Abstract: A process for preparing saturated carboxylic acids having from 1 to 4 carbon atoms at a reaction temperature of from 100° C. to 400° C. and pressures of from 1.2×105 Pa to 51×105 Pa by gas phase oxidation of saturated and/or unsaturated C4-hydrocarbons, with an oxygen-containing gas and water vapor in the presence of at least one catalyst. The gas leaving the reactor is partly recirculated in a reaction gas circuit. This reaction gas circuit is configured such that part of the organic acids formed in the gas-phase oxidation is taken from the gas leaving the reactor so that the acid content of the recirculated part of the gas leaving the reactor is from 0.01% to 6.0% by volume.

Abstract: Process for broadening cholesteric reflection bands of photopolymerizable cholesteric liquid crystals, and optical elements produced by this process. The invention relates to a process for broadening the cholesteric reflection bands of photopolymerizable cholesteric liquid crystals, which comprises the following process steps:1) partial polymerization of a layer containing photopolymerizable cholesteric liquid crystals by exposure to actinic light for a defined brief period at a defined temperature,2) observance of a defined waiting time without exposure (dark phase) at a defined temperature,3) fixing of the resultant layer by exposure to actinic light at a defined temperature.