NZ211807A - Preparation of olefinic hydrocarbons - Google Patents

Description

New Zealand Paient Spedficaiion for Paient Number £11 807 2 1 1807 Priority Date(s): )Q.~ lir 7^,^., Complete Specification Filed: Class: Publication Date: ...

P.O. Journal, No: . ...mi.

NEW ZEALAND PATENTS ACT, 1953 /ft No.: Date.

COMPLETE SPECIFICATION PROCESS FOR THE PREPARATION OF HYDROCARBONS K/We, SHELL INTERNATIONALE RESEARCH MAATSCHAPPIJ B.V.

Carel van Bylandtlaan 30, 2596 HR The Hague, the Netherlands, a Netherlands Company, hereby declare the invention for which 4 / we pray that a patent may be granted to KMH/us, and the method by which it is to be performed, to be particularly described in and by the following statement: - - 1 - (followed by page la) i -LjL 2 1 1 i - la - K 5713 rnocEss ron ttie preparation of [iydrocahdon: •w The invention relates to a process for the preparation of linear olefins having at least 10 and at most 20 carbon atoms per molecule.

Linear olefins having at least 10 and at most 20 carbon 5 atoms per molecule (hereinafter referred to as "linear C1Q-C2O olefins") are valuable starting materials for the preparation of synthetic detergents. Said olefins can be obtained by mild thermal cracking of mixtures of linear paraffins having at least 20 carbon at cms per molecule (hereinafter referred to as "linear C20+ 10 paraffins"). Linear C£o+ paraffins, together with branched C2o+ paraffins are found in heavy mineral oil fractions, such as lubricating oil fractions. The paraffins can be separated from said mineral oil fractions by cooling. Fran the paraffin mixtures obtained the desired linear paraffins can be isolated by way of 15 fractional crystallisation or complexing with urea. The linear C2o+ paraffins thus obtained are generally contaminated with sulphur- and nitrogen compounds from the mineral oil, as well as cyclic compounds. Prepartory to being suitable for use as feed for the preparation of linear C-|g-C20 olefins by mild thermal crack-20 ing the Cjo* paraffins should be freed from these contaminants.

Linear Cjo* paraffins which can suitably be used as starting material for the preparation of linear C-\ 0-C20 o:1-efin3 by way of mild thermal cracking may also be synthesized starting from a mixture of carbon monoxide and hydrogen. In this what is called 25 Fischer-Tropsch synthesis a H2/CO mixture is contacted at elevated temperature and pressure with a catalyst comprising one or more metals frcm the iron group together with one or more promoters and a carrier material. The preparation of these catalysts can suitably be carried out by the known techniques, such as pre-30 cipitation, impregnation, kneading and melting. As compared with I I T': , / . 2 1 1807 f. i | waxy heavy mineral oil fractions the products prepared by the t Fischer-Tropsch synthesis have the advantage that they contain 'i virtually no sulphur- and nitrogen compounds and cyclic compounds. Nevertheless the use of the products obtained over the usual 5 Fischer-Tropsch catalysts for the preparation of linear C10-C20 olefins has two drawbacks which are connected with their composition. In the first place these products contain but a relatively small amount of C2o+ compounds as compared to the quantities of C-|g~ compounds present. Furthermore the C20+ compounds are made 10 up to a considerable extent of branched paraffins, branched and unbranched olefins and oxygen-containing compounds.

Recently there has been found a class of Fischer-Tropsch catalysts which have the property of yielding a product in which considerably more C20+ compounds are present than in the products 15 prepared by the usual Fischer-Tropsch catalysts, which C2o+ can-pounds consist virtually exclusively of linear paraffins. The Fischer-Tropsch catalysts belonging to the above-mentioned class contain silica, alumina or silica-aluni.na as carrier materials, and cobalt together with zirconium, titaniun and/or chromiun as 20 catalytically active metals, in such quantities that per 100 pbw of carrier material the catalysts comprise 3-60 pbw of cobalt and 0.1-100 pbw of zirconium, titanium, and/or chromiun. The catalysts are prepared by depositing the metals involved on the carrier material by kneading and/or impregnation. For ftirther information 25 concerning the preparation of these catalysts by kneading and/or N£vo ZLeoJa^d &pec i-ficflho^ impregnation reference may be made to Netherlands patent applioat-—1 P /, • ac>S3«3 ion No. 8301952, recently filed by the Applicant. Considering the fe r composition of the product prepared over the cobalt catalysts it is extremely attractive to separate from the product a heavy 30 fraction substantially consisting of C20+ paraffins and to con-_ vert at least part of this heavy fraction by mild thermal cracking ^—/ into a mixture of hydrocarbons substantially consisting of linear olefins and containing the desired C1Q-C20 olefins.

