US3533766A - Process for reforming hydrocarbons under high pressure - Google Patents

Description

Oct. 13 1970 I ,Lp, m n ErAL I 3,533,766

' raocnss FOR am-onumemnnocmaons UNDER men rnns smua Filed May 3', 1967 1 5 Sheet-Sheet 1 Oct. 13, 1970 p, G G E ETAL 7 3,533,766

I PROCESS FOR REFORMING HYDROOARBONS UNDER RIGH PRESSURE Filed May 5, 1967 I s Sheets-Sheet a Oct. 13, 1970 J. P. GIGNIER S ,5

rnocnss FOR anronume nvnnocmoxs unnsa man PREssUnE Filed Bay 3, 1967 5 Sheets-Sheet 3 I r/fiji'u w ilak zn" gag am Oct. 13, 1970 Filed May 3, 11967 J. P. GIGNIER L PROCESS FOR REFORMING HYDROCARBONS 'UNDER HIGH PRESSURE 5 Sheets-Sheet 4 Oct. 13, 1970 Y Y J, P, GIGMER ETAL 3,533,766

PROCESS FOR REFORMING HYDROGARBONS UNDER HIGH PRESSURE Filed May 3, 1967 s Sheets-Sheet 3 Fig.8

United States Patent Ofice 3,533,766 Patented Oct. 13, 1970 3,533,766 PROCESS FOR REFORMING HYDROCARBONS UNDER HIGH PRESSURE Jean P. Gignier, Meudon, Pierre LHonore, Douai, Jacques Quibel, Paris, and Michel Senes, Saint-Nazaire, France, assignors to La Societe Chimique de la Granrle Paroisse, Azote et Produits Chimiques Filed May 3, 1967, Ser. No. 635,837 Claims priority, application France, May 11, 1966, 61,061; Apr. 14, 1967, 102,684 Int. Cl. C01b 2/14 US. Cl. 48214 6 Claims ABSTRACT OF THE DISCLOSURE A process for the catalytic reforming with steam of gaseous and liquid hydrocarbons having a boiling point not greater than 350 C., wherein the process is carried out under an effective pressure in the range of from 70 to 200 bars.

This invention relates to the catalytic reforming of gaseous and liquid hydrocarbons, particularly methane, propane, butane, residual gases from refining, light and heavy petroleum fractions and fuels, having a final boiling point not greater than 350 C.

Hydrocarbons can be converted to fuel and synthesis gas, for example, by cracking, partial combustion or reforming. In reforming the hydrocarbons are reacted with steam, usually in the presence of a catalyst, at relatively high temperatures. The reformed gas can be used as town gas, for the production of hydrogen, for the synthesis of ammonia or methanol or in oxo synthesis reactions.

In the know catalytic reforming processes, the reaction with the steam is carried out under effective pressures which usually do not exceed 30-40 bars in order to preserve the mechanical stability of the catalyst being used, to obviate the danger of coking and to take into account the mechanical resistance of the reforming tubes and the desired methane content of the reformed gas which normally increases 'with pressure.

According to one aspect of the present invention there is provided a process for the catalytic reforming with steam of gaseous and liquid hydrocarbons having a boiling point not greater than 350 C., wherein the process is carried out under an eflective pressure in the range of from 70 to 200 bars.

The process of the invention in particular makes it possible to avoid, or appreciably to reduce, all compression of the reformed gas before it is subsequently used in, for example, the low-pressure synthesis of ammonia or as town gas. The process of the invention also makes it possible to use a gas which has been compressed, before the reforming thereof, to a volume smaller than that of the reformed gas or to use a liquid hydrocarbon. Thus the process is applicable to gaseous and liquid hydrocarbons, particularly to the light petroleum fractions, the hydrocarbons being saturated or unsaturated. Advantageously, these hydrocarbons contain from 4 to 12 carbon atoms and, preferably, comprise up to 30% of aromatic hydrocarbons.

When the reforming process of the invention is applied to light petroleum fractions having a final boiling point lower than 250 C., the reforming reaction is preferably carried out under an effective pressure of the order of 100 bars.

