(FR2772896-A1)   NOVELTY - The process is for liquefying a compound (A), e.g. methane, from a mixture consisting of at least the compound (A) and one or more compounds (B), e.g. nitrogen and helium with a lower boiling point, where the compounds (B) are separated from the compound (A) by distillation. Liquefaction is performed by at least two successive expansion steps, the distillation step for separating the compounds occurring after the first expansion step and before the second expansion step.    USE - For extracting methane and/or helium during a gas liquefaction process, such as natural gas containing methane as its main constituent and nitrogen and/or helium as constituents to be extracted, or for extracting argon and/or nitrogen during an air liquefaction process (both claimed).    ADVANTAGE - Extracts unwanted compounds during the liquefaction process.    (JP11248346-A)   NOVELTY - The process is for liquefying a compound (A), e.g. methane, from a mixture consisting of at least the compound (A) and one or more compounds (B), e.g. nitrogen and helium with a lower boiling point, where the compounds (B) are separated from the compound (A) by distillation. Liquefaction is performed by at least two successive expansion steps, the distillation step for separating the compounds occurring after the first expansion step and before the second expansion step.    USE - For extracting methane and/or helium during a gas liquefaction process, such as natural gas containing methane as its main constituent and nitrogen and/or helium as constituents to be extracted, or for extracting argon and/or nitrogen during an air liquefaction process (both claimed).    ADVANTAGE - Extracts unwanted compounds during the liquefaction process.    (US6105391-A)   NOVELTY - The process is for liquefying a compound (A), e.g. methane, from a mixture consisting of at least the compound (A) and one or more compounds (B), e.g. nitrogen and helium with a lower boiling point, where the compounds (B) are separated from the compound (A) by distillation. Liquefaction is performed by at least two successive expansion steps, the distillation step for separating the compounds occurring after the first expansion step and before the second expansion step.    USE - For extracting methane and/or helium during a gas liquefaction process, such as natural gas containing methane as its main constituent and nitrogen and/or helium as constituents to be extracted, or for extracting argon and/or nitrogen during an air liquefaction process (both claimed).    ADVANTAGE - Extracts unwanted compounds during the liquefaction process.