Acrolein Yield Research Articles

Physical and Chemical Characterization of Aerosols Produced from Experimentally Designed Nicotine Salt-Based E-Liquids.

Nicotine salt-based e-liquids deliver nicotine more rapidly and efficiently to electronic nicotine delivery system (ENDS) users than freebase nicotine formulations. Nicotine salt-based products represent a substantial majority of the United States ENDS market. Despite the popularity of nicotine salt formulations, the chemical and physical characteristics of aerosols produced by nicotine salt e-liquids are still not well understood. To address this, this study reports the harmful and potentially harmful constituents (HPHCs) and particle sizes of aerosols produced by laboratory-made freebase nicotine and nicotine salt e-liquids. The nicotine salt e-liquids were formulated with benzoic acid, citric acid, lactic acid, malic acid, or oxalic acid. The nicotine salt aerosols had different HPHC profiles than the freebase nicotine aerosols, indicating that the carboxylic acids were not innocent bystanders. The polycarboxylic acid e-liquids containing citric acid, malic acid, or oxalic acid produced higher acrolein yields than the monocarboxylic acid e-liquids containing benzoic acid or lactic acid. Across most PG:VG ratios, nicotine benzoate or nicotine lactate aerosols contained the highest nicotine quantities (in %) and the highest nicotine yields (per milligram of aerosol). Additionally, the nicotine benzoate and nicotine lactate e-liquids produced the highest carboxylic acid yields under all tested conditions. The lower acid yields of the citric, malic, and oxalic acid formulations are potentially due to a combination of factors such as lower transfer efficiencies, lower thermostabilities, and greater susceptibility to side reactions because of their additional carboxyl groups serving as new sites for reactivity. For all nicotine formulations, the particle size characteristics were primarily controlled by the e-liquid solvent ratios, and there were no clear trends between nicotine salt and freebase nicotine aerosols that indicated nicotine protonation affected particle size. The carboxylic acids impacted aerosol output, nicotine delivery, and HPHC yields in distinct ways such that interchanging them in ENDS can potentially cause downstream effects.

Unexpected high yield of acrolein underlies the importance of the hydrogen-abstraction mechanism in photooxidation of allyl methyl sulfide (AMS).

This work explores theoretically the gas phase oxidation of allyl methyl sulfide (AMS, H2CCHCH2SCH3) initiated by •OH radicals, focusing on the H-abstraction pathway at the M06-2X-D3/aug-cc-pVTZ and MN15/aug-cc-pVTZ levels of theory (m06Tz and mn15Tz). The formation of a prereactive complex (PRC) is involved in H-abstraction processes with two potential directions of approach for the OH radical, denoted as “α” and “β”. The PRCs, demonstrate increased reactivity, primarily due to the interaction between the sulfur atoms and the hydroxyl hydrogen. A scheme for the H-abstraction mechanism that supports the experimentally identified products and predicts the formation of some S-containing low volatility products is proposed. The comparison of the potential energy surface (PES) between the double bond addition and H-abstraction paths in the AMS molecule shows that at the m06Tz level of theory, the H-abstraction on C3 and the addition to C1 have nearly the same profile of energy, while at the mn15Tz level, the minimum energy channel is the addition to C1. The theoretical rate coefficient for each reaction channel was calculated, considering the formation of a PRC prior to reaching the transition state of each channel and assuming thermal equilibrium between reactants and the PRC. The rate constants were calculated in a multi-TS/multi-conformer way at the SVECV-f12/m06Tz and SVECV-f12/mn15Tz levels of theory. The SVECV-f12 method is consistent in its predictions in both systems and exhibits only minor deviations from the experimental rate constants. Despite some specific differences due to the DFT method supporting the SVECV-f12 calculations, both methodologies predict a significant H-abstraction contribution in the AMS + OH gas phase reaction, which explains the high formation yield for acrolein determined experimentally.

