Dual-bed Catalyst Research Articles

Hydrocarbon generation through pyrolysis of high-lipid-content microalgae within a dual-catalyst bed

The presence of oxygenated and nitrogenated compounds formed during the pyrolysis of microalgae poses challenges for utilizing bio-oil as a competitive alternative to fossil fuels. In an effort to mitigate the formation of these undesirable substances and enhance the production of aromatic hydrocarbons, this study delved into the catalytic analytical pyrolysis of Schizochytrium limacinum using a tandem catalytic bed. The research involved the characterization of Schizochytrium limacinum biomass and examining the impact of reaction temperature and the dual-catalytic bed (hydrotalcite followed by zeolite) on the formation of pyrolytic compounds and hydrocarbons. In the analytical pyrolysis, the dual-catalytic bed comprising NiHTC followed by NiHZSM-5 showed superior efficiency in deacidification and deoxygenation. Through the calcination and reduction/passivation of both catalysts, hydrocarbon production achieved noteworthy levels, reaching 89 % and 92 %, respectively, with a catalyst-to-biomass ratio set at 5:1. Under these optimized conditions, aromatic formation consistently remained between 60 % and 70 %. Furthermore, pathways were delineated to elucidate potential chemical reaction routes. The satisfactory results suggest that high-lipid content microalgae can serve as successful feedstock for hydrocarbon generation.

Conversion of C8 aromatics over a dual-bed catalyst.

A dual-bed catalyst was prepared for the conversion of C8 aromatics. The upper bed layer consisted of ZSM-5 covered with SiO2, primarily utilized for ethylbenzene dealkylation. By employing tetraethyl orthosilicate (TEOS) as a deposition agent through the chemical liquid deposition (CLD) method, the modified ZSM-5 catalyst exhibited optimal catalytic performance at a TEOS addition of 0.6 g per gram of catalyst. The lower bed layer contained ZSM-39 catalyst, mainly employed for xylene isomerization reaction. ZSM-39 was synthesized using pyrrolidine as the template, and the best catalytic performance was achieved when the OH-/SiO2 molar ratio in the synthesis system was 0.05. The mass ratio between the upper and lower agents was maintained at 1 : 1. Compared to traditional single-bed ZSM-5 catalysts, the dual-bed catalyst demonstrated enhanced activity and selectivity.

Proposal of a parabolic-trough-oriented photo-thermo-reactor with coaxial baffles and dual-bed for high-efficient solar-driven hydrogen production from methanol steam reforming

A novel tubular photo-thermo-reactor with coaxial baffles and dual (photo-thermo- and thermo-) catalyst beds is proposed, integrated with the commercially-mature parabolic trough concentrators (EuroTrough ET-100 model) with high scalability for high-efficient H2 production from solar-driven methanol steam reforming. The optical-flow-thermal-chemical multiphysics coupled model, which incorporates the experimental data of photo-thermo-catalytic reaction kinetics, have been established to optimize the geometric and operational conditions of the proposed reactor. It is demonstrated that the systematic solar hydrogen production efficiency up to 21.2 % considering the pumping power and the solar-to-hydrogen efficiency up to 30.6 % without considering the energy cost have been achieved in the best case. The reason for the excellent performance is two-fold. On the one hand, the existence of coaxial baffles guides multiple penetrations of the gaseous reactants through the catalyst beds thus guarantees sufficient contact between them. On the other hand, the design of coaxial dual-bed guarantees cascaded utilizations of both photo-thermo-catalysis and thermo-catalysis thus realizes higher utilization efficiency of full-spectrum solar energy. Considering the compatibility to the commercially-mature optical concentrator, this work exemplifies a practically promising route of effective full-spectrum solar-to-chemical conversion.

Probing the Pyrolysis Process of Rice Straw over a “Dual-Catalyst Bed” for the Production of Fuel Gases and Value-Added Chemicals

