Two-step calcination

The largest volume of synthetic red iron oxide is produced by the two-step calcination of iron(II) sulfate. In the first step, the iron(II) sulfate heptahydrate is dehydrated to a monohydrate ... 

Fluidized beds are ideal for the combustion of high sulfur coals since the sulfur dioxide produced by combustion reacts with the introduced calcined limestone to produce calcium sulfate. The chemistry involved can be simplified and reduced to two steps, calcination and sulfation. 

Uchino and Azuma [504] developed and proposed a two-step calcination process of tantalum and niobium hydroxides to obtain oxides. The first treatment is recommended to be performed at 500-700°C, and the second- at 750-1000°C. It is reported that the above method ensures the production of oxides that contain only negligible concentrations of fluorine and silicon impurities. 

The first option is to improve the calcination process, usually by a two-step calcination. Other different mild template-destructive methods have been proposed. 

High-temperature calcination Two-step calcination [187e-f 190]... 

For making the porous materials, the surfactant must be removed from the solid product. The main methods include calcination at high temperature and extraction with solvent. Heat treatment has a great influence on product structure. Shrinkage of pores or channels is a common phenomenon for calcined samples. Two-step calcination can reduce the... 

Comparison of the metal particle size in the samples prepared in two steps, calcined (ENien 600+INi) or not (ENien+INi) before reduction... 

The TS-l/MCM-41 catalysts were synthesized in two steps [8]. The first step was involved with the preparation of TPAOH impregnate mesoporous materials and the second stq) was the DGC process. The TPAOH impregnated H-MCM-41 was prepare with calcine Ti-MCM-41, TPAOH (1 M solution of water) and ethanol under stirring by impregnation method. The parent gels were prepared with a TPAOH/Ti-MCM-41 ratio of 1/3 by weight. After 4 h, ethanol and water were removed in a rotary evaporator at room temperature and solid products were dried in a convention oven at 373 K for 48 h. The DGC process was carried out at 448 K for 3 h to obtain TS-1/MCM-41-A and for 6 h to obtain TS-1/MCM-41-B. However, the mesoporosity of Ti-MCM-41 was lost when the DGC process was carried out for 9 h. 

Two different methods were used to produce Iron oxide (Fe203) particles on Grafoll. One method was a simple Impregnation-calcination based on the method of Bartholomew and Boudart (20). The exact method used 1s described elsewhere (27). The second method used was a two step process. First, metallic iron particles were produced on the Grafoll surface via the thermal decomposition of Iron pentacarbonyl. This process Is also described in detail elsewhere (25). Next, the particles were exposed to air at room atmosphere and thus partially oxidized to 2 3 Following the production of Iron oxide particles (by... 

Preparation of mixed metal oxides - The sulfated metal oxides (zircoiua, titaiua and tin oxide) were synthesized using a two-step method. The first step is the hydroxylation of metal complexes. The second step is the sulfonation with H2SO4 followed by calcination in air at various temperatures, for 4 h, in a West 2050 oven, at the temperature rate of 240°C hSulfated zirconia Zr0Cl2.8H20 (50 g) was... 

Pt/H-MCM-22 catalysts for methane combustion have been prepared by ion-exchange. The influence of two different calcination routes on platinum electronic properties have been studied by XRD, HRTEM and FTIR. This step plays a fundamental role in the final properties of platinum active species. 

Figure 6.12 shows the IR spectra of Ag/Si02 composites prepared by different methods calcined at 550°C. Because it appears no difference in chemical bond indicates physical structures of the three composite systems are similar. The IR spectra of Ag/Si02 composites prepared by the two-step method are shown in Fig. 6.13. The mixture ofthe silver solution and Si02 solution exhibits two peaks at 1382cm and 949 cm which can be attributed respectively to the vibration of and the vibration...

FIGURE 6.12. IR spectra of Ag/Si02 samples prepared by different method calcined at 550 C (a) one-step method, (b) two step method (2.0 h), (c) two step method (2.5 h). 

Ag/Si02 composites prepared by the one-step method and two-step methods were characterized by TGA/DTA, FTIR, XRD, and TEM. The results showed that Ag or silver oxide nanoparticles in 20 to30 nm were dispersed on the surface of the carrier Si02. The calcination temperature and prepared method affect the crystal phase of the functional component. 

This study demonstrated that the micro-mesoporous composite materials could be synthesized with two-step treatment by microwave using two different templates system with TPABr and MTAB. This formation was controlled by the self-assembly formation of supramolecular templates between MTA micelles and SiO /TPA gels. As varying microwave irradiation time of micro-mesoporous materials, gradually transition from the mesophase to micro-mesophase was occurred. These materials have higher dm spacing of mesoporous materials and lead to transition from mesophase to micro-microphase by an increment of synthetic time, while the calcined products is formed with bimodal and trimodal pore size distribution under microwave irradiation within 3 h. From TG-DTA and PL analysis, the self-assembly formation of supramolecular templates between MTA+ micelles and SiO /TPA+ gels were monitored. 

Prior to monitoring of the Cu+ and Zn2+ photoluminescence spectra, the Cu2+ and Zn2+ molecular sieves were calcined in an oxygen stream at 620 K for 3 hrs with a heating rate of 1 K/min. For monitoring emission spectra of Zn2+- and absorption spectra of Co2+-(A1)MCM-41, samples were then dehydrated at 750 K under vacuum of 7xl0 2 Pa in a silica flask connected with a optical cell. Dehydration was carried out with a heating rate of 5 K/min in two steps 370 K for 30 min and 750 K for 3 h. For monitoring spectra of Cu+-(A1)MCM-41, samples were dehydrated at 750 K for 1 h, subsequently reduced in a stream of carbon... 

During the calcination at 773 K, the sol particles were converted into oxide particles within the interlayer region and rigid pillared layered framework formed in the sol-PILM sample. A two-step procedure is proposed to modify the micropore openings of the solid to enhance the ability of recognizing different molecules. 

The micropores of sol-PILM were modified to enhance the molecular recognition ability by the proposed two-step procedure. In the first step, Ca2+ cations together with their coordinating water were introduced into the pore system. In the second step, silica formed by the hydrolyzation of TEOS as well as the subsequent calcination. The modified product... 

Pure molybdic oxide (99.95% MnO.O is prepared by sublimation of technical oxide or by calcining ammonium molybdate. Metallic molybdenum powder is prepared commercially by hydrogen reduction of either pure molybdic oxide ctr ammonium molybdate in a two-step process. The first step, carried out at about 500 C yields MoO-. The second step, reduction of M0O2 to Mo, is carried out al about I 00°C. 

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