Single-step process

Process. The QSL process (14) is a continuous single-step process having great flexibiUty in regard to the composition of the raw materials. In this process the highly exothermic complete oxidation, ie, the roasting reaction, can be avoided to some extent in favor of a weakly exothermic partial oxidation directly producing metallic lead. However, the yield of lead as metal is incomplete due to partial oxidation of lead to lead oxide. 

MMA from Propyne. Advances in catalytic carbonylation technology by Shell researchers have led to the development of a single-step process for producing MMA from propyne [74-99-7] (methyl acetylene), carbon monoxide, and methanol (76—82). 

Polymerization of the dianhydride and diamine proceeds through an intermediate poly(amide acid) stage before ring closure converts the adjacent acid and amide groups to the polyetherimide (94). The polymerization can be carried directiy to the polyetherimide as a single-step process, or first to an ainide—acid-containing prepolymer, which can be isolated, and then to the polyetherimide. 

NMP are examples of suitable solvents for PES and PPSF polymerizations. Chlorobenzene or toluene are used as cosolvents at low concentrations. These cosolvents form an azeotrope with water as they distill out of the reaction mixture, thereby keeping the polymerization medium dehydrated. Potassium carbonate is a suitable choice for base. The synthesis of PES and PPSE differ from the PSE case in that the reaction is carried out in a single-step process. In other words, the formation of the dipotassium salt of the bisphenol is not completed in a separate first step. Equations 2 and 3 represent polymerizations based on the dipotassium salts of bisphenol S and biphenol to make PES and PPSE, respectively. 

The manufacture of vitreous sihca by flame hydrolysis can be a single- or multistep process. In the single-step process, sihca particles are formed and... 

Using a single-step process, 6-azauracil can be prepared from chloral 3-methylisothiosemicarbazone (59), The apparent intermedi-... 

Extruded composites of plasticized PVC and short cellulose fibers have been investigated by Goettler [103]. Pronounced increases in tensile modulus, yield, and ultimate tensile strength are observed. Single step processing of reinforcement and polymer with good product performance are key characteristics of the material whose field of application lies in the vinyl hose industry. 

Measurements of product gas evolution, mass loss or evolved gas analysis may all be used to study the kinetics of a solid—solid interaction provided that there is strict adherence to the condition that gas evolution occurs concurrently with the solid state process. Clearly this approach is only applicable if there is direct experimental support for a single step process. For example, carbon dioxide release is identified [410] as being... 

It is concluded [634] that, so far, rate measurements have not been particularly successful in the elucidation of mechanisms of oxide dissociations and that the resolution of apparent outstanding difficulties requires further work. There is evidence that reactions yielding molecular oxygen only involve initial interaction of ions within the lattice of the reactant and kinetic indications are that such reactions are not readily reversed. For those reactions in which the products contain at least some atomic oxygen, magnitudes of E, estimated from the somewhat limited quantity of data available, are generally smaller than the dissociation enthalpies. Decompositions of these oxides are not, therefore, single-step processes and the mechanisms are probably more complicated than has sometimes been supposed. 

The Alfen process can also be conducted as a single-step process the growth and displacement reactions occur simultaneously in the same reactor at 200°C and 250 bar ethylene pressure with catalytic amounts of triethylaluminum. 

The catalytic single-step Alfen process has a good space-time yield, and the process engineering is simple. The molecular weight distribution of the olefins of the single-step process is broader (Schulz-Flory type of distribution) than in the two-step Alfen process (Poisson-type distribution) (Fig. 2). As a byproduct 2-alkyl-branched a-olefins also are formed, as shown in Table 6. About... 

In the peaking process of the Ethyl Corporation, the catalytic single-step process and the stoichiometric two-step process are combined. The result is an olefin mixture with a narrowed molecular weight distribution [25]. In this combined process low molecular weight olefins (preferably n-butene-1) obtained by a single-step process are used as displacement olefins (instead of ethylene) in the second step of the stoichiometric two-step Alfen process. Table 7 shows the composition of an olefinic mixture produced by the combination process of the Ethyl Corporation. The values in Table 7 show that the olefin mixtures of the... 

