API correlations

Where constants vary with molecular weight range given below  

V = Saybolt Universal Viscosity 210°F in seconds Refractive Index 20°C (68°F)  

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The API method is a generalized method that predicts mole fraction of paraffinic, naphthenic, or aromatic compounds for an olefin-Ifee hydrocarbon. The development of the equations is based on dividing the hydrocarbon into two molecular ranges heavy fractions (200 < MW < 600) and light fractions (70 < MW <200). Appendix 7 contains API correlations applicable to the FCC feed. 

R , from n-d-M correlation to determine composition, f M R/ from API correlation to determine composition. 

Cucumber fruits were studied by using the same analytical approach as they contain only five key volatiles and their concentration in cucumber tissue seems to be less variable than in tomato (see, for example. Ref. 12). Table 4 shows the El and API correlations for the five compounds each one could be attributed to a single ion mass on the API, and calibration with authentic standards allowed conversion of the ion signal into concentration units (parts per billion by volume). The amount of the Cg volatiles present in the macerated tissue was estimated by microwaving a sample of cucumber to inactivate the enzyme system that produces Cg and Cg volatile compounds. Inactivation was confirmed by APIMS analysis of the headspace above the treated samples. Microwaved samples were macerated after spiking them with known amounts of the Cg volatiles, then measuring volatile compound release in the blender apparatus. The values obtained from the spiked standards were then compared with the release traces from cucumber samples and the amounts of nonenal and nona-2,4-dienal estimated as 5 and 8mg/kg fresh tissue, respectively. These values compare well with the... 

Convert the ASTM D-1160 to a TBP curve using standard API correlations... 

This method requires the total PNA content expressed in either weight%, volume% or mole%. If this information is not available, the API correlation [42] (requiring viscosity) can provide these values. 

In our experience, the last end points of a typical 5-point TBP curve (the end point or EBP, 90% vaporization point, and 70% vaporization point), the molecular weight (measured or estimated from API correlation) and specific gravity are good candidate bulk projjerties to rninirnize against This is a basic optimization problem. We have used the SOLVER add-in in Microsoft Excel with considerable success. We note that once an optimized solution has been reached for a base feed, it is often very simple (even manually) to adjust the parameters of the statistical distribution to fit a new feed type. We report the optimal values for the fitting parameters in Table 5.10. 

We apply this method to the feed specified in Table 5.1 using the ASTM D-86 distillation, specific gravity and individual PNA composition. We convert the ASTM D-86 distillation curve to a TBP curve and estimate the molecular weight (using standard API correlations). We then optimize the parameters to match the EP, 90% and 70% of the TBP curve, molecular weight and specific gravity. We compare the calculated and measured values in Figure 5.12 and Table 5.9. 

We update API correlations of flash point and freezing point to plant operation and production. 

The integrated HCR process models also gives good estimations on liquid product qualities - density, flash point and freezing point of diesel fuel (MP HCR) and jet fuel (HP HCR) - by using updated API correlations. 

The flash curve at atmospheric pressure can be estimated using the results of the ASTM D 86 distillation by a correlation proposed by the API. For the same volume fraction distilled one has the following relation ... 

A crude-oil assay always includes a whole crude API gravity and a TBP curve. As discussed by Nelson (op. cit., pp. 89-90) and as shown in Fig. 13-85, a reasonably consistent correlation (based on more than 350 distillation curves) exists between whole crude API gravity and the TBP distillation curve at 101.3 kPa (760 torr). Exceptions not correlated by Fig. 13-85 are highly paraffinic or naphthenic crude oils. 

Because of the time and expense involved in conducting laboratoiy distillation tests of all three basic types, it has become increasingly common to use empirical correlations to estimate the other two distillation curves when either the ASTM, TBP, or EFN- curve is available. Preferred correlations given in the API Technical Data Book—Petroleum Refining (op. dt.) are based on the work of Edmister and Pollock [Chem. Eng. Prog., 44, 905 (1948)], Edmister and Okamoto [Pet. Refiner, 38(8), 117 (1959) 38(9), 271 (1959)], Maxwell Data Book on... 

