US3161696A - Autothermal cracking of hydrocarbons to cracked gas rich in olefines - Google Patents

Description

Dec. 15, 1964 EDER E AL K. AUTOTHERMAL CRACKING OF HYDROCARBONS TO CRACKED GAS RICH IN OLEFINES Filed Sept. 3, 1959 3 Sheets-Sheet 1 FIG. 1

TEMPERATURE PROFlLE OF THE REACTOR CATALYST ZONE 'C 1/ 000 900- i 8O0 V 100- eoosoo 400- %1 DIRECTION OF FLOW INVENTORS:

KURT EDER HELMUT NONNENMACHER PAUL SCHMULDER ATT'YS Dec. 15, 1964 K. EDER ETAL 3,161,696

AUTOTHERMAL CRACKING 0F HYDROCARBONS T0 CRACKED GAS RICH IN OLEFINES Filed Sept. 3, 1959 3 Sheets-Sheet 2 FIG. 2

INVENTORS KURT EDER HELMUT NONNENMACHER PAUL SCHMULDER Dec. 15, 1964 E ER ETA K. D L AUTOTHERMAL CRACKING OF HYDROCARBONS TO CRACKED GAS RICH IN OLEFINES Filed Sept. 3, 1959 3 Sheets-Sheet 3 IOO INVENTORSI KURT EDER HELMUT NONNENMACHER PAUL SCHMULDER ATT'YS United States Patent Ofifice 3,161,696 AUTOTHERMAL CRACKING F HYDROCARBGNS T0 CRACKED GAS RICH IN OLEFIh-ES Kurt Eder, Ursenhach, and Helmet Nonnenmacher and Paul Schmulder, Lndwigshafen (Rhine), Germany, assiguors to Badische Anilin- & Soda-Fabrik Aktiengesellschaft, Ludwigshafen (Rhine), Germany Filed Sept. 3, 1959, Ser. No. 837,832 Claims priority, application Germany Sept. 6, 1958 Claims. (Cl. 260-683) This invention relates to a process for the autothermal cracking of hydrocarbons to a cracked gas rich in olefines; especially it relates to a process of this kind in which gaseous and/or vaporizable hydrocarbons are reacted without flame formation in contact with rigidly arranged bodies of inert nonporous refractory material in two stages with an amount of oxygen insufiicient for the complete combustion of the hydrocarbons.

According to prior methods, hydrocarbons, for example ethane or propane or mixtures thereof and also higher vaporizable hydrocarbons were reacted by mixing these previously heated-up hydrocarbons with an amount of oxygen insuflicient for complete combustion, possibly with admixture of steam, and autothcrmal reaction at a rigidly arranged layer of inert substances. The heat set free in the exothermic reaction stage is directly utilized for the local endothermic cracking of the unburnt remainder of the hydrocarbons which then takes place.

There is formed a cracked gas which is rich in oletines and contains the combustion products carbon monoxide and carbon dioxide.

It has not hitherto been possible however locally to fix the exothermic reaction zone in the cracking vessel and thus to achieve a constantreaction chamber when working at furnace inlet temperatures of the gas of 500 to 600 C. with high throughputs and/or'with the addition of large amounts of steam.

High throughputs in this known procedure cause a migration of the exothermic reaction peak, which is preferably adjusted to a temperature range between 800 and 900 C., to the end of the reactor, i.e., the reaction migrates out from the furnace. In a similar way, addition of large amounts of steam to the initial gases also has the efiect of extinguishing the reaction.

One object of the invention is the production of gaseous olcfines, especially ethylene and propylene. Another object of this invention is to fix locally the exothermic reaction'zone or the reaction temperature peak which characterizes this reaction zone. The advantage of fixing the reaction temperature peak is that the reaction chamber remains constant.

A further object of this invention is to carry out in a trouble-free manner the autothermal cracking of hydrocarbons and to prevent interruptions to its continuous course due to migration of the reaction zone out from the cracking furnace or extinction of the reaction.

.A further object of the invention is to prevent carbon deposits in the autothermal cracking of hydrocarbons, especially at a high degree of cracking, high space-time yields and high cracking temperatures.

The present inv tion starts from a process for the fiamelcss reaction of gaseous and/or vaporizable hydrocarbons in two stages in contact with rigidly arranged bodies of inert non-porous refractory material, especially ceramic material, wherein in the first stage a part of the preheated hydrocarbon is reacted with an amount of oxygen insutficient for complete combustion, preferably in the presence of steam, until the oxygen has been completely used up, and in the second stage the residual hydrocarbons are cracked to olefines.

