Deoxygenation Activity Research Articles

Hydrodeoxygenation of guaiacol over modified coconut carbon supported Ni nanoparticles catalysts under alkaline condition

The efficient utilization of lignin from the papermaking black liquor has attracted interest due to its carbon-neutral value and industrial application. This work illustrates a simple support-phosphate-pretreatment strategy to develop superdispersed Ni species in activated carbon (AC) to enhance the hydrodeoxygenation (HDO) reactions of the lignin model compound guaiacol into biohydrocarbons under alkaline conditions. For the first time, sodium polyphosphate was applied as a pretreatment agent for coconut carbon in the synthesis of carbon-supported Ni catalysts. Superdispersed Ni nanoparticles were achieved on Ni/NaPnOAC with a particle size of 2.5 nm, which was much smaller than that on unmodified Ni/C (13.1 nm). The characterization results and reactions revealed that the P−O that formed served as anchoring sites for the Ni species and strengthened the interaction between the Ni species and support (SMSI), which resulted in significantly improved dispersion of the Ni metal sites and, thus, a nearly 6-fold greater yield of hydrocarbons was obtained on Ni/NaPnOAC (58.1%) than on Ni/C (10.1%). In addition, compared with Ni2P/NaPnOAC and NiS/NaPnOAC, Ni/NaPnOAC exhibited higher HDO activity, especially higher direct deoxygenation (DDO) activity and higher benzene yield, reducing hydrogen consumption during the HDO reaction.

Deoxygenation and isomerization activity balance for NiMo/ZSM-23 catalysts as an effect of Mo/(Ni+Mo) ratio in hydroprocessing of fatty acids

Series of Ni-Mo catalysts based on ZSM-23 zeolite were synthesized by incipient wetness impregnation – with a fixed content of Ni (5 wt. %). These catalysts were tested in a hydroprocessing of a mixture of fatty acids (C16-C18) in a flow reactor at a temperature of 300 °C, a pressure of 2.5 MPa and WHSV = 8.4 h-1. The influence of the ratio of metals on the formation of forms of the active component, as well as on the activity, selectivity to iso-alkanes and the stability of catalysts during the hydroprocessing of a mixture of undiluted fatty acids was determined. The ratio of metals was investigated in the range from 0 to 1. The highest deoxygenation activity and highest isoalkanes yield were found for sample with Mo/(Ni+Mo) ratio equal 0.25, in which, according to the XPS, the Mo/(Ni+Mo) ratio on the surface is 0.4.

Soybean oil-based green diesel production via catalytic deoxygenation (CDO) technology using low-cost modified dolomite and commercial zeolite-based catalyst

Green diesel derived from sustainable biomass is an alternative and potential energy source to petroleum fossil fuel replacement in response to reducing carbon footprint and achieving a circular economy, which has sparked public interest and concern in advancing renewable energy development. Catalytic deoxygenation (CDO) is a promising method because it can process a wide variety of feedstocks and produce a diverse range of fuels. The CDO of soybean oil (SO) was executed using a modified low-cost dolomite catalyst denoted as NiO-CD catalyst and its performance has been compared with commercial zeolite heterogeneous-based catalysts such as ZSM-5, HY-zeolite and FCC. The NiO-CD catalyst exhibited exceptional deoxygenation ability, attaining an 88.6 % removal efficiency of oxygenated compounds, markedly surpassing all commercially available zeolite catalysts. The highest degree of CDO of SO via decarboxylation/decarbonylation (deCOx) reaction was achieved due to improvement in particle size, mesoporous structure and the presence of the synergistic effect of modified bi-functional acid-base properties of NiO-CaO/MgO catalyst. To investigate the effect of NiO-CD catalyst loading ranging from 1 to 7 wt%, a One Factor At a Time (OFAT) optimisation study was performed. The current study found that an optimised NiO-CD catalyst loading of 5 wt% yielded the highest green diesel (50.5 wt%) with an 88.63 % hydrocarbon composition. The influence of catalyst loading on deoxygenation activity is significant in green diesel production using NiO-CD catalyst.

