Recent Patents on the Direct Synthesis of

In the direct catalytic synthesis of H202 the main findings of the earlier patents can be summarized as follows  

Several patents were issued on this topic. For example, Rueter [34] in his patent cited about 120 US patents and about 40 foreign patents in the period 1987-2004. The actual number of patents is higher, but already these numbers indicate that many aspects of catalyst and process technology are covered. Patents in the last five years (2003-2008) were thus focused either on the improvement of catalyst preparation and/or improvement of reaction/reactor operations, particularly with strong attention on the safety of operations. However, often in the cited patents operations are still 

The use of methanol (typically CH30H/H20 solutions in a 95 5 ratio) allows us to improve of one order of magnitude the productivity. Zhou et al. [35, 36] (formerly Hydrocarbon Techn. Inc. - HTI, and then Headwaters Nanokinetix Inc.) reported a productivity of about 900 g-H202 g-Pd-1 h 1 in methanol and the presence of NaBr, and about 400 g-H202 g-Pdh-1 in the same solvent without NaBr. They related the productivity to a parameter indicated as the solvent selection parameter (SSP), which is defined as  

In Equation (8.1) SSP is the sum for each i component of the products of the weight fraction of solvent component (w) per the solubility of H2 in the pure component at standard conditions (S). The SSP is thus related to the concentration of dissolved H2 in solution. SSP is 1.6 for pure methanol and 0.14 for pure water. The productivity to H202 was found to depend linearly on this parameter. Increasing the alcohol s carbon chain increases the H2 solubility. For pure isopropanol the SSP is 2.7. The effect of promoters such as NaBr on H2 solubility is unclear, but at equivalent SSP the catalyst productivity is nearly half, as indicated above. 

Assignee and Ref. Main feature Catalyst H2O2 H2O2 concentration selectivity (wt%) (%) Feed (H2/02) (%) P (bar)/T (C) Solvent Notes 

CSIR [39] Incorporation of halogen promoters in the catalyst Pd(5%) on alumina 

---