Fuel Processing Technology最新文献

In this study, we demonstrate the continuous catalytic hydrotreating of sewage sludge-derived hydrothermal liquefaction oil on a versatile, pilot-scale testing unit, equipped with both a slurry and a fixed-bed reactor. Comparison of the two reactors shows that slurry hydrocracking is consistently more efficient in both heteroatom removal and cracking performance compared to the fixed-bed operation. The upgraded HTL oil from the slurry reactor contains 35% less nitrogen that the equivalent oil produced from the fixed-bed reactor at 350 °C and is lighter, consisting of 84 wt% molecules in the gasoline and diesel range, compared to 63 wt% in its counterpart. This is tentatively ascribed to the higher residence time and the lower mass-transfer limitations in the slurry reactor that enhance the hydrogenation and cracking reactions. Upgrading the HTL oil in a two-stage configuration improves only the nitrogen removal, which increases from 40‐55% in the one-stage process to 83%. Overall, slurry hydrocracking appears to be a promising strategy for the upgrading of bio-oils from renewable feedstocks, such as waste and biomass. Further research is required to study operability and stability issues for longer time-on-stream and investigate the process in the presence of dispersed liquid catalysts.

MSW pyrolysis and gasification technologies have been recognized as effective means to enhance the resource utilization of MSW and promote a circular economy. However, the presence of HCl gas can significantly impact the quality and application of syngas. To maximize syngas resource utilization, develop highly efficient HCl adsorbent, this study investigates the performance and mechanism of HCl removal from syngas using a conventional hydrotalcite (Mg-Al-CO₃) and modified Ca-based hydrotalcite (Ca-Mg-Al-CO₃). The impact of CO₂, a component naturally presents in syngas, on the performance of both materials, were also investigated. Characterization techniques, including XRD, TGA, SEM, and analysis of pore properties and specific surface area, were employed to understand the underlying reaction mechanism. The results demonstrated that the performance of Ca-Mg-Al-CO₃ was significantly superior to that of conventional Mg-Al-CO₃ sorbents, particularly in the presence of CO₂ However, the presence of CO₂ had a detrimental impact on the performance of Ca-Mg-Al-CO₃ in HCl removal, and this effect became increasingly pronounced with higher concentrations of CO₂. TGA results revealed a competitive relationship between HCl and CO₂ during the adsorption process. Additionally, the fitting results of adsorption kinetics suggested that the adsorption reaction of HCl and CO₂ by Ca-Mg-Al-CO₃ followed multiple rate-controlling mechanisms.

To overcome the defects of the traditional selective non-catalytic reduction (SNCR) process (e.g., low efficiency, narrow temperature range), a new modified SNCR technology based on the solid complex polymer reducing agents, also called polymer non-catalytic reduction (PNCR), was investigated both in the laboratory and pilot scale to reveal its reaction characteristics and mechanism. The PNCR process demonstrates excellent removal efficiency (about 90%) of NO in furnace in the wide temperature range (850–1150 °C), and possesses promising application feasibility with an average NO_x emission concentration of 68.72 mg·m⁻³ even on unstable industrial operating conditions. The NO removal behaviors influenced by O₂, temperature, or water steam illuminate the unique O₂-independent and H₂O-promoted reaction characteristics of PNCR in the wide temperature range. The thermogravimetric infrared spectra/mass spectrometry (TG-IR/MS) results further reveal a pyrolysis-assisted formation mechanism of active NH₂/NH free radicals without the requirement of O₂ and high temperature, which avoids the overoxidation of active radicals and accounts for the wide denitrification temperature window, low oxygen compliance and high denitrification efficiency of PNCR process. The excellent NO removal performance as well as the unique reaction characteristics/mechanism of PNCR forebode its broad industrial application prospect in the field of flue gas cleaning.

Methanol steam reforming (MSR) for hydrogen production is a significant and promising clean energy technology. So, a comprehensive review focused on the analysis of high-temperature reforming, low-temperature reforming, autothermal reforming, and CO removal in MSR is conducted. The selection and design of catalysts play a crucial role in enhancing the efficiency and stability of MSR, which can improve the selectivity of methanol decomposition and hydrogen generation, and reduce the occurrence of side reactions. The optimized reactor design and better thermal management technology effectively reduce heat loss and achieve high energy efficiency in methanol autothermal reforming. Furthermore, gaining profound insights into the reaction mechanisms plays a pivotal role in guiding catalyst development and reactor enhancements, which is instrumental in addressing catalyst deactivation, catalyst longevity, and undesired side reactions. CO removal technology plays a pivotal role in the hydrogen production process of MSR. It is employed to eliminate CO impurities, thus enhancing the purity of the hydrogen production. This review contributes valuable insights into high-purity hydrogen production, catalyst stability improvement, and key challenges linked to CO removal in MSR, facilitating advancements in hydrogen technology.

