Decomposition Of Polyoxymethylene Dimethyl Ethers For The Synthesis Of Bisphenol F

This work mainly involved in the decomposition process of polyoxymethylene dimethyl ethers (PODEn) and its application in the synthesis of bisphenol F (BPF). The synthesis process of BPF was "coupled" with the decomposition process of PODEn, which realized the dual goals of rational use of PODEn byproducts and the improvement of synthesis performance of BPF. The main results were summarized as follows:(1) The decomposition processes of PODEn with and without the presence of water were studied in this work. Without the presence of water, the decomposition of PODEn (n=2-5) produced the homologues PODEn±1 with smaller and larger molecular weights that followed the Schulz-Flory rule. However, the decomposition of PODEn (n=2-5) in water produced only formaldehyde (FA), methanol and dimethoxymethane (PODE1). The reaction kinetics of decomposition of PODEn in water was investigated and found to be a pseudo-zero order reaction. The rate constants (kn), pre-exponential factors (An) and apparent activation energies (Ea,n) were obtained for the decomposition reactions of PODEn in water.(2) FA formed from the decomposition of PODEn (n=1-5) could react with phenol (Ph) to produce BPF catalyzed by phosphorous acid (PA). The yields of BPF showed a parabolic trend with n, i. e., the yield first increased and then decreased with n of PODEn. When PODE2 was used as a reactant, the yield of BPF reached the maximum of 95.8%. The selectivity to BPF decreased with the increase of n, but it was still better when a PODEn was used as compared to that when FA was used. It could be concluded that PODE2 was the best in the PODEn for the synthesis of BPF.(3) The effects of n(Ph):n(PODE2), n(PA):n(PODE2), temperature and time on the yield, selectivity and isomer distributions of BPF were carefully studied. Based on single factor experiments, a response surface methodology was conducted to create a quadratic regression equation and to obtain the optimal conditions for the synthesis of BPF from PODE2, which were found to be n(Ph):n(PODE2) of 16.4, n(PA):n(PODE2) of 5.49 and temperature of 363 K. At the optimized conditions, the yield of BPF reached 99% with 95.8% selectivity to BPF.(4) Treatment of polyphenyl in concentrated H2SO4 at 443 K resulted in the carbonization and sulfonation reactions for the formation of an acidic resin-carbon composite material (PP-170) with the surface area of about 18 m2/g and density of strong acid sites of about 0.6 mmol/g related to-SO3H groups. This was apparently a solid acid catalyst that was used to replace PA for the synthesis of BPF. The yield and selectivity reached 52.3 and 95.1%, respectively, when PP-170 was applied as a catalyst for the synthesis of BPF from PODE2 and Ph. Such a solid catalyst did not look successful for the target reaction, but it was the very first try. It exhibited the lower yield but higher selectivity to BPF for the reaction as compared to homogeneous inorganic acid catalysts (H2SO4 and PA). Selective poisoning of the catalyst indicated that the active acidic sites were mainly located inside of pores, while those on the out surface were few. The effects of reaction conditions on the yield, selectivity and isomer distribution of BPF were investigated and the reaction conditions were optimized. Finally, the catalyst was regenerated and recycled for the synthesis of BPF. It was found that the catalyst could be regenerated by calcination at 473 K for 4 h. After two recycles, the catalyst almost retained the original activity with 49.8% yield and 94.6-95.8% selectivity to BPF.(5) Quantum chemical calculations were performed to study the energy difference (AE) between the highest occupied molecular orbitals (HOMO) and lowest unoccupied molecular orbitals (LUMO) of three BPF isomers. The results showed that AE in the isomers followed the order 4,4’-dihydroxydiphenylmethane (4,4-BPF)< 2,4’-dihydroxydiphenylmethane (2,4-BPF)< 2,2’-dihydroxydiphenylmethane (2,2-BPF). Thus, the electron transition must be easier in 4,4-BPF than in 2,4-BPF and 2,2-BPF. In addition, the effects of solvent, number of hydroxyl groups and elemental substitution of an oxygen atom in the hydroxyl group on the spectroscopic properties of BPF isomers were studied. It was found that infrared spectroscopic intensities increased significantly for 4,4-BPF in the polar solvent (methanol and water), although not proportionally to the increase of electric constants of the polar solvents. An increase in the number of hydroxyl groups resulted in the new characteristic peaks of FTIR and Raman spectra, and smoother characteristic peaks of UV spectra in the range of 240-300 nm. The elemental substitution resulted in the red shifts in UV spectra of the substituted 4,4-BPF, and the shifts were found to be larger with the substituted element with smaller electronegativity.