Production of biobutanediols by the hydrogenolysis of erythritol

Highly Efficient Iridium-Iron-Molybdenum Catalysts Condensed on Boron Nitride for Biomass-Derived Diols' Hydrogenolysis to Secondary Monoalcohols

A trade-off of activity-selectivity exists in primary C-O hydrogenolysis of biomass-derived diols to secondary alcohols over bimetallic catalysts, especially the combination of noble metal and early transition metal in the metallic state and metal oxide state, respectively. Herein, the combination of high surface concentration of boron nitride (BN)-supported metals and the addition of Mo as third metal broke the trade-off. High yields (>50%) of secondary alcohols were obtained with robust productivity up to 25-fold based on Ir over Ir-Fe0.13-Mo0.08/BN (Ir = 20 wt %, Fe/Ir = 0.13, Mo/Ir = 0.08) than previously reported Ir-Fe catalysts. In contrast, simply increasing the loading amount of Ir-Fe catalysts or the addition of Mo species only enhanced the productivity by <2-4-fold. Various characterizations showed that large Ir loading enables the formation of condensed nanostructures (∼2 nm) on the BN support, which further alloy with Mo and Fe to form an face centred cubic (fcc)-type trimetallic alloy with surface enrichment of Fe. On the other hand, in Ir-Fe0.25-Mo0.08/BN with lower Ir (5 wt %) and lower Ir-based activity, the Mo species were rather bound on the support surface possibly as the MoBx state. These structures were formed by simple impregnation and reduction with H2 at the reaction temperature (453 K). The high activity of Ir-Fe0.13-Mo0.08/BN (20 wt % Ir) is derived from two aspects: (1) the formation of condensed nanostructures (∼2 nm) exposing more active sites and (2) alloying with Mo to modify the electronic state of Ir to enhance the H2 activation ability, as shown by the decreased Ea (82-84 → 67 kJ mol-1).

Construction of a xylose metabolic pathway in Trichosporonoides oedocephalis ATCC 16958 for the production of erythritol and xylitol

PURPOSE

Erythritol is a valuable compound as sweetener and chemical material however cannot be fermented from the abundant substrate xylose.

METHODS

The strain Trichosporonoides oedocephalis ATCC 16958 was employed to produce polyols including xylitol and erythritol by metabolic engineering approaches.

RESULTS

The introduction of a substrate-specific ribose-5-phosphate isomerase endowed T. oedocephalis with xylose-assimilation activity to produce xylitol, and eliminated glycerol production simultaneously. A more value-added product, erythritol was produced by further introducing a homologous xylulose kinase. The carbon flux was redirected from xylitol to erythritol by adding high osmotic pressure. The production of erythritol was improved to 46.5 g/L in flasks by fermentation adjustment, and the process was scaled up in a 5-L fermentor, with a 40 g/L erythritol production after 120 h, and a time-space yield of 0.56 g/L/h.

CONCLUSION

This study demonstrated the potential of T. oedocephalis in the synthesis of multiple useful products from xylose.

C–O Hydrogenolysis of C3–C4 Polyols Selectively to Terminal Diols over Pt/W/SBA-15 Catalysts

Pt/W/SBA-15 catalysts (with Pt-loading = 0.5–4 wt% and W-loading = 1 wt%) prepared by the sequential impregnation method were evaluated for selective C–O cleavage of erythritol and glycerol in an aqueous medium. The Pt and W particles dispersed on SBA-15 approached close proximity at higher Pt loadings and afforded synergistic enhancement in C–O hydrogenolysis activity/selectivity. 1,4-Butanediol yields of 30.9% (at 190 °C, 50 bar H2 and 24 h) and 1,3-propanediol yields of 34.4% (at 190 °C, 50 bar H2 and 12 h of reaction) were obtained over these catalysts. Pt nanoparticles (facilitating dissociative H2 adsorption and spillover) and W (present as acidic oligomeric WOx species; activating and coordinating the polyol via 1°-OH group) worked in tandem for the selective hydrogenolysis of polyols yielding terminal diols of industrial demand.

