H2 production by the photocatalytic reforming of cellulose and raw biomass using Ni, Pd, Pt and Au on titania

Here, we report a method for sustainable hydrogen production using sunlight and biomass. It is shown that cellulose can be photoreformed to produce hydrogen, even in solid form, by use of metal-loaded titania photocatalysts. The experiments performed verified that the process is enabled by initial hydrolysis via glucose, which itself is shown to be efficiently converted to produce hydrogen by photocatalysis. Importantly, it is shown that not only precious metals such as Pt, Pd and Au can be used as the metal component, but also much more economic and less environmentally damaging Ni is effective. Even more importantly, we show for the first time, to the best our knowledge, that fescue grass as raw biomass can be effective for hydrogen production without significant pretreatment. This provides additional benefits for the efficiency of biomass hydrogen production, because fewer processing steps for the raw material are required than in the production of purer forms of cellulose, for example

Pd/ZnO catalysts for direct CO2 hydrogenation to methanol

The direct hydrogenation of CO2 into methanol is crucial for providing a means of CO2 fixation and a way to store cleanly produced hydrogen in a more energy-dense and transportable form. Here we have prepared two series of Pd/ZnO catalysts, both by immobilisation of PVA-protected Pd colloids and by Pd impregnation of PdCl2 to investigate structure activity relationships for direct CO2 hydrogenation. Very different performances were found for the different preparation methods, and the Pd loading and pre-reduction of the catalysts were shown to be important factors for optimising methanol yield. The crucial factor for high methanol yield is the formation of a Pd–Zn alloy, either during the reaction itself, or better by high temperature pre-reduction. The formation of the alloy greatly reduces CO production by the reverse water gas shift reaction. The catalysts prepared by sol-immobilisation were relatively stable to thermal treatment. In contrast, the impregnated catalysts were much less thermally stable, due to the presence of remnant chloride on the surface of the catalyst, which was absent for the case of sol immobilisation preparation. The results illustrate the importance of controlling the PdZn particle size and its surface structure for the catalysts to achieve high methanol selectivity (60%, the rest being CO) and conversion (11%) at 250 °C and 20 bar. Selectivity for sol-immobilised catalysts decreases from 60% at 3 nm average diameter, to 20% at 7 nm

Photocatalytic hydrogen production with supported Au and Au-alloy nanoparticles

Photocatalytic reforming reactions of simple alcohols and amines have been studied as a method of hydrogen production. The reactions were carried out with synthesised catalysts consisting of noble metal nano-particles (NP) supported on semiconductor supports. The aim was to develop an alternative environmentally friendly approach to hydrogen production. Primarily catalysts were synthesised by the sol immobilisation method, which allows for the formation of a colloidal dispersion of noble metals in solution which can then be deposited onto the surface of an appropriate support. By exploring the parameters during the sol immobilisation method a standard synthesis procedure was decided upon and used throughout this thesis. This procedure allowed for the reproducible preparation of Au and Pd NPs in the order of ~ 3 nm as well as bimetallic AgAu and Pd Au NPs on the surface of a TiO2 support. The sol immobilisation method was used to prepare two sets of bimetallic AgAu NPs supported on TiO2 (P25). AgAu-TiO2 catalysts with a 1:1 weight ratio were prepared and they were found to be more active than the monometallic Au-TiO2 and Ag-TiO2. The most active of the AgAu-TiO2 catalysts was synthesised by first preparing a Au colloid followed by reduction of the Ag precursor onto the surface of the Au to make a core-shell structure NP. A second set of AgAu-TiO2 catalysts was prepared starting with Au NPs followed by deposition of a controlled shell thickness of Ag on the surface supported on TiO2, by three different methods. Characterisation for these samples was performed by X-ray absorption spectroscopy (XAS) techniques at the Diamond light source. The deposition of thin layers of Ag onto the preformed Au NPs results in the activity being poorer than the reference catalyst of Au-TiO2. Preparation of Au NPs supported on TiO2 with the subsequent deposition of thin layers of Pd onto the surface of the Au by three methods was also undertaken, and again characterised by XAS. Here all of the PdAu-TiO2 catalysts which were made exhibited improved activity over the reference samples tested. This improvement in H2 was attributed to the NPs having a Au core and PdAu shell on the surface of TiO2. Finally graphitic carbon nitride (g-C3N4) was investigated as a visible light active semiconductor for hydrogen production by photocatalytic reforming reactions. In recent years graphitic carbon nitride has gain interest as an alternative semiconductor support for photocatalytic reactions. Direct activity comparisons between Pd loaded g-C3N4 (urea derived) and TiO2 (P25) were undertaken by performing two sets of reactions under identical conditions. The results from these reactions show that under the full arc condition of the solar simulator (150 W Xe arc lamp) TiO2 was the most active, despite having a larger band gap (3.2 eV) compared to the g-C3N4 (2.8 eV). Also investigated was the choice of molecule being reformed (or hole scavenger) by Pd-TiO2 and Pd-C3N4 with triethanolamine and methanol compared, as well as a variety of simple amines

Costs of delivering human papillomavirus vaccination to schoolgirls in Mwanza Region, Tanzania.

