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The current upgrading catalysts are mainly based on the use of expensive noble metals, which are subject to deactivation due to sintering and coking. An alternative would be to introduce a non-noble metal-based catalyst. In this work, supported molybdenum carbide based systems have been assessed for this purpose. These catalysts were formed by impregnation of zirconia (and zirconium hydroxide) and sulfated zirconia (and zirconium hydroxide) with different loadings of MoO3, with an aim of finding a balance between acid sites and metal-like sites (a site capable of performing dehydrogenation and hydrogenation function without necessarily being a metal). The synthesised catalysts were carburised between 823 and 1123 K using a mixture of methane and hydrogen (4:1) in an attempt to obtain β-Mo2C/ZrO2 or β-Mo2C/S ZrO2. Carburisation at 923 K and above resulted in molybdenum carbide with minimal or no oxygen contents. The conversion and specific rate increased with temperature. Conversion was inversely proportional to space velocity. Analysis of the products distribution as a function of conversion implies that the reaction did not simply follow a consecutive reaction pathway, but that other parallel routes were involved. Conversion increased the research octane number (RON) to ca. 66 due to the increased fraction of pentane isomers. Catalyst carburised at 823 K was approximately four times more active compared to those carburised at 923 K and above, but were of similar activity with Pt/sulfated zirconia. The non-noble metal based catalysts were stable at the reaction temperature while the Pt/sulfated zirconia catalyst deactivates.

1. Polarographic and spectrophotometric methods for the determination of molybdenum were reviewed. 2. The inclusion of salicylaldoxine in several supporting electrolytes was examined with a view to developing a polarographic procedure, suitable for routine analyses, which did not necessitate a preliminary time-consuming separation stage. A stable molybdenum wave was obtained from an electrolyte having a composition similar to the test solution obtained after the wet digestion of plant material. The height of the wave was found to be, over an optimum range, independent of the reagent concentrations. The wave was however distorted by a maximum, which rendered it unsuitable for quantitative analytical application. 3. The spectrophotometric procedure for molybdenum using thiocyanate is virtually specific and was examined critically. Modifications were found to improve the sensitivity of the procedure, and the stability of the chromatic compound. 4. The modified spectrophotometric procedure is recommended for the routine determination of molybdenum in plant material.

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Molybdenum (Mo) is an essential micronutrient required by plants. It is biologically inactive until bound in a pterin compound named the molybdenum cofactor (Moco) that binds to apoproteins used in both reductive and oxidative reactions such as nitrate reductase (NR), xanthine dehydrogenase (XDH), aldehyde oxidase (AO) and sulfite oxidase (SOX). In Vitis vinifera cv. Merlot, molybdenum deficiency is common amongst vines grown on own roots in acidic soils often resulting in yield reductions. Foliar application of molybdenum sprays increases yield and remedies deficiency indicating that Merlot grown on own roots has a reduced capacity for molybdenum uptake from the soil. Molybdenum generally occurs as molybdate (MoO₄ ²⁻) within the soil solution. The mechanism(s) involved in molybdenum transport have recently been discovered in plants, although are well characterised within prokaryotic systems. Unfortunately, no homologues of prokaryotic genes involved in molybdate transport exist within eukaryotes. It has been suggested that molybdenum transport in plants may occur through other systems including sulfate transporters due to chemical similarities between sulfate and molybdate. A yeast functional complementation approach using a sulfate transport mutant was initially used to identify novel putative plant molybdenum transport proteins. A cDNA library derived from Pinot noir roots starved of molybdenum was screened for transporters. Unfortunately, no cDNAs were identified that met the requirements of a molybdenum transporter when screened on media containing low amounts of molybdenum. However, a number of putative cDNA’s partially complemented the yeast mutant YSD1, however none of these could be validated in second round screens. A candidate gene approach was then initiated to identify pre-characterised genes that may also have capacity to transport molybdenum. The plant sulfate transporter, SHST1, restored growth of YSD1 on media containing low amounts of molybdenum. Kinetic analysis using ⁹⁹MoO₄²⁻ to trace molybdenum transport in yeast cells demonstrated that SHST1 enhanced the uptake of molybdenum at nM concentrations. The uptake was not inhibited by sulfate, but the transport of sulfate was reduced with molybdenum. Further analysis demonstrated that SHST1 did prefer sulfate as the substrate but molybdenum could compete at higher concentrations. This result is the first measurement of molybdenum being transported through a pre characterised sulfate transport protein. Whole plant experiments using rooted grapevine cuttings and ⁹⁹MoO₄²⁻ to trace molybdenum movement into plants indicated that Merlot did not have reduced capacity to uptake molybdenum compared to other varieties that do not suffer from molybdenum deficiencies such as Chardonnay. When plants were grown with molybdenum, Merlot accumulated more molybdenum than Chardonnay, with the reverse being true when plants were grown without molybdenum. Similar experiments were performed on symbiosomes isolated from Glycine max grown with and without molybdenum. Symbiosomes absorbed more molybdenum when plants were grown without molybdenum. A field site was established to look at the molybdenum profiles within petioles against yield responses over a 3-year period. Molybdenum application did not increase the yield amongst vines despite all vines initially being deficient in molybdenum. There were no cumulative effects of molybdenum application over the trial, however, molybdenum did have limited translocation ability within the vine system. / http://proxy.library.adelaide.edu.au/login?url= http://library.adelaide.edu.au/cgi-bin/Pwebrecon.cgi?BBID=1318770 / Thesis (Ph.D.) -- University of Adelaide, School of Agriculture, Food and Wine, 2008

