Latest highlights in liquid-phase reactions for organic synthesis in microreactors

The attention for microreactors for organic synthesis reactions, in both academia and industry, has considerably increased over the past few years, as indicated by the progressively growing number of publications. A review of articles on liquid-phase organic syntheses in microreactors in 2011-2012 is presented in this contribution. The main topics discussed in this review are noncatalytic and homogeneously catalyzed reactions, multistep syntheses, heterogeneously catalyzed reactions, microwave-assisted reactions, and photocatalytic reactions. A number of important publications from the period 2008-2010 are also mentioned to complete the overview. The goal of the present review is to illustrate the important topics of the publications during the past few years on organic synthesis in microreactors

Control of the thickness of mesoporous titania films for application in multiphase catalytic microreactors

A new method of sol–gel polymer template synthesis of mesoporous catalytic thin films has been proposed which allows controlling the chemical nature of the film, the porosity, thickness and loading with an active species. The mesoporous films with a long-order structure can be obtained in a narrow range of surfactant-to-metal precursor molar ratios from 0.006 to 0.009. The catalytic film thickness was varied from 300 to 1000 nm while providing a uniform catalyst distribution with a desired catalyst loading (1 wt. % Au nanoparticles) throughout the film. The films were characterized by TEM, SEM, ethanol adsorption and contact angle measurements. The calcination of the as-synthesized films at 573 K reduced Ti4+ sites to Ti3+. A 300 nm thick Au-containing film showed an initial TOF of 1.4 s-1 and a selectivity towards unsaturated alcohols as high as 90% in the hydrogenation of citral. Thicker films demonstrated a high selectivity towards the saturated aldehyde (above 55%) and a lower intrinsic catalytic activity (initial TOF of 0.7–0.9 s-1) in the absence of internal diffusion limitations