Patent Publication Number: US-3876529-A

Title: Aromatics hydrogenation in the presence of sulfur

Description:
[ 1 Apr. 8, 1975 I AROMATICS HYDROGENATION IN THE PRESENCE OF SULFUR [75] Inventor: Manfred Josef Michlmayr, Walnut Creek, Calif.  
 [73] Assignee: Chevron Research Company, San  
 Francisco, Calif.  
 [22] Filed: June 22, 1973 [21] Appl. N0.: 372,894  
 [52] US. Cl. 208/144; 208/217; 260/667; 260/683.68 [51] Int. Cl Cl0g 23/04 [581 Field of Search 208/143, 217, 57, 111; 260/667, 683.74  
 [56] References Cited UNITED STATES PATENTS 3,197,398 7/1965 Young 208/143 3,239,449 3/1966 Graven et a1. 208/143 3,527,695 9/1970 Lawrance et a1. 208/143 3,576,895 4/1971 Wise 260/668 A 3,647,681 3/1972 Egan 208/59 FOREIGN PATENTS OR APPLICATIONS 1,236,223 6/1971 United Kingdom Primary E,\&#39;aminer-Paul M. Coughlan, Jr.  
 Assistant E.\&#39;aminer.l. M. Nelson Anorney, Agem, 0r FirmG. F. Magdeburger; R. H. Davies [57] ABSTRACT A process is disclosed for reducing the amount of sulfur and aromatics contaminants in a hydrocarbon feedstock comprised predominantly of paraffin hydrocarbons to no more than about 5 ppm sulfur and 5 ppm aromatics. The feedstock, together with hydrogen, is contacted in a reaction zone with a catalyst comprising palladium and mordenite at a temperature in the range of from 300700F., an LHSV from 0.5 to 20, a pressure of form 100 psig to 3,000 psig. and a hydrogen supply rate of 500 to 20,000 SCF/barrel of feedstock. The mordenite has been exchanged to an extent of 5-807( of the available ionexchange sites with a multivalent metal.  
 10 Claims, No Drawings AROMATICS HYDROGENATION IN THE PRESENCE OF SULFUR BACKGROUND OF THE INVENTION 1. Field of the Invention For some hydrocarbon conversion processes. it is desirable. and even necessary. to have a hydrocarbon feedstock with as low a content of aromatics and sulfur as possible. For example. low temperature isomerization processes such as are described in US. Pat. Nos. 3,394,202 and 3.201.494. as well as in British Pat. Nos. 953.188 and 953.189. preferably utilize a feedstock having as low a level of aromatics and sulfur as possible.  
  Economic considerations strongly favor catalysts which (1) can remain on stream for long periods of time without regeneration. and (2) permit single-step desulfurization and hydrogenation of the feedstock with as little cracking as possible.  
  This invention is directed to a process combining the desirable features outlined above.  
 2. Description of the Prior Art Numerous patents have issued directed to hydrogenation of aromatics. A significant number have also issued directed to hydrogenation of aromatics in the presence of sulfur. Exemplary of these are US. Pat. Nos. 3.239.449. 3.269.939. now Re. 26.883. Re. 3.012.963. Re. 3.197.398. Re. 3.527.695. and British Pat. No. 1.186.869.  
  U.S. Pat. No. 3.197.398 teaches a process for the catalytic hydrogenation of hydrocarbons boiling in the range above about 300F. and containing up to 571 by weight of sulfur by subjecting the feedstock to the hydrogenating conditions with a catalyst comprising a zeolitiic molecular sieve having a pore diameter between 6 and 14 A. and having deposited thereon a minor proportion of Group VIII metal hydrogenating component.  
  U.S. Pat. No. 3.527.695 discloses a process for the hydrogenation of aromatics in the presence of 0.1 to 1.000 ppm of sulfur with a catalyst comprising palladium incorporated in a Zeolite with pore opening of at least 6 A. Suitable zeolites include Zeolite Y or faujasite. mordenite and Zeolite Z.  
  While the patents cited above are directed in all cases at least in a general way to the hydrogenation of aromatics in the presence of sulfur compounds. none of the references teach the low levels of aromatics and sulfur content that can be obtained using the process and catalyst of the subject invention. That is. there is no teaching of reducing both aromatics and sulfur content to less than ppm combined with less than 5% hydrocracking of the hydrocarbon feedstock and preferably less than 1% hydrocracking.  
