Zeolite and non-zeolite catalysts for CO2 valorization into hydrocarbon fuels.
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•Excessive amount of CO2 emission in the atmosphere causes global warming.•Chemical methods for CO2 ...conversion are highlighted as the best options.•Catalysts based on zeolites are currently being explored for hydrocarbons production.•Fe-based non-zeolitic catalysts are the most widely used for hydrocarbons production.•Zeolitic-imidazole frameworks (ZIFs), covalent-organic frameworks (COFs), and metal-organic frameworks (MOFs) are probably selective catalysts for CO2 conversion to hydrocarbons.
Meeting the ever-increasing global energy demands is one of the serious challenges of the 21st century. It is estimated that about 80% of the global energy demand is supplied by the fossil fuels which in turn promote global warming upon their consumption and cause harmful effects on the environment. One of the major causes of global warming is the excessive accumulation of CO2 into the atmosphere. An important way for mitigating the excessive amount of CO2 is to transform it into the hydrocarbons (HC) fuels. In this article, we have addressed various issues aroused by CO2 emission and their possible solutions. Various routes for CO2 upgrading into HC fuels are comprehensively elaborated. Furthermore, we have focused on the heterogeneous catalysis for CO2 conversion to value-added HC fuels by utilizing zeolite and non-zeolite based catalysts. The role of noble metals-based catalysts (such as Rh and Ru) and the transition metals containing Ni-species supported on zeolites in CO2 conversion to (HC) fuels is discussed. In addition, the role of Fe- and MOFs based non-zeolite based catalysts for the generation of HC fuels via the CO2 hydrogenation is also discussed. Finally, this review article highlights the prospective areas for research and technology advances. In brief, this review is focused on zeolite and non-zeolite based catalytic route for CO2 to HC fuel and reflects its importance for both the industries and academia.
The problem of efficiency and universal optimality of RMDs has been widely studied in the literature. Recently, Rajab et al. proposed CBRMDs for equal, two, three, and four different period sizes. In ...this article, the universal optimality of the proposed designs by Rajab et al., by using the Method of cyclic shifts (Rule I), have been proved under three different models. The information matrices for both direct and residual effects of these designs have also been expressed in the simple form which can be further used for proving conditions of universal optimality. Lastly, the construction of optimal designs through generators has been mentioned.
Background. One of the common characteristics of preclinical genetic experimentation is the result of repeated measurements, and for this purpose, repeated measurements designs (RMDs) have gained ...much more significance. In the class of RMDs, balanced repeated measurements designs (BRMDs) are preferred as they balance out the residual effects since the experimentation is repeated over time on different subjects. This study provides the theoretical framework of universal optimal criteria proposed by Kiefer (1975) for the newly proposed circular balanced repeated measurements designs (CBRMDs) by Rajab et al. (2018). These universal optimality criteria were proved for the special class of designs where the number of treatments is equal to the number of periods. Universal optimality has been discussed considering all the possible effects in the models, i.e., units, subjects, treatments, and periods. Methodology. This study characterized CBRMDs, where several treatments and periods are equal in the contest of three separate models with their matrices of information in simplified form. We used these simplified matrices of information to ascertain the criteria for universally optimal CBRMDs under different conditions. These new CBRMDs have been constructed using the well-known method of cyclic shifts (MCS) rule II. Results. Universal optimality of the new proposed classes of designs has been discussed theoretically. Universally optimal CBRMDs were constructed for v=podd using the MCS rule II along with the confirmation of the universal optimality criteria proposed in the existing theory. Conclusions. The proposed class of new CBRMDs has been proven to have theoretically universally optimal designs, which have been constructed by the method of cyclic shifts rule II when the number of treatments is equal to the number of periods.
This paper reports the study of in‐situ incorporation of NiFe‐(Anion) layered double hydroxides (LDH) in the ethylene‐propylene (EP) (95:05 molar ratio) copolymerization. NiFe LDHs were synthesized ...with different intercalated anions using the coprecipitation method. The EP/LDH nanocomposites showed improved thermal stability, nevertheless, the various types of intercalated anions in the LDH showed a remarkable effect on the thermal stability and the degradation mechanism of the resultant polymer nanocomposites. EP/LDH constituted with NiFe‐CO3/A (A = acetone washed) showed maximum improvement in the thermal stability concerning neat EP. The LDH incorporation in the composite influenced the polymer microstructure which was evident from the DSC and CRYSTAF analysis. The degradation kinetics of neat EP and EP/LDH nanocomposites were studied by employing the isoconversional method. The degradation kinetics models of different polymer samples were predicted by applying a generalized master plot. Moreover, EP nanocomposites exhibited higher storage modulus and elasticity as compared to neat EP copolymer.
This article discusses the effect of microwave irradiation on the thermal properties of poly(vinyl alcohol)/graphene nanocomposites, prepared using a solution casting technique. Samples were ...subjected to microwave radiation for 5, 10 and 15 min at a constant power of 200 watts. The crystallinity and thermal stability of the irradiated samples were studied by differential scanning calorimetry (DSC) and thermogravimetric analysis. Reduction in crystallinity and thermal stability of PVA was observed with incorporation of graphene due to restricted dynamic movement of chains and synergistic instability, respectively. Microwave irradiation for 5 min improved the crystallinity and thermal stability of the nanocomposites. However, further irradiation caused a decrease in the crystallinity as well as in the thermal stability due to degradation. Moreover, the isothermal crystallization kinetics were studied by DSC. An increase in the crystallization rate was observed with graphene incorporation.
