HD — hexadecane

Fig. X-12. Advancing and receding contact angles of various liquids [water (circles), Gly = glycerol (squares), Form = formamide (diamonds), EG = ethylene glycol (circles), BN = abromonapthalene (squares), BCH = bicyclohexyl (diamond), HD = hexadecane (circles)] on monolayers of HS(CH2)i60R having a range of R groups adsorbed on gold and silver (open and filled symbols respectively). (From Ref. 171.)...

Table 4.1 Advancing contact angles on derivatized thiol monolayers on gold. HD = hexadecane.

Figure 8-7. Correlation between equilibrium constant for esterification and solubility of water in the solvent. Equilibrium constant was defined as [Ester]/([Alcohol].[Acid]), for reactions at fixed water activity (close to 1). Solvents are bb, butyl benzoate be, bromoethane bk, dibutyl ketone bp, dibutyl phthalate bz, benzene ca, 1,1,1-trichloroethane cf, chloroform ct, carbon tetrachloride cy, trichloroethylene ee, ethyl ether ek, diethyl ketone ep, diethyl phthalate hd, hexadecane hx, hexane me, methylene chloride mk, methyl iso-butyl ketone nm, nitromethane oc, /so-octane pe, iso-propyl ether tl, toluene. Valivety et al...

St, styrene MMA, methyl methacrylate AN, acrylonitrile BA, n-butyl acrylate MA, methyl acrylate VAc, vinyl acetate CA, cetyl alcohol HD, hexadecane PMM A, polymethyl methacrylate SDS, sodium dodecyl sulfate SHS, sodium hexyldecyl sulfate KPS, potassium persulfate AMBN, 2,2 -azobis-(2-methylbutyronitrile). 

The catalyst pretreatment process for both the clay-supported and the reference catalysts consists of loading into the HDS reactor under N2, purging in N2 at 20°C for 30 min at 1000 cmVmin., drying in N2 at 150°C for 60 min and at 400°C for 60 min, and finally sulfiding in a 5% H2S/H2 mixture at 400°C for two hr prior to use as catalysts. The laboratory scale liquid-phase continuous-flow HDS reactor consists of a thick-walled 0.375" ID 316 SS tube, with 1 g catalyst diluted with 5 g tabular alumina (LaRoche T-1061, 10 m2/g) sitting between plugs of quartz wool. Beneath the lower plug is a 0.125" ID, 0.375" OD deadman used to minimize volume between the reactor and the liquid receiver. The liquid test feed consisted of 0.75 wt % sulfur as dibenzothiophene (DBT), dissolved in hexadecane and is representative of a middle distillate oil. All liquid-filled lines were heated to 50°C. The reaction was carried out at 400°C LHSV = 10-40/hr. 

The use of clays as supports for hydroprocessing has been reported and summarized [9-11], Dibenzothiophene (DBT) diluted with hexadecane (0.75 wt% S) was the liquid feed for HDS tests. The pore diameter of the MSC catalysts is seen to have a strong effect on both the HDS activity and selectivity (Figure 4). A commercial catalyst (Crosfield 465, Co/Mo alumina) was also measured under these conditions where it gave 77% DBT conversion and 61% BP selectivity. In a previous study [12], other synthetic hectorites were compared using these conditions except that a 1 wt% S feed was utilized. One sample was a control made without template that consisted of only micropores. The DBT conversion and BP selectivity were very low for this microporous material. The Crosfield material has significant macroporosity (42% of the pore volume) in addition to a broad distribution of mesoporosity, and has clearly been optimized to perform well under these HDS conditions. 

Sample Preparation. The homologous series of the even n-alkanoic acids, abbreviated as C10 through C were used as the adsorbates. Hexadecane (HD), which is nonpolar and has a rather high boiling point, was used as the solvent. Microscope glass slides and evaporated aluminum (on silicon wafers) were used as the substrates. Pyrene end-tagged hexadecanoic acid (Py-C16) was used as the fluorescence probe. 

Guang Hui Ma et al. [83] prepared microcapsules with narrow size distribution, in which hexadecane (HD) was used as the oily core and poly(styrene-co-dimethyla-mino-ethyl metahcrylate) [P(st-DMAEMA] as the wall. The emulsion was first prepared using SPG membranes and a subsequent suspension polymerization process was performed to complete the microcapsule formation. Experimental and simulated results confirmed that high monomer conversion, high HD fraction, and addition of DMAEMA hydrophilic monomer were three main factors for the complete encapsulation of HD. The droplets were polymerized at 70 °C and the obtained microcapsules have a diameter ranging from 6 to 10 pm, six times larger than the membrane pore size of 1.4 p.m. 

In their original discovery of miniemulsion polymerization, Ugelstad and co-workers [5] used either cetyl alcohol (CA water solubility estimated at 6x10 [43]) or hexadecane (HD water solubihty estimated at 1x10 [43]) to retard monomer diffusion from submicron monomer droplets. Both CA and HD, referred to here as costabilizers, are volatile organic components and are therefore not entirely desirable in the final product. Other researchers have used polymers, chain transfer agents, and comonomers as stabiUzers, as will be discussed later. 

One or two additional functional groups introduced via other a-hydrosulfide bolaamphiphiles can be characterized by measurements of the contact angle 0a of water and hexadecane (= HD) droplets, depending on the hydrophobicity and the position of the end groups (Table 1). They also attest to the short-range... 

