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chemical engineering research and design 9 6 ( 2 0 1 5 ) 130'137

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Chemical Engineering Research and Design

journal h om epage: www.elsevier.com/locate/cherd

Intensification and improvement of petrolatumdeoiling process by using pure n-alkanes asnon-polar modifiersMagdy T. Zaky', Nermen H. Mohamed, Amal S. Farag, Fathi S. SolimanPetroleum Refining Division, Egyptian Petroleum Research Institute (EPRI), Nasr City, P.O. Box: 11727 Cairo, Egypta r t i c l e i n f oArticle history:Received 5 October 2014Received in revised form 13February 2015Accepted 21 February 2015Available online 27 February 2015Keywords:Crude petrolatumDeoiling processNon-polar modifiersXRDSEMMicrocrystalline waxa b s t r a c tIn order to intensify and improve the deoiling process, Alexandria crude petrolatum wassubjected to one-stage fractional crystallization (deoiling process) using butyl acetate andmethyl isobutyl ketone solvents at different solvent feed ratios of dilution ranging from 2:1to 8:1 at fixed washing solvent ratio of 2:1 and ambient fractionating temperature of 20'Cto produce micro-crystalline waxes. Non-polar modifiers such as individual pure n-alkaneswith an even number of carbon atoms such as C20H42, C22H46and C24H50were added to thepetrolatum deoiling solvent mixture in the percentages ranging from 0.05 to 1 wt.% basedon the feed to intensify petrolatum deoiling. Two tools of analysis such as XRD and SEM,beside the physical characteristics, were used to compare the crystal size and to observethe surface, shape and holes between crystals of the hard waxes separated without andwith modifiers. Data revealed that, microcrystalline waxes with high quality are producedby using butyl acetate solvent at dilution and washing solvent ratios of 8:1 and 2:1 by weight,respectively with the addition of 1 wt.% of a non-polar modifier; C20'24n-alkanes. The resultsare the increase of the filtration rate, growth of crystal size with more holes between thelarge crystals and improvement in the physical characteristics of the separated wax.'' 2015 The Institution of Chemical Engineers. Published by Elsevier B.V. All rights reserved.1. IntroductionCommercial processes for dewaxing and deoiling of residualfeedstocks are complex and laborious. The greatest diffi-culties are related to the stage of filtering slurries of solidhydrocarbons that tend to form an inter-crystalline structure.Improving the filtration rate for obtaining solid hydrocarbons,use was made of various additives that have a modifying effecton the crystal structure of solid hydrocarbons. The modifiersoffer a means for a considerable improvement in the basicindices of the process and in the quality of the end-productwithout any additional costs, using existing equipment. Theeffect of a modifier on the crystallization of solid hydrocarbonsis usually rated on the basis of the melting point of the micro-crystalline wax, the oil content in the microcrystalline wax,'Corresponding author. Tel.: +202 22745902; fax: +202 22747433.E-mail address: [email protected] (M.T. Zaky).and the slurry filtration rate (Kazakova et al., 1986; Solimanet al., 2014).Some authors used ionic modifiers, surfactants and addi-tives for optimization of crystallization of solid hydrocarbons.Nigmatullin et al. (1995) and Nigmatullin (1997) investigatedthe use of ionic modifiers; aqueous sodium chloride andaqueous iron sulfate; for deoiling petrolatum and slack wax,respectively. They concluded that the aqueous sodium chlo-ride solution increases the selectivity of the highest-meltinghydrocarbons from the petrolatum. But modifier did not affectthe filtration rate and the modification function of iron sul-fate was related to co-crystallization because crystal latticesof iron and solid paraffin waxes were similar. Zolotarev andNigmatullin (1997) studied the purification and deoiling ofslack wax with aluminum chloride complex. It can be used

http://dx.doi.org/10.1016/j.cherd.2015.02.017

0263-8762/'' 2015 The Institution of Chemical Engineers. Published by Elsevier B.V. All rights reserved.

