Hydrocarbons from West Siberian crude oils

Petrol. Chem. U.S.S.R. Vol. 25, No. 2, pp. 76-82, 1985

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HYDROCARBONS FROM WEST SIBERIAN CRUDE OILS* I. A. MUSAYEV,E. KH. KURASHOVA,R. N. SIMANYUK,A. A. POLYAKOVA L . S. YERMAKOVA, M . B. SMIRNOV and P. L SANIN A. V. Topchiyev Institute of Petrochemical Synthesis, .U.S.S.R. Academy of Sciences All-Union Scientific Research Institute for the Processing of Oil and Gases and the Production of Synthetic Liquid Fuel THE petroleum used in this study was a mixture of West Siberian oils, which in composition is similar to Samotlor petroleum. According to Verfolomeyev and Khabibulin, this petroleum contains, 1.28% sulphur, 0.15% nitrogen, 1.24% asphaRhenes, 11.5 % resinous substances and 6.6 % paraffins. Distillation gave a 350°-540°C cut (vacuum gas oil) 30.4 wt. % on crude oil, which was examined. This distillate had a density of p]O 0.9164 and average MW 391 with sulphur content 2.2% and nitrogen 0.17~. Particular attention was paid to the naphthene (cyclane) content of this distillate using the investigation scheme given below. The distillate was eluted from ASK silica gel to give paraffln-naphthene hydrocarbons (39.9 wt. %), aromatic hydrocarbons (53.5 wt. %) and resins (6.6 wt. 9/oo). n-Hexane, benzene and benzene/alcohol were the chosen eluants. n-Paraffins were isolated from the N + P portion by urea adduction [1]. However, the chromatographic analysis of the isolated paraffins showed that they contain a significant proportion of other hydrocarbons. Accordingly the n-paraffins were separated from the concentrate obtained using molecular sieves (zeolite, calcium form, pore size 5 A) [2]. n-Paraffins (63 9/00,4.3 % of the 350°-540°C distillate) were separated from the concentrate; 37 % of the concentrate was a mixture of isoalkanes plus cyclanes. The latter, which are now being investigated in detail apparently contained long n-paraffin chains which adducted with urea. The isolated n-paraffins were analysed by gas-liquid chromatography ("Tsvet-2" chromatograph, a flame-ionization detector, column 15 m × 0.25 mm, stationary phase Apiezone L, hydrogen carrier gas, temperature programmed 130° to 315°C at 2 deg/min.) The n-paraffins fall in the carbon number range (Cj 8-C4o) (Table 1). The overall n-paraffin content (Cls-C2o and C31-C4o) in terms of the total of nparaffins was 6.4 and 19.7 %, respectively. Most of these paraffins were in the carbon number range C2t-C3o, thier overall content was 73.9 9/0. * Neftekhimiya25, No. 3, 315-321, 1985. 76

Hydrocarbons from West Siberian crude oils

77

TABLE 1. n-PARAFFINSFROM A 350°-540°C DISTILLATE n-Paraffin content, n-Paraffins

ClaHas C19H4o C2oH42

C21 H44 C22H46 C23H48 C24H5o C25Hs2 C26H54 C27H56 C28Hss C29H6o

n-Paraffin content,

wt. %

b.~*

on total n-paraffins

on 350540oc distilate

0.76 1"70 3-94 6"71 7"60 7-36 9"70 8"11 10"02 7"58 6-46 5"74

0'03 0.07 0"17 0"29 0-33 0'32 0"42 0"35 0"43 0"32 0-28 0"25

317"5 331'7 345"3 358"4 370"8 382'7 394"6 405"9 416"7 427'3 437-5 447'4

n-Paraffins

C3oH62

CalH64 C32H66

Ca3H6s C34H7o C a s H 72 C36H74 C37H76 C3aH78 C39H8o C4oH82

wt. ~o

b.~*

n-paraffins

on 350540°C distillate

4'62 3.82 2.83 2.72 2.04 1'90 1.75 1.50 1-10 1.12 0.95 100.0

0-20 0.16 0.12 0.12 0.09 0.08 0.07 0.06 0.05 0.06 0.04 4.30

on total 457"0 466'3 475"4 484-3 492"7 501'0 509"3 517'3 524'9 532"6 539'8

* Literature boiling points. TABLE 2. COMPOSITION OF AROMATIC HYDROCARBONS FROM A 3 5 0 - 5 4 0 ° C DISTILLATE AND OF AROMATIC HYDROCARBONS FROM DEH YDROGENATION OF THE NAPHTHENE HYDROCARBONS IN THIS DISTILLATE

