Catalyst steaming conditions

Catalyst hydrothermal deactivation was carried out in two different equipments a lOOg capacity fixed bed steamer was used for the advanced cracking evaluation (ACE) unit tests and a 5 kg capacity fluidized bed steamer was used for the other testing protocols. Steaming conditions in the two cases were the same 788°C for 5 hours under 100% steam flow. Although conditions were similar, higher pressure buildup in the fixed bed steamer led to lower surface area retentions. 

Reuse et al. [24] applied a reactor carrying micro structured plates for methanol steam reforming over commercial copper-based low-temperature water-gas shift catalyst from Sud-Chemie. The reactor took up 20 plates made of FeCrAl alloy of size 20 mm x 20 mm x 0.2 mm. The channel size was 200 pm x 100 pm (Figure 2.5). The catalyst was conditioned by oxygen and hydrogen treatment. 

The conventional faujasite catalysts were steamed at 1400 F in 2 atmospheres steam at varying times in order to achieve the same activity as measured by our standard Fluid Activity Index (FAI). Table I summarizes the steaming conditions employed. 

Lab-Steamed Catalyst Steam-Treat Conditions Unit Cell A Micropore area m2/e Matrix area m2/g Cryst Relative to Fresh... 

A simple vanadium mobility test can be setup, in which the vanadium which migrates from vanadium-loaded catalyst towards non-vanadium loaded catalyst can be measured under catalyst aging (usually steaming) conditions (2). 

More than 80% of the emissions from cars equipped with catalysts steam from the first three minutes of driving [1]. Substantial efforts are therefore made to develop catalysts possessing high activity at low-temperature conditions. 

Laboratory simulation of catalyst aging in oxidation atmosphere was realized in muffle furnace in static air, nitrogen and steam conditions. Temperature of treatment was 500, 600, 700 and 800 °C and treatment duration 1, 3, 6 and 9 h. 

Figure 1. Effect of Sr/La ratio on the ethane and O2 conversion, product selectivity and CO/CO2 ratio in the oxidative dehydrogenation of ethane to ethylene over Sr-La2O3/SA-5205 catalyst [ Reaction condition Temperature = 700°C, C2H5/O2 = 6.0, steam/C2H6 = 1.0, space velocity = 100,104 cm. g. h ].

Sodium sulfate was prepared from sodium chloride by passing sulfur dioxide, steam, and air at atmospheric pressure through a fixed bed impregnated with catalyst. Optimum conditions of temperature, partial pressure of reagent gases, and total flow rate were determined. 

TABLE 3.1 Catalytic Activities of Various Bimetallic Catalysts (Reaction Conditions Temperature 250 °C, GHSV 3000 h , Steam/CO Ratio 6, Gas Composition 3% CO, 14% CO2, 37% H2, 23% H2O, Ar Balance... 

An interesting survey was conducted by Engelhard a few years back of 15 companies and their testing philosophies. The conclusion drawn was that the choice of steaming procedure and MAT procedure, and what combination of them is chosen, will affect the observed ranking of catalyst performance. Furthermore, if you want to realistically assess catalysts, the steaming conditions as well as the MAT conditions should be related to commercial experience. 

Catalytic conditioning. With the use of catalysts, steam and dry reforming reactions become an effective way to convert the tar components in the fuel gas at lower temperatures, compatible with those of the gasification processes. 

Reversed-flow gas chromatography (RF-GC) has been successfully used to characterize solid catalysts under conditions compatible with the operation of real catalysts. RF-GC is not limited to chromatographic separation since RF-GC is accompanied by suitable mathematical analysis of the chromatographic data, the simultaneous determination of various physicochemical parameters is possible. Thus, various catalytic processes related to the operation of fuel cell units such as steam reforming, catal3dic partial oxidation, autothermal reforming, as well as water-gas shift (WGS) reaction and selective CO oxidation can be studied. 

