PPG process

Two cocrystallization processes employ dibasic crystals as intermediates. The PPG process (199—202) is discussed under commercial processes. The PPC process (203) forms dibasic crystals from lime and recovered filtrates. The dibasic crystals are separated from thek mother liquor by decantation, slurried in caustic solution and chlorinated to produce a cocrystalline slurry of Ca(OCl)2 and NaCl. The slurry is sent to a flotation cell where the larger salt crystals settle out and the smaller hypochlorite crystals float to the top with the aid of ak and flotation agent. The hypochlorite slurry is centrifuged the cake going to a dryer and the centrate to the flotation cell. The salt-rich bottoms from the flotation cell are centrifuged and washed with dibasic mother Hquor. The centrates are recycled to the precipitation step. 

The problem of CaCl2 formation is ckcumvented by use of hypochlorous acid essentially free of chloride and chlorine and treating it with hydrated lime. A PPG process is based on hypochlorous acid (208). 

Significant improvements over the PPG process involve reaction of lime with concentrated HOCl (50%) and drying of the resultant slurry in a spray grainer or fluidized-bed spray dryer to produce hydrated product with av CI2 as high as 82% (126,127,129,210,211). 

A fluid-bed reactor is used at moderate pressures at approximately 450°C. The reactor effluent, containing chlorinated organics, water, a small amount of HCl, carbon dioxide, and other impurities, is condensed in a water-cooled graphite exchanger, cooled in a refrigerated condenser, and then scrubbed. Separation of perchlor from the trichlor occurs by successive distillation. Figure 7-6 shows the PPG process. 

In the PPG-process, chlorine is reacted in a carbon dioxide stream with sodium carbonate to dichlorine monoxide and hypochlorous acid, which is dissolved in water. Reaction with a calcium hydroxide slurry yields calcium hypochlorite ... 

PPG = processed plasterboard gypsum PSP = poljmier superplasticiser RA = recycled aggregate SP = superplasticiser... 

Caustic Soda. Diaphragm cell caustic is commercially purified by the DH process or the ammonia extraction method offered by PPG and OxyTech (see Fig. 38), essentially involving Hquid—Hquid extraction to reduce the salt and sodium chlorate content (86). Thus 50% caustic comes in contact with ammonia in a countercurrent fashion at 60°C and up to 2500 kPa (25 atm) pressure, the Hquid NH absorbing salt, chlorate, carbonate, water, and some caustic. The overflow from the reactor is stripped of NH, which is then concentrated and returned to the extraction process. The product, about 62% NaOH and devoid of impurities, is stripped free of NH, which is concentrated and recirculated. MetaUic impurities can be reduced to low concentrations by electrolysis employing porous cathodes. The caustic is then freed of Fe, Ni, Pb, and Cu ions, which are deposited on the cathode. 

Pish protein concentrate and soy protein concentrate have been used to prepare a low phenylalanine, high tyrosine peptide for use with phenylketonuria patients (150). The process includes pepsin hydrolysis at pH 1.5 ptonase hydrolysis at pH 6.5 to Hberate aromatic amino acids gel filtration on Sephadex G-15 to remove aromatic amino acids incubation with papain and ethyl esters of L-tyrosine and L-tryptophan, ie, plastein synthesis and ultrafiltration (qv). The plastein has a bland taste and odor and does not contain free amino acids. Yields of 69.3 and 60.9% from PPG and soy protein concentrate, respectively, have been attained. 

The principal U.S. producers of 1,1,1-trichloroethane include The Dow Chemical Company, PPG Industries Inc., and Vulcan Materials Co. Several European and Japanese companies also produce large amounts aimually. Over 70% of the production is based on the vinyl chloride-1,1-dichloroethane process, 20% on the 1,1-dichloroethylene process, and about 10% on the direct chlorination of ethane. 

Figure 7-6. The PPG Industries Inc. Chloroethylene process for producing perchloro- and trichloroethylene (1) reactor, (2) graphite exchanger, (3) refrigerated condenser, (4) scrubber, (5) phase separation of perchlor from trichlor, (6, 7) azeotropic distillation, (8) distillation train, (9-11) crude trichlor separation—purification, (10-16) crude perchlor separation—purification.

