Batch composition

Typical ranges of enamel compositions are Hsted in Table 2. Raw materials (Table 1) for the glass batch include minerals, such as feldspars and quartz, because these are inexpensive sources of Si02 and AI2O2 (see Clays). The batch composition for cover coats is comprised primarily of manufactured chemicals of known, controlled levels of purity to maintain reproducible, clean colors. 

The operation of the reactor is inherently unsteady-state for example, batch composition changes with respect to time. 

You have supplies of kaolin, silica, and mullite as raw materials. Using kaolin plus either silica or mullite, calculate the batch composition (in weight percent) necessary to produce a final microstructure that is equimolar in silica and mullite. 

Figure 1. Crystallization curves of mordenite from a batch composition 8.5 N avO-AWz-85 SiD2 182 H20 as a function of temperature and NaCl content filled symbols, no NaCl open symbols, 4.5 moles of NaCl/mole Al2Oz)...

The fast conversion rate of amorphous batch into mordenite, once the crystallization has started, indicates that the rate-limiting step in the overall process is the nucleation. To substantiate this, mordenite was crystallized with the same batch composition but with the addition of seed... 

The activation energies of the nucleation and crystal growth can be determined from the crystallization curves at various temperatures with the same batch composition. Assuming that the formation of nuclei of a size stable enough not to redissolve but to grow into a crystal is an energetically activated process, and since the nucleation process is rate-deter-... 

Figure 6. Effect of seeding on crystallization rates of mordenite from a batch composition of 8.5 Na20-Al20s-35 Si02-18 2H20 at 120°C (A) no seed, ( ) seeding with 3X3X8 /meter crystals, (A, , O) seeding with 0.5-5 /meter crystals)...

Figure 7. Crystallization curves of zeolite X from a batch composition 4 Na O-Al Os-5 Si02-200 H20 at 90°C (O) no seed crystals (A) 0.5-5 /meter seed crystals, 29% initial conversion ( ) 30-70 /meter seed crystals, 15% initial conversion...

Figure 8. Crystallization curves for zeolite A from a batch composition 2.5 NdzO-AUOs-l. 7 SiOz-150 H%0 (solid curves) no seed crystals, (broken curve) 0.5-5 nmeter seed crystals, 25% initial conversion...

This study showed that the overall crystallization processes for mor-denite, zeolite X, and zeolite A were similar. However, the physical properties of the crystallizing system determine the rate-limiting step for a particular zeolite synthesis. In the case of mordenite in which both the viscosity of the batch composition and the morphology of seed crystals were varied, it was observed that diffusion in the liquid phase was the ratedetermining step. For zeolite X the actual growth rate on the crystal-liquid interface was the rate-limiting factor as shown by identical conversion rates for the seeded and unseeded systems. For zeolite A in the system chosen, both processes influenced the conversion rate. 

Additionally a template-free synthesis route has been followed in order to obtain pure ZSM-5 or ZSM-35 products. The batch compositions were the following ... 

Kostic, E. and Momcilovic, I., Reaction sintered MgAl204 bodies from different batch compositions , Ceramurgia International, 1977 3(2) 57-60. 

Batch Composition (wt%) Carbon black/graphite added to batch (wt%) Ball milling (ethanol) at 360 rpm Attritor milling (ethanol) at 600 rpm Hot pressing 1800°C, 2 h nitrogen atm. (MPa)... 

The third category of drugs are phytotherapeutical preparations 80% of the world population use exclusively plants for the treatment of illnesses [11]. Chromatography is relied on to guarantee preparations contain therapeutically effective doses of active drug and maintain constant batch composition. A quantitative determination of active principles is performed when possible, using pure reference standards. In many phytotherapeutic preparations, the active constituents are not known, so marker substances or typical constituents of the extract are used for the quantitative determination [11]. The Applications chapter of this book (Chapter 8) contains numerous references to the use of chromatographic methods in the control of plant extracts. 

