NO120846B - - Google Patents

Description

Catalytic reforming process.

The invention relates to reforming processes for hydrocarbons and more particularly to a new catalytic material and a method for reforming a naphtha fraction in the presence of the new catalyst

* In ;lysator. The new catalyst comprises platinum <p>g rhenium supported j ; on a porous solid support material. Catalytic reforming is well known within the petroleum industry and relates to the treatment of naphtha fractions to improve octant. The more significant hydrocarbon reactions that occur! ;i ;during the reforming using catalysts comprising <1>dehydrogenation-promoting metal constituents, includes dehydrogenation of naphthenes to aromatic compounds, dehydrocyclization of normal paraffins to naphthenes and aromatic compounds, isomerization of normal paraffins to isoparaffins and jhydrocracking of relatively long-chain paraffins. Hydrocracking reactions that give high yields of light, gaseous hydrocarbons, such as methane and ethane, must be especially avoided during (the reforming as this reduces the yield of products in the gasoline range" Since hydrocracking is also an exothermic process in contrast to reforming which is generally endothermic, ad-following hydrocracking reactions which cause the production of large quantities of light, gaseous products, • severe temperature fluctuations which can cause the temperature to not be kept under control during the reforming. ;Because of the need for hbyoctane gasolines for use as motor fuel etc. much research is being done to develop improved reforming catalysts and catalytic reforming processes. Catalysts for good reforming processes must have good selectivity, i.e. So they must be able to give high yields of petrol products with a high octane number and possibly low yields of light, gaseous hydrocarbons or carbonaceous by-products. In general, high octane gasoline products can be obtained from a given feedstock by applying more severe conditions with respect to temperature or lower space velocity. However, the petrol yield gradually decreases as the product's octane number increases. The catalysts are thus often evaluated with regard to their yield/octane selectivity, i.e. compared on the basis of the achievable bone-to-sine yield at the desired octane number for the product. Catalyst properties must also "have good activity so that it will not be necessary to use an elevated temperature for the production of a certain quality product. Apart from good selectivity and activity, it is also necessary that the catalysts have good stability so that activity - and the selectivity properties can be retained over long periods of operation. Catalysts comprising platinum, e.g. platinum supported on aluminum oxide, are well known and widely used for reforming naphthas and gasoline materials for the production of high octane gasolines. Platinum catalysts are highly selective with respect to production of aromatic compounds with a high octane number and very active in connection with the majority of reactions that occur during the reforming. Platinum catalysts are, however, also very expensive due to platinum's high price, and catalysis will be difficult "IflT enf VnérncbsTibåré "p"å""grunfr"å"v~a€'_meta!.-let is only available in limited m meadows. These economic factors have led the petroleum industry to seek less expensive substitutes for platinum and to initiate research into catalytic promoters for use with the platinum catalysts to increase their activity, stability and, in particular, selectivity with respect to to petrol yield/octane number, thereby making platinum catalysts more economical for use in reforming processes. Rhenium has been proposed for use in catalytic reforming as a replacement for the more common catalytic constituents, such as in platinum. However, rhenium has proved to be very poor for use in reforming. Rhenium alone supported on charcoal or aluminum oxide thus proved to have only limited reforming activity, while very large concentrations of the metal, over 5% by weight, were necessary to achieve good activity. iIt has also been proposed to use rhenium together with palladii.m ji reforming processes. Thus, a pre-sulfidized series I catalyst comprising palladium and rhenium impregnated on aluminum oxide proved to have a better initial reforming activity than a j, previously sulfidized palladium-aluminum oxide catalysts when used for reforming a sulfur-containing naphtha. However, the activity of the previously sulphided catalyst of palladium and rhenium decreased considerably after a short period of use. In connection with the development of the present invention, a catalyst comprising platinum and rhenium together with aluminum oxide was prepared, but it turned out that when used for reforming a naphtha fraction, the catalyst caused a very strong hydrocracking. The production a<y> large quantities of light gases,; such as methane and ethane, was considerably greater than the production of light gases using a catalyst comprising platinum alone on aluminum oxide. In other words, the catalyst based on platinum and rhenium proved to be less selective for the production of high octane gasoline products than a platinum aluminum oxide catalyst. When introducing the naphtha fraction into the reaction zone, a strongly exothermic reaction was also observed in the catalyst layer. A catalyst comprising platinum and rhenium on aluminum oxide was also prepared, after which the catalyst was sulphide-treated and examined by using For reforming a sulfur-containing feedstock. The catalyst was found to have poor selectivity and activity. The yield of high-octane products were low and the reforming process was apparently economically unattractive. Although rhenium has thus been proposed for use together with noble metals, such as palladium, it turned out that such cocafination was not satisfactory under the above-mentioned conditions. ;i . It has now very surprisingly been shown that if certain process conditions are met and/or the catalyst is exposed to certain pre-treatments, a catalyst comprising platinum and rhenium supported on aluminum oxide will have a high activity and especially a good selectivity and stability when used for reforming