The invention consists in using in the first stage a rigidly arranged body of inert non-porous refractory ma- 3,161,696 Patented Dec. 15, 1964 terial which has been coated with a small amount of copper and/or compounds thereof, preferably with the addition of an activator. In general, a coating which is applied to the surface of these non-porous materials in an amount of 0.05 to 2.0% by weight based on the weight of the inert material produces satisfactory results. The amount of catalytically active substance to be applied preferably lies between 0.1 and 1.0% by weight. It is advantageous to use copper or copper compounds.

The invention efiects a stabilization of the reaction zone in the reactor even at high gas thronghputs with optimum space-time yields and/ or with additions of large amounts of steam.

High throughputs improve the space-time yields, permit higher cracking temperatures and diminish the undesirable side reactions leadingto carbon deposition, even at degree of cracking of the hydrocarbons of about 96 0.

According to the process of the present invention there may be reacted gaseous hydrocarbons, especially ethane, propane and butane, and vaporizable hydrocarbons, for example light gasolines and mixtures oi these hydrocarbons, i.e., liquid hydrocarbons having a' boiling point between 40 and 200 C. The said hydrocarbon mixtures may also contain a proportionfot olefines, for example up to 30% by volume. The process is especially suitable for the cracking of hydrocarbon mixtures containing ethane and propane as the main constitutents and up to 15% by volume of olefines, especially ethylene and p py 1-. I L1."

The amount of steam to be'added varies in g ene'raibetween 5 and 30% by volumewith reference to the con tent of hydrocarbon; it is adjusted appropriately according to the olefine content of the initial gas, i.e., larger amounts of steam are added for larger olefinecontent's. In the industrially usual gaseousihydrcbcarbons, olefine proportions of 10% by volumeor m -amay occur. The added steam avoids carbon deposits i'n the heating-up path of the initial gas and also pre-ignitions when the initial gas is mixed with oxygen." It is preferable to'mix the initial gas with the oxygen in a suitable mixer prior to entry of the gas into the reactor.. In general 10 to 40% by volume, advantageously about 30% by volume, of oxygen with reference to the hydrocarbon content is added. The reaction can be carried out in one or more reactors. It is not necessary completely to fill the reactor space of the first stage with bodies which are coated withcopper and/ or their compounds according to the invention. According to a particularly useful embodiment of our invention there is provided a common reactor ,for both stages, i.e., the exothermic stage and the endothermic stage, which reactor is charged with the bodies 'in three superposed layers and only the central layer consists of bodies which have been coated with copper and/or their compounds according to this invention. This layer, which occupies about one third of the height of the reactor, is intercalated between untreated,

The first layer, which occupies about one-third of the filled height, serves to effect a uniform distribution of the introduced gas mixture. In the second layer, in which the bodies present have been coated with catalyst, the ignition and consequently the start of the exothermic reaction is efiected. In this layer there thereby takes place a relatively steep rise in temperature. As a rule the maximum temperatpre is set up in the middle, advantageously in the last third, of this layer. This siting of the maximum temperature is regulatable in a simple way by the extent of the preheating and the speed of flow of the gas mixture introduced. It is especially advantageous to regulate the temperature peak so that it is displaced into the space immediately behind the catalyst Zone, i.e., at the entrance to the third zone, which again is filled with inert may pass through a'temperature'range of 650 to 950 C. fromthe point of entry to the point of exit. in the third layer of'filler bodies, which again consists of inert nonporous refractory material, the temperature, after passing through a temperature at about 800 to 9 0 C., falls to about 750 to 900 C. at the point of exit. Y a

reaction zone in which the endothermic cracking takes place, and by the use of catalysts the endothermic cracking is in general localized behind the catalyst zone, there is no increased deposition of carbon. Since however the catalysts direct the oxidation more in the direction of the combustion of the hydrocarbons first reacted with oxygen to form carbon monoxide, a smaller proportion of the hydrocarbons is used up for the production of the heat necessary for cracking, the oxygen is better utilized, and the absolute yield of olefines is increased.

The following example, which is given with reference to FIGURES Zand 3 of the accompanying drawings,