Glycerol dehydration catalyzed by solid acid in nonthermal plasma and simulation analysis of plasma electric field

AbstractNonthermal plasma (NTP), for the first time, was integrated in glycerol dehydration reaction catalyzed by silicotungstic acid supported on mesoporous silica with argon as the carrier and discharge gas. A range of reaction temperatures (220–320°C) and NTP discharge field strengths (2.06–6.87 kV/cm) were studied for the individual and interactive effects regarding the glycerol conversion and product selectivity. Results showed that the presence of NTP always improved the glycerol conversion, and NTP increased acrolein selectivity if properly conditioned. An optimal condition of 275°C and 4.58 kV/cm NTP field strength achieved a glycerol conversion of 94.4 mol%, acrolein selectivity of 88.0 mol%, with an acrolein yield of 83.1 mol%, representing a 10% improvement in acrolein production over that conducted at the same temperature but without NTP. Results of this study will also have significant implication for other heterogeneously catalyzed dehydration reactions. Simulation of the high‐voltage electric field distribution as function of NTP electrical conductivity and relative permittivity of catalyst materials also offers insight for the future design of reactors and catalysts.

Microwave-Assisted Facile Sol–Gel Synthesis of WO3-Based Silica Catalysts for Enhanced Activity in Glycerol Dehydration

WO3 is a promising catalyst for the production of acrolein from glycerol due to its high activity and selectivity. In this study, various metal oxides (W, Zr, and Nb) over colloidal silica (cSiO2) catalysts were obtained using a novel microwave-assisted synthesis method. The enhancement in the sol–gel grafting of metal oxides onto the cSiO2 support was achieved by microwave irradiation (MW) and compared to the conventional heating (CH). WO3-cSiO2 catalysts synthesized by microwave-assisted facile sol–gel synthesis were tested in the gas-phase glycerol dehydration reaction. The best catalytic performance (52.4% acrolein yield) was obtained over a 25%W-cSiO2 sample prepared by the MW method. The best yield results were obtained with a B/(B + L) ratio over 0.50 and with an optimum medium-strength acidity. The activity loss was correlated with the high-strength surface acidity.

Glycerol Dehydration to Acrolein Catalyzed by Silicotungstic Acid: Effect of Mesoporous Support

To facilitate value-added chemical production from renewable glycerol, gas-phase glycerol dehydration to acrolein was conducted using supported silicotungstic acid as solid acid catalysts, focusing on the effects of mesoporous catalyst supports on the catalytic performance. One alumina (Al) support with average mesopore size of 30 nm and two silica supports (Si1254 and Si1252) with mesopore size of 6 nm and 11 nm, respectively, were comparatively evaluated in this study. It was found that the Si1254 silica support with the smallest pore size (6 nm) deactivated the fastest, decreasing both the glycerol conversion and acrolein selectivity along the time-on-stream. The other silica support Si1252 with 11 nm pore size provided an acrolein yield comparable to the Al support over the tested 7.5 h time-on-stream (73.9 mol% for Si1252 vs. 74.1 mol% for Al). However, the mechanisms for achieving the comparable yield are different. Si1252 showed higher acrolein selectivity than Al, but it also deactivated faster than Al due to its quicker coking. On the other hand, Al showed more stable performance in terms of glycerol conversion rate and less coking, but it had lower acrolein selectivity and a higher selectivity to byproducts, especially the undesired byproducts of acetaldehyde and propionaldehyde, which posed difficulties in downstream separation.

Carbonyl Yields in Cigars under Three Smoking Regimens Using a Linear Smoking Machine.

This study used standard linear smoking machines and puffing protocols to generate data on carbonyl yields in mainstream smoke from 11 unfiltered sheet-wrapped cigars (SWC), seven leaf-wrapped cigars (LWC), and two Kentucky reference cigarettes (3R4F, 1R6F). Carbonyl yields in cigar and cigarette products were determined using three different smoking regimens: International Organization for Standardization (ISO), Canadian Intense (CI), and Cooperation Centre for Scientific Research Relative to Tobacco (CORESTA) Recommended Method (CRM) No. 64 (CRM64, Routine Analytical Cigar-Smoking Machine─Specifications, Definitions and Standard Conditions). Mainstream tobacco smoke was collected using a smoking machine fitted with an impinger containing 2,4-dinitrophenylhydrazine (DNPH) and carbonyl compounds quantified using liquid chromatography with an ultraviolet detector. Commercial SWC and LWC generated comparable formaldehyde yields (SWC, 9.4-28 μg/cigar [ISO], 8.2-43 μg/cigar [CI], 8.6-13 μg/cigar [CRM64]; LWC, 11-13 μg/cigar [ISO], 11-22 μg/cigar [CI], 16-21 μg/cigar [CRM64]) and acrolein yields; however, LWC generated higher acetaldehyde yields compared to SWC, using CI and CRM64 regimens. Reference cigarettes using standard puffing regimens generated carbonyl yields within reported ranges and 5-10% RSDs, whereas the CRM64 regimen generated lower carbonyl yields and 12-14% RSDs. Reference cigarettes generated higher formaldehyde yields using cigarette smoking regimens (21-28 μg/cigarette under ISO, 76-96 μg/cigarette under CI) but comparable formaldehyde yields under CRM64 (12-14 μg/cigarette). In addition, this study evaluated physical parameters (e.g., tobacco weight, length, diameter, circumference, tobacco rod density) that show the correlation between tobacco weight, tobacco rod density, and acetaldehyde yields under the three smoking regimens. Carbonyl yields in the mainstream smoke of cigar products using the three smoking regimens were highly variable; however, the CI smoking regimen may provide meaningful analytical information regarding cigar smoke constituents, with lower likelihood of self-extinguishment due to the short puffing intervals.

