The increasing energy consumption has made heavy oil more and more important in world energy system. However, the exploitation of heavy oil is still very challenging due to the high viscosity. Catalysts which can effectively promote heavy oil aquathermolysis to reduce the viscosity are in urgent demand. In this work, a Ni-based nanocatalyst for heavy oil aquathermolysis is fabricated through a sol-gel method. Characterizations with SEM, TEM, XRD, XPS, and VSM indicate that the fabricated nanocatalyst is magnetic Ni20(NiO)80 nanoparticles with diameter about 20 nm. The fabricated Ni20(NiO)80 catalyst shows excellent catalytic performance in promoting heavy oil aquathermolysis with the assistance of tetralin. The composition analyses of heavy oil after Ni20(NiO)80-catalyzed aquathermolysis demonstrate that the contents of light compositions in oil increase significantly and those of heavy compositions decrease significantly, resulting in up to 86.47% oil viscosity reduction. This will greatly improve the recoverability of heavy oil. Moreover, as the catalyst is magnetic, it could be easily separated from the reaction mixture, which will minimize the effect of aquathermolysis catalyst on the refining of the recovered oil.

As the aviation sector grows and fossil fuels are utilized, the environment and economy depend on biomass-based aviation fuel. This study investigated acid sites in aldol condensation to produce aviation fuel from biomass-derived aldehydes and ketones over the bifunctional catalyst Ni/HZSM-5. Due to its excellent 10-member ring channels structure, HZSM-5 yielded 63.81% of the targeted condensates as aviation fuel precursor. At 200 °C for 9 h, aldehydes and ketones were converted to 90.32% and 69.53% of the required condensates. Sodium ion-exchange HZSM-5 with different Brönsted acid site quantities was tested for condensation. Brönsted acid sites were the active center for aldol condensation of aldehydes and ketones, increasing product yield. In γ-Al2O3, the overall amount of Brönsted acid and Lewis acid was equivalent to that of HZSM-5, the amount of Lewis acid was much more. The yield of the targeted condensates over γ-Al2O3 was only 46.11%, much lower than that of HZSM-5 (69.53%). Thus, Brönsted acid sites were better than Lewis acid sites for aldol condensation of aldehydes and ketones. The balance of active sites for aldol condensation and hydrogenation increased the intended alkane yield to 62.91% with 20 wt% Ni loading. This study involves improving biomass-based aviation fuel generation.

In order to resolve the global warming problem, Ammonia-Diesel Dual-Fuel (ADDF) combustion has been a feasible strategy for burning ammonia to reduce carbon emissions from internal combustion engines. In the research of this paper, an ADDF engine experimental platform was developed and established. Premixed-Charge Compression Ignition (PCCI) combustion and diesel-piloted combustion modes under different operating conditions were investigated to achieve the goals of high thermal efficiency and low emissions. Moreover, the influence of diesel injection strategy and intake pressure on combustion, gaseous and particle emissions were explored. The results indicate that high thermal efficiency can be obtained using PCCI mode with early injected diesel, which forms a homogeneous mixture with ammonia under the low load condition. Under medium and high load conditions, less diesel was injected early, and ignition was delivered by a pilot injection of diesel close to the top dead centre. Under all operating conditions, the gross indicated thermal efficiency (ITEg) exceeded 48%, and the maximum ITEg was 51.5%, which was comparable to the diesel-only mode. Meantime, the emission of ammonia, NO and N2O were normally below 6 g/kWh, 7 g/kWh, and 1 g/kWh, respectively. With increasing ammonia energy substitution ratio, the particle emission changed from accumulation-mode particles to nucleation-mode particles, but the mass of accumulation-mode particles dominated.

