CS252524B1 - Method of n-alkanes production - Google Patents

Abstract

n-Alkanes are produced by dewaxing boiling in the range of 200 to 450 ° C with n-alkanes content at least 20% wt. from the hydrocracking of petroleum substances boiling above 300 ° C (vacuum distillates, extracts and mixtures thereof).

Description

The invention relates to a process for the production of C 10 -C 50 n-alkanes, in particular C 1 -C 18 n-alkanes, by dewaxing fractions of low aromatic, non-traditional hydrocarbon feedstocks with only a low sulfur and nitrogen content. Then, unlike a similar petroleum fraction, it does not require pre-refining prior to use in the manufacture or recovery of n-alkanes by adsorption processes.

Much attention has already been paid to the hydrogenolysis of hydrocarbons (Brcoks CT: Ing. Eng. Chem. Tundam 6, 236 (1967); CA 68, 23263 f; Kohloefl K., Bazant V .: J. Catal. 10, 140 (1968)) Sinfelt: Catal. Rev. 3, No 2, 175 (1969), Eiichii Kikuchi et al., J. Catal. 22, 226 (1971), Japanese Pat 7396477 (1973), CA 80, 95205 et al. ) on conventional hydrogenation catalysts, especially on precious metals (Pt, Rh, Ru, Pd), but also on nickel, cobalt, molybdenum, tungsten, uranium, chromium and iron, usually on acidic supports (alumina, aluminosilicates and others) but Conversely, however, the hydrogenolysis of the organic and hydrocarbon compounds of sulfur and nitrogen with the formation of the hydrocarbon and hydrogen sulfide and ammonia, respectively in the above-mentioned catalysts, has been studied quite carefully. metal on carriers, oxides or sulphides [V. Bri U.S. Pat. No. 1,311,473, Japanese Pat 76, 26686 (1976), Ozimek et al., Chem. Stosowne. 19, 97 (1975); Sotani: Rev. Phys. Chem. Jap. 48, 9 (1976); C.A. 86, 54697 b; Benson et al., Hydrocarbon Process 53, No 4, 81 (1974), paying attention also to the capture of hydrogen sulfide and ammonia from the hydrogenolysis gas fractions.

Also earlier is known [Cernožukov NI Technologija pererabotki nefti i gaza, 'part 3. Izdatefstvo' Khimija 'Moskva 1978; Ogorodnikov SK (ed.: Nephtechimics Episode 1 and 2. "Khimija" Leningrad (1978); Indian Pat. 152 240 (1983); Lactic et al.: Gaziva Maziva 22, No 5-6, 253 (1983) Ind. Eng. Chem Prod. Res., Dev., 23, 634 (1984); Isunaylov et al., Chim Technol. Butter No. 6, 32 (1984); US Pat. 4,455,444 et al. .] that petroleum fractions, most often petroleum fraction, diesel fuel fraction, or wider gas oil fraction, are used for dewaxing, either by the urea-reduction process or by 5A molecular sieves (zeolites CaA, NaX, etc.). However, all of these feedstocks need to be more or less hydrotreated prior to deparaffinization, depending on process choice, limiting the content of sulfur, aromatics and unsaturated hydrocarbons, such as the adsorption process of n-alkane production. in the gas phase, which is relatively energy intensive, e.g. permissible in the feed max. 0.2 wt.% of sulfur and nitrogen 2.ÍO ^4%, but the energy-efficient and more preferred process the liquid phase is the maximum. 2.10 ^-4 sulfur and 1.. ⁴ 10% N, which in all variations have minimal aromatic content.

Hydrocracking is also well known to be mainly used to produce supplementary amounts of light petroleum products by catalytic decomposition of a heavier feedstock in the presence of hydrogen. Further, there are numerous modifications of hydrocracking production units. Depending on the raw material and products being manufactured, they employ single-stage and two-stage processes with stationary catalyst layers, both fluidized and suspended catalysts. The one-stage variant is usually used when the hydrocracking is mainly diesel fuels and two-stage to obtain lighter products.

Its products are, in addition to hydrogen sulphide and ammonia, which are carefully removed from the recirculation gas, the gases C1-C4,1'light gasoline, which has an isoalkanic character and therefore a high octane number (OCM = 82-84). The naphtha usually has a high content of cycloparaffinic hydrocarbons and therefore is also an excellent feedstock for the catalytic reforming of gasolines, which yields a reformate with aromatics above 70%. It is also well known about kerosene from hydrocracking. "Khimija", Leningrad (1978), Jurchacko; Oil and Coal 27, 69 (1985); jap. pat. 60 08392 (1985 j), which is low in aromatics and virtually free of sulfur and alkenes, and similar gas oil has low sulfur content and reduced aromatics content, as well as attention paid to hydrocracking catalysts [Gofdfarb et al. 25, 370 (1984), Strobel et al., Proc Int Conf Conf Coal Sci 1983, 216, J. Catal. 22, 226 (1971); 31, 264 (1973); (1973); CA 80, 95205 [mu]], but the investigation of the n-alkane content of the individual product fractions remained out of focus depending on the conditions and other parameters of hydrocracking of the petroleum fractions.