sulfur-free feedstocks It was particularly unexpected that a supported platinum/rhenium ka lysator would initially show an undesirable hydrocracking after which the hydrocracking became negligible; 'Continued reformation. After the first period, the catalyst comprising platinum and rhenium on aluminum oxide is superior to a catalyst comprising platinum alone on aluminum oxide in that the initially poor reforming which causes "production of large quantities of light gaseous hydrocarbons can be tolerated for the time being necessary to reduce the catalyst engine's extremely strong hydrocracking activity. It is possible to achieve longer operating periods with higher yields of hbyoctane products by using the platinum/rhenium supported catalyst instead of a platinum catalyst without rhenium. In accordance with the present invention, an improved reforming process is carried out in the presence of catalysts comprising platinum and rhenium on or in porous solid support materials. Small concentrations of rhenium, i.e. below about 5% by weight, are effective as activators for platinum reforming In ;catalysts as they measurably lower the decreasing yield rate, i.e. that they increase the stability of the catalyst when the feed material does not contain sulphur. According to the invention, a reforming of a sulphur-free naphtha fraction is thus accomplished by bringing the fraction into contact under reforming conditions and in the presence of hydrogen with a catalyst comprising a porous, solid catalyst substrate with an intimate mixture of 0.01-3 wt. $ platinum, and 0.01-5 wt$ rhenium. In accordance with the invention, a new catalyst composition is also provided, comprising a first catalyst, a catalyst with an intimate mixture of 0.01-3 wt% platinum and 0 .01-5 weight? rhenium. The new catalyst according to the invention has been shown to be very active and stable during the reforming of naphtha and hydrocarbons within the boiling point range for gasoline and is far better than commercially available reforming catalysts containing platinum, but without rhenium. ;The invention will be described in more detail with reference to ; the curves in Fig. 1 and 2 which, for comparison, show data from simulated lifetime experiments indicating the reforming activity and stability of a common catalyst comprising platinum on an aluminum oxide substrate, and a catalyst comprising platinum and rhenium on an aluminum oxide substrate. The operating conditions were stronger than those normally used during a reformer in order to simulate the reaction of the catalysts on a much longer test (lifetime test). The curve in Fig. 1 shows the average catalyst temperatures as a function of test times and hours during operation which are necessary to maintain a jlOO-octane product (F-1 pure) for each of the two catalysts. The curve in Fig. 2 shows the yield of 0^+ liquid product or 100-octane gasoline as a function of operating time during reforming with each of the two catalysts. It is clear from Fig.2 that by using the platinum-rhenium catalyst considerably larger amounts of 100-octane petrol product are obtained than by using the platinum catalyst. The catalyst temperatures and volume percentages of influent with more than 5 carbon atoms used to j perform the comparisons according to icurvehe were obtained only after j the hydrocracking activity of the platinum-rhenium catalyst had been reduced to that of the platinum catalyst. The catalysts had thus been in operation for several hours before the comparisons shown on the curves according to Fig. 1 and 2 were carried out. It is not unequivocally clear why rhenium activates platinum-containing catalysts when reforming naphtha. Although it is not intended to limit the scope of the invention or to be bound by any theoretical explanation, there are indications that the rhenium forms an alloy with the platinum and that this alloy <:>may be partly responsible for the improved results obtained when using the platinum-rhenium catalyst in relation to a conventional platinum catalyst. ;i'' Ro ri tg én- ~6 g electron difTr axion s u h d or b ole e 1 r, c f' of' 'the Iri "é talli "slk o :fa.ses present in the catalysts comprising various j ; .concentrations of platinum and rhenium supported on aluminum oxide, indicate that the platinum-rhenium phase changes noticeably in a similar way to the change that can be observed in pure platinum-rhenium alloy systems, i.e. systems without bar material. For a reference to a phase diagram for a pure platinum-rhenium alloy system, see e.g. Hansen, M., and Anderko, K., "Constitution of jBinary Alloys", MoGraw Hill (1958), suggest that for concentrations of rhenium of from 0 to about 40 atomic weight percent and at temperatures below at least 1750°0 there is only one platinum-rhenium phase, i.e. the face-centered cubic (fsk) crystal structure for platinum. Above 40 atomic percent rhenium, the hexagonal close-packed (htp) rhenium structure can also be observed. Investigations carried out with catalyst samples comprising platinum alone on aluminum oxide, rhenium alone on aluminum oxide and different concentration levels of platinum and rhenium on aluminum oxide have shown that for rhenium concentrations on the catalyst of below approx. 50 atomic weight percent, the hexagonal close-packed rhenium structure was not present, or at least could not be detected. Only the face-centered 'cubic platinum structure was present. At higher concentrations of rhenium on the catalyst, i.e. over approx. 