Hydrogenation pathways

No rate enhancement of the enantioselective hydrogenation pathway is expected, in the manner adduced for the Pt-catalysed reaction, because the process is not one of simple H-atom addition across a carbon-oxygen double bond. 

Simbeck, D. and Chang, E., Hydrogen supply, cost estimate for hydrogen pathways—scoping analysis, USDOE NREL/SR-540-32525, July 2002. 

Some significant findings concerning the mechanistic details of well-established hydrogenation pathways (e.g., the insertion and reductive-elimination steps) have been published (see Section II), while at the other end of the scale in terms of characterized systems, the enzymatic hydro-genase system is beginning to draw attention (see Section IX). The well-established systems are reviewed first, as new systems are often compared to them in terms of reactivity and mechanism. 

Scheme 39.9 Deuterium labeling as a mechanistic probe for hydrogenation pathways in scC02.

HySociety (The European hydrogen based society) (2004). Technology Database for Hydrogen Pathways, Analysis of Hydrogen Pathways. European Commission (DG TREN), FhG-ISI. www.eu.fhg.de/h2database/index.html. 

The SSCHISM infrastructure model calculates the cost of the potential hydrogen pathway-supply options shown in Table 15.3 for 73 of the largest US urbanised areas and selects the cheapest supply pathway in each city at a specified market penetration. The cheapest pathway choice for any given city depends on the size of the city, level of demand, demand density, and local energy and feedstock prices. 

In this comparison, the biggest emission reduction is achieved by the CAES paths. They are of the order of 317 to 373g/kWh wind electricity, while the emission reduction of the hydrogen pathways is between 159 and 169g/kWh wind electricity. 

A palladium phosphine complex [e.g., BCPE = l,2-bis(l,5-cyclooctylenephos-phino)ethane] was also reported to produce propanediols and n-propanol from glycerol at 443 K under 6 MPa CO/H2 atmosphere in acidic conditions, n-Propanol is the dominant product, while a slight preference for the formation of propane-1,3-diol is seen in the diol fraction. Reactions were performed at different temperatures in the range 413-448 K. Since acrolein was monitored at high temperature, a reaction network was proposed following a sequential dehydration/hydrogenation pathway [20]. 

D.R. Simbeck, E. Chang, Hydrogen Supply Cost Estimate for Hydrogen Pathways - Scoping Analysis, NREL report, 2002, NREL/SR-540-32525. 

By taking both experimental (Darwish et al. 1996b) and theoretical (Clare and Kepert 1994) (Cahill and Rohlfmg 1996) studies into account it is established that the most dominant hydrogenation pathway to C60H18 follows the scheme 1-2-3-6 in Fig. 9.10 below. 

Therefore, in an initial phase - for the near- and mid-term luture - three hydrogen pathways should be deployed ... 

Direct funding is defined by the DOE as funding that would not be requested if there were no hydrogen-related activities. Associated efforts are those necessary for a hydrogen pathway, such as hybrid electric components in the DOE s budget within the FreedomCAR Partnership, a cooperative research effort between the DOE and the United States Council for Automotive Research (USCAR). 

Associated = Efforts that are necessary for a Hydrogen pathway, i.e., hybrid electric components of FreedomCAR, high-temperature stationary fuel cells, sequestration, etc. 

Hydrogenation pathways of cinnamaldehyde over palladium catalysts. 

Scheme 5.7 Hydrogenation pathway of 5,5-dimethyl-l,3-cyclohexanedione leading to 3,3-dimethylcyclohexanone.

Scheme 9.5 Hydrogenation pathways of nitrocycloalkane (the uptake of hydrogen is based on monomeric compound).

Scheme 9.8 The hydrogenation pathway of dimethyl y-nitropimelate leading to pyrrolizidine.

Over Raney Ni at 200-250°C, however, the main reactions of the dihydrocoumarin formed were saturation of the benzenoid ring to give octahydrocoumarin (3) and its conversion to the cyclic ether, hexahydrochroman (4), although polymeric products were also formed in 6-27% yields. The hydrogenation pathways and the products of coumarin and related compounds over copper-chromium oxide and Raney Ni are summarized in Scheme 10.4. For the formation of the cyclic ether 4 over Raney Ni,... 

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