It has been found that it is possible, when using catalysts which are mechanically stable and of Which the efficiency increases with pressure and when carrying out the process using reforming tubes having diameters smaller than those of the reforming tubes used in reforming processes carried out under the conventional, lower pressures, to increase the operating pressure up to 200 bars without causing the disadvantages previously referred to. It is therefore possible to make reforming tubes from a conventional steel, for example of the 25/20 type, having a thickness which is not prohibitive for pressures in the range of from to 200 bars.

The reaction of hydrocarbons with steam is of the free-radical type and, in accordance with a development of the present invention, catalysts have been found which are sufficiently active and selective to lead to the production of reformed gas having a methane content which is between 10 and 15% using steam/carbon mol ratios which are in the range of from 3 to 5; these catalysts are described hereinafter. On the other hand, in order to obtain a reformed gas with a high proportion of methane, for example a gas which can be used as a substitute for natural gas, it is possible to operate at steam/ carbon mol ratios of from 1.5 to 3, preferably in the region of 2. It has moreover been confirmed that the catalysts of the present invention do not coke the hydrocarbons in the presence of a steam/carbon mol ratio higher than 1.5 even when operating under high pressures in accordance with the process of the present invention.

The influence of the proportion of steam on the methane contents of the reformed gases at a given pressure, in this case at 100 bars, can be seen from the curve in FIG. 1 of the accompanying drawings in which figure the proportions of steam employed, expressed as steam/ carbon in mols (H O/C), are plotted as abscissae and the methane contents of the reformed gas, expressed as a percentage (CH percent), are plotted as ordinates.

The influence of the pressure on the methane content of the reformed gas for a given volumetric velocity, in this case 1, can be seen from FIG. 2 of the accompanying drawings in which figure the pressures (P) expressed in bars, are plotted as abscissae and the methane contents of the reformed gases, expressed as a percentage (CH percent), are plotted as ordinates.

In order to profit from the main advantage of the process of the present invention, viz the reduction in the consumption of energy, it is frequently desirable to proceed with the reforming process at the highest possible pressure.

The internal diameter of the reforming tubes is advantageously in the range of from 10 to 100 mm. when, in accordance with the present invention, the reforming process is carried out at a pressure in the range of from 70 to 200 bars. Advantageously, when working under a pressure of 70 bars, the internal diameter of the reforming tubes lies in the range of from 70 to 100 mm., when working under a pressure of 100 bars, the reforming tubes have an internal diameter which is in the range of from 20 to 60 mm., and when working under a pressure of 200 bars, the internal diameter of the reforming tubes is in the range of from 10 to 50 mm.

Generally, the effective length of the reforming tubes is in the range of from 6 to 15 metres. By tube there is meant not only unitary members but also any tube made up from similar separate units which are Welded or otherwise joined directly together. However, two tubes connected by a part not containing catalyst and two tubes which although joined together have different diameters and not considered as being a single reforming tube in the present invention but are considered to be two tubes.

