Yield Of Olefins Research Articles

Modeling and simulation of microwave assisted catalytic pyrolysis system of waste plastics polymer for fuel production

Pyrolysis is a promising method of chemically recycling plastic waste, as it allows for the recovery of both energy and materials. In this work, a comprehensive mathematical model has been developed to predict the pyrolysis of plastic wastes over ZSM-5 catalyst in microwave-assisted pyrolysis (MAP) system for fuel production. To conduct a transient numerical analysis of the underlying processes, a lumped kinetic model that takes into account three lumped pyrolysis products (olefins, paraffins, and aromatics) is coupled with the equations that govern the microwave field, heat transfer, mass transfer, and fluid flow (Darcy's law). The distributions of electric field, temperature, and pyrolysis products within MAP are presented. The study investigated the effects of several factors on the rate of production and consumption in the pyrolysis reactions of a waste plastic mixture when using MAP. These factors include the microwave power input, the inlet velocity of the fluidizing gas, as well as the mass and particle size of the catalyst used. Increasing the input power leads to a higher intensity of the electric field, which causes a greater increase in temperature within the same time frame. The mass and particle size of the catalyst used also have a significant impact on the yield of olefins, paraffins, and aromatics. Reducing the particle size of the catalyst generally increases the reaction rate, but particle sizes smaller than 50 μm are not ideal for fluidization due to increased intermolecular forces. Increasing the inlet velocity of the fluidizing gas may result in an incomplete consumption of intermediates and a low yield of products. All in all, The MAP system is a highly efficient and effective design for using plastic waste as a source of energy, due to its superior energy efficiency and lower processing temperature compared to traditional fluidized-bed reactors.

Modulated oxygen mobility of perovskite oxides for efficient redox oxidative cracking of cycloalkane to light olefins

Oxidative cracking is a promising process to reduce the energy and carbon intensities for light olefins production by combing catalytic oxidation and cracking reactions. This work reports an efficient redox oxidative cracking (ROC), which could avoid the potential hazard of co-feed oxygen with hydrocarbons and save the air separation process in an oxidative cracking process to achieve a much safer reaction process and more energy saving. Highly efficient redox catalysts, i.e. composites of the Li2CO3 promoted perovskite oxides (La0.8Sr0.2FeO3 and CaMnO3), were applied in ROC of naphtha by using a model compound of cyclohexane. Among the catalysts, La0.8Sr0.2FeO3@Li2CO3 exhibits excellent ROC performance (57.52 % yield of olefins and extremely low COx yield of 0.28 %), and it demonstrates high structural stability and cycling ability as well. The olefins yield in this work increased by > 19 % compared to conventional non-oxidative catalytic cracking (38 % yield of olefins), and the COx yield also decreased from 18 % to extremely low of 0.28 % compared with the best-reported O2-cofeed cyclohexane oxidative cracking. The characterization results indicated that La0.8Sr0.2FeO3@Li2CO3 attributed to being a core–shell structure with a La0.8Sr0.2FeO3 core covering with a molten Li2CO3 layer. Further characterization indicates that the modification of Li2CO3 affected the migration rate of oxygen and inhibited the excessive oxidation of olefins, which enhancing the selectivity of light olefins and inhibits COx formation. The oxygen migration rate of LSF is 5.81 × 10−11 mol/(g·s) compared with 3.37 × 10−11 mol/(g·s) of LSF@20 %Li. These findings offer a new strategy to design effective redox catalysts for redox oxidative cracking.

Feasibility of the Optimal Design of AI-Based Models Integrated with Ensemble Machine Learning Paradigms for Modeling the Yields of Light Olefins in Crude-to-Chemical Conversions.

