Hydrocarbon Selectivity Research Articles

One-Step Carbothermal Reduction Synthesis of Metal-Loaded Biochar Catalyst for In Situ Catalytic Upgrading of Plastic Pyrolysis Products

A novel biochar-supported metal catalyst was prepared in this study using a one-step carbothermal reduction synthesis method for the catalytic pyrolysis of plastics. Several catalysts with different metals (Cu, Fe, Ni, and Ru) loaded on three biochar supports from lignin, soybean straw, and Chlorella vulgaris were evaluated using XRD, FTIR, NH3-TPR, and TEM. Zerovalent metal nanoparticles, including Ni, Cu, and Ru, and various functional groups were observed on the biochar surface. The chemical selectivities of gasoline hydrocarbons (C4–C12 hydrocarbons) reached 76.2% with a remarkable catalytic cracking effect of Ni/lignin biochar on low density polyethylene (LDPE). Catalytic performance was comparable to that of the Ru-based catalyst, which contributed to 85.6% of gasoline hydrocarbons. The Ni/lignin catalytic cracking of plastic waste simulated by LDPE, polypropylene (PP), and polystyrene (PS) showed a maximum selectivity of 87.9% for C4–C12 hydrocarbons and yields of 78.1 mg/g for benzene, toluene, and xylene (BTX). The mechanism related to the cleavage of long chain radicals of polyethylene, polypropylene, and polystyrene as well as the aromatization of aliphatics were proposed.

Effects of Rare Earth Metal Promotion over Zeolite-Supported Fe-Cu-Based Catalysts on the Light Olefin Production Performance in Fischer-Tropsch Synthesis.

Fischer-Tropsch synthesis (FTS), a significant reaction for effective H2 utilization, is a promising approach for direct production of light olefins from syngas (H2 + CO). For the FT-Olefin process, an efficient catalyst restricting the product distribution of FTS to light olefins is required. Aligned with this goal, we synthesized 24 catalysts comprising Fe and Cu in combination with rare earth metals (La, Ce, Nd, Ho, Er) and zeolite supports (ultrastable Y and mordenite). FT-Olefin performances of these catalysts were screened using a high-throughput test system at atmospheric pressure, and then promising catalysts were tested under high pressure in a conventional test system. Results show that Nd increases selectivity to light olefins and Ho suppresses C5+ and coke formation. It is also demonstrated that zeolite-metal interaction, leading to a mixture of both acidic and basic sites, is significant in increasing light olefin production. The mordenite-supported 20 wt % Fe, 0.5 wt % Cu, and 0.5 wt % Ho catalyst provides the highest light olefin yield with the lowest coke and heavier hydrocarbon selectivity.

Mechanism study on gliding arc (GA) plasma reforming: Unraveling the decisive role of CH4/CO2 ratio in the dry reforming reaction

AbstractAiming at understanding the role of CH4/CO2 ratio on gliding arc (GA)‐based dry reforming of methane (GA‐DRM), the GA‐DRM at CH4/CO2 ratio range of 0.11 to 1 was studied with kinetics simulation. The radicals of H, OH, and CH3 are identified as the main reactive species to induce the reactant conversion and product formation in GA‐DRM. The increase of CH4/CO2 raises the concentrations of H and CH3 and reduces the OH concentration. Subsequently, the CH4/CO2 ratio regulates the main reaction routes of GA‐DRM. The dehydrogenation coupling reaction enhances with CH4/CO2 and thus raises the selectivities of C2 hydrocarbons. The OH‐induced reactions for OH to H2O weaken with CH4/CO2, thereby increasing the H2 selectivity.

