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US 9,051,536 B2Granted
Process for the hydrogenation of hop resin acids
AssigneeS.S. Steiner, Inc.
InventorsRichard J. H. Wilson, Robert J. Smith
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AssigneeS.S. Steiner, Inc.
InventorsRichard J. H. Wilson, Robert J. Smith
Estimating the term…
A process for the direct hydrogenation of hop resin acids in the absence of a liquid, organic solvent by reacting the hop resin acids with hydrogen in the presence of a noble metal catalyst at a temperature at which the resin acids are sufficiently fluid to allow easy mixing with the catalyst and suitably facilitate the hydrogenation reaction. Alternatively, the necessary fluidity may be achieved at relatively low temperature by subjecting the reactants to a high pressure of CO2 gas such that the quantity of this gas that dissolves into the resin is sufficient to substantially reduce its viscosity, the pressure of the CO2 gas being either less than the liquefaction pressure at temperatures below the critical temperature or less than that which would cause the density to exceed that at the critical point for temperatures above the critical temperature. A further variant allows for the hydrogenation of the resin acids as a suspension in water and is considered most appropriate for the processing of resins that are of relatively more viscous nature in circumstances where the application of a high pressure of gas may not be possible for mechanical reasons. Particularly useful applications for the process are the conversion of iso-α-acids to tetrahydroiso-α-acids and rho-iso-α-acids into hexahydroiso-α-acids. The resinous products of the hydrogenation process may be readily converted to aqueous, alkaline solutions suitable for use in brewing beer. The process may also be worked in a continuous manner, wherein hop resin acids in suitably fluid state and under high pressure are contacted with hydrogen gas and the resultant mixture passed over a bed of noble metal catalyst particles. The necessary fluidity is achieved either by heating the hop resin acid or by dissolving CO2 gas into it or a combination of both. The resinous product of the hydrogenation reaction is collected by depressurization of the fluid exiting the catalyst bed, conveniently causing release of any excess dissolved gas.
A process for the direct hydrogenation of hop resin acids which comprises contacting an undiluted, solvent-free mixture of isomerized hop resin acids, in their naturally acid state, with hydrogen gas in the presence of a noble metal catalyst, wherein the hydrogenation proceeds by contacting said reaction mixture of hop resin acids with hydrogen gas in the presence of a noble metal catalyst under partial pressure of carbon dioxide (CO2), the pressure of said CO2 gas being (a) sufficient to fluidise said reaction mixture, and (b) below that at which the said CO2 gas will liquefy at below the critical temperature for CO2, or at pressure less than that at which the density of the CO2 gas exceeds its value at the critical point if the temperature is at or above the said critical temperature.
A continuous process for the hydrogenation of hop resin acids, comprising the steps of supplying hydrogen to an undiluted, solvent-free fluidized mixture of isomerized hop resin acids, under high pressure in at least a stoichiometric amount sufficient for completion of the desired reaction;
Dependencies are inferred from the claim text.