About 8 tons of dry undigested solid waste is generated by the MixAlco process for every 40 tons of food residue waste fed into the process. This MixAlco process produces liquid fuels and the sludge generated can be further converted into synthesis gas using the process of pyrolysis. The hydrogen component of the product synthesis gas may be separated by pressure swing adsorption and used in the hydrogenation of ketones into fuels and chemicals. The synthesis gas may also be catalytically converted into liquid fuels via the Fischer-Tropsch synthesis process. The auger-type pyrolyzer was operated at a temperature between 630-770 degrees C and at feed rates in the range of 280-374 g/minute. The response surface statistical method was used to obtain the highest syngas composition of 43.9 +/- 3.36 v % H2/33.3 +/- 3.29 v % CO at 740 degrees C. The CH4 concentration was 20.3 +/- 2.99 v %. For every ton of sludge pyrolyzed, 5,990 g H2 (719.3 MJ), 65,000 g CO (660 MJ) and 21,170 g CH4 (1055.4 MJ) were projected to be produced at optimum condition. At all temperatures, the sum of the energies of the products was greater than the electrical energy needed to sustain the process, making it energy neutral. To generate internal H2 for the MixAlco process, a method was developed to efficiently separate H2 using pressure swing adsorption (PSA) from the synthesis gas, with activated carbon and molecular sieve 5A as adsorbents. The H2 can be used to hydrogenate ketones generated from the MixAlco process to more liquid fuels. Breakthrough curves, cycle mass balances and cycle bed productivities (CBP) were used to determine the maximum hydrogen CBP using different adsorbent amounts at a synthesis gas feed rate of 10 standard lpm and pressure of 118 atm. A 99.9 % H2 purity was obtained. After a maximum CBP of 66 % was obtained further increases in % recovery led to a decrease in CBP. The synthesis gas can also be catalytically converted into liquid fuels by the Fischer-Tropsch synthesis (FTS) process. A Co-SiO2/Mo-Pd-Pt-ZSM-5 catalyst with a metal-metal-acid functionality was synthesized with the aim of increasing the selectivity of JP-8 (C10-C17) fuel range. The specific surface areas of the two catalysts were characterized using the BET technique. The electron probe microanalyzer (with WDS and EDS capabilities) was then used to confirm the presence of the applied metals Co, Mo, Pd and Pt on the respective supports. In addition to the gasoline (C4-C12) also produced, the synthesis gas H2:CO ratio was also adjusted to 1.90 for optimum cobalt performance in an enhanced FTS process. At 10 atm (150 psig) and 250 degrees C, the conventional FTS catalyst Co-SiO2 produced fuels rich in hydrocarbons within the gasoline carbon number range. At the same conditions the Co-SiO2-Mo-Pd-Pt/HZSM-5 catalyst increased the selectivity of JP-8. When Co-SiO2/Mo-Pd-Pt-HZSM-5 was used at 13.6 atm (200 psig) and 250 degrees C, a further increase in the selectivity of JP-8 and to some extent diesel was observed. The relative amounts of olefins and n-paraffins decreased with the products distribution shifting more towards the production of isomers.

The indiscriminate emission of CO2 is drastically aggravating climate change. Carbon Capture and Utilization (CCU) was born as a complementary solution to this issue. This thesis studies the consumption of carbon dioxide in industrial processes, starting from synthesis gas, and using this building block in subsequent syntheses; ultimately integrating CO2 utilization with previously non-CO2 consuming processes.

Autoignition characteristics of pre-vaporized iso-octane, primary reference fuels, gasolines, and dimethyl ether (DME) have been investigated experimentally in a coflow with elevated temperature of air. With the coflow air at relatively low initial temperatures below autoignition temperature Tauto, an external ignition source was required to stabilize the flame. Non-autoignited lifted flames had tribrachial edge structures and their liftoff heights correlated well with the jet velocity scaled by the stoichiometric laminar burning velocity, indicating the importance of the edge propagation speed on flame stabilization balanced with local flow velocity. At high initial temperatures over Tauto, the autoignited flames were stabilized without requiring an external ignition source. The autoignited lifted flames exhibited either tribrachial edge structures or Mild combustion behaviors depending on the level of fuel dilution. For the iso-octane and n-heptane fuels, two distinct transition behaviors were observed in the autoignition regime from a nozzle-attached flame to a lifted tribrachial-edge flame and then a sudden transition to lifted Mild combustion as the jet velocity increased at a certain fuel dilution level. The liftoff data of the autoignited flames with tribrachial edges were analyzed based on calculated ignition delay times for the pre-vaporized fuels. Analysis of the experimental data suggested that ignition delay time may be much less sensitive to initial temperature under atmospheric pressure conditions as compared with predictions. For the gasoline fuels for advanced combustion engines (FACEs), and primary reference fuels (PRFs), autoignited liftoff data were correlated with Research Octane Number and Cetane Number. For the DME fuel, planar laser-induced fluorescence (PLIF) of formaldehyde (CH2O) and CH* chemiluminescence were visualized qualitatively. In the autoignition regime for both tribrachial structure and mild combustion, formaldehyde were found mainly between the fuel nozzle and the lifted flame edge. On the other hand, they were formed just prior to the flame edge for the non-autoignited lifted flames. The effect of fuel pyrolysis and partial oxidation were found to be important in explaining autoignited liftoff heights, especially in the Mild combustion regime. Flame structures of autoignited flames were investigated numerically for syngas (CO/H2) and methane fuels. The simulations of syngas fuel accounting for the differential diffusion have been performed by adopting several kinetic mechanisms to test the models ability in predicting the flame behaviors observed previously. The results agreed well with the observed nozzle-attached flame characteristics in case of non-autoignited flames. For autoignited lifted flames in high temperature regime, a unique autoignition behavior can be predicted having HO2 and H2O2 radicals in a broad region between the nozzle and stabilized lifted flame edge. Autoignition characteristics of laminar nonpremixed methane jet flames in high- temperature coflow air were studied numerically. Several flame configurations were investigated by varying the initial temperature and fuel mole fraction. Characteristics of chemical kinetics structures for autoignited lifted flames were discussed based on the kinetic structures of homogeneous autoignition and flame propagation of premixed mixtures. Results showed that for autoignited lifted flame with tribrachial structure, a transition from autoignition to flame propagation modes occurs for reasonably stoichiometric mixtures. Characteristics of Mild combustion can be treated as an autoignited lean premixed lifted flame. Transition behavior from Mild combustion to a nozzle-attached flame was also investigated by increasing the fuel mole fraction.