However, according to the present invention, the process for producing n-alkanes by dewaxing such as selective adsorption on molecular sieves followed by desorption or urea via intermediate n-alkane-urea adducts is such that the starting material for dewaxing is a boiling range of 200 ° C to 200 ° C. 450 ^C with a n-alkane content of at least 20% by weight, from the hydrocracking product of an oil fraction boiling above 300 ° C and / or extracts of selective oil and / or slack refining.

The advantage of using petroleum fraction hydrocracking products according to the present invention, based on the surprising finding that hydrocracking of petroleum fractions, especially vacuum distillates, results in significantly higher n-alkane content than in similar petroleum fractions and, in addition, low aro252524 m-content. particularly low sulfur content. In contrast, the lower boiling fractions from hydrocracking have a higher content of isoalkanes and cyclohexanes than similar petroleum fractions. This is related to the lower strength of the C-C and C-H bonds at the isoalkane branching sites and the alkyl bonding to the rings due to the inducing effect of the alkyl groups. At these sites, the hydrocarbon molecules occur to a greater extent. their catalytic-thermopiopia, including hydrogenolysis. This also allows the medium and higher hydrocracking fractions to be used immediately for the production of n-alkanes, to increase the performance of the n-alkane production equipment, but also to further lower the freezing point and thus the quality of the odorantized hydrocracking fraction.

The petroleum fraction is the primary and vacuum gas oil, the vacuum oil distillate, especially the vacuum distillate from paraffinic oil or sulfur-paraffinic oil, as well as petroleum.

According to the present invention, the products of the pre-physicochemical crude oil processing are oil refining extracts, slacks, heavy oils from the asphalting of residual petroleum fractions, gas oils and heavy distillates from thermal cracking and thermal coking products. The space velocity of hydrocracking depends on the quality of the hydrocracking feed, the hydrogen partial pressure reaction temperature, the type and activity of the catalyst, and the desired depth of hydrocracking of the hydrocarbon feedstocks. It is possible to work at temperatures of 290 to 500 ° C, but usually in the range of 380 to 430 ° C is most suitable.

Hydrocracking catalysts are most often based on metals or compounds VI. and VIII. groups of the periodic system of elements, generally on acidic supports such as alumina, aluminosilicates naturally, but in particular synthetic, other oxides: aluminum, silica, titanium and zirconium. The metal compounds are most often in the form of oxides and in particular sulfides. Of the metals (and their compounds), the most important are nickel, cobalt, molybdenum, tungsten, uranium, chromium, platinum and palladium. Less effective but useful is iron and its compounds. Relatively high-performance but technically economically feasible are precious metals: platinum, palladium, ruthenium, rhenium and radium.

The content of the individual metal or more metals in the hydrocracking catalyst is in the range of 0.2 to 35% by weight. The more refined the metal component is, the less is sufficient in the catalyst. For the most common catalysts such as molybdenum, iron, cobalt and nickel oxides or sulphides on supports containing alumina, silica, titanium dioxide and zirconium dioxide, for example, about 2.5% CoO, 8% MoO3, 15% S1O2 and about 75% Al 2 O 3. Then 6% Ni and 15% W in the form of oxides or sulphides on the aluminosilicate; oxides or sulfides of Ni or Co, W and Mo in a total amount of 16% on the crystalline alumosilicate and the like.

Other known effective hydrocracking catalysts may also be applied. To a lesser extent, catalysts may also contain additives of other elements.

Hydrocracking also deprives sulfur, nitrogen in hydrogen sulphide and ammonia, as well as other impurities such as phosphorus and the like. They are most often removed by scrubbing recirculated hydrogen. For the production of n-alkanes can be used a number of fractions of the hydrocracking product, but in terms of the content of n-alkanes, and the conventional equipment, the most suitable telephone frakciao 200-360 DEG C., or 200-340 ^C C. From the fraction of higher than 360 ° C the n-alkanes can be removed primarily by urea dewaxing.

Further characteristics as well as other advantages of the production method according to the invention are evident from the examples.

Example 1

Vacuum petroleum distillate from sulfur-paraffinic oil is fed to continuous hydrocracking on a nickel-molybdenum catalyst (containing Ni + Mo = 18.3% by weight) on an amorphous aluminosilicate carrier carried out at a space velocity of 1.3 h ^-1 , temperature 415 + 5. ° C in the presence of hydrogen at a pressure of 14.5 MPa. The crude product obtained from the hydrocracking reactor (after deduction of hydrogen) contains 0.12% ammonia; 2.11% hydrogen sulfide; 0.40% C1-C gases; 6.65% propane / butane / isobutane mixture; 13.01% 50.25% naphtha, 10.25% kerosene and 17.08% gas oil The crude product, its individual components are recovered Ammonia, hydrogen sulfide as well as Cl-Ca gases are separated from the recirculated gas (hydrogen) ), then a mixture of C3-Cr hydrocarbons is separated and distilled, by rectification of another hydrocarbon fraction, to isolate the fraction having a boiling point of 200-360 ° C, which has the following properties: pour point = -7 ° C, density at 20 ° C 781.2 kg.m ^3, an average molar weight - 232,4 g.mol ^-1, sulfur content = - 10.1 ~ ⁴ ° / o by weight of n-.; alkanes -C Cu - 66.4%; 6.2% of aromatics, the rest being isoalkanes and cycloalkanes.