Molybdenum (Mo) is an essential micronutrient required by plants. It is biologically inactive until bound in a pterin compound named the molybdenum cofactor (Moco) that binds to apoproteins used in both reductive and oxidative reactions such as nitrate reductase (NR), xanthine dehydrogenase (XDH), aldehyde oxidase (AO) and sulfite oxidase (SOX). In Vitis vinifera cv. Merlot, molybdenum deficiency is common amongst vines grown on own roots in acidic soils often resulting in yield reductions. Foliar application of molybdenum sprays increases yield and remedies deficiency indicating that Merlot grown on own roots has a reduced capacity for molybdenum uptake from the soil. Molybdenum generally occurs as molybdate (MoO₄ ²⁻) within the soil solution. The mechanism(s) involved in molybdenum transport have recently been discovered in plants, although are well characterised within prokaryotic systems. Unfortunately, no homologues of prokaryotic genes involved in molybdate transport exist within eukaryotes. It has been suggested that molybdenum transport in plants may occur through other systems including sulfate transporters due to chemical similarities between sulfate and molybdate. A yeast functional complementation approach using a sulfate transport mutant was initially used to identify novel putative plant molybdenum transport proteins. A cDNA library derived from Pinot noir roots starved of molybdenum was screened for transporters. Unfortunately, no cDNAs were identified that met the requirements of a molybdenum transporter when screened on media containing low amounts of molybdenum. However, a number of putative cDNA’s partially complemented the yeast mutant YSD1, however none of these could be validated in second round screens. A candidate gene approach was then initiated to identify pre-characterised genes that may also have capacity to transport molybdenum. The plant sulfate transporter, SHST1, restored growth of YSD1 on media containing low amounts of molybdenum. Kinetic analysis using ⁹⁹MoO₄²⁻ to trace molybdenum transport in yeast cells demonstrated that SHST1 enhanced the uptake of molybdenum at nM concentrations. The uptake was not inhibited by sulfate, but the transport of sulfate was reduced with molybdenum. Further analysis demonstrated that SHST1 did prefer sulfate as the substrate but molybdenum could compete at higher concentrations. This result is the first measurement of molybdenum being transported through a pre characterised sulfate transport protein. Whole plant experiments using rooted grapevine cuttings and ⁹⁹MoO₄²⁻ to trace molybdenum movement into plants indicated that Merlot did not have reduced capacity to uptake molybdenum compared to other varieties that do not suffer from molybdenum deficiencies such as Chardonnay. When plants were grown with molybdenum, Merlot accumulated more molybdenum than Chardonnay, with the reverse being true when plants were grown without molybdenum. Similar experiments were performed on symbiosomes isolated from Glycine max grown with and without molybdenum. Symbiosomes absorbed more molybdenum when plants were grown without molybdenum. A field site was established to look at the molybdenum profiles within petioles against yield responses over a 3-year period. Molybdenum application did not increase the yield amongst vines despite all vines initially being deficient in molybdenum. There were no cumulative effects of molybdenum application over the trial, however, molybdenum did have limited translocation ability within the vine system. / http://proxy.library.adelaide.edu.au/login?url= http://library.adelaide.edu.au/cgi-bin/Pwebrecon.cgi?BBID=1318770 / Thesis (Ph.D.) -- University of Adelaide, School of Agriculture, Food and Wine, 2008

