Selective hydrogenation of oleic acid to fatty alcohols over a Rh–Sn–B/Al2O3 catalyst: kinetics and optimal reaction conditions,Reaction Chemistry & Engineering

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Selective hydrogenation of oleic acid to fatty alcohols over a Rh–Sn–B/Al2O3 catalyst: kinetics and optimal reaction conditions
Reaction Chemistry & Engineering ( IF 3.4 ) Pub Date : 2021-3-23 , DOI: 10.1039/d0re00488j
Cristhian A. Fonseca Benítez _{1,

2,

3} , Vanina A. Mazzieri _{1,

2,

3} , Carlos R. Vera _{1,

2,

3} , Viviana M. Benitez _{1,

2,

3} , Carlos L. Pieck _{1,

2,

3}

Affiliation

The selective hydrogenation of oleic acid to oleyl alcohol over a Rh(1 wt%)–Sn(4 wt%)–B/Al₂O₃ catalyst was studied. A comprehensive set of experimental data was used for elucidating the reaction mechanism. In the range of reaction conditions of this work, the optimal conditions found were 290 °C and 2 MPa, with a yield of 82–83% of oleyl alcohol. Kinetic models were written which considered the whole network of reactions taking place: double bond hydrogenation, acid hydrogenation to alcohol, and esterification of acids and alcohols. Different combinations of elementary steps led to the formulation of a big number of models. Models posing the surface reactions as rate-limiting fitted the data better. Adsorption of the acids, the alcohols or hydrogen was not rate-limiting. The best-fit model had the following hypotheses: (i) only one kind of adsorption site is needed for all species and reactions; (ii) H₂ is dissociatively adsorbed; (iii) fatty molecules are adsorbed on only one site; (iv) pairwise insertion of H to fatty molecules is the rate-limiting step; (v) reduction of the carboxylate group occurs via an aldehyde intermediate that is subsequently hydrogenated to the corresponding alcohol; (vii) hydrogen and oleic acid are the main adsorbates; (vii) heavy esters are formed but do not contribute as intermediates of the main mechanism.

中文翻译：

在Rh–Sn–B / Al2O3催化剂上将油酸选择性氢化为脂肪醇：动力学和最佳反应条件

在Rh（1 wt％）– Sn（4 wt％）– B / Al ₂ O ₃上将油酸选择性氢化为油醇研究了催化剂。使用一组全面的实验数据来阐明反应机理。在这项工作的反应条件范围内，发现的最佳条件是290°C和2 MPa，油醇的收率为82–83％。编写了动力学模型，其中考虑了发生的整个反应网络：双键加氢，酸加氢成醇，以及酸和醇的酯化。基本步骤的不同组合导致大量模型的提出。将表面反应视为速率限制的模型可以更好地拟合数据。酸，醇或氢的吸附不受速率的限制。最佳拟合模型具有以下假设：（i）所有物种和反应仅需要一种吸附位点；（ii）H ₂解离地吸附；（iii）脂肪分子仅吸附在一个部位上；（iv）将H成对插入脂肪分子是限速步骤；（v）羧酸酯基的还原是通过醛中间体发生的，该醛中间体随后被氢化为相应的醇；（vii）氢和油酸是主要吸附物；（vii）形成重酯，但不作为主要机理的中间体。

更新日期：2021-03-23

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