Nano-scaled carbons were produced by thermal treatment of pine wood chips and bio-char. The influence of temperature, heating rate, pyrolysis time, and type and flow rate of purge gas on the production of nano-carbons was investigated. Using TEM and SEM, different carbon-based nanomaterials were observed in the prepared samples. The effect of metal ion doping on the bio-char was also investigated. Highly functionalized nano carbonaceous materials were synthesized by low temperature hydrothermal carbonization (HTC) using glucose, sucrose, xylose, and cellulose. Carbon-encapsulated iron (Fe@C) core-shell particles were also synthesized by the HTC method and used as catalyst for Fischer-Tropsch synthesis to produce liquid hydrocarbons from syngas; it showed excellent activity. Nano-structured Co-Mo carbides over several nano-sized carbon materials were prepared using the carbothermal reduction and carbothermal hydrogen reduction methods. Nano-structured Co-Mo carbides derived from Vulcan® XC-72 were used as the catalyst to produce higher alcohols.

Trace component analysis in gasification processes are important part of elemental component balances in order to understand the fate of these participating compounds in the feedstock. Residual traces in the raw synthesis gas after quench could bring about the poisoning of catalysts and corrosion effects on plant facilities. The objective of this work is to investigate the effects of quenching operation on the trace components during test campaigns of the autothermal non-catalytic reforming of natural gas (Gas-POX) mode in the HP POX (high pressure partial oxidation) test plant. In order to achieve this, Aspen Plus simulation model of the quench chamber of the HP POX test plant was developed to re-calculate the quench chamber input amount of different trace compounds from their output amount measured during test points of the Gas-POX campaigns. Variation in quench water temperatures from 130 °C to 220 °C and pH value of quench water as well as the resulting variation in Henry´s and Dissociation constant of the traces (CO2, H2S, NH3 and HCN) changed the distribution of traces calculated in the quench water. The formation of traces of organic acid (formic acid and acetic acid) and traces of BTEX, PAHs and soot in the quench water effluent were discussed. The discrepancies between equilibrium constant and reaction quotient (non-equilibrium or real) for the formation of NH3 and HCN at the exit of the gasifier were discussed. The assessment of the results in this work should lead to the improvement in the understanding of trace components and concepts that could be employed to influence their formation and reduction.

Trace component analysis in gasification processes are important part of elemental component balances in order to understand the fate of these participating compounds in the feedstock. Residual traces in the raw synthesis gas after quench could bring about the poisoning of catalysts and corrosion effects on plant facilities. The objective of this work is to investigate the effects of quenching operation on the trace components during test campaigns of the autothermal non-catalytic reforming of natural gas (Gas-POX) mode in the HP POX (high pressure partial oxidation) test plant. In order to achieve this, Aspen Plus simulation model of the quench chamber of the HP POX test plant was developed to re-calculate the quench chamber input amount of different trace compounds from their output amount measured during test points of the Gas-POX campaigns. Variation in quench water temperatures from 130 °C to 220 °C and pH value of quench water as well as the resulting variation in Henry´s and Dissociation constant of the traces (CO2, H2S, NH3 and HCN) changed the distribution of traces calculated in the quench water. The formation of traces of organic acid (formic acid and acetic acid) and traces of BTEX, PAHs and soot in the quench water effluent were discussed. The discrepancies between equilibrium constant and reaction quotient (non-equilibrium or real) for the formation of NH3 and HCN at the exit of the gasifier were discussed. The assessment of the results in this work should lead to the improvement in the understanding of trace components and concepts that could be employed to influence their formation and reduction.:List of Figures vii List of Tables xii List of Abbreviations and Symbols xiii 1 Introduction 1 1.1 Background 1 1.2 Objective of the Work 4 1.3 Overview of the Work 5 2 Process and test conditions 6 2.1 HP POX test plant 6 2.2 Test campaign procedure 8 2.2.1 Gas-POX operating parameter range 8 2.2.2 Gas-POX experiments 9 2.2.3 Net reactions of partial oxidation 9 2.3 Gaseous feedstock characterization 11 2.3.1 Natural gas feedstock composition 11 2.4 Analytical methods for gaseous products 12 2.4.1 Hot gas sampling 12 2.4.2 Raw synthesis gas analysis after quench 13 2.5 Aqueous phase product analysis 14 2.5.1 Molecularly dissolved trace compounds and their ions trace analysis 14 2.5.2 Other trace analysis 15 2.6 Limit of accuracy in measurement systems 15 2.7 Summary 17 3 Simulation and methods 18 3.1 Test points calculation of the HP POX test campaign 18 3.1.1 Aspen Plus model for HP POX quench water system 19 3.2 Gas-POX 201 VP1 quench water system model simulation by Aspen Plus 23 3.2.1 Measured and calculated input parameters 23 3.2.2 Calculated sensitivity studies of species and their distribution for test point (VP1) 24 3.3 Used calculation tools related to the work 25 3.3.1 VBA in Excel 25 3.3.2 Python as interface between Aspen Plus and Microsoft Excel 26 3.3.3 Aspen Simulation Workbook 27 3.4 Summary 29 4 Trace components in quench water system 30 4.1 Physico-chemical parameters of quench water 31 4.1.1 Quench water pH adjustment 32 4.1.2 Henry constant 34 4.1.3 Dissociation constant 35 4.1.4 Organic acids in quench water 38 4.2 Carbon dioxide (CO2) 39 4.2.1 Results of sensitivity study: quench water temperature variation effects on CO2 41 4.2.2 Results of sensitivity study: quench water pH variation influence on CO2 42 4.3 Nitrogen compounds 43 4.3.1 Ammonia (NH3) 44 4.3.2 Results of sensitivity study: quench water temperature variation effects on NH3 46 4.3.3 Results of sensitivity study: quench water pH variation influence on NH3 47 4.3.4 Hydrogen Cyanide (HCN) 48 4.3.5 Results of sensitivity study: quench water temperature variation effects on HCN 50 4.3.6 Results of sensitivity study: quench water pH variation influence on HCN 50 4.4 Sulphur compounds: H2S 51 4.4.1 Results of sensitivity study: quench water temperature variation effects on H2S 53 4.4.2 Results of sensitivity study: quench water pH variation influence on H2S 54 4.5 Summary 55 5 Organic acids trace studies in quench water 57 5.1 Organic acids interaction with ammonia compounds