BACKGROUND: Cervical cancer is the leading cause of female cancer-related deaths in Tanzania. Vaccination against human papillomavirus (HPV) offers a new opportunity to control this disease. This study aimed to estimate the costs of a school-based HPV vaccination project in three districts in Mwanza Region (NCT ID: NCT01173900), Tanzania and to model incremental scaled-up costs of a regional vaccination program. METHODS: We first conducted a top-down cost analysis of the vaccination project, comparing observed costs of age-based (girls born in 1998) and class-based (class 6) vaccine delivery in a total of 134 primary schools. Based on the observed project costs, we then modeled incremental costs of a scaled-up vaccination program for Mwanza Region from the perspective of the Tanzanian government, assuming that HPV vaccines would be delivered through the Expanded Programme on Immunization (EPI). RESULTS: Total economic project costs for delivering 3 doses of HPV vaccine to 4,211 girls were estimated at about US$349,400 (including a vaccine price of US$5 per dose). Costs per fully-immunized girl were lower for class-based delivery than for age-based delivery. Incremental economic scaled-up costs for class-based vaccination of 50,290 girls in Mwanza Region were estimated at US$1.3 million. Economic scaled-up costs per fully-immunized girl were US$26.41, including HPV vaccine at US$5 per dose. Excluding vaccine costs, vaccine could be delivered at an incremental economic cost of US$3.09 per dose and US$9.76 per fully-immunized girl. Financial scaled-up costs, excluding costs of the vaccine and salaries of existing staff were estimated at US$1.73 per dose. CONCLUSIONS: Project costs of class-based vaccination were found to be below those of age-based vaccination because of more eligible girls being identified and higher vaccine uptake. We estimate that vaccine can be delivered at costs that would make HPV vaccination a very cost-effective intervention. Potentially, integrating HPV vaccine delivery with cost-effective school-based health interventions and a reduction of vaccine price below US$5 per dose would further reduce the costs per fully HPV-immunized girl

Correction to: Solvent free synthesis of PdZn/TiO2 catalysts for the hydrogenation of CO2 to methanol

The article Solvent Free Synthesis of PdZn/TiO2 Catalysts for the Hydrogenation of CO2 to Methanol by Hasliza Bahruji, Jonathan Ruiz Esquius, Michael Bowker, Graham Hutchings, Robert D. Armstrong, Wilm Jones was originally published Online First without open access. After publication in volume 61, issue 3–4, pages 144–153, the author decided to opt for Open Choice and to make the article an open access publication. Therefore, the copyright of the article has been changed to ©The Author(s) 2018 and the article is forthwith distributed under the terms of the Creative Commons Attribution 4.0 International License (http://creativecommons.org/licenses/by/4.0/), which permits use, duplication, adaptation, distribution and reproduction in any medium or format, as long as you give appropriate credit to the original author(s) and the source, provide a link to the Creative Commons license, and indicate if changes were made

Adsorbate-Induced Structural Evolution of Pd Catalyst for Selective Hydrogenation of Acetylene

ACKNOWLEDGMENT: This work was financially supported by National Natural Science Foundation of China (21908002), project funded by China Postdoctoral Science Foundation (2019M660416, 2020T130045) and the Fundamental Research Funds for the Central Universities (buctrc201921, JD2004, XK1802-6). We would like to thank the UK catalysis Hub for help collecting the XAS.Peer reviewedPostprin

Octane isomer dynamics in H-ZSM-5 as a function of Si/Al ratio:a quasi-elastic neutron scattering study

Dynamical behaviour of n-octane and 2,5-dimethylhexane in H-ZSM-5 zeolite catalysts of differing Si/Al ratios (15 and 140) was probed using quasi-elastic neutron scattering, to understand molecular shape and Brønsted acid site density effects on the behaviour of common species in the fluid catalytic cracking (FCC) process, where H-ZSM-5 is an additive catalyst. Between 300 and 400 K, n-octane displayed uniaxial rotation around its long axis. However, the population of mobile molecules was larger in H-ZSM-5(140), suggesting that the lower acid site concentration allows for more molecules to undergo rotation. The rotational diffusion coefficients were higher in H-ZSM-5(140), reflecting this increase in freedom. 2,5-dimethylhexane showed qualitative differences in behaviour to n-octane, with no full molecule rotation, probably due to steric hindrance in the constrictive channels. However, methyl group rotation in the static 2,5-dimethylhexane molecules was observed, with lower mobile fractions in H-ZSM-5(15), suggesting that this rotation is less hindered when fewer Brønsted sites are present. This was further illustrated by the lower activation barrier calculated for methyl rotation in H-ZSM-5(140). We highlight the significant immobilizing effect of isomeric branching in this important industrial catalyst and show how compositional changes of the zeolite can affect a range of dynamical behaviours of common FCC species upon adsorption

Carbidisation of Pd nanoparticles by ethene decomposition, with methane production

In the presence of oxygenated organic molecules pure Pd, which is widely used in chemicals processing and the pharmaceutical industry, tends to defunctionalise and dehydrogenate such molecules to H2, CO and surface/bulk carbon, in the form of a palladium carbide. We have investigated the formation of this carbide by ethene adsorption using a variety of techniques, including pulsed flow reaction measurements, XAS and DFT calculations of the lattice expansion during carbidisation. These experiments show that two main reactions take place above 500K, that is, both total dehydrogenation, but also disproportionation to methane and the carbide, after which the activity of the Pd is completely lost. We estimate the value of x in PdCx to be 0.28 (±0.03), and show by computer modelling that this fits the lattice expansion observed by XAFS, and that there is charge transfer to C from Pd of around 0.2-0.4 e

Identification of single-site gold catalysis in acetylene hydrochlorination

There remains considerable debate over the active form of gold under operating conditions of a recently validated gold catalyst for acetylene hydrochlorination. We have performed an in situ x-ray absorption fine structure study of gold/carbon (Au/C) catalysts under acetylene hydrochlorination reaction conditions and show that highly active catalysts comprise single-site cationic Au entities whose activity correlates with the ratio of Au(I):Au(III) present. We demonstrate that these Au/C catalysts are supported analogs of single-site homogeneous Au catalysts and propose a mechanism, supported by computational modeling, based on a redox couple of Au(I)-Au(III) species. View Full Tex