Catalyst steaming

The saturated, cleaned raw synthesis gas from a Texaco partial oxidation system is first shifted by use of a sulfur resistant catalyst. Steam required for shifting is already present ia the gas by way of the quench operation ia the generator. The shifted gas is then processed for hydrogen sulfide and carbon dioxide removal followed by Hquid nitrogen scmbbiag. 

A small fraction of the hydrocarbons decompose and deposit on the catalyst as carbon. Although the effect is minute ia terms of yield losses, this carbon can stiU significantly reduce the activity of the catalyst. The carbon is formed from cracking of alkyl groups on the aromatic ring and of nonaromatics present ia certain ethylbenzene feedstocks. It can be removed by the water gas reaction, which is catalyzed by potassium compounds ia the catalyst. Steam, which is... 

In the past several years, more attentions have been given to improving mechanical performance of the reactor stripper. Proprietary stripper designs are being offered by the FCC technology licensers in attempts to improve the catalyst/steam contact. 

In addition to natural gas, steam reformers can be used on light hydrocarbons such as butane and propane and on naphtha with a special catalyst. Steam reforming reactions are highly endothermic and need a significant heat source. Often the residual fuel exiting the fuel cell is burned to supply this requirement. Fuels are typically reformed at temperatures of 760 to 980°C (1,400 to 1,800°F). 

Figure 3B. Continued. Microprobe analysis of a DFCC system containing 2% V on the host catalyst. Steaming induced V migration to the sepiolite surface. Continued.

Figure 4 Infra-red spectra of pyridine adsorbed on sample G5-Ce steamed at 550°C (spectrum a) and 650°C (b) and on a FCC commercial catalyst steamed at 775°C (c). Pyridine adsorption at 25°C and desorption at different temperatures.

FIGURE 7.9 Catalyst steam stripping—an annual stripper configuration. (Reprinted from Jack Wilcox, R., Published in Petroleum Technology Quarterly, Troubleshooting Complex FCCU Issues, http //www.ePTQ.com, Q3, 2009. With permission.)... 

Johnson Matthey (2005), Johnson Matthey Catalysts, Steam Reforming, http // www.synetix.com/refineries/hydrogen-steamreforming.htm accessed on Feb. 13, 2005. 

Catalyst Steamed Catalyst Properties Surface Area, irfVgram X-Ray Crystallinity, wt % Total Rare Earth, wt % Unit Cell Size, A FAI Activity, % Fresh Catalyst Properties Unit Cell Size, A Surface Area, rr /gram A 75 8 3 24.36 66 24.51 221 B 162 28 0.2 24.28 66 24.43 202... 

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

Chester et a) 6] indicate that the relative contributions of zeolite deactivation (e.g, loss of crystallinity) and matrix deactivation (e.g, loss of porosity) in different temperature ranges can be significantly different. They therefore conclude that increasing temperature as a means of increasing catalyst steam deactivation severity can give misleading estimates of overall catalyst stability. This has also been confirmed with today s" FCC catalysts [10]. 

Assuming that the metals and other poisons on catalyst are low, we can expect that traditional catalyst steaming will be sufficient to simulate catalyst deactivation. Keyworth et a) [16] recommend to make a composite of several steamings in order to address the age distribution of equilibrium catalyst in a commercial unit. Beyerlein et al [17, 21] critically question the possibility of improving catalyst ageing procedures, which rely onfy on steam treatment at constant temperature for varying times. 

Assuming that the metals and other poisons on catalyst are low, we may expect that traditional catalyst steaming will be sufficient to simulate catalyst deactivation. 

Hydrothermal stability. Steam or water vapor is sometimes present in the reaction mixture not necessarily as a reactant or product. It is a convenient form of heat source for endothermic reactions such as dehydrogenation of hydrocarbons. It can also oxidize carbon deposits that deactivate many catalysts. Steam is regularly used in the dehydrogenation of ethylbenzene to produce styrene for the above reasons. 

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. 

The commercial production of hydrogen is carried out by treating natural gas with steam at high temperatures and in the presence of a catalyst ( steam reforming of methane ) ... 

By temperature compensations, such results can be sustained for periods of a few hundred hours. However, a slow continuing deactivation occurs, and eventually the catalyst must be regenerated by combustion of the deposited coke. After regeneration, reasonable dehydrogenation results are again obtained after a rapid initial deactivation of the catalyst. Steam was found to be a particularly useful diluent with this type of catalyst. In contrast to this, the best results with molybdena-alumina for catalytic reforming are obtained over fresh catalyst and when steps such as dilution with hydrogen are employed to repress the initial rapid deactivation. 

In another of the commercial processes, cumene is also oxidized in liquid phase with oxygen at 105-135 C in the absence of any added catalyst. Steam is used in the gas-vapor zone of the reactor to prevent explosions. 

Attrition of the catalyst] steam flowrate > expected/air flowrate > expected/local velocities into the dense phase > 60 m/s/catalyst too fragile. 

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. 

The dehydrogenation of ethylbenzene is carried out at temperatures up to approx. 600 °C. At higher temperatures, the thermal decomposition of styrene and ethylbenzene increases and reduces the yield. Since dehydrogenation is endothermic, high temperatures and low pressure (less than 1 bar in modem units) favor the reaction (Le Chateliers s principle). In order to lower the partial pressure and prevent carbon deposits or the need for the frequent regeneration of the catalyst, steam is injected into the reactor. In industrial practice, the primary conversion is restricted to limit the formation of undesirable by-products the unconverted ethylbenzene is recycled, to achieve a high styrene yield thus only small amounts... 

Inertness. Activated carbon is inert. The interaction between carrier and active phase (most times noble metals) is small. Thus the qualities of the metals are less influenced by the activated carbon as carrier than by other carriers. Because of the inertness activated carbon hardly shows activity as acid catalyst and does not decompose hydrocarbons resulting in carbon deposition on the metals and causing poisoning of the catalyst. Steam activated carbons are more inert than chemical activated carbons. ... 

---