chemical engineering research and design 9 6 ( 2 0 1 5 ) 130'137 131

as a means for obtaining paraffin waxes with quality at theexport-grade level, and for increasing the paraffin yield by2'4%.Trends in improving production of oils and solid hydrocar-bons were examined by optimization of crystallization of solidhydrocarbons by using surfactants and ultrasound. Surfac-tants structural modifiers significantly affect crystallizationof solid hydrocarbons. Concentrated on the phase interface,they form very thin layers that change the molecular natureand properties of the surface. Primarily resins are adsorbedon an energetically inhomogeneous surface of arising crys-tallization centers consisting of high melting paraffins andnaphthenes due to the strongly developed hydrocarbon partof their molecules. In treating a suspension with ultrasound,the bonds between solid hydrocarbon crystals are destroyedand conditions are created for their growth, so that the rateand efficiency of separation of the solid phase from the liq-uid phase increase. To enhance the deoiling process, the slackwax (melting point of 54'C, oil content of 5.5 wt.%) was treatedwith ultrasound. Exposure to ultrasound before deoiling stageI accelerated filtration in the following stages as well. In deoil-ing of slack wax in two stages with ultrasound treatmentbefore the first stage for 10 min, the wax product contains a0.43 wt.% oil content and has melting point of 58'C (Sochevkoand Tugusheva, 2010).Few literatures were found about using a non-polar mod-ifier (n-alkanes) during the deoiling of petrolatum to producemicrocrystalline wax. Thus, our work aims to intensify petro-latum deoiling process for improving the crystallization ofsolid hydrocarbons; to produce microcrystalline wax; by usinga non-polar modifier; especially individual pure n-alkaneswith an even number of carbon atoms in the molecule(C20'C24).2. Materials and methods2.1. MaterialsTwo crude petrolatums (petroleum wax by products) obtainedfrom Alexandria Petroleum Company and Suez Oil ProcessingCompany are used and evaluated in this study for deoilingprocess and isolation of microcrystalline waxes.2.2. Deoiling processAlexandria crude petrolatum was subjected to one stage frac-tional crystallization (deoiling process) (Zaky et al., 2007;Mohamed et al., 2008; Zaky and Mohamed, 2010) using butylacetate (BA) and methyl isobutyl ketone (MIBK) solvents atdifferent solvent feed ratios of dilution (S/F, by weight) ran-ging from 2:1 to 8:1 at fixed washing solvent ratio of 2:1and ambient fractionating temperature of 20'C to producemicro-crystalline waxes. In this technique, the high meltingcomponents of the wax (hard wax) got precipitated while thelow melting ones (soft or slop wax) remained in the solution.2.2.1. One stage fractional crystallization techniqueA known weight of crude petrolatum was dissolved in the cor-responding amount of solvent in a beaker and heated till themixture becomes homogeneous. Then the mixture was cooledgradually at room temperature for two hours. The beaker andthe buchner funnel were transferred to a controlled tempera-ture unit and gradually cooled to the desired temperature 20'Cfor 12 h. The beaker contents were transferred to the funneland filtered through a Whatman filter paper no.43 by usingcontrolled suction (8.6 Psi). The wax cake was washed withan additional solvent at the same temperature and added atsmall increments. Solvents were removed from the wax cakeby distillation.2.3. Addition of individual pure non-polar modifiersNon-polar modifiers of individual pure n-alkanes with an evennumber of carbon atoms such as Eicosane (C20H42), Docosane(C22H46) and Tetracosane (C24H50); purchased from Aldrichand Fluka Chemical Company; were added to the petrolatum-deoiling solvent mixture in the percentages ranging from 0.05to 1 wt.% based on the feed to intensify petrolatum deoiling.2.4. Methods of analysisThe two crude waxes and the isolated hard waxes were phys-ically characterized according to American Society for Testingand Materials (ASTM) standard methods (ASTM, 1999). Thefiltration rate was calculated by the following equation:

Filtration rate

=

Weight of the filtrate/Area of funnel bottom

''

Time of filtration

=

kg/m2 h

where the weight of the filtrate produced through deoilingprocess is in kg:

