Steam Reforming Of Toluene Research Articles

Iron Oxide over Silica-Doped Alumina Catalyst for Catalytic Steam Reforming of Toluene as a Surrogate Tar Biomass Species

An iron oxide over silica-doped alumina catalyst was successfully synthesized using one-pot, solvent-deficient method. The prepared Fe2O3/SiO2–Al2O3 catalyst was characterized using TGA/DTG, XRD, N2 adsorption isotherm, NH3-TPD, and SEM. The TGA/DTG and XRD results show that the presence of Si enhances the stability of γ-Al2O3 support at high temperatures. The prepared Fe2O3/SiO2–Al2O3 catalyst was obtained by calcination at 950 °C, with a high BET specific surface area (49 m2/g). The NH3-TPD showed that Fe addition can significantly increase catalyst acidity. SEM images confirmed the textural properties of the catalysts in term of surface morphology. The catalytic activity of Fe2O3/SiO2−Al2O3 catalysts was examined in a CREC fluidized riser simulator using toluene as model compound for biomass tar. Experiments with this catalyst yielded high toluene conversions. Composition of gases produced (H2, CO, CO2, and CH4) were close to chemical equilibrium at 25 s and 600 °C. These results indicate that the Fe2O...

Study of the performance of Pt/Al2O3 and Pt/CeO2/Al2O3 catalysts for steam reforming of toluene, methane and mixtures

This work studied the effect of reactant mixture on the performance of Pt/Al2O3 and Pt/CeO2/Al2O3 catalysts for the SR of toluene, methane and toluene/methane mixture. Both catalysts only slightly deactivated during SR of toluene or methane, separately. However, they underwent a strong deactivation when both reactants were present in the feed. The Raman spectra of the used catalysts after different reaction conditions revealed the formation of very few carbon deposits, which were more significant for the SR of the mixture. in situ X-ray absorption spectroscopy showed that oxygen vacancies were formed on Pt/CeO2/Al2O3 but they did not inhibit catalyst deactivation. Therefore, the main cause of deactivation of Pt/Al2O3 and Pt/CeO2/Al2O3 catalysts is likely due to the competitive adsorption of toluene and methane on the same active sites that leads to an accumulation of carbon on the surface.

Opposite effects of self-growth amorphous carbon and carbon nanotubes on the reforming of toluene with Ni/α-Al2O3 for hydrogen production

Ni-based catalysts are prone to be deactivated by carbon deposition. This study aims to investigate the influence mechanism of different types of carbon deposition on the activity of Ni/α-Al2O3 catalyst at various steam-to-carbon (S/C) ratios during steam reforming of toluene for hydrogen production. At a low S/C ratio of 1, the catalytic activity of Ni/α-Al2O3 was inhibited due to the covering and blocking of Ni active sites by the formation of amorphous carbon on the Ni surface. While at a high S/C ratio of 3, more than 80 wt% of carbon deposition was found to be self-growth carbon nanotubes (CNTs) with an average diameter of around 15 nm. The activity of Ni/α-Al2O3 in steam reforming of toluene was unusually promoted, which can be attributed to the tip-growth mechanism of CNTs, whereby the Ni particles migrated to the tip or the surface of CNTs, resulting in the improved active site dispersion.

Ni nanoparticles supported on carbon as efficient catalysts for steam reforming of toluene (model tar)

Abstract This paper investigated the influences of surface properties of carbon support and nickel precursors (nickel nitrate, nickel chloride and nickel acetate) on Ni nanoparticle sizes and catalytic performances for steam reforming of toluene. Treatment with nitric acid helped to increase the amount of functional groups on the surface and hydrophilic nature of carbon support, leading to a homogeneous distribution of Ni nanoparticles. The thermal decomposition products of nickel precursor also played an important role, Ni nanoparticles supported on carbon treated with acid using nickel nitrate as the precursor exhibited the smallest mean diameter of 4.5 nm. With the loading amount increased from 6 wt% to 18 wt%, the mean particle size of Ni nanoparticles varied from 4.5 nm to 9.1 nm. The as-prepared catalyst showed a high catalytic activity and a good stability for toluene steam reforming: 98.1% conversion of toluene was obtained with the Ni content of 12 wt% and the S/C ratio of 3, and the conversion only decreased to 92.0% after 700 min. Because of the high activity, good stability, and low cost, the as-prepared catalyst opens up new opportunities for tar removing.

