CS241948B1 - Process for obtaining pure C7, CR or C8 aromatic hydrocarbons from the catalytic reformate - Google Patents

Abstract

The solution is a method of obtaining pure aromatic hydrocarbons C7 and C8, or Co, from catalytic reformate after extraction with diethylene glycol using percolation on activated clay and redistillation of the aromatic mixture with separation of part of the olefin impurities by fractionation and part by adsorption and polymerization under mild conditions.

Description

The invention relates to a process for obtaining pure aromatic hydrocarbons Ογ and Cg, respectively. Cg from the catalytic reformate after extraction with diethylene glycol using percolation on active clay and redistillation of the aromatic mixture with separation of part of the olefinic impurities by fractionation and part by adsorption and polymerization. under mild conditions ·

The catalytic reformate is now the main source of the aromatic hydrocarbons of toluene and C8 aromatics and possibly C8 aromatics. Benzene is already produced mainly by other processes, esp. by dealkylation and / or disproportionation of higher aromatics. The catalytic reformate contains aromatics of ^C 6 ^-C 10 and the same types of alkane hydrocarbons and a small amount of olefins. When extracting aromatics with selective solvents, some olefins get into the aroma mixture, which are more polar and contaminate the produced aromas. percolation on active natural clay at elevated temperature. The first procedure requires a pressurized hydrogenation apparatus, and there is always the risk of reformate rehydrogenation and loss of aromatics. The second process, usually in the liquid phase at about 19 ° C to 200 ° C, is simpler, but for the reformate feedstocks the percolation clay life is low; acids corroding subsequent distillation, devices where ixolují aromatics, benzene, _Q .O C _Ol -aromáty and aromatics.

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241 948

The invention provides an improvement in the isolation of pure aromatics with a reduced concentration of olefinic impurities passed from the reformate into an aromatic hydrocarbon extract obtained by diethylene glycol. The aromatic extract with a bromine index of 20 to 150 mg Br / 100 g is passed directly to three times. 10 to 40-tier stacked columns and 0.1 to 5 wt. distillates together or separately outside the production of pure flavorings. Pure aromatics C _? and Cg and e withdraw from the second to sixth floors of the second and third columns. Alternatively, the extract can be passed through said redistillation at percolation at fine temperatures of 80 to 200 ° C under a pressure of 0.5 to 2.0 MPa at a volumetric rate of 0.2 to 2.0 volumes per clay volume per hour. In the redistillation process, the aromatics are removed from at least a portion of the distillate from the first column in series. The distillates are preferably fed to the thermal or catalytic dealkylation of benzene, optionally to aromatic solvents or db, respectively. The aromatic percolation is included only periodically when the bromine index of the extract exceeds 35 to 50 mg Br / 100 g, respectively. the extract is percolated permanently and the temperature in the reactor is controlled between 80 and 200 ° C and the bromine index of the percolated extract is between 20 and 100 mg Br / 100 g.

From the above description of the invention there are new features over the conventional process in which the aromatic isolation columns are totally refluxed and the percolation is conducted at a maximum temperature of about 200 ° C to obtain salable products distillated from olefins. In the process of the present invention, the first column serves to separate most of the olefins that contaminate toluene. Its quality is very strictly monitored by the so-called HgSO ^ test, when shaking with ktoc. a yellow color develops compared to the standard of KgCrO2 solutions. This allows percolation to be performed at lower temperatures, preferably by maintaining the limit value of the H 2 SO 4 test during production. This is in contrast to the usual way in which percolation gets rid of all olefins initially and the clay must be replaced when the percolation product limits are reached. It is obvious from the new

The advantages of saving clay and reducing energy requirements result from the 3 241 948 process. Last but not least, the corrosion of the product also decreases, and some glycol residues do not decompose.

In the example below, all the advantages of the procedure are documented.

Example

In the aromatic production plant, 50% of the raffinate with a Br-index of about 3000 and 50% of an aromatic extract, whose Br-index varied between 50 to 150 mg Br / 100 g, was obtained by extracting the reformate with a bromine index of about 1500. 4 times more intense coloration of toluene produced than all reformate olefins when reacted with 9 # hf HgSO4.

In conventional production, the extract contains a target®; 3% benzene,

30-40% toluene, 30or40% %θ-aromatics and the remainder of 0θ ₊ aromatics led to percolation at 180 ° -19 ° C, where initially all olefins (up to 5mg / Br / 100g) were stripped at a volumetric rate of 2.0h ". and with gradual aging min. 20 <e30%, when already produced toluene was at the limits of standard (35 mg Br / 100 g and color with HgSO4)

2-3). Redistillation of the aromatics in the three columns was controlled so that the distillates were totally refluxed and benzene, toluene and Οθ-aromatics were removed from 4 »plates. Benzene circulated back into the raw material and only periodically withdrawn into production.

With the introduction of the invention, the arrangement has changed: the temperature of the percolation has been reduced to 140 ° C, and the head of column 1 has been discharged 1a. a distillate containing 20 to 90% benzene and 90 to 20% toluene having a Br index of three to five times the percolation product. The table compares the data for both procedures.

It can be seen that by removing the olefins, the olefin content in toluene was kept up to three times lower than in the conventional process, energy savings were achieved in heating and the lifetime of the percolating clay was extended to more than double.

- 4 Table

241 948

Comparison of the normal process of producing pure aromatics C? and reformθ of the reformate and method of the invention.

way • V »in z ordinary according to the invention percolation cycle start end cycle start cycle end cycle temperature ° C ’190 190 130 180 clock 50 650 <k700 0a £ -5O 1800bž2000 extract-Br.index 50 50 50 50 percolate- 5 25 40 40 toluene-Br.index 6 30 13 25 HgSO4 -test 0 2 1 2 xylenes-Br.index 8 35 15 Dec 20 May HgSC1 -test 1 4 7 c.2 2 3

Claims (5)

SUBJECT OF THE INVENTION 241 948 1 · Method of obtaining pure aromatic hydrocarbons C? and G _g , respectively C, from the catalytic reformate by a combination of the extraction of the aromatic fraction with diethylene glycol, respectively. percolation on active clay and redistillation, characterized in that the aromatic extract with a bromine index of 20 to 150 mg Br / 100 g is fed directly into three successive columns of about 10 to 40 trays and 0.1 to 5% is removed from the column heads hm. distillates together or separately outside the production of flavorings and pure C? and Οθ aromatics are removed from 2 · ax6. of the second and third columns or the extract before the said redistillation is conducted for percolation with fine-grained natural clay at temperatures of 80 to 200 ° C under a pressure of 0.5 to 2.0 MPa and a volume rate of 0.2 to 2.0 volumes per clay volume hour. 2 ·. 3. The process of claim 1 wherein the distillates are removed from the aromatic at least from the first column in series. 3. Process according to claim 2, characterized in that the distillates are preferably fed to the dealkylation of benzene, thermic or catalytic, optionally into aromatic solvents, or into petrol. 4. A process according to claim 4, wherein percolation is periodically incorporated into the process by transgressing the bromine index of the extract to 35 to 50 mg Br / 100 g. Fifth method of claim 1 £ _R 3, characterized in that the extract is percolated continuously and the temperature in the reactor is controlled in the range of 80-200 ° C and a bromine index percolated extract between 20 and 100 mg of Br / 100 g.