Area of funnel bottom

=

(m2 =

r2)

where  = 3.14 and r = radius of funnel used in deoiling processin m and time of filtration is in hour = h.The type of the isolated hard waxes was specified accordingto Technical Association of the Pulp and Paper Industry (TAPPI)' ASTM equation (Ferris, 1963; Gottshall and McCue, 1973).The n-paraffin content was determined by using chromato-graphic technique (GC). The GC apparatus used was model(Perkin Elmer, Clarus 500, England), equipped with a hydrogenflame ionization detector and fused silica capillary column(30 cm '' 0.25 mm i.d.), packed with poly (dimethyl siloxane)HP-1 (non-polar packing) of 0.5 m film thickness. The appa-ratus was also equipped with an integrated data handlingsystem for computing the peak area and concentration.The aromatic content of the crude waxes and the isolatedhard waxes was determined using liquid'solid column chro-matography technique. Liquid'solid column chromatographytechnique was used to determine the molecular type compo-sition; the total saturates and total aromatics for the crude andisolated hard waxes by using silica gel (60'200 mesh size) asan adsorbent. Stepwise elution was employed with n-heptane,benzene and mixture of methanol and benzene (Snyder, 1975).The fractionation between total saturates and total aromaticswas carried out by making use of refractive indices values at20'C (Mair and Rossini, 1958; Deutsch et al., 1987).2.5. X-ray diffractionThe X-ray diffraction patterns were run to study the crystalsize of the hard waxes separated without and with modifierson a P Analytical-XPert Pro, Netherlands, with a step size ('2)of 0.02 and scan step time (s) of 0.4. The 2, full width at halfmaximum (FWHM) and d spacing were obtained. Wax crystal

132 chemical engineering research and design 9 6 ( 2 0 1 5 ) 130'137

Table 1 ' Physical characteristics and molecular type composition of the two crude petrolatums.

Characteristics Test method Crude petrolatums

Suez Alexandria

Congealing point, 'C ASTM D-938 59 66

Kinematic viscosity, 98.9 'C ASTM D-445 15.01 14.25

Refractive index, 98.9 'C ASTM D-1747 1.4606 1.4478

Density, 70 'C ASTM D-1418 0.8500 0.8262

Mean molecular weight ASTM D-2502 591 680

Oil content, wt.% ASTM D-721 43.14 11.01

Needle penetration, 25 'C ASTM D-1321 138 93

Sulfur content, wt.% ASTM D-4294 1.8545 0.65

Color ASTM D-1500 9.0 4.0

Molecular type composition

Total saturates, wt.% 50.13 73.83

n-Paraffin content, wt.% 10.52 43.92

Iso- and cyclo-paraffins content, wt.% 39.61 29.91

Iso- and cyclo-paraffins/n-paraffins ratio 3.77 0.68

Total aromatics, wt.% 49.87 26.17

Mono-aromatics, wt.% 24.80 12.14

Di-aromatics, wt.% 25.07 14.03

size was calculated according to Scherrer equation (Langfordand Wilson, 1978). It is as follows:

Crystal size

=

0.9

''

/B

''

cos(2/2)

B

=

FWHM/57.3

where  = 1.54''A and B is the peak width2.6. Scanning electron microscope (SEM)SEM was used to observe the surface, shape and crystal sizeof the hard waxes separated without and with modifiers. Thewax was coated with gold by K550X sputter coater, Englandthen scanned by scanning electron microscope (SEM; Quanta250 FEG, Netherlands).3. Results and discussion3.1. Characterization and evaluation of crudepetrolatumsThe physical characteristics and the molecular type composi-tion for the two crude petrolatums are represented in Table 1.The physical characteristics of Suez crude petrolatum such asrefractive index, density and kinematic viscosity are higherthan those of Alexandria crude petrolatum. It may be due toits higher total aromatic content. The oil content is an indica-tion of the quality of the wax whereas, the higher oil contentof Suez crude petrolatum (43.14 wt.%) than that of Alexan-dria crude petrolatum (11.01 wt.%) is an indication of its lowquality. An increase in oil content results in an increase inpenetration value and decrease in congealing point (Table 1).Molecular type composition data indicate that Suez crudepetrolatum has appreciable total aromatic content (49.87 wt.%)as compared with that of Alexandria crude petrolatum(26.17 wt.%). These aromatic constituents are mainly mono-and di-aromatic ones of nearly equal contents (24.80 and25.07 wt.%, respectively) for Suez crude petrolatum.Meanwhile, Alexandria crude petrolatum has highersaturate content (73.83 wt.%) specially, n-paraffin content(43.92 wt.%) which is about four folds the n-paraffin contentof Suez crude petrolatum (10.52 wt.%). This value of n-paraffincontent (10.52 wt.%) is lower than the n-paraffin contentlimit (15 wt.%) of microcrystalline wax crudes (Edwards, 1963).Thus, it can be deduced that Alexandria crude petrolatum isa preferable crude petrolatum for deoiling process.3.2. Solvent deoiling of crude petrolatum withoutusing a modifierAlexandria crude petrolatum was subjected to fractional crys-tallization technique (deoiling process) by using butyl acetate(BA) and methyl isobutyl ketone (MIBK) solvents under dif-ferent dilution solvent ratios (S/F by weight) and at ambientfractionating temperature of 20'C. Data are represented inTable 2.4050607080901000 10020 0 300 40050 0Filtration rate, Kg/m2.hYield, wt.%00.511.522.53Oil content, wt.%Yield (BA)Yield (MIBK)Oil con tent (BA )Oil con tent (MIBK)70717273747576010 020 030 040 050 0Filtration rate, Kg/m2.hCongealing point, 0C24252627282930Needle penetration at 250CCongealing point (BA)Cong ealing point (MIBK )Needle penetration (BA)Needle penetration (MIBK)(a)(b)Fig. 1 ' Correlation between filtration rate with the yieldand oil content (a), and congealing point and needlepenetration (b) of the hard waxes isolated by using BA andMIBK solvents at different dilution solvent ratios.