Deoxydehydration of Biomass-Derived Polyols Over Silver-Modified Ceria-Supported Rhenium Catalyst with Molecular Hydrogen

Olefin production from polyols via deoxydehydration (DODH) was carried out over Ag-modified CeO₂ -supported heterogeneous Re catalysts with H₂ as a reducing agent. Both high DODH activity and low hydrogenation ability for C=C bonds were observed in the reaction of erythritol, giving a 1,3-butadiene yield of up to 90 % under "solvent-free" conditions. This catalyst is applicable to other substrates such as methyl glycosides (methyl α-fucopyranoside: 91 % yield of DODH product; methyl β-ribofuranoside: 88 % yield), which were difficult to be converted to the DODH products over the DODH catalysts reported previously. ReO_x -Ag/CeO₂ was reused 3 times without a decrease of activity or selectivity after calcination as regeneration. Although the transmission electron microscopy energy-dispersive X-ray spectroscopy and X-ray absorption fine structure analyses showed that Re species were highly dispersed and Ag was present as metal particles with various sizes from well-dispersed species (<1 nm) to around 5 nm particles, the catalysts prepared from size-controlled Ag nanoparticles showed similar performance, indicating that the catalytic performance is insensitive to the Ag particle size.

Sustainable Routes for the Synthesis of Renewable Adipic Acid from Biomass Derivatives

Adipic acid (AA) is a key industrial dicarboxylic acid intermediate used in nylon manufacturing. Unfortunately, the traditional process technology is accompanied by serious environmental pollution. Given the growing demand for adipic acid and the desire to reduce its negative impact on the environment, considerable efforts have been devoted to developing more green and friendly routes. This Review is focused on the latest advances in the sustainable preparation of AA from biomass-based platform molecules, including 5-hydroxymethylfufural, glucose, γ-valerolactone, and phenolic compounds, through biocatalysis, chemocatalysis, and the combination of both. Additionally, the development of state-of-the-art catalysts for different catalytic systems systematically is discussed and summarized, as well as their reaction mechanisms. Finally, the prospects for all preparation routes are critically evaluated and key technical challenges in the development of green and sustainable processes for the manufacture of AA are highlighted. It is hoped that the green adipic acid synthesis pathways presented can provide insights and guidance for further research into other industrial processes for the production of nylon precursors in the future.

Metabolic engineering of the oleaginous yeast Yarrowia lipolytica PO1f for production of erythritol from glycerol

BACKGROUND

Sugar alcohols are widely used as low-calorie sweeteners in the food and pharmaceutical industries. They can also be transformed into platform chemicals. Yarrowia lipolytica, an oleaginous yeast, is a promising host for producing many sugar alcohols. In this work, we tested whether heterologous expression of a recently identified sugar alcohol phosphatase (PYP) from Saccharomyces cerevisiae would increase sugar alcohol production in Y. lipolytica.

RESULTS

Y. lipolytica was found natively to produce erythritol, mannitol, and arabitol during growth on glucose, fructose, mannose, and glycerol. Osmotic stress is known to increase sugar alcohol production, and was found to significantly increase erythritol production during growth on glycerol. To better understand erythritol production from glycerol, since it was the most promising sugar alcohol, we measured the expression of key genes and intracellular metabolites. Osmotic stress increased the expression of several key genes in the glycerol catabolic pathway and the pentose phosphate pathway. Analysis of intracellular metabolites revealed that amino acids, sugar alcohols, and polyamines are produced at higher levels in response to osmotic stress. Heterologous overexpression of the sugar alcohol phosphatase increased erythritol production and glycerol utilization in Y. lipolytica. We further increased erythritol production by increasing the expression of native glycerol kinase (GK), and transketolase (TKL). This strain was able to produce 27.5 ± 0.7 g/L erythritol from glycerol during batch growth and 58.8 ± 1.68 g/L erythritol during fed-batch growth in shake-flasks experiments. In addition, the glycerol utilization was increased by 2.5-fold. We were also able to demonstrate that this strain efficiently produces erythritol from crude glycerol, a major byproduct of the biodiesel production.