The present patent application therefore relates to a process 35 for the preparation of linear C10-C20 olefins, in which a mixture ... \ 7 2 11807 o ■ j. j. p. £ MH H-14.- % KJ of carbon monoxide and hydrogen is converted into a mixture of hydrocarbons substantially consisting of linear paraffins by contacting it at elevated temperature and pressure with a catalyst comprising 3-60 pbw of cobalt and 0.1-100 pbw of at least one other 5 metal chosen from the group formed by zirconium, titanium and chromiun per 100 pbw of silica, alumina or silica-alumina carrier, which catalyst has been prepared by kneading and/or impregnation, in which frcm the paraffin mixture thus prepared a heavy fraction is separated which consists substantially of C2o+ paraffins, and 10 in which at least this heavy fraction is converted by mild thermal cracking into a mixture of hydrocarbons which consists substantially of linear olefins and contains the desired C1Q-C20 olefins.

In the process according to the invention the starting material should be a Hj/CO mixture. Suitable Hg/CO mixtures can 15 be prepared by the gasification of heavy carbonaceous materials, such as coal and residual mineral oil fractions. It is preferred to start frcm a H2/CO mixture which has been obtained by the steam reforming or partial oxidation of light hydrocarbons, in ■particular natural gas.

In the process according to the invention preference is given to the use of. the cobalt catalysts which form the subject matter klev^j 'Zea.tairia spec • (ric ahori ao?3i3 of Netherlands patent application No. 8301952. They are catalysts which satisfy the relation: (3 + 4 R) > — > (0.3 + 0.4 R), wherein 25 S L = the total quantity of cobalt present on the catalyst, expressed as rag Co/ml catalyst, S = the surface area of the catalyst, expressed as n^/ml catalyst, and R = the weight ratio of the quantity of cobalt deposited on the catalyst by kneading to the total quantity of cobalt present on the catalyst.

In the process of the invention use is further preferably made of cobalt catalysts which have been prepared by one of the r "Ml 80 three procedures mentioned hereinafter: a) first cobalt is deposited in one or more steps by impregnation and subsequently the other metal is deposited in one or more steps, also by impregnation, b) first the other metal is deposited in one or more steps by impregnation and subsequently the cobalt is deposited in one or more steps, also by impregnation, and c) first cobalt is deposited in one or more steps by kneading and subsequently the other metal is deposited in one or more steps by impregnation.

In the process according to the invention use is further preferably made of cobalt catalysts containing 15-50 pbw of cobalt per 100 pbw of carrier. The preferred quantity of other metal present in the cobalt catalysts depends on the way in which this metal has been deposited. In the case of catalysts where first cobalt has been deposited on the carrier, followed by the other metal, preference is given to catalysts containing 0.1-5 pbw of the other metal per 100 pbw of carrier. In the case of catalysts where first the other metal has been deposited on the carrier, followed by the cobalt, preference is given to catalysts containing 5-40 pbw of the other metal per 100 pbw of carrier. Preference is given to zirconium as the other metal and to silica as carrier material.

In the process according to the invention the conversion of the H2/CO mixture is preferably carried out at a temperature of 125-350°C and a pressure of 5-100 bar and in particular at a temperature of 175-275°C and a pressure of 10-75 bar. The mild thermal cracking which according to the invention is applied to at least part of the heavy fraction of the product prepared over the cobalt catalyst is preferably carried out in the presence of steam. Further the mild thermal cracking is preferably carried out at a temperature of 535-675°C, a pressure of 1-5 bar abs., a residence time of 0.5-15 seconds and in the presence of a quantity of steam which is at most 40 $w, calculated on the hydrocarbon feed, 180 and in particular at a temperature of 540-600°C, a residence time of 2-10 seconds and in the presence of a quantity of steam of 3-20 %w, calculated on the hydrocarbon feed.

In the process according to the invention the product ob-5 tained by mild thermal cracking consisting substantially of linear olefins is divided into a light Cg~ fraction, the C10-C20 fraction desired as end product, and a heavy C21+ fraction. The yield ' of linear C10-C20 olefins may be increased by recycling at least part of the heavy C21+ fraction to the mild thermal cracking, or 10 by dividing the light Cg~ fraction into a C^" fraction and a C5-C9 fraction, subjecting at least part of the latter fraction, together with at least part of the heavy C2i+ fraction to a combination of isomerization and disproportionation in order to prepare a mixture of linear olefins, and separating from the olefin 15 mixture thus obtained an additional quantity of C-|q-C20 linear olefins. From the 04" fraction which remains after the separation of the Cg"* fraction, there can be separated ethene, from which linear olefins can be prepared by oligomerization, part of which linear olefins consist of C10-C2O olefins. The Cg~ and C21+ 20 olefins present in the mixture can be converted by means of the afore-mentioned combination of isomerization and disproportionation into a mixture of linear olefins from which C 10-^20 olefins can be separated.

