Methods for producing ethylene and propylene from naphtha

Abstract

The presently disclosed subject matter relates to methods of producing ethylene and propylene by the catalytic steam cracking of naphtha using an HZSM-5 catalyst. An example method can include providing a naphtha feedstock, providing steam, and providing an HZSM-5 catalyst. The method can further include preparing the HZSM-5 catalyst by titanium modification or alkaline treatment, followed by phosphorus modification. The method can further include feeding the naphtha feedstock and steam to a reactor containing the catalyst and removing an effluent from the reactor having a combined yield of ethylene and propylene of greater than about 45 wt-%.

The invention claimed is: 
     
       1. A method for producing ethylene and propylene from catalytic steam cracking of naphtha, the method comprising:
 (a) providing a naphtha feedstock; 
 (b) providing steam; 
 (c) providing a catalyst consisting of phosphorus modified Ti-containing HZSM-5; 
 (d) feeding the naphtha feedstock and the steam to a reactor comprising the catalyst, thereby producing an effluent comprising ethylene and propylene; and 
 (e) removing the effluent from the reactor, the effluent having a combined yield of ethylene and propylene greater than about 45 percent by weight; 
 wherein the catalyst comprises from about 1.0 to about 10.0 percent by weight P 2 O 5 , and 
 wherein the catalyst comprises from about 1.0 to about 5.0 percent by weight Ti. 
 
     
     
       2. The method of  claim 1 , wherein the naphtha feedstock comprises light straight run naphtha. 
     
     
       3. The method of  claim 1 , wherein the steam is co-fed with the naphtha feedstock. 
     
     
       4. The method of  claim 1 , wherein the phosphorus modified Ti-containing HZSM-5 has a Si/Al 2  ratio of about 27 to about 30. 
     
     
       5. The method of  claim 1 , wherein, 6 hours after first feeding the naptha feedstock and the steam to the reactor, a spent catalyst comprises less coke deposits based on a the weight of the spent catalyst 6 hours after first feeding the naphtha feedstock and the steam to the reactor comprise less than about 5 percent by weight based on the weight of the spent catalyst than a Ti-containing HZSM-5 catalyst that is not phosphorus modified, wherein the spent catalyst comprises the catalyst and the coke deposits. 
     
     
       6. The method of  claim 1 , wherein the catalyst is not steamed prior to feeding the naphtha feedstock to the reactor. 
     
     
       7. A method for producing ethylene and propylene from catalytic steam cracking of naphtha, the method comprising:
 (a) providing a naphtha feedstock; 
 (b) providing steam; 
 (c) providing a catalyst consisting of phosphorus modified Ti-containing HZSM-5; 
 (d) feeding the naphtha feedstock and the steam to a reactor comprising the catalyst, thereby producing an effluent comprising ethylene and propylene; and 
 (e) removing the effluent from the reactor, the effluent having a combined yield of ethylene and propylene greater than about 45 percent by weight; 
 wherein the catalyst comprises from 1.0 to 10.0 percent by weight P 2 O 5 , and 
 wherein the catalyst is prepared by titanium modification followed by phosphorus modification. 
 
     
     
       8. The method of  claim 7 , wherein the phosphorus modification uses mono-ammonium phosphate. 
     
     
       9. The method of  claim 7 , wherein the naphtha feedstock comprises light straight run naphtha. 
     
     
       10. The method of  claim 7 , wherein the steam is co-fed with the naphtha feedstock. 
     
     
       11. The method of  claim 7 , wherein the phosphorus modified Ti-containing HZSM-5 has a Si/Al 2  ratio of about 27 to about 30. 
     
     
       12. The method of  claim 7 , wherein the catalyst comprises from about 1.0 to about 5.0 percent by weight Ti. 
     
     
       13. The method of  claim 7 , wherein the catalyst is prepared by titanium modification followed by phosphorus modification. 
     
     
       14. The method of  claim 13 , wherein the phosphorus modification uses mono-ammonium phosphate. 
     
     
       15. The method of  claim 7 , wherein coke deposits on a spent catalyst 6 hours after first feeding the naphtha feedstock and the steam to the reactor comprise less than about 5 percent by weight based on the weight of the spent catalyst, wherein the spent catalyst comprises the catalyst and the coke deposits. 
     
     
       16. A method for producing ethylene and propylene from catalytic steam cracking of naphtha, the method comprising:
 (a) providing a naphtha feedstock;   (b) providing steam;   (c) providing a catalyst consisting of phosphorus modified Ti-containing HZSM-5;   (d) feeding the naphtha feedstock and the steam to a reactor comprising the catalyst, thereby producing an effluent comprising ethylene and propylene; and   (e) removing the effluent from the reactor, the effluent having a combined yield of ethylene and propylene greater than about 45 percent by weight.