Hero Heeres

Experimental and kinetic modelling studies on the acid-catalysed hydrolysis of the water hyacinth plant to levulinic acid

A comprehensive experimental and modelling study on the acid-catalysed hydrolysis of the water hyacinth plant (Eichhornia crassipes) to optimise the yield of levulinic acid (LA) is reported (T=150-175 degrees CH2SO4 = 0.1-1M, water hyacinth intake=1-5wt%). At high acid concentrations (>0.5M), LA was the major organic acid whereas at low acid concentrations (<0.1M) and high initial intakes of water hyacinth, the formation of propionic acid instead of LA was favoured. The highest yield of LA was 53mol% (35wt%) based on the amount of C6-sugars in the water hyacinth (T=175 degrees CH2SO4 =1M , water hyacinth intake=1wt%). The LA yield as a function of the process conditions was modelled using a kinetic model originally developed for the acid-catalysed hydrolysis of cellulose and good agreement between the experimental and modelled data was obtained.

Identification and classification of components in flash pyrolysis oil and hydrodeoxygenated oils by two-dimensional gas chromatography and time-of-flight mass spectrometry

Hydrodeoxygenated pyrolysis oils (HDO) are considered promising renewable liquid energy carriers. To gain insights in the various reaction pathways taking place during the hydrodeoxygenation reaction of pyrolysis oil, two-dimensional gas chromatography with time-of-flight mass spectrometric analyses (2D-GC-TOF-MS) was applied on the feedstock and product oil. Chromatographic parameters like injection temperature and column choice of the 1D-(2)D ensemble are discussed. Fractionation of the oils by hexane extraction was applied to show the distribution of analytes over the phases. Some 1000 and 2000 components in the pyrolysis and HDO oil, respectively could be identified and classified. The TOF-MS detection considerably improved the understanding of the molecular distribution over the 1D-(2)D retention time fields in the contour plot, in order to classify the analytes in functional groups. By group-type classification of the main components (>0.3% relative area), it was possible to characterize the oils by 250 and 350 analytes, respectively pyrolysis oil and HDO oil, describing 75% of the chromatographable fraction. The 2D-GC-TOF-MS method showed to be a useful and fast technique to determine the composition of (upgraded) pyrolysis oil and is potentially a very useful tool for exploratory catalyst research and kinetic studies. The 2D-GC-TOF-MS technique is not only useful for the chemical study as such, but also provides the basic knowledge for method transfer to a 2D-GC-FID (flame ionization detector) application.

On the synthesis of monopentamethylcyclopentadienyl derivatives of yttrium, lanthanum, and cerium

Abstract Two routes leading to monopentamethylcyclopentadienyl-yttrium, -lanthanum and -cerium complexes have been explored. Transmetallation of LnCl3(THF)x with Cp⋆Li (Cp⋆ C5Me5) proved useful only in some particular cases. Acid-base reactions of homoleptic complexes LnR3 with Cp⋆H generally gave Cp⋆2LnR compounds, although Cp⋆LnR2 complexes were observed as intermediates. The mono-Cp⋆ complex Cp⋆Y(o-C6H4CH2NMe2)2 was obtained from Y(o-C6H4CH2NMe2)3 and Cp⋆H, and is the first salt-free mono-Cp⋆ yttrium complex with two carbyl ligands.

Acetic Acid Recovery from Fast Pyrolysis Oil. An Exploratory Study on Liquid-Liquid Reactive Extraction using Aliphatic Tertiary Amines

Abstract Flash pyrolysis oil or Bio-oil (BO), obtained by flash pyrolysis of lignocellulosic biomass, is very acidic in nature. The major component responsible for this acidity is acetic acid, present in levels up to 2–10 wt%. Here, we report an exploratory study on BO upgrading by reactive extraction of acetic acid using long-chain tertiary amines in a batch set-up. Factors affecting the extraction efficiency, such as the type and concentration of tertiary amine and co-solvents, were investigated. More than 90 wt% of the acetic acid could be extracted in a single equilibrium step (BO diluted in THF (26 wt% BO), trioctylamine (TOA) in octane as the extractant phase, T = 20°C). However, the amine has considerable affinity for the BO phase and about 10 wt% on initial intake was transferred to the BO. A considerable improvement was obtained when using the aqueous phase of a thermally treated BO containing 6 wt% acid of acetic acid. In a single extraction step, acetic acid extraction efficiencies up to 75 wt% were achieved without significant amine transfer to the aqueous phase.

The application of fine TiO2 particles for enhanced gas absorption

The physical absorption of pure CO2 in various liquids (water, hexadecane, and sunflower oil) containing micron sized TiO 2 particles has been investigated. Absorption studies were carried out in a batch stirred cell reactor at 298 K and initial pressures of 0.08 MPa. Solid loading and stirring intensities were varied systematically between 0–15 kg/m 3 and 3.3–12.5 s −1 , respectively. Gas absorption rates are enhanced significantly in the presence of TiO 2 particles. Enhancement factors are a function of the solids loading and stirring intensity. Maximum enhancement factors of about 2 were observed for all solvents at low stirring intensities. The rate of gas absorption was theoretically analyzed using a heterogeneous unsteady state mass transfer model based on the Danckwerts surface renewal theory and a Langmuir-type of particle to interface adhesion isotherm. This model not only predicts the trends in the observed enhancement factors very well but also gives an accurate quantitative picture.

