Platinum Catalysts in Refining

By S. W. Curry, B.s., M.B.A.

Universal Oil Products Company, Des Plnines, Illinois

Rejbriiiirig processes using platinunz catalysts have beconie oj- major importance in petroleum rejining during the past seven years. The?. enable the octane rating of to be greatly increased, am1 cue more economicnl than any other rejiningyrocess for the production of high octane . In this article the general nature of the processes is described and the Platforniing process is considwed iti iiiore rletnil.

Platinum in any form was virtually unused years. The end is by no means in sight, in the petroleum industry until 1949. Then since the trend in octane number requirement, Universal Oil Products Company introduced particularly for automobiles, has continued it on an unprecedented scale as the active to creep upward year by year. catalytic agent in its Platforming process for To have advocated the use of 400 ounces catalytically upgrading low octane petroleum of a noble metal, selling at about $70 per naphthas to high quality products. ounce at that time, in a catalyst charge for a Prior to the installation of the first UOP single small commercial refinery unit, would Platforming unit, platinum was found chiefly doubtless have been branded prior to 1949 in laboratories in the oil industry. In sharp as the impractical idea of a dreamer. UOP's contrast with 1949, platinum today may be announcement surprised many in the oil regarded as a most essential item in the pro- industry for that matter. duction of high octane gasoline for automo- Even after the first Platformer had been biles and piston-engine aircraft. Moreover, proven a practical success (it is still operating), substantial portions of the world's , it was over a year before the next Platformer toluene and xylenes are extracted from the was placed in operation. This, of course, is product obtained by catalytically reforming an understandable reflection of the natural petroleum naphthas. These chemicals are in prudence of the industry towards any new large demand as intermediates in the manu- process. Indeed, while facture of many other chemical products had first been used as early as 1940, and more such as plastics, man-made fibres, explosives, units were installed during the early days of rubber, insecticides and so forth. World War 11, the shortcomings of the From less than 400 ounces of platinum non-platinum catalyst and the complexity of metal contained in the catalyst charge of that the regenerative operation had categorised first Platforming unit, the use of platinum by catalytic reforming in the opinion of the in- the oil industry-as distinguished from con- dustry as too expensive for the peacetime sumption-has climbed to a matter of tons. production of motor and aviation . Thus the oil industry has risen from It was nearly two years after Universal's insignificance to the rank of one of the Platforming process had shown the industry world's foremost platinum users in seven an economically feasible route to high octanes

Platinum Metals Rev., 1957, 1 , (2), 3843 38 and aromatic chemicals from low octane molybdena-alumina, and bauxite catalysts.) naphthas, that the first competitive processes, Two processes employing platinum- also employing platinum-containing catalyst, containing catalysts of undisclosed nature were brought out by several oil companies have been announced during 1956 for the and other engineering research organisations. isomerisation of Cs and Cg It was 1952 before units employing these (Universal’s “ Penex ” process and Atlantic processes were ready to run. Refining Company’s “ Pentafining ”). No There are now six other reforming pro- commercial units employing either of them cesses in addition to Platforming available to have yet been constructed. the industry. All employ platinum- containing catalyst. Universal also has de- Increase in Octane Rating veloped a variation on the Platforming process, The response of the petroleum industry to called “ Rexforming ”, which is in com- an economically practicable catalytic reform- mercial use and employs the Platforming ing process has thus been enormous, since the catalysts. Similarly, another licensor offers particular forte of the processes is greatly to a variation on his original process. This increase the octane rating of naphthas over brings the total of platinum-catalyst reforming that which can be secured readily and processes to nine. (There are five other economically by other refinery processes. For reforming processes, too, which variously use a time, non-platinum catalyst reforming c hromia- alumina, cobalt- mol yb dena, processes enjoyed popularity because of the

The Platforming unit at the Kent Refinery of the British Petroleum Company Ltd. on the Isle of Grain. This has a capacity OJ 6,000 burrels per day

