CS260563B1 - Method of pure aromatic hydrocarbons production from catalytic reforming's product - Google Patents

Abstract

The solution describes the technological procedure production of pure aromatic hydrocarbons from the catalytic reforming product aromatic extraction, in which it is not circulated whole aromatic extract, but only distilled water-free and decomposed toluene diethylene glycol products. manufactured technical xylene is obtained only by rectification.

Description

The invention relates to a process for producing pure aromatic hydrocarbons from a catalytic reforming product after extraction with diethylene glycol. The aromatic extract obtained is dehydrated by distillation, only toluene is percolated and the mixture of C8-aromatics is separated from the impurities by distillation by rectification.

Aromatic hydrocarbons esp. C _? and _Cg monocyclic types are permanently basic raw material for a variety of organic syntheses. Their main source is the product of catalytic reforming of naphtha. This product contains 60 to 75 wt. aromatics predominantly C _? and Cg types and from non-aromatics are usually separated by extraction. A common solvent is diethylene glycol and the extract obtained therefrom is redistilled to pure aromatics after percolation on active clay. to toluene and C8 aromatics. The aromatic extract contains water, dissolved and apparent, and diethylene glycol residues that decompose at 160 ° C to organic acids, aldehydes and resinous substances. Percolating natural clay rapidly loses its activity because it is deactivated by water, resins and unsaturated hydrocarbons. They have to work at high temperature, ie at high energy consumption. Its service life is limited and the quality of the animals deteriorates. for toluene, less for C8-aromatics.

The process according to the invention solves the problem of production of aromatics from diethylene glycol extract. Aromatic extract containing C? to C18 g of aromatic hydrocarbons contaminated with olefins, diethylene glycol residues and water are first de-watered, the residue is distilled to toluene distillate, which is transferred at 20 to 250 ° C through natural clay under a pressure of 0.2 to 1.5 MPa, the residue It is then redistilled to technical xylene and another C8 to C18 alkylaromate residue without percolation. The toluene percolation is preferably carried out at temperatures of 30 to 120 ° C with a toluene to clay volume ratio of 0.2 to 1: 1 per hour. For the redistillation of the toluene residue, the preferred distillate is 0.001 to 0.01 volumes of C8 aromatics per volume of C8 aromatics present, and technical xylene containing ethylbenzene and a mixture of dimethylbenzenes are removed from the 1 to 5 distillation tray.

The description of the process shows that only pure toluene free of water and decomposition products of diethylene glycol is subjected to percolation under very mild conditions. Technical xylene is not perfused and its purity corresponds to the norm. At the same time, the percolation clay reduces the throughput and thus improves the removal of the polymerizable substances at low temperatures. In the case of passing a higher concentration of olefinic impurities into the column in which xylenes are obtained), a small amount of distillate containing these impurities is preferably discharged from the top of the column. This distillate may be returned to the extracting feedstock or discharged for other uses where the olefins did not wither.

In the example below, the results of the operational testing of the process according to the invention are shown.

Example

To produce C ₇ and C 8 aromatics from the catalytic reformate, its fraction 100-160 ° C was extracted with diethylene glycol at 145 ° C to give an aromatic extract containing C? to C 18 g aromatics.

In the conventional procedure, the aromatic extract was fed to a percolation reactor filled with finely grained natural clay at temperatures between 125-190 ° C and under a pressure of 1.5 MPa at a volumetric rate of 2-3 h ^-1 . The percolate is featured successively in 3 columns in which are successively separated: water with a little toluene, toluene, xylene and what technical residue Cg to C _1Q aromatics. The temperature on the percolating clay increased to a maximum as a result of the loss of activity, and the clay had to be replaced or subjected to steam regeneration after 1000 to 1500 hours. Table 1 lists the product qualities. A measure of the purity of aromatic hydrocarbons is the sulfuric acid test, the layer of which is colored after shaking with the product and the color intensity is compared to the scale modeled by the chemical solutions of the animal. chromium, iron and cobalt compounds.

The same table gives the process data according to the invention. This was accomplished by passing the extract directly into a water removal column with a small amount of toluene, and the pure toluene collected from the second column was passed to a percolation reactor at 50-60 ° C. There he was contacted with fine-grained natural clay under a pressure of 0.35 MPa at a volumetric rate of 0.5 to 1 h ^-1 . There was no decrease in clay activity over 2,000 hours. Technical xylene obtained without percolation by distillation of the residue from the second toluene column complied with the quality requirements of the standard. By correcting the process according to the invention, the water separated in the 1 column was not of an acidic corrosive character and the distillation residue after xylene was not darkly colored with the resinous decomposition products of diethylene glycol.

Table

Comparison of processes for production of pure aromatics common according to the invention standard

extract t / h 10 10 - water from 1 column pH 3 to 5 7 to 7.5 - toluene X) coloration with H ₂ SO ₄ 0 to 3 ^xx) 0 to 1 max. xylene staining with H 2 SO 4 2 to 4 4 to 5 max Cg + C _1Q aromatics color Brown yellowish - percolation temperature ° C beginning 125 55 after 1000 hours 190 65 x 1 the scale is 0 to 6, 0 is the best (ASTM-D 848-62)

at the beginning and end of the cycle

Claims (4)

SUBJECT OF THE INVENTION Process for the production of pure aromatic hydrocarbons from a product of catalytic reforming of gasoline after extraction with diethylene glycol, characterized in that the aromatic extract containing C? aromatic hydrocarbons, especially C? monocyclic alkylbenzenes, frees water by distillation, the residue is distilled to toluene distillate, which is transferred at 20 to 250 ° C through natural clay under a pressure of 0.2 to 1.5 MPa, then the residue is redistilled to technical xylene and the residue containing Cg to C 1-6 alkylaromates. 2. Process according to claim 1, characterized in that the percolation is preferably carried out at temperatures of 30 to 120 [deg.] C. with a volume ratio of toluene to clay of 0.2 to 1: 1 per hour. 3. Process according to claim 1, characterized in that, in the redistillation of the toluene residue, preferably from 0.001 to 0.01 volumes of xylene per volume of C8 aromatics present and from 1 to 1 volume of xylene are removed. In the distillation tray, technical xylene containing ethylbenzene and a mixture of dimethylbenzenes is obtained.