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The Use of Small Particle Catalysts in Pursuit of Green and Sustainable Chemistry
Published in Ahindra Nag, Greener Synthesis of Organic Compounds, Drugs and Natural Products, 2022
Hydrogen is synthesized from steam by reforming methane, and oxygen is drawn from the atmosphere. A mixed solvent solution of 2-ethylanthraquinone is catalytically reduced to a mixture of the corresponding hydroquinone and tetra-hydroquinone with H2 using palladium on alumina (Pd/Al2O3) catalyst at a temperature of 45°C. The reduction proceeds rapidly to consume all available hydrogen. Fixed bed catalyst reactors currently in use permit the necessary control of Pd in the catalyst which could catalytically decompose the newly formed H2O2. The cooled solution is non-catalytically oxidized through the introduction of air at low pressure. After a short residence time, a resultant solution is formed composed of H2O2 and regenerated anthraquinone is formed. Demineralized water is used to extract H2O2. Steam-heated distillation provides different commercial grades which are treated with stabilizers. This process has been criticized for energy consumption and as an unstainable production process based on the use of palladium as a critical material.58 The Pd catalyst is largely conserved throughout the process and the waste streams consist of low-level contaminated water. Energy consumption of the commercial process is not as high as it is often claimed.59 The commercial process has been staged at a large scale over the last century requiring a large physical footprint and the plant is generally situated at central locations.60
Palladium supported on nano-hybrid Zr–Al–La catalyst for hydrogenation of 2-ethylanthraquinone
Published in Indian Chemical Engineer, 2021
Anjali A. Ingle, Shahid Z. Ansari, Diwakar Z. Shende, Kailas L. Wasewar, Aniruddha B. Pandit
Hydrogen peroxides (H2O2) have a wide range of applications in the field of paper and pulp, oxidative chemical synthesis, mining, textile, waste water treatment, etc. due to its eco-friendly oxidising properties. More than 34% of its total production has been used in the pulp and paper industries as a bleaching agent and for washing of wool and cotton fibre in the textile industries. Hence, a significant research work on the synthesis of H2O2 is in progress. H2O2 is a natural metabolite of many organisms and hence, the only by-product formed from its decomposition is water and oxygen. [1–4]. The main raw material required for commercial production of H2O2 through auto-oxidation (AO) process is anthraquinone (AQ) derivatives, typically 2-ethylanthraquinone (2-EAQ) and tetrahydro-2-ethylanthraquinone. Scheme 1 depicted the systematic representation of the sequential hydrogenation and oxidation of an AQ derivative [5]. In a typical AO process, 2-ethylanthrahydroquinone (EAHQ) is formed through the hydrogenation of EAQ by dissolving it in a mixture of organic solvents. Further, oxidation of EAHQ leads to the formation of H2O2 and EAQ. Due to high solubility of H2O2 in water, it is extracted through the mixture using water as a solvent to recover H2O2 of various strength upto 50% concentration as an aqueous solution [6,7].