In-situ catalytic upgrading of biomass-derived vapors using HZSM-5 and MCM-41: Effects of mixing ratios on bio-oil preparation

In this paper, two molecular sieves with different pore sizes, namely HZSM-5 and MCM-41, were mixed using different ratios and used in the in-situ catalytic pyrolysis of rape straw. The effects of different HZSM -5 and MCM -41 mixing ratios on the quality of the bio-oil were studied by physicochemical properties, product yields and compositions. Moreover, Brunauer-Emmett-Teller (BET) catalyst analysis was performed. The results showed that the liquid yield and organic phase decreased first and then increased, whereas the gas yield showed an opposite trend. The density, O/C and kinematic viscosity of the bio-oil organic phase decreased first then increased, whereas the H/C, pH values and higher heating values initially increased, then declined. The oxygen content, H/C, O/C, kinematic viscosity, density, higher heating value and pH value of the bio-oil organic phase obtained at 1:1 mixed ratio were 12.81%, 1.701, 0.126, 5.06 mm²/s, 0.94 g/cm³, 34.31 MJ/kg and 5.41, respectively. The organic phase included numerous organic compounds, such as carboxylic acids, aldehydes, ketones, hydrocarbons, alcohols, ethers and esters. The hydrocarbon content in the bio-oil organic phase gradually increased and the carbonyl groups content gradually decreased as the MCM-41 content increased from 0 to 50%. In contrast, the hydrocarbon content gradually decreased and the carbonyl groups content gradually increased as the MCM-41 content increased from 50% to 100%. The hydrocarbon and carbonyl groups contents were 53.83% and 6.35%, respectively, at the MCM-41 content of 50%. The mixed catalyst activity increased with the increase in MCM-41 content (up to 50%), and tended to be stable once the MCM-41 contents surpassed 50%.     

Hydrogen production via methane decomposition over nickel supported on synthesized ZSM-5/MCM-41 zeolite composite material

Catalytic decomposition of methane (CDM) for CO_x-free hydrogen production is carried out over 20 wt% Ni supported on H-ZSM-5/MCM-41 composite material, synthesized from alkaline desilication of a conventional H-ZSM-5(Si/Al = 40) and surfactant-recrystallization process. The composite material is used, for the first time, as support of Ni-catalyst in CDM. Tested for 6 h at 620 °C under atmospheric pressure, the 20 wt% Ni/H-ZSM-5/MCM-41 exhibits relatively higher H₂ production rate than 20 wt% Ni supported on the parent H-ZSM-5(Si/Al = 40) or on the pure MCM-41 in the order H-ZSM-5/MCM-41 > H-ZSM-5 > MCM-41. All catalysts display a remarkable catalytic stability. The higher catalytic activity of Ni/composite could be related to an improvement in both the access to active Ni metal atoms and the dispersion of the latter as evidenced by H₂-chemisorption measurement. The fresh catalysts are characterized by several techniques while the reacted ones are studied by the Raman spectroscopy.     

Effect of base promoter on activity of MCM-41-supported nickel catalyst for hydrogen production via dry reforming of methane

Dry reforming of methane (DRM) is considered a promising reforming technology that converts natural gas in the Natuna Sea into synthesis gas, which can be further utilized to produce beneficial chemicals such as olefins, alcohols, and liquid hydrocarbons. However, the challenges in commercializing the DRM process are carbon deposition and sintering of the catalyst at high temperatures, because of which the catalyst is easily deactivated. This study aimed to test the activity and stability of MCM-41-based catalysts for the DRM; determine the effect of promoter type on the activity and stability of MCM-41-based catalysts; and determine the effect of base promoter addition on the amount of carbon deposition. MCM-41-based catalysts were synthesized using incipient wetness impregnation method. XRD, N₂ Physisorption, H₂-TPR, CO₂-TPD, and TGA analysis were conducted to determine the physicochemical properties of the catalysts. The catalysts activity was tested in a fixed-bed reactor, under atmospheric pressure at 700 °C. Overall, all catalysts exhibited good stability for 240 min. Moreover, catalysts with Mg and Ca promoters showed the highest CH₄ and CO₂ conversion among all catalysts. Ni–Mg/MCM-41 catalyst yielded 72% CH₄ conversion and 54% CO₂ conversion, meanwhile Ni–Ca/MCM-41 yielded 69% CH₄ conversion and 55% CO₂ conversion. Furthermore, MCM-41-based catalysts with base promoter produced small amount of carbon deposition.     