CONCLUSIONS

We demonstrated the application of a promising enzyme for increasing erythritol production in Y. lipolytica. We were further able to boost production by combining the expression of this enzyme with other approaches known to increase erythritol production in Y. lipolytica. This suggest that this new enzyme provides an orthogonal route for boosting production and can be stacked with existing designs known to increase sugar alcohol production in yeast such as Y. lipolytica. Collectively, this work establishes a new route for increasing sugar alcohol production and further develops Y. lipolytica as a promising host for erythritol production from cheap substrates such as glycerol.

Achievements and Perspectives in 1,4-Butanediol Production from Engineered Microorganisms

1,4-Butanediol (1,4-BDO), a significant commodity chemical, is currently manufactured exclusively from a host of energy-intensive processes, accompanied by severe environmental issues, such as the greenhouse effect and air pollution. As a result of the ever-increasing global market demands and increasing applications of 1,4-BDO, attention has turned to the sustainable bioproduction of 1,4-BDO, and several bio-based approaches for 1,4-BDO production have been successfully established in engineered Escherichia coli, including de novo biosynthesis and biocatalysis. Recent achievements in enhancing the accumulation of 1,4-BDO have been achieved by metabolic engineering strategies, such as improving precursor supply, enhancing activities of critical enzymes, and fewer byproduct synthesis. Here, we summarize the primary advances of the biological pathway for 1,4-BDO synthesis and put forward the future development prospect of bio-based 1,4-BDO production.

Selective Hydrogenolysis of Erythritol over Ir-ReOx /Rutile-TiO2 Catalyst

Partial hydrogenolysis of erythritol, which can be produced at large scale by fermentation, to 1,4-butanediol (1,4-BuD) is investigated with Ir-ReO_x /SiO₂ and Ir-ReO_x /rutile-TiO₂ catalysts. In addition to the higher conversion rate over Ir-ReO_x /TiO₂ than over Ir-ReO_x /SiO₂ , which has been also reported for glycerol hydrogenolysis, Ir-ReO_x /TiO₂ showed higher selectivity to 1,4-BuD than Ir-ReO_x /SiO₂ , especially at low conversion levels, leading to high 1,4-BuD productivity of 20 mmol_1,4-BuD  g_Ir ^-1  h^-1 at 373 K (36 % conversion, 33 % selectivity). The productivity based on the noble metal amount is higher than those reported previously, although the maximum yield of 1,4-BuD (23 %) is not higher than the highest reported values. The reactions of various triols, diols and mono-ols are tested and the selectivity and the reaction rates are compared between catalysts and between substrates. The Ir-ReO_x /TiO₂ catalyst showed about twofold higher activity than Ir-ReO_x /SiO₂ in hydrogenolysis of the C-OH bond at the 2- or 3-positions in 1,2- and 1,3-diols, respectively, whereas the hydrogenolysis of C-OH at the 1-position is less promoted by the TiO₂ support. Lowering the loading amount of Ir on TiO₂ (from 4 wt % to 2 or 1 wt %) decreases the Ir-based activity and 1,4-BuD selectivity. Similarly, increasing the loading amount on SiO₂ from 4 wt % to 20 wt % increases the Ir-based activity and 1,4-BuD selectivity, although they remain lower than those for TiO₂ -supported catalyst with 4 wt % Ir. High metal loadings on the support seem to be important.

