for hydrogenation of naphthalene in the presence and absence of 4,6-DMDBT, it demonstrates that the catalyst has an enhanced activity and sulfur tolerance. When pyrene is hydrogenated, the material shows a remarkable enhancement over the USY supported eatalyst. 

Copper ore minerals maybe classified as primary, secondary, oxidized, and native copper. Primaryrninerals were concentrated in ore bodies by hydrothermal processes secondary minerals formed when copper sulfide deposits exposed at the surface were leached by weathering and groundwater, and the copper reprecipitated near the water table (see Metallurgy, extractive). The important copper minerals are Hsted in Table 1. Of the sulfide ores, bornite, chalcopyrite, and tetrahedrite—teimantite are primary minerals and coveUite, chalcocite, and digenite are more commonly secondary minerals. The oxide minerals, such as chrysocoUa, malachite, and azurite, were formed by oxidation of surface sulfides. Native copper is usually found in the oxidized zone. However, the principal native copper deposits in Michigan are considered primary (5). 

Gamo, T. (1995) Wide variation of chemical characteristic of submarine hydrothermal fluids due to secondary modification processes after high temperature water-rock interaction, a review. In Sakai, H. and Nozaki, Y. (eds.), Biogeochemical Processes and Ocean Flux in the Western Pacific, Terra Sci. Publ., pp. 425-451. 

Richter S, Goldberg SA, Mason PB, Traina AJ, Schwieters JB (2001) Linearity tests for secondary electron multipliers used in isotope ratio mass spectrometry. Inti J Mass Spectrom 206 105-127 Rihs S, Condomines M, Sigmarsson O (2000) U, Ra, and Ba incorporation dining precipitation of hydrothermal carbonates imphcations for Ra-Ba dating of impure travertines. Geochim Cosmochim Acta 64 661-671... 

The development of composite micro/mesoporous materials opens new perspectives for the improvement of zeolytic catalysts. These materials combine the advantages of both zeolites and mesoporous molecular sieves, in particular, strong acidity, high thermal and hydrothermal stability and improved diffusivity of bulky molecules due to reduction of the intracrystalline diffusion path length, resulting from creation of secondary mesoporous structure. It can be expected that the creation of secondary mesoporous structure in zeolitic crystals, on the one hand, will result in the improvement of the effectiveness factor in hydroisomerization process and, on the other hand, will lead to the decrease of the residence time of products and minimization of secondary reactions, such as cracking. This will result in an increase of both the conversion and the selectivity to isomerization products. 

Recently, mesoporous aluminosilicates with strong acidity and high hydrothermal stability have been synthesized via self-assembly of aluminosilicate nanoclusters with templating micelles. The materials were found to contain both micro- and mesopores, and the pore walls consist of primary and secondary building units, which might be responsible for the acidity and stability (181). These materials were tested in isobutane/n-butene alkylation at 298 K, showing a similar time-on-stream behavior to that of zeolite BEA. No details of the product distribution were given. 

James et al. (1999) reported findings from ODP Site 1038 (Fig. 16b), adjacent to the Gorda Ridge, an area of active hydrothermal venting through a thick sedimentary pile. Pore fluids there had a range in isotopic compositions (8 Li = -0.6 to +27.5) that were modeled in terms of initial hydrothermal removal of Li from sediments followed by down-temperature fluid fractionation during crystallization of secondary minerals, and ultimately dilution with... 

In Eq. 19.2, talc represents the magnesimn hydroxide component of various secondary minerals such as chlorite and amphibole.) As a result, sulfete is stripped out of the hydrothermal fluids. 

Silica is also solubilized from the igneous rocks during high-temperature reactions. This causes dissolved silica to become supersaturated, leading to the precipitation of quartz and other secondary silicates, such as albite, within the hydrothermal conduits. The formation of albite is an important reaction because it serves as a sink for Na and and a source of Ca ... 

Another recent modification to the secondary growth method as applied to MFI-type zeolite membranes is to perform the hydrothermal growth on the seeded... 

O, H, C, S, and N isotope compositions of mantle-derived rocks are substantially more variable than expected from the small fractionations at high temperatures. The most plausible process that may result in variable isotope ratios in the mantle is the input of subducted oceanic crust, and less frequent of continental crust, into some portions of the mantle. Because different parts of subducted slabs have different isotopic compositions, the released fluids may also differ in the O, H, C, and S isotope composition. In this context, the process of mantle metasomatism is of special significance. Metasomatic fluids rich in Fe +, Ti, K, TREE, P, and other large ion lithophile (LIE) elements tend to react with peridotite mantle and form secondary micas, amphiboles and other accessory minerals. The origin of metasomatic fluids is likely to be either (1) exsolved fluids from an ascending magma or (2) fluids or melts derived from subducted, hydrothermally altered crust and its overlying sediments. 

In spite of a rich life, no signaling or defensive secondary metabolite has ever been reported from organisms thriving on the hydrothermal vents. Lack of competition in these areas, where the hostile environment provides protection from invaders, has not stimulated the formation of defensive metabolites. Defensive heat-stable enzymes and cell walls were raised against the hostile environment. 

The quartz monzonite samples (U15E-7 and U15E-7a) were originally composed of 70-80 percent feldspar, 10-15 percent biotite, 3-8 percent quartz, and 2-8 percent opaques. Both samples have been hydrothermally altered U15E-7a being the more altered. The original feldspars in both samples have been sericitized and/or altered to clinozoisite. Secondary cal cite also occurs in both samples. Pyrite is an abundant secondary mineral and minor amounts of both epidote and chlorite replace biotite and fill fractures. 

Fiydrothermal plants produce electric power at a cost competitive with the cost of power from fossil fuels. Besides generating electricity, hydrothermal energy is used directly to heat buildings. Across the United States, geothermal hot-water reservoirs are much more common than geothermal steam reservoirs. Most of the untapped hot-water reservoirs are in California, Nevada, Utah, and New Mexico. The temperatures of these reservoirs are not hot enough to drive steam turbines efficiently, but the water is used to boil a secondary fluid, such as butane, whose vapors then drive gas turbines. 

Niobium and titanium incorporation in a molecular sieve can be achieved either by hydrothermal synthesis (direct synthesis) or by post-synthesis modification (secondary synthesis). The grafting method has shown promise for developing active oxidation catalyst in a simple and convenient way. Recently, the grafting of metallocene complexes onto mesoporous silica has been reported as alternate route to the synthesis of an active epoxidation catalyst [21]. Further the control of active sites, the specific removal of organic material (template or surfactant) occluded within mesoporous molecular sieves during synthesis can also be important and useful to develop an active epoxidation catalyst. Thermal method is quite often used to eliminate organic species from porous materials. However, several techniques such as supercritical fluid extraction (SFE) and plasma [22], ozone treatment [23], ion exchange [24-26] are also reported. 

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