Performance of the ZrO2 promoted CuZnO catalyst supported on acetic acid-treated MCM-41 in methanol steam reforming

ZrO₂-promoted CuZnO catalysts were prepared through the sol-gel, conventional impregnation and modified impregnation methods using MCM-41 as support material and applied to the methanol steam reforming (MSR) reaction. The synthesized catalysts were characterized by the XRD, BET, FESEM, TEM, XRF, FTIR, H₂-TPR and TGA methods. The determined physiochemical properties suggested that pretreatment of MCM-41 with acetic acid before metal impregnation remarkably decreases the size of the metal particles and improves their dispersion and reduction behavior. Among the synthesized catalysts, the CuZnOZrO₂/MCM-41 sample prepared through the modified impregnation method exhibited the best catalytic performance with 97.8% methanol conversion, 99.0% H₂ selectivity, 0.4% CO selectivity and the lowest level of coke deposition, at 300 °C. In addition, all catalysts resisted against deactivation by conserving their catalytic activity over 40 h operation, indicating that the use of high surface area MCM-41 as support, the ZrO₂ promoter, and the proper synthesis methods significantly enhanced the catalytic activity in the MSR process.     

Performance of Fe-Ba/ZSM-5 catalysts in NO + O2 adsorption and NO + CO reduction

Fe-Ba/ZSM-5 catalysts were prepared for NO + O₂ adsorption and NO reduction by CO at 250–400 °C. NO adsorption and reduction were investigated for different Fe contents, while the Ba content was fixed at 5 wt.%. The catalysts were characterized by BET, SEM, XRD, XPS, H₂-TPD, and in situ DRIFTS. The NO + CO activity tests of Fe-Ba/ZSM-5 catalysts showed that the NO reduction efficiencies were strongly affected by temperature. The NO_x adsorption capacity of Fe-Ba/ZSM-5 catalysts increased with increasing Fe loading. The results of catalyst characterization showed that the dispersion of Fe species is one of the most important factors affecting NO reduction and adsorption performance. High Fe loading increased the amount of adsorbed NO_x, while the NO + CO reaction was favored by good dispersion of Fe species. However, the NO_x adsorption capacity decreased for Fe loadings above 8.3% due to the aggregation of metal oxides.     

Hydrogen production by aqueous phase reforming of phenol over Ni/ZSM-5 catalysts

Hydrogen production from biomass in particular bio-oils appears interesting as bio-oils is easy to transport and storage with high conversion towards hydrogen. Phenol as presentation of lignin-derived bio-oils was chosen in this paper and was studied under aqueous phase reforming (APR) reaction using Nickel-based catalysts with ZSM-5 as support. The catalysts were synthesized by incipient wetness impregnation, and their physical and chemical properties were characterized by XRD, NH₃-TPD, H₂-TPR, SEM, TEM and N₂ adsorption–desorption. Ni/ZSM-5 was studied with different Si/Al molar ratio and different Ni content on APR of phenol. The reactant concentration, reaction pressure and temperature were also evaluated. Ni/ZSM-5 with Si/Al molar ratio of 25 and nickel content of 16% exhibited the highest catalytic activity. Hydrogen production were maximized over the temperature of 240 °C, reaction pressure of 4 MPa and the phenol concentration of 0.2 mol/L.     

Transformation of levoglucosan over H-MCM-22 zeolite and H-MCM-41 mesoporous molecular sieve catalysts

Catalytic transformation of levoglucosan (1-6-anhdyro-??-d-glucopyranose) was carried out in a fixed bed reactor at 573 K over zeolite and mesoporous material catalysts. Proton forms of MCM-22-30 and MCM-41-20 catalysts were tested in the conversion, changing also the residence time. The yield of the transformation product phases was substantially influenced by the structures, at the same time the formation of the different compounds were dependent on the structures of the acidic zeolite catalysts. Oxygenated species were the main liquid product, consisting mainly of aldehydes and furfurals (glycolaldehyde, formaldehyde, acetaldehyde, furfural, 5-methylfurfural, acetic acid). The formation of the liquid products was higher over MCM-41-20 than over MCM-22-30 for all the oxygenated species except acetic acid, indicating larger formation of non-condensable products over the microporous material. By increasing the residence time the formation of acetic acid increased in transformations over MCM-22, however, such increase also led to generation of more gases with both catalysts. The deactivation due to coking was more severe over the zeolite compared to the mesoporous material. It was, however, possible to successfully regenerate the spent zeolites without changing the structure.     

