Project Summary

The recent interest for bio-plastics has raised the interest for production of organic acids as bi-functional monomers, completing their traditional uses in feed and food. Furan-2,5-dicarboxylic acid (FDCA), for instance, is a promising biomass-derived chemical with wide application in different industrial segments. Most important, since it has similar functional groups as terephtalic acid, FDCA is an extremely high potential platform chemical which can substitute for petrochemical derived terephthalic acid (PTA) in the production of polyesters and other current polymers containing aromatic moiety. Nevertheless, in spite of its huge industrial potential, FDCA is commercially (industrially) not yet produced because of the high price production.

The present project challenges the direct FDCA catalytic synthesis from renewable raw materials such as cellulose. Such concept requires the development of a cost effective and industrially viable oxidation of HMF to FDCA technology able to operate in concert with the necessary dehydration processes of cellulose to HMF. To reach the project challenge, multi-functional Me(Me=Co, Mn, Fe)@M(M= Sn, Nb)-Si@MNP core-shell magnetic nanoparticles, combining non-noble metal (Co, Mn, Fe) and acid sites (Sn(IV), Nb(V)), will be designed and developed for the one-pot synthesis of FDCA from cellulose. The flow chemistry approach by using multi-phase systems will be also designed for the best batch reactions. Moreover, an advanced integrated strategy to maximize the value of the eventually formed humins wastes to bio-fuels will be developed.

The implementation degree of the project:

Phase I/2017 (12.07.2017– 31.12.2017): Synthesis of Sn @ MNP and Nb @ MNP core-shell catalysts with high efficiency in dehydration of glucose / cellulose to HMF

In order to achieve this phase, the following activities were carried out:

Activity 1.1. - Synthesis of "core-shell" Sn@MNP and Nb@MNP catalysts

Activity 1.2. - Physico-chemical characterization of the synthesized catalysts

Activity 1.3. - Dehydration of glucose and cellulose to HMF

Summary of the research report (Phase I):

In the reported phase, "core-shell"-like Sn@MNP and Nb@MNP (“core” – magnetic nanoparticles incorporated into the MCM walls, “shell” – mesoporous silica (MCM-41 structure) doped with Sn or Nb) catalysts (in which, Si/Sn or Si/Nb ratio of 18, 22, 47 and 50 respectively) were prepared by a modified Atran method.

Different characterization techniques were applied in order to study the structure and composition of the obtained materials. Accordingly to this, bi-functional materials, comprising residual framework Al-acid sites, extra-framework isolated Nb(V) sites which correspond to Nb(V)O-H species (associated with strong Brønsted acid sites), where niobium is linked by Nb-OSi bonds to the zeolitic walls, and Nb₂O₅ pore-encapsulated clusters were produced after the post-synthetic insertion of Nb in the zeolite matrix. The Sn samples (Sn@MNP) follow the same trend with the specification that the maximum amount of Sn (IV) that can be dispersed in the silica matrix corresponds to a Si/Sn = 22 ratio whereas, in the case of Nb samples, a maximum amount of Nb (V) which can be dispersed in the silica matrix corresponds to a Si/Nb ratio of 18. A further increase in the amount of tin or niobium over the specified ones leads to a collapse of the mesoporous structure by the formation of amorphous materials. The typical porous architecture of MCM-41 materials is only slightly altered by incorporating magnetic nanoparticles. Importantly, the existence of magnetite ensures a very simple separation of the catalysts from the reaction medium.

The main reaction products obtained in the dehydration of glucose in the presence of the catalysts prepared in this phase were: -hydroxyacids (lactic and glycolic acid), levulinic acid and 5-hydroxymethylfurfural (HMF). Moreover, large amounts of condensation products, generically called humine, were formed, which provoked not only a high decrease in HMF selectivity but also a gradual deactivation of the catalysts. An efficient method of suppressing the unwanted side reactions consisted in combining the dehydration of glucose in aqueous medium with in situ extraction of the formed HMF from the aqueous phase in an organic phase. Thus, the use of a biphasic aqueous solution of NaCl / methyl isobutyl ketone (MIBK) brings the advantage of a high partition coefficient between the two immiscible phases favoring the extraction of HMF formed in water in the organic phase. In such biphasic systems, synthesis took place with 58-63% selectivity to HMF for 61-67% glucose conversion in the presence of Nb@MNP catalysts (Si/Nb = 18) and Sn@MNP (Si/Sn = 22). The catalysts are characterized by a high stability being recycled several runs without significant decreases of the glucose conversion and HMF selectivity. Similar tests with cellulose as raw material instead of glucose were also performed.

Phase II/2018 (01.01.2018-31.12.2018): Synthesis of bifunctional catalysts (Pd@zeolite beta) and Co@MNP, Fe@MNP and Mn@MNP catalysts for the humins transformation into liquid hydrocarbons and the oxidation of HMF to FCDA

In order to achieve this phase, the following activities were carried out:

Activity 2.1. - Synthesis of bifunctional Pd@zeolite beta catalyst.

