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Methyl oleate and methyl elaidate (two industrially relevant FAMEs, methyl esters of fatty acids) were hydrogenated in a batch slurry autoclave using a supported palladium catalyst. The mixture of reaction products formed as a result of the competitive reaction network of positional isomerization, geometrical isomerization, and hydrogenation were analyzed using gas chromatography and combined peak fitting. Diffusion limitations, even at low Thiele modulus, were found to have a significant impact on the product distribution. Depending on the starting material, either the cis or the trans double bonds apparently migrated faster along the carbon chain. Also, with increasing Thiele modulus, the conversion level at which cis−trans equilibrium was reached increased:  if significant intraparticle gradients were present, the equilibrium was never reached. Several of these phenomena have previously been ascribed to different kinetics of the various isomers, which would stem from the differences in adsorption strength. For the experimental data of this work, mass transfer effects were found to satisfactorily account for the differences in product composition using a simple reaction−diffusion model for all the isomers involved, without needing to assume significant differences in adsorption strength. The result presented in this work gives fundamental insight into the product composition of fat hardening processes.

In this paper, the advantages and disadvantages of using segmented flow in microchannels to intensify biocatalytic processes are discussed. We consider both suspended cell cultures and immobilized enzymes. Once bubbles are formed in microchannels, they can no longer coalesce and, hence, no energy is required to break up larger bubbles. As a result, the same gas−liquid mass-transfer behavior can be obtained at an order of magnitude lower power input. The gas−liquid−solid mass transfer, i.e., to a catalyst on the channel walls, improves with decreasing energy input, allowing the combined reduction of power input and reactor size. These findings are supported by a scaling analysis based on the pressure drop work of Kreutzer et al.¹ and the mass-transfer work of Van Baten and Krishna.² For the practical application of monoliths for liquid-phase cell cultures, the stability of a downflow monolith reactor with respect to clogging by biofilm was investigated experimentally. The results indicated that, as long as flushing out of the suspended cells was prevented, stable operation was possible.

The size of the channels in a monolith reactor is an important geometric factor which affects gas and liquid (G−L) distribution in monolith channels significantly and therefore axial-mixing behavior. In the present work the axial-mixing behavior of the liquid phase in cocurrent down flow square channel monoliths of different sizes (200, 400, and 600 cells per square inch or cpsi) has been studied by analyzing the residence time distribution (RTD) of the injected tracer pulse. Simultaneous pressure drop measurements were used to estimate the average liquid slug length. The liquid hold-up in all monoliths was found to be in reasonable agreement (within 30%) with that of a Taylor flow in a single capillary. Axial dispersion and liquid slug length were observed to decrease with increase in cpsi. When intermonolith G−L redistribution occurred between stacked monolith pieces, the axial dispersion decreased further. The ratio of gas bubble length to total slug length (βG), the total G−L velocity, and the liquid slug length affected the degree of axial mixing in a monolith with βG having a strong negative impact. The liquid corner flow in the square channels appeared to be the main cause of axial mixing and not a liquid film between a gas bubble and a channel wall. Overall axial mixing in the monolith could also be partly attributed to maldistribution of the G−L phases at the monolith entrance. A dimensionless correlation is proposed to estimate the overall flow Peclet number.

The use of monolithic catalysts in multiphase applications has received increasing interest throughout the last years. In this paper the use of monolithic catalysts in the hydrogenation of edible oils is studied. In comparative experiments the monolithic catalysts have shown a lower tendency to form trans-fatty acids compared to slurry catalysts with equal composition. It is also demonstrated that the monolithic catalyst could be reused several times without significant changes in the product composition. With respect to the effect of the operating parameters on the performance, common knowledge applies. By using a monolithic-catalyst-based technology, the process complexity can be significantly reduced as the separation of the oil and the catalyst becomes straightforward and the filtration and bleach steps are eliminated. An economic evaluation showed a significant reduction in the product cost when monoliths are used instead of a conventional slurry system.