The kinetics and diffusion effects of methanol steam reforming reaction over commercial Cu/ZnO/Al₂O₃ catalyst was studied for steam to methanol (S/M) ratios of 0 to 1 and pressures below 6 bar. Our objective is the development of a novel high-pressure propulsion technology based on the concepts of thermochemical recuperation (TCR) and onboard hydrogen production. A simple kinetic model assuming methanol decomposition followed by water–gas-shift was used to estimate the rate constants (k_MD, k_WGS). The apparent activation energy of k_MD was estimated as 45–55 kJ/mol for large pellets and S/M = 1.0, 0.5, and 0.0; k_MD for S/M = 0 (and the conversions obtained) were smaller than those of S/M = 1, probably due to CO inhibition. At temperatures above ∼500 K, the WGS is at equilibrium. Strong pore-diffusion limitations are evident at 1 bar for the 3 mm catalyst, evident experimentally as well as by analysis; the apparent k_MD is almost diffusion free for particles of 0.7 mm in diameter. This resistance increases, of course, with P. The selectivity of CO (dry basis) increases with W/F_meth (weight of the catalyst divided by flow rate of methanol in units of kgcat s mmol⁻¹) and increases with decreasing particle size. As the pressure increases, the ratio of CO and CO₂ increases moderately up to 4 bar; at 6 bar the change is drastic. Similar observations were made with S/M = 0.5 and 1.0. Deactivation rates and coke formation were also studied and were found to be marginal under atmospheric pressures over a period of 10 h and became evident only at S/M = 0 and 275 °C; at 6 bar the decline was evident already at S/M = 0.5. The source of deactivation was attributed to coking, a conclusion based on TPO of spent catalyst. In the case of S/M = 1 and 0.5, and at 6 bar, there was a shift in the composition from CO₂ to CO with time over a period of 10 h at 275 °C. However, the carbon deposition in all cases was estimated to be about the same.

中文翻译：

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甲醇蒸汽重整动力学中压力，扩散和S / M比的影响

研究了水蒸气与甲醇（S / M）比为0到1且压力低于6 bar时，在工业Cu / ZnO / Al ₂ O ₃催化剂上甲醇水蒸气重整反应的动力学和扩散效应。我们的目标是根据热化学换热（TCR）和机载制氢技术开发一种新型高压推进技术。一个简单的动力学模型（假设甲醇分解，然后进行水煤气变换）用于估算速率常数（k _MD，k _WGS）。对于大颗粒，k _MD的表观活化能估计为45-55 kJ / mol，S / M = 1.0、0.5和0.0。ķ _MDS / M = 0时（和获得的转化率）小于S / M = 1时，可能是由于CO抑制。在高于约500 K的温度下，WGS处于平衡状态。对于3 mm催化剂，在1 bar时很明显存在很强的孔扩散限制，无论是实验还是分析都很明显。表观k _MD对于直径为0.7 mm的颗粒几乎没有扩散。当然，该阻力随P增大。CO（干基）的选择性随W / F _meth（催化剂的重量除以甲醇的流速，以kgcat s mmol ^-1为单位）而增加，并随粒径的减小而增加。随着压力增加，CO和CO ₂的比例适度增加至4 bar；在6 bar时变化很大。在S / M = 0.5和1.0的情况下也得到了类似的观察结果。还研究了失活率和焦炭的形成，发现在大气压下经过10小时的时间失活率很小，仅在S / M = 0和275°C时才明显。在6 bar时，S / M = 0.5时已经明显下降。失活的原因归因于焦化，这是基于废催化剂的TPO得出的结论。在S / M = 1和0.5且在6 bar的情况下，在275°C下经过10 h的时间，组成随时间从CO ₂变为CO。然而，在所有情况下，碳沉积估计都大致相同。