Aluminosilicate Research Articles

Mechanistic classification and benchmarking of polyolefin depolymerization over silica-alumina-based catalysts

Carbon-carbon bond cleavage mechanisms play a key role in the selective deconstruction of alkanes and polyolefins. Here, we show that the product distribution, which encompasses carbon range and formation of unsaturated and isomerization products, serves as a distinctive feature that allows the reaction pathways of different catalysts to be classified. Co, Ni, or Ru nanoparticles immobilized on amorphous silica-alumina, Zeo-Y and ZSM-5, were evaluated as catalysts in the deconstruction of n-hexadecane model substrate with hydrogen to delineate between different mechanisms, i.e., monofunctional- (acid site dominated) or bifunctional-hydrocracking (acid site & metal site) versus hydrogenolysis (metal site dominated), established from the product distributions. The ZSM-5-based catalysts were further studied in the depolymerization of polyethylene. Based on these studies, the catalysts are plotted on an activity-mechanism map that functions as an expandable basis to benchmark catalytic activity and to identify optimal catalysts that afford specific product distributions. The systematic approach reported here should facilitate the acceleration of catalyst discovery for polyolefin depolymerization.

Application of different quantitative analytical techniques for estimation of aspirin and omeprazole in pharmaceutical preparation

Several quantitative analytical methods were used to estimate aspirin and omeprazole in recently FDA-approved tablets. The first derivative of the ratio spectra was used to resolve the recorded overlapping spectra between aspirin and omeprazole. The first derivative of the ratio spectra of the studied drug mixtures was divided by a spectrum of a standard solution of omeprazole for the estimation of aspirin. Also, the first derivative of the ratio spectra of the studied drug mixtures was divided by a spectrum of the standard solution of aspirin for the estimation of omeprazole. For the simultaneous quantitative analysis of aspirin and omeprazole, the TLC densitometry technique was applied using TLC aluminum silica gel plates, toluene–acetonitrile–methanol (7:2:0.5, by volume) as the mobile phase, and UV detection at 272 nm. The advantages and disadvantages of the proposed techniques were discussed in the context of the results and the sensitivity limits of the methods. The proposed techniques were validated and successfully applied to the analysis of drugs in pure and pharmaceutical forms. A statistical comparison of the data obtained by the described methods with other data obtained by a previously published HPLC method was performed. The results agreed well with respect to the recommended statistical tests. Furthermore, the greenness of the described methods was assessed using different tools, the analytical eco-scale, the green analytical procedure index and the AGREE evaluation method. The proposed methods showed more adherence to the greenness characters in comparison to the previously reported HPLC method.

Dehydration of levoglucosan to levoglucosenone over solid acid catalysts. Tuning the product distribution by changing the acid properties of the catalysts

The effect of the catalytic properties of various types of solid acids, including oxides (ZrO2, SOX/ZrO2, WOX/ZrO2, Nb2O5, NbOPO4, Al2O3, TiO2), silica–aluminas (ZSM5 and USY zeolites) and acidic ion-exchange resins (Amberlyst-70 and Dowex 50wx8) were investigated for liquid-phase levoglucosan (LGA) conversion. H2SO4 was also evaluated as a reference catalyst. The concentration of both Brønsted and Lewis acid sites in the catalysts was measured by FTIR of adsorbed pyridine and titration with NaOH. The catalysts were tested under different reaction conditions (110–170 °C and 30–60 bar of N2) for 1 h using tetrahydrofuran (THF) as solvent. The product distribution obtained from the LGA conversion can be tuned depending on the type of acid site of the catalyst or the reaction conditions used. Catalysts containing only Bronsted acid sites were selective to LA while those with both Bronsted and Lewis acid sites favored the formation of 5-hydroxymethylfurfural (HMF). LGO was mainly produced by the homogeneous catalyst. The USY and HZM5 (SiO2/Al2O3 ratio of 23) promoted the production of HMF and glucose, respectively. A reaction mechanism was proposed taking into account the acid properties of the catalysts. The reactions of dehydration of LGA to LGO or hydration of glucose requires Brønsted acid sites. Catalysts with only Lewis acid sites produced only humins. For the catalysts containing both Brønsted and Lewis acid sites, LGA is mainly hydrated to glucose on the Bronsted acid sites. Then, glucose is preferentially isomerized to fructose on the Lewis acid sites, followed by its dehydration to HMF. The low LA formation shows that the hydration of HMF to LA requires a higher concentration of Brønsted acid sites.

