DE1645728B2 - PROCESS FOR PREPARING A HEAVY AROMATIC SOLVENT - Google Patents

Description

3. A method according to any one of claims 1 or 2. 2c characterized in that the catalytically hydrofined iiedende 177-288 ° C fraction at temperatures between 26C and 427 ⁰ C.

4. The method according to any one of claims 1 to 3, characterized in that the softened tar is subjected to a destructive distillation in order to obtain this fraction boiling ^{between 177 and 288 ° C.}

The invention relates to a method for producing a heavy aromatic solvent having improved odor and solution virtue II by cracking of a hydrocarbon oil with steam and fractionation of the mixture thus obtained, which is characterized in that the Kohlenwasterstofföl to form an above 260 ⁰ C boiling " aromatic tar with steam cracks this aromatic tar softens at temperatures between 371 and 38 ° C, the softened tar is fractionated and a fraction boiling between 177 and 288 ° C is obtained, which is treated catalytically hydrogenating.

Aromatic hydrocarbon fractions with a boiling range between 177 and 288 ³ C are used as solvents for insecticides, such as. B. Chlorophenotane Aldrin and Dieldrin.

Gas oil fractions obtained from steam-cracked products can optionally be used as heavy aromatic solvents. Be used. However, for many agricultural uses, the color, sulfur content, and smell of steam cracked gas oil leave much to be desired. Hydrofining treatment and fine distillation improve the color and sulfur content, but the odor remains unsatisfactory, presumably because of the olefins in (x> the heavy feed, which are difficult to hydrogenate with cobalt-molybda catalysts.

From CA-PS 6 27 307 the use of tars, which by carbonizing at relatively low temperatures (below about 704 ⁰ C) of hard coal was. (> 5 lignite and the like have been obtained, for the production of electrode coke and refined liquid hydrocarbons that can be used as solvents superatmospheric pressure for its conversion into coke, gaseous products and phenolic oil and middle oil containing condensable oils thermally decomposed, whereby a part of condensable hydrocarbons mixed with a certain amount of the residue is returned to the stage before the thermal decomposition. The phenolic constituents are extracted, and the middle oil is at a temperature of 425 to 620 ^c C.

hydrofined.

In contrast, the Dean-claimed process, which starts from another tar, namely an aromatic tar which comprises products containing heteroatoms, as the starting material is characterized by its simplicity, with substantially lower hydrofining temperatures being used .

According to the invention, an overhead product from the distillation of tar is treated after the aromatic Tar has been thermally softened or destructively distilled. During this process, the most olefins and other impurities are thermally cracked and with the lowest boiling point Removed material, resulting in considerable staining and Odor improvement leads. The heart fraction obtained in this way, boiling between 77 and 288 ° C Top product is catalytically hydrogenated, z. B. hydrofined; it can then if necessary be finely fractionated. In some cases the hydrofining product does not require fine fractionation. However a fine fractionation is used to achieve good color and residue fractionation Vacuum to about 90% overhead is preferred. with most of the color bodies remaining in the swamp.

The aromatic tar feed required to produce the solvent can be obtained by cracking a gas oil or a gas oil-heavy gasoline mixture with steam. So far, this tar has only been viewed as a waste product and has only been used as a dark resin of inferior quality or, more often, as bunker heating oil. Cracking with steam is a very well-known process and consists in the fact that a gas oil with an initial ^{boiling point between 204 and 274 0} C and an end boiling point between 400 and 440 ⁰ C in the presence of 60 to 85 mol% steam in a furnace located, externally heated coiled pipes cracks, whereby the temperature of the feed stream is kept at 650 to 788 ° C at the exit of the coil from the furnace and immediately quenched with an oil that has a boiling range between 260 and 357 ° C, namely to a temperature of 282 to 293 ° C. The gas oil feed has a density of 0.935 to 0.905, a molecular weight of 210 to 270, 10 to 15 weight percent aromatic rings, and 30 to 40 weight percent naphthenic rings.