Cells were suspended in 0. IM sodium phosphate buffer (pH 7.0) and sonicated for 5 min in an ice bath to prepare the cell lysates. The reaction mixture contained 160 ]aM CfU)-hexadecanal or i4c(U)-palmitic acid (850mCi/mmol), 0.1 M sodium phosphate (pH 7.0), 0.1% Triton X-100, and 159 mg (dry wt.) cell extracts in a total volume of 25 ml. C(U)-hexadecanal was chemically synthesized from C(U)-palmitic acid. Reaction mixture from which HD-1 cell lysates were omitted was used as control samples. The reaction mixture was bubbled with Ar gas for several minutes and then the vessel was closed tightly. 

The data for catalysts treated with a mixture of n-butylamine (BA) or N-phenylcarbazole (PC) in hexadecane are also shown in Fig. IB. Since these runs involved a lower temperature of 300 C, little coke was produced, while significant amounts of nitroyen were added to the catalyst (BA-treated catalyst 0.16% Nr 0.7% C PC-treated catalyst 0.11% N, 1.1% C). At a carbon level comparable to the VGO-coked catalysts, the BA-treated catalyst exhibits a different effect on each functionality, viz., no effect on HDS, a mild depressing effect on CNH, and a stronger depressing effect on HYD. On the other hand, the PC-treated catalyst shows practically the same strong deactivating effect on all functionalities. This remarkable effect is verified by a duplicate run with the same results ... 

N,N-dimethylaminoethyl methacrylate) (DMAEMA) by an SPG emulsification technique [34]. The process consists of two steps - emulsification and polymerization. The oil phase containing monomers (styrene and DMAEMA), hexadecane (HD) and an initiator N.hf-azobis (2,4-dimethyl valeronitrile) (ADVN) is pressed by nitrogen gas through the SPG membrane into the aqueous phase. The aqueous phase contains stabilizer polyvinyl alcohol (PVA), surfactant sodium lauryl sulfate (SLS), electrolyte Na2S04 and water-soluble inhibitor (NaN02 or diaminopheny-lene). The emulsion obtained is then transferred to a separate reaction kettle and polymerization is started by raising the reaction temperature to 70 °G. After 24 h, microcapsules with uniform size are obtained. 

Figure 6.1. Chemisorption and alkane ordering for a thiol monolayer on gold. The table summarizes water and hexadecane (HD) contact angles, measured as a function of observed and expected thicknesses of various Ci8 adsorbents on gold (adapted from...

Further evidence for Ostwald ripening was obtained by using a more soluble oil, namely a branched hexadecane (Arlamol HD). The results are shown in Fig. 1.31 for nanoemulsions prepared using 4% surfactant. It can be seen that the more soluble oil (Arlamol HD) give a higher rate of Ostwald ripening when compared with a less soluble oil such as hexadecane. 

Until recently, there was only one report about the use of reactive costabilizers in miniemulsion polymerization [125]. In that study, dodecyl methacrylate (DMA) and stearyl methacrylate (SMA) were been used as cosurfactants with SDS and compared with cetyl alcohol (CA) and hexadecane (HD). It has been shown that DMA behaves like CA, whereas SMA displays a behavior similar to HD in terms of droplet size stability as well as in the particle size distribution of latexes. However, the distribution obtained using these reactive hydrophobes is in both cases somewhat narrower than for the model compounds. More recently, the same team published a study where in the polymerization of styrene in miniemulsions stabilized using DMA or SMA, small quantities of acrylic acid or methacrylic acid were added [126]. The authors were chiefly interested in the nucleation mechanism. Surprisingly, the addition of these hydrophilic monomers tends to favor nucleation within the droplets more than homogeneous nucleation, which is the dominating mechanism in the absence of these water-soluble monomers. The explanation lies in the fact that the styrene-carboxylic co-oligomers, because they are much more hydrophilic, are more reluctant to nucleate new particles. 

Different sized nanocapsules are formed by a miniemulsion polymerization of variety of monomers in the presence of larger amounts of hydrophobe [117]. Hydrophobe and monomer form a common miniemulsion before polymerization, whereas the polymer is immiscible with the hydrophobe and phase-separates throughout the polymerization to form particles with a morphology consisting of a hollow polymer structure surrounding the hydrophobe. Differences in the hydrophilicity of oil and polymer turned out to be the driving force for the formation of nanocapsules. In the case of poly(methyl methaciylate) (PMMA) and hexadecane (HD), the pronounced differences in hydrophilicity are suitable for direct nanocapsule formation. In the case of styrene as the monomer, the hydrophilicity of the polymer phase has to be adjusted in order to favor the nanocapsule structure, which is done either by the addition of an appropriate comonomer or initiator. 

Shulai Lu prepared magnetic polymeric composite particles by miniemulsion polymerization of styrene in the presence of hydrophobic magnetic nanoparticles with hexadecane (HD] as hydrophobe, 2,2 -azobisisobutyronitrile (AIBN], and sodium dodecyl sulfate (SDS] as an emulsifier or sodium p-styrenesulfonate (NaSS] as an ionic comonomer [151], The results showed that miniemulsion polymerization is an effective method for encapsulation of magnetite into a hydrophobic polymer. 

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