The influence of the volumetric velocity on the methane content of the reformed gas is small. A threefold increase in the volumetric velocity affects the methane content by less than 30% depending on whether the process is for the reforming of one hydrocarbon or a mixture of hydrocarbons. The volumetric velocity of a liquid hydrocarbon is preferably chosen to be in the range of from 1 to 30 litres per litre of catalyst. The influence of the volumetric velocity on the methane content of the reformed gas can be seen more clearly in FIG. 3 of the pressure do not suffer from mechanical degradation due to the chemical action of the reactants. These catalysts contain, as stabilisers, at least one of potassium oxide, chromium trioxide, sodium oxide and barium oxide in an amount which does not exceed 15% and is preferably accompanying drawing in which figure the volumetric D from 1 to 5% by weight of the catalyst composition. Sevvelocity v, in litres, is plotted as abscissae and the methane eral examples of these new catalyst compositions are content of the reformed gas, expressed as a percentage given in the examples below. (CH percent), is plotted as ordinates for a given pres- The reforming process of the invention offers a further sure, in this case 100 bars. advantage, viz. that of operating with or without the addi- Preferably, the mixture to be reformed is introduced tion of different gases at the inlet to the reforming tubes. to the catalyst at a temperature which is in the range of For those hydrocarbons which can be desulphurised by from 300 to 700 C., preferably 500 to 600 C. At the hydrogenation of the organic sulphur, which contain too outlet from the reforming tube, the temperature of the much carbon with respect to hydrogen, hydrogen recycled reformed gas is in the range of from 500 to 9 0 C, in a suitable proportion is introduced into the reforming preferably 800 to 900 C. tubes. When the reformed gas is intended for the prepara- In 4 0f the accompanying drawings there is tion of town gas, air or nitrogen are possibly introduced. shown a curve which gives the temperature inside a re- In cases where it is desired to modify the composition of f rm ng tu as a fun ti n of its length, Which ak s it the effiuent mixture, it is possible to introduce carbon possible to change from the minimum to the maximum onoxide or carbon dioxide. without depositing carbon and without destroying the The reforming process of the invention is particularly Catalyst The temperatures in are given s Ordiapplicable to the preparation of hydrogen or of synthesis hates, While the lengths in centimetres are given as gas intended for synthesising ammonia, which contains 5 abscissae. to 20% of residual methane and has a discharge temy Catalyst Permitting the reforming Process to P perature of 700 to 900 C. It is also applicable to the ceed with volumes which are smaller in proportion as atio f town gas which is rich in methane, conthe pressure is raised can be used in the present invention. t in between 5 and 40% of hydrocarbons equivalent to 111 general terms, the Catalysts Which are Suitable for methane and has a discharge temperature of 500 to 750 y g out the invention have one of more of the C. The process is also applicable to the preparation of lowing Characteristics! town gas having a calorific power of 3,000 to 5,000 th (a) They give rise to an increase in efficiency with inc creasing Pressure; The invention is illustrated in the following examples. (b) They give rise to an increase in the selectivity with EXAMPLE 1 increasing pressure, the selectivity being wlth respect to methane, ethane and ethylene at the outlet; Light petroleum fractions of empirical formula (C) They have a composition such that there is no C H were treated in the reforming tube, having an increase in the methane content of the reformed gas internal diameter of 18 mm., which is shown diagram- When the reforming process is carried out at pressures in matically in FIG. 5 of the accompanying drawings. In the range of from 70 to 200 bars and it is possible to FIG, 5 th points C C C C represent points in the Obtain, at 100 bars, a g Which is little different from 40 reforming tube at which the temperature is measured by that which is obtained when operating at pressures in the means of thermocouples each situated in a sheath of exegi n f 2 i0 30 bars Under te p a re C n i ternal diameter 9 mm. The reforming tube contained such that it is possible industrially to provide reforming 170 1, of a reforming atalyst having the following tubes at a cost which is of the same order as that of recomposition and designated type A: forming tubes adapted for use at lower pressures, this Nio 9 3 being due to a decrease in the diameter of the reforming M20 tubes and an increase in efiiciency of the catalyst. Z r

r0 5.1 Su1table catalysts comprise nickel, as the catalytlcally SiO 0 3 active component, on supports comprising refractory c2102 oxides. The catalytically active metal content of these catu alyst compositions is in the range of from 8 to 30% by A series of tests was carried out under an effective presby weight, calculated as nickel oxide. The refractory sure of 100 bars. The rates of flow of hydrocarbon, steam oxides on which the nickel catalyst is supported are one and hydrogen, the proportions of steam used, the temperor more of magnesium oxide, calcium oxide, zirconium tures recorded at the different points C C C and C dioxide, aluminium oxide and silicon dioxide. Advantaand the composition of the reformed gas are set out in geously, the catalyst compositions contain from 0 to 45% the following Table I:

TABLE I Rates of flow Recordedcttgiaperatuies Hydro- Analysis of reformed gas carbon, Steam H2, H20 0 C1 n1l./l. l./h. l./h 11l11l01S CO2 00 H2 CH4 (inlet) C2 C C4 by weight of magnesium oxide, from 0 to by weight of aluminium oxide, not more than 25% of calcium oxide and not more than 10% of silicon dioxide. The

present invention also provides catalysts which satisfy the above conditions and which when under a very high lion Chromatographic analyses confirmed that the reformed gas did not contain any C hydrocarbons.

