Tetrapropylammonium bromide

Silicalite-1 was synthesised according to published recipe [5], Fumed silica was added to an aqueous solution of tetrapropylammonium bromide and ammonium fluoride, and... 

In an attempt to produce TS-1 at low cost, alternative, cheaper sources of Ti and Si and other bases such as binary mixtures of (tetrabutylammonium and tetraethylammonium hydroxides), (tetrabutylphosphonium and tetraethylpho-sphonium hydroxides), (tetrapropylammonium bromide and ammonia, water, hexanediamine, n-butylamine, diethylamine, ethylenediamine, or triethanolamine) in place of TPAOH have been used (284—294). TS-1 was synthesized in the presence of fluoride ions but the material thus formed contained extraframework Ti species (295-297). 

The Ti02 used here was made by hydrolyzing TNBT in distillated H2O with subsequent calcination at 500 °C. ETS-10, which is a titanium silicate molecular sieve with titanium in octahedral coordination, was provided by Engelhard, Co. For comparison, pure-silica ZSM-5 was also synthesized in the absence of alkali metal cations. Its synthesis involves the use of tetrapropylammonium bromide (TPABr) and piperazine. 

The zeolite ZSM-5 is prepared by heating a mixture of silicic acid, Si02./ H20, NaOH, AI2SO4, water, /3-propylamine, and tetrapropylammonium bromide in an autoclave for several days at 160°C. The product from this reaction is then heated in air. Why is tetrapropylammonium bromide used in the reaction and what is the effect of the subsequent oxidation reaction ... 

Thermochemical cycles (Figure 2) involving the formation of compounds (a-quartz, gibbsite, amines, tetrapropylammonium bromide, etc.), the dissolution of these compounds and of the HFI-type samples in 25% HF, and the dilution of aqueous HF allow the calculation of the standard enthalpy of formation of the samples. 

The reactants used in this study were a colloidial silica, Ludox AS-40 (Dupont), reagent-grade tetrapropylammonium bromide (Aldrich Chemical Co.) and a 50wt% sodium hydroxide solution (Mallinckrodt Inc.). The reaction mixture had the oxide formula, 2.55Na20-5.0TPABr-100Si02-2800H20. The mole ratios of the... 

Zeolite ZSM-5. Zeolite samples were crystallized from a gel containing colloidal silica (Ludox AS-40), deionized water, aluminiumtriisopropylate (ATIP, Merck), as source of aluminium, and tetrapropylammonium bromide, (TPABr, Aldrich). Ammonia solutions were prepared by saturating a thermostated aqueous solution with... 

Starting materials for the direct synthesis of (Si,B)-ZSM-5 were fumed silica (Cabosil), tetrapropylammonium bromide (TPA-Br), ammonium fluoride and orthoboric acid (16). The source of silica was mixed with TPA-Br and water and then a mixed solution of NH4F and H3BO3 was added under vigorous stirring. The resultant gel was homogenized for 1.5 h and transferred into a Teflon-lined stainless steel autoclave which was then heated at 200°C for 17 days. Zeolite crystals were washed, dried at 60°C and hydrated in a desiccator. 

We used three kinds of quaternary ammonium bromides, R4N+Br tetrabutylam-monium bromide (TBAB), (C4H9)4N+Br tetrapropylammonium bromide (TPRAB), (C3H7)4N Br and tetraethylammonium bromide (TEAB), (C2H5)4N+Br . 

The N values for protic solvents in Fig. 4 are referred to the generally accepted value of six for Br in water. The values for aptotic solvents arc determined by using tetrapropylammonium bromide crystal as a reference material, for which the XRD result is known. The N values are distributed over a wide range and do not seem to correlate with., 4 value. However, careful inspection gives us the following conclusions. Firstly, the N values for alcohols arc linearly correlated with values. The solvents, water (2), acetic acid (4) and formamide (7) are exceptions again. Mayer has... 

Similarly, Sano et al. [1994] added colloidal silica to a stirred solution of tetrapropylammonium bromide and sodium hydroxide to synthesize a hydrogel on a stainless steel or alumina support with a mean pore diameter of 0.5 to 2 pm. The composite membrane is then dried and heat treated at 500 C for 20 hours to remove the organic amine occluded in the zeolite framework. The silicalite membranes thus obtained are claimed to be free of cracks and pores between grains, thus making the membranes suitable for more demanding applications such as separation of ethanol/water mixtures where the compound molecules are both small. The step of calcination is critical for synthesizing membranes with a high permselectivity. 

N,N-dimethyloctylamine N,K-dimethylethylamine tetrapropylammonium bromide tetrabutylammonium bromide... 

In the high Si/Al regime, tetrapropylammonium bromide generally favours the formation of polycrystalline spherulitic particles whereas 1,6-diaminohexane favours the formation of large lath-shaped particles/crystals. 

Column Lichrosorb Si500 10 ym, coated with 0.1 M naphtalene-2-sulfonate in 0.1 M choline citrate buffer (pH 3.8)(250x4 urn ID), mobile phase chloroform - 1-pentanol (9 1) saturated with the stationary phase, flow rate 1.0 ml/min, detection UV 254 nm. Peaks 1, tripropyl-butyl amnoni urn bromide 2, tetrapropylammonium bromide 3, tripropylmethylammonium iodide. 

Figure 13.2 Analysis of a-keto acids in plasma [afterT. Hayashi, H. Tsuchiya and H. Naruse, J. Chromatogr., 273,245 (1983)]. Conditions sample, extract from 50 pi of human plasma, derivatized with o-phenylenediamine column, 25cm x 4mm i.d. stationary phase, LiChrosorb RP-8, Spm mobile phase, 1 ml min of 1 mM tetrapropylammonium bromide in 50 mM phosphate buffer-acetonitrile, gradient from 5 to 60% acetonitrile temperature, 50 C fluorescence detector, 350/ 410 nm. Peaks 1 = a ketoglutaric acid 2 = pyruvic acid (a-ketopropionic acid) 3 = a-ketoisovaleric acid 4 —a-ketoisocaproic acid 5 —a-keto-/3-methylvaleric acid IS = a-ketocaprylic acid (internal standard).

Fig. 1. Raman spectra of [TPA]+ occluded in (A) silicalite, (B) 20 % aqueous solution of tetrapropylammonium hydroxide and (C) crystalline tetrapropylammonium bromide. (All traces, exciting line, 514 nm. Top trace laser power, 90 mW bandpass, 10 cm-l Middle trace laser power, 250 mW bandpass, 10 cm"l Bottom trace, laser power, 60 mW, bandpass, 5 cm-1).

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