Maximizing the production of hydrogen and carbon nanotubes: Effect of Ni and reaction temperature

With the objective of maximizing hydrogen and CNTs production, the catalytic cracking of naphtha has been carried out at progressive reaction temperatures i.e. from 600 to 750 °C. The ZSM-5 and nickel impregnated ZSM-5 were used as catalysts for cracking purpose in fluidization mode. The catalyst analysis imparted that impregnation of metallic nickel induces a strong adhesion on MFI structure of ZSM-5 associated with an enhancement in textural properties and acid density. In addition, the results disclose that the incorporation of nickel on ZSM-5 leads to increment in stability of catalyst which in turn pushes the yields of H₂, CNTs and conversion to greater values of 3.29%, 4.84% and 90%, respectively. The as-grown carbon structures over the catalyst surface were found to be multiwall carbon nanotubes confirmed by Raman spectra and TGA analysis where they exhibited high quality (I_D/I_G = 0.65) and purity, respectively, at 750 °C.     

Nickel supported over MCM-41 coated ceramic membrane for steam reforming of real tar

A novel catalyst, Nickel supported over MCM-41 coated ceramic membrane (NMC), was developed using coating method and deposition-precipitation method and applied for steam reforming of real tar in fixed bed. The effects of reaction conditions such as Ni loading amount, reaction temperature and mass ratio of steam to tar were also studied. The good dispersion of Ni nanoparticles and the strong interaction between Ni particles and the support were identified by BET, XRD, H₂-TPR and SEM/EDS, resulting in the excellent performance of NMC catalysts. Maximum tar conversion of 96.4% and H₂ yield of 98.7 mmol g^?1 were obtained using 20NMC with a mass ratio of steam to coal tar of 2 at 800 °C. Moreover, 20 NMC exhibited a good stability in 10 h of lifetime test and the resistance of graphitic carbon formation prone to easier regeneration of catalysts illustrated by Raman spectroscopy. It indicates that the utilization of NMC catalysts for tar steam reforming is a promising way.     

Effects of synthesis methods on performance of CuZn/MCM-41 catalysts in methanol steam reforming

CuZn-based catalysts are active in production of hydrogen by methanol steam reforming. However, there is a need to have further insight on their physico-chemical properties to improve selectivity to hydrogen. Therefore, a series of CuZn/MCM-41 catalysts was synthesized by four different routes; one pot hydrothermal synthesis (OPMCM), co-impregnation (COMCM), serial impregnation (SRMCM) and copper impregnated on Zn-MCM-41 (ZNMCM). Samples of catalysts were characterized by X-ray diffraction (XRD), transmission electron microscopy (TEM), scanning electron microscopy (SEM) coupled with energy dispersive X-ray spectroscopy (EDS), inductively coupled plasma (ICP) emission spectrometry, Fourier transform infrared (FTIR) spectroscopy, thermogravimetric analysis (TGA) and X-ray photoelectron spectroscopy (XPS). XRD revealed disruption in the ordered pore network typical in MCM-41 for all catalysts synthesized and also showed that the one pot synthesis catalyst had wide spread dispersion of Cu and Zn. SEM micrographs captured irregularly shaped particles of different sizes. While XPS showed that different Cu and Zn species were formed within the catalyst matrix. XPS also confirmed that there was wide spread dispersion and interaction of Cu and Zn with MCM-41 matrix in the OPMCM catalyst. COMCM and OPMCM demonstrated the highest activity with 88 and 65% methanol conversion with corresponding H₂ selectivity of 91 and 86% respectively. They are better than SRMCM and ZNMCM which had average H₂ selectivity of 19% and 31% respectively. CO selectivity was less than 1.8% for the COMCM and OPMCM catalysts. While SRMCM and ZNMCM had CO selectivity's as high as 8.9% and 7.2% respectively. The data generated shows that catalytic activity is largely affected by the nature of Cu species within the catalyst matrix.     