Rice straw is an agricultural byproduct primarily produced in Asian regions. It is crucial to discover an effective method for converting this waste into chemicals that can be utilized to substitute goods derived from fossil fuels. Pyrolysis serves as an interesting procedure to obtain bio-oil from this rice straw. The composition of the bio-oil obtained after the pyrolysis procedure contains a small quantity of value-added chemicals in addition to various gas components in the gas product. Therefore, the development of catalytic systems that improve this pyrolytic reaction is mandatory. Herein, the design of a dual catalyst bed (CEM/ZSM-5) that catalyzes the volatiles that it releases has been developed. The highest output of 42.1 wt.% of bio-oil, 29.9 wt.% of gases and 28.0 wt.% of bio-char was obtained. Nevertheless, the inclusion of single zeolites to biomass yields biofuel outputs of 42.8 wt.%, gas yields of 27.7 wt.%, and a bio-char yielding of 29.5 wt.%. Additionally, the addition of cement to biomass results in a bio-oil yield of 40.4 wt.% and 30.5 wt.% of gas, along with 29.1 wt.% of char. Regarding pyrolysis gas products, the H2 yield in the produced biogas was increased from 35.9 mL/g to 45.7 mL/g, and the CH4 output was increased from 21.1 mL/g to 27.4 mL/g. The bioenergy output was evaluated employing GC-FID and GC-MS (gas and biofuel). The dual catalytic bed had a significant impact on the contents of the generated biofuel, increasing the quantity of hydrocarbons and other value-added compounds.

Conversion of low-density polyethylene into monocyclic aromatic hydrocarbons through continuous microwave pyrolysis with ex-situ dual-catalyst beds

The single-use of polyolefins-based individual protective equipment has led to the rapid generation of substantial plastic waste. This study aimed at cleaner disposal of the polyolefin waste, and carried out the continuous microwave pyrolysis (CMP) of low-density polyethylene (LDPE) over dual-catalyst beds of MCM-41 and HY. The dual-catalyzed trial was able to produce more condensate fractions with higher selectivity of monocyclic aromatic hydrocarbons (MAHs), compared with using only MCM-41 or HY zeolite. It was because the larger pore size of the MCM-41 catalyst (4.00 nm) could crack long-chain polyolefin intermediates into shorter chains. This alleviates steric and diffusional resistance while entering and exiting the micropores of the HY zeolite (0.74 × 0.74 nm). The maximum liquid yield (63.75 wt%) and MAHs selectivity (78.21%) were achieved at a catalysis temperature of 450 °C, feedstock to catalyst ratio of 8:3, and HY to MCM-41 ratio of 2:1. In addition, the performance of the CMP reactor was also compared favorably with the batch microwave pyrolysis (BMP) reactor under the same conditions. It has been found that the CMP reactor generated more MAHs products, whereas the BMP reactor was more selective for the generation of polycyclic aromatic hydrocarbons (PAHs) and gas products. The combination of CMP and the co-catalysis process offers new insight into sustainable management and value-added recovery of medical plastic waste.

Preparation of bio-jet fuels by a controllable integration process: Coupling of biomass fermentation and olefin polymerization

This work demonstrated that bio-jet fuels can be directionally prepared from bagasse (a typical lignocellulose biomass) by integrating bio- and chemical catalysis reaction processes. This controllable transformation started with the preparation of acetone/butanol/ethanol (ABE) intermediates through the enzymolysis and fermentation of bagasse. Pretreatment of bagasse by deep eutectic solvent (DES) promoted the enzymatic hydrolysis and fermentation because it destroyed the structure of biomass and remove lignin in lignocellulose. Subsequently, the selective catalytic conversion of sugarcane derived ABE broth to jet range fuels was achieved through an integrated process: ABE dehydration to light olefins over the HSAPO-34 catalyst and olefin polymerization to bio-jet fuels over the Ni/HBET catalyst. The dual catalyst bed synthesis mode improved the selectively of bio-jet fuels. High selectivity of jet range fuels (83.0 %) and high conversion of ABE (95.3 %) were obtained by the integrated process.

A Dual-Bed Strategy for Direct Conversion of Syngas to Light Paraffins

The authors studied the direct conversion of syngas to light paraffins in a dual-bed fixed-bed reactor. A dual-bed catalyst composed of three catalysts, a physically mixed methanol synthesis catalyst (CZA), and a methanol dehydration to dimethyl ether (DME) catalyst (Al2O3(C)) were put in the upper bed for direct conversion of syngas to DME, while the SAPO-34 (SP34-C) zeolite was put in the lower bed for methanol and DME conversion. The effects of the mass ratio of CZA to Al2O3(C), the H2/CO molar ratio, and the space velocity on catalytic performance of syngas to DME were studied in the upper bed. Moreover, a feed gas with a CO/CO2/DME/N2/H2 molar ratio of 9/6/4/5 balanced with H2 was simulated and studied in the lower bed over SP34-C; after optimizing the reaction conditions, the selectivity of light paraffins reached 90.8%, and the selectivity of propane was as high as 76.7%. For the direct conversion of syngas to light paraffins in a dual bed, 88.9% light paraffins selectivity in hydrocarbons was obtained at a CO conversion of 33.4%. This dual-bed strategy offers a potential route for the direct conversion of syngas to valuable chemicals.