chemical engineering research and design 9 6 ( 2 0 1 5 ) 130'137 133

Table 2 ' Effect of dilution solvent ratio on the physical characteristics, molecular type composition and type of the

isolated waxes by deoiling of Alexandria crude petrolatum using BA and MIBK solvents at fractionating temperature of

20 'C and S/F for washing of 2:1.

Characteristics Hard waxes isolated by using BA and MIBK at different dilution solvent ratios (S/F)

2/1 4/1 6/1 8/1

BA MIBK BA MIBK BA MIBK BA MIBK

Yield on crude petrolatum, wt.% 60.3666.0458.5862.32 56.71 61.89 54.67 60.03

Congealing point, 'C 71.5 71 72.5 72 73 72.5 74 73

Kinematic viscosity at 98.9 'C, mm2/s 14.00 14.15 13.50 14.00 13.25 13.70 13.00 13.5

Refractive index at 98.9 'C 1.4408 1.4420 1.4402 1.4415 1.4398 1.4411 1.4396 1.4408

Refractive index by TAPPI-ASTM equation 1.4306 1.4304 1.4310 1.4308 1.4311 1.4310 1.4315 1.4311

Mean molecular weight 738 731 743 740 747 743 751 748

Oil content, wt.% 1.89 2.33 1.65 2.19 1.35 2.04 1.16 1.90

Needle penetration at 25 'C 28 29 26 28 25 27 25 26

Sulfur content, wt.% 0.27 0.28 0.26 0.27 0.25 0.26 0.24 0.25

Color 2.5 3.0 2.5 3.0 2.0 2.5 2.0 2.5

Filtration rate, kg/m2 h 70 48 197 151 278 266 415 404

Crystal size (X-ray diffraction) 241.5 228.3 273.9 252.4 293.2 283.3 316.3 306.2

Molecular type composition

Total saturates content, wt.% 78.50 78.50 81.00 79.20 81.25 79.85 81.80 81.00

Total aromatics content, wt.% 21.50 21.50 19.00 20.80 18.75 20.15 18.20 19.00

Mono-aromatic content, wt.% 14.99 14.90 17.00 15.80 17.50 15.90 18.20 16.00

Di-aromatic content, wt.% 6.51 6.60 2.00 5.00 1.25 4.25 0.00 3.00

Type of wax Microcrystalline wax

The dilution has an obvious effect upon the yield and qual-ity of the waxes isolated from Alexandria crude petrolatum byusing the two solvents. The wax yield decreases with increas-ing of solvent dilution ratio. It may be attributed to the increaseof the solvent power toward the oil inherent to such waxcrystals. This conclusion is in line with the data of congeal-ing points and mean molecular weights of the isolated waxeswhich give higher values on increasing the dilution solventratio. Also, it can observe that the wax yield isolated by usingBA solvent is lower than that obtained with MIBK solvent. Thismay be related to the higher solvent power for BA over MIBKsolvent (Table 2).Generally, the rate of filtration increases with dilution andis accompanied with a decrease in the oil contents, viscositiesand refractive indices of the hard waxes separated from crudepetrolatum. This attributed to the removal of the oil which ismainly aromatic constituents. Consequently, the sulfur con-tent and color value of the isolated hard waxes decrease withincreasing the dilution solvent ratios. Data of molecular typecomposition confirm the previous results as there is a valuabledecrease in the total aromatic contents specially the di- aro-matic constituents which disappeared by using BA solvent atdilution solvent ratio of 8:1 by weight. Consequently, the totalsaturate contents of the isolated hard waxes increase (Table 2).Fig. 1 exhibits the correlations between rate of filtrationwith the yield, oil content, congealing point and needle pen-etration of the hard waxes isolated from Alexandria crudepetrolatum. It is clear from the plots that, as the filtrationrate increases, the yield, the oil content and consequentlythe needle penetration of the wax decrease while the con-gealing point increases and the hard waxes isolated by usingBA solvent have higher filtration rate and congealing pointFig. 2 ' SEM photographs of the hard waxes isolated from Alexandria crude petrolatum by using BA (a) and MIBK (b)solvents at dilution solvent ratio of 8:1 by weight.