Anchoring effect and oxygen redox property of Co/La0.7Sr0.3AlO3-δ perovskite catalyst on toluene steam reforming reaction

To elucidate specific functions of supports, we investigated steam reforming of toluene as a model compound of biomass tar over Co catalyst supported on perovskite-type oxide. Co-supported La0.7Sr0.3AlO3-δ catalyst showed the highest activity among various Co-supported catalysts. STEM measurements and XPS measurements revealed the coexistence of La cation and lattice oxygen defect produces an anchoring effect to Co particles. The lattice oxygen release rate on each catalyst was measured with H218O steady-state isotopic transient kinetic analysis (SSITKA). The anchoring effect, higher dispersion of Co and redox property, are important for the high catalytic performance of Co/La0.7Sr0.3AlO3-δ catalyst on toluene steam reforming.

Perovskite-based catalysts for tar removal by steam reforming: Effect of the presence of hydrogen sulfide

One of the greatest problems in biomass gasification processes is the conditioning of the produced synthesis gas, which contains various contaminants, including tar and hydrogen sulfide. Nickel catalysts, designed for steam reforming of aliphatic hydrocarbons (natural gas and nafta), are usually deactivated by coke deposition and sulfur poisoning. In this work, nickel and/or manganese catalysts derived from perovskites were prepared by the citrate method and characterized by X-ray diffraction, N2 physisorption and temperature programmed reduction. The catalysts were evaluated in the steam reforming of toluene, used as tar model compound, in the absence of H2S at 700 °C and in the presence of 50 ppm H2S at 800 °C. LaNi0.5Mn0.5O3 catalyst showed higher activity and stability in the absence of H2S. LaMnO3 catalyst, although less active in the absence of H2S, showed increased stability in the presence of H2S, with conversion of about 60%. H2 production was only observed in the absence of H2S.

Performance of nickel supported catalysts in steam reforming of toluene as a tar model compound for use in hot-syngas clean-up

Performance of nickel supported catalysts in steam reforming of toluene as a tar model compound for use in hot-syngas clean-up

A highly carbon-resistant olivine thermally fused with metallic nickel catalyst for steam reforming of biomass tar model compound

The Ni/olivine catalyst prepared by thermal fusion showed high catalytic activity and carbon deposition resistance during toluene steam reforming.

Promotive effect of Ba addition on the catalytic performance of Ni/LaAlO3 catalysts for steam reforming of toluene

Ba addition to supported Ni catalysts was investigated on steam reforming of toluene, as a model compound of biomass tar. Ba addition showed drastic promotive effects on catalytic activity and tolerance against oxidation. Various catalytic tests and characterization were conducted, including pressure dependence, Arrhenius plots, STEM and XAFS observations, dispersion of supported Ni, and temperature programmed reduction. Results revealed that the electron donation from Ba to Ni enabled high catalytic performance of Ba/Ni/LaAlO3 perovskite catalyst.

An insight into the effect of calcination conditions on catalytic cracking of toluene over 3Fe8Ni/palygorskite: Catalysts characterization and performance