Efficient pyrolysis process of lignin over dual catalyst bed for the production of Phenols and Aromatics

In this study, we developed an effective method for converting lignin into useful compounds to replace fossil-based products. The dual catalyst bed was used to catalyze the resulting pyrolysis vapors over it. A maximum bio-oil yield of 44.058 wt.% and gas yield of 28.9 wt.% along with 26.52 wt.% of bio-char is achieved. The biomass product (gas and Bio-oil) was characterized using GC-FID and GC–MS. The dual catalyst bed showed a considerable effect on the bio-oil composition and oxygenates were reduced. The bio-oil exhibit a high quantity of phenols and aromatic. In the gas product, the hydrogen yield has been enhanced from 14.6% to 21.4% and methane yield was enhanced from 20.8% to 23.1%.

Steering CO2 hydrogenation coupled with benzene alkylation toward ethylbenzene and propylbenzene using a dual-bed catalyst system

Utilization of CO2 as a C1 resource for the synthesis of aromatics is of great significance and is also related to carbon recycling. However, forming an ethylated or propylated side chain at the benzene ring by this strategy is difficult, and the products reported are methylated aromatics. Here, we show the first CO2 hydrogenation in tandem coupling with benzene alkylation to synthesize ethylbenzene and propylbenzene over a dual-bed system containing ZnZrOx, SAPO-34, and phosphorus-modified ZSM-5 catalysts. Controlled experiments and density functional theory studies reveal that the intermediate reactive species CHxO∗ (x = 1–3) of CO2 hydrogenation are preferentially alkylated with benzene to give methylated aromatics, rather than to form ethylated and propylated aromatics, when the three catalysts are simply mixed. By contrast, the three catalysts with rationally spatial distribution in the dual-bed system can afford 83.5% selectivity to ethylbenzene or 64.7% to propylbenzene in total aromatics without deactivation after 100 h.

Simultaneously Achieving High Conversion and Selectivity in Syngas-to-Propane Reaction via a Dual-Bed Catalyst System

Simultaneously Achieving High Conversion and Selectivity in Syngas-to-Propane Reaction via a Dual-Bed Catalyst System

Highly selective, energy-free, and environmentally friendly one-pot production of linear α-olefin from biomass-derived organic acid in a dual-bed catalyst system

An efficient and environmentally-friendly process to produce linear α-olefin from biomass-derived organic acid in a dual-bed catalyst system with high selectivity and stability.

The influence of dual-catalyst bed system of zeolitic and metal oxide catalysts on the production of valuable hydrocarbons during co-pyrolysis of rice straw and waste tire

The influence of dual-catalyst bed system of zeolitic and metal oxide catalysts on the production of valuable hydrocarbons during co-pyrolysis of rice straw and waste tire

Versatile One-Pot Tandem Conversion of Biomass-Derived Light Oxygenates into High-Yield Jet Fuel Range Aromatics

Valorization of biomass-derived oxygenates to jet fuel range aromatics harbors tremendous practical value due to growing concerns about the sustainable production of fuels and chemicals. Herein, bioderived C3 oxygenates with different functional groups including aldehydes, ketones, and alcohols were converted to jet fuel range hydrocarbons with high yield (maximum 86.1%) and purity (maximum 98.2%) and remarkably enhanced stability in a single continuous-flow reactor using nonprecious dual-bed catalysts. Instead of the conventional pathway (i.e., olefin generation following oligomerization), our strategy first transforms pronanal, propanol, and acetone into C9–C12 oxygenates via aldol condensation and ring closure reactions on the upstream Cu/SiO2 + TiO2 catalyst and subsequently converts the aldol-derived oxygenates through hydrogenation–dehydration–aromatization reactions on the downstream Ni/HZSM-5 catalyst at a relatively moderate temperature (573 K) and atmospheric pressure. This versatile and atom-economic strategy opens new opportunities for the efficient upgradation of bio-oil-derived oxygenates to renewable jet fuel range aromatics.

Selectively and effectively converting syngas into gasoline fuel

Selectively converting syngas to target hydrocarbon products is highly desired but challenging. In this issue of Chem Catalysis, Liu, Zhu, and co-workers report a (CZA + Al2O3)/N-ZSM-5(97) dual-bed catalyst for direct syngas conversion to gasoline, with which they achieved C5–11 selectivity as high as 80.6% at 86.3% CO conversion with no deactivation in 110 h.

