Process for monitoring the catalytic activity of an ionic liquid and for the regeneration of the ionic liquid in continuous conversion of an olefin in an alkylation, comprising the steps of: (a) providing a halogen-aluminate ionic liquid; (b) subjecting a hydrocarbon mixture comprising at least an isoparaffin or an aromatic hydrocarbon and an olefin to a continuous alkylation reaction between the isoparaffin or the aromatic hydrocarbon and the olefin, wherein the hydrocarbon mixture is reacted with the ionic liquid of step (a) to obtain an effluent comprising at least an alkylate product and an ionic liquid phase; (c) taking a sample of the ionic liquid phase; (d) adding a portion of an organic compound to a sample of the ionic liquid phase of step (c) or adding a portion of the ionic liquid phase of step (c) to a sample of an organic compound; (e) recording an infrared spectrum of a mixture as obtained in step (d) to obtain at least one absorption peak, wherein the adsorption peak relates to a product between the organic compound and an acidic species in the ionic liquid or to the disappearance of the organic compound when adding ionic liquid to the organic compound; (f) repeating steps (d) and (e) until at least one absorption peak obtained in step (e) reaches a maximum value or a minimum value; (g) determining at the maximum value or minimum value of the absorption peak of step (f): the total amount of the organic compound added in portions to the sample of the ionic liquid phase or determining the total amount of the ionic liquid phase added in portions to the sample of organic compound; (h) calculating the catalytic activity of the ionic liquid on the basis of: the total amount of the organic compound added in portions as determined in step (g) or the total amount of ionic liquid phase added in portions as determined in step (g); and (i) adding one or more aluminium halides or a mixture of aluminium halides to the continuous alkylation reaction of step (b) when the activity of step (h) decreases to a level of activity 10% higher than the level of activity at which the conversion of the olefin in step (b) is 100%. (a) providing a halogen-aluminate ionic liquid; (b) subjecting a hydrocarbon mixture comprising at least an isoparaffin or an aromatic hydrocarbon and an olefin to a continuous alkylation reaction between the isoparaffin or the aromatic hydrocarbon and the olefin, wherein the hydrocarbon mixture is reacted with the ionic liquid of step (a) to obtain an effluent comprising at least an alkylate product and an ionic liquid phase; (c) taking a sample of the ionic liquid phase; (d) adding a portion of an organic compound to a sample of the ionic liquid phase of step (c) or adding a portion of the ionic liquid phase of step (c) to a sample of an organic compound; (e) recording an infrared spectrum of a mixture as obtained in step (d) to obtain at least one absorption peak, wherein the adsorption peak relates to a product between the organic compound and an acidic species in the ionic liquid or to the disappearance of the organic compound when adding ionic liquid to the organic compound; (f) repeating steps (d) and (e) until at least one absorption peak obtained in step (e) reaches a maximum value or a minimum value; (g) determining at the maximum value or minimum value of the absorption peak of step (f): the total amount of the organic compound added in portions to the sample of the ionic liquid phase or determining the total amount of the ionic liquid phase added in portions to the sample of organic compound; (h) calculating the catalytic activity of the ionic liquid on the basis of: the total amount of the organic compound added in portions as determined in step (g) or the total amount of ionic liquid phase added in portions as determined in step (g); and (i) adding one or more aluminium halides or a mixture of aluminium halides to the continuous alkylation reaction of step (b) when the activity of step (h) decreases to a level of activity 10% higher than the level of activity at which the conversion of the olefin in step (b) is 100%.