In this paper, the effect of calcination conditions on catalytic cracking of toluene over 3Fe8Ni/PG (PG: palygorskite) was investigated. The experimental parameters including the calcination temperature, time and atmosphere and reaction temperature were evaluated. The catalysts were characterized using X-ray diffraction (XRD), H2 temperature-programmed reduction (TPR), transmission electron microcopy (TEM) and Raman spectroscopy. The gas composition was analyzed by a gas chromatograph (GC). The results showed that 3Fe8Ni/PG catalyst exhibited a higher catalytic reactivity for catalytic cracking of toluene than that of thermal cracking over quartz. In consideration of the thermal stability and catalytic reactivity of catalyst, a proper calcination temperature and time should be employed in the preparation of 3Fe8Ni/PG catalyst. The 3Fe8Ni/PG reduced in hydrogen at 700°C for 2h showed the highest catalytic reactivity as evidenced by the toluene conversion of 100% at the reaction temperature of 550°C. The catalytic reactivity of 3Fe8Ni/PG reduced in hydrogen for toluene conversion was superior to that of 3Fe8Ni/PG calcinated in air, 3Fe/PG, and 8Ni/PG, which revealed that the awaruite (NiFe) was the active component for the decomposition of toluene. Moreover, steam reforming of toluene over 3Fe8Ni/PG catalysts suggested that 80% toluene conversion can be achieved and most of toluene was converted into H2 and CO. Both amorphous carbon and graphitic carbon species were formed on 3Fe8Ni/PG catalysts after the catalytic reaction. The D/G ratio (the relative intensity of D-band to G-band ratio) was positively correlated to the catalytic reactivity of 3Fe8Ni/PG catalysts.

Ni based catalysts promoted with cerium used in the steam reforming of toluene for hydrogen production

NixMg6−xAl1.8Ce0.2 (with 0 ≤ x ≤ 6) mixed oxides catalysts were prepared by hydrotalcite route. All the oxides were calcined at 800 °C and characterized by different physico-chemical methods. The catalysts are then reduced before their use in the steam reforming of toluene. The XRD and TG/DTA confirmed the formation of the hydrotalcite structure for the non-calcined samples. The N2 adsorption/desorption results revealed that all catalysts correspond to mesoporous materials. The study by temperature programmed reduction (H2-TPR) showed that the reducibility of the catalysts is influenced by the nickel content. The CO2-TPD results showed that the catalyst with high magnesium content present the highest basicity. The Ni2Mg4Al1.8Ce0.2 shows the best toluene conversion among all the catalysts and it was then compared to a non-promoted catalyst. The spent catalysts were characterized by TPO, TG/DTA and XRD and they didn't reveal any coke formation.

Fe-Ca interactions in Fe-based/CaO catalyst/sorbent for CO2 sorption and hydrogen production from toluene steam reforming

After biomass gasification, tar can be removed by steam reforming and additional hydrogen production. This latter can be enhanced by CO2 sorption using the global process known as sorption enhanced hydrogen production (SEHP). Toluene was studied as tar model compound and its reforming was carried out at a compromise temperature (700°C) to permit simultaneous activation of iron based catalyst and CO2 sorption on CaO based sorbent.Fe-Ca interactions on Fe-based/CaO catalyst/sorbent performances occur during steam reforming of toluene. In order to determine the specific conditions for the formation of the different iron species, Fe-based/CaO bi-functional materials have been prepared following three different methods with various calcium and iron precursors. The characterizations (XRD, Mossbauer spectroscopy, TGA, TPR, SEM, and BET/BHJ) performed before and after steam reforming of toluene provide information about the evolution of the iron species and Fe-Ca interactions during catalytic tests. The results suggest that the activity of Fe/CaO materials depends not only on the presence of Fe2O3 but also on the stability of the interactions between iron and calcium under reaction conditions.The bi-functional material prepared from iron acetate and calcium acetate by mechanical mixing (FeAc/CaO (M)) has properties (large specific surface area, appropriate sorption capacity at 700°C, and the lowest deactivation) that play an important role for CO2 capture. Moreover, the presence of the α-Fe2O3 phase, precursor of the active phase in steam reforming of tar, reducible at 700°C, intervenes in the hydrogen production rate by enhancing the Water Gas Shift reaction. Finally, its higher availability of iron (Fe2O3) limit the selectivity towards undesirable products such as benzene.

