Direct con­ver­sion from meth­ane to methanol us­ing gold-pal­la­dium nano par­ti­cles

Chemical Industry Digest - - New Developments -

Con­vert­ing meth­ane - the pri­mary com­po­nent of abun­dant nat­u­ral gas into methanol is cur­rently achieved by an in­di­rect process which re­quires high heat and pres­sure. Now re­searchers have dis­cov­ered a new ap­proach that al­lows the direct con­ver­sion of meth­ane to methanol uti­liz­ing molec­u­lar oxy­gen un­der much milder re­ac­tion con­di­tions.

For the study pub­lished in the jour­nal, Sci­ence, a team led by Gra­ham J. Hutch­ings at the Cardiff Catal­y­sis In­sti­tute, and Christo­pher J. Kiely at Le­high, used col­loidal gold-pal­la­dium (Au-Pd) nanopar­ti­cles to di­rectly ox­i­dize meth­ane to methanol with high se­lec­tiv­ity in aque­ous so­lu­tion at low tem­per­a­tures. “Our work has shown that if a sta­ble sup­ply of methyl rad­i­cals can be es­tab­lished—for ex­am­ple, by in­cor­po­rat­ing a very small amount of hy­dro- gen per­ox­ide into the re­ac­tion mix­ture—then the se­lec­tive ox­i­da­tion of meth­ane to methanol us­ing molec­u­lar oxy­gen is en­tirely fea­si­ble,” said Kiely, the Harold B. Cham­bers Se­nior Pro­fes­sor of Ma­te­ri­als Sci­ence and Chem­i­cal En­gi­neer­ing. Ac­cord­ing to Kiely, the re­searchers were sur­prised to find that for this par­tic­u­lar re­ac­tion to pro­ceed they needed the Au-Pd nanopar­ti­cles to ex­ist as free-float­ing col­loids in a very weak hy­dro­gen per­ox­ide so­lu­tion into which they in­jected pres­sur­ized meth­ane and oxy­gen gas.

“Usu­ally when we use Au-Pd nanopar­ti­cles as cat­a­lysts they are nearly al­ways dis­persed on high sur­face area ox­ide sup­ports such as ti­ta­nia,” said Kiely. “In this case how­ever, the pres­ence of the ce­ramic sup­port turned out to be highly detri­men­tal.In the chem­i­cal in­dus­try meth­ane is cur­rently con­verted in­di­rectly to methanol via the pro­duc­tion of syn­the­sis gas (car­bon monox­ide and hy­dro­gen) at high tem­per­a­tures and pres­sures, which is an ex­pen­sive and en­ergy in­ten­sive process. The new sim­pli­fied ap­proach we have demon­strated brings us a step closer to mak­ing the direct con­ver­sion of meth­ane to methanol- a prac­ti­cally vi­able propo­si­tion,” said Kiely.

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