In the process according to the invention a further increase 25 of the yield of linear C1Q-C20 olefins can be realised starting frcm the C-|g~ fraction obtained in the hydrocarbon synthesis over the cobalt catalyst, or frcm lighter fractions separated therefrom. By subjecting these fractions, which consist substantially of linear paraffins to steam cracking, a mixture of lower olefins can 30 be obtained which consists substantially of ethene. The ethene can be oligomerized to prepare a mixture of linear olefins which consists partly of C10-C20 olefins. The Cg~ and C21+ olefins formed in the oligomerization can be converted by the afore-mentioned combinaticxi of isomerization and disproportionation into a mixture 35 of linear olefins from which the desired C10-C20 olefins can be 180 separated. An increase of the yield of linear C10-C2O olefins, starting from the C-jg" faction obtained in the hydrocarbon synthesis over the cobalt catalyst, can also be realised by separating from the C-|g~ fraction a heavy fraction and subjecting it to 5 dehydrogenation or chlorination, followed by dehydrochlorination. From the C10-C19 or the C5-C9 fraction of the product obtained over the cobalt catalyst can thus be prepared linear C1Q-C19 or C5-C19 olefins. The 05-0-19 olefins present in the mixture of C5-C19 olefins can suitably be used as feed components in the 10 disproportionation mentioned hereinbefore. The afore-mentioned processes for the preparation of linear C10-C20 olefins, starting from the C-|g~ fraction obtained in the hydrocarbon synthesis over the cobalt catalyst, can very suitably be combined by dividing the C-jg" ft-action into a light and a heavy fraction (for instance a 15 Cij~ and a C5-C19 fraction, or a Cg~ and a C-jo-Cig fraction), and converting the light fraction by steam cracking/oligomerization and the heavy fraction.by dehydrogenation or chlorination/dehydro-chlorination.

In the present patent application there has thus far only 20 been mention of the use of the product obtained over the cobalt catalyst as feed for the preparation of linear C10-C20 olefins. According to the invention, to this end at least part of the C2o+ fraction should be subjected to mild thermal cracking. Optionally the entire C2o+ fraction may be converted in this way. In addit-25 ion, as described hereinbefore, part or all of the C-jg" fraction can be used for the preparation of linear C10-C20 olefins. In view of the special composition of the product obtained over the cobalt catalyst which consists virtually entirely of linear paraffins, this product is also excellently suitable for a number 30 of other applications, which can be combined with the process according to the invention. To this end use may be made either of part of the C2o+ fraction or of at least part of the 0-19" fraction. 2 11 8 C In addition to its use according to the invention as feed for the preparation of linear C1Q-C2O olefins by mild thermal cracking, the C2o+ faction is very suitable for the uses following: 1) Valuable solid paraffins can be separated from the C2o+ fraction by fractional crystallization. 2) A mixture of lower olefins substantially consisting of ethene can be obtained frcm the C20+ fraction by steam cracking. 3) A product from which a lubricating oil with a high viscosity index can be obtained frcm the C204" fraction by catalytic hydro-isomerization. 4) The C20+ fraction can be converted into middle distillates by catalytic hydrocracking.

In addition to its use as feed for the preparation of linear C1Q-C20 olefins the C-jg" fraction is very suitable for the uses following: 1) A mixture of lower olefins substantially consisting of ethene can be obtained from the Cig~ fraction by steam cracking. 2) By treating the C10-C19 fraction at an elevated temperature with a peroxide of the general formula R-O-O-R1, wherein R and r1 represent alkyl, aryl or acyl groups, said fraction can be converted into a product from which a lubricating oil with a high viscosity index can be separated. 3) Certain fractions with a narrow boiling range which are present in the C5-C11 fraction can be suitably used as special solvents either such as they are or after a mild hydrogenation or hydro-isomerization carried out to convert minor amounts of olefins and/or oxygen-containing compounds, or to introduce sane branching. In this connection may be mentioned extraction liquors for oil seeds, spraying oils for insecticides and pesticides and as solvents for medicinal and pharmaceutical uses and in the food-stuff industry.

