RU2173330C1 - Method of decaptanization of hydrocarbon stock - Google Patents

Abstract

FIELD: gas, petroleum refining, petroleum extracting and petrochemical industries, more particularly decaptanization of dry and liquefied hydrocarbon gases, gasoline fractions, light petroleums and gas condensates. SUBSTANCE: hecaptanization of hydrocarbon stock is carried out by extraction of mercaptans with alkaline agent followed by oxidative regeneration of mercaptide-saturated extractive agent in the presence of catalyst for oxidation of sulfurous compounds. Alkaline extractive agent is product of conversion acid impurities of high-boiling hydrocarbon fractions resulting from oxidative catalyst purification from mercaptans in alkaline medium. High sulfur capacity of alkaline extractive agent used in process makes it possible to reduce substantially overall dimensions of production equipment, cut down capital outlays and service expenses of claimed process as compared with methods well known in the art. EFFECT: more efficient demercaptanization method. 3 cl, 5 tbl

Description

 The invention relates to methods for demercaptanization of hydrocarbons (dry and liquefied hydrocarbon gases, gasoline fractions, light oils, gas condensates, etc.) and can be used in gas, oil refining, oil and petrochemical industries.

 Known methods for the purification of hydrocarbons - gasolines, gas condensates from mercaptans with aqueous alkali solutions containing polar organic additives: methanol and dimethyl sulfoxide or dimethylformamide / a.s. USSR N 1694625 / / 1 /, ethanol and acetone with formaldehyde / a.c. USSR N 1583435 / / 2 /; or ethanol with a ketone selected from the group methyl ethyl ketone, methyl butyl ketone, acetophenone and cyclohexanone / a.s. USSR N 1579927 / / 3 /.

 These methods are associated with the continuous consumption of organic solvents and with additional costs for their separation from the product to be purified and regeneration.

 Methods are also known for the purification of hydrocarbon feedstocks (HCS) from mercaptans with alkali solutions containing 0.5-4.0 vol.% / A.s. as a polar organic additive in ethylene glycol. USSR N 1773930 / / 4 /, polyethylene glycol / a.s. USSR N 1268604 / / 5 /, followed by catalytic regeneration of a mercaptide-containing alkaline solution by oxidation of mercaptides to disulfides in the presence of phthalocyanine catalysts.

 The disadvantage of these methods is the contamination of the product to be purified with partially hydrocarbon-soluble organic additives and alkali, which leads to the need for subsequent water washing of the demercaptanized feed and the formation of corresponding sulfur-alkaline effluents.

 In terms of technical nature and the achieved result, the closest to the proposed one is a method for purifying hydrocarbons from mercaptans with aqueous alkali solutions (NaOH, KOH), followed by catalytic regeneration of an alkaline solution saturated with mercaptides with air oxygen treatment / Petroleum Refining and Naphthochemistry, 1994, N 2 / / 6 / .

 The disadvantages of this method are the insufficient depth of purification of the UVS from mercaptans, especially when cleaning heavy gasoline fractions and gas condensates containing high molecular weight mercaptan compounds that are difficult to extract with alkali, and the formation of rather stable emulsions of the raw material to be purified with an aqueous alkaline solution, the separation of which requires a long settling time and additional water washing of the purified product from alkali.

 The objective of the present invention is to remedy these disadvantages and to eliminate the stage of water washing the purified product from an alkaline extractant.

According to the invention, HCS demercaptanization is carried out by extraction of mercaptans from the raw material with an alkaline extractant, followed by separation and catalytic regeneration of the mercaptide-containing alkaline extractant by oxidation with atmospheric oxygen. As an alkaline extractant or an additive to a known extractant, the product of the interaction of alkali (NaOH, KOH) with acidic impurities of high-boiling hydrocarbon fractions (VUV), formed during the oxidative-catalytic purification of VUV from mercaptans by treating with atmospheric oxygen / is used. RF N 2110555 / / 7 /. The specified product is an alkaline solution insoluble in hydrocarbons, characterized by the following physicochemical parameters:
Appearance - viscous liquid
Color Reddish Brown
Alkalinity, g-equiv / l, - not less than 0.1
Density, kg / l - not less than 1.0
A distinctive feature of the proposed method is the use of the above product as an extractant or additive to a known extractant. This distinguishing feature determines the significant differences of the proposed method from the prototype and the prior art in this field, since the use of the specified product for the extraction of mercaptans is not described in the literature and allows, in comparison with the prototype, to increase the depth of demercaptanization of HCS, to accelerate the processes of sludge and regeneration mercaptide-containing extractant and exclude the stage of water washing of purified hydrocarbons.

 In the proposed method DEMERUS during the regeneration of the extractant can be used both homogeneous and heterogeneous catalysts for the oxidation of sulfur compounds. In the first case, the catalyst is dissolved in an alkaline extractant, and in the second case, it is placed in an oxidative regeneration apparatus of a mercaptide-containing extractant.

 The proposed method was tested in laboratory conditions on a model solution of 2-methylpropanethiol-1 (2-MPT) in decane, on a wide fraction of light hydrocarbons (BFLH) of the Orenburg condensate, on the gasoline fraction of the Karachaganak condensate (CCC), as well as on stable Perm and Karachagan gas condensates (GK). As an extractant in the experiments, we used the product of the interaction of KOH with acidic impurities of the kerosene fraction (PVC), which was formed during the oxidative-catalytic purification of kerosene from mercaptans and acidic impurities in the presence of a phthalocyanine catalyst on polypropylene - KS catalyst. Below are examples and results of the experiments.

