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Selective Hydrogenation of Crotonaldehyde over Pt Catalysts

Author: ZhengHaiYing
Tutor: LuoMengFei；XieGuanQun
School: Zhejiang Normal University
Course: Physical and chemical
Keywords: Crotonaldehyde Crotyl alcohol Selective hydrogenation The Pt catalyst Lewis acid Inactivation
CLC: TQ203.2
Type: Master's thesis
Year: 2011
Downloads: 19
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Abstract


α, β-unsaturated alcohols are spices, pharmaceuticals and other fine chemical products, an important raw material. α, β-unsaturated aldehyde synthesis of selective hydrogenation of the unsaturated alcohol is the main method, the thermodynamically C = C C = O is easier than the hydrogenation of aldehydes, thus improving the selectivity of unsaturated alcohol has been a hard orientation. This article was prepared supported Pt catalyst for vapor phase selective hydrogenation of crotonaldehyde. By H2-TPR (temperature-programmed reduction of hydrogen), XRD (X-ray powder diffraction analysis), FTIR (Fourier transform infrared spectra), TEM (transmission electron microscope), NH3-TPD (NH3-TPD), Ramani (Raman) and CO-Chemisorption (CO chemisorption) were characterized by means of research and exploration nature of the catalyst reaction mechanism and activity center. The results are as follows: 1, Pt/ZrO2 Selective catalytic hydrogenation of crotonaldehyde with high specific surface area of ??ZrO2 as the carrier prepared by impregnation of the supported Pt catalysts for the gas-phase hydrogenation of crotonaldehyde investigated the Pt loading and reduction temperature on the selective hydrogenation of crotonaldehyde performance. Experimental results show that, Pt loading of 3wt.% Of 3Pt/ZrO2 catalyst after reduction at 500 ℃, with a high selectivity of hydrogenation of crotonaldehyde: conversion rate of 27% crotonaldehyde, crotyl alcohol selectivity of 55% . Characterization results showed Pt/ZrO2 Lewis acid sites on the catalyst and appropriate Pt particles (about 8 nm) in favor selective hydrogenation of crotonaldehyde crotyl alcohol. 2, Cr catalyst species on Pt/ZrO2 selective hydrogenation of crotonaldehyde doping effect of Cr Species Pt/ZrO2 catalyst for vapor phase selective hydrogenation of crotonaldehyde was found with the catalytic activity decreased with increasing Cr content, but crotyl alcohol target product selectivity increases with increasing Cr content. Cr-modified catalyst activity decreased because the Pt particle size of the organic matter and the adsorption. Cr is added to increase the Lewis acidity of the catalyst and the Cr-Pt mutual transfer between the electron crotyl alcohol is the main reason to improve selectivity. 3, Pt/CeO2 and Pt/NaCl/ZrO2 comparative study of catalyst deactivation compare Pt/CeO2 and Pt/NaCl/ZrO2 catalyst vapor selective hydrogenation of crotonaldehyde and found both the catalyst deactivation but different trends crotyl alcohol selectivity . FTIR characterization results, found that the reaction during the polymerization reaction of a polymer of two C8 cause catalyst deactivation. On the selectivity of the two catalysts show different trends: For Pt/NaCl/ZrO2 catalyst selectivity remained unchanged crotyl alcohol; while for Pt/CeO2 catalyst selectivity dropped sharply. By in situ Raman Spectroscopy results show, Pt/CeO2 selectivity decreased mainly due to the oxidation of Ce3 ion Ce4 simultaneously stabilize the reaction of CO with Ce3 carbon (in-situ Raman). In contrast, in the catalyst during the reaction Pt/NaCl/ZrO2 no carbon, selectivity to crotyl alcohol remained stable.

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