State Key Laboratory of Coal Conversion

1. State Key Laboratory of Coal Conversion STUDY ON THE REACTION OF UREA WITH PHENOL OVER ZINC COMPOUNDS Weicai Peng Wei Wei and Yuhan Sun Institute of Coal Chemistry Chinese Academy of Sciences, Taiyuan, China ICC.CAS

2. State Key Laboratory of Coal Conversion Why to do this work? • Urea can be considered as a potential feed for indirect carbon dioxide utilization. • Urea, which is very cheap and safe, is a useful building block in fine synthetic chemistry. • Synthesis of linear and cyclic carbonates by alcoholyzing urea with alcohlos or diols has been carried out to replace toxic phosgene in our lab. ICC.CAS

3. State Key Laboratory of Coal Conversion Synthesis of DMC from urea and methanol Urea Methyl Carbamate(MC) DMC High yield of DMC could successively be achieved on solid catalysts when the product could be effectively removed by catalytic distillation.

4. + PG DMC PG NH3+ PC urea MeOH CO2 State Key Laboratory of Coal Conversion Synthesis of cyclic carbonates by urea and diols A prospective green chemical route High yield of PC could successively be achieved on solid catalysts in our laboratory.

5. phenyl carbamate (Trace) (Little) 4-hydroxybenzamide (Main) salicylamide State Key Laboratory of Coal Conversion Synthesis of diphenyl carbonate from urea and phenol Unlike the reaction of urea with alcohols, salicylamide was mainly produced rather than phenyl carbamate.

6. or State Key Laboratory of Coal Conversion Why salicylamide rather than phenyl carbamate? B A △E(B-A)=-0.5435Kcal/mol The formation of salicylamide rather than 4-hydroxybenzamide or phenyl carbamate was due to the internal H bonding with the amido nitrogen or the oxygen of amidogen, and salicylamide was more stable than phenyl carbamate at their energies.

7. State Key Laboratory of Coal Conversion Diphenyl carbonate from urea and phenol 1 No catalyst 2 ZnO 3 ZnCO3 4 ZnCl2 5 Zn 6 Zn(AcO)2 7 Zn(OH)2 urea, 0.017mol phenol,0.25mol catalyst, 0.10 g 235oC and 12 h A series of znic compounds was used for synthesis of salicylamide by the reaction of urea with phenol, and ZnO was the most effective catalyst among them.

8. State Key Laboratory of Coal Conversion Diphenyl carbonate from urea and phenol Effect of temperature on the performance Phenol, 23.5g; urea, 1.56g; n(phenol):n(urea)= 10:1; ZnO, 0.2g; 12h The selectivity of salicyamide increased with the rise of reaction temperature, but the conversion of urea showed a maximum due to the formation of a yellowish product .

9. State Key Laboratory of Coal Conversion Diphenyl carbonate from urea and phenol Effect of the amount of catalyst on the performance Phenol, 23.5g; urea, 1.56g; n(phenol):n(urea)= 10:1; 205 oC and 12h The selectivity of salicyamide seemed to be independent on the catalyst content, but the conversion of urea reached constant.

10. State Key Laboratory of Coal Conversion What took place in the reaction? Decomposition of urea with or without ZnO It was obvious that urea decomposition was promoted by ZnO.

11. State Key Laboratory of Coal Conversion What took place in the reaction? FTIR spectra of the mixture of different catalysts and urea The sample was prepared by mixing urea and catalyst and then heated under the protection of N2 with n (urea): n (catalyst) =1: 4 at 150 oC for 30 min. The band around 2217cm-1 (assigned to N=C=O) illustrated that isocyanic acid group easily formed on znic compounds

12. 2.0 1.8 214 ZnO 1.6 3# T% 4# 1.4 1.2 1.0 0.8 0.6 0.4 0.2 0.0 200 300 400 500 600 700 800 wavelength/nm State Key Laboratory of Coal Conversion What took place in the reaction? UV-vis of ZnO before (a) and after (b) the reaction ZnO showed a red shift due to the fill of electron into 3d, which should be a result of the interaction between Zn2+ and isocyanics.

13. State Key Laboratory of Coal Conversion What took place in the reaction? FTIR of ZnO before (a) and after (b) the reaction The absorbance at 2217cm-1appeared due to N=C=O,but the Zn-O at 457 cm-1 disappeared after the reaction, implying the presence of a relatively stable Zn-complex probably via the interaction between isocyanic acid group and ZnO.

14. State Key Laboratory of Coal Conversion What took place in the reaction? XRD patterns of ZnO before (a) and after (b) the reaction The amorphous state of ZnO further indicated the formation of the Zn-complex after the reaction, which should be responsible for the activity.

15. 35000 163.03064 114.8509 167.95223 30000 120.03152 25000 20000 127.54341 15000 137.38659 87.91168 10000 79.88173 57.08701 5000 97.49583 34.81035 0 -5000 0 50 100 150 200 250 State Key Laboratory of Coal Conversion Why urea converted less at higher temperature? 13CNMR of yellowish solid after the reaction Ph-H Ph-O Ph-C Composition, C7H5NO A yellowish product was obtained with the composition of C7H5NO, and NMR indicated the presence of Ph-C, Ph-O and Ph-H.

16. State Key Laboratory of Coal Conversion Why urea converted less at higher temperature? 13CNMR, UV-vis and FTIR of tris(2-hydroxyphenyl)-s-triazine C1 ( 163.984ppm) C2 ( 121.324ppm) C3 ( 138.572ppm) C4 ( 122.749ppm) C5 ( 133.074ppm) C6 ( 120.720ppm) C7 ( 172.401ppm)

17. State Key Laboratory of Coal Conversion Why urea converted less at higher temperature? GC-MS of tris(2-hydroxyphenyl)-s-triazine

18. State Key Laboratory of Coal Conversion Possible mechanism of urea activation Urea was decomposed over ZnO to form isocyanic group which was then “trapped” by Zn compound to form a relatively stable Zn-complex favorable for the reaction, but salicyamide converted into tris(2-hydroxyphenyl)-s-triazine which chelated and deactivated “active” zinc. ICC.CAS

19. State Key Laboratory of Coal Conversion Conclusions The synthesis of salicylamides from urea and phenols was firstly developed by using znic compounds as the catalyst, which was closely related to the formation of a relatively stable Zn-complex. The main product was salicylamide rather than phenyl carbamate due to their different energies. But at a relatively higher temperature, salicyamide could be converted into tris(2-hydroxyphenyl)-s-triazine which chelated and deactivated “active” zinc.

20. State Key Laboratory of Coal Conversion Acknowledgments Dr. F.K. Xiao, Dr.N.Zhao and Dr.J.P.Li and CAS for financial support

21. State Key Laboratory of Coal Conversion Thanks for your attention !