 SUMMARY OF THE INVENTION The subject invention is a process for reducing the amount of sulfur and aromatics contaminants in a hydrocarbon feedstock by contacting the feedstock and hydrogen in a reaction zone with a catalyst comprising palladium and mordenite. The mordenite has been ionexchanged to an extent of 5-80/(. preferably -50%. more preferrably 10-30%. of the available ionexchange sites with a multivalent metal, e.g.. rare earths having an atomic weight of 57-71. calcium, barium. strontium and magnesium. The reaction is carried out at a temperature in the range of from 300-700F. and an LHSV of from 0.5 to 20. A pressure of from psig to 3.000 psig is utilized. A hydrocarbon product containing no more than about 5 ppm aromatics and no more than about 5 ppm sulfur is recovered.  
  The subject invention also encompasses the combination of the hydrodesulfurization and hydrogen process described above with the isomerization of the hydrocarbon product having a reduced sulfur and aromatics content.  
 DETAILED DESCRIPTION OF THE INVENTION As described above. this invention is directed to treatment of the hydrocarbon feedstock to reduce sulfur and aromatics contaminants to a very low level. For purposes of this invention. the level of hydrogenation of the aromatics must be such as to reduce aromatics content in the hydrocarbon product obtained to a level of no more than about 5 ppm and preferably no more than about 1 ppm. Similarly. the level of sulfur content of the hydrogen product must be no more than about 5 ppm. and preferably no more than about 1 ppm. more preferably no more than 0.1 ppm (all parts by weight).  
 HYDROCARBON FEEDSTOCK The hydrocarbon feedstocks utilized in the present invention boil in the range from about 50F. to 210F. and comprise as a major portion thereof paraffin hydrocarbons of from 5 to 7 carbon atoms. The minor portion of the feedstock will include aromatics. organosulfur compounds. and may include unsaturated hydrocarbons such as olefins and acetylenes as well as saturated hydrocarbons. which are cyclic in nature. e.g.. cyclohexanc. The aromatics content will. in general. range from 1 to 5 weight percent. although amounts up to 10% may be present. and the sulfur content will. in general. vary from 10 to 1.000 ppm.  
 PROCESS CONDITIONS The process conditions for the single-step hydrogenation/desulfurization will depend on the feedstock. the amount of sulfur present. and the extent of aromatic hydrogenation required. They fall into the following ranges:  
 Prefcrred Range Temperature. F. 300-700 400-550 Pressure. psig IOU-3.000 300-1200 Space Velocity. \/V Hr. 0.5-20 l-5 H Gas Rate. SC F/Barrel 500-20000 3.000-10.000  
  The temperature at which the process is carried out is particularly important since we have found that a threshold temperature exists below which rapid deactivation of the catalyst by sulfur poisoning occurs. Above this temperature. substantially no deactivation is apparent. A temperature above this minimum must be utilized in order to maintain both acceptable desulfurization and hydrogenation levels. although the catalyst is restored to full activity after a plant upset when temperatures are again raised to the threshold temperature.  
 CATALYST COMPOSITION The catalyst of the subject invention comprises (1) palladium and (2) mordenite. which has been ion exchanged to an extent of from 580%. preferably -50%. and more preferably 10-30% of the available exchangeable sites with a multivalent metal. Exemplary metals include the rare earths of atomic numbers 57-71. calcium, barium. strontium. and magnesium. mordenite zeolite is described in some detail in US. Pat. Nos. 3.647.681 and 3.576.895. No additional detailed description of the preparation is believed necessary. The hydrogen form. which is the preferred starting material for preparing the mordenite used in the subject catalyst. may be obtained by various methods. e.g.. by ion exchanging the monovalent metal. e.g.. sodium or potassium. with an ammonium salt followed by heating to decompose the zeolite ammonium ion to form a zeolitic hydrogen ion. Alternatively. the hydrogen form mordenite may be prepared by direct acid treatment of the alkali metal sieves. Preferably. as little monovalent metal remains in the mordenite as possible. For purposes of this invention. the mordenite may contain monovalent metals in an amount up to about 30% of the available ion exchange sites. The hydrogen ion form of the mordenite is ionexchanged with a metal selected from the class consisting of rare earths of atomic numbers 57-71. calcium, magnesium. barium and strontium. preferably calcium or mixed rare earths. The level of ion exchange for purposes of this invention must be in the range from 5-80% of the ion exchange sites available. If less than this number of sites are exchanged with the multivalent metal. e.g.. the divalent alkaline earth metals or the rare earth metals. the level of hydrocracking of the resulting catalyst will be excessive at the process temperatures. lf greater than 80% of the ion exchange sites available in the hydrogen mordenite are exchanged. the level of hydrogenation and desulfurization decreases rendering the resulting products undesirable as feedstocks to downstream processes. It is critical for purposes of this invention that the level of ion exchange be within the range specified above.  
