ie990262d

CORRELATIONS

Estimation of Sulfur Content of Petroleum Products and Crude Oils

Mohammad R. Riazi,* Nasrin Nasimi, and Yousef A. Roomi

Chemical Engineering Department, Kuwait University, P.O. Box 5969, Safat 13060, Kuwait

In this paper simple estimation methods are presented to predict sulfur weight percentage inpetroleum fractions and crude oils. Input data needed to use this method are molecular weight,refractive index, and specific gravity (SG). In cases in which molecular weight and refractiveindex are not available they can be estimated from the boiling point and SG of the fractionusing appropriate methods. For crude oils, the C7+ part of the crude mixture was split into severalpseudocompounds using the two-parameter distribution model proposed by Riazi (Ind. Eng.Chem. Res. 1997, 36, 4299-4307), and then for each fraction sulfur content was determined.The sulfur content of crude was then determined from its carbon number distribution (or boilingpoint distribution) and the estimated sulfur content of each pseudocompound. For 132 differentfuels and petroleum products with molecular weight ranging from 75 to 1500 and sulfur contentsup to 6%, an average deviation of about 0.15% was obtained to estimate sulfur weight percentagefrom the proposed method. For seven crude oils with sulfur contents up to 2.4%, the proposedmethods gave an average deviation of 0.31%.

Introduction

Sulfur in various fuels and petroleum products pro-mote corrosion of engine parts and contribute to theformation of engine deposits. A high content of sulfurcompounds in lubricating oil lower resistance to oxida-tion and increase the deposition of solids. Knowledgeof the amount of sulfur present in a fuel is importantin appropriate design and operation of burners andrelated equipment. In refineries, knowledge of sulfurcontent of crude oil and its products is important indesign and operation of various units.

As discussed in detail by Speight,2 most sulfurcompounds in a petroleum mixture are in asphaltenesand heavy aromatics. Heavy fractions [low API or highspecific gravity (SG)] contain more sulfur than lightfractions. In addition, fractions that have higher amountsof asphaltene and resin contain more sulfur compounds.Van Nes and van Westen3 have shown that sulfurweight percentage in a petroleum fraction is related tothe percentage of carbon in naphthenic compounds ofthe fraction. Riazi and Daubert4,5 developed methodsfor prediction of composition and molecular type analy-sis of petroleum fractions in terms of molecular weight,refractive index, density, and viscosity. These methodswere also included in the American Petroleum Institute(API) Technical Data Book.6 One parameter that wellcharacterizes different types of hydrocarbon compoundsis the refractivity intercept (RI), defined as:4

where n is the refractive index at 20 C and d is theliquid density at 20 C and 1 atm. Highly aromatic

fractions have higher RI values, and those fractions richin paraffins have lower RI values. For pure hydrocar-bons RI varies from 1.03 to 1.07. Another usefulcharacterization parameter is parameter m defined as5

where M is the molecular weight. For pure compoundsm varies from -10 to 45. Aromatics have positive valuesof m and paraffins have negative m values. In addition,values of m for benzenes and monoaromatics are muchlower than values of m for condensed multicyclicaromatics as shown in Table 1. Other characterizationparameters for description of molecular types of petro-leum fractions as examined by Riazi and Daubert5 arecarbon-to-hydrogen weight ratio (CH), SG, and viscositygravity constant (VGC). These parameters are the basisfor development of a method to estimate sulfur contentof a fraction.

Characterization techniques for crude oils and reser-voir fluids have been discussed in details by Riazi.1,7 Inthis method a simple distribution model is used toestimate property distributions in crude oils and thenthe C7+ portion of the crude is split into several (usuallythree or five) pseudocompounds by using the distribu-tion model and carbon number range chosen for eachpseudocompound. The minimum information needed forthis technique are molecular weight and SG of the

* To whom all correspondence should be addressed. Fax:(+965) 4839498; tel: (+965) 4817662; e-mail: [email protected].

RI ) n - d/2 (1)

m ) M(n - 1.475) (2)

Table 1. Values of Parameter m for Different Types ofHydrocarbons

hydrocarbon type m

paraffins -8.79cyclopentanes -5.41cyclohexanes -4.43benzenes 2.64naphthenes 19.5condensed tricyclics 43.6

4507Ind. Eng. Chem. Res. 1999, 38, 4507-4512

10.1021/ie990262d CCC: $18.00 1999 American Chemical SocietyPublished on Web 10/08/1999

heptane-plus fraction of the crude. However, if trueboiling point for a crude is known, more accuratepseudocomponents can be obtained from the distributionmodel. We use this technique in this work for develop-ment of a method for estimation of sulfur content ofcrude oils and reservoir fluids. The main objective ofthis work is to propose a method for accurate estimationof the amount of sulfur in a crude oil or variouspetroleum products and fuels using easily measurableor readily available properties. To the best of ourknowledge such methods do not currently exist in theliterature.

