Development of technologies for producing high-octane ethers

To produce alkyl(C₁-C₂)-tert-alkyl(C₄-C₇) ethers, different process designs are necessary depending on the raw materials and production rate. New production processes using catalytic distillation and cocurrent reactors are described and compared with conventional processes. The justification of the choice of efficient flow diagrams, reactors, and new methods for recovering C₁-C₂ alcohols from hydrocarbon product streams is given.     

Alkyl Chain Growth on a Transition Metal Center: How Does Iron Compare to Ruthenium and Osmium?

Industrial Fischer-Tropsch processes involve the synthesis of hydrocarbons usually on metal surface catalysts. On the other hand, very few homogeneous catalysts are known to perform a Fischer-Tropsch style of reaction. In recent work, we established the catalytic properties of a diruthenium-platinum carbene complex, [(CpRu)₂(μ²-H)(μ²-NHCH₃)(μ³-C)PtCH₃(P(CH₃)₃)₂](CO)_n⁺ with n = 0, 2 and Cp = η⁵-C₅(CH₃)₅, and showed it to react efficiently by initial hydrogen atom transfer followed by methyl transfer to form an alkyl chain on the Ru-center. In particular, the catalytic efficiency was shown to increase after the addition of two CO molecules. As such, this system could be viewed as a potential homogeneous Fischer-Tropsch catalyst. Herein, we have engineered the catalytic center of the catalyst and investigated the reactivity of trimetal carbene complexes of the same type using iron, ruthenium and osmium at the central metal scaffold. The work shows that the reactivity should increase from diosmium to diruthenium to diiron; however, a non-linear trend is observed due to multiple factors contributing to the individual barrier heights. We identified all individual components of these reaction steps in detail and established the difference in reactivity of the various complexes.     

Removal of Dibenzothiophene from Diesels by Extraction and Catalytic Oxidation with Acetamide‐Based Deep Eutectic Solvents

A series of acetamide‐based deep eutectic solvents (DESs) with different proportions were prepared. Extraction and catalytic oxidation desulfurization (ECODS) of the acetamide‐based DESs were investigated and the process was optimized. Such DESs with a molar ratio of acetamide and p‐TsOH of 1/3 (C₂H₅NO/3p‐TsOH) exhibits such a remarkable catalytic activity that the dibenzothiophene (DBT) removal could reach 100 % under optimized conditions. C₂H₅NO/3p‐TsOH was used for the oxidative desulfurization of actual commercial diesel. The sulfur removal of diesel achieved up to 98 %. C₂H₅NO/3p‐TsOH could be recycled six times and the desulfurization activity was slightly decreased. Evaluation of the mechanism indicated that oxidative desulfurization (ODS) was realized via dual activation of acetamide‐based DESs. A novel and effective way for deep desulfurization of diesel is provided.     

Enhanced direct electron transfer reactivity of hemoglobin in cationic gemini surfactant-room temperature ionic liquid composite film on glassy carbon electrodes

A novel composite film comprising cationic gemini surfactant butyl-α,ω-bis(dimethylcetylammonium bromide) (C₁₆H₃₃N(CH₃)₂-C₄H₈-N(CH₃)₂C₁₆H₃₃, C₁₆-C₄-C₁₆) and ionic liquid 1-octyl-3-methylimidazolium hexafluorophate (OMIMPF₆) has been prepared. The composite film shows good biocompatibility and it can promote the direct electron transfer between hemoglobin (Hb) and glassy carbon (GC) electrode. On the C₁₆-C₄-C₁₆ (dissolved in ethanol)-OMIMPF₆ film coated GC electrode, the immobilized Hb can exhibit a pair of well-defined, quasi-reversible and stable redox peaks with a formal potential of −0.317 V (vs SCE) in 0.10 M pH 7 phosphate buffer solutions. The electron transfer coefficient (α) of Hb is calculated to be 0.44 and the heterogeneous electron transfer rate constant is 6.08 s⁻¹. With the length of alkyl chains of gemini surfactant increasing and the ethanol concentration rising, the redox peaks of the resulting electrode C₁₆-C₄-C₁₆-OMIMPF₆-Hb/GC become bigger. The electrode presents good electrocatalytic response to peroxide hydrogen. The kinetic parameters I_max and k_m for the catalytic reaction are estimated. In addition, UV-vis spectra and reflectance absorption infrared spectra demonstrate that the Hb immobilized in the C₁₆-C₄-C₁₆-OMIMPF₆ film almost retains the structure of native Hb.     