Reversible Carbon-Carbon Bond Formation in Organolanthanide Systems. Preparation and Properties of Lanthanide Acetylides [Cp*2LnC≡CR], and Their Rearrangement Products [Cp*2Ln]2(μ-η2 : η2-RC4R) (Ln = La, Ce, R = Alkyl)

Lanthanide carbyls Cp*{sub 2}LnCH(SiMe{sub 3}){sub 2}{sup 1} (1, Ln=Ce;2, Ln=La) react with terminal alkynes HC{triple_bond}CR (R = Me, t-Bu) to yield oligomeric acetylides [Cp*{sub 2}LnC{triple_bond}CR]{sub n} (3, Ln = Ce, R = Me; 4, Ln = La, R = Me; 5, Ln = Ce, R = t-Bu). The acetylides are not stable in solution and rearrange to give the carbon-carbon coupled products, [Cp*{sub 2}Ln]{sub 2}({mu}-{eta}{sup 2}:{eta}{sup 2}-RC{sub 4}R) (6, Ln = Ce, R = Me; 7, Ln = La, R = Me; 8, Ln = Ce, R = t-Bu). Thermodynamic and kinetic studies of the C-C coupling process were studied as were the structures of 6 and 8 via XRD.

Highly active, recyclable catalyst for the manufacture of viscous, low molecular weight, CO-ethene-propene-based polyketone, base component for a new class of resins

Abstract A highly active, recyclable homogeneous palladium(II) catalyst is described for the manufacture of viscous, low molecular weight CO–ethene–propene-based polyketone (Carilite Oligomer), used for the manufacture of a new class of resins (Carilite Resins). The catalyst is composed of palladium acetate, and a sulfonated diphosphine ligand, bdompp-S (1,3-bis(di-(2-methoxy, 5-sulfonatophenyl)phosphino)propane). In comparison with its non-sulfonated counterpart this catalyst not only exhibits a much more favourable partitioning coefficient in liquid–liquid separation of the polyketone product and solvent, but it also exhibits an approximately 2.5 times higher catalytic activity (up to 11.2 kg PKxa0(g Pd)−1xa0h−1) in the manufacture of PK-PE-30 (polyketone terpolymer built up of CO, ethene and propene in a molar ratio of 100:30:70). A variety of salts were found to exert a positive influence on the activity of the catalyst. Possible origins of this ‘salt-effect’ are briefly discussed. The bdompp-S ligand was synthesised by sulfonation of bdompp using either a boric acid–oleum mixture or sulfuric acid as the sulfonation reagent. The product was isolated either as sodium-salt (bdompp-S[Na]4·nNa2SO4), by extraction with methanol after neutralisation, or, in acidic, hydrated form (bdompp-S[H]4·nH2O), via a new and highly efficient procedure, i.e. cooling the reaction mixture after dilution with water. The X-ray crystal structure of bdompp-S[H]4·nH2O is discussed.

Two‐Phase (Bio)Catalytic Reactions in a Table‐Top Centrifugal Contact Separator

A new spin on catalysis: A table-top centrifugal contact separator allows for fast continuous two-phase reactions to be performed by intimately mixing two immiscible phases and then separating them. Such a device has been used to produce biodiesel from sunflower oil and MeOH/NaOMe. A lipase-catalyzed esterification of oleic acid with nBuOH (see picture) also proceeds with high conversion and can be run for up to 13 h.

Monocyclopentadienyl Yttrium Chemistry: Incorporation of Alkoxides as Supporting Ligands and Synthesis of [Y(C5Me5)(OC6H3But2)(μ-H)]2

Reaction of the crystallographically characterised [Y(C5Me5)(OC6H3But2)2]2 with LiCH(SiMe3)2 affords the mixed alkyl–alkoxide species [Y(C5Me5){CH(SiMe3)2}(OC6H3But2)]3 which, on subsequent hydrogenation, gives the hydride bridged dimer [{Y(C5Me5)(OC6H3But2)(µ-H)}2]4; 89Y NMR spectra of these, and related complexes, allows C5Me5, OC6H3But2 and CH(SiMe3)2 group contributions to be determined.

Synthesis of cationic cerium compounds [Cp*2Ce(L)2][BPh4] (L = tetrahydrofuran or tetrahydrothiophene) and the crystal structure of the tetrahydrothiophene derivative

Abstract Protolysis of the cerium alkyl Cp*2CeCH(SiMe3)2 (1) by triethylammoniumtetraphenylborate provides a useful route to cationic cerium compounds [Cp*2Ce(L)2][BPh4] (2, L = tetrahydrofuran; 3, L= tetrahydrothiophene). The crystal structure of the tetrahydrothiophene derivative was determined by X-ray diffraction, which showed it to consist of discrete [Cp*2Ce(THT)2]+ and BPh4ovbar ions. The Cp* ring-centroids (cent) and the sulphur atoms in the cation form a distorted tetrahedron with a Cent-Ce- Cent angle of 134.57(6)° and Ce-S distances of 3.058(1) and 3.072(1)A˚.