Glycerol selective oxidation to dihydroxyacetone was investigated systematically in a semibatch reactor over Pt-Bi/C catalyst. Catalysts with different metal loadings, supports, and preparation methods were synthesized, characterized, and tested. The sequential impregnation of Pt and then Bi, followed by NaBH 4 reduction, was the optimum synthesis method for high glycerol oxidation rate and maximum DHA yield. The optimum catalyst composition was determined to be 3 wt % Pt, 0.6 wt % Bi, supported on Norit Darco 20-40 mesh activated carbon (BET surface area 600 m 2 /g, average pore size 4 nm, average pore volume 0.53 cm 3 /g). In addition to the catalyst, the reaction conditions were also optimized by conducting experiments in the range of temperature 30-90 °C, oxygen pressure 0-180 psig, and initial pH 2-12. The optimum reaction conditions were identified as 80 °C, 30 psig, and initial pH ) 2. Under these conditions, a maximum DHA yield of 48% was obtained at 80% glycerol conversion. The catalysts were characterized by using BET, ICP-OES, TEM, XRD, and XPS techniques.

p-Amyrin has been converted into 3P-acetoxy-I 3-hydroxyoleanane. Photolysis of the nitrite of this alcohol and further standard transformations gave oleanolic acid lactone acetate and thence oleanolic acid. This conversion of p-amyrin into oleanolic acid represents, in the formal sense, a total synthesis of the latter.By a similar series of reactions ursolic acid has been obtained from a-amyrin. THE structures of oleanolic acid (I; R1 = R2 = H, R3 = Me) and ursolic acid (I; R1 = R3 = H, R2 = Me) were established as an integral part of earlier work1 on the structures of p-amyrin (11; R1 = R2 = H, R3 = Me) and cc-amyrin (11; R1 = R3 = H, R2 = Me), respectively. These two acids are representative of a considerable number of pentacyclic triterpenoids belonging to the a-and p-amyrin families which are oxygenated at C-28.l We now report the conversion of p-amyrin into oleanolic acid and of a-amyrin into ursolic acid. By virtue of a prior synthesis of p-amyrin,2 the former conversion also represents, in the formal sense, a total synthesis of oleanolic acid. The first step in the synthesis of oleanolic acid was the conversion of p-amyrin benzoate (3 p-benzoyloxyolean-12-ene) (11; R1 = Bz, R2 = H, R3 = Me) into 3pbenzoyloxy-12~,13-epoxyoleanane (I11 ; R1 = Bz, R2 = H, R3 = Me). Prior attempts to effect this conversion gave 3 ~-benzoyloxyoleanan-12-one as the only isolated product. This ketone was considered to arise by rearrangement of the desired epoxide (111; R1 = Bz,R2 = H, R3 = Me), and so care was taken to avoid conditions which might promote this process. P-Amyrin benzoate was treated with perbenzoic acid in chloroform a t 0"; a slow but clean, reaction occurred. Careful work-up gave the desired epoxide in high yield, accompanied by only traces of 3 p-benzoyloxyoleanan-12-one.

Although the classical 1955 paper by Bilous and Amundson was largely devoted to the study of nonisothermal systems, they also found it worthwhile to establish the stable behavior of a model isothermal multireaction continuous flow stirred tank reactor for all values of residence time, rate constants, and feed concentrations. Over a half century later, there remains a predisposition to the idea that isothermal reactors are prone to dull, stable behavior even when the underlying chemistry is complex. That idea is revisited in light of some recent findings in chemical reaction network theory. © 2013 American Institute of Chemical Engineers AIChE J, 59: 3403–3411, 2013

Across the landscape of all possible chemical reaction networks there is a surprising degree of stable behavior, despite what might be substantial complexity and nonlinearity in the governing differential equations. At the same time there are reaction networks, in particular those that arise in biology, for which richer behavior is exhibited. Thus, it is of interest to understand network-structural features whose presence enforces dull, stable behavior and whose absence permits the dynamical richness that might be necessary for life. We present conditions on a network’s Species-Reaction Graph that ensure a high degree of stable behavior, so long as the kinetic rate functions satisfy certain weak and natural constraints. These graph-theoretical conditions are considerably more incisive than those reported earlier.

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