The monoenic fatty acid methyl ester hydrogenation and isomerization over a supported nickel catalyst was studied at 0.02 e P H 2 e 0.50 MPa and 333 e T e 443 K. Batch hydrogenations at constant and variable hydrogen pressure were carried out to investigate the rate-determining steps. On the basis of the Horiuti-Polanyi mechanism, involving a half-hydrogenated surface intermediate, kinetic rate equations were systematically derived following the Langmuir-Hinshelwood-Hougen-Watson approach. Each set of rate equations was tested by means of a χ 2 method on its ability to describe the experimental curves simultaneously. The χ 2 was minimized by a stepwise optimization of model parameters. Furthermore, we used Bartlett's test to reduce the set of most-likely rate expressions. The statistically most significant model assumes the formation of the half-hydrogenated surface intermediate as the rate-determining step and an equilibrium associative hydrogen adsorption. The rate equations are R O )

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Intraparticle diffusion limitation in the hydrogenation and isomerization of fatty acid methyl esters (FAMEs) and edible oils (triacylglycerol, TAG) in porous nickel catalyst was investigated both under reactive and under inert conditions. Under reactive conditions, the diffusion coefficients were determined from the best fits of the model simulations applying the intrinsic reacting kinetics of monounsaturated FAME hydrogenation to experiments under diffusion limited conditions. For 0.02 < P H 2 < 0.50 MPa, an effective hydrogen diffusion coefficient of D e,H 2 = (1.6 ± 0.7) × 10-10 m2/s (T = 443 K) was obtained in Pricat 9910 (sample 1992). TAG hydrogenations, at 373 < T < 443 K and 0.30 < P H 2 < 0.50 MPa, appear to be limited by diffusion limitation of TAG, yielding D e,TAG = (4.5 ± 2.2) × 10-13 (T = 373 K), (2.0 ± 0.9) × 10-12 (T = 403 K), and D e,TAG = (3.3 ± 1.1) × 10-12 m2/s (T = 443 K). The temperature dependency of D e follows the relation D eη/T = 2 × 10-7 (m2 Pa)/K (η is the fluid viscosity, Pa s) for 373 < T < 443 K. Independent determination of D e in porous nickel catalyst (Pricat 9933, sample 1992:  average particle diameter, d p = 10 μm) was performed with tracer pulse column experiments using the HPLC (high-performance liquid chromatography) technique, in the absence of reaction. The packed columns (length 0.05 and 0.10 m; diameter 4.6 × 10-3 m) were eluted with n-octane, 3 × 10-10 < Φv < 80 × 10-10 m3/s (η = 0.5 mPa s), and MCT oil (medium C10−C12 chain triglyceride, η = 17 mPa s) in the temperature range 313 < T < 353 K. The response curves indicated a regular packing of the column. Intraparticle effective diffusivities were measured with more viscous MCT oil as an eluent:  1.4 × 10-11 < D e < 2.7 × 10-11 m2/s for methyl palmitate and 4 × 10-12 < D e < 7 × 10-12 m2/s for trioleate and triacyl octadecenoic ester (95% confidence limit, T = 313 K). Due to the absence of reaction (hydrogenation of double bonds), the obtained D e with the HPLC technique is volume averaged and thereby determined by the larger intercrystalline pores (<30% of the total pore volume) only. Moreover, D e measured under reaction conditions reflected the influence of the micropores, resulting in a 10-fold lower value.

In a bid to help address the environmental footprints associated with products and services, life cycle assessment (LCA) applications have become increasingly popular throughout the years. This review summarizes some important methodological developments in recent years, such as the advent of dynamic LCA, as well as highlighting recent LCA applications in the context of plastics/recycling with a focus on their methodological choices. Furthermore, this review aims to offer a set of possible research lines to improve the gap between LCA and decision-making (policy). It was found that the majority of reviewed papers are mostly conservative in their methodological practice, employing mostly static analyses and making little use of other methods. In order to bridge the gap between LCA and policy, it is suggested to broaden system boundaries through the integration of dynamic modelling methods, incorporating interactions between fore- and background systems, and including behavioral components where relevant. In addition, advanced sampling routines to further explore and assess the policy space are recommended. This is of paramount importance when dealing with recycling processes as the molecules/polymers constituting the output of those processes have to be benchmarked in terms of costs and, crucially, their sustainability character against virgin ones.

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