Porous hollow nanospheres nickel phosphide and its high catalytic hydrogenation performance on naomaohu coal soluble portion and model compounds

The catalytic conversion of oxygen-containing aromatic ring in lignite under mild conditions is crucial to obtain clean liquid fuel. Here, hollow nanosphere Ni3P-500–24 catalysts were prepared at a calcination temperature of 500 °C and acid-etching time of 24 h. The porous hollow nanospheres structure could expose more catalytic sites, and the electron-rich nickel exhibited a good catalytic activity. The conversion rate of benzyl phenyl ether (BPE) was 100 % (140 ℃, 1 MPa H2, 2 h), and the main products were methylcyclohexane and cyclohexanol, indicating that the catalyst had good catalytic hydrocracking performance. In addition, the catalyst exhibited certain deoxygenation activity and high product selectivity for other oxygen-containing model compounds. For the catalytic hydrogenation of Naomaohu coal (NMHC) soluble portion, the content of alkanes increased from 19 % to 47 %, while the content of oxygen-containing compounds decreased from 56 % to 21 %, which further demonstrate that the catalyst have good catalytic hydrogenation and deoxygenation performance. Density Functional Theory (DFT) calculations showed that the properties of the Ni3P-500–24 catalyst was similar to noble metal, which could activate H2 to produce two kind of active hydrogen: H radical and diatomic hydrogen. The synergistic pathways for the transfer of active hydrogen during the catalytic hydroconversion (CHC) process were analyzed. Above results could provide theoretical guidance for the conversion of lignite into high-quality clean liquid fuels.

Catalytic deoxygenation of waste cooking oil for sustainable bio-jet fuel: A comparative study of Ni-Co/SBA-15 and Ni-Co/SBA-15-SH catalysts

This study focuses on the sustainable production of bio-jet fuel through the catalytic deoxygenation of waste cooking oil. The properties of two distinct catalysts at different Ni and Co loading (5 and 10 wt%), 5Ni5Co/SBA-15, 5Ni10Co/SBA-15, 10Ni5Co/SBA-15, 5Ni5Co/SBA-15-SH, 5Ni5Co/SBA-15-SH, and 10Ni5Co/SBA-15-SH were explored. It was observed that the functionalization of SBA-15 with silane (-SH addition) has successfully maintained the porous hexagonal structure, which is proven in the XRD and HRTEM analysis. Indeed, the presence of -SH in the bimetallic catalysts has contributed to increased surface area and pore size, as observed in the 5Ni5Co/SBA-15-SH catalyst. It was revealed that the bimetallic catalysts with 10 wt% of Ni and Co were not favorable as high metal content possibly blocked the porous support, reducing the active sites of the catalysts and decreasing deoxygenation activity. Indeed, the 5Ni5Co/SBA-15-SH catalyst showed superior performance of deoxygenation activity by producing 80 % of yield with 92 % of bio-jet selectivity, owing to the porous properties of the catalyst, which exhibits a substantial surface area (509 m2/g) and a significant pore size (4.4 nm). Furthermore, adding silane has successfully increased the acidic strength of the catalyst and promoted an efficient deoxygenation reaction. The result revealed that the wt% of metal loading and the functionalization of SBA-15 with silane has successfully improved the catalytic performance, leading to an efficient deoxygenation activity.

Efficient and stable Fe-Ce-Al catalyst for catalytic deoxygenation of lignin for phenol and hydrocarbon-rich fuel: Effect of the synthesis method

To develop a structure-tailoring catalyst for catalytic conversion of lignin for value-added chemicals, a series of novel Fe-Ce-Al metal oxide catalysts was synthesized via different methods to tailor activity and structure for catalytic pyrolysis of lignin to enhance hydrocarbon-rich bio-oil. The results revealed that FeCeAl-CO catalysts derived from coprecipitation method with smaller particle sizes exhibited excellent catalytic deoxygenation activity due to higher Lewis/Brønsted acid, reversible Ce3+/Ce4+ redox pairs, tailorable oxygen vacancies and promoted β-O-4, aromatic-OCH3 and side-chain cleavage. Additionally, coprecipitation method was facilitated to enhance hydrogen transfer, side-chain cleavage and aromatization reactions, while wet impregnation was beneficial to enhance demethoxylation and H-abstraction activity. During catalytic pyrolysis process, over 57.91% of hydrocarbon, including 20.21% and 25.71% for aromatics and olefins were achieved over FeCeAl-CO catalyst. Over 60.74% phenols and 52.48% alkylphenols were obtained over Fe-Ce/Al2O3-IM catalyst due to synergistic effect of FeOx and CeOx species. Fe-Ce-Al catalyst exhibited great activity and stability after fourth run, greater Brønsted acid-favored lignin cleavage and coke deposition, and metal active species leaching, oxidation and pore blockage were the key reasons for deactivation. Therefore, these findings could provide a cost-effective method for designing structure-tailoring catalysts for direct catalytic deoxygenation of lignin to generate hydrocarbon-rich upgrading bio-oil.