Photocatalytic oxidative coupled in situ hydrogenation is an emerging and alternative route to the traditional costly hydrodesulfurization strategy for the eradication of organosulfur compounds from transportation fuels under mild operating conditions. In this study, Cd/Ni-doped CeO2 catalysts were prepared by improved hydrothermal method, and were in turn applied for the ultra-deep desulfurization of highly resilient 4,6-dimethyldibenzothiophene (4,6-DMDBT) from diesel oil under visible light irradiation. The prepared photocatalyst were characterized by transmission electron microscopy (TEM), X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), Raman, Fourier transform infra-red (FTIR) spectroscopy, ultra-violet visible (UV–vis) spectroscopy and Brauner-Emmette-Teller (BET) analyses. Characterization results revealed that bimetallic doped CeO2 mesoporous nanorods were of uniform size (length: 100–200 nm and width: 30–40 nm) having different oxygen vacancies. Catalytic activity evaluation results revealed that under visible light irradiation, 20%Cd/Ni@CeO2 achieved 100% desulfurization performance of 4,6-DMDBT within 50 min at 60 °C, thus surpassing many state of the art catalysts reported in literature. Cd/Ni@CeO2 remained highly active after 10 successive reuses with rapid recovery by simple washing and filtration. Based on the experimental and characterization results, a suitable reaction mechanism was speculated for the photocatalytic desulfurization of 4,6-DMDBT using Cd/Ni@CeO2.

The development and utilization of bifunctional catalysts facilitated hydrogen-rich gas production from biomass pyrolysis to achieve high-value biomass conversion. The effects of different secondary metals (Fe, Mo, Ce) doping and Mo addition ratios on the performance of biomass catalytic pyrolysis for hydrogen production were investigated. The results showed that the Mo0.5Ni1Ca7 catalyst had the best catalytic activity, where the H2 percentage was 69.59 vol%, and the yield reached 617.57 mLgbiomass−1. The CO2 concentration of the Mo0.5Ni1Ca7 catalyst was reduced by 10.6% compared to the Ni1Ca7 catalyst, which enhanced the adsorption performance of the catalyst. The intense interaction between Mo and Ca formed CaMoO4, which inhibited the formation of CaCO3 and promoted the dispersion of the active phase. The Mo0.5Ni1Ca7 catalyst had the largest NiO/Ni (OH)2 ratio and Mo6+/Mo5+ ratio, further enhancing the catalyst's stability and catalytic activity. Considering the effect of pyrolysis temperature on H2 concentration and yield, it was found that 600 °C was a relatively suitable catalytic pyrolysis temperature. This paper explored using Mo-modified catalysts in biomass catalytic pyrolysis for the first time, providing new ideas for developing bifunctional adsorption catalysts. Eventually, it provided a new way for biomass pyrolysis for hydrogen production technology.

Exhaust gas recirculation (EGR) is one effective strategy to improve the thermal efficiency of the heavy-duty spark-ignition (SI) methanol engine. The high EGR tolerance of methanol engine raises new requirements for the EGR system. In this study, the influences of three different EGR routes, high-pressure EGR (HP-EGR), low-pressure EGR (LP-EGR), and high-low-pressure EGR (HLP-EGR) on the engine performance were studied by the one-dimensional simulation with the predictive combustion sub-model. The investigation was conducted at 1000 rpm and 1400 rpm, and 50% and 100% full load. Results show that EGR routes influence both the combustion characteristics and pumping mean effective pressure (PMEP), thus affecting the brake specific fuel consumption (BSFC). The EGR route with the lower internal EGR rate has a lower in-cylinder temperature at the compression stroke, a weaker knock tendency and a more advanced combustion phase. The effects of EGR routes on BSFC are more significant at the higher engine speed. The optimal BSFC of HP-EGR is lower than that of HLP-EGR and LP-EGR by up to 16.4 g/k·Wh and 21.2 g/k·Wh. Considering the engine performance at all engine operating conditions, HP-EGR is the optimal EGR route while LP-EGR is the worst one for the heavy-duty SI methanol engine.

