US3166492A - Desulfurization of hydrocarbons - Google Patents

Description

J 3,166,492 f r 'DESULFURIZATION 6F HYDROCARBONS Georg Richard Schultze, Friedrich Boberg, and Gerhard Menzel, Hannover, Germany, assignors to Deu'tsche Goldand Silher-Scheideaustalt' .vormals Roessler, Frankfurt am Main, Germany N Drawing. Filed Dec. 13, 1960, Ser. No. 556,919 1 Claim. (Cl. 208237) The present invention relates to an improved process for the desulfurization ofhydrocarbons.

It is known that sulfur compounds on treatment with metallic sodium or sodium alloys undergo changes and can even lose their sulfur. especially active and has been proposed as preferred for the desulfurization of petroleum products.

In the desulfurization of hydrocarbons, it is of particular advantage iftthe process only effects removal of the sulfur anddoes not efiect removal of the hydrocarbon residues of the sulfur compounds originally present. This would, for example, signify that, when sodium is used, the sulfur present in the hydrocarbons should after completion of the treatment be converted to sodium sulfide while the hydrocarbon radicals originally bonded to the sulfur should be altered in such a way that they remain with desulfurized hydrocarbon. However, with the exception of hydrogenation processes, most of the desulfurizing processes used today in mineral oil technology remove the sulfur compounds. as a whole, that is, the organic components bound to the sulfur are removed along with the sulfur.

The sulfur compounds occurring in mineral oils exhibit different activities with sodium. Mercaptans react easily with sodium with the formation of mercaptides. The sodium mercaptides formed are difficultly soluble in hydrocarbons, so that the precipitating reaction products can be filtered off or centrifugedoff. According to German Patent 956,439 this procedure, however, does not lead to a complete desulfurization and as a consequence a sulfuric acid treatment is used after the sodium treatment. The sulfur remaining in the treated mineral oil product is derived from the small quantities of dissolved mercaptides. The removal of the dissolved mercaptide by washing with water is not possible as a hydrolysis equilibrium occurs with formation of sodium hydroxide and reformation of the mercaptans. Further reaction of sodium with sodium mercaptide or the thermal treatment of the mercaptide does not elfect conversion of the sulfur into sodium sulfide.

As tests have shown, mixtures of hydrocarbons and sodium mercaptides remain unchanged even after heating for 10 hours at 260 C. in contact with an excess of sodium.

According to the invention it was unexpectedly found that the formation of sodium sulfide from sodium mercaptides can easily be effected in the presence of organic sodium compounds, that is, sodium compounds containing a direct sodium to carbon bond. The organic sodium compounds can be added to the reaction mixture of the hydrocarbons being desulfurized or they may be formed therein in situ. Most simply the organic sodium compounds can be produced in the reaction mixture by reacting organic halogen compounds with sodium. Aliphatic, cycloaliphatic, aromatic or mixed aromaticaliphatic halogen compounds can be employed for this purpose.

Finely dispersed sodium is thiophe'ne, aliphatic disulfides, aliphatic polysulfides and aliphatic sulfides do not or do not completely yield their white oil).

3,166,492 Patented Jan. 19, 1965 ice sulfur with formation of sodium sulfide upon treatment with sodium at temperatures up to 250 C. In contrast thereto, in the presence of organic sodium compounds,

the sulfurin such compounds in each instance was converted completely to the desired sodium sulfide.

The sodium sulfide produced in the process accordingto the invention can be removed by. filtration, centrifuging,

for the desulfurization of crude oils, mineral oil products, coke oven products, synthetic hydrocarbons and the like.

It can be used in combination with other desulfurization procedures to remove the last traces of sulfur.

The treatment with the organic sodium compounds can be effected at temperatures between 20 C. and 200 0, preferably betwen 20 C. and C. The quantity of organic sodium compound employed should be sufiicient to provide 2.1 gram atoms of sodium per gram atom of sulfur. In this operation it is possible to add part of the sodium required-in the form of sodium dispersion.

The following examples will serve to illustrate several embodiments of the process according to the invention. The reactions described in such examples were carried out in a four necked flask provided with a stirrer, thermometer, dropping funnel (with pressure equalizer connected 'to the reaction flask) and a reflux condenser (closed with a drying tube).

