Catalytic routes towards acrylic acid, adipic acid and epsilon-caprolactam starting from biorenewables

The majority of bulk chemicals are derived from crude oil, but the move to biorenewable resources is gaining both societal and commercial interest. Reviewing this transition, we first summarise the types of today's biomass sources and their economical relevance. Then, we assess the biobased productions of three important bulk chemicals: acrylic acid, adipic acid and epsilon-caprolactam. These are the key monomers for high-end polymers (polyacrylates, nylon 6.6 and nylon 6, respectively) and are all produced globally in excess of two million metric tons per year. The biobased routes for each target molecule are analysed separately, comparing the conventional processes with their sustainable alternatives. Some processes have already received extensive scientific attention. Other, more novel routes are also being considered. We find several common trends: For all three compounds, there are no commercial methods for direct conversion of biobased feedstocks. However, combinations of biotechnologically produced platform chemicals with subsequent chemical modifications are emerging and showing promising results. We then discuss several distinct strategies for implementing biorenewable processes. For each biotechnological and chemocatalytic route, current efficiencies and limitations are presented, but we urge that these routes should be assessed mainly on their potential and prospects for future application. Today, biorenewable routes cannot yet compete with their petrochemical equivalents. However, given that most of them are still in the early stages of development, we foresee their commercial implementation in the next two decades

Organosilane oxidation by water catalysed by large gold nanoparticles in a membrane reactor

We show that gold nanoparticles catalyse the oxidation of organosilanes using water as oxidant at ambient conditions. Remarkably, monodispersions of small gold particles (3.5 nm diameter) and large ones (6-18 nm diameter) give equally good conversion rates. This is important because separating large nanoparticles is much easier, and can be done using ultrafiltration instead of nanofiltration. We introduce a simple setup, constructed in-house, where the reaction products are extracted through a ceramic membrane under pressure, leaving the gold nanoparticles intact in the vessel. The nominal substrate/ catalyst ratios are ca. 1800 : 1, with typical TONs of 1500-1600, and TOFs around 800 h(-1). But the actual activity of the large nanoparticles is much higher, because most of their gold atoms are "inside", and therefore unavailable. Control experiments confirm that no gold escapes to the membrane permeate. The role of surface oxygen as a possible co-catalyst is discussed. Considering the ease of product separation and the robustness of the ceramic membrane, this approach opens opportunities for actual applications of gold catalysts in water oxidation reactions

Supported Cu Nanoparticles as Selective and Stable Catalysts for the Gas Phase Hydrogenation of 1,3-Butadiene in Alkene-Rich Feeds

Supported copper nanoparticles are a promising alternative to supported noble metal catalysts, in particular for the selective gas phase hydrogenation of polyunsaturated molecules. In this article, the catalytic performance of copper nanoparticles (3 and 7 nm) supported on either silica gel or graphitic carbon is discussed in the selective hydrogenation of 1,3-butadiene in the presence of a 100-fold excess of propene. We demonstrate that the routinely used temperature ramp-up method is not suitable in this case to reliably measure catalyst activity, and we present an alternative measurement method. The catalysts exhibited selectivity to butenes as high as 99% at nearly complete 1,3-butadiene conversion (95%). Kinetic analysis showed that the high selectivity can be explained by considering H2 activation as the rate-limiting step and the occurrence of a strong adsorption of 1,3-butadiene with respect to mono-olefins on the Cu surface. The 7 nm Cu nanoparticles on SiO2 were found to be a very stable catalyst, with almost full retention of its initial activity over 60 h of time on stream at 140 °C. This remarkable long-term stability and high selectivity toward alkenes indicate that Cu nanoparticles are a promising alternative to replace precious-metal-based catalysts in selective hydrogenation

Supported Cu Nanoparticles as Selective and Stable Catalysts for the Gas Phase Hydrogenation of 1,3-Butadiene in Alkene-Rich Feeds

Supported copper nanoparticles are a promising alternative to supported noble metal catalysts, in particular for the selective gas phase hydrogenation of polyunsaturated molecules. In this article, the catalytic performance of copper nanoparticles (3 and 7 nm) supported on either silica gel or graphitic carbon is discussed in the selective hydrogenation of 1,3-butadiene in the presence of a 100-fold excess of propene. We demonstrate that the routinely used temperature ramp-up method is not suitable in this case to reliably measure catalyst activity, and we present an alternative measurement method. The catalysts exhibited selectivity to butenes as high as 99% at nearly complete 1,3-butadiene conversion (95%). Kinetic analysis showed that the high selectivity can be explained by considering H2 activation as the rate-limiting step and the occurrence of a strong adsorption of 1,3-butadiene with respect to mono-olefins on the Cu surface. The 7 nm Cu nanoparticles on SiO2 were found to be a very stable catalyst, with almost full retention of its initial activity over 60 h of time on stream at 140 °C. This remarkable long-term stability and high selectivity toward alkenes indicate that Cu nanoparticles are a promising alternative to replace precious-metal-based catalysts in selective hydrogenation