Abstract:

Methanol is a crucial hydrogen energy transporter, and producing hydrogen through methanol decomposition provides a practical solution to the challenges associated with transporting and storing hydrogen. Industrial methanol decomposition typically employs copper-based catalysts, which are usually synthesized through neutralization precipitation and calcination to yield the desired metal oxides. However, traditional single-step calcination often leads to the aggregation of copper species and an increase in crystallite size, which limits catalytic activity and reduces the accessibility of active sites. This study investigated the phase composition of the zincian malachite precursor for copper-based catalysts. By separating the precursor calcination into dehydroxylation and decarbonation phases, a novel stepwise calcination technique was developed that effectively prevents excessive thermal degradation, which can result in the sintering of active particles. The catalyst derived from stepwise calcination exhibits enhanced structural properties compared to conventional single-step calcined catalysts: the size of the CuO crystallites decreases from 9.0nm to 6.3nm, and the most probable pore diameter decreases from 36.5nm to 8.1nm, along with more ordered pore channel structures. Consequently, the stepwise calcination catalyst has a lower initiation temperature for methanol decomposition than conventional catalysts, leading to significantly improved methanol conversion efficiency and hydrogen selectivity.

Key words: catalyst, hydrogen production, reactivity, calcination, grain size

摘要：

甲醇是一种重要的氢能载体，利用甲醇裂解制氢是解决氢能储存、运输难题的有效解决方案。铜基催化剂是目前工业化应用最为广泛的甲醇裂解制氢催化剂，其常规制备方法为中和沉淀得到前体、再焙烧成相应金属氧化物。然而，热焙烧过程往往会导致铜活性组分团聚、晶粒度增大，影响活性位点的可接触程度，从而制约甲醇裂解制氢的反应活性。本工作剖析了铜基催化剂前体锌孔雀石物相组成，创新性地将前体焙烧过程拆分为脱羟和脱碳两部分，避免过于剧烈的热解过程导致活性颗粒过热烧结。相较于传统一步焙烧催化剂，经脱羟/脱碳分步焙烧制得的催化剂，CuO晶粒度从9.0nm减至6.3nm，最可几孔径由36.5nm缩至8.1nm，孔道结构规整度更高。因此，分步焙烧催化剂实现了比一步焙烧催化剂更低的甲醇裂解起活温度，同时甲醇裂解转化率和选择性也显著提升。

关键词: 催化剂, 制氢, 活性, 焙烧, 晶粒度