Novel synthesis of thick wall coatings of titania supported Bi poisoned Pd catalysts and application in selective hydrogenation of acetylene alcohols in capillary microreactors

Abstract

A novel synthesis method for thick coatings inside long capillary reactors was reported and applied to the semihydrogenation of 2-methyl-3-butyn-2-ol.

Process Intensification of Alkynol Semihydrogenation in a Tube Reactor Coated with a Pd/ZnO Catalyst

“…The observed selectivity is notably higher than the one observed over the Pd catalysts supported on conventional supports, such as TiO 2 or SiO 2 , where the selectivity reaches around 92% at a low conversion [24,49]. These data are in excellent agreement with the previous studies over Pd/ZnO catalysts [41,48] and are comparable to the best examples of MBY semihydrogenation reported in literature over more complex metal-poisoned bimetallic catalysts which show selectivity of in the range of 97-98% [28,32,36,[50][51][52].…”

“…The macroporous structure formed by such needle-shaped crystals of the coating is greatly beneficial for the internal mass transfer as it provides high diffusion coefficients when compared to microporous materials. that provides a simple hydrodynamics and excellent control of residence time due to the Taylor flow regime [28,[35][36][37].…”

“…In our previous works, we have demonstrated that the catalyst-coated tube reactors are very efficient in providing high selectivity towards intermediate hydrogenation products over the Bi-poisoned Pd catalysts [28,36]. The selectivity in such reactors was demonstrated to be as high as in an ideal batch reactor with the same catalyst.…”

“…Hence, the maximum product selectivity obtained is determined only by the catalyst chemistry with no handicap being brought by the reactor [24,28]. However, the catalyst-coated tubes were demonstrated so far only at the milligram [38] to 10 g a day throughput levels [28,36], which are not suitable for industrial applications [35,39,40]. We have extrapolated the experimental performance of the tube reactors wall-coated with the Pd/ZnO catalyst and showed that a throughput of above 4 kg a day is feasible in a single 5 m long 1.5 mm ID reactor in the solvent-free MBY semihydrogenation [41].…”

“…An alternative approach is the application of structured reactors; however, they demonstrate low heat removal rates and are often operated in a recycle mode requiring high energy input into the reactant pumping [32][33][34]. The high operational costs can be overcome using a single tubular reactor that provides a simple hydrodynamics and excellent control of residence time due to the Taylor flow regime [28,[35][36][37].…”