Olefins conversion catalysts

Liu, Z. and Liang, J. (1999) Methanol to olefin conversion catalyst Current Opinion in Solid State Material Science, 4 80-84. 

Future Trends. In addition to the commercialization of newer extraction/ decantation product/catalyst separations technology, there have been advances in the development of high reactivity 0x0 catalysts for the conversion of low reactivity feedstocks such as internal and a-alkyl substituted a-olefins. These catalysts contain (as ligands) ortho-/-butyl or similarly substituted arylphosphites, which combine high reactivity, vastiy improved hydrolytic stabiUty, and resistance to degradation by product aldehyde, which were deficiencies of eadier, unsubstituted phosphites. Diorganophosphites (28), such as stmcture (6), have enhanced stabiUty over similarly substituted triorganophosphites. 

T. Inui, "Stmcture-Reactivity Relationship in Methanol to Olefin Conversion on Various Microporous Crystalline Catalysts," paper presented at... 

Run no. Catalyst Reactant Initial/ before H202 addition pH After H202 addition At die end of die reaction TOF Olefin conversion (mol%) h2o2 efficiency Epoxide selectivity (mol%)... 

Liu et al. [18] investigated the possibility of catalyst recycling in the nonaqueous hydroformylation of 1-decene by using the thermomorphic polyether phosphite 2a described earlier under phase-transfer conditions. Catalyst recovery with the procedure of phase-separable catalysis was possible with 0.92% rhodium loss in the seventh cycle. Complete olefin conversion and aldehyde yields of 98% were reached, but linear and branched aldehydes were formed in almost equal amounts. 

The reactor effluent is fed to the spent catalyst separation section where catalyst is removed, treated to remove any volatile hydrocarbons, and sent to be regenerated. The effluent is then distilled to remove and recycle unreacted ethylene, then fractionated into high purity alpha olefins. The reaction solvent is also recovered for recycling. Olefin conversion per pass is 50—60%, with the combined yields of C4-C10 alpha olefins of 93%. 

Although this process has shown much promise, decomposition of the olefin metathesis catalyst appears to limit the conversion nonetheless, it is expected that a more robust and compatible olefin metathesis catalyst will yield higher TONs. 

The composition of the gasoline obtained by catalytic cracking and used as a feedstock for the ZSM-5 catalyst is given in Table VI. Product analyses, also given in Table VI, show that 80% of the olefins and less than 10% of the paraffins are converted by the ZSM-5 catalyst with about 30% of the olefin conversion attributable to the matrix present in the catalyst. This is not surprising due to the well-known higher reactivity of olefins. 

Light hydrocarbons (Ci to C4) and aromatics (mainly Ce to Ce) were produced by ZSM-5 due to the the conversion of olefins and paraffins. Thus,these results provide evidence for cracking of olefins, paraffins and cyclization of olefins by ZSM-5 at 500 C. The steam deactivated ZSM-5 catalyst exhibited reduced olefin conversion and negligible paraffin conversion activity. 

Table 8.6 ROMP of low-strained cyclic olefins using catalysts XXVIIIa, XXVIIId in toluene at RT. Substrate Catalyst Monomer/Catalyst Time Conversion %) 10 xM M /M ...

DSM370 has patented platinum systems based upon tetrasulfonated bidentate water soluble ligand 29 (Table 2 x=4, m=0, n=0) as catalysts for the hydroformylation of a mixture 1-butene (45%) and 2-butene (22%) with 33% butane at 100°C and 80 bar CO/H2 in an aqueous/methanol (300/32), CF3SO3H acidic medium. The olefin conversion was 86% and the selectivity to the aldehydes 95% (n/i ratio of 2.8) together with small amounts of aldolcondensation products and acids. The products were isolated from the aqueous catalyst mixture leaving the reaction zone by extraction with ether and the aqueous phase recycled to the reactor. 

All these catalytic results, however, were usually achieved at very low (2-3%) conversions. The only exception is a paper reporting up to 80% selectivity at 20% conversion over a M0CI5—R4Sn-on-silica olefin metathesis catalyst (700°C, 1 atm, CH4 air = l).42 In general, higher temperature and lower—about ambient— pressure compared to homogeneous oxidation, and high excess of methane are required for the selective formation of formaldehyde in catalytic oxidations.43 The selectivity, however, decreases dramatically at conversions above 1%, which is attributed to the decomposition and secondary oxidation of formaldehyde.43,44 It is a common observation that about 30% selectivity can be achieved at about 1% conversion. 