API Filtration. A filter press is used to determine the wall building characteristics of mud. The press consists of a cylindrical mud chamber made of materials resistant to strongly alkaline solutions. A filler paper is placed on the bottom of the chamber just above a suitable support. The filtration area is 7.1 ( 0.1) in.-. Below the support is a drain tube for discharging the filtrate into a graduate cylinder. The entire assembly is supported by a stand so that a 100-psi pressure can be applied to the mud sample in the chamber. At the end of the 30-min filtration time volume of filtrate is reported as API filtration in milliliters. To obtain correlative results, one thickness of the proper 9-cm filter paper, Whatman No. 50, S S No. 5765, or the equivalent, must be used. 

However, physical properties such as API gravity and distillation are easy to measure. As a result, empirical correlations have been developed by the industry to determine chemical properties from tlicsv physical analyses. 

The findings from TOTAL, n-d-M, and API are summarized in Table 2-10. The comparison illustrates how sensitive the predicted feed composition is to the refractive index 20°C. For instance, using the TOTAL correlation, there is a 35% drop in the aromatic content in using RIpo) = 1.5000 instead of RI(2o> = L5105. When using these correlations, every effort should be made to obtain accurate and consistent values for the refractive index at 20°C. With the refractive... 

Cetane number is measured in a single-cylinder laboratory engine, but cetane index (Cl) is more commonly used. Cetane index is a calculated value and correlates adequately with the cetane number. Most refiners use the ASTM equation (Method D-976-80) to calculate the cetane index. The equation uses the 50% boiling point and API gravity (Example 6-1). 

By defining a property index [( jLL/p,G)02(pL/pG)], Baroczy obtained a correlation for 2lo that was independent of pressure. He also observed that his correlation could be used with the gas-phase pressure drop, (API AL)G, by noting that... 

Adverse effects of fenvalerate on survival of terrestrial arthropods were observed at 0.002 to 0.015 pg whole-body topical application, O.llkg/ha aerial application, 5.4 mg/kg in the soil, 50 mg/kg in the diet, and 1.4 g/ant mound (Table 20.4). Synthetic pyrethroids are more effective in biological systems at low temperatures. The relative sensitivity of insects when compared with mammals is attributed in part to this negative temperature coefficient. Thus, warm-blooded animals are less affected than insects and other poikilotherms (Klaassen etal. 1986). Fenvalerate, for example, showed a negative correlation between temperature and toxicity to crickets (Acheta pennsylvanicus), being up to 1.9 times more toxic at 15°C than at 32°C (Harris etal. 1981). A similar case is made for honey bees (Apis mellifera) (Mayer et al. 1987) and for many species of aquatic invertebrates and fish (Mayer 1987). 

Figure 8-14 Drag coefficient correlation. Data from API RP 521, Guide for Pressure-Relieving and Depressurizing Systems, 2d ed. (Washington, DC American Petroleum Institute, 1982).

The FIA-APCI-MS data showed improved detection limits, reproducibility and correlation of standards over the HPLC-LSD results. However, extension of the FIA-MS method to other systems yielded erroneous quantitative data, attributed to signal response discrimination through competitive ionisation effects, and as such incorporation of online HPLC separation methods was determined to be the preferred API-MS method for quantitative analyses [29]. 

Wilson, G.M., "A New Correlation of NH, CO and H2S Volatility Data from Aqueous Sour Water Systems. Final Report to API Committee on Refinery Environmental Control under EPA Grant No. R804364010, Thermochemical Institute, BYU, Provo, Utah, February 9, 1978. 

Improved In Vivo/In Vitro Correlation for Bioavailability Screening of New APIs... 

The linearity of the method is demonstrated using 3-5 concentration levels. For APIs, the correlation coefficient should be greater than 0.999. The range is derived from linearity, precision, and accuracy studies and should be established based on the intended application of the method. 

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