Method for on-line prediction of conjunct polymer concentration in a hydrocarbon conversion process

A method for predicting a concentration of conjunct polymer in a spent ionic liquid of unknown conjunct polymer concentration, during a continuous hydrocarbon conversion process, the method comprising:

• (a) contacting a hydrocarbon feed with an ionic liquid in a hydrocarbon conversion reaction zone under hydrocarbon conversion conditions to form a mixture comprising reaction products and spent ionic liquid containing conjunct polymer;
• (b) acquiring an infrared spectrum for each of a plurality of samples of the mixture in (a) using an in-line infrared spectrometer configured with a measurement flow cell to allow the mixture to flow therethrough, wherein absorbance values indicative of conjunct polymer are measured in each infrared spectrum over a wavenumber range of from 800 cm−1 to 1800 cm−1;
• (c) collecting a sample from the mixture in (a) at each of a plurality of corresponding time points during the continuous hydrocarbon conversion process and separately determining off-line a concentration of conjunct polymer in the spent ionic liquid by acquiring a corresponding infrared spectrum for each sample using an off-line infrared spectrometer, wherein absorbance values indicative of conjunct polymer are measured in each infrared spectrum over a wavenumber range of from 800 cm−1 to 1800 cm−1;
• (d) analyzing the infrared spectra acquired in (b) and (c) using a multivariate chemometric technique to provide a training data set, wherein the multivariate chemometric technique comprises a partial least squares (PLS) analysis;
• (e) generating a predictive model for conjunct polymer concentration based on the training data set, wherein the predictive model is established using partial component analysis (PCA);
• (f) applying the predictive model to the infrared spectra acquired in (b);
• and thereafter
• (g) quantitatively predicting the conjunct polymer concentration in the spent ionic liquid during the continuous hydrocarbon conversion process.