The demand for hydrogen peroxide is booming since it is considered as one of the most environmentally friendly and versatile chemical oxidants available and has a wide range of applications. The annual market, close to 3000 kt per year being produced via the auto-oxidation process (with 2-ethyl anthraquinone (traditional) or amyl anthraquinone for mega-plants), is mostly supplied by the company Solvay (30%), followed by Evonik (20%) and Arkema (13%). Nevertheless, the dream of a direct synthesis process is close to a century old and it has gained momentum in research efforts during the last decade with more than 15 groups active in the world. In this review, we focus the discussion on the targets, e.g. plant tonnage, the reactors and the most feasible industrial operational conditions, based on our experience and point of view using the chemical engineering tools available. Thus, direct synthesis can be competitive when on-site production is required and capacities less than 10 kt per year are demanded. The total investment cost should be approximately 40.3 ± 12.1 MM$ (in 2012) for a 10 kt per year size process to be comparable to the traditional process in terms of costs. Moreover, all kinds of reactors used are hereby discussed emphasizing the pros and cons; the most common ones are batch and semi-continuous modes of operation. However, at the moment, demonstrations of continuous operations as well as carefully determined kinetics are needed in order to scale up the process. Finally, operational conditions, including the catalyst composition (active metal, oxidation state and support), promoters (halides and acids–pH–isoelectric point), solvents, pressure and temperature need to be carefully analysed. In our opinion, as we try to show here, H₂O₂ direct synthesis is a competitive process and is ready for larger scale demonstration. Also, more than a hundred patents within the area support this claim, although the barriers of technology demonstration and further licensing are still pending.

Producción CientíficaOptimal conditions for hemicellulose extraction from wooden biomass in a semi-continuous system have been assessed in thiswork. This studywould constitute the first stage for a profitable and green industrial process. Eucalyptus globuluswas selected as rawmaterial due to its lowwater consumption, high growth and its efficiency in lignocellulose production.Moreover its cultivation is very popular in southern Europe. Samples of 5.0 g of wood were fractioned using a pressurized hot water semi-continuous system, to produce sugars (pentoses and hexoses) and a solid residue enriched in lignin. Five flow rates between 2.50 and 20.00 mL/min and four temperatures between 135.0 and 285.0 °C were tested in order to maximize the production of sugars, avoiding the formation of degradation products. Optimumconditions for the extraction of hemicellulose were identified at 185.0 °C and 5.00 mL/min, leading to a pentoses yield of 67.409wt%,with 0.702 wt% of degradation products. Almost all the pulp is extracted at 285.0 °C. SEM images show very well the changes in the wood structure at different temperatures. A kinetic model was developed, describing the extraction and hydrolysis of hemicellulose and cellulosewith absolute average deviations around 10% for sugar extracted mass.Junta de Castilla y León (programa de apoyo a proyectos de investigación – Ref. VA330U13