Analisis Pengaruh Penambahan Kaolin Sebagai Subtitusi Semen Terhadap Kuat Tekan Beton Ringan

Concrete is a very important construction material and has good compressive properties. According to its mass, concrete is divided into ordinary concrete and lightweight concrete. Light weight concrete is 1000-2000 kg/m3. In high construction projects the use of lightweight concrete can reduce the mass of the building itself. The latest innovation in lightweight concrete is the addition of kaolin as a cement substitute. Kaolin is a clay or clay mineral that contains a lot of aluminum silica. Stryofoam is one of the materials that can be used in lightweight concrete mixes. The use of kaolin and styrofoam waste is sought to support construction materials that are more environmentally friendly. The purpose of this study was to determine the effect of the addition of kaolin on compressive strength so that it can be used as an admixture in lightweight concrete. The results showed that the weight of concrete mixed with 5%, 10%, 15% kaolin and 60% Styrofoam at the age of 28 days was 1836 kg/m³, 1845 kg/m³, 1852 kg/m³. The average compressive strength for the kaolin variants 5%, 10%, 15% were 8.28 MPa, 8.46 MPa, 10.11 MPa. Based on this it was concluded that concrete using a mixture of kaolin and 60% stryofoam can be used in light construction. Because the weight of the lightweight concrete tested was lower than normal concrete and met the specified requirements, namely the specific gravity of the resulting concrete was in the range of 1000-2000 kg/m³.

Steam catalytic cracking of crude oil over novel hierarchical zeolite–containing mesoporous silica–alumina core-shell catalysts

The direct conversion of crude oil to basic chemicals was studied over novel core-shell structured ZSM-5 zeolite containing mesoporous silica-alumina (MSA) composites. A template-directed sol-gel method in an alkaline medium was used to prepare a core-shell structured ZSM-5 containing MSA composites employing CTAB as template, tetraethyl orthosilicate (TEOS), and aluminum sulfate. This approach resulted in the formation of a uniform mesoporous silica-alumina shell around the zeolite crystal. The shell thickness (tune in the 8–26 nm range) and its alumina content were controlled by varying the TEOS/zeolite and TEOS/aluminum sulfate ratios. The physicochemical properties and steam catalytic cracking performance of Arab Extra Light (AXL) crude oil were investigated to enhance the yield of C2-C4 light olefins. For comparative study, conventional and mesoporous silica-alumina composites were mixed with kaolin (50%), steam deactivated (810 °C for 6 h) and tested in a fixed-bed reactor operated at 675 °C, residence time of 10 s and steam/oil ratio (g/g) of 0.5. The optimized mesoporous silica-alumina composite Z30 @ MSA (TEOS/zeolite = 0.85 and TEOS/aluminum sulfate = 15.86) had improved textural characteristics, moderate acidity, and AXL crude oil cracking potential at higher conversion (~70%) and selectivity towards light olefins (49.4%) than the unmodified ZSM-5(30). The mesoporous core-shell composite's distinct reaction pattern resulted in the formation of a unique mesoporous silica-alumina core-shell catalyst, which eased the rapid diffusion of desired products from intra-framework channels while inhibiting the formation of coke deposits.

Mechanical properties and calcium–magnesium–alumino–silicate corrosion behaviour of Ce/Gd co-doped SrZrO3 ceramics

Sr(Zr1-2xCexGdx)O3-0.5x (x = 0, 0.05, 0.1 and 0.15) ceramics were prepared by pressureless sintering using powders that were synthesized by solid-state reaction. The mechanical properties and calcium–magnesium–alumino–silicate (CMAS) early corrosion behaviour of the prepared ceramics were reported. The mechanical properties of rare-earth-doped SrZrO3 improved significantly. The reaction products of the Sr(Zr1-2xCexGdx)O3-0.5x ceramics after CMAS corrosion were similar: zirconia, SrAl2O4, akermanite, and anorthite. The mechanism of CMAS corrosion resistance is summarized as follows: elemental Sr easily enters the CMAS melt, because of its high diffusivity, and promotes crystallization. Rare-earth elements can prevent melt infiltration because of their low diffusivity.