The prediction of the yields of light olefins in the direct conversion of crude oil to chemicals requires the development of a robust model that represents the crude-to-chemical conversion processes. This study utilizes artificial intelligence (AI) and machine learning algorithms to develop single and ensemble learning models that predict the yields of ethylene and propylene. Four single-model AI techniques and four ensemble paradigms were developed using experimental data derived from the catalytic cracking experiments of various crude oil fractions in the advanced catalyst evaluation reactor unit. The temperature, feed type, feed conversion, total gas, dry gas, and coke were used as independent variables. Correlation matrix analyses were conducted to filter the input combinations into three different classes (M1, M2, and M3) based on the relationship between dependent and independent variables, and three performance metrics comprising the coefficient of determination (R2), Pearson correlation coefficient (PCC), and mean square error (MSE) were used to evaluate the prediction performance of the developed models in both calibration and validations stages. All four single models have very low R2 and PCC values (as low as 0.07) and very high MSE values (up to 4.92 wt %) for M1 and M2 in both calibration and validation phases. However, the ensemble ML models show R2 and PCC values of 0.99-1 and an MSE value of 0.01 wt % for M1, M2, and M3 input combinations. Therefore, ensemble paradigms improve the performance accuracy of single models by up to 58 and 62% in the calibration and validation phases, respectively. The ensemble paradigms predict with high accuracy the yield of ethylene and propylene in the catalytic cracking of crude oil and its fractions.

Tailoring the CO2 Hydrogenation Performance of Fe-Based Catalyst via Unique Confinement Effect of the Carbon Shell.

Even though Fe-based catalysts have been widely employed for CO2 hydrogenation into hydrocarbons, oxygenates, liquid fuels, etc., the precise regulation of their physicochemical properties is needed to enhance the catalytic performance. Herein, under the guidance of the traditional concept in heterogeneous catalysis-confinement effect, a core-shell structured catalyst Na-Fe3 O4 @C is constructed to boost the CO2 hydrogenation performance. Benefiting from the carbon-chain growth limitation, tailorable H2 /CO2 ratio on the catalytic interface, and unique electronic property that all endowed by the confinement effect, the selectivity and space-time yield of light olefins (C2 = -C4 = ) are as high as 47.4 % and 15.9 g molFe -1 h-1 , respectively, which are all notably higher than that from the shell-less counterpart. The function mechanism of the confinement effect in Fe-based catalysts are clarified in detail by multiple characterization and density functional theory (DFT). This work may offer a new prospect for the rational design of CO2 hydrogenation catalyst.

ZSM‐5@KIT‐6‐encapsulated composite molecular sieves for the catalytic cracking of waste cooking oil model compound to produce light olefins

AbstractBACKGROUNDA series of ZSM‐5@KIT‐6 composite molecular sieve catalysts was prepared by encapsulating ZSM‐5 as a substrate in the mesoporous material KIT‐6. The intent was to use these catalysts to promote the catalytic cracking of a waste cooking oil model compound (WCOMC) to produce light olefins.RESULTSThe morphology, structural characteristics and acidity of each of the resulting catalysts were characterized by X‐ray diffraction, transmission electron microscopy, N2‐Brunauer–Emmett–Teller (N2‐BET) surface area analysis and temperature‐programmed ammonia desorption. The results showed that ZSM‐5 was successfully coated with KIT‐6. The BET surface areas of these catalysts ranged from 345 to 792 m2 g−1 and the specimens had average pore sizes in the range of 2.37–5.51 nm. Total acidity increased with increases in the mass‐based proportion of ZSM‐5 in the material.CONCLUSIONThe catalytic cracking of WCOMC was studied in a lab‐scale fixed‐bed apparatus. Trials at a reaction temperature of 600 °C using the material having a mass‐based ZSM‐5 proportion of 80.0% (ZK‐80) gave the highest gas‐phase yield of light olefins of 43.8%. After 6000 min, the catalytic performance of this material remained stable, demonstrating a resistance to carbon deposits. The superior activity of the present composite catalysts can be ascribed to improvements in pore structure and acid strength distribution. © 2023 Society of Chemical Industry (SCI).