Aromatic hydrocarbons, mole

Molecular ring General formula polymethylene*

in fraction initial

from dehydrogenation of naphthenes

CnH2n- 6 CnH2n-8

0

CnH2n - to CnH2n - 12

2 0

C~H2~_ ~4 CnH2,,_ ~6 C~H2~- ~s

2 0

21.7 17.9 18'2 8.7 8-5 4-3 6"4 7-6 4.4 2"3

38"2 21'3 5"7 7"2 2"7 3"7 4"4 6"0 6"5 4"3

benzene

1

1

1

CnH2n - 20 CnH2n-22

0 0

C~H2n- 2 C, H2~_ 2~

1

* C5 and C6 naphthene rings condensed with benzene rings.

A r o m a t i c h y d r o c a r b o n s f r o m the 530°-540°C distillate were e x a m i n e d by M S [3] ( M X 1320 m a s s - s p e c t r o m e t e r at 70 eV with the source at 250°C using a d i r e c t i n l et system at 150°C). Results are s h o w n in T a b l e 2. T h e d a t a in T a b l e 2 indicate that the a r o m a t i c h y d r o c a r b o n s o f the 3 5 0 ° - 5 4 0 ° C distillate (39-9 700) c o n t a i n e d h y d r o c a r b o n s with 1-4 benzene rings, those w i t h o n e benzene ring ( a b o u t 6 0 ~ )

p r e d o m i n a t e d . H y d r o c a r b o n s w i t h t w o b e n z e n e rings

78

I.

MUSAYEV et al.

A.

TABLE 3. AVERAGE NUMBER OF ALKYL GROUPS PER MOLECULES OF AROMATIC HYDROCARBONS (13C

100 AVERAGE

NMR)

Aromatic hydrocarbons Alkyl group

350°-540°C ~actions

from dehydrogenation of naphthenes

CHaCH2CH2CH2 CHaCH2CH2CH2CH2 CHaCH2CH2CH2CH2CH 2C H a C H 2 C H 2 C H 2 C H 2 C H 2CH2 -

75 64 37 37 6

75 69 37 37 6

No.

CHaCHCHzCH2CH2

-

L CH3 CH3CHCH2CH2CH2CH2

2-5

3"5

I CHa CHBCH2CHCH2

-

CH3

CHaCH2CHCH2CH2

-

-

I CH3 CHaCH2CHCH2CH2CH2

-

I 10

CH3 CH3CH2CH2CH-

6'5

I 11

CH3 CHaCH2CH2CHCH2

5'5

--

I 12

CH3 CH3CH2CH2CHCH2CH2

13

CH3 CHaCH2CH2CH2CH--

-

4"5

5"5

I 4"5

I 14

CH3 CHaCH2CH2CH2CH2CHCHz-

4"5

5'5

I CH3 15

CHaCHCH2CH2CH2CHCH2-

16

CH3 CHa -CH2CHCH2CH2CH2CHCHz-

17

CH3 CH3 -CH2CH2CHCH2CH2-

I

2"5

I

1 CHa

10

25"5

36"5

Hydrocarbons from West Siberian crude oils

79

TABLE 3 (cont.)

No.

Alkyl group

18

-CH2CH2CH2CHCH2CH~CH2-

19

-CH2CHCH2-

Aromatic hydrocarbons from de350°-540°C hydrogenafractions tion of naphthenes 11 15"5

CH3 1'5

I CH2

F CHa

TABLE4.

AVERAGE CARBON ATOM (~/o) CONTENT IN VARIOUS STRUCTURAL FRAGMENTS OF AROMATIC

HYDROCARBONS

FROM A 3 5 0 ° - 5 4 0 ° C DISTILLATE AND IN AROMATIC HYDROCARBONS

EROM DE-

HYDROGENATION OF NAPHTHENES IN THIS FRACTION (13C N M R )

Aromatic hydrocarbons

Aromatic hydrocarbons p

from

dehydroon genation 350°-540°C of distillate naphthenes

Fragment

Alkyl groups (C1-C3)* Alkyl groups higher than Ca

8"7

10"0

29-2

34.7

Fragment

Naphthene rings Benzene rings

from

350°-540°C dehydroon genation of distillate i I naph[ thenes 26"1 [ 25"4 36"0 i 29-9

* Mainly methyl groups.