Recycling of aluminum dross and silica fume wastes for production of mullite-containing ceramics: Powder preparation, sinterability and properties

The improper disposal of industrial wastes causes environmental pollution so their recycling for fabrication of new products became an interesting research issue. In this work, sintered mullite-containing ceramics were prepared from aluminum dross and silica fume (up to 40 wt%) waste materials after sintering up to 1500 °C. Before sintering, the starting waste materials were converted into nano powders by mechanical milling alloying method up to 15 h. The obtained waste nano powders were investigated using different techniques as X-ray diffraction (XRD), transmission electron microscope (TEM) and scanning electron microscope (SEM). On the other hand, phase identification by XRD, physical properties determination (bulk density and apparent porosity), microstructure by SEM, mechanical and electrical properties of sintered bodies were investigated. The results revealed that mullite phase was formed in higher amounts with increasing both sintering temperature (1500 °C) and silica fume content. At 1300 °C, amorphous mullite was formed in addition to the alumina phase. It is also noted that the apparent porosity and bulk density were reduced with increasing silica content. However, they exhibited opposite trend when the temperature increased from 1300 into 1500 °C. Moreover, with increasing the mullite content, the microhardness, compressive strength, Younges modulus and electrical conductivity were decreased and reached 10.2 GPa, 216.9 MPa, 119.7 GPa and 4.9 × 10 −12 S/m, respectively, for the sample that contained higher amount of mullite, while the fracture toughness was improved and reached to 3.44 MPa m0.5.

Upscaling degradation of cementitious calcium (aluminate) silicate hydrate upon ultra-low temperature attack: A multiscale insight and a bottom-up enhancement route

Low-carbon calcium (alumino)silicate hydrate (C-(A)-S-H) based composites (e.g., blended cement-based materials and alkali-activated materials) have broad application potential in ultra-low-temperature engineering areas. This study devotes to reveal the structural stability of C-(A)-S-H under ultra-low temperature attack (−170 °C) and evaluating the role of aluminum as a bottom-up enhancement strategy for C–S–H. The atomic structure, interlayer structure, internal basic building block structure, pore network, and micro-morphology were experimentally studied using 29Si MAS NMR, XRD, helium pycnometry, nitrogen adsorption, and SEM. These results indicate that an ultra-low temperature attack can deteriorate C-(A)-S-H structure, even though without the presence of bulk water, whereas the incorporation of aluminum positively stabilizes C-(A)-S-H structure. The silicate chains of Al-free C–S–H are ruptured with more defective vacant sites, which consequently initiates a decline in its d002 interlayer space and the volume collapse of basic building blocks, further resulting in the formation of microcracks. In contrast, aluminosilicate chains of C-A-S-H are more stable and even polymerized with longer chain length, stabilizing the micro/mesostructure. An upscaling degradation route from the atomic scale to mesoscale was proposed, providing a multiscale view to understand the degradation of concrete composites upon ultra-low temperature attack. We also confirm that incorporating aluminum in the silicate chains is an effective bottom-up strategy to enhance the cryogenic stability of C-(A)-S-H.

Novel silica-modified boehmite aerogels and fiber-reinforced insulation composites with ultra-high thermal stability and low thermal conductivity

Alumina–silica composite aerogels have drawn vast attention due to their enhanced thermal stability compared to pristine alumina aerogels. However, they are generally weakly-crystallized and tend to experience inevitable sintering and significant surface area loss especially above 1200 °C. In this study, we developed a hydrothermal treatment and supercritical drying strategy for synthesizing novel, well-crystallized, silica-modified boehmite aerogels and fiber-reinforced composites. For the prepared aerogel, network coarsening was significantly hindered and the α-Al2O3 transition was completely prevented even at 1400 °C. As a result, the aerogel exhibits extremely high surface area maintenance (87 % and 53 % after 1300 °C and 1400 °C calcination, respectively) and low linear shrinkage (14 % after 1300 °C calcination) at elevated temperatures. The composite with good toughness shows excellent heat resistance and thermal insulating performance up to 1500 °C. These findings provide a general, direct new idea to improve the thermal tolerance of alumina-based aerogels and extend their applications to higher temperatures.

