Eastern Illinois University The Keep Masters Theses Student Theses & Publications 1992 New Reagents and Reactions for Desulfurization of Coal Shan Wang This research is a product of the graduate program in Chemistry at Eastern Illinois University. Find out more about the program. Recommended Citation Wang, Shan, "New Reagents and Reactions for Desulfurization of Coal" (1992). Masters Theses. 2143. https://thekeep.eiu.edu/theses/2143 This is brought to you for free and open access by the Student Theses & Publications at The Keep. It has been accepted for inclusion in Masters Theses by an authorized administrator of The Keep. For more information, please contact [email protected]. New Reagents and Reactions for Desulfurization of Coal (TITLE) BY Shan Wang THESIS SUBMITIED IN PARTIAL FULFILLMENT OF THE REQUIREMENTS FOR THE DEGREE OF ~­ Master of Science in Chemistry- IN THE GRADUATE SCHOOL, EASTERN ILLINOIS UNIVERSITY CHARLESTON, ILLINOIS 1992 YEAR I HEREBY RECOMMEND THIS THESIS BE ACCEPTED AS FULFILLING THIS PART OF THE GRADUATE DECREE CITED ABOVE DATE .w~-- - DATE ~~~i·~~:::~··~~~.·~·~~~·~~.:..;~~~1<';,.o:,,..~,~_,-,,·1-ii.~~"~:,:fiJl.·•::~;7;i,:.Z:;c·i~:;· I ' , NEW REAGENTS AND REACTIONS FOR ~ESULFURIZATION OF COAL Thesis Approved by: )ate ··~ ... Dr. T. H. Black Date Thesis Title: "New Reagents and Reactions for Desulfurization of Coal" Author: Shan Wang Thesis directed by: Dr. David H. Buchanan Abstract Searching for new reagents and reactions for pre-combustion desulfurization of coal was the goal of this work. In this study, modifications of mild desulfurization reactions, which were found to work with organosulfur model compounds, have been investigated systemetically for improvements in sulfur removal and reduction of reagent cost. The screening of reagents and new reactions utilized substituted thiophenes plus aryl sulfides as the initial models for organosulfur compounds in coal. Tetrahydrofuran extracts of Illinois Basin Coals were also used as second generation targets for desulfurization reac­ tions. Dibenzothiophene was converted to biphenyl using potassium metal/tetrahydrofuran without the addition of electron transfer agents. Similar desulfurization reactions of tetrahydrofuran extracts of Illinois Basin coals gave up to an 82.8% reduction in organo­ sulfur content. A soluble chlorovinyl nickel complex added to the reaction increased the desulfurization to 85.6%. Attempts to produce active desulfurization reagents from iron pentacarbonyl with reduc­ 1 ing agents in alcohol solvents (conditions for the production of [H-Fe(C0)4r ) did not lead to useful desulfurization of dibenzothiophene, benzothiophene or benzyl sulfide. Tetrabutylammonium hydroxide in aprotic solvents is known to react with elemental sulfur to produce trisulfide anion radical by the single electron transfer pathway. Reac­ tion of tetrabutylammonium hydroxide with dibenzothiophene in aprotic solvents led to large amounts of unreacted starting material and gave no evidence of hydrocarbon products. Desulfurized products bibenzyl, biphenyl, and 2-phenyl phenol were produced by reac­ tion of benzyl phenyl sulfide using potassium hydroxide/n-butyl lithium/18-crown-6 in dimethyl sulfoxide. No desulfurization of dibenzothiophene was observed using the same reaction system. Acknowledgement I would like to thank my advisor Dr. David H. Buchanan for his great patience and help during this work. Also I would like to thank those who gave me supports in many respects during my staying at Eastern Illinois University. List of Tables Table 1. Desulfurization of coal THF soluble fractions Table 2. Desulfurization of organosulfur model compounds using iron pentacarbonyl Table 3. Desulfurization of dibenzothiophene using tetrabutylammonium hydroxide List of Figures Figure 1. 1H NMR of NiCl(CCl=CC12)(PP~)2 31 Figure 2. P NMR of NiCl(CCl=CC12)(PPh3) 2 Figure 3. FT-IR of NiCl(CCl=CC12)(PPh3) 2 Figure 4. HPLC of reaction products of DBT/K!TI:IF/Naph. Figure 5. HPLC of reaction products of DBT/K!TI:IF Figure 6. FT-IR of Coal-105 THF Extracts Figure 7. FT-IR of reaction products of Coal-105/K!TI:IF Figure 8. FT-IR of reaction products of Coal-105/K!TI:IF/NiCl(CCl=CC1z)(PPh3) 2 Figure 9. FT-IR of Coal-106 THF Extracts Figure 10. FT-IR of reaction products of Coal-106/K!TI:IF/NiCl(CCl=CC1z)(PPh3) 2 Figure 11. FT-IR of Coal-108 THF Extracts Figure 12. FT-IR of reaction products of Coal-108/K!TI:IF/NiCl(CCl=CC1z)(PPh3)2 Figure 13. HPLC of reaction products of DBT/NaBHJFe(CO)/BuOH Figure 14. HPLC of reaction products of DBT/NaOH/Fe(CO)/BuOH Figure 15. HPLC of reaction products of DBT/NaOH/Fe(CO)/BuOH Figure 16. HPLC of reaction products of DBT/NaBH/Fe(CO)/EtOH Figure 17. HPLC of reaction products of DBT/NaBH/Fe(CO)/EtOH Figure 18. HPLC of reaction products of DBT/NaOH/Fe(CO)/EtOH Figure 19. HPLC of reaction products of BT/NaOH/Fe(CO)/BuOH Figure 20. HPLC of reaction products of BS/NaOH/Fe(CO)/BuOH Figure 21. UVNIS of