Catalytic fast pyrolysis of waste pine sawdust over solid base, acid and base-acid tandem catalysts

Catalytic pyrolysis is an effective means for high-value utilization of biomass. This study investigated the effect of solid base catalysts (CaO, calcium aluminate catalysts CaAl-1, CaAl-2, CaAl-3), acid zeolite catalysts (ZSM-5, Fe/ZSM-5, Co/ZSM-5, Ni/ZSM-5, Cu/ZSM-5, Zn/ZSM-5) and base-acid tandem catalysts on pine sawdust pyrolysis using Py-GC/MS. Acid zeolite catalysts exhibited robust deoxidation and aromatization capabilities, favoring aromatics, while solid base catalysts yielded more phenols and ketones. Among the solid base catalysts, CaAl-3 (CaO-Ca12Al14O33) showed comparable deoxygenation activity to CaO and optimal aromatic selectivity with structural stability. Zn/ZSM-5 excelled in deoxygenation and aromatic selectivity (70.42%) among metal-modified ZSM-5 catalysts. Base-acid tandem catalysis promoted the formation of aliphatics and BTX (benzene, toluene, xylene) while suppressing polycyclic aromatics. The highest BTX content (44.35%) was achieved with CaO-Ca12Al14O33&Zn/ZSM-5 tandem catalysts in a 1:3 ratio. This work demonstrates base-acid tandem catalysis as a promising approach for converting pine sawdust into valuable chemicals.

Synthesis of LaNiCeO2 Mixed Oxide with Various Microcrystalline Cellulose Templated for Deoxygenation of Waste Cooking Oil

The synthesis of LaNiCeO2 mixed oxides utilizing varying proportions of microcrystalline cellulose (MCC) (12.5%, 25%, and 37.5%) has been successfully achieved. The resulting materials were characterized through XRD, FESEM, N2 adsorption-desorption isotherms, and TGA- DTG. XRD analysis confirmed that all synthesized LaNiCeO2 mixed oxides exhibited a stable CeO2 phase. Notably, increasing the MCC content led to an improvement in the catalysts’ pore volume and surface area, with the LaNiCeO2-12.5% MCC sample exhibiting a primarily mesoporous structure and minimal micropore contribution. The LaNiCeO2-25% MCC catalyst demonstrated optimal physicochemical properties, indicating its high suitability for catalytic applications. The catalytic deoxygenation of waste cooking oil (WCO) was carried out in a semi-batch reactor at 380 °C for a duration of 4 hours, with a catalyst loading set at 1% of the WCO’s weight. The LaNiCeO2-12.5% MCC catalyst exhibited exceptional deoxygenation activity, achieving a 100% conversion, a liquid product yield of 45%, and hydrocarbon selectivity of 98%. The excellent catalytic performance is due to the synergistic interaction between Ni, Ce, and La metals, combined with improved properties that promote the deoxygenation reaction. These results highlight the potential of LaNiCeO2 as an effective catalyst for biofuel production.

Adsorption variations on the Ni(111) surface: electron density diversity from oxygen-containing functional groups

The disparities in adsorption stem from surface charge polarization effects, which may originate from the bond-order-induced effect, serving as a driving force to promote additional deoxygenation activities.