Degradation of waste High-density polyethylene into fuel oil using basic catalyst

High-density polyethylene (HDPE) has been degraded thermally and catalytically using MgCO₃ at 450 °C into liquid fraction in a batch reactor. Different conditions like temperature, time and catalyst ratio were optimized for the maximum conversion of HDPE into liquid fraction. Catalytic degradation yielded 92% liquid fraction whereas 90% wax was obtained with thermal degradation. The composition of the liquid fraction was characterized by physicochemical properties of petroleum fuel tests. The catalytic liquid fraction consisted of high concentration of C₈-C₉, C₁₃-C₁₄ and C₁₇-C₁₈ hydrocarbons. The distillation data showed that ∼50% of the fraction has boiling point in the range of gasoline and ∼50% in the range of diesel oil.     

Crosslinking of cotton cellulose in the presence of alkyl diallyl ammonium salts. I. Physical properties and agent distribution

We used three kinds of alkyl diallyl ammonium salts (methyl, ethyl, and propyl) in combination with dimethyloldihydroxyethyleneurea (DMDHEU) as crosslinking agents. The nitrogen content, dry crease recovery angle (DCRA), moisture regain, and wicking height for the DMDHEU/alkyl diallyl ammonium salts were in the order of ? CH₃ > ? C₂H₅ > ? C₃H₇, but the wet crease recovery angle (WCRA) and tensile strength retention (TSR) were in the opposite order at the same resin concentration. For the same DCRA and TSR, the WCRA values for only DMDHEU were lower than those for DMDHEU/alkyl diallyl ammonium salts, and the WCRA values for DMDHEU/alkyl diallyl ammonium salts were in the order of ? C₃H₇ > ? C₂H₅ > ? CH₃. Both the ? OH group of the cellulose and DMDHEU could react with the vinyl or epoxy groups of the alkyl diallyl ammonium salts during the pad–dry–cure process. The surface migration for DMDHEU/alkyl diallyl ammonium salts was in the order of ? CH₃ > ? C₂H₅ > ? C₃H₇. Fabrics treated with DMDHEU/alkyl diallyl ammonium salts showed good antibacterial properties. © 2003 Wiley Periodicals, Inc. J Appl Polym Sci 90: 1662–1669, 2003     

Adsorptive and stripping behavior of methylene blue at gold electrodes in the presence of cationic gemini surfactants

The adsorptive and stripping behavior of methylene blue (i.e. methylene blue chloride, MB) at a gold electrode has been studied with voltammetry, alternating current impedance spectra (ACIS) and quartz crystal microbalance (QCM). MB exhibits a pair of cyclic voltammetry peaks at about −0.3 V (versus SCE) in 0.05 M pH 6.9 phosphate buffer solutions. In the presence of cationic gemini surfactants such as C₁₆H₃₃N(CH₃)₂-C₄H₈-N(CH₃)₂C₁₆H₃₃Br₂ (C₁₆-C₄-C₁₆), C₁₆H₃₃N(CH₃)₂-C₄H₇OH-N(CH₃)₂C₁₆H₃₃Br₂ (C₁₆-C₄OH-C₁₆), C₁₆H₃₃N(CH₃)₂-CH₂-C₆H₄-CH₂-N(CH₃)₂C₁₆H₃₃Br₂ (C₁₆-ph-C₁₆) and C₁₆H₃₃N(CH₃)₂-C₁₂H₂₄-N(CH₃)₂C₁₆H₃₃Br₂ (C₁₆-C₁₂-C₁₆), the anodic peak grows rapidly and moves in positive direction, but the cathodic peak gradually decreases, due to the association adsorption and electrostatic interaction of the geminis with MB and its reduced product (i.e. leuko methylene blue, LMB). With the aid of geminis the adsorption amount of MB increases under open-circuit, but the impedance of the mixed adsorption film to Fe(CN)₆^3−/4− almost keeps unchanged, compared with either bare gold electrodes or MB film, while the adsorption film of geminis exhibits greater impedance. This probably is due to the electron medium action of MB in the film. Gemini surfactants with same alkyl-chain (i.e. -(CH₂)₁₅CH₃) but different molecular structure, exhibit different influence. The enhancing action of geminis studied follows such order as: C₁₆-ph-C₁₆ > C₁₆-C₄-C₁₆ > C₁₆-C₄OH-C₁₆ > C₁₆-C₁₂-C₁₆. The change of peak potential was ascribed to the interaction between MB and surfactants, as well as the blocking action of surfactant film. For comparison, the influence of dihexadecyldimethylammonium bromide (DCAB) and cetyltrimethylammonium bromide (CTAB) was studied, and the influence of other factors is discussed as well.     

