PROCESS FOR REACTIVATING NOBLE METAL CATALYSTS ON A CARRIER FOR THE SYNTHESIS OF H2O2 BY ANTHRAQUINONE PROCESS

摘要

1312149 Hydrogen peroxide DEUTSCHE GOLDUND SILBER-SCHEIDEANSTALT 10 July 1970 [12 July 1969] 33514/70 Heading C1A In the preparation of hydrogen peroxide by the anthraquinone process the catalyst used is regenerated by an oxidative treatment at a pH below 7 and a reductive treatment, both treatments being carried out at below 200‹ C., the catalyst comprising palladium, if desired mixed with other metals of the platinum group (Ru Rh, Os, Ir, and Pt) precipitated upon carrier materials containing silica. Less than 1% by weight of palladium or mixed metals related to the total weight of the carrier may be used. The silica carrier may have a BET surface area below 50 m.SP2/SP/g. The inactive catalyst may be subjected to a pretreatment to remove traces of working solution or degradation products. Reagents for the oxidation may include gaseous chlorine/hydrogen chloride mixtures, moist chlorine, hydrogen peroxide/hydrochloric acid mixtures or nitric acid/hydrochloric acid mixtures. The reduction may be by a dry process (e.g. using free hydrogen containing gas) or a wet process (e.g. with formic acid, formaldehyde or hydrazine). Pressures in the reactivation may be up to 6 kg./cm.SP2/SP. The pretreatment may comprise such operations as water scrubbing or steam treatment of the carrier catalyst, extraction from catalyst with organic solvent, e.g. acetone, isopropanol, trichloroethylene or xylene or drying of catalyst at temperatures below 250‹ C. In Example 1 a catalyst of 0À2% Pd precpitated on filter gravel was pretreated with 1,1,1-trichloroethane, placed in 1À6 ton charges in a rotary drum 1, sprayed with a 15 weight per cent HCl/50 weight per cent H 2 O 2 mixture and then steam heated at about 100‹ C. under a current of N 2 to form a coating of PdCl 2 . Reduction of PdCl 2 to Pd was then carried out by passing a current of H 2 and N 2 . In Example 2 a HCl/Cl 2 gas mixture was used as the oxidizing agent. Apparatus which may be used for carrying out the process is described in the Specification and drawings.