in the quench water 57 5.2 Formic acid 62 5.2.1 Trace of formic acid in quench water 64 5.3 Acetic acid 67 5.3.1 Trace of acetic acid in quench water 69 5.4 Summary 72 6 Temperature approach studies for NH3 and HCN formation in gasifier 74 6.1 Nitrogen compounds: NH3 and HCN 74 6.2 Ammonia (NH3) formation in the gasifer 77 6.3 Hydrogen cyanide (HCN) formation in the gasifier 79 6.4 Discrepancies between back-calculated reaction quotients and equilibrium constants of the NH3 formation 81 6.4.1 Case 1: calculated equilibrium distribution between N2, NH3 and HCN 81 6.4.2 Case 2: calculated equilibrium distribution between NH3 and HCN 83 6.5 Summary 84 7 Traces of BTEX, PAHs and soot in quench water 86 7.1 Quench water behaviour 87 7.2 BTEX compounds 88 7.2.1 BTEX in quench water effluent 90 7.3 PAH compounds 93 7.3.1 PAHs in quench water effluent 95 7.4 Soot formation 99 7.4.1 Soots in quench water effluent 101 7.5 Summary 102 8 Summary and outlook 103 Bibliography 106 9 Appendix 135 List of Figures Figure 2.1: HP POX test plant main facility components and material flow courtesy of [Lurgi GmbH, 2008] 6 Figure 2.2: Simplified scheme of HP POX plant (including quench system) [Lurgi GmbH, 2008] 7 Figure 2.3: Overview of reactions of methane 10 Figure 3.1: Simplified scheme for HP POX quench water system 18 Figure 3.2: Aspen Plus flow diagrams of simulated HP POX quench water system 19 Figure 3.3: Integration of information and functions in VBA via Microsoft Excel to Aspen Plus model 25 Figure 3.4: Integration of information and functions in Python via Microsoft Excel to Aspen Plus model 26 Figure 3.5: ASW enables Excel users to rapidly run scenarios using the underlying rigorous models to analyze plant data, monitor performance, and make better decisions. 27 Figure 4.1: Vapour-liquid equilibria system of CO2, H2S, NH3, HCN and organic acids in the quench water and extended mechanisms according to [Kamps et al., 2001], [Alvaro et al., 2000], [Kuranov et al., 1996], [Xia et al., 1999] and [Edwards et al., 1978]. 30 Figure 4.2: HP POX quench water system with pH regulator for sensitivity studies 34 Figure 4.3: Henry´s constant for CO2, H2S, NH3 and HCN derived from [Edwards et al., 1978] for CO2, [Alvaro et al., 2000] for NH3, [Kamps et al., 2001] for H2S, and [Rumpf et al., 1992] for HCN 35 Figure 4.4: Dissociation constants for CO2, H2S, NH3, HCN and H2O derived from [Alvaro et al., 2000], [Kamps et al., 2001], and [Edwards et al., 1978] 37 Figure 4.5: The flow of CO2 in the quench water cycle (test point VP1). 40 Figure 4.6: Calculated quench water temperature variation and effects on CO2 distribution 42 Figure 4.7: Calculated influence of pH regulation and effects on CO2 distribution 43 Figure 4.8: The flow of NH3 in the quench water cycle (test point VP1). 46 Figure 4.9: Calculated quench water temperature variation and effects on NH3 distribution 47 Figure 4.10: Calculated influence of pH regulation and effects on NH3 distribution 48 Figure 4.11: The flow of HCN in the quench water cycle (test point VP1). 49 Figure 4.12: Calculated quench water temperature variation and effects on HCN distribution 50 Figure 4.13: Calculated influence of pH regulation and effects on HCN distribution 51 Figure 4.14: The flow of H2S in the quench water cycle (test point VP1) 53 Figure 4.15: Calculated quench water temperature variation and effects on H2S distribution 54 Figure 4.16: Calculated influence of pH regulation and effects on H2S distribution 55 Figure 5.1: Aspen Plus back-calculated (real) formic acid concentration, quench water temperature and the calculated equilibrium formic acid concentration against back-calculated (real) ammonia concentration for the 47 test points (using amongst others sampled HCOO- and NH4+ values according to Table 2.6). 59 Figure 5.2: Aspen plus back-calculated (real) formic acid concentration, back-calculated (real) ammonia concentration and the calculated equilibrium formic acid concentration against quench water temperature for the 47 test points (using amongst others sampled HCOO- and NH4+ values according to Table 2.6). 60 Figure 5.3: Aspen plus back-calculated (real) acetic acid concentration, quench water temperature and the calculated equilibrium acetic acid concentration against back-calculated (real) ammonia concentration for the 47 test points. 61 Figure 5.4: Aspen plus back-calculated (real) acetic acid concentration, back-calculated (real) ammonia concentration and the calculated equilibrium acetic acid concentration against quench water temperature for the 47 test points. 62 Figure 5.5: Concentration of formic acid (Aspen plus calculated m_eq and back-calculted m_real) formation in the quench and quench water temperature for the 47 test points. 64 Figure 5.6: Concentration of formic acid (Aspen plus calculated m_eq and back-calculted m_real) in the quench against quench water temperature for the 47 test points (as in Fig.5.2). 65 Figure 5.7: Comparison between formic acid equilibrium constant (Keq), reaction quotient (Kreal) and the quench water temperature for the 47 test points. 66 Figure 5.8: Comparison between formic acid equilibrium constant (Keq) and reaction quotient (Kreal) against quench water temperatures for the 47 test points. 67 Figure 5.9: Concentration of acetic acid (Aspen plus calculated m_eq and back-calculted m_real) in the quench and quench water temperature for the 47 test points. 69 Figure 5.10: Concentration of acetic acid (Aspen plus calculated m_eq and back-calculted m_real) in the quench against quench water temperature for the 47 test points (as in Fig.5.4). 70 Figure 5.11: Comparison between acetic acid equilibrium constant (Keq), reaction quotient (Kreal) and the quench water temperature for the 47 test points. 71 Figure 5.12: Comparison between acetic acid equilibrium constant (Keq) and reaction quotient (Kreal) against quench water temperatures for the 47 test points. 72 Figure 6.1: Mole fraction of gas compoents in the hot gas outlet out of gasifier against hot gas temperature for the 47 test points 76 Figure 6.2: Calculated reaction quotient (Q) and equlibrium constant (Keq) for NH3 against hot gas temperature for the 47 test points (see Fig. 9.10 in Appendix) 77 Figure 6.3: NH3 temperature approach against hot gas temperature for the 47 test points (see Fig. 9.11 in Appendix) 78 Figure 6.4: Calculated reaction quotient (Q) and equlibrium constant (Keq) for HCN against hot gas temperature for the 47 test points (see Fig. 9.13 in Appendix) 79 Figure 6.5: HCN temperature approach against hot gas temperature for the 47 test points (see Fig. 9.14 in Appendix) 80 Figure 6.6: Comparison between calculated real and equilibrium hot gas N2, NH3 and HCN mol fractions against their respective hot gas temperature (case 1). 