50 atomic weight percent - rhenium, the hexagonal close-packed rhenium structure could be observed. The platinum-rhenium catalyst samples that were used to investigate the crystal structure of the metals were prepared by heating the catalysts to elevated temperatures, e.g. 815°C, either in the presence of wet or dry hydrogen to thereby reduce the metals to metallic state. ;i It is also known from investigations with pure platinum-rhenium systems that the addition of rhenium to platinum reduces the lattice spacing in the planar cubic platinum unit cell. This reduction in the lattice spacing gradually as rhenium is added to platinum under such conditions that an alloy is formed, can be observed by the increase in the diffraction angle, 28, when applying:-jav OuKa-^ radiation, from the (311) plane to the face-centered cubic platinum structure. A change in the rhenium concentration in platinum The aluminum oxide catalysts also cause a bending of the diffraction angle, 26, from the (311) plane to the face-centered cubic platinum structure. the enium-j catalyst causes a t ilstretch al - i e ntnr f nmk- kyvn- l ne m<g>rt ;the expected stbrrelsretnirig"' in"diffraction'JonswinkelerT,™ 29", "to" that" a -strong indication that an alloy is forming. Further evidence supporting the theory that alloying is formed for platinum-rhenium supported catalysts is the observation that the size of the face-centered cubic platinum particles decreases as rhenium is added to the platinum-aluminum catalysts. The particle size of the face-centered cubic platinum, as determined by electron diffraction studies of catalyst samples reduced in hydrogen at constant temperature, decreases with each addition of rhenium until practically the equiatomic platinum-rhenium composition has been reached. The metal particle size is related to the density with which the metal sinters, i.e. the smaller the particles, the less the metals have sintered. 'This ease with which sintering takes place is in turn connected with the melting point of the metals, i.e. the higher the metals; melting point, the more difficult it will be for sintering to occur. The reduction in the size of the face-centered cubic particles as rhenium is added to platinum-aluminum oxide catalysts is thus assumed to be due to the increase in the melting point of the alloy formed. This observation is in agreement with the chemistry of pure platinum-rhenium alloy systems which show that the addition of rhenium to platinum causes a bending of the j f face-centred cubic crystals!. melting point. j ;I ;The porous, solid carrier material or support material which is used in the production of the platinum-rhenium catalyst according to the invention can comprise a large number of materials on which the catalytically active amounts of platinum and rhenium can be deposited. The porous, solid carrier material can, for example, be made of silicon carbide, charcoal or carbon. The porous, solid carrier material is preferably composed of an inorganic oxide. It is particularly preferred to use a support material of inorganic oxide with a large surface area, e.g. an inorganic oxide with a surface area of 50-700 m /g. The carrier material can be a natural or synthetically produced inorganic oxide or a combination of inorganic oxides. Of typical acidic inorganic oxide carrier materials that can be used, mention can be made of the naturally occurring aluminum silicates, especially if they have been acid treated to increase their activity, and the synthetically produced cracking carrier materials, such as silicon dioxide aluminum oxide, silicon dioxide zirconium dioxide, silicon ;(iioxyd -aluminium oxide-zirconium dioxy pxyd, silicon dioxide-aluminium oxide-magnesium oxide" and crystalline peolitic aluminum silicates. In general, however, ojfrination processes are carried out in the presence of catalysts with low cracking activity, i.e. in the presence of catalysts with limited acidic. Inorganic oxides, such as magnesium oxide and aluminum oxide, are therefore preferred carrier materials. Aluminum oxide is a particularly preferred catalytic carrier material for use in the present invention. Any form of aluminum oxide that is suitable as a support material for reforming catalysts can be used. Aluminum oxide can also be produced using a number of methods which are satisfactory for the purposes of the present invention. The preparation of aluminum oxide for use in connection with reforming catalysts is well known. The new reforming catalyst comprises a desired porous solid catalyst support material with an intimate mixture of catalytically active amounts of platinum and rhenium. The preferred ^catalyst according to the invention preferably comprises approx. 0.01-5 wt$, and more especially approx. 0.2-1 wt.$, platinum based on the finished catalyst. Platinum concentrations below approx. 0.01 wt% is too low for the reforging to proceed satisfactorily, on the other hand, platinum concentrations above approx. 3 by weight as a rule is unsatisfactory because they cause too strong cracking. Furthermore, due to the fact that platinum is very expensive, the quantity of platinum that can be used is somewhat limited. The rhenium concentration in the finished catalyst mixture is preferably 0.01-5 by weight $, and more particularly 0.1-2 wt#. Higher concentrations of rhenium could be used with advantage, but the price of rhenium limits the amount that can be used on the catalyst. It is preferred to use an atomic ratio of rhenium to platinum of about 0.2 - about 2.0. More particularly, it is preferred that the atomic ratio between rhenium and platinum should not be greater than 1. Higher j ratios, i.e. over | of rhenium to platinum can be used, but it is usually obtained no further significant improvement by using My«ye conditions. Although platinum and rhenium can be intimately associated with the porous, solid support material by means of a suitable technique, such as ion exchange, co-precipitation, etc., the metals are associated as jl.;, I am eT "m"é d' "d et 'por ose"raw"srU'é~"Carrier"S'aTeriale"" vea ~Tmpr egTI"SrT! T[g~." ^Furthermore, one of the metals can be connected to the carrier material using one method, e.g. ion exchange, and the other metal can be connected to the carrier material using another method, e.g. impregnation. As stated however, the metals are preferably connected to the carrier material by means of impregnation. The catalyst can be produced either by simultaneous impregnation of the two metals or by impregnation in sequence. In general, the carrier material is impregnated with an aqueous solution of a cleavable compound , of the metal in sufficient concentration to obtain the desired amount of metal in the finished catalyst. The resulting mixture is then heated to remove water. It is generally preferred to use chloroplatinic acid as a source of platinum. Other suitable platinum-containing compounds, eg ammonium chloroplatinates and polyamineplatinum salts can also be used Of