Experimental binary and ternary equilibrium data for the adsorption of hydrocarbon mixtures of methane, ethane, ethylene, and propylene on activated carbon at 20°C are presented and discussed. Reproduction of binary adsorption equilibria and prediction of ternary adsorption equilibria exclusively with data of binary systems have been carried out using a real adsorbed solution theory, which requires the calculation of the activity coefficients for the components in the adsorbed phase.Predicted equilibrium data are found to be in excellent agreement with experimental values using Wilson and UNIQUAC equations to calculate the activity coefficients. The real absorbed solution theory provides a much more accurate method for predicting multicomponent adsorption equilibria than the ideal adsorbed solution theory. SCOPEThe use of adsorption for the separation of gas mixtures has been continuously increasing. The main advantages of adsorption as compared with other separation techniques are the high selectivity that can be attained and the relatively high capacity of the adsorbents for volatile compounds, even at low partial pressures. Some applications of interest include the purification of methane, ethylene, and other light hydrocarbons; the covery of LPG from natural and refinery gas streams; the separation of olefins from cracked gases; and the recovery of acetylene and other pretrochemicals from dilute mixtures with other hydrocarbon gases.Although there are a great deal of publications on adsorption of mixtures of hydrocarbons on porous solids (Hill, 1949 On the other hand, most of the theoretical work based on the analogy between the thermodynamics of solutions and the thermodynamics of mixed adsorbates predicts adsorption equilibria using the assumption of an ideal behavior of the adsorbates on the solid surface, which can be expressed in terms of a Raoult's type law (Myers, 1965). However, predicted adsorption equilibria are not always found to be in good agreement with experimental data. Certainly, there is a competition of the adsorbed molecules for the active centers of the solid surface, due to the different adsorption capacity of the adsorbates, so that the ideal adsorbed solution theory can be improved modifying the Raoult's law by the introduction of the activity coefficients for the components in the adsorbed phase. This paper discusses new experimental data on adsorption for binary and ternary hydrocarbon mixtures on activated carbon at 20°C and a total pressure up to 760 mm Hg (101.33 K Pa). A thermodynamic method based on a real adsorbed solution theory is applied to reproduce experimental binary adsorption equilibria and to predict ternary adsorption equilibria, only with binary systems data, calculating the activity coefficients for the components in the adsorbed phase by means of Wilson and UNIQUAC equations for vapor-liquid equilibrium. CONCLUSIONS AND SIGNIFICANCEAn experimental technique based on a fluidized adsorbent bed can be used to determine adsorption equilibria of gaseous mixtures in por...

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The conversion of ethanol to hydrocarbons by use of a ZSM-5 zeolite catalyst was studied. The effects of zeolite Si/AI ratio, ethanol dilution, and process variables (temperature, space velocity, pressure, and recycle rate of gaseous products) were established. Results were justified in accordance with a carbenium ion mechanism previously suggested in the literature. This process could be described by a second-order reaction with simultaneous formation of paraffinic and aromatic hydrocarbons. The experimental data agreed with the model with a mean deviation of less than 10%. The thermochemistry of the ethanol to hydrocarbon process is considered.

The internal diffusion coefficients, Di, of pure methane, ethane and ethylene as well as some of their binary and ternary mixtures, have been calculated at 20°C for solid particles of a commercial activated carbon. It has been observed that the contribution of the surface migration mechanism to the global mass transfer process inside the adsorbent particles can be as much as 7040%. Values for the surface migration coefficient Ds have also been calculated from the relation Di = Dg + KD,, where K is a dimensionless mean slope factor. Values found for both coefficients are of the same order of magnitude as those reported in the literature for similar systems.All the values for the internal diffusion coefficients of these pure components and their mixtures fit into a single correlation curve, the characteristic kinetic curve of the adsorbent. SCOPEThe increasing importance of adsorption processes for the separation of gaseous mixtures is due to the high selectivity and adsorption capacity of solid adsorbents, the less extreme operation conditions needed, and the small energy consumption required. Adsorption is becoming a competitive operation that can advantageously substitute for other separation operations such as distillation or liquid-liquid extraction. The advantages are especially attractive when the problem is the separation of light gases such as methane, ethane, ethylene and other typical hydrocarbons of gaseous refinery streams, since their separation by distillation requires expensive high pressure units.Although there are some commercial processes for the separation of hydrocarbons using gas adsorption (Milton, 1963; Priegnitz, 1973; Yatsurugi, 1974;Broughton, 1977), the extension of this method to other cases of practical interest is generally limited by the lack of reliable fundamental data for estimating the feasibility of a given separation and for reducing the empiricism of the present design of adsorbers. Among these fundamental data, the equilibrium adsorption isotherms and the internal diffusion coefficients of individual species of the mixture should be emphasized. Although substantial attention has been paid in the literature to the adsorp tion isotherms of pure compounds and their mixtures, even to the point of predicting multicomponent adsorption equilibria (Lewis et al., 1950 shown that the adsorption rates of pure propane, n-butane, ibutane, l-butene and other light gases into molecular sieves were lower when these compounds were present in binary mixtures. Feng et al. (1973Feng et al. ( ,1974 have extensively studied the diffusion of gaseous mixtures inside the pores of solid adsorbents, using several diffusion models. Their results, which were achieved by assuming a single pore size for the adsorbent and a reasonable tortuosity factor, were erroneous for not considering surface migration. We present here new values for the internal diffusion coefficients of methane, ethane, and ethylene, both as pure components and as part of the mixtures of methane-ethylene, ethaneethylene, and methane...

SUMMARYWe present a statistical method, the extended canonical correlation analysis, to extract intermittent propagative coupled oscillations. We have applied this technique to a 136-year-long North Atlantic sea-level-pressure and sea-surface-temperature dataset. Nine ocean-atmosphere coupled oscillations with periods between 2.3 and 18 years were found. The 7.7 y period oscillation is presented in some detail and its links with the North Atlantic Oscillation are discussed.

Pure gas adsorption Isotherms of methane, ethane, ethylene, and propylene on activated carbon have been determined at 323 K and pressures In the range 0-100 kPa. Binary and ternary adsorption Isotherms were also determined at the same temperature and pressures for all the mixtures of these adsorbates, with the exception of methane-propylene mixtures due to their difference in adsorption capacity. Two models have been applied for correlation and prediction of mixture adsorption equilibria-the Ideal adsorbed solution (IAS) and the real adsorbed solution (RAS). This second model provides better results for all the systems.

The synthesis of 4A zeolite from calcined kaolins has been investigated. The process variables of the different synthesis steps have been optimized in order to produce 4A zeolite at a lower price with the established specifications for use in detergents. The recovery of the mother liquors required for the economical viability of this process has been verified. An economical evaluation of this process has been carried out with an estimated price for the zeolite of 54 peseta ($0.43)/kg.