Activity 2.2. – Synthesis of Co@MNP, Fe@MNP and Mn@MNP catalysts

Activity 2.3. - Physico-chemical characterization of the synthesized catalysts

Activity 2.4. – Oxidation of HMF to FDCA

Summary of the research report (Phase II):

In the reported phase Co@MNP, Fe@MNP and Mn@MNP catalysts were prepared following a procedure in three steps: a. synthesis of magnetite nanoparticles by co-precipitation, b. covering of magnetite with a silica shell by sol-gel method, and c. deposition of Co, Fe or Mn oxide particles by precipitation-deposition method. For each kind of material, catalysts with 1, 5 and 10 % heteroatomic oxide were prepared. The prepared catalysts were characterized by using different techniques in order to study the structure and composition of the obtained materials. Briefly, for low concentrations of MO_x (M = Mn, Co and Fe, 1-5wt%) the incorporated heteroatomic oxides are homogeneously highly dispersed on the silica shell. However, at high concentrations (ie, 10wt%) different phases of MnO_x and CoO_x were evidenced in XRD patterns, as akhtenskite (ε-MnO₂), Mn₃O₄, and Co₃O₄ species.

In monophasic solvent (ie, water) and in the presence of a base (ie, NaOH or n-butylamine) the HMF oxidation lead to three important reaction products, in different proportions, as a function of the catalyst nature and reaction conditions, namely succinic acid (SA), maleic acid (MAc) and 5-hydroxymethyl-2-furancarboxylic acid (HMFA intermediate to FDCA). In the presence of Na2CO3 the HMF oxidation leads to HMFA with total selectivity. All the investigated catalysts showed very good stability (ICP-OES analysis).

Apart from magnetite based samples, bifunctional Pd@zeolite beta catalysts, with 0.5wt% and 1.0wt% Pd were also prepared and characterized. The catalytic tests of these catalysts in the hydrodeoxygenation reaction of humines will be carried out in Phase III of the project, according to the project's realization plan.

Phase III/2019 (01.01.2019-31.12.2019): Synthesis of multifunctional catalytic materials for the one-pot synthesis of FDCA. Transferring the catalytic approach from batch reactor to flow chemistry concept

In order to achieve this phase, the following activities were carried out:

Activity 3.1. - Synthesis of multi-functional Me(Me=Co, Mn, Fe)@M(M= Sn, Nb)-Si@MNP catalysts.

Activity 3.2. – Hydrodeoxygenation of water-soluble humins and unprocessed glucose

Activity 3.3. - The one-pot synthesis of FDCA from glucose/cellulose

Activity 3.4. – Transferring the catalytic approach from batch reactor to flow chemistry concept

Summary of the research report (Phase III):

In the reported phase multi-functional Me(Me=Co, Mn, Fe)@M(M= Sn, Nb)-Si@MNP, catalysts were prepared following a procedure in two stages: a. synthesis of mono-functional catalytic materials (Nb@MNP and Sn@MNP), followed by b. precipitation/deposition of MnOx, CoOx or FeOx species. For the first stage of synthesis the methodology used and described in Phase I, Activity 1.1 was applied. The second stage involved a methodology of synthesis by precipitation/deposition starting from M(II)acetate precursors. The ratios Si/Nb and Si/Sn, as well as the quantities of Co, Mn and Fe were chosen as a result of the experimental observations from Phases I and II: in agreement with them, the maximum of Sn (IV) that can be dispersed in the mesoporous silica matrix corresponds to a ratio of Si/Sn = 22 whereas, for samples with Nb - the maximum of Nb that can be dispersed in the silica matrix corresponds to a ratio of Si/Nb = 18. A further increase in the quantity of tin or niobium over the specified ones leads to a collapse of the mesoporous structure with the formation of an amorphous material. On the other hand, the amount of transition metal that generated the best results in HMF oxidation was 10wt%.

The prepared catalysts were characterized by using different techniques (ie, adsorption-desorption of liquid nitrogen at 77 K, XRD, FT-IR, XPS) in order to study the structure and composition of the obtained materials. Briefly, the obtained results for Me(Me=Co, Mn, Fe)@Nb-Si@MNP, for instance, show the presence of extracellular isolated species of Nb(V) sites corresponding to Nb(V)O-H species and of clusters of Nb2O5 encapsulated in silica mesopores. The addition of Co, Mn and Fe to the Nb@MNP lead to homogeneously highly dispersed species of Mn₂O₃, CoO and Fe2O3. Moreover, resulted materials are characterized by a bi-modal mesoporous structure.

In the presence of the 10%Co@22Nb@MNP catalyst, the direct glucose conversion to FDCA occurs with a selectivity of 37.1% for a total conversion of glucose, whereas in the presence of 10%Mn@22Nb@MNP catalyst, the reaction proceeded with a selectivity of 28.6% FDCA for a conversion of glucose of 73.3%. The addition of NaHCO3 in the reaction medium leads to an improved selectivity to FDCA in the presence of 10%Co@22Nb@MNP catalyst.

