Combining Bio- and Chemo-Catalysis for the Conversion of Bio-Renewable Alcohols: Homogeneous Iridium Catalysed Hydrogen Transfer Initiated Dehydration of 1,3-Propanediol to Aldehydes

Combining whole cell biocatalysis and chemocatalysis in a single reaction sequence avoids unnecessary separations, and the associated waste and energy consumption. Bacterial fermentation has been employed to convert waste glycerol from biodiesel production into 1,3-propanediol. This 1,3-propanediol can be extracted selectively from the aqueous fermentation broth using ionic liquids. 1,3-propanediol in ionic liquid solution was converted to propanal by hydrogen transfer initiated dehydration (HTID) catalysed by a Cp*IrCl2(NHC) (Cp* = pentamethylcyclopentadienyl; NHC = carbene ligand) complex. The use of an ionic liquid solvent enabled the reaction to be performed under reduced pressure, facilitating the isolation of the product, and improving the reaction selectivity. The Ir(III) catalyst in ionic liquid was found to be highly recyclable.

Structural basis of substrate selectivity in the glycerol-3-phosphate: phosphate antiporter GlpT.

Major facilitators represent the largest superfamily of secondary active transporter proteins and catalyze the transport of an enormous variety of small solute molecules across biological membranes. However, individual superfamily members, although they may be architecturally similar, exhibit strict specificity toward the substrates they transport. The structural basis of this specificity is poorly understood. A member of the major facilitator superfamily is the glycerol-3-phosphate (G3P) transporter (GlpT) from the Escherichia coli inner membrane. GlpT is an antiporter that transports G3P into the cell in exchange for inorganic phosphate (Pi). By combining large-scale molecular-dynamics simulations, mutagenesis, substrate-binding affinity, and transport activity assays on GlpT, we were able to identify key amino acid residues that confer substrate specificity upon this protein. Our studies suggest that only a few amino acid residues that line the transporter lumen act as specificity determinants. Whereas R45, K80, H165, and, to a lesser extent Y38, Y42, and Y76 contribute to recognition of both free Pi and the phosphate moiety of G3P, the residues N162, Y266, and Y393 function in recognition of only the glycerol moiety of G3P. It is the latter interactions that give the transporter a higher affinity to G3P over Pi.

Kinetics of Aqueous Phase Dehydration of Xylose into Furfural Catalyzed by ZSM-5 Zeolite

ZSM-5 zeolite in H+ form with an average pore size of 1.2 nm was used for aqueous phase dehydration of xylose to furfural at low temperatures;, that is, from 413 to 493 K. The selectivity in furfural increased with the temperature to a value of 473 K. Beyond this temperature, condensation reactions were significant and facilitated by the intrinsic structure of ZSM-5. A reaction mechanism that included isomerization of xylose to lyxose, dehydration of lyxose and xylose to furfural, fragmentation of furfural to organic acids, oligomerization of furfural to bi- and tridimensional furilic species, and complete dehydration of organic acids to carbonaceous deposits was developed, and the associated kinetic parameters were estimated. The rate of furfural production was found to be more sensitive to temperature than the rates of side reactions, with an estimated activation energy of 32.1 kcal/mol. This value correlated well with data in the literature obtained by homogeneous catalytic dehydration.

Adding value to renewables: a one pot process combining microbial cells and hydrogen transfer catalysis to utilise waste glycerol from biodiesel production

Waste glycerol was converted to secondary amines in a one pot reaction, using Clostridium butyricum and catalytic hydrogen transfer-mediated amination.

Amination and dehydration of 1,3-propanediol by hydrogen transfer: reactions of a bio-renewable platform chemical

1,3-propanediol was subjected to a range of amination conditions. The N-heterocyclic carbene piano stool complex [Cp*IrCl2(bmim)] was found to be a good catalyst for amination and dehydration in toluene or ionic liquid; product compositions could be tuned by altering the ratio of diol to amine.

The effect of glycerol inclusion on broiler performance and nutrient digestibility

1. Crude glycerol from biodiesel production was offered ad libitum to broiler chickens in a 21-d feeding and digestibility trial. The study was designed as a 3*2+1 factorial design with 3 concentrations (33, 67, 100 g/kg) of glycerol from 2 sources, A and B (PRS Environmental Ltd and John Thompson and Sons Ltd) and a control diet. The diets were formulated to contain apparent metabolisable energy (AME) of 12.95 MJ/kg (assuming 14.6 MJ/kg for glycerol).

