Heteroatom Removal Research Articles

Sustainable Resource Recovery from Dairy Waste: A Case Study of Hydrothermal Co-liquefaction of Acid Whey and Anaerobic Digestate Mixture

Uncontrolled emission of carbon and nutrients due to mismanagement of dairy waste leads to global warming, eutrophication of water bodies, aerosol pollution, and acidification of ecosystems. We studied hydrothermal liquefaction (HTL) to sustainably recover resources by converting the dairy wastes into carbon-dense biocrude oil and a nutrient-rich aqueous-phase coproduct. We evaluated acid whey as an alternative source of acid catalyst, replacing acetic acid, for the HTL of anaerobically digested cattle manure (manure digestate). Using well-designed HTL experiments, we investigated the effects of several factors on the product formation and the fate of elements as well as the underlying chemistry. The investigated factors included reaction temperature (280–360 °C), reaction time (10–50 min), mixing ratio of acid whey to manure digestate (AW/MD of 0–2), and the amount of additional acetic acid required, that is, specified based on the final feedstock pH between 3.5 and 5.5. The experimental results suggested the following optimal conditions for enhanced biocrude oil formation and maximal nutrient yield in the aqueous-phase coproduct: AW/MD of 1.21, feedstock mixture pH of 4.5, and reaction temperature and time of 354 °C and 21 min, respectively. Under such conditions, the biocrude oil yield was enhanced to 40–50% (equivalent to 60–80% energy recovery) via cyclic acetalization, hydroxymethylation, isomerization, Piancatelli rearrangement, oxidation, and condensation with heteroatom removal via several deoxygenation and denitrogenation mechanisms. Moreover, these conditions provided adequate acidification to solubilize Mg-carbonate and Ca-phosphate minerals and catalyzed the deamination of N-heterocyclics and other nitrogenous compounds, producing a higher recoverable yield of Mg, NH3-N, P, and K nutrients in the aqueous-phase coproduct, that is, 60–70, 30–40, ∼40, and >95%, respectively. This study demonstrated the potential of using HTL for coprocessing manure digestate and acid whey to measurably valorize biomass waste as a key component of achieving a circular bioeconomy for the dairy industry.

Selective hydrogenation and defunctionalization of heavy oil model compounds using an unsupported iron catalyst

Developing practical, inexpensive catalysts for the partial upgrading of crude oil is essential for converting heavy oil to meet pipeline standards without diluent. Here we report that air-stable unsupported iron sulfide nanoparticles derived from a single-source homogeneous precatalyst, Fe2S2(CO)6, are highly effective catalysts for the partial hydrogenation of substituted anthracenes and aromatic nitrogen and sulfur heterocycles. The reactivity of the anthracene series is governed by stereoelectronic effects imposed by the phenyl substituents, decreasing in the order anthracene > 9-phenylanthracene > 9,10-diphenylanthracene. Nitrogen- and sulfur-containing heterocycles are partially hydrogenated, with limited heteroatom removal for benzothiophene, showing that the unsupported iron sulfide catalyst is well-suited for the selective partial hydrogenation and limited defunctionalization, which are key for catalytic partial upgrading of heavy petroleum. The unsupported iron sulfide nanoparticles also catalyze hydrogenation of mixed “feeds” comprising combinations of model compounds, demonstrating that carbocyclic and heterocyclic molecules can be processed simultaneously with little self-inhibition of overall activity, a key requirement for compositionally challenging bitumen feeds. Several techniques were used to characterize the iron sulfide nanoparticles, as well as the organic reaction products. The heterogeneous catalyst, generated in situ, was more active than a ball-milled commercial iron sulfide catalyst. The heterobimetallic precatalyst Co2FeS(CO)9 does not enhance the rates of hydrogenation.

Direct Hydrogen Production from Extra-Heavy Crude Oil under Supercritical Water Conditions Using a Catalytic (Ni-Co/Al2O3) Upgrading Process

