A screening test was devised to rapidly evaluate catalysts for hydroprocessing residua in which demetalation and desulfurization are carried out as a batch reaction. This test was used to evaluate the performance of fresh water manganese nodules and cobalt-molybdenum on a wide pore alumina as catalysts for demetalizing and desulfurizing residua. The effects of temperature, hydrogen pressure, and reaction time were explored and the results indicate that, up to about 83% metals and sulfur removal, demetalation and desulfurization reactions are best described by second-order kinetics. Above 83% metals and sulfur removal the data can be described by a first-order rate equation. The reaction rate was dependent on particle size from 8 to 150 mesh manganese nodules. Second-order demetalation rate constants obtained with the cobalt-molybdenum on alumina catalyst were about 2.5 times greater than those measured using fresh water manganese nodules at 2000 psig of H2 and were about the same at 1000 and 500 psig of H2.
Zeolites normally provide a number of distinct intracrystalline environments for cations. These cations then have different exchange properties for each such environment. The standard free energy, enthalpy, entropy and equilibrium constant for exchange in the whole crystal have been related to those of cations in the several environments. Three possible limiting cases of partial ion exchange can be visualised : (1) a pseudo-equilibrium is rapidly attained but a further slow exchange takes place over still longer times ; (2) true equilibrium is reached rapidly, but exchange for certain entering ions never proceeds beyond a temperature independent limit ; (3) true equilbrium is rapidly attained but exchange for certain entering ions never proceeds beyond a limit which in this case is reversibly dependent on temperature. A thermodynamic treatment of case 1 is not possible. For cases 2 and 3 a simple extension of the thremodynamic treatment for complete exchange is fully adequate.In some crystalline zeolites and for certain entering ions, B, the exchange reactions reach a limit before all the A ions initially present are replaced. Thus it is not always possible to produce the homoionic B-zeolite. The treatment of Gaines and Thomas has therefore been so as to allow for this behaviour. A normalised Kielland selectivity quotient KF is expressed in terms of the equivalent cation fractions, NB and NA = (1 -ATB), of the exchangeable cations only. The essential step in obtaining the thermodynamic equilibrium constant then involves evaluating J: In KF dNB.Recently however, a different procedure has been suggested in which the unnormalised selectivity quotient, K,, is expressed in terms of the equivalent cation fractions N i and Nh for the whole crystal. To evaluate what the authorsclaim to be the thermodynamic equilibrium constant the essential step is, as will be shown later, to evaluate
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