Ruthenium is the most selective metal to produce intermediate olefins. Certain catalyst additives and water100-102 increase the yield of cyclohexene from benzene up to 48% at 60% conversion.103 Alkylbenzenes are hydrogenated at somewhat lower rates then benzene itself. As a general rule the rate of hydrogenation decreases as the number of substituents increases, and the more symmetrically substituted compounds react faster than those with substituents arranged with less symmetry.9,10 Highly substituted strained aromatics tend to undergo ready saturation, even over the less active palladium. 

Catalyst Temp. (°C) D2/olefin Conversion (%) Ethylenes Ethanes ... 

The catalytic hydration of olefins can also be performed in a three-phase system solid catalyst, liquid water (with the alcohol formed dissolved in it) and gaseous olefin [258,279,280]. The olefin conversion is raised, in comparison with the vapour phase processes, by the increase in solubility of the product alcohol in the excess of water [258]. For these systems with liquid and vapour phases simultaneously present, the equilibrium composition of both phases can be estimated together with vapour-liquid equilibrium data [281]. For the three-phase systems, ion exchangers, especially, have proved to be very efficient catalysts [260,280]. With higher olefins (2-methylpropene), the reaction was also performed in a two-phase liquid system with an ion exchanger as catalyst [282]. It is evident that the kinetic characteristics differ according to the arrangement (phase conditions), i.e. whether the vapour system, liquid vapour system or two-phase liquid system is used. However, most kinetic and mechanistic studies of olefin hydration were carried out in vapour phase systems. 

Results on epoxidation of cyclohexene with H2O2 with freshly prepared catalysts are given in Table 2. With Mo blue, exchanged on Mg,Al-LDH, the olefin conversion is low, even if all peroxide is consumed within 4 h. Upon addition of the H2O2 to the reaction mixture, the suspended catalyst has the yellow hue of the Movl form of the isopolyacid. However, the suspension soon turns brick red. This color is characteristic for tetraperoxomolybdate Mo(02)42 [17], This indicates that the isopolyacid structure degrades rapidly, with formation of Mo monomers. Peroxo complexes such as Mo(0 )42 or particularly MoO(C>2)32 are known to decompose with formation of 02 the overall process is a decomposition of two molecules of H2O2 into water and C>2 [18] ... 

All hydroformylation experiments were performed in a continuously operated reactor. The concentration of the catalyst was varied from 0.1 to 0.4 wt % to keep olefin conversion at the same level (80-90% ) for all reaction temperatures. The total pressure for all experiments was 280 atm, and n-octene was used as typical straight chain olefin of medium chain length. 

The best per pass yield to C2 + C3 products (aldehydes plus acids with two and three C atoms) with the said catalyst was obtained at a propene conversion of 61.3% (selectivity to acrolein 83.7%), at the reaction temperature of 355 °C, with the following feed composition C3H6/H20/N2 11.6 10.0 78.4 (mol.%), with a gas contact time of 2.4 s. A decrease in solids circulation rate, while keeping gas residence time constant, led to a considerable decrease in propene conversion, while selectivity to C2 + C3 oxygenated products was not much affected by circulation rate. With a less concentrated feed, the amount of solid to be circulated for a defined olefin conversion is lower, but productivity also becomes lower. Other catalysts based on Bi/Mo/O or on V/Mo/W/Cu/O [72c] afforded conversions >70% and selectivity >90% industrial... 

New Copper Pyrophosphate Catalyst requires an activating period before satisfactory olefin conversion can be obtained. This activating period may range up to 1 or 2 days, a factor which requires additional plant capacity if high conversions are required during these periods. 

Early commercial units utilized 10- to 20-mesh quartz but, because of the low surface area and consequent low activity of the catalyst, the quartz size was reduced to 28 to 35 mesh. The quartz is activated by pumping the reactor full of 75% phosphoric acid, allowing the excess acid to drain out, and then charging hot hydrocarbon to the unit. Even with the smaller quartz particles the catalyst activity is much lower than that of the Solid Phosphoric Acid catalyst. This lower activity has resulted in lower olefin conversion in this type of unit. Increased conversion has been obtained by separating the olefins from the product with very efficient fractionators and returning them to the reactor. However, this factor requires relatively large units with high utility consumption. 

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