Kinetics of surface reactions in carbon deposition from light hydrocarbons

Carbon deposition from ethene, ethine and propene as a function of pressure was studied at various temperatures and two different surface area/volume ratios. Deposition rates as a function of pressure of all hydrocarbons indicate Langmuir-Hinshelwood kinetics which suggests that the deposition process is controlled by the heterogeneous surface reactions (growth mechanism). These kinetics are favored at decreasing reactivity (C₃H₆>C₂H₂>C₂H₄), decreasing temperature and residence time as well as increasing surface area/volume ratio. A linear rate increase at high pressures suggests that carbon is additionally or preferentially deposited by aromatic condensation reactions between polycyclic aromatic hydrocarbons large enough to be physisorbed or condensed on the substrate surface (nucleation mechanism). The results completely agree with earlier results obtained with methane.     

Sustainable Desulfurization Processes Catalyzed by Titanium-Polyoxometalate@TM-SBA-15

A titanium-polyoxometalate with a µ-hydroxo dimeric structure [(PW₁₁O₃₉Ti)₂OH]^7? ((PW₁₁Ti)₂OH) was used efficiently for the desulfurization of a model diesel containing a mixture of various refractory sulfur compounds present in real fuels. The catalytic performance of the µ-hydroxo dimeric compound was compared in its homogeneous form and also when immobilized in the trimethylammonium-functionalized SBA-15 ((PW₁₁Ti)₂OH@TM-SBA-15). An optimization study was performed using the homogeneous and heterogeneous catalysts to obtain high catalytic efficiency, sustainability and cost-effectiveness of the system. Different optimized conditions were found using the homogeneous and heterogeneous catalysts. Lower amounts of solvent extraction (MeCN, 175 µL), catalyst (0.5 µmol of active center) and oxidant (50 µL) were used to produce sulfur-free model diesel after 2 h at 70?°C, using the heterogeneous (PW₁₁Ti)₂OH@TM-SBA-15 catalyst. On the other hand, complete desulfurization was achieved with homogeneous (PW₁₁Ti)₂OH catalyst after only 40 min, although higher amounts of MeCN (750 µL), catalyst (1.5 µmol) and oxidant (75 µL) were used. Both systems combined liquid–liquid extraction and catalytic oxidation. Using the heterogeneous catalyst, adsorption of oxidized-sulfur compound was also observed. Both homogeneous and heterogeneous desulfurization systems presented a high capacity to be reused/recycled for consecutive desulfurization cycles.     

Study on 2-thiophenecarbonyl chloride-quenched olefin polymerization with <Emphasis Type="Italic">α</Emphasis>-diimine nickel catalysts

The number of active centers in α-diimine nickel-catalyzed olefin homogeneous polymerization system is rarely studied before. A systemic study on quenching method with 2-thiophenecarbonyl chloride (TPCC) in homogeneous catalytic system is presented. Ethylene and propylene polymerizations catalyzed with homogeneous α-diimine nickel catalysts (ArN=C(An)–C(An)=NAr)NiBr₂ (cat.1, Ar=2,6-C₆H₃(i-Pr)₂) and (ArN=C(C₁₂H₈)C=NAr)NiBr₂ (cat.2, Ar=2,6-C₆H₃(i-Pr)₂, C₁₂H₈=acenaphthene-1,8-diyl) were quenched by TPCC. The potential side reaction between TPCC and alkyl aluminum-terminated polymer chain caused by chain transfer to cocatalyst under different quenching conditions was investigated. Samples were obtained with different TPCC/Al_MAO molar ratios and had similar sulfur contents; a confirmation that the excess TPCC in the system did not cause obvious side reactions which could lead to place more thiophene groups to the polymer chains. Moreover, when the quenching time was in the range of 3–20 min, the sulfur contents remained stable and the value of N_pol (number of moles of polymer chains) was not obviously changed, supporting that sufficient quenching reaction had already accomplished within the first 3 min. We claimed that the side reaction could be ignored under controllable conditions. TPCC was confirmed to be an effective quenching agent in homogeneous catalytic system. The quenching method with TPCC was also established.     