Methane direct conversion to olefins, aromatics, and hydrogen over silica entrapped bimetallic MeFe-SiO2 (Me = Co, Ni, Pd, Pt) catalysts

Here, MeFe-SiO2 (Me = Co, Ni, Pd, Pt) catalysts with bimetallic sites entrapped in a highly crystalline SiO2 structure were synthesized and used for the conversion of methane to olefins, aromatics, and hydrogen (MTOAH) at 1020°C. The MeFe-SiO2 catalysts showed polymorphic forms of cristobalite, quartz, and tridymite after reaction. Among the bimetallic catalysts, 0.5Pt1.0Fe-SiO2 exhibited the highest methane conversion (10.0%) with high hydrocarbon selectivity (79.9%) at 1020°C. In C2 (ethane, ethylene, acetylene) conversion with hydrogen co-feeding at 1020°C, acetylene was identified as a major coke precursor. MTOAH with different gas hourly space velocities (GHSV) showed that the 0.5Pt1.0Fe-SiO2 catalyst exhibited higher methane conversion and aromatics selectivity than the 1.0Fe-SiO2 catalyst. Density functional theory calculations showed that the Pt-Fe3C surface is energetically favorable for methane activation and inhibits graphitic coke deposition by C2 dehydrogenation. Consequently, a modification of the entrapped Fe sites by Pt addition improved the methane conversion and hydrocarbon selectivity of the catalyst.

Production of hydrocarbon-rich bio-oil from catalytic pyrolysis of waste cooking oil over nickel monoxide loaded corn cob-derived activated carbon

The bio-oil produced by the catalytic pyrolysis of waste cooking oil (WCO) has great potential to become a substitute for fossil fuels. However, the low yield and high oxygen content of pyrolysis oil result in low added value. The low-cost production of high-yield and high-quality hydrocarbon-rich pyrolysis oil remains challenging. To efficiently convert WCO to high quality hydrocarbon-rich pyrolysis oil, a nickel oxide loaded activated carbon catalyst (Ni/AC) was introduced in the ex-situ catalytic system. The catalytic pyrolysis results showed that the catalyst exhibited high deoxygenation activity and the hydrocarbon content in the bio-oil could reach up to 99%. The selectivity of total aromatic hydrocarbons and monocyclic aromatic hydrocarbons in liquid oil could reach 86.38% and 68.47%, respectively. By extracting hydrogen from hydrocarbon fragment, the NiO site facilitates dehydrogenation, resulting in a gaseous product with syngas (CO, H2) as the main component, with a maximum syngas concentration of 70%. The hydrogen produced is favorable for hydrogen transfer reactions and as a result promotes deoxygenation and hydrocarbon production. This study provides valuable insight into a low-cost, efficient, and high-value-added way to recover WCO. It will avoid the risk of environmental pollution caused by WCO and provide a reference for the sustainable use of waste.

The effects of CO co-feed on the catalytic performance of Methanol-to-Hydrocarbons conversion on HZSM-5

Methanol-to-hydrocarbons catalysis over HZSM-5 at low methanol partial pressure exhibited low steady-state ethylene and aromatics selectivity at sub-complete methanol conversion. Co-feeding CO increases cumulative carbon ratio of ethylene to the sum of 2-methylbutane and 2-methyl-2-butene (>3×) at the expense of catalyst stability, quantified by >18× increase in site-loss yield, and hydrocarbons selectivity (<80 %). These observations can be rationalized by CO incorporation into the hydrocarbon pool via carbonylation of methyl groups to increase propagation of the aromatics-cycle and of termination sequences relative to that of the olefins cycle. The effects of CO become more prominent at higher partial pressures of CO, at lower inlet concentrations of methanol, olefins, and aromatics, and upon decreasing proton density (per unit volume) and crystallite size in MFI materials. The morphology- and process-dependent effects of CO during MTH on MFI are manifestations of differences in space- and time-averaged relative carbonylation and methylation rates. Both structural catalyst properties and process conditions affect reaction rates during MTH by affecting diffusional constraints, number and contact time of active chain carriers. These results extend to syngas-to-hydrocarbons conversion where high-pressure CO is present to guide the choice of reaction conditions and materials that maximize catalyst lifetime and modulate product selectivity.