A process for thej production of olefines byitherrhal 1 cracking of highboilinghydroc'arbons' in the vapor phase is known "in which similarlythe heating up'of the }material to be cracked is effected by complete combustion of apart of the same and wherein a solid substance pro- 'rnoting, the oxidation is used in a small heating zone arranged in front ofthe actual cracking zone. In this 7 process, howevenfsubstances with a large active surface, for example a surface of more than 40 square meters per gram, are the oxidation zone. In contrast, in the process according to this invention, bodies of noneporous refractory, especiallyfceramic, material are used which have a compact structiire with the smallest possible active surface, "zindfinded in both stages, As the refractory substance it is preferable to use porcelain, sillimanite or 1 corundum inpiecesorballs, having a diameter r 1p and 6f one'eighth of the diameter offthe. reac'tdnfin general of ajsiz'e' of 20 tof100'inm. eter. WheQ J Ig these substances" eir'ainpletheform. of porcelain halls, having a diameter .f of about 20 10.160 only small of carbon areidepos'itd 'tlie lifejoi. ItheIoxidatidn catalyst makesfpossiblebarryingoutthe'pr ss cdntiii 'In order to ve i ineraries cube catalysts to thelinaterialswitha'sinall rheanl'ysrs arsja s ueafiom'a solution or dispersiomadvantageously bkde'pos'ition by vaporization in vaciio '61- by sprayin on. The catalysts be iPlQve'd in their action by actiyating additions. addition bf. 0.5 to 5% of ceiium for example has proved an excellentfactivator.

FIGURE}, a s ss-Panamanian riprtidiices a, typical'temperature profile of a reactor with inbuilt catalystlayer. On the'abscissa' 'is plotted the local positiono f the temperature given'i'nthe ordinates. The direction of new of the gas is from left to right the draw, ing. temperature profile is obtained "in a reactor. with three. superposed, layers of non porous refractory ies or jam 'dnlyit h'e middle layer is mammal:

catalysts to invention. From the diagram it can be seen that the temperaturefofthe 'gas mixentering the reactor; starting from the preheattemperature between 550. and 600 C., rises only slowly up to the point of entry into the catalyst layer, then however in the catalyst or shortly thereafter the peak height of ab out800 to1900 C. is reached, and. then during the e "othermic cracking reaction in the last third of the reactor, it fallsfslowly to' outlet temperature of about 800 For the stabilization of the exothermic reaction, the fixation of the peak of the reaction temperature the catalyst layer itself is not a prerequisite. The peak of thereaction temperature may rather be displaced in the direction of the flo g gas behind the catalyst layer and into the layer'of untreated bodies. I

The addition of catalyst is without influence on the endothermic cracking process and therefore on the yield of olefines with reference to the hydrocarbons reacted endothermically. Since in the autotherrnal cracking process it is known that carbon deposits take place chiefly in the further illustrate this invention but the invention is not restricted to this example. 1

' Example 300 -'cubic meters per hour of a mixture of ethane and propane with an addition of 50 to 60 kilograms of steam pass through a countercurrent heatexchanger 1 (see FIGURE 2) into-a mixer 2 wherein a'mixing nozzle withan attached diifusor cubic meters per hour of oxygen and about 10 kilograms of steam are admixed. The mixture passes into the bottom of a reactor 3 which is 2 meters'in heightand 60 centimeters in width and which contains in'thel'ower third 'of itsheight a distributing layer Aj of uhpretreate'd porcelain balls (diameter 30 min.), in' "tlie middle third B of the filled height porcelain ballsicoatedjwith copper and in the upper third C again nripr'etreated porc lain balls. fIn the stationary operating condition, the gas mixture enters the reactor at 550 C.,' reaches the't'e'mpe'rature'peakof the exothermic reacv830 10..[The h'ot'crack'ed gas enters thecountercurrent heat e;changer, rand gives up its sensible heat'therein to the fresh gas (ethane, propane) and steam, which is thereby preheated to. 550 to 600 C. The cracked gas, cooledto about 300 C'., 'thenjpasse's through a cooling and Washing system 4 where it'iscooled directly with water and freed from water-soluble byproducts.

During the setting in superman ofthe rea'ctor, the initialgas mixture passes in the mixer land the entry into the reactor at on 1y about 5001C. Without a copper catalyst to catalyze the. exothermic reaction, this temperature would not be sufiicientto start the exothermic reaction. Even whenythe hydrocarbon gas is preheated to the technicalIyreaIizable extent of 500 to 600 C. in a preheater heated by extraneous gas, the reaction, in theabsence of the stabilizing catalyst, does not remain in the reactor and the reaction fails.

reaction is initiated at 400 C. and with a, preheating to about 540" C. remains in the reactor. for a practically unlimited period. Without the use of catalyststdotted line, curve 2), the reaction migrates spontaneously from the reactor, even when the preheating is 570 ,C.

To prepare the, catalyst used, 1 kilogram of copper bronze or 1.25 kilograms of'copper oxide powder are homogenized inlliters of water with the addition of 0.4 kilogram of a water-soluble glue paste. The dispersion is thensprayed with a conventional paint spray-gun onto 0.2 cubic meter of porcelain balls preheated to C.

and spread out on netting. The sensible heat of the balls causes the water in the dispersion to evaporate and after the balls have been homogeneously coated in this way with an adherent layer of catalyst and glue, the material is ready to be installed in the reactor. The Cu proportion is about 0.5% by weight with reference to the whole material (carrier and catalyst).

