Laboratory-steamed catalyst

The heavier portion of the fresh and laboratory steamed catalyst (Float B) exhibits a decreased micropore volume with respect to the lighter portion (Float A), suggesting that the density fractionation within each catalyst reflects the presence of a finite range of zeolite crystallinities. Particularly for the fresh catalyst, this inhomogeneity is small (Table VIII). 

The comparison of physical properties of laboratory-steamed catalyst with those of equilibrium catalyst fractions given in Table VII indicates that a wide range of steaming temperatures is necessary to reproduce the equilibrium catalyst deactivation profile for lab steaming times of one day or less. These results indicate that an improved catalyst aging procedure for simulating... 

These results on commercially-aged samples show that silica is transported from the cracking catalyst particles to the Additive R particles during commercial-unit aging, just as it is during a laboratory steam deactivation. More Importantly, the data show that silica deactivates Additive R in a commercial unit (loss of SOx capability) just as it does in a laboratory deactivation. 

The amount of wash coat which was deposited in the testing reactors was in the same range, between 14 and 17 mg, for the rhodium, platinum and palladium samples tested. The platinum sample was calcined after impregnation at a lower temperature of 450 °C, all other samples at 800 °C. The reason for this will be explained below. The content of the active noble metal was around 5 wt.%. All noble metal-containing samples were laboratory-made catalysts. A commercial a-alumina-based catalyst containing 14 wt.% Ni was added for comparison, as nickel catalysts are applied in industrial steam reforming [52],... 

Laboratory steam deactivations represent a significant compromise in the effort to simulate equilibrium catalyst. Since hydrothermal deactivation of FCC catalysts is not rapid in commercial practice, deactivation of the fresh catalyst in the laboratory requires accelerated techniques. The associated temperatures and steam partial pressures are often in substantial excess of those encountered in commercial units. In some instances, the effect of contaminant metals is measured by an independent test not affiliated with steam deactivation. In subsequent yields testing, interactions between different modes of deactivation may be overlooked. Finally, single mode deactivation procedures can not reproduce the complex profile of ages and levels of deactivation present in equilibrium catalyst. 

Comparison with Lab Steam Deactivations. Catalyst fractions which exhibit 50% or greater loss in micropore volume/crystallinity comprise less than 15% of equilibrium catalyst. The major portion of this particular equilibrium catalyst is remarkably similar to the material which results from increasingly severe laboratory steam deactivations at 815°C or less (Tables VI and VII). Dealumination is rapid, the associated crystallinity loss is small, and the matrix surface area shows little change. Crystallinity retention falls below 70% only after dealumination is complete. 

While ASTM procedures for both steaming and MAT testing have been established (ASTM D-4463 and D-3907, respectively), a general survey of the petroleum industry indicates that neither of these methods are specifically practiced. Instead, each laboratory has developed individualized steaming and MAT testing procedures that best suit their needs. While many laboratories perform complete chemical and physical analyses on fresh FOC catalysts, the vast majority do not perform such analyses on the steamed catalysts. The latter actually represent the catalysts evaluated vhile the former are in essence a "precursor". While it may be argued that fresh properties can be used as an indicator of steamed properties, a thorough evaluation of catalysts should include an examination of the steamed chemical and physical properties. 

Pyrolysis, steam gasification and CO gasification experiments were carried out at 700 T using a Nt-Al coprecipitated catalyst prepared in our laboratory. This catalyst was chosen because of its mechanical strength and initial activity. These three processes were compared using a similar W/mb ratio because of the important influence of this ratio on catalytic processes (5,18). 

It was shown in laboratory studies that methanation activity increases with increasing nickel content of the catalyst but decreases with increasing catalyst particle size. Increasing the steam-to-gas ratio of the feed gas results in increased carbon monoxide shift conversion but does not affect the rate of methanation. Trace impurities in the process gas such as H2S and HCl poison the catalyst. The poisoning mechanism differs because the sulfur remains on the catalyst while the chloride does not. Hydrocarbons at low concentrations do not affect methanation activity significantly, and they reform into methane at higher levels, hydrocarbons inhibit methanation and can result in carbon deposition. A pore diffusion kinetic system was adopted which correlates the laboratory data and defines the rate of reaction. 