Catalytic Hydropyrolysis of Lignin for the Preparation of Cyclic Hydrocarbon-Based Biofuels

The demand for biomass utilization is increasing because of the depletion of fossil resources that are non-renewable in nature. Lignin is the second most renewable organic carbon source, but currently it has limited scope for application in the chemical and fuel industries. Lignin is a side product of the paper and pulp, sugar, and 2G bioethanol industries. Many research groups are working on the value-addition of lignin. Among the lignin depolymerization methods, catalytic hydropyrolysis is gaining attention and is playing a crucial role in developing biorefinery. The hydropyrolysis of lignin was conducted at a higher temperature in the presence of H2. The hydropyrolysis of lignin results in the selective formation of non-oxygenated cyclic hydrocarbons in a shorter reaction time. It is possible to use the cyclic hydrocarbons directly as a fuel or they can be blended with conventional gasoline. This review focuses on the prior art of pyrolysis and hydropyrolysis of lignin. Possible products of lignin hydropyrolysis and suitable synthetic routes to obtain non-oxygenated cyclic hydrocarbons are also discussed. The influence of various process parameters, such as type of reactor, metal catalyst, nature of catalytic supports, reaction temperature, and H2 pressure are discussed with regard to the hydropyrolysis of lignin to achieve good selectivity of cyclic hydrocarbons.

Effect of different oxygen species on the oxidative coupling of methane over TiO2 catalysts

TiO2 is widely used in oxidative coupling of methane (OCM) reaction because of its low cost, reducibility and nontoxicity, but pure TiO2 has poor activity on methane activation. Density functional theory with an additional Hubbard-like parameter (DFT + U) was used to research OCM reaction on Ir/TiO2(001), Pt/TiO2(001) and Mn/TiO2(001) catalysts to explore catalysts with high activity and C2 hydrocarbon selectivity. The results indicate that Ir, Pt and Mn doping can significantly improve the activity of lattice oxygen and reduce the activation energy of methane dissociation. Additionally, the evolution of oxygen species on Ir/TiO2(001) Pt/TiO2(001) and Mn/TiO2(001) catalysts show that the lattice oxygen species and peroxide species have the strongest activity to activate methane. However, the superoxide species has the worst activity. Furthermore, the formation paths of ethane and ethylene were researched on Ir/TiO2(001), Pt/TiO2(001) and Mn/TiO2(001) surfaces. And we expect that Ir/TiO2(001) is effective for catalyzing OCM reaction.

The promotion role of different crystal phase MnO2 in iron-based Fischer-Tropsch catalysts

Manganese oxide additive is an effective promoter for modulating the catalytic performance of iron-based Fischer-Tropsch synthesis (FTS) catalysts and studied extensively, however, the promotion effects of MnO2 crystal structures on iron-based FTS catalysts have never been reported. In this work, four types of MnO2 with crystal phases corresponding to α-, β-, γ- and δ-MnO2 were prepared, and their promotion functions on iron-based FTS catalysts were studied. These four types of MnO2 exhibit dramatically distinct promotion effects on the structure evolution and catalytic performances. The ferrite MnFe2O4 only forms in the α-MnO2 modified catalysts, while the β-, γ- and δ-MnO2 also present different existing forms in the catalysts. The presence of abundant oxygen vacancies on the surface of α- and δ-MnO2 notably facilitates the cleavage of Fe-O bonds and the dissociation of CO, leading to the enhancing formation of iron carbides in the activated and spent catalysts. Meanwhile, the strong Mn-Fe electronical interactions formed in α- and δ-MnO2 modified catalysts lead to high density of surface carbon species with a long residence time, dramatically improving the selectivity of linear high carbon α-olefins and heavy hydrocarbons. In contrast, the β- and γ-MnO2 modifying dramatically increases the catalytic activity, but suppresses the formation of olefins and long chain hydrocarbons, due to their relatively few amounts of surface oxygen vacancies and moderate Mn-Fe electronical interactions. This work provides new insights and in-depth understanding of the promotion roles of Mn additive, benefiting for the rational design of high performance iron-based FTS catalysts.

