Photocatalytic Direct Conversion Of Ethanol To 1,1-diethoxyethane Over Noble-metal-loaded TiO₂

With the depletion of fossil resource and environmental problem caused by fossil fuel combustion, people have been driven to exploit alternative and renewable sources. Biomass energy has drawn great attention due to its advantages, such as large reserves, the renewable raw material and so on.Ethanol, one of the most important bio-alcohols, can be obtained from biomass by fermentation. Bioethanol production rapidly increased over the last decade, and the total annual capacity reached 100 billion liters in 2013. Bioethanol is very important to rationally utilize for future energy and chemical industry needs. Bioethanol can be used as fuel or fuel additive and can act as a versatile platform molecule because of its rich chemistry for the production of numerous chemicals or fuels, such as ethylene, acetaldehyde, acetic acid, esters, and acetals.Traditional alcohol into acetal usually adopts two-step, alcohol oxidized into aldehyde first, and then alcohol and aldehyde acetal reaction of acid catalyzed by into corresponding acetal.This method is not only a complex process, and the catalyst is not friendly to the environment.Thus to develop more simple, the green synthesis of acetal is very urgent. Atom economy has the characteristics of alcohol without receptors in the direct synthesis of acetal dehydrogenation process will is the ideal way to alcohol green transformation.As one of the most important biomass platform molecules, ethanol needs to have its product chain chemically extended to meet future demands in renewable fuels and chemicals. Additionally, chemical conversion of ethanol under mild and green conditions is still a major challenge. In this work, ethanol is directly converted into 1,1-diethoxyethane (DEE) and H2 under mild photocatalytic conditions over platinum-loaded TiO2 nanotubes and nanorods. This photocatalytic dehydrogenation C-O coupling of ethanol is a new green approach to the direct efficient conversion of ethanol into DEE and provides a promising channel for sustainable bioethanol applications.Main contents are as follows:1. We obtained anatase and brookite TiO2 by hydrothermal process. Rutile TiO2 was prepared by calcination treatment of commercial P25.2. Commercial P25 as catalyst for example, photocatalytic alcohol under uv irradiation, it has the new product.By gas chromatography (GC) and mass spectrometry (MS) analysis, the product is determined to be acetal (DEE), and the selective reachs as high as 99%.3. Using the above preparation of photocatalyst, examines the different crystalline phase and morphology of the photocatalyst to ethanol step synthesis of acetal reaction the influence of the photocatalytic activity and selectivity.Found reactivity depends on the structure of catalyst crystal phase, dosage of catalyst and cocatalyst, TiO2- NR has the highest catalytic activity, selectivity was 99.1%, and the conversion rate of 29.3%, the reaction rate is as high as 110.8 mmol·g-1·h-1.4. The reaction follows a tandem dehydrogenation-acetalization mechanism, in which ethanol is first dehydrogenated into acetaldehyde and H+ ion by photogenerated holes, and then acetalization between acetaldehyde and ethanol proceeds through promotion by H+ions formed in real time. Excess H+ ions are simultaneously reduced into H2 by photogenerated electrons.5. The tradition acetalization is formed by ethanol and acetaldehyde in under the action of the proton acid catalytic synthesis.However in the photocatalytic reaction conditions or material ethanol step synthesis of acetal directly, through the study found that under the condition of photocatalysis ethanol lost after being oxidized to acetaldehyde H+ proton in the reaction system have played an important role in the proton acid, catalytic the acetal reaction of acetaldehyde and ethanol.Based on the above research, the design of the ethanol and acetaldehyde in photocatalytic acetal reaction under the conditions of verification, the experiment proved that under the condition of photocatalytic ethanol and acetaldehyde in response to balance within 40 minutes, reaction selectivity was 98.63%, the acetaldehyde conversion rate of 88.58%.6.Explores the light catalytic organic synthesis based on biomass of small molecules.Using tetrahydrofuran (THF) and ethanol, methanol, water respectively under the condition of TiO2 photocatalytic reaction, respectively, got 2-ethoxy tetrahydrofuran,2-methoxy tetrahydrofuran and 2-hydroxy tetrahydrofuran and a series of fine chemical products.