Remarkable results were obtained by using t-butyl hydroperoxide (t-BuOOH) as oxidizing agent and acetonitrile as solvent. Thus, FDCA was obtained with selectivity of 98.3% for almost total conversions, values much higher than most reports in the literature. The transfer of the reaction under flow conditions has resulted in net inferior results, FDCA being obtained with selectivity up to 15% but, even in these conditions, these results are promising and deserve further investigation in order to optimize the operational conditions.

Preliminary tests performed in the presence of cellulose show a high complexity of the processes that take place during cellulose degradation, with the formation of a large number of reaction products. However, among these products glucose is obtained in the largest quantities. As such, the possibility of direct cellulose transformation is actually tested by adopting a two-stage methodology: cellulose degradation to glucose in the presence of the Nb@MNP catalyst, followed by the catalyst separation and the subsequent oxidation of the obtained mixture, in the presence of multi-functional catalysts (Me(Me=Co, Mn, Fe)@Nb-Si@MNP).

Results obtained in the humin valorization show that it can be transformed by catalytic hydrodeoxygenation reactions into humin oil. For this activity, a number of nine catalytic samples of Pd (0.5, 1.0 and 1.5wt%)@zeolite (Beta, Y and USY) were prepared and characterized. The transformation yields of humin and the obtained quantities of humin oil vary depending on the type of used catalyst and the imposed reaction conditions. GC-MS analyzes highlight the predominance of aromatic and phenolic compounds, along with cycloalkanes.

The activities carried out until now have provided interesting results for the international scientific community, some of them already being published in high impact factor journals. A number of other results are included in two other manuscripts, to be proposed for publication in Catal Today and Molecules, by the end of the current year. The results also were communicated by attending international conferences and congresses in the field, as listed bellow.

Dissemination

Papers:

1. M. El Fergani, N. Candu, S. M. Coman, V. I. Parvulescu, Molecules, 2017, 22(12), 2218.

2. A. Tirsoaga, M. El Fergani, V. I. Parvulescu, S. M. Coman, ACS Sustain. Chem. Eng., 2018, 6(11), 14292-14301.

3. N. Candu, M. El Fergani, M. Verziu, B. Cojocaru, B, Jurca, N. Apostol, C. Teodoresu, V. I. Parvulescu, S. M. Coman, Catal. Today, 2019, 325, 109-116.

4. V. I. Parvulescu, S. M. Coman, Current Catalysis, 2019, 8, 2-19.

Communications:

1. N. Candu, S. M. Coman, V. I. Parvulescu, 9^th International Symposium on Group Five Elements, 22-24 November 2017, New Delhi, India (ORAL PRESENTATION)

2. I. Podolean, B. Cojocaru, H. Garcia , S. M. Coman, V. I. Parvulescu, 4th International Congress on Catalysis for Biorefineries, 11-15 December 2017, Lyon, France (ORAL PRESENTATION)

3. S. M. Coman, I. Podolean, C. Rizescu, H. Garcia, V. I. Parvulescu, 27th Organic Reactions Catalysis Society Meeting, 8-12 April 2018, San Diego, CA USA (ORAL PRESENTATION)

4. M. El Fergani, S. M. Coman, V. I. Parvulescu, Young Researchers' International Conference on Chemistry and Chemical Engineering (YRICCCE II), 3-5 May 2018, Budapest, Hungary (ORAL PRESENTATION)

5. C. Rizescu, I. Podolean, J. Albero, V. I. Parvulescu, S. M. Coman, C. Bucur, M. Puche, H. Garcia, EFCATS School on Catalysis, 25-29 June 2018, Liblice Castle, Czech Republic (ORAL PRESENTATION)

6. N. Candu, M. El Fergani, S. M. Coman, V. I. Parvulescu, EFCATS School on Catalysis, 25-29 June 2018, Liblice Castle, Czech Republic (ORAL PRESENTATION)

7. E. Kemnitz, V. I. Parvulescu, S. M. Coman, 14^th Pannonian International Symposium on Catalysis, Starý Smokovec, 3 – 7 September, 2018, Slovacia (KEYNOTE LECTURE)

8. M. EL. Fergani, N. Candu, V. I. Parvulescu, S. M. Coman, 4rd International Symposium on Green Chemistry (ISCG 2019), 13-17 May 2019, La Rochelle, France (ORAL PRESENTATION)

9. N. Candu, M. El Fergani, A. Tirsoaga, V. I. Parvulescu, S. M. Coman, The 8th Asia Pacific Congres son Catalysis (APCAT-8), August 4-7, 2019, Bangkok, Thailand (ORAL PRESENTATION)

10. N. Candu, M. El Fergani, A. Tirsoaga, V. I. Parvulescu, S. M. Coman, The 12^th International Symposium of the Romanian Catalysis Society (ROMCAT 2019), June 5-7, 2019, Bucharest, Romania (ORAL PRESENTATION)

11. M. El Fergani, N. Candu, V.I Parvulescu, S. M. Coman, The 12^th International Symposium of the Romanian Catalysis Society (ROMCAT 2019), June 5-7, 2019, Bucharest, Romania (POSTER)

12. M. El Fergani, A. Tirsoaga, V. I. Parvulescu, S. M. Coman, 14th European Congres on catalysis (EuropaCat 2019), August 18-23 2019, Aachen, Germany (POSTER)