Erythritol: Another C4 Platform Chemical in Biomass Refinery

The potential of erythritol as a platform chemical in biomass refinery is discussed in terms of erythritol production and utilization. Regarding erythritol production, fermentation of sugar or starch has been already commercialized. The shift of the carbon source from glucose to inexpensive inedible waste glycerol is being investigated, which will decrease the price of erythritol. The carbon-based yield of erythritol from glycerol is comparable to or even higher than that from glucose. The metabolic pathway of erythritol biosynthesis has become clarified: erythrose-4-phosphate, which is one of the intermediates in the pentose phosphate pathway, is dephosphorylated and reduced to erythritol. The information about the metabolic pathway may give insights to improve the productivity by bleeding. Regarding erythritol utilization, chemical conversions of erythritol, especially deoxygenation, have been investigated in these days. Erythritol is easily dehydrated to 1,4-anhydroerythritol, which can be also used as the substrate for production of useful C4 chemicals. C-O hydrogenolysis and deoxydehydration using heterogeneous catalysts are effective reactions for erythritol/1,4-anhydroerythritol conversion.

Reduction of sugar derivatives to valuable chemicals: utilization of asymmetric carbons

Recent progress on non-furfural routes from sugar derivatives to valuable chemicals including chiral chemicals was reviewed.

Tungsten–zirconia-supported rhenium catalyst combined with a deoxydehydration catalyst for the one-pot synthesis of 1,4-butanediol from 1,4-anhydroerythritol

Biomass-derived 1,4-anhydroerythritol is reduced to 1,4-butanediol over a reusable mixture of heterogeneous catalysts, ReO_x–Au/CeO₂ and ReO_x/WO₃–ZrO₂.

C-O Bond Hydrogenolysis of Aqueous Mixtures of Sugar Polyols and Sugars over ReOx-Rh/ZrO2 Catalyst: Application to an Hemicelluloses Extracted Liquor

The recovery and upgrade of hemicelluloses, a family of heteropolysaccharides in wood, is a key step to making lignocellulosic biomass conversion a cost-effective sustainable process in biorefinery. The comparative selective catalytic C-O bond hydrogenolysis of C5-C6 polyols, sugars, and their mixtures for the production of valuable C6 and C5 deoxygenated products was studied at 200 °C under 80 bar H2 over ReOx-Rh/ZrO2 catalysts. The sugars were rapidly converted to the polyols or converted into their hydrogenolysis products. Regardless of the reactants, C-O bond cleavage occurred significantly via multiple consecutive deoxygenation steps and led to the formation of linear deoxygenated C6 or C5 polyols. The distribution of products depended on the nature of the substrate and C-C bond scission was more important from monosaccharides. In addition, we demonstrated effective hydrogenolysis of a hemicellulose-extracted liquor from delignified maritime pine containing monosaccharides and low MW oligomers. Compared with the sugar-derived polyols, the mono- and oligosaccharides in the liquor were more rapidly converted to hexanediols or pentanediols. C-O bond scission was significant, giving a yield of desired deoxygenated products as high as 65%, higher than in the reaction of the synthetic mixture of glucose/xylose of the same C6/C5 sugar ratio (yield of 30%).

Preparation of Highly Active Monometallic Rhenium Catalysts for Selective Synthesis of 1,4-Butanediol from 1,4-Anhydroerythritol