Trichloroethylene is currently produced in the United States using ethylene dichloride (a produet of ethylene and chlorine feedstocks) (EPA 1985e). PPG Industries uses a single-step oxychlorination proeess, which yields triehloroethylene and tetraehloroethylene. In the PPG proeess, ethylene dichloride is reaeted with chlorine and/or hydrogen chloride and oxygen to form the triehloroethylene and tetraehloroethylene. DOW Chemical produces trichloroethylene by a direct chlorination process, in which ethylene dichloride is reacted with chlorine to form trichloroethylene and tetraehloroethylene. 

Equation A1 in the Appendix shows that P is a function of p, and thereby the sol fraction (eq A2) depends solely on p and certain mole and weight fractions given by the a s and w s (Table II). From the determined minima values of the sol fraction (Table I), p and Pxi for the LHT-240 and the Tri-NCO elastomers were first evaluated by an iterative process, and then G ax, vc, and t>e were obtained from eqs 4 and 5. These quantities are given in Table III. Those for the TIPA elastomer are not included because its composition is somewhat questionable, as mentioned earlier. However, if its initial ingredients were in fact 1.00 x 10 4 mole/g of TIPA, PPG, and a stiochiometric amount of TDI, the calculated values of G ax, 104pc, and 104pg are 0.350 MPa, 0.966, and 0.741, respectively. 

Glanor A Chlor-Alkali process using a bipolar diaphragm cell. Developed by PPG Industries and Oronzio de Nora Impianti Elettrochimic in the early 1970s. 

PPG [Pittsburgh Plate Glass Company] A process for making calcium hypochlorite. Hypochlorous acid and chlorine monoxide, generated by reacting chlorine and carbon dioxide with sodium carbonate monohydrate, are passed into lime slury. Invented in 1938 by I. E. Muskatt and G. H. Cady at the Pittsburgh Plate Glass Company. 

PPG-Sipsy. License for selected catalyst systems, process R D, custom manufacturing. Several processes [139]. 

One of the most observed degradation pathways of non-ionic surfactants of ethoxylate type in the biochemical wastewater treatment process is the bond scission between the lipophilic alkyl chain and the hydrophilic ethoxylate moieties. The resulting ethoxylate compounds, PEG or PPG, are highly polar and are not quite easy to degrade, therefore often they can be observed in wastewater discharges. So, APCI— FIA-MS(+) product ion spectra of selected [M + NH4]+ ions, which were under suspicion as PEG (general formula HO—(CH2—CH2—0) H)... 

Fig. 2.9.10. Interdependences of temperature and ions examined in the APCI-FIA-MS(+) process. Overview spectra of AP blend ionised at source temperatures ((a) 400°C and (b) 200°C) resulting in [M + NH4]+ and [M + H]+ ions and [M + NH4P ions of PPG...

PPG Industries has developed a substitute for lead in a coating process used widely in the auto industry. The replacement is yttrium that, though much less studied than lead, is considered orders of magnitude lower in hazard. In addition it was discovered that as yttrium is used in the process it is converted to yttrium oxide that is appears to be non-toxic by ingestion, in stark contrast to lead. As PPG customers implement yttrium overthe next several years, it is projected that the use of approximately one million pounds (some 454 tonnes) of lead will be avoided. 

This transformation has been applied to several chiral production processes, the first being the synthesis of a pheromone (Disparlure) intermediate (S) albeit with low turnover numbers and only 91 % ee. Another industrial product is the epoxide of allyl alcohol as developed by PPG-Sipsy, to give a process where catalyst loading was decreased by molecular sieve addition and the safety factors involving peroxide contamination were overcome. These examples are shown in Figure 1.46. 

Harada et al. explored the compatibility of CD with various polymeric backbones including polyethylene oxide) (PEG), polypropylene oxide) (PPG), polyisobutylene (PIB), and polyethylene (PE) [77-87]. The corresponding polyrotaxanes (36 to 47) were prepared by Method 2, simply by mixing a solution of CD and the polymer. The cavity size of CD was found to be the main factor in the threading process. While one a-CD (20) was threaded per two repeat units in PEG (m/n=0.50) and every three repeat units for PE (m/n=0.333), it was too small for PIB and PPG. On the other hand, two PPG units complexed per /(-CD (21). Because the upper limit of the min value is controlled by the depth of the CD cavity, the m/n value remained constant for the same type of backbone, irrespective of the end group. However, the nature and concentration, i.e., polymer... 

Fig. 6. Transition map for PPG showing the primary glass-rubber relaxation (a process) and the secondary relaxation (J3 process)...

---