The content of n-alkanes is determined by known methods [Anal. Chem. 34, 82 (1962); Nelson Κ. H., Grimes M. D., Heinrich B. J .: Anal. Chem. 29, 1026 (1957)], in addition combined with liquid-gas chromatography to determine the distribution of individual n-alkanes in fractions. The principle of the method is based on adsorption of n-alkanes dissolved in isooctane, used (added to the sample) as a solvent, on a tableted molecular sieve 5A for 4 h of reflux. The sutures are filtered off, the solvent is evaporated, the residue consisting of branched paraffins is weighed. The content of n-alkanes in the sample is given by the weight difference between the unadsorbed residue and the original sample.

Similar but less accurate results are obtained by methods based on the formation of crystalline adducts of n-alkanes with urea [Domask, Kobl .: Petroleum Ref. 34, no. 4, 128 (1955); Zimmerschield et al., Ind. Chem. EUG. 42, 1300 (1950); Schliessler, Flitter, J. Am. Chem. Soc. 74, 1720 (1952)]. However, these methods are useful for determining even higher n-alkanes (above C24).

The distillation residue, ie the hydrocarbon mixture above 360 ° C, has a mean molar. weight 402.8 grams. mol ^-1 .

The fraction thus obtained, m.p. in. 200-360 ° C is used to produce or recover n-alkanes by dewaxing in the liquid) phase on molecular sieves (processes: Molex, Parex) instead of the petroleum hydrogenated fraction of m.p. in. 200-360 ° C, obtained from a similar West Siberian sulfur-paraffinic oil containing 28.3% n-alkanes, 25.3% aromatics and 0.04% sulfur by weight. In addition, due to the high content of sulfur and its compounds, as well as aromatics, prior to dewaxing in the liquid phase, it is necessary to hydrotreat.

Example 2

Vacuum petroleum distillate from West Siberian sulfur-paraffinic petroleum is fed to continuous hydrocracking on a sulphide-nickel-molybdenum-tungsten aluminosilicate catalyst containing metal constituents

21.3 wt. at a space velocity of 1.5 hours ¹ , a temperature of 395 + 5 ° C in a hydrogen atmosphere at a pressure of 15 MPa.

The crude product obtained from the hydrocracking reactor contained 0.12% ammonia after deduction of hydrogen; 2.11% hydrogen sulfide; 0.31% of C1-C2 gases; 3.00% change of propane with n-butane and isobutane; 5.69 percent 1'light naphtha; 23.85% naphtha; 25.34% kerosene and 39.66% gas oil.

In addition to the removal of ammonia, hydrogen sulphide, the isolation of methane, ethane, the propane-butane fraction, which can also be used as a valuable pyrolysis feed, in particular after separation of isobutane, 1'-light naphtha having isoalkanic character and octane number by research method 83, The naphtha fraction, having a catalytic reforming at 508 DEG C. of 73% aromatics and having an octane number as determined by Research Method 101, is further isolated from a boiling point of 200-360 ^c / 101 kPa having a mole. weight 233 g. mol ^-1 ; pour point —8 ° C; sulfur content = 1.4.10 ^-4 % by weight; content of n-alkanes 52.6%, aromatics 7.2%, the remainder being isoalkanes and cycloalkanes.

This fraction is directly led to the production or recovery of n-alkanes by means of molecular sieves - CaA or NaX zeolites as adsorbents and a mixture of n-alkanes Cg-CÝ as desorbent and ammonia (temperature 320 ± 5 ° C, pressure 0.17 MPa) wherein the yield of n-alkanes is 91%.

The distillation residue from the hydrocracking product, i.e. boiling point above 360 ° C / 101 kPa, has a mean mol. weight 404 g. mol ^-1 ; density at 20 ° C = 860 kg. m ^-3 ; sulfur content = 1.8.10 ^-4 %; elemental analysis: C = 85.51%, H = 14.15%; alkanocycloalkanes = 96.4% by weight: monoaromatics = 1.5% by weight; di- and triaromates = 0.43% by weight; % resin and residue = 0.5 wt.

Claims (1)

SUBJECT Process for the production of n-alkanes by dewaxing, such as by selective adsorption on molecular sieves followed by desorption or urea via intermediate adducts of n-alkanes with urea, characterized in that the starting material for dewaxing BACKGROUND OF THE INVENTION is a fraction boiling in the range of 200 ° C to 450 ° C, containing at least 20% by weight of n-alkanes, from the hydrocracking product of the petroleum fraction boiling above 300 ° C and / or selective oil refining extracts and / or Slack.