Deep desulfurization of hydrodesulfurized diesel oil by Pseudomonas delafieldii R‐8

Biodesulfurization is a promising technology for deep desulfurization. The remaining alkylated DBTs (dibenzothiophenes) in the HDS‐treated (hydrodesulfurized‐treated) diesel oil could be selectively and efficiently desulfurized by resting cells of Pseudomonas delafieldii R‐8, a Gram‐negative bacterium. The desulfurization activities of resting cells were greatly affected by W/O ratio (the volume ratio of aqueous phase to oil phase) and cell concentration. The desulfurization activity increased with the increase in the W/O ratio. When the W/O ratio and cell concentration were 2 and 25 mg cm^?3, the desulfurization activity was as high as 0.41 mg(total sulfur) g^?1(dry cell weight, DCW) h^?1, ie higher than that reported previously. GC‐AED (gas chromatography with an atomic emission detector) analysis showed that the total reductions for all the C1DBTs and C2DBTs were approximately 100%, 94.63% for C3DBT, and 97.09% for C4DBT (designated CxDBT, where x is the number of alkyl groups attached). The rates of biodesulfurization relate to the number and position of alkyl groups attached to the DBT. Copyright © 2005 Society of Chemical Industry     

Catalytic properties of Ru-η-C6H6-diphosphine complexes for hydrogenation of benzene in aqueous-organic biphasic system

The influences of pH on the catalytic properties of Ru-η⁶-C₆H₆-diphosphine complex [RuCl(η⁶-C₆H₆)(BISBI)]Cl (1) (BISBI = 2,2′-bis(diphenylphosphinomethyl)-1,1′-biphenyl), [RuCl(η⁶-C₆H₆)(BDPX)]Cl (2) (BDPX = 1,2-bis(diphenylphosphinomethyl)benzene), Ru₂Cl₄(η⁶-C₆H₆)₂(μ₂-BDNA) (3) (BDNA = 1,8-bis(diphenylphosphinomethyl)naphthalene), [RuCl(η⁶-C₆H₆)(BISBI)]BF₄ (4), [RuCl(η⁶-C₆H₆)(BDPX)]BF₄ (5), and [(η⁶-C₆H₆)₂Ru₂Cl₂(μ₂-Cl)(μ₂-BDNA)]BF₄ (6) for the hydrogenation of benzene were investigated in aqueous-organic biphasic system. The hydrogenation of benzene catalyzed by all complexes yielded only cyclohexane. The catalytic results revealed that the stabilities of these complexes were not only closely relative with their compositions or molecular structures but also the pH value of aqueous solution. Complexes 1 and 2 were homogeneous catalysts at pH <5, but complexes 3, 4, 5 and 6 were partly decomposed in the same reaction conditions and played simultaneously the roles of homogeneous and heterogeneous catalysts. When the pH was up to 12, all of six complexes were gradually decomposed to Ru(0) particles. The addition of extra phosphine ligand was favorable to prevent these complexes from decomposing in the catalytic process. The experiment of mercury poisoning and the curve of conversion vs time strongly supported above conclusions.     

Ultra-deep desulfurization of coker and straight-run gas oils: Effect of lowering feedstock 95% boiling point

Production of diesel fuels with ultra-low-sulfur levels by deep desulfurization of gas oil feeds has received considerable importance in the petroleum refineries in recent years. The type of the gas oil feed and its distillation temperature play a key role in the deep desulfurization process. In the present research project, the effect of lowering the 95% distillation temperature (T₉₅) of two gas oil feeds, namely, straight-run gas oil (SRGO) and coker gas oil (CGO), on deep desulfurization to ultra-low-sulfur levels was investigated. The results showed that for both types of feeds a higher degree of desulfurization was achieved with reduction of T₉₅ from > 360 °C to < 340 °C. The refractory alkyl dibenzothiophenes boiling above 320 °C were present in very low concentrations in the low-boiling cuts and deep HDS to ultra-low-sulfur levels (< 50 ppm) was achieved at low severity operating conditions. Among the two feeds, the CGO that contained high nitrogen content, high concentrations of sterically hindered alkyl DBTs and high aromatics content (low feed saturation) was more difficult to desulfurize than SRGO.     