Sequence of Ni/SiO2 and Cu/SiO2 in dual catalyst bed significantly impacts coke properties in glycerol steam reforming

Coke formation is a major challenge in steam reforming reactions. In addition to development of robust catalyst for tackling coking, in this study we explored the approach of using dual catalyst bed with the catalyst on top as the guard or sacrifice catalyst while with the bottom catalyst to catalyze the steam reforming. The rationale is that some oxygen-containing reactants are prone to polymerize on heating, and the polymeric coke could directly fall on surface of catalyst and leads to the rapid deactivation. Hence, glycerol was selected as the reactant for steam reforming in the catalyst bed with the Cu/SiO2 placed on the top of Ni/SiO2 catalyst. Our results demonstrate that first contact of glycerol to Cu/SiO2 on top changed abundance/type of small intermediates and the π-conjugated oligomers reached the Ni/SiO2 catalyst, rendering the Ni catalyst with a higher resistivity towards coking and deactivation. In addition, the carbon nanotube form of coke over Ni/SiO2 was thinner in wall thickness and larger in inner diameter of the cavity due to the impact of D-Cu/SiO2. Substantial polymeric coke with amorphous structure and low thermal stability formed over Cu/SiO2 via polymerisation of reaction intermediates. The characterization (in-situ diffuse reflectance infrared Fourier transform spectroscopy (DRIFTS)) for the glycerol steam reforming indicated that the Cu/SiO2 and Ni/SiO2 catalyst induced the formation of the very different functionalities of the reaction intermediates.

Realizing high conversion of syngas to gasoline-range liquid hydrocarbons on a dual-bed-mode catalyst

Achieving high conversion of syngas to fuels and basic chemicals with excellent selectivity and stability remains a challenge. Here, we report an 80.6% selectivity of gasoline-range C 5–11 hydrocarbons at 86.3% CO conversion over a dual-bed catalyst (CZA + Al 2 O 3 )/N-ZSM-5(97) that consists of an upper-bed syngas-to-dimethyl ether (DME) catalyst (CZA + Al 2 O 3 ) and a lower-bed DME-to-gasoline catalyst (nano-sized N-ZSM-5(97) zeolite). This dual-bed catalyst exhibits an excellent stability in a 110-h reaction test. The iso / n -paraffin ratio in the C 5–11 is up to 18. For the lower-bed zeolite catalyst, the nano-sized structure is beneficial to reduce coke and prolong lifetime; meanwhile, the low acid content is advantageous to increase C 5–11 selectivity. The 2,3-dihydro-1H-inden-1-one species can be definitely detected and identified in the spent lower-bed micro-sized M-ZSM-5(18) catalyst. They are regarded as intermediates to generate polycyclic aromatics, which generally lead to catalyst deactivation. The dual-bed catalyst (CZA + Al 2 O 3 )/N-ZSM-5(97) suggests a promising application in producing gasoline from syngas. • High and selective conversion of syngas to gasoline is achieved by a dual-bed catalyst • The dual-bed catalyst contains upper CZA + Al 2 O 3 and lower N-ZSM-5(97) catalysts • Nano-sized structure of N-ZSM-5(97) is beneficial to reduce coke and prolong lifetime • The low acid content of N-ZSM-5(97) helps to increase gasoline selectivity Because of the gradual depletion and non-renewability of petroleum, the use of non-petroleum resources instead of petroleum is of great significance. This alternative route can be generally achieved through syngas chemistry. The primary transportation fuel gasoline, which contains hydrocarbons with 5–11 carbons and is now almost derived from petroleum, can also be produced from non-petroleum syngas by some methods. However, stably obtaining high gasoline selectivity at high syngas conversion is still challenging. We have achieved this goal by designing a dual-bed catalyst (CZA + Al 2 O 3 )/N-ZSM-5(97) that includes a syngas-to-dimethyl ether (DME) catalyst CZA + Al 2 O 3 in the upper bed and a DME-to-gasoline catalyst N-ZSM-5(97) in the lower bed. This dual-bed catalyst suggests a promising application in producing gasoline from syngas. An 80.6% selectivity of gasoline-range hydrocarbons at 86.3% CO conversion can be achieved over a dual-bed catalyst that consists of a syngas-to-DME catalyst CZA + Al 2 O 3 (a mixture of CuZnAl methanol synthesis catalyst and acidic γ-Al 2 O 3 catalyst) in the upper bed and a DME-to-gasoline catalyst N-ZSM-5(97) (nano-sized H-ZSM-5 zeolite with Si/Al ratio = 97) in the lower bed. The dual-bed catalyst suggests a promising application in producing gasoline from syngas.