82 Figure 6.7: Relations between back-calculated real and equilibrium hot gas N2, NH3 and HCN mol fractions (for chemical equilibrium according to equations (6.1) and (6.4)) against their respective hot gas temperature (see Case 1, Section 6.4.1, and Fig. 6.6) 82 Figure 6.8: Comparison between calculated real and equilibrium hot gas HCN mol fraction against their respective hot gas temperature (case 2). 83 Figure 6.9: Relations between back-calculated real and equilibrium hot gas HCN mol fractions, and change in NH3 mol fractions (for chemical equilibrium according to equation (6.4)), against their respective hot gas temperature (see. Case 2, Section 6.4.2 and Fig. 6.7) 84 Figure 6.10 Comparison between NH3 and HCN formation (mole fraction) calculated equilibrium constant (Keq) and calculated reaction quotient (Q), N2 consumption and hot gas temperatures for the 47 test points (case 1 and case 2). 85 Figure 7.1: HP POX test plant quench water system 88 Figure 7.2: Traces of BTEX measured in the Gas-POX 203 – 207 quench water effluent sample. 91 Figure 7.3: Individual component of BTEX measured in the Gas-POX 203 – 207 quench water effluent sample. 92 Figure 7.4: (a) Alkyl radical decomposition and (b) C1 and C2 hydrocarbons oxidation mechanism [Warnatz et al., 2000] 93 Figure 7.5: Recombination of C3H3 to form benzene 94 Figure 7.6: The Diels - Alder reaction for the formation of PAHs 95 Figure 7.7: Amount of PAHs that were detected in Gas-POX 203 – 207 test points quench water effluent samples. 97 Figure 7.8: Distribution of PAH compounds in Gas-POX 203 – 207 quench water effluent samples. 98 Figure 7.9: Some steps in soot formation [McEnally et al., 2006]. 99 Figure 7.10: Illustration of soot formation path in homogenous mixture [Bockhorn et al., 1994] 100 Figure 9.1: Aspen flow sheet set up for HP POX quench system GasPOX 201 VP1 (simplified and extension of Fig. 3.2, organic acids not taken into account). Tabulated values are given in Table 9.11. 135 Figure 9.2: Comparison between the Henry´s constant profiles: Aspen Plus (markers) and Literatures (solid lines) ([Edwards et al., 1978] for CO2, [Alvaro et al., 2000] for NH3, [Kamps et al., 2001] for H2S, and [Rumpf et al., 1992] for HCN as it can be seen in Fig. 4.3) 137 Figure 9.3: Henry´s constant profiles derived from literatures ([Edwards et al., 1978] for CO2, [Alvaro Pérez-Salado et al., 2000] for NH3, [Kamps et al., 2001] for H2S, and [Rumpf et al., 1992] for HCN as it can be seen in Fig. 4.3) 137 Figure 9.4: Comparison between the dissociation constant profiles: Aspen Plus (markers) and Literatures (solid or dashed lines) [Alvaro et al., 2000], [Kamps et al., 2001], and [Edwards et al., 1978] as in Fig.4.4. 138 Figure 9.5: Dissociation constant profiles derived from literatures [Kamps et al., 2001], and [Edwards et al., 1978] as in Fig.4.4. 138 Figure 9.6: Calculated pH values, temperature range and species 139 Figure 9.7: Aspen Plus flow sheet setup for organic acid compounds calculations (GasPOX 201 VP1, see also Table 9.12) 142 Figure 9.8: Aspen Plus flow sheet setup for nitrogen compounds calculations (GasPOX 201 VP1, see also Table 9.12, organic acids are taken into account in the aqueous streams of the quench system) 145 Figure 9.9: Yield of ammonia in gasifier (calculated real) and hot gas temperature against the 47 test points 146 Figure 9.10: Kreal or reaction quotient for ammonia formation in the gasifier against the 47 test points. 146 Figure 9.11: Temperature approach studies for ammonia and the 47 test points 147 Figure 9.12: Yield of HCN from the gasifier (calculated real and equilibrium) and hot gas temperature and the 47 test points 147 Figure 9.13: Comparison between equilibrium constant and reaction quotient for HCN and 47 test points 148 Figure 9.14: Temperature approach studies for HCN and the 47 test points 148 Figure 9.15: Comparison among equilibrium constants of reactions against temperature, T [°C] 149 Figure 9.16: Comparison among equilibrium constants of reactions against temperature, 1/T [1/K] 150 List of Tables Table 2.1: Outline of Gas-POX mode operating parameter range 8 Table 2.2: Outline of test runs operating mode and parameters of chosen test campaigns 9 Table 2.3: Natural gas feedstock compositions 12 Table 2.4: Product synthesis gas analysis method (hot gas before quench) [Brüggemann, 2010] 12 Table 2.5: Analysis methods for raw synthesis gas [Brüggemann, 2010] 13 Table 2.6: Analysis methods for aqueous phase products [Brüggemann, 2010] 14 Table 2.7: Relative accuracy for the measured value for temperature, pressure and flow of each feed and product stream [Meyer, 2007] and [Brüggemann, 2010] 17 Table 3.1: Description of blocks used in Aspen Plus simulation. 20 Table 3.2: HP POX test plant quench water cycle parameters Gas-POX 201 VP1* 23 Table 3.3: pH regulator parameters 24 Table 4.1: Organic acids distribution in streams for VP1 based on calculation from Aspen Plus. 38 Table 4.2: The distribution of CO2 and its ions in all the streams 40 Table 4.3: The distribution of NH3 and its ions in all the streams 45 Table 4.4: The distribution of HCN and its ions in all the streams 49 Table 4.5: The distribution of H2S and its ions in all the streams 52 Table 7.1: Relative sooting tendency [Tesner et al., 2010] 101 Table 9.1: Natural gas feed analysis method [Brüggemann, 2010] 135 Table 9.2: pH scale with examples of solution [NALCO 2008] 136 Table 9.3: Gas-POX test campaigns and with designated serial numbers 140 Table 9.4: Summary of correlation coefficient (r) from Figures in Chapter 5 144 Table 9.5: Comparison among reactions temperatures and heat of reactions 149 Table 9.6: Content of BTEX compounds in Gas-POX quench water samples 151 Table 9.7: BTEX in quench water effluent samples results 152 Table 9.8: Content of PAH compounds in Gas-POX quench water samples 157 Table 9.9: PAHs in quench water effluent samples results 160 Table 9.10: Soot in quench water effluent samples results 169 Table 9.11: Aspen Plus flow sheet setup stream details (GasPOX 201 VP1, according to Fig.3.2 and Fig.9.1, organic acids not taken into account) 170 Table 9.12: Aspen Plus flow sheet setup for organic acid and nitrogen compounds calculations for GasPOX 201 VP1 (according to Figures 9.7 and 9.8, organic acids are taken into account) 174