 Example 1

To assess the extracting properties of the proposed alkaline extractant, 45 ml of purified HCS and a predetermined amount of PVC are placed in a separatory funnel. The contents of the funnel are intensively mixed by shaking for 3 minutes at 30 ^o C and then visually, by the disappearance of turbidity in the upper hydrocarbon layer, determine the time required for the complete separation of the hydrocarbon and alkaline phases. For quality control over the completeness of the phase sludge using phenolphthalein, the alkalinity of the aqueous extract of the hydrocarbon layer is checked. The effectiveness of the demercaptanization process under experimental conditions is evaluated by potentiometric titration according to GOST 17323-71 of the residual content of mercaptan sulfur in the HCF treated with the studied extractant.

 In the table. 1 shows comparative data on the depth of extraction of mercaptan sulfur from various types of hydrocarbons proposed and known alkaline extractants. The volume ratio of the hydrocarbon and alkaline phases in the experiments was taken equal to 25: 1.

 In the table. Figure 2 shows data on the effect of PVA additives (with a density of 1.4 kg / l) to a 15% aqueous KOH solution on the depth of demercaptanization of a solution of 2-MPT in decane and on the settling time of alkaline and hydrocarbon phases. The initial concentration of mercaptan sulfur in decane is 0.2 wt.%, The ratio of decane to alkaline extractant in the experiments is 9: 1.

 From the above table. 1 and 2 of the data shows that the proposed extractant and its mixtures with aqueous solutions of alkali are much more effective compared to traditionally used aqueous solutions of alkali, both in terms of extracting ability with respect to mercaptans and in the rate of sedimentation of alkaline extractant from purified raw materials.

 Example 2

 To determine the absorption capacity (sulfur intensity) of extractants, the above described experiment in a separatory funnel is carried out with the same portion of the studied extractant, pouring the necessary amount of fresh portions (45 ml each) of the purified HCS to it. The content of mercaptide sulfur in the extractant is determined by potentiometric titration according to GOST 22985-90. In the table. Figure 3 shows the data on the sulfur capacities of 1 ml of PVC with a density of 1.3 kg / l and 1 ml of a 20% aqueous KOH solution upon sequential treatment of 4 portions of a solution of 2-MPT in decane with an initial concentration of mercaptan sulfur of 0.28 wt.%.

 As can be seen from the data table. 3, the proposed alkaline extractant, in contrast to the aqueous alkali solution, has a significantly higher extracting ability even at high degrees of saturation of the extractant with mercaptide sulfur, which makes it possible to achieve the required purification depth of HCS with a significantly smaller number of contact steps in the extractor, i.e. in a smaller device.

 Example 3

The effect of PVA and its additives on the efficiency of catalytic regeneration of mercaptide-containing alkaline extractants with an initial content of 2.78 wt.% Mercaptide sulfur extracted from CFC gasoline is estimated by the loss of residual mercaptide sulfur content over time with vigorous stirring with a magnetic stirrer 10 ml of extractant in the presence of 2 g catalyst KS at 70 ^o C in an atmosphere of air (table. 4).

In the table. 5 shows data on the regeneration of 15% aqueous KOH solutions containing 1.0 wt.% Mercaptide sulfur, obtained by dissolving the appropriate amount of 2-MPT in an alkaline extractant, and various amounts of PVC additives. Regeneration is carried out for 5 minutes at 55 ^o C in an atmosphere of air according to the above method.

 As can be seen from the data table. 4 and 5, the regeneration rate of the proposed mercaptide-containing PVA extractant and a 15% aqueous KOH solution containing PVA additives is noticeably higher, ceteris paribus, than a 15% aqueous KOH solution without additives.

 Thus, the proposed method DEMERUS has significantly higher performance characteristics than the known method according to the prototype both at the stage of extraction of mercaptans from HCS and at the stage of regeneration of mercaptide-containing extractant. The high sulfur intensity of the alkaline extractant used in the DEMERUS process and the short settling time of the hydrocarbon and alkaline phases can significantly reduce the size of the process equipment, reduce the amount of capital and operating costs for the implementation of this process. The achieved completeness of the phase separation avoids water washing.

Claims (3)

 1. The method of demercaptanization of hydrocarbons by extraction of mercaptans with an alkaline extractant, followed by separation of the mercaptide-containing extractant and its oxidative regeneration by treating with oxygen in the presence of sulfur oxidation catalyst, characterized in that the product of the interaction of alkali (NaOH, KOH) with acidic impurities is used high boiling hydrocarbon fractions formed during their oxidation-catalytic purification from mercaptans and acidic impurities treatment with oxygen, or a mixture of said product with known extractants.  2. The method according to claim 1, characterized in that said alkaline extractant has a total alkalinity of at least 0.1 g-equiv / l and a density of at least 1.0 kg / l.  3. The method according to PP.1 and 2, characterized in that the content of the specified alkaline extractant in a mixture with known extractants, for example with an aqueous solution of sodium hydroxide or potassium, is at least 0.5 vol.%.

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