Continuous flow upgrading of lignin pyrolysis oils to drop-in bio-hydrocarbon fuels over noble metal catalysts

Although there are many studies on the noble metal-based catalysts for the hydrodeoxygenation (HDO) of lignin model compounds such as phenols, HDO studies on lignin biomass pyrolysis oil are relatively scarce. Owing to its complex composition (i.e., a mixture of phenolic monomers and oligomers), the activity and stability of the catalysts for the HDO of pyrolysis oil are significantly different from those for the model compounds. In this study, the catalytic performances of typical HDO catalysts, that is, Ru, Pd, Ru-Re supported on carbon, and the effects of process parameters such as solvent, temperature, and space velocity were investigated for the real lignin pyrolysis oils in a continuous-flow trickle bed reactor system for the first time. We demonstrated that proper tuning of catalyst composition and process parameters allows for producing the deoxygenated hydrocarbon mixtures which can be used for gasoline, jet fuel, and diesel fuels. Specifically, activated carbon promoted the HDO of lignin oil more effectively than acidic supports like HZSM-5 and TiO2 due to the weak adsorption of phenolic molecules. Among the different metals, Ru-Re supported on carbon exhibited the highest deoxygenation activity due to the synergy of the two metals. Tetrahydrofuran was the best solvent for lignin oil processing due to its high solubility and inertness to other side reactions (e.g., excess alkylation with ethanol solvent). The use of low space velocity of 0.2 h−1 and intermediate temperature of 350 °C resulted in the highest yield of the upgrade oil (∼25 wt%) simultaneously with the high level of deoxygenation (O/C < 0.04), mainly consisting of branched cycloalkanes. The causes of the catalyst deactivation and regeneration process are also discussed to provide practical significance.

Heterogeneous La and CeOx co-promoted SAPO-11 catalyst for catalytic upgrading of cellulose-derived volatile and methanol into hydrocarbon-rich fuels

In this paper, a series of La–Ce co-doped SAPO-11 catalysts with various La to Ce ratio were developed via wet impregnation method then employed in catalytic cellulose and methanol co-pyrolysis to produce hydrocarbon-rich biofuels. Comprehensive characterization technologies including X-ray diffraction, X-ray photoelectron spectroscopy, N2 physisorption, scanning electron microscope, transmission electron microscope, ammonia temperature-programmed desorption, Pyridine-infrared, and thermal gravimetric analyzer, were conducted to unveil the physicochemical properties, structure properties and acidity of as-prepared catalysts. Additionally the product content; aromatic selectivity and synergetic effect were also investigated. Additionally possible conversion pathway, deactivation mechanism and reusability were also deduced. La and Ce showed a certain synergetic effect and exhibited superior catalytic deoxygenation activity due to La–O and Ce-Ox species, suitable Brønsted acidity, abundant oxygen vacancies and enhanced mesopores structure, which was facilitated to promote the selectivity of hydrocarbon. Higher La content was fascinated to generate furans and ketones compounds, due to lower Brønsted acid site and smaller specific surface area. In contrast, higher CeOx content was beneficial to hydrocarbon formation via Diels-Alder reaction and dehydro-aromatization due to higher Brønsted acid site, total acidity, higher specific surface area, mesoporous pore volume as well as strong oxygen affinity of CeOx. The maximum proportion hydrocarbon, aromatics and minimum contents coke was obtained over 1La–1Ce/SAPO-11 were 77.96 %, 55.82 % and 9.81 %, respectively. Additionally, 1La–1Ce/SAPO-11 catalyst exhibited outstanding reusability and stability after four cycles; nearly ∼96 % relative content of hydrocarbon was maintained after regeneration test. Hence, the insight into the synergetic catalysis between La and CeOx species could provide a new potential possible pathway for design and synthesized efficient and eco-friendly bimetallic catalyst for selective catalytic deoxygenation organic solid waste biomass for valuable chemicals.

Effect of polypropylene pyrolyzate as the solvent on hydrodeoxygenation of palm oil using Ni-Cu/ZrO2 catalyst