Single-step catalytic deoxygenation-cracking of tung oil to bio-jet fuel over CoW/silica-alumina catalysts

Bifunctional Co-W catalysts with variable Co-W dosages on silica-alumina (SA) were prepared and tested for the catalytic deoxygenation-cracking of tung oil (TO) for the production of jet fuel (n-(C10-C16)) fractions. The CoW/SA catalyst appeared to be most active (hydrocarbon yield = 69%, jet fuel selectivity = 60%) and outperformed the monometallic Co and W analogues. Based on the effect of metal dosage, Co– and W-rich catalysts do not provide a workable approach in enhancing deoxygenation-cracking of the TO for jet fuel production, and overly cracking can be successfully controlled at lower metal dosages (5 wt% Co, 10 wt% W). The CoW/SA reusability study showed a consistent deoxygenation-cracking ability for four runs with hydrocarbon yields within the range of 77–84% and 64–77% jet fuel selectivity. GCMS analysis and physicochemical properties of TO oil fuel (TO-gasoline, TO-jet, TO diesel) confirmed that rich aromatic species in TO-diesel negatively affected the quality of the fuels. TO-fuels with a short chain had better combustion properties than those with a longer chain hydrocarbon. The TO-jet qualities are complied with standard Jet A-1 in accordance to ASTM D1655 and DEF STAN 91–91 specification standards. The TO-jet also exhibited excellent cold properties and superior combustion characteristic than Jet A-1.

Development of potentials for molecular dynamics simulations of dry and hydrated calcium aluminosilicate glasses by force matching and refinement

Potential development and refinement to improve the applicability and transferability of the forcefield is important to atomistic simulations of glass materials and their interactions with the environment. In this paper, we demonstrate potential development of calcium aluminosilicate glasses with and without water using a reactive potential framework by adopting the force matching technique and subsequent refinement. Accordingly, we have reproduced the forces on atoms of the system from a DFT based ab-initio molecular dynamics (AIMD) simulations by adjusting the potential parameters. We chose the diffuse charge reactive potential (DCRP) as the classical potential as it has been previously demonstrated to accurately and efficiently simulate interactions between water and silicate-glasses. The obtained force matched parameters were further refined to accurately reproduce the structures and dynamics of dry and hydrated calcium alumino silicate glass and gel structures. The Ca2+ behavior in solution was correctly reproduced with an average local coordination equal to 6.12 and a diffusion coefficient close to the experimental values. This force field also correctly reproduces the local environment of Al3+ in glass, but it falls short in describing Al3+ ion coordination in solutions as compared to AIMD results, suggesting a direction of future improvement. This set of potential can thus be used for simulations of calcium aluminosilicate glasses with various technological applications and hydrated gel structures resulted from corrosions of boroaluminosilicate glasses.

Hierarchically porous glass–ceramics by alkaline activation and crystallization from municipal solid waste incineration ashes

As a hazardous waste, municipal solid waste incineration (MSWI) fly ash poses a serious threat to the environment, and considerable efforts have been made to achieve its harmless treatment. Herein, a novel approach for handling MSWI fly ash has been proposed to prepare porous glass–ceramics by alkali activation–crystallization, which overcomes the difficulty of controlling air bubbles under high temperatures. MSWI bottom ash rich in Al2O3 and SiO2 are co-treating as raw material to develop glass framework structure. The alkali activation mechanism shows that the development of MSWI ashes based basic glass from monomer to silica–aluminate gel under alkaline condition. The influence of H2O2 addition on the morphology and physical properties of porous glass–ceramics were evaluated. Porous glass–ceramics with uniform hierarchical pore structure have been fabricated at 3 mol/L NaOH, a solid loading of 55 wt%, and 1–4 wt.% H2O2, then crystallization treatment at 1150 °C for 2 h, the porosity and the bulk density of which varies from 77.22 to 82.94% and 0.68–0.91 g/cm3 respectively, while their relatively high compressive strength ranges from 1.62 MPa to 3.85 MPa. Attributed to the hierarchical porous structure, uniform distribution of pores and excellent physical properties, porous glass–ceramics has potential applications in construction, filtration, and adsorption materials, providing a convenient and feasible method for the efficient and comprehensive utilization of MSWI ashes.

