Abstract: The invention relates to a process for preparing a mercury collecting solid mass containing a carrier and copper, at least partly as copper sulfide, comprising the following steps of:(a) incorporating with the carrier at least one copper compound other than a sulfide,(b) optionally roasting said carrier,(c) incorporating therewith at least one organic polysulfide, and(d) thermally treating the resultant mass, in non-oxidizing atmosphere, under gas scavenging.The invention also concerns a regenerating process for a mercury recovery mass, containing a carrier, and copper, at least partly as copper sulfide, comprising incorporating with said mass, after a decrease of its mercury recovery efficiency and after removal of at least a part of its mercury content, an organic polysulfide, and finally subjecting it to a thermal treatment, in non-oxidizing atmosphere, under gas scavenging.

Abstract: There are described catalysts containing, as oxides, iron, chromium and potassium, the latter being optionally partly in form of kaliophyllite Al.sub.2 O.sub.3, 2 SiO.sub.2, K.sub.2 O, as well as lanthanum, in a proportion, calculated in oxide weight, of 1-15% with respect to the final catalyst.The presence in the catalyst of lanthanum oxide, optionally previously combined with cobalt or vanadium, at least in part in the form of a mixed oxide of the perovskite type, confers to the catalyst an improved activity and/or selectivity in dehydrogenation reactions, particularly of ethylbenzene to styrene.

Abstract: A process for manufacturing catalysts containing, as oxides, iron, chromium, potassium, as well as a rare earth metal in a proportion, calculated in oxide weight, of 1-15% with respect to the final catalyst, comprises:a first step, wherein a product is prepared by a reaction between compounds of rare earth metal(s) and of another metal selected from Fe, Cr, Co, Al or V, and a calcination; anda second step wherein a mixture is formed between the product resulting from the first step, the other necessary reactants and water; the resulting paste is dried after optional shaping and calcined. A clayish material can be used in the step.The catalysts obtained present an improved efficiency in dehydrogenation reactions, particularly of ethylbenzene to styrene.

Abstract: The invention concerns floating cathode elements which are intended for the electrolytic production of aluminum using the Hall-Heroult process in an electrolysis tank comprising a molten cryolite-base bath, between a carbon anode, and a cathodic layer of molten aluminum, said elements comprising at least one active cathode element (30) formed of electrically conductive refractory material such as titanium diboride and supported by an intermediate support (31) which is inert with respect to the liquid aluminum and the electrolyte, the mean relative density of the assembly of the acitve cathode element and the inert intermediate support being lower than the relative density of the liquid aluminum under the normal conditions of operation of the electrolysis tank.