Temperature-programmed Gasification Research Articles

Deactivation and in-situ regeneration of Dy-doped Ni/SiO2 catalyst in CO2 reforming of methanol

The self-regeneration of Ni-based catalysts has been considered as a promising approach to maintain not only a continuous but also economical process. However, the effect of catalyst nature, operating temperature, amount and types of carbon deposits on the effectiveness of the in-situ regeneration is still not well-investigated. Therefore, in this work, the self-regeneration ability of the undoped and Dy-doped Ni/SiO2 catalysts, which were prepared by the same impregnation method, were examined in the dry reforming of methanol. The physicochemical properties of the fresh and spent catalysts were analyzed by various techniques such as X-ray diffraction (XRD), hydrogen temperature-programmed reduction (H2-TPR), oxygen temperature-programmed desorption (O2-TPD), transmission electron microscopy (TEM), N2-BET isothermal adsorption. The nature and chemical reactivity of coke deposits formed during dry reforming at various temperatures (550, 600, and 650 °C) and the regeneration possibility of used catalysts through CO2 gasification at these temperatures were investigated by the in-situ temperature-programmed gasification by CO2 (TPCO2). The Dy additive significantly improves the dispersion of the nickel active sites of Ni/SiO2 catalyst, as demonstrated by the decreased Ni crystal size as well as the increased specific surface area and reduction degree of the catalyst. Furthermore, Dy promotion increases the quantity of oxygen vacancies and the nature of oxygen species, thereby improving the catalyst activity and stability. Specifically, methanol conversion dropped from 93% to 96%–61% and 31% for undoped Ni/SiO2 at 600 °C and 650 °C, respectively and from about 99% to 87% (at 600 °C) and 52% (at 650 °C) for Dy-doped catalyst.

Production of CO-rich hydrogen gas from glycerol dry reforming over La-promoted Ni/Al2O3 catalyst

Dry reforming of glycerol has been carried out over alumina-supported Ni catalyst promoted with lanthanum. The catalysts were characterized using EDX, liquid N2 adsorption, XRD technique as well as temperature-programmed reduction. Significantly, catalytic glycerol dry reforming under atmospheric pressure and at reaction temperature of 1023 K employing 3 wt%La–Ni/Al2O3 catalyst yielded H2, CO and CH4 as main gaseous products with H2:CO < 2.0. Post-reaction, XRD analysis of used catalysts showed carbon deposition during glycerol dry reforming. Consequently, BET surface area measurement for used catalysts yielded 10–21% area reduction. Temperature-programmed gasification studies with O2 as a gasification agent has revealed that La promotion managed to reduce carbon laydown (up to 20% improvement). In comparison, the unpromoted Ni/Al2O3 catalyst exhibited the highest carbon deposition (circa 33.0 wt%).

Hydrogen production from wood gasification promoted by waste eggshell catalyst

Bio-hydrogen renowned as a future potential hydrogen source and studies were devoted in developing the efficient way to obtain the hydrogen. Biomass gasification of Azadirachta excelsa wood was carried out with addition of naturally derived CaO catalyst using temperature-programmed gasification (TPG) technique. The reaction (TPG) was performed at 50–1000°C in 5% O2/He with flow rate 10 ml/min, and the product gas evolution (H2, CH4, CO and CO2) was detected by online mass spectrometer. The waste eggshell was chosen as a natural source of CaO, and the effect of catalyst loading was investigated in this study. All the fresh and used catalysts were characterized, and the physicochemical changes of the eggshell were observed through scanning electron microscopy, X-ray fluorescence and X-ray diffraction techniques. Hydrogen yield were increased along with the catalyst loading (20%, 40% and 60%) from 57 to 73%, respectively, compared to the reaction without catalyst. The additions of waste eggshell enhanced the catalytic activity and suppressed CO2 production through CaO absorption property which induced the water gas shift reaction that promotes H2 production at lower temperature. Copyright © 2013 John Wiley & Sons, Ltd.