1,4-Butanediol can be produced from 1,4-anhydroerythritol through the co-catalysis of monometallic mixed catalysts (ReO_x /CeO₂ +ReO_x /C) in the one-pot reduction with H₂ . The highest yield of 1,4-butanediol was over 80 %, which is similar to the value obtained over ReO_x -Au/CeO₂ +ReO_x /C catalysts. Mixed catalysts of CeO₂ +ReO_x /C showed almost the same performance, giving 89 % yield of 1,4-butanediol. The reactivity trends of possible intermediates suggest that the reaction mechanism over ReO_x /CeO₂ +ReO_x /C is similar to that over ReO_x -Au/CeO₂ +ReO_x /C: deoxydehydration (DODH) of 1,4-anhydroerythritol to 2,5-dihydrofuran over ReO_x species on the CeO₂ support with the promotion of H₂ activation by ReO_x /C, isomerization of 2,5-dihydrofuran to 2,3-dihydrofuran catalyzed by ReO_x on the C support, hydration of 2,3-dihydrofuran catalyzed by C, and hydrogenation to 1,4-butanediol catalyzed by ReO_x /C. The reaction order of conversion of 1,4-anhydroerythritol with respect to H₂ pressure is almost zero and this indicates that the rate-determining step is the formation of 2,5-dihydrofuran from the coordinated substrate with reduced Re in the DODH step. The activity of ReO_x /CeO₂ +ReO_x /C is higher than that of ReO_x -Au/CeO₂ +ReO_x /C, which is probably related to the reducibility of ReO_x /C and the mobility of the Re species between the supports. High-valent Re species such as Re⁷⁺ on the CeO₂ and C supports are mobile in the solvent; however, low-valent Re species, including metallic Re species, have much lower mobility. Metallic Re and cationic low-valent Re species with high reducibility and low mobility can be present on the carbon support as a trigger for H₂ activation and promoter of the reduction of Re species on CeO₂ . The presence of noble metals such as Au can enhance the reducibility through the activation of H₂ molecules on the noble metal and the formation of spilt-over hydrogen over noble metal/CeO₂ , as indicated by H₂ temperature-programmed reduction. The higher reducibility of ReO_x -Au/CeO₂ lowers the DODH activity of ReO_x -Au/CeO₂ +ReO_x /C in comparison with ReO_x /CeO₂ +ReO_x /C by restricting the movement of Re species from C to CeO₂ .

Polymers Based on Cyclic Carbonates as Trait d'Union Between Polymer Chemistry and Sustainable CO2 Utilization

Given the large amount of anthropogenic CO₂ emissions, it is advantageous to use CO₂ as feedstock for the fabrication of everyday products, such as fuels and materials. An attractive way to use CO₂ in the synthesis of polymers is by the formation of five-membered cyclic organic carbonate monomers (5CCs). The sustainability of this synthetic approach is increased by using scaffolds prepared from renewable resources. Indeed, recent years have seen the rise of various types of carbonate syntheses and applications. 5CC monomers are often polymerized with diamines to yield polyhydroxyurethanes (PHU). Foams are developed from this type of polymers; moreover, the additional hydroxyl groups in PHU, absent in classical polyurethanes, lead to coatings with excellent adhesive properties. Furthermore, carbonate groups in polymers offer the possibility of post-functionalization, such as curing reactions under mild conditions. Finally, the polarity of carbonate groups is remarkably high, so polymers with carbonates side-chains can be used as polymer electrolytes in batteries or as conductive membranes. The target of this Review is to highlight the multiple opportunities offered by polymers prepared from and/or containing 5CCs. Firstly, the preparation of several classes of 5CCs is discussed with special focus on the sustainability of the synthetic routes. Thereafter, specific classes of polymers are discussed for which the use and/or presence of carbonate moieties is crucial to impart the targeted properties (foams, adhesives, polymers for energy applications, and other functional materials).

Aerobic oxidation of C4–C6 α,ω-diols to the diacids in base-free medium over zirconia-supported (bi)metallic catalysts

Aerobic oxidation of (C₄–C₆) α,ω-diols in water produces the corresponding α,ω-diacids in high 83–96% yields over a Au–Pt/ZrO₂ catalyst.

Silica-supported Cu–Pt bimetallic catalysts for liquid-phase diethyl oxalate hydrogenation

Silica-supported copper catalysts were prepared by different methods, and Cu/SiO2 prepared by the urea-assisted gel method was modified with co-catalyst platinum to obtain Cu-Pt/SiO2 bimetallic catalysts. The prepared catalysts were characterized by nitrogen adsorption–desorption, XRD, TEM, hydrogen chemisorption, ammonia gas chemisorption, and X-ray photoelectron spectroscopy. The characterization results show that the modification of platinum is helpful to the reduction and dispersion of copper species, which increase the hydrogen uptake quantity and metal surface area. The 30%Cu–3.0%Pt/SiO2-6 presents the best catalytic performance in liquid-phase diethyl oxalate hydrogenation; it gives 77.32% conversion of diethyl oxalate and 94.37% selectivity to the main products under 473 K and 3.0 MPa for 4 h. A possible reaction route was also proposed.