reaction products of Sg1Bu4NOH/CH3CN Figure 22. UVNIS of reaction products of Sg1Bu4NOH/DMSO Figure 23. GC of reaction products of DBT/Bu4NOH/DMSO Figure 24. GC of reaction products of DBT/Bu4NOH/CH3CN Figure 26. GC of reaction products of DBT/Bu4NOH in H20ffoluene Figure 27. GC of reaction products of DBT/Bu4NOH in MeOHffoluene Figure 28. GC of reaction products of DBT/KOH/n-BuLi/18-crown-6/foluene Figure 29. GC of reaction products of BPS/KOH/n-BuLi/18-crown-6/DMSO Figure 30. GC of reaction products of DBT/KOH/n-BuLi/18-crown-6/DMSO Figure 31. FT-IR of unknown compound from reaction DBT/NaOH/Fe(CO)/EtOH Figure 32. Be NMR of unknown compound from reaction DBT/NaOH/Fe(CO)/ EtOH Figure 33. FT-IR of iron pentacarbonyl in CH2Cl2 Figure 34. Be NMR of iron pentacarbonyl Figure 35. Cyclic voltammetry of DBT Figure 36. Cyclic voltammetry of elemental sulfur Table of Content Abstract Table of Content List of Tables List of Figures Chapter I. Introduction and Background - - - - - - - - - - - - - - - - - 1 Chapter II. Experimental --------------------------- 15 Chapter III. Results and Discussion -------------------- 30 Chapter IV. Conclusion ----------------------------- 46 Reference -------------------------------------- 48 Appendix. Tables and Figures Chapter I Introduction and Background The United States has about a third of the world coal reserve that can be utilized for several hundred years, in contrast with the petroleum resources in the U.S. It can be expected that the future will see the increasing use of coal as a substitute for oil as fuel supply. However, this shift from oil to coal is hampered by the high sulfur contents in the coal. According to current and pending U.S. Federal regulations, the burning of high­ sulfur coal will require either pre-combustion removal of up to 90% of the sulfur in the coal or the use of post-combustion stack gas scrubbing. Since the latter choice is both difficult and expensive, a major breakthrough in cleaning of high-sulfur coal mainly depends on the pre-combustion desulfurization. Sulfur forms in coals are scientifically classified into: (1) pyritic sulfur, (2) sulfatic sulfur, and (3) organic sulfur. However, as the names imply, an understanding of sulfur compo­ sition in coal, especially at the molecular level, has not yet been achieved. The procedure for determination of the sulfur content in coal is according to ASTM D-2492. 1 Through the research of previous workers, great success has been achieved in the removal of mineral forms of sulfur (mainly pyrite) from coal. For instance, various mechanical methods for coal cleaning now in use or near commercialization are able to remove 80% or more of the mineral sulfur from coai.2-4 However, mineral forms of 1 sulfur often constitute only half of all sulfur present.5•6 So, in order to achieve the neces­ sary degree of cleaning of coal, pre-combustion desulfurization must remove both miner­ al and organic forms of sulfur. Unfortunately, because of the lack of a chemical strategy for the selective cleavage of the carbon-sulfur bond in the matrix of coal, the removal of organic sulfur from coal for the purpose of pre-combustion desulfurization still remains a very serious challenge. Unlike the mineral forms of sulfur in coal, organic sulfur, which is chemically bonded to the matrix of the coal, can not be removed from coal by simple physical cleaning or solvent extraction.7 In earlier work at Eastern Illinois University,7 simple solvent extrac­ tion methods were shown to be unable to selectively remove the organic content of sulfur from coal. Through research on perchloroethylene extraction of coal, it was shown that pyrite, not organosulfur compounds, is the source of the S0 extracted by perchloroethyl­ ene. And, within experimental error, almost no organic sulfur was removed by perchloro­ ethylene extraction.7 Therefore, selective chemical reactions will be necessary for pre­ combustion desulfurization. Various methods have been investigated for the removal of the organic sulfur from coal. A very severe desulfurization process involves molten caustic leaching of coal. 8 In the first step, the coal is leached with molten sodium hydroxide or sodium hydroxide-potas­ sium hydroxide mixtures at 370-390°C for several hours. During this process, most minerals in the coal are converted to soluble alkali-metal salts and the sulfur-containing 2 organic components of coal are converted to soluble sulfides.9 After leaching, the caus­ tic-treated coal is washed with water, dilute acid, and then again with water to remove the soluble sulfides. There is a 90% reduction in the sulfur content. 8 Another chemical method for desulfurization exploits the chlorinolysis of coal. 10 The coal is mixed with carbon tetrachloride and water and is heated at 65-70°C in the presence of dichlorine. The chlorinated coal is hydrolyzed at 70-80°C for 2 hours and then dechlorinated at 350- 4000C in the presence of steam.