In the search for sustainable fuels, high-performing, cost-effective, and abundant catalysts are needed for bio-oils hydrodeoxygenation refining, with single-atom-alloy (SAA) catalysts showing potential for outstanding activity and economic bi-metallic assembly. Hydrodeoxygenation upgrading of modelled bio-oil molecules, namely, phenol, anisole, benzaldehyde, and vanillin, has been systematically explored here over a wide-range of SAA Ni(111)-based catalysts (Pd, Pt, Cu, Co, Fe, Ru, Re, Rh, V, W, and Mo) using density functional theory (DFT) and microkinetic modeling. Stability, adsorptive, and activity structural-property-relationships were established for bio-oil derivatives that can direct the synthesis process of cost-effective SAA combinations. DFT revealed the thermodynamic atomic dispersion tendency of the SAA catalysts. Furthermore, the OH*- and O*$-$induced on the catalyst surface enhanced the SAA upper-layer stability. Single-atoms shifted the d-band center towards the fermi-level in agreement with bio-oils adsorption energies and C_aryl$-$O lengths. The free-energy pathways at 573 K unveiled the SAAs role in lowering the activation barriers, with WNi(111) best-performing towards selective phenol and anisole direct deoxygenation, whilst MoNi(111) directs the facile activation of benzaldehyde and vanillin CO scission. The microkinetic/thermodynamic analysis of O*-poisoning showed that MoNi(111) withstands high O*-coverage, indicative by higher deoxygeneration rates in 350-950 K and greater coverage of the desired product.

This work explores a novel approach for improving the sodium-ion battery performance of coal char using flash pyrolysis and an ether-based electrolyte. Coal char is an ultra-low cost hard carbon with promising application as an anode material in sodium-ion batteries. During flash pyrolysis, char is heated at 1000 °C/s in a drop-tube furnace to create a highly-irregular structure. The larger d-spacing and smaller closed micropore diameter of flash-pyrolyzed char increases anode capacity compared to traditional slow-pyrolyzed char electrodes. The sodium-ion battery anode performance of flash-pyrolyzed char is further improved using an ether-based electrolyte in place of the traditional ester-based electrolyte. Performance improvements include greater initial Coulombic efficiency (58% in ester- vs. 64% in ether-based electrolyte) and improved specific capacity in an ether-based electrolyte. Overall, the combination of flash pyrolysis and ether-based electrolyte increases the sodium-ion battery discharge capacity of coal char by over 50%, from 72.5 mAh g⁻¹ (slow-pyrolyzed char in ester-based electrolyte) to 109.4 mAh g⁻¹ (flash-pyrolyzed char in ether-based electrolyte) (50 mA g⁻¹ discharge rate). The results highlight improvements that can be realized through flash pyrolysis of coal char for battery applications and the numerous processing advantages of flash vs. slow pyrolysis.

Biomass-H₂O gasification facilitated by multi-metal synergistic catalysis for H₂ production. Oxygen transfer, carbon dissolution, lateral/vertical etching mechanism, and hydrogen production capacity of biomass self-contained K and added Ni catalytic gasification were studied through biomass loaded with K and Ni pyrolysis, biochar gasification experiments, and DFT calculations. The H₂ yield from KNi catalytic gasification was 67.09 mmol/g (increased by 13.51%). Driven by *OH, K migrates and transforms from the inside of the carbon matrix to form active sites (C_K), increasing carbon defects (40–50%) and reactivity. The vertical etching ability of Ni on biochar is enhanced from outside to inside (forming NiC and C_K to reduce carbon dissolution energy barrier) and the gasification reaction rate is increased. The competition between the strong attraction of Ni on OH and the van der Waals force of K on OH leads to a 7.7% increase in the energy barrier of the rate-determining step (H transfer). The work enhances the understanding of the multi-metal catalytic gasification of rich H₂ and provides a foundation for developing catalytic gasification technology.