Catalytic reforming of toluene and naphthalene (model tar) by char supported nickel catalyst

The purpose of this study was to utilize gasification derived char as a catalyst support for tar removal. Red cedar char collected from downdraft bed gasification was chemically activated into activated carbon and impregnated with nickel acetate and nickel nitrate. The effects of nickel salts precursor, nitric acid treatment of support and reduction of nickel in hydrazine medium on catalyst performance were studied. It was found nickel nitrate was a better nickel precursor than nickel acetate for preparation of char supported nickel catalyst. The catalyst impregnated with nickel nitrate was found more active in steam reforming of toluene than the catalyst impregnated with nickel acetate. TEM results indicated that nickel particle size of the catalyst impregnated with nickel nitrate was much smaller than that of the catalyst impregnated with nickel acetate. Toluene showed higher removal efficiency than naphthalene. The presence of naphthalene decreased the toluene removal.

Steam reforming of plastic pyrolysis model hydrocarbons and catalyst deactivation

Catalytic steam reforming of n-hexane, 1-hexene, tetradecane and toluene over a Ni commercial catalyst has been carried out in a fluidized bed reactor at 700°C. These compounds have been selected as model compounds of the volatiles formed in the pyrolysis of waste plastics in order to study in detail the performance of the catalyst in the pyrolysis-reforming of different plastic wastes. High carbon conversions and hydrogen yields are obtained at zero time on stream, with peak values being 96.5% and 82.8%, respectively, when n-hexane is used as model compound. Similar reactivity has been observed for tetradecane and 1-hexene, whereas lower carbon conversion (82%) and hydrogen yields (65%) are obtained for toluene. Concerning catalyst stability, olefinic compounds (1-hexene) and aromatic compounds (toluene) cause faster catalyst deactivation than paraffinic compounds (tetradecane and n-hexane). These disparities are explained by the different nature of the coke deposited and the different potential of the compounds to block Ni active sites, with olefins and aromatics being encapsulating coke precursors (amorphous and structured, respectively) and paraffins being filamentous and inert coke precursors.

Effects of oxygen species from Fe addition on promoting steam reforming of toluene over Fe–Ni/Al2O3 catalysts

A series of Fe-modified Ni/Al2O3 (FNA) catalysts with different Fe/Ni ratios (Fe/Ni = 0.5, 2, 3) was investigated during steam reforming of toluene as a model compound of biomass tar. The percentages of hydrogen in the product gas reached about 65% over prepared catalysts. The addition of Fe remarkably increased the toluene conversion and reduced the amount of coke. According to X-ray photoelectron spectrometer and pulse injection experiments, the addition of Fe increased the amount of lattice oxygen and adsorbed oxygen on the surface of FNA. The Fe in alloy was easily oxidized to FeOx by steam. The lattice oxygen in FeOx could oxidize the carbon deposited or intermediates on adjacent Ni atoms to produce CO. Meanwhile, the more adsorbed oxygen promoted the further reaction with the intermediates during the steam reforming of toluene. Both the adsorbed oxygen and lattice oxygen from the addition of Fe played important roles in the steam reforming of toluene. For the two types of cokes (amorphous/paraffinic and graphitic/filamentous), the formation of graphitic/filamentous carbon was remarkably suppressed due to the oxidization property of oxygen species from the addition of Fe.

Steam reforming of toluene as biomass tar model compound in a gliding arc discharge reactor

