Boron-phosphorous

Figure 5.1-10 IR absorption spectrum of a boron-phosphorous-silicate glass coated wafer for the determination of the boron and phosphorous content of the Si02 coating (sample thickness less than 1 pm, resolution 4 cm ).

Several contending technologies are presently being used to achieve local and global planarizations that include spin on deposition (SOD), reflow of boron phosphorous silicate glass (BPSG), spin etch planarization (SEP), reactive ion etching and etch back (RIE EB), spin on deposition and etch back... 

Boron-nitrogen and boron-phosphorous compounds are classical textbook examples of donor-acceptor complexes. The chemical bonds of the Lewis-acid Lewis-base complexes are usually explained in terms of frontier orbital interactions and/or quasiclassical electrostatic attraction in the framework of the Hard and Soft Acid and Base (HSAB) model [73]. We were interested in seeing if the differences between the bond strengths of boron-nitrogen and boron-phosphorous complexes for different boranes, amines and phosphanes can be explained with the EDA method. 

Table 13.8 shows the EDA results of the boron-phosphorous bonds in complexes Y3B-PX3. Note that the preparation energies are rather high. The rather large AEp p... 

The goal of chemical modification of phenolics is the improvement of chemical and physical properties and to tailor the polymer to specific applications. Phenolics can be modified during synthesis by use of substituted monomers or monomer mixtures and after synthesis by electrophilic ring substitution, nucleophilic hydroxyl group capping, and reactions with compounds of boron, phosphorous, silicon, and titanium. 

Molten salt electrolysis should be developed for the production of MG-Si and SOG-Si as energy-efficient and environmentally sound processes. Since the required purity and cost are different between Mg-Si and SOG-Si, a proper approach should be taken for each purpose. For SOG-Si, special attention should be paid for the impurities of boron, phosphorous, and carbon, because they are very difficult to be removed by after treatment like unidirectional solidification process. 

Carbon Rhenium Nitrogen 9 Oxygen L Sulphur Boron Phosphorous... 

Each metal phosphate has different crystal structures depending on the preparation and activation conditions. Acid — base properties and catalytic activities usually vary with the crystal structure. By changing the metals and preparetion conditions, it is possible to obtain wide varieties of catalysts of different acid —base properties, surface areas and, crystalline structure. This flexibility enables metal phosphates to be used in many types of reactions. Selected reactions catalyzed by phosphorous metal oxides are listed in Table 3.40. In this section, the acid —base properties and catalytic activities of aluminum phosphorous oxide, boron phosphorous oxide, zirconium phosphorous oxide, and calcium phosphorous oxide are described. 

Boron phosphorous oxide has acidic sites on the surface and catalyzes acid-catalyzed reactions. The oxide possesses acid sites of /fo= —5.6 to —8.2, which are comparable to those on aluminum phosphorous oxide. The base sites, however, have not been measured. 

Boron phosphorous oxide is usually prepared by heating a mixture of boric acid and phosphoric acid at about 313 K followed by calcination at about 630 K. Before use for catalyst, the resulting boron phophorous oxide is further pretreated at higher temperatures in a vacuum or in air, because the acidic properties and consequently catalytic activities are dependent on the pretreatment conditions. 

The existence of both Lewis and Bronsted acid sites on boron phosphorous oxides of different compositions is evidenced by IR measurements of adsorbed alkene and substituted pyridines. On adsorption of alkenes, carbenium ions are formed, and on adsorption of substituted pyridines, both pyridinium ions and coordinated pyri-dines are formed. 

Dehydration of alcohols is catalyzed by boron phosphorous oxide. The reactivity of alcohols in the dehydration decreases as follows /ert-amyl alcohol > 3-pentanol > > 2-propanol > 1-pentanol > ethanol.The catalytic activities of the oxides composed of different amounts of B and P for propanol dehydration correlate with the total amount of acid sites.Butanol undergoes dehydration on boron phosphorous oxide. The maximum activity is obtained at the P/B ratio of 0.6. The activity correlates with the sum of Lewis and Bronsted acid sites. 2-Butanol, 2-methyl — 2-butanol, and 3-methyl — 2-butanol also undergo dehydration. The formation of tnw -2-butene and 2-methyl — 2-butene increases with increasing surface acidity. In these reactions, the carbenium ion mechanism is operating. 

Boron phosphorous oxide shows a high catalytic activity for 1-decane oligomerization. The optimum composition of the oxide and pretreatment temperature are P/B = 1.1 and 873 K, respectively. For the reaction, acid sites stronger than ffo— —5.6 are effective. Although the surface area of boron phosphorous oxide is less than one-tenth those of silica alumina and alumina boria, the conversion of 1-decane on the former catalyst is much higher than those on the latter catalysts. 

In addition to the reactions mentioned above, boron phosphorous oxide shows catalytic activities for the following reactions alkylations of phenol and 1,2-bcnzenediol with methanol,hydrogen transfer of cyclohexane to cydohexene and methylcyclopentene-1, and conversion of amides to nitriles. The acid sites on... 

Alkylation of phenol with methanol is effectively cattJyzed by calcium phosphate which is much more active than boron phosphorous oxide. The selectivity to ortho methylation products, o-cresol and 2,6-xylenol, is 88%. The high selectivity is caused by the basic properties on the surface,... 

In the alkylation of toluene with methanol, the yields of the ring alkylation products and side-chain alkylation products correlate well with the acidity and basicity, respectively, as shown in Fig. 3.86. Among phosphorous metal oxides, boron phosphorous oxide shows the highest yield of the ring alkylation product xylene and the largest number of acid sites, while potassium phosphorous oxide supported on active carbon shows the highest yield of the side-chain alkylation products ethylbenzene and styrene and the largest number of base sites. 

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