Self-evolved BOx anchored on Mg2B2O5 crystallites for high-performance oxidative dehydrogenation of propane

Oxidative dehydrogenation of propane (ODHP) is a promising process for producing propene. Recently, some boron-based catalysts have exhibited excellent olefin selectivity in ODHP. However, their complex synthetic routes and poor stability under high-temperature reaction conditions have hindered their practical application. Herein, we report a self-evolution method rather than conventional assembly approaches to acquire structures with excellent stability under a high propane conversion, from a single precursor-MgB2. The catalyst feasibly prepared and optimized exhibited a striking performance: 60% propane conversion with a 43.2% olefin yield at 535°C. The BOx corona pinned by the strong interaction with the borate enabled zero loss of the high conversion (around 40%) and olefins selectivity (above 80%) for over 100h at 520°C. This all-in-one strategy of deriving all the necessary components from just one raw chemical provides a new way to synthesize effective and economic catalysts for potential industrial implementation.

Aromatization of HDPE and PP over Ga-promoted zeolite: Effects of pretreatment and zeolite type

The effects of pretreatment and structure of zeolite on aromatization of high-density polyethylene (HDPE) and polypropylene (PP) over different Ga-promoted zeolites (HZSM-5, hierarchical HZSM-5, HY, Hβ, and USY) were investigated. Hydrogen reduction of Ga-promoted HZSM-5 resulted in a higher yield of alkenes during HDPE pyrolysis but did not lead to increased production of total aromatic hydrocarbons. The reduction and subsequent oxidation of Ga/Z5 led to the formation of GaO+ species with high dehydrogenation activity. This resulted in a remarkable 65% yield of aromatics, with a BTEX (benzene, toluene ethylbenzene and xylene) overall yield of 60% and a selectivity of 90% of the liquid product. Increasing the Ga loading decreased the BTEX yield due to pore blockage and a decrease in the amount of Brønsted acid sites. The BTEX yield over Ga-promoted zeolites was found to be strongly related to the pore size of the zeolite, whereas its yield over the parent zeolite was not strongly dependent on the pore size. Diffusion of the cracking intermediates was found to have a more significant impact on the aromatization of PP than HDPE. The highest BTEX yield for HDPE was achieved with Ga-promoted HZSM-5, while Ga-promoted hierarchical HZSM-5 exhibited the highest BTEX yield for PP. Furthermore, Ga(1)/Hβ-Redox demonstrated remarkable selectivity (90%) towards ethylene and propylene in the gas phase, surpassing other zeolites (37%-68%).

Effect of alkaline-earth metals (Mg, Ca, Sr, and Ba) on precipitated iron-based catalysts for high-temperature Fischer-Tropsch synthesis of light olefins

For the high-temperature Fischer-Tropsch synthesis (HTFT) of light olefins (C2=-C4=), alkaline-earth metals (Mg, Ca, Sr, and Ba) modified FeMn catalysts were prepared using precipitation and impregnation methods. It was demonstrated that the electron-giving interaction of Ca, Sr, and Ba decreased the adsorption of H species while improving the dissociative adsorption of CO. This interaction resulted in the production of χ-Fe5C2, which increased CO conversion and C2=-C4= selectivity. Compared with Ca and Ba, the FeMnSr catalyst had the strongest CO dissociative adsorption capacity and the highest χ-Fe5C2 content with the best FTS performance. When Sr and Na were introduced simultaneously, the synergistic effect of Sr and Na inhibited the formation of θ-Fe3C and the aggregation of catalyst particles, and also increased the χ-Fe5C2 content. This synergistic effect resulted in the highest surface basicity of FeMnSrNa catalyst, the highest electron cloud density on the surface of Fe atoms, the weakest H species adsorption, the strongest CO dissociative adsorption, and the highest total amount of active iron carbide, which improved the FTS performance. The light olefins yield of FeMnSrNa catalyst (427.0 g/(h·kgCat)) was significantly higher than that of FeMnSr catalyst (341.4 g/(h·kgCat)) and FeMnNa catalyst (80.6 g/(h·kgCat)).

