Catalysts feed characterization

FCC feed characterization is one of the most important activities in monitoring cat cracking operation. Understanding feed properties and knowing their impact on unit performance are essential. Troubleshooting, catalyst selection, unit optimization, and subsequent process evaluation all depend on the feedstock. 

In the previous examples, the feed characterizing correlations in Chapter 2 are used to determine composition of the feedstock. The results show that the feedstock is predominantly paraffinic (i.e., 61.6% paraffins. 19.9% naphthenes, and 18.5% aromatics). Paraffinic feedstocks normally yield the most gasoline with the least octane. This confirms the relatively high FCC gasoline yield and low octane observed in the test run. This is the kind of information that should be included in the report. Of course, the effects of other factors, such as catalyst and operating parameters, will also affect the yield structure and will be discussed. 

Application of H-NMR for Fluid Catalytic Cracking Feed Characterization 195 and for catalyst B... 

A feasibility study on the application of H-NMR petroleum product characterization to predict physicochemical properties of feeds and catalyst-feed interactions has been performed. The technique satisfactorily estimates many feed properties as well as catalyst-feed interactions to forecast products yield. There are, however, limitations that have to be understood when using the H-NMR method. The technique, in general, is not capable either to estimate the level of certain contaminants such as nitrogen, sulfur, nickel, and vanadium when evaluating feed properties or the effect of these contaminants on products yields while testing catalyst-feed interactions. 

When iron is added as a second promoter, the performance of PtFeWZ catalysts is dramatically improved in the presence of dihydrogen in the feed.19,21 Under identical reaction conditions, PtFeWZ(S) is characterized by an n-pentane isomerization rate of 9 x 10 x mol s 1 m 2. Whereas the PtWZ catalyst is characterized by a nearly stable selectivity of about 95% (see Table 2), the PtFeWZ(S) catalyst develops a selectivity (increasing with TOS) of up to 98%, and PtFeWZ(N) shows a stable selectivity greater than 99%. The suppression of the hydrogenolysis products, which are formed on the platinum in PtWZ by the addition of iron as a second promoter, might be a consequence of the suppression of the formation of metallic platinum. Furthermore, the redox properties of the Fe3+/Fe2+ pair in the surface solid solution (see above) might... 

Our catalysts were simple mixtures of a-Sb204 and Fc2(Mo04)3 powders prepared separately. The catalysts were tested in the oxidation of isobutene to meihacrolein (ISOB) and ethanol to acetaldehyde (ETH). In order to show more dramatically the influence of a-Sb204 the oxygen ratio in the feed (O2/ISOB) was kept at a value lower than that normally used in the first reaction, With respect to the second reaction, different values of O2/ETH were taken. A special long-run experiment (30 h) was made for the reaction of ethanol. Catalysts were characterized by XRD. XPS, electron microscopy, and Fc Mdssbauer spectroscopy before and after reaction. 

A Cu0/Ti02 catalysts was characterized by NH3 temperature programmed desorption (TPD) and Fourier transform infrared (FT-IR) spectroscopy and tested for NH3 oxidation. TPD measurements showed two forms of adsorbed NH3, one of which could be removed by treatment with water vapour. FT-IR spectra showed NH3 coordinated to Lewis acid sites, which gave rise, after treatment at 150°C, to adsorbed hydrazine and nitrxyl species. In NH3 oxidation tests conversions up to 90% were observed. N2 was the main product, N2O and NO being formed to lower extents. The addition of water vapour in the feed influenced the product distribution. A reaction mechanism was proposed, involving adsorbed hydrazine, nitroxyl and amido species as intermediates for N2, N2O and NO production, respectively. 

The reforming reaction was carried out in a continuous flow quartz-fixed-bed reactor (i.d., 6 mm) under atmospheric pressure, at 973 K, and with a ratio of CH4/CO2 1.05. 150 mg catalyst was loaded into the reactor and weight hourly space velocity (WHSV) was controlled at 12.5 h. The catalyst was reduced again in situ at the reaction temperature in the H2 flow for 2 hrs. The flow rates of the feed gases were controlled by mass flow meters (Matheson Mass Flow Controller Model 8240). The temperature of the catalyst bed was measured by a chromel-alumel thermocouple, and it was kept constant within 1 K. The composition of reactants/products mixture was analyzed with an on-line SP-3420 gas chromatograph equipped with a TCD and a Porapak QS column. The catalysts were characterized after 4 hrs reaction. 