Platinum Metals Rev., 1957, 1 , (21, 39 '\ A

I f"1oio dingrant of n Plntfonning unit cheaper catalyst they employ and the relative production) with a given charge insensitivity to poisons. This is no longer an stock. advantage because increased by-product hy- The reactions may be summed up thus for drogen availability has encouraged refiners simplicity: to install facilities to clean up contaminated (I) The naphthenes present in the charge charge stocks, and thus protect the platinum are converted to aromatic hydro- catalyst . by dehydrogenation Most of the reforming processes other than (2) Some of the paraffins are isomeriscd, Platforming employing platinum catalysts other paraffins are converted to utilise regeneration in situ to prolong catalyst aromatics, and still other paraffins are life. Because the catalyst does not require it, hydrocracked Platforming is unique in not employing a (3) Sulphur compounds which may be separate regeneration system. This is one of present are decomposed to the reasons why Platforming requires in sulphide and the corresponding general less catalyst per barrel of daily charge hydrocarbon capacity than do most of the other processes. (4) Olefins are saturated and then under- But in doing so, however, it suffers no penalty go any of the reactions previously in effective catalyst life, as measured in barrels mentioned. of charge processed per pound of catalyst The dehydrogenation reaction is par- employed in the reactor system. Moreover, ticularly energy-consuming and is largely the higher initial cost and operating compli- responsible for the decrease in temperature cations of regeneration are avoided. which characterises catalytic reforming. Since the temperature level affects the reaction Reactions in Reforming kinetics and equilibria, heat must be supplied The numerous reactions comprising cata- as the reactions proceed. lytic reforming over platinum are complex, Because the writer is most familiar with it, interdependent and proceed at different rates. the Platforming process is used here to Conditions of temperature, pressure, hydro- illustrate the comrncrcial catalytic reforming gen recycle ratio and space velocity therefore of petroleum naphthas by means of platinum. are chosen to achieve the optimum overall The flow diagrap above illpstrates a typical equilibrium as indicated by the desired octane Platforming process. The raw charge stock is level (in thc case of high octane fuels) or a petroleum which is prefractionated aromatisation (when running for aromatic to separate for the reactor charge a cut boiling

Platinum Metals Rev., 1957, 1 , (21, 40 roughly between 200 and 4m'F (93 to 204OC) Kent Refinery of The British Petroleum from lower and higher boiling hydrocarbons Company Ltd. This has a capacity of 6,000 which may be present. The reactor charge barrels per stream day. A smaller Platforming is then mixed with hydrogen generated in the unit installed in a refinery in Southwestern process and heated to the desired reaction United States is shown below, while the figure temperature, ranging from 850 to 950°F overpage shows a close-up of the heart of a (454 to 51o'C). The hot charge is admitted Platforming unit-the heater and reactor to the first of four (sometimes three) reactors. sections. The platinum catalyst is contained Effluent from the first reactor is con- in the four cylindrical vessels in the centre of siderably cooler than when it entered, as a the picture. consequence of the endothermic reactions Characteristics of Charge and which occur, and is reheated to the operating temperature before it enters the next reactor. Product This is repeated with the material entering the The table on page 43 shows the character- third and the fourth reactors. istics of the depentanised charge to the reactor The final effluent is usually heat-exchanged section of a Platforming unit and the Platfor- against incoming charge, then further cooled, mate product. The reactor chargc had an and finally enters the products separator. octane rating of 48 Research, which probably Enough hydrogen for process requirements is would have increased to 70 octane or so upon compressed and recycled to the charge enter- the addition of 3 ml. of tetraethyl lead per ing the first reactor, while the remainder is gallon. This would not be a suitable fuel for by-product hydrogen of high purity. The a modern automobile. After Platforming, separator liquid is fractionated to the initial however, the octane number was 93 Research, boiling point desired by the refiner, the light unleaded, and upon the addition of 3 ml. of hydrocarbons so separated being available for tetraethyl lead per gallon was rated at over other uses in the refinery. IOO octane. Moreover, the distillation range The illustration on page 39 is an overall suits this material for use as an automotive view of the Platforming unit installed in the fuel upon the addition of " outside " light

A typical 5,000 barrels per day Platfonning unit processing mid-continent naphtha

