Vacuum producing equipment Costs

Packed columns are favored in the distillation of thermally unstable materials such as cumene hydroperoxide, acrylic monomers, diisocyanates, amines, and terpenes. Top column pressures below 5 mm Hg absolute frequently are not used because of the high operating and capital costs of the vacuum-producing equipment. Thus, it may be nec-... 

There are, of course, some limitations. An obvious one is that this method cannot be applied yet to the preparation of industrial catalysts, another one is its cost because ultra-high-vacuum (UHV) equipment is required. This drawback explains why this method is usually coupled to surface techniques such as XPS, UPS, RHEED, and AES, which also require UHV. The last disadvantage is that the best suited supports are those that are flat, i.e., oxide single-crystal faces, oxides produced by oxidation of a metal single crystal, or compressed powder oxides. There have been several examples where the preparation chamber also serves as sample chamber for surface techniques and is coupled to a catalytic reactor. Whereas there are a number of works using this approach for bulk metals (80), there are, by contrast, few studies dealing with metals supported on either single crystals (81) or polycrystalline supports (78, 79,82, 83). The latter type of system appears to be the model catalysts closest to the real catalyst. 

These films have been produced by sputtering, chemical vapor deposition, and vacuum evaporation. The sol-gel method has also received some attention as a way to prepare these films because of its low cost. But these film preparation methods have disadvantages, such as a need for vacuum equipment and high-temperature heat treatment, and difficulties in coating large areas. 

The subfab is a utility distribution and cleanroom support level that is located immediately beneath the cleanroom. The use of a subfab allows the installation of contamination-producing support equipment, such as vacuum pumps and chillers, outside of the cleanroom airflow path, and provides a location for the distribution of inert gases. A major advantage in the use of a subfab is the ease of modification of utilities. Changes can be made in utility distribution systems in the subfab, and the new utility runs can penetrate the cleanroom floor to the area needed. This reduces the cost of malfing utility modifications and increases the flexibility of the facility (Figpire 8.5). 

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