The afore-mentioned steam cracking for the preparation of a mixture of lower olefins substantially consisting of ethene may very suitably be carried out at a temperature of 700-1000°C, a i 1 i i Os 807 pressure of 1-5 bar abs., a residence time of 0.04-0.5 seconds and in the presence of a quantity of steam which amounts to 20-100 $w, calculated on hydrocarbon feed.

The invention is now illustrated with the aid of the follow-5 ing example.

Example Five hydrocarbon synthesis experiments were carried out by using the following catalysts.

Catalyst A This catalyst comprised 10 pbw of iron, 5 pbw of copper, 2 pbw of potassium and 30 pbw of kieselguhr, and had been prepared by precipitation of iron and copper from an aqueous solution by using potassium carbonate, while kieselguhr was being added.

Catalyst B This catalyst comprised 97.5 pbw of iron, 2.5 pbw of aluminium and 0.5 pbw of potassium, and had been prepared by melting a mixture of FegOij. and the oxides of aluminium and potassium in an arc. Catalyst C This catalyst comprised 100 pbw of cobalt, 5 pbw of thoriun oxide, 20 7.5 pbw of magnesium oxide and 200 pbw of kieselguhr, and had been prepared by precipitation of cobalt and thorium from an aqueous solution, while kieselguhr was being added.

Catalyst D This catalyst comprised 25 pbw of cobalt and 0.9 pbw of zirconium 25 per 100 pbw silica, and had been prepared by kneading a silica carrier in a solution of cobalt nitrate in water, followed by single-step impregnation of the cobalt-loaded carrier with a solution of zirconylchloride in water.

Catalyst E This catalyst comprised 23 pbw of cobalt and 17 pbw of zirconium per 100 pbw of silica, and had been prepared by three-step impregnation of a silica carrier with solution of zirconiumtetra n-prop-oxide in a mixture of n-propanol and benzene, followed by single-step impregnation of the zirconium-loaded carrier with solution of cobalt nitrate in water. 2 11 During the preparation of Catalysts D and E, such a quantity of solution was used in each impregnation step that its volume corresponds substantially with the pore volume of the carrier. After each impregnation step the solvent was removed by heating 5 and the material was calcined at 500°C. When a kneading step was used, the quantity of solution used had a volume substantially corresponding with 150$ of the pore volume of the carrier. When a kneading step was used, the mixture was kneaded in a kneading machine for three hours. During the kneading a small portion of 10 the solvent was removed by heating. After the kneading step the paste obtained was recovered from the kneading machine, the remainder of the solvent was removed by heating, and the material was ground and calcined at 500°C.

Hydrocarbon synthesis experiments (1-5) After Catalysts A-E had been activated by means of treatment with a hydrogen-containing gas at 250°C they were used in the preparation of hydrocarbons from a mixture of carbon monoxide and hydrogen. The experiments were carried out in a reactor containing a fixed catalyst bed. The conditions under which the experiments were 20 carried out and the results of these experiments are given in Table I. Of these experiments only Experiments 4 and 5 are part of the invention. Experiments 1-3 fall outside the scope of the invention. They have been included in the patent application for comparison.

Cracking experiment (6) The C20+ fraction of the product prepared in accordance with Experiment 4 was cracked in the presence of steam at a temperature of 575°C, a pressure of 1 bar, a space velocity of 3.2 kg.l"1 .h""1, calculated on the volume of the cracking zone, a steam dose rate 30 of 6.5 $w, calculated on feed and a nominal residence time in the cracking zone of 2.5 seconds. After cooling and separation of the condensed water a product was obtained of which 5 %w consisted of a gas fraction, 14 ?w of a light liquid fraction substantially boiling below 300°C, and 81 %u of a residual fraction substant- • '•> >%» 1 1 8 ( ially boiling above 300°C. The gas fraction obtained in the cracking was made up of hydrogen and light hydrocarbons. The cracking gas comprised 35 %v ethene and 17 %v propene. The light liquid fraction consisted substantially of linear c5-c20 olefins. The 5 olefins content was 95$ and the oC-olefins content 90%.

Cracking experiment (7) The c5-C9 fraction of the product prepared according to experi-o ment 4 was cracked in the presence of steam at an average tempe rature of 760°C, an average pressure of 1.5 bar, a residence time 10 of 0.5 seconds and a steam/hydrocarbon weight ratio of 0.5. The composition of the product obtained is as given in Table II.

TABLE I Experiment Mo. 1 2 Catalyst No.