The gaseous, steam-cracked products containing hydrogen, saturated hydrocarbons, Olefins and diolefins containing are taken overhead, and the liquid hydrocarbons are fractionated to produce an aromatic gasoline that boils between 38 and 238 ° C and a higher temperature to separate the aromatic fraction boiling between 188 and 299 ° C and partly in the quenching zone the steam cracking plant can be returned. The amount of residual aromatic tar obtained is 5 to 25 volume percent of the feed and has one

Initial boiling point of 260-316 ^C C and a 50% boiling point 371-427 ° C

The aromatic tar obtained in this way is then _{softened at a temperature between 371 and 538 ° C 1,} preferably between 427 and 482 ° C. The pressure can vary between 104 and 21.1 atmospheres, with 14.1 atmospheres being preferred. The space velocity of the feed depends on the size of the system. For a continuous pilot plant with a ^{capacity of 700 cm 3} , a room flow rate of the feed between Op and 8.9 vol / vol / hour. (VoI liquid charge / VoL reactor space / hour) Satisfactory. The softening time can range from a few minutes to 5 hours, depending on the temperature, with 2 hours being preferred in the Teinperaturbereico of 427 to 482 ° C.

After softening, the tar is fractionated. The fractionation can take place under vacuum or under atmospheric pressure . The latter is applied, then specifies a maximum or a tar nut Endiemperaiur 371-482 "C, preferably w ith 454-460" C. before. In general, fractionation is carried out at atmospheric pressure, but pressures from 0.5 to 2.1 atmospheres can be used if desired; in this case a hydrocarbon overhead stream and tar pitch with a softening point of 38 to 204 ^° C. is obtained as the bottom. The vapors are condensed and a fraction boiling between 177 and 288C is recovered. This distillate is sent to a hydrofining plant.

Another Frakiionierungsme: hode to obtain this 177-288'C fraction consists in the destructive distillation of the aromatic tar obtained from the steam cracking. The destructive distillation w ill in the absence of air at a Kessehemperatur performed, which is between ambient temperature and 482 ^C C progresses distillation, wherein a boiler temperature from 454 to 469 "C when working at atmospheric pressure preferred as the final temperature.

In each case, the 177-288 ¹ C fraction is then passed to a hydrofining plant. In this the temperatures can be in the range above. 260 to 427 ^s C, a temperature of 33O ~ C preferably being used. The applied pressure is 7.03 to 211 atm. preferably between 14.1 and 70.3 atm. Depending on the operating conditions, the space flow velocity of the feed can be between \ and 3 vol. Liquid oil / vol. Catalyst hours lie. The hydrogen is used in an amount of 8.9 to '7.SmVhI charge.

The Hydrofinie besteh ^r ungskatalysator; made of cobalt oxide and molybdenum oxide. which may be cobalt molybdate combined on a solid carrier and available in the hand. The carrier can be selected from a variety of materials such as adsorbent clay, bauxite, silica gel, clay, and alumina activated with hydrofluoric acid, as are commonly used eck be used for this Zw The carrier as particularly preferred material is:... However, alumina The catalyst contains preferably from 2 to 5 wt .-% of cobalt oxide and 8 to 15 wt molybdenum 3.6 wt ⁰ O ¹ ^ Kobahoxid and 12.5 wt% molybdenum oxide have been found to be particularly effective.

The catalyst may be in the inventive method & en, as fixed. Apply fluidized bed or moving bed catalyst.

Example

In a specific embodiment of the invention, a hydrofined distillate was produced from thermally softened aromatic tar. The tar was obtained as a residue of cracking products which, when cracking with steam, made a charge of gas oil and heavy gasoline in a weight ratio of 60: 4Ci at the temperatures and at a 40-43% conversion to C3 and lighter products. The tar had the following characteristics:

Analysis of the tar

ASTM Destilla non CC)

1.045 Beginning 300 } 60 ^D C 5% 324 213 \ '·} 336 90.4 20th 358 6.8 30th 375 2.0 • Ό 38S 0.0i 50

density

Flash point
viscosity
(Saybolt Universal
Sec'iprin at 99 ^; C)
0'fa by weight of carbon
% By weight hydrogen
% Sulfur by weight
Wt% ash
% By weight, c asphaltenes

The operating conditions were as kiigt:
Steam cracking conditions:

Temperature of
Feed stream on
Exit of the coiled tube from the furnace
Dwell time
Inlet pressure