Technical Development

As discussed earlier, parameters RI, m, SG, CH, andVGC have the ability to describe molecular type analysisof petroleum fractions. Overall, 132 petroleum fractionswith information on the amount of sulfur as well assome general properties such as SG, viscosity at one ortwo temperatures, and boiling point have been collectedusing private and open literature sources. Upon exten-sive analysis of data we found that parameters RI, m,and SG best describe sulfur composition of petroleumfractions, and the following equations were obtainedfrom the data bank.

For fractions with M < 250

For fractions with M > 200

where RI and m are defined by eqs 1 and 2. For fractionswith molecular weights between 200 and 250 both eqs3 and 4 may be used. In this range of molecular weight,the difference between accuracies of these two equationsis within the accuracy of these equations. For lightfractions in which eq 3 may give very small negativevalues, S% would be considered as zero. General infor-mation for the fractions used to develop eqs 3 and 4 aregiven in Table 2. Sulfur weight percentage in thefractions varies from 0.01 to 6.2%. Equation 3 canestimate S% with an average deviation of 0.09%,whereas eq 4 predicts S% with average deviation of0.24%. Overall average error for all 132 fractions is0.15%. Values of R2 for these equations were 0.95. Assulfur generally is present more in heavier fractions,eq 4 is more important than eq 3. For example, for thefractions used in this work, sulfur content of fractionswith molecular weight less than 200 was usually lessthan 1%. A detailed evaluation of eq 4 with completeinformation on various fractions used to evaluate eq 4are given in Table 3. Generally for heavy fractions, dataon API gravity (or SG), sulfur content, and viscositywere available from the literature. Other propertieswere estimated through appropriate correlations.

In using the proposed method the only input dataneeded are molecular weight, refractive index at 20 C,liquid density at 20 C, and SG at 15.5 C (or APIgravity). In cases in which these data are not availablethey can be predicted from appropriate correlations. Forexample, molecular weight of heavy fractions can beestimated from viscosity at two temperatures as pro-posed by Riazi and Daubert.8 If boiling point and SGare known, then methods given by Riazi Daubert9,10 thatare also included in the API Technical Data Book6 canbe used to estimate parameters M, n, and d needed tocalculate RI and m from eqs 1 and 2.

For heavy fractions, usually SG and one viscosity data(either at 100 or at 210 F) are known. The followingequations proposed by Riazi and Daubert8 which arealso recommended by the API, were used to estimateviscosity at other temperatures and molecular weights:

in which 100 and 210 are kinematic viscosities at 100and 210 F (37.8 and 98.9 C), respectively. Equation 5can be used to estimate 100 if 210 and SG are knownand it has accuracy of 1.5%. Then eq 6 can be used toestimate molecular weight M. Equation 6 can estimatemolecular weight of petroleum fractions with an averagedeviation of 2.7% for 158 fractions. Having M and SG,the following equation given by Riazi and Daubert10 canbe used to estimate average boiling point (Tb):

where Tb is in K. Accuracy of eq 7 is 1%. Once Tb andSG are known for any fraction the following equationsproposed by Riazi and Daubert9 may be used to estimatedensity (d) and refractive index (n) at 20 C.

where Tb is in K, d is liquid density at 20 C in g/cm3,and n can be calculated from the following equation.

Average errors for eqs 8 and 9 are 0.03% and 0.5%,respectively. For light fractions in which Tb is knownfrom distillation data, M can be estimated from thefollowing equation given by Riazi and Daubert.9

where Tb is in K. Accuracy of this equation is about2.5%. However, for fractions with molecular weightsgreater than 300, the following equations may be usedto estimate I and M as recommended by Riazi andDaubert.10

Table 2. Prediction of Sulfur Content of PetroleumFractions

errorafractiontype

no. ofpoints

mol. wt.range

sp. gr.range

sulfur wt %range AAD% MAD%

light 76 76-247 0.57-0.86 0.01-1.6 0.09 0.7heavy 56 230-1500 0.80-1.05 0.07-6.2 0.24 1.6overall 132 76-1500 0.57-1.05 0.01-6.2 0.15 1.6

a AAD% ) abs. average deviation %. MAD% ) max. averagedeviation %.