EXAMPLE 1 Desulfurization with the aid. of organic halogen compounds (a) Desulfurization of solutions of mercaptans in hydr0carb0ns.A sufficient quantity of arsodium dispersion in the hydrocarbon was added to 250 cc. of a solution of the mercaptan in the hydrocarbon at room tem perature while stirring so that the sulfur content (1.07%) was converted to the sodium mercaptide. Then a sufficient quantity of the organic halogen compound was added to the mixture while stirring so that the molar ratio of sulfur compound to organic halogen compound was 1:1. The reaction mixture was then heated to 50-60" C. and a sufiicient quantity of further sodium dispersion added until the molar ratio of organic halogen compound to sodium was 112.2; The mixture was then heated with stirring to 120 C. and such temperature maintained for a further 30 minutes. The reaction caused typical discolorations to deep blue black. After the reaction mixture had cooled down, methanol was added to decompose the unreacted sodium and the mixture washed with water. The discolorations disappeared during such washing. After such washing the hydrocarbon layer was sulfur free. The sulfur was in the aqueous phase as sodium sulfide and could be determined iodometrically.

The above desulfurization was carried out on heavy petrol (RP. ISO- C.) and on white oil (B.P. 250- 350 0.), solutions of heptane thiol and of hexane thiol.

The following compounds were used as the organic halogen compounds: phenyl chloride, phenyl bromide, benzyl chloride, butyl chloride, butyl bromide and cyclohexyl bromide.

(b) Desulfnrization of solutions of n-butyl sulfide, nheptyl disulfide, amyl polysulfide and dimezhylthiophene.Phenyl bromide was first added at room temperature with stirring to 250 cc. of solutions of the sulfur compounds indicated in hydrocarbons (heavy petrol, The sulfur content of such solutions was 1.07%. Thereafter a sodium dispersion was added. The ratio of sulfur compoundzphenyl bromidezsodium was with sodium alone (that is, without addition of an organic halogen compound) onlyv a portion of the sulfur was converted into sodium sulfide even when using reaction periods up to 10 hours. only 20% was converted into sodium sulfide and in the case of the sulfur compounds concerned under (b) only 60% was converted in the best instances, namely, the

V polysulfides.

Solutions of tetraphenylthiophene and dibenzothiophene remained completely unaltered upon treatment with sodium alone. Upon addition of phenyl bromide as under (b) or butyl bromide, complete desulfurization was achieved.

(d) Different quantities of the following sulfur compounds were dissolved in 250 cc. of mineral spirits, B.P. 100-180" C., to provide solutions having a total sulfur content of 2.7% in each each case: hexane thiol, tetrahydrothiopyrane, benzyl mercaptan, heptyl disulfide, phenyl ethyl sulfide, thionaphthene and thiophenol.

These solutions were reacted according to (b). The ratio of sulfur compound: phenyl bromidezsodium was so selected that 1 mol of phenyl bromide and 3 gram atoms of sodium were provided for every gram atom of sulfur present. A 100% desulfurization was attained. When the halogen compound was added the desulfurization was demonstrably not complete.

EXAMPLE 2 Desulfurization using an organic sodium compound (a) Desulfurization with phenyl s0dium.A 0.1 molar suspension of sodium heptyl mercaptide in xylene was added with stirring to 250 cc. of a 0.1 molar solution of phenyl sodium in xylene. The mixture was heated to 120 C. and after minutes assumed a deep brown coloration. The mixture was stirred for a further'30 minutes at 120 C. and after cooling was washed with water as in Example 1(a). The hydrocarbon phase Was completely free of sulfur,

In the case of the mercaptans' was added. The mixture was heated while stirring to 120 C. and such temperature maintained for a further 30 minutes. The contents of the flocks assumed a brownish black coloration. Upon washing with water the organic phase became free of sulfur.

EXAMPLE 3 Desulfurizalion of a technical diesel fuel The diesel fuel employed contained 1.03% of sulfur, had a boiling range of ISO-358 C. and a density of (=0.829.

250 cc. of the diesel fuel were stirred together with 2.84 g. of sodium dispersed in the same fuel for 30 min; utes at C. After usual processing the. sulfur content had decreased to 0.79%. Even when longer heating periods were employed the sulfur content did not decrease further. On the other hand, when 4 g. of phenyl bromide were added, the diesel fuel was sulfur free after the 30 minutes treatment of 120 C.

We claim:

A process for desulfurizing hydrocarbons contaminated with sulfur which comprises reacting at a temperature between 20 and 200 C. metallic sodium with a hydrocarbon halide in contact with said hydrocarbon contaminated with sulfur to form an organic sodium compound in which the sodium is directly bonded to carbon in situ in said hydrocarbon, the quantity of sodium supplied to said hydrocarbon contaminated with sulfur by said organic sodium compound and any residual metallic sodium being at least 2.1 gram atoms of sodium per gram atom of sulfur contained in said contaminated hydrocarbon.

References Cited in the file of this patent UNITED STATES PATENTS