Volatility amplification, supercritical fluid

An investigation was made to determine the feasibility of the combination process of volatility amplification of nonvolatile mixtures by the addition of supercritical fluids followed by contacting the vapor with molecular sieves to separate specific materials from the mixtures. Two potential advantages of this novel combination become possible. 

With supercritical fluid volatility amplification, a lower temperature can place a satisfactory concentration of the material to be separated into the vapor phase, and since the capacity of molecular sieves increases as the temperature is lowered, a more economical process may be attainable. Higher purity paraffin product may be produced without intermediate washing or purging of the molecular sieves. 

At a given temperature level of operation, supercritical fluid volatility amplification makes it possible to increase the molecular weight range of materials that can be volatilized into the vapor phase in sufficient concentrations to be separated satisfactorily by molecular sieve contacting. 

In conventional vapor phase molecular sieve operations, the operating temperature must be high and the operating pressure must be in the vacuum range in order to get the high molecular weight molecules into the vapor phase for contacting with the molecular sieves. The use of volatility amplification with supercritical fluid obviates these requirements. 

It appears that temperatures in the range of 500.to 670 K for the adsorption of n-paraffins in the 560-740 K boiling range on type 5A molecular sieves should be considered for investigating the combination supercritical fluid volatility amplification-vapor phase molecular sieve process. The pressure of operation will be governed by the critical pressures of potential solvents with critical temperatures in this range. The supercritical solvent of choice should not be adsorbable on type 5A molecular sieves and should not be expensive. 

The combination supercritical fluid volatility amplification-molecular sieve process has the potential for producing two valuable products simultaneously from gas oil-lube oil petroleum stocks. In a flow-through molecular sieve bed, the leading adsorption front operates in the lean molecular sieve loading range, providing the conditions needed for the n-paraffin removal needed to produce low pour lube oil, while the trailing adsorption... 

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