Green diesel is a biofuel that can be used directly in diesel engines and can be synthesized by hydrodeoxygenation (HDO) reaction of triglyceride (TG). Generally, this reaction requires a high hydrogen pressure (40–150 bar) and a high composition of organic solvent to facilitate a higher hydrogen solubility in the liquid phase. In many cases, long carbon-chain alkanes, mostly n-dodecane, have been used as solvents. The present work aims to investigate the potential of hydrogenated and non-hydrogenated polypropylene (PP) pyrolyzate as solvents in an effort to utilize plastic wastes in HDO reaction of palm oil. The reaction was carried out using bimetallic catalyst Ni-Cu/ZrO2 in a reactor with a hydrogen gas self-inducing impeller to facilitate a higher load-up hydrogen gas in the liquid phase. The effect of reaction time in HDO involving two solvents, i.e., PP pyrolyzate and hydrogenated PP pyrolyzate, was elucidated in this work. The results showed that hydrogenated PP pyrolyzate facilitates a higher deoxygenation activity than PP pyrolyzate. In addition, the synthesized bimetallic catalyst promoted the decarbonylation/decarboxylation route over the hydrodeoxygenation route at reaction temperatures of 280–350 °C. The conversion of TG increased from 51 % to 93 % by increasing the reaction temperature from 280 °C to 350 °C, with the corresponding highest yield of green diesel was 82 %. Therefore, the hydrogenated PP pyrolyzate can substitute the usual long carbon-chain alkanes.

Catalytic conversion of lignin into monoaromatic hydrocarbons over a Ni/Al hydrotalcite-derived catalyst

Lignin is the most abundant aromatic biopolymer. Thus, preparation of BTX (benzene, toluene and xylenes) by catalytic fast pyrolysis (CFP) of lignin is attractive. Ni-Al mixed metal oxide (MMO) catalysts, derived from pyrolyzing Ni-Al layered double hydroxides (LDH), were prepared for the catalytic fast pyrolysis of lignin. The effects of catalyst Ni/Al ratio, catalyst dosage and pyrolysis temperature on the liquid products were investigated by Py-GC/MS. The Ni3Al3-MMO produced the best liquid product distribution from lignin at 700 ℃. The selectivity of Ni3Al3-MMO for aliphatic hydrocarbons and monocyclic aromatic hydrocarbons (MAHs) was 18.0% and 78.2%, respectively. The selectivity to polyaromatic hydrocarbons (PAHs) was 3.8%. No phenols and phenolic derivatives were produced. This is related to the mesoporous catalytic structure (pore size of 14.37 nm), large external surface area (134.74 m2/g) and strong acidity (4.92 mmolNH3/g) of Ni3Al3-MMO. In addition, a mechanistic study was performed with the lignin model compound (guaiacol) showing that Ni3Al3-MMO exhibits strong deoxygenation activity for aromatic C–O bond cleavage of lignin.

Preparation of Co–Co9S8–MoS2 catalyst for efficient deoxygenation of lignin-derived aromatic oxy-compounds into arenes

The formidable challenge for the deoxygenation of lignin-derived aromatic oxy-compounds into arenes under mild conditions is how to engineer a robust catalyst. In this study, Co–Co9S8–MoS2 catalyst was prepared via thermal decomposition, in–situ sulfidation and following by H2 reduction, where Co was highly dispersed and mainly existed in the species of metallic Co and Co9S8. This catalyst exhibited high activity, allowing the reaction temperature for cleaving Caromatic–O bond lowered to 120 °C, which was attributed to that metallic Co accelerated the H2 dissociation and then enhanced the deoxygenation activity. Co–Co9S8–MoS2 also presented a high stability: both the conversion and product selectivity were unchanged after 8 continuous cycles, and the characterization results evidenced almost no structure change and sulfur loss during the deoxygenation reaction. In addition, other 20 aromatic oxy-compounds including acid, ester, guaiacol and dimer lignin linkages were also successfully deoxygenated, and the arenes selectivity could maintain higher than 98 %. This work offered a new strategy for constructing metal–sulfide–MoS2 type catalysts and provided an efficient route towards the practical application in bio-oil upgrading.

Lithium–Sodium Fly Ash-Derived Catalyst for the In Situ Partial Deoxygenation of Isochrysis sp. Microalgae Bio-Oil

The catalytic potential of Na and LiNa fly ash (FA) obtained through a simple solid-state synthesis was investigated for the pyrolysis of Isochrysis sp. microalgae using a fixed bed reactor at 500 °C. While both LiNa-FA and Na-FA catalysts reduced the bio-oil yield and increased char and gas production, LiNa-FA was found to enhance the quality of the resulting bio-oil by decreasing its oxygen content (−25 wt.%), increasing paraffins and olefins and decreasing its acidity. The deoxygenation activity of LiNa-FA was attributed to the presence of weak and mild base sites, which enabled dehydration, decarboxylation, ketonisation, and cracking to form olefins. The bio-oil generated with LiNa-FA contained higher amounts of alkanes, alkenes, and carbonated esters, indicating its capacity to chemisorb and partially desorb CO2 under the studied conditions. These findings suggest that LiNa-FA catalysts could be a cost-effective alternative to acidic zeolites for in situ deoxygenation of microalgae to biofuels.