rhenium compounds suitable for coating on the support material , perrhenium acid and ammonium or telium perrhenates can be mentioned, among other things. The aim of the present invention is that the introduction of metals together with the carrier material should be able to be carried out at any particular stage of the catalyst production. If, for example, the metals are to be applied to an aluminum oxide substrate, the application can take place while the aluminum oxide is present as a sol or gel, after which the aluminum oxide is precipitated. A previously prepared aluminum oxide carrier material can also be impregnated with an aqueous solution of the metal compounds. Regardless of which procedure an- ; used for the preparation of the supported platinum-rhenium catalyst, it is preferred that the platinum and rhenium be intimately associated with and dispersed throughout the porous, solid catalyst support material. After platinum and rhenium have been added to the support material, the resulting composition is usually dried by heating to a temperature of e.g. not over approx. 260°G, and preferably at a temperature of approx. 93.3-204t4°C. Then, if desired, the composition can be calcined at an elevated temperature of, for example, up to approx. 649°0. ;7 - The carrier material containing platinum and rhenium is heated ~ cf. or. step by step at a high temperature to convert the platinum and the rhenium into a metallic state. The heating is preferably carried out in the presence of hydrogen, preferably dry hydrogen. It is particularly preferred to carry out this pre-reduction at a temperature of 315.5-704.4°G, preferably 315.5-537.8°C. Reforming using certain of the catalysts according to the invention initially produces a very large amount of light hydrocarbon gases unless a suitable pretreatment or start-up technique is used. The light hydrocarbon gases are produced due to the catalyst's high hydrocracking action or metal cracking action. It has been shown that the hydrocracking effect is reduced if the catalyst is sulfidized before it is brought into contact with naphtha. This presulphidation can be carried out in situ or 3X in situ by passing a sulphurous gas, e.g. F^S, through the catalyst layer. Other sulfidizing pretreatments are also useful. ,,, It has also been shown that at start-up a small amount of sulphur, e.g. HgS or dimethyl disulfide added to the reforming loop zone effectively reduce the catalyst's initial hydrocracking action. The near-type form of sulfur used for sulphidation is not critical. The sulfur may be introduced into the reaction zone in any suitable manner and at any suitable location. It may be contained in the liquid hydrocarbon feed, the hydrogen-rich gas, the recovered liquid ether stream or a recovered gas stream or in any combination. After the reforming has been carried out in the presence of sulfur for a short period of time compared to the total operating period achievable with the new catalyst, the sulfur addition must be discontinued in order to obtain the full benefits, such as a reduced yield reduction rate or improved stability. according to the invention must be achievable. The time required to reduce the initial hydrocracking activity will vary from several hours to several hundred hours depending on the amount of sulfur used, the severity of the operating conditions and the platinum/rhenium alloy. The time required to reduce the initial hydrocracking activity varies inversely proportionally with the sulfur content, the severity of the cracking conditions and the platinum/rhenium ratio. It has also been shown that the addition of an ethoxygen oxide anion of sulfur, such as a sulfate, sulfite, bisulfate, or bisulfite, associated with the catalyst composition provides the catalyst with beneficial properties in that it helps to with controlling its <:>initially high hydrocracking activity Thus, the presence of sulfate together with a catalyst comprising aluminum oxide and catalytically active amounts of platinum and rhenium reduces the yield of light hydrocarbon gases initially produced during the reforming as well as during the dehydrocyclization of n-heptane to aromatic compounds. The oxygen-containing anions of sulfur can be introduced into the catalyst material during the production of the porous, solid carrier material. Thus, for example, in the production of an aluminum oxide carrier material, the aluminum salt used as starting material can be present in sulfate form. - the precipitation of aluminum oxide usually means that a smaller amount of isulphate will v honor associated with the aluminum oxide. An oxygen-containing anion of sulfur can also be applied to the catalyst support material by contacting the previously prepared support material with suitable compounds containing oxygen-containing anions of sulfur, e.g. SO^ , SO^ , HS0^~, or HSO^<-. > The oxygen-containing anions of sulfur can advantageously be present in the finished catalyst in an amount of 0.05-2% by weight, preferably 0.1-1% by weight. During the reforming, the catalyst according to the invention preferably has platinum and rhenium in a metallic state. Thus, although the catalyst is brought into contact with sulfur and the metals are apparently converted to sulfides before or during the reforming to thereby reduce the catalyst's original hydrocracking activity, the catalyst is freed of sulfur during the original reforming period. The sulfur (ril') is therefore removed and the metals, j ;i platinum, and rhenium, are converted to the metallic state for approximately the same time that is necessary to reduce the high j hydrocracking activity. during the reforming process, sulfur will have to be continuously added to the catalyst, an addition of sulfur during the entire reforming process is not satisfactory according to the invention. The catalyst can be activated for the reforming by the addition of halides, especially fluoride or chloride. The halides give the catalyst apparently a limited acidity which is advantageous in most reforming processes. A halide-activated catalyst preferably contains 0.1-3 wt% total halide content. The halides can be introduced into the catalyst support material at any suitable stage during the preparation 4v the