Catalysts of type A do not have sufficient mechanical strength to make them suitable for use in industrial opera- EXAMPLE 2 The tests carried out in Example 1 were repeated, using a light petroleum fraction of empirical formula C H in a reforming tube identical to that described in Example 1 but containing 170 ml. of a reforming catalyst having the following composition and designated type B:

The rates of flow, proportions of steam, temperatures and compositions of the reformed gas were measured, as in Example 1, and are set out in Table II below:

there were treated light petroleum fractions having the empirical formula C H The catalysts used had the following compositions and designations:

The following experimental results as set out in the following Table III, were obtained using an effective pressure to 100 bars, with 0.1 mol of recycled hydrogen. per mol of hydrocarbon for the desulphurisation. In Table III the volumetric velocity is given in litres of hydrocarbon per litre of catalyst.

TABLE II Rates of flow Hydro- Analysis of reformed gas Temperatures,0. carbon, Steam, Hz,

mL/h. l./h. l./h. HzQ/C CO2 CO H2 CH4 C1 C2 C3 C4 TABLE III Temperatures, C.

At% 011 Analysis of reformed gas of leaving Catalyst Volumetric At catalyst the type velocity H2O/C CO; 00 Hz CH4 inlet length catalyst Catalysts of type B, like those of type A, do not have sufiicient mechanical strength to enable them to be used in industrial operations in which a long effective life of the catalyst is required.

EXAMPLE 3 In a reforming tube, identical to that described in Example 1, having an internal diameter of 18 mm. and heated by electric resistances of which the power is reg- The catalysts C, D, E and F functioned for 200 hours without any apparent defect and, on discharge, were free from carbon. 1

In FIG. 6 of the accompanying drawings there is shown curves A and B, which were obtained by plotting the ratio H O/C, in mols, as abscissae against the percentage methane contents (CH percent) of the reformed gas as ordinates, for the case of the catalyst E, the reforming process being carried out at pressures of 100 bars ulated by thermocouples placed in the reforming tube and 30 bars, respectively.

7 EXAMPLE 4 In a reforming tube identical to that described in Example 1 and containing 170 ml. of a catalyst having the composition given below and designated type G:

there were carried out a series of tests, the results of 8 an effective length of 12 metres. Each tube contained 34 litres of catalyst of type G.

The hydrocarbon to be reformed was a light petroleum fraction having a boiling point of 40-140 C. The rate of fiow of this hydrocarbon was 48 litres per hour. The steam ratio, H O/C, was 3 and 0.1 mol of hydrogen per mol of hydrocarbon was recycled. The temperature of the mixture to be reformed on entering the catalyst was 500 C. and that of the mixture leaving the catalyst was 950 C. Under these working conditions, the gas mixture produced had the following composition (based on dry gas):

which are set out in the following Table IV. The tests Per ent were carried out under an effective pressure of 100 bars CO 13 with 0.1 mol of hydrogen per mol of light petroleum CO fraction of empirical formula C H being recycled H 65 in order to hydrogenate the sulphur. CH 12 TABLE IV Temperatures at $4 41 on Analysis of reformed gas of leaving olumetrie catalyst the velocity H2O/C CO2 00 H2 CH4 At inlet length catalyst It was found that the catalysts of type G are particularly eflicient when reforming under high pressure.

EXAMPLE 5 In a reforming tube identical to that described in Example 1 and containing 170 ml. of a catalyst having the composition given below and designated type H:

there were carried out a series of tests, the results of which are set out in the following Table V. The tests were carried out under an effective pressure of 100 bars with 0.1 mol of hydrogen per mol of light petroleum fraction of empirical formula C H being recycled in order to hydrogenate the sulphur.

In FIG. 7 of the accompanying drawings there are shown diagrammatically embodiments of this installation adapted for different uses of the reformed gas.