Statistical optimization of process conditions for pyrvinium pamoate elimination using UV/zeolite‐based nanostructures/H 2 O 2

Statistical optimization of process conditions for pyrvinium pamoate elimination using UV/zeolite‐based nanostructures/H ₂ O ₂

Adsorption mechanism of hydrated Lu(OH)2+ and Al(OH)2+ ions on the surface of kaolinite

Density functional theory was used to study the adsorption mechanism of hydrated Lu(OH)2+ and Al(OH)2+ ions on (001) kaolinite surface. Calculation results showed that the respective most stable hydration configurations in the water system were Lu(OH)(H2O)72+ and Al(OH)(H2O)52+. Both hydrated ions were adsorbed on the outer layer of the (001) kaolinite aluminium octahedral and silica tetrahedral surfaces through hydrogen bonding. The two hydrated ions were adsorbed on the deprotonated (001) aluminium octahedral kaolinite surface via coordination bonds, with electrons transferred from the water ligand O 2p to the Al 2 s, Lu 5d, and the surface O 2p orbitals. Owing to its smaller radius and fewer water ligands, hydrated Al(OH)2+ was more easily adsorbed on the (001) kaolinite surface than hydrated Lu(OH)2+. The experimental adsorption and microcalorimetry results supported this conclusion, and it is hypothesised that hydrated ions mainly act on the kaolinite surface via inner-layer adsorption.

In vitro evaluation of the effects of different particle types in toothpastes on the efficacy against enamel erosion and wear

The effects of the particle fraction in toothpastes in the context of erosion and erosive tooth wear has not been fully elucidated. Thus, aim of this study was to investigate experimental toothpastes, each with one specific particle type. Toothpastes with seven different types of silica or alumina were prepared as slurry either with or without active ingredients (NaF or F/Sn). Human enamel samples were exposed to a cyclic erosion/abrasion model, and were either treated with the respective slurries only or additionally brushed in a brushing machine. Tissue loss was profilometrically monitored. After treatment with slurries without active ingredients or with NaF, tissue loss increased significantly within groups over time (p < 0.001 each). At the end of the trial, there were minor differences between groups (not exceeding 10–20%; p > 0.05 for most comparisons). After treatment with the F/Sn slurries, tissue loss stagnated completely over time, with the exception of one silica type and alumina, but both still reduced tissue loss by 40–50% (compared to control p < 0.001 each). Relative to the type of the active ingredient, the particle type seems to be a secondary factor for the efficacy of toothpastes on erosion and erosive tooth wear in enamel.

Application of Induced Polarization and Resistivity Methods to Identify Subsurface Layers in Bauxite Deposits Area of Kendawangan, West Kalimantan

Kendawangan Sub-district, Ketapang Regency is one of the areas in West Kalimantan Province containing minerals of economic value, namely bauxite deposits. This study has applied both induced polarization and resistivity methods. It aims to identify subsurface layers in the Kendawangan bauxite deposit area based on resistivity and chargeability distribution. Measurements in the field apply a north-south line using the dipole-dipole configuration, have a length of 144 m, and electrode distance of 3 m. The results showed that the subsurface layer in the study area identified the presence of bauxite deposits. In addition, it showed that the subsurface layers were topsoil, bauxite deposits, saprolite, and bedrock. Topsoil has a thickness of about 1 m, and it is a product of the weathering process. The bauxite deposit has a thickness of about 9 m, and it contains the minerals aluminum oxide, quartz, hematite, and titanium oxide. Saprolite has a thickness of about 2 - 4 m, and it contains aluminum silica (kaolinite) and minerals quartz, titanium oxide, zircon, and it is a weathering product of bedrock. The bedrock is at a depth of more than 10 m, which is interpreted as volcanic tuff, sandstone, and claystone.

An Investigation Study on Partial Replacement of Cement with Bagasse Ash in Concrete Mix

Abstract: The utilization of industrial and agricultural waste produced by industrial processes has been the focus of waste reduction research for economical, environmental, and technical reasons. Sugar-cane bagasse is a fibrous waste- product ofthe sugar refining industry, along with ethanol vapor. This waste product (Sugar-cane Bagasse ash) is already causing serious environmental pollution, which calls for urgent ways of handling the waste. Bagasse ash mainly contains aluminum ion and silica. In this paper, Bagasse ash has been chemically and physically characterized, and partially replaced in the ratio of 0%,5%, 15% and 25% by weight of cement in concrete. Fresh concrete tests like compaction factor test and slump cone test were undertaken was well as hardened concrete tests like compressive strength, split tensile strength, flexural strength and modulus of elasticity at the age of seven and 28 days was obtained. The result shows that the strength of concrete increasedas percentage of bagasse ash replacement increased. Keywords: bagasse ash, concrete

The High-Throughput In Vitro CometChip Assay for the Analysis of Metal Oxide Nanomaterial Induced DNA Damage.

