US2203470A - Cracking hydrocarbon mixtures - Google Patents

Description

June 4, 1940. M. PIER l-:T AL l 2,203,470

CRACKIHG HYDROCRBMI IIXTURES rma .my 21, 19:51

Sm/ref/ /22 20 Sepa/'afar Slime Bleue/zing aff/z Slime Patented `lune 4, 1940 UNITED STATES NPATENT OFFICE 2,203,470 CRACKING HYDRooARnoN MTXTURES Application July 21, 1937, Serial No. 154,752

In Germany July 29, 1936 2 Claims.

The present invention relates to improvements in the cracking of hydrocarbon mixtures obtained by the reduction of carbon monoxide.

, In the cracking of oils loss by the formation of 5 coke is frequently encountered which is partly attributable to the impurities contained in the oils and partly to the small hydrogen content of the initial materials. In order to avoid this drawback it has been proposed to free the initial materials from asphalt and impurities containing sulphur or nitrogen and the like and to provide that they contain suflicient hydrogen.

We have now found that even oils having the said nature, from the composition of which a marked formation of coke during cracking would not be expected, frequently form large amounts of coke, contrary to expectation. In particular it is impossible to crack without a strong formation of coke the higher fractions of the mixtures of hydrocarbons prepared from carbon monoxide and hydrogen. Although these products have been prepared from carefully purified gases and are therefore free from the substances know to lead to the formation of coke, such as asphalt or 5 l'impurities containing sulphur or nitrogen and are moreover very rich in hydrogen (they contain about 18 parts of hydrogen for each 100 parts of carbon) unusually high waste by the formation of coke takes place in the cracking of the said oils.

0 Thus for example an oil boiling above 325 C. which has been prepared by reduction of carbon monoxide and which has been freed from parain wax gives a coke residue offabout 14 per cent when cracked at from 550 to 600 C. This is the 6 more surprising because other substances of quite similar composition, even when they are not so pure' and are poorer in hydrogen, -as for example petrolatum which lcontains only 15 parts of hydrogen for each 100`- parts of carbon, give only o quite a small formation of coke when cracked.

We have now found that the said diiiiculties attributable to a hitherto unexplained cause can beavoided by subjecting the hydrocarbon mixtures of high boiling point formed by the hydro- 5 genation of carbon monoxide to a pretreatment with an agent known to be suitable for the refining of oils (hereinafter referred to as refining agent), in spite of the high hydrogen content` `and a degree of purity which `would apparently 0 render arening unnecessary.

As renng agents there may be mentioned in particular concentrated sulphuric d acid, metal halides, as for example aluminum chloride, ferrie chloride, boron fluoride, zinc chloride and tita- 5 nium chloride. When using the said substances d it is preferable subsequently to carry out an aftertreatment with bleaching earths or alkali.

Substances having a refining effect by physical action may also be used for the pretreatment of the oils, asfor example selective solvents, such as 5 phenols, keto acids, glycol acetate, liquid sulphur dioxide and liquid ammonia.

In spite of their very high hydrogen content, the initial oils are also changed by a pretreatment with hydrogen in such manner that a con- 10 siderably smaller formation of coke takes place in the subsequent cracking. This treatment with hydrogen may be carried out by leading the oils of high boiling point prepared from carbon monoxide and hydrogen, preferably directly after the 16 separation of the constituents of lower boiling point, together with the residual gas formed in the reduction of the carbon monoxide or with fresh hydrogen, over known hydrogenation catalysts, such as metal compounds of the 5th to the 30 8th groups of the periodic system, in particular the sulphides or oxides, and especially those of the 6th group, at atmospheric or, preferably, at increased pressure, as for example from 20 to 200 atmospheres or more, and at temperatures of g5 from 250 to 475 C.

The refining with agents, such as sulphuric acid, metal halides or hydrogen, having a chemical action as well as with agents having a physical action is effected under conditions of temperature and duration of time as may be used for the refining of other hydrocarbon mixtures, such as mineral oils or tars or their distillation products and the like. t

As initial materials there may be mentioned the higher fractions, in particular those boiling above 250 C., and preferably above 325 C., of products which have been prepared from carbon monoxide and hydrogen at temperatures of from 150 to 250 C., at atmospheric or increased preso sure, as for example 1 to 20 atmospheres or higher, in the presence of catalysts, as for example a substance containing cobalt or iron or nickel. It is preferable to free the said oils from parafn wax before the treatment with the said substances. `The cracking of the pretreated oils is carried out at atmospheric or increased pressure at temperatures of from about 500 to 700 C., or

more, preferably in the presence of catalysts, as for example metals, oxides, halides, phosphates, sulphides of metals, metalloid halides, halogens or hydrogen halides or mixturesof the said substances. The cracking products thus obtained, in particular the benzine and middle oil fractions. constitute especially good initial materials for le ne production or high quality lubricating. om;v

by polymerization or condensation.

The inventionwil-l be better understood' by reference to the accompanying drawing which depicts i5` schematically the operations involved. A mixture passes from separator 6 by way of line TI, thence through heater 8 to the fractionator 8. In said fractionator the liquidproduct is split into fractions comprising benzene, middle oil and the fraction boiling over 350 C. The latter fraction, after traversing cooler I0, is introduced in stirring vessel II with a mixture of benzol and acetone stored in vessel I2, for the purpose of removing paramn. The product from the stirring vessel passes' by way of cooler I4 to iilter I3 where the paraiiln is removed. The oil is conveyed to vessel Il and is therein treated with bleaching earth and sulfuric acid conducted .to vessel I8 from vessels I5 and I0 by way oi lines I1 and Ila respectively. The sulfuric acid component of the mixture passes to vessel I9. The loil is filtered in lter 20 to remove the bleaching earth slime and is then subjected to cracking into coil 2| and its associated soaking drum 22. The products are cooled Example treated with about 2 per cent suiphuric acid and subsequently with bleaching earth. The'oilthus prepared is cracked at from 550 to 600 C.- while returning the products oi high boiling point; in this way 'I2 per cent of oil, consisting to the extent of 58 percent of benzine and middle oil, 27 per cent of gaseous hydrocarbons and 0.5 per cent oi coke are obtained. If the pretreatment of the oil be carried out with phenol, the formation of coke amounts to 0.9 per cent. It the same initial oil be cracked under the same conditions but without the pretreatment, 52 per cent of 011,'33 per cent of gaseous hydrocarbons and 14 percent of coke are obtained.

What we claim is:

1. A process for thecracking of hydrocarbon mixtures, boiling above 250 C., which are substantially free from asphalts, sulphur and nitrogen compounds, and which result from the reduction of carbon monoxide which comprises pretreating such hydrocarbon mixture with a refining agent having anv acid reaction and then subjecting the mixture to cracking.

2. In the process as claimed in claim l treating a hydrocarbon mixture resulting from the reduction of carbon monoxide which -boils at a temperature above 325 C. MATHIAS PIER. FRIEDRICH CHRISTMANN.

Images