Biomass valorization is a booming field. Especially, the valorization of platform molecules by catalytic processes has driven a large interest in the recent years, and many groups are actively working on the transformation of biosourced substrates to a variety of upgraded chemicals. In this context, in the present paper we put in perspectives the scientific works of our research team. We first classified catalytic transformations of industrial interest according to the number of carbons of the starting material, from C1 to C6. They involve, among others, acid catalysts (e.g., for glycerol dehydration), redox catalysts (e.g., for 5-HMF conversion to diformylfuran), acid and redox catalysts (e.g., for direct acetalization of alcohols), or complex multifunctional catalysts, especially for the Guerbet reaction. Further, we also developed what we called ‘toolboxes,’ which are general concepts or technologies with a broader field of applications. For example, we adapted the two zones fluidized bed reactor (TZFBR) concept to the single reactor continuous regeneration of coking catalysts. Further, we designed a completely new high throughput platform enabling synthetizing, characterizing and testing the performances of many catalysts for considerably accelerating the catalysts discovery/optimization loop.
Efficient cold-start process of hydrogen production by oxidative reforming (OR) of hydrocarbon was developed using Rh catalyst supported on carriers with redox properties. In this process, the heat generated by re-oxidation of reduced catalyst rapidly heats the catalyst from ambient temperature to the catalytic auto-ignition temperature of the OR. OR was triggered at ambient temperature over Rh/CeO2 after reduction at 873 K, but not over Rh catalysts supported on Pr6O11 and Tb4O7, oxides of rare earth elements with redox characters like cerium. Over the latter catalysts, reduction of the carrier occurred at lower temperatures than over CeO2, but the reduced oxides were not re-oxidized at ambient temperature. Our results emphasized that re-oxidation as well as reduction of the catalyst are the key characteristics of the carrier for triggering OR at ambient temperature. With the use of Rh/Ce0.5Zr0.5O2 with excellent redox properties at low temperature, triggering OR of hydrocarbons at ambient temperature was achieved even under non-adiabatic conditions, where heat losses occur, over the catalyst after reduction at 373 K and after in-situ reduction by hydrogen formed during the OR. This new catalytic process is expected to be useful for the development of self-sufficient reforming processes for a new generation of fuel cells.
Fluid catalytic cracking (FCC) processes are now required to produce gasoline fractions with high octane number and less heavier fuel oil such as slurry oil (SLO), due to the need for environmental preservation and changes in the fuel oil demand structure. The authors previously discovered that addition of mono aluminum phosphate (Al–P) is effective to decrease heavier fuel oil and increase gasoline yield with higher octane number compared to conventional catalyst. In this study, catalyst containing Al–P was operated in the commercial FCC unit to verify the effect of Al–P. Catalyst containing Al–P achieved higher cracking activity and higher octane number than conventional catalyst. In addition, Al–P can suppress zeolite collapse under hydrothermal conditions.
Production of new hydrocarbon biodiesel, which can be synthesized from various vegetable oils by catalytic decarboxylation, was investigated with a fixed bed rector. The diesel fraction oils of C10-C20 aliphatic hydrocarbons as the major products were obtained smoothly with the reactor using waste cooking oil, jatropha oil, dark oil, and palm oil. Higher yields of C21 + compounds, compared to the case of the agitating reactor, show that heavier products could flow out from the catalyst bed before decomposition to the lighter hydrocarbons. An MgO/SiO2 catalyst was found to be more effective than an active carbon-supported catalyst. In particular, cracked oil with a lower acid value (AV) was obtained with the former catalyst. Influence of reaction temperature and the feed rate of the reactant was examined to find that optimal conditions are 450 °C and LHSV = 0.3 h−1. Although catalyst activity was maintained for about 24 h at LHSV = 0.3 h−1, deactivation by carbon deposition, especially for an increase in AV, was observed thereafter. However, the activity could be regenerated by a simple calcination with air.
Novel carbon and oxide-supported Ni (Ni/C/TiO2, SiO2 or ZrO2) catalysts were prepared by the sol-gel method and investigated for hydrothermal gasification of aqueous solution of phenol (phenol water) as a model of wastewater, and compared with carbon and Al2O3 supported Ni catalysts. Catalysts were prepared by the combination of titanium tetraisopropoxide (TIP), tetraethylorthosilicate (TEOS) or zirconium tetrabutoxide (ZB) and polyethylene glycol (PEG) as an organic template, with the addition of active metal, nickel nitrate hexahydrate, at the preparation of catalysts. After calcination under a nitrogen atmosphere, larger amounts of active metal species were deposited on the carbon skeleton in the catalysts. The introduction of PEG dispersed metal Ni with high loading on carbon derived from PEG. Hydrothermal gasification was performed under the following conditions: 350 °C, pressure 20 MPa, phenol water 2-20 g/L, catalyst 5 mL, LHSV 48 h−1. 16N11C73Z catalyst, which represents 16 wt% Ni, 11 wt% carbon in PEG, and 73 wt% ZrO2 at the preparation of the catalyst, showed the highest activity among the 16N11C73Oxide catalysts (Oxide: TiO2, SiO2, ZrO2 or Al2O3). The conversion of phenol decreased in the order 16N11C73Z>16N11C73A>16N11C73T>16N11C73S (16N: 16 wt% Ni; 11C: 11 wt% carbon in PEG; 73Z, A, T or S: 73 wt% ZrO2, Al2O3, TiO2 or SiO2). As the amount of PEG added was increased, TiO2, ZrO2 and Al2O3 containing catalysts showed 100 % of conversion whereas the yields of carbon and methane decreased in the order 16N63C21A>16N53C31Z>16N53C31T (16N: 16 wt% Ni; 53 or 63C: 53 or 63 wt% carbon in PEG; 21 or 31A, Z or T: 21 or 31 wt% Al2O3, ZrO2 or TiO2). 16N53C31Z and 16N53C31T did not show change in pore structure after the reaction, although the sizes of Ni species increased.