Firstly, the installation shown in FIG. 7A of the accompanying drawings is one which can be used for the separation of hydrogen or synthesis gas. In this installation, the primary reforming combustion is conventional and is carried out at atmospheric pressure. The mixture to be treated arrives by way of the conduit 1 at a primary reforming reactor 2 under a pressure of to 200 bars and the reformed gases leaving at 3 at about 700 to 800 C. contain 10 to 25% of methane. To reduce the methane content, peroxidised air is used if the mixture is intended for the synthesis of ammonia or oxygen is used if it is desired to obtain a nitrogen-free gas. The peroxidised air or the oxygen, which is produced at 4, is united by way of the conduit 5 with the gas which has undergone a primary reforming and these gases are sent by way of the conduit 6 into a secondary reforming reactor 7, where TABLE V Temperatures At rd Analysis of reformed gas of cat- On leav- Volumetric At alyst ing the Test N0. velocity 1120/0 CO2 00 Hz 0H4 inlet length catalyst EXAMPLE 6 their temperature is raised on leaving to 1000 to 1100 C. The methane content of the gases leaving the reactor 7 and flowing through conduit 8 is between 0.1 and 1%. The gases then undergo a high and low temperature conversion at 9 and then a decarbonation at 10. After methanisation at 11, the gases leaving at 12 contain 0.3 to 1% internal diameter of 60 mm., a thickness of 36 mm. and of methane and 0 to 25% of nitrogen, under a pressure of 9 60 to 140 bars, and can be used for obtaining hydrogen or for the preparation of the synthesis gas.

In addition to the saving in energy over the compression energy due to the increase in the working pressure, the diagram of the installation shows the advantage of a high degree of compactness, due to the reduction in quantities of catalysts for the primary and secondary reforming steps, and for the conversion and methanisation, which are much more active at the working pressure of the installation than at 20 to 30 bars. The result is a saving in investment costs and the possibility of large productions being treated in a single line, i.e., the gas necessary for 1000 to 2000 tons per day of ammonia.

Secondly, the installation shown in FIG. 7B of the accompanying drawings is one which can be used for the preparation of synthesis gas. The gases treated in this installation are light fracitons of petroleum, of natural gas or of refinery gas. These gases, under a pressure of 70 to 200 bars, are introduced through an inlet 13 to a primary reforming reactor 14 and, on leaving the latter at 15, they have a temperature of 700 to 800 C. and contain 10 to 25 of methane. A secondary reforming is carried out at reactor 18 in air, which is introduced by way of conduit 16 into conduit 17 containing the gases which are to be subjected to the secondary reforming. The gases leave the reactor 18 at a temperature of 800 to 900 C. and contain to 15% of methane. These gases are conveyed by way of conduit 19 to high and low temperature conversion units 20. The carbon monoxide leaving with the lowtemperature conversion is transformed catalytically at 21 into carbon dioxide gas by the addition of air or oxygen or peroxidised air through tube 22. The excess of methane or air does not produce town gas and it is condensed at 23 in a cold housing, in which the carbon dioxide gas is Washed at low temperature; the residual gases are returned through the conduit 24 to the primary reforming combustion stage and the synthesis gas is liberated at 25 under a pressure of 60 to 140 bars. It may be noted that the layout of this installation is particularly simple and economic.

In the FIG. 8C of the accompanying drawings there is shown an installation for the preparation of hydrogen or synthesis gas. In order to limit the thickness of the reforming tubes for the reforming, the combustion of the primary reforming is effected under pressure, and the vapours are expanded in a turbine. The pressure in reforming tubes 26 is from 70 to 200 bars and, in jacket 27, it is from 50 to 200 bars. The fuel is introduced into jacket 27 at from 50 to 200 bars by way of conduit 28, as is the combustion supporter introduced through conduit 29. The vapours leaving the jacket 27 are expanded from 40 to 140 bars to atmospheric pressure at 30.

The gases which have undergone the primary reforming in the reforming tubes 26 have a methane content of 0.5 to and are at a temperature of 850 to 1050 C. The secondary reforming is carried out in air, oxygen or peroxidised air which is introduced by way of the conduit 31. The gases originating from the primary reforming step and the air, oxygen or peroxidised gas are conveyed to the secondary reforming reactor 33 through conduit 32. After the double reforming, the gases leave at a temperature between 950 and 1100" C. and contain from 0.1 to 2% of methane.