The role of vanadium oxide species on the performance of Pd/VOx/SiO2 catalysts for HDO of phenol

This work investigates the effect of vanadia species on the performance of Pd/VOx/SiO2 catalysts containing different vanadia loadings for HDO of phenol in the gas phase. in situ XANES experiments reveal the presence of a mixture of V2O4 and V4O7 species for all catalysts after reduction at 573 K. In situ XRD and XANES demonstrate that Pd particles and VOx species are in close contact, which is likely due to the presence of polymerized vanadate species, regardless of vanadia content, as shown by UV–Vis spectroscopy. This close contact promotes the selective hydrogenation of the C = O bond or the cleavage of the C-O bond, producing benzene. The strong interaction between the oxygen of the tautomer intermediate molecule and the oxygen vacancies associated with the presence of V3+ and V4+ cations is responsible for the deoxygenation activity of Pd/VOx/SiO2 catalysts.

In-situ deoxygenation of methyl palmitate to hydrocarbons on highly dispersed Ni–Re/TiO2 catalyst in aqueous phase using methanol as a hydrogen donor

Herein, TiO2 supported Ni–Re alloy catalysts (i.e., NiRe(x:y)/TiO2, x:y denotes the Ni/Re atomic ratio) were prepared and tested for in situ deoxygenation of methyl palmitate to hydrocarbons in aqueous phase using methanol as hydrogen donor. Raman spectra indicates that there is interaction between NiO and ReO4− species via forming Ni–O-Re(=O)3 species in the calcined catalysts, which contributes to the formation of Ni–Re alloy and promotes the Ni dispersion during the reduction with H2. Particularly, the Ni–Re alloy particles with average size of ∼1.4 nm highly disperse on spherical TiO2 particles (∼14 nm in diameter) in NiRe(3:4)/TiO2 (the nominal Ni content of 3 wt%). XPS reveals a charge transfer from metallic Ni to Re in the Ni–Re alloy. In in situ deoxygenation of methyl palmitate, compared with Ni/TiO2, NiRe(x:y)/TiO2 give remarkably higher deoxygenation activity and lower activity for the C–C bond hydrogenolysis, ascribed to the synergistic effect between Ni and Re species and the geometrical effect of Re, respectively, which are further verified by propanoic acid-TPD and TPSR. The yield of C6∼C16 liquid hydrocarbons can achieve as high as 98.0% on NiRe(3:4)/TiO2 at 330 °C. There is no obvious sintering of Ni–Re alloy and support TiO2 particles during the recycling of NiRe(3:4)/TiO2, while the carbon deposition and the leaching of Re species slightly reduce the catalyst activity.

Increased high selectivity light aromatics and furans production by co-feeding methanol to catalytic pyrolysis of cellulose with Lanthanum–Cerium bimetallic modified MCM-41 catalysts

To develop a cost-effective La-based catalyst for conversion waste biomass into high valuable chemicals, bimetallic La–Ce modified MCM-41 catalysts with different La to Ce ratios were prepared by wet impregnation method, and successfully applied to catalytic pyrolysis of cellulose with methanol as hydrogen-donor. The synergistic effect, conversion pathway for promotion of furans and aromatic and deactivation mechanism were also evaluated in co-conversion process with different technologies. Results showed that, modified MCM-41 maintained mesoporous structure, and combination La, Ce-modified MCM-41 catalysts showed the best catalytic activity due to synergistic interaction of La–O species and Ce–O species with support as well as suitable mild strong acidity. Higher La content had remarkable advantage for advancing HCs and olefin content due to higher Brønsted acid intensity, and higher Ce content was facilitated to aromatic and furans conversion due to higher mesoporous volume. 1La–3Ce/MCM-41 demonstrated the most potential for furan formation (50.18%) and 1La–1Ce/MCM-41 exhibited best deoxygenation activity and obtained more than 61.16% HCs content and 35.15% MAHs selectivity via Diels-Alder reaction assist with acid centers and metal dispersion, furthermore, 1La–1Ce/MCM-41exhibited outstanding reusability and anti-coking performance, nearly 95% yield of HCs were still maintained after regeneration. Hence, catalytic pyrolysis vapor upgrading of waste biomass with La–Ce/MCM-41 had great potential to produce valuable fuels and chemical.