TABLE 5. CYCLANES FROM 3 5 0 ° C - 5 4 0 ° C

Cyclanes

Monocyclic Bicyclic Tricyclic

Number of rings cyclocyclohexpentane* ane (C6) (Cs) 1 1

0 1

2

0

1

2

2 3

1 0

DISTILLATE

Cyclanes

Tetracyclic

Pentacyclic

Number of rings cyclocyclohex- pentane* ane (C6) (Cs) 2 2 3 1 4 0 4 1

* The presence of cyclohexane rings containing geminal substituents is possible; like cyclopentane rings, they ar~

not dehydrogenated.

80

I.A. MUSAYEVet

al.

are represented by substituted naphthalenes. Substituted phenanthrenes, pyrenees chrysenes etc. may be present among other polycyclic aromatic hydrocarbons. 350°-540°C destillate Liquid chromatography on silica gel t

n-Paraffins, isoparaffins and naphthenes (39"9%)

.Aromatic hydrocarbons (53 %)

I

!

+ Spectroscopic analysis

I Urea adduct

I

Hydrocarbon non-adducts, isoparaffinsand naphthenes (33 %)

Adducting hydrocarbons (6"9%) Treatment with molecular sieves

Dehydrogenation

[

~n-Paraffins(4.3 %)

lsoparaffins, naphthenes (2'6 ~)

Aromatic hydrocarbons, isoparaffins, naphthenes (nondehydrogenating) Liquid chromatography on silica gel

GLC analysis + Aromatic hydrocarbons from dehydrogenationof napthenes (17.7%) l Spectroscopic analysis

lsoparaffins, naphthenes (non-dehydrogenating (! 5-3 %)

The structure of the aromatic hydrocarbon alkyl groups was obtained using 13C NMR [3]. ("Brooker" WP-80 spectrometer at 20, 115 MHz, broad-band suppression of 1H nuclei, storage memory volume 8 K, reproduction memory volume 8 K, machine clearance 0"46 Hz, pulse duration 3-2 #sec (25°C), data collection 1.092 sec and sample temperature 35°--40°C). Table 3 shows that the aromatic hydrocarbons in the 350°-540°C distillate contain the highest number of normal (C+-C7) alkyl groups (No. 1 to 4); longer alkyl groups not determined by this method may also be present. The content of branched alkyl groups carrying a methyl substituent at various positions in the chain (No. 5 to 14) is also high. These hydrocarbons also contained a considerable number of isoprenoid alkyl groups (No. 15 and 16) and possibly their fragments (No. 17 and 18). Alkyl groups with an ethyl substituent in the chain (No. 19) were also found.

Hydrocarbons from West Siberian crude oils

81

Aromatic hydrocarbons in the 350°-540°C distillate also contain short alkyl groups (C~-C3), mainly methyl (Table 4). MS analysed showed that the isoparaffin and naphthene concentrate contains 33"5 ~ isoparaffins and 66.5 700 naphthenes with one to six rings in the molecule. The isoparaffin and naphthene content of the 3500-540°C distillate (mole~) is shown below: Isoparaffinic hydrocarbons Naphthenes monocyclic bicyclic tricyclic tetracyclic pentacyclic hexacyclic