Test reactions- Th catalysts were characterized by means of the test reactions of dehydrogenation of cyclohexane (CH), isomerization of n-Cj and accelerated deactivation using n-C as a feed. Before performing the test reactions, the catalysts were reduced at 500°C for 2 h. 

Fig. 52. Left In situ IR spectra of LaCl3/NH4-Y after heat-treatment in high vacuum at (a) 455, (b) 575, (c) 675 K, (d) rehydroxylation by 1 min contact with 0.1 kPa water vapor, (e) contact with feed stream of 1.3 vol.-% of ethylbenzene (EB) in dry helium, respectively. Right (1), total EB conversion on a catalyst wafer characterized by spectrum c (2), total EB conversion on a catalyst wafer characterized by spectra d and e (from [888])...

Quench Converter. The quench converter (Fig. 7a) was the basis for the initial ICl low pressure methanol flow sheet. A portion of the mixed synthesis and recycle gas bypasses the loop interchanger, which provides the quench fractions for the iatermediate catalyst beds. The remaining feed gas is heated to the inlet temperature of the first bed. Because the beds are adiabatic, the feed gas temperature increases as the exothermic synthesis reactions proceed. The injection of quench gas between the beds serves to cool the reacting mixture and add more reactants prior to entering the next catalyst bed. Quench converters typically contain three to six catalyst beds with a gas distributor in between each bed for injecting the quench gas. A variety of gas mixing and distribution devices are employed which characterize the proprietary converter designs. 

The hterature consists of patents, books, journals, and trade Hterature. The examples in patents may be especially valuable. The primary Hterature provides much catalyst performance data, but there is a lack of quantitative results characterizing the performance of industrial catalysts under industrially reaHstic conditions. Characterizations of industrial catalysts are often restricted to physical characterizations and perhaps activity measurements with pure component feeds, but it is extremely rare to find data characterizing long-term catalyst performance with impure, multicomponent industrial feedstocks. Catalyst regeneration procedures are scarcely reported. Those who have proprietary technology are normally reluctant to make it known. Readers should be critical in assessing published work that claims a relevance to technology. 

A slurry bed reactor is in a pilot stage investigation. This type is characterized by having the catalyst in the form of a slurry. The feed gas mixture is bubbled through the catalyst suspension. Temperature control is easier than the other two reactor types. An added advantage to slurry-bed reactor is that it can accept a synthesis gas with a lower H2/CO ratio than either the fixed-bed or the fluid-bed reactors. 

Characterizing FCC feed provides quantitative and qualitative csti mates of the FCC unit s performance. Process modeling uses the feed properties to predict FCC yields and product qualities. The process model should be used in daily unit monitoring, catalyst evaluations, optimization, and process studies. 

We may thus conclude after this short overview on DeNO technologies that NH3-SCR using catalysts based on V-W-oxides supported on titania is a well-established technique for stationary sources of power plants and incinerators, while for other relevant sources of NO, such as nitric acid tail gases, where emissions are characterized from a lower temperature and the presence of large amounts of NOz, alternative catalysts based on transition metal containing microporous materials are possible. Also, for the combined DeNO -deSO, alternative catalysts would be necessary, because they should operate in the presence of large amounts of SO,.. Similarly, there is a need to develop new/improved catalysts for the elimination of NO in FCC emissions, again due to the different characteristics of the feed with respect to emissions from power plants. 

In Fischer-Tropsch synthesis the readsorption and incorporation of 1-alkenes, alcohols, and aldehydes and their subsequent chain growth play an important role on product distribution. Therefore, it is very useful to study these reactions in the presence of co-fed 13C- or 14 C-labeled compounds in an effort to obtain data helpful to elucidate the reaction mechanism. It has been shown that co-feeding of CF12N2, which dissociates toward CF12 and N2 on the catalyst surface, has led to the sound interpretation that the bimodal carbon number distribution is caused by superposition of two incompatible mechanisms. The distribution characterized by the lower growth probability is assigned to the CH2 insertion mechanism. 

Characterization of Equilibrium Catalyst Used for Comparison of Eeed-B and Feed-C... 

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