catalyst, eg before or after the introduction of platinum into rhenium Some halide is often introduced into the carrier material during the impregnation with platinum. Thus, for example, impregnation with chloroplatinic acid usually adds chlorine to the carrier material. Additional halide can, if desired, be incorporated onto the base material simultaneously with the incorporation of the metal. As a rule, the halides are combined with the catalyst support material by bringing suitable compounds, such as hydrogen fluoride, ammonium! fluoride, hydrogen chloride or ammonium chloride, either in gaseous form or dissolved in water, in contact with the carrier material. The fluoride or chloride preferably incorporates onto the support material from an aqueous solution containing the halide. ;The form in which the catalyst is produced is usually determined by the handling to which it will be subjected. If, therefore, the forming process according to the invention is to be carried out by an-;^ytelandndeilnsge ean v frfaemsst tisklilkes t i elfloerr aj baeyvlteagbelleig ttesrki,k. pte, lvleitl sk, actuallyefsaortmore-de -articles or extruded particles. If, on the other hand, saliva is taken on to use a fluidized bed, the catalyst is prepared in fine gelled form. The feedstock to be used during the reforming is a light hydrocarbon oil, for example a naphtha fraction. The naphtha generally boils within a temperature range of about 21, 1-287.8°C, preferably 65.5-232.2°0. The feed material can, for example, be either a directly distilled naphtha or a thermally cracked oil or catalytically cracked naphtha or mixtures thereof. The feed material should be practically sulphur-free , i.e. that the supply material should preferably contain less than about 10 ppm sulphur, preferably less than 5 ppm and the whole less than in ppm. The presence of sulfur in supply material it reduces both the catalyst's activity and its stability. When using a feed material that does not already have a low sulfur content, acceptable amounts can be obtained by applying it to a small ferrial t" T "e n~" f forme triage zone where the haftha is brought into contact with a hydrogenation catalyst that is resistant to sulfur poisoning. A suitable catalyst for this hydrodesulfurization process is, for example, an aluminum oxide-containing support material and a small amount of molybdenum oxide and cobalt oxide. The hydrodesulfurization is usually carried out at a temperature of 371.1-454.4°C, an overpressure of 14.061-140.61 kg/cm<2> and at $n liquid space velocity per hour of 1-5. The sulfur present in the naphtha is converted into hydrogen sulphide which can be removed for the reforming by means of suitable conventional methods. ;The reforming conditions will largely depend on the feed material used, whether this is strongly aromatic, paraffinic or naphthenic, and on the desired octane number of the product. j The temperature below r the eformation ,,vtfJi generally be approx. j ;15.5-593.3°0, preferably approx. 371.1-565.6°G. The pressure in reform-! The ring reaction zone can be atmospheric or superatmospheric. i However, the pressure will generally be an overpressure within the j cm range 1.7577-70.31 kg/cm2, preferably approx. 3.5153-52.73 kg/cm2j the temperature and pressure can be adjusted in accordance with the 'liquid space velocity per hour (PRHT) to promote any j dom particularly desirable reformation reaction, such as! g(romatization, isomerization or dehydrb~g eirerl~ njg. The liquid !rlom rate per hour will generally be 0.1-10, preferably 1-5 ;i ; ;i Hydrogen is usually formed during the reforming. An excess j ajv hydrogen thus does not necessarily need to be added to the reforming system. However, it is generally preferred to introduce an excess of hydrogen at one stage or another during the process, for example during start-up. The hydrogen can be introduced into the feed material because it is brought into contact with the catalyst or it can be brought into contact simultaneously with the introduction of the feed material into the reaction zone. In general, the hydrogen is recycled over the catalyst before the feed material is brought into contact with it. The presence of hydrogen causes a reduction in the formation of coke which tends to poison the catalyst. In addition, the the presence of the hydrogen is used to promote certain reforming reactions. Hydrogen is introduced preferably in the red propagation reactor in an amount of approx. 0.5- approx. 20 moles of hydrogen : pjr. mol supply method material. The hydrogen can be present in a mixture i i ; t ;méd Light, gaseous hydrocarbons. An excess of hydrogen """ - removed after separation from the products, is generally cleaned and recycled to the reaction zone. After a period of operation where the catalyst has been deactivated by the presence of carbonaceous deposits, the catalyst can be reactivated or regenerated by conducting an oxygen-containing gas, such as air, in contact with the catalyst at an elevated temperature to burn off carbonaceous deposits from the catalyst'. The method used for regeneration of the catalyst will depend on whether a static bed, moving bed or j fluidized bed. Regeneration methods and conditions are well known. j ;EXAMPLE 1 I ;A common rhenium-free catalyst containing 0.7 wt% platinum on aluminum oxide was examined and compared for its dehydrogenation activity for cyclohexane with a variety of j catalysts containing different amounts of rhenium on it in said platinum-aluminium oxide mixture. j ;Platinum-aluminium the oxide catalyst was prepared by impregnating the aluminum oxide with chloroplatinic acid. The platinum-rhenium: aluminum oxide catalysts were prepared by impregnating pre-impregnated platinum-alumina catalysts with aqueous solutions containing perrhenic acid in sufficient concentrations that the finished catalysts contained the desired amount of rhenium. Treatment was carried out by heating the catalysts* for 12 hours at on temperature of 76.67°C and then for 3 hours at a temperature of 204.44°C. Catalysts impregnated with platinum or platinum and rhenium were treated with a hydrogena tabsphere in an amount of 6.9 liters per minute per grams of catalyst for 2 j hours at different temperatures.

