Photocatalytic process alcohol

Two semiconductor materials—n-type CdS and TiOi—have been the focus of much attention in such photocatalytic processes as the photocleavage of water and hydrogen sulphide, and the photooxidation of alcohols, carboxylates and various other organics. The majority of photoinduced processes on these materials are examined when they are in powder form. Enquiries into photocatalytic processes centre on the... 

Major limitation associated with carbon dioxide reduction is the accuracy of the analytical measurements employed. The photocatalytic process is a multielectron transfer process, hence the reaction leads to the formation of a variety of products like carbon monoxide, methane, higher hydrocarbons, alcohol, aldehydes, carboxylic acid etc., with some intermediates. The identification and quantification of the products are needed for the best selection of photocatalyst, comparison and elucidation of reaction mechanisms. Currently there is no standard analysis method that has been developed for product analysis of carbon dioxide reduction. Hence the results of these measurements also include the products derived from the carbon contamination invariably present in the reaction sys-... 

Ohtani B, Osaki H, Nishimoto S, Kagiya T (1986) A novel photocatalytic process of amine N-alkylation by platinized semiconductor particles suspended in alcohols. J Am Chem Soc 108(2) 308-310... 

Catalytic dehydrogenation of alcohol is an important process for the production of aldehyde and ketone (1). The majority of these dehydrogenation processes occur at the hquid-metal interface. The liquid phase catalytic reaction presents a challenge for identifying reaction intermediates and reaction pathways due to the strong overlapping infrared absorption of the solvent molecules. The objective of this study is to explore the feasibility of photocatalytic alcohol dehydrogenation. 

Chen J, Ollis DF, Rulkens WM (1999) Kinetic processes of photocatalytic mineralization of alcohols on metallized titanium dioxide. Water Res 33 1173-1180... 

In the photocatalytic production of amines from alcohols and ammonia, the efFiciency varied with alcohol structure ethanol > methanol > 2-propanol > t-butanol. A hydrogen atmosphere enhanced the formation of amines, a process which was inhibited by oxygen ... 

On the other hand, the production of desired compounds through reduction of starting material requires the electron donors to be oxidized (reductant). Alcohols are often used not only as a solvent but as the donor to produce useful compounds, e.g., anilines from nitrobenzenes,22) alcohols from aldehydes,23) and secondary amines from the corresponding Schiff bases.24) From the organic synthetic point of view, however, the separation of undesired products, aldehydes or ketones, from the alcohols is necessary unless subsequent reaction processes consume them25,26) or they are easily removed by distillation or other procedures. A recent report has shown that water acts as the electron donor and is converted into 02 in the photocatalytic regio-selective reduction of terpenes mixed with aqueous suspension of Ti02.27,28) It is notable that isolation of the desired product from the reaction mixture is simple in this type of photocatalytic reduction. 

Cyclizations of hydroxy esters under basic conditions have been achieved.475 Aldol reactions of a-kclo esters with aldehydes give unsaturated lactones.476 477 The photocatalytic addition of alcohols 17 to a,/ f-unsaturated acids (e. g., I8)478 or esters479 is an example of a radical process that gives fluorinated lactones (e.g.. 19). Cycloadditions to alkenes480 or alkynes481 are also successful. 

A similarly efficient, selective and environmentally benign photocatalytic system has been developed for the oxidation by oxygen of activated benzylic and allylic alcohols into their corresponding carbonyls in moderate to excellent yields (Scheme 2.32). The process did not require a transition metal to occur. 

Reduction of carbon dioxide produces a number of products like alcohols, acids, aldehydes etc. Since the photocatalytic reduction is a multielectron process, the products formed in the reaction system consist of many compounds, both in liquid (alcohols, aldehydes, acids etc.) as well as gaseous state (CO, CH4, and unreacted CO2 etc.). The exact identification and quantification of these products are required for the analysis of the overall reaction efficiency and hence the design of a better photocatalyst. Normally used analytical techniques are GC, HPLC, LC-MS, IR, IEC, UV-Vis, or 13C NMR. 

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