IPCC reported in its climate change report 2013 that the atmospheric concentrations of the greenhouse gases (GHG) carbon dioxide (CO2), methane, and nitrous oxide now have reached the highest levels in the past 800,000 years. CO2 concentration has increased by 40% since pre-industrial times and the primary source is fossil fuel combustion. It is vital to reduce anthropogenic emissions of GHGs in order to combat climate change. Industry accounts for 20% of global anthropogenic CO2 emissions and the iron and steel industry accounts for 30% of industrial emissions. The iron and steel industry is at date highly dependent on fossil fuels and electricity. Energy efficiency measures and substitution of fossil fuels with renewable energy would make an important contribution to the efforts to reduce emissions of GHGs. This thesis studies energy efficiency measures and fuel substitution in the iron and steel industry and focuses on recovery and utilisation of excess energy and substitution of fossil fuels with biomass. Energy systems analysis has been used to investigate how changes in the iron and steel industry’s energy system would affect the steel plant’s economy and global CO2 emissions. The thesis also studies energy management practices in the Swedish iron and steel industry with the focus on how energy managers think about why energy efficiency measures are implemented or why they are not implemented. In-depth interviews with energy managers at eleven Swedish steel plants were conducted to analyse energy management practices. In order to show some of the large untapped heat flows in industry, excess heat recovery potential in the industrial sector in Gävleborg County in Sweden was analysed. Under the assumptions made in this thesis, the recovery output would be more than three times higher if the excess heat is used in a district heating system than if electricity is generated. An economic evaluation was performed for three electricity generation technologies for the conversion of low-temperature industrial excess heat. The results show that electricity generation with organic Rankine cycles and phase change material engines could be profitable, but that thermoelectric generation of electricity from low-temperature industrial excess heat would not be profitable at the present stage of technology development. With regard to fossil fuels substituted with biomass, there are opportunities to substitute fossil coal with charcoal in the blast furnace and to substitute liquefied petroleum gas (LPG) with bio-syngas or bio synthetic natural gas (bio-SNG) as fuel in the steel industry’s reheating furnaces. However, in the energy market scenarios studied, substituting LPG with bio-SNG as fuel in reheating furnaces at the studied scrap-based steel plant would not be profitable without economic policy support. The development of the energy market is shown to play a vital role for the outcome of how different measures would affect global CO2 emissions. Results from the interviews show that Swedish steel companies regard improved energy efficiency as important. However, the majority of the interviewed energy managers only worked part-time with energy issues and they experienced that lack of time often was a barrier for successful energy management. More efforts could also be put into engaging and educating employees in order to introduce a common practice of improving energy efficiency at the company. / Halterna av växthusgaserna koldioxid (CO2), metan och kväveoxider har under de senaste 800 000 åren aldrig varit högre i atmosfären än vad de är idag. Detta resultat redovisades i IPCCs klimatrapport år 2013. CO2-koncentrationen har ökat med 40 % sedan förindustriell tid och denna ökning beror till största delen på förbränning av fossila bränslen. Ökade koncentrationer av växthusgaser leder till högre global medeltemperatur vilket i sin tur resulterar i klimatförändringar.  För att bromsa klimatförändringarna är det viktigt att vi arbetar för att minska utsläppen av växthusgaser. Industrin står för 20 % av de globala utsläppen av CO2 och järn- och stålindustrin står för 30 % av industrins utsläpp. Järn- och stålindustrin är i dag till stor del beroende av fossila bränslen och el för sin energiförsörjning. Energieffektiviseringsåtgärder och byte av fossila bränslen mot förnybar energi i järn- och stålindustrin skulle kunna bidra till minskade utsläpp av växthusgaser. Denna avhandling studerar åtgärder för effektivare energianvändning och möjligheter för bränslebyte i järn- och stålindustrin. Avhandlingen fokuserar på återvinning och utnyttjande av överskottsenergier och ersättning av fossila bränslen med biomassa. Energisystemanalys har använts för att undersöka hur förändringar i järn- och stålindustrins energisystem skulle påverka ekonomin och de globala utsläppen av CO2. Avhandlingen studerar också betydelsen av energiledning och nätverkande för att uppnå en effektivare energianvändning. Fokus har här varit på att studera hur energiansvariga resonerar kring varför energieffektiviseringsåtgärder genomförs eller varför de inte genomförs. Djupintervjuer med energiansvariga vid elva svenska stålverk genomfördes för att analysera denna fråga. För att ge ett exempel på den stora outnyttjade potentialen av överskottsvärme från industrin analyserades potentialen i Gävleborgs län. Möjligheterna att använda överskottsvärmen som fjärrvärme eller för att producera el analyserades. Här visar resultaten att fjärrvärmeproduktionen skulle bli mer än tre gånger så stor som elproduktionen. En ekonomisk utvärdering gjordes där tre tekniker för produktion av el från lågtempererad industriell överskottsvärme jämfördes. Resultaten visar att elproduktion med organisk Rankine-cykel eller en så kallad fasändringsmaterialmotor kan vara lönsam, men att termoelektrisk elproduktion inte är lönsam med dagens teknik och prisnivåer. Det är möjligt att ersätta en del av det fossila kolet i masugnen med träkol och på detta sätt introducera förnybar energi i stålindustrin. Man kan också ersätta gasol som används som bränsle i stålindustrins värmningsugnar med syntesgas eller syntetisk naturgas (SNG) som produceras genom förgasning av biomassa. Under de antaganden som gjorts i avhandlingen skulle det dock inte vara lönsamt för det skrotbaserade stålverk som studerats att ersätta gasolen med bio-SNG. För att uppnå lönsamhet behövs i detta fall ekonomiska styrmedel. Hur olika åtgärder påverkar de globala utsläppen av CO2 beror till stor del på hur framtidens energimarknad ser ut. Elproduktion från industriell överskottsvärme skulle minska de globala CO2-utsläppen i alla scenarier som studerats, men för de andra åtgärderna varierar resultaten beroende på vilka antaganden som gjorts. Resultaten från intervjustudien visar att svensk stålindustri anser att energifrågan är viktig, men det finns fortfarande mycket att göra för att effektivisera energianvändningen i denna sektor. Flera av de intervjuade arbetade bara deltid med energifrågor och de upplevde att tidsbrist hindrade dem från ett effektivt energiledningsarbete. En rekommendation till företagen är därför att anställa en energiansvarig på heltid och/eller fler personer som kan arbeta med energifrågor. Det bör också läggas mer resurser på att engagera och utbilda anställda för att på så sätt introducera en företagskultur som främjar effektiv energianvändning.

