Thermal Catalytic Process Research Articles

Simulated solar light-driven photothermal preferential oxidation of carbon monoxide in H2-rich streams over fast-synthesized CuCeO2–x nanorods

Aiming for purification the trace amount of CO in H2-rich streams with reduced energy consumption and low cost, solar-driven photothermal preferential oxidation of carbon monoxide on the non-precious metal oxide catalyst is proposed in this work. Cu doped CuCeO2−x nanorods catalysts were synthesized with a fast and simple coprecipitation method at the room temperature, which shows high CO oxidation activity in photothermal preferential oxidation of CO (CO-PROX) under UV-Vis-IR light irradiation. Rely on the various characterization methods such as UV-Vis-IR diffuse reflection spectrum (UV-Vis-IR DRS), photoluminescence spectrum (PL), transient photocurrent test, HRTEM, XRD, XPS, UV-Raman and H2-TPR, the optical and chemical properties of the CuCeO2−x nanorods catalysts were uncovered. The photothermal catalytic activity of CuCeO2−x nanorods doped with 10 wt% Cu reaches to 90% CO conversion under Xe lamp illumination (2.5 suns), and the solar driven photothermal CO-PROX reaction on CuCeO2−x nanorods were proposed to be proceeded by the light-to-thermal conversion and subsequently to drive a thermal catalytic process. The catalytic performance of CuCeO2−x nanorods in photothermal CO-PROX is closely related to the photo-to-thermal conversion efficiency and Cu-Ce synergetic interaction of CuCeO2−x nanorods catalyst. The introduction of CuOx greatly broaden the optical absorption range and promotes the light absorption capacity of ceria nanorods, which induces the catalyst with high photo-to-thermal conversion capability. Moreover, the optimal copper dopant benefits to enhance the Cu-Ce synergetic interaction and accelerate the oxidation reaction taking place at low temperature. CuCeO2−x nanorods catalyst shows promising competitive activity and ultra-low cost compared with the noble-based catalyst for the purification of hydrogen streams by the clean and eco-friendly sunlight sources.

Promotion Mechanism of CaSO4 and Au in the Plasma-Assisted Catalytic Oxidation of Diesel Particulate Matter.

Plasma-assisted catalysis has been demonstrated to be an innovative technology for eliminating diesel particulate matter (DPM) efficiently at low temperature (≤200 °C). Moreover, past studies have demonstrated that CaSO4, which exists in small concentrations (<2%) in DPM and is toxic in thermal catalytic oxidation processes, actually enhances DPM oxidation during plasma-assisted catalytic processes. However, the role CaSO4 plays in this promotion of DPM oxidation still remains unclear. The present study addresses this issue by investigating the underlying mechanisms of DPM oxidation during plasma-assisted catalytic processes using graphitic carbon as a surrogate DPM material in conjunction with CaSO4- and Au-impregnated γ-Al2O3 catalysts. The results of mass spectrometry and in situ diffuse reflectance infrared Fourier transform spectroscopy, which employs an in situ cell with a small dielectric barrier discharge space over the catalyst bed, demonstrate that CaSO4 can save and release O atoms contributing to graphite oxidation via the −S=O units of CaSO4 through a reversible surface reaction (−S=O + O → −S(−O)2). The results are employed to propose a formal mechanism of graphite oxidation catalyzed by CaSO4 and Au. These findings both improve our understanding of the plasma-assisted catalytic oxidation mechanisms of DPM and support the development of efficient plasma-assisted catalysts.

Platinum−Copper Bimetallic Nanoparticles Supported on TiO2 as Catalysts for Photo−thermal Catalytic Toluene Combustion