Molybdenum (Mo) is an essential micronutrient required by plants. It is biologically inactive until bound in a pterin compound named the molybdenum cofactor (Moco) that binds to apoproteins used in both reductive and oxidative reactions such as nitrate reductase (NR), xanthine dehydrogenase (XDH), aldehyde oxidase (AO) and sulfite oxidase (SOX). In Vitis vinifera cv. Merlot, molybdenum deficiency is common amongst vines grown on own roots in acidic soils often resulting in yield reductions. Foliar application of molybdenum sprays increases yield and remedies deficiency indicating that Merlot grown on own roots has a reduced capacity for molybdenum uptake from the soil. Molybdenum generally occurs as molybdate (MoO₄ ²⁻) within the soil solution. The mechanism(s) involved in molybdenum transport have recently been discovered in plants, although are well characterised within prokaryotic systems. Unfortunately, no homologues of prokaryotic genes involved in molybdate transport exist within eukaryotes. It has been suggested that molybdenum transport in plants may occur through other systems including sulfate transporters due to chemical similarities between sulfate and molybdate. A yeast functional complementation approach using a sulfate transport mutant was initially used to identify novel putative plant molybdenum transport proteins. A cDNA library derived from Pinot noir roots starved of molybdenum was screened for transporters. Unfortunately, no cDNAs were identified that met the requirements of a molybdenum transporter when screened on media containing low amounts of molybdenum. However, a number of putative cDNA’s partially complemented the yeast mutant YSD1, however none of these could be validated in second round screens. A candidate gene approach was then initiated to identify pre-characterised genes that may also have capacity to transport molybdenum. The plant sulfate transporter, SHST1, restored growth of YSD1 on media containing low amounts of molybdenum. Kinetic analysis using ⁹⁹MoO₄²⁻ to trace molybdenum transport in yeast cells demonstrated that SHST1 enhanced the uptake of molybdenum at nM concentrations. The uptake was not inhibited by sulfate, but the transport of sulfate was reduced with molybdenum. Further analysis demonstrated that SHST1 did prefer sulfate as the substrate but molybdenum could compete at higher concentrations. This result is the first measurement of molybdenum being transported through a pre characterised sulfate transport protein. Whole plant experiments using rooted grapevine cuttings and ⁹⁹MoO₄²⁻ to trace molybdenum movement into plants indicated that Merlot did not have reduced capacity to uptake molybdenum compared to other varieties that do not suffer from molybdenum deficiencies such as Chardonnay. When plants were grown with molybdenum, Merlot accumulated more molybdenum than Chardonnay, with the reverse being true when plants were grown without molybdenum. Similar experiments were performed on symbiosomes isolated from Glycine max grown with and without molybdenum. Symbiosomes absorbed more molybdenum when plants were grown without molybdenum. A field site was established to look at the molybdenum profiles within petioles against yield responses over a 3-year period. Molybdenum application did not increase the yield amongst vines despite all vines initially being deficient in molybdenum. There were no cumulative effects of molybdenum application over the trial, however, molybdenum did have limited translocation ability within the vine system. / http://proxy.library.adelaide.edu.au/login?url= http://library.adelaide.edu.au/cgi-bin/Pwebrecon.cgi?BBID=1318770 / Thesis (Ph.D.) -- University of Adelaide, School of Agriculture, Food and Wine, 2008

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