Moderate pressure boosts the aromatization activity of HZSM-5 zeolite during catalytic pyrolysis of lignocellulosic materials

Lignocellulose pyrolysis has been deeply investigated in the past years as a potential route for the production of advanced biofuels and biochemicals from residues and wastes. However, the effect of pressure has rarely been addressed in catalytic pyrolysis processes. Accordingly, the current work reports a comprehensive study on the pressure influence during the catalytic pyrolysis of different lignocellulosic materials (oak wood, cellulose, hemicellulose, and lignin) using nanocrystalline HZSM-5 zeolite as a catalyst and a downflow fixed-bed reactor. In thermal pyrolysis tests, pressure increase affects negatively the bio-oil* (organic components in the liquid products) since it reduces its yield in favor of the production of char and gases. However, in the case of the catalytic pyrolysis tests, working under moderate pressure (10 bar) has very positive effects on bio-oil upgrading, minimizing its oxygen concentration (< 10 wt.%) and sharply increasing the carbon yield of aromatic hydrocarbons, while the undesirable coke deposited on the catalyst surface can be even reduced. This finding denotes the occurrence of a remarkable synergistic effect between the pyrolysis pressure and the catalyst loading. These outstanding results are attributed to a more efficient activity of the zeolite under mild pressurization since both oxygenated species and light olefins are more strongly adsorbed over the catalyst surface, facilitating their subsequent transformation into aromatic hydrocarbons. The sharp enhancement of the deoxygenation and aromatization activity does not involve higher coke deposition over the zeolite surface, thus attenuating one of the major limitations of the lignocellulose catalytic pyrolysis process.

EFFECT OF MoO3 LOADING ON PRODUCT SELECTIVITY FOR CALCIUM PYROPHOSPHATE CATALYZED VAPOR PHASE LACTIC ACID DEHYDRATION

Calcium pyrophosphate and hydroxyapatite catalysts with varying C/P ratios have been previously used by our group for vapor phase dehydration of lactic acid to acrylic acid with almost 100&amp;#37; conversion and up to 78&amp;#37; acrylic acid selectivity. The activity was highly sensitive to acidity and basicity of the catalyst. Hence the catalyst with maximum activity, calcium pyrophosphate, was modified with MoO&lt;sub&gt;3&lt;/sub&gt; for modifying its acidity and to study its effect on product selectivity for lactic acid dehydration. The MoO&lt;sub&gt;3&lt;/sub&gt; modified calcium pyrophosphate with 5&amp;#37; MoO&lt;sub&gt;3&lt;/sub&gt; loading was used for vapor phase dehydration of lactic acid at 375&amp;deg;C using 50&amp;#37; lactic acid concentration with WHSV of 3 h&lt;sup&gt;-1&lt;/sup&gt;. The activity was compared with nonmodified calcium pyrophosphate catalyst. Surprisingly, deoxygenation was predominant compared to dehydration. Acidity was observed to play a crucial role in product selectivity (i.e,. with less acidic support, calcium pyrophosphate with 5 wt&amp;#37; MoO&lt;sub&gt;3&lt;/sub&gt; showed more deoxygenation activity as compared to acidic support &amp;gamma;-Al&lt;sub&gt;2&lt;/sub&gt;O&lt;sub&gt;3&lt;/sub&gt; as well as SiO&lt;sub&gt;2&lt;/sub&gt; with same MoO&lt;sub&gt;3&lt;/sub&gt; loading). Higher acidity led to formation of acetaldehyde as the only product. The results confirmed formation of propionic acid by deoxygenation of lactic acid using in situ generated hydrogen after decarboxylation of lactic acid to acetaldehyde.