The experiments with dehydrogenation of cyclohexane were carried out at ; a temperature of 251.66UC, a pressure of one atmosphere and a hydrogen to hydrocarbon (cyclohexane) ratio of 10. The hydrogen feed rate to the reactor was 6.9 liters Hp per minute in pr. grams of catalyst. Cyclohexane was brought into contact with the catalyst at a rate of 0.17 liters of liquid hydrocarbon J per hour per grams of catalyst. Dehydrogenation rateee for ! cyclohexane, measured as micromoljT>ene\produced per grams of catalyst

•:per hour, was determined for the different catalysts with different rhenium contents and pre-reduced at different temperatures. The results are reproduced in Table I. The catalysts containing platinum and rhenium were in all cases more active in the dehydrogenation of cyclohexane than the catalyst containing only platinum. Thus, for example, the catalyst containing 0.7 wt% rhenium and 0.7 wt% platinum and which was pre-reduced at 537.78°G had a dehydrogenation rate for cyclohexane of 54 compared to a dehydrogenator j ing rate of 37 for the platinum catalyst which was pre-reduced in lo i .at 537>78 C, but which contained no rhenium. It also appears that the dehydrogenation rate for the catalyst containing only platinum decreased faster with increasing pre-reduction temperature than the catalysts containing rhenium in addition to platinum" The catalyst containing only platinum and pre-reduced; at a temperature of 537.78°C, for example, had a dehydrogen- ; jeration rate of 37 while the same catalyst pre-reduced at a j itemperature of 871»11°C had a dehydrogenation rate of tworej 15. This is a reduction of over 50$. However, the catalyst containing 0.2 wt% rhenium in addition to platinum and pre-reduced at a temperature of 537.78°C had a dehydrogenation rate of 48 compared to a dehydrogenation rate of 35 for the same catalyst pre-reduced at a temperature of 871.11°0. This is a reduction of less than 1/3 and indicates that the platinum-rhenium catalysts are more stable than platinum catalysts which do not contain rhenium. A catalyst containing 0.7 wt% platinum and 0.7 wt% rhenium on an aluminum oxide support material was compared with a catalyst containing 0.7 wt% platinum in an accelerated reforming process. The catalysts were prepared and used as described in example 1 and then heated in hydrogen for half an hour at 232.22°C and for 1.5 hours at 371.11°C. The flow rate •for the hydrogen was in all cases 4.0 ml H9 per minute per fir: ;catalyst. The feedstock used in the reforming was a hydrorefined, catalytically cracked naphtha with an initial boiling point of 66.11°C, a final boiling point of 220°C and a 50% boiling point of 152.77°C. The tested octane number of the supply material without the addition of anti-knock agents (P-l clear) was 64.6. The naphtha contained less than 0.1 ppm nitrogen or sulphur. In the reaction zone, an overpressure of 21.092 kg/cm 2 , a (fluid space velocity per hour of 3 and a temperature sufficient to give a product with an octane number (P-l pure) of 100 was maintained.