Lignin valorization is an important part of increasing the economic viability of sustainable biorefineries. Various methods have been proposed for lignin depolymerization. However, the relationship between lignin structure and its depolymerization behavior hasn't been extensively investigated. This research aims to clarify how the structure and composition of lignins derived from different pretreatment processes affect the downstream catalytic conversion. Herein, optimal organosolv lignin yield above 50% in three different solvent systems were obtained. Meanwhile, three types of hydrolyzed lignin were used as reference lignins. Various lignins were comprehensively characterized by elemental analysis, FT-IR, TGA-DSC and Py-GC/MS techniques. Compared with hydrolyzed lignin, organosolv lignin has higher purity, wider functional group distribution, more uniform structure, as well as a lower G/S ratio. Moreover, lignin depolymerization was carried out with a non-noble metal catalyst Ni/Al2O3 and without the addition of H2. The results showed that transetherification and alkylation reaction were enhanced significantly for organosolv lignin. Total depolymerized aromatics yield from organosolv lignin was 4 to 11 times higher than that of hydrolyzed lignin-rich residues. Notably, Methanol-extracted lignin obtained an optimal yield of 29.7 wt% of monomeric aromatics. Methanol can effectively protect benzylic carbocations formed during organosolv pretreatment, thus minimizing the formation of CC bonds.

Herein, the biochar-supported Ni catalysts was synthesized by carbothermal reduction and its catalytic activity for biomass-derived heavy components was investigated in a pyrolysis-catalysis two stage reactor at the catalytic cracking temperature of 700 °C. The change in catalytic activity of biochar-supported Ni catalyst was divided into three stages according to conversion efficiency of heavy components: rapid reduction stage (from 95.30% to 85.58%), stabilization stage (from 84.65% to 82.98%), and slow reduction stage of activity (from 81.21% to 76.98%), corresponding to rapid decreasing stage (from 88.95% to 63.53%), stable stage (from 62.1% to 57.55%), and slow increasing stage (57.66% to 60.17%) of the mass retention percentage of catalyst. The characterizations of catalyst after different cycles showed that the initial deactivation mainly caused by the sintering of Ni active sites. With the severe sintering of Ni nanoparticles, coke deposition became the main reason of later catalyst deactivation. Particularly, the carbon elimination reaction promoted by highly dispersed Ni particle was observed which contributed to enrich the mesoporous structure and retarded the deactivation of the catalyst. The research marks a further understanding of the interaction and deactivation mechanisms between biochar support and Ni active sites during catalytic cracking of biomass-derived heavy components.

Biomass gasification produces syngas composed mainly of hydrogen, carbon monoxide, carbon dioxide, methane, water, and higher hydrocarbons, till C4, mainly ethane. The hydrocarbon content can be upgraded into richer hydrogen streams through the steam reforming reaction. This study assessed the steam reforming process at the thermodynamic equilibrium of five streams, with different compositions, from the gasification of three different biomass sources (Lignin, Miscanthus, and Eucalyptus). The simulations were performed on Aspen Plus V12 software using the Gibbs energy minimization method. The influence of the operating conditions on the hydrogen yield was assessed: temperature in the range of 200 to 1100 °C, pressures of 1 to 20 bar, and steam-to‑carbon (S/C) molar ratios from 0 (only dry reforming) to 10. It was observed that operating conditions of 725 to 850 °C, 1 bar, and an S/C ratio of 3 enhanced the streams' hydrogen content and led to nearly complete hydrocarbon conversion (>99%). Regarding hydrogen purity, the stream obtained from the gasification of Lignin and followed by a conditioning phase (stream 5) has the highest hydrogen purity, 52.7%, and an hydrogen yield of 48.7%. In contrast, the stream obtained from the gasification of Lignin without any conditioning (stream 1) led to the greatest increase in hydrogen purity, from 19% to 51.2% and a hydrogen yield of 61.8%. Concerning coke formation, it can be mitigated for S/C molar ratios and temperatures >2 and 700 °C, respectively. Experimental tests with stream 1 were carried out, which show a similar trend to the simulation results, particularly at high temperatures (700–800 °C).