The generation of hydrogen from unconventional oil is expected to increase significantly during the next decade. It is commonly known that hydrogen is an environmentally friendly alternative fuel, and its production would partially cover the gap in energy market requirements. However, developing new cheap catalysts for its production from crude oil is still a challenging area in the field of petroleum and the petrochemical industry. This study presents a new approach to synthesizing and applying promising catalysts based on Ni, Co, and Ni-Co alloys that are supported by aluminum oxide Al2O3 in the production of hydrogen from extra-heavy crude oil in the Tahe Oil Field (China), in the presence of supercritical water (SCW). The obtained catalysts were characterized via scanning electron microscopy (SEM), Brunauer-Emmett-Teller (BET) surface area analysis, transmission electron microscopy (TEM), and, X-ray diffraction analysis (XRD). The obtained XRD data showed 3.22% of Co2+ in the Co/Al2O4 catalyst, 10.89% of Ni2+ in the Ni/Al2O4 catalyst, and 1.51% of Co2+ and 2.42% of Ni2+ in the Ni-CoAl2O3 bimetallic catalyst. The BET measurements of the obtained catalysts showed a surface area ranging from 3.04 to 162 m2/g, an average particle size ranging from 0.037 to 0.944 µm, and micropore volumes ranging from 0.000377 to 0.004882 cm3/g. The thermal, SCW, and catalytic upgrading processes of the studied samples were conducted in a discontinuous autoclave reactor for 2 h at a temperature of 420 °C. The obtained results revealed that thermal upgrading yielded 1.059 mol.% of H2, and SCW led to 6.132 mol.% of H2; meanwhile, the presence of Ni-CoAl2O3 provided the maximal rate of hydrogen generation with 11.783 mol.%. Moreover, Ni-CoAl2O3 and NiAl2O3 catalysts have been found to possess good affinity and selectivity toward H2 (11.783 mol.%) and methane CH4 (40.541 mol.%). According to our results, the presence of SCW increases the yield of upgraded oil (from 34.68 wt.% to 58.83 wt.%) while decreasing the amount of coke (from 51.02 wt.% to 33.64 wt.%) due to the significant amount of hydrogen generation in the reaction zone, which reduces free-radical recombination, and thus, improves oil recovery. Moreover, the combination of SCW and the synthetized catalysts resulted in a significant decrease in asphaltene content in the upgraded oil, from 28% to 2%, as a result of the good redistribution of hydrogen over carbons (H/C) during the upgrading processes, where it increased from 1.39 to 1.41 in the presence of SCW and reached 1.63 in the presence of the Ni-CoAl2O3 catalyst. According to the XRD results of the transformed form of catalysts (CoNi3S4), after thermal processing, heteroatom removal from extra-heavy crude oil via oxidative and adsorptive desulfurization processes is promoted. These findings contribute to the expanding body of knowledge on hydrogen production from in situ unconventional oil upgrading.

Flash pyrolysis of oil shale assisted by Zr-doped TiOSO4 nanocomposites: Excellent selectivity for hydrocarbons and toluene

Oil shale (OS) is among the most promising alternatives to replace/complement the conventional fossil fuels of limited reserves. The manufacture of qualified petroleum-like fuels and/or value-added chemicals by a catalytic OS pyrolysis with low energy consumptions has drawn broadattention from numerous scientific and engineering communities. While the past decades have witnessed great advancements in this regard, it is still strongly desired to inaugurate new catalysts for efficient OS utilizations, since most of the currently existing catalysts either suffer from tedious pretreatments on OS, complicated fabrication, high costs, easy deactivation by pore blockage, time-consuming impregnation, or unsatisfied selectivity etc. Herein, we report that Zr-doped TiOSO4 nanocomposites could be facilely synthesized via a simple wet-chemical-calcination method. It is found that the as-fabricated nanohybrids could induce ∼10% decrements in the activation energy of OS pyrolysis, and the quality of the pyrolyzates could be greatly enhanced, where the content of heteroatomic compounds decreases from ca. 38.3% to 17.1% (55.4% reduction), that of the medium/long-chain aliphatic hydrocarbons decreases from ca. 27.7% to 17.8% (35.7% decrease), while that of hydrocarbons and short-chain aliphatic hydrocarbons increases from ca. 61.7% to 82.9% (34.4% increase) and from ca. 19.6% to 46.3% (136.2% enhancement), respectively. More significantly, our catalyst could also induce an evident increase in the content of monoaromatic hydrocarbons, especially toluene (466.7% enriched, substantially), which is an important value-added platform chemical of broad interests, and a distinct decrease in the content of polyaromatic coke precursors (36.4% reduction), which are among the most frequently encountered undesired species during OS pyrolysis. It is proposed that the synergistic yet competitive effects of Brønsted and Lewis acid sites play important roles in the excellent catalytic performances of our nanocatalyst. Considering the strategic significance of OS and the easy availability of zirconium/titanium-based nanohybrids, our nanocatalyst with excellent heteroatom removal, anti-coke and cracking capabilities, and high selectivity for hydrocarbons, short-chain aliphatic and monoaromatic hydrocarbons (especially toluene), likely initiates new opportunities for OS pyrolysis, which is a subject of broad interest and general concern.