Enhanced production and control of liquid alkanes in the hydrogenolysis of polypropylene over shaped Ru/CeO2 catalysts

The hydrogenolysis of polypropylene waste to liquid hydrocarbons offers a promising pathway for the chemical recycling of waste polymers. This work describes the importance of reaction conditions and support morphology to produce high liquid yields with enhanced control of chain length over highly active shaped and non-shaped Ru/CeO2 catalysts. The shaped 2 wt% Ru/CeO2 exhibit high liquid alkane yields (58–81%) when compared to the non-shaped 2 wt% Ru/CeO2 (liquid yield: 34–58%) under optimized reaction conditions (220 °C, 16 h, 30 bar H2). In particular, the 2 wt% Ru/CeO2 nanocube catalyst exhibits the highest activity yielding lighter hydrocarbons. This was rationalized to be a combination of small Ru cluster formation and enhanced metal-support interactions. The influence of larger Ru particles (≥1.5 nm) was confirmed mechanistically using a computational density functional theory study on the hydrogenolysis of pentane (C5) to determine the favorable formation of methane in the non-shaped Ru/CeO2 catalyst.

Development of porous MIL-101 derived catalyst application for green diesel production

A novel three-dimensional MIL-101 derived porous carbon-based Ni-doped catalyst was synthesised via slow pyrolysis of Ni/MIL-101(Cr) precursor at 600 °C for 4 h. The catalytic activities were evaluated via one-pot hydrodeoxygenation (HDO) reactions by using palmitic acid (PA) as a model compound to produce green diesel within the range of a paraffinic hydrocarbon. The results show that Ni/P-MIL-101 exhibited excellent catalytic activity and recyclability in the HDO reaction of PA at a reaction temperature of 400 °C for 3 h under 3 MPa purified H2 pressure with 5 wt% catalyst loading. The conversion of PA and hydrocarbon selectivity were found to be 100 % with Ni loading > 8 wt% on P-MIL-101. In addition, both 25 and 14 wt% Ni/P-MIL-101 catalysts were able to recycle up to 7 and 15 times, respectively, and nearly 100 % alkane yield was achieved. The unique properties of Ni/P-MIL-101 catalyst such as finely dispersed added Ni, abundant acid and basic sites, and the presence of Cr2O3 active sites from pyrolysed MIL-101 with its mesoporous structures play a synergetic role in obtaining a very efficient catalyst for hydrodeoxygenation reaction. It is worth mentioning that the catalyst has an excellent catalytic effect on different kinds of fatty acid (ester) raw materials. Therefore, this Ni/P-MIL-101 catalyst has good prospects and potential for industrial application in green diesel production.

Acid-driven architecture of hierarchical porous ZSM–5 with high acidic quantity and its catalytic cracking performance

Controllable synthesis of ZSM–5 zeolites with hierarchical pores and high acidities is an efficient way for cracking of naphtha to produce light olefins. Here, nanocrystalline ZSM-5 aggregates (NCs) with n(Si)/n(Al) of ∼18 were hydrothermally synthesized via acid hydrolysis of a silicon source for the cracking of n–pentane. Compared with conventional microporous ZSM–5 zeolite, NCs catalysts with preserved micropores and newly generated intercrystalline mesopores promote cracking conversion as well as selectivity of light olefins. Moreover, enhanced acidities with high Al concentration in zeolite benefit the conversion of n–pentane. Interestingly, it is found that with moderate amount of framework Fe, the strength of the Brønsted acid sites of the catalysts increases and Lewis acid sites are formed in zeolite, while maintaining the total acidities. Owing to the restricted bimolecular reaction of the olefins on the adjacent acid sites, the catalysts with an Al–Fe co–framework (NC–5Al–1Fe) affords increased yield of light olefins (ethylene and propylene) up to ∼40 wt% with enhanced catalytic stability after 16 h reaction at 600 °C.

One‐pot synthesis of V doped mesoporous SiO2 catalysts for selective oxidation of ethane and propane