In FIG. SD of the accompanying drawings there is shown an installation in which, for the purpose of limiting the thickness of the tubes and making this installation even more compact, the primary and secondary reforming steps are carried out in the same chamber, the combustion supporter being peroxidised air or oxygen. This installation is intended for the preparation of synthesis gas or oxygen. The combustion supporter, being either peroxidised air or oxygen, is produced in 35 and introduced under a pressure of 70 to 150 bars and through pipe 36 into jacket 37. The primary reforming of the gases, introduced under a pressure of 70 to 150 bars, takes place in reforming tubes 38. The treated gases are introduced bymeans of the tube 39 into the secondary reforming chamber 37, and the gas leaving at 40 is at a temperature of 950 to 1100 C. and its methane content is from 0.5 to 1%. In this installation, which is of greatly reduced size, the catalytic reactions are carried out both inside and outside the tubes.

From a study of the results of the tests described in the examples, it will be seen that a family of catalysts has been found, of which the efficiency is very similar. The new catalysts are characterised by the following points:

(a) the contents of residual methane are higher, all other things being equal at bars than at 30 bars, but the increase in the proportion of steam used is not prohibitive and methane contents between 10 and 15% are easily obtained with steam/ carbon ratios of 3 to 5;

(b) in order to obtain a gas with a high proportion of methane, for example so as to produce a gas which can be substituted for natural gas, it is possible to operate at a steam/ carbon ratio of 2 or at a lower temperature (below 800 C.) with higher steam/ carbon ratios;

(c) there is no obstruction of the reforming tubes, due to carbon deposition;

(d) the mechanical resistance of the catalysts is good; and

(e) the influence of the volumetric velocity is low.

What we claim is:

1. In a process for catalytic reforming with steam of light fractions of petroleum containing about 030% of aromatic hydrocarbons, with a boiling point lower than 350 C., in which the saturated and unsaturated hydrocarbons contain 4 to 12 carbon atoms in their molecule, the improvement wherein after a preliminary operation of pre-heating said hydrocarbons to 300-600 C., the reforming process is carried out under an effective pressure of 100 to 200 bars, the volumetric supply of the hydrocarbons to be reformed is between 1 to 30 liters per liter of catalyst and per hour, the reforming mixture is introduced to the catalyst, which is present in a reforming tube having an internal diameter of 10-100 millimeters and an effective length of 6-15 meters, at a temperature which is between 300700 C., and the ratio steam to carbon in moles is 1.5-5; said catalyst comprising 8-30% nickel calculated as nickel oxide and a refractory oxide metal support comprising 045% magnesium oxide, calcium 0X- ide, zirconium dioxide, 060% aluminum oxide, with about 0 and no more than 10% by weight of silicon dioxide.

2. A process according to claim 1, wherein said volumetric supply does not exceed 15 liters per liter.

3. A process according to claim 1, wherein steam to carbon said ratio is in the range of from 3 to 5.

4. A process in accordance with claim 1, wherein said catalyst support comprises up to 25% by weight of calcium oxide based on the total weight of catalyst composition.

5. A method in accordance with claim 1, wherein said catalyst composition further comprises at least one stabilizer selected from the group consisting of potassium oxide, chromium trioxide, sodium oxide and barium oxide, said stabilizer being present in an amount not exceeding 15% by weight of the catalyst composition.

6. A method in accordance with claim 5, wherein said stabilizer is present in an amount of from 15% by weight of the catalyst composition.

References Cited UNITED STATES PATENTS 2,028,326 1/1936 Hanks et al 23-288 3,119,667 1/ 1964 McMahon 23--212 3,132,010 5/1964 Dwyer et al. 48196 X (Other references on following page) 1 1 UNITED STATES PATENTS Pearce et a1 252472 X Fox et a1. 48196 X Pfefferle 48-214 X Poehler et a1 23288 Van Hook et a1. 252472 X Taylor et a1 48214 X Housett et a1. 482l4 12 FOREIGN PATENTS 772,787 4/1957 Great Britain.

US. Cl. X.R.

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