Flow-hydrothermal conditions

Beta/montmorillonite composite was prepared under dynamic hydrothermal conditions. Firstly, montmorillonite calcined at 800 °C were added to a diluted solution of sodium hydroxide, potassium chloride and TEAOH in distilled water and the resulting mixture was vigorously stirred for 1 h secondly, silica sol was added into the above uniform mixture to allow at least 3 h stirring finally, the gel was moved into stainless steel autoclaves (1L) and heated at 413 K for 48 h. The samples were characterized by XRD, N2 adsorption-desorption, FT-IR and SEM-EDS. The catalytic assessment experiments were carried out in a flowing-type apparatus designed for continuous operation. 

Catalyst hydrothermal deactivation was carried out in two different equipments a lOOg capacity fixed bed steamer was used for the advanced cracking evaluation (ACE) unit tests and a 5 kg capacity fluidized bed steamer was used for the other testing protocols. Steaming conditions in the two cases were the same 788°C for 5 hours under 100% steam flow. Although conditions were similar, higher pressure buildup in the fixed bed steamer led to lower surface area retentions. 

In addition to these conventional methods of examining catalyst deactivation we have examined the effects of hydrothermal conditioning (using D2O) of TS-1 in the in situ neutron powder diffraction cell capable of flow studies described above. The TS-1 sample was steamed using D2O saturated He at progressively higher temperatures for successive periods of an hour... 

The above lines of evidence suggest that the precipitation of minerals in. submarine hydrothermal ore deposits on the seafloor is taking place from the fluids with high flow rate at the orifices of the chimney (ca. 1-10 m/s) and with high degree of supersaturation under the non-equilibrium conditions. 

However, as already noted, the barite content in Kuroko ore inversely correlates to the quartz content and the occurrences of barite and quartz in the submarine hydrothermal ore deposits are different. The discrepancy between the results of thermochemical equilibrium calculations based on the mixing model and the mode of occurrences of barite and quartz in the submarine hydrothermal ore deposits clearly indicate that barite and quartz precipitated from supersaturated solutions under non-equilibrium conditions. Thus, it is considered that the flow rate and precipitation kinetics affect the precipitations of barite and quartz. 

The electrochemical precipitation of gold is considered here the main mechanism for gold precipitation. Such a mechanism can be viewed as a filter to extract gold in solution, even in low concentration, during hydrothermal fluid flow in the veins. It can also be considered as independent of physico-chemical condition variations, hence accounting for the vertically and laterally extensive gold mineralization in the prolific Poderosa-Pataz district. The most important contribution of our study lies in the fact that the As enrichment is not a primary feature of pyrite growth but... 

In natural crystals, whose growth processes cannot be directly observed, the difference in R is recorded as the difference in separation in growth banding (see Chapter 6). Based on these observations, several papers were reported in which the direction of flow of ore-forming fluid was evaluated in pegmatite and hydrothermal veins. In many cases in which the natural mineral crystals exhibited extensively malformed Habitus from that predicted by the structural form, the malformation could be considered to be due to the remarkable anisotropy involved in the environmental conditions, such as the directional flow of the solution, which is similar to the situation of growth of NaCl from solution in between two glass plates, as discussed above. 

The addition of water-soluble polymers such as polyethylene oxide (PEO) or polyvinyl alcohol (PVA) into the synthetic mixture of the C TMAX-HN03-TE0S-H20 system (n = 16 or 18 X = Br or Cl) under shear flow is found to promote uniformity and elongation of rope-like mesoporous silica. The millimeter-scaled mesoporous silica ropes are found to possess a three-level hierarchical structure. The addition of water-soluble polymer does not affect the physical properties of the silica ropes. Moreover, further hydrothermal treatment of the acid-made material under basic ammonia conditions effectively promotes reconstruction of the silica nanochannels while maintaining the rope-like morphology. As a result, a notable enhancement in both thermal and hydrothermal stability is found. 

All zeolite samples were synthesized by the hydrothermal method described in detail in [6]. The experiments were performed in a completely automated laboratory setup including an integrally operated plug flow tubular reactor. Reaction components were analyzed by on-line gas chromatography with FID and TCD [5-7]. Table 1 summarizes the reaction conditions for the benzene hydroxylation on the H-Ga-ZSM5 catalyst. Nitrogen was used as balance. 

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