RU2203306C2 - Method of preparing feedstock for catalytic cracking and hydrocracking - Google Patents

Abstract

FIELD: petroleum processing. SUBSTANCE: catalytic cracking and hydrocracking feedstock is preliminarily purified to remove polycyclic aromatic hydrocarbons, heteroatom-containing compounds, and heavy metal compounds via liquid extraction of undesired impurities from vacuum gas oil (cracking process feedstock) with two immiscible solvents: polar N-methylpyrrolidone or dimethylacetamide containing 3% water (at 30-50 C) and nonpolar pentane or heptane at weight ratio of nonpolar solvent to feedstock (0.5-1):1. EFFECT: enhanced process efficiency and reduced losses of solvents with extract phase. 3 tbl, 3 ex

Description

 The invention relates to the refining industry and can be used in the purification of raw materials for hydrocracking and catalytic cracking from polycyclic aromatic hydrocarbons, heteroatomic compounds and compounds of heavy metals.

 The raw materials of hydrocracking and catalytic cracking processes are vacuum gas oils, which have rather stringent requirements for the content of polycycloarenes, heteroatomic compounds, and heavy metals. Their increased content in vacuum gas oils reduces the technical and economic indicators of cracking processes: it leads to increased coke formation, accelerated catalyst deactivation, a decrease in the degree of conversion of raw materials and the yield of gasoline fractions, and low quality of the resulting fuels [Ind. Eng. Chem. Res. 1998. V.37. N 12. R. 4637-4640].

 Known methods for cleaning vacuum gas oils in order to obtain lubricating oils, the operational properties of which also decrease with an increased content of polycyclic aromatic hydrocarbons and heteroatomic compounds, liquid extraction using selective solvents - furfural, phenol, N-methylpyrrolidone, dimethylformamide, dimethylacetamide, etc. [Kazakova L P., Crane S.E. Physico-chemical fundamentals of the production of petroleum oils. M .: Chemistry, 1978. - 320 p.]. The closest in technical essence and the achieved effect method of purification of oil fractions of oil with N-methylpyrrolidone.

 The main disadvantage of these methods is the insufficiently selective removal of undesirable components: in selective purification processes with the extract, up to 20 wt.% Of saturated hydrocarbons contained in the feed are lost.

 In order to increase the selectivity of the process of removing undesirable components from vacuum gas oils, it is proposed to carry out extraction with two solvents - polar and non-polar, with N-methylpyrrolidone or dimethylacetamide containing 3-5 wt. % water, and as non-polar - pentane or heptane containing 1 wt. % toluene. The latter mixture simulates the composition of the raffinate from a benzene and toluene extraction unit from reforming catalysts.

 In the table. Figure 1 shows the characteristic of vacuum gas oil, which is the feedstock for catalytic cracking and hydrocracking obtained from the AVT-6 primary oil distillation unit at Kirishinefteorgsintez PO.

 Selective purification of vacuum gas oil was carried out by countercurrent extraction with N-methylpyrrolidone and dimethylacetamide in the presence of nonpolar solvents (pentane and heptane) under the conditions shown in table. 2.

The results of extraction cleaning of vacuum gas oil according to the prototype and the proposed method are given in table. 3:
example 1 - according to the prototype (with N-methylpyrrolidone, without using a non-polar solvent),
example 2 - according to the proposed method (with N-methylpyrrolidone and non-polar displacing solvent pentane),
example 3 - according to the proposed method (with dimethylacetamide and non-polar displacing solvent heptane containing 1 wt.% toluene).

 As follows from the data given in table. 3, the use of pentane or heptane as a non-polar washing solvent, better soluble in N-methylpyrrolidone and dimethylacetamide compared to saturated hydrocarbons of the feed, reduces their losses with the extract phase. So, with a close concentration of aromatic hydrocarbons in the raffinate (experiments 1 and 3), the loss of saturated hydrocarbons with the extract phase decreases by more than 3 times - from 19.6 wt.% (Without pentane, according to the prototype) to 6.2 wt.% From amounts of these valuable components (for subsequent hydrocracking or catalytic cracking processes) in the feed.

 The extract obtained using the N-methylpyrrolidone-pentane extraction system is characterized by a higher content of aromatic compounds, as evidenced by the increased sulfonation content and aromaticity factor compared to extraction with one solvent, N-methylpyrrolidone without pentane (cf. examples 1 and 2 of the table . 3).

