Refractory support

Externally lined with 1 inch (2.5 cm) thick, erosion-resistant refractory supported by 304H stainless steel hexmetal anchors or other individually unitized anchors. The refractory should be cut out flush with the top of hex. The hexmetal should be discernible after the refractory installation. 

Spalled coke or refractory is lodged in the diplegs. This can be caused by improper curing or inadequate refractory supports. 

Nickel. As a methanation catalyst, nickel is presently preeminent. It is relatively cheap, it is very active, and it is the most selective to methane of all the metals. Its main drawback is that it is easily poisoned by sulfur, a fault common to all the known active methanation catalysts. The nickel content of commercial nickel catalysts is 25-77 wt %. Nickel is dispersed on a high-surface-area, refractory support such as alumina or kieselguhr. Some supports inhibit the formation of carbon by Reaction 4. Chromia-supported nickel has been studied by Czechoslovakian and Russian investigators. 

These relative chemisorption strengths enable us to make some simple predictions regarding suitable metal catalysts for specific reactions. For example, a catalyst for the Haber process must chemisorb both N2 and H2, but not too strongly. Since N2 is the less readily bound, we choose Fe, Ru, or Os. The latter two are expensive, so our best choice is iron—usually finely divided, on a suitable refractory support. 

Among the more important catalysts are metals, which may be promoted by other metals, or by oxides and oxides, which are usually rendered more effective by mixing with other oxides. It is usual to distinguish between supported catalysts, generally metals in a finely divided condition on the surface of silicate minerals, and promoted catalysts, where an oxide, or occasionally some other compound, is mixed with the metal the mixture being sometimes also supported on an inert refractory support. The distinction is not, however, absolutely sharp. 

Co-precipitation. - The preparation of supported catalysts by the coprecipitation of metal ions with the support ions usually produces an intimate mixing of catalysts and support. An example of this technique is the coprecipitation of metal ions with aluminium ions to produce a precipitated alumina gel containing the metal hydroxide. This precipitate when calcined produces a refractory support with active component dispersed throughout the bulk as well as at the surface. However, in the preparation of multi-component catalysts, it is possible under improper conditions to obtain a heterogeneous product because of the different solubility products of the constituents. Care should be taken therefore to avoid this undesirable situation by appropriate forethought. 

Advantages of Organonetallies Directly Deposited on Refractory Supports... 

Inert refractory supports have long been used as economizers to extend the surface of active catalysts 1,2 thus asbestos has been used to support platinum to catalyze the oxidation of the S02. The original purpose of supports seems to have been to extend the surface of expensive catalysts. Atoms that are buried in the bulk phase, when a catalyst acts as its own support, are brought to the active surface when distributed over another, cheaper, support. 

In contrast with platinum, Cullis and Willatt found that palladium is more sensitive to oxidizing environments than is Pt on alumina or titania supports. This effect was attributed to the ability of Pd to absorb 02- As they note the formation of Pd hydroxides may contribute to its higher mobility than that found for Pt. Hucknall, Willatt, and Hockham found that palladium also responds dramatically differently to exposure to halogen containing hydrocarbons. The presence of halogen enhances the mobility of Pd and thereby promote its sintering on alumina. On titania and other less refractory supports, the influence of halogens is not as detrimental to Pd dispersion. 

Specific Site Poisoning- Crucial to our understanding of the activity of mixed oxide catalysis or oxides on more refractory supports is the ability to measure the surface area of the active oxide. Two methods come readily to mind selective chemisorption and selective poisoning. In each case the critical question will be the selectivity of the adsorbent and considerable further research is still required. As an example, can N2O decomposition be employed for V+4 analysis as it is for reduced copper ... 

Figure 9.8 shows some more typical monolithic refractory supports. 

For the direct analysis of in biological species, an interface is available [43]. The liquid samples are deposited into a bed of CuO powder which is held on a refractory support in an enclosed chamber. The CuO matrix is heated locally by an infrared laser, and the CO2 evolved is swept away by a flow of He into the ion source. 

Graphite connectors must be supported by Insulating refractory supports... 

Disc. A thin refractory support used to protect other kiln furniture from glaze attack during glost firing. Discharge-end Block. See nose-ring... 

Serrated Saddle. A refractory support for pottery-ware during kiln firing this particular item is a rod of triangular section, its upper edge being serrated to facilitate the rearing (q.v.) of the ware. 

CATALYST (Platinum or chromium oxide on refractory support)... 

Ceramic industry and industrial thermics Furnaces refractories, supports, crucibles, sheaths, parts for burners... 

---