Metal oxide nanomaterials (MONMs) are among the most highly utilized classes of nanomaterials worldwide, though their potential to induce DNA damage in living organisms is known. High-throughput in vitro assays have the potential to greatly expedite analysis and understanding of MONM induced toxicity while minimizing the overall use of animals. In this study, the high-throughput CometChip assay was used to assess the in vitro genotoxic potential of pristine copper oxide (CuO), zinc oxide (ZnO), and titanium dioxide (TiO2) MONMs and microparticles (MPs), as well as five coated/surface-modified TiO2 NPs and zinc (II) chloride (ZnCl2) and copper (II) chloride (CuCl2) after 2–4 h of exposure. The CuO NPs, ZnO NPs and MPs, and ZnCl2 exposures induced dose- and time-dependent increases in DNA damage at both timepoints. TiO2 NPs surface coated with silica or silica–alumina and one pristine TiO2 NP of rutile crystal structure also induced subtle dose-dependent DNA damage. Concentration modelling at both post-exposure timepoints highlighted the contribution of the dissolved species to the response of ZnO, and the role of the nanoparticle fraction for CuO mediated genotoxicity, showing the differential impact that particle and dissolved fractions can have on genotoxicity induced by MONMs. The results imply that solubility alone may be insufficient to explain the biological behaviour of MONMs.

Influence of ASA composition on its supported Mo catalyst performance for the slurry-phase hydrocracking of vacuum residue

To deeply illuminate the effect of ASA composition on its corresponding Mo catalyst properties and performance for the slurry-phase hydrocracking of vacuum residue, the amorphous silica-alumina (ASA) samples with the various ratios of Al to Si were successfully synthesized by a simple co-precipitation method, which have the different acid properties and pore structure, especially ASA-1 with lowest ratio of Al to Si owning the largest number of B acid sites and the highest volume of mesoporous. Additionally, the Mo catalyst supported on ASA-4 possesses the highest dispersion of MoS2 slabs and largest amount of Mo atoms located at the edge sites among all the catalyst, possibly due to the appropriate surface properties of ASA-4 derived from the ratio of Al to Si, it demonstrates that the most exposure Mo active sites are present on Mo/ASA-4 catalyst. The hydrocracking evaluation results show that the VR conversion over the different catalysts are similar, it may be ascribed to the variation of acid properties and pore structure insufficient to change VR cracking pathway because of the low catalyst dosage. Furthermore, the Mo/ASA-4 catalyst exhibits the higher yield of naphtha and middle distillate and inversely the lower yield of gas and coke in comparison with other catalysts, it should be attributed that the higher hydrogenation activity derived from the more exposure Mo active sites can efficiently restrain the over-cracking of the intermediate product and aggregation of the polycyclic aromatic hydrocarbon in the hydrocracking process.

Amorphous Silica‐Alumina as Suitable Catalyst for the Diels‐Alder Cycloaddition of 2,5‐Dimethylfuran and Ethylene to Biobased p‐Xylene

AbstractThe potential of amorphous silica‐alumina (ASA) to substitute zeolites (HBeta‐25) for the synthesis of p‐xylene via Diels‐Alder cycloaddition (DAC) of ethylene to 2,5‐dimethylfuran (2,5‐DMF) is investigated. ASA were prepared via homogeneous deposition‐precipitation of Al on SiO2. ASA shows good yields of p‐xylene (20–25 % after 18 hours) compared to bare silica and γ‐alumina. Brønsted acid sites (BAS) were identified as the active sites for the DAC reaction. The catalytic performance correlated strongly with the BAS concentration. Increasing the acidity of ASA is, however, limited by formation of agglomerated alumina‐type clusters at higher Al3+ content. While HBeta‐25 zeolite shows initially a slightly higher performance in terms of p‐xylene yield, ASA is the better catalyst upon calcination‐regeneration of the used catalyst. These results furthermore confirm that confinement in zeolite micropores is not a prerequisite for the DAC reaction between 2,5‐DMF and ethylene.