1,3-Butadiene is produced as a by-product during ethylene production from steam crackers. Increasing demand for sustainable chemicals has driven the search for substitute petrochemicals from renewable biomass-derived chemical resources. 1,3-Butadiene is an important commodity chemical and an alternative route for its production, from ethanol, was developed about a hundred years ago. In the current climate, the development of a new high-performance catalyst for the bio-based synthesis of 1,3-butadiene is an important challenge. This paper reviews our recent studies into the synthesis of 1,3-butadiene from ethanol using MgO alone, and Zn-containing talc (Zn-Talc) that has not previously been used as a catalyst for this reaction. In particular, we focus on catalysis by MgO and the role that Zn2+ in the Zn-Talc catalyst plays in the selective production of 1,3-butadiene. The reaction mechanism for the formation of 1,3-butadiene from ethanol over MgO, and the effect of Zn2+ on the rate of ethanol conversion are discussed.
A major bottleneck of computational chemistry in heterogeneous catalysis is found at the difficulty and resultant inaccuracy of molecular models for catalyst surfaces. Here, we review our recent efforts to establish a high-precision molecular model of heterogeneous Ziegler-Natta catalysts for olefin polymerization, which was mainly based on the validation of potential molecular models for a set of experimentally known facts in density functional calculations. The coadsorption of donor molecules with Ti mononuclear species on MgCl2 surfaces is proposed as an experimentally consistent molecular model, and its successful utilization in a structure-performance relationship study for donors is described.
Steam explosion conditions were evaluated as pretreatment for unbleached pulp waste to prepare fermentable sugars with xylose fermenting yeast, Candida intermedia 4-6-4T2. The hydrolysates pretreated under low or moderate severity conditions (severity factor (Ro) = 3.53 or 4.12) did not contain known inhibitors to fermentation such as organic acids, furans and lignin-derived aromatic compounds in the LC-Mass (LC-MS) and HPLC analyses. C. intermedia 4-6-4T2 simultaneously converted both xylose and glucose in these hydrolysates to ethanol within 24 h. The ethanol yield was 0.40 (g/g) or 0.41 (g/g), respectively. In contrast, hydrolysates pretreated under high severity conditions (Ro = 4.71) contained thirteen lignin-derived aromatic compounds, of which eleven were quantified by HPLC analyses. The concentrations of furans or lignin-derived aromatic compounds in the hydrolysate were less than 0.2 g/L or 0.02 g/L, respectively. The ethanol yield was 0.21 (g/g) after 24 h fermentation. C. intermedia 4-6-4T2 did not completely convert xylose and glucose to ethanol even during longer fermentation periods (48 h). Model sugar solutions containing higher concentrations of furans and lignin-derived aromatic compounds in 0.1 M KH2PO4 containing 3 g/L of acetic acid adjusted to pH 6 with KOH than in the high severity hydrolysate did not affect the fermentation of C. intermedia 4-6-4T2. Therefore, the inhibitory effect on the hydrolysate pretreated under high severity conditions (Ro = 4.71) was not induced by previously identified compounds such as furfural, HMF and lignin-derived aromatic compounds, but may be induced by other unidentified compounds.
Single-walled carbon nanotubes (SWCNTs) were employed to obtain glucose from lignocellulose effectively via hydrothermal pretreatment. Hydrothermal pretreatment of eucalyptus and cellulose was conducted with and without SWCNT catalysts. SWCNT catalysts modified via oxidation and/or acid treatment were also applied. Oxidation treatment was conducted in the air at 500 °C for 30 min and acid treatment was conducted in the 96 % sulfuric acid for 18 h. Hydrothermal pretreatment was conducted using an 84 mL autoclave by heating samples that contained 0.6 g of cellulose to 200 °C with a heating rate of 4 °C/min and then cooling down at once. The initial SWCNTs were basic, and oxidation resulted in increased basicity. Acid treatment successfully increased the acid site density of the SWCNTs. The glucose yield increased with acid site density, showing the effectiveness of the acid-treated SWCNTs.