Oxidation of toluene into CO2 and H2O under mild conditions via a photo-promoted catalytic process has been regarded as a promising tactic to solve the toluene pollution issues in air. In this work, we examined the performance of Pt–Cu/TiO2 nanocatalysts with tunable mass ratios between Pt and Cu elements for photocatalytic, thermocatalytic, and photo–thermal catalytic degradation of toluene. In the photo–thermal catalytic process, 80% of the inlet toluene could be decomposed over Pt0.4 wt %Cu0.1 wt %–TiO2 catalyst at 77 °C under light irradiation, while 100 °C was needed for Pt0.5 wt %–TiO2 to achieve the same catalytic efficiency. The greatly enhanced activity could be ascribed to the synergistic effects arising from photothermal effects of the high dispersion of PtCu alloy nanoparticles, intimate interaction between the metal elements, and the photoexcitation of TiO2. In the photocatalytic process, the highest photocatalytic toluene conversion rate was obtained on the PT-4 catalyst (55%) and there was a negligible conversion rate (0.38%) of toluene under thermocatalytic conditions at 110 °C, delineating that the efficiency of photo–thermal catalytic degradation of toluene was much higher than that of a thermocatalytic or a photocatalytic process, illustrating the synergistic effects between light irradiation and heat. This work highlights the high photo–thermal catalytic toluene degradation performance of PtCu alloy nanoparticles and the synergistic effects of light irradiation and heat.

Dielectric Barrier Discharge Plasma-Assisted Catalytic CO2 Hydrogenation: Synergy of Catalyst and Plasma

CO2 hydrogenation is an effective way to convert CO2 to value-added chemicals (e.g., CH4 and CH3OH). As a thermal catalytic process, it suffers from dissatisfactory catalytic performances (low conversion/selectivity and poor stability) and high energy input. By utilizing the dielectric barrier discharge (DBD) technology, the catalyst and plasma could generate a synergy, activating the whole process in a mild condition, and enhancing the conversion efficiency of CO2 and selectivity of targeted product. In this review, a comprehensive summary of the applications of DBD plasma in catalytic CO2 hydrogenation is provided in detail. Moreover, the state-of-the-art design of the reactor and optimization of reaction parameters are discussed. Furthermore, several mechanisms based on simulations and experiments are provided. In the end, the existing challenges of this hybrid system and corresponding solutions are proposed.

Recent Advances in Catalysis Based on Transition Metals Supported on Zeolites.

This article reviews the current state and development of thermal catalytic processes using transition metals (TM) supported on zeolites (TM/Z), as well as the contribution of theoretical studies to understand the details of the catalytic processes. Structural features inherent to zeolites, and their corresponding properties such as ion exchange capacity, stable and very regular microporosity, the ability to create additional mesoporosity, as well as the potential chemical modification of their properties by isomorphic substitution of tetrahedral atoms in the crystal framework, make them unique catalyst carriers. New methods that modify zeolites, including sequential ion exchange, multiple isomorphic substitution, and the creation of hierarchically porous structures both during synthesis and in subsequent stages of post-synthetic processing, continue to be discovered. TM/Z catalysts can be applied to new processes such as CO2 capture/conversion, methane activation/conversion, selective catalytic NOx reduction (SCR-deNOx), catalytic depolymerization, biomass conversion and H2 production/storage.

Non-Faradaic Promotion of Ethylene Hydrogenation under Oscillating Potentials.

The acceleration of Faradaic reactions by oscillating electric potentials has emerged as a viable tool to enhance electrocatalysis, but the non-Faradaic dynamic promotion of thermal catalytic processes remains to be proven. Here, we present experimental evidence showing that oscillating potentials are capable of enhancing the rate of ethylene hydrogenation despite no promotion effect being observed under static potentials. The non-Faradaic dynamic enhancement reaches up to 553% on a Pd/C electrode when cycling between −0.25 and 0.55 VNHE under optimized conditions with a frequency of around 0.1 Hz and a duty cycle of 99%. Under those conditions, the catalytic reaction rates were promoted beyond the rate of charge transfer to the electrode surface, confirming the non-Faradaic nature of the process. Experiments in different electrolytes reveal a good correlation between the catalytic enhancement and the double-layer capacitance, a measure for the interfacial electric field strength. Preliminary kinetic data is consistent with cyclic removal of adsorbates from the surface at negative potential and the subsequent adsorption of H2 and C2H4 and hydrogenation reaction at the positively polarized surface.