AbstractA series of vanadium‐doped mesoporous SiO2 catalysts were prepared using a one‐pot emulsion method. The effects of VOx species with different structures on C−H bond activation and product selectivity in ethane and propane selective oxidation were investigated using X‐ray diffraction (XRD), N2 adsorption‐desorption, scanning electron microscopy (SEM), transmission electron microscopy (TEM), Raman, ultraviolet‐visible diffuse reflectance spectroscopy (UV‐Vis DRS), hydrogen temperature programmed reduction (H2‐TPR), and ammonia temperature programmed desorption (NH3‐TPD) characterizations. The results revealed that the highly dispersed isolated tetrahedral VOx species on the catalyst gradually polymerized into highly dispersed oligomeric VOx species with the increased V loading. The former is beneficial for the formation of olefins and total aldehydes during the selective oxidation of propane. Oligomeric VOx species are conducive to improving the selectivity of ethylene and acetaldehyde in the selective oxidation of ethane. The highest catalytic performances for selective oxidation of ethane and propane were obtained at a temperature of 650 °C. The conversion of ethane was 41.6 %, with a corresponding yield of ethylene and acetaldehyde of 23.6 % over a 0.5 V−SiO2 catalyst. In contrast, the propane conversion was 61.5 %, with a corresponding total yield of olefins and aldehydes of 41.3 % over a 1.0 V−SiO2 catalyst.

Influence of oxidative conditions on the deactivation of an equilibrium FCC catalyst in the fast pyrolysis of HDPE in a conical spouted bed reactor

This study approaches the continuous catalytic fast pyrolysis of plastics in a flexible and original technology, i.e., a conical spouted bed reactor equipped with fountain confiner and draft tube. The catalyst is an inexpensive equilibrium fluid catalytic cracking (FCC) one. Moreover, operation under oxidative conditions is proposed to solve heat supply to the pyrolysis reactor, as a previous study revealed a remarkable difference in the performance of the cracking catalyst when pyrolysis was carried out under inert (conventional) and oxidative conditions. Therefore, the aim of this paper is to assess the role played in the catalyst stability and deactivation mechanism by the presence of air in the reaction environment. A comparative study has been conducted by operating in long continuous runs under the same conditions (550 °C and a space time of 15 gcatalyst min gHDPE−1) in inert and oxidative atmospheres, i.e., equivalence ratios (ER) of 0 and 0.2, respectively. The evolution of product distribution with time on stream was evaluated. Moreover, samples of catalysts were taken from the reactor at different reaction times to correlate catalyst performance with the deactivated catalyst properties, and therefore progress in the understanding of the deactivation mechanism. The amount and nature of the coke deposited on the catalyst and its influence on catalyst properties was ascertained using thermogravimetry (TG-TPO), Raman spectroscopy, and NH3 and N2 adsorption–desorption techniques. The operation under oxidative conditions improved product distribution, with higher yields of light olefins. Moreover, catalysts activity and stability were also enhanced under oxidative conditions. Therefore, the results obtained involve a step forward towards the scaling up of plastics continuous catalytic pyrolysis.

Modeling and Research on the preparation of C4 olefins based on ethanol coupling

C4 olefin is a chemical material widely used in chemical and pharmaceutical products, and ethanol is the main raw material for the production of C4 olefins. Exploring the process of using ethanol to produce C4 olefins has important practical significance and practical value. In the process of preparing C4 olefins by catalytic coupling of ethanol, the combination and temperature of catalysts have an important impact on the yield and conversion efficiency of C4 olefins. The effects of different catalyst combinations and temperatures on the yield and conversion efficiency of C4 olefins were modeled by function fitting and neural network algorithm. In this paper, the relationship between ethanol conversion, C4 olefin selectivity and temperature is sought through curve fitting method. Firstly, the correlation between ethanol conversion, C4 olefin selectivity and temperature under each group of catalyst combination is analyzed. It is found that the relationship between ethanol conversion and temperature is the best through exponential function curve fitting. When fitting the relationship between C4 olefin selectivity and temperature, for the catalyst combination with peak data, the double exponential function is selected for fitting, and the other combinations are fitted by exponential function. The catalyst combination was divided into four independent variables: total catalyst (mg), CO loading (wt%), Co / SiO2 and HAP loading ratio and ethanol concentration (ml / min). After normalization combined with temperature, the relationship between the five variables and ethanol conversion and C4 olefin selectivity was obtained through Spearman correlation analysis. Considering that the correlation of some single independent variables to dependent variables is not high, it is considered that the data provided is too dense, and there are few change data for reference, so it is impossible to analyze the real correlation normally. The response surface equation is fitted. When solving the response surface equation, the solution of each coefficient of the equation is obtained by multiple linear regression, so as to obtain the relationship between catalyst combination and temperature and ethanol conversion and C4 olefin selectivity.