V-Mo based catalysts for oxidative desulfurization of diesel fuel

Catalytic oxidative desulfurization (ODS) of a Mexican diesel fuel on a spent HDS catalyst, deactivated by metal deposits, was carried out during several reactive-batch cycles in order to study the catalytic performance to obtain low sulfur diesel. To explain catalytic activity results, Mo and/or V oxides supported on alumina pellets were prepared and evaluated in the ODS of a model diesel using tert-butyl hydroperoxide (TBHP) or H₂O₂ as oxidant. The catalytic results show that V-Mo based catalysts are more active during several ODS cycles using TBHP. The performance of the catalysts was discussed in terms of reduced species of vanadium oxide, prevailing on the catalysts, which increase the sulfone yield of refractory HDS compounds (DBT, 4-MDBT and 4,6-DMDBT).     

Dehydrochlorination of Intermediates in the Production of Vinyl Chloride over Lanthanum Oxide-Based Catalysts

Lanthanum oxide-based catalysts are active in the elimination of HCl from C₂H₅Cl, 1,2-C₂H₄Cl₂ and 1,1,2-C₂H₃Cl₃ leading to the formation of their respective chlorinated ethenes. An oxygen-rich catalytic surface may form CO, CO₂ and C₂HCl as side products, whereas with chlorine-rich catalytic surfaces a stable product distribution is achieved with 100% selectivity towards the formation of ethenes, such as the valuable C₂H₃Cl intermediate.     

Viscosity Adjustment of Aqueous Micellar Solutions of Gemini Surfactants by Interaction with Additional Surfactants

The viscosity of aqueous micellar solutions depends on the size and shape of the aggregates and thus can be adjusted by addition of another surfactant interacting with the original component, which alters the geometry of the molecule-pair consisting of two surfactants and influences strongly the size and shape of the mixed micelles. Ethanediyl-α,ω-bis(dimethyl dodecyl ammonium bromide), referred to as C₁₂-2-C₁₂·2Br, forms generally large micelles. Addition of a cationic surfactant (dodecyltrimethylammonium bromide, C₁₂TMABr) or a nonionic surfactant (alkyl polyoxyethylene ether, C _m E _n ), the mixed micelle size is reduced violently since the electrostatic repulsion between the same charged heads of C₁₂-2-C₁₂·2Br and C₁₂TMABr or the steric hindrance of the PEO chain of C _m E _n in the palisade layers of the mixed micelle, which leads to a decrease in the packing parameter P of the molecule-pair. As a result, the zero-shear viscosity (η ₀) of the mixed solution reduces rapidly. In contrast, on adding an oppositely charged surfactant, η ₀ of the mixed solution increases strongly since the P of the molecule-pair increases through electrostatic attraction between the oppositely charged heads. The typical cases occur in the mixtures of the anionic gemini surfactant, O,O′-bis(sodium 2-lauricate)-p-benzenediol C11pPHCNa, and the cationic surfactant C₁₂-2-C₁₂·2Br, C₁₂TMABr or its homologue with a different size of heads.     

柴油氧化脱硫技术研究进展

介绍了近年来柴油氧化脱硫技术研究的进展情况,主要包括:H2O2均相、非均相催化氧化脱硫,超声波氧化脱硫,光催化氧化脱硫和分子氧直接氧化脱硫等。认为分子氧直接氧化脱硫技术克服了H2O2价格较高、稳定性差等缺点,并且该法具有操作条件缓和,反应时间短等优点,将成为柴油氧化脱硫的主要研究方向。     

Physicochemical and corrosive properties of oxidation catalysts based on solutions of Mo-V-phosphoric heteropoly acids