  The palladium can be combined with the mordenite either prior to or after ion exchange treatment with the rare earths and/or alkaline earths has been completed. The palladium is preferably incorporated into the zeolite by impregnating or as a cation by ion exchange. The amount of palladium present in the mordenite will range from about 0.05 to 10 weight percent (based on the total catalyst). preferably 0.1 to 5 percent. and more preferably 0.2 to 2.5 weight percent.  
  Suitable compounds for combining the palladium with the mordenite include palladium chloride. palladium nitrate and palladium tetraamine dinitrate.  
 PRODUCT COMPOSITION The hydrocarbon product recovered from the reaction zone of the subject process contains less than about 5 ppm by weight aromatics and less than about 5 ppm by weight sulfur. preferably both the aromatics and sulfur content of the hydrocarbon product will be reduced to less than 1 ppm. No more than about 5% by weight conversion to lower boiling products by hydrocracking. preferably less than 1%, will occur. The recovered hydrocarbon product from the reaction zone is comprised of the hydrocarbon feedstocks substantially in the form that was fed to the reaction zone with substantially all aromatics and sulfur removed. Any other unsaturated hydrocarbons will also be saturated. The hydrocarbon product is in a form for use as the feedstock to other hydrocarbon conversion processes. e.g.. a low temperature isomerization process.  
  This invention will be better understood by reference to the following examples, which are offered by way of illustration and not by way of limitation.  
 EXAMPLES EXAMPLE 1 Before After one exchange After two exchanges After three exchanges 0.02% weight (dry basis) This corresponds to about 20% of the available cationic sites occupied by calcium ion.  
 This extrudate was then dried in vacuo at 300F. for  
 24 hours and had after drying a pore volume of 0.32 cc/g.  
  The appropriate amount of palladium nitrate solution (10 g Pd/ cc) to give 1% Pd on the catalyst was contacted with the dried extrudate and shaken until all the liquid was soaked up. The material was then dried for 16 hours at 300F. in vacuo. subsequently calcined for 15 minutes at 500F. and then for 60 minutes at 900F.  
  This catalyst was reduced in hydrogen for 2 hours at 300450F. and was then used for the desulfurizationlaromatics hydrogenation of a C feedstock of the following composition (boiling range l50160F.):  
 64.5% n-hexane 18.8% i-hexanes 3.3% heptanes 1 1.7% naphthenes 1 .79 benzene 20 ppm sulfur Hydrogen was used at 1,000 psig, 6.000 SCF/barrel of feed on a once-through basis. Table 1 summarizes the results:  
 TABLE 1 CONDITIONS Hours Product Product On Temp.. Benzene Sulfur Stream F. LHSV ppm ppm TABLE 2 TABLE 4 lsomerized Product Product Cracked .P Hours Temp. Benzene Sulfur Product Hydrogenated (i-Butane 5 on Stream F- PP PP Feed Feed Free Basis) 0-163 400 0.5 0.1 0.1 w; l63330 450 ().5 0.l 0.l 330-550 400 0.5 0.1 0.02 2.2-d1methylbutane 32.0  
 2.3-dimethyl- 10 butane 0.47 .5 5.9  
 Z-methyl- EXAMPLE 4 pent-tine 6.3 6.3 1.5  
  m This examples shows the importance of the level of p g ion exchange. At lower exchange levels, the undesirmethylcydw able cracking activlty is much higher at a gn en temperpentane 10.0 10.1 1.3 ature than at higher exchange levels. However. more isflhepwfleh extensive exchange (50% e.g.) reduces the desirable cyclohexane L7 3.4 l7.4 h V v I V WC7 A b &#34;1 ydrogenation activity significantly. The optimum benzene 1.7 range is l0207c of the available sites exchanged. All  
  catalysts tested contained 1% palladium on a partially calcium exchanged hydrogen mordenite (mordenite ex 807 h &#39;dro en f) in used The catalyst.  
