Patent ID: 8843324
Filing Date: 2014-09-23
Classification: G01N

Abstract:
1. An on-line real-time process to control the polymerization of one or more alpha olefin monomers having from 2 to 8 carbon atoms in a process from which physical samples of the reaction mixture cannot be obtained comprising: i) collecting on-line NIR calibration spectra of sample mixtures of solvent and monomers in a polymerization process, in the absence of reaction, at one or more locations in the polymerization process, over a range of temperature, pressures and monomer concentration representative of a broad envelope of polymerization conditions to generate a set of calibration NIR spectra; ii) pre-processing all or a portion of said calibration NIR spectra to eliminate baseline shift; iii) regressing the said pre-processed calibration NIR spectra to the monomer(s) concentration as determined by mass balance, using the mass flow of each component going through the polymerization process, in absence of reaction, over wavelengths at which the absorbance of the polymer product does not significantly impact the absorbance of the monomer(s) to obtain the independent regression coefficients for each monomer of interest; iv) validating the regression coefficients by collecting sample spectra, with the presence of polymer, without the presence of polymer, or both and subjecting the sample spectra to the same preprocessing of step ii) and applying the regression coefficients to the sample spectra at which the absorbance of the polymer product does not significantly impact the absorbance of the monomer(s) of interest and plotting the calculated concentration of the monomer of interest against the known concentration and determining the root mean square error of the calculated concentration of the monomer of interest; v) if the root mean square error of the predicted concentration of the monomer of interest is greater than 5 wt. % repeating steps ii), iii) and iv) using one or more different preprocessing methods, different regression techniques, different numbers or locations of wavelength, different pressures, temperature and concentrations of monomers of interest until the root mean square error of the predicted concentration of the one or more monomers of interest is less than 5 wt. % then; vi) during polymer production continuously or periodically obtaining NIR sample spectra of at one or more locations in the process; vii) pre-processing the said polymerization NIR sample spectra to eliminate baseline shift and applying the regression coefficients determined in step v) over wavelengths at which the absorbance of the polymer product does not significantly impact the absorbance of the monomer(s) of interest to determine the concentration of one or more monomer(s) of interests at said one or more locations; viii) calculating the monomer conversion (or degree of reaction) using a method selected from the group consisting of the monomer mass flow in the feed and the measured monomer concentration at said one or more locations; ix) comparing the value obtained from step viii) to the conversion set point in the process control algorithms; and x) as required, adjusting one or more of catalyst flow to the reactor monomer concentration; reaction temperature; catalyst activity and amount of chain transfer agent to achieve the desired conversion.