Abstract

Global warming, the environmental curse, created mainly by anthropogenic uses of fossil resources causing an excessive amount of CO₂ emission in the earth’s atmosphere. Scientists are focusing to utilize CO₂ to produce value added chemicals, i.e. methanol, DME, formic acid, etc. to reduce the effect of this greenhouse gas (GHG) and also provide an alternative carbon source and carbon neutral pathway for valuable chemicals. Despite significant achievements so far on the conversion of CO₂ to methanol via hydrogenation over Cu–ZnO–Al₂O₃ catalyst, palladium and palladium based bimetallic catalysts showed a superior activity (> 10% CO₂ conversion) and selectivity (~ 100%) to methanol over Cu based catalysts especially at low pressure (≤ 30 bar) and low temperature (≤ 250 °C). The alloying effect of Pd with the support ZnO, ZrO₂, Ga₂O₃, etc. forming PdZn, PdZr₂, PdGa species, which are identified as the main active phase of methanol synthesis. Also, reducible oxidic supports like CeO₂, ZrO₂, Ga₂O₃, etc. played important roles in adsorbing and activating CO₂ as CO and or CO₃⁻ over the surface and hydrogenated to formate species, which has been regarded as the pivotal intermediate for methanol synthesis. Though there are challenges involving the costs of noble metal palladium, hydrogen production from renewable sources and carbon capture and storage (CSS) processes. There are several review articles on CO₂ hydrogenation to methanol in the past few years but none of the existing review articles uniquely dealt with Pd-based catalysts. On this premise, this article presents a brief review comprising catalytic activity of Pd and Pd based bimetallic catalysts, effects of supports and promoters, reaction mechanism (DRIFTS studies) and perspectives on future researches necessary to achieve industrial acceptability of Pd-based catalyst for CO₂ hydrogenation to methanol.

Graphic Abstract

中文翻译：

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基于Pd的CO 2加氢制甲醇催化剂的深度活性和DRIFTS机理研究

抽象的

全球变暖是环境的祸害，主要是由于人为地使用化石资源造成地球大气中过量的CO ₂排放。科学家正在集中精力利用CO ₂生产增值化学品，例如甲醇，DME，甲酸等，以减少这种温室气体（GHG）的影响，并为有价值的化学品提供替代性的碳源和碳中和途径。尽管到目前为止在通过Cu–ZnO–Al ₂ O ₃催化剂加氢将CO ₂转化为甲醇方面取得了重大成就，但钯和钯基双金属催化剂显示出优异的活性（> 10％CO ₂铜基催化剂对甲醇的转化率和选择性（〜100％），特别是在低压（≤30 bar）和低温（≤250°C）下。Pd与ZnO，ZrO ₂，Ga ₂ O ₃等载体形成合金化作用，形成PdZn，PdZr ₂，PdGa物种，被确定为甲醇合成的主要活性相。此外，像的CeO还原氧化载体₂，的ZrO ₂，镓₂ ö ₃等中吸附和活化CO扮演着重要角色₂ CO和CO或₃ ^-在表面上加氢并氢化成甲酸盐，已被认为是甲醇合成的关键中间体。尽管存在贵金属钯成本，可再生资源制氢和碳捕集与封存（CSS）工艺的挑战。在过去的几年中，有几篇有关将CO ₂加氢成甲醇的评论文章，但是现有的评论文章中没有一篇专门涉及基于Pd的催化剂。在此前提下，本文简要概述了Pd和Pd基双金属催化剂的催化活性，载体和助催化剂的作用，反应机理（DRIFTS研究）以及对实现Pd基催化剂对CO的工业可接受性所必需的未来研究的观点。_2个 加氢成甲醇。

图形摘要