Spinel Co3O4 oxides-support synergistic effect on catalytic oxidation of toluene

Bulk spinel Co3O4 oxide and supported Co3O4 catalysts (Co3O4/YSZ and Co3O4/TiO2) were synthesized by one-step hydrothermal method. Their physicochemical properties were characterized by inductively coupled plasma optical emission spectroscopy, N2-sorption, powder X-ray diffraction, scanning electron microscopy, transmission electron microscopy, hydrogen-temperature programmed reduction and X-ray photoelectron spectroscopy.These characterization strategies were applied to corroborate and better understand the interaction between Co3O4 and the supports induced by the synergistic effect of support and the subsequent catalytic performance in toluene oxidation. The catalytic stability was evaluated by three consecutive runs and a long-term test. A highest toluene catalytic activity was achieved over Co3O4/YSZ supported catalyst comparing to that of the bulk Co3O4 and Co3O4/TiO2 catalysts, which could be attributed to its better low-temperature reducibility, oxygen activation and mobility induced by the intrinsic support properties. Thus, the positive interaction between spinel Co3O4 phase and YSZ support promoted the intrinsic catalytic properties for toluene oxidation, which was verify by testing a dual catalyst bed system consisting of bulk Co3O4 catalyst and YSZ support beds. These results were further confirmed by temperature-programmed oxygen isotopic exchange experiments, which indicated that the activation and diffusion of oxygen species on the YSZ oxygen vacancy sites were promoted by Co3O4, resulting in a significant increase of the reaction rate for toluene oxidation.

Highly converting syngas to lower olefins over a dual-bed catalyst

High conversion of syngas to light olefins was realized with 85% CO conversion, 80% C 2 –C 4 olefins in hydrocarbon products and only 21% CO 2 selectivity over a dual-bed catalyst (CuZnAlO x +H-ZSM-5)/SAPO-34.

Process design and techno-economic evaluation for the production of platform chemical for hydrocarbon fuels from lignocellulosic biomass using biomass-derived γ-valerolactone

Abstract We report a strategy for production of 5-nonanone which is a bio-based platform chemical that can be produced in large quantity from a variety of lignocellulosic biomass sources. In this strategy, the cellulose and hemicellulose fractions of lignocellulosic biomass are catalytically converted to γ -valerolactone (GVL) using the biomass derived GVL as a solvent. To generate the integrated strategy, we develop separation subsystems to achieve high purity of product. Importantly, GVL can be upgraded to 5-nonanone with high yield in a single reactor using a dual catalyst bed of Pd/Nb2O5 plus ceria-zirconia. We design a heat exchanger network to satisfy the total energy requirements of the integrated process via combusting lignin fraction of biomass. Economic feasibility of the process is investigated using discounted cash flow analysis.

Catalyst combination strategy for hydrogen production from methanol partial oxidation

Abstract Methanol is a promising feedstock for hydrogen production. This study experimentally investigates hydrogen production from the partial oxidation of methanol (POM) in sprays and dual-catalyst bed. Two different catalysts of h-BN-Pt/Al2O3 and h-BN-Pd/Al2O3 with low Pt and Pd contents (0.2 wt%) are utilized. The effects of preheating temperatures, O2-to-methanol molar (O2/C) ratios, and Pt/Pd ratios on POM are examined. POM can be triggered at room temperature when using the Pt catalyst. In contrast, POM can occur for a preheating temperature no less than 100 °C once the Pd catalyst is used. On account of the cold start of POM by the Pt catalyst, a dual-catalyst bed strategy is proposed where the Pt catalyst serves as the upper layer. In the dual-catalyst bed with the equivalent amounts of the two catalysts, the maximum H2 yield is 1.61 mol (mol methanol)−1 developing at O2/C = 0.6. Reducing the Pt catalyst amount does not obviously affect the POM performance where methanol conversion is close to 100% and the H2 yield is between 1.55 and 1.57 mol (mol methanol)−1. Accordingly, depending on the prices of Pt and Pd costs, economic and flexible operation of POM for hydrogen production can be achieved from the catalyst combination strategy.