Machine learning algorithms are rapidly deploying and have made manifold breakthroughs in various fields. The optimization of algorithms got abundant attention of researchers being a core component ...for deploying the machine learning model (MLM) abled to learn the parameters in significant ways for the given data. Modeling crop productivity through innumerable agronomical constraints has become a crucial task for evolving sustainable agricultural policies. The cross-sectional datasets of 26430 (D1) crop-cut experiments are taken by 2nd-stage area frame sampling, collected from crop reporting service. This research is taken as follows: firstly three more effective numerical optimized datasets are generated (D1, D2, and D3) from D1 by taking the centroid points of features which decrease the sample size; secondly MLM is integrated with the traditional statistical models (TSMs) for multiple linear regression (MLR), and thirdly decision tree regression (DTR) and random forest regression (RFR) are deployed to get the optimized models able to predict the wheat productivity well with 75% datasets to train and 25% to test the model using the evaluation metrics (R2, RMSE), information criterion (AIC) with weights (AICW), evidence ration (E.R), and decompositions of prediction error. The MLR outperformed for MLM than TSM. The performance capability of MLM and TSM got upswing for generated datasets. RFR got optimized and superperformed for D1, D2, D3, and D4. This study demonstrated strong evidences for deploying MLM for prediction of wheat productivity as an alternative of traditional statistical modeling.
Repeated Measurements Designs have been widely used in agriculture, animal husbandry, education, biology, botany and engineering. Balanced or strongly balanced repeated measurements designs are ...useful to balance out the residual effects. In this article, some new generators and construction procedures are proposed to obtain circular strongly balanced repeated measurements designs in periods of (a) equal sizes, (b) two different sizes, and (c) three different sizes.
This study reports the heterogenization of metallocene catalysts on sodium dodecyl sulfate (DDS)‐modified layered double hydroxides (LDHs) for efficient ethylene–propylene (EP) slurry‐phase ...copolymerization. The LDH support offers considerable compositional tunability. NiFe LDHs with different anions (CO32−,NO3−,andDDS−${\mathrm{CO}}_3^{2 - },{\mathrm{\ NO}}_3^ - ,{\mathrm{\ and\ DDS}}^ - $) and metallic compositions are applied as support for the metallocene catalysts; these significantly influence the catalytic properties of the heterogenized catalyst system. The supported‐catalyst intercalating DDS− anion in the galleries of NiFe and ZnAl LDHs demonstrates a high catalytic activity. They produce EP copolymers with high molecular weights (Mw) and wide polydispersity, compared with the homogeneous Zr catalyst. Further, the supported catalyst complex containing CO32−${\mathrm{CO}}_3^{2 - }$ anion produces EP with a tenfold high Mw and demonstrate subdued catalytic activity. The higher basicity of the support is associated with the enhanced activity and the wider polydispersity of the EP pertaining to the different interactions of the catalyst molecule with the support. Overall, Ni‐containing LDH favors a higher activity, whereas Fe‐containing LDH favors a higher Mw. Therefore, NiFe‐based LDH results in both higher activity and molecular weight. 13C and 27Al magnetic angle spinning solid‐state nuclear magnetic resonance confirm the formation of the supported catalyst complex.
Metallocene catalysts are heterogenized over surfactant‐modified layered double hydroxides (LDHs). Enhanced activity of the NiFe‐LDH and ZnAl‐LDH‐based supported catalyst complex is attributed to the high surface basicity. Polymers produced by these catalysts have shown multimodal molecular weight distribution due to multiple active site formations.
The synthesis of polar functionalized polyolefin (PFP) offers improvement in mixing properties, polymer surface, and rheological properties with the potential of upgraded polyolefins for modern and ...ingenious applications. The synthesis of PFP from metal‐based catalyzed olefin (non‐polar in nature) copolymerization with polar comonomers embodies energy‐efficient, atom‐efficient, and apparently an upfront methodology. Despite their outstanding success during conventional polymerization of olefin, 3rd and 4th group (early transition metal)‐based catalysts, owing to their electrophilic nature, face challenges mainly due to Lewis basic sites of the polar monomers. On the contrary, late transition metal‐based catalysts have also made progress, in recent years, for PFP synthesis. The recent past has also witnessed several advancements in the development of dominating palladium‐based catalysts while their lower resistance towards ligand functional groups has limited the practical application of abundant and cheaper nickel‐based catalysts. However, the relentless efforts of the scientific community, during the past half‐decade, have indicated rigorous progress in the development of nickel‐based catalysts for PFP synthesis. In this review, we have abridged the recent research trends in both early as well as late transition metal‐based catalyst development. Furthermore, we have highlighted the role of transition metal‐based catalysts in influencing the polymer properties.
The synthesis of polar functionalized polyolefin, in particular, polyethylene offers unique and superior characteristics of these functionalized materials. The transition metal‐based ethylene copolymerization with a wider range of polar comonomers has emerged in recent years and advancement in the field has seen a rapid increase quite recently. These advancements have provided an opportunity to the scientists to explore ways for commercialization of functionalized polyolefins.