Catalytic hydrocracking of inedible palm stearin for the production of drop-in aviation fuel and comparison with other inedible oils

This work describes the use of palm stearin oil as a feed for the catalytic hydrocracking to produce the renewable aviation kerosene and diesel using the hydrocracking catalyst in a continuous flow fixed bed reactor. The efficacy of this method is evaluated using several reaction parameters, including hydrocracking temperature, hydrogen pressure, liquid hourly space velocity (LHSV), hydrogen to feed ratio (H2/feed) and time on stream (TOS). Higher temperatures and lower LHSVs are dominant to produce kerosene with maximum selectivity of 55.7%, while lower temperatures and LHSVs favoured the diesel production with maximum of 75.4% selectivity. The isomerization reactions were promoted by higher hydrocracking temperature due to the increase in iso-paraffins. The products consist of paraffins (96.9–99.3%), naphthenes (0.1–1.86%) and aromatics (0.2–1.59%). Aromatization reactions were also taking place in the process which is a considerable benefit of this method as aromatization reactions decrease hydrogen consumption. Moderate hydrogen pressure and H2/feed ratio favour the kerosene yield. The reaction mechanistic pathway was also proposed for converting palm stearin to biofuels. Furthermore, product yield, selectivity, heteroatom removal, and double bond saturation were also explored. The stability and activity of the catalyst were studied for 600 h without observable deactivation of the catalyst.

Effect of sequential thermal dissolution on the structure and pyrolysis characteristics of Naomaohu lignite

Cyclohexane-insoluble portion (CHISP), ethanol-insoluble portion (EISP) and isopropanol-insoluble portion (IPISP) were obtained by sequential thermal dissolution (STD) from Naomaohu lignite (NL), with cyclohexane (CH), ethanol (E) and isopropanol (IP) as the solvent. The insoluble portions were characterized by Ultimate analysis, Scanning electron microscope (SEM), X-ray photoelectron spectrometer (XPS), Fourier transform infrared spectrometer (FTIR), Thermogravimeter (TG-DTG) and Pyrolysis-chromatography/mass spectrometry (Py-GC/MS). As a result, compared to NL, the gradually increased of C element and decreased of O, N and S in the insoluble portion (ISP) demonstrated that STD is a carbon-rich and heteroatom removal process. The yield of CHISP reached 98.64 % and exhibited smooth surface. The existence of –COO– species in EISP and IPISP indicated that E and IP might be esterified or ester-exchanged with carboxylic acid, while the reduced >CO species illustrated that the nucleophilic oxygen atom in E and IP attacked the carbon atom on the carbonyl group in NL. The comprehensive structural parameter (CSPM) and comprehensive volatile release characteristics index (CVRCI) of NL, CHISP, EISP and IPISP were calculated by FTIR and TG-DTG, respectively. Results showed that STD process improves pyrolysis reactivity, and the CSPM was directly related to CVRCI, presenting a linear relationship (R2=0.952). That is, CSPM can be used as an important parameter to predict the pyrolysis reactivity (CVRCI) of coal. Py-GC/MS showed that, compared to NL, the number of group component was increased in CHISP and decreased in EISP and IPISP during the sequential thermal dissolution process, indicating that there might be non-covalent bond break and formation during the process

The effect of reaction time and temperature on the aquathermolysis process of heavy crude oil

Hydrothermal upgrading (HTU) performance during aquathermolysis process of heavy crude oil was conducted. All upgrading tests were conducted using a 300-ml autoclave batch reactor at 250 °C and 300°C under high pressure for 12, 24, 48, and 72 h in a nitrogen environment. Comprehensive analyses of physical and chemical characteristics of the upgraded oils, including viscosity, elemental composition, SARA fractions as well as Carbon number distribution in saturates of oil samples before and after upgrading, were studied to evaluate the hydrothermal upgrading performance. The results showed that, by increasing the reaction temperatures and times the upgrading performance was improved. The maximum upgrading performance was observed at 300 °C and 72 h for in terms of viscosity reduction, increasing the quantity and quality of saturates as a result of thermal decompositions of resin and asphaltenes, and increasing their quantity. In addition, an improvement in upgrading performance can be observed in the increasing of the H/C ratio, removing sulfur and nitrogen due to their desulfurization and denitrogenation. Generally, the obtained data showed that, HTU under studied conditions might be useful for heavy oil pretreatment due to the significant influence on viscosity reduction, heteroatoms removal as well as improving on its the main physical and chemical composition.

