US 3268439 A
Description (OCR text may contain errors)
United States Patent 3,268,439 CONVERSION OF WAXY HYDROCARBONS Kenneth Tupman and Anthony George Goble, Sunburyon-Thames, England, assignors to The British Petroleum Company Limited, London, England, a British joint-stock corporation No Drawing. Filed Jan. 15, 1963, Ser. No. 251,473 Claims priority, application Great Britain, Jan. 26, 1962, 3,017/62 2 Claims. (Cl. 208112) This invention relates to the conversion of waxy hydrocarbons by hydrocatalytic treatment, to give products which are characterised by a higher isoparaflin content than the feedstock. I
A principal object of the invention is the production of lubricating oil fractions of high viscosity index. In addition other fractions boiling in the gasoline, kerosine and gas oil ranges may also be produced and these fractions will have desirable characteristics such as are associated with isoparaflins, e.g. high octane number, low freezing point, low pour point and high diesel index.
It has been previously proposed to isomerise paraflin wax or hydrocarbon mixtures containing at least 20% by weight of waxy hydrocarbons at elevated temperature in the presence of hydrogen and a catalyst. The present invention is concerned with the use, in such a process, of a particularly active catalyst.
According to the present invention waxy hydrocarbons are converted at elevated temperature and in the presence of hydrogen, by contacting the hydrocarbons with a catalyst comprising a platinum group metal, a halogenatable inorganic oxide support and at least 1% wt. of fluorine, the catalyst having been prepared by contacting the support at elevated temperature with the vapour of a fluorine compound of general formula:
(where X is carbon or sulphur and Y is fluorine or hydrogen) to give said catalyst containing at least 1% wt. of fluorine.
The term waxy hydrocarbon means any normally solid paraflinic hydrocarbon. Such hydrocarbons may be prepared synthetically but their most common source is the higher boiling fractions of petroleum oils. Thus the term includes paraflin wax and microcrystalline wax as well as mixtures of waxy hydrocarbons with other hydrocarbons, for example slack waxes and waxy fractions boiling in the lubricating oil range or above. The feedstock desirably contains at least of waxy hydrocarbons and preferably at least 50% by weight of the hydrocarbon mixture.
It is believed that the principal reactions in the hydrocatalytic conversion are the isomerisation and isocracking of paraflins, but other reactions also occur including aromatisation and cracking and, when sulphur is present in the feedstock, desulphurisation. The precise characteristics of the products will depend in part on the nature of the feedstock used and in part on the process conditions and the activity of the catalyst. In general, the catalysts used in the process of the present invention are characterised by high fluorine contents. This gives high activity and in turn allows the use of milder process conditions 3,268,439 Patented August 23, 1966 for a given conversion when compared, for example, with the platinum-alumina-halogen catalysts normally used for the reforming of gasoline fractions which contain less than 1% of halogen.
The process conditions for the hydrocatalytic treatment may be selected from the following ranges:
Temperature, F. 500-1000 Pressure, p.s.i.g Atmospheric to 3000 Space velocity, v./v./hr. 0.01-10 Gas rate (recycle or once through),
s.c.f./b. up to 15000 conditions are:
Temperature, F. 650-800 Pressure, p.s.i.g 500-2500 Space velocity, v./v./hr. 0.1-5 Gas rate,s.c.f./b. 1000-10,000
The process may be operated with a fixed, moving or fluidised bed of catalyst and under liquid, vapour or mixed phase conditions. However, with the higher molecular weight feedstocks, high gas rates will be required for vapour phase operation. p
v The platinum group metal of the catalyst is preferably platinum and is preferably present in an amount from 0.1-5% wt. by weight of total catalyst, preferably from 0.1 to 1% wt. The inorganic oxide support besides being halogenatable under the conditions specified, should also clearly have the desired physical characteristics to render it suitable asa component of a hydrocarbon conversion catalyst. It is preferably a refractory oxide selected from Groups II to V of the Periodic Table, for example alumina, boria, silica, titania or Zirconia. Mixtures of two or more inorganic oxides may be used if desired. Preferred supports are alumina or mixtures containing a major proportion by weight of alumina.
Preferably the platinum group metal is added to the inorganic oxide support before the addition of the fluorine. If necessary the oxide containing the platinum group metal may be dried and/or calcined before contact with the fluorine.
The fluorine compounds within the general formula are carbon tetrafluoride, fluoroform, methylene fluoride, and the corresponding sulphur compounds, carbon tetrafluoride being preferred. Carbon tetrafluoride is an extremely stable compound and is not, prima facie, an obvious choice for preparing fluorine containing catalysts. Nevertheless it has been found suitable and it has ad vantages over other fluorinating compounds. As compared With hydrogen fluoride, for example, it is noncorrosive, easier to handle, readily utilisable in the vapour phase, less liable to damage the alumina and more suitable for preparing catalysts with high fluorine contents. As compared with alkyl fluorides containing a higher number of carbon atoms, for example tertiary butyl fluoride, it is less likely to produce carbonaceous or hydrocarbonaceous deposits on the catalyst during fluorination.
