Calcium Aluminate Catalysts Research Articles

Catalytic dehydrogenation cracking characteristics of vacuum residue over solid basic catalyst

The basic calcium aluminate with appropriate catalytic cracking activity, excellent anti-coking performance, and hydrothermal stability is of great potential for the utilization of heavy oil. However, there is a lack of systematic research on the catalytic dehydrogenation cracking characteristics of vacuum residue (VR) over solid basic catalyst. Thus, by combining the TG and Py-GC/MS methods, the dehydrogenation cracking behavior of S-VR was investigated. The results indicated that S-VR cracking on calcium aluminate leads to less coking and higher olefin content in liquid products compared with FCC catalyst and quartz sand. Then, the activation energy Ea is computed from the catalytic dehydrogenation cracking of S-VR on calcium aluminate. The results show that the Ea values from Friedman and OFW methods range from 68 to 143 kJ∙mol−1 and 114 to 192 kJ∙mol−1, respectively. After that, the molecular-level carbon number distributions of the products obtained from cracking S-VR on different reaction conditions are investigated, and the optimal reaction temperature and the heating rate are 650 °C and 1000 °C/s, respectively. Finally, the free radical regulation theory was constructed to explain the catalytic dehydrogenation cracking mechanism of basic calcium aluminate catalyst.

Catalytic fast pyrolysis of waste pine sawdust over solid base, acid and base-acid tandem catalysts

Catalytic pyrolysis is an effective means for high-value utilization of biomass. This study investigated the effect of solid base catalysts (CaO, calcium aluminate catalysts CaAl-1, CaAl-2, CaAl-3), acid zeolite catalysts (ZSM-5, Fe/ZSM-5, Co/ZSM-5, Ni/ZSM-5, Cu/ZSM-5, Zn/ZSM-5) and base-acid tandem catalysts on pine sawdust pyrolysis using Py-GC/MS. Acid zeolite catalysts exhibited robust deoxidation and aromatization capabilities, favoring aromatics, while solid base catalysts yielded more phenols and ketones. Among the solid base catalysts, CaAl-3 (CaO-Ca12Al14O33) showed comparable deoxygenation activity to CaO and optimal aromatic selectivity with structural stability. Zn/ZSM-5 excelled in deoxygenation and aromatic selectivity (70.42%) among metal-modified ZSM-5 catalysts. Base-acid tandem catalysis promoted the formation of aliphatics and BTX (benzene, toluene, xylene) while suppressing polycyclic aromatics. The highest BTX content (44.35%) was achieved with CaO-Ca12Al14O33&Zn/ZSM-5 tandem catalysts in a 1:3 ratio. This work demonstrates base-acid tandem catalysis as a promising approach for converting pine sawdust into valuable chemicals.

Catalytic pyrolysis behavior of heavy crude oil over acid-base composite catalysts

Direct pyrolysis of crude oil to petrochemical feedstocks (light olefins and aromatics) is a trend for the transformation of refineries. In order to combine the advantages of solid base and acid catalysts to boost the yields of light olefins and BTX (benzene, toluene and xylene), catalytic pyrolysis behavior of heavy crude oil over acid, base and composite catalysts were studied using Py-GC/MS. The results showed that maximum content of alkenes was obtained over the calcium aluminate (CaAl) catalyst due to the inhibited hydrogen transfer reactions, but its catalytic activity was lower than ZSM-5 with Si/Al ratio of 40 (Z-40). For different composite catalyst ratios, maximum light olefins and BTX content of 65 % was obtained with 40Z catalyst (60 %CaAl + 40 %Z-40), which was higher than that obtained with pure Z-40 and CaAl catalysts. Compared to commercial ZSM-5 based and USY based catalysts, the 40Z catalyst demonstrated superior catalytic cracking performance, with the highest content of light olefins and BTX, while significantly higher content of C9+ aromatics were obtained over FCC catalyst. This revealed that catalyst type and appropriate composite catalyst blend ratio all play important role in enhancing the generation of light olefins and aromatics.