Quantum chemical hydrogenolysis strategy for elimination of heteroatoms in biomass homologous organic compounds based on oxolane and thiolane

Bio-oils obtained from biomass contain heteroatoms compounds, like oxolane and thiolane. It is quite difficult for industrialist to purify such refractory bio-oils. One of the efficient strategies for the elimination of heteroatoms is hydrogenolysis process, which results in the formation of H2O and H2S residues as by-products. In this work, quantum chemical studies have been used to analyse the reaction mechanism for the removal of hetero atoms (S and O) as H2O and H2S. We selected B3LYP functional of DFT with Pople's basis set 6-311G(d,p) for computing the hydrogenolysis steps without catalyst. LANL2DZ basis set, is used for studying hydrogenolysis steps involving AlCl3 and WS3H3+ as catalysts. All the reactions are analysed at the temperature of 600 K and pressure of 40 bars. Structural, thermodynamic, kinetic properties have been employed to study this process. The analysis of variations parameters during the hydrogenolysis process reveals that these two organic biomass compounds undergo sequential ring opening at C-X (X = O, S) bonds. Butanol and Butanethiol are obtained as a result of first hydrogenolysis process, and these compounds are converted to butane during second catalytic process while eliminating heteroatoms.

The structural evolution and mutation of graphite derived from coal under the influence of natural igneous plutonic intrusion

Graphite can be formed from coal under the influence of a pluton intrusion. However, the mechanism by which polyaromatic rings of disordered structure extend laterally and stack vertically during graphitization from coal to graphite remains unknown. Therefore, proximate and ultimate analysis, X-ray diffraction (XRD), Raman spectroscopy, Fourier-transform infrared spectrometer (FTIR), X-ray photoelectron spectroscopy (XPS), and high-resolution transmission electron microscopy were used to characterize a series of naturally graphitized coals collected from Lower Carboniferous strata in Xinhua county, Hunan province, China. The parameters derived from various analyses such as d002 and full width at half maximum (002) from XRD, ID/IG and I2D/ID + G from Raman spectroscopy, the proportion of sp2 and sp3 + Cvacancy from XPS, and the Aπ1 and Aπ2 from FTIR regularly change, indicating that the ordered graphite increased along with the removal of heteroatoms when approaching the pluton and the small condensed sp2–sp3 hybridized aromatic rings gradually transform to sp2 hybridized aromatic rings during graphitization. Furthermore, some parameters, such as ID/IG, La, Lc, and the proportion of sp2, changed dramatically in the semi-graphite stage, indicating that structural mutation of graphitized coal happens at the semi-graphite stage and the growth of Lc occurs slower than that of La during graphitization. The structural evolution can be divided into three stages: a. basic structural unit growth stage (<10 layers); b. fast growth stage of two-dimensional multilayer “ribbon-shaped” graphene (10–20 layers); c. three-dimensional-ordered microcrystal graphite growth stage (20–50 layers). The carbon-free radicals at layer edges and the conjugated π–π interaction force between graphite layers may be crucial in the stitching and stacking of polyaromatic rings.

Transformation of asphaltenes of vacuum residues in thermal and thermocatalytic processes

The work deals with the study of high molecular weight components of oils, namely with asphaltenes. The relevance of research aimed at studying the structural changes and thermal properties of asphaltenes under the conditions of heavy residual feedstock processing increases every year. It has been shown that the addition of NiCr-WC promotes the retardation of gas formation and an increase in the destruction of resins and asphaltenes of the vacuum residue.The average diameter of the aromatic layers (L a) increases from 8.10 to 10.58 Å in the cluster and decreases the number of aromatic layers in a cluster (M) and the average height of a cluster of aromatic layers (L c) from 7.58 to 5.09 and 26.70 to 18.34 Å respectively in the series ‘initial asphaltenes – asphaltenes after thermal processing – asphaltenes after thermocatalytic processing. Based on differential scanning calorimetry in the temperature range 400–700 °C, the destruction of asphaltenes is accompanied not only by the formation of low molecular weight hydrocarbon structures but the intensive removal of heteroatoms (S and N).