Platinum Metals Rev., 1957, 1 , (2), 41 The heart of a Plutforming unit. The catalyst is contained in the four squat vessels in the foreground ; the heater is on the left of the photograph ends to bring the initial boiling point to climbed enormously from the modest 1,500 approximately IOO'F and increase the vapour barrels per stream day represented by the first pressure to the range of 9 to 13 pounds. Platformer. Latest published reports (I, 2) Another important point shown in these data indicate that there are now I,IOO,OOO barrels is that a yield of 83.5 per cent Cs+ by volume per day of platinum-catalyst reforming units was achieved, despite the very high octane in operation in the world, of which nearly rating secured in the final product and the 800,000 daily barrels of capacity is in United inherent volume shrinkage which accompanies States refineries. These and other (3) aromatisation. reports show that another 775,100 daily Higher octane ratings than are illustrated barrels of capacity are either planned or under in the table have been achieved by Platform- construction since January I, 1956. A grand ing. Using the variation called Rexforming, total of 1,885,100 barrels per day of catalytic which includes solvent extraction to make the reforming capacity is thus in sight. desired product, octane ratings of up to It is a little difficult to estimate how much nearly 105 Research, leaded, have been re- catalyst or what weight of platinum is repre- ported in commercial operations. Even sented in these units, since the platinum higher octane ratings can be secured with this content of the various catalysts varies with process. the process and with the type of catalyst World capacity of catalytic reforming units within processes. Moreover, there is no employing platinum-containing catalysts has uniformity in either the weight of catalyst

Platinum Metals Rev., 1957, 1 , (21, 42 employed per daily barrel of charge capacity or in the bulk density of the catalyst. Jensen Yield and Properties of Mid-continent Charge and Platformate (4) reports that typical catalyst compositions range from 0.3 to 0.8 weight per cent of 11,000 Barrels per Stream Day Commcrcial Unit platinum, and that from three to five pounds of catalyst are required per daily barrel of lecoverec capacity. rlaphtha Plat- charge forrnate

Variations in Practice Yield, volume per cent 100 83.5 There are a number of reasons for these Gravity, "API ...... 55.0 49.0 variations, among them respective catalyst Hydrocarbon analysis, manufacturing techniques, differences in volume per cent: composition intended to permit the catalyst Paraffins ...... 40 I Olefins ...... trace - to be used under various operating con- Naphthenes ...... 52 I ditions, and different processing schemes. Aromatics ...... 8 - One of UOP's catalysts, for instance, contains ASTM distillation, OF: more platinum than any of this company's Initial boiling point ... 200 I10 10 per cent ...... 222 I54 other catalysts and is tailored particularly for 20 ...... 235 I80 the production of very high octane Plat- -50 ...... -265 -245 formates. In order to achieve continuity of 90 ...... 332 336 operations, some regenerative-type processes End point ...... 384 419 employ a " swing reactor " which takes the Sulphur, weight per cent 0.012 Nil place of that one of the other reactors under- going regeneration of spent catalyst. Still Reid vapour pressure, Ib. - 4.8 other processes use more catalyst per barrel Research octane ratings: of rated capacity in order to extend the time Clear ...... 48 93.0 Plus 3 rnl. tetraethyl between regenerations, but taking a broad lead per gallon ... - 100.3 view of the industry it can be said that the amount of platinum embodied in existing reforming installations is measured in hun- bility of widening the range of hydrocarbons dreds of thousands of ounces, while installa- economically suitable for feed stocks is being tions now planned or under construction will studied. Active expansion of catalytic re- absorb further correspondingly large amounts. forming capacity is therefore probable for

The continuing upward trend of octane some time to come, but a " saturation point '' number requirement for automobile engincs must ultimately be reached after which the shows no sign of ending; there is still a building of reforming facilities is likely to slow margin of virgin gasolines and naphthas down and run parallel with thc growth of available as reformer feed, while the possi- general refining capacity.

References

I Anon...... Journal Survey of Refineries in the U.S. Oil GasJ., 1956, 54, Mar. 19, 213-246 2 Anon...... Oil Refineries of the World. World Petroleum (Annual Refinery Review Issue) 1956, 27, Jul., 148 3 Courtesy of G. H. Weber ... Prepublication survey estimate, Oil GasJ. 4 J. T.Jensen ... Catalysts for the Petroleum Industry, Chem. Eng. News, 1956, 34, Aug. 20, 4090-4095

Platinum Metals Rev., 1957, 1 , (21, 43