Hydrogen donation is the key to supercritical water upgrading of heavy oil, because it benefits light distillate production and inhibits condensation , but the mechanism is still unclear. In this work, an isotope tracing method, combined with Fourier transform infrared spectroscopy and nuclear magnetic resonance spectroscopy analyses, was used to elucidate the hydrogen donation mechanism in supercritical water upgrading of asphaltenes . In asphaltenes upgrading, it was found that the aliphatic carbon at the end of the side chain of asphaltene macromolecules could capture deuterium from supercritical heavy water via free radical reactions , and the deuteration ratio at this position was 11 %. For supercritical water upgrading of vacuum residue which is generally considered as a system of asphaltenes dissolved in maltenes, the existing maltenes enhanced hydrogen donation to asphaltenes. Further, a possible hydrogen donation pathway was proposed. This work provides an in-depth understanding of the hydrogen donation mechanism for supercritical water upgrading.
A green protocol for refining industrial chemicals containing formaldehyde (FA) impurities is presented here for the first time. FA, as an unreactant or a byproduct, causes separation problems in many industrial processes. It can be removed to a level of less than 1 ppm with easily separable methanol formation using commercial Cu/ZnO/Al 2 O 3 catalyst at atmospheric pressure in the absence of external hydrogen. The formation of methanol is achieved by the transfer of hydrogen species generated with the assistance of water to free FA, affording high methanol selectivity (62 %). By investigating potential intermediates and implementing deuterium labeling experiments, together with carbon and hydrogen balance calculations, a plausible pathway of water-assisted FA removal is proposed. Moreover, the in situ generated hydrogen species can be transferred directly into unsaturated compounds for selective reduction.
Seven new chelated cyclometalated Ir complexes of ABON,P, ABON,O, and ABON,C(carbene) based on a rigid and tunable 2-arylbenzo[d]oxazole backbone have been prepared for the N-methylation of amines. Among these three coordinated modes, ABON,C(carbene)-chelated iridium-based catalysts exhibited good performance in the monomethylation of aromatic amines with methanol (MeOH) as the green methylation reagent. The steric-modified synthesis of ABON,C(carbene) complexes was described. The most active ABON,C(carbene) complex with marginal steric hindrance as a catalyst was obtained from the benzoxazole ring without a substituent and methyl group of the benzimidazole ring on the N-heterocyclic carbene (NHC) ligand. A variety of amines including para- and meta-substituted aromatic amines, as well as heterocyclic amines, were formulated as suitable substrates. Importantly, this catalyst considerably promoted the yield of the N-methylation of ortho-substituted aromatic amines. Controlled kinetic experiments and deuterium-labeling reactions of these ortho-substituted amines were conducted under optimized conditions. On the basis of the experimental results, a plausible mechanism was proposed.
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