Simutaneusly Determing The Multi-properties Of Residues By Attenuated Total Renectance Infrared Spectroscopy

The residue properties, including SARA (saturates, aromatics, resin, asphaltine), residual carbon, viscosity, density, elemental analysis (H, C, N, S), are very important data for residue processing. The analytical method for SARA of residue is the traditional eluting chromatography (EC) method, which is time-consuming and using poisonous solvents. Many conventional analytical methods are also used for the determination of other properties of residues. The preceding tedious methods don’t satisfy the fast analysis needed by the residue oil process control. The Infrared Spectroscopy (IR), as a new highly efficient analytical technique, was used in fuel property analysis, with advantages of better accuracy and repeatability, short time of testing and easy operation. But few literatures had been published for the application of IR technique in determination of the properties of residues. In this paper, a new analytical method for determing simultaneously the aforementioned properties by attenuated total reflection(ATR) infrared spectroscopy was proposed.Choosing the attenuated total reflectance (ATR) accessory for measuring the infrared spectroscopy of residue can overcome inconvenience of sample injection and cleaning of the commonly used middle infrared cell for residue measurement. An advantage of ATR has a constant light path length, which is useful for accuracy of spectroscopy measurement of residue. The effect of sample temperature on ATR spectroscopy also was studied. It was found that the intensity of the spectra decreases as the sample temperature increases, and there are peak shifts incurred by sample temperature variations. This suggests that the sample temperature should hold constant in order to get a better accuracy of spectral measurement. It was discovered that there is not a linear relationship between the intensity of the spectral feature peaks and the saturate and/or aromatics content of residues. It means that the SARA calibration is complicated, the maltivariate calibration method should be used.Three types of residues, including atmospheric residues, vacuum residues and hydrocracked residues, have been collected in this paper. The result of the feasibility test showed that it is impossible to predict SARA contents by using a single combination calibration model. Different models should be established for different types of residue, respectively. The first step of the analytical method establishment is the classification of the residue samples. The soft independent modeling of class analogy (SIMCA), a popular recognition pattern method, is often used in near infrared spectral analysis. The SIMCA was applied to the three types of residues. But, the validation results showed that SIMCA method couldn’t classify the three types of residues successfully. This paper found that using partial least squares (PLS) projection discrimination method could succeed to distinguish the three types of residues. The established model’s estimate rate and identification rate for the three types of residues all reach to100%.The PLS1algrithm was chosen to correlate the infrared spectral data with the residue’s properties, making one model for one property. For SARA of one type of residues, four calibration models were established. For SARA of three types of residues, twelve calibration models were established. Other seven calibration models were established for the viscosity, density, carbon residue, element of (C, H, S, N) of the hydrocracked residues. Their SECs and SEPs are listed in table1. For the SARA contents of the three types of residues, and the carbon residue, element of (H, S, N) of the hydrocracked residues, the standard deviations between the results by IR method and that by standard methods are not greater than the uncertainties of standard methods correspondingly. The results of paired t tests showed that the result of IR method and that of standard method were coincident. But for the viscosity, density and C content of hydrocracking residue, the residual between the results of the IR method and the conventional methods are morelarge, it should be investigated continuously later.In comparison with the traditional testing methods, the new method by IR has more advantages in terms of rapid, good repeatability, simple operation, no poisonous solvent needed and no waste disposal problem. The IR analytical method could be used as an alternative for analyzing the SARA contents of three types of residues and carbon residue, element of (H, S, N) in hydrocracked residues.