WO3-based porous MCM-48 catalysts for renewable acrolein synthesis by the dehydration of glycerol

The gas-phase selective dehydration of glycerol to acrolein was studied over x%W (x: 5, 15, 25, and 35 %, w/w) supported on MCM-48. Microporous silica MCM-48 was synthesized to produce three-dimensional cubic crystals with a high surface area and resistance to hydrolytic pressure. Tungsten oxide (WO3) based solid acid catalysts supported on MCM-48 were prepared by two distinct synthesis methods, namely, oxalic acid added sol–gel (HSG) and nonhydrolytic sol–gel (NHSG) methods. The morphological and textural properties of catalysts were characterized by XRD, BET, SEM, Raman, XPS, and FT-IR techniques. The acidic properties of catalysts were elucidated by FTIR pyridine-adsorption and NH3-Temperature Programmed Desorption (NH3-TPD). The total surface acid sites’ concentration, Brønsted (B) and Lewis (L) acid concentrations, and B/(B+L) ratios were calculated from NH3-TPD and pyridine-FTIR. The steady acrolein yields were obtained with the optimal catalysts (15 %W and 25 %W loaded MCM-48 for HSG and NHSG, respectively). This study demonstrated that the medium-strength surface acidity and B/(B+L) ratios for glycerol dehydration to acrolein were correlated with both the activity and the selectivity of acrolein.

Glycerin to Acrolein: Can Renewable Processes Challenge Traditional Processes?

AbstractThe production of acrolein by the dehydration of glycerin (GTA) was compared with formaldehyde/acetaldehyde aldolization (FAA) and propylene oxidation (PO) by using the Aspen Plus 11.1 process design software. The fixed assets cost of the FAA, PO, and GTA process were estimated as 61.95, 41.73, and 39.09 million CNY, respectively, for a 40‐kt a−1 plant, and the total manufacturing costs were estimated as 10637, 8873, and 8974 CNY t−1, respectively. The PO process is the most economical under current market and technology conditions. Nevertheless, the renewable process outshone traditional processes if the propylene price was greater than or equal to 8200 CNY t−1 at a glycerin price of 3800 CNY t−1, as long as the yield of acrolein from GTA was greater than or equal to 93 %.

Insight into Active Centers and Anti-Coke Behavior of Niobium-Containing SBA-15 for Glycerol Dehydration

Niobium containing SBA-15 was prepared by two methods: impregnation with different amounts of ammonium niobate(V) oxalate (Nb-15/SBA-15 and Nb-25/SBA-15 containing 15 wt.% and 25 wt.% of Nb, respectively) and mixing of mesoporous silica with Nb2O5 followed by heating at 500 °C (Nb2O5/SBA-15). The use of these two procedures allowed obtaining materials with different textural/surface properties determined by N2 adsorption/desorption isotherms, XRD, UV-Vis, pyridine, and NO adsorption combined with FTIR spectroscopy. Nb2O5/SBA-15 contained exclusively crystalline Nb2O5 on the SBA-15 surface, whereas the materials prepared by impregnation had both metal oxide and niobium incorporated into the silica matrix. The niobium species localized in silica framework generated Brønsted (BAS) and Lewis (LAS) acid sites. The inclusion of niobium into SBA-15 skeleton was crucial for the achievement of high catalytic performance. The strongest BAS were on Nb-25/SBA-15, whereas the highest concentration of BAS and LAS was on Nb-15/SBA-15 surface. Nb2O5/SBA-15 material possessed only weak LAS and BAS. The presence of the strongest BAS (Nb-25/SBA-15) resulted in the highest dehydration activity, whereas a high concentration of BAS was unfavorable. Silylation of niobium catalysts prepared by impregnation reduced the number of acidic sites and significantly increased acrolein yield and selectivity (from ca. 43% selectivity for Nb-25/SBA-15 to ca. 61% for silylated sample). This was accompanied by a considerable decrease in coke formation (from 47% selectivity for Nb-25/SBA-15 to 27% for silylated material).

