Since the catalyst productivity is inverse first order regarding the Al alkyl concentration, high amounts of Al lead to low monomer insertion. Consequently, relatively short chains are transferred to Al. Another effect of high Al concentrations is an increase in the chain displacement rate. Chain displacement is first order regarding Al.
The solubility of ethylene in toluene is influenced by the pressure applied and, therefore, the rate of monomer insertion can be tuned. The length of the mean alkyl chain formed at Al is dependent mainly on the number of monomer insertions done by the CCTP catalyst within a given time frame, where time is defined as the mean time after which displacement takes place. The productivity increases linearly with increased pressure over the pressure range investigated.
The increasing TON of Al can again be explained by the presence of more extended alkyl Al chains in the high-pressure experiments. In addition, we varied the Ni concentration. Ethylene pressure and Y catalyst concentration were kept constant. A second extreme product distribution can be obtained by using 1.
This product distribution blue, Fig. Discussion A highly flexible trimetallic synthesis concept of LAOs from ethylene has been introduced. Both catalysts do alkyl or polymeryl chain transfer with Al alkyls in a similar rate regime.
In addition, TEA is formed and, thus, recycled. The key to the many product spectra or selective LAO formation is the independent adjustability of the rates of the Y- and Ni-catalyzed sub-processes. We have demonstrated that these rates can be adjusted by the concentration of the Y catalyst, the Ni catalyst and the chain-transfer agent, and the ethylene pressure. In addition, it is important that the two catalysts do not poison each other significantly.
Our broadly tunable synthesis concept of LAOs is also substoichiometric or formally catalytic regarding Al. The problem of low catalyst economy in CCTP is addressed by multiple usage of the chain-transfer agent. Afterwards, the polymerization temperature was adjusted, charged with the desired amount toluene typically ml and pressurized with ethylene.
Subsequently activator, CTA and nickel solution were added as stock solutions via a syringe. Afterwards the catalyst 1 ml stock solution was added. The ethylene flow was measured over the course of the polymerization procedure and is given as V eth under normal conditions.
After the procedure the reaction mixture was quenched with acidified ethanol and the obtained products were analyzed. Data availability Crystallographic data CCDC contains the Supplementary crystallographic data for this paper. All other data is available from the authors upon reasonable request References Arpe, H. Wiley-VCH, Esters are usually derived from an inorganic acid or organic acid in which at least one -OH hydroxyl group is replaced by an -O-alkyl alkoxy group, most commonly from carboxylic acids and alcohols.
That is to say, esters are formed by condensing an acid with an alcohol. Many chemically different "esters" due to their usually excellent lubricity are used for various reasons as either "additives" or "base stocks" for lubricants. Motul introduced the first semi-synthetic motor oil in In general, the ratio of the synthetic base stock is used to define commodity codes among the customs declarations for tax purposes. Stubbs,, Jeffrey J.
Potoff, and, J. The Journal of Physical Chemistry B , 45 , Peter A. Jabbarzadeh,, J. Atkinson, and, R. Macromolecules , 36 13 , Loukas I. Kioupis and, Edward J. The Journal of Physical Chemistry B , 32 , Punit Kumar, M. Journal of Tribology , 4 , Jorge Castillo-Tejas, Juan F. Nonequilibrium molecular dynamics of the rheological and structural properties of linear and branched molecules. Simple shear and poiseuille flows; instabilities and slip.
The Journal of Chemical Physics , 5 , Jaroslaw T. Bosko, B. Todd, Richard J. Viscoelastic properties of dendrimers in the melt from nonequlibrium molecular dynamics. The Journal of Chemical Physics , 23 , Junfang Zhang, B. Pressure tensor and heat flux vector for inhomogeneous nonequilibrium fluids under the influence of three-body forces.
Atkinson, and, R. James M. Several synthetic base oil types fall into the SHC category. Jabbarzadeh,, J.
Coordinative chain-transfer polymerization CCTP 6 , 7 , 8 , a polymerization protocol characterized by polymeryl chain-transfer between dormant states of a chain-transfer agent CTA and a polymerization catalyst responsible for the chain growth, allows the controlled polymerization of ethylene towards metal-terminated polyethylenes. Pressure tensor and heat flux vector for inhomogeneous nonequilibrium fluids under the influence of three-body forces. Afterwards the catalyst 1 ml stock solution was added. Olefin oligomerization via metallacycles: dimerization, trimerization, tetramerization, and beyond. Punit Kumar, M.
Junfang Zhang, B. Fluid transport properties by equilibrium molecular dynamics. Neeraj Rai,, Alexander J. In this two-step procedure, product formation is stoichiometric to the Zn alkyl. Different Ni catalyst concentrations were applied and the initial rates were determined. Not all three ethyl groups on aluminum have to be extended; partial chain exchange to Al and extension can be sufficient.
We believe that there is a maximum amount of Ni concentration in this system. We have demonstrated that these rates can be adjusted by the concentration of the Y catalyst, the Ni catalyst and the chain-transfer agent, and the ethylene pressure. Its molecular structure determined by X-ray single crystal structure analysis is shown in Fig.
The policy promotes consumption of oils with biodegradable base, leading to increasing opportunities for regional industry growth. DOI: Chain displacement is first order regarding Al. A molecular-level explanation for this behavior is given in terms of the energy barriers for intramolecular reorientation.
A slow displacement reaction reduced the flexibility of the synthesis drastically. The reaction is substoichiometric or formally catalytic regarding the chain transfer agent. The ethylene flow was measured over the course of the polymerization procedure and is given as V eth under normal conditions. Based on these calculations, it appears that PAO molecules with long, widely spaced branches should yield a higher VN than those with short, closely spaced branches.
Here, a change in concentration may affect both partial reactions. These include PAOs and also relatively common polyisobutenes PIB , which are sometimes used as oil additives or as base oils in two-stroke engines. Lower CTA to Y catalyst ratios resulting from a higher Y catalyst concentration will shift the equilibrium towards the chain-growing state leading to an increase in productivity. Viscoelastic properties of dendrimers in the melt from nonequlibrium molecular dynamics. Jabbarzadeh,, J. Other dynamic properties, such as the diffusivity and rate of tumbling, were also computed and found to have similar dependencies on temperature as the viscosity.