Surface area of catalyst

Standard Test Methodfor Surface Area of Catalysts. (D3663—78) Standard Test Method for Hydrogen Chemisorption on Supported Platinum on Alumina Catalysts. (D3908-80) American Society for Testing and Materials (ASTM), Philadelphia, PA. 

However, in view of the large specific surface area of catalysts used in conventional fixed-bed reactors for this reaction, attempts have to be made to realize catalyst coatings of similar porosity in micro channels [17]. 

In heterogeneous catalysis reactions take place at the surface of the catalyst. In order to maximize the production rates, catalysts are, in general, porous materials. In practice, the surface area of catalysts ranges from a few up to 1500 square metres per gram of catalyst. It is instructive to calculate the specific surface area as a function of the particle size. 

S is the metal surface area of catalyst charged into the reactor ... 

The catalysts used in these experiments included those already employed in the infrared measurements in addition to some others. The results are presented in Tables VI and VII along with some older measurements on Raney-nickel and a nickel-on-kieselguhr catalyst. These older measurements are slightly less accurate because the cyclohexane content of the reaction product was determined by mass spectrometry. The surface area of catalyst E was not determined hence, its reaction rates per unit of surface area could not be calculated. 

Surface area of catalyst tubes per unit length of reactor = 10 m... 

Figure 7-24 Adsorption equilibrium apparatus to determine adsorption isotherms and surface areas of catalysts. From the saturation of a sample of known weight, the surface area can be determined if the area occupied by a...

The naphtha yield was lower for Catalyst B than for the reference and this illustrates the necessity to have enough zeolite surface area in the catalyst to be able to crack all the components in the feed, both those that can be cracked directly and those that must be precracked on the matrix before they can be cracked by the zeolite. Catalyst C had a slightly higher naphtha maximum than the reference catalyst, despite its high matrix surface area. The high matrix surface area of Catalyst C,... 

However, the high matrix surface area of catalyst C made it possible to crack more heavy components than the other two catalysts, but the matrix cracking was too intense for this catalyst. Catalyst B showed the highest HCO yield of the... 

Gas adsorption is the most commonly used method for characterizing the surface area of catalysts. Both physical adsorption and chemisorption may be used. Furthermore, EM can provide supplementary information. A large surface area is desirable since activity is defined as the rate per unit active surface area ((per metre) ), and this necessitates porous catalysts. Eor an idealized porous system. 

EM techniques provide important information in the characterization of the dispersion of metallic catalysts. Surface areas of catalysts are measured by the standard BET method described previously. An isotherm is produced using nitrogen as the adsorbate chemisorption of certain gases (e.g. H2 or CO) is also used, including for particle size distributions. We give some examples in chapter 5. 

Ss = tlie surface area per unit mass of catalyst Sex = the external surface area of catalyst. 

It is possible to combine the resistances of internal and external mass transfer through an overall effectiveness factor, for isothermal particles and first-order reaction. Two approaches can be applied. The general idea is that the catalyst can be divided into two parts its exterior surface and its interior surface. Therefore, the global reaction rates used here are per unit surface area of catalyst. 

The coefficient k° introduces the external surface area of catalyst per unit volume of reactor au, which is more appropriate in fixed- and trickle-bed reactor analysis. 

In the determination of the specific surface area of catalysts, emphasis is placed on the determination of the catalyti-cally active surface area rather than the total surface area. 

Liquid-phase hydrogenation of 1,4 butynediol to cis-1,4-butenediol and 1,4-butanediol has been carried out on nickel catalysts supported on thirteen different supports. Some commercial nickel catalysts were used as references. Furthermore, metal loading and Ni-Cu alloying have also been studied. The results obtained indicates that catalytic activity, selectivity and metal surface area of catalysts are closely correlated to some textural and/or acid-base properties of the corresponding support. Similarly, the influence of Cu as a second metal in catalyst behaviour is also related to the nature of the support. 

Fig. 10. Activity parameters A and As as a function of alloy composition (at. % Cu). Upper curves Aw and A, are for cyclopropane at 90°C lower curves Aw and As are for propane at 320°C. A = log(a/w) A, = log(a/sw) a is conversion, s specific surface area of catalyst, iv weight of catalyst. From Beelen et al. (102).

C is the rate of reaction per unit surface area of catalyst... 

Fig. 17. Correlation of hydrocarbon conversion with lead concentration and surface area of catalyst. [From Weaver et at. (29).] (Reprinted with permission of the American Institute of Chemical Engineers.)...

Fig. 8. Surface areas of catalysts 8333-37 ( ) and their residues (O) as a function of Ni/Si02 ratio. All samples contain 1 g. Si02.

Figure 1. Effect of the time of pretreatment on surface area of catalysts. A SA-13 O SA-27 SA-59...

The specific surface area depends on both the size and shape and is distinctively high for colloidal-sized species. This is important in the catalytic processes used in many industries for which the rates of reactions occurring at the catalyst surface depend not only on the concentrations of the feed stream reactants, but also on the surface area of catalyst available. Since practical catalysts are frequently supported catalysts, some of the surface area is more important than the rest. Also, given that the supporting phase is usually porous, the size and shapes of the pores may influence the reaction rates as well. The final rate expressions for a catalytic process may contain all of these factors surface area, porosity, and permeability. 

Activity and selectivity for the HDO of 4-methyl phenol and BET surface area of catalyst samples treated under different conditions... 

Co. surface area = 300 m2/g ) with aqueous solutions of Cu, Cr, Mg, Ca, Sr, and Ba in Nitrate. All the catalysts have Cu to Si02 weight ratio of 14/86. For promoted catalyst, the Cr to Cu molar ratio was varied from 1/4 0 to 1/4, and the alkaline earth metal to Cu molar ratio was kept at 1/10. The impregnated catalysts were dried at 100 °C overnight, calcined at 450 for 3 h and then reduced in a stream of 10% H2 in Ar at 300 °C for 2 h. The copper surface areas of catalysts were determined by the N20 decomposition method described elsewhere [4-5J. The basic properties of the catalysts were determined by temperature-programmed desorption ( TPD ) of adsorbed carbon dioxide. Ethanol was used as reactant for dehydrogenation reaction which was performed in a microreactor at 300°C and 1 atm. 

Figure 3. Effect of coke on surface area of catalyst. Catalyst used Shell 244 (Co-Mo on alumina).

The thermal treatment is one of the factors which controls the properties of the final catalyst [56]. The total surface area (in the range between 100 and 300m2g l) decreases with increasing reduction temperature however, the nickel surface area (typically 20-50 m2g l) increases which is probably due to a higher degree of reduction. The best precursor with respect to a high surface area is the hydroxycarbonate. The surface areas of catalysts prepared from hydroxy-chlorides and nitrates are smaller by about a factor of two. Nickel particle sizes are in the order of 5nm for such catalysts. 

British Standard 4359 Part 1 1969. Nitrogen adsorption (BET method). Deutsche Normen DIN 66131, 1973. Bes-timmung der spezifischen Oberflache von Feststoffen durch Gasadsorption nach Brunauer, Emmett and Teller (BET). Norme Franpaise 11-612, 1975. Determination de l aire mas-sique (surface specifique) des poudres par adsorption de gaz. American National Standard, ASTM D 3663-78. Standard test method for surface area of catalysts. 

D-3363 Surface Area of Catalysts Multi-point volumetric (BET) surface area by nitrogen adsorption ... 

D-4567 Single-point Determination of the Specific Surface Area of Catalysts Using Nitrogen Adsorption by the Continuous Flow Method Single-point surface area using continuous flowing nitrogen-helium gas mixture ... 

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