S% ) 177.4482 - 170.9463RI + 0.2258m +4.054SG (3)

S% ) -58.02 + 38.4628RI - 0.0229m + 22.4SG (4)

SG ) 0.7717 [1000.1157][1000.1157] (5)M ) 223.56

[100(-1.245+1.1228SG)][210

(3.4758-3.038SG)][SG-0.6665] (6)

Tb ) 3.76587 exp(3.7741 10-4M + 2.98404SG -4.252 10-3MSG)M0.40167SG-1.58262 (7)

d ) 0.98372Tb0.00202SG1.0055 (8)

I ) 0.3773Tb-0.02269SG0.9182 (9)

n ) (1 + 2I1 - I )1/2

(10)

M ) 1.6607 10-4Tb2.1962SG-1.0164 (11)

I ) 1.8429 10-2 exp(1.16352 10-3Tb +5.1445G - 5.9202 10-4TbSG)Tb-0.407SG-3.333 (12)

4508 Ind. Eng. Chem. Res., Vol. 38, No. 11, 1999

where Tb is in K and SG is the specific gravity at 60 F(15.5 C). Equations 12 and 13 give average errors ofabout 0.5% and 2%, respectively.

To further evaluate the proposed method, four differ-ent petroleum products (naphtha, kerosene, diesel oil,

and gas oil) were obtained from Shuaiba Refinery ofKuwait National Petroleum Company (KNPC). Mea-sured values of boiling point, SG, refractive index, andsulfur content as well as estimated properties neededfor eqs 3 and 4 and predicted sulfur content are all givenin Table 4. These data were not used in development ofeqs 3 and 4, yet estimated sulfur contents are very closeto measured values. These equations can be also evalu-

Table 3. Evaluation of Eq 4 for Estimation of Sulfur Content of Heavy Fractions with Estimated Properties

no. fraction SGa 210Fa (cst) Tb, K M d20 n20 RI m S%, exp S%, pred abs. dev. %

1 Kuwait crude cut # 1 0.8370 - 543a 202 0.8331 1.4676 1.0511 -1.4849 1.03 1.19 0.162 Kuwait crude cut # 2 0.8425 - 553a 209 0.8386 1.4707 1.0514 -0.9012 1.21 1.31 0.103 Kuwait crude cut # 3 0.8477 - 563a 216 0.8438 1.4735 1.0516 -0.3133 1.37 1.42 0.054 Kuwait crude cut # 4 0.8528 - 573a 223 0.8490 1.4764 1.0519 0.3165 1.50 1.54 0.045 Kuwait crude cut # 5 0.8577 - 583a 230 0.8539 1.4791 1.0522 0.9479 1.60 1.64 0.046 Kuwait crude cut # 6 0.8624 - 593a 238 0.8586 1.4817 1.0524 1.5925 1.67 1.74 0.077 Kuwait crude cut # 7 0.8712 - 613a 253 0.8675 1.4866 1.0528 2.930 1.86 1.92 0.068 Kuwait crude cut # 8 0.8753 - 623a 261 0.8716 1.4888 1.0530 3.606 2.05 2.05 0.09 vacuum gas oil crude