Enhancement of hydrogen production by secondary metal oxide dopants on NiO/CaO material for catalytic gasification of empty palm fruit bunches

The increase of fossil fuel burning to meet massive energy demands has resulted in major environmental problems. Extensive green house gas emissions and the depletion of non-renewable resources have promoted the use of hydrogen as an alternative energy source. Empty palm fruit bunches (EFB) are a type of agricultural waste that have a high potential for use as a sustainable biomass feedstock for hydrogen production. This study is focused on generation of biomass-derived hydrogen through catalytic biomass gasification using a modified CaO-based catalyst. The catalyst was prepared by adding 5% Ni as a primary dopant, followed by the addition of secondary dopants (La, K, Co, Fe) through a wet impregnation method, and characterised by X-ray diffractometer (XRD), N2 adsorption (BET) and Thermogravimetric Analysis (TGA). The synthesised catalysts were used as the primary catalysts in the reaction and were tested in temperature programmed gasification (TPG). The reaction was carried out in a partial oxygen environment by incorporating the biomass with the catalyst in a ratio of 1:2 from 50 to 900 °C and the product gases were detected by an online mass spectrometer. Interestingly, the addition of secondary dopants significantly increased the hydrogen production with notable changes in the CO2 absorption capacity of the catalyst. Moreover, K, Co and Fe dopants showed tar reforming properties and the highest hydrogen yield was observed with K as the added catalyst.

Hydrogen Production from Rice Straw Gasification over Modified-Limestone Catalyst

Malaysian limestone modified with and additions of transition metal promoters (Ni, Fe, and Co) were used for gasification of biomass. The effects of selected metal oxide loading and the addition of sodium carbonate, Na2CO3 as additive and its influence on limestone catalytic activity during gasification for hydrogen conversion were investigated. The catalysts were synthesized through deposition-precipitation (DP) method and characterized by using X-ray diffraction (XRD), Brunauer-Emmet-Teller (BET) surface area, thermal gravimetric analysis (TGA) and scanning electron microscopy (SEM). Temperature programmed gasification (TPG) was conducted to investigated the gasification reaction of rice straw and the product gases were analysed using online mass spectrometer. The gasification process was carried out in partial oxygen (5% O2/Helium) environment heating from 50 to 900 °C with mass ratio biomass to catalyst of 2:1. From the results, Ni promoter was found to give the highest H2 conversion followed by Co and Fe. The calcined limestone had shown to act as a catalyst and CO2 sorbent thus enhancing the production of hydrogen. Moreover, additional of Na2CO3 during gasification process had shown a further increment of H2 production.

The effect of particle size of CaO and MgO as catalysts for gasification of oil palm empty fruit bunch to produce hydrogen

Finely ground and dried palm oil empty fruit bunch (EFB) was gasified using a temperature-programmed technique which online with mass spectrometer. Temperature-programmed gasification (TPG) was done under 5% oxygen in helium to determine the production of hydrogen, as well as CO, CO2 and CH4. TPG was performed from 50–700 °C at the heating rate of 10 °C min−1. The temperature was held for 1 h at the final temperature. The effect of mass ratio of metal oxide:EFB was also investigated. Different particle size of calcium oxide and magnesium oxide were chosen as the catalysts. Bulk calcium oxide has shown to enhance the evolution of hydrogen. Nanosized calcium oxide enhanced the production of hydrogen compared to the bulk one and consequently reduced the production of carbon dioxide. Interestingly, when the mass ratio of metal oxide:EFB was changed to 1:2, nanosized MgO showed very significant increase of H2 production. All the used catalysts were analyzed by XRD to show the transformation of both bulk and nanosized metal oxides to metal carbonates.

Calcium Oxide as Potential Catalyst for Gasification of Palm Oil Empty Fruit Bunch to Produce Syngas

Gasification of dry palm oil empty fruit bunch (EFB), by using a temperature-programmed instrument was performed to determine the amount of synthesis gas produced. Dry and finely crushed EFB was pre-mixed with calcium oxide. Temperature-programmed gasification (TPG) was done at temperature from 50oC – 550oC and also from 50oC – 700oC using 5% oxygen in He. Both experiments were held for 1hr at the final temperature. The products were monitored using an online mass spectrometer. Major products detected from this reaction were H2, CO, CO2 and CH4. The effect of calcium oxide amount (CaO : EFB ratio) was also investigated. A very significant increase of H2 and CO was observed when nano-sized calcium oxide was used as catalyst compared to bulk one. Reaction at 700oC using nano-sized CaO reduces the production of carbon dioxide during gasification. The characteristics of the catalyst used were analyzed by using XRD and XPS show some significant changes from CaO to CaCO3.