Effect of agglomerated NiMo HZSM-5 catalyst for the hydrocracking reaction of Jatropha curcas oil

Catalytic hydrocracking of Jatropha curcas oil over ZSM-5-supported catalyst was carried out to produce biofuels. The agglomerated catalyst was successfully prepared by a simple technique and characterized using several techniques. The hydrocracking reactions were studied in a batch reactor at 400°C under initial H₂ atmosphere for 2 h reaction using 1 wt% catalyst loading. The effect of agglomerated catalysts on the yield of liquid fuels and hydrocarbon number distribution was discussed. The results showed that the hydrocarbon distribution largely changed depending on the type of catalyst. The powder catalysts seem selectively to produce hydrocarbon in the diesel range (C₁₂–C₂₂), whereas gasoline (C₅–C₁₂) and kerosene (C₈–C₁₆) had high formation after agglomerated catalyst was used. For agglomerated NiMo ZSM-5 catalyst, hydrocracking of Jatropha curcas oil produced more hydrocarbons in the gasoline range (about 43.23% in liquid fuels).     

Ni-BTC metal-organic framework loaded on MCM-41 to promote hydrodeoxygenation and hydrocracking in jet biofuel production

To improve catalytic performance of metal active sites in hydrodeoxygenation and hydrocracking conversion of methyl palmitate into high-quality jet biofuel, Ni-1,3,5-benzenetricarboxylate (Ni-BTC) metal-organic framework loaded on MCM-41(Mobil Composition of Matter No. 41) was prepared to enhance the accessibility of Ni active sites, facilitating hydrodeoxygenation to increase alkane yield with suitable arene content. The distance (0.98 nm) between Ni active sites within Ni-BTC structure, which was much larger than that (0.20 nm) within Ni nanoparticles, enabled methyl palmitate with maximum molecule width of 0.68 nm to go through Ni-BTC crystalline plane and get access to Ni active sites more easily. Ni-BTC nanosheets newly assembled in pore channels of MCM-41 were beneficial to effectively screen chain molecules of alkane products. With the largest BET surface area of 1014.2 m²/g, the Ni-BTC@MCM-41 catalyst with 2.5 wt% nickel (2.5Ni-BTC@MCM-41) reduced the nickel metal consumption by 75% comparing to nickel nanoparticle loading (10Ni@MCM-41), but achieved the best catalytic performances through hydrodeoxygenation on Ni active sites and hydrocracking on -SiOH acid sites. The alkane yield increased from 23.3% to 33.9%, while arene yield reduced from 22.4% to 6.5% in jet biofuel products. This resulted in an overall jet biofuel yield of 53.2% with uniform distribution along carbon numbers. The higher heating value of jet biofuel products thus increased to a peak of 45.90 MJ/kg.     

Hydrogen production by aqueous phase reforming of phenol derived from lignin pyrolysis over NiCe/ZSM-5 catalysts

Incipient wetness impregnation was used to synthesized the NiCe/ZSM-5 catalysts with different ratio of Ni:Ce, and CeO₂ was added as an assistant in the synthesis process. The physicochemical properties of the prepared catalysts were characterized by Transmission electron microscopy (TEM), X-ray diffraction (XRD), N₂-Sorption, H₂ temperature programmed reduction (H₂-TPR), X-ray photoelectron spectroscopy (XPS), Fourier Transform infrared Spectroscopy (FTIR) and ultraviolet–visible diffuse reflectance spectra (UV–Vis DR). The catalytic activities of the obtained catalysts were tested by using the reaction of aqueous phase reforming of phenol to produce hydrogen. Adding appropriate doze of Ce to the catalysts can increase the dispersion of nickel on the ZSM-5 support. The results showed that hydrogen selectivity was higher over 8Ni8Ce/ZSM-5 than using 8Ni/ZSM-5 as aqueous phase reforming catalysts. The content of carbon monoxide in the products after reaction over different catalysts was very low. However, the dispersion of carbon dioxide and hydrocarbons was significantly different over the two catalysts.     