assay 940.9189 - 662a 337 0.9154 1.5028 1.0451 9.375 2.81 2.55 0.26

10 vacuum gas oil crudeassay 91

0.9240 - 676a 360 0.9206 1.5068 1.0465 11.4436 2.70 2.67 0.03

11 atmospheric residue crudeassay 94

0.9710 50.9 748 573 0.9679 1.5516 1.0677 43.8892 4.20 3.79 0.41


0.9800 81.8 752 628 0.9769 1.5629 1.0745 55.2273 4.20 3.99 0.21


0.9760 68.2 752 609 0.9729 1.5580 1.0716 50.5717 4.20 3.90 0.30

14 kerosene 31 API # 1 0.7772 0.95 (100) 585 246 0.7734 1.4326 1.0459 -10.4499 0.07 0.0 0.0715 kerosene 31 API # 2 0.8001 1.43 (100) 574 237 0.7962 1.4448 1.0467 -7.1641 0.30 0.33 0.0316 kerosene 31 API # 3 0.8066 1.63 (100) 573 236 0.8027 1.4483 1.0469 -6.3171 0.36 0.46 0.1017 kerosene 31 API # 4 0.8110 1.79 (100) 573 237 0.8072 1.4507 1.0471 -5.7596 0.41 0.55 0.1418 gasoline 31 API # 1 0.8316 2.71 (100) 572 236 0.8278 1.4619 1.0481 -3.0794 0.93 0.99 0.0619 gasoline 31 API # 2 0.8551 4.79 (100) 583 244 0.8513 1.4747 1.0491 -0.0706 1.54 1.49 0.0520 vacuum gas oil 31 API # 1 0.9065 25.4 (100) 651 321 0.9030 1.4947 1.0432 6.3146 2.56 2.26 0.321 vacuum gas oil 31 API # 2 0.9367 13.04 713 429 0.9334 1.5177 1.0510 18.3263 3.10 2.97 0.1322 vacuum gas oil 31 API # 3 0.9189 49.4 (100) 677 359 0.9155 1.5034 1.0456 10.1811 2.81 2.55 0.2623 residue 31 API # 1 1.0025 324 740 793 0.9994 1.5970 1.0973 96.8158 4.80 4.42 0.3824 residue 31 API # 2 1.0285 2134 681 1006 1.0253 1.6483 1.1356 174.2679 5.20 4.70 0.5025 marine diesel oil T-093-96 0.8217 2.306 (100) 576 239 0.8179 1.4564 1.0474 -4.4575 0.69 0.77 0.0926 marine diesel oil T-075-96 0.8232 2.361 (100) 576 239 0.8194 1.4572 1.0475 -4.2444 0.75 0.81 0.0527 diesel oil T-106-96 0.8114 1.898 (100) 578 241 0.8076 1.4507 1.0470 -5.8533 0.54 0.56 0.0228 diesel oil T-097-96 0.8104 1.849 (100) 578 241 0.8066 1.4502 1.0469 -5.9681 0.52 0.54 0.0229 marine diesel oil (avg.) 0.8222 2.32 (100) 576 239 0.8184 1.4567 1.0475 -5.9681 0.73 0.79 0.0530 D-1 diesel oil (avg.) 0.8118 1.913 (100) 578 241 0.8080 1.4510 1.0470 -4.3821 0.55 0.57 0.0231 petroleum cut # 1 0.7930 1.49 (100) 576 257 0.7887 1.4406 1.0462 -5.7997 0.20 0.19 0.0132 petroleum cut # 2 0.8010 2.00 (100) 578 269 0.7968 1.4444 1.0460 -8.8412 0.41 0.34 0.0733 petroleum cut # 3 0.8440 2.90 (100) 447 221 0.8400 1.4694 1.0494 -1.2398 1.16 1.28 0.1234 petroleum cut # 4 0.8460 3.70 (100) 475 238 0.8420 1.4699 1.0489 -1.2173 1.35 1.30 0.0535 petroleum cut # 5 0.8500 4.80 (100) 508 253 0.8461 1.4714 1.0484 -0.9005 1.50 1.36 0.1436 deasphalting unit feed 1.0030 345 525 804 0.9999 1.5982 1.0983 99.0491 4.05 4.42 0.3737 deasphalting unit DAO C4 0.9590 631 548 658 0.9559 1.5431 1.0652 44.8482 3.30 3.40 0.1038 deasphalting unit DAO C5 0.9740 105 772 704 0.9709 1.5599 1.0744 59.7173 3.65 3.75 0.1039 deasphalting unit feed

lube oil1.0246 1565 693 972 1.0214 1.6396 1.1289 160.0637 4.9 4.68 0.22

40 deasphalting unit DAO(lube oil)