The effects of zeolite structure on rhodium phosphide (Rh2P) formation, dispersion and hydrodesulfurization (HDS) activity were investigated. TPR showed that the order of maximum peak temperature for phosphates reduction was Na-beta>NaMFI>NaMOR. The XRD patterns of reduced catalysts revealed that the order of Rh2P formation temperature agreed with that of phosphate reducibility. CO uptake of NaMOR-supported catalyst was much lower than those of other zeolite-supported catalysts. These results suggested that since the NaMOR support had a one-dimensional channel, the phosphates and Rh species did not easily diffuse into the micropores. The order of thiophene HDS conversion was NaMFI>Na-beta>>NaMOR. The order of average particle size of Rh2P calculated from TEM images was NaMOR>Na-beta ≈ NaMFI. Since formation of Rh2P on the Na-beta needed high reduction temperature, the beta structure might be partially collapsed. Well-dispersed Rh2P was formed on NaMFI at lower reduction temperature, so that this catalyst exhibited the highest HDS activity among the zeolite-supported catalysts.
Nanostructured (Cu–ZnO/SiO2 and Cu/ZnO) catalysts are prepared by sol-gel and surface impregnation combustion methods with inexpensive raw materials and easily-operated conditions. The X-ray diffraction patterns and SEM analysis reveal that Cu crystallite and particle sizes prepared by surface impregnation combustion method are rather smaller. During the combustion process, the support SiO2 can absorb heat and promote heat transfer, realizing a significantly mild and smooth catalyst-preparation process. As-prepared catalysts are tested in low-temperature methanol synthesis from syngas containing CO2, with ethanol as a catalyst and solvent at 443 K and 5.0 MPa for 8 h. The activity and methanol selectivity of the supported Cu–ZnO/SiO2 catalyst are much higher, which are closely related the metallic Cu surface area and Cu crystalline sizes. The different properties of as-prepared catalysts are investigated by XRD, TG-DTA, FT-IR, Raman spectrum, SEM, BET and N2O chemisorption techniques in detail. Here, the support SiO2 has a function of heat transfer to make catalysts preparation process much smoother, besides the dispersion effect.
This study investigated the transfer of oxygen and hydrogen species from steam to product during the catalytic cracking of heavy oil with iron oxide-based catalysts containing zirconia and alumina. Light oil and carbon dioxide were produced in the catalytic oxidative cracking of petroleum residual oil in the presence of steam. The alkene/alkane ratio of light aliphatic hydrocarbons decreased and carbon dioxide yield increased with higher flow rate ratio of steam to feedstock. The steam catalytic cracking of dodecylbenzene as a model compound of heavy oil showed lower alkene/alkane ratio and generation of a small amount of oxygen-containing compounds. The oxygen species derived from steam reacted with heavy oil and were transferred to carbon dioxide and a small amount of oxygen-containing compounds, producing hydrogen species from the steam. The hydrogen species were transferred to light hydrocarbons, thus suppressing alkene generation. The alkene/alkane ratio decreased with higher supporting zirconia content in the catalyst because zirconia promotes hydrogen generation from steam.
Desulfurization of heavy oil using steam was examined by catalytic cracking of atmospheric residual oil (AR) with iron oxide-based catalyst. The yield of hydrogen sulfide increased with higher ratio of steam to feedstock, whereas hydrogen sulfide was little produced in AR cracking without steam. Sulfur concentration of oil decreased to half that of feedstock, and some sulfur compounds were deposited on the catalyst. Oxidative cracking of heavy oil using oxygen species derived from steam produced hydrogen species from steam, so part of the hydrogen species reacted with heavy sulfur compounds on the catalyst to produce hydrogen sulfide, light sulfur compounds, and hydrocarbons. Some oxygen species could be transferred to sulfur dioxide. Therefore, hydrogenation and oxidation by the hydrogen and oxygen species derived from steam can cause desulfurization of AR. Cyclic sulfur compounds containing a thiophene ring in heavy oil are less reactive than acyclic sulfur compounds, so the reactivity of cyclic sulfur compounds was examined by catalytic cracking of dibenzothiophene. Dibenzothiophene was decomposed with the catalyst to produce carbon dioxide and hydrogen sulfide. Therefore, both acyclic and cyclic sulfur compounds can be decomposed with the catalyst and steam.
Dependence of hydrogen production via the catalytic steam reforming of ethanol on the metal oxide support and first row transition metal catalyst was investigated. Ni supported on CeO2 was more easily reduced and began to produce hydrogen at a lower temperature than Ni supported on ZrO2, SiO2, Al2O3, and MgO. Ni/CeO2 also maintained a high activity at a constant reaction temperature of 673 K and inhibited carbon deposition. Therefore, CeO2 was adopted as the catalytic support. Compared with Ni/CeO2, Fe/CeO2 and Mn/CeO2 were less active. Contrarily, Co/CeO2 was slightly less active at 673 K, but exhibited a comparable hydrogen yield at 873 K. The Cu/CeO2 system was reduced more readily and produced hydrogen at a lower temperature, but its activity gradually deteriorated by carbon deposition. Thus we concluded that Ni/CeO2 exhibited the best combination of properties with the highest hydrogen yield at 673 K and a long stability.