134 chemical engineering research and design 9 6 ( 2 0 1 5 ) 130'137

0400800120016002000Counts/s0400800120016002000Counts/s0400800120 0160 020000 10 20 30 40 50 60 70 802 ''Counts/s0400800120016002000010203040506070802 ''Counts/s(a)(b)(d)(c)Crystal size=24 1.5Crystal size=228.3Crystal size=316.3Crystal size=30 6.2Fig. 3 ' X-ray diffraction patterns for the hard waxes separated by using BA and MIBK solvents at dilution solvent ratios of2:1 (a and b) and 8:1 (c and d), respectively.and lower oil content than those separated by using MIBKsolvent.SEM photographs of the isolated hard waxes are parallelto the above findings as the hard waxes isolated by using BAsolvent seem to be somewhat more crystalline and possesmore holes than those separated by MIBK solvent at the samedilution solvent ratio of 8:1 by weight (Fig. 2).Moreover, X-ray diffraction patterns confirm the previ-ous results whereas, the hard waxes isolated by using BAand MIBK solvents become well crystalline and have highcrystal size with dilution; as an example from 2:1 to 8:1 byweight. Also, it is interest to observe that, the hard waxesisolated by using BA solvent appear to be more crystallineand have higher crystal sizes than those isolated by using48495051525354550 0.2 0.4 0.6 0.8 1 1.2Non-polar modi fier concentration, w t.%Yield, wt.%C20C22C24727374757677780 0.2 0.4 0.6 0.8 1 1.2Non-polar modi fier concentration, wt.%Congealing point, 0CC20C22C247307407507607707807908000 0.2 0.4 0.6 0.8 1 1.2Non-polar modi fier concentration, wt.%Mean molecular weightC20C22C241618202224260 0.2 0.4 0.6 0.8 1 1.2Non -pol ar modi fier conce ntration, wt.%Needle penetration, 250CC20C22C24(a)(b)(c)(d)Fig. 4 ' Effect of non-polar modifier addition on the yield (a), congealing point (b), mean molecular weight (c) and needlepenetration (d) of the hard waxes isolated from Alexandria crude petrolatum by using BA solvent.

chemical engineering research and design 9 6 ( 2 0 1 5 ) 130'137 135

3203604004404805205606000 0.2 0.4 0.6 0.8 1 1.2Non-polar modi fier concentration, wt.%Filtration rate, Kg/m2.hC20C22C2400.20.40.60.811.21.40 0.2 0.4 0.6 0.8 1 1.2Non-polar modifier conce ntration, wt.%Oil content, wt.%C20C22C2411.51212.51313.50 0.2 0.4 0.6 0.8 1 1.2Non-polar modi fier concentration, wt.% Viscosity, mm2/sC20C22C241.4371.43751.4381.43851.4391.43951.440 0.2 0.4 0.6 0.8 1 1.2Non-polar modifier concentration, wt.%Refractive index, 98.90CC20C22C24(d)(c)(b)(a)Fig. 5 ' Effect of non-polar modifier addition on the filtration rate (a), oil content (b), viscosity (c) and refractive index (d) ofthe hard waxes isolated from Alexandria crude petrolatum by using BA solvent.050010001500200025000 20 40 60 802 ''Counts/s050010001500200025000 20 40 60 802 ''Counts/s050010001500200025000 20 40 60 802 ''Counts/s0500100 0150 0200 0250 00 20 40 60 802 ''Counts/s(d)(c)(b)(a)Crystal size= 316.3Crystal size=410.9Crystal si ze=410.2Crystal size= 411 .3Fig. 6 ' X-ray diffraction patterns for the hard waxes separated by using BA solvent without modifier (a) and with 1% of puren-C20(b), 1% n-C22(c) and 1% n-C24(d) at dilution solvent ratio of 8:1 by weight.