Selective Hydrogenolysis of Furfural Derivative 2-Methyltetrahydrofuran into Pentanediol Acetate and Pentanol Acetate over Pd/C and Sc(OTf)3 Cocatalytic System

It is of great significance to convert platform molecules and their derivatives into high value-added alcohols, which have multitudinous applications. This study concerns systematic conversion of 2-methyltetrahydrofuran (MTHF), which is obtained from furfural, into 1-pentanol acetate (PA) and 1,4-pentanediol acetate (PDA). Reaction parameters, such as the Lewis acid species, reaction temperature, and hydrogen pressure, were investigated in detail. ¹ H NMR spectroscopy and reaction dynamics study were also conducted to help clarify the reaction mechanism. Results suggested that cleavage of the primary alcohol acetate was less facile than that of the secondary alcohol acetate, with the main product being PA. A PA yield of 91.8 % (150 °C, 3 MPa H₂ , 30 min) was achieved by using Pd/C and Sc(OTf)₃ as a cocatalytic system and an 82 % yield of PDA was achieved (150 °C, 30 min) by using Sc(OTf)₃ catalyst. Simultaneously, the efficient conversion of acetic esters into alcohols by simple saponification was carried out and led to a good yield.

Complementary function of two transketolase isoforms from Moniliella megachiliensis in relation to stress response

Two transketolase isogenes, MmTKL1 and MmTKL2, isolated from Moniliella megachiliensis were investigated for their roles in stress response and erythritol biosynthesis. The encoded proteins were highly homologous in amino acid sequence and domain structure. Two stress response elements (STREs) were found upstream of MmTKL1, while no STRE was found upstream of MmTKL2. In contrast, two Ap-1 elements were present upstream of MmTKL2, but none were detected upstream of MmTKL1. MmTKL2 partially complemented the aromatic amino acid auxotrophy of a Saccharomyces cerevisiae tkl1 deletion mutant, suggesting that at least one of the MmTKLs functioned as a transketolase in vivo. In response to short-term osmotic stress (20% glucose or 1.2 M NaCl) in Moniliella cells, MmTKL1 expression increased rapidly through the first 40 min before subsequently decreasing gradually, while MmTKL2 expression showed no significant change. In contrast, short-term oxidative stress (0.15 mM menadione) induced considerable increases in MmTKL2, while MmTKL1 expression remained low under the same conditions. Long-term osmotic stress (20% glucose) yielded increased expression of both genes starting at 12 h and continuing through 72 h. During either osmotic or oxidative stress, intracellular erythritol accumulation could clearly be correlated with the pattern of expression of either MmTKL1 or MmTKL2. These results strongly suggested that MmTKL1 is responsible primarily for the response to osmotic stress, while MmTKL2 is responsible primarily for the response to oxidative stress. Thus, we postulate that the two transketolase isoforms of M. megachiliensis play distinct and complementary roles in coordinating erythritol production in response to distinct environmental stresses.

Catalytic Hydrodeoxygenation of High Carbon Furylmethanes to Renewable Jet-fuel Ranged Alkanes over a Rhenium-Modified Iridium Catalyst