Co-pyrolysis of biomass and polyethylene: Insights into characteristics, kinetic and evolution paths of the reaction process

Investigation on the distribution and mechanism of co-pyrolysis products is vital to the directional control and high-value utilization of agriculture solid wastes. Co-pyrolysis, devolatilization, kinetics characteristics, and evolution paths of corn stalk (CS) and low-density-polyethylene (LDPE) were investigated via thermogravimetric experiments. The co-pyrolysis behaviors could be separated into two stages: firstly, the degradation of CS (150– 400 °C); secondly, the degradation of CS (400– 550 °C). The devolatilization index (DI) increased with the addition of LDPE. Furthermore, a combination of devolatilization chemical analysis with product analysis to analyze the intrinsic mechanism during co-pyrolysis. The results indicated that the yield of alkanes and olefin in gas products increased with the addition of LDPE. Additionally, LDPE pyrolysis maybe abstract hydrogen from CS pyrolysis and evolved into hydrogen, methane, and ethylene. Further, the co-pyrolysis kinetic parameters were computed by using model-free isoconversion methods, which showed promotion of CS pyrolysis and the reduced activation energy. All the activation energy were declined, which indicated a “bidirectional positive effect” during co-pyrolysis. The mean activation energy of P-cellulose (P-CE), P-hemicellulose (P-HM), P-lignin (P-LG), and LDPE decreased by 23.49 %, 12.89 %, 15.36 %, and 27.82 %, respectively. This study further proves the hydrogen donor transfer pathway in the co-pyrolysis process of CS and LDPE, providing theoretical support for the resource utilization of agricultural solid waste.

Research and analysis on the preparation of C4 olefin by ethanol coupling method based on regression algorithm with computer technology

Computer technology has been used to study the different combination of catalyst and temperature on the ethanol conversion (one-way conversion rate of 100% per unit time ethanol (alcohol intake - ethanol residue)/ethanol intake) and C4 olefin selectivity (the proportion of all products of C4 olefin), it is necessary to decompose the catalyst composition into several indicators. The effects of several indexes on ethanol conversion and C4 olefins selectivity were analyzed by computer technology. Canonical correlation analysis was used to study them, and the coefficient before each component represented the degree of importance. The results showed that the higher the catalyst combination temperature, the higher the weight of hydroxyapatite, the higher the ethanol conversion and C4 olefins selectivity, and vice versa. When the C4 olefin yield (its value is the selectivity of C4 olefin to ethanol conversion) is as high as possible, the multiple linear stepwise regression function of catalyst parameters and temperature on C4 olefin yield is obtained. MATLAB software was used to calculate the function formula. The absolute value of coefficients determines the importance of each index to C4 olefin yield. Combined with chemical reaction, when the mass ratio is 200:200 and the temperature is 400℃, the yield of C4 olefins can be maximized, and the yield of C4 olefins is 44.728%. Through the establishment of decision tree regression model by computer technology, it can be intuitively concluded that when the temperature is lower than 350℃, the best experimental condition is the C4 olefins yield of 17.264%.

Study on the process conditions of C4 olefin preparation based on statistical method

Due to the wide application of C4 olefins, it is of profound research significance and important value to explore the process conditions for the preparation of C4 olefins by catalytic coupling of ethanol. This paper calculates and analyzes the data generated in the C4 olefin preparation process by establishing a mathematical model and provides targeted suggestions based on statistical methods. First, one-dimensional linear regression was used to analyze the relationship between ethanol conversion, C4 olefin selectivity and temperature so as to obtain the regression coefficients of each group and test their significance; Secondly, SPSS is used for matrix scatter plot to observe the linear trend and spearman correlation coefficient is used for correlation analysis. Hypothesis test is conducted to draw relevant conclusions; Then the fuzzy synthesis is used to draw the conclusion that the catalyst has a greater impact on the reaction. Finally, the neural network is used to train the data and arrange them to obtain all the combination of catalyst and temperature. It is obtained that at 400°C, the combination of "200mg 2wt% Co/SiO2-200mg HAP ethanol concentration 2.1ml/min" can obtain 45.259% of the maximum C4 olefin yield without limiting the temperature; If the temperature is lower than 350°C, the catalyst is "50mg 5wt% Co/SiO2-50mg HAP ethanol concentration 0.3ml/min" and the temperature is 275°C. The maximum C4 olefin yield is 30.75%.