Evolution of Light Hydrocarbons from a Coked Ferrierite Catalyst during Temperature-Programmed Gasification

The evolution of light hydrocarbons during temperature-programmed gasification with helium (TPHe) of a coked ferrierite catalyst was studied to gain information on partial coke removal by heat treatment under inert flow. The catalyst had been deactivated in the skeletal isomerization of alkenes. Characterization by DRIFTS, GC−MS, and 13C CPMAS NMR revealed that the coke contained two- and three-ring aromatic hydrocarbons, as well as polyaromatics. Evolution predominantly of C2−C5 hydrocarbons was observed during TPHe between 200 and 500 °C. The main components were propene and ethene. The carbon content of the catalyst dropped from 4.3 to 3.5 wt % during TPHe. Kinetic models suitable for the purpose of designing a coke removal unit were derived for the evolution of carbon fractions between C2 and C5 from the ferrierite zeolite. The results of the kinetic modeling suggest that one or several bimolecular reactions are relevant in the formation of light hydrocarbons from coke.

Effects of Fe- and Ca-based additives on NO emission during gasification of N-containing model compound under different atmospheres

The effects of iron and calcium compounds on NO emission during CZC (carbazole char) gasification under different O 2 concentrations have been investigated in a quartz tube fixed bed reactor. Temperature-programmed gasification was preformed to determine the influence of O 2 concentration and catalytic effects of iron and calcium on NO emission. The results show that the O 2 concentration strongly influences NO emission during CZC gasification; suitable O 2 concentration could largely reduce NO emission, but high or low O 2 concentration is unfavorable to reduce NO pollution. Iron catalysts increase NO emission during CZC gasification in O 2 concentration ranging from 20.9 to 1.2%, and their catalytic effects are strongly depended on O 2 concentration. The order of their catalytic effects is Fe(AC) 2>FeCl 2≈FeCl 3. Different kinds of iron compounds show different catalytic activities for their different dispersion on CZC and their different decomposition tendency to form active sites. Calcium compounds show different effects on NO emission depending on O 2 concentration. Ca(AC) 2 and CaCl 2 increase NO emission under high O 2 concentration (such as 20.9%), but they decrease NO under low O 2 concentration (such as 1.2%). When CZC gasification under 4.8% O 2–Ar, Ca(AC) 2 decreases NO emission, but CaCl 2 increases NO emission.

Catalytic Gasification of Sawdust Derived from Various Biomass

A systematic study is conducted for the steam gasification of biomass materials (cellulose, Cedar, and Aspen) using temperature-programmed gasification (TPG) and constant-temperature gasification (CTG) methods in order to produce H2-rich gas. The performance of catalyst (CaO) was also studied by varying the catalyst loading from 0 to 8.9 wt % during TPG and CTG processes. The TPG and CTG experiments showed that the use of CaO as a catalyst reduced the maximum gasification temperature by ∼150 °C. Also, the rate of H2 and cumulative H2 productions were increased with the impregnation of CaO in cellulose, Cedar, and Aspen during TPG and CTG processes. In TPG, the rate of production of H2 was increased from 0.21 to 0.38 cm3 (STP)/min/(0.04 g of sample) when 5.5 wt % CaO was impregnated in cellulose. Higher CaO loading of 8.9 wt % did not improve H2 production. In CTG, the rate of H2 production and cumulative production of H2 increased from 0.18 to 0.31 cm3 (STP)/min and from 11 to 14 cm3 (STP)/(0.04 g of sample) when 5.5 wt % CaO was impregnated in cellulose. The rate of production and cumulative production of H2 from Cedar and Aspen were significantly higher than those from cellulose for catalytic as well as for noncatalytic TPG and CTG processes. Total fuel yield, H2, and carbon yields were also significantly increased with the impregnation of CaO in cellulose, Cedar, and Aspen.