Effect of precursor on the performance of alumina for the dehydration of methanol to dimethyl ether

Dimethyl ether (DME) is amongst one of the most promising alternative, renewable and clean fuels being considered as a future energy carrier. In this study, the comparative catalytic performance of γ-Al2O3 prepared from two common precursors (aluminum nitrate (AN) and aluminum chloride (AC)) is presented. The impact of calcination temperature was evaluated in order to optimize both the precursor and pre-treatment conditions for the production of DME from methanol in a fixed bed reactor. The catalysts were characterized by TGA, XRD, BET and TPD-pyridine. Under reaction conditions where the temperature ranged from 180 °C to 300 °C with a WHSV = 12.1 h−1 it was found that all the catalysts prepared from AN(η-Al2O3) showed higher activity, at all calcination temperatures, than those prepared from AC(γ-Al2O3). In this study the optimum catalyst was produced from AN and calcined at 550 °C. This catalyst showed a high degree of stability and had double the activity of the commercial γ-Al2O3 or 87% of the activity of commercial ZSM-5(80) at 250 °C.

Phosphotungstic Acid Encapsulated in Metal-Organic Framework as Catalysts for Carbohydrate Dehydration to 5-Hydroxymethylfurfural

MIL-101, a chromium-based metal-organic framework, is known for its very large pore size, large surface area and good stability. However, applications of this material in catalysis are still limited. 5-Hydroxymethylfurfural (HMF) has been considered a renewable chemical platform for the production of liquid fuels and fine chemicals. Phosphotungstic acid, H3PW12O40 (PTA), encapsulated in MIL-101 is evaluated as a potential catalyst for the selective dehydration of fructose and glucose to 5-hydroxymethylfurfural. The results demonstrate that PTA/MIL-101 is effective for HMF production from fructose in DMSO and can be reused. This is the first example of the application of a metal-organic framework in carbohydrate dehydration.

Development of a heterogeneous catalyst for lignocellulosic biomass conversion:Glucose dehydration by metal chlorides in a silica-supported ionic liquid layer

An attempt is made to immobilize the homogeneous metal chloride/EMIMCl catalyst for glucose dehydration to 5-hydroxymethylfurfural. To this end, ionic liquid fragments were grafted to the surface of SBA-15 to generate a heterogenized mimick of the homogeneous reaction medium. Despite a decrease in the surface area, the ordered mesoporous structure of SBA-15 was largely retained. Metal chlorides dispersed in such ionic liquid film are able to convert glucose to HMF with much higher yields as is possible in the aqueous phase. The reactivity order CrCl > AlCl > CuCl > FeCl is similar to the order in the ionic liquid solvent, yet the selectivity are lower. The HMF yield of the most promising CrCl-Im-SBA-15 can be improved by using a HO:DMSO mixture as the reaction medium and a 2-butanol/MIBK extraction layer. Different attempts to decrease metal chloride leaching by using different solvents are described. © 2013 American Institute of Chemical Engineers Environ Prog.

Mechanochemical interconversion between discrete complexes and coordination networks - formal hydration/dehydration by LAG

Using a small planetary ball mill, liquid-assisted grinding (LAG) of metal salts or oxides (ZnO, CdO, CdCO3, Cu(OAc)(2)center dot H2O, Co(OAc)(2)center dot 4H(2)O, Mn(OAc)(2)center dot 4H(2)O, Ni(OAc)(2)center dot 4H(2)O, FeSO4 center dot 7H(2)O) with two equivalents of isonicotinic acid (HINA) and small amounts of water ( up to 5.6 molar equivalents) gave discrete aquo complexes trans-[M(INA)(2)(OH2)(4)] (M = Zn, Cd, Cu, Fe, Co, Ni, Mn) efficiently within 30 min. For M = Zn, Cd and Cu these complexes readily undergo reversible formal dehydration to the extended network structures [M(INA)(2)] (M = Zn, Cu) or [Cd(INA)(2)(OH2)]center dot DMF by further LAG with non-aqueous liquids such as methanol or DMF. Overall, the mechanochemical dehydrations are more effective than heating or immersion in bulk solvents. The work demonstrates a two-step mechanochemical synthesis of coordination networks via discrete aquo complexes which may be preferable to single step reactions or grinding-annealing procedures in some cases. For example, the two step method was the only way to prepare [Cd(INA)(2)(OH2)]center dot DMF mechanochemically and the porous network Cu(INA)(2) could not be obtained from the aquo complex by heating.