Nitrogen-doped porous carbon supported nickel nanoparticles as catalyst for catalytic hydroconversion of high-temperature coal tar

A novel and highly active nitrogen-doped porous carbon-supported nickel catalyst Ni@N-PC was successfully developed by a thermolysis of nickel-based zeolitic imidazolate frameworks growing on both sides of graphitic carbon nitride and used for catalyzing hydroconversion of isopropanol soluble portion from ultrasonic extraction of high-temperature coal tar (ISPHTCT). The active nickel nanoparticles were mainly encapsulated on the top of carbon nanotubes and partially dispersed on the surface of carbon nanosheets. Naphthalen-1-ol was used as a model compound to investigate the catalytic hydroconversion activity under different reaction conditions and reveal the mechanism for catalytic hydroconversion. The ISPHTCT and catalytic hydroconversion products of ISPHTCT (ISPCHCP) were analyzed with gas chromatograph/mass spectrometer. The results show that 70% of naphthalen-1-ol was converted at 160°C and completely converted at 200°C for 120 min, and the ISPHTCT was greatly upgraded. A total of 180 organic compounds including 33 nitrogen-containing organic compounds, 11 sulfur-containing organic compounds and 39 oxygenates were identified in ISPHTCT, while no obvious nitrogen-containing organic compounds, sulfur-containing organic compounds and oxygenates were detected in ISPCHCP, indicating the excellent performance of Ni@N-PC for heteroatom removal. All the alkenes, cyclenes and alkynes were saturated and the majority of arenes were converted to cyclanes by catalytic hydroconversion over Ni@N-PC, which exhibited high catalytic hydrogenation activity.

Catalytic ethanolysis of Dahuangshan lignite and directional upgrading of two derived soluble mixtures

An in-situ and ex-situ cascade upgrade strategy was designed and used for upgrading Dahuangshan lignite-derived soluble mixtures (LDSMs) to obtain value-added chemicals and clean liquid fuels (CLFs), respectively. In the H2-free catalytic ethanolysis, Ni/mordenite can effectively activate ethanol and promote the transfer of various free radicals including H·, CH3CH2·, and CH3CH2O·, which synchronously facilitates the cleavage of bridged bonds in Dahuangshan lignite and the in-situ removal of heteroatoms (HAs) from LDSMs. As a result, the total yield of LDSMs increased from 40.6 to 66.5 wt%, wherein that of ethanol-soluble portion (ESP) increased from 21.4 to 32.4 wt%. Interestingly, alkanes and arenes with higher relative content (RC, 38.1%) were detected in ESPC (for catalytic ethanolysis), while arenols (24.7%) dominate ESPN (for ethanolysis). The analysis with a quadrupole exactive orbitrap mass spectrometer further confirmed the significant decrease in the relative abundance of HAs, especially Ox class species, in ESPC. In addition, ESPN and ESPC with different properties were further used for enriching derived chemicals and for obtaining CLFs by catalytic hydroconversion (CHC), respectively. After the CHC, the total RCs of alkanes and cyclanes in the soluble portion (SP) are as high as 71.3%, and the content of HA-containing organic compounds was further decreased. Therefore, such SP containing less HAs is an attractive CLF precursor. A ternary mixed solvent was also designed for rapidly separating the SP from ESPN. The total RC of alkanes and arenes in PE5 as well as arenols in M5 are as high as 79.4 and 70.9%, respectively. Molecular dynamics simulations were further used to reveal the rapid enrichment mechanisms with ternary mixed solvents.

Transition metal carbides and nitrides as catalysts for thermochemical reactions

Transition metal carbides and nitrides (TMCs and TMNs) have attracted much attention due to their unique physical and chemical properties brought by the incorporation of interstitial carbon and nitrogen into the crystal lattice of the parent metals. Recent advances in utilizing TMCs and TMNs have revealed their intriguing catalytic properties in many industrially important reactions, including heteroatom removal, CO2 activation, alcohol reforming, and water–gas shift reactions. The promising activity, selectivity, and stability of TMCs and TMNs, either as catalysts or as supports for other metals, are often attributed to their strong interactions with the adsorbates, tunable surface properties, as well as the synergy with supported metals. This review summarizes the synthesis and characterization of TMC and TMN model surfaces and powder catalysts, and uses several case studies to demonstrate their unique catalytic properties in these important reactions. A discussion is also provided regarding the challenges and opportunities associated with the utilization of TMCs and TMNs in thermocatalysis.

