I need to perform hydrogenation reactions in a batch/semi-batch slurry reactor at high pressure (40-60bar) and high temperature 240-260°C..I need also some details on catalyst charging (Nickel)..
Sure, there are. However, it is essential that your reactor (autoclave) should be equipped with a liquid sampling pipe-line (~1/8 or 1/16 inch), which enables you to take samples (to follow conversion and selectivity in time) from the liquid phase under reaction conditions. As you have slurries, it is advisable to fit a small filter-cage (with ~1-2 micrometer pores) to the bottom end of the liquid sampling line in order to avoid solid catalyst-loss. It might also be useful to stop stirring for a minute or so before taking a liquid sample to avoid clogging of your filter. Furthermore, before taking a new sample the sample-line should be purged to remove old sample rests, i.e. for refreshing). In view of your goal (i.e. to investigate kinetics, you need to minimize the total amount of samples taken (~ less then 10 % of the total solution volume) in order to minimize errors in calculations. It could also be very handy if you were able to find a truly inert (under the reaction condition) internal standard to compare it against your substrate/products. Once you have a series of samples you can carry out the most appropriate analysis (GC, NMR, etc.) Last but absolutely not for least, extreme caution should be taken (education and practice is necessary) when taking sample at these conditions (cooling or heating the outside part, placing it behind a polycarbonate shield might be required) . In lack of knowledge about the chemistry I am not able to advice you about nickel loading. Success!
If you are using reduced metal (reactive in air) it is reduced in external vessel and then transferred into reactor in organic solvent (non reactive at low temperature). There are a number of research papers (thesis publications) which describe the procedure..
Batch experiments is a good idea and will give you the best results.
Semi-batch experiments must be avoided for kinetic data acquisition. Indeed you'll have to solve transient differential equations (mass is not constant), and you don't want to do that !