Study on photocatalytic performance for hydrogen evolution over CdS/M-MCM-41 (M = Zr, Ti) composite photocatalysts under visible light illumination

A series of CdS/M(x)-MCM-41 (M = Zr, Ti, x stands for molar ratio of M/Si) photocatalysts were preprared by hydrotherm, ion-exchange and sulfidation process. The catalysts were characterized by X-ray diffraction, UV-vis spectra and N₂ adsorption-desorption isotherm et al. The characterization results shown that Zr or Ti was successfully doped into the mesoporous of MCM-41, and CdS was also successfully incorporated into such modified mesoporous. The results of photocatalytic performance for hydrogen production shown that CdS/Zr(0.005)-MCM-41 and CdS/Ti(0.02)-MCM-41 had the highest hydrogen evolution activity in triethanolamine aqueous solution under visible light (λ > 430 nm) irradiation, which can be explained by the diffusion velocity of the reactants and resultants and the protection which MCM-41 provided for CdS.     

Hydrogen production over Rh/Ce-MCM-41 catalysts via ethanol steam reforming

1 wt%Rh/Ce-MCM-41 catalysts were synthesized using Ce-MCM-41 as support where Si/Ce molar ratio varied from 10 to 30 and 50. During hydrogen reduction process, metallic Rh particles were formed on the Ce-MCM-41 at around 130 °C with an average particle size 6.8 nm. These catalysts were tested in the ethanol steam reforming (ESR) under atmospheric pressure between 225 and 425 °C. Compared to Rh/MCM-41 catalyst, cerium introduction would significantly enhance both the catalytic activity and hydrogen yield by approximately 2–3 times. However, the amount and the method of Ce incorporation in the framework of MCM-41 could greatly impact the catalytic performance of the Rh/Ce-MCM-41 catalysts. The ethanol conversion at 425 °C over the Rh/Ce-MCM-41 catalysts increased from 90.0% to 95.1% and 99.9%, as the Si/Ce molar ratio increases from 10 to 30 and 50. However, product selectivity is almost independent of the cerium content. The direct hydrothermal method of introducing Ce into the framework of MCM-41 is much superior to the impregnation route in the ESR reaction. After 6 h of reaction, the catalysts remain the mesostructure and the chemical state of cerium ions unchanged. Trace coke with graphite-like structure deposited on the surface does not modify the catalytic performance.     

Preparation and application of metal loaded ZSM-5 and y-zeolite catalysts for thermo-catalytic pyrolysis of real end of life vehicle plastics waste

In this work synthetic zeolite catalysts were modified by metal loading and used for real end of life vehicle plastic waste pyrolysis. ZSM-5 and y-zeolite catalysts were loaded by Ce²⁺, Cu²⁺, Fe²⁺, Fe³⁺, H⁺, Mg²⁺, Ni²⁺, Sn²⁺ and Zn²⁺ and the catalytic effects of both parent and metal loaded catalysts were tested by thermogravimetric method. The catalysts morphology and other properties were followed by N₂ adsorption/desorption isotherms, Fourier transformed infrared spectroscopy, Scanning Electron Microscopy and energy dispersive x-ray fluorescent spectroscopy. Significant difference in micropore, mesopore and macropore surface area, and average pore diameter was concluded. In general, the surface areas could be decreased by metal loading onto the catalyst surface. Parent y-zeolite had larger surface areas than that of parent ZSM-5 catalyst. Based on EDXRFS analysis, catalysts were loaded by 8–10% metals. Regarding grain size, in general y-zeolite based catalysts had smaller grains and the distribution was also narrower, than ZSM-5 based catalysts. The Si/Al ratio was 17.11–21.75 in case of ZSM-5 catalysts and 2.04–2.91 regarding y-zeolite catalyst. Based on first order kinetic approach, the reaction kinetic parameters were also calculated and evaluated. Waste end-of life vehicle (ELV) started to decompose at 426 °C (T_5%) and finished at 525 °C (T_95%). Catalysts can decrease the activation energies of decomposition. Same order of the activation energy decreasing of both ZSM-5 and y-zeolite based catalysts was found: Cu<Ce<Mg<Ni<Fe(III)<Fe(II)<Zn<Sn, however, y-zeolite based catalysts had advanced properties in activation energy decreasing than ZSM-5 based.     

Temperature dependence of hydrogen adsorption properties of nickel-doped mesoporous silica

The temperature dependence of the hydrogen adsorption properties of nickel-doped mesoporous silica (MCM-41) synthesized by a direct hydrothermal method was investigated by measuring the amount of hydrogen adsorbed at pressures up to 100 kPa at 298, 373, and 473 K. Nickel-doped MCM-41 adsorbed more hydrogen than undoped MCM-41 and metallic nickel at ≈298/0, 373/0, and 473 K/0 kPa due to chemical adsorption enhanced by the highly dispersed nickel particles. Chemical adsorption increased with increasing nickel content and adsorption temperature, suggesting the presence of adsorption sites. The nickel doping also brought the spillover effect, which enhances the physical adsorption of hydrogen. The spillover effect was enhanced at high nickel contents and adsorption temperatures.     