136 chemical engineering research and design 9 6 ( 2 0 1 5 ) 130'137

Fig. 7 ' SEM photographs of the hard waxes isolated by using BA solvent without modifier (a) and with addition of 1% ofpure n-C20(b), 1% n-C22(c) and 1% n-C24(d) at dilution solvent ratio of 8:1 by weight.MIBK solvent at all the dilution solvent ratios (Fig. 3a'd andTable 2).Examining the isolated wax type in Table 2; on the basisof TAPPI-ASTM equation (Ferris, 1963; Gottshall and McCue,1973) and petroleum wax specifications (Sequeria, 1994); it canbe noticed that all the hard waxes isolated from Alexandriacrude petrolatum by using BA and MIBK solvents at all thedilution solvent ratios lie in the category of microcrystallinewaxes as they characterized by refractive indices higher thanthose obtained by the equation and by viscosities at 98.9'Chigher than 10.2 centistokes.Also, it can be deduced that, the microcrystalline waxes;isolated by using butyl acetate solvent at dilution solventratio of 8:1 by weight; have the highest filtration rate, crystalsize and congealing point and they possess more holes andthe lowest oil content and total aromatics whereas, the di-aromatic constituents disappeared. Thus, it can be deducedthat BA solvent is suitable for deoiling of crude petrolatum atdilution solvent ratio of 8:1 by weight.3.3. Solvent deoiling of crude petrolatum usingindividual n-alkane modifiersThe effect of addition of a non-polar modifier; pure C20'24n-alkanes with an even carbon number in the range of0.05'1 wt.%; during the deoiling process of Alexandria crudepetrolatum on the filtration rate and the isolated hard waxquality was studied at fractionating temperature of 20'C anddilution solvent ratio of 8:1 by weight by using BA solvent.It can be observed that, the yield of the isolated hardwaxes decreases with increasing the modifier concentration;n-alkanes (Fig. 4a). It may related to the improvements of thecrystallization of the solid hydrocarbons by creation of thecrystal nuclei with a portion of the modifier; C20'24n-alkanes,and the remainder built in the surface of the growing crys-tals. This enhanced on contact with other crystals that includealkyl radicals and formed densely packed coagulated struc-tures. The result was the squeezing of substantial amountof oil and low molecular weight components to the solventlayer, which decreased the yield of the isolated hard waxes.This conclusion is in line with the data of congealing pointsand mean molecular weights (Fig. 4b and c) of the isolatedwaxes which are increased by increasing the non-polar mod-ifier concentrations and consequently the penetration valuedecreases (Fig. 4d). The rate of increase is smaller by increas-ing the modifier concentration from 0.5 to 1 wt.% than thatobtained by increasing the modifier concentration from 0.05to 0.5 wt.% (Fig. 4b and c).It is interest to note that, the filtration rate; themost important property for the fractional crystallizationprocess; increases by the addition of a modifier; C20'24n-alkanes. It increases smoothly with increasing the modifier

chemical engineering research and design 9 6 ( 2 0 1 5 ) 130'137 137

1.431.43 21.43 41.43 61.43 81.440 0.2 0.4 0.6 0.8 1 1.2Non-po lar modifier conc entration, wt.%Refractive index, 98.90CExp R.I