Influence of the ZnCrAl Oxide Composition on the Formation of Hydrocarbons from Syngas.

The conversion of syngas into value-added hydrocarbons gains increasing attention due to its potential to produce sustainable platform chemicals from simple starting materials. Along this line, the "OX-ZEO" process that combines a methanol synthesis catalyst with a zeolite, capable of catalyzing the methanol-to-hydrocarbon reaction, was found to be a suitable alternative to the classical Fischer-Tropsch synthesis. Hitherto, understanding the mechanism of the OX-ZEO process and simultaneously optimizing the CO conversion and the selectivity toward a specific hydrocarbon remains challenging. Herein, we present a comparison of a variety of ZnCrAl oxides with different metal ratios combined with a H-ZSM-5 zeolite for the conversion of syngas to hydrocarbons. The effect of aluminum on the catalytic activity was investigated for ZnCrAl oxides with a Zn/Cr ratio of 4:1, 1:1, and 1:2. The product distribution and CO conversion were found to be strongly influenced by the Zn/Cr/Al ratio. Although a ratio of Zn/Cr of 1:2 was best to produce lower olefins and aromatics, with aromatic selectivities of up to 37%, catalysts with a 4:1 ratio revealed high paraffin selectivity up to 52%. Notably, a distinct effect of aluminum in the oxide lattice on the catalytic activity and product selectivity was observed, as a higher Al content leads to a lower CO conversion and a changed product spectrum. We provide additional understanding of the influence of different compositions of ZnCrAl oxides on their surface properties and the catalytic activity in the OX-ZEO process. Furthermore, the variation of the zeolite component supports the important role of the channel topology of the porous support material for the hydrocarbon production. In addition, variation of the gas hourly space velocity showed a correlation of contact time, CO conversion, and hydrocarbon selectivity. At a gas hourly space velocity of 4200 mL/gcat h, CO conversion as high as 44% along with a CO2 selectivity of 42% and a lower paraffin (C2 0-C4 0) selectivity of 41% was observed.

Improvement of wheat (T. aestivum) straw catalytic fast pyrolysis for valuable chemicals production by coupling pretreatment of acid washing and torrefaction

The present work investigated the coupling pretreatment of acid washing and torrefaction to address secondary cracking of target products and condensation of intermediates and improved bio-oil quality and hydrocarbon selectivity of the catalytic fast pyrolysis (CFP) process. The total hydrocarbon yields in CFP increased from 28.06 wt% to 55.31 wt% by torrefaction and 46.29 wt% by coupling pretreatment. The acid washing resulted in fewer acids and phenols and more sugars in bio-oil by decreasing the AAEMs. The removal rate of the potassium was up to 96.7 %, and other elements were above 83 %. Torrefaction elevated the C/O ratio and the higher calorific value of biomass. It could also decrease the acid content in obtained bio-oil in the CFP process. In addition, the TG/TGA results showed that higher torrefaction temperature decreased the total weight loss of biomass. Meanwhile, the acid washing pretreatment improved the resolution of the two pyrolysis peaks of the DTG curve. These results showed that the AAEMs removal and intermediates inhibition could elevate the selectivity of the valuable chemical. • Acid washing removed 83 wt% of AAEMs to facilitate valuable chemicals conversion; • Torrefaction elevated the C/O ratio and the higher calorific value of wheat straw; • The coupling pretreatment improved bio-oil quality and hydrocarbons selection; • The CFP with pretreated biomass reduced phenols, acids, and ketones production.

