Method and apparatus for determining a property or yield of a hydrocarbon product based on NIRA of the feedstock

An apparatus for carrying out a method for determining at least one of a property of a product and a yield of a product from a process selected from the group consisting of a hydrocarbon conversion process and a hydrocarbon separation process, wherein the method comprises the following steps:

• (a) determining with an infrared spectrometer an absorbance of a feedstock to the process at a certain number of frequencies in the spectral range 16667 to 3840 cm.sup.-1, starting from a defined base line, and
• (b) determining at least one of (i) the property by applying a correlation between the property of the product and the absorbance values of the feedstock, and (ii) the yield by applying a correlation between the yield of the product and the absorbance values of the feedstock, wherein the correlation is determined experimentally by multivariate regression and dependent upon the spectrometer used, the property or yield to be determined, and the frequencies used;
• said apparatus comprises an infrared spectrometer and a computer wherein the computer is programmed to receive and utilize the absorbance from the infrared spectrometer to determine the at least one of the property and yield continuously and in real time.