Sizing of a washcoated reactor for the catalytic oxidation of propylene to acrolein on a solid bismuth/molybdate catalyst

Catalytic oxidation of propylene to acrolein is usually performed in a multi-tubular fixed bed catalytic reactor at industrial scale. Nevertheless, the production of side products is not optimal as well as the use of molten salt to cool the reactants. This is mainly due to heat transfer issues resulting of the high exothermicity of the reactions. This paper deals with the reactor intensification for the propylene oxidation on a solid bismuth/molybdate catalyst. A simple but robust power law kinetic model, based on the recent published literature, is first proposed, and kinetic parameters are identified by comparison between experiments performed on an isothermal micro fixed bed catalytic reactor and simulations obtained from a pseudo-homogeneous reactor model. The determined parameters are in good agreement with published ones. This kinetic model is then used for the design of an intensified heat-exchanger reactor (HEX reactor). This device consists in several reactive catalyst washcoated channels alternatively distributed with coolant channels. Three performance parameters (acrolein yield, propylene conversion and maximal temperature elevation) are defined, and their variations against process parameters are determined in order to size the HEX reactor and to identify optimal process conditions, for a given feed flow rate.

Direct conversion of gas-glycerol to Allyl alcohol over V, Ti or Nb modified MoFe/KIT-6 oxide catalysts

The porous MoFe/x-KIT-6 (x = V, Nb, or Ti) oxide catalysts with high specific surface area were prepared through in-situ modification and wet impregnation methods for direct conversion of gas-glycerol into allyl alcohol. The modification of V, Nb or Ti on KIT-6 effectively altered and adjusted the mesoporous structure, surface Mo6+/Fe3+ distribution, and surface acid density of the MoFe/x-KIT-6 catalysts, leading to a promotion on the catalytic performance of the MoFe/V-KIT-6 but negative effects on that of the MoFe/Nb-KIT-6 and MoFe/Ti-KIT-6, comparing with the MoFe/KIT-6. The selectivity of allyl alcohol over the MoFe/V-KIT-6 increased to 31.4 % from gas-glycerol (Con. 92 %) most probably through dehydration of glycerol to an intermediate and consecutive reduction, and the yield of allyl alcohol, acrolein, and acetaldehyde reached 58.5 %. Moreover, the MoFe/V-KIT-6 showed improved catalytic stability and good regeneration ability benefiting from the ordered developed mesoporous structure and reduced surface moderate acid density.

Effect of Cerium Addition to Bismuth–molybdenum Complex Oxide Catalyst for Partial Oxidation of Propylene to Acrolein

The effect of Ce addition to a Bi–Mo complex oxide catalyst supported on SiO2 was examined on the partial oxidation of propylene to acrolein. The catalyst consisted of an oxygen-supply phase in which the lattice oxygen in Mo-oxide was doped with transition metals such as Fe, Ni and Co and was supported by SiO2 and a catalytic-active phase that involved hydrogen abstraction from a reactant in the Bi-center of Bi–Mo oxide, which was supported by the oxygen-supply phase. In the present study, Ce was added to the oxygen-supply phase to enhance its redox nature. Ce addition was advantageous particularly under oxygen-rich conditions in the feed stream. For example, at P(C3H8) = 10.1 kPa and P(O2) = 15.5 kPa at 623 K, the yield of acrolein was slightly enhanced from 57.6 % with 0 % Ce doping to 65.3 % with 20 % Ce doping at 6 h on-stream. However, under more oxygen-rich conditions at P(C3H8) = 10.1 kPa and P(O2) = 31.0 kPa at 623 K, the yield of acrolein was approximately doubled from 27.7 % with 0 % Ce doping to 61.8 % with 20 % Ce doping at 6 h on-stream. Analysis using XPS of the previously used catalysts for the reaction in the absence of gaseous oxygen confirmed the unique redox behavior between the catalytic-active phase and the oxygen-supply phase as the lattice oxygen in the catalytic-active phase was replenished from the oxygen-supply phase to maintain the surface properties of the catalytic-active phase. The XPS results and the remarkable effect of Ce addition to the oxygen-supply phase under oxygen-rich conditions confirmed the validity of the concept of the catalyst preparation consisting of an oxygen-supply phase and a catalytic-active phase.

