Xiaoli Gu

La-modified SBA-15/H2O2 systems for the microwave assisted oxidation of organosolv beech wood lignin

In this manuscript, the inuence of organosolv beech wood lignin (LOB) on its oxidative conver- sion to high added-value phenolic aldehydes is discussed. Environmental friendly and low-cost H 2 O 2 was used as the oxygen atom donor. � e catalyst was prepared by immobilizing Lanthanum com- pounds onto the periodic mesoporous channels of siliceous SBA-15. � e activity of the La/SBA-15 was investigated towards oxidation of LOB in the presence of hydrogen peroxide as oxidant with microwave irradiation. Considering the characteristics of LOB, an unexpected low syringaldehyde concentration at 10min of reaction time (1.47 g/L, corresponding to 15.66% yield) was obtained; the other major product was vanillin at 25min (0.78 g/L, i.e., 9.94% yield). � e high reactivity of syringyl nuclei may be pointed out as the main reason for the faster production and degradation of syringaldehyde in oxida- tion. Other low molecular weight phenolic products were found: vanillic acid, syringic acid and minor quantities of aceto-derivatives. � e prole of products concentration with the reaction time of catalytic oxidation with microwave irradiation are shown and discussed with reference to the investigated lignin features. � e mechanism of the microwave catalytic oxidation for LOB under alkaline conditions was proposed.

LA-CONTAINING SBA-15/H2O2 SYSTEMS FOR THE MICROWAVE ASSISTED OXIDATION OF A LIGNIN MODEL PHENOLIC MONOMER

A convenient and efficient application of heterogeneous Lanthanum-containing SBA-15 systems for the microwave assisted oxidation of a lignin model phenolic monomer, 3-methoxy- 4-hydroxybenzyl alcohol, is reported. Environmental friendly and low-cost H2O2 was used as the oxygen atom donor. The catalyst was prepared by immobilizing Lanthanum species on to the periodic mesoporous channels of siliceous SBA-15. Powder X-ray diffraction data and Inductively Coupled Plasma-Atomic Emission Spectroscopy (ICP-AES) revealed that the host retains its hexagonal mesoporous structure after immobilization and most of the lanthanum species are better dispersed in the calcined materials. The surface area and pore size of La/SBA-15 was considerably decreased indicating the intrapore confinement of the Lanthanum species. The activity of the La/SBA-15 was investigated in the oxidation of 3-methoxy-4-hydroxybenzyl alcohol in the presence of hydrogen peroxide as oxidant. 68% conversion of 3-methoxy-4-hydroxybenzyl alcohol to vanillin or other undetectable by-products was obtained after 30 min of reaction under 200W microwave irradiation, compared to a poor 25% degradation after 24 h under conventional heating. The possibility of recycling the catalyst was studied.