(

C20)Exp R.I (C22)Exp R.I (C24)Calc R.I (C20)Calc R.I (C22)Calc R.I (C24)Fig. 8 ' Effect of non-polar modifier concentration on theexperimental and calculated refractive indices of the hardwaxes isolated from Alexandria crude petrolatum.concentration from 0.05 to 0.5 wt.% and then increases sharplywhen the modifier concentration reaches to 1 wt.% (Fig. 5a).Also, it can be noticed that the filtration rate increase isaccompanied with decrease in the oil contents, viscositiesand refractive indices of the hard waxes separated from crudepetrolatum. This attributed to the removal of the oil whichis mainly low melting point wax; cyclo-paraffin and aromaticconstituents which have higher viscosities and refractiveindices than the other constituents of the wax (Fig. 5b'd).Moreover, it can be observed that, the highest filtrationrate was achieved by using 1 wt.% of a modifier; C20'24n-alkanes and the three membered n-alkanes C20, C22and C24gave more or less the same filtration rates, yields, congealingpoints and oil contents at the same modifier concentration(Figs. 4a and b and 5a and b).Comparing between the X-ray diffraction patterns of thehard waxes isolated without and with addition of 1 wt.% of amodifier; C20'24n-alkanes, it can be observed that the peaksof hard waxes isolated appear to be well crystalline and havethe higher crystal sizes by the addition of 1 wt.% of a modifier;C20'24n-alkanes (compare Fig. 6a with b'd).SEM photographs of the isolated hard waxes are parallel tothe above findings whereas, the crystals of the hard waxes iso-lated are growing up and became more crystalline and possessmore holes with addition of 1 wt.% of a modifier; C20'24n-alkanes (compare Fig. 7a with b'd).Examining the type of the isolated waxes from Alexandriacrude petrolatum with addition of many concentrations of anon-polar modifier (C20'24n-alkanes) (Fig. 8); on the basis ofTAPPI-ASTM equation (Ferris, 1963; Gottshall and McCue, 1973)and petroleum wax specifications (Sequeria, 1994); it can benoticed that all the hard waxes isolated lie in the category ofmicrocrystalline waxes. Thus, it can be concluded that, inten-sifying and improvement of the fractional crystallization ofcrude petrolatum to isolate the hard wax; microcrystallinewax with high quality are achieved by using butyl acetate sol-vent with addition of 1 wt.% of a non-polar modifier; C20'24n-alkanes. The results are the increase of the filtration rate,growing up of crystal size, elevation of the congealing point ofthe wax and the decrease in its oil content, needle penetrationand viscosity.4. ConclusionsThe study shows that Alexandria crude petrolatum is thepreferable crude for deoiling process and butyl acetate sol-vent is suitable for deoiling of crude petrolatum at dilutionsolvent ratio of 8:1 by weight at fixed washing solvent ratio of2:1 and ambient fractionating temperature of 20'C to producemicro-crystalline waxes. Also, addition of 1 wt.% of a non-polar modifier; C20'24n-alkanes is highly effective to intensifyand improve the fractional crystallization of crude petrola-tum to isolate the hard waxes; microcrystalline waxes withhigh quality, filtration rate, crystal size, congealing point andhaving more holes between their large crystals and low oilcontent.ReferencesAnnual Book of ASTM-Standards (American Society for Testingand Materials), 1999 Petroleum Products, Lubrications, Sect. 5,West Conshohocken.Deutsch, K., Kuehn, H.J., Polzing, M., Deutsch, I., Gruow, S.,Stoecker, J., 1987. Prakt. Chem. 329 (4), 681.Edwards, R.T., 1963. Molecular Arrangement and the Properties ofPetroleum Waxes. Technical Association of the Pulp and PaperIndustry. Special Technical Association Publication, Publ. No.2, New York, pp. 95'111.Ferris, S.W., 1963. Petroleum Waxes, Characterization,Performance and Additives. Technical Association of the Pulpand Paper Industry. Special Technical Association Publication,STAP No. 2, New York, pp. 1'19.Gottshall, R.I., McCue, C.F., 1973. Petroleum waxes includingpetrolatums. In: Allinson, J.P. (Ed.), Criteria for Quality ofPetroleum Products. Applied Science Publishers Ltd., OnBehalf of The Institute of Petroleum, London, pp. 209'225.Kazakova, L.P., Kolesnikov, S.I., Vyboichenko, E.I., Mosidze, M.V.,1986. Mechanism of action of non polar modifiers incrystallization of solid hydrocarbons (petroleum waxes).Chem. Technol. Fuels Oils 22, 538'541.Langford, J.I., Wilson, A.J.C., 1978. Scherrer after sixty years: asurvey and some new results in the determination ofcrystallite size. J. Appl. Crystallogr. 11, 102'113.Mair, B.J., Rossini, F.D., 1958. Symposium on Composition ofPetroleum Oils, Determination and Evaluation. ASTM STP224., pp. 9.Mohamed, N.H., Zaky, M.T., Farag, A.S., Fahmy, A.F.M., 2008.Separation of paraffin wax using solvent fractionation. Petrol.Sci. 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