The temperature in the reaction zone as measured by the average temperature of the catalyst layer was thus changed with time to maintain a product with 100 octane. The reforming process was carried out under conditions that mimicked a life cycle for the catalyst; That is, the conditions did not necessarily remain; maintained at the same levels as used in a commercial reforming process, but that they were generally more powerful by examining in the lab of a relatively short time of a couple of hundred hours how well the catalyst would work under a |

in •commercial process. Hydrogen produced during the reforming process | was then recirculated to the reaction zone so that there was raised | reached approx. 5.3 moles of hydrogen per moles of hydrocarbon supply.

The above comparison in Example 2 between the catalyst containing platinum and rhenium and the catalyst containing baie platinum is shown in the drawings. The change in the average catalyst temperature that was necessary to maintain the desired 100-octane product (P-1 pure) is shown in Fig. 1, and the yield of gasoline with an octane number of 100 is shown in Fig. 2. The behavior of the catalyst during the simulated lifespan trials were very poor. It will appear from Pig.l that it was necessary to increase the temperature very strongly to maintain a

100-octane product (F-l pure). Dock;; the liquid product with more than 5 carbon atoms and the desired octane number changed considerably with time as shown in Fig. 2. On the other hand, the catalyst containing platinum, and rhenium a be^ 'remarkable activity during the accelerated ireformerinjrsfnr- - isok. It appears from Fig. 2 that the naphthalene feedstock was reformed in such a way that practically 86 percent by volume of a product with an octane number of 100 (F-1 pure) was obtained over practically the entire trial period. It appears from Fig. 1 that the necessary reform

in

reaction temperature to maintain the production of a product j |with an octane number of 100 (P-1 pure) increased only to a small extent together with the temperature increase during the reforming with the platinum catalyst. It is clear that rhenium improves the stability and activity of the platinum catalyst during reforming.

In Example 2, reforming with the catalyst comprising platinum and rhenium initially gave high yields of light hydrocarbon gases, particularly methane and ethane, compared to reforming with the catalyst containing platinum but no rhenium. iGa. 170 hours of reforming were necessary to bring the production of light gases with the platinum-rhenium catalyst down to the amount of light gases produced by the platinum catalyst. A strong exothermic reaction was also observed during the initial reforming period with the platinum-rhenium catalyst. As an indication of the high yield of light gases produced during this initial run-in period, measurements were made after 143 hours of operation and showed that 25.7% by weight of the feed material had been converted to light hydrocarbon gases. The data used for the equation shown by means of the curves in Figs. 1 and 2 were obtained only after the yield of light gases when using the platinum-rhenium catalyst was approximately the same as when using the platinum catalyst, i.e. after the first 170 operating hours.

IN

! The following examples show the destructive effect that sulfur in the feed material has on the current catalytic reforming process.

IN

j EXAMPLE 3

Two catalyst samples were prepared and dried as described in example 1, the catalysts containing C_ ~~ ' _ ! . in

■ i

0.7 wt% platinum, and 0.7 wt% rhenium on an aluminum oxyiTBearer material. The samples were pre-reduced under various conditions and examined for their ability to dehydrocyclize n-heptane to aromatic compounds. A sample analyzer, catalyst A, was contacted with hydrogen for 2 hours at a temperature of 537.78°C and atmospheric pressure and then for 2 hours at a temperature of 402.22°C and an overpressure of 17.577 kg/rev". The ; another catalyst, catalyst B, was brought into contact with hydrogen for 2 hours at a temperature of 537.78°C and an overpressure of ] 17.577 kg/cm 2. The flow rate of the hydrogen was 1.4 ml j

in gas per minute per grams of catalyst. The two catalyst samples j were examined with regard to their ability to dehydrocyclize ji ■ nt-ehmpepertaa.n tuur nadv er 4d82e ,a2n2 go C ittoe g reet akovs j erontrsbyekk tianv gel17se,r 577 omfkag/tctm en2d. e Heyndrogen

was added to the reaction zone in a molar ratio of hydrogen to n-heptane of 6. The added n-heptane was brought into contact with the j catalyst at a rate of 80 ml of n-heptane per hour per, grim in 'catalyst. The added n-heptane was sulfur-free when used together with catalyst A. However, 200 ppm sulfur was present in the feed to catalyst B. The results of the dehydro4 cyclization experiments are reproduced in Table II.

It will appear from the above table that by allowing sulfur to act on the catalyst containing platinum and rhenium, an adverse effect on the catalyst selectivity is obtained.