0.9321 35.4 804 633 0.9291 1.5181 1.0536 27.3183 2.7 2.76 0.06

41 F. C. C. heavy gas oil M. C. 0.9529 12 688 390 0.9495 1.5286 1.0539 20.9175 3.1 3.38 0.2842 hydroc. VGO 0.9242 - 683 370b 0.9208 1.5072 1.0468 11.9166 2.5 2.67 0.1743 hydroc. Feed VGO 0.9250 9 697 393 0.9216 1.5083 1.0475 13.0997 3 2.69 0.3144 FCC H. G.O cut M. C. 0.9529 12 688 390 0.9495 1.5286 1.0539 20.9175 3.1 3.38 0.2845 Deasphalting unit feed 1.0030 345 739 804 0.9999 1.5982 1.0983 99.0491 4.05 4.42 0.3746 DAO C4 0.9590 63 781 658 0.9559 1.5431 1.0652 44.8482 3.3 3.40 0.1047 DAO C5 0.9740 105 772 704 0.9709 1.5599 1.0744 59.7173 3.65 3.75 0.1048 D. A. feed lube oil 1.0246 1565 693 972 1.0214 1.6396 1.1289 160.0637 4.9 4.68 0.2249 D. A. feed crack stock 1.0254 1870 687 1006 1.0222 1.6433 1.1322 169.3553 3 4.61 1.6150 DAO L.O 0.9321 35.4 804 633 0.9291 1.5181 1.0536 27.3183 2.7 2.76 0.0651 Kuwait vacuum 1.0328 1900 682 939 1.0297 1.6498 1.1349 164.1416 5.45 5.00 0.4552 Buzurgan 1.0513 3355 661 881 1.0481 1.6737 1.1497 175.1727 6.2 5.73 0.4753 Cambimas vacuum 1.0231 7800 622 1439 1.0198 1.6711 1.1613 282.1741 3.26 3.09 0.1754 Arabian light atmosphere 0.9541 27 740 510 0.9510 1.5341 1.0586 30.1384 3 3.38 0.3855 Saudi Arabia vacuum 1.0366 2700 670 977 1.0334 1.6590 1.1423 179.7868 5.2 5.01 0.1956 Boscan 0.9979 20000 (100) 746 762 0.9948 1.5895 1.0921 87.2318 5.6 4.34 1.2657 tar sand triangle 0.9923 7000 (100) 743 649 0.9892 1.5770 1.0824 66.2079 4.38 4.32 0.0658 Athambasaca 1.0298 110 697 509 1.0267 1.6088 1.0954 68.0595 4.9 5.62 0.7259 Cold Lake 1.0000 79.0 722 553 0.9969 1.5796 1.0812 57.8722 4.4 4.64 0.2460 Jobo 1.0100 515.4 728 844 1.0069 1.6098 1.1063 113.7255 3.9 4.55 0.6561 TIA Juan vacuum 1.0209 7959 620 1484 1.0175 1.6699 1.1611 289.2786 2.6 2.87 0.27

a Properties are measured values (such as SG, , and some values of Tb). Viscosity data (210) are given at 210 F (98.9 C); for kinematicviscosity data at 100 F (37.8 C), values of temperature (100 F) are specified in the parentheses. b For this fraction the aniline point was180 F. Using API method,6 M was estimated from aniline point and SG. References: Fractions 1-24, private communication, industrialsource, Kuwait;13 fractions 25-30, private communication, industrial source, Saudi Arabia;14 fractions 31-35, Jones;15 fractions 36-43,Refining Handbook;16 fractions 44-50, Refining Processes;17 fractions 51-61, Speight.2

M ) 42.965[exp(2.097 10-4Tb - 7.78712SG +2.0848 10-3TbSG)]Tb1.26007SG4.98308 (13)

Ind. Eng. Chem. Res., Vol. 38, No. 11, 1999 4509

ated indirectly through estimation of sulfur contents ofcrude oils as outlined below.

Estimation of Sulfur Content of Crude Oils. Dataanalyzed by Gary and Handwerk11 and Speight2 onsulfur content of crude oils indicate that the amount ofsulfur in various distillates from a crude increases withincrease in carbon number (or molecular weight orboiling point). Analysis of crude by gas chromatographygives weight fractions of pure hydrocarbons up ton-pentane, hexanes (C6 fraction), and heptane-plusfraction (C7+). The C7+ portion of the crude can bepresented by a distribution model proposed by Riazi,7and then using a technique proposed by Riazi,1 it canbe presented by a number of defined pseudocompounds.The distribution model is presented by the probabilitydensity function F(P*) given as:

where P* is defined by:

in which P is a property such as M, Tb, SG, or I.Parameters A, B, and Po can be determined fromproperties of C7+ as described by Riazi.7 Once theseparameters are known, the gaussian quadrature tech-nique can be used to estimate weight percentage,molecular weight, boiling point, and SG of variouspseudocomponents. Using boiling point and SG, refrac-tive index and density at 20 C can be estimated frommethods previously discussed. After calculation of RIand m from eqs 1 and 2 for each pseudocomponent, eqs3 and 4 can be used to estimate sulfur content of eachpseudocomponent. Sulfur content of the whole crudethen is calculated from the following equation:

in which Xwi is the weight fraction of pseudocomponenti in the crude. The method can be best explained by anexample with Kuwaiti crude for export. The crude hasAPI gravity of 31 and sulfur content of 2.4%. The C7+portion of the crude has 93.9 wt % with molecularweight of 266.6 and specific gravity of 0.891. The C7+fraction was split into five pseudocomponents withknown molecular weight, boiling point, and SG accord-ing to the method outlined by Riazi.1 The refractiveindex and density for each pseudocomponent werecalculated by correlations of Riazi and Daubert9 givenby eqs 8 and 9 (or 12).

