Synthesis of higher alcohols from syngas with a heterogeneous catalyst
Lind, Noora (2023)
2023
Julkaisu on tekijänoikeussäännösten alainen. Teosta voi lukea ja tulostaa henkilökohtaista käyttöä varten. Käyttö kaupallisiin tarkoituksiin on kielletty.
Julkaisun pysyvä osoite on
https://urn.fi/URN:NBN:fi-fe202401041441
https://urn.fi/URN:NBN:fi-fe202401041441
Tiivistelmä
As the demand for more air traffic increases in the coming years, it is necessary to manufacture sustainable aviation fuel. One method is to do so by turning syngas, which is made from biomass, into higher alcohols. Syngas may be produced more cheaply through the gasification of biomass or even waste.
Higher alcohols are an important chemical intermediate and can be used as a drop-in fuel for the aviation sector. However, there is still a need for optimization of the process of higher alcohol synthesis (HAS), finding the right catalysts with the highest selectivity and activity and increasing the higher alcohol yield.
The objective of this work was to test different multi-metallic rhodium-based catalysts and their performance in higher alcohol production and characterize them. Rhodium is a very active catalyst and promising for higher alcohol synthesis but the very expensive and with a very limited supply. Only 1% of rhodium may be combined with another metal to provide a bimetallic catalyst with two active sites, this makes rhodium more suitable for HAS.
The 1Rh1.52MnOx/SiO2 catalyst was tested as is but also combined with a 2Pd/ZrO2 catalyst. The additional palladium increased slightly CO conversion from 34.5% to 37.9% but the alcohol concentration increased significantly from 84.1 to 179.6 g/l at 300 °C. At the same time, it was confirmed with a GC-MS that a ketonization reaction occurred when Rh/MnOx catalyst was combined with palladium. This ketonization reaction resulted in that undesired acetic acid concentration decreased by 79%. In this same experiment, the gas hourly space velocity was half of the original which further helped in alcohol production. Thus, according to this study, the combination of 1Rh1.52MnOx/SiO2 and 2Pd/ZrO2 was the most successful. 1Rh5Co/ZrO2 catalyst produced a lower concentration of alcohols (17.7 g/l) but had the highest CO conversion of 88.3%. 1Rh5Cu/ZrO2 and 1Rh5Cu1Pd/ZrO2 were unsuccessful in higher alcohol synthesis due to the low CO conversion.
Higher alcohols are an important chemical intermediate and can be used as a drop-in fuel for the aviation sector. However, there is still a need for optimization of the process of higher alcohol synthesis (HAS), finding the right catalysts with the highest selectivity and activity and increasing the higher alcohol yield.
The objective of this work was to test different multi-metallic rhodium-based catalysts and their performance in higher alcohol production and characterize them. Rhodium is a very active catalyst and promising for higher alcohol synthesis but the very expensive and with a very limited supply. Only 1% of rhodium may be combined with another metal to provide a bimetallic catalyst with two active sites, this makes rhodium more suitable for HAS.
The 1Rh1.52MnOx/SiO2 catalyst was tested as is but also combined with a 2Pd/ZrO2 catalyst. The additional palladium increased slightly CO conversion from 34.5% to 37.9% but the alcohol concentration increased significantly from 84.1 to 179.6 g/l at 300 °C. At the same time, it was confirmed with a GC-MS that a ketonization reaction occurred when Rh/MnOx catalyst was combined with palladium. This ketonization reaction resulted in that undesired acetic acid concentration decreased by 79%. In this same experiment, the gas hourly space velocity was half of the original which further helped in alcohol production. Thus, according to this study, the combination of 1Rh1.52MnOx/SiO2 and 2Pd/ZrO2 was the most successful. 1Rh5Co/ZrO2 catalyst produced a lower concentration of alcohols (17.7 g/l) but had the highest CO conversion of 88.3%. 1Rh5Cu/ZrO2 and 1Rh5Cu1Pd/ZrO2 were unsuccessful in higher alcohol synthesis due to the low CO conversion.