Two new three-branched s-triazine derivatives with near-octupolar symmetry have been synthesized. In each of them, two branches have donor groups attaching to their ends, while the other one has none. Their photophysical characteristics, such as UV–vis spectra, fluorescence spectra and two-photon excited fluorescence spectra, are compared with their octuplar analogs in which all the three branches are ended by donor group. The little structural difference results in great decline of single-photon absorptivity and single-photon excited fluorescence, as well as the two-photon excitated fluorescence.

In order to develop small-scale natural gas liquefaction equipment, a small expansion natural gas liquefaction process was designed, which was based on the technical parameters of the single screw compressor and expander developed by Beijing University of Technology. The effect of the key parameters on the natural gas liquefaction rate and specific power consumption was simulated and optimized. The results showed that the liquefaction rate of the process can reach 100% and the specific power consumption was relatively low under the optimal operation conditions. These research results can provide theoretical basis for the design of small-scale natural gas liquefaction equipment.