Renewable jet-fuel-range alkanes are synthesized by hydrodeoxygenation of lignocellulose-derived high-carbon furylmethanes over ReO_x -modified Ir/SiO₂ catalysts under mild reaction conditions. Ir-ReO_x /SiO₂ with a Re/Ir molar ratio of 2:1 exhibits the best performance, achieving a combined alkanes yield of 82-99 % from C₁₂ -C₁₅ furylmethanes. The catalyst can be regenerated in three consecutive cycles with only about 12 % loss in the combined alkanes yield. Mechanistically, the furan moieties of furylmethanes undergo simultaneous ring saturation and ring opening to form a mixture of complex oxygenates consisting of saturated furan rings, mono-keto groups, and mono-hydroxy groups. Then, these oxygenates undergo a cascade of hydrogenolysis reactions to alkanes. The high activity of Ir-ReO_x /SiO₂ arises from a synergy between Ir and ReO_x , whereby the acidic sites of partially reduced ReO_x activate the C-O bonds of the saturated furans and alcoholic groups while the Ir sites are responsible for hydrogenation with H₂ .

Highly Selective Deoxydehydration of Tartaric Acid over Supported and Unsupported Rhenium Catalysts with Modified Acidities

The deoxydehydration (DODH) of sugar acids to industrially important carboxylic acids is a very attractive topic. Oxorhenium complexes are the most-often employed DODH catalysts. Because of the acidity of the rhenium catalysts, the DODH products of sugar acids were usually in the form of mixture of free carboxylic acids and esters. Herein, we demonstrate strategies for the selective DODH of sugar acids to free carboxylic acids by tuning the Lewis acidity or the Brønsted acidity of the rhenium-based catalysts. Starting from tartaric acid, up to 97 % yield of free maleic acid was achieved. Based on our strategies, functional polymer immobilized heterogeneous rhenium catalysts were also developed for the selective DODH conversion of sugar acids.

Synthesis of 2-Butanol by Selective Hydrogenolysis of 1,4-Anhydroerythritol over Molybdenum Oxide-Modified Rhodium-Supported Silica

Rh-MoOx /SiO2 (Mo/Rh=0.13) is an effective catalyst for the hydrogenolysis of 1,4-anhydroerythritol (1,4-AHERY) and provides 2-BuOH in high yield of 51 %. This is the first report of the production of 2-BuOH from 1,4-AHERY by hydrogenolysis. 1,4-AHERY was more suitable as a starting material than erythritol because the 2-BuOH yield from erythritol was low (34 %). Based on the kinetics and comparison of reactivities of the related compounds using Rh-MoOx /SiO2 and Rh/SiO2 catalysts, the modification of Rh/SiO2 with MoOx leads to the high activity and high selectivity to 2-BuOH because of the generation of reactive hydride species and the strong adsorption of 1,4-AHERY on MoOx species. The reaction proceeds by main two routes, (I) the combination of single C-O hydrogenolysis with the desorption of intermediates, a usual route in hydrogenolysis, and (II) multiple C-O hydrogenolysis without the desorption of intermediates from the active site, and the reaction mechanism for Route (II) is proposed.

Catalytic total hydrodeoxygenation of biomass-derived polyfunctionalized substrates to alkanes

The total hydrodeoxygenation of carbohydrate-derived molecules to alkanes, a key reaction in the production of biofuel, was reviewed from the aspect of catalysis. Noble metals (or Ni) and acid are the main components of the catalysts, and group 6 or 7 metals such as Re are sometimes added as modifiers of the noble metal. The main reaction route is acid-catalyzed dehydration plus metal-catalyzed hydrogenation, and in some systems metal-catalyzed direct CO dissociation is involved. The appropriate active metal, acid strength, and reaction conditions depend strongly on the reactivity of the substrate. Reactions that use Pt or Pd catalysts supported on Nb-based acids or relatively weak acids are suitable for furanic substrates. Carbohydrates themselves and sugar alcohols undergo CC dissociation easily. The systems that use metal-catalyzed direct CO dissociations can give a higher yield of the corresponding alkane from carbohydrates and sugar alcohols.

