Overview of catalytic methods for production of next generation biodiesel from natural oils and fats

Production of biodiesel from natural oils and fats can be achieved using various technologies briefly discussed in this review. A particular appealing concept for production of green diesel is selective catalytic deoxygenation of renewables leading to diesel fuel products. This reaction can be performed over Pd on active carbon supports with saturated and unsaturated fatty acids and their derivatives.     

Functionalised Bicyclic exo‐Glycals by Alkynol Cycloisomerisation of Hydroxy 1,3‐Diynes and Hydroxy Haloalkynes

Functionalised bicyclic exo‐glycals are readily obtained by base‐catalysed (typically MeONa in MeOH) alkynol cycloisomerisation of ethynylated cyclic saccharides. Thus, base treatment of the phenylethynyl‐ and halogenoethynylated 1‐O‐acetyl‐ribofuranoses 22 – 24 and the 4‐ethynylated 1‐thioglucopyranosides 30 – 33 gave – after deacetylation – selectively the (Z)‐configured exocyclic enol ethers 26 – 28 (84–91%) and 34 – 37 (63–76%), respectively, resulting from a trans‐5‐exo‐dig cyclisation. The ring closure to the trans‐dioxahexahydroindans 34 – 37 is favoured by a concerted intramolecular protonation of the intermediate vinyl anion by the neighbouring HO C(3). Cycloisomerisation of the 6‐O‐acetyl‐4‐(phenylethynyl)‐1‐thio‐α‐D ‐glucopyranoside 39 occurred via the corresponding phenylethynylated allenes to provide the galacto‐configured (Z)‐ and (E)‐cis‐dioxahexahydroindans 40 (30%) and 41 (51%). Surprisingly, the HO C(4) unprotected α‐d‐ galactopyranosyl‐buta‐1,3‐diyne 15 and the β‐D ‐glucopyranosyl‐buta‐1,3‐diyne 51 (and its 2‐bromoethynyl analogue) undergo a 6‐exo‐dig ring closure to the 2,5‐dioxabicyclo[2.2.2]octanes 16 – 19 and 52 / 53 , respectively, the ring closure requiring a boat conformation (B_1,4 for 15 , ^1,4B for 51 ). Ring strain (anti‐reflex effect) prevents an alkynol cycloisomerisation of 4‐(phenylbuta‐1,3‐diynyl, bromoethynyl, or iodoethynyl)levoglucosan 56 – 59 , and 56 reacted by elimination to the hex‐1‐ene‐3,5‐diyne 59 (82%), while isomerisation of 57 and 58 led to epimeric mixtures of the haloallenes 60 (82%) and 61 (68%).     

Sol-gel technique for the generation of europium-doped mesoporous and dense thin films: A luminescent study

In this paper, a series of europium-activated titania mesoporous and dense thin films were prepared by sol-gel process. Structural characterizations show that high europium ion loadings can be incorporated into titanium dioxide walls without destroying the mesoporous arrangement. However, high europium content locks the titanium dioxide crystallization process. Upon 10% europium ions loading, mesoporous thin films are mainly amorphous, whereas dense ones are still partially crystallized. Eu³⁺ ion luminescence has been investigated by exciting through the semiconductor host lattice. Emission features reveal that europium ions adopt similar environments (nanocrystalline and glassy-like ones) in both dense and mesoporous thin films. Fluctuations of europium emission under continuous UV excitation have been observed. One observes that the effect strongly depends on the thin films’ crystalline character which is strongly related with the texturation and existence at the mesoscopic length scale.     

Red long-lasting luminescence in clinoenstatite

A long-lasting phosphor Ca_0.2Zn_0.9Mg_0.9Si₂O₆:Eu²⁺, Dy³⁺, Mn²⁺ was prepared by a sol-gel method. Nanoparticles crystallizing in a clinoenstatite structure were obtained. Long persistent phosphorescence in the red has been observed with persistence time over one hour at 680 nm and was attributed to Mn²⁺ emission. The persistent luminescence is suggested to involve Eu²⁺ as a sensitizer, Dy³⁺ or Dy³⁺-related defect as a trap center and Mn²⁺ as the luminescent center. However, the details of the mechanism are still under further investigation.     

Existence and Construction of H 1-Splines of Class C k on a Three Directional Mesh

Let be the uniform triangulation generated by the usual three directional mesh of the plane and let H ₁ be the regular hexagon formed by the six triangles of surrounding the origin. We study the space of piecewise polynomial functions in C ^k (R ²) with support H ₁ having a sufficiently high degree n, which are invariant with respect to the group of symmetries of H ₁ and whose sum of integer translates is constant. Such splines are called H ₁-splines. We first compute the dimension of this space in function of n and k. Then we prove the existence of a unique H ₁-spline of minimal degree for any fixed k0. Finally, we describe an algorithm computing the Bernstein–Bézier coefficients of this spline.     

Vinyl C-F cleavage by Os(H)3Cl(P(i)Pr3)2

Os(H)(3)ClL(2) (L = P(i)Pr(3)) reacts at 20 degrees C with vinyl fluoride in the time of mixing to produce OsHFCl([triple bond]CCH(3))L(2) and H(2). In a competitive reaction, the liberated H(2) converts vinyl fluoride to C(2)H(4) and HF in a reaction catalyzed by Os(H)(3)ClL(2). A variable-temperature NMR study reveals these reactions proceed through the common intermediate OsHCl(H(2))(H(2)C=CHF)L(2), via OsClF(=CHMe)L(2) and OsHCl(H(2))(C(2)H(4))L(2), all of which are detected. DFT(B3PW91) calculations of the potential energy and free energy at 298 K of possible intermediates show the importance of entropy to account for their thermodynamic accessibility. Calculations of unimolecular C-F cleavage of coordinated C(2)H(3)F confirms the high activation energy of this process. Catalysis by HF is thus suggested to account for the fast observed reactions, and scavenging of HF with NEt(3) changes the product to exclusively Os(H)(2)Cl(CCH(3))L(2). The analogous reaction of Os(H)(3)ClL(2) with H(2)C=CF(2) produces exclusively OsHFCl(=CCH(3))L(2) and HF, and the latter is again suggested to catalyze C-F scission via the observed intermediates Os(H)(2)Cl(CF(2)CH(3))L(2) and OsHCl(=CFMe)L(2).     

Dynamic behavior in diplatinum metalloreceptors

Diplatinum metalloreceptors anti-4a and anti-4b exhibit dynamic behavior in solution that is modified by anion binding. An X-ray crystal structure determination of anti-4a supports its proposed solution structure.