Experimental Study on Thermal and Catalytic Decomposition of a Dual-Mode Ionic Liquid Propellant

With the increasing of space activities and people’s awareness of environmental protection, it is necessary to develop a new non-toxic space propulsion system with high performance. Hydroxylammonium nitrate (HAN)/1-ethyl-3-methyl-imidazolium ethylsulfate([Emim][EtSO4]) blend ionic liquid propellant is a potential replacement with non-toxic and high-performance characteristics for hydrazine type liquid propellants, which can be used in both chemical and electrical propulsion system. This paper introduced the thermogravimetric experimental analysis (TGA-DSC) results of HAN/[Emim][EtSO4] ionic liquid propellant with the thermal decomposition and catalytic decomposition process. Its mass-loss process and exothermic process under different reaction conditions at a heating rate of 5K/min~15K/min were studied. Generally, the mass-loss results showed that there were four characteristic stages during the decomposition process of the HAN/[Emim][EtSO4] ionic liquids, which were the evaporation of the water solvent, decomposition of the HAN component, further decomposition of the [Emim][EtSO4], and slow loss of the residual substances. At the same time, two exothermic peaks were observed, which respectively corresponded to the decomposition of HAN and the further decomposition of [Emim][EtSO4]. Using catalyst can significantly reduce the decomposition temperature of the propellant and the residual mass. The contents in this paper proved that this propellant had a good application prospect within the catalytic ignition aerospace thruster.

Liquid Metals in Catalysis for Energy Applications

Summary To keep up with the fast-paced transitioning of the global energy sector, which is constantly thriving to enable reliable, economic, and sustainable energy production, catalysis research has been required to continuously evolve in response. The challenges in the existing systems are predominantly due to dependencies on heterogeneous solid catalysts that are susceptible to coking. In this respect, liquid-metal (LM) catalysts have been demonstrated to have a critical advantage over conventional catalysts. Recently, LMs acquired a place in catalysis, with a reputation often synonymous with interesting properties and a remarkable ability to break trade-offs between homogeneous and heterogeneous catalysis. This review bridges the fundamental principles of LM research and the recent advances in LM-based thermal and electrochemical catalysis for energy applications. Moreover, emerging approaches for the improved utilization of LMs are outlined, and the concepts requiring greater research attention that could enable the development of exciting energy solutions are highlighted.

Hybrid Photo- and Thermal Catalyst System for Continuous CO2 Reduction.

Heterogeneous thermal catalytic processes are vital for industrial production of fuels, fertilizers, and other chemicals necessary for sustaining human life. However, these processes are highly energy-intensive, requiring a vast consumption of fossil fuels. An emerging class of heterogeneous catalysts that are thermally driven but also exhibit a photochemically enhanced rate can potentially reduce process energy intensity by partially substituting conventional heat (where fossil fuels are needed) with solar energy. Such catalyst systems have yet to be practically utilized. Here, we demonstrate a compact electrically heated photo- and thermal annular reactor module to reduce CO2 to CO, via the reverse water gas shift reaction. A first-principles-based design approach was taken in developing a SiO2 on an Al photo- and thermal catalyst system for the model photo- and thermal indium oxide hydroxide (In2O3-x(OH)y) catalysts. A 5-fold light enhancement in the CO production rate and over 70 h of stable CO production were achieved. This represents the highest light enhancement effect reported for this model photocatalyst to date. The reactor presented herein allows continuous operation and a significant reduction of 31% in heater power consumption when provided with an additional 2 suns of irradiation, demonstrating the strong photo- and thermal-harvesting performances of the catalyst system developed in this work.

The performance analysis of a purified PV/T-Trombe wall based on thermal catalytic oxidation process in winter

On one hand, PV/T air system is in unused condition in summer while PV/T water system exists the freezing problem in winter. On the other hand, the indoor air pollution has been gotten more and more attention. Therefore, this article proposed a purified PV/T-Trombe wall, which could produce sustainable electricity and degrade gaseous formaldehyde in whole year, realize space heating in winter and supply hot water in summer. The focus in this article was the comprehensive performance investigation in winter. Firstly, continuous six full-day experiments were conducted to investigate the thermal and electrical performance. Secondly, based on the verified system heat and mass transfer model, the formaldehyde degradation performance was investigated. Thirdly, the performance comparisons of the proposed system with other PV/T systems were conducted. Main results were: (1) The average daily electrical efficiency and air thermal efficiency were 11.9% and 36.6%, respectively. (2) The dependence between the air thermal efficiency and the modified normalized temperature difference well fitted the linear relationship under natural convection condition. (3) The clean air delivery rate was in the range of 42.5–81.6 m3/h and the daily generated volume of clean air was 202.9 m3/(m2·day). (4) The thermal and electrical efficiency considering formaldehyde degradation was 50.3%, with the increase of 3.7% due to the contribution from formaldehyde degradation. (5) The ratio of the electrical efficiency considering formaldehyde degradation to the standard PV cell efficiency approached up to 98.6%, which indicated a high utilization on the PV cells.