Non-thermal plasma is considered a promising and attractive approach for the removal of tars from biomass gasification to deliver a clean and high quality syngas (a mixture of H2 and CO). In this study, an AC gliding arc discharge (GAD) reactor has been developed for the conversion of toluene as a tar model compound using nitrogen as a carrier gas. The presence of steam in the plasma reaction produces OH radicals which open a new reaction route for the conversion of toluene through a stepwise oxidation of toluene and intermediates, resulting in a significant enhancement in both the conversion of toluene and the energy efficiency of the plasma process. The effects of steam-to-carbon (S/C) molar ratio, toluene feed rate and specific energy input (SEI) on the performance of the plasma steam reforming of toluene have been investigated. The optimal S/C molar ratio was found to be between 2 and 3 for high toluene conversion and energy efficiency. The maximum toluene conversion of 51.8% was achieved at an optimal S/C molar ratio of 2, a toluene feed flow rate of 4.8ml/h and a SEI of 0.3kWh/m3, while the energy efficiency of the plasma process reached a maximum (∼46.3g/kWh) at a toluene feed flow rate of 9.6ml/h and a SEI of 0.19kWh/m3. H2, CO and C2H2 were identified as the major gas products with a maximum syngas yield of 73.9% (34.9% for H2 and 39% for CO). Optical emission spectroscopy (OES) has been used to understand the role of steam on the formation of reactive species in the plasma conversion of toluene. The possible reaction pathways in the plasma conversion of toluene have also been proposed by combined means of the analysis of gas and liquid samples and OES diagnostics.

Low-temperature catalytic steam reforming of toluene over activated carbon supported nickel catalysts

In order to decrease the reaction temperature of catalytic cracking of tar derived from biomass gasification and prolong the lifetime of catalyst, nickel supported on activated carbon (Ni/AC) catalysts were prepared by impregnation method and used in steam reforming of toluene, a model tar compound, in a fixed bed reactor. The physiochemical properties of the catalysts were analyzed by N2 adsorption, X-ray diffraction (XRD), and transmission electron microscopy (TEM), etc. The effects of nickel content, calcination temperature and reaction temperature on carbon conversion were investigated, and the catalytic performance of the Ni/AC catalyst was compared with those of Al2O3/olivine-supported nickel catalysts. The results showed that the Ni/AC catalyst with 10 wt% of nickel loading and 600°C of calcination temperature had the best low-temperature catalytic activity at 600°C for toluene reforming, and the carbon conversion achieved about 99%. The high performance of the 600-10%Ni/AC catalyst was probably accounted for the AC support, which had a large BET surface area and unique porous structure, and therefore, a fine nickel particle size distribution on it. It also could be known by XRD analysis that nickel loaded on the surface of AC was in the form of metallic state after calcination, thus decreasing the use of hydrogen for reduction before reaction, so the catalyst preparation process can be simplified and the cost will be saved.

Effect of Zeolite Membrane Shell Thickness on Reactant Selectivity for Hydrocarbon Steam Reforming Using Layered Catalysts

A composite catalyst consisting of an outer layer of zeolite membrane encapsulating an inner reforming catalyst core was synthesized by a double physical coating method to investigate reactant selectivity (ratio of methane/toluene conversion rate) in steam reforming of methane (CH4) and toluene (C7H8). A double encapsulation (51 wt % H-β zeolite) of a 1.6 wt % Ni–1.2 wt % Mg/Ce0.6Zr0.4O2 steam reforming catalyst was compared to a singly coated composite catalyst (34.3 wt % H-β zeolite) to investigate zeolite thickness effects on the conversion of different sized hydrocarbons. Several characterization methods {scanning electron microscopy (SEM), energy-dispersive spectroscopy (EDS), physisorption analysis [Brunauer–Emmett–Teller (BET) surface area, pore volumes, and pore size distributions], and X-ray diffraction (XRD)} were used to analyze pre- and post-reaction samples. SEM and EDS analyses showed that the H-β zeolite was coated successfully on the steam reforming catalyst. The increase in the zeolite co...