Since the oxidation of SO to SO is a step in the operation of SOx catalysts, an increase in oxygen concentration should favor the reaction, and thereby increase the efficiency of SOx catalysts. The evidence indicates that this occurs. Baron, Wu and Krenzke (9) have shown that an increase in excess oxygen from 0.9% to 3.4% resulted in a 20% reduction in SOx emissions. This was for a steam-deactivated catalyst in a laboratory unit at 1345 F (no combustion promoter). 

In the laboratory, the two deactivation mechanisms can be separated by steaming the cracking catalyst and Additive R separately. In this case, there can be no transfer of silica from the cracking catalyst to Additive R during the steaming. The Additive R only loses surface area. The steamed components are then blended together for SOx activity measurements. 

In Table II, the product yields of REY-PILC are compared with PILC, a commercial equilibrium catalyst, and with the same commercial catalyst that had been deactivated in the laboratory to near constant conversion. The addition of REY to PILC maintained activity in the presence of steam while coke yield was reduced and the LCO/HCO ratio was slightly higher than for either of the commercial catalysts. This suggests that the microstructure of the PILC after pretreatment D will still convert large molecules into gasoline range products instead of generating coke as seen in PILC alone. 

The catalyst used in this study corresponds to a fresh commercial catalyst used in one FCC unit of ECOPETROL S.A. This solid is hydrothermal deactivated at the laboratory in cycles of oxidation-reduction (air-mixture N2/Propylene) at different temperatures, different times of deactivation, with and without metals (V and Ni), and different steam partial pressures. Spent catalysts (with coke) are obtained by using microactivity test unit (MAT) with different feedstocks, which are described in Table 10.1. 

FCC catalyst, supplied by Grace Davison, at three different cat-to-oil ratios, 4,6, and 8. The feed was injected at a constant rate of 3 g/min for 30 seconds. The catalyst to oil ratio was adjusted by varying the amonnt of catalyst in the reactor. Two catalysts used for this evaluation were laboratory deactivated using the cyclic propylene steaming (CPS) method [6]. Properties of these catalysts after deactivation are listed in Table 12.3. 

Hydrothermal (steam) stability is also important, in as much as the catalyst must pass through a high temperature stripping zone in which the usual fluid stripping medium is steam. In our laboratory, zeolite hydrothermal stability is measured by comparing the x-ray crystallinity of the unknown faujasite sample with that of a fully rare earth exchanged reference standard following a 3 hour, 100% steam, 1500 F treatment. 

As discussed, XRD has for many years been the standard, everyday characterization method for solid catalysts, and in almost every laboratory in this field there is access to an X-ray diffractometer. This instrument allows a wide variety of different characterizations, but there are also limitations of such equipment. For example, the limited resolution of an in-house diffractometer may often be insufficient for a detailed analysis. This point is illustrated in Fig. 5a, which shows the diffractogram of an industrial type steam-reforming catalyst consisting of nickel crystallites on a spinel support (35). The Ni(lll) and the spinel(400) lines overlap so that a detailed analysis is impossible. This problem can be overcome if the XRD... 

It follows that most work reported over the last few years on steam reforming and methanation has been concerned with nickel catalysts. The following sections will therefore deal mostly with nickel-based catalysts, particularly those which have some importance in commercial practice. Particular stress will be laid on work, with which the author has been associated, concerned with steam reforming and methanation catalysts but mention will also be made of parallel studies from other laboratories. In sections on the catalysts for steam dealkylation and steam reforming of methanol, where catalyst selectivity is a prerequisite, other types of catalyst will also be discussed. 

---