The current work, through experimental and numerical investigations, analyses the process and cycle level deviations in engine response on fuelling multi-cylinder natural gas engines with producer gas. Producer gas is a low calorific value bio-derived alternative with composition of 19 ± 1% CO and H2, 2 ± 0.5 % CH4, 12 ± 1% CO2 and 46 ± 1% N2 and has thermo-physical properties significantly different from natural gas. Experimental investigations primarily address the energy balance (full cycle analysis) and in-cylinder response (process specific analysis) at various operating conditions covering naturally aspirated and turbocharged mode of operation with natural gas and producer gas. Numerical investigations are based on two thermodynamic scope mathematical models, a zero dimensional model (Wiebe function) and a quasi-dimensional model (propagating flame front heat release). A detailed diagnostic analysis on a six cylinder (E6) indicates, turbocharger mismatch, the first explicit impact of fuel thermo-physical property variation. Turbocharger matching and optimization resulted in a peak load of 72.8 kWe (BMEP 9.47) at a maximum brake torque ignition angles of 22 deg before TDC and compressor pressure ratio of 2.25. Engine energy distribution analysis indicates skewed energy balance with higher cooling load (in excess of 30%) as compared to fossil fuel operation. This is attributed to the presence of nearly 20% H2 which enhances the convective cooling through the higher thermal conductivity. Parametric variation of H2 fraction on a two cylinder engine (E2) with four different syngas compositions (mixture H2 varying from 7.1% to 14.2%) depicts enhanced cooling load from 33.5% to 37.7%. Process level comparison indicates significant deviations in the heat release profile compared to fossil fuels. It has been observed that with an increase in mixture hydrogen fraction (from 7.1% to 14.2%), the fast burn phase combustion duration reduces from 59.6% to 42.6% but the terminal stage duration increases from 25.5% to 48.9%. The enhanced cooling of the mixture (due to the presence of hydrogen), particularly in the vicinity of walls is argued to contribute towards the sluggish terminal phase combustion. Immediate implication of thermo-kinematic response variation is on the magnitude and sensitivity of combustion descriptors and the need for dependent control system calibration for producer gas fuelled operation is established. Descriptor analysis is extended to knocking pressure traces and a new simple methodology is proposed towards identifying the occurrence and regime of knock. Analysing the implications through numerical investigation, the influence of the altered thermo-kinematic response for producer gas fuelled operation impacts 0D simulations. Zero dimensional simulations fail with conventional coefficients requiring fuel specific coefficients. Based on fuel specific coefficients, the suitability of 0D model for the simulation of varying operating conditions ranging from naturally aspirated to turbo charged engines, compression ratios and different engine geometries is established. The analysis is extended to quasi-dimensional through the eddy entrainment and laminar burn up model. The choice of laminar flame speed and turbulent parameters is validated based on the assessment of the flame speed ratio (4.5 ± 0.5 for naturally aspirated operation, turbulent Reynolds number of 2500 ± 250 and 9.0 ± 1.0 for turbocharged operation, turbulent Reynolds number of 5250 ± 250). In the estimation of laminar flame speed, the limitation of GRIMech 3.0 mechanism for H2-CO-CH4 systems is explicitly established and GRIMech 2.11 is used to arrive at experimentally comparable results. In-cylinder engine simulation results covering parametric variation of load, ignition angle and mixture quality, for engine natural gas fuelled naturally aspirated operation and producer gas fuelled naturally aspirated and turbocharged after cooled are compared with experimental results. The quasi dimensional analysis is extended to simulate end gas auto-ignition and is validated by using experimental manifold conditions for turbocharged operation for which knock has been observed. Extending the model to a Waukesha cooperative fuels research engine, motor methane number of 110 is reported for standard composition producer gas. The use of quasi dimensional models with end gas reaction kinetics enabled for knock rating of fuels represents first of its kind initiative.

The present work focuses on the study of biomass gasification process for generating hydrogen rich synthetic gas with oxy-steam as reactants using experiments and modeling studies. Utilization of the syngas as a fuel in general applications like fuel cells, Fischer-Tropsch FT) process and production of various chemicals like DME, etc. are being considered to meet the demand for clean energy. This study comprises of experiments using an open top down draft reactor with oxygen and steam as reactants in the co-current configuration. Apart from the standard gasification performance evaluation; parametric study using equivalence ratio, steam-to-biomass ratio as major variables towards generation of syngas is addressed towards controlling H2/CO ratio. The gasification process is modeled as a packed bed reactor to predict the exit gas composition, propagation rate, bed temperature as a function of input reactants, temperature and mass flux with variation in thermo-physical properties of biomass. These results are compared with the present experiments as well as those in literature. Experiments are conducted using modified open top downdraft configuration reactor with lock hoppers and provision for oxy-steam injection, and the exit gas is connected to the cooling and cleaning system. The fully instrumented system is used to measure bed temperatures, steam and exit gas temperature, pressures at various locations, flow rates of fuel, reactants and product gas along with the gas composition. Preliminary investigations focused on using air as the reactant and towards establishing the packed bed performance by comparing with the experimental results from the literature and extended the study to O2-N2 mixtures. The study focuses on determining the propagation rate of the flame front in the packed bed reactor for various operating conditions. O2 is varied between 20-100% (vol.) in a mixture of O2-N2 to study the effect of O2 fraction on flame propagation rate and biomass conversion. With the increase in O2 fraction, the propagation rates are found to be very high and reaching over 10 mm/s, resulting in incomplete pyrolysis and poor biomass conversion. The flame propagation rate is found to vary with oxygen volume fraction as XO22.5, and stable operation is achieved with O2 fraction below 30%. Towards introducing H2O as a reactant for enhancing the hydrogen content in the syngas and also to reduce the propagation rates at higher ER, wet biomass is used. Stable operating conditions are achieved using wet biomass with moisture-to-biomass (H2O:Biomass) ratio between 0.6 to 1.1 (mass basis) and H2 yield up to 63 g/kg of dry biomass amounting to 33% volume fraction in the syngas. Identifying the limitation on the hydrogen yield and the criticality of achieving high quality gas; oxy-steam mixture is introduced as reactants with dry biomass as fuel. An electric boiler along with a superheater is used to generate superheated steam upto 700 K and pressure in the range of 0.4 MPa. Steam-to-biomass ratio (SBR) and ER is varied with towards generating hydrogen rich syngas with sustained continuous operation of oxy-steam gasification of dry biomass. The results are analysed with the variation of SBR for flame propagation rates, calorific value of product syngas, energy efficiency, H2 yield per kg of biomass and H2/CO ratio. Hydrogen yield of 104 g per kg of dry casuarina wood is achieved amounting to 50.5% volume fraction in dry syngas through oxy-steam gasification process compared to air gasification hydrogen yield of about 40 g per kg of fuel and 20% volume fraction. First and second law analysis for energy and exergy efficiency evaluation has been performed on the experimental results