Preferably the contacting of the inorganic oxide with the fluorine compound is carried out under non-reducing conditions. A convenient method of contacting is to pass a stream of the vapour over the alumina either alone or in admixture with an inert gas, for example nitrogen, or in admixture with an oxygen-containing gas, for example air. The vapour may be recycled, desirably until all the fluoride has been used, and in this way an accurate control of the amount of fluorine taken up by the catalyst may be obtained.
The temperature, time of contact and amount of fluorine compound used affect the amount of fluorine taken up by the catalyst, increase of any of these increasing the amount taken up. Preferred temperatures are in the range 300500 C. particularly 350-450 C. and the time of contact may be from minutes to 24 hours, particularly minutes to 10 hours. In general higher temperatures are used with lower contact times and vice versa. The amount taken up should not be suflicient to destroy the oxide structure as indicated by X-ray diffraction nor form detectable amounts of free fluoride or volatile hydrogenating metal-fluorine complexes. It is believed that the fluorine compound reacts with surface groups of the oxide, with loss of an oxygen atom. Thus carbon dioxide is a product of the reaction, and, in certain cases, water may also be given off.
The amount of fluorine which can be taken up without altering the oxide structure or forming further compounds on the surface is believed to be a function of the specific surface area. For maximum fluorination of the available surface groups of an alumina support the amount of fluorine will be of the order of 3.4 10- for example 3.0 to 3.4x 10 g./ sq. metre of original surface area, the variation being due to possible slight variation of the amount of surface groups per unit of surface area between :aluminas prepared in different ways. An amount of fluorine in excess of 3.4 l0- grams/sq. metre of surface area implies either that reaction with the alumina proper is occurring, or that the fluorine is not adequately held on the catalyst and amounts in excess of this amount are preferably avoided.
Fluorination up to the limit specified results in little or no loss of surface area, for example not more than 10%, but an excess of fluorine results in a greater loss of surface area. Desirably, therefore, there is not more than 10% diflerence between the surface area of the original alumina and the fluorinated alumina.
It is believed that catalysts used in the process of the present invention have an increased isomerising activity with increased fluorine content. High fluorine contents per unit of surface area are, therefore, preferred and a convenient range is from 1.2)(10- to 3.4)(10- g./sq. In. High fluorine contents by weight of catalyst will be obtained by the use of oxides of high surface area, for example those with a surface area, as measured by nitrogen adsorption using the BET method, of at least 300 sq. m./ gram and preferably at least 400 sq. m./-gram. Such oxides give a preferred fluorine content of at least 3.6% wt. and it may be in excess of 6.0% wt.
The products from the hydrocatalytic treatment was separated into desired materials by physical or chemical means. Thus the products may be fractionated into a number of distillate cuts and a residue, the higher boil ing cuts and the residue being norm-ally suitable for use in lubricating oils. The higher boiling products are also desirably dewaxed. This is partly to remove unconverted waxy hydrocarbons, which may then be recycled to the hydrocatalytic treatment stage, and partly to improve the quality of the materials produced. This dewaxing may be given to the products from the hydrocatalytic treatment before fractionation, or to the residue and distillate cuts after fractionation, or, if desired, dewaxing may be carried out both before and after the fractionation. Any convenient dewaxing process may be used, and a convenient dew-axing temperature is in the region of 10 to -30 F. The lubricating oil fraction may also receive a'finishing treatment for example clay treatment or hydrofinishin The invention is illustrated by the following example.
Example 1 Catalyst preparation.--500 ml. of a commercial platihum-alumina reforming catalyst (designated catalyst A) containing 0.58% wt. platinum and 0.8% wt. chlorine and having a surface area of 400 m. g. were charged to a 500 ml. reactor system. Moisture was removed from the reactor system and catalyst by recycling dry nitrogen to the reactor at 800 F. and p.s.i.g. over a period of 48 hours. After the drying period the catalyst bed temperature was reduced to 670 F. and C1 vapour was admitted to the system so ias to increase the system pressure from 90 p.s.i.g. to p.s.i.g. Gas recycle was maintained during this period and continued for a further period of 10 hours, during which time substantially all the CE; vapour in the system reacted with the catalyst. The reactor was then allowed to cool and the catalyst was discharged and designated catalyst B. The platinumalumina-fluorine composite (catalyst B) contained 7.3% wt. fluorine (1.8)(10 g./m. of original surface area).
Comparison of catalysts.100' ml. charge of each catalyst were used to treat a bright-stock slack wax under the following process conditions:
Direction of flow Downwards Pressure, p.s.i.g. 1000 Temperature, F. 800 LHSV, v./v./hr. 1.0
Gas rate (once-through hydrogen) s.c.f./b 4000 The yields of the various products obtained were as follows:
Catalyst; Feed Gas and Oil to 430 0. percent wt 4. 1 89. 5 Oil above 430 0., perdent wt" 11. 1 32. 5 l0. 5 Wax, percent wt 88. 9 63. 4 Nil These data demonstrate that catalyst B is much more active for converting waxy hydrocarbons than catalyst A.