Selective hydrogenation of lactic acid to 1,2-propanediol over highly active ruthenium-molybdenum oxide catalysts

Modification of Ru/C with a small amount of MoOx (RuMoOx /C) enhanced the catalytic activity in the hydrogenation of L-lactic acid to form 1,2-propanediol and maintained high selectivity. The turnover frequency based on the amount of Ru over the optimized RuMoOx /C catalyst (Mo/Ru molar ratio=1:16) was 114 h(-1) at 393 K, which was about 4 times higher than that over Ru/C. The same effect of MoOx was obtained over RuMoOx /SiO2 , although RuMoOx /SiO2 showed slightly lower activity than that of RuMoOx /C. RuMoOx /C achieved a high yield of 95 % in 18 h at 393 K and was applicable to various carboxylic acids to provide the corresponding alcohols in high yields. Modification with MoOx also brought about suppression of racemization and (S)-1,2-propanediol was obtained in high enantiomeric excess at 353 K. Based on kinetic analysis and characterization data, such as XRD, TEM, CO adsorption by a volumetric method, FTIR spectroscopy, and X-ray absorption spectroscopy, for RuMoOx /C and RuMoOx /SiO2 , the catalyst structure and reaction mechanism are proposed.

Erythritol production by Moniliella megachiliensis using nonrefined glycerol waste as carbon source

The number of naphtha plants is being reduced due to a worldwide shift in energy sources. Consequently, a shortage of chemical materials heavily dependent on naphtha-oil, especially C4 compounds such as butene and butane-diol, is an urgent issue in chemical manufacturing. Erythritol is a rare C4 compound produced by fermentation processes using glucose as the carbon source. Since erythritol is considerably more expensive than hydrocarbons derived from naphtha-oil, a reduction in its cost is critical. We found that Moniliella megachiliensis, a highly osmotolerant yeast strain, can utilize nonrefined glycerol waste derived from palm oil or beef tallow and convert it to erythritol. Cell growth on glycerol was almost the same as on glucose, and the cells could grow in up to 300 mg ml(-1) glycerol. When 200 mg ml(-1) nonrefined glycerol was supplied, the yield of erythritol from the glycerol was approx. 60%, which is slightly higher than that obtained using glucose. The cost of glycerol waste is considerably lower than that of glucose. Thus, the conversion of glycerol waste into valuable erythritol, proposed here, is attractive and promising from the viewpoint of ensuring a supply of C4 hydrocarbons and utilizing a waste natural resource.

SIGNIFICANCE AND IMPACT OF THE STUDY

A shortage of C4 hydrocarbon depending much on naptha-oil has become urgent problem due to rapid reduction of naphtha plants together with global energy revolution. Erythritol, obtained by fermentation, is a rare C4 polyol that can be converted to C4 hydrocarbons. Erythritol is considerably expensive than hydrocarbons, a reduction in cost is critical issue. To meet this, we proposed to utilize low-cost glycerol waste from bio-diesel fuel as a carbon source. Moniliella megachiliensis successfully converted glycerol waste to erythritol. This proposal is promising to obtain C4 hydrocarbon substitute, and concomitantly to dispose a large amount of glycerol waste discharged.

Production of renewable hexanols from mechanocatalytically depolymerized cellulose by using Ir-ReOx /SiO2 catalyst

Hexanols were produced in high yield by conversion of cellulose over Ir-ReOx /SiO2 (molar ratio Re/Ir=2) catalyst in biphasic reaction system (n-decane+H2 O). The cellulose was depolymerized by mechanocatalysis with the aid of H2 SO4 . The influence of solvent amount, reaction temperature and hydrogen pressure was systematically investigated and the highest yield of hexanols reached 60 % under the conditions of n-decane/water ∼2 (v/v), 413 K, 10 MPa H2 for 24 h. Mechanocatalytic depolymerization of cellulose with the aid of H2 SO4 or HCl and the use of sufficient n-decane were very crucial for the production of hexanols. H2 SO4 not only catalyzed cellulose to water-soluble oligosaccharides but also promoted the hydrogenolysis activity of Ir-ReOx /SiO2 catalyst. The role of n-decane was to extract hexanols and to suppress over-hydrogenolysis of hexanols to n-hexane.