Hydrocarbon regulation and lower temperature pyrolysis of balikun oil shale kerogen

Oil shale kerogen is a kind of composite nature of fossil energy polymer. Kerogen pyrolysis is a feasible and alternative strategy to produce fossil fuels from shales. However, the disadvantages including the high energy consumption, the high cost, and the low hydrocarbon conversion, significantly hinder the development and utilization of unconventional hydrocarbon resources. Herein, the hexagonal crystal structural layered double hydroxides (LDHs) with the Ni/Fe ratio of 5.64:2.36 is proposed as pyrolysis catalyst to improve the catalytic efficiency, the selectivity of target hydrocarbons, and lower the temperature for the process of kerogen pyrolysis. As a result, needle-like nanoscale NiFe-LDHs are prepared successfully to perform the fast thermal upgrading of Balikun oil shale kerogen. The catalytic pyrolysis performance has been observed that the temperature for maximum conversion (Tmax) is 401.18 °C, presenting a Tmax reduction of 37.84 °C, the yield of shale oil is increased by 7.83 wt%. And during 350°C– 400°C, a progressive increment of 147.67%, 230.86%, and 310.61% is obtained corresponding to the content of C1-C5, C6-C14, and C14 + hydrocarbons, respectively. This finding enriches the catalyst candidates for kerogen pyrolysis and provides new insights into industrial applications of in-situ pyrolysis technology for oil shale recovery processes.

Fabrication of a sinter-resistant Fe-MFI zeolite dragonfruit-like catalyst for syngas to aromatics conversion

Direct conversion of syngas to aromatics has great potential to decrease fossil fuel dependence. Here, a unique structured hybrid catalyst composed of Fe3O4 nanoparticles intimately dispersed inside an acidic zeolite is developed. 1 to 4 nm sized Fe3O4 nanoparticles end up evenly dispersed in an acidic and slightly mesoporous Al-ZSM-5 based on Fe3O4 restructuring during co-hydrothermal synthesis using organosilane modification. A very high aromatic productivity of 214 mmolaromatics h−1 gFe−1 can be obtained with a remarkable 62% aromatic selectivity in hydrocarbons. This catalyst has excellent sintering resistance ability and maintains stable aromatics production over 570 h. The synthetic insights that postulate a mechanism for the metastable oxide-zeolite reorganization during hydrothermal synthesis could serve as a generic route to sinter-resistant oxide-zeolite composite materials with uniform, well-dispersed oxide nanoparticles in close intimacy with - and partially confined in - a zeolite matrix.

Fast co-pyrolysis of lignin with spent bleaching clay into monocyclic aromatic hydrocarbons over a novel low-cost composite catalyst

Improving the anti-coking performance of catalyst during lignin-catalyzed pyrolysis without affecting the selectivity of the monocyclic aromatic hydrocarbons (MAHs) is a challenge. In this paper, a low-cost composite catalyst (CSHZ) was prepared using calcined spent bleaching clay (CSBC) as a binder for HZSM-5 to resolve the issue. In order to evaluate the performance of the composite catalyst, an ex-situ fast catalytic co-pyrolysis experiment was performed in a fixed-bed reaction system with lignin and spent bleaching clay (SBC) as raw materials. The impacts of the temperature, CSBC-to-HZSM-5 ratios, raw material-to-catalyst ratios, and cycle-regeneration times on MAHs distribution, are then studied. The selectivity of CSHZ11 (CSBS-to-HZSM-5 ratio of 1:1) for MAHs in bio-oil reached 78.02 % at 550 ℃ and the raw material-to-catalyst ratio of 1:1, which exceeded those of HZSM-5 alone by 19.12 %. After 3 reaction-regeneration cycles, the catalytic activity of CSHZ11 for MAHs was 71.11 % of fresh catalyst. The characterization (TEM, Py-IR, TGA, etc.) of the catalysts (fresh and discarded) revealed that the addition of CSBC regulated the acidity and pore channels of HZSM-5 and inhibited the formation of catalyst graphite-like coke. This study demonstrates the feasibility of using binder modification to improve the anti-coking performance of HZSM-5. It also serves as a reference for the integrated utilization of SBC and lignin.