The active sites of copper-based catalysts and their impacts on activity and selectivity are first examined in this work, after which an overview of the regulation of the active sites and the pathways for CO₂ hydrogenation reactions follows. The primary active sites influencing CO₂ conversion and methanol yield and selectivity include Cu⁺/Cu⁰ species, Cu-oxide interfaces, Cu surface defect sites and M-Cu alloys. Strategies including additive control, carrier effect, and morphological modification can alter the kind and distribution of active sites. The main intermediates in the hydrogenation of CO₂ to synthesize methanol are HCOO^⁎ and COOH^⁎. The main intermediates in the synthesis of methanol by CO₂ hydrogenation are carboxyl species (COOH^⁎) and formate species (HCOO^⁎). The formate pathway can be further divided into the HCOO^⁎ pathway and the r-HCOO^⁎ pathway, depending on the intermediate involved. In the formate pathway, the hydrogenation of formate is the rate-determining step in the synthesis of methanol by CO₂ hydrogenation. The carboxylate species pathway is subdivided into the RWGS+CO-Hydro pathway and the trans⁃COOH pathway. The rate-limiting steps for these two pathways are the formation of CO/HCO species and the dissociation of COHOH^⁎ species, respectively. The review serves as the foundation for further developing copper base methanol catalysts that are extremely active, highly selective, and stable.

Pressurized O₂/H₂O combustion is a potential CCS technology. In this study, a pressurized horizontal furnace was used to prepare pyrolysis char under pressurized inert atmosphere, and then a pressurized drop tube furnace was used to carry out char combustion under pressurized O₂/H₂O atmosphere (5% O₂, 20% H₂O) at the same pressure and temperature as the pyrolysis process. The carbon conversion of char under different pressures (0.4/0.7/1.0 MPa), temperatures (900/950/1000 °C), and residence time (1.38/2.76/4.14 s) was studied by proximate analysis. The random pore model was used to calculate reaction kinetic parameters of char combustion at different pressures. The results show that when the pressure increased from 0.4 MPa to 0.7 MPa, the carbon conversion increased significantly, with the increment reaching up to 9.90 percentage points. The marginal diminishing effect became significant when the pressure was greater than 0.7 MPa. The reaction activation energy and pre-exponential factor at 0.4/0.7/1.0 MPa were 66.53/66.29/35.79 kJ/mol and 20.54/36.84/1.69 s⁻¹, respectively.

In this work, ReaxFF molecular dynamics (MD) simulation was adopted to investigate the effect of superheated steam on the conversion of the kaolinite-associated Barkol kerogen (BLK) and reveal the corresponding mechanism. The ReaxFF simulated weight loss rate (DTG) and release tendency of H₂O, H₂ and CO₂ for BLK and the kaolinite-associated BLK agreed well with the results of Py-MS experiments. H-rich rate, double bond equivalents (DBEs), and hydrocarbon content were adopted to assess the quality of C₅-C₄₀, and configurations of C₄₀₊ were extracted to investigate the characteristics of residues. And the H₂O_steam- and kaolinite-involved (_steam refers to the superheated steam) reactions were analyzed. The results indicate that B- and L-acid sites of kaolinite co-catalyzed decomposition of BLK into heavy oil and shale gas in the kaolinite-pyrolysis system, and in steam/kaolinite-pyrolysis system, H₂O_steam further promoted decomposition of BLK into higher quality shale oil, especially for C₅-C₁₃ components, remaining higher aromatic and porous residues. And this enhanced effect of H₂O_steam is attributed to kaolinite and the induced decomposition of H₂O_steam molecules and their participation as reactants in reactions in two aspects: i) interaction between kaolinite and H₂O_steam, on one hand, inhibited formation of L-acids and facilitated generation of B-acids to catalyze carbocation ion reactions process, further weakened dehydrogenation of organics catalyzed by L-acid sites, and enhanced cracking of residues catalyzed by B-acaid sites, on the other hand, promoted decomposition of H₂O_steam molecules to form H-rich environment and further weakened dehydrogenation of organics; ii) attacking C_ar directly, H₂O_steam promoted shedding of alkyl side chains and ring-opening of aromatics to increase the –CH₂– content in shale oil. This paper provides theoretical guidance for further understanding mechanism of H₂O_steam on pyrolysis of kaolinite-associated kerogen and corresponding catalyst development and preparation.