Aldol condensation of biomass-derived aldehydes and ketones followed by hydrogenation over Ni/HZSM-5 to produce aviation fuel: Role of acid sites

As the aviation sector grows and fossil fuels are utilized, the environment and economy depend on biomass-based aviation fuel. This study investigated acid sites in aldol condensation to produce aviation fuel from biomass-derived aldehydes and ketones over the bifunctional catalyst Ni/HZSM-5. Due to its excellent 10-member ring channels structure, HZSM-5 yielded 63.81% of the targeted condensates as aviation fuel precursor. At 200 °C for 9 h, aldehydes and ketones were converted to 90.32% and 69.53% of the required condensates. Sodium ion-exchange HZSM-5 with different Brönsted acid site quantities was tested for condensation. Brönsted acid sites were the active center for aldol condensation of aldehydes and ketones, increasing product yield. In γ-Al2O3, the overall amount of Brönsted acid and Lewis acid was equivalent to that of HZSM-5, the amount of Lewis acid was much more. The yield of the targeted condensates over γ-Al2O3 was only 46.11%, much lower than that of HZSM-5 (69.53%). Thus, Brönsted acid sites were better than Lewis acid sites for aldol condensation of aldehydes and ketones. The balance of active sites for aldol condensation and hydrogenation increased the intended alkane yield to 62.91% with 20 wt% Ni loading. This study involves improving biomass-based aviation fuel generation.

Catalytic pyrolysis of fatty acids and oils into liquid biofuels and chemicals over supported Ni catalysts on biomass-derived carbon

Herein, biomass-derived activated carbon (bio-AC) was synthesized using rice husk as a biotemplate and natural carbon source. After immobilization of Ni, the supported Ni/bio-AC showed excellent catalytic activity in the pyrolysis of fatty acids to paraffin-based biodiesel in H2-free and solvent-free conditions, corresponding to the conversion of 99.6% and a total alkane yield of 95.1%, including 88.9% heptadecane. Based on comprehensive characterizations, the calculated turnover frequency of Ni/bio-AC was 3.9 times that of conventional Ni/AC. Significantly enhanced olefin selectivity was further obtained by N-doping of Ni/bio-AC, which was attributed to the inhibition of -COO* dissociation by the Ni-N sites. The possible catalytic reaction pathways from stearic acid to heptadecane via aliphatic alcohol as a reaction intermediate were investigated. Besides, efficient conversions of saturated and unsaturated plant oils were also achieved over Ni/bio-NAC catalysts in Py-GC/MS through pulsed catalytic pyrolysis manner, showing a promising prospect for sustainable biofuels and chemical production.

A facile strategy to prepare ZSM-5-based composites with enhanced light olefin selectivity and stability in the HTO process.

In this study, the influence of different ZSM-5 composite materials (ASA, γ-alumina, η-Al2O3, SiO2, and attapulgite) and their performance in the n-hexane catalytic cracking process in a fixed bed microreactor at 550 °C under atmospheric pressure was studied. XRD, FT-IR spectroscopy, NH3-TPD, BET, FE-SEM, and TG analyses were performed to characterize the catalysts. The result of the n-hexane to olefin process indicated that the A2 catalyst (γ-alumina composition with ZSM-5) showed the highest conversion of 98.89%, highest propylene selectivity of 68.92%, highest yield of light olefins of 83.84%, and highest propylene to ethylene ratio of 4.34. The reason for the significant increase in all these factors and the lowest amount of coke in this catalyst is the use of γ-alumina, which increased the hydrothermal stability and resistance to deactivation, improved the acidic properties with a strong to weak acid ratio of 0.382, and increased the mesoporosity to 0.242. This study indicates the effect of the extrusion process and the composition and the major effect of the properties of this material on the physicochemical properties and distribution of the product.