Exploring the Cumulative Selectivity of Polycyclic Aromatic Hydrocarbons in Phytoplankton, Water, and Sediment in Typical Urban Water Bodies

To understand the interactions among eutrophication, algal bloom, and POPs (persistent organic pollutants) in freshwater ecosystems, the cumulative selectivity of PAHs (polycyclic aromatic hydrocarbons) in phytoplankton, water, and sediment with different eutrophication level waters were identified in a typical plain river network region located in Nanjing City. Results showed that a total of 33 algal species belonging to 27 genera and 4 phyla were identified in 15 sites of urban water bodies, and most of them belonged to the type Cyanobacteria–Bacillariophyta. The eutrophication level of these rivers and lakes led to the sample site specificity of algal composition and abundance. The planktonic algae mainly accumulated the 2-ring and 3-ring PAHs, and the sediment mainly enriched the high-ring PAHs. However, the enrichment capacity of planktonic algae on PAHs was much higher than that of sediment. Cyanophyta and some species of Bacillariophyta and Chlorophyta in mesotrophic (βm) and meso-eutrophic water bodies (ßαm) preferentially accumulated lower-ring PAHs (naphthalene, acenaphthylene, and phenanthrene). Some other specific algae species, such as Euglenophyta, some species of Bacillariophyta, and most Chlorophyta in mesotrophic and moderate eutrophic water bodies, had strong capacities to enrich high-ring PAHs subsuming benzo[a]anthracene, chrysene, and anthracene. The eutrophication level of water bodies affected the cumulative selectivity of PAHs by shaping the site specificity of phytoplankton composition, which may be related to water quality, sediment characteristics, phytoplankton composition, and the algal cell walls.

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.

Co-pyrolysis of corn stalk and coal fly ash: A case study on catalytic pyrolysis behavior, bio-oil yield and its characteristics

In this paper, industrial solid waste coal fly ash and agricultural solid waste corn stalk were used as the research object. The aim is to realize the comprehensive utilization of solid waste and obtain high-quality bio-oil. Thus, the effects of pyrolysis conditions on the pyrolysis process were discussed, and the catalytic effects of coal fly ash were explored using the TGA, SEM-EDS, XRD, FTIR, and GC-MS. The results of TGA coupled with the Coats-Redfern model indicate that the total apparent activation energy varied from 408.40 kJ/mol to 387.39 kJ/mol and co-pyrolysis is a endothermic process while the initial pyrolysis temperature(T i ) is advanced after adding coal fly ash. The highest yield of bio-oil is 30.06 ± 0.03 wt%. It is obtained at 500 °C with a 50% mass fraction of coal fly ash. Additionally, ketonization reactions are promoted, leading to the content of ketones in bio-oil increased by about 10.28%. The selectivity of hydrocarbons is also improved, especially, aliphatic hydrocarbons increase by about 7.89%. The reasons are deeply analyzed and discussed. Overall, the results demonstrate that the participation of coal fly ash not only improves the pyrolysis behavior of biomass but also promotes the enrichment of ketone chemicals in the bio-oil.

Highly Selective Production of Valuable Aromatic Hydrocarbons/Phenols from Forestry and Agricultural Residues Using Ni/ZSM-5 Catalyst

