Esterification of lactic acid with butanol catalysed by cation‐exchange resin was carried out in a batch reactor in dioxane and toluene. The reaction rate was found to be first order with respect to catalyst and acid concentrations. The inhibiting effect of water and butanol has been evaluated. The rate data were correlated with a kinetic model based on inhibition by water and butanol.
Low-emissivity glasses
rely on multistacked architectures with
a thin silver layer sandwiched between oxide layers. The mechanical
stability of the silver/oxide interfaces is a critical parameter that
must be maximized. Here, we demonstrate by means of quantum-chemical
calculations that a low work of adhesion at interfaces can be significantly
increased via doping and by introducing vacancies
in the oxide layer. For the sake of illustration, we focus on the
ZrO2(111)/Ag(111) interface exhibiting a poor adhesion
in the pristine state and quantify the impact of introducing n-type
dopants or p-type dopants in ZrO2 and vacancies in oxygen
atoms (nVO; with n =
1, 2, 4, 8, 10, 16), zirconium atoms (mVZr; with m = 1, 2, 4, 8), or both (nVO + mVZr; with m/n = 1:2, 1:4, 2:2, 2:4). In the case of doping,
interfacial electron transfer promotes an increase in the work of
adhesion, from initially 0.16 to ∼0.8 J m–2 (n-type) and ∼2.0 J m–2 (p-type) at 10%
doping. A similar increase in the work of adhesion is obtained by
introducing vacancies, e.g., VO [VZr] in the oxide layer yields a work of adhesion of ∼1.5–2.0
J m–2 at 10% vacancies. An increase is also observed
when mixing VO and VZr vacancies in a nonstoichiometric
ratio (nVO + mVZr; with 2n ≠ m), while a
stoichiometric ratio of VO and VZr has no impact
on the interfacial properties.
SummaryThe oil extracted from the trunk of the copaiba tree (Copailferu offieinalis) i s composed of sesquiterpenes, C15H24, and a small amount (c7 %) of sesquiterpenols, C15H260; these were identified from their Kovats indices and mass spectra. The use of zeolites in the catalytic transformation of this renewable source of hydrocarbons is of interest in the search for new chemicals and ecologically clean fuels. Oil samples from copaiba trees growing in Colombia's Oriental Plains were circulated over zeolite ZSMJ in a continuous flow fixed-bed micro reactor at 225,265, and 325 "C, for 1 h and subsequently analyzed by HRGC and GC-MS. Whereas only thirty four sesquiterpenes were identified in the original oil, over two hundred compounds were found in the product of the treatment of copaiba oil with zeolite ZSM-5. This complex mixture of sesquiterpenes, light aromatic compounds, and indene and naphthalene derivatives resulted from reactions such as isomerization, hydrogenation, cracking, and dehydrogenation with and without cracking. The amount of cracking products and aromatic compounds increased with reactor temperature but decreased with catalyst aging.
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