Parameters RI and m were calculated through eqs 1and 2 and then sulfur content of each pseudocomponentwas determined using eqs 3 and 4. Sulfur content of thewhole crude was then calculated from eq 16. Details of

calculations are given in Table 5. Estimated sulfurweight percentage for the crude is 2.1%, which differsby 0.3% from the experimental value. As can be seenfrom Table 5, sulfur content of C6 fraction is very lowand sulfur compounds are mainly in the C7+ part of thecrude. For pure hydrocarbons up to C5, no sulfurcompound is present. Therefore, if only information onC7+ part of a crude is available, its sulfur content canbe estimated through the proposed method.

In many cases analysis of a crude is given by boilingpoint and SG of various cuts. Such data for Kuwaiticrude for export are given in Table 6. Actually this isthe same crude that was presented in Table 5. Usuallyin boiling point distribution of crudes or heavy fractions,boiling point of the residue is not known. This boilingpoint can be determined through the distribution modelpresented by eq 14. On the basis of data available forboiling point versus cumulative weight fraction, param-eters A, B, and To (for Po) in eq 14 were determined asA ) 1.989, B ) 1.5, and To ) 333 K. Then the averageboiling point is calculated by the following equation asgiven by Riazi:7

where both To and Tavg are in K. This equation givesan average boiling point of 696 C. Knowing the averageboiling point of whole crude and boiling points of variouscuts with their weight percentage, one can determinethe boiling point of the residue. For the crude in Table6, the boiling point of residue was determined to be628.5 C.

Having boiling point and SG of different cuts, variousproperties and sulfur content of each cut can be esti-mated as discussed earlier. Sulfur content of the wholecrude is calculated from eq 16. As shown in Table 6,estimated sulfur content of crude is within 0.02% ofmeasured value. This method is more accurate than themethod shown in Table 5, because more detailed data

Table 4. Estimation of Sulfur Content of Four Kuwaiti Petroleum Productsa

petroleumproduct Tb,a K SGa n2Oa M n2O pred. dZO RI m Sa %, exp S%, pred. abs. dev. %

naphtha 373 0.715 1.405 104 1.400 0.710 1.045 -7.801 0.001 0 0kerosene 468 0.791 1.441 154.4 1.442 0.787 1.049 -5.086 0.001 0.17 0.17diesel oil 583 0.860 1.480 229.8 1.480 0.856 1.052 1.264 1.3 1.3 0gas oil 707 0.928 1.526 324.8 1.510 0.925 1.048 11.307 2.4 2.8 0.4a Values have been measured in laboratory. These data were not used in development of eqs 3 and 4. Samples were obtained from

Kuwait National Petroleum Company, Shuaiba Refinery.

F(P*) ) B2

AP*B-1 exp(- BAP*B) (14)

P* )P - Po

Po(15)

sulfur wt % of crude ) i

Xwi (sulfur wt %)i (16)

Table 5. Prediction of Sulfur Content of Kuwaiti Crudefor Exporta

cut wt % mol. wt. sp. gr. Tb, Cpredicted

sulfur wt. %

C2 0.03 30.1 0.0C3 0.39 44.1 0.0iC4 0.62 58.1 0.0nC4 1.08 58.1 0.0iC5 0.77 72.2 0.0nC5 1.31 72.2 0.0C6 1.93 82 0.690 64 0.2C7+(1) 9.1 112.0 0.753 123 0.1C7+(2) 15.2 169.1 0.810 216 0.7C7+(3) 26.4 267.1 0.864 333 1.9C7+(4) 18.5 405.8 0.904 438 2.9C7+(5) 24.8 660.9 0.943 527 3.8total 100 2.1

a Measured C7+ properties: mol. wt. ) 266.6, sp. gr. ) 0.891,wt % in the crude ) 93.9.

Tavg ) To(1 + 0.689AT2/3) (17)


were available for the crude. A graphical presentationof estimated and experimental sulfur distribution versusboiling point for the crude of Table 6 is shown in Figure1. In cases in which only boiling point for various cutsof crudes are known, SG of each cut can be calculatedusing the relations given by Riazi and Al-Sahhaf.12

For each cut, M can be estimated from eq 18 usingthe given boiling point, and SG can be estimated fromeq 19. Therefore, for each cut Tb and SG are known.

Using this technique, sulfur contents of seven differ-ent Kuwaiti crudes were estimated. Experimental datafor these crudes were received from a local industrialsource,13 and summary of estimated and experimentaldata are given in Table 7. As shown in this table,estimated values are within 0.3% of experimentalvalues.

