The hydrolysis of MgH 2 delivers high hydrogen capacity (15.2 wt%), which is very attractive for real-time hydrogen supply. However, the formation of a surface passivation Mg(OH) 2 layer and the large excess of H 2 O required to ensure complete hydrolysis are two key challenges for the MgH 2 hydrolysis systems. Now, a low-cost method is reported to synthesize MgH 2 @Mg(BH 4 ) 2 composite via ball-milling MgH 2 with cheap and widely available B 2 O 3 (or B(OH) 3 ). By adding small amounts of B 2 O 3 , the in-situ formed Mg(BH 4 ) 2 could significantly promote the hydrolysis of MgH 2 . In particular, the MgH 2 –10 wt% B 2 O 3 composite releases 1330.7 mL·g −1 H 2 (close to 80% theoretical hydrogen generation H 2 ) in H 2 O and 1520.4 mL·g −1 H 2 (about 95%) in 0.5 M MgCl 2 in 60 min at 26 °C with hydrolysis rate of 736.9 mL·g −1 ·min −1 and 960.9 mL·g −1 ·min −1 H 2 during the first minute of the hydrolysis, respectively. In addition, the MgCl 2 solution allows repeated use by filtering and exhibits high cycle stability (20 cycles), therefore leading to much reduced capacity loss caused by the excess H 2 O. We show that by introducing B 2 O 3 and recycling the 0.5 M MgCl 2 solution, the system hydrogen capacity can approach 5.9 wt%, providing a promising hydrogen generation scheme to supply hydrogen to the fuel cells.
Tungsten-based catalyst has been widely investigated in the field of selective hydrogenolysis of secondary C O bond, such an important yet challenging strategy, in glycerol conversion, in which the product 1,3-propanediol (1,3-PDO) is of great value in polyester industry. Unfortunately, though it has been proved to be highly active, the identification of the intrinsic tungsten oxide active sites still remains unrevealed to date due to its complex microstructure. Herein, we incorporate atomically dispersed alumina as promoter in the context of the selective hydrogenation of glycerol and report a Pt/Al-WO x catalyst. This catalyst decidedly outperforms the unpromoted Pt/WO x , which elevates the 1,3-PDO yield to 2 times. Spectroscopy characterizations and chemisorption experiments have revealed that the high activity and selectivity of Pt/Al-WO x catalyst results from the more oxygen vacancies on WO x in-situ generation by the acceleration of atomically dispersed alumina in hydrogen atmosphere, which increases the selective adsorption of glycerol and the in-situ Brønsted acid sites for the selective activation of secondary C O bonds, thus largely augmenting the hydrogenolysis performance. This discovery not only provides the new strategy of defect engineering to enhance hydrogenolysis performance of secondary C O bond in biomass compounds, but reveals the unique role of the unsaturated coordination structure of WO x in chemoselective hydrogenolysis reactions.
Xiaohong Hu,Haiyong Wang,Qiying Liu,Yuhe Liao,Chenguang Wang,Longlong Ma
Both alkaline organosolv and formaldehyde stabilization pretreatment can yield high-quality lignin by preventing condensation. For the hydrogenolysis of the pretreated solid residues , the highest yield of C2–C4 chemicals was 66.8% under alkaline organosolv pretreatment for 60 min. Specifically, the crimped fibers and residual lignin and hemicellulose increased the surface roughness of the residue by 40.6%, the crystallinity index decreased to 44.4%, and the crystal size was reduced to 2.15 nm, which in turn promoted hydrogenolysis of the residue. However, the increase of crystallinity and crystal size and the decrease in surface roughness of the formaldehyde stabilization pretreatment residue greatly hindered the conversion of polysaccharides. In addition, residual formaldehyde on the residue may also inhibit catalyst activity. Overall, this study provides novel perspectives on the full utilization of biomass, as well as new insights into the conversion of polysaccharides.
危险品化学品经营许可证（带存储）