 EXAMPLE 2 trudate y g r t y s were used to hydrogenate the same feedstock de- A catalyst of 2% palladium on a partially Cascribed in Example 1. LHSV was 1. Hydrogen was used exchanged hydrogen mordenite was reduced in hydrO- at 1000 psig. 6000 SCF/barrel. on a once-through bagen at 400F. for 2 hours and was then used to hydrogesis. Table 5 summarizes the results. nate benzene and sulfur compounds in a feedstock hav- TABLE 5 ing a boiling range of 145F. to 160F. and the followmg composition: CALCIUM PRODUCT in Sites Cata- Cracking 0.89; pentanes Total Exchanged lyst (Wt. 9i 66.792 n-hexanc Cata- With Temp. Benzene Sulfur Based on 12.0% methylerclopentane lyst Calcium 1F.) ppm ppm Feed 3.2)? cyclohcxane 12.50 isohexanes 3 q 400 2 0.2 0.8 l.3&#39;. isoheptanes 0 0 500 1 0.2 7.5 3.4% benzene 600 1 01 35 160 ppm total sulfur 400 3 0.2 nil I 0.61 10 500 1 0.2 0.7  
  Hydrogen was used at L000 psrg and a hydrogen gas 000 1 0.2 104 rate of 6.000 SCF/barrel of feedstock. LHSV was 1. 40 400 n Table 3 summarizes the results. 1.15 20 500 1 0: 0.3  
  000 1 0.2 0.8 TABLE 3 400 1.7% 0.2 nil .93 500 1.761 0.2 nil Product Product Cracked 4g 600 I000 0.2 nil Hours Benzene Sulfur Product On Stream Temp. ppm ppm &#34;/1 (L69 400 5 0, Differentembodiments of the subject invention 69-196 450 1 0.1 0.4 be made without departing from the scope and sp1r1t 450 1 50 thereof; and, therefore. it is not intended to be limited except as indicated in the appended claims. What is claimed is:  
  It can be seen that v1rtually complete 06SUlfUtlZdUOIl A process for Without substantial hydrocmckingg and armat&#39;cshydrogenanon of a relat&#39;vely. hlgh reducing the amount of sulfur and aromatic contamimatics and sultur content feedstock was achieyed over SS mmts in a hydrocarbon feedstock comprised predomi a long period of time. while hydrocrackmg activity was nanny of pal-affms Said feedstock boiling in the range mlmmal of from 50 to 210F. and containing from 0.1 to 10.0%  
 EXAMPLE 3 aromatics and 5 to 1,000 ppm sulfur, which comprises:  
 A. contacting said feedstock and hydrogen in a reac- A catalyst 0f Pillllldlum a pllrtwlly earth tion zone with a catalyst comprising palladium and exchanged hydrogen mordemt (a mlXed rare earth mordenite exchanged to an extent of 5-807r of the Chloride. 44% e th oXides. 21.1%, C602. 1057! available ion exchange sites with a multivalent gQ-h z m 2.2% 1104. 215 used) as metal selected from the class consisting of rare duced in hydrogen at 400F. for 2 hours and was then earths of atomic numbers 57-71, calcium, barium, used to hydrogenate the same feedstock described in strontium, and magnesium at a temperature in the Example 1. Hydrogen was used at 1,000 psig, 6,000 SCF/barrel feedstock on a once-through basis. LHSV was 1. Table 4 summarizes the results.  
 range of from 300-700F., and LHSV of from 05-20. and at a pressure of from 0 to 3,000 psig, and  
 . B. recovering from said reaction zone a hydrocarbon product containing less than ppm aromatics and less than 5 ppm sulfur.  
  2. The process of claim 1 wherein said feedstock contains from 0.5 to 5.0% aromatics and from 5 to 500 ppm sulfur.  
  3. The process of claim 1 wherein said hydrocarbon product contains no more than about 1 ppm aromatics and no more than about 1 ppm sulfur.  
  4. The process of claim 1 wherein said palladium is present in an amount of from 0.2 to 2.5 weight percent based on the total catalyst.  
  5. The process of claim 1 wherein said metal is a rare earth of atomic numbers 57-71.  
  6. The process of claim 5 wherein said temperature is about 500F.. said LHSV is about 2. said pressure is about 1.000. and said palladium is present in an amount of about 0.5 to 2.0 weight percent based on the total catalyst.  
  7. The process of claim 1 wherein said hydrocarbon product containing less than 5 ppm aromatics and less than 5 ppm sulfur is contacted with an isomerization catalyst at isomerization conditions thereby obtaining an isomerized product.  
  8. The process of claim 1 wherein mordenite is exchanged to an extent of 10 to 50% of the available ion exchange sites with said multivalent metal.  
  9. The proecess of claim 1 wherein mordenite is exchanged to an extent of 10 to 30% of the available ion exchange sites with said multivalent metal.  
  10. The process of claim 1 wherein mordenite is exchanged to an extent of 10 to 20% of the available ion exchange sites.