Bio-CH4 from palm empty fruit bunch via pyrolysis-direct methanation: Full plant model and experiments with bio-oil surrogate

Abstract A promising, cleaner alternative process of thermochemical conversion of lignocellulosic biomass to biomethane is proposed and rigorously investigated via modelling and experiments for the first time. Using a conventional nickel on calcium aluminate catalyst, operated in bench scale at 1 atm, 400 °C, and with a feed molar steam to carbon ratio of 2, the Low Temperature Steam Reforming of acetic acid, representing a single compound bio-oil surrogate, achieves a promising 81.9% fuel carbon conversion to gases with a methane yield of 15.7 wt% of the feed. This compares to 21 wt% methane yield at equilibrium, thus demonstrating encouraging first time performance and scope for future catalyst optimisation. A comprehensive Aspen Plus model is developed for the first time for an industrial plant producing biomethane from palm empty fruit bunch (50 wt% initial moisture), an under-used agro-industrial waste produced in vast amounts in South-East Asia and Sub-Saharan Africa. Dependency on external heating is completely eliminated by heat recovered from combusting 25% of the gas product. Based on the simulation results of the autothermal plant, a final gas product consisting of 99.2 wt% of CH4 and 0.8 wt% of H2 is predicted with a plant thermal efficiency of 80.6%, i.e., comparable to modelled efficiencies found in the literature for wood gasification to biomethane plants that generate syngas as a necessary intermediate.

Utilization of bifunctional catalyst for upgrading petroleum residue via cracking and gasification: Effect of catalysts

Vacuum residue is stepwise and high-efficient converted by the base cracking and coke gasification process. Cracking effect of vacuum residue was carried out with different bifunctional catalysts in a fluidized bed reactor, respectively. Calcium aluminate catalyst specialized for cracking and gasification procedure is selected with the activities of cracking and gasification. In comparison with silica sand, calcium aluminate catalyst showed the higher vacuum residue cracking activity, and cracking activity gradually increased with increasing the Ca/Al ratios. The results indicated that C2C4 olefinicity of above 60.4%, cracking-generated coke of about 5.0 wt%, and light oil yields is over 84.0 wt% at 650 °C with a catalyst-to-oil ratio of 7.0. Moreover, it was also found that calcium aluminate catalyst synthetized with the Ca/Al molar ratio of 12:7 and carbon black as pore-forming agent displayed a better cracking properties than that of the other catalysts. VR cracking properties over calcium aluminate catalysts was closely related to their basicity, as indicated by the Hammett indicators method. Cracking-generated coke on the base catalyst was well gasified with pure steam at 800 °C and produced the syngas with the total content of H2 and CO2 up to 81.5 vol%, the coke conversion over the tested catalysts is of above 93.6% in 30 min. Also, the alternating base cracking and gasification operations were performed three times to verify the stability of the optimal calcium aluminate catalyst. The selected catalysts presented high hydrothermal stability and stable cracking activity, which could be potentially used for vacuum residue stepwise and high-efficient utilization via vacuum residue catalytic cracking and gasification regeneration process.

Coupling Process of Heavy Oil Millisecond Pyrolysis and Coke Gasification: A Fundamental Study

To realize the clean and high-efficiency utilization of the inferior heavy oil, a novel conceptional process coupling heavy oil millisecond pyrolysis and coke gasification processes was proposed. The effects of reaction temperature and residence time on the flash pyrolysis behavior of vacuum residue (VR) were first investigated using Py-GC/TOF-MS. Results show that increasing the reaction temperature from 600 to 800 °C, as well as shortening the residence time from 400 to 200 ms could reduce the coke yield by approximately 28%. 1-Alkenes are the most abundant class in the cracked products, and the selectivity of total olefins in the light products from C3 to C16 could be over 75%. Then the cracking performance of VR over Y zeolite-based equilibrium FCC catalysts, silica sands, and calcium aluminate catalysts were studied by a fluidized bed reactor. Furthermore, the coked catalysts were gasified in steam and steam–O2 mixture atmosphere, respectively. Results show that the calcium aluminate catalyst has app...

Study on preparation of Ca/Al/Fe3O4 magnetic composite solid catalyst and its application in biodiesel transesterification

A magnetic composite solid catalyst was prepared by loading calcium aluminate onto Fe3O4 nanoparticles via a chemical synthesis method. The optimum conditions for the catalyst preparation were investigated. The influences of the molar ratio of Ca to Fe, calcining temperature, calcining time on the catalytic performance were studied. The catalyst with the highest activity was obtained when the molar ratio of Ca to Fe was 5:1; calcining temperature was 600°C and calcining time was 6h. The catalyst was characterized by thermogravimetric analyses (TGA), X-ray diffraction (XRD), scanning electronic microscope (SEM), Brunauer–Emmett–Teller method (BET) and vibrating sample magnetometer (VSM). Furthermore, the magnetic composite solid catalyst showed high catalytic activity for transesterification reaction for preparing biodiesel and the biodiesel yield reached 98.71% under the optimum conditions. The activity and recovery rate of this magnetic composite catalyst can be well maintained after 5cycles of catalysis. This catalyst showed magnetism and can be easily separated magnetically. Both the catalytic activity and the recovery rate of the magnetic composite solid catalyst were much higher than those of pure calcium aluminate catalyst.