Maximizing production of high-quality tar from catalytic upgrading of lignite pyrolysis volatiles over Ni-xCe/Y under CH4/CO2 atmosphere

In this paper, a novel process for integrating lignite pyrolysis volatiles upgrading with methane dry reforming (MDR) was carried out over Ni-Ce bimetallic catalysts in a fixed-bed reactor. The effects of Ni-xCe/Y catalysts on CH4/CO2 conversions, products distributions and tar compositions were investigated. The results indicated that the Ni-Ce bimetallic catalysts could significantly decrease coke deposit and obviously improve tar components, especially for light aromatics (LAs). The Ni-7Ce/Y catalyst exhibited better catalytic performance in pyrolysis volatiles upgrading in the respects of high light tar yield, selectivity to LAs, the resistance of coke deposition and the removal of heteroatoms in tar. The resultant high-quality tar could be attributed to the moderate acidity with suitable ratio of Brønsted/Lewis acid sites, better dispersion and strong interaction of Ni and Ce species on supports. The 2H NMR and GC–MS results confirmed that methane dry reforming participated in the tar formation, especially aromatic rings. This work could provide more insights into catalytic upgrading of lignite pyrolysis volatiles and sufficient utilization of CH4/CO2 greenhouse gases.

Effect of raw material composition on the structure of needle coke

The refined raw material was first prepared from the low-medium temperature coal tar through hydrogenationfor 1.5h under 330–390°C and 8MPa, with a catalyst/oil mass ratioof 1/40, which was then used to produce needle coke through thermalpolymerization and calcination. The composition of refined raw materials was analyzed by elemental analysis, Fourier-transform IR spectroscopy (FT-IR) and gas chromatography-mass spectrometry (GC-MS) and the structure of needle coke was characterized by scanning electron microscope (SEM), X-ray diffractometer (XRD) and polarizing microscope; the effect of raw material composition (related to the hydrogenation temperature) on the structure of needle coke was then investigated. Theresults indicate that a proper increase in thehydrofining temperature is beneficial to the removal of heteroatoms (especially sulfur). By hydrogenation at 390°C, the aromatics in the feedstock are polarized due to the cracking and polycondensation. In addition, a highercontent of tricyclic and tetracyclic aromatics in the refined raw materials may also lead to a highergraphitization degree for the needle coke product.

Progress of Phase Transfer Removal of Heteroatoms From Heavy Crude Oil

Progress of Phase Transfer Removal of Heteroatoms From Heavy Crude Oil

Monitoring single-heteroatom loss during deoxygenation and denitrogenation of soluble organic matter in coal using mass spectrometric methods

The structure-reactivity relationship during catalytic reactions for coal has been extensively simulated by using model compounds. However, the direct study of structure-reactivity relationship is not sufficient for coal, the complex mixture, partially due to the challenging task of monitoring catalytic reactions in complex mixtures at the molecular level. In this study, a tandem mass spectrometry (MS) approach was designed for selective observation of catalytic single-atom denitrogenation and deoxygenation reactions of a coal. According to the tandem MS data, structure of aromatic cores, total carbon number in alkyl chains, heteroatom release efficiency and preference of heteroatom removal on aromatic cores versus alkyl chains were explored and compared to reveal the relationship between heteroatom release pattern and molecular structure. Structure-reactivity relationship was not clearly observed in deoxygenation patterns due to majorities of molecules contain multiple oxygen atoms. However, structure-reactivity relationships were revealed in denitrogenation patterns due to the presence of single nitrogen atom in most nitrogen-containing molecules.

Hydrothermal Liquefaction of Water Hyacinth: Effect of Process Conditions and Magnetite Nanoparticles on Biocrude Yield and Composition