Mesoporous silica supported phosphotungstic acid catalyst for glycerol dehydration to acrolein

Conversion of glycerol to acrolein is a useful reaction for value-added application of biodiesel-derived glycerol and bioenergy development. The high-performance solid acid catalyst is essential to this dehydration reaction. In this paper, tungsten-based heteropolyacids (HPA) were supported on non-ordered mesoporous silica (MSU-x) to increase their dispersion and used as catalysts for glycerol dehydration to acrolein. Aiming to reveal the surface structure of HPA and resulting acidic properties, as well as the relationship between acidic properties and dehydration activity, different loadings of H3PW12O40 were supported on MSU-x (10–50 wt%) and the catalysts were characterized by X-ray diffraction (XRD), BET, SEM/TEM, UV–vis diffuse reflectance spectra (DRS), Raman and FT-IR techniques. Their acidic properties were studied by NH3-Temperature Programmed Desorption (NH3-TPD) and Pyridine adsorption methods. The molecular structure and dispersion of H3PW12O40 supported on the catalysts was revealed. The Keggin unit preserved well but with different hydration level for various loadings. The total acid concentration and respective Brønsted/Lewis acid identification were calculated. The acrolein yield increased with H3PW12O40 loading until 30 wt% and showed less change with higher loadings. Based on the correlation of acrolein formation rate with acidic properties, the active role of Brønsted acid and the cooperative role of Brønsted/Lewis acid sites for glycerol dehydration to acrolein were discussed. This work provides new insight into the structure evolution of heteropolyacids and the catalyst design for the glycerol to acrolein.

Gas-Phase Dehydration of Glycerol into Acrolein in the Presence of Polyoxometalates

The activity of catalytic systems based on polyoxometalates in the gas-phase dehydration of glycerol into acrolein has been investigated. The catalysts synthesized have been characterized using FTIR spectroscopy, X-ray phase analysis, scanning electron microscopy, and low-temperature nitrogen adsorption/desorption (BET method). It has been shown that the nature of the surface acid sites of catalysts has a significant effect on the direction of glycerol transformation. An increase in the fraction of Bronsted acid sites in the catalyst leads to an increase in the yield of acrolein. At the same time, an increase in the fraction of Lewis acid sites in the catalyst leads to an increase to the yield of acetol, which is formed through a competing route. Among the catalytic systems considered, the best results have been obtained with the silicomolybdic acid anion supported onto alumina (SiMo/A). The main patterns of the gas-phase glycerol dehydration have been studied using SiMo/A as a catalyst, and the conditions responsible for the highest yield of acrolein have been determined.

Cooperation of hierarchical pores with strong Brønsted acid sites on SAPO-34 catalysts for the glycerol dehydration to acrolein

The hierarchical SAPO-34 zeolites have been prepared with the simultaneous generation of strong Brønsted acid sites (BASs) via a post-synthetic method, which allows the cooperation of the positive effects of both porous structure and acidity in the dehydration of glycerol to acrolein. The cooperation of strong BASs only in enhancing the acrolein selectivity and the hierarchical pores in improving the glycerol conversion has significantly increased the overall acrolein yield to 89.8% on the hierarchical SAPO-34 zeolite at 345 °C and WHSV = 3.7 h−1. This kind of cooperation also limited the catalyst deactivation and prolonged the lifetime of zeolites, which is another significant challenge for glycerol dehydration. The knowledge from this research is very valuable to design the high-efficient nanoporous catalysts for hydrocarbon conversion and bio-refining.