To better understand this solgel procedure, the synthesis of silica microspheres using the Stobe-Fink-Bohn (SFB) method [46] and a modification of the SFB method [47-49] are excellent examples. The SFB method consists of the hydrolysis of TEOS (Si(C2H50)4) in ethanol, methanol, //-propanol, or //-butanol in the presence of ammonia as a catalyst [46], In Table 3.3, the batch composition for the synthesis of silica microspheres, by means of TEOS in an alcohol (methanol or isopropanol) in the presence of ammonia as a catalyst, with and without double-distilled water (DDW) in the synthesis media, is presented [47],... 

Batch Composition for the Synthesis of the Silica Microspheres by Means of the Hydrolysis of Tetraethylorthosilicate... 

Batch Composition for the Synthesis of Silica in the Presence of an Amine as a Catalyst With and Without DDW in the Synthesis Media... 

Figure 5.13 DTA and DTG traces, simultaneously measured, of the base glass batch composition of various particle sizes.

There are several ways to carry out the precipitation process (Fig. 3) [14]. The simplest implementation of the precipitation reaction is the batch operation where the solution from which the salt is to be precipitated is usually present in the precipitation vessel and the precipitating agent is added. The advantage of this mode of operation is the simple way in which the product can be obtained the most severe disadvantage is the variation of batch composition during the precipitation process. This can lead to differences between the product formed during the initial stages of the precipitation and the precipitate formed at the end of the process. If a coprecipitation is carried out this way, it is important to decide which compounds are present in the vessel and which compounds are to be added. If the pre-... 

Figure 3. Possible implementations of precipitation processes (after [14]). In the batchwise process (a) the pH and all other parameters except for the temperature change continuously during the precipitation due to consumption of the metal species. Coprecipitation should be carried out in the reversed arrangement by addition of the metal species to the precipitating agent to avoid sequential precipitation. In process (b) the pH is kept constant, but the batch composition and the residence time of the precipitate change continuously. In process (c) all parameters are kept constant.

Table II. Characteristics of the aluminosilicate gels of 4.24 Na20-Al203-3.56 Si02- 230.6 H20 batch composition aged for various times tQ at 25°C...

The oxide batch composition tested for cancrinite crystallization was as follows ... 

Silicalite was synthesized from a batch composition of 2.55Na20-5.0TPABr-100Si02-2800H20... 

The template containing samples were synthesized using a procedure based on those given by Union Carbide (30). The batch composition expressed in mole ratios was as follows ... 

Some of the samples were synthesized ithout A190 . The syntheses with tetrapropylammonium iodide (TPA J ) as template were carried out with a varying Si09/Al90 ratio in the range 25 - 400. The batch composition of the template-free synthesis was... 

Figure 2. Overall batch composition of faujasite syntheses reported by several investigators (H2O content not shown).

The synthesis of zeolite A, mixtures of A and X, and zeolite X using batch compositions not previously reported are described. The synthesis regions defined by triangular coordinates demonstrate that any of these materials may be made in the same area. The results are described in terms of the time required to initiate crystallization at a given reaction temperature. Control of the factors which can influence the crystallization time are discussed in terms of "time table selectors" and "species selectors . Once a metastable species has preferentially crystallized, it can transform to a more stable phase. For example, when synthesis conditions are chosen to produce zeolite A, the rate of hydroxysodalite formation is dependent on five variables. These variables and their effect on the conversion of zeolite A to hydroxysodalite are described mathematically. 

Figure 1. Patented batch compositions for the synthesis of zeolites A, X, and Y. Coordinates expressed as mole percent.

Figure 3. Effect of batch composition on the synthesis of zeolites A and X.

When preparing these zeolites, this dual effect must be considered. Any variation from the desired batch composition can present problems if the test is designed to react for a fixed period of time. Variations which slow down the reaction could produce a zeolite which has poor properties simply because it has not completely crystallized. If one has variations which speed up the reaction, one could produce a mixture of zeolite phases. 

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