and compared with air gasification. Individual components of the energy input and output are analysed and discussed. H2 yield is found to increase with SBR with the reduction in energy density of syngas and also energy efficiency. Highest energy efficiency of 80.3% has been achieved at SBR of 0.75 (on molar basis) with H2 yield of 66 g/kg of biomass and LHV of 8.9 MJ/Nm3; whereas H2 yield of 104 g/kg of biomass is achieved at SBR of 2.7 with the lower efficiency of 65.6% and LHV of 7.4 MJ/Nm3. The energy density of the syngas achieved in the present study is roughly double compared to the LHV of typical product gas with air gasification. Elemental mass balance technique has been employed to identify carbon boundary at an SBR of 1.5. Controlling parameters for arriving at the desired H2/CO ratio in the product syngas have been identified. Optimum process parameters (ER and SBR) has been identified through experimental studies for sustained continuous oxy-steam gasification process, maximizing H2 yield, controlling the H2/CO ratio, high energy efficiency and high energy density in the product syngas. Increase in ER with SBR is required to compensate the reduction in O2 fraction in oxy-steam mixture and to maintain the desired bed temperature in the combustion zone. In the range of SBR of 0.75 to 2.7, ER requirement increases from 0.18 to 0.3. The sustained continuous operation is possible upto SBR of 1.5, till the carbon boundary is reached. Operating at high SBR is required for high H2 yield but sustained highest H2 yield is obtained as SBR of 1.5. H2/CO ratio in the syngas increases from 1.5 to 4 with the SBR and depending on the requirement of the downstream process (eg., FT synthesis), suitable SBR and ER combination is suggested. To obtain high energy density in syngas and high energy efficiency, operations at lower SBR is recommended. The modeling study is the extension of the work carried by Dasappa (1999) by incorporating wood pyrolysis model into the single particle and volatile combustion for the packed bed of particles. The packed bed reactor model comprises of array of single particles stacked in a vertical bed that deals with the detailed reaction rates along with the porous char spheres and thermo-physical phenomenon governed by the mass, species and energy conservation equations. Towards validating the pyrolysis and single particle conversion process, separate analysis and parametric study addressing the effects of thermo-physical parameters like particle size, density and thermal conductivity under varying conditions have been studied and compared with the available results from literature. It has been found that the devolatilisation time of particle (tc) follows closely the relationship with the particle diameter (d), thermal conductivity (k), density () and temperature (T) as: The complete combustion of a single particle flaming pyrolysis and char combustion has been studied and validated with the experimental results. For the reactor modeling, energy, mass and species conservation equations in the axial flow direction formulate the governing equations coupled to the detailed single particle analysis. Gas phase reactions involving combustion of volatiles and water gas shift reaction are solved in the packed bed. The model results are compared with the experimental results from wood gasification system with respect to the propagation rate, conversion times, exit gas composition and other bed parameters like conversion, peak bed temperatures, etc. The propagation rates compare well with experimental data over a range of oxygen concentration in the O2- N2 mixture, with a peak at 10 mm/s for 100 % O2. In the case of oxy-steam gasification of dry biomass, the results clearly suggest that the char conversion is an important component contributing to the bed movement and hence the overall effective propagation rate is an important parameter for co-current reactors. This is further analyzed using the carbon boundary points based on elemental balance technique. The model predictions for the exit gas composition from the oxy-steam gasification matches well with the experimental results over a wide range of equivalence ratio and steam to biomass ratio. The output gas composition and propagation rates are found to be a direct consequence of input mass flux and O2 fraction in oxy-steam mixture. The present study comprehensively addresses the oxy-steam gasification towards generating hydrogen rich syngas using experimental and model studies. The study also arrives at the parameters for design consideration towards operating an oxy-steam biomass gasification system. The following flow chart provides the overall aspects that are covered in the thesis chapter wise.

[ES] El panorama industrial actual se enfrenta a desafíos significativos mientras transita hacia la descarbonización y la sostenibilidad, impulsado por el imperativo de lograr emisiones netas cero para 2050. Se espera una importante contribución hacia este objetivo al conectar materias primas no convencionales y renovables, alternativas a los materiales fósiles convencionales como el petróleo, a las cadenas de valor existentes de la industria química. Actualmente, existe un creciente interés industrial en la producción de nitrilos de cadena corta como HCN y acetonitrilo, mientras que se espera que las tasas de demanda global disminuyan en los próximos años en el caso del acrilonitrilo. Como reemplazo para materias primas convencionales para la producción de nitrilos, como las olefinas ligeras C2-3 de origen fósil, el desarrollo de rutas de conversión selectivas a partir de bloques de construcción C1 renovables, como el bio/e-syngas o su derivado metanol, y precursores N1 renovables, como el amoníaco verde, proporciona rutas hacia los productos químicos nitrilos, prospectivamente con una huella de carbono más baja. La presente tesis desarrolla y estudia catalizadores sólidos capaces de dirigir simultáneamente reacciones de acoplamiento C-N y C-C para la producción de nitrilos alifáticos C2+, particularmente acetonitrilo. Se hace hincapié en desvelar la naturaleza y estructura del verdadero catalizador activo, que se desarrolla bajo las condiciones del proceso. Específicamente, la tesis estudia efectos promocionales provocados por la combinación de dos metales en compuestos intersticiales mixtos de metales, aleaciones y compuestos intermetálicos. En primer lugar, se realizan estudios catalíticos y teóricos complementarios de Teoría del Funcional de la Densidad (DFT) sobre la conversión de mezclas de amoníaco (N1) y gas de síntesis (C1, CO+H2) a acetonitrilo con un (pre)catalizador monometálico MoO3. Estos estudios demuestran que MoN1-x, que se desarrolla mediante nitridación superficial, es el catalizador activo real y sugieren que la activación disociativa de HCN, asistida por oxígeno, es el paso controlante de la cinética de formación de acetonitrilo. A continuación, se estudian efectos promocionales de metales de transición divalentes de primera fila en catalizadores basados en molibdeno, utilizando un conjunto de compuestos de molibdato mixto cristalino, estructuralmente análogos, como precursores de catalizador. El dopado con Mn (Mn:Mo ~1) proporciona un catalizador particularmente selectivo y estable para la síntesis de acetonitrilo a partir de mezclas de NH3/gas de síntesis, logrando una tasa de formación de acetonitrilo de 50·10-3 mmol gcat-1 min-1 a 723K. Un conjunto de métodos in situ y operando con sensibilidad bulk y superficial, proporcionan evidencias de que un oxinitruro mixto MnM, con una simetría Fm-3m, y rico en defectos estructurales, representa el catalizador activo. Se sugiere que la mayor oxofilia del oxinitruro mixto MnMo, junto con el papel clave del oxígeno superficial para la activación disociativa de HCN, subyacen al efecto sinérgico de ambos metales. Finalmente, se estudió la conversión de mezclas en fase vapor de metanol (C1) y amoníaco (N1) a compuestos nitrogenados sobre nanocristales bimetálicos GaNi soportados en SiO2. Las aleaciones desordenadas de GaNi (Ga/(Ga+Ni)< 20%) son particularmente selectivas hacia la síntesis de nitrilos, mientras que los compuestos intermetálicos GaNi (Ga/(Ga+Ni)> 40%) catalizan principalmente la aminación de metanol a metilaminas. La difracción de rayos X y espectroscopía de absorción de rayos X, in situ y operando, revelan que el galio es un promotor necesario, el cual contribuye a la estabilización de fases expandidas de fcc Ni(C,N) así como Ni3C, a temperaturas relevantes para la catálisis (673-773K), cuyo desarrollo en la superficie del catalizador corresponde al inicio de la producción de nitrilos C2+ mediante la integración de reacciones de acoplamiento C-N y C-C. / [CA] El panorama industrial actual s'enfronta a desafiaments significatius mentres transita cap a la descarbonització i la sostenibilitat, impulsat per l'imperatiu d'aconseguir emissions netes zero per a 2050. S'espera una important contribució cap a este objectiu en connectar matèries primeres no convencionals i renovables, alternatives als materials fòssils convencionals com el petroli, a les cadenes de valor existents de la indústria química. Actualment, existix un creixent interés industrial en la producció de nitrils de cadena curta com HCN i acetonitril, mentres que s'espera que les taxes de demanda global disminuïsquen en els pròxims anys en el cas del acrilonitrilo. Com a reemplaçament per a matèries primeres convencionals per a la producció de nitrils, com les olefines lleugeres C2-3 d'origen fòssil, el desenvolupament de rutes de conversió selectives a partir de blocs de construcció C1 renovables, com el bio/e-syngas o el seu derivat metanol, i precursors N1 renovables, com l'amoníac verd, proporciona rutes cap als productes químics nitrils, prospectivament amb una petjada de carboni més baixa. La present tesi desenvolupa i estudia catalitzadors sòlids capaços de dirigir simultàniament reaccions d'acoblament C-N i C-C per a la producció de nitrils alifàtics C2+, particularment acetonitril. Es posa l'accent a revelar la naturalesa i estructura del verdader catalitzador actiu, que es desenvolupa sota les condicions del procés. Específicament, la tesi estudia efectes promocionals provocats per la combinació de dos metalls en compostos intersticials mixtos de metalls, aliatges i compostos intermetàl·lics. En primer lloc, es realitzen estudis catalítics i teòrics complementaris de Teoria del Funcional de la Densitat (DFT) sobre la conversió de mescles d'amoníac (N1) i gas de síntesi (C1, CO + H2) a acetonitril amb un (pre)catalitzador monometálico MoO3. Estos estudis demostren que MoN1-x, que es desenvolupa mitjançant nitridació superficial, és el catalitzador actiu real i suggerixen que l'activació dissociativa de HCN, assistida per oxigen, és el pas controlante de la cinètica de formació d'acetonitril. A continuació, s'estudien efectes promocionals de metalls de transició divalentes de primera fila en catalitzadors basats en molibdé, utilitzant un conjunt de compostos de molibdat mixt cristal·lí, estructuralment anàlegs, com a precursors de catalitzador. El dopat amb Mn (Mn:Mo ~1) proporciona un catalitzador particularment selectiu i estable per a la síntesi d'acetonitril a partir de mescles de NH3/gas de síntesi, aconseguint una taxa de formació d'acetonitril de 50·10-3 mmol gcat-1 min-1 a 723 K. Un conjunt de mètodes in situ i operant amb sensibilitat bulk i superficial, proporcionen evidències que un oxinitrur mixt MnM, amb una simetria Fm-3m, i ric en defectes estructurals, representa el catalitzador actiu. Se suggerix que la major oxofilia del oxinitrur mixt MnMo, juntament amb el paper clau de l'oxigen superficial per a l'activació dissociativa de HCN, subjauen a este efecte sinèrgic de tots dos metalls. Finalment, es va estudiar la conversió de mescles en fase vapor de metanol (C1) i amoníac (N1) a compostos nitrogenats sobre nanocristalls bimetàl·lics GaNi suportats en SiO2. Els aliatges desordenats de GaNi (Ga/(Ga+Ni)< 20 %) són particularment selectives cap a la síntesi de nitrils, mentres que els compostos intermetàl·lics GaNi (Ga/(Ga+Ni)> 40 %) catalitzen principalment l'aminació de metanol a metilamines. La difracció de raigs X i espectroscòpia d'absorció de raigs X, in situ i operant, revelen que el gal·li és un promotor necessari, el qual contribuïx a l'estabilització de fases expandides de fcc Ni(C,N) així com Ni3C, a temperatures rellevants per a la catàlisi (673-773 K), el desenvolupament de la qual en la superfície del catalitzador correspon a l'inici de la producció de nitrils C2+ mitjançant la integració de reaccions d'acoblament C-N i C-C. / [EN] The current industrial landscape is facing significant challenges as it transitions towards decarbonization and sustainability, driven by the imperative of achieving net-zero emissions by 2050. An important contribution towards this goal is expected from connecting unconventional and renewable feedstocks, alternative to conventional fossil raw materials such as crude oil, to existing value chains of the chemical industry. There is currently growing industrial interest in the production of short-chain nitriles such as acid cyanide and acetonitrile, while lower global demand rates are expected in the next years for acrylonitrile. Departing from conventional raw materials for nitrile production, such as C2-3 light olefin petrochemicals, the development of selective conversion routes from renewable C1 building blocks, such as bio/e-syngas or its derivative methanol, and renewable N1 precursors, like green ammonia, provides prospectively lower carbon footprint routes towards nitrile commodity chemicals. The present thesis develops and studies solid catalysts able to concomitantly steer C-N and C-C coupling reactions for the production of C2+ aliphatic nitrile N-chemicals, precisely acetonitrile. Emphasis is placed on unveiling the nature and structure or the true working catalyst, which develops under relevant process conditions. Specifically, the thesis studies promotional effects brought about by the combination of two metals in mixed-metal interstitial compounds, alloys and intermetallic compounds. First, complementary catalytic and theoretical Density Functional Theory studies on the conversion of mixtures of ammonia (N1) and syngas (C1, CO and H2) to acetonitrile with a monometallic MoO3 (pre)catalyst show MoN1-x, which develops upon near-surface nitridation, as the actual working catalyst and suggest O-assisted dissociative activation of HCN as a kinetically controlling step towards acetonitrile and higher nitriles. Next, promotional effects by first-row divalent transition metals on molybdenum-based catalysts are studied, using a set of structurally analogous crystalline ammonium mixed-metal molybdate compounds as catalyst precursors. Doping with Mn (Mn:Mo ~1) affords a particularly selective and stable catalyst for acetonitrile synthesis from NH3/syngas mixtures, achieving an acetonitrile formation rate of 50·10-3 mmol gcat-1 min-1 at 723 K. A battery of in situ and operando bulk and near-surface sensitive methods provide evidence that a defective MnMo mixed-metal oxynitride, with a Fm-3m symmetry, best represents the working catalyst. The higher oxophilicity of the mixed-metal MnMo oxynitride, alongside the key role of surface oxygen for HCN dissociative activation, is suggested to underlie the Mn-Mo bimetallic synergistic effect. Finally, the conversion of vapor mixtures of methanol (C1) and ammonia (N1) to N-compounds was studied on SiO2-supported GaNi bimetallic nanocrystals. Disordered GaNi alloys (Ga/(Ga+Ni)< 20 %) show to be particularly selective towards nitrile synthesis, whereas GaNi intermetallic compounds (Ga/(Ga+Ni)> 40 %) catalyzed primarily methanol amination to methylamines. In situ and operando X-ray diffraction and X-ray absorption spectroscopy reveal that Ga is a necessary promoter in nickel-based nanocrystals, contributing to the stabilization of expanded fcc Ni(C,N) and Ni3C phases at catalysis relevant temperatures (673-773 K), whose development on the catalyst surface corresponds to the onset of C2+ nitrile production by integration of C-N and C-C coupling reactions. / Martínez Monje, ME. (2024). Catalytic co-valorization of C1 and N1 compounds towards nitrile chemicals [Tesis doctoral]. Universitat Politècnica de València. https://doi.org/10.4995/Thesis/10251/207107