Instead of preheating the porcelain balls, the dispersion can be sprayed onto the cold balls which are then dried in the air or if desired in a drying chamber.

We claim:

1. A continuous process for the autotherrnal cracking of hydrocarbons to produce olefines which comprises preheating hydrocarbons selected from the group consisting of normally gaseous hydrocarbons, normally liquid bydrocarbons having a boiling point of up to about 200 C. and mixtures thereof to a temperature of from 300 to 650 C., leading the vapors of said hydrocarbons together with an amount of oxygen insuflicient for the complete combustion of said hydrocarbons through a reactor containing three adjacent layers of inert non-porous refractory bodies, said bodies in each layer having a minimum diameter of mm. and a maximum diameter of one eighth of the diameter of the reactor, only the bodies in the middle layer having been previously coated with from 0.05 to 2.0% by weight with reference to the weight of said bodies of a catalytic material selected from the group consisting of copper and compounds thereof.

2. The process as claimed in claim 1 wherein the coating applied to the middle layer also contains 0.5 to 5.0% by weight of cerium.

3. The process as claimed in claim 2 wherein steam is added to the vapors of preheated hydrocarbons in an amount of 5 to 30% by volume with reference to the hydrocarbon content.

4. A two-stage continuous process for the flameless reaction of hydrocarbons to produce olefines by autothermal cracking which comprises reacting preheated hydrocarbons selected firom the group consisting of normally gaseous hydrocarbons, normally liquid hydrocarbons having a boiling point of up to about 200 C. and mixtures thereof with oxygen in a first stage in contact with catalyst-coated inert non-porous refractory bodies at temperatures of from about 650 C. to 950 C., the amount diameter of 10 millimeters and a maximum diameter of one-eighth of the diameter of the reaction stage, only the inert bodies of said first stage having been previously coated with a catalytic material selected from the group consisting of copper and compounds thereof.

5. A process as claimed in claim 4 wherein the hydrocarbons are introduced into said first stage with the addition of steam in an amount of about 5 to by volume with reference to the hydrocarbon content.

6. A process as claimed in claim 4 wherein the inert refractory bodies in said first stage are coated with a copper catalyst in an amount of about 0.05 to 2.0% by weight with reference to the inert refractory material.

7. A process as claimed in claim 6 wherein the catalyst coating also contains about 0.5 to 5.0% by weight of cerium as an activator.

8. A process as claimed in claim 4 wherein the maximum temperature produced by the exothermic reaction in said first stage is displaced and maintained immediately behind said first stage at about the entrance to said second stage.

9. A process as claimed in claim 4 wherein the hydrocarbon feed for cracking contains up to about 30% by volume of olefines.

10. A process as claimed in claim 4 wherein the hydrocarbon feed for cracking consists essentially of a mixture of ethane and propane with up to about 15% by volume of olefines.

References Cited in the file of this patent UNITED STATES PATENTS 2,629,753 Frevel et al Feb. 24, 1953 2,824,148 Keulemans et a1 Feb. =18, 1958 2,872,472 Fenske et al Feb. 3, 1959 2,898,292 Halik et al Aug. 4, 1959

Claims (1)

1. A CONTINUOUS PROCESS FOR THE AUTOTHERMAL CRACKING OF HYDROCARBONS TO PRODUCE OLEFINES WHICH COMPRISES PREHEATING HYDROCARBONS SELECTED FROM THE GROUP CONSISTING OF NORMALLY GASEOUS HYDROCARBONS, NORMALLY LIQUID HYDROCARBONS HAVING A BOILING POINT OF UP TO ABOUT 200*C. AND MIXTURES THEREOF TO A TEMPERATURE OF FROM 300 TO 650*C., LEADING THE VAPORS OF SAID HYDROCARBONS TOGETHER WITH AN AMOUNT OF OXYGEN INSUFFICIENT FOR THE COMPLETE COMBUSTION OF SAID HYDROCARBONS THROUGH A REACTOR CONTAINING THREE ADJACENT LAYERS OF INERT NON-POROUS REFRACTORY BODIES, SAID BODIES IN EACH LAYER HAVING A MINIMUM DIAMETER OF 10 MM. AND A MAXIMUM DIAMETER OF ONE EIGHTH OF THE DIAMETER OF THE REACTOR, ONLY THE BODIES IN THE MIDDLE LAYER HAVING BEEN PREVIOUSLY COATED WITH FROM 0.05 TO 2.0% BY WEIGHT WITH REFERENCE TO THE WEIGHT OF SAID BODIES OF A CATALYTIC MATERIAL SELECTED FROM THE GROUP CONSISTING OF COPPER AND COMPOUNDS THEREOF.

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