In this work, an efficient way of converting the water hyacinth to biocrude oil using magnetite nanoparticles (MNPs) as potential catalysts was demonstrated for the first time. MNPs were synthesised by co-precipitation and used in the hydrothermal liquefaction (HTL) of water hyacinth at different reaction conditions (temperature, reaction time, MNPs to biomass ratio and biomass to water ratio). The best reaction conditions were as follows: temperature— 320, reaction time—60 minutes, MNPs to biomass ratio – 0.2 g/g and biomass to water ratio – 0.06 g/g. HTL in presence of MNPs gave higher biocrude yields compared to HTL in absence of MNPs. The highest biocrude yield was 58.3 wt% compared to 52.3 wt% in absence of MNPs at similar reaction conditions. The composition of biocrude oil was analysed using GC-MS and elemental analysis. GC-MS results revealed that HTL in presence of MNPs led to an increase in the percentage area corresponding to hydrocarbons and a reduction in the percentage area corresponding to oxygenated compounds, nitrogenated compounds and sulphur compounds. Elemental analysis revealed an increase in the hydrogen and carbon content and a reduction in the nitrogen, oxygen and sulphur content of the biocrude when HTL was done in presence of MNPs compared to HTL in absence of MNPs. The nanoparticles were recovered from the biochar by sonication and magnetic separation and recycled. The recycled MNPs were still efficient as HTL catalysts and were recycled five times. The application of MNPs in the HTL of water hyacinth increases the yield of biocrude oil, improves the quality of biocrude through removal of hetero atoms, oxygen and sulphur compounds and is a potentially economical alternative to the traditional petroleum catalysts since MNPs are cheaper, widely available and can be easily recovered magnetically and recycled. This will potentially lead to an economical, environmentally friendly and sustainable way of producing biofuels from biomass.

Surface-Dependent Activation of Model α-Al2 O3 -Supported P-Doped Hydrotreating Catalysts Prepared by Spin Coating.

Requirements for improved catalytic formulations is continuously driving research in hydrotreating (HDT) catalysis for biomass upgrading and heteroatom removal for cleaner fuels. The present work proposes a surface-science approach for the understanding of the genesis of the active (sulfide) phase in model P-doped MoS2 hydrotreating catalysts supported on α-Al2 O3 single crystals. This approach allows one to obtain a surface-dependent insight by varying the crystal orientations of the support. Model phosphorus-doped catalysts are prepared via spin-coating of Mo-P precursor solutions onto four α-Al2 O3 crystal orientations, C(0001), A(11 0), M(10 0) and R(1 02) that exhibit different speciations of surface -OH. 31 P and 95 Mo liquid-state NMR are used to give a comprehensive description of the Mo and P speciation of the phospho-molybdic precursor solution. The speciation of the deposition solution is then correlated with the genesis of the active MoS2 phase. XPS quantification of the surface P/Mo ratio reveal a surface-dependent phosphate aggregation driven by the amount of free phosphates in solution. Phosphates aggregation decreases in the following order C(0001)≫M(10 0)>A(11 0), R(1 02). This evolution can be rationalized by an increasing strength of phosphate/surface interactions on the different α-Al2 O3 surface orientations from the C(0001) to the R(1 02) plane. Retardation of the sulfidation with temperature is observed for model catalysts with the highest phosphate dispersion on the surface (A(11 0), R(1 02)), suggesting that phosphorus strongly intervene in the genesis of the active phase through a close intimacy between phosphates and molybdates. The surface P/Mo ratio appears as a key descriptor to quantify this retarding effect. It is proposed that retardation of sulfidation is driven by two effects: i) a chemical inhibition through formation of hardly reducible mixed molybdo-phosphate structures and ii) a physical inhibition with phosphate clusters inhibiting the growth of MoS2 . The surface-dependent phosphorus doping on model α-Al2 O3 supports can be used as a guide for the rational design of more efficient HDT catalysts on industrial γ-Al2 O3 carrier.

Heterogeneous catalyst stability during hydrodenitrogenation in supercritical water

The catalytic removal of heteroatoms from renewable bio-oils in supercritical water (SCW) is challenged by the lack of sufficiently stable catalysts. We identified a library of catalytic materials that are thermodynamically stable under hydrodenitrogenation (HDN) conditions, based on oxygen fugacity–pH diagrams. From among these, we selected a Pt/TiO2 catalyst for HDN of propylamine in SCW at 380–500 °C and 22–38 MPa. Flow experiments with aqueous feeds of formic acid, ammonia, and propylamine were designed to isolate interactions between the catalyst, the SCW solution, and the reactants and products. The Pt/TiO2 catalyst was highly active and experienced negligible dissolution at 500 °C, 2% Pt loss at 380 °C, and no changes in oxidation state. Overall, the experimentally observed hydrothermal stabilities of the catalyst agreed with the thermodynamic stabilities predicted. The results and methodology applied in this work may be useful to identify and design catalysts for bio-oil upgrading in hydrothermal media.