Marcus theory can be applied to any single-step process where something is transferred from one particle to another. It was originally derived for electron... 

SINGLE-STEP PROCESS CONVERTS PLASTICS TO FUEL... 

A commercial pectinase, immobilised on appropriately functionalised y-alumina spheres, was loaded in a packed bed reactor and employed to depolymerise the pectin contained in a model solution and in the apple juice. The activity of the immobilized enzyme was tested in several batch reactions and compared with the one of the free enzyme. A successful apple juice depectinisation was obtained using the pectinase immobilised system. In addition, an endopolygalacturonase from Kluyveromyces marxianus, previously purified in a single-step process with coreshell microspheres specifically prepared, was immobilised on the same active support and the efficiency of the resulting catalyst was tested. 

RW Korsmeyer, SM Herbig, KL Smith, JR Cardinal, AC Curtiss, MB Fergione, RA Wilson. Single-step process for coating multiparticulates with asymmetric membranes. Proceedings of the International Symposium on the Controlled Release of Bioactive Materials, Stockholm, 1997, pp 531-532. 

The enzyme creatine kinase (CK) facilitates the transfer of phosphate and energy to a molecule of ADP to form ATP. Stores of creatine phosphate are sufficient to sustain approximately 15 more seconds of muscle contraction. Because this is a single-step process, it provides ATP very rapidly and is the first pathway for formation of ATP to be accessed. 

Balasubramanian, U. et al., Hydrogen from methane in a single-step process, Chem. Eng. Sci., 54, 3543,1999. 

The scheduling task can be simplified by a reduction of the model (e.g., using single-step process orders that only consider the bottleneck resources). As usual, one has to compromise between effort and precision. 

While gas atomization of liquid metals is generally viewed as a three-step process, the Kohlswa ultrasonic gas atomization is suggested to be a single-step process.[172] When particles of an atomization gas at extremely high velocities strike a liquid metal... 

OCOH)(PH3)2 and a dihydrogen molecule [44], The introduction of a NH3 molecule in the system converts this single-step process in a three-step process, with three transition states. The energy change occurs smoothly and the highest barrier is only 2.1 kcal/mol (MP2//MP2) which is much smaller than the barrier in the absence of NH3 (11.4 kcal/mol, Table 4). This means that the four-center metathesis occurs with nearly no barrier in the presence of base. However, the base effects are likely overestimated in this calculations. The experimental triethylamine system cannot do all the interactions ammonia does, and polar or protic solvents should weaken the interaction between the base and the complex. 

A concerted (single-step) process, to give the product P ... 

There is ample evidence that the reductive elimination of alkanes (and the reverse) is a not single-step process, but involves a o-alkane complex as the intermediate. Thus, looking at the kinetics, reductive elimination and oxidative addition do not correspond to the elementary steps. These terms were introduced at a point in time when o-alkane complexes were unknown, and therefore new terms have been introduced by Jones to describe the mechanism and the kinetics of the reaction [5], The reaction of the o-alkane complex to the hydride-alkyl metal complex is called reductive cleavage and its reverse is called oxidative coupling. The second part of the scheme involves the association of alkane and metal and the dissociation of the o-alkane complex to unsaturated metal and free alkane. The intermediacy of o-alkane complexes can be seen for instance from the intramolecular exchange of isotopes in D-M-CH3 to the more stable H-M-CH2D prior to loss of CH3D. 

A possible economically attractive alternative would be the production of acrylic acid in a single step process starting from the cheaper base material propane. In the nineteen nineties the Mitsubishi Chemical cooperation published a MoVTeNb-oxide, which could directly oxidise propane to acrylic acid in one step [6], Own preparations of this material yielded a highly crystalline substance. Careful analysis of single crystal electron diffraction patterns revealed that the MoVTeNb-oxide consists of two crystalline phases- a hexagonal so called K-Phase and an orthorhombic I-phase, which is the actual active catalyst phase, as could be shown by preparing the pure phases and testing them separately. 

An alternative method for producing thin deposits consists in avoiding single-step processes by chemisorbing the precursor and then having it decomposed thermally [1]. Such a method, often named atomic layer deposition or gas phase impregnation-deposition, provides very thin deposits due to the presence of a... 

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