In this work, a novel SnS2@MoO3 composite catalyst was designed as the photocathode for PEC to catalytic conversion of nitrogen into ammonia under ambient conditions for the first time. The composite catalyst shows high yield, high stability and high product selectivity by taking advantage of not only photocatalysis but also electrocatalysis mechanism. The best nitrogen fixation performance was 30.04 μg h−1 mg−1 (−0.7 V) and the best Faraday efficiency was 13.41% (−0.6 V) at room temperature and atmospheric pressure. Compared to pure MoO3 and SnS2, the nitrogen fixation performance is improved by 2.3 times and 4.6 times, and the Faraday efficiency is enhanced by 2.0 times and 3.5 times, respectively. The double layer capacitance of the heterojunction is 1.5 times that of SnS2 and 1.7 times that of MoO3 according to linear analysis, indicating that the composite has a higher electrochemically active area than SnS2 and MoO3. It can be concluded that the photoelectric synergistic effect between SnS2 and MoO3 further promote electron transfer under the light and electric conditions and exhibit higher nitrogen fixation catalytic performance. The strong stability in both photoelectric catalytic performance and crystal structures was also confirmed in the SnS2@MoO3 composite.

Ammonia has been supposed to be an important carbon-neutral fuel for the applications in future engines. Its unique physical and chemical properties have great effect on engine combustion. The pre-chamber jet-induced ignition mode can yield very high turbulent jet ignition energy, which should be favorable for the ammonia combustion. To study the effects of key initial parameters in this combustion mode, the ammonia combustion and NOx formation processes were analyzed deeply in constant volume combustion chamber. A 3D CFD model was developed and validated with the visualization experiments, and the initial pressures (Pin) and temperatures (Tin) were numerically studied. The comparisons of different Pin for constant fuel mass (CFM) and constant equivalence ratio (CER) showed that Pin with CFM affects the combustion phase and burning rate more obviously. A higher Pin reduces the NOx emission slightly for CER but leads to higher NOx obviously for CFM, and a higher Pin for CFM also results in a slightly higher N2O emission due to the lower combustion temperature. The comparisons of different Tin showed that a higher Tin can enhance the combustion process greatly, while it also results in higher NOx due to high activity of OH and HNO for HNO + OH → NO+H2O.

Since existing reduced mechanisms of ethylene oxidation are either too large or lack of sufficient chemical reactions to describe aromatics formation, the study aims at developing a skeletal mechanism with extended predictive capability and lowered computational cost in computational fluid dynamics modeling of ethylene combustion. The newly assembled and refined kinetic mechanism composed of 664 species and 3582 reactions is minimized to 79 species and 538 reactions without empirically adjusting kinetic parameters. In the 1-D simulation for a premixed flame of ethylene, the ethylene-PAH mechanism generally well predicts experimental profiles of five hydrocarbons and nine aromatics. Integrated into a 2-D axisymmetric laminar finite-rate model, the ethylene-PAH mechanism reproduces experimental data of seven C2–C5 hydrocarbons, five aromatic hydrocarbons and soot in a diffusion flame of ethylene. In comparison with the 158-species (Narayanaswamy) mechanism, the newly proposed ethylene mechanism leads to a speedup of approximately 5.5 times in the 2-D laminar diffusion flame simulation and improved accuracy for predicting species formation in both premixed and nonpremixed flames. Moreover, we unveil the correlation between reaction pathways and intermediate formation from ethylene oxidation at the low temperature regime.