A B Temperature, °C 230 320 Pressure, bar Hg/CO volume ratio 1.7 2.5 Space velocity, N1.1"^.h~ ^ 1750 1750 Conversion H2+CO, %v 22 Product distribution, %w Gas (C1-C4) 22.6 54.1 Gasoline (C5-200°C) 28.3 31.9 Kerosine+gasoil (200-350°C) 19.5 2.5 Waxy residue (350°C+) 26.4 0 Water-soluble oxygen compounds 3.4 11.3 Properties of Cc;+ product Olefins content, $mol 50 80 Aromatic content, $mol 0.3 .0 Linearity, % 90 50 (percentage linear paraffins and olefins calculated on total of paraffins and olefins) Number of C atoms in tertiary structure, % 2 1180 7 3 4 C D E 190 220 204 1 2.0 2.0 3.0 75 500 900 70 75 62 28.5 18.0 23.0 42.5 .1 19.0 19.5 28.4 22.4 8.0 38.0 .4 1.5 0.5 0.2 34 8 2 0.1 0 0 60 95 97 4 0.2 0.1

Claims (12)

TABLE II Composition in %w of product prepared according to Experiment 7 Hydrogen 1 Methane 14 Ethane 5 Ethene 40 Propane 0.5 Propene 14 C4 8 C5 5 C6+ 12 7 \r. 807 WHAT flat CLAirl if : - 13 - K 5713 CLAIMS

1. Process for the preparation of linear C10-C20 olefins, characterized in that a mixture of carbon monoxide and hydrogen is converted into a mixture of hydrocarbons substantially consist-:\_y ing of linear paraffins by contacting it at elevated temperature 5 and pressure with a catalyst comprising 3-60 pbw of cobalt and 0.1-100 pbw of at least one other metal chosen from the group formed by zirconiim, titanium and chromiun per 100 pbw of silica, alumina or silica-alumina carrier, which catalyst has been pre- f N

{\^J pared by kneading and/or impregnation, in which from the paraffin 10 mixture thus prepared a heavy fraction is separated which consists substantially of C2o+ paraffins, and in which at least this heavy fraction is converted by mild thermal cracking into a mixture of hydrocarbons which consists substantially of linear olefins and contains the desired C10-C20 olefins. 15 2. A process as claimed in claim 1, characterized in that a H2/CO mixture is used which has been obtained, starting from light hydrocarbons, by steam reforming or partial oxidation.

3. A process as claimed in claim 2, characterized in that a H2/CO mixture is used which has been obtained starting frcm 20 natural gas.

4. A process as claimed in any one of claims 1-3, characterized ^ in that a cobalt catalyst is used which satisfies the relation ^ (3 + 4 R) > — > (0.3 + 0.4 R), wherein S 25 L s the total quantity of cobalt present on the catalyst, expressed as mg Co/ml catalyst, S = the surface area of the catalyst, expressed as m^/ml catalyst, and R = the weight ratio of the quantity of cobalt deposited on the 30 catalyst by kneading to the total quantity of cobalt present on the catalyst. - 14 - 2 11807

5. A process as claimed in any one of claims 1-4, characterized in that a cobalt catalyst is used which, per 100 pbw of carrier, comprises 15-50 pbw of cobalt and either 0.1-5 pbw of the other metal when during the preparation cobalt was deposited 5 first and the other metal next, or 5-40 pbw of the other metal when during the preparation the other metal was deposited first and the cobalt next.

6. A process as claimed in any one of claims 1-5, characterized in that a cobalt catalyst is used which comprises zirconium 10 as other metal and silica as carrier.

7. A process as claimed in any one of claims 1-6, characterized in that the conversion of the H2/CO mixture is carried out O at a temperature of 125-350°C and a pressure of 5-100 bar.

8. A process as claimed in claim 7, characterized in that the 15 conversion of the Hg/CO mixture is carried out at a temperature of 175-275°C and a pressure of 10-75 bar.

9. A process as claimed in any.one of claims 1-8, characterized in that the mild thermal cracking of the heavy fraction of the product prepared over the cobalt catalyst is carried out in 20 the presence of steam.

10. A process as claimed in claim 9, characterized in that the mild thermal cracking is carried out at a temperature of 535-675°C, a pressure of 1-5 bar abs., a residence time of 0.5-15 seconds and in the presence of a quantity of steam which amounts to at 25 most 40 %w, calculated on the hydrocarbon feed. „ 11. A process for the preparation of linear C10-C20 olefins

'O' and, substantially as described hereinbefore and in particular with reference to Experiments 4, 5, 6 and 7.

12. Linear C10-C20 olefins, whenever prepared according to 30 a process sis claimed in any one of claims 1-11. /H. J- ■" ''r\ 92 °ER /t(jUc&L ' " 4GtNTS FOR 7Hi APAJCA .W*.