Hydrodeoxygenation HDO

Oxygenate refining was limited to chemicals recovery from the Fischer-Tropsch aqueous product and acidic isomerization of the C5-C6 naphtha. The naphtha and distillate range oxygenates were removed by hydrodeoxygenation (HDO) in hydrotreaters, before further refining. 

The copper-chromium oxide has two different active sites in a reduced state. The cuprous ions associated with a hydride and two anionic vacancies are the hydrogenation (HYD) sites. The chromium ions in the same environment are the sites where occur the isomerization (I) and the hydrodeoxygenation (HDO) reactions. The use of unsaturated ethers permits to confirm and to precise the nature and the role of the active sites. With the compounds which have the oxygen atom kept away of the catalyst s surface, the HYD activity is very low and the HDO/I ratio too, whereas, in the opposite case, these values increase. With the vinylic ethers, the saturated compound is the main product because the I and the HDO reactions proceed via a concerted mechanism with a common preliminar step and an allylic rearrangement which is impossible with geminate functions. 

Catalytic hydrodenitrogenation (HDN) and hydrodeoxygenation (HDO) are the processes of removing nitrogen and oxygen, respectively, from petroleum feedstocks to provide more processable and environmentally compatible liquid fuels. A review of heterogeneous HDN process and homogeneous models summarized the research till ca. 1997. ... 

Conversion of biomass at a temperature of 300 350 °C and a pressure of 120-180 bar within the so-called HydroThermal Upgrading (HTU) process yields a mixture of hydrocarbons, carbon dioxide, water and dissolved organics, which can be further processed in a catalytic HydroDeOxygenation (HDO) step to yield diesel with characteristics similar to fossil diesel. A major advantage is that wet biomass feedstocks can be employed without drying in contrast, water at hydrothermal conditions acts as a solvent and reactant at the same time, leading to a product with less oxygen compared to biocrude prepared by pyrolysis. 

In recent years, the production of simple hydrocarbrnis from biomass has attracted strong interest in the renewables community, due to the fact that the products are considered drop-in substitutes for petroleum-derived alkanes, with evident applications to fuels and chemical production. HMF has received much attention in this regard as a platform for extended carbon chain products, the hydrodeoxygenation (HDO) of which gives products which are essentially diesel or aviation fuels, depending on their hydrocarbon distribution. Aldol-type condensation reactions can take place in aqueous solution between HMF (or its derivatives) and biogenic ketones... 

Among the various compounds models, we will demonstrate the reaction mechanism of phenol hydrodeoxygenation (HDO) published by various authors (Weigold et al., 1982 Viljava et al., 2000 Senol et al., 2007). The activation procedure on the catalyst is very significant. The phenol HDO follows mechanism in parallel, according to Figure 23.9. 

An extensive study of heteroatom removal has been carried out at the Gulf Research and Development Company. This and a few other studies have been summarized by Shah and Cronauer (55) and Shah and Krishnamurthy (56) and they will not be repeated here. Instead, in the following pages, a few other reported works on hydrodesulfurization (HDS), hydrodeoxygenation (HDO), and hydro-denitrogenation (HDN) of real systems and model compounds, that may be relevant to coal liquefaction, are briefly discussed. 

Robert (68,69) and Polozov (70) studied the catalytic activity of commercial catalysts CoS, M0S2 for the hydrodeoxygenation (HDO) of phenol to cyclohexane. Their conclusion was that the reaction followed a path via cyclohexanol while Moldavskii and Livshits (104) found the direct dehydration rate to dominate at least at low pressures. Hall and Cawley (71) studied the HPO of dlbenzofuran on a M0S2 catalyst and presented two different possible schemes. Benjamin et al. (105) have presented a summary of reactions of oxygen compounds (phenols and ethers) in tetralin at 673 K for 18 hour reaction time. A brief summary of some of the reported model compound studies is given in Table 4. 

The reactions that take place during the HDT process are hydrodesulfurization (HDS), hydrodenitrogenation (HDN), hydrodearomatization (HDA), hydrodeoxygenation (HDO),... 

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