Catalytic hydroconversion of C10+ heavy aromatics (C10+ Aro) from an aromatic complex was studied to produce benzene, toluene, and xylenes (BTX), rich in xylenes. Two catalytic schemes, direct hydrocracking (HDC) and hydrotreating (HDT) followed by HDC, were explored. The Mo2C/γ-Al2O3 catalyst exhibits excellent selectivity for mono-aromatics and catalytic stability in the HDT of C10+ Aro. HDC catalysts containing BZ (H-Beta/H-ZSM-5 = 9/1 weight ratio) exhibited a significantly enhanced yield of BTX but significantly reduced the formation of alkylbenzenes (other than BTX) and heavy aromatic residues compared to the HDC catalyst without H-ZSM-5. H-ZSM-5 with smaller pore size and higher Brönsted acidity than H-Beta promoted dealkylation of alkylbenzenes into BTX while limiting heavy residue formation. HDC of HDT-C10+ Aro over NiMo/BZ catalyst resulted in BTX and BTX + C9 Aro yields as high as 47.7 and 61.1 wt%, respectively, which were significantly higher than those obtained from direct HDC of C10+ Aro (44.4 and 53.8 wt%). Unlike model tetralin HDC, the BTX distribution was in the order X > T > B from the HDC of HDTC10+ Aro. Transalkylation reactions between benzene/toluene and tetramethylbenzenes (in C10+ Aro) have been suggested as possible mechanisms for the formation of xylene-rich BTX.

Metal oxide loaded carbon-based materials have attracted extensive attention as promising desulfurizers to solve the problem of H2S emission at room temperature. However, low desulfurization capacity, difficult regeneration and high economic cost are the main problems of metal oxide loaded carbon-based desulfurizers, which limit their industrial application. Herein, a novel and low-cost CaCO3-ZnO loaded biochar (RCZ) was synthesized by one-step pyrolysis of scrap rice and metal salts for highly efficient H2S removal at room-temperature. The optimized RCZ-1-1-1-800 sample showed an excellent H2S removal ability of 834.48 mg/g at the reaction temperature of 25 °C, oxygen content of 10%, and relative humidity of 70% as compared to 29.31 mg/g achieved by the inactivated biochar (prepared without activator). Such an RCZ-1-1-1-800 desulfurizer also delivered a high H2S removal ability under different desulfurization conditions. The associated desulfurization mechanism of RCZ was the coupling of reactive adsorption and catalytic oxidation with sulfur being the main desulfurization product. Moreover, the as-fabricated RCZ also exhibited a high reusability, retaining about 95% of the initial H2S removal capacity after five adsorption/regeneration cycles. This work provides a promising idea for the preparation of low-cost and high-capacity metal oxide- and carbonate-loaded carbon-based desulfurizers.

2-methyl furan (MF) is a fuel additive with improved fuel characteristics compared to bio-ethanol. Unfortunately, the production of MF (from furfural (FF) hydrogenation) is not economically feasible. Interestingly, molten salts in biomass pyrolysis have shown to promote the formation of furans (mainly FF). Because molten salts hydropyrolysis could be an alternative route to both produce FF and convert it into MF, an assessment is indispensable. Molten salts pyrolysis and hydropyrolysis of pinewood and wheat straw and related model compounds were studied in a micro-reactor. The effect of hydropyrolysis process variables was assessed on the total detectable condensable vapors and MF formation.At low pressures (0.4 MPa), the chloride salts favored the production of FF and acetic regardless of the reaction atmosphere. Under a high pressure of hydrogen though (1.6 and 3.0 MPa), the conversion of FF to MF was enhanced through hydrogenation, hydrodeoxygenation and demethylation reactions. Molten salts hydropyrolysis at 350 °C and pressures of either 1.6 MPa (biomass mass fraction of 0.09) or 3.0 MPa (biomass mass fraction of 0.24) were optimal and yielded ca. 8 wt% to 9 wt% MF. Reaction temperatures >350 °C were unfavorable for the MF yield and instead promoted furfural decarbonylation to furan.