Conclusions

In this work a method is presented to estimate sulfurweight percentage of various petroleum fractions andproducts using molecular weight, refractive index, anddensity as input parameters. Minimum informationneeded for a fraction is its SG and boiling point orviscosity. A method is also outlined to estimate sulfurcontent of crude oils. The only information needed forthe crude is its distillation data or weight percentageof C7+ fraction with molecular weight and SG at 15.5C.

Acknowledgment

This paper was presented at the Division of PetroleumChemistry of the American Chemical Society (ACS)Annual Meeting, Boston, August 23-27, 1998. Theauthors are grateful to KNPC for providing data andthe petroleum samples.

Nomenclature

d ) liquid density of fraction at 20 C and 1 atm, g/cm3I ) refractive index parameterM ) molecular weight of the fractionm ) parameter defined by eq 2n ) refractive index of fraction at 20 C and 1 atmP ) parameter such as M, Tb, or SG

Table 6. Boiling Point Distribution and Sulfur Contentof Kuwaiti Crude for Export

Tb,C

mass%

wt% SG

S%,exp

S%,pred

abs.dev.

(S%) wt %

20.00 1.70 1.70 0.57 0.006 0.000 0.006 0.0025.00 1.96 0.26 0.58 0.006 0.000 0.006 0.0030.00 2.25 0.29 0.60 0.006 0.000 0.006 0.0035.00 2.56 0.31 0.61 0.006 0.000 0.006 0.0040.00 2.89 0.33 0.62 0.006 0.000 0.006 0.0045.00 3.26 0.37 0.63 0.007 0.000 0.007 0.0050.00 3.64 0.38 0.64 0.007 0.000 0.007 0.0055.00 4.06 0.42 0.65 0.007 0.002 0.005 0.0060.00 4.50 0.44 0.66 0.007 0.008 0.001 0.0065.00 4.97 0.47 0.67 0.008 0.013 0.005 0.0070.00 5.46 0.49 0.68 0.008 0.017 0.009 0.0075.00 5.98 0.52 0.69 0.008 0.021 0.013 0.0080.00 6.53 0.55 0.70 0.008 0.025 0.017 0.0085.00 7.11 0.58 0.70 0.008 0.028 0.020 0.0090.00 7.71 0.60 0.71 0.009 0.032 0.023 0.0095.00 8.34 0.63 0.71 0.009 0.036 0.027 0.00

100.00 9.00 0.66 0.72 0.009 0.040 0.031 0.00105.00 9.40 0.40 0.72 0.01 0.015 0.035 0.00110.00 9.92 0.52 0.73 0.011 0.050 0.039 0.00115.00 10.51 0.59 0.73 0.016 0.055 0.039 0.00120.00 11.17 0.66 0.74 0.019 0.062 0.043 0.00125.00 11.88 0.71 0.74 0.022 0.068 0.046 0.00130.00 12.61 0.73 0.75 0.026 0.076 0.050 0.00135.00 13.37 0.76 0.75 0.031 0.085 0.051 0.00140.00 14.13 0.76 0.75 0.036 0.094 0.058 0.00145.00 14.90 0.77 0.76 0.041 0.104 0.063 0.00150.00 15.66 0.76 0.76 0.047 0.115 0.068 0.00155.00 16.41 0.75 0.76 0.054 0.128 0.074 0.00160.00 17.16 0.75 0.77 0.061 0.141 0.080 0.00165.00 17.90 0.74 0.77 0.068 0.155 0.087 0.00170.00 18.63 0.73 0.77 0.077 0.171 0.091 0.00175.00 19.35 0.72 0.78 0.086 0.188 0.102 0.00180.00 20.06 0.71 0.78 0.095 0.206 0.111 0.00185.00 20.77 0.71 0.78 0.106 0.227 0.121 0.00190.00 21.48 0.71 0.79 0.117 0.249 0.132 0.00195.00 22.19 0.71 0.79 0.129 0.272 0.143 0.00200.00 22.90 0.71 0.79 0.142 0.296 0.154 0.00210.00 24.35 1.45 0.80 0.17 0.350 0.180 0.01220.00 25.82 1.47 0.80 0.201 0.411 0.210 0.01230.00 27.33 1.51 0.81 0.31 0.481 0.171 0.01240.00 28.89 1.56 0.82 0.46 0.556 0.096 0.01250.00 30.47 1.58 0.82 0.64 0.639 0.001 0.01260.00 32.07 1.60 0.83 0.83 0.730 0.100 0.01270.00 33.66 1.59 0.83 1.03 1.191 0.161 0.02280.00 35.22 1.56 0.84 1.21 1.311 0.101 0.02290.00 36.71 1.49 0.84 1.37 1.424 0.054 0.02300.00 38.13 1.42 0.85 1.5 1.535 0.035 0.02310.00 39.45 1.32 0.85 1.6 1.639 0.039 0.02320.00 40.68 0.23 0.86 1.67 1.738 0.068 0.00330.00 41.86 1.18 0.86 1.75 1.831 0.081 0.02340.00 43.04 1.18 0.87 1.86 1.922 0.062 0.02350.00 44.33 1.29 0.87 2.05 2.005 0.045 0.03360.00 45.89 1.56 0.88 2.4 2.00 0.40 0.03449.00 71.89 26.00 0.92 2.81 2.86 0.05 0.74628.46 100.09 28.20 1.0285 5.2 4.80 0.40 1.35

