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Functionalized mesoporous carbon catalysts can be used in the acid catalyzed dehydration of fructose to 5-hydroxymethyl furfural (HMF). However, strong deactivation can be observed after preconditioning of the material in the reaction solvent 2-butanol. Surface changes caused by the pretreatment have been studied by XPS. The comparison of the pristine sample and the pretreated carbon sample showed similar distribution of oxygen functional groups by ex-situ XPS, as well as similar behavior during heating in vacuum. However, the addition of water (0.1 mbar vapor pressure) and subsequent heating to 130°C exhibited prominent differences in the evolution of the O1s, as well as for the C1s spectra of the two samples. Changes in the surface termination and hydrophobicity of the materials are discussed under the aspect of possible reactions of surface functional groups with the alcoholic solvent and water.

Specific control of morphology and chemical structure of hydrothermal carbon (HTC) is of crucial importance for its application, both in catalyst supports or electrochemical devices. Within the present study we show how the morphology, i.e. particles size and homogeneity, and the distribution of functional groups can be controlled by the control of the synthesis pH of the hydrothermal carbonization. The complementary analysis of liquid byproducts by HPLC provides useful information on the nature of the polymeric species produced during the poly-condensation in the hydrothermal process and reveals the potential implementation of the process into the biorefinery concept. The acidic byproduct levulinic acid and formic acid determine the hydrothermal carbonization autocatalytically by additional supply of protons to the reaction medium. Thus, for starting pHs > 3 only minor structural differences can be detected for the HTC. The use of oxidizing acids favors higher yields of HTC and improves the carbonization towards higher condensed carbon domains. Scale-up of the process in a stirred 2 l batch reactor favours carbonization leading to higher condensed carbonaceous products. The relative trends of pH variation are maintained.

The basic N-functionalized vapor-grown carbon nanofibers (N-VGCF) were synthesized by post-treating oxidized VGCFs in gaseous NH3 at high temperature (ammonolysis) prior to Pd addition by sol immobilization. The catalysts were characterized by nitrogen adsorption, hydrogen temperature programmed desorption, adsorption microcalorimetry and by SEM and TEM. Catalytic activity was evaluated in a model reaction, synthesis of (R)-1-phenylethyl acetate starting from hydrogenation of acetophenone to racemic 1-phenylethanol over Pd supported on N-VGCFs, at 70 °C under atmospheric hydrogen pressure in toluene, followed by acylation over an immobilized lipase in the same reaction pot. The main parameters investigated in this work were the role of the basic N-VGCF supports as well as the reduction procedure of the supported Pd catalysts (Pd-N-VGCF). The results revealed that the catalytic activity of the Pd-N-VGCF catalysts was highly dependent on the reduction procedure. The highest desired product yield, 35%, was obtained over a Pd-N-VGCF catalyst when the support was treated at 400 °C with gaseous ammonia prior to Pd addition.

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