Hydrogen production from CH4 dry reforming over Sc promoted Ni / MCM-41

The activity of Ni supported on MCM-41 catalyst with/without scandium promoter was investigated for hydrogen production. The performance of the catalysts with different Sc loadings (0.00, 0.10, 0.25, 0.50, 0.75, 1.00 and 3.00 wt%) was examined. N₂ adsorption-desorption, X-ray diffraction (XRD), temperature-programmed reduction (TPR), thermo-gravimetric analysis (TGA), scanning electron microscopy (SEM) and transmission electron microscopy (TEM) were used for the characterization of the catalytic materials. The prepared catalysts were tested in dry reforming of methane. The effect of Sc addition on activity, hydrogen yield, H₂/CO ratio and stability are discussed. CH₄ and CO₂ conversions were measured under atmospheric pressure at 800 °C. Low Sc loading (<0.75 wt%) showed a positive effect on H₂ yield, CH₄ and CO₂ conversions. Addition of Sc strengthened the interaction of Ni with support and also increased the basicity which in turn affected the amount of CO₂ adsorbed on the surface of the catalyst. Notably, promoting with Sc almost suppressed the carbon formation leading to outstanding catalytic stability; thus 17% carbon deposition reduction was attained. The effect of different reaction temperatures, GHSV and CH₄:CO₂ ratio was also investigated.     

Effects of mesoporous fillers on properties of polybenzimidazole composite membranes for high-temperature polymer fuel cells

In this study, we elucidated the effects of the addition of various mesoporous silicates (0–20 wt%) to the membranes used for high-temperature proton exchange membrane fuel cells (HT-PEMFCs) on cell performance. Two types of polybenzimidazole (PBI)-based hybrid membranes were prepared by homogeneously dispersing a predetermined amount of MCM-41 or SBA-15 within the PBI matrix. Compared to the pure PBI membrane, those with MCM-41 and SBA-15 exhibited significantly enhanced phosphoric acid doping and better mechanical properties, leading to improved HT-PEMFC performance and reduced acid migration. However, the membranes with 20 wt% silicate showed inferior performance compared to those with 10 wt% silicate. In addition, the membranes with SBA-15 exhibited noticeable aggregation, lower phosphoric acid doping, and greater phosphoric acid migration during the leaching test than did the membranes with MCM-41. Finally, during the short-term durability test, the PBI/MCM-41 (10 wt%) membrane showed the best performance (maximum power density of 310  mW cm^?2).     

Ni–Cu–Zn/MCM-22 catalysts for simultaneous production of hydrogen and multiwall carbon nanotubes via thermo-catalytic decomposition of methane

Pure hydrogen and carbon nanotubes were produced via thermo-catalytic decomposition (TCD) of methane over Ni-loaded MCM-22 catalysts in a vertical fixed-bed reactor. The effect of reaction temperature, gas hourly space velocity (GHSV), Cu/Zn promoter and time on stream on the methane conversion, hydrogen and carbon yields were studied over the synthesized catalysts. The catalytic performance of the 50%Ni–5%Cu–5%Zn/MCM-22 catalyst was found to be highly stable compared to other catalysts. The highest conversion of methane over 50%Ni–5%Cu–5%Zn/MCM-22 catalyst reached 85% with 947% carbon yield. Methane conversion increased on increasing the reaction temperature up to 750 °C and decreased thereafter at higher temperatures. XRD and TEM analysis of the carbon byproduct revealed that graphitic carbon appeared as a major crystalline phase during the reaction. HRTEM results revealed that most of the Ni particles were located on the tip of the carbon nanofibers/nanotubes formed on the spent catalysts. The carbon nanofibres have an average outer diameter of approximately 20–40 nm with an average length of 450–500 nm. Four types of carbon nanofibers were detected and their formation strongly depended on the reaction temperature, time on stream and degree of the interaction between the metallic Ni particle and support. The optimum conditions for CNT production within the experimental ranges were found at a reaction temperature of 750 °C.