Catalytic Hydrogenation/Hydrogenolysis of Biomass-Derived Platform Chemicals
- Autores: Abdulaziz Aldureid Kadi Amin
- Directores de la Tesis: Daniel Montané Calaf (dir. tes.), Francesc Medina Cabello (codir. tes.)
- Lectura: En la Universitat Rovira i Virgili ( España ) en 2023
- Idioma: inglés
- Número de páginas: 216
- Tribunal Calificador de la Tesis: Jordi Llorca Piqué (presid.), Sandra Contreras Iglesias (secret.), Alberto Tampieri (voc.)
- Programa de doctorado: Programa de Doctorado en Nanociencia, Materiales e Ingeniería Química por la Universidad Rovira i Virgili
- Materias:
- Enlaces
- Tesis en acceso abierto en: TDX
- Resumen
- català
A causa de l'actual escenari polític mundial i a la mancança de fonts d'energia, la biomassa s'ha proposat com a una de les matèries primeres alternatives i sostenibles per a fer front a la urgent necessitat de recursos energètics renovables. Aquesta tesi es centra en el furfural, considerat un dels productes químics de major valor afegit derivats de la biomassa. Hem sintetitzat diferents catalitzadors per a utilitzar-los en la hidrogenació del furfural i posterior conversió a productes químics importants com el 1,2-pentanediol, 1,5-pentanediol, alcohol furfurílic i tetrahidrofurfurílic. Aquests compostos derivats del furfural poden utilitzar-se en la producció de biocombustibles, la producció de polímers, com a additius per a combustibles, dissolvents, etc. Tots els catalitzadors utilitzats es van preparar a base de metalls no nobles (Ni, Co, Cu, Mg, Al), i derivats d'hidròxids dobles laminars (HDL). A continuació, es van calcinar en aire atmosfèric a 673 K durant 4 hores i es van reduir en H2 pur a 773 K durant 1 hora. Finalment es van caracteritzar per XRD, FESEM-*EDX, H2-TPR, TPD-NH3, ICP i BET.
- English
Since the utilization of fossil fuels for the production of energy and chemicals has caused several environmental changes, biomass has been proposed as a solution to be an alternative and sustainable raw material. Biomass is one of the promoting sources in the production of high-value chemicals to be used as fuels, fuel additives and industrial green solvents. Furfural is a biomas-derived chemical, it is produced in lignocellulosic biorefineries from xylose and other five-carbon polysaccharides materials. By the hydrogenation reaction, furfural can be converted into other compounds that have a significant role in the chemical industry.
The general objective of this thesis is to obtain a group of non-noble hydrogenation catalysts that are suitable for producing commodity chemicals from furfural, while the specific objectives are: I) To synthesize and characterize a group of catalyst based on hydrotalcite (HT) precursors which are also known as layered double hydroxides (LDHs), suitable for the hydrogenation of furfural.
II) To assess the performance of the synthesized materials under a wide variety of liquid-phase and gas-phase conditions.
III) To select a reduced group of high-performance materials to conduct stability tests with extended time-on-stream under constant conditions.
The methodology of the thesis includes several steps: First, studying the synthesis of a family of catalysts involving combinations of different active metals and the performance of its full structural and textural characterization. Second, studying the performance of the catalyst under different reaction conditions. Third, studying of how the parameters can drive the reaction path between hydrogenation, hydrogenolysis, opening-ring and condensation.
We can highlight the conclusion of this thesis as the following: 1) Conditions Since hydrogen is a reactant in our process, hydrogen pressure is one of the main parameters that affect the performance of the reaction. Also, since hydrogen solubility is related to hydrogen pressure, this influences the amount of available hydrogen capable of reacting with the other reactant (furfural) in the reaction medium.
In our experiments we found that, to guide the reaction towards the preferred products (TFA, FA, 12PD, 15PD) and avoid consumption of the substrate (furfural) in the formation of by-products, the conversion reaction should be performed at 5 MPa of hydrogen pressure. This enables a suitable amount of hydrogen to be in contact with furfural in the reaction medium. The by-products are probably formed because the reaction took the nucleophilic addition route on acidic sites of the catalyst surface, in which furfural reacts with either ethanol or the formed FA to produce some other undesired products whose presence has been shown to decrease the reaction rates.
Conducting the furfural conversion at low hydrogen pressure led to form FA as the main product and may produce other chemicals such as FUR through the decarbonylation, or mFUR through the hydrogenation. Also, other reactions that formed acetals which finally produced DFE and TFEE as final products may occur.
Furthermore, since activation energy is needed to carry out the hydrogenation of furfural, suitable thermal conditions, among other factors, are crucial for directing furfural conversion towards the desired compounds. In general, we found that a temperature of 463 K led to a high conversion of furfural and the formation of the desired products. Performing the reaction at lower temperatures would not achieve the expected results and may synthesize undesired products.
With regard to reaction time, two hours was the minimum recorded time in which the reaction completed 100% conversion with most catalysts. This short time produced only simple alcohols such as furfuryl alcohol. The hydrogenolysis process for forming liner C5 di-alcohols required a longer time (at least four hours). The impact of the catalyst and the economic concerns of energy consumption notwithstanding, reaction time played a highly significant role, with reactions lasting four hours achieving the best results.