Gas-phase dehydration of glycerol to acrolein over different metal phosphate catalysts

We conducted a comparative study of gas phase dehydration of glycerol to acrolein over aluminium phosphate, iron phosphate and nickel phosphate catalysts prepared by a simple replacement reaction method (AlP, FeP and NiP). The textural properties, acid amounts, acid types, and coke contents of the samples were studied. The results showed that all metal phosphate catalysts remained in an amorphous state. The glycerol conversion was proportional to the acid amount of metal phosphate catalyst in the glycerol dehydration reaction. Higher value of B/L was more likely to produce acrolein. Among the metal phosphate catalysts, FeP showed superior performance due to its suitable textural and acid properties. After 2 h on stream, high glycerol conversion (96%), acrolein selectivity (82%) and acrolein yield (79%) were achieved on the FeP catalyst at 280 °C. The catalyst deactivation was ascribed to carbon deposition on the catalyst surface blocking the active sites during the glycerol dehydration reaction.

Highly active and durable WO3/Al2O3 catalysts for gas-phase dehydration of polyols.

Gas-phase glycerol dehydration over WO3/Al2O3 catalysts was investigated. WO3 loading on γ-Al2O3 significantly affected the yield of acrolein and the catalyst with 20 wt% WO3 loading showed the highest activity. The WO3/Al2O3 catalyst with 20 wt% WO3 loading showed higher activity and durability than the other supported WO3 catalysts and zeolites. The number of Brønsted acid sites and mesopores of the WO3/Al2O3 catalyst did not decrease after the reaction, suggesting that glycerol has continuous access to Brønsted acid sites inside the mesopores of WO3/Al2O3, thereby sustaining a high rate of formation of acrolein. Dehydration under O2 flow further increased the durability of the WO3/Al2O3 catalyst, enabling the sustainable formation of acrolein. In addition, the WO3/Al2O3 catalyst with 20 wt% WO3 loading showed high activity for the dehydration of various polyols to afford the corresponding products in high yield.

Nanoparticle cages as microreactors for producing acrolein from glycerol in the liquid phase

A highly viscous oil phase forms a smaller Pickering emulsion, increasing the acrolein yield from glycerol by intensified mass transfer.

Oxidative coupling of a mixture of bio-alcohols to produce a more sustainable acrolein: An in depth look in the mechanism implying aldehydes co-adsorption and acid/base sites

The industrial synthesis of acrolein is mainly performed by propylene oxidation over bismuth-iron-molybdate catalysts. Among cleaner alternatives to produce acrolein, oxidative coupling of methanol and ethanol represents a promising way. In this work, the reaction has been performed in two separate reactors (for oxidation and aldolization) to study the role of the acid/base properties but also the competition of aldehydes adsorption over environmentally friendly spinel catalysts with various Al/Mg ratios. The acid/base properties of catalysts were investigated by NH3 and SO2 adsorption microcalorimetry. Further adsorption microcalorimetry studies were performed with methanol, formaldehyde, acetaldehyde and propionaldehyde to investigate the bounding properties of the reactants. The acid/base properties were correlated with acrolein yield and selectivity under oxidizing conditions. Co-adsorption of aldehydes was also investigated allowing justification of the absence of crotonaldehyde formation.

Mass transfer intensification by microinterface: Efficient dehydration of glycerol into acrolein in a water/oil pickering emulsion system

Abstract Chemical reactions with products of high reactivity generally suffer from low yields due to the severe side reactions. This is the case for the synthesis of acrolein from glycerol dehydration. To improve the yield of acrolein, fast removal of high reactive acrolein molecules from the reaction system is desirable but remains a major challenge, due to the high viscosity of glycerol. To tackle this problem, the Pickering emulsion was chosen as the reaction system in this work to accelerate the removal of acrolein. A water-in-oil Pickering emulsion was fabricated for the liquid phase dehydration of glycerol to acrolein, which exhibits twice yield of acrolein compared with the homogeneous system. The combination of the transfer experiments and IR analysis confirmed the drastic restrain of the side reactions between acrolein and glycerol, due to the intensified mass transfer of acrolein from the liquid phase by the larger microinterface of emulsion. Furthermore, the transfer rate of acrolein through the water-oil interface can be tuned via a shift in the interfacial properties of the silica emulsifier by silylation treatment. The highest acrolein yield of nearly 50% was obtained with the highest transfer rate of acrolein on the silica silylated by (MeO)3Si(CH2)11CH3.