The synthesis of liquid fuels from CO 2 , e.g., separated from flue gases of power plants, and H 2 from renewables, i.e., water electrolysis, is a concept for substituting fossil fuels in the transport sector. It consists of two steps, syngas production via reverse water-gas shift (RWGS) and synfuel production by Fischer-Tropsch synthesis. Research is concentrated on the RWGS using a Ni-catalyst. The catalyst shows an appropriate performance in catalyzing the RWGS. The catalyst is stable at technically relevant temperatures. The intrinsic and effective kinetics were determined and considerations on a technical application of the process are proposed.

No abstract

Past land‐use changes, intensive cropping with large proportions of root crops, and preferred use of mineral fertilizer have been made responsible for proceeding losses of soil organic C (SOC) in the plough layer. We hypothesized that in intensive agriculturally managed regions changes in SOC stocks would be detectable within a decade. To test this hypothesis, we tracked the temporal development of the concentrations and stocks of SOC in 268 arable sites, sampled by horizon down to 60 cm in the Cologne‐Bonn region, W Germany, in 2005 and in 2013. We then related these changes to soil management data and humus balances obtained from farmers' surveys. As we expected that changes in SOC concentrations might at least in part be minor, we fractionated soils from 38 representative sites according to particle size in order to obtain C pools of different stability.We found that SOC concentrations had increased significantly in the topsoil (from 9.4 g kg−1 in 2005 to 9.8 g kg−1 in 2013), but had decreased significantly in the subsoil (from 4.1 g kg−1 in 2005 to 3.5 g kg−­1 in 2013). Intriguingly, these changes were due to changes in mineral‐bound SOC rather than to changes in sand‐sized organic matter pools. As bulk density decreased, the overall SOC stocks in the upper 60 cm exhibited a SOC loss of nearly 0.6 t C (ha · y)−1 after correction by the equivalent soil mass method. This loss was most pronounced for sandy soils [−0.73 t SOC (ha · y)−1], and less pronounced for loamy soils [−0.64 t SOC (ha · y)−1]; silty soils revealed the smallest reduction in SOC [−0.3 t SOC (ha · y)−1]. Losses of SOC occurred even with the overall humus balances having increased positively from about 20 kg C (ha · y)−1 (2003–2005) to about 133 kg C (ha · y)−1 (2005–2013) due to an improved organic fertilization and intercropping. We conclude that current management may fail to raise overall SOC stocks. In our study area SOC stocks even continued to decline, despite humus conservation practice, likely because past land use conversions (before 2005) still affect SOC dynamics.

No abstract

A method for the determination of the thermophysical properties of thin films is introduced. The procedure is based on the contact-free thermal analysis of free standing thin films by means of a lock-in thermography system. The thermophysical properties are deduced from the thermal diffusion length and the temperature amplitude of a thermal wave propagating in the sample excited by a laser heat source. An infrared camera images the wave and the thermal diffusion length Λa of the amplitude and the thermal diffusion length Λp of the phase are measured. Thermal losses influence both Λa and Λp. Their geometric mean ΛaΛp is, however, not effected by thermal losses. In turn 1∕Λa2−1∕Λp2 is determined by the thermal losses and does not depend on the lock-in frequency, as Λa and Λp do. These theoretical predictions are experimentally verified in this work. The measured values of Λa and Λp yield the in-plane thermal diffusivity and a damping factor. The latter quantifies the thermal losses to the ambient. The use of a vacuum chamber and a temperature calibration are not required. If, however, the camera is calibrated, the in-plane thermal conductivity and the volumetric heat capacity are obtained from the temperature amplitude of the thermal wave. The measurement accuracy is 10% for the thermal diffusivity, thermal conductivity, and volumetric specific heat. The thermophysical properties measured for thin films of copper, nickel silver, and polyimide agree with literature values.