Methane or natural gas steam reforming performed on an industrial scale over nickel catalysts is described above. Nickel catalysts are also used in large scale productions for the partial oxidation and autothermal reforming of natural gas [216]. They contain between 7 and 80 wt.% nickel on various carriers such as a-alumina, magnesia, zirconia and spinels. Calcium aluminate, 10-13 wt.%, frequently serves as a binder and a combination of up to 7 wt.% potassium and up to 16 wt.% silica is added to suppress coke formation, which is a major issue for nickel catalysts under conditions of partial oxidation [216]. Novel formulations contain 10 wt.% nickel and 5 wt.% sulfur on an alumina carrier [217]. The reaction is usually performed at temperatures exceeding 700 °C. Perovskite catalysts based upon nickel and lanthanide allow high nickel dispersion, which reduces coke formation. In addition, the perovskite structure is temperature resistant. 

Czerwosz et al. s findings might be of particular interest to readers familiar with carbon formation on nickel and nickel-coated catalysts that had been exposed to hydrocarbons or carbon monoxide in hydrocarbon synthesis or in so-called re-forming reactions carried out in petroleum refineries. For example, the formation of filamentous carbon on such solids at temperatures in the same range as that used by Czerwosz et al. was reported by McCarthy in 1982 [115]. However, these authors did not analyze the carbon deposits by Raman spectroscopy, nor were they aware of the existence of fullerenes. Their concern was the removal of these carbons by steam or by combustion, because these carbons inactivated the catalyst. It was also unknown to them that these carbons had the lubricating properties that were demonstrated by Lauer and co-workers [60,62]. By using these catalysts under conditions of continuous wear, they could maintain the catalytic effect of the surface. 

Li et al. [106] removed aluminum from NH4Y at 95 with an aqueous solution of oxalic acid and ammonium oxalate prior to heat treatment at 600°C under typical self-steaming conditions. The product with a fi-amework Si/Al ratio of 2.95 was then subjected to acid leaching with 1 M sulfuric add followed by a second self-steaming treatment The final zeolite, used as catalyst for alkylation of phenol with long-chain olefins, retained 90 % of the initial crystallinity at a final Si/Al ratio of 5.71 and had a catalytically favorable mesopore volume of about 0.3 ml/g. 

The Chevron process was used in two U.S. plants, although it is no longer used. Cycle lengths tanged from 6—30 d, depending on catalyst age and OX content of the feed. Operating conditions were temperature of 370—470°C and space velocity of about 0.5/h. Addition of 5 wt % steam reduced disproportionation losses. 

Single-reaction-step processes have been studied. However, higher selectivity is possible by optimizing catalyst composition and reaction conditions for each of these two steps (40,41). This more efficient utilization of raw material has led to two separate oxidation stages in all commercial faciUties. A two-step continuous process without isolation of the intermediate acrolein was first described by the Toyo Soda Company (42). A mixture of propylene, air, and steam is converted to acrolein in the first reactor. The effluent from the first reactor is then passed directiy to the second reactor where the acrolein is oxidized to acryUc acid. The products are absorbed in water to give about 30—60% aqueous acryUc acid in about 80—85% yield based on propylene. 

Oxidation Step. A review of mechanistic studies of partial oxidation of propylene has appeared (58). The oxidation process flow sheet (Fig. 2) shows equipment and typical operating conditions. The reactors are of the fixed-bed shell-and-tube type (about 3—5 mlong and 2.5 cm in diameter) with a molten salt coolant on the shell side. The tubes are packed with catalyst, a small amount of inert material at the top serving as a preheater section for the feed gases. Vaporized propylene is mixed with steam and ak and fed to the first-stage reactor. The feed composition is typically 5—7% propylene, 10—30%... 

The reaction occurs at essentially adiabatic conditions with a large temperature rise at the inlet surface of the catalyst. The predominant temperature control is thermal ballast in the form of excess methanol or steam, or both, which is in the feed. If a plant is to produce a product containing 50 to 55% formaldehyde and no more than 1.5% methanol, the amount of steam that can be added is limited, and both excess methanol and steam are needed as ballast. Recycled methanol requited for a 50—55% product is 0.25—0.50 parts per part of fresh methanol (76,77). 

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