Ni/Ru-X/Al2O3(X=K or Mn) 촉매를 이용한 바이오매스 가스화 타르의 수증기개질

바이오매스 가스화 시 발생하는 타르의 개질 연구가 다양한 Ni 촉매를 이용하여 수행되었다. 바이오매스 타르의 주요 성분인 톨루엔을 이용하여 실험실 규모의 수증기개질을 수행하였다. 고정층 형태의 개질기를 이용하였고 반응온도 범위는 400-800 ℃로 변화시켰다. Ni 촉매에 증진제로 Ru (0.6 wt%)와 Mn 또는 K (1 wt%)를 적용하였다. Ni/Ru-K/Al₂O₃ 촉매가 Ni/Ru-Mn/Al₂O₃ 촉매보다 전반적으로 높은 톨루엔 개질 전환 성능을 보였으며, X-선 회절분석과 열중량분석을 통해 촉매의 안정성을 확인하였다. 실험실 규모 연구 결과를 바탕으로 모노리스와 펠렛 형태의 촉매를 제작하고 1 톤/일 규모의 바이오매스 가스화 시스템에 적용하였다. 모노리스 촉매의 경우 Ni/Ru-K/Al₂O₃ 촉매가 고온에서 특히 우수한 성능을 보였으며, Ni/Ru-Mn/Al₂O₃ 촉매는 운전 시간 경과에 의한 활성저하가 관찰되었다. 펠렛 촉매의 경우 Ni/Ru-K/Al₂O₃ 는 587 ℃에서 66.7%의 타르 전환율을 보였으며, 사용된 촉매의 재생 후 타르 개질 성능을 비교하였다. 본 연구에서 사용된 촉매 중 Ni/Ru-K/Al₂O₃ 펠렛 촉매가 가장 우수한 촉매 활성과 안정성을 보였다. Steam reforming of tar produced from biomass gasification was conducted using several Ni-based catalysts. In labscale, the catalytic steam reforming of toluene which is a major component of biomass tar was studied. A fixed bed reactor was used at various temperatures of 400-800 ℃. Ru (0.6 wt%) and Mn or K (1 wt%) were applied as a promoter in Ni based catalysts. Generally, Ni/Ru-K/Al₂O₃ catalyst shows higher performance on steam reforming of toluene than Ni/Ru-Mn/Al₂O₃ catalyst. Used catalysts were analyzed by XRD and TGA to detect sintering and carbon deposition. Base on the lab-scale studies, the monolith and pellet type catalysts were tested in 1 ton/day scale biomass gasification system. Ni/Ru-K/Al₂O₃ monolith catalyst shows high tar reforming performance at high temperature. In addition, Ni/Ru-Mn/Al₂O₃ monolith catalyst was showed deactivation with operation time. Reforming performance of Ni/Ru-K/Al₂O₃ pellet catalyst which showed 66.7% tar conversion at 587 ℃ was compared to regenerated one. Overall, Ni/Ru-K/Al₂O₃ pellet catalyst shows higher stability and performance than other used catalysts.

Catalytic gasification of biomass (Miscanthus) enhanced by CO2 sorption.

The main objective of this work concerns the coupling of biomass gasification reaction and CO2 sorption. The study shows the feasibility to promote biomass steam gasification in a dense fluidized bed reactor with CO2 sorption to enhance tar removal and hydrogen production. It also proves the efficiency of CaO-Ca12Al14O33/olivine bi-functional materials to reduce heavy tar production. Experiments have been carried out in a fluidized bed gasifier using steam as the fluidizing medium to improve hydrogen production. Bed materials consisting of CaO-based oxide for CO2 sorption (CaO-Ca12Al14O33) deposited on olivine for tar reduction were synthesized, their structural and textural properties were characterized by Brunauer-Emmett-Teller (BET), X-ray diffraction (XRD), and temperature-programmed reduction (TPR) methods, and the determination of their sorption capacity and stability analyzed by thermogravimetric analysis (TGA). It appears that this CaO-Ca12Al14O33/olivine sorbent/catalyst presents a good CO2 sorption stability (for seven cycles of carbonation/decarbonation). Compared to olivine and Fe/olivine in a fixed bed reactor for steam reforming of toluene chosen as tar model compound, it shows a better hydrogen production rate and a lower CO2 selectivity due to its sorption on the CaO phase. In the biomass steam gasification, the use of CaO-Ca12Al14O33/olivine as bed material at 700°C leads to a higher H2 production than olivine at 800°C thanks to CO2 sorption. Similar tar concentration and lighter tar production (analyzed by HPLC/UV) are observed. At 700°C, sorbent addition allows to halve tar content and to eliminate the heaviest tars.