Temperatures, industrial optimum

A thickness of 0-(XX) 38 mm may be regarded as a good quality finish for general decorative and industrial use for tarnish protection at normal temperatures. For optimum tarnish resistance at temperatures up to 500°C,... 

Prevulcanised compounds, which have undergone the necessary cross-linkage while in the liquid state, are becoming more popular in industry. Articles made from these can often be merely dried to be adequate for a purpose, but to achieve optimum physical properties it is usually necessary to give the articles a short, low temperature (ca 80°C) cure in an oven. 

The various types of reaetors employed in the proeessing of fluids in the ehemieal proeess industries (CPI) were reviewed in Chapter 4. Design equations were also derived (Chapters 5 and 6) for ideal reaetors, namely the eontinuous flow stirred tank reaetor (CFSTR), bateh, and plug flow under isothermal and non-isothermal eonditions, whieh established equilibrium eonversions for reversible reaetions and optimum temperature progressions of industrial reaetions. 

Can we predict the optimum conditions for a high yield of NH3 Should the system be allowed to attain equilibrium at a low or a high temperature Application of Le Chatelier s Principle suggests that the lower the temperature the more the equilibrium state will favor the production of NHS. Should we use a low or a high pressure The production of NH3 represents a decrease in total moles present from 4 to 2. Again Le Chatelier s Principle suggests use of pressure to increase concentration. But what about practicality At low temperatures reaction rates are slow. Therefore a compromise is necessary. Low temperature is required for a desirable equilibrium state and high temperature is necessary for a satisfactory rate. The compromise used industrially involves an intermediate temperature around 500°C and even then the success of the... 

It is known that NHase used in industry has a lower optimum temperature," therefore many reports have been concerned with screening for thermostable NHase. Miyanaga et al. has succeeded to analyze the X-ray structure of such a thermostable NHase from Pseudomonas thermophila. Bacillus sp. BR449 producing NHase with optimum temperature of 55°C has been isolated. Similarly, Bacillus sp. RAPc8 has a growth optimum at 65°C. Takashima et al. has isolated Bacillus smithii strain SC-J05-1, with optimum temperature at 40°C, and whose NHase has an optimum temperature and pH of 50°C and 10, respectively. Its crystal structure has also been elucidated. Bacillus pallidus strain Dac521 has... 

Fig. 3 A shows the effluent NH3 concentration observed for Ru/MgO as a function of reaction temperature for three different Pn, / Phj / Paf ratios at 20 bar total pressure. It is obvious that the reaction orders for N2 and H2 have opposite signs. Fig. 3B illustrates that the reaction orders for N2 and H2 partly compensate each other in the kineticaliy controlled temperature regime. Hence an increase in total pressure with a constant Pnj / Phj 1/3 ratio does not lead to a significant increase in conversion at lower temperatures. For the plication of alkali-promoted Ru catalysts under industrial synthesis conditions, it is necessary to find a compromise between kinetics and thermodynamics by increasing the Pn, / Phj ratio. The optimum observed for Cs-Ru/MgO prepared from CS2CO3 at 50 bar is at about Pnj / Phj 40 / 60 [15]. The high NH3 concentration of about 8 % obtained with 0.138 g catalyst using a total flow of 100 Nml/min clearly shows that Ru catalysts have indeed the potential to replace Fe-based catalysts in industrial synthesis [15].

Pressure ratio. As the design pressure ratio across the compressor increases, the power output initially increases to a maximum and then starts to decrease. The optimum pressure ratio increases with increasing expander inlet temperature. Pressure ratios for industrial machines are typically in the range 10 to 15 but can be higher. For aero-derivative machines, pressure ratios are typically 20 to 30. 

The optimum choice of operating conditions are around a steam to methanol ratio of 1.5 and a temperature range of 250°C to 399°C. Pressure does not influence the reaction rate, but very high pressures limit the equilibrium conversion, which otherwise is better than 99% at the preferred range of 5 to 15 bars. The CU/Zn/Al and Cu/Zn/Cr based catalysts have been used in large units in industry for many years (12). 

For example, classic thermodynamic methods predict that the maximum equUi-brium yield of ammonia from nitrogen and hydrogen is obtained at low temperatures. Yet, under these optimum thermodynamic conditions, the rate of reaction is so slow that the process is not practical for industrial use. Thus, a smaller equilibrium yield at high temperature must be accepted to obtain a suitable reaction rate. However, although the thermodynamic calculations provide no assurance that an equUibrium yield will be obtained in a finite time, it was as a result of such calculations for the synthesis of ammonia that an intensive search was made for a catalyst that would allow equilibrium to be reached. 

The standard CGTase employed in the cyclodextrin industry is produced by Bacillus mascerans. This enzyme is reported to be stable only at temperatures around 50 C and loses activity rapidly above 50 C (19), A more thermostable CGTase compared to the B, mascerans CGTase is produced by Bacillus stearothermophilus with a temperature optimum of 1(PC (20). However, the Thermoanaerobaaer CGTase is far more thermostable with its optimum of 950C, and is to our knowledge, the most thermostable CGTase. 

The ammoxidation of propene to acrylonitrile is of great industrial importance and accordingly the literature is abundant. The reaction is very similar to the oxidation of propene to acrylonitrile and carried out at the same conditions and over the same kind of catalysts. The famous bismuth phosphomolybdate catalyst developed by Sohio was the first of a series of highly effective mixed-oxide catalysts. The optimum yields are generally obtained at temperatures of 400—500°C. Initial selectivities over 95% and yields up to 80% are feasible. The superior selectivity of the ammoxida-... 

Method development is vastly simplified by computer simulations using commercial software. With input from a small number of real experiments, a program can predict the effects of solvent composition and temperature in isocratic or gradient separations. You can select optimum conditions in minutes with the computer instead of days in the lab. Of course, you must verify the prediction by a real experiment. Commercial software saves huge expenses in method development in industrial laboratories. 

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