Product yield. Weight ^{- 0} : -:

782'- C. e; w; i 3 sec. 5.62 ti ν Ii 25-27 20-21 14.5 13th ! 3

Ethylene

Propylene

Butylene \

Butadiene j

C _{5 to} 93'-C

93 to 204 "C

Full% tar 7 - Ί ί

The tar was then at a temperature before. 454 ^: C with a space velocity; of loading of! .0 volume of cold liquid loading volume of reactor space hours thermally softening .. The pressure was kept at 14.1 atm. The softened product was then be; 'Ci mm a? between 221 and 282 C sic-dendes. Des-.üia :: akiion; he :. The mineral distillate was hydrogenated in the presence of a cobalt molybdenum catalyst.

The hydrofin-erer: was done at a Tc-mivjrat'jr \ on 33O ¹ C and a pressure of; 7.6 atmospheres. The spatial flow velocity of the Bf-c. ^ Kurig be- '. Rug 0.5 \' oi. Vol. Hours, the Wasserstc.fimer.jc · 6.9 m ³ / h 'feed. Da ¹ - hydrofined Des ;; i'd: v. j'de 'a ^f rir; pioneer! or distilled. where em Dostsrai (up to ^ O \ 'cl.- ^: ·' ·. ·) with a boiling range

2Ί6 and

289 ^: C was obtained. This Destii! ;; ·. Was washed with! 5 ^{%! - 0} 'of a caustic soda solution from 20 trees in order to remove traces of hydrogen sulphide. derived from the hydrofimerization stage, and finally mi; about 3 volumes of water ·· volume of distillate washed.

The final distillate provides the improved, heavy aromatic solvent as desired froduki: of the method according to the invention and has the characteristics shown in the table. The solvent obtained according to the invention is thereby compared with a commercial product.

Tabel

Analysis of heavy, aromatic solvents

determination Trade Thermally softened Teerdesiillai usual aromatic difficult. hydrofined aromatic as such fraction petrol 0.965 density 0.935 0.985 93 Flash point ') ( ⁰ C) 66 1.0 % Sulfur by weight 0.25 1.74 1 B Corrosion, 30 min. At 100 ° C 1 B 22nd Color (Tag Robinson Scale) 18th 14- Va 2.3 Bromine number 2 2.5 4th Olefins no 100 + Kauri butanol value 100 + 19.4 "C Mixed aniline point ') 24.4 ° C -48.4 Pour point ( ⁰ C) -62.2 ASTM distillation ( ⁰ C) 216 Beginning 188 238 22; 5% 204 248 236 10 213 251 253 50 232 263 271 90 260 280 277 95 274 285 289 End point 288 293 ') Determined according to ASTM method D5b. with a same - ') Determined according to ASTM method D61I after mixing the sample Volume of n-heptane.

As can be seen from the table, tar treated according to the invention occurs even without fine distillation Improvements, the extent of which can be increased by fine distillation. Regarding of the solvency, the distillate or solvent obtained according to the invention is significantly better than the expensive commercial aromatic solvent. This is shown in the table by the lower mixed aniline point (19.4 instead of 24.4 ° C). That improved Solvent also has a better solvency for chlorophenotane at 23.3 ° C (40 instead of 35 g / ICO solution, dissolved at the saturation point). This is the most important criterion from the point of view of the insecticide producer. The higher solvency is based on the formation of condensed aromatic ring structures, which have a high dissolving power for insecticides. The distillate from the thermally softened Tar had a pour point 14 ° C higher, but both pour points are so low that the difference is is not essential.

In addition, the according to the invention was produced in an odor test carried out with 20 people Distillate or solvent rated better than the commercial solvent.

Claims (2)

Patent claims: 1. A method for hearing a heavy aromatic solvent with improved odor and solvent power by cracking a hydrocarbon oil with steam and fractionating the mixture obtained, characterized in that the hydrocarbon oil is cracked with steam to form an aromatic tar boiling above 260 'C ο aromatic tar at temperatures from 371 to 538 ⁰ C softens the softened tar fractionated and a boiling 177-288 ° C fraction which is recovered catalytically hydrogenating behandelu 2. The method according to claim 1, characterized that a gas oil is used as the hydrocarbon oil.