Modified aqueous solutions of Mo-V-phosphoric heteropoly acids (HPAs) are used as high-performance catalysts for the oxidation of substrates from different classes with oxygen. The oxidation of n-butenes to methyl ethyl ketone (MEK) with oxygen in the presence of aqueous solution (6 × 10⁻³ M Pd + 0.25 M HPA-7′), where HPA-7′ is a modified HPA whose molecular formula is H₁₂P₃Mo₁₈V₇O₈₅, is an industrially important process. At the first Pd-catalyzed stage of the process, n-C₄H₈ is oxidized with HP acid. At the second stage, the catalyst is regenerated and the reduced form of HPA-7′ is oxidized with atmospheric oxygen, closing the catalytic cycle. In such two-stage redox processes, HPA solutions act as reversible oxidizers whose physicochemical properties are continuously changing. The modified solutions of HPAs are attractive because of their thermal stability and increased regeneration rates. However, no data have yet been reported in the literature about their physicochemical and corrosive properties. This undoubtedly hinders the practical application of processes involving these solutions. Using the 0.25 M HPA-7′ solution as an example, we show how the physicochemical properties of the catalyst change. During the first stage of the process, the pH, density (ρ), and viscosity (η) of the HPA solution increase to their maxima, but its redox potential (E) decreases to its minimum. At the second stage, E increases, while ρ, η, and pH decrease to their initial values. Thus, in the processes with the alternating reduction and oxidation of the HPA-based catalyst solution, the changes in the physicochemical properties of the catalyst are completely reversible. We first have obtained the data on the corrosive properties of the modified HPA-7′ solution with respect to metals and alloys widely used in industrial processes. The corrosion stability of various engineering materials against 0.25 M solution of HPA-7′ was found to decrease in the series Ti (∼0.009 mm year⁻¹) > 06KhN28MDT > 10Kh17N13M2T > 12Kh18N10T > KhN65MV (∼0.68 mm year⁻¹). The unique ability of the modified Mo-V-P HPA solutions to recover completely their properties after regeneration with oxygen permits one to use them successfully for long periods of time in the many-cycled processes. This opens up good prospects for the development of industrial homogeneous catalytic oxidative processes involving these HPAs.     

Homogeneous hydroxyethylation of cellulose in NaOH/urea aqueous solution

Summary The 6 wt.% NaOH/4 wt.% urea aqueous solution was proved to be an aqueous non-derivatizing solvent for cellulose by ¹³C NMR. O-(2-hydroxyethyl)cellulose (HEC) was prepared by a totally homogeneous hydroxyethylation of cellulose using this new solvent for the first time, and the distribution of substituents within anhydroglucose units (AGU) was examined by ¹³C NMR. It was found that the relative reactivity of the hydroxyl groups within AGU and the new hydroxyl group was in the order C-x > C-6 > C-2 > C-3, an analogous functionalization pattern as HEC obtained by the heterogeneous slurry process. The ethylene oxide efficiency in this homogeneous etherification reaction was 20 – 30%.     

Mineralogical phase analysis of alkali and sulfate bearing belite rich laboratory clinkers

The activation of laboratory belite clinkers has been carried out by adding variable amounts of alkaline salts (K₂CO₃, Na₂CO₃), and/or SO₃ as gypsum in the raw materials but keeping almost constant the main elements ratios, Ca/Si/Al/Fe. Quantitative phase analyses by the Rietveld method using high resolution synchrotron and strictly monochromatic CuKα₁ laboratory X-ray powder diffraction data has been performed. Quantitative phase analysis results have been compared to validate the protocol using laboratory X-ray data. The agreement in the results is noteworthy, which indicates that good quantitative phase analyses can be obtained from laboratory X-ray powder data. Qualitative studies have confirmed that the addition of alkaline salts to raw mixtures promotes the stabilization, at room temperature, of the highest temperature polymorphs: α′_H-C₂S and α-C₂S. Quantitative studies gave the phase assemblage for ten different laboratory belite clinkers. As an example, an active belite clinker with 1.0 wt.% of K₂O and 1.0 wt.% of Na₂O (amounts added to the raw mixtures) contains 8.5(3) wt.% of β-C₂S, 21.2(3) wt.% of α'_H-C₂S, 24.1(2) wt.% of α-C₂S, 18.9(3) wt.% of total C₃S, 17.3(2) wt.% of C₃A and 10.0(2) wt.% of C₄AF. A belite clinker with 0.8 wt.% SO₃ (nominal loading) contains 60.7(1) wt.% of β-C₂S, 6.7(2) wt.% of α′_H-C₂S, 12.3(7) wt.% of C₃S, 9.1(2) wt.% of C₃A and 11.2(2) wt.% of C₄AF. Overall, quantitative phase analyses have shown that alkaline oxides stabilize α′_H-C₂S and α-C₂S, sulfur stabilizes β-C₂S, with a large unit cell volume, and the joint presence of alkaline oxides and sulfur promotes mainly the stabilization of the α′_H-C₂S polymorph.