Nitrogen-doped carbon-13 materials as models for the release of NO x and N 2O during coal char combustion

The gasification of carbon-13 doped with nitrogen was used as a model for coal char gasification. The nitrogen was inserted into the carbon-13 by treatment with ammonia at high temperatures. N 2O and N 2 could thus be distinguished from CO 2 and CO respectively in a thermogravimetric analysis-mass spectrometry instrument. The results of temperature-programmed gasification in oxygen-argon mixtures showed that the nitrogen in the carbon matrix was gasified to nitric and nitrous oxides with clearly bimodal gas evolution profiles, whereas the corresponding carbon monoxide and carbon dioxide profiles were symmetrical. The results are interpreted in terms of the gasification of different types of nitrogen functionality.

A comparison of NO release from coals and entrained-flow reactor chars during temperature-programmed combustion

A comparison was made of the temperature-programmed gasification in 20% oxygen in argon of six coals covering a wide range of rank and the chars produced from the coals in an entrained-flow reactor (EFR) at 1000 °C. The temperature-programmed oxidative gasification of the coals has two main regions, representing mainly gasification of the volatiles released and of the char formed during pyrolysis. The NO gas evolution profiles reach a maximum after the corresponding CO and CO 2 profiles for both the coals and EFR chars. The temperature at which these peaks occur increases with increasing rank. In the lower-temperature range where the primary devolatilization of the coal occurs, the NO CO 2 and NO CO ratios decrease with increasing temperature. For the low-rank coals, a peak due to HCN is also detected in this region as well as at the initial char formation stage. In the char gasification region of the coals and for the EFR chars, the NO CO 2 and NO CO ratios increase with increasing temperature and extent of burnoff. The ratio of NO released during gasification to the total nitrogen varies from 0.14 to 0.44 for the EFR chars and from 0.31 to 0.57 for the coals. It is apparent that there are similarities in the release of nitrogen during the combustion of coals of a wide range of rank and of EFR chars derived from these coals.

Temperature-programmed gasification of the coke on spent hydrotreating catalysts with oxygen and hydrogen

ADVERTISEMENT RETURN TO ISSUEPREVArticleNEXTTemperature-programmed gasification of the coke on spent hydrotreating catalysts with oxygen and hydrogenJoep Van Doorn, Henny A. A. Barbolina, and Jacob A. MoulijnCite this: Ind. Eng. Chem. Res. 1992, 31, 1, 101–107Publication Date (Print):January 1, 1992Publication History Published online1 May 2002Published inissue 1 January 1992https://doi.org/10.1021/ie00001a015RIGHTS & PERMISSIONSArticle Views221Altmetric-Citations24LEARN ABOUT THESE METRICSArticle Views are the COUNTER-compliant sum of full text article downloads since November 2008 (both PDF and HTML) across all institutions and individuals. These metrics are regularly updated to reflect usage leading up to the last few days.Citations are the number of other articles citing this article, calculated by Crossref and updated daily. Find more information about Crossref citation counts.The Altmetric Attention Score is a quantitative measure of the attention that a research article has received online. Clicking on the donut icon will load a page at altmetric.com with additional details about the score and the social media presence for the given article. Find more information on the Altmetric Attention Score and how the score is calculated. Share Add toView InAdd Full Text with ReferenceAdd Description ExportRISCitationCitation and abstractCitation and referencesMore Options Share onFacebookTwitterWechatLinked InReddit PDF (901 KB) Get e-Alerts Get e-Alerts

Characterization of carbon deposits on alumina supported cobalt and nickel by temperature programmed gasification with O 2, CO 2 and H 2

Temperature-programmed gasification with O 2, CO 2 and H 2 is used for the characterization of carbon deposits on Ni/Al 2O 3 and Co/Al 2O 3, based on the difference in reactivity of the several types of deposits. These deposits were formed by CO disproportionation at 675 K, 725 K and 775 K. The gasification patterns show the existence of mainly two types of carbon deposits. One form is attributed to filamentous carbon, the second form is believed to have a more graphitic structure. The TPG patterns are strongly influenced by the oxidation state and the catalytic activity of the metal(oxide) on the gasification of carbon.