Thermo–Photo Catalysis for Methanol Synthesis from Syngas

It is well-known that the synthesis of methanol from syngas is based on thermal catalysis (TC). However, in this work, light was introduced into the thermal catalytic process, creating a novel ther...

From Solar Energy to Fuels: Recent Advances in Light-Driven C1 Chemistry.

Catalytic C1 chemistry based on the activation/conversion of synthesis gas (CO+H2 ), methane, carbon dioxide, and methanol offers great potential for the sustainable development of hydrocarbon fuels to replace oil, coal, and natural gas. Traditional thermal catalytic processes used for C1 transformations require high temperatures and pressures, thereby carrying a significant carbon footprint. In comparison, solar-driven C1 catalysis offers a greener and more sustainable pathway for manufacturing fuels and other commodity chemicals, although conversion efficiencies are currently too low to justify industry investment. In this Review, we highlight recent advances and milestones in light-driven C1 chemistry, including solar Fischer-Tropsch synthesis, the water-gas-shift reaction, CO2 hydrogenation, as well as methane and methanol conversion reactions. Particular emphasis is placed on the rational design of catalysts, structure-reactivity relationships, as well as reaction mechanisms. Strategies for scaling up solar-driven C1 processes are also discussed.

Effect of DEE and MEA as additives on a CRDI diesel engine fueled with waste plastic oil blend

ABSTRACTThe unavoidable rise in plastic usage creates a dangerous threat to the environment due to its non-biodegradable nature. Disposal of waste plastics is carried out using various techniques. Among that pyrolysis process is effective one to convert waste plastics into oil. This plastic oil is used as an alternative fuel in internal combustion engines. In this present work, plastic oil is produced through thermal pyrolysis and catalytic pyrolysis processes using polyethylene plastic wastes (HDPE, LDPE) as feedstock. In the catalytic pyrolysis process, fly ash used as catalyst. Then, the effect of diethyl ether (DEE) and methoxy ethyl acetate (MEA) on the performance, combustion and emission characteristics of the CRDI diesel engine fueled with waste plastic oil blend is analyzed and compared with the diesel fuel operation. The experiments are carried out for six load conditions varying from 0% to 100% and without any engine modification. The experimental results showed that improvement in brake thermal efficiency is attained with test fuel D50W40MEA10 than neat diesel. It is observed from investigation that test fuel 50D40W10MEA has produced lower CO, HC and smoke emission than neat diesel. NOX emission with test fuel D50W40MEA10 is slightly higher than neat diesel, but lower than neat diesel with test fuel D50W40DEE10.

The conversion of expanded polystyrene waste to liquid fuel using Cu-Al2O3 by the thermal catalytic cracking process

The high use of plastic and the length of time the decomposition will worsen environmental conditions. The processing of plastic waste by incineration was not a safe method for the environment because it will produce gas emissions that potentially become pollutants. The catalytic cracking process is one of the ways to process polystyrene plastic waste into liquid fuel. The purpose of this study is to identify the effect of cracking temperature and mass of catalyst towards the volume and fuel quality of the production. The research conducted through the thermal catalytic cracking process. The mass of catalyst Cu-Al2O3 is 0.5 g, 1 g, 1.5 g. The cracking temperature is 150 °C, 200 °C, 250 °C. Cracking time is 90 minutes. The highest volume of the liquid fuel was 113 mL at a 250°C cracking temperature and the addition of 1g catalyst. The results of the best density analysis obtained at 0.74 g/mL, and the octane number of RON is 100, MON is 90, and AKI is 94.4.

