1.2.3 Results

Figure 1-2: The microreactor-setup used for production of HMF For a reasonable productivity, 10% aqueous solutions of either fructose or glucose were prepared and subjected to the catalyst under heat. The output from the flow reactor was diluted for HPLC analysis and quantified using a calibration curve. This allows for a protocol for rapid testing different conditions such as temperature and retention time without too much sample preparation or long down-times for reloading catalyst etc. To isolate HMF, the aqueous solution can be extracted with a suitable solvent, eg. 2-methyl tetrahydrofuran or ethyl acetate.

The calcium phosphate catalyst was also the catalyst that gave the most promising results in this project. In short, higher temperature yielded better conversions into HMF. Unfortunately, both the carbohydrate and the formed products can be degraded or polymerized thermally, thus competing with efficient production of HMF. At 220 ˚C the reactor could be operated only a short time before clogging forced stopping the process and cleaning the reactor. This gives us an efficient span of between 170 ˚C and 220 ˚C with yields between a few percent up to nearly 30%. The different tested temperatures and the corresponding yields can be seen in Table 1-1.

Catalyst loading, tested via varying the concentration of the carbohydrate solution, was of less consequence for the reaction. Yields were similar for a 10% solution as for a 5% solution. At higher concentrations, blockage of the reactor was more prevalent.