11"1 8"3 5.1 3.6 3"5 1'2 0.2

The isoparaffin-naphthene concentrate was dehydrogenated and naphthenes containing cyclohexane rings were assumed to be dehydrogenated with the formation of aromatic hydrocarbons, which can be related to the original naphthenes. Dehydrogenation was carried out in three stages, liquid phase at 330°C with platinized charcoal (18 ~o platinum, 2 ~ iron) [5, 6]. 20 ~ of the weight of the concentrate (10 g) required catalyst (2 g). After each stage the aromatic hydrocarbons formed were separated from the non-dehydrogenated part by elution from silica gel. After three-stage dehydrogenation and chromatographic separation, aromatic hydrocarbons (53.7 ~ ) and isoparaffins plus non-dehydrogenating naphthenes (46-3 ~ ) were obtained. The group composition of aromatic hydrocarbons obtained by dehydrogenation and determined by MS - is shown in Table 2. It follows from Tables 2 and 3 that the aromatic hydrocarbons from dehydrogenation of naphthenic hydrocarbons ex 350°-540°C distillate are similar in structure to those from the 350°-540°C distillate itself. The distribution of hydrocarbons with 1-4 benzene rings according to types is practically the same. Aromatic hydrocarbons with one benzene ring (57.8 and 65.2 ~; Table 2) predominate in both cases. The structures and content of alkyl groups in aromatic hydrocarbons of the fraction and in aromatic hydrocarbons obtained by dehydrogenation of naphthenes (Table 3), are also very similar. Table 4 shows (~3C NMR) the average carbon number of the various structural fragments of aromatics in the 350°-540°C distillate, compared with the aromatic hydrocarbons from dehydrogenation of the naphthenes in this distillate. (Benzene rings were determined" from spectra in deuterochloroform (with chromium acetylacetonate (III) 0"2 mole/l.), under conditions of "invertion gated decoupling", delay 3 sec, pulse duration 11 /~sec (90°C), data collection 0.546 sec, storage memory volume 4 K, reproduction 4 K, numerical clearance 0.92 Hz). The data obtained confirm the aromatic hydrocarbon structure similarity of each type and hence the structure of the aromatic hydrocarbons and naphthenes in the initial distillate.

82

I . A . MUSAYEVet

aL

Accordingly the 350°-540°C distillate contains mono-, bi-, tri-, tetra- and pentacyclic naphthenes (cyclanes), which incorporate (in addition to monocyclic hydrocarbons) condensed systems of cyclohexane and cyclopentane rings with alkyl substituents (normal and branched), including isoprenane substituents (Tables 3 and 5). SUMMARY

1. The hydrocarbon composition of a West Siberian distillate b.p. 350-540~'C, was examined. 2. The fraction contains normal paraffins (C~8-C4o), 74% of which fell in the carbon number range (C2~-C3o). 3. Aromatic hydrocarbons in the 350°-540°C distillate, containing 1--4 benzene rings, were determined. Hydrocarbons containing one benzene ring are present in the highest concentration (about 60%), they contain both normal and branched alkyl groups, the latter include those with methyl groups in different positions as well as those with an isoprenoid structure. 4. Naphthenes f r o m the distillate were dehydrogenated to aromatic hydrocarbons which were analysed. These aromatic hydrocarbons from the initial fraction were structurally similar to those obtained by dehydrogenation of known naphthenes. There is apparently a relationship between petroleum naphthenes and aromatics, which has to be confirmed in other crude oils. 5. The 350°-540°C fraction contains cylanes with I-5 rings, these include systems with condensed cyclohexane and cyclopentane rings. The alkyl substituents are of both normal and branched structure and include those with and isoprenoid structure. REFERENCES

1. A. V. TOPCHIYEV, L. M. ROZENBERG, Ye. M. TERENT'YEVA and N. A. NECHITAILO, In: Sostav i svoistva vysokomolekulyarnoi ¢hasti nefti, p. 208, Izd. AN SSSR, Moscow, 1958 2. J. V. BRUNNOCK, Analyt. Chem. 38, 12, 1648, 1966 3. A. A. POLYAKOVA, Molekulyarnyi mass-spektral'nyi analiz neftei, p. 180, Nedra, Moscow, 1973 4. M. B. SMIRNOV and A. M. KRAPIVIN, In: Metody issledovaniya sostava organicheskikh soyedinenii neftei i bitumoidov (Methods of Investigating the Composition of Organic Compounds of Petroleum and Bitumoids), Nauka, Moscow, 1985 5. S. R, SERGIYENKO and Ye, V. LEBEDEV, Izbiratel'naya kataliticheskaya degidrogenizatsiya vysokomolekulyarnykh uglevodorodov, p. 73, Izd. AN TSSR, Ashkhabad, 1961 6. 1. A. MUSAYEV and G. D. HAL'PERN, Dokl. AN SSSP 88, 1, 71, 1953