The aim of this research is to design and synthesize an efficient catalyst to enhance high value-added products, such as aromatic hydrocarbons and phenols, from the catalytic fast pyrolysis (CFP) of different types of forestry and agricultural residues. All three biomasses (rape straw, wheat straw, and bamboo powder) had no aromatic production via thermal pyrolysis alone; however, the aromatic selectivity and monocyclic aromatic selectivity were largely enhanced using ZSM-5, with suitable silica-alumina ratios and Ni loadings. Specifically, for rape straw, the optimum catalyst was 15 wt.% Ni/ZSM-5 (silica-aluminum ratios = 85), and the selectivity of aromatic hydrocarbons was achieved at 39%, of which 71% were monocyclic aromatic hydrocarbons. For wheat straw, the optimum catalyst was 10 wt.% Ni/ZSM-5 (silica-aluminum ratios = 18), and the selectivity of aromatic hydrocarbons was 67%, of which 55% were monocyclic aromatic hydrocarbons. For bamboo powder, the optimum catalyst was 10 wt.% Ni/ZSM-5 (silica-aluminum ratios = 18), and the selectivity of aromatic hydrocarbons was achieved at 21%, of which 80% were monocyclic aromatic hydrocarbons. Meanwhile, biomass types have significant effects on the pyrolyzed product distribution due to their different components. Cellulose and hemicellulose promoted the production of aromatic hydrocarbons, while lignin enhanced the production of phenols. The promotion of phenol by Ni was better and more efficient than that by the molecular sieve.

Preparation of Nitrogen Doped Biochar-Based Iron Catalyst for Enhancing Gasoline-Range Hydrocarbons Production.

Developing catalysts to obtain high space time yield (STY) of gasoline-range hydrocarbons via Fischer-Tropsch synthesis (FTS) is a huge challenge due to the restriction of Anderson-Schulz-Flory distribution. Herein, a nitrogen doped biochar-based iron catalyst was synthesized by a one-step method using sugar cane bagasse as carbon precursor, which exhibited an excellent gasoline STY of 8.65 gC5-12 gFe-1 h-1, exceeding most reported catalysts. A strong positive relationship between the amount of pyrrolic N and long-chain hydrocarbons selectivity was displayed. The characterization results indicated that pyrrolic N configuration on anchor sites tuned effectively the dispersion of iron species and metal-support interaction as well as CO adsorption, improving the FTS performance.

Catalytic hydropyrolysis of lignocellulosic biomass to BTX and biofuels over zeolite beta based catalysts

Catalytic hydropyrolysis of eucalyptus leaves was investigated in a batch reactor over four catalysts (H-BEA, Ni/BEA, Ni/Fe-BEA and Fe/BEA). HBEA catalyst exhibited a higher monoaromatic hydrocarbons (MAHs) selectivity compared to non-catalytic pyrolysis. However, the selectivity to polyaromatic hydrocarbons (PAHs) was not significantly reduced by the addition of a protonic zeolite. The highest cycloalkanes selectivity (78.5%) was observed over Ni/BEA, owing to its high concentration of Ni sites as well as acid sites, facilitating the hydrogenation and ring-opening of polyaromatic hydrocarbons together with the hydrodeoxygenation of phenols. In contrast, the Ni/Fe-BEA exhibits the highest selectivity of MAHs, suggesting the Ni-Fe species facilitate the partial hydrogenation of PAHs and hydrogenolysis of phenols but restrict the further hydrogenation of aromatic monomers. Moreover, the reduction of CO to CH4 was restricted over Ni-Fe/BEA compared to Ni/BEA. A high selectivity of phenols and PAHs was detected over Fe/BEA due to the high oxophilicity but low hydrogenation activity of Fe species, hindering the hydrogenation of PAHs and HDO of phenols. The spent Ni/BEA and spent Ni/Fe-BEA catalysts exhibited a higher surface area and pore volume as well as lower mass of deposited carbon compared to spent HBEA and spent Fe/BEA catalysts, suggesting the catalyst deactivation was restricted by hydrogenation metal (Ni, Ni-Fe) and dissociated H species. Besides, high H2 pressure promoted the hydrogenation and ring-opening of polyaromatic hydrocarbons, and high reaction temperature hindered the hydrogenation of MAHs to cycloalkanes. The highest selectivity to MAHs (85.1%) with a 62% selectivity of BTEX was observed over Ni/Fe-BEA catalyst at 400 °C and an initial H2 pressure of 3.0 MPa.