Visible light-induced diastereoselective semihydrogenation of alkynes to cis-alkenes over an organically modified titanium(IV) oxide photocatalyst having a metal co-catalyst

Hydrogen (H2)-free and poison (lead and quinoline)-free semihydrogenation of alkynes to cis-alkenes under gentle conditions is one of the challenges to be solved. In this study, a titanium(IV) oxide photocatalyst having two functions (visible light responsiveness and semihydrogenation activity) was prepared by modification with 2,3-dihydroxynaphthalene (DHN) and a copper (Cu) co-catalyst, respectively. The photocatalyst (DHN/TiO2-Cu) showed high performance for diastereoselective semihydrogenation of alkynes to cis-alkenes in water-acetonitrile solution under visible light irradiation without the use of H2 and poisons. Alkynes having reducible functional groups were converted to the corresponding alkenes with the functional groups being preserved. The addition of water to acetonitrile changed the amount of alkynes adsorbed on the photocatalyst, which was a decisive factor determining the rate of hydrogenation. A relatively large apparent activation energy, 27 kJ mol−1, was obtained by a kinetic study, indicating that the rate-determining step of this reaction was not an electron production process but a thermal catalytic semihydrogenation process over the Cu co-catalyst. Semihydrogenation and hydrogen evolution occurred competitively on Cu metals and the former became predominant at slightly elevated temperatures, which is discussed on the basis of the kinetic parameters of two reactions.

Hydrides, Amides and Imides Mediated Ammonia Synthesis and Decomposition

Ammonia is feeding nearly half the world population and also holds the promise as a carbon‐free energy carrier. The development of ammonia synthesis and decomposition processes under milder conditions is a grand challenge for more than a century. Increasing effort is devoted to this area in recent years and encouraging progress has been achieved. In this paper, we summarize our recent research using alkali or alkaline earth metal amides, imides and hydrides for ammonia synthesis and decomposition. These materials could serve as either indispensible component of active center in thermal catalytic process or nitrogen carrier for chemical looping ammonia synthesis. The synergy of amide, imide, or hydride with transition metals enables ammonia synthesis or decomposition with unprecedented high efficiency under milder reaction conditions, and thus opens an avenue to advance the chemistry or catalysis of N2 fixation reaction. The compositional and structural diversity of the amide, imide and hydride materials provides plenty of opportunity and potential for further exploration and optimization.

Thickness effects of Ni on the modified boron doped diamond by thermal catalytic etching for non-enzymatic glucose sensing

Sputtered nickel (Ni) layers modified boron-doped diamond (BDD) electrodes for non-enzymatic glucose sensor were fabricated by the thermal catalytic etching process in the hydrogen ambient. The effect of Ni thickness on the thermal catalytic etching and the electrochemical behavior of Ni/BDD electrodes for glucose oxidation were investigated. Scanning electron microscopy(SEM)and Raman spectroscopy were utilized to characterize the electrode morphology and composition, respectively. Marked by different thickness and morphology of Ni layer, three kinds of surfaces were obtained after thermal catalytic etching. The first is a roughened surface with most Ni nano-particles sinking into the BDD film, the second is with Ni micro-particles presented on the BDD film, the third is with residual lamellar Ni. Electrochemical results indicated that the electrochemical behaviors of those Ni/BDD electrodes were related to the surface structure. The second Ni/BDD electrode has the limit of detection (LOD) of 1.23μM with a sensitivity of 839.3μAmM−1cm−2, which was ascribed to the numerous agglomerated Ni nano- and micro-particles presented on the roughed surface.

Sunlight-assisted hydrogenation of CO2 into ethanol and C2+ hydrocarbons by sodium-promoted Co@C nanocomposites

The hydrogenation of CO2 into hydrocarbons promoted by the action of sunlight has been studied on Co nanoparticles covered by thin carbon layers. In particular, nearly 100% selectivity to hydrocarbons is obtained with increased selectivities towards C2+ hydrocarbons and alcohols (mainly ethanol) when using nanostructured materials comprising metallic cobalt nanoparticles, carbon layers, and sodium as promoter (Na-Co@C). In the contrary, larger amount of CH4 and lower selectivity to C2+ hydrocarbons and alcohols were obtained in the conventional thermal catalytic process. When using Co@C nanoparticles in the absence of Na or bare Co3O4 as catalyst, methane is essentially the main product (selectivity >96%). Control experiments in the presence of methanol as a hole scavenger suggest the role of light in generating charges by photon absorption as promoting factor. The reaction mechanism for photoassisted CO2 hydrogenation on the Co-based catalysts was investigated by near ambient-pressure X-ray photoelectron (AP-XPS) and in situ Raman spectroscopies, which provided information on the role of light and Na promoter in the modulation of product distribution for CO2 hydrogenation. Spectroscopic studies suggested that surface CO2 dissociation to CO, the stabilization of CO adsorbed on the surface of Na-Co@C catalyst and the easy desorption of reaction products is a key step for photothermal CO2 hydrogenation to ethanol and C2+ hydrocarbons.