Example 2 100 ml. of a platinum-alumina-fluorine composite prepared in, the same way as catalyst B of Example 1 and containing 6.8 wt. fluorine (l.7 10- g./m. was used to treat a finished F. paraflin wax. The process conditions used and the yields obtained were as follows:
These data again demonstrate the high conversion activity of the catalyst of the present invention and show the effect of lowering the operating temperature from 800 F. to 750 F.
Inspection data on the two heaviest product fractions from Test Period 2 are given below:
Fraction '371-430j 0. 430 C.FBP
Yield (on feed), percent wt 23. 3 18. 8 Wax Content, percent wt 9.-1- 33. 2 MI. of Wax, F 121 132 Fraction Dewaxed 1 Dewaxed 1 371-430 0.. 430 C.FBP
Yield (on feed), percent wt 21. 2 12.6 F s 12. 45 22. 74 3.13 4.81 VI 126 149 Pour Point, F -10 1 Dewaxed at -2s 1 with cinch.
These fractions are suitable-as lubricating oil fractions and are particularly characterised by high viscosity indices.
Inspection data on the lighter product fractions from Test Periods 1 and 2, given below, ,indicate the high quality of the kerosine and gas oils that may be produced .as well.
. o o o a 343- Fractlon 149 232 C. 232 343 0. 371 0.
Test Period 1 2 1 2 2 n-Parafiins, percent vol. i-Parafiins, percent vol. 98 5 1 96 Naphthenes, percent vol Aromatics, percent vol. Olefins, percent vol-.." SG at 60/60 F Cloud Point, F" Pour Point, F Freezing Point, 0.... Aniline Point, C Diesel Index 1 The n-paraflm content of this fraction was found to be less than 5.0
Example 3 ml. portions of the IatinumaIumina-fiuorine composite of Example 2 were used to treat (a) A deasphalted short residue containing 2.58% wt. sulphur 1 (b) The waxy rafiinate obtained after furfural treating the above residue; this contained 1.44% wt. sulphur (c) The slack Wa obtained by dewaxing the above raffinate in the presence of MEK/toluene.
' The operating conditions employed and yields obtained were as follows:.
1 End Point 377 C.
Inspection data on the residues from runs 1 to 3 are 0 given below:
Run No 1 2 3 Process Temperature 800 F. 800 F. 800 F. 750 F.
Fraction 430 C.FBP 430 C.FBP 430 C.FBP 430 0,-FBP
Yield (on feed), percent wt. 46. 1 47. 2 17. 1 73. 0 Wax Content, percent wt 19. 6 17. 2 52. 3 58. 8 Wax M.P.. F 156 155 159 Sulphur Content, perce wt 0. 24 0.10 After Dewaxing: 1
Yield (on feed), percent wt 37- 1 39- 1 8. 2 30. 3 195. 7 118. 9 93. 42 122. 2 16. 86 12. 91 11. 68 13. 65 VI 99 109 118 111 Four Point, F 10 0 -15 5 1 Dewaxed at 25 F. with OHzCig.
Inspection data on the distillate fractions obtained from runs 1 to 3 at 800 F. processing temperature are given below:
Fraction Run Number-..
149-232 C. 232343 C. 343-371 C.
saturates Aromatics SG at 60 F./60 F Sulphur Content Freezing Point Smoke Point. Cloud Point. Pour Point.--
The data of this example demonstrate that lubricating oil fractions characterised by high viscosity indices can be produced together with high quality kerosine and gas oil fractions from a wide variety of waxy feedstocks. It is also clear that a substantial degree of desulphurisation occurs simultaneously with the conversion.
. We claim:
1. A process for the conversion of waxy hydrocarbons comprising contacting a petroleum feedstock containing at least 50% -by weight of waxy hydrocarbons at a temperature of from 650 to 800 F., a pressure of from 500 to 2500 p.s.i.g., a space velocity of from 0.1 to 5 v./v./hr. and in the presence of from 1000 to 15000 8.0.1:. of hydrogen/B with a catalyst consisting essentially of from 0.1 to 5% wt. of a platinum group metal, alumina, and from 6 to 15% wt. of fluorine, said catalyst having been prepared by contacting the support at a temperature of from 300 to 500 C. under non-reducing conditions with the vapor of a fluorine compound of'general formula References Cited by the Examiner UNITED STATES PATENTS 2,642,384 6/1953 Cox 208--139 2,668,790 2/1954 Good et a1. 260683.65 2,914,461 PM 1959 Ciapetta 208111 2,944,097 7/1960 Sternes et a1. 260683.65 3,066,176 11/1962 Schwarzenbek 260-68365 3,142,635 7/1964 Coonradt et a1. 208-111 DELBERT E. GANT'Z, Primary Examiner. ALPHQNSO D. SULLIVAN, Examiner. A. RIMENS, Assistant Examiner.