2) Catalysts Our approach focused on heterogeneous catalysts that after the reaction are easily separated from the mixture, easily prepared, available from abundant elements, and cheaper than most other catalysts in the literature that use noble metals.
All our catalysts contained nickel and aluminum and were derived from layered double hydroxides (LDHs). Three catalysts contained cobalt, while copper was added to another three, a pair of catalysts were modified by magnesium and a catalyst that consisted only of aluminum and nickel as a reference for the activity.
Our catalysts can be divided into three groups based on their activity to hydrogenate furfural. The first group comprises catalysts that promote the hydrogenation of the aldehyde group into alcohols. The second group comprises catalysts that are capable of opening the furan ring. The third group comprises catalysts that support hydrogenation by other routes such as the cleavage of C=O and/or the decarbonylation of furfural.
The first group comprises Cu-based and Mg-based catalysts due to their high capacity to direct furfural hydrogenation into the reduction of the aldehyde group and produce high yields of furfuryl alcohol and tetrahydrofurfuryl alcohol (cyclic alcohol)..
The second group contains Co- based catalysts because of the greater amount of pentanediols it obtained compared to the other catalysts. This shows that cobalt is necessary in the catalyst structure to drive furfural hydrogenation into a ring-opening route and produce pentanediols in large amounts.
The third group consists of Cu-based catalysts, which led to the formation of valued compounds such as 2-methyl furan, 2-methul Tetrahydrofuran, Furan, and THF. These compounds were produced in all reactions but higher selectivities were obtained in Cu-based catalysts than in those over Co-based catalysts and Mg-based catalysts.
In other words: >> Cu-based catalysts were suitable for forming furfuryl alcohol. Compared to the other catalysts, a slight amount of furfuryl alcohol was produced when Mg-based catalysts were used but no furfuryl alcohol was produced when Co-based catalysts were used. The highest amount of furfuryl alcohol was obtained with the copper catalysts.
>> Mg-based catalysts were not very active in ring-opening. However, since they were the most active catalysts in both the aldehyde group hydrogenation and the furanic ring's double bond, they became the catalysts of choice for producing tetrahydrofurfuryl alcohol.
>> Co-based catalysts appear to be more active than the other catalysts when it comes to opening the furan ring and generating two groups of alcohols to form pentanediols. Since the production of pentanediols is not yet on a large scale, this characteristic may make cobalt a promising candidate for designing catalysts to produce 1,5-pentanediol and 1,2-pentanediol in up-scale amounts by combining multiple stages of the synthesized catalyst, where the reactant is exposed to different phases of hydrogenation in a continuous packed-bed.
3)Reactors By comparing the results from the continuous packed-bed reactor (PBR) with those from the high-pressure slurry reactor (SSR), we can clearly determine the role of the reactor.
Monitoring the formation of tetrahydrofurfuryl alcohol, furfuryl alcohol, and pentanediols enabled us to determine how the reactor played a role in encouraging the reaction to take certain routes over others. Under the same thermal conditions, reaction time and over the same catalyst, furfural reacted differently.
In PBR, the dominant product was furfuryl alcohol, while in SSR it was tetrahydrofurfuryl alcohol.
The PBR reactor may make furfural suppressed as furfuryl alcohol and allow just a small amount of it to be converted into other products of furan ring hydrogenation and/or opening-ring rearrangement. However, in SSR the hydrogenation process persisted towards the double bonds in the furan ring and produced tetrahydrofurfuryl alcohol, which may be followed by the ring-opening and produce pentanediols.
These results could therefore be attributed to the short contact time between furfural and the catalyst surface, which enables furfural to remain adsorbed for a short time and impede the attack of hydrogen. Products of only one hydrogenation process were therefore formed in higher amounts in the PBR. Moreover, the small amount of pentanediols formed in the PBR explained the high energy needed to open the furan ring, which was not available in the reaction occurred PBR.
- English
En la actual crisis energética y contexto político, la biomasa ha emergido con fuerza como una de las materias primas alternativas y sostenibles para hacer frente a la urgente necesidad de recursos energéticos renovables. Esta tesis se centra en el estudio del furfural, considerado uno de los productos químicos de mayor valor añadido derivados de la biomasa. Para ello, se sintetizaron diferentes catalizadores diferentes para evaluarlos en la reacción de hidrogenación del furfural y transformarlo en productos químicos de interés industrial como 1,2-pentanodiol, 1,5-pentanodiol, alcohol furfurílico y alcohol tetrahidrofurfurílico. Estos compuestos derivados del furfural pueden ser utilizados en la producción de biocombustibles, la producción de polímeros, como aditivos para combustibles, disolventes, etc. Todos los catalizadores estudiados se sintetizaron con base de metales no nobles (Ni, Co, Cu, Mg, Al), y derivados de hidróxidos doble laminares (HDL). A continuación, se calcinaron en atmósfera de aire a 673 K durante 4 horas, se redujeron en hidrógeno gas puro a 773K durante 1 hora y se caracterizaron por XRD, FESEM-EDX, H2-TPR, TPD-NH3, ICP y BET.
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