A kinetic model for methanol (MeOH) synthesis over Cu/ZnO/Al2O3/ZrO2 catalyst has been developed and selected to evaluate the effect of carbon dioxide on the reaction rates due to its high activity and stability. Detailed kinetic mechanism, on the basis of different sites on Cu for the adsorption of carbon monoxide and carbon dioxide, is applied, and the water−gas shift (WGS) reaction is included in order to provide the relationship between the hydrogenations of carbon monoxide and carbon dioxide. Parameter estimation results show that, among 48 reaction rates from different combinations of rate determining steps (RDSs) in each reaction, the surface reaction of a methoxy species, the hydrogenation of a formate intermediate HCO2, and the formation of a formate intermediate are the RDS for CO and CO2 hydrogenations and the WGS reaction, respectively. It is shown that the CO2 hydrogenation rate is much lower than the CO hydrogenation rate, and this affects the methanol production rate. However, carbon dioxide decreases the WGS reaction rate, which prevents methanol from converting to dimethyl ether, a byproduct. In such a way, a small fraction of carbon dioxide accelerates the production of methanol indirectly within a limited range, showing a threshold value of the CO2 fraction for the maximum methanol synthesis.
The electrocatalytic oxidation technology of biomass-derived oxygenates such as glycerol presents a promising method of coproducing renewable chemicals and hydrogen in an electrochemical reactor system that uses oxidation chemistry and existing proton exchange membrane technology to electrocatalytically convert oxygenates into value-added chemicals and hydrogen. In this paper, we first demonstrate the techno-economic feasibility of the electrocatalytic glycerol oxidation technology with our experimental investigations. Simple and direct conversion of glycerol into glyceraldehyde (GAD), glyceric acid (GLA), and hydroxypyruvic acid (HPA) by anodic oxidation in an electrocatalytic batch reactor over Pt/C catalysts was performed with only water as a stoichiometric chemical oxidant. We also conducted conventional catalytic (non-electrocatalytic) glycerol oxidation using a catalytic batch reactor with pressurized oxygen as the oxidant to compare conventional catalytic performances to that of the electrocatalytic reactor. The electrocatalytic glycerol oxidation process had a yield for GAD, GLA, and HPA production that was ∼1.7 times higher than that of the nonelectrocatalytic process. The turnover frequency of the electrocatalytic process is comparable to and even higher than that of a non-electrocatalytic system. On the basis of the experimental results, we develop process simulation models for both the electrocatalytic and non-electrocatalytic processes and then analyze the energy efficiency and economics of the process models. The minimum selling price (MSP) of GLA for the electrocatalytic process was $2.30/kg of GLA compared to $4.91/kg of GLA for the non-electrocatalytic process.
We propose large‐pore titanium‐containing organosilylated mesoporous silica (Ti‐SBA‐15) as a highly efficient catalyst for the oxidative desulfurization (ODS) of refractory aromatic sulfur compounds with the aim to produce ultra‐low sulfur diesel. To achieve this, we synthesized a series of mesoporous Ti‐SBA‐15 catalysts according to a new procedure. The procedure is based on the controlled grafting of titanium chelates on SBA‐15 silica at low temperatures (5 °C). This specific synthesis procedure ensured a high dispersion of the required 4‐coordinate tetrahedral Ti4+ sites located on the mesopore surface. To substantiate the influence of the titanium content and mesopore size on the ODS performance of the catalysts, the parameters were varied in the range of 0.7 to 4.7 mol % (Si/Ti) and 5.1 to 9.0 nm, respectively. The resulting Ti‐SBA‐15 catalysts were then tested in the oxidative desulfurization (ODS) of model sulfur‐containing compounds in the presence of cumene hydroperoxide (CHP) as the organic oxidant. The ODS of a real industrial diesel fuel was also carried out in a continuous fixed bed reactor with the same Ti‐SBA‐15 catalysts and CHP. The catalytic results revealed that the Ti‐SBA‐15 catalysts with the largest pore sizes (>7.3 nm) and highest Ti contents (>2.8 mol %) were highly active catalysts for ODS reactions. Moreover, the catalysts with large pores and high Ti loadings appeared to be stable for over 30 h and were far less prone to deactivation than their equivalent Ti‐SBA‐15 samples with smaller pore diameters and lower Ti contents.
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