EXAMPLE 4'

A catalyst containing 0.6 wt% platinum and 0.46 wt%; rhenium was prepared by impregnating a previously impregnated 1 platinum-alumina support material with an aqueous solution containing perrhenic acid. The catalyst was dried overnight I

in nitrocene at a temperature of 148.'3g°G and then heated for 200 { hours in air at a temperature of 371.11 o G and for 400 hours in airj1

at a temperature of 482.22°G. Then the aluminum catalyst was

oxide impregnated, with platinum, and rhéhium treated 'In eh hydrogen-j atmosphere for 1/2 hour at a temperature of 371.11°0 to reduce the metals.. The catalyst was used in a reforming process using the described in example 2 supply method material. 'Various amounts of sulfur were introduced into the feed material during the process. The reforming conditions comprised an overpressure of 35.153 kg/em, an FRHT of 2 and a mole ratio of hydrogen to hydrocarbon of approx. 8.

The feedstock initially contained less than 0.1 ppm sulfur. The pure octane number of the product produced during the reforming was 97 and the catalysts average temperature 493.33°0. 50 ppm sulfur was introduced into the feed material.

! The product's octane number fell to 91 and the average catalyst temperature increased to 498.33°CLtfed addition of 500 ppm I sulfur to the feed material the octane number fell to 86 and the ; average catalyst temperature increased to 501.66°C. Voluoj-I yield of liquid hydrocarbon with more than 5 carbon atoms was j

In approximately the same in all cases, i.e. about. 84-85 volume- i

in percentage. The results are reproduced in table III.

i ' i

The unfortunate effect of sulfur in the feed material is

! easily recognisable. The presence of sulfur in the feedstock reduces the endothermic reforming reactions that yield j hbyoctane gasoline. Thereby the catalyst temperature increases, and octane-;

! 1 the number decreases. j

In EXAMPLE 5

I A catalyst containing 0.66 wt% platinum and 0.22 wt% rhenium was prepared by simultaneously impregnating an aluminum

j oxide carrier material with platinum, in the form of chloroplatinic acid and

In rhenium in the form of perrhenium acid. The catalyst was dried and then reduced with hydrogen. j

iThe catalyst- -was- --an-<rend't 'for -to ref orm-ere"-the---hydr©Fa-££i«ej?±e,

catalytically cracked naphtha described in example 2. Reaction

the conditions included an overpressure of 35.153 kg/cm, an FRHT of 3 and a mole ratio of hydrogen to hydrocarbon of 5.3. Temperature

the trip was controlled throughout the reform process for the

.' position .of a P-1 pure product with an octane number of 100. To-

: the foreskin material initially contained less than 0.1 ppm

■ sulfur o The output temperature during the reforming process vfar ; 504.44°C. During the first 845 operating hours, the catalyst showed a low contamination rate. Thus, for example, from :, 200 hours to 845 hours the pollution rate was approx. 0.0133°C

: per hour. After an operating time of 845 hours, 10 ppm sulfur was added to the feed material. The temperature that was necessary for

production of a P-1 pure octane petrol with an octane number of 100,

at an angle of 20 degrees, i.e. the catalyst became 20 degrees less active due to the sulfur addition. After removing the sulfur I, the catalyst recovered a small amount of the activity, but it

i did not get the activity that it had for the addition of sulfur to the feed material. The contamination rate of the catalyst after the sulfur addition was 0.025°0 per hour. It appears then-

is led that even a small amount of sulfur in the feed material, j e.g. 10 ppm, has adverse effects on the catalyst. J

in

Claims (6)

1. Procedure for reforming a practically sulfur-free naphthalene production material under reforming conditions and in the presence of hydrogen using a reforming catalyst comprising a dehydrogenation-promoting metal component distributed through a porbst, solid catalyst carrier material, characterized in that the naphthalene carrier material is brought into contact with a catalyst comprising a porous inorganic catalyst support material containing an intimate mixture of 0.01-3 wt# of platinum and 0.01-5 wt# of rhenium, where the catalyst has optionally been activated with a total amount of 0.1-3 wt# of chloride and/or fluoride, and to begin with optionally contains 0.05-2% by weight of an oxygen-containing anion of sulfur and that below 1. during the original start-up period, a sulphur-containing supply method material may be supplied. 2. Method according to claim 1, characterized in that a catalyst is used with a carrier material of aluminum oxide. 3. Method according to claim 1 or 2, characterized in that a catalyst containing 0.2-1% by weight of platinum and 0.1-2% by weight of rhenium is used. k. Catalyst for carrying out the method according to claims 1-3, characterized in that it comprises a porous catalyst support material of inorganic oxide with an intimate mixture thereon of 0.01-3 wt.$ platinum, 0.01-5 wt.$ rhenium and 0.1- 3% by weight of chloride and/or fluoride and optionally 0.05-2% by weight of an oxygen-containing anion of sulphur. 5. Catalyst according to NOK of V, characterized in that the support material is aluminum oxide. 6. Catalyst according to claim h or 5, characterized in that it comprises 0.2-1% by weight of platinum and 0.1-2% by weight of rhenium.