Abstract not available

With the green and economic development of distributed power source, the medium temperature flat-chip SOFCs using hydrogen rich gases obtained from MSR as fuel are paying great attention. The power generation performance and durability of SOFC are affected by the fuel composition. In this paper, the actual composition of hydrogen rich gas obtained from methanol steam reforming (MSR) is imitated to study the fuel adaptability of flat-chip SOFC at 600– 700 °C by experiment. As shown in the results fuel utilization rate and power generation performance are most affected by CO concentration. The large temperature gradient variation caused by the flat-chip structure leads to methanation reaction, especially when the hydrogen rich gas contains CO2. Overpotential has a greater impact on the stack which use hydrogen rich fuel containing CO2 as fuel. As the overpotential increases, the fuel utilization rate increases and the methanation rate decreases. The uneven performance caused by flat-chip production is the main reason for the difference in power generation performance. CO and CO2 have a significant impact on the resistance of electrolytes of flat-chips. The reactor can stably supply fuel to SOFC for a long-time. Using reforming gas for power generation, fuel utilization rate of SOFC reduces by 0.06%.

Seven typical lignin monomers with different number of methoxyl groups and different 4-substituted patterns were pyrolyzed at 500 °C and 700 °C for 120 s to simulate the secondary polymerization and side chain conversion reactions of primary pyrolytic lignin monomers. The pyrolytic heavy oil components were identified at molecular scale with Fourier transform-ion cyclotron resonance mass spectrometry (FT-ICR-MS) and analyzed with Kendrick mass defect (KMD) and van Krevelen diagrams. The detected heavy components were typically phenolic oligomers formed dominantly through the radical coupling reactions of phenol radicals (C6H4O) and methoxyl radicals (OCH2). Model compounds with CC type 4-substituted groups were prone to produce more phenolic oligomers with more aromatic units. For the CO type model compounds, the number of methoxyl groups have significant influence on the generation of heavy components, thereby affecting the char yields. Rising temperature promotes the generation of heavy components through three main routes, namely the additions of CH2, OCH2 and C6H4O. These routes were mapped on van Krevelen diagrams, shedding light on the evolution patterns of both polymerization and side chain conversion reactions during the secondary pyrolysis of lignin.

Hydrogen spillover is the key step during the CO2 methanation process that provides active hydrogen species for hydrogenation and facilitates the reaction at lower temperatures. This work features the synthesis of CeO2-supported NiFe alloy catalysts, and the subsequent activation using plasma treatment (PT). The PT catalysts exhibit a considerable improvement in performance at low temperatures as compared to the calcined (untreated) catalysts. The considerable enhancement in catalytic properties could be appropriate to the abundant hydroxyl (OH−) groups and the great hydrogen spillover ability of the PT catalysts. Furthermore, temperature-programmed surface reduction (TPSR) was used to determine the hydrogenation and CH4 generation temperatures and to reveal the promotion of PT catalysts. Formate was considered the key intermediate during the CO2 methanation process according to the in-situ diffuse reflectance infrared Fourier transform spectroscopy (DRIFTS) results.

Dry reforming of methane (DRM) is considered a promising process to convert CH4 and CO2 into syngas for achieving carbon neutrality. However, sintering and carbon deposition of Ni pose significant challenges to the industrialization of DRM. The size of Ni particles significantly affects the generation of carbon deposits. In this study, a series of Ni/MSS catalysts were prepared using four different methods, including common impregnation, glycine-assisted impregnation, ethylene glycol-assisted impregnation and ammonia evaporation. The effects of preparation methods on the anti-sintering and anti-coking properties were explored through various characterization techniques. Results showed that glycine-assisted impregnation and ethylene glycol-assisted impregnation effectively improved the dispersion of Ni, resulting in small Ni particles while preserving the unique pore structure of MSS supports. Smaller Ni particles expose more active sites, which facilitate the resistance to carbon accumulation. These catalysts show the highest activity and excellent stability. The catalyst prepared by ammonia evaporation showed the best stability due to the synergistic effect of the strongest basicity and metal-support interaction. However, nickel phyllosilicate generation consumed a small amount of MSS, resulting in reduced specific surface area. Compared with the common impregnation method, the other three methods reduced the particle size of Ni and improved the interaction between support and metal, effectively enhancing the ability of the catalyst to resist coking and sintering. Kinetic studies also showed a significant decrease in the apparent activation energy of methane and carbon dioxide cracking due to the reduced particle size of Ni particles.