total predicted S ) 2.38% dev. ) 0.02

M ) [355.395 - 50.9165 ln(1080 - Tb)]1.5 (18)

SG ) 1.07 - exp(3.56073 - 2.93886M0.1) (19)

Figure 1. Sulfur distribution of Kuwaiti crude for export fromTable 6.

Table 7. Results of Estimation of Sulfur Contents ofKuwaiti Crude Oilsa

crude API gravity S%, exp S%, pred. abs. dev.%

1 31 2.4 2.1 0.32 40.2 1.08 1.58 0.53 37.2 1.74 1.7 0.044 36.3 1.9 1.57 0.335 32.7 2.14 1.71 0.436 36.4 1.8 1.67 0.137 32.7 2.2 1.76 0.44total 31-40.2 1.1-2.4 - 0.31a Data obtained from local industrial source.13

Ind. Eng. Chem. Res., Vol. 38, No. 11, 1999 4511

RI ) refractivity intercept defined by eq 1Tb ) normal boiling point, KS% ) sulfur weight percentage of the fractionSG ) specific gravity of the fraction at 15.5 CXwi ) weight fraction of pseudocomponent i in a crude oil ) kinematic viscosity at 100 or 210 F, cSt

Literature Cited

(1) Riazi, M. R. A Distribution Model for C7+ Fractions Char-acterization of Petroleum Fluids. Ind. Eng. Chem. Res. 1997, 36,4299-4307.

(2) Speight, J. G. The Chemistry and Technology of Petroleum,2nd ed.; Marcel Dekker: New York, 1991.

(3) Van Nes, K.; Van Westen, H. A. Aspects of the Constitutionof Mineral Oils; Elsevier: New York, 1951.

(4) Riazi, M. R.; Daubert, T. E. Prediction of the Compositionof Petroleum Fractions. Ind. Eng. Chem. Process Des. Dev. 1980,19, 289-294.

(5) Riazi, M. R.; Daubert, T. E. Prediction of Molecular TypeAnalysis of Petroleum Fractions and Coal Liquids. Ind. Eng. Chem.Process Des. Dev. 1986, 25, 1009-1015.

(6) API Technical Data Book - Petroleum Refining, 5th ed.;Daubert, T. E., Danner, R. P., Eds., American Petroleum Insti-tute: Washington, DC, 1989; Chapter 2, pp 15-30.

(7) Riazi, M. R. Distribution Model for Properties of Hydrocarbon-Plus Fractions. Ind. Eng. Chem. Res. 1989, 28, 1831-1735.

(8) Riazi, M. R.; Daubert, T. E. Molecular Weight of HeavyFractions from Viscosity. Oil Gas J. 1987, 58, 110-113.

(9) Riazi, M. R.; Daubert, T. E. Simplify Property Predictions.Hydrocarbon Process. 1980, 59, 115-116.

(10) Riazi, M. R.; Daubert, T. E. Characterization Parametersfor Petroleum Fractions. Ind. Eng. Chem. Res. 1987, 26, 755-759.

(11) Gary, J. H., Handwerk, G. E. Petroleum RefiningsTechnology and Economics, 3rd ed.; Marcel Dekker: New York,1994.

(12) Riazi, M. R.; Al-Sahhaf, T. A. Physical Properties of HeavyPetroleum Fractions and Crude Oils. Fluid Phase Equilib. 1996,117, 217-224.

(13) Industrial Source, Private Communication, Kuwait, 1997.(14) Industrial Source, Private Communication, Saudi Arabia,

1997.(15) Jones, D. S. J. Elements of Petroleum Processing; Wiley:

New York, 1995.(16) Refining Handbook 90, A Special Report. Hydrocarbon

Process. 1990, 69, 83.(17) Refining Processes 94, A Special Report. Hydrocarbon

Process. 1994, 73, 87.

Received for review April 13, 1999Revised manuscript received July 12, 1999

Accepted August 18, 1999

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