 With the addition of a washing non-polar solvent, the content of sulfur and nitrogen-containing compounds and heavy metals in the raffinate also decreases. The sulfur content in raw materials is reduced from 1.38 wt.% To 0.57-0.76% by the proposed method (according to the prototype to 0.97%); nitrogen - from 0.24% to 0.10-0.09% (prototype up to 0.16%).

 The proposed method allows you to more fully remove from raffinate - raw materials for catalytic cracking and hydrocracking - compounds of heavy metals: the degree of extraction of tungsten 75.6-77.6% (prototype 53.0%), vanadium - 66.7-71.9% (by prototype 50.9%), nickel - 70.3-72.0% (by prototype 62.4%), iron - 68.6-71.4% (by prototype - 56.2).

 Thus, the introduction of a non-polar washing solvent (pentane or heptane) leads to an increase in the selectivity of purification of vacuum gas oil from undesirable components.

 The extract can be used as a plasticizer of rubber compounds and polymer compositions, in particular, as a plasticizer petroleum PN-6Sh (oil softener for tire rubbers).

 Example 1 (prototype).

Vacuum gas oil (flow rate 100 g / h) is supplied at the bottom of a packed extraction column with an efficiency of 5 theoretical stages at 30 ^° C, and N-methylpyrrolidone with 5 wt.% Water (flow rate 500 g / h) is fed to the upper part. As a result of countercurrent extraction, after reaching a stable regime, the raffinate and extract phases are simultaneously selected.

 From the raffinate phase, N-methylpyrrolidone is washed with water, the hydrocarbon portion (raffinate) is analyzed. Received 58.0 g of raffinate containing 27.4 wt. % aromatic hydrocarbons, which can be used as high-quality raw materials for catalytic cracking and hydrocracking processes. The extract phase is fed to the regeneration of N-methylpyrrolidone by vacuum distillation. The bottom residue of the vacuum column (extract) is washed with water and analyzed. The extract (42.0 g) contains 82.5% sulfonated compounds.

 Example 2

Vacuum gas oil (flow rate 100 g / h) and pentane (100 g / h) are supplied at the bottom of the packed extraction column with an efficiency of 5 theoretical stages at 30 ^° С, and N-methylpyrrolidone with 3 wt.% Water (flow rate 500) is fed to the upper part g / h). As a result of countercurrent extraction, after reaching a stable regime, the raffinate and extract phases are simultaneously selected.

 Pentane is distilled off from the raffinate phase on a distillation column (20 theor. Plates), then N-methylpyrrolidone is vacuum. The bottom residue — the hydrocarbon portion (raffinate) —was washed with water and analyzed. Received 60 g of raffinate containing 22.6 wt.% Aromatic hydrocarbons, which can be used as high quality raw materials for catalytic cracking and hydrocracking processes.

 Pentane is distilled off from the extract phase, then N-methylpyrrolidone is vacuum. VAT residue (40 g) contains 85.1% sulfonated and can be used as a plasticizer for rubber and polymer compositions.

 Example 3

At 30 ^{° C.,} vacuum gas oil (100 g / h flow rate) and heptane containing 1 wt.% Toluene (100 g / h) are fed into the lower part of the packed extraction column with an efficiency of 5 theoretical stages, and dimethylacetamide with 3 wt. % water (consumption 500 g / h). As a result of countercurrent extraction, after reaching a stable regime, the raffinate and extract phases are simultaneously selected.

 Heptane is distilled off from the raffinate phase on a distillation column (20 theor. Plates), then dimethylacetamide under vacuum. The bottom residue — the hydrocarbon portion (raffinate) —was washed with water and analyzed. Received 67.3 g of raffinate containing 27.0 wt.% Aromatic hydrocarbons, which can be used as high quality raw materials for catalytic cracking and hydrocracking processes.

 Pentane is distilled off from the extract phase, then dimethylacetamide is vacuum. VAT residue (32.7 g) contains 90.1% sulfonated and can be used as a plasticizer for rubber and polymer compositions.

Claims (1)

A method of preparing raw materials for catalytic cracking and hydrocracking processes by liquid extraction of aromatic hydrocarbons, heteroatomic compounds and heavy metal compounds from vacuum gas oil with N-methylpyrrolidone or dimethylacetamide containing 3 wt.% Water at a temperature of 30-50 ^o C, characterized in that the extraction is carried out in the presence of a non-polar washing solvent of pentane or heptane in a mass ratio of non-polar solvent: feedstock 0.5 = 1: 1.

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