Low temperature reforming of biogas over K-, Mg- and Ce-promoted Ni/Al2O3 catalysts for the production of hydrogen rich syngas: Understanding the plasma-catalytic synergy

Plasma-catalytic biogas reforming over Ni-X/Al2O3 catalyst (X=K, Mg and Ce) has been carried out in a coaxial dielectric barrier discharge (DBD) plasma reactor at 160°C. Three different process modes: plasma-alone, catalysis-alone and plasma-catalysis have been investigated to get new insights into the synergistic effect resulted from the interaction of the plasma with the promoted Ni catalysts. Compared to the biogas reforming using either plasma-alone or catalysis-alone mode at the same temperature (160°C), the combination of the plasma with the Ni-based catalysts exhibited a low temperature synergistic effect, as evidenced from the much higher reforming performance of the plasma-catalytic process compared to that of the sum of the individual processes (plasma-alone and catalysis-alone). The addition of promoters (K, Mg and Ce) into the Ni/Al2O3 catalyst enhanced the conversion of CH4, the yield of H2 and the energy efficiency of the plasma process. In this study, the behaviour of K, Mg and Ce promoters in the low temperature plasma-catalytic biogas reforming was clearly different from that in high temperature thermal catalytic process in terms of the conversion of CH4 and carbon deposition, which could be ascribed to the temperature-dependent character of the promotors. In the plasma-catalytic biogas reforming, the Ni-K/Al2O3 catalyst showed the best performance, enhancing the conversion of both CO2 and CH4, the yield of H2, CO and C2–C4 alkanes and the energy efficiency of the plasma process. The highest conversion of CO2 (22.8%) and CH4 (31.6%) was achieved by placing the K-promoted catalyst in the plasma reforming process. The Mg-promoted catalyst remarkably increased the H2/CO molar ratio in the gas products (up to 2.2) due to the decreased CO2 conversion. In addition, compared to the un-promoted Ni/Al2O3 catalyst, although the use of the promoted catalysts increased the carbon deposition on the surface of the spent catalysts by 22%–26%, the total amount of deposited carbon was still less than that reported in high temperature catalytic dry reforming processes. More than 80% of the increased carbonaceous species was in the form of reactive carbon species, which can be easily oxidized by CO2 and O atoms and maintain the stability of the catalysts during the reforming reaction.

Metallic-substrate-supported manganese oxide as Joule-heat-ignition catalytic reactor for removal of carbon monoxide and toluene in air

Structured catalysts and reactors have wide applications in environmental remediation and production of important energy-related chemicals. In thermal catalytic processes, external heater are often required to raise the temperature and ignite the reactions, which might lead to huge setups. Herein, we introduce a novel Joule-heat-ignition catalytic reactor. Using Fe-Cr-Al alloy as catalyst substrate, electric currents can pass directly through the substrate, generating Joule heat and bringing the catalysts to the target temperatures. Therefore, the setup can be simplified by omitting the additional heater; the heat produced inside the substrates can be transferred directly to the catalyst coat to achieve rapid ignition; and the reaction temperature can be flexibly controlled by adjusting the input power. In this work, we loaded manganese oxide catalyst onto an alloy wire and used it to build a Joule-heat-ignition reactor for the catalytic oxidation of carbon monoxide and toluene. The anodization pretreatment generated channels on the alloy surface, which effectively enhanced the catalyst loading. The use of alumina as a secondary support also favored catalyst loading and promoted catalyst dispersion. By adding proper amounts of zirconium, the mechanical stability of the catalyst layer increased. The Joule-heat-ignition catalytic system might provide some inspiration in related environmental catalysis.