Catalytic pyrolysis of n-heptane on unpromoted and potassium promoted calcium aluminates

Steam pyrolysis of n-heptane has been studied over different calcium aluminates and potassium impregnated calcium aluminate in a fixed bed reactor at atmospheric pressure. Various calcium aluminate catalysts were prepared by changing the precursor salt for obtaining CaO, which was subsequently used with Al 2O 3 for catalyst preparation. Depending on the source of CaO, the catalytic properties such as X-ray diffraction patterns, surface area, weight loss during reduction and the amount of CO 2 chemisorbed (basicity) were different. Compared to the unpromoted catalysts, K 2CO 3 impregnated catalyst significantly reduced the coke deposited on the catalyst, but only had marginal effect on the products selectivities. The activation energy for the coke gasification reaction was 140 kJ/mol.

Carbon dioxide reforming of methane over 5 wt.% nickel calcium aluminate catalysts – effect of preparation method

The effect of the preparation method on the catalytic properties and performance of 5 wt.% Ni on calcium aluminate (molar CaO/Al 2O 3=1/2) in the reaction of CO 2 reforming of CH 4 was investigated. The techniques employed for the preparation were the incipient wetness and total blending. The catalyst sample prepared by the deposition of Ni on already formed calcium aluminate proved to be more active with lower coke deposition for the reaction of reforming than the samples prepared by the total blending technique where the nickel compound was premixed with Ca and Al compounds. The differences in activity were attributed to different amounts of active NiO on the surface of the prepared samples as it was proved from XPS spectra and H 2-TPD profiles. Specific desorption peaks, which appeared in TPD profiles of catalysts prepared by total blending technique and calcined at 700°C and 900°C, were associated with hydrogen spillover to the support. Furthermore, long term testing of the catalyst prepared by the incipient wetness technique showed no loss of activity with low coke deposition. TPO experiments conducted using 13 CH 4 /CO 2/He mixture demonstrated that the adsorbed carbon species are formed via the CH 4 and CO 2 molecular routes.

Catalytic pyrolysis of methylcyclohexane: kinetics and modeling

Steam pyrolysis of methylcyclohexane has been studied over potassium carbonate impregnated calcium aluminate catalyst in a fixed bed reactor at atmospheric pressure in the temperature range of 973–1073 K. Compared to noncatalytic pyrolysis, the conversion was significantly higher but the hydrocarbon product selectivities were not affected in the presence of the catalyst. Incorporation of K 2CO 3 in the catalyst significantly reduced the coke deposited on the catalyst. The overall catalytic pyrolysis reaction could be represented by a first-order reaction with a preexponential factor of 1.1 × 10 3 m 3/(kg s) and an activation energy of 106.9 kJ/mol. The experimental product yields could be satisfactorily modeled by use of a molecular reaction scheme, consisting of a first-order primary reaction and twenty four secondary reactions among the primary products.

Potassium-containing calcium aluminate catalysts for pyrolysis of n-heptane

The effectiveness of potassium promoted calcium aluminate to catalyze the steam pyrolysis of n-heptane has been investigated at 1023 K and atmospheric pressure. Various amounts of potassium were incorporated on calcium aluminate (12CaO7Al 2O 3) by three different methods. Compared to thermal pyrolysis, addition of the calcium aluminate catalyst (either promoted or unpromoted) significantly increased the conversion as well as the yields of CH 4, C 2H 4 and C 3H 6. The presence of potassium significantly reduced the coke deposited on the catalysts due to the enhanced rate of the coke gasification reaction. A significant amount of potassium was lost from the catalysts during preparation as well as during reaction. The gasification activity was higher for the catalysts in which the K 2CO 3 was incorporated by incipient wetness method but the potassium loss during reaction was also higher in comparison to catalysts in which the potassium was incorporated by co-sintering.

Catalytic Pyrolysis of n-Heptane: Kinetics and Modeling

Steam pyrolysis of n-heptane has been studied over potassium carbonate impregnated calcium aluminate (12CaO−7Al2O3) catalyst in a fixed bed reactor at atmospheric pressure in the temperature range of 953−1023 K. Compared to noncatalytic pyrolysis, the conversion and product yields of methane, ethylene, and propylene were significantly higher in the presence of the catalyst. Incorporation of K2CO3 in the catalyst significantly reduced the coke deposited on the catalyst. The overall catalytic pyrolysis reaction could be represented by a first-order reaction with a preexponential factor of 1.7 × 103 m3/(kg·s) and an activation energy of 103.8 kJ/mol. The experimental product yields could be satisfactorily modeled by use of a molecular reaction scheme, consisting of a first-order primary reaction and 24 secondary reactions among the primary products.

Partial oxidation of methane to synthesis gas over unpromoted and (0.1-0.5 wt%) Ni-promoted calcium aluminate catalysts

The partial oxidation of methane towards synthesis gas is catalyzed over calcium aluminate (CaO·2 Al2O3) catalysts, either unpromoted or promoted with small amounts of Ni (0.1-0.5 wt%), at medium temperatures (800°C) and methane-to-oxygen ratios of 2 : 1. Carbon monoxide and hydrogen appear to be primary products of the reaction, along with carbon dioxide and small amounts of C2+ hydrocarbons. Methane conversions of 35% and carbon monoxide-to-carbon dioxide ratios of 0.5-0.6 are obtained with the unpromoted or 0.1 wt% Ni-promoted catalysts at complete oxygen consumption. Near thermodynamic equilibrium synthesis gas mixtures are realized with the 0.5 wt% Ni-promoted calcium aluminate catalyst at sufficiently long gas contact times.

Methane partial oxidation to synthesis gas using nickel on calcium aluminate catalysts

Nickel was supported on calcium aluminate carriers that were obtained with varying CaO to Al 2O 3 molar ratios and calcination temperatures. The variations of the supports lead to catalysts of different surface properties and catalytic performance. Metallic nickel (Ni 0) was proven to be the active species for the methane partial oxidation reaction. The presence of filamentous carbon on used catalysts was also suggested. The differences in the catalytic activity and selectivity for the methane partial oxidation reaction was ascribed to a varying degree of reducibility of the surface nickel species.

Catalytic pyrolysis of naphtha on calcium aluminate catalysts. Effect of potassium carbonate impregnation

Steam pyrolysis of naphtha has been studied over potassium carbonate impregnated calcium aluminate (12CaO-7Al 2 O 3 ) catalysts in a fired-bed reactor at atmospheric pressure in the temperature range of 1033-1093 K. The K 2 CO 3 loading on the catalyst was varied from 0 to 8.8 wt %. Incorporation of K 2 CO 3 in the catalyst significantly reduced the coke deposited on the catalyst. Compared to 12CaO-7Al 2 O 3 catalyst, the yield of CO 2 was considerably higher whereas the hydrocarbon yields were marginally reduced due to addition of K 2 CO 3 . A significant amount of potassium loss from the catalyst occurred during the pyrolysis operation

Mechanistic model for the catalytic cracking of n-hexane over calcium aluminate catalysts for producing light alkenes

A detailed chemical kinetic mechanism describing the thermal and catalytic cracking of n-hexane over a 12CaO·7Al 2O 3 catalyst is presented. The model was based on balance equations for both molecular and radical species describing an experimental bench scale fixed bed reactor system. Using Gear's algorithm for solving the differential equations, a satisfactory fit of experimental results was obtained both at low residence time where the alkenes are the main products and at high residence time where the formation of hydrogen plus carbon monoxide predominates.

Thermal desorption study of catalytic systems Communication 20. Adsorption of water vapors on the calcium aluminate components of catalysts

Ca aluminates are used as a component of catalysts of gas-phase processes, some of which take place with the participation of water. Nickel calcium aluminate catalysts are thus used for hydrogenation of CO and CO/sub 2/ to CH/sub 4/ and water; zinc calcium aluminate catalysts are used for sulfur purification of process gases, where water is liberated during sulfiding of ZnO; and copper zinc calcium aluminate catalysts are used in low-temperature conversion of CO with water vapor. It is also known that Ca aluminates undergo various transformations in aqueous media with the formation of Ca hydroaluminates. This paper discusses the adsorption of water from the gas phase on